U.S. patent application number 10/706095 was filed with the patent office on 2004-05-27 for method and apparatus of detecting positioning error of electric component held by suction nozzle, and method of mounting the electric component.
This patent application is currently assigned to Fuji Machine Mfg. Co., Ltd.. Invention is credited to Kawada, Tosuke.
Application Number | 20040098857 10/706095 |
Document ID | / |
Family ID | 26599848 |
Filed Date | 2004-05-27 |
United States Patent
Application |
20040098857 |
Kind Code |
A1 |
Kawada, Tosuke |
May 27, 2004 |
Method and apparatus of detecting positioning error of electric
component held by suction nozzle, and method of mounting the
electric component
Abstract
A method of detecting a positioning error of an electric
component with respect to a suction nozzle by which the electric
component is held by suction under a negative pressure, wherein
image data representative of images of the suction nozzle and a dog
disposed near the suction nozzle are processed to obtain a relative
position between the suction nozzle and the dog, a second
image-taking step of taking an image of said electric component
held by said suction nozzle and an image of said dog, and the
positioning error of the electric component with respect to the
suction nozzle is obtained on the basis of image data
representative of images of the electric component and the dog, and
the obtained relative position between the suction nozzle and the
dog. Also disclosed in a method of mounting the electric component
on a circuit substrate, on the basis of the obtained positioning
error of the electric component.
Inventors: |
Kawada, Tosuke; (Chiryu-shi,
JP) |
Correspondence
Address: |
OLIFF & BERRIDGE, PLC
P.O. BOX 19928
ALEXANDRIA
VA
22320
US
|
Assignee: |
Fuji Machine Mfg. Co., Ltd.
Chiryu-shi
JP
|
Family ID: |
26599848 |
Appl. No.: |
10/706095 |
Filed: |
November 13, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10706095 |
Nov 13, 2003 |
|
|
|
09947363 |
Sep 7, 2001 |
|
|
|
Current U.S.
Class: |
29/740 ;
250/559.29; 29/739; 29/833 |
Current CPC
Class: |
Y10T 29/49131 20150115;
Y10T 29/53004 20150115; Y10T 29/53191 20150115; H05K 13/0812
20180801; H05K 13/0452 20130101; Y10T 29/53052 20150115; Y10S
29/044 20130101; Y10T 29/53091 20150115; Y10T 29/53178 20150115;
Y10T 29/49133 20150115; Y10T 29/53174 20150115 |
Class at
Publication: |
029/740 ;
029/739; 029/833; 250/559.29 |
International
Class: |
G01V 008/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 13, 2000 |
JP |
2000-277902 |
Dec 11, 2000 |
JP |
2000-376153 |
Claims
What is claimed is:
1. A method of detecting a positioning error of an electric
component with respect to a suction nozzle by which the electric
component is held by suction under a negative pressure, comprising:
a first image-taking step of concurrently taking an image of said
suction nozzle and an image of at least one dog disposed in the
vicinity of said suction nozzle; and a first data processing step
of processing image data representative of said images of said
suction nozzle and said at least one dog which have been taken in
said first image-taking step, and obtaining and storing a relative
position between said suction nozzle and said at least one dog; a
second image-taking step of taking an image of said electric
component held by said suction nozzle and an image of said at least
one dog; and a second data processing step of obtaining said
positioning error of said electric component with respect to said
suction nozzle, on the basis of image data representative of said
images of said electric component and said at least one dog which
have been taken in said second image-taking step, and said relative
position between said suction nozzle and said at least one dog
obtained in said first data processing step.
2. A method according to claim 1, wherein said first image-taking
step comprises a step of rotating said suction nozzle at least once
and taking images of an end face of said suction nozzle placed in
at least two angular positions thereof, and said first data
processing step comprises a step of obtaining an axis of rotation
of said suction nozzle on the basis of the images of said end face
of said suction nozzle in said at least two angular positions.
3. A method according to claim 1, wherein a plurality of dogs are
provided, and images of said plurality of dogs are taken in said
first image-taking step, and an inclination of an imaging area in
which said images of said dogs are formed is obtained on the basis
of a relative position of said plurality of dogs in said first data
processing step.
4. A method of obtaining relative positions of a plurality of
sections of an electric-component mounting system wherein an
electric component is held by suction by a suction nozzle under a
negative pressure and is mounted on a circuit substrate, said
plurality of sections influencing an accuracy of mounting of said
electric component on said circuit substrate, comprising: a first
image-taking step of operating a first image-taking device to
concurrently take an image of said suction nozzle and an image of
at least one dog disposed in the vicinity of said suction nozzle; a
first data processing step of processing image data representative
of said images of said suction nozzle and said at least one dog
which have been taken in said first image-taking step, and
obtaining and storing a relative position between said suction
nozzle and said at least one dog; a second image-taking step of
operating said second image-taking device to concurrently take an
image of a fiducial chip as held by said suction nozzle and an
image of said at least one dog; a second data processing step of
obtaining a positioning error of said fiducial chip with respect to
said suction nozzle, on the basis of image data representative of
said images of said fiducial chip and said at least one dog, and
said relative position between said suction nozzle and said at
least one dog obtained in said data processing step; a
chip-mounting step of moving said suction nozzle and a
circuit-substrate support device supporting said circuit substrate,
relative to each other, and placing said fiducial chip on a
mounting surface which is disposed immovably relative to said
circuit-substrate support device; a third image-taking step of
operating a second image-taking device to take an image of said
fiducial chip placed on said mounting surface; and a third data
processing step of obtaining relative positions among said suction
nozzle and said first and second image-taking devices, on the basis
of image data representative of said image of said fiducial chip
taken in said third image-taking step, wherein said fiducial chip
is placed on said mounting surface in said chip-mounting step after
a relative position between said suction nozzle and said
circuit-substrate support device is compensated for said
positioning error of said fiducial chip with respect to said
suction nozzle which has been obtained in said second data
processing step, or said relative positions among said suction
nozzle, and said first and second image-taking devices are obtained
in said third data processing step, on the basis of said
positioning error of said fiducial chip obtained in said second
data processing step, as well as said image data representative of
said image of said fiducial chip taken in said third image-taking
step.
5. A method of mounting an electric component on a circuit
substrate comprising: a method of obtaining relative positions of a
plurality of sections of an electric-component mounting system, as
defined in claim 4; a fourth image-taking step of operating said
second image-taking device to take an image of a fiducial mark
provided on said circuit substrate supported by said
circuit-substrate support device; a fourth data processing step of
obtaining a positioning error of said circuit substrate on the
basis of image data representative of said image of said fiducial
mark taken in said fourth image-taking step; a fifth image-taking
step of holding said electric component by said suction nozzle, and
operating said first image-taking device to take an image of said
electric component held by said suction nozzle; and a
component-mounting step of compensating the relative position
between said circuit-substrate support device and said suction
nozzle, on the basis of image data representative of said image of
said electric component obtained in said fifth image-taking step,
said relative positions among said suction nozzle and said first
and second image-taking devices, and said positioning error of said
circuit substrate obtained in said fourth data processing step, so
that said electric component is mounted at a predetermined position
on said circuit substrate.
6. A recording medium storing a control program for practicing the
method according to claim 1, such that said control program is
readable by a computer.
7. A recording medium storing a control program for practicing the
method according to claim 4, such that said control program is
readable by a computer.
8. A recording medium storing a control program for practicing the
method according to claim 5, such that said control program is
readable by a computer.
9. An apparatus for obtaining relative positions of a suction
nozzle, a first image-taking device and a second image-taking
device, in an electric-component mounting system wherein an
electric component is held by suction by said suction nozzle and is
mounted on a circuit substrate supported by a circuit-substrate
support device, said first image-taking device being operable to
take an image of said suction nozzle in a direction of extension of
a centerline of said suction nozzle, and said second image-taking
device being operable to take an image of a fiducial mark provided
on said circuit substrate, said electric-component mounting system
further including (a) a component supply device for supplying said
suction nozzle with said electric component, (b) a
relative-movement device for moving said component supply device,
said suction nozzle and said circuit-substrate support device
relative to each other, (c) a component-mounting control device for
controlling said relative-movement device and said suction nozzle
such that said electric component received by said suction nozzle
from said component supply device is mounted at a predetermined
position on said circuit substrate supported by said
circuit-substrate support device, and (d) a data processing device
for processing image data representative of said images taken by
said first and second image-taking device, said apparatus
comprising: at least one dog located such that an image of each of
said at least one dog can be taken by said first image-taking
device, together with said image of said suction nozzle;
image-taking control means for controlling said first image-taking
device to concurrently take said images of said suction nozzle and
said at least one dog, and to concurrently take an image of a
fiducial chip held by said suction nozzle and said image of said
each dog; positioning-error obtaining means for obtaining a
relative position between said suction nozzle and said at least one
dog, on the basis of said images of said suction nozzle and said at
least one dog which have been concurrently taken under the control
of said image-taking control means, said positioning-error
obtaining a positioning error of said fiducial chip with respect to
said suction nozzle, on the basis of said images of said fiducial
chip and said at least one dog which have been concurrently taken,
and said relative position between said suction nozzle and said at
least one dog; fiducial-chip mounting control means for moving said
suction nozzle and said circuit-substrate support device, and
placing said fiducial chip on a mounting surface which is disposed
immovably relative to said circuit-substrate support device;
fiducial-chip imaging control means for operating said second
image-taking device to take said image of said fiducial chip placed
on said mounting surface; and relative-position obtaining means for
obtaining relative positions among said suction nozzle and said
first and second image-taking devices, on the basis of image data
representative of said image of the fiducial chip, wherein said
fiducial-chip mounting control means is operable to compensate a
relative position between said suction nozzle and said
circuit-substrate support device for said positioning error of said
fiducial chip with respect to said suction nozzle before said
fiducial chip is placed on said mounting surface, or said
relative-position obtaining means is operable to obtain said
relative positions among said suction nozzle and said first and
second image-taking devices on the basis of said positioning error
of said fiducial chip, as well as said image data representative of
said image of said fiducial chip taken under the control of said
fiducial-chip imaging control means.
10. An electric-component mounting system including (a) a component
supply device for supplying an electric component, (b) a suction
nozzle for holding said electric component by suction, (c) a
circuit-substrate support device for supporting a circuit
substrate, (d) a relative-movement device for moving said component
supply device said suction nozzle and said circuit-substrate
support device, relative to each other, (e) a component-mounting
control device for controlling said relative-movement device and
said suction nozzle such that said electric component received by
said suction nozzle from said component supply device is mounted at
a predetermined position on said circuit substrate supported by
said circuit-substrate support device, (f) a first image-taking
device operable to take an image of said suction nozzle in a
direction of extension to take an image of said suction nozzle in a
direction of extension of a centerline of said suction nozzle, (g),
a second image-taking device operable to take an image of a
fidicial mark provided on said circuit substrate supported by said
circuit-substrate support device, and (h) a data processing device
for processing image data representative of said images taken by
said first and second image-taking devices, said electric-component
mounting system comprising: at least one dog located such that an
image of each of said at least one dog can be taken by said first
image-taking device, together with said image of said suction
nozzle; image-taking control means controlling said first
image-taking device to concurrently take said images of said
suction nozzle and said at least one dog, and to concurrently take
an image of a fiducial chip held by said suction nozzle and said
image of said each dog; positioning-error obtaining means for
obtaining a relative position between said suction nozzle and said
at least one dog, on the basis of said images of said suction
nozzle and said at least one dog which have been concurrently taken
under the control of said image-taking control means, said
positioning-error obtaining a positioning error of said fiducial
chip with respect to said suction nozzle, on the basis of said
images of said fiducial chip and said at least one dog which have
been concurrently taken, and said relative position between said
suction nozzle and said at least one dog; fiducial-chip mounting
control means for moving said suction nozzle and said
circuit-substrate support device, and placing said fiducial chip on
a mounting surface which is disposed immovable relative to said
circuit substrate support device; fiducial-chip imaging control
means for operating said second image-taking device to take said
image of said fiducial chip place on said mounting surface;
relative-position obtaining means for obtaining relative positions
among said suction nozzle and said first and second image-taking
devices, on the basis of image data representative of said image of
said fiducial chip, said fiducial-chip mounting control means being
operable to compensate a relative position between said suction
nozzle and said circuit-substrate support device for said
positioning error of said fiducial chip with respect to said
suction nozzle before said fiducial chip is placed on said mounting
surface, or said relative-position obtaining means being operable
to obtain said relative positions among said suction nozzle and
said first and second image-taking devices on the basis of said
positioning error of said fiducial chip, as well as said image data
representative of said image of said fiducial chip taken under the
control of said fiducial-chip imaging control means; fiducial-mark
imaging control means for operating said second image-taking device
to take an image of said fiducial mark provided on said circuit
substrate supported by said circuit-substrate support device;
substrate-positioning-error obtaining means for obtaining a
positioning error of said circuit substrate on the basis of image
data representative of said image of said fiducial mark taken under
the control of said fiducial-mark imaging control means;
electric-component imaging control means for operating said suction
nozzle to hold said electric component, and operating said first
image-taking device to take an image of said electric component
held by said suction nozzle; and mounting control means for
compensating the relative position between said circuit-substrate
support device and said suction nozzle, on the basis of image data
representative of said image of said electric component, said
relative positions among said suction nozzle and said first and
second image-taking devices, and said positioning error of said
circuit substrate obtained by said substrate-positioning-error
obtaining means, so that said electric component is mounted at said
predetermined position on said circuit substrate.
11. An electric-component mounting system according to claim 10,
wherein said relative-movement device includes an X-axis slide
movable in an X-axis direction in a plane parallel to a surface of
said circuit substrate supported by said circuit substrate support
device, and a Y-axis slide which is supported by said X-axis slide
movably in said plane in a Y-axis direction perpendicular to said
X-axis direction and which holds said suction nozzle, and said
first image-taking device is fixedly disposed on said X-axis
slide.
12. An electric-component mounting system according to claim 10,
wherein said relative-movement device includes an X-axis slide
movable in an X-axis direction in a plane parallel to a surface of
said circuit substrate supported by said circuit substrate support
device, and a Y-axis slide which is supported by said X-axis slide
movably in said plane in a Y-axis direction perpendicular to said
X-axis direction and which holds said suction nozzle, and said
first image-taking device is fixed to a stationary member which
supports said X-axis slide.
13. An electric-component mounting system according to claim 10,
wherein said relative-movement device includes an X-axis slide
movable in an X-axis direction in a plane parallel to a surface of
said circuit substrate supported by said circuit substrate support
device, and a Y-axis slide which is supported by said X-axis slide
movably in said plane in a Y-axis direction perpendicular to said
X-axis direction and which holds said suction nozzle, and said
second image-taking device is fixedly disposed on said Y-axis
slide.
14. An electric-component mounting system according to claim 11,
wherein said mounting surface includes a first mounting surface
located at a first position near zero points of said X-axis slide
and said Y-axis slide, and a second mounting surface located at a
second position remote from said zero points of said X-axis slide
and said Y-axis slide, and said fiducial-chip mounting control
means is operable to place said fiducial chip on both of said first
and second mounting surfaces.
15. An electric-component mounting system according to claim 10,
wherein said relative-movement device includes an angular
positioning device operable to turn said suction nozzle about a
turning axis such that said suction nozzle is stopped at a
plurality of working stations arranged along a path of turning of
said suction nozzle, and an XY positioning device operable to move
said circuit-substrate support device in mutually perpendicular
X-axis and Y-axis directions in a plane parallel to a surface of
said circuit substrate supported by said circuit-substrate support
device, and said first image-taking device is fixedly disposed so
as to be opposed to an end face of said suction nozzle stopped at
one of said plurality working stations, while said second
image-taking device is fixedly disposed so as to be opposed to said
circuit substrate supported on said circuit-substrate support
device.
16. An electric-component mounting system according to claim 15,
wherein said XY positioning device includes an X-axis slide movable
in said X-axis direction, and a Y-axis slide movable in said Y-axis
direction, and said mounting surface includes a first mounting
surface located at a first position near zero points of said X-axis
slide and said Y-axis slide, and a second mounting surface located
at a second position remote from said zero points of said X-axis
slide and said Y-axis slide, and said fiducial-chip mounting
control means is operable to place said fiducial chip on both of
said first and second mounting surfaces.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an electric-component
mounting system arranged to mount electric components (including
electronic components) on a circuit substrate such as a
printed-wiring board, a method of obtaining relative positions of
specific sections of the electric-component mounting system which
influence the accuracy of mounting of the electric components, and
a method and an apparatus of obtaining a positioning error of each
electric component as held by a suction nozzle.
[0003] 2. Discussion of Related Art
[0004] Electric-component mounting systems often use a suction
nozzle arranged to hold an electric component by suction under a
negative pressure. Usually, the actual position of the electric
component held by the suction nozzle deviates from the nominal
position. In view of this positional deviation of the electric
component, it has been practiced to detect an error of positioning
of the electric component with respect to the suction nozzle by
operating an image-taking device to take an image of the electric
component as held by the suction nozzle, and compensate the
position of the electric component for the detected positioning
error before the electric component is mounted on the circuit
substrate. The positioning error includes at least one of an error
of positioning of the center position or other reference position
of the electric component in a plane perpendicular to an axis of
rotation of the suction nozzle, and an error of angular positioning
of the electric component about the axis of rotation of the suction
nozzle. The circuit substrate on which the electric components are
mounted is usually also positioned by a substrate supporting
device. However, the actual positions of pads in a circuit pattern
formed on the circuit substrate, on which the electric components
are to be mounted, more or less deviate from the nominal positions.
In view of this deviation, it is practiced to form a fiducial mark
on the circuit substrate upon formation of the circuit pattern,
detect the positioning error of the circuit substrate by operating
an image-taking device to take an image of the fiducial mark,
estimate the positional deviation of the pads on the basis of the
detected positioning error, and compensate the position of each
electric component for the estimated positional deviation before
the electric component is mounted on the corresponding pad.
[0005] To obtain the positioning error of the electric component
with respect to the suction nozzle and the positioning error of the
fiducial mark on the circuit substrate with respect to the
substrate supporting device, it is necessary to know the positions
of the electric component and the fiducial mark relative to the
suction nozzle and the image-taking devices when the images of the
electric component and the fiducial mark are taken by the
image-taking devices. The positioning errors of the electric
component and the fiducial mark may be obtained by detecting those
relative positions using exclusively designed detecting devices,
when the electric-component mounting system is assembled or
inspected for maintenance purpose. In this case, the obtained
positioning errors are used on an assumption that the detected
relative positions are maintained in operation of the system. To
obtain the positioning errors in this manner, the detecting devices
are required to be complicated and tend to be expensive. Further,
ballscrews used in relative-movement devices provided to move the
suction nozzle, substrate supporting device and image-taking
devices relative to each other undergo elongation and contraction
due to a change in the temperature, and elastic deformation due to
loads acting thereon. In addition, the machine frame of the
electric-component mounting system, brackets which hold the
image-taking devices and other portions of the system are also
subject to deformation due to a temperature variation. Accordingly,
the actual relative positions of the suction nozzle, substrate
supporting device and image-taking devices may vary with respect to
the detected relative positions, due to the elongation and
contraction and elastic deformation of the ballscrews of the
relative-movement devices, and deformation of the machine frame and
brackets. The above-indicated elongation and contraction and
deformation due to the temperature variation will be collectively
referred to as "thermal deformation".
[0006] It is further noted that the relative positions of the
suction nozzle, substrate supporting device and image-taking
devices may vary due to chronological changes of the individual
elements of the electric-component mounting system, wearing of the
elements during use, and displacements of the elements due to
loosening of fastening or fixing devices used in the system. To
reduce this variation of the relative positions in an
electric-component mounting system which is required to assure a
high degree of component mounting accuracy, it has been practiced
to provide the system with linear encoders to detect the actual
relative positions of the suction nozzle, substrate supporting
device and image-taking devices, and/or form the brackets for
supporting the image-taking devices, of highly rigid materials
having a relatively low coefficient of thermal expansion, and/or
design the lenses of the image-taking devices such that the lenses
are highly resistant to vibrations. However, such measures
inevitably result in an increase in the cost of manufacture of the
electric-component mounting system, and cannot therefore be said to
be completely satisfactory.
SUMMARY OF THE INVENTION
[0007] The present invention was made in view of the problems
encountered in the prior art described above. It is therefore an
object of the present invention to make it possible to accurately
detect the error of positioning of the electric component with
respect to the suction nozzle while minimizing an increase of the
cost of manufacture of the electric-component mounting system, to
improve the component mounting accuracy of the system, or to obtain
the relative positions of those sections of the system which
influence the component mounting accuracy.
[0008] The above object may be achieved according to any one of the
following modes of the present invention in the form of a method of
and an apparatus for detecting the positioning error of an electric
component- to be mounted by an electric-component mounting system,
a recording medium storing a control program for practicing the
method of detecting the positioning error, a method of and an
apparatus for obtaining the relative positions of selected sections
of the electric-component mounting system, a recording medium
storing a control program for practicing the method of obtaining
the relative positions, a method of and a system of mounting an
electric component on a circuit substrate, and a recording medium
storing a control program for practicing the method of mounting the
electric component. Each of the following modes of the invention is
numbered like the appended claims and depends from the other mode
or modes, where appropriate, to indicate and clarify possible
combinations of elements or technical features. It is to be
understood that the present invention is not limited to the
technical features or any combinations thereof which will be
described for illustrative purpose only. It is to be further
understood that a plurality of elements or features included in any
one of the following modes of the invention are not necessarily
provided all together, and that the invention may be embodied
without some of the elements or features described with respect to
the same mode.
[0009] (1) A method of detecting a positioning error of an electric
component with respect to a suction nozzle by which the electric
component is held by suction under a negative pressure,
comprising:
[0010] a first image-taking step of concurrently taking an image of
the suction nozzle and an image of at least one dog disposed in the
vicinity of the suction nozzle:
[0011] a first data processing step of processing image data
representative of the images of the suction nozzle and the at least
one dog which have been taken in the first image-taking step, and
obtaining and storing a relative position between the suction
nozzle and the at least one dog;
[0012] a second image-taking step of taking an image of the
electric component held by the suction nozzle and an image of the
at least one dog; and
[0013] a second data processing step of obtaining the positioning
on the basis of image data representative of the images of the
electric component and the at least one dog which have been taken
in the second image-taking step, and the relative position between
the suction nozzle and the at least one dog obtained in the first
data processing step.
[0014] The positioning error of the electric component with respect
to the suction nozzle includes a center position error of the
center position or other reference position of the electric
component in a plane perpendicular to a centerline of the suction
nozzle, and an angular positioning error of the electric component
about the centerline (axis of rotation) of the suction nozzle.
[0015] In the second data processing step, the position of the at
least one dog is first obtained, and the position of the suction
nozzle is obtained on the basis of the obtained position of the at
least one dog, and the relative position between the at least one
dog and the suction nozzle obtained in the first data processing
step, so that the position (positioning error) of the electric
component with respect to the thus obtained position of the suction
nozzle is obtained. Alternatively, the relative position between
the at least one dog and the electric component is first obtained,
and the positioning error of the electric component with respect to
the suction nozzle is obtained on the basis of the obtained
relative position of the at least one dog and the electric
component, and the relative position between the at least one dog
and the suction nozzle obtained in the first data processing
step.
[0016] An image-taking device used to take images of the suction
nozzle, at least one dog and electric component may consist of only
a camera such as a CCD camera, or both a camera, and a suitable
waveguide device which includes at least one light reflecting
surface or a multiplicity of optical fibers, for guiding a light
along a suitable path, to be incident upon the camera. In the
former case, the camera is oriented so as to be opposed to the end
face of the suction nozzle. In the latter case, the waveguide
device is arranged such that the light is incident upon the
camera.
[0017] In the method according to the above mode (1) of the present
invention, the relative position between the at least one dog and
the suction nozzle is detected before the electric component is
held by the suction nozzle, and then the relative position between
the electric component and the at least one dog is obtained, since
the image of the electric component held by the suction nozzle
cannot be taken in the presence of the suction nozzle hiding the
electric component. Thus, the position of the suction nozzle can be
accurately estimated on the basis of the detected position of the
at least one dog and the detected relative position between the at
least one dog and the suction nozzle. The deviation of the electric
component with respect to the estimated position of the suction
nozzle can be considered to be the actual positioning error of the
electric component with respect to the suction nozzle, as long as
the relative position between the suction nozzle and the at least
one dog remains unchanged. For instance, the at least one dog is
supported by a support member holding the suction nozzle, or by a
structure which holds the support member such that the support
member is rotatable or axially movable relative to the structure.
In this instance, it is comparatively easy to substantially prevent
a change in the relative position between the suction nozzle and
the at least one dog, which would take place due to thermal
deformation, elastic deformation, chronological change and wear of
those support member or structure. Accordingly, the positioning
error of the electric component with respect to the position of the
suction nozzle as estimated on the basis of the position of the at
least one dog can be considered to be the actual positioning error
of the electric component with respect to the actual position of
the suction nozzle, so that the actual position of the electric
component relative to the suction nozzle is compensated for the
thus detected positioning error of the electric component, as well
as for an error in the relative position between the suction nozzle
and the image-taking device, which error would take place due to
the above-indicated reasons such as the thermal and elastic
deformation. Therefore, the present method permits mounting of the
electric component on a circuit substrate with a high degree of
positioning accuracy.
[0018] (2) A method according to the above mode (1), wherein the
first image-taking step comprises a step of rotating the suction
nozzle at least once and taking images of an end face of the
suction nozzle placed in at least two angular positions thereof,
and the first data processing step comprises a step of obtaining an
axis of rotation of the suction nozzle on the basis of the images
of the end face of the suction nozzles in the at least two angular
positions.
[0019] For instance, the suction nozzle is rotated by 180.degree.,
and the two images of the end face of the suction nozzle are taken
before and after the 180.degree. rotation of the suction nozzle. In
this case, the coordinate values of the axis of rotation of the
suction nozzle are obtained by averaging the coordinate values of
the center position of the end face of the suction nozzle as
obtained from the two images. Alternatively, the suction nozzle is
rotated three times in angular increment of 90.degree., so that
four images of the end face of the suction nozzle placed in the
four angular positions of 0.degree., 90.degree., 180.degree. and
270.degree. are taken. In this case, the coordinate values of the
rotation axis of the suction nozzle are obtained by averaging the
coordinate values of the center position of the end face of the
suction nozzle as obtained from the four images. Where the images
of the end face of the suction nozzle in at least three angular
positions are taken, these angular positions need not be
equiangularly spaced from each other. The axis of rotation of the
suction nozzle is obtained as the center of a circle on which the
center positions of the end face of the suction nozzle in the
obtained images lie on the circle.
[0020] Where the suction nozzle is not rotatable, the position of
the end face of the suction nozzle can be regarded as the position
of the suction nozzle when the electric component is mounted on the
circuit substrate. Where the suction nozzle is rotatable to permit
the mounting of the electric component on the circuit substrate, at
any desired angular position of the electric suction nozzle must be
used as the position of the suction nozzle when the electric
component is mounted on the circuit substrate. Otherwise, the
accuracy of the position at which the electric component is mounted
on the circuit substrate is deteriorated.
[0021] (3) A method according to the above mode (1) or (2), wherein
the at least one dog consists of a plurality of dogs, and images of
the plurality of dogs are taken in the first image-taking step, and
an inclination of an imaging area in which the images of the dogs
are formed is obtained on the basis of a relative position of the
plurality of dogs in the first data processing step.
[0022] A dog device consisting of at least one dog may be inclined
with respect to the imaging area due to assembling errors and
thermal deformation of the image-taking device and a support
structure holding the image-taking device. This inclination may be
detected where the dog device consists of two or more dogs. For
example, the dog device consists of two dogs disposed such that
images of the two dogs are formed at two adjacent corners of the
imaging area of a first image-taking device, which corners are
spaced from each other in a direction exactly parallel to the
X-axis or Y-axis direction of the imaging area. In this case, a
straight line passing predetermined reference points such as apexes
of the two dogs can be used as a reference for detecting the
inclination of the first image-taking device (inclination of its
imaging area). Alternatively, the angle of inclination of the
above-indicated straight line passing the reference points of the
two dogs with respect to the X-axis or angle of inclination is used
as the reference for detecting the inclination of the first
image-taking device. Further, the inclination of the straight line
passing the reference points can be detected by utilizing the
function of the electric-component mounting system, for example, by
utilizing a fiducial chip, the first image-taking device and a
second image-taking device, as discussed later in the following
DESCRIPTION OF THE PREFERRED EMBODIMENTS. The dog device per se may
be inclined due to the assembling error and thermal deformation of
a support device holding the dog. The method indicated above
permits detection of the inclination of the dog device, by
utilizing the straight line passing the reference points of the two
dogs as the reference for detecting the inclination of the imaging
area of the first image-taking device. Further, the use of the
fiducial chip permits detection of the inclination of the second
image-taking device with respect to the first image-taking device.
Although the use of a single dog having a comparatively large size
and a shape suitable for detecting its inclination permits
detection of the inclination of the imaging area, the comparatively
large dog should not be hidden by the electric component held by
the suction nozzle, in order to permit the dog to perform the
assigned function. In this respect, it is preferable to use a
plurality of comparatively small dogs which are disposed so that
the images of the dogs are formed at peripheral portions of the
imaging area, desirably, at corner portions of the rectangular
imaging area.
[0023] (4) A method of obtaining relative positions of a plurality
of sections of an electric-component mounting system wherein an
electric component is held by suction by a suction nozzle under a
negative pressure and is mounted on a circuit substrate, the
plurality of sections influencing an accuracy of mounting of the
electric component on the circuit substrate, comprising:
[0024] a first image-taking step of operating a first image-taking
device to concurrently take an image of said suction nozzle and an
image of at least one dog disposed in the vicinity of said suction
nozzle;
[0025] a first data processing step of processing image data
representative of the images of the suction nozzle and the at least
one dog which have been taken in the first image-taking step, and
obtaining and storing a relative position between the suction
nozzle and the at least one dog;
[0026] a second image-taking step of operating the second
image-taking device to concurrently take an image of a fiducial
chip as held by the suction nozzle and an image of the at least one
dog;
[0027] a second data processing step of obtaining a positioning
error of the fiducial chip with respect to the suction nozzle, on
the basis of image data representative of the images of the
fiducial chip and the at least one dog, and the relative position
between the suction nozzle and the at least one dog obtained in the
first data processing step;
[0028] a chip-mounting step of moving the suction nozzle and a
circuit-substrate support device supporting the circuit substrate,
relative to each other, and placing the fiducial chip on a mounting
surface which is disposed immovably relative to the
circuit-substrate support device;
[0029] a third image-taking step of operating a second image-taking
device to take an image of the fiducial chip placed on the mounting
surface; and
[0030] a third data processing step of obtaining relative positions
among the suction nozzle and the first and second image-taking
devices, on the basis of image data representative of the image of
the fiducial chip taken in the third image-taking step,
[0031] and wherein the fiducial chip is placed on the mounting
surface in the chip-mounting step after a relative position between
the suction nozzle and the circuit-substrate support device is
compensated for the positioning error of the fiducial chip with
respect to the suction nozzle which has been obtained in the second
data processing step, or the relative positions among the suction
nozzle, and the first and second image-taking devices are obtained
in the third data processing step, on the basis of the positioning
error of the fiducial chip obtained in the second data processing
step, as well as the image data representative of the image of the
fiducial chip taken in the third image-taking step.
[0032] In the electric-component mounting system provided with the
first image-taking device and the second image-taking device, the
positioning error of the electric component with respect to the
suction nozzle is generally detected on the basis of positioning
error of the circuit substrate with respect to the
circuit-substrate support device is generally detected on the basis
of image data obtained by the second image-taking device, so that
the relative position between the suction nozzle and the
circuit-substrate support device is compensated for the positioning
errors of the electric component and the circuit substrate when the
electric component is mounted on the circuit substrate according to
a component mounting control program. In the presence of errors
between the suction nozzle and the first and second image-taking
devices, the accuracy of mounting of the electric component on the
circuit substrate is deteriorated. According to the present method,
the relative positions among the suction nozzle and the first and
second image-taking devices, for instance, positioning errors of
two of those three elements relative to the other one element are
detected are detected, and the relative position between the
suction nozzle and the circuit substrate is compensated for the
detected positioning errors as well as the positioning errors of
the electric component and the circuit-substrate support device,
before the electric component is mounted on the circuit substrate,
whereby the accuracy of mounting of the electric component on the
circuit substrate is improved.
[0033] The fiducial chip is a chip designed exclusively for
obtaining the relative positions of the suction nozzle and the
first and second image-taking devices. Alternatively, one of
electric components to be mounted on the circuit substrate is
utilized as the fiducial chip. In the former case, the fiducial
chip is manufactured so as to have high degrees of geometrical and
dimensional accuracy and optical properties suitable for the
detection, so that the accuracy of detection of the above-indicated
relative positions can be easily improved.
[0034] The mounting surface may be provided permanently on a
selected component or element of the mounting system, for instance,
may be temporarily provided on the circuit substrate on which the
electric component is to be mounted. All that is required for the
mounting surface is that the mounting surface is immovable or fixed
in position relative to the circuit-substrate support device in the
chip-mounting step and the third image-taking step.
[0035] The method of obtaining the relative positions according to
the above mode (4) of the invention may be practiced upon
assembling or maintenance inspection of the electronic-component
mounting system, or at a suitable point of time during the
component mounting operation. In the former case, the component
mounting control program is adjusted or changed on the basis of the
obtained relative positions, so as to improve the component
mounting accuracy of the electric-component mounting system. In the
latter case, changes in the relative positions among the
appropriate sections of the mounting system due to thermal
deformation are obtained, and the relative position between the
suction nozzle and the circuit-substrate support device is
compensated on the basis of the detected changes, for thereby
further improving the component mounting accuracy of the system.
The present method assures a sufficiently high degree of component
mounting accuracy even where the component mounting operation is
initiated before the operating temperatures of the individual
sections of the system have become stable.
[0036] (5) A method of mounting an electric component on a circuit
substrate, comprising:
[0037] a method of obtaining relative positions of a plurality of
sections of an electric-component mounting system, according to the
above mode (4) of this invention;
[0038] a fourth image-taking step of operating the second
image-taking device to take an image of a fiducial mark provided on
the circuit substrate supported by the circuit-substrate support
device;
[0039] a fourth data processing step of obtaining a positioning
error of the circuit substrate on the basis of image data
representative of the image of the fiducial mark taken in the
fourth image-taking step;
[0040] a fifth image-taking step of operating the suction nozzle to
hold the electric component, and operating the first image-taking
device to take an image of the electric component held by the
suction nozzle: and
[0041] a component-mounting step of compensating the relative
position between the circuit-substrate support device and the
suction nozzle, on the basis of image data representative of the
image of the electric component obtained in the fifth image-taking
step, the relative positions among the suction nozzle and the first
and second image-taking devices, and the positioning error of the
circuit substrate obtained in the fourth data processing step, so
that the electric component is mounted at a predetermined position
on the circuit substrate.
[0042] The positioning error of the circuit substrate (positioning
error of the fiducial mark) obtained in the fourth data processing
step indicated above may be an error of positioning of the circuit
substrate within the imaging area of the second image-taking device
(positioning error of the circuit substrate with respect to the
second image-taking device), or a deviation of the actual position
of the circuit substrate with respect to a nominal position of the
circuit substrate. In the former case, the positioning error of the
circuit substrate with respect to its nominal position may be
represented, for example, by a sum of a positioning error of the
circuit substrate with respect to the second image-taking device,
and a positioning error of the second image-taking device with
respect to the first image-taking device, provided the position of
the first image-taking device represents the reference position of
the electric-component mounting system as a whole.
[0043] (6) A recording medium storing a control program for
practicing the method according to any one of the above modes
(1)-(3), such that the control program is readable by a
computer.
[0044] (7) A recording medium storing a control program for
practicing the method according to the above mode (4), such that
the control program is readable by a computer.
[0045] (8) A recording medium storing a control program for
practicing the method according to the above mode (5), such that
the control program is readable by a computer.
[0046] (9) An apparatus for detecting a positioning error of an
electric component with respect to a suction nozzle by which the
electric component is held by suction under a negative pressure,
comprising:
[0047] an image-taking device operable to take an image of the
suction nozzle in a direction of extension of a centerline of the
suction nozzle;
[0048] at least one dog each disposed at a position at which an
image of the at least one dog can be taken together with an image
of the suction nozzle by the image-taking device;
[0049] an image-taking control device operable to operate the
image-taking device to concurrently take the images of the suction
nozzle and the at least one dog, and to concurrently take an image
of the electric component as held by the suction nozzle and the
image of the at least one dog; and
[0050] a data processing device operable to obtain a relative
position between the suction nozzle and the at least one dog, on
the basis of the images of the suction nozzle and the at least one
dog which have been concurrently taken, and obtaining the
positioning error of the electric component with respect to the
suction nozzle, on the basis of the images of the electric
component and the at least one dog which have been concurrently
taken, and the relative position between the suction nozzle and the
at least one dog.
[0051] The apparatus according to the above mode 9) of the
invention is suitable for practicing the method according to the
above mode (1) of detecting the positioning error of the electric
component with respect to the suction nozzle.
[0052] (10) An apparatus according to the above mode (9), wherein
the image-taking control device comprises a plural-imaging control
portion operable to rotate the suction nozzle at least once and
take images of an end face of the suction nozzle placed in at least
two angular positions thereof, and a rotation-axis obtaining
portion operable to obtain an axis of rotation of the suction
nozzle on the basis of the images of the end face of the suction
nozzle in the at least two angular positions.
[0053] (11) An apparatus according to the above mode (9) or (10),
wherein the at least one dog consists of a plurality of dogs which
are located such that images of the plurality of dogs are formed at
respective peripheral portions of an imaging area of the
image-taking device, when the images of the dogs are taken by the
image-taking device, concurrently with the image of the suction
nozzle.
[0054] (12) An apparatus according to any one of the above modes
(9)-(11), wherein the data processing device obtains an inclination
of the imaging area of the image-taking device on the basis of the
images of the plurality of dogs.
[0055] (13) An apparatus according to any one of the above modes
(9)-(12), wherein each of the at least one dog has a generally
rectangular shape, and includes a sensed portion having an apex
which is defined by adjacent two sides of a rectangle of the
generally rectangular shape.
[0056] The apex defined by the adjacent two sides of the rectangle
of the generally rectangular shape of the sensed portion of each
dog can be accurately detected, as the reference position of the
dog.
[0057] (14) An apparatus according to the above mode (13), wherein
the sensed portion has two chamfered surfaces formed along the
adjacent two sides, so as to provide two sharp edges of an acute
angle which intersect each other at right angles at the apex.
[0058] Where the a portion of the dog defining the adjacent two
sides of the sensed portion have a relatively large thickness,
sharp images of the two sides cannot be obtained by the
image-taking device. In this respect, the apex is ideally defined
by a point of intersection of two sharp edges of an actuate angle
which are provided by the two chamfered surfaces so that the
thickness at the apex is substantially zero, for accurate detection
of the dog. From the standpoint of ease of manufacture, durability
and safety of the dog, however, the portion defining the adjacent
two sides of the sensed portion may have an extremely small
thickness value.
[0059] (15) An apparatus for obtaining relative positions of a
suction nozzle, a first image-taking device and a second
image-taking device, in an electric-component mounting system
wherein an electric component is held by suction by the suction
nozzle and is mounted on a circuit substrate supported by a
circuit-substrate support device, the first image-taking device
being operable to take an image of the suction nozzle in a
direction of extension of a centerline of the suction nozzle, and
the second image-taking device being operable to take an image of a
fiducial mark provided on the circuit substrate, the
electric-component mounting system further including (a) a
component supply device for supplying the suction nozzle with the
electric component, (b) a relative-movement device for moving the
component supply device, the suction nozzle and the
circuit-substrate support device relative to each other, (c) a
component-mounting control device for controlling the
relative-movement device and the suction nozzle such that the
electric component received by the suction nozzle from the
component supply device is mounted at a predetermined position on
the circuit substrate supported by the circuit-substrate support
device, and (d) a data processing device for processing image data
representative of the images taken by the first and second
image-taking device, the apparatus comprising:
[0060] at least one dog located such that an image of each of the
at least one dog can be taken by the first image-taking device,
together with the image of the suction nozzle;
[0061] image-taking control means for controlling the first
image-taking device to concurrently take the images of the suction
nozzle and the at least one dog, and to concurrently take an image
of a fiducial chip held by the suction nozzle and the image of the
each dog;
[0062] positioning-error obtaining means for obtaining-a relative
position between the suction nozzle and the at least one dog, on
the basis of the images of the suction nozzle and the at least one
dog which have been concurrently taken under the control of the
image-taking control means, the positioning-error obtaining means
obtaining a positioning error of the fiducial chip with respect to
the suction nozzle, on the basis of the images of the fiducial chip
and the at least one dog which have been concurrently taken, and
the relative position between the suction nozzle and the at least
one dog;
[0063] fiducial-chip mounting control means for moving the suction
nozzle and the circuit-substrate support device, and placing the
fiducial chip on a mounting surface which is disposed immovably
relative to the circuit-substrate support device;
[0064] fiducial-chip imaging control means for operating the second
image-taking device to take the image of the fiducial chip placed
on the mounting surface; and
[0065] relative-position obtaining means for obtaining relative
positions among the suction nozzle and the first and second
image-taking devices, on the basis of image data representative of
the image of said fiducial chip,
[0066] and wherein the fiducial-chip mounting control means is
operable to compensate a relative position between the suction
nozzle and the circuit-substrate support device for the positioning
error of the fiducial chip with respect to the suction nozzle
before the fiducial chip is placed on the mounting surface, or the
relative-position obtaining means is operable to obtain the
relative positions among the suction nozzle and the first and
second image-taking devices on the basis of the positioning error
of the fiducial chip, as well as the image data representative of
the image of the fiducial chip taken under the control of the
fiducial-chip imaging control means.
[0067] The apparatus constructed according to the above mode (15)
is suitable for practicing the method of obtaining the relative
position according to the above mode (4).
[0068] (16) An electric-component mounting system including (a) a
component supply device for supplying an electric component, (b) a
suction nozzle for holding the electric component by suction, (c) a
circuit-substrate support device for supporting a circuit
substrate, (d) a relative-movement device for moving the component
supply device, the suction nozzle and the circuit-substrate support
device, relative to each other, (e) a component-mounting control
device for controlling the relative-movement device and the suction
nozzle such that the electric component received by the suction
nozzle from the component supply device is mounted at a
predetermined position on the circuit substrate supported by the
circuit-substrate support device, (f) a first image-taking device
operable to take an image of the suction nozzle in a direction of
extension of a centerline of the suction nozzle, (g) a second
image-taking device operable to take an image of a fiducial mark
provided on the circuit substrate supported by the
circuit-substrate support device, and (h) a data processing device
for processing image data representative of the images taken by the
first and second image-taking devices, the electric-component
mounting system comprising:
[0069] at least one dog located such that an image of each of the
at least one dog can be taken by the first image-taking device,
together with the image of the suction nozzle;
[0070] image-taking control means for controlling the first
image-taking device to concurrently take the images of the suction
nozzle and the at least one dog, and to concurrently take an image
of a fiducial chip held by the suction nozzle and the image of the
each dog;
[0071] positioning-error obtaining means for obtaining a relative
position between the suction nozzle and the at least one dog, on
the basis of the images of the suction nozzle and the at least one
dog which have been concurrently taken under the control of the
image-taking control means, the positioning-error obtaining a
positioning error of the fiducial chip with respect to the suction
nozzle, on the basis of the images of the fiducial chip and the at
least one dog which have been concurrently taken, and the relative
position between the suction nozzle and the at least one dog;
[0072] fiducial-chip mounting control means for moving the suction
nozzle and the circuit-substrate support device, and placing the
fiducial chip on a mounting surface which is disposed immovably
relative to the circuit-substrate support device;
[0073] fiducial-chip imaging control means for operating the second
image-taking device to take the image of the fiducial chip placed
on the mounting surface;
[0074] relative-position obtaining means for obtaining relative
positions among the suction nozzle and the first and second
image-taking devices, on the basis of image data representative of
the image of the fiducial chip;
[0075] the fiducial-chip mounting control means being operable to
compensate a relative position between the suction nozzle and the
circuit-substrate support device for the positioning error of the
fiducial chip with respect to the suction nozzle before the
fiducial chip is placed on the mounting surface, or the
relative-position obtaining means being operable to obtain the
relative positions among the suction nozzle and the first and
second image-taking devices on the basis of the positioning error
of the fiducial chip, as well as the image data representative of
the image of the fiducial chip taken under the control of the
fiducial-chip imaging control means;
[0076] fiducial-mark imaging control means for operating the second
image-taking device to take an image of the fiducial mark provided
on the circuit substrate supported by the circuit-substrate support
device;
[0077] substrate-positioning-error obtaining means for obtaining a
positioning error of the circuit substrate on the basis of image
data representative of the image of the fiducial mark taken under
the control of the fiducial-mark imaging control means;
[0078] electric-component imaging control means for operating the
suction nozzle to hold the electric component, and operating the
first image-taking device to take an image of the electric
component held by the suction nozzle; and
[0079] mounting control means for compensating the relative
position between the circuit-substrate support device and the
suction nozzle, on the basis of image data representative of the
image of the electric component, the relative positions among the
suction nozzle and the first and second image-taking devices, and
the positioning error of the circuit substrate obtained by the
substrate-positioning-error obtaining means, so that the electric
component is mounted at the predetermined position on the circuit
substrate.
[0080] The electric-component mounting system constructed according
to the above mode (16) is suitable for practicing the method
according to the above mode (5).
[0081] (17) An electric-component mounting system according to the
above mode (16), wherein the relative-movement device includes an
X-axis slide movable in an X-axis direction in a plane parallel to
a surface of the circuit substrate supported by the circuit
substrate support device, and a Y-axis slide which is supported by
the X-axis slide movably in the plane in a Y-axis direction
perpendicular to the X-axis direction and which holds the suction
nozzle, and the first image-taking device is fixedly disposed on
the X-axis slide.
[0082] (18) An electric-component mounting system according to the
above mode (16), wherein the relative-movement device includes an
X-axis slide movable in an X-axis direction in a plane parallel to
a surface of the circuit substrate supported by the circuit
substrate support device, and a Y-axis slide which is supported by
the X-axis slide movably in the plane in a Y-axis direction
perpendicular to the X-axis direction and which holds the suction
nozzle, and the first image-taking device is fixed to a stationary
member which supports the X-axis slide.
[0083] (19) An electric-component mounting system according to any
one of the above modes (16)-(18), wherein the relative-movement
device includes an X-axis slide movable in an X-axis direction in a
plane parallel to a surface of the circuit substrate supported by
the circuit substrate support device, and a Y-axis slide which is
supported by the X-axis slide movably in the plane in a Y-axis
direction perpendicular to the X-axis direction and which holds the
suction nozzle, and the second image-taking device is fixedly
disposed on the Y-axis slide.
[0084] (20) An electric-component mounting system according to any
one of the above modes (17)-(19), wherein the mounting surface
includes a first mounting surface located at a first position near
zero points of the X-axis slide and the Y-axis slide, and a second
mounting surface located at a second position remote from the zero
points of the X-axis slide and the Y-axis slide, and the
fiducial-chip mounting control means is operable to place the
fiducial chip on both of the first and second mounting
surfaces.
[0085] (21) An electric-component mounting system according to the
above mode (16), wherein the relative-movement device includes an
angular positioning device operable to turn the suction nozzle
about a turning axis such that the suction nozzle is stopped at a
plurality of working stations arranged along a path of turning of
the suction nozzle, and an XY positioning device operable to move
the circuit-substrate support device in mutually perpendicular
X-axis and Y-axis directions in a plane parallel to a surface of
the circuit substrate supported by the circuit-substrate support
device, and the first image-taking device is fixedly disposed so as
to be opposed to an end face of the suction nozzle stopped at one
of the plurality working stations, while the second image-taking
device is fixedly disposed so as to be opposed to the circuit
substrate supported on the circuit-substrate support device.
[0086] (22) An electric-component mounting system according to the
above mode (21), wherein the XY positioning device includes an
X-axis slide movable in the X-axis direction, and a Y-axis slide
movable in the Y-axis direction, and the mounting surface includes
a first mounting surface located at a first position near zero
points of the X-axis slide and the Y-axis slide, and a second
mounting surface located at a second position remote from the zero
points of the X-axis slide and the Y-axis slide, and the
fiducial-chip mounting control means is operable to place the
fiducial chip on both of the first and second mounting
surfaces.
BRIEF DESCRIPTION OF THE DRAWINGS
[0087] The above and other objects, features, advantages and
technical and industrial significance of the present invention will
be better understood by reading the following detailed description
of presently preferred embodiments of the invention, when
considered in connection with the accompanying drawings, in
which:
[0088] FIG. 1 electronic-component mounting system constructed
according to one embodiment of this invention;
[0089] FIG. 2 is a side elevational view of the
electronic-component mounting system of FIG. 1;
[0090] FIG. 3 is a front elevational view showing a component
mounting device in the electronic-component mounting system;
[0091] FIG. 4 is a side elevational view partly in cross section of
the electronic-component mounting system;
[0092] FIG. 5 is a side elevational view schematically showing a
printed-wiring board support device of the electronic-component
mounting system;
[0093] FIG. 6 is a side elevational view showing an electronic
component accommodated in a component tray in the
electronic-component mounting system;
[0094] FIG. 7 is a side elevational view partly in cross section
showing a component mounting unit of the component mounting device
of FIG. 3;
[0095] FIG. 8 is a side elevational view in cross section showing a
component holding device of the component mounting unit of FIG.
7;
[0096] FIG. 9 is a lock diagram schematically illustrating a
control device of the electronic-component mounting system;
[0097] FIG. 10 is a plan view showing a part of a dog provided in
the electronic-component mounting system;
[0098] FIG. 11 is a front elevational view of a part of the dog of
FIG. 10;
[0099] FIG. 12 is a view for explaining a manner of taking an image
of the dog together with an image of the electronic component;
[0100] FIG. 13 is a view for explaining a manner of obtaining the
position of the axis of rotation of a suction nozzle in the
electronic-component mounting system;
[0101] FIG. 14 is a view for explaining a manner of taking an image
of a fiducial chip as held by the suction nozzle in the
electronic-component mounting system;
[0102] FIG. 15 is a view for explaining a manner of obtaining a
positioning error of a fiducial mark camera in the
electronic-component mounting system;
[0103] FIG. 16 is a view for explaining a manner of obtaining an
operational error of an XY positioning device in the
electronic-component mounting system;
[0104] FIG. 17 is a view indicating a relative position between the
dog and the axis of the suction nozzle, errors of relative position
among the suction nozzle, an image-taking device and the fiducial
mark camera, and an operational error of the XY positioning device,
in the electronic-component mounting system;
[0105] FIG. 18 is a view for explaining a manner of obtaining a
positioning error of the electronic component with respect to the
axis of rotation of the suction nozzle in the electronic-component
mounting system;
[0106] FIG. 19 is a view for explaining a manner of obtaining an
angular positioning error of the image-taking device in an
electronic-component mounting system according to another
embodiment of the present invention;
[0107] FIG. 20 is a view for explaining a manner of obtaining an
angular positioning error of the fiducial mark camera in the
electronic component mounting system of FIG. 19;
[0108] FIG. 21 is a view for explaining a manner of detecting
inclination of a plurality of dogs provided in an
electronic-component mounting system according to a further
embodiment of this invention;
[0109] FIG. 22 is a plan view showing an electronic-component
mounting system according to a still further embodiment of this
invention; and
[0110] FIG. 23 is a plan view showing an electronic-component
mounting system according to a yet further embodiment of this
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0111] Referring first to FIGS. 1 and 2, reference numeral 10
denotes a machine base of an electronic-component mounting system.
The electronic-component mounting system includes a printed-wiring
board conveyor (PWB conveyor) 14, a component mounting device 18
and component supply devices 20, 22, which are mounted on the
machine base 10. The PWB conveyor 14 is arranged to transfer a
circuit substrate in the form of a printed-wiring board 12 in an
X-axis direction (in the left and right directions as seen in FIG.
1). The component mounting device 18 is arrange-d to mount electric
components in the form of electronic components on the
printed-wiring board 12. The component supply devices 20, 22 are
arranged to supply the component mounting device 18 with the
electronic components.
[0112] In the present embodiment, the printed-wiring board 12 is
transferred by the PWB conveyor 14 such that the printed-wiring
board 12 maintains a horizontal attitude or posture. The PWB
conveyor 14 is stopped by a suitable stopper device (not shown), to
locate the board 12 at a predetermined component-mounting position.
The board 12 located at the component-mounting position is
supported by a circuit-board support device in the form of a
printed-wiring board support device 26 which will be described by
reference to FIG. 5. In the present electronic-component mounting
system, the printed-wiring board 12 is supported such that a
component-mounting surface 28 of the board 12 on which the
electronic components are mounted is parallel to the horizontal
plane. The above-indicated X-axis direction in which the board 12
is transferred by the PWB conveyor 14 is parallel to an X axis of
an XY coordinate system in an XY plane parallel to the horizontal
component-mounting surface 28.
[0113] The printed-wiring board conveyor or PWB conveyor 14 is
provided with a pair of guide rails 30, 32, as schematically shown
in FIGS. 1 and 5. One of the guide rails 30, 32 is a stationary
guide rail fixed on the machine base 10, while the other guide rail
is a movable guide rail which is movable toward and away from the
stationary guide rail, to change a distance between the stationary
and movable guide rail, depending upon the width of the PWB
conveyor 14, which is a dimension as measured in a Y-axis direction
perpendicular to the X-axis direction in which the PWB conveyor 14
is transferred.
[0114] Each of the two guide rails 30, 32 is constructed to guide
an endless conveyor belt 34 such that the belt 34 can travel in a
hoop. The printed-wiring board 12 is placed on the conveyor belts
34, and is transferred by the conveyor belts 34 when the conveyor
belts 34 are rotated in synchronization with each other by a drive
source in the form of a printed-wiring board feed motor (PWB feed
motor) 36 indicated in the block diagram of FIG. 9.
[0115] As schematically shown in FIG. 5, the printed-wiring board
support device 26 includes a pair of clamping members 40 and a
plurality of supporting members 42. Each of the clamping members 40
takes the form of a plate fixed upright at a corresponding one of
opposite ends of an elevator platform 44 such that the two clamping
members 40 extend in the X-axis direction, namely, in the direction
of movement of the board 12. The plurality of supporting member 42
are fixed upright in an intermediate width portion of the elevator
platform 44 which is located intermediate between the two clamping
members 40. The elevator platform 44 is located under the
printed-wiring board 12 at the predetermined component-mounting
position, such that the elevator platform 44 is opposed to the
lower surface of the board 12 which is opposite to the
component-mounting surface. 28 on which the electronic components
are mounted by the present electronic component mounting
system.
[0116] The elevator platform 44 is lifted and lowered by an
elevator drive device 50, which includes a drive source in the form
of a fluid-operated actuator such as a fluid-operated cylinder. In
the specific example of FIG. 5, the elevator drive device 50 uses,
as the drive source, an elevator cylinder 52 which is a pneumatic
cylinder. The elevator cylinder 52 is disposed so as to extend in
the vertical direction, and includes a piston rod 54 for engagement
with the elevator platform 44. The printed-wiring board support
device 26 further includes a guiding device 60, which includes two
or more sets of guide rods 56 and guide sleeves 58. The guide rod
56 of each set is fixed to the elevator platform 44 and is guided
by the corresponding guide sleeve 58. When the piston rod 54 of the
elevator cylinder 52 is moved up and down, the elevator platform 44
is lifted and lowered by the piston rod 54 while the elevator
platform 44 is guided by the guiding device 60, so that the
clamping members 40 and the supporting members 42 are moved
perpendicularly to the component-mounting surface 28 of the
printed-wiring board 12, in opposite directions toward and away
from the board 12. When the elevator platform 44 is placed at its
elevated operating position, the clamping members 40 hold the board
12 apart from the upper surfaces of the conveyor belts 34 such that
the board 12 is clamped at its opposite ends corresponding to the
conveyor belts 34, in pressing contact with the upper ends of the
clamping members 40 and hold-down portions 62 provided in the guide
rails 30 32, and such that the supporting members 42 support the
board 12, with their upper ends held in contact with the lower
surface of the board 12.
[0117] The component supply devices 20, 22 are spaced from each
other in a Y-axis direction perpendicular to the X-axis direction,
and located on the opposite sides of the PWB conveyor 14, as shown
in FIGS. 1 and 2. In the present embodiment, the component supply
device 20 is of tape feeder type, while the component supply device
22 is of tray type. The component supply device 20 of tape feeder
type includes a multiplicity tape feeders 70 which are arranged in
the X-axis direction. Each tape feeder 70 has a tape cartridge
arranged to feed a carrier tape which accommodates electronic
components. The carrier tape includes a carrier substrate which has
a multiplicity of component-accommodating recesses formed at a
suitable interval along the length of the carrier tape. The
electronic components are accommodated in the respective
component-accommodating recesses. The opening of each
component-accommodating recess is closed by a covering film bonded
to the carrier substrate, to prevent the electronic components from
moving out of the recesses when the carrier tape is fed. In
operation of each tape feeder 70, the carrier tape is fed from the
tape cartridge, with a predetermined pitch in the Y-axis direction,
while the covering film is separated from a length portion of the
carrier substrate which has been fed from the tape cartridge. Thus,
the electronic components are fed one after another to a
predetermined component-supply position. The electronic components
accommodated in the tape feeders 70 include electronic components
having leads, and electronic components not having leads. Since the
electronic components of either kind are substantially accurately
positioned within the respective component-accommodating recesses,
each electronic component fed to the predetermined component-supply
position can be held at an almost central portion thereof by the
component mounting device 18, and can be taken out of the recess,
while the electronic component almost maintains predetermined
attitude and position relative to the component mounting device
18.
[0118] The component supply device 22 of tray type includes a
multiplicity of component trays 76 (FIGS. 1 and 3) accommodating
electronic components. The component trays 76 are accommodated in
respective multiple tray boxes 78, which are vertically arranged
and are supported by respective support members. The tray boxes 78
are elevated one after another by an elevator device disposed
within a column 79 (FIG. 1), to a predetermined component-supply
position. For a component holding device 100 (which will be
described) of the component mounting device 18 to receive the
electronic components from the component tray 76 in the tray box 78
located at the component-supply position, some vertical space must
be provided above the component-supply position. To provide this
vertical space, the tray box 78 from which the electronic
components have been transferred to the component holding device
100 is moved further upwards from the component-supply position to
a predetermined retracted position when the next tray box 78 is
moved to the component-supply position, so that the required
vertical space is provided between the component-supply position
and the retracted position. The component supply device 22 of tray
type is identical in construction to a component supply device
disclosed in JP-B2-2-57719.
[0119] Thus, the component mounting device 18 receives the
electronic components one after another from the component tray 76
in the tray boxy 78 at the component-supply position above which
the required vertical space is provided. Each component tray 76
accommodates the electronic components 82 in component
accommodating recesses 80 (FIG. 6) which are arranged in a matrix.
Each electronic component 82 accommodated in the corresponding
recess 80 is substantially positioned, so that the electronic
component 82 can be held at an almost central portion thereof by
the component mounting device 18, and can be taken out of the
recess 80, while the electronic component almost maintains
predetermined attitude and position relative to the component
mounting device 18. In the specific example of FIG. 6, the
electronic component 82 has a multiplicity of leads 92 extending
from the four side faces of a rectangular body 90. The electronic
component 82 is mounted at its bottom surface 96 on the
printed-wiring board 12 so that the leads 92 are connected to the
printed wiring of the board 12. The electronic component 82 has a
top surface 94 opposite to the bottom surface 96. The electronic
component 82 may be provided with a ball-grid array, or may not
have the leads 92.
[0120] The component holding device 100 of the component mounting
device 18 is movable in the mutually perpendicular X-axis and
Y-axis directions, so that the component holding device 100 can
take a linear movement having X-axis and Y-axis components, to move
each electronic component 82 to a desired position on or above the
component-mounting surface 28 of the printed-wiring board 12. To
move the component holding device 100 in the X-axis direction, the
component mounting device 18 includes two ballscrews 104 disposed
on the machine base 10, on the opposite sides of the PWB conveyor
14, so as to extend in the X-axis direction, as sown in FIG. 1, and
an X-axis slide 106 having two ballnuts 108 (only one of which is
shown in FIG. 4) which engage the respective ballscrews 104. The
device 18 further includes two X-axis drive motors 110 for rotating
the ballscrews 104, for moving the X-axis slide 106 in the X-axis
direction. As shown in FIG. 2, the X-axis slide 106 extends in the
Y-axis direction across the PWB conveyor 14, and has a length
corresponding to the distance between the component supply device
20 of feeder type and the component supply device 22 of tray type.
On the machine base 10, there are disposed two guide rails 112
located under the respective ballscrews 104. The X-axis slide 106
has two guide blocks 114 which slidably engage the guide rails 112,
for guiding the X-axis slide 106 in the X-axis direction. It will
be understood that the ballscrews 104, ballnuts 108 and X-axis
drive motors 110 cooperate with each other to constitute an X-axis
drive device 116.
[0121] On the X-axis slide 106, there is disposed a ballscrew 120
so as to extend in the Y-axis direction, as shown in FIG. 4. The
X-axis slide 106 carries a Y-axis slide 122 having a ballnut 124
which engages the ballscrew 120. The ballscrew 120 is rotated by a
Y-axis drive motor 126 (FIG. 1) through gears 128, 130, so that the
Y-axis slide 122 is moved in the Y-axis direction while being
guided by a pair of guide rails 132 (FIG. 4). It will be understood
that the ballscrew 120, ballnut 124 and Y-axis drive motor 124
constitute a Y-axis drive device 134, and that the Y-axis drive
device 134 cooperates with the X-axis slide 106, X-axis drive
device 116 and Y-axis slide 122, to constitute an XY positioning
device 136 for moving the component holding device 100 to a desired
position in the XY plane.
[0122] The Y-axis slide 122 has an upright side surface 140 on
which there are mounted the above-indicated component holding
device 100, a Z-axis drive device 144 for moving up and down the
component holding device 100 in a Z-axis direction, and a rotary
drive device 146 for rotating the component holding device 100
about its axis. The component holding device 100, the Z-axis drive
device 144 and the rotary drive device 146 constitute a component
mounting unit. Although the component mounting device 18 in the
present electronic-component mounting system includes only one
component mounting unit, the electronic-component mounting system
may include a plurality of component mounting units. For instance,
the two or more component mounting units are disposed on the Y-axis
slide 122 such that the units are arranged in a row in the Y-axis
direction.
[0123] The component mounting unit in the present embodiment is
identical with a component mounting unit as disclosed in
JP-B2-4-3093339. The component mounting Unit will be described only
briefly. The Y-axis slide 122 carries a support portion 150 mounted
on the side surface 140. As shown in FIG. 7, the support portion
150 supports a nut 152 and a splined member 154 such that the nut
152 and splined member 154 are coaxial with each other, spaced
apart from each other in the axial direction, and rotatable about
their axis of rotation extending in the vertical or Z-axis
direction. The nut 152 engages an externally threaded portion 158
of a hollow rod 156 while the splined member 154 engages a splined
portion 160 of the hollow rod 156. The splined portion 160 is
formed below the externally threaded portion 158. The nut 152 and
splined member 154 are ballnut and ball-splined member which hold a
multiplicity of balls.
[0124] The nut 152 is rotated by a rotary drive device including a
Z-axis drive motor 164 and gears 166, 168, so that the hollow rod
156 is axially moved, that is, lifted and lowered. Thus, the nut
152, gears 166, 168 and Z-axis drive motor 164 constitute the
Z-axis drive device 144. The Z-axis drive device 144 arranged to
move the hollow rod 156 in the axial direction functions to move
the component holding device 100 in the axial direction, that is,
in the Z-axis direction perpendicular to the component-mounting
surface 28 of the printed-wiring board 12, so that the component
holding device 100 is moved toward and away from the printed-wiring
board 12. The amount of operation of the Z-axis drive motor 164 is
detected by a rotary encoder 170.
[0125] To the lower end portion of the splined member 154 which
projects from the support portion 150, there is fixed a gear 172
which meshes with a gear fixed to the output shaft of a nozzle
rotating motor 174 (FIG. 9). The hollow rod 156 is rotated about
its axis when the splined member 154 is rotated by the nozzle
rotating motor 174. Thus, the component holding device 100 is
rotatable about its axis so that the electric component 82 held by
the component holding device 100 can be rotated about an axis which
extends in the vertical direction perpendicular to the top surface
94 of the electronic component 82, through an almost central part
of the top surface 94.
[0126] On the lower end portion of the hollow rod 156, there is
removably mounted a chuck adapter 180 on which a chuck 182 is
removably mounted, as shown in FIG. 8. The hollow rod 156, chuck
adapter 180 and chuck 182 constitute a nozzle holder 186 for
removably holding a suction nozzle 184. The nozzle holder 186 and
the suction nozzle 184 constitute the component holding device
100.
[0127] The suction nozzle 184 has a sleeve 190 and a suction pipe
192 which is partially fitted in the sleeve 190. The sleeve 190 is
fitted at its upper portion in the chuck adapter 180 such that the
sleeve 190 is biased by a compression coil spring 198 (hereinafter
referred to simply as "spring 198") in a direction that causes an
exposed lower portion of the sleeve 190 to be moved away from the
lower end of the chuck adapter 180. The spring 198 is interposed
between the exposed lower portion of the sleeve 190 and the lower
end of the chuck adapter 180. The exposed lower portion of the
sleeve 190 has a pair or radially extending lugs 200, which are
opposed to each other in a diametric direction of the sleeve 190
and which has a pair of slant surfaces 202 lying in the same plane.
The chuck 182 has a pair of pins 204 which engage the respective
slang surfaces 202, so that the suction nozzle 184 is held by the
chuck 182 such that the suction nozzle 184 is not axially movable
and not rotatable relative to the chuck 180. The spring 198 serves
as biasing means in the form of an elastic member.
[0128] A light emitting plate 206 is fixedly mounted on the outer
circumferential surface of the lower end portion of the sleeve 190
which is located outside the chuck 182, while the suction nozzle
192 is partially fitted in the inner circumferential surface of the
lower end portion of the sleeve 190, such that the suction nozzle
192 extends downwards through the light emitting plate 206. When
the position of the electronic component 82 held by the suction
nozzle 184 is detected, the light emitting plate 206 receives a
ultraviolet radiation, and generates a visible light toward the
electronic component 82.
[0129] The suction nozzle 184 is arranged to hold the electronic
component 82 by suction under a negative pressure, when the
electronic component 82 is mounted on the printed-wiring board 12.
To this end, the suction nozzle 184 is connected to a negative
pressure source, a positive pressure source and the atmosphere,
through: a pipe 210 which is axially movably fitted in the hollow
rod 156, as shown in FIG. 7; a housing 212 fixed to the upper end
portion of the pipe 210 which extends from the hollow rod 156, as
also shown in FIG. 7; a nipple 214 attached to the housing 212; and
a solenoid-operated directional control valve (not shown). With a
switching action of the solenoid-operated directional control
valve, the suction pipe 192 is selectively communicated with one of
the negative pressure source, positive pressure source and
atmosphere. When a negative pressure is applied from the negative
pressure source to the suction pipe 192, the electronic component
82 is held by suction at the top surface 94 of its body 90 by the
sucking end of the suction pipe 192. When a positive pressure is
applied from the positive pressure source to the suction pipe 192,
the electronic component 82 is released from the suction pipe 192.
In the present embodiment, the suction nozzle 184 is arranged to
43. hold the electronic component 82 in its horizontal
attitude.
[0130] The pipe 210 is held, by its own weight, in abutting contact
with the upper end face of the sleeve 190 of the suction nozzle 184
which is held by the nozzle holder 186. In this state, the pipe 210
is lifted and lowered with the suction nozzle 184. In the present
embodiment, initiation of a relative movement between the nozzle
holder 186 and the suction nozzle 184 is detected on the basis of a
movement of the pipe 210. To this end, the pipe 210 is provided at
its upper end with a reflector dog 222 fixed thereto, and a
photoelectric switch 226 is fixedly disposed at an upper portion of
the housing 212.
[0131] When the component mounting device 18 is not in operation to
mount the electronic component 82, the reflector dog 222 is located
below the photoelectric switch 226. In the present embodiment, the
photoelectric switch 226 is of a reflection type which includes a
light emitter and a light receiver and which generates an ON signal
when a portion of the light emitted from the light emitter is
reflected by the reflector dog 222 and received by the light
receiver, and an OFF signal when the light emitted from the light
emitter is not reflected by the reflector dog 222 and is not
received by the light receiver. When the suction nozzle 184 is
located at its lowermost position relative to the nozzle holder
186, therefore, the light emitted from the photoelectric switch 226
is not reflected by the reflector dog 222 and is not received by
the photoelectric switch 226, so that the OFF signal is generated.
When the suction nozzle 184 is moved upwards by a small distance
from the lowermost position toward the nozzle holder 186, the
emitted light is reflected by the dog 222, so that the ON signal is
generated by the photoelectric switch 226. Thus, the initiation of
the relative movement of the suction nozzle 184 and the nozzle
holder 186 can be detected by the photoelectric switch 226. In the
present embodiment, the pipe 210, reflector dog 222 and
photoelectric switch 226 cooperate with each other to constitute a
detecting device for detecting the initiation of a movement of the
suction nozzle 184 relative to the nozzle holder 186.
[0132] A plurality of kinds of suction nozzle 184 are used to mount
a plurality of kinds of electronic component 82 on the
printed-wiring board 12. The different kinds of electronic
component 82 usually have different sizes (at least one of the
cross sectional area and the height dimension). Depending upon the
sizes of the electronic component 82 of different kinds, the
different kinds of the suction nozzle 184 whose suction pipes 192
have different diameters are used. Accordingly, the different kinds
of the suction nozzle 184 whose suction pipes 192 have the
respective different diameters are accommodated in a nozzle storage
device, and are selectively used depending upon the kinds of the
electronic component 82 to be mounted on the board 12. The suction
pipes 192 having different diameters may have accordingly different
lengths. For easier understanding of the present invention, the
following description is based on an assumption that the suction
pipes 192 of the suction nozzle 184 of different kinds have the
same length.
[0133] The Y-axis slide 122 further carries a stationary
image-taking device in the form of a fiducial mark camera 240
operable to take an image of a fiducial mark provided on the
printed-wiring board 12, as shown in FIG. 1. In the present
embodiment, the fiducial mark camera 240 is a CCD camera including
CCDs (charge-coupled devices) and a lens system and capable of
taking a two-dimensional image of an object. An illuminating device
242 is provided to illuminate the fiducial mark on the board 12,
and its vicinity, when the image of the fiducial mark is taken by
the fiducial mark camera 240.
[0134] The X-axis slide 106 is provided with two stationary
image-taking devices 248, which are disposed at respective Y-axis
positions at which the respective two ballscrews 104 are disposed.
Namely, one of the two image-taking devices 248 is located between
the component supply device 20 of feeder type and the PWB conveyor
14 (printed wiring board 12 placed thereon), while the other
image-taking device 248 is located between the component supply
device 22 of tray type and the PWB conveyor 14. The two
image-taking devices 248 are identical in construction with each
other.
[0135] Each image-taking device 248 includes a component camera 250
for taking an image of the electronic component 82, and a waveguide
device 251. The waveguide device 251 includes a reflecting device
in the form of reflecting mirrors 252, 254, which are attached
through respective brackets to the underside of the X-axis slide
106. The reflecting mirror 252 is disposed at a position within a
path of movement of the component holding device 100 in the Y-axis
direction, and has a reflecting surface 256 which is inclined about
45.degree. with respect to a vertical plane including the
centerline of the suction nozzle 184, such that one of the opposite
ends of the reflecting surface 256 (as viewed in the X-axis
direction) which is closer to the X-axis slide 106 is the lower
end, that is, the left end of the reflecting surface 256 is the
lower end.
[0136] The other reflecting mirror 254 is disposed on the side of
the X-axis slide 106 which is remote from the reflecting mirror
252, and has a reflecting surface 258 which is inclined with
respect to the vertical plane, symmetrically with the reflecting
surface 256. The component camera 250 for taking the image of the
electronic component 82 held by the suction nozzle 184 is located
on the side of the X-axis slide 106 remote from the component
holding device 100, such that the component camera 250 faces
downwards toward the reflecting surface 258 of the reflecting
mirror 254. In this arrangement, the image of the electronic
component 82 held by the suction nozzle 184 can be taken by the
component camera 250 when the component holding device 100 is moved
by the XY positioning device 136 to the Y-axis position of the
corresponding ballscrew 104 at which the electronic component 82 is
located right above the reflecting mirror 252. Thus, the
image-taking device 248 is arranged to image the electronic
component 82 located at the predetermined image-taking position
which lies within a path of movement of the electronic component 82
when the Y-axis slide 122 is moved in the Y-axis direction relative
to the X-axis slide 106. In the present embodiment, the component
camera 250 is a two-dimensional CCD camera, like the fiducial mark
camera 240 described above. The reflecting mirror 254 may be
eliminated. In this case, the component camera 250 is disposed so
as to have a horizontal attitude and face toward the reflecting
mirror 252.
[0137] A stroke light 260 as a UL irradiating device is disposed
near the reflecting mirror 252, for irradiating the light emitting
plate 206 of the suction nozzle 184 with a ultraviolet radiation.
The light emitting plate 106 absorbs the ultraviolet radiation, and
emits a visible light for illuminating the bottom surface 96 of the
electronic component 82 held by the suction nozzle 184. The
component camera 250 takes a silhouette image of the electronic
component 82 in the axial direction of the suction nozzle 184, with
the light emitting plate 206 used as a light background. In the
present embodiment, the light emitting plate 206 and the stroke
light 260 provided as the UV irradiating device cooperate to
constitute an illuminating device for the image-taking device 248.
Another strobe light 262 for emitting a visible light is disposed
nearer to the suction nozzle 184 than the above-indicated strobe
light 260. This strobe light 262 serves as an illuminating device
for illuminating the ball-grid array at a relatively small angle
with respect to the bottom surface 96 of the electronic component
82. The strobe light 260 may be used as an illuminating device for
irradiating the bottom surface 96 of the electronic component 82
with a visible light, for taking a normal image of the electronic
component 82 rather than a silhouette image. If necessary, the
image-taking device 248 may use two illuminating devices which are
selectively used for taking the silhouette image and the normal
image of the electronic component 82, respectively.
[0138] In the vicinity of the component holding device 100, there
is disposed a dog 266 as shown in FIGS. 3 and 4. The dog 266 is
attached to the Y-axis slide 122 through a bracket 267, and has a
sensed portion 268 at its lower end, as shown in FIGS. 10 and 11.
The sensed portion 268 has a rectangular shape, and is chamfered at
adjacent two sides of the rectangle, so as to provide two sharp
edges 270, 272 of an acute angle which intersect each other at
right angles, at an apex 274, as indicated in FIG. 10. The position
of the apex 274 is used as the position of the dog 266. The dog 266
is positioned so that an image of the sensed portion 268 of the dog
266 is taken in one corner portion of an imaging area 276 of the
component camera 250, together with an image of the electronic
component 82, as shown in FIG. 12. In the example of FIG. 12, the
electronic component 82 has a ball-grid array. In FIG. 12, the
images of the electronic component 82 and the sensed portion 268
are indicated by the same reference numerals as used for these
elements 82, 268. The same is true in FIGS. 13-21 which will be
referred to in the following description.
[0139] The present electronic-component mounting system is provided
with two mounting surfaces 282, 284, which are located near
respective two diagonally opposed corners of a rectangular region
in which the component holding device 100 is moved by the XY
positioning device 136. Described more specifically by reference to
FIG. 1, the first mounting surface 282 is located near the end of
the ballscrew 104 on the side of the component supply device 20 of
feeder type, which end is nearer to the corresponding X-axis drive
motor 110, while the second mounting surface 282 is located near
the end of the other ballscrew 104 on the side of the component
supply device 22 of tray type, which end is remote from the
corresponding X-axis drive motor 110. The first mounting surface
282 is located near zero points or home positions of the X-axis and
Y-axis slides 106, 122, while the second mounting surface 282 is
located farthest from the zero points in the X-axis and Y-axis
directions. A fiducial chip 286 is placed on a selected one of the
two mounting surfaces 282, 284. The ballscrews 104, 120 are
rotatably supported, at their end portions connected to the X-axis
and Y-axis drive motors 110, 126, by the machine base 10 and the
X-axis slide 106, respectively, such that these end portions are
not axially movable relative to the machine base 10 and the X-axis
slide 106, respectively, but are rotatably supported at the other
end portions such that these other end portions are axially movable
relative to the machine base 10 and the X-axis slide 106,
respectively. Accordingly, the amounts of thermal deformation and
elastic deformation of the ballscrews 104, 120 are smaller at their
end portions near the mounting surface 282, than those at their end
portions near the mounting surface 284. The mounting surface 282 is
desirably located at a position at which the thermal deformation
and elastic deformation of the ballscrews 104, 120 are negligibly
small. However, the two mounting surfaces. 282, 284 may be located
near respective two diagonally opposite corners of the rectangular
printed-wiring board 12 supported by the printed-wiring board
support device 26, at its component mounting position. In this
case, the two diagonally opposite corners of the board 12
correspond to the above-indicated two corners of the rectangular
region of movement of the component holding device 100. The
fiducial chip 286 is a planar member having rectangular opposite
major surfaces. The four sides of the rectangular planar member may
be used as detected portions when an image of the fiducial chip 286
is taken. Alternatively, the upper surface of the rectangular
planar member has detected portions whose optical properties are
different from the other portion. For easier understanding, the
following description is based on an assumption that the four sides
of the rectangular fiducial chip 286 are used as the detected
portions.
[0140] The present electronic-component mounting system is provided
with control means in the form of a control device 300 illustrated
in FIG. 9. The control device 200 is principally constituted by a
computer incorporating a processing unit (PU) 302, a read-only
memory (ROM) 304, a random-access memory (RAM) 306, and a bus 308
interconnecting those elements 302, 304, 306. The bus 308 is
connected to an image input interface 312 to which are connected
the fiducial mark camera 240 and component camera 250 which have
been described above. The bus 308 is also connected to a servo
interface 314 to which are connected various actuators such as the
X-axis drive motors 110, Y-axis drive motor 126, Z-axis drive motor
164 and nozzle rotating motor 174. In the present embodiment, the
X-axis drive motors 110 are servo motors. However, the X-axis drive
motors may be electric motors of other types such as stepping
motors, as long as the amount of operation of the electric motors
can be controlled.
[0141] The bus 308 is also connected to a digital input interface
318 and a digital output interface 320. To the digital input
interface 318, there are connected the encoders 170, 176 described
above, and other encoders such as those for detecting the amount of
operation of the X-axis drive motors 110. To the digital output
interface 320, there are connected the printed-wiring board feed
motor (PWB feed motor) 36, a control valve for the elevator
cylinder 52, and other actuators. The RAM 306 stores various
control programs such as those for executing a main control
routine, a relative-position obtaining routine, and a component
mounting control routine. The control device 360 also controls
operations of the fiducial mark camera 240 and the image-taking
devices 248.
[0142] The present electronic-component mounting system is arranged
to obtain actual relative positions of those sections of the system
which influence the component mounting accuracy, and compensate the
position of the electronic component 82 for deviations of the
obtained actual relative positions with respect to the nominal
relative positions, before mounting of the electric component 82 on
the printed-wiring board 12, in order to avoid deterioration of the
component mounting accuracy due to the deviations. Described in
detail, the electric-component mounting system is adapted to
automatically detect the amounts and directions of deviations of
the actual relative positions among the image-taking devices 248
(each consisting of the component camera 250 and waveguide device
251), the fiducial mark camera 240 and the suction nozzle 184, with
respect to the nominal relative positions, so that the position of
the electronic component 82 is compensated for the detected
deviations, before the electronic component 82 is mounted on the
printed-wiring board 12. In the present embodiment, the positions
of the image-taking devices 248 and fiducial mark camera 240 are
represented by the positions of their optical axes, that is, by the
center points of the imaging areas of the image-taking devices 248
and fiducial mark camera 240. The present embodiment is further
arranged such that the positions of the fiducial mark camera 24U
and the suction nozzle 184 are defined with respect to the center
point of the imaging area of each image-taking device 248 in the XY
coordinate system in which the X-axis and Y-axis slides 106, 122
are moved in the X-axis and Y-axis directions. The XY coordinate
system has the zero point which is located at one corner of the
rectangular region of movements of the slides 106, 122, which
corner is nearest to the X-axis drive motors 110 and the Y-axis
drive motor 126.
[0143] Initially, the relative-position obtaining routine is
executed to move the suction nozzle 184 to coordinate position (X1,
Y1) of the optical axis of the image-taking device 248. The
movement of the suction nozzle 184 to the coordinate position (X1,
Y1) by the XY positioning device 136 is controlled by the control
device 300 on the basis of the output signals of the encoders
provided for the X-axis drive motors 110 and the Y-axis drive motor
126. If the electronic-component mounting system is manufactured
according to the designed specification, the center position of the
end face of the suction nozzle 184 is located on the optical axis
of the image-taking device 248, namely, aligned with the center of
the imaging area of the image-taking device 248. Actually, however,
the center position of the end face of the suction nozzle 184 is
usually more or less offset from the center of the imaging area. To
detect the amount of this offset, the image-taking device 248 is
operated to take an image of the end face of the suction nozzle
184, and an image of the sensed portion 268 of the dog 266, as
indicated by solid lines in FIG. 13.
[0144] Then, the component holding device 100 (nozzle holder 186)
is rotated by 180.degree., and an image of the end face of the
suction nozzle 184 is taken as indicated by two-dot chain line in
FIG. 13. Alternatively, the component holding device 100 is rotated
three times at an angular interval of 90.degree., and an image of
the end face of the suction nozzle 184 is taken at each of the
three angular positions of 90.degree., 180.degree. and 270.degree..
By processing image data representative of the images of the end
face of the suction nozzle 184 at the two or four different angular
positions, the X-axis and Y-axis coordinate values of the center
position of the suction nozzle 184 at the different angular
positions are obtained. Coordinate values X2, Y2 of the axis of
rotation 322 of the suction nozzle 184 are obtained by calculating
averages of the X-axis and Y-axis coordinate values of the center
position of the suction nozzle 184 obtained at the different
angular positions. Coordinate values X3, Y3 of the apex 274 of the
sensed portion 268 of the dog 266 are calculated by processing
image data representative of the image of the sensed portion 268.
The rotation axis 322 is the axis of rotation of the nozzle holder
186. A difference DX=X3-X2 between the X-axis coordinate values X2
and X3, and a difference DY=Y3-Y2 between the Y-axis coordinate
values Y2 and Y3 are stored in the RAM 306 as coordinate data
representative of a relative position between the dog 266 (apex 274
of its sensed portion 268) and the rotation axis 322 of the suction
nozzle 184. In addition, differences .DELTA.X1=X2-X1, and
.DELTA.Y1=Y2-Y1 are, stored in the RAM 306, as data representative
of a positional deviation of the rotation axis 322 of the suction
nozzle 184 with respect to the optical axis of the image-taking
device 248. Thus, the relative position between the dog 266 and the
rotation axis 322 of the suction nozzle 184, and the relative
position between the rotation axis 322 and the optical axis of the
image-taking device 248 are detected. Although an operation to
detect each of those relative positions may be performed only once,
it is desirable to perform two or more operations to obtain a
plurality of data sets so that each relative position is determined
on the basis of the two or more data sets. The same is true for
other kinds of data which will be described.
[0145] Then, the suction nozzle 184 is moved to a predetermined
Z-axis position right above the mounting surface 282, and is
lowered to hold the fiducial chip 286. The suction nozzle 184
holding the fiducial chip 286 is then moved in the XY plane to a
position in alignment with the image-taking device 248. At this
time, the suction nozzle 184 is moved such that the rotation axis
322 detected as described above is aligned with the optical axis
(X1, Y1) of the image-taking device 248, by compensating the
distances of movement by .DELTA.X1=X2-X1, and .DELTA.Y1=Y2-Y1, in
the X-axis and Y-axis directions. Then, an image of the fiducial
chip 286 as held by the suction nozzle 184 is taken. By processing
image data representative of the image of the fiducial chip 286,
coordinate values X4, Y4 of the center position of the chip 286 are
obtained. Differences .DELTA.X2=X4-X1, and .DELTA.Y2=Y4-Y1 are
stored in the RAM 306, as data representative of a positional
deviation of the fiducial chip 286 with respect to the rotation
axis 322 of the suction nozzle 184, that is, with respect to the
optical axis of the image-taking device 248. Actually, the center
position of the fiducial chip 286 is usually more or less offset
from the optical axis of the image-taking device 248, and the
angular position of the fiducial chip 286 in the imaging area 276
of the image-taking device 248 more or less deviates from the
nominal angular position, that is, the fiducial chip 286 has an
angular positioning error as well as the center position error. In
the interest of simplification, the following description is based
on an assumption that there is no angular positioning error among
the image-taking device 248, fiducial mark camera 240 and fiducial
chip 268.
[0146] Then, the position of the suction nozzle 184 in the XY plane
is compensated for the center position error of the fiducial chip
286 with respect to the position (X1, Y1) of the optical axis of
the imaging-device 248, and the suction nozzle 184 is moved to a
position at which the center of the fiducial chip 286 is aligned
with a predetermined mounting position (X5, Y5) on the mounting
surface 282. With the suction nozzle 184 located at this position,
the fiducial chip 286 is placed on the mounting surface 282.
Theoretically, the center of the fiducial chip 286 thus placed on
the mounting surface 282 is located at the predetermined mounting
position (X5, Y5). Then, the fiducial mark camera 240 is moved so
that its optical axis is aligned with the predetermined mounting
position (X5, Y5), and an image of the fiducial chip 286 is taken
by the fiducial mark camera 240, as indicated in FIG. 15. By
processing image data representative of the image of the fiducial
chip 286, coordinate values X6, Y6 of the center position of the
fiducial chip 286 are obtained. In the presence of some
misalignment of the optical axis of the fiducial mark camera 240
with respect to the optical axis of the image-taking device 248,
the center position of the fiducial mark 268 as represented by the
obtained image actually deviates from the predetermined mounting
position (X5, Y5) by .DELTA.X3=X6-X5, and .DELTA.Y3=Y5-Y6. This
means that the amounts of misalignment of the optical axis of the
fiducial mark camera 240 with respect to the optical axis of the
image-taking device 248 are equal to -.DELTA.X3=-(X6-X5), and
-.DELTA.Y3=-(Y5-Y6) in the X-axis and Y-axis directions.
[0147] It will be understood from the above description that in the
coordinate system of the image-taking device 248, the suction
nozzle 184 has a center position error of .DELTA.X1=X2-X1, and
.DELTA.Y1=Y2-Y1, while the fiducial mark camera 240 has an optical
axis misalignment of -.DELTA.X3=-(X6-X5), and -.DELTA.Y3=-(Y5-Y6).
The data representative of the center position error of the suction
nozzle 184, and the data representative of the optical axis
misalignment of the fiducial mark camera 240 are stored in the RAM
306, as data representative of the relative position between the
image-taking device 248 and the suction nozzle 184, and data
representative of the relative position between the image-taking
device 248 and the fiducial mark camera 240.
[0148] Then, the position of the suction nozzle 184 in the XY plane
is adjusted for alignment of its rotation axis 322 with the
predetermined mounting position (X5, Y5), and the suction nozzle
184 is lowered to again hold the fiducial chip 286. Accordingly,
the center position of the fiducial chip 286 held by the suction
nozzle 184 is theoretically aligned with the rotation axis 322 of
the suction nozzle 184. In the present embodiment, whether this
alignment is established or not is checked by taking an image of
the fiducial mark 268 by the image-taking device 248 and processing
the thus obtained image data. However, this checking is not
essential. If the checking reveals that the center position of the
fiducial chip 286 is not aligned with the rotation axis 322, it
means that the operations to detect the relative positions among
the image-taking device 248, suction nozzle 184 and fiducial mark
camera 240 have not been correctly performed. In this case, the
operations to detect the relative positions are repeated to
establish the alignment. Usually, however, the alignment is
established by an initial cycle of the operations.
[0149] Then, the suction nozzle 184 is moved in the XY plane to a
predetermined mounting position (X7, Y7) on the mounting surface
284, and is lowered to place the fiducial chip 286 on the mounting
surface 284. This movement of the suction nozzle 184 to the
coordinate position (X7, Y7) is also controlled by the control
device 300 on the basis of the output signals of the encoders
provided for the X-axis drive motors 110 and the Y-axis drive motor
126. Then, the fiducial camera 240 is moved so that its optical
axis is aligned with the predetermined mounting position (X7, Y7),
and an image of the fiducial chip 286 is taken by the fiducial mark
camera 240. The movement of the suction nozzle 184 and the movement
of the fiducial mark camera 240 are effected after the XY positions
of the suction nozzle 184 and the fiducial mark camera 240 are
compensated for the image-taking position error of the suction
nozzle 184 and the misalignment of the fiducial mark camera 240
with respect to the image-taking device 240, which have been
obtained. In the absence of an operating error of the XY
positioning device 136, therefore, the coordinate values of the
center position of the fiducial chip 286 as obtained by processing
the obtained image data are theoretically equal to the coordinate
values X7, Y7 of the predetermined mounting position on the
mounting surface 284. Actually, however, coordinate values X8, Y8
of the center position of the fiducial chip 286 are different from
the coordinate values X7, Y7 of the predetermined mounting
position, by .DELTA.X4=X8-X7, and .DELTA.Y4=Y8-Y7.
[0150] The above-indicated differences .DELTA.X4=X8-X7, and
.DELTA.Y4=Y8-Y7 are considered to arise from an operating error of
the XY positioning device 136, which takes place due to
manufacturing errors, elastic deformation and thermal deformation
of the ballscrews 104, 120 and other elements of the XY positioning
device 136. The manufacturing error and the elastic deformation do
not change with the operating time of the electronic-component
mounting system, but the thermal deformation changes with the
operating time. In this respect, it is desirable to detect the
above-indicated positional error .DELTA.X4=X8-X7, and
.DELTA.Y4=Y8-Y7 in the same manner as described above, at a
suitable time interval during an operation of the
electronic-component mounting system, or at a suitable point or
points of time at which the detection does not disturb the mounting
operation of the electronic component 82. For a similar reason, it
is desirable to detect the relative positions among the
image-taking device 248, suction nozzle 184 and fiducial mark
camera 240, with the fiducial chip 286 placed on the mounting
surface 282, at a suitable time interval or at a suitable point or
points of time during the operation of the system. That is, the
members which support the image-taking device 248, suction nozzle
184 and fiducial mark camera 240 also undergo thermal deformation
due to a variation of the operating temperature.
[0151] As described above, the following sets of data are obtained
before the electronic component 32 is mounted on the printed-wiring
board 12 according to the component mounting control routine:
relative position data DX=X3-X2, DY=Y3-Y2 representative of the
relative position between the dog 266 and the rotation axis 322 of
the suction nozzle 184, as indicated by a vector V0 in FIG. 17;
positional deviation data .DELTA.X1=X2-X1, and .DELTA.Y1=Y2-Y1
representative of the deviation of the rotation axis 322 of the
suction nozzle 184 with respect to the optical axis of the
image-taking device 248, as indicated by a vector V1 in FIG. 17;
optical misalignment data -.DELTA.X3=-(X6-X5), and
-.DELTA.Y3=-(Y5-Y6) representative of the optical axis misalignment
of the fiducial mark camera 240 with respect to the optical axis of
the image-taking device 248, as indicated by a vector V2 in FIG.
17; and operating error data .DELTA.X4=X8-X7, and .DELTA.Y4=Y8-Y7
representative of the operating error of the XY positioning device
136, as indicated by a vector V3 in FIG. 17.
[0152] The component mounting operation is initiated with detection
of the positioning error of the printed-wiring board 12 which has
been transferred by the PWB conveyor 14 and supported by the
printed-wiring board support device 26. This detection is effected
by processing the image data representative of the image of the
fiducial mark 286 taken by the fiducial mark camera 240. Then, the
electronic component 82 is received by the suction nozzle 184 from
the component supply device 20 or 22, and the positioning error of
the electronic component 82 with respect to the rotation axis 322
of the suction nozzle 184 is detected by processing the image data
representative of the image of the electronic component 82 taken by
the image-taking device 248. The positioning errors of the
printed-wiring board 12 and the electronic component 82 are
eliminated by adjusting predetermined component mounting control
data, so that the electronic component 82 is mounted in position on
the printed-wiring board 12.
[0153] The aspects of the component mounting operation of the
present electronic-component mounting system which have been
described are the same as in the conventional system. However, the
component mounting operation in the present embodiment is different
from that in the conventional system, in that the suction nozzle
184 and the fiducial mark camera 240 are moved to eliminate the
deviation .DELTA.X1=X2-X1, and .DELTA.Y1=Y2-Y1 of the rotation axis
322 of the suction nozzle 184 with respect to the optical axis of
the image-taking device 248, and the optical axis misalignment
-.DELTA.X3=-(X6-X15) and -.DELTA.Y3=-Y5-Y6) of the fiducial mark
camera 240 with respect to the optical axis of the image-taking
device 248, when the positioning errors of the printed-wiring board
12 and the electronic component 82 are detected.
[0154] Further, the image of the sensed portion 268 of the dog 266
is taken together with the image of the electronic component 82,
upon detection of the positioning error of the electronic component
82 with respect to the rotation axis 322 of the suction nozzle 184,
in order to obtain coordinate values X9, Y9 of the apex 274 of the
sensed portion 268, so that coordinate values X10, Y10 of the
rotation axis 322 of the suction nozzle 184 are estimated on the
basis of the obtained coordinate values X9, Y9 of the apex 274, and
the already obtained relative position data DX=X3-X2, and DY=Y3-Y2
representative of the relative position of the apex 274 and the
rotation axis 322 of the suction nozzle 184. Coordinate values X11,
Y11 of the center position of the electronic component 82 are
detected n the basis of the thus obtained coordinate values X10,
Y10 of the rotation axis 22. In this aspect, too, the present
embodiment is different from the prior art.
[0155] The end face of the suction nozzle 184 is hidden by the
electronic component 82 and is not visible, while the sensed
portion 268 of the dog 266 is visible, so that the image of the
sensed portion 268 is taken by the image-taking device 248, to
estimate the position of the rotation axis 322 of the suction
nozzle 184 on the basis of the thus obtained image data of the
sensed portion 268 and the already detected relative position
between the sensed portion 268 and the rotation axis 322 of the
suction nozzle 184. In this respect, it is noted that the rotation
axis 322 of the suction nozzle 184 is theoretically located on the
optical axis of the image-taking device 248 immediately after the
position of the suction nozzle 184 is compensated for the
positioning error of its rotation axis 322 with respect to the
optical axis of the image-taking device 248, on the basis of the
detected relative position therebetween. However, the rotation axis
322 tends to deviate from the optical axis of the image-taking
device 248 due to a rise of the operating temperature at various
local portions of the electronic-component mounting system with an
increase in the operating time of the system. In view of this
tendency, the present system is arranged to estimate the position
of the rotation axis 322 of the suction nozzle 184 at the
predetermined time interval during the operation of the system.
Since this estimation can be made in a relatively short time, the
estimation may be made upon detection of the positioning error of
each electronic component 82 relative to the suction nozzle 184,
that is, for each component 82 to be mounted on the printed-wiring
board 12.
[0156] The present electronic-component mounting system is further
arranged to adjust the component mounting control data so as to
eliminate the operating, error .DELTA.X4=X8-X7, and .DELTA.Y4=Y8-Y7
of the XY positioning device 136, as well as the positioning errors
of the center position of the electronic component 82 with respect
to the rotation axis 322 of the suction nozzle 184 and the
positioning error of the printed-wiring board 12, when the
electronic component 82 is positioned relative to the suction
nozzle 184 before mounting of the component 82 on the
printed-wiring board 12. The adjustment of the component mounting
control data to eliminate the operating error of the XY positioning
device 136 may be made on an assumption that the operating error
increases in proportion to distances in the X-axis and Y-axis
directions between the predetermined mounting position on the
mounting surface 282 and the position at which the electronic
component 82 is mounted on the printed-wiring board 12.
[0157] Described more specifically, the operating error of the XY
positioning device 136 for the movement of the suction nozzle 184
from the mounting surface 282 to the mounting surface 284 is
represented by the X-axis error .DELTA.X4=X8-X7, and the Y-axis
error .DELTA.Y4=Y8-Y7, as indicated by the vector V3 in FIG. 17.
Therefore, the operating error of the XY positioning device 136 at
the specific component mounting position on the printed-wiring
board 12 is represented by a product K.sub.X.multidot..DELTA.X4 and
a product K.sub.Y.multidot..DELTA.Y4, where "K.sub.X" represents a
ratio of the distance in the X-axis direction between the
predetermined mounting position on the mounting surface 282 and the
component mounting position on the board 12, to a distance in the
X-axis direction between the predetermined mounting positions on
the two mounting surfaces 282, 284, while "K.sub.Y" represents a
ratio of the distance in the Y-axis direction between the
predetermined component mounting position on the mounting surface
282 and the component mounting position on the board 12, to a
distance in the Y-axis direction between the predetermined mounting
positions on the mounting surfaces 282, 284. Accordingly, the
component mounting control data are adjusted by adding the products
K.sub.X.multidot..DELTA.X4 and K.sub.Y.multidot..DELTA.Y4 to the
nominal distances of movement of the suction nozzle 184 in the
X-axis and Y-axis directions, for eliminating the operating error
of the XY positioning device 136 for the specific component
mounting position on the board 12. Since the operating error
.DELTA.X4 and .DELTA.Y4 of the XY positioning device 136 for the
distances between the mounting surfaces 282, 284 varies with the
operating time of the electronic-component mounting system, the
operating error is updated from time to time during the operation
of the system.
[0158] Where the angular position of the electronic component 82 as
received by the suction nozzle 184 from the component supply device
20, 22 is different from the angular position of the electronic
component 82 as mounted on the printed-wiring board 12, the suction
nozzle 184 is rotated by a suitable angle before the electronic
component 84 is mounted on the board 12. In this case, too, the
electronic component 82 can be mounted on the board 12 with high
accuracy of positioning of the center position of the electronic
component 82 relative to the board 12. Namely, the present
electronic-component mounting system is arranged to detect the
positioning error of the electronic component 82 relative to the
rotation axis 322 of the suction nozzle 184, for accurately
calculating the center position error of the electronic component
82 which arises from the rotation of the suction nozzle 184, so
that the relative position between the suction nozzle 184 and the
printed-wiring board 12 can be compensated for the calculated
center position error of the electronic component 82.
[0159] While the foregoing description is based on an assumption
that the fiducial chip 286 and the electronic component 82 held by
the suction nozzle 184 do not have an angular position error
relative to the suction nozzle 184, there are actually the angular
positioning errors between the fiducial chip 286 and electronic
component 82 and the suction nozzle 184. To eliminate these angular
positioning errors, the angular positions of the fiducial chip 286
and the electronic component 82 are obtained by processing the
image-data representative of the images of the fiducial chip 286
and the electronic component 82 in the imaging area 276 of the
image-taking device 248. Before When the fiducial chip 286 is
mounted on the mounting surfaces 282, 284 and before the electronic
component 82 is mounted on the board 12, the suction nozzle 184
holding the fiducial chip 286 or electronic component 82 is rotated
by a suitable angle to eliminate the angular positioning error. To
this end, the image-taking device 248 and the fiducial mark camera
240 must be adjusted to reduce their angular positioning errors to
a negligibly small value. The angular positioning errors of the
image-taking device 248 and the fiducial mark camera 240 can be
detected as described below in detail.
[0160] It will be understood from the foregoing description of the
first embodiment of this invention that the XY positioning device
136 serves as a relative-movement device operable to move the
suction nozzle 184 and the fiducial mark camera 240 relative to the
component supply devices 20, 22 and the printed-wiring board
support device 26, and that the control device 300 serves as a
component-mounting control device operable to control the XY
positioning device 136 and the suction nozzle 184 such that the
electric component in the form of the electronic component 82
received by the suction nozzle 184 from the component supply
devices 20, 22 is mounted at a predetermined position on the
printed-wiring board 12 supported by the printed-wiring board
support device 26. It will also be understood that the image-taking
device 284 and the fiducial mark camera 240 respectively function
as a first and a second image-taking device which are arranged to
take an image of the suction nozzle in a direction of extension of
the suction nozzle and an image of the fiducial mark provided on
the circuit substrate in the form of the printed-wiring board 12,
respectively, while the control device 300 functions as an
image-taking control device or image-taking control means for
controlling the image-taking device 0.248 and the fiducial mark
camera 240 to take the images of the suction nozzle 184 and the
fiducial mark provided on the board 12, respectively, and that the
control device 300 also functions as a data processing device
operable to process image data obtained by the image-taking device
248 and the fiducial mark camera 240. It will further be understood
that a portion of the data processing device constitutes a
rotation-axis obtaining portion operable to obtain the position of
an axis of rotation of the suction nozzle, while a portion of the
image-taking control means constitutes a plural-imaging control
portion operable to rotate the suction nozzle 184 at least once and
control the image-taking device 248 for taking images of the end
face of the suction nozzle 184 placed in at least two different
angular positions. It will also be understood that the control
device 300 further functions as positioning-error obtaining means
for obtaining a positioning error of the fiducial chip 286 with
respect to the suction nozzle 184 on the basis of the images of the
fiducial chip and the dog, and the relative positions among the
suction nozzle 184, dog 266 and fiducial chip 286, fiducial-chip
mounting control means for moving the suction nozzle 184 and the
printed-wiring board support device 26, and controlling the suction
nozzle 184 to place the fiducial chip 286 on the mounting surfaces
282, 284, and fiducial-chip imaging control means for operating the
fiducial mark camera 240 to take an image of the fiducial chip 286
placed on the mounting surfaces 282, 284. It will further be
understood that the control device 300 also functions as:
relative-position obtaining means for obtaining relative positions
among the suction nozzle 184, image-taking device 284 and fiducial
mark camera 240; fiducial-mark imaging control means for operating
the fiducial mark camera 240 to take an image of the fiducial mark
provided on the printed-wiring board 12 supported by the support
device 26; substrate-positioning-error obtaining means for
obtaining a positioning error of the printed-wiring board 0.12 on
the basis of the image of the fiducial mark 286; electric-component
imaging control means for controlling the suction nozzle 184 to
hold the electric component in the form of the electronic component
82, and operating the image-taking device 284 to take an image of
the electric component held by the suction nozzle 184; and mounting
control means for compensating the relative position between the
printed-wiring board support device 26 and the suction nozzle 184,
on the basis of image data of the electric component taken by the
image-taking device 248, the relative positions among the suction
nozzle 184, image-taking device 284 and fiducial mark camera 240
which have been obtained by the above-indicated relative-position
obtaining means, and the positioning error of the printed-wiring
board 12 obtained by the substrate-positioning-error obtaining
means, so that the electric component is mounted at a predetermined
position on the printed-wiring board 12.
[0161] It will also be understood that the RAM 306 function as: a
first recording medium for storing a control program for detecting
the positioning error of the electric component; a second recording
medium for storing a control program for obtaining the relative
positions among the suction nozzle 184, image-taking device 248 and
fiducial mark camera 240; and a third recording medium for storing
a control program for controlling the XY positioning device 136 and
the suction nozzle 184 to accurately mount the electric component
at the predetermined position on the printed-wiring board 12, while
utilizing data indicative of the above indicated relative
positions, the operating error of the XY positioning device 136 and
the positioning errors of the electric component and the
printed-wiring board 12 in this respect, it is noted that the
control programs indicated above are stored in a memory device of a
host computer to which the present electronic-component mounting
system is connected, and are down-loaded into the RAM 306 as
needed. However, the control programs may be stored in a floppy
disc or other removable recording medium which is readable by a
reading device provided in the present mounting system per se or
the host computer, so that the appropriate control program is
executed by the control device 300, as needed.
[0162] In the first embodiment of FIGS. 1-18, only one dog 266 is
provided. However, two dogs 332 may be provided as shown in FIG.
19, so that images of sensed portions 334, 336 of the two dogs 332
are formed at respective two adjacent corner portions of a
rectangular imaging area 278 of the image-taking device 248, which
two corner portions are spaced apart from each other in the X-axis
or Y-axis direction, for instance, in the Y-axis direction, as
indicated in FIG. 19. In the embodiment of FIG. 19, an angle
.DELTA..theta.1 of the imaging area 276 with respect to a straight
line 342 passing apexes 338, 340 of the sensed portions 334, 336 is
obtained as the angular positioning error of the imaging error 276,
that is, the angular positioning error of the image-taking device
248. To this end, the two dog 332 should be positioned such that
the straight line 342 passing the apexes 338, 340 of the two sensed
portions 334, 336 is precisely parallel to the guide rails 132 of
the Y-axis slide 122 mounted on the X-axis slide 106.
[0163] Further, an image of the fiducial chip 286 held by the
suction nozzle 184 is taken by the image-taking device 248 as shown
in FIG. 20, and an angle .DELTA..theta.2 of the fiducial chip 286
with respect to the imaging area 276 is obtained. A sum of the
angles .DELTA..theta.1 and .DELTA..theta.2 represents the angular
positioning error of the fiducial chip 286.
[0164] The suction nozzle 184 is rotated to eliminate the angular
positioning error of the fiducial chip 286, and the fiducial chip
286 held by the suction nozzle 184 is placed on the mounting
surface 282. In this state, an image of the fiducial mark 286 is
taken by the fiducial mark camera 240. An angle of the fiducial
mark 286 with respect to the imaging area of the fiducial mark
camera 240 is obtained. This angle represents an angular
positioning error of the fiducial mark camera 240 with respect to
the image-taking device 248. A sum of this angular positioning
error of the fiducial mark camera 240 and the angular positioning
error of the image-taking device 248 represents an absolute angular
positioning error of the fiducial mark camera 240 in the XY
coordinate system defined by the guide rails 30, 32 of the X-axis
slide 106 and the guide rails 132 of the Y-axis slide 122. In the
present second embodiment of FIGS. 19 and 20, a portion of the
control device 300 assigned to detect the angular positioning error
of the imaging area 276 of the image-taking device 248 on the basis
of the images of the two dogs 332 constitutes an angular-position
obtaining portion operable to obtain the angular positioning error
of the imaging area 276.
[0165] In the second embodiment of FIGS. 19-20, the two dogs 332
are positioned such that the straight line 342 passing the apexes
338, 340 of the sensed portions 334, 336 of the dogs 332 is
precisely parallel to the guide rails 0.132 of the Y-axis slide
122. However, the electronic-component mounting system may be
arranged to detect the angle of inclination of the straight line
342 passing the apexes 338, 340. For example, the angular
positioning error .DELTA..theta.1 and .DELTA..theta.2 of the
fiducial chip 286 with respect to the straight line 342 is obtained
in the manner as described above, and the suction nozzle 184 is
rotated so as to eliminate this angular positioning error, before
the fiducial chip 286 is placed on the mounting surface 282. Then,
an image of the fiducial chip 286 on the mounting surface 282 is
taken by the fiducial mark camera 240. After the fiducial mark
camera 240 is moved by a predetermined small distance in the X-axis
or Y-axis direction, an image of the fiducial chip 286 is again
taken by the fiducial mark camera 240. The two images of the
fiducial chip 286 thus taken are superimposed on each other, as
indicated in FIG. 21. Since a straight line 350 passing the
corresponding corners of the rectangular images of the fiducial
chip 286 is theoretically parallel to the Y-axis, and since the
angular positioning error of the fiducial chip 286 with respect to
the straight line 342 passing the apexes 338, 340 of the sensed
portions 334, 336 has been eliminated by rotation of the suction
nozzle 184 as described above, an angle .DELTA..theta.3 of the
fiducial chip 286 with respect to the straight line 350 is
considered to represent an angular positioning error of the
straight line 342 (passing the apexes 338, 340) with respect to the
Y-axis.
[0166] Thus, the angular positioning error of the straight line 342
(passing the apexes 338, 340 of the sensed portions 334, 336 with
respect to the Y-axis can be obtained, so that the absolute angular
positioning errors of the image-taking device 248 and fiducial mark
camera 240 can be obtained by compensating the angular positioning
errors of the image-taking device 248 and the fiducial mark camera
240 with respect to the straight line 342, for the obtained angular
positioning error of the straight line 342.
[0167] The principle of the present invention is equally applicable
to an electronic-component mounting system of a type shown in FIG.
22. The electronic-component mounting system of the embodiment of
FIG. 22 is different from that of the first embodiment in that a
component camera 356 of an image-taking device for obtaining the
positioning error of the electronic component with respect to the
axis of rotation of the suction nozzle is fixedly disposed on the
machine base 10. Described more specifically, the component camera
356 is fixedly disposed on the machine base 10, at a position
between the component supply device 20 and the PWB conveyor 14 as
viewed in the Y-axis direction, and at an almost intermediate
position of the printed-wiring board 12 supported by the support
device 0.26, as viewed in the X-axis direction in which the board
12 is fed by the PWB conveyor 14. The suction nozzle 184 and the
fiducial mark camera 240 are fixed on the Y-axis slide 122, as in
the electronic-component mounting system of FIGS. 1 and 2. In the
present electronic-component mounting system of FIG. 22, too, the
relative positions (including the center position error and angular
positioning error) of the suction nozzle 184, fiducial mark camera
240 and component camera 356 can be obtained on the basis of the
images of a dog and fiducial chip which are similar to the dog 266
and fiducial chip 286 used in the first embodiment.
[0168] The principle of the present invention is also applicable to
an electronic-component mounting system of a type shown in FIG. 23,
which includes a multiplicity of component holders 360 which have
respective suction nozzles and which are fixedly disposed on one
index table 362. The component holders 360 are turned about the
axis of rotation of the index table 362 when the index table 362 is
intermittently rotated at a predetermined angular interval. The
present system further includes an angular positioning device 364
for rotating the index table 362 at a plurality of predetermined
working stations which are arranged on a circular path of movement
of the component holders 360, so that the suction nozzle 184 held
by each component holder 360 can be turned about a turning axis
(axis of the index table 362) and stopped at the working stations.
The system further includes a PWB support device 366 for supporting
the printed-wiring board 12, and an XY positioning device 370 for
positioning the PWB support device 366 in the X-axis and Y-axis
directions in the XY plane parallel to the surface of the
printed-wiring board 12. The XY positioning device 370 includes an
X-axis slide 376 movable by an X-axis drive motor 372 and a
ballscrew 374, and a Y-axis slide which is movable on the X-axis
slide 376 by a Y-axis drive motor 378 and a ballscrew 380. The PWB
support device 366 is mounted on the Y-axis slide. An image-taking
device 384 which includes a component camera and a waveguide device
and which is operable to take an image of the electronic component
82 is fixedly disposed at a position at which the component camera
is opposed to the end face of the suction nozzle of the component
holder 360 located at one of the above-indicated working stations.
A first rotating device (not shown) is fixedly disposed above the
image-taking device 380 and the corresponding component bolder 360,
for rotating this component holder 360. A second rotating device
(not shown) is fixedly disposed at the working station between the
working station at which the image-taking device 384 is disposed,
and the working station at which the electronic component 82 is
mounted on the printed-wiring board 12. The second rotating device
is provided to rotate the component holder 360 to eliminate an
angular positioning error of the electronic component 82. A Z-axis
drive device (not shown) is provided to lift and lower the suction
nozzle for holding the electronic component 82 and for mounting the
electronic component 82 on the board 12. A fiducial mark camera 386
is fixedly disposed for taking an image of a fiducial mark provided
on the printed-wiring board 12 supported on the PWB support device
366. In the interest of simplicity, FIG. 23 does not show support
structures for supporting the index table 362, image-taking device
384, fiducial mark camera 386, and a dog 390. The index table 362
may be replaced by a plurality of rotary members which are rotated
about a common axis of rotation by a cam device, at a controlled
rotating velocity, so that the rotary members are stopped at a
plurality of working stations at different times. For instance, the
rotary members hold respective component holders 360 such that the
component holder 360 held by each rotary member is rotatable and
axially movable relative to the rotary member.
[0169] In the electronic-component mounting system of FIG. 23, the
dog 390 is fixedly disposed near the working station at which the
image-taking device 384 is disposed. The dog 390 is positioned
relative to the above-indicated working state, so that an image of
the dog 390 is taken by the image-taking device 384, together with
an image of the electronic component held by the suction nozzle of
the component holder 360 at the above-indicated working station.
The present system is also provided with first and second mounting
surfaces 392, 394 on which a fiducial chip 396 is placed. In
substantially the same manner as in the first embodiment, the
rotation axis of each component holder 360, that is, the position
of the rotation axis of the suction nozzle is estimated on the
basis of an image of the dog 390, and the positioning error of the
electronic component 82 with respect to the thus estimated position
of the rotation axis of the suction nozzle. Further, the positions
of the rotation axis of the suction nozzle and the fiducial mark
camera 386 relative to the image-taking device 386, and the
operating error of the XY positioning device 370 can be obtained as
in the first embodiment.
[0170] In the illustrated embodiments, the first image-taking
device 248, 356, 384 and the second image-taking devices in the
form of the fiducial mark camera 240, 386 are arranged to take a
two-dimensional image at one time. However, any of these first and
second image-taking devices may be replaced by a line-sensor type
imaging device using a straight array of multiple imaging elements
which is intermittently moved relative to an object by a
predetermined pitch to obtain multiple lines of image which
collectively form a two-dimensional image. Where the first
image-taking device is replaced by a line-sensor type imaging
device, the line-sensor type imaging device may be constructed such
that a straight array of multiple imaging elements is disposed so
as to extend in a first direction parallel to the top surface of
the electronic component. In this case, the straight array of
imaging elements is intermittently moved in a second direction
which is parallel to the top surface of the electronic component
and which perpendicular to the first direction (line of extension
of the straight array).
[0171] While the presently preferred embodiments of the present
invention have been described in detail, for illustrative purpose
only, it is to be understood that the present invention may be
embodied with various changes and improvements, such as those
described in the SUMMARY OF THE INVENTION, which may occur to those
skilled in the art.
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