U.S. patent application number 10/220535 was filed with the patent office on 2003-08-28 for method and device for determining the pick-up position of electrical components in a component in a components placement device.
Invention is credited to Bachthaler, Thomas, Grasmueller, Hans-Horst, Liebeke, Thomas, Schwiefert, Michael.
Application Number | 20030159279 10/220535 |
Document ID | / |
Family ID | 7632968 |
Filed Date | 2003-08-28 |
United States Patent
Application |
20030159279 |
Kind Code |
A1 |
Bachthaler, Thomas ; et
al. |
August 28, 2003 |
Method and device for determining the pick-up position of
electrical components in a component in a components placement
device
Abstract
A device and appertaining method for picking up devices in a
component placement device permits even very small components and
even a first component of a new belt to be picked up by scanning
the structural features of the belt directly in the proximity of
the components. The positional tolerances can be disregarded so
that even the first component of a new belt can be reliably
detected by the pick-up tool.
Inventors: |
Bachthaler, Thomas;
(Stockdorf, DE) ; Grasmueller, Hans-Horst;
(Mammendorf, DE) ; Liebeke, Thomas; (Ottobrunn,
DE) ; Schwiefert, Michael; (Munich, DE) |
Correspondence
Address: |
SCHIFF HARDIN & WAITE
6600 SEARS TOWER
233 S WACKER DR
CHICAGO
IL
60606-6473
US
|
Family ID: |
7632968 |
Appl. No.: |
10/220535 |
Filed: |
February 20, 2003 |
PCT Filed: |
February 28, 2001 |
PCT NO: |
PCT/DE01/00740 |
Current U.S.
Class: |
29/833 ; 29/740;
29/832 |
Current CPC
Class: |
Y10T 29/53178 20150115;
Y10T 29/4913 20150115; Y10T 29/49133 20150115; H05K 13/0419
20180801; Y10T 29/49131 20150115 |
Class at
Publication: |
29/833 ; 29/832;
29/740 |
International
Class: |
B23P 019/00; H05K
003/30 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 1, 2000 |
DE |
100 09 765.0 |
Claims
1. A method of determining the pick-up position of electrical
components (4) in a component placement device for populating
substrates with the components (4), which are made ready in pockets
(3) in at least one belt (1), the belt (3) being inserted into a
feed module (5), which delivers the components (4) to a pick-up
point (12) in a defined pick-up position, the components (4) being
removed from the pockets (3) by means of a freely positionable
component placement head (6), position-resolving scanning optics
(10) of the component placement head (6) being moved over centering
marks in the area of the pickup point (12) and determined with the
aid of an image evaluation unit (13) belonging to the component
placement device, characterized in that the scanning optics (10) is
aimed at structural features (14) that are associated directly with
the pockets (3) and which are used as the centering marks, and in
that the image evaluation unit (13) calculates the average position
of the pockets (3) from the position of the structural features
(14).
2. The method as claimed in claim 1, characterized in that the
component (4) lying in the pocket (3) is scanned.
3. The method as claimed in claim 1, characterized in that the
structural features of the pocket (3) are scanned directly.
4. The method as claimed in claim 3, characterized in that the
edges of the pocket (3) are detected.
5. The method as claimed in one of the preceding claims,
characterized in that the scanning optics (10) is assigned an
illuminating means (11), whose variable optical characteristics are
adapted to different belt types.
6. A device for carrying out the method as claimed in one of the
preceding claims, characterized in that a control unit belonging to
the component placement device contains control means for
positioning the scanning optics over the pocket (3), in that type
data about the component belt can be transmitted to the control
unit, in that the scanning optics (10) can be moved over the
structural features of the belt (1) by using the type data and in
that the image evaluation unit (13) is equipped with means for
detecting and processing different structural features of the
various belt types.
7. The device as claimed in claim 6, characterized in that the
image evaluation unit (13) and a control system for the
illuminating means (11) are connected to a self-teaching adaptation
module, which adjusts the illumination (11) to a sufficient
contrast effect of the structural features.
Description
[0001] The invention relates to a method and a device for
determining the pick-up position of electrical components in a
component placement device for populating substrates with the
components, which are made ready in pockets of at least one belt,
the belt being inserted into a feed module which delivers the
components to a pick-up point in a defined pick-up position.
[0002] Feed modules of this type are usually provided with a pin
wheel which, with its radially projecting pins, engages in
transport holes in the belt and which is rotated in defined angular
steps corresponding to the pitch spacing of the pockets in the
belt. The pockets have a defined positional relationship with the
transport holes. Fitted to the feed modules at the end of the
production process, in the area of the pick-up point, are centering
marks which have a defined positional relationship with the pins of
the pin wheel and which are intended to compensate for production
tolerances.
[0003] The feed modules are fixed in a defined position to a
component table. Since the centering means for this purpose can be
provided only at some distance from the pick-up points, it is
possible for positional deviations to occur in the centering marks.
A component placement head for handling the components is provided
with the CCT camera, which is used to determine the exact position
of the substrate to be populated in the component placement device.
In order to be able to take into account the aforementioned
positional deviations, it is usual, following the installation of
the feed module, to determine the position of the centering marks
on the feed module by means of this printed circuit board camera,
with which, because of the defined positional relationships, the
position of the component to be picked up can also be determined.
Deviations in the drive system caused by operation cannot be
eliminated completely in this case.
[0004] In the course of modern technologies, the components to be
placed are being increasingly miniaturized. It is usual to provide
the component placement head with a suction gripper, which is set
down on the components to be picked up and sucks up the latter at
its end. Here, the gripper has to dip into the pocket in order to
be placed on the component. The permissible tolerances between the
transport hole and the pocket are so great that the suction gripper
making the pick-up cannot with certainty be set exactly onto the
component to be picked up, and is placed on the edge of the pocket
and, as a result, misses the component. In this case, however, this
is a systematic error, at least over a relatively long section of
the belt.
[0005] It is usual, in the case of each of the components picked
up, to measure their position with respect to the suction gripper
and to place the component onto the substrate with a corresponding
correction value. In order to be able to determine the systematic
error, at least after a belt change, a series of components was
removed from the start of the belt and measured, and an average
deviation was determined. However, this is a problem when the
component is not found during the first attempt at a pick-up. The
gripper then has to be moved step by step over the aforementioned
tolerance range until it finds the component.
[0006] The invention is based on the object of accelerating the
determination of the pick-up position of the components.
[0007] This object is achieved by the invention as claimed in claim
1. The structural features associated with the pockets, for example
the edges of the pockets, are now independent of the positional
relationship with respect to the transport holes and the centering
marks. The scanning optics has such a large field of view that,
even with the first setting, it safely finds the pocket and its
surrounding area.
[0008] The position-resolving scanning optics transmits the
measured values to the electrical evaluation unit, which calculates
the accurate center position of the pockets from the appropriate
data. The suction gripper can then immediately be aligned reliably
on the component to be picked up.
[0009] All the positional tolerances between the component
placement device and the centering marks and between the centering
marks and the transport pins and between the transport pins and the
pockets are therefore unimportant, and the suction gripper can be
aligned with the center of the component with high accuracy without
a failed attempt. The component is then removed reliably. The
placement operation can then begin without further time delay.
[0010] The belts and the components can have very variable optical
characteristics. For example, the belts can consist of transparent
material. For this reason, it may be necessary to select different
structural features, depending on the type of belt.
[0011] Advantageous developments of the invention are identified in
the subclaims.
[0012] The development as claimed in claim 2 is suitable in
particular for transparent belts, with which the component has a
sufficient contrast. Although the components lie in the pocket with
play, so that exact calibration is not immediately possible, the
play is low as compared with the dimensions of the component, so
that here, too, the component can be found with sufficient
reliability. The precise position of the pockets can be determined
with the aid of statistical methods in the case of optical
measurement.
[0013] The development as claimed in claim 3 makes it possible to
measure the position of the pocket exactly. This is made easier by
the fact that, as a rule, the first pockets in a belt are left free
of components.
[0014] It is particularly beneficial in this case to determine the
edges of the pockets, as claimed in claim 4. In particular in the
case of very small components, it is usual to punch the pockets out
of a flat material and to close them at the bottom by means of a
film. These punched pockets have sharp defined edges, which
represent structural features that can be distinguished easily.
[0015] The development as claimed in claim 5 makes it possible to
adjust the illumination of the structural features to different
conditions, as is also done when scanning centering marks on the
substrates. The illumination makes it possible to illuminate the
pockets from different directions at different angles and with
different wavelengths, so that the structural features can stand
out optimally.
[0016] The device as claimed in claim 6 makes it possible to
register the different structural features of the various belt
types automatically, each full belt which differs from the others
in terms of its optical and geometric characteristics being
assigned to its own type.
[0017] The adaptation module as claimed in claim 7 permits optimal
adaptation to the different optical conditions of the belts.
[0018] In the following text, the invention will be explained in
more detail using an exemplary embodiment illustrated in the
drawing.
[0019] FIG. 1 shows a side view of a component placement head and a
feed module in a component belt,
[0020] FIG. 2 shows a plan view of the feed module according to
figure 1.
[0021] According to FIGS. 1 and 2, a strip-like belt 1 is provided
with lateral transport holes 2 and pockets 3 for components 4 laid
therein and is inserted into a disk-like flat feed module 5 which
is fixed in a defined position in the range of movement of a
component placement head 6 of a component placement device. The
feed module 5 has a pin wheel 7 which can be driven step by step
and has transport pins 8 which stand out peripherally and engage
without play in the transport holes 2 in the belt 1. The positional
relationship between the pockets and the transport holes is defined
by relevant standards. However, the permissible tolerances here are
virtually as great as the lateral dimensions of the smallest
components.
[0022] On its underside, facing the belt, the component placement
head has a suction gripper 9 and scanning optics 10 in the form of
a CCT camera, whose objective is surrounded by an illuminating
means 11 which illuminates the field of view of the scanning optics
10. The illuminating means 11 can, for example, comprise a large
number of light-emitting diodes of different wavelengths and
different orientations. Matching the various belt types, it is
possible to activate a beneficial selection of the diodes in such a
way that the structural features stand out with good contrast and
can be detected reliably.
[0023] The scanning optics 10 is aimed at a pick-up point 12 of the
components in the feed module 5. It is capable of detecting
structural features 14, for example the edges of an empty pocket.
It is connected to an image evaluation unit 13, in which the
central position of the pocket 3 is calculated by using this data,
so that the following component 4 can be gripped reliably by the
suction gripper, all the tolerances being eliminated.
[0024] Over a relatively long section of the belt, the position of
the pocket 3 in relation to the transport hole can change. In a
further optical scanning unit, not illustrated, the position of the
components removed on the suction gripper 9 is measured accurately
in order to increase the placement accuracy. In this way, the
sliding positional change of the pockets can be registered reliably
and taken into account during operation in such a way that
remeasurement of the belt (1) with the aid of the scanning optics
10 might only be required following a loss of data on the component
placement device, for example following an interruption.
* * * * *