U.S. patent application number 09/947323 was filed with the patent office on 2002-04-25 for component mounter and mounting method.
Invention is credited to Inoue, Masafumi, Morimitsu, Yasuhiro, Onizaki, Hikaru, Yamamoto, Yusuke, Yanai, Youichi.
Application Number | 20020046462 09/947323 |
Document ID | / |
Family ID | 18758876 |
Filed Date | 2002-04-25 |
United States Patent
Application |
20020046462 |
Kind Code |
A1 |
Inoue, Masafumi ; et
al. |
April 25, 2002 |
Component mounter and mounting method
Abstract
A component mounter for picking up a component and mounting it
on a board using a transfer head. A position of solder paste
printed on an electrode on a board is previously measured and a
measurement result is stored. Mounting coordinates for mounting the
component using the transfer head is calculated based on this
measurement result. In the mounting operation, the transfer head is
controlled using mounting coordinates determined based on the
solder printing position so as to mount the component on each
electrode on the board. This prevents the occurrence of positional
deviation between the mounted component and printed solder paste.
Defective mounting, which may occur in a reflow process due to
positional deviation, is thus preventable.
Inventors: |
Inoue, Masafumi; (Saga,
JP) ; Yamamoto, Yusuke; (Fukuoka, JP) ;
Onizaki, Hikaru; (Fukuoka, JP) ; Yanai, Youichi;
(Saga, JP) ; Morimitsu, Yasuhiro; (Saga,
JP) |
Correspondence
Address: |
RATNER AND PRESTIA
Suite 301
One Westlakes, Berwyn
P.O. Box 980
Valley Forge
PA
19482-0980
US
|
Family ID: |
18758876 |
Appl. No.: |
09/947323 |
Filed: |
September 5, 2001 |
Current U.S.
Class: |
29/834 ; 29/739;
29/832 |
Current CPC
Class: |
Y10T 29/53174 20150115;
Y10T 29/53178 20150115; Y10T 29/49131 20150115; Y10T 29/49144
20150115; H05K 13/08 20130101; H05K 13/0469 20130101; Y10T 29/4913
20150115; Y10T 29/49133 20150115; Y10T 29/49004 20150115; Y10T
29/53087 20150115 |
Class at
Publication: |
29/834 ; 29/832;
29/739 |
International
Class: |
B23P 019/00; H05K
003/30 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 8, 2000 |
JP |
2000-272823 |
Claims
What is claimed is:
1. A component mounter for picking up a component from a component
feeder carriage and mounting the component on a board using a
transfer head, said component mounter comprising: (a) a positioner
for relatively positioning said board with respect to said transfer
head; (b) a first memory for storing a position measurement result
of solder printed on an electrode on said board; (c) a calculator
for calculating mounting coordinates for mounting the component
using said transfer head based on said measurement result; and (d)
a controller for driving said positioner based on said mounting
coordinates.
2. The component mounter as defined in claim 1 further comprising a
second memory for storing said mounting coordinates.
3. The component mounter as defined in claim 1, wherein said
measurement result is a result of measurement performed by a
measuring apparatus installed in the component mounter.
4. The component mounter as defined in claim 1, wherein said
measurement result is a result of measurement performed by a
testing function installed in a screen printer for printing solder
on the electrode on the board.
5. The component mounter as defined in claim 1, wherein said
position measurement result is a result of measurement performed by
a separate appearance inspection device other than the component
mounter.
6. A method for picking up a component from a component feeder
carriage and mounting the component on a board using a transfer
head, said method comprising: (a) storing a position measurement
result of solder printed on an electrode on said board; (b)
calculating mounting coordinates for mounting the component by said
transfer head based on said measurement result; and (c) controlling
a positioner for relatively positioning said board with respect to
said transfer head based on said mounting coordinates.
7. The method as defined in claim 6, further comprising:
recognizing a position of said board by a recognition mark on said
board; and obtaining image data for the electrode on said
board.
8. The method as defined in claim 7, further comprising the step of
measuring a printing position of solder printed on said electrode
as relative coordinates with respect to the recognition mark on
said board based on said image data.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to component mounters and
mounting methods for mounting typically electronic components on a
board, and more particularly to component mounters and mounting
methods that prevent defective mounting caused by positional
deviation of solder printing on the board.
BACKGROUND OF THE INVENTION
[0002] The need for positional accuracy when mounting components on
electrodes formed on a board has been becoming ever more stringent
as electronic components become smaller and mounting density
becomes higher. For example, micro-components of only about 0.6
mm.times.0.3 mm in size are already commercialized. These small
components require extremely accurate mounting positions. The
electrode position has conventionally been confirmed by identifying
a recognition mark provided on the board to ensure correct
positioning of a component onto an electrode when the component is
placed on the electrode on the board by means of a transfer
head.
[0003] However, micro-components as described above may show
defects after being mounted due to lack of mounting position
accuracy for the reasons described below.
[0004] A conventional method for mounting micro-components is
described next with reference to drawings.
[0005] FIGS. 5A to 5C are process charts of the conventional
component mounting method.
[0006] In FIG. 5A, numerous electrodes 1a onto which electronic
components are soldered are provided on board 1. Solder paste S is
printed on electrodes 1a before the mounting process. In the
mounting process, the position of each electrode 1a is identified
based on mounting position data by detecting recognition mark 1b
provided at the corner of board 1. Component 2 is then mounted on
identified electrode 1a.
[0007] However, the position of solder paste S printed on electrode
1a does not completely coincide with the position of electrode 1a
due to changes of shape with time in board 1 or screen mask, and a
slight positional deviation d may occur as shown in FIG. 5A. If
component 2 is placed in relation to the position of electrode 1a
in this state, as described above, the center line of a terminal of
component 2 will deviate with respect to solder paste S as shown in
FIG. 5B.
[0008] If board 1 is heated in a reflow process in this state,
component 2 may rotate in the direction shown by an arrow in FIG.
5C as solder paste S melts. The rotation occurs due to non-uniform
distribution of solder paste S contacting component 2 with respect
to the center line of the terminal of component 2. In other words,
component 2 rotates in the soldering process because the force of
attraction generated by surface tension is applied to component 2
when melted solder wets and spreads on the terminal surface, and
this force is applied asymmetrical with respect to the center line
of component 2. Positional deviation in the direction of the arrow
remains if solder paste S solidifies in this state, resulting in
defective mounting. Accordingly, the conventional component
mounting method may cause defective mounting due to positional
deviation occurring at the time of solder printing.
SUMMARY OF THE INVENTION
[0009] The present invention solves the aforementioned
disadvantage, and aims to offer a component mounter and mounting
method that prevents defective mounting due to positional deviation
of solder printing in component mounting.
[0010] A component mounter of the present invention picks up a
component from a component feeder carriage using a transfer head,
and mounts the component on a board. The component mounter of the
present invention comprises:
[0011] (a) a positioner for positioning the board relative to the
transfer head;
[0012] (b) a primary memory for storing position measurement
results of solder printed on an electrode on the board;
[0013] (c) a calculator for calculating mounting coordinates for
mounting the component using the transfer head based on the
measurement results; and
[0014] (d) a controller for driving the positioner based on the
mounting coordinates.
[0015] A mounting method of the present invention is to pick up a
component from a component feeder carriage using the transfer head,
and mount it on the board. The mounting method of the present
invention comprises the next steps:
[0016] (a) storing position measurement results of solder printed
on an electrode on the board;
[0017] (b) calculating mounting coordinates based on the
measurement results when mounting the component using the transfer
head; and
[0018] (c) controlling a positioner for positioning the board
relative to the transfer head based on the mounting
coordinates.
[0019] The mounting coordinates for mounting the component using
the transfer head are calculated based on the solder printing
position measurement results, and the board is relatively
positioned with respect to the transfer head based on these
mounting coordinates. No positional deviation between the component
and printed solder thus occurs when the component is mounted.
Accordingly, defective mounting, which may occur in a reflow
process due to positional deviation, is preventable.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a plan view of a component mounter in accordance
with a preferred embodiment of the present invention.
[0021] FIG. 2 is a block diagram illustrating the configuration of
a control system of the component mounter in accordance with the
preferred embodiment of the present invention.
[0022] FIG. 3 is a flow chart illustrating how mounting coordinate
data is processed in the component mounter in accordance with the
preferred embodiment of the present invention.
[0023] FIGS. 4A to 4C are process charts illustrating a component
mounting method in accordance with the preferred embodiment of the
present invention.
[0024] FIGS. 5A to 5C are process charts illustrating a
conventional component mounting method.
DETAILED DESCRIPTION OF THE INVENTION
[0025] A preferred embodiment of the present invention is described
below with reference to drawings.
[0026] FIG. 1 is a plan view of a component mounter, FIG. 2 is a
block diagram of a control system for the component mounter, and
FIG. 3 is a flow chart illustrating how mounting coordinate data is
processed in the component mounter in the preferred embodiment of
the present invention. FIGS. 4A to 4C are process charts
illustrating a component mounting method in the preferred
embodiment of the present invention.
[0027] First, the configuration of the component mounter is
described with reference to FIG. 1.
[0028] In FIG. 1, numerous parts feeders 4 are provided on
component feeder carriage 3. Parts feeders 4 are attached to a
feeder base (not illustrated), and move horizontally by rotating
feed screw 5.
[0029] Rotary head 6 is disposed at the front of feeder carriage 3.
This rotary head 6 rotates in the direction of arrow `a` centering
on main shaft O. Several transfer heads 7 are disposed on the
periphery of rotary head 6. Each head 7 has several suction nozzles
(not illustrated). Head 7 moves vertically at pickup position P on
a vacuum-suction station, and picks up components from parts
feeders 4. Here, parts feeders 4 move horizontally by screw 5 so
that head 7 can pick up a required component.
[0030] Each head 7 is disposed on the periphery of rotary head 6,
centering on main shaft O, and rotates on the shaft of head 7
(centering on head rotation) by means of a driving mechanism (not
illustrated). This rotation determines selection of multiple
suction nozzles provided on head 7 and setting of horizontal
rotation angle of the component held by the suction nozzle.
[0031] The component picked up at position P sequentially moves in
the direction of arrow `a` as a result of the rotation of rotary
head 6. Height measurement station 8 is disposed on the moving
path, and station 8 measures the height of the component held by
head 7.
[0032] Component recognition station 9 is provided next to station
8. An image of the component held by the suction nozzle of head 7
is captured from the bottom by a camera (not illustrated) at
station 9. The image captured is then processed to detect the
dimensions of a plan image of the component, i.e., length and
width.
[0033] XY table 11 is disposed at the front of rotary head 6. This
table 11 horizontally positions board 1. Table 11 thus acts as a
positioner for horizontally positioning board 1 relative to
transfer head 7. Transfer head 7 moving from station 9 reaches
mounting position M on a mounting station over board 1, and mounts
the component on board 1 by vertical movement.
[0034] Camera 13 is disposed next to table 11. Table 11 is driven
to move board 1 to under camera 13. Camera 13 then captures a
predetermined recognition point on board 1 to detect the position
and shape of a recognition target. For example, as shown in FIG.
4A, the position of recognition mark 1b formed on board 1 and the
position of electrode 1a are detected; also, positional deviation
of solder S with respect to electrode 1a is detected by capturing
an image of solder paste S printed on electrode 1a.
[0035] Next, the configuration of a control system of the component
mounter in the preferred embodiment of the present invention is
described with reference to FIG. 2.
[0036] In FIG. 2, controller 20, such as a CPU, controls the
movement and calculations carried out in the entire component
mounter. Solder printing position measurement result memory 23,
which is the primary memory, stores measurement results of solder
printing positions. Mounting position data memory 21, the secondary
memory, stores mounting coordinates indicating each position of a
mounting point on which the component will be mounted. Solder
printing position measuring apparatus 22 measures the position of
solder paste S printed on each electrode, as shown in FIG. 4A,
based on image data obtained through capturing an image of each
electrode position by camera 13 for board recognition, and outputs
relative position coordinates data with respect to recognition mark
1b on board 1.
[0037] Controller 20 reads out solder printing position measurement
results stored in memory 23, and calculates component mounting
coordinates based on solder printing position. In other words,
controller 20 is a mounting coordinates calculator. Calculated
mounting coordinates are fed to memory 21 to revise data on
mounting coordinates. More specifically, mounting coordinates
determined based on electrode position coordinates in accordance
with design data are initially stored in memory 21, but this data
is updated by rewriting mounting coordinates in the data based on
actual measurement results after measuring the solder printing
position. Table driver 24 drives XY table 11 which holds and moves
the board. This table 11 is moved based on the aforementioned
mounting coordinates by controlling driver 24 with controller
20.
[0038] The component mounter in the preferred embodiment is
configured as described above.
[0039] Next, a mounting method using the above component mounter is
described with reference to FIG. 3 and FIGS. 4A to 4C. The position
of solder paste printed on each electrode on the board in a
previous process is measured before mounting the component. The
mounting position is determined based on the printing position
measurement result.
[0040] In FIG. 3, board 1 after printing solder is placed on XY
table 11 (ST1). Recognition mark 1b on board 1 (FIG. 4A) is
captured by camera 13, thus detecting the position of board 1
(ST2). Next, XY table 11 is driven to position electrode 1a, whose
printing position is to be measured, under camera 13 (ST3). Image
data is then obtained by capturing the image of electrode 1a by
camera 13 (ST4). For moving XY table 11 when capturing the image of
each electrode 1a, mounting positions stored in mounting position
data memory 21 prepared in advance based on design data are
used.
[0041] Next, the printing position of solder paste S printed on
electrode 1a, as shown in FIG. 4A, is measured based on the image
data obtained as relative coordinates xa, ya of printing point A (a
barycentric position of solder paste printed on a pair of
electrodes 1a) with respect to recognition mark 1b (ST5). The
position is recognized by solder printing position measuring
apparatus 22.
[0042] Next, the presence of electrode 1a to be measured next is
determined (ST6). If there is a next electrode 1a to be measured,
the operation returns to ST3 to repeat the measurement of the
solder printing position. If all electrodes to be measured are
completed at ST6, measurement results of solder printing positions
are stored in solder printing position measurement result memory 23
(ST7). Mounting position data to be used for actual mounting is
then prepared based on the obtained solder printing position
measurement results, and stored in mounting position data memory 21
(ST8). This completes the preparation and processing of the
mounting position data that compensates for the positional
deviation of solder printing.
[0043] Next, mounting starts for board 1 whose measurements of
solder printing positions are completed. Here, component 2 is
placed in accordance with mounting coordinates prepared based on
the aforementioned solder printing position measurement results
when placing component 2 on each electrode 1a. In other words,
component 2 is placed on printing point A of solder paste S as a
target position instead of electrode 1a when printed solder paste S
deviates from electrode 1a, as shown in FIG. 4B. Accordingly, the
position of terminal 2a of component 2 mounted on the board
deviates from electrode 1a but is mounted without positional
deviation with respect to solder paste S.
[0044] After components are placed on each electrode position,
board 1 is sent to the reflow process to heat and melt solder paste
S so as to solder terminal 2a onto electrode 1a. Terminal 2a whose
position has deviated from electrode 1a before heating is attracted
by electrode 1a by the self-alignment effect when solder paste S
melts. The self-alignment effect is a phenomenon by which terminal
2a is attracted to electrode 1a when melted solder wets and spreads
over the surface of electrode 1a. Accordingly, as shown in FIG. 4C,
terminal 2a is soldered onto electrode 1a in the right position and
right direction without experiencing any positional deviation.
[0045] Since mounting coordinates are set so as not to cause
positional deviation between terminal 2a and solder paste S, as
mentioned above, in the reflow process, no external force for
moving component 2 in the rotating direction is applied, ensuring
the self-alignment effect.
[0046] As described above, the preferred embodiment prepares
mounting position data based on measurement results for solder
printing positions on the actual board. This enables the prevention
of deviated component mounting positions caused by variations in
solder printing positions on each board. Accordingly, defective
mounting may be reduced, even for micro-components which require
high mounting accuracy, by preventing positional deviation of
components after soldering.
[0047] The preferred embodiment shows an example of measuring
solder printing positions by means of a camera installed in the
component mounter. However, testing function installed in a
screen-printing device may also be used. Alternatively, a separate
exclusive appearance-testing device, other than the component
mounter, may be used for measuring solder printing positions.
[0048] In the present invention, mounting coordinates for mounting
components using the transfer head are calculated based on solder
printing position measurement results in order to relatively
position the board to the transfer head based on the mounting
coordinates. This avoids the occurrence of positional deviations
between the mounted components and printed solder, thus preventing
defective mounting which may occur during the reflow process due to
these positional deviations.
* * * * *