U.S. patent application number 10/576787 was filed with the patent office on 2007-06-14 for method and apparatus for mounting conductive ball.
This patent application is currently assigned to ATHLETE FA CORPORATION. Invention is credited to Shigeaki Kawakami, Toru Nebashi.
Application Number | 20070130764 10/576787 |
Document ID | / |
Family ID | 35782807 |
Filed Date | 2007-06-14 |
United States Patent
Application |
20070130764 |
Kind Code |
A1 |
Nebashi; Toru ; et
al. |
June 14, 2007 |
Method and apparatus for mounting conductive ball
Abstract
A method of mounting conductive balls comprises a step of
setting, on a substrate, a mask that includes a plurality of
apertures for disposing conductive balls on the substrate and a
filling step. The filling step includes using a head that moves
along a surface of the mask, holding a group of conductive balls in
an area that is part of the surface of the mask, and moving the
area so that parts of a path taken by the area overlap. By limiting
the area where filling is carried out and moving the conductive
balls while gathering the conductive balls in this area, it is
possible to prevent losses for the conductive balls, to increase
the filling efficiency, and to suppress the number of unfilled
apertures.
Inventors: |
Nebashi; Toru; (Suwa-shi,
JP) ; Kawakami; Shigeaki; (Suwa-shi, JP) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
ATHLETE FA CORPORATION
2970-1, Ohaza Shiga
Suwa-shi
JP
392-0012
|
Family ID: |
35782807 |
Appl. No.: |
10/576787 |
Filed: |
June 30, 2005 |
PCT Filed: |
June 30, 2005 |
PCT NO: |
PCT/JP05/12095 |
371 Date: |
April 21, 2006 |
Current U.S.
Class: |
29/843 ; 174/264;
228/180.21; 228/180.22; 257/E21.508; 29/740; 29/745; 29/832;
29/840; 29/860; 438/612 |
Current CPC
Class: |
B23K 2101/42 20180801;
Y10T 29/49144 20150115; Y10T 29/53178 20150115; H05K 2203/0557
20130101; H01L 2924/14 20130101; Y10T 29/532 20150115; H05K 3/3478
20130101; H05K 2203/041 20130101; Y10T 29/53174 20150115; H01L
21/4853 20130101; H01L 2924/01079 20130101; Y10T 29/49149 20150115;
H01L 2924/01082 20130101; H01L 2924/014 20130101; H01L 2924/01078
20130101; H01L 2924/01029 20130101; H01L 2924/01033 20130101; H01L
2924/01023 20130101; Y10T 29/49179 20150115; H01L 2224/11334
20130101; H01L 2924/01006 20130101; H01L 2924/01018 20130101; H01L
24/742 20130101; B23K 3/0623 20130101; H01L 2224/13099 20130101;
Y10T 29/4913 20150115; H01L 2924/01005 20130101; H01L 2924/01015
20130101; H01L 24/11 20130101; H01L 2924/01047 20130101 |
Class at
Publication: |
029/843 ;
029/740; 029/840; 029/860; 029/832; 228/180.21; 228/180.22;
029/745; 174/264; 438/612 |
International
Class: |
B23K 31/02 20060101
B23K031/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 30, 2004 |
JP |
2004-192364 |
Dec 21, 2004 |
JP |
2004-369087 |
Claims
1. A method of mounting conductive balls comprising: a step of
setting, on a substrate, a mask that includes a plurality of
apertures for disposing conductive balls on the substrate; and a
filling step that includes using a head that moves along a surface
of the mask, holding a group of conductive balls in an area that is
part of the surface of the mask, and moving the area so that parts
of a path taken by the area overlap.
2. The method of mounting according to claim 1, wherein the filling
step further includes moving the area in a zigzag or a spiral
path.
3. The method of mounting according to claim 1, wherein the filling
step further includes gathering conductive balls by the head toward
the area from around the area.
4. The method of mounting according to claim 1, wherein the area is
circular or shaped like a polygon that circumscribes a circle.
5. The method of mounting according to claim 1, wherein the filling
step further includes rotating the head about an axis that is
perpendicular to the mask, moving the axis across the surface of
the mask, and gathering conductive balls in the area by rotation of
the head.
6. The method of mounting according to claim 1, wherein the filling
step further includes rotating the head about an axis that is
perpendicular to the mask, moving the axis across the surface of
the mask, the area being a circular area that moves together with a
center of rotation of the head, and sweeping part of the surface of
the mask around the circular area by members protruding from the
head or by blowing out gas to gather conductive balls in the
area.
7. The method of mounting according to claim 6, wherein the filling
step further includes pressing part of the mask around the area by
the members protruding from the head or by the blowing out gas.
8. The method of mounting according to claim 1, wherein the filling
step further includes rotating the head about an axis that is
perpendicular to the mask, moving the axis across the surface of
the mask, and sweeping part of the surface of the mask around the
area by squeegees that protrude from the head toward the surface of
the mask.
9. The method of mounting according to claim 8, wherein the filling
step further includes pressing part of the mask around the area by
the squeegees.
10. The method of mounting according to claim 1, wherein the
filling step further includes sweeping part of the surface of the
mask around the area by gas blown out from the head to gather
conductive balls in the area.
11. A method of mounting conductive balls comprising: a step of
setting, on a substrate, a mask that includes a plurality of
apertures for disposing conductive balls on the substrate; and a
filling step of moving a head for moving conductive balls along a
surface of the mask so that at least parts of a path taken by the
head overlap.
12. A method of mounting conductive balls comprising: a step of
setting, on a substrate, a mask that includes a plurality of
apertures for disposing conductive balls on the substrate; and a
filling step that includes using a head that is movable along a
surface of the mask, gathering conductive balls into an area that
is part of the surface of the mask from around the area, and moving
the area.
13. A filling device for filling conductive balls, after setting a
mask on a substrate, in a plurality of apertures in the mask for
disposing conductive balls on the substrate, the device comprising:
a head for holding a group of conductive balls in an area that is
part of a surface of the mask; and a head supporting means for
supporting the head so as to move along the surface of the
mask.
14. The filling device according to claim 13, wherein the head
supporting means moves the head across the surface of the mask in a
direction that traces a zigzag or a direction that traces a spiral
so that parts of a path taken by the area overlap.
15. The filling device according to claim 13, wherein the head
supporting means is capable of moving the head in every direction
across the surface of the mask.
16. The filling device according to claim 13, wherein the head
includes a means for gathering conductive balls toward the area
from around the area.
17. The filling device according to claim 13, further comprising a
means for supplying conductive balls to the area.
18. The filling device according to claim 13, wherein the
conductive balls are solder balls, gold balls, or copper balls with
a diameter of around 30 to 300 .mu.m.
19. A mounting apparatus comprising: a filling device according to
claim 13; and a device for setting the mask on a substrate.
20. A filling device for filling conductive balls, after setting a
mask on a substrate, in a plurality of apertures in the mask for
disposing conductive balls on the substrate, the device comprising:
a head including a means for gathering conductive balls toward an
area that is part of a surface of the mask from around the area;
and a head supporting means for supporting the head so as to move
along the surface of the mask.
21. The filling device according to claim 20, wherein the head
supporting means is capable of moving the head across the surface
of the mask in at least one of an arbitrary direction, a direction
that traces a zigzag, and a direction that traces a spiral.
22. The filling device according to claim 20, wherein the head
supporting means includes a means for rotating the head about a
shaft that is perpendicular to the mask and a means for moving the
shaft across the surface of the mask, and the means for gathering
conductive balls moves conductive balls, by rotating the head,
toward the area that is a circular area centered on a center of
rotation of the head.
23. The filling device according to claim 22, wherein the means for
gathering conductive balls is a sweeper for sweeping a part of the
surface of the mask around the circular area by using members that
protrude from the head or by blowing out gas.
24. The filling device according to claim 23, wherein the sweeper
presses the part of surface of the mask around the area by using
the members that protrude from the head or by blowing out gas.
25. The filling device according to claim 22, wherein the means for
gathering conductive balls includes a plurality of squeegees that
protrude from the head toward the surface of the mask and sweep a
part of the surface of the mask around the circular area.
26. The filling device according to claim 25, wherein the plurality
of squeegees extend in a tangential direction for the circular
area.
27. The filling device according to claim 25, wherein the plurality
of squeegees are arranged so as to overlap in a direction of
movement thereof.
28. The filling device according to claim 25, wherein the plurality
of squeegees press the part of the surface of the mask the circular
area.
29. The filling device according to claim 20, wherein the means for
gathering conductive balls includes a nozzle for sweeping together
conductive balls by blowing out gas from the head to the around the
area.
30. A mounting apparatus comprising: a filling device according to
claim 20; and a device for setting the mask on a substrate.
31. A filling device for filling conductive balls, after setting a
mask on a substrate, in a plurality of apertures in the mask for
disposing conductive balls on the substrate, the device comprising:
a head for holding a group of conductive balls in an area that is
part of a surface of the mask; and a head supporting means for
supporting the head so as to move with at least part of a path
taken by the area overlap.
32. A mounting apparatus comprising: a filling device according to
claim 31; and a device for setting the mask on a substrate.
33. A head that moves across a surface of a mask, which includes a
plurality of apertures for disposing conductive balls on a
substrate, while rotating about an axis that is perpendicular to
the mask, the head comprising a means for gathering the conductive
balls to a circular area around a center of rotation of the head
when the head rotates.
34. A head according to claim 33, wherein the means for gathering
conductive balls is a sweeper for sweeping a part of the surface of
the mask around the circular area by using members that protrude
from the head or by blowing out gas.
35. A head according to claim 34, wherein the sweeper presses the
part of the surface of the mask around the circular area by using
the members that protrude from the head or by the blowing out gas.
Description
TECHNICAL FIELD
[0001] The present invention relates to an apparatus and method for
mounting conductive balls to predetermined positions on a
substrate.
BACKGROUND ART
[0002] When installing or implementing semiconductor devices and/or
optical devices as represented by LSIs (Large Scale Integrated
circuits) and LCDs (Liquid Crystal Displays), solder balls are used
to produce electrical connections. In recent years, investigations
have been carried out into mounting minute particles that are
conductive balls includeing solder balls and other type of balls
made of any conductive metals or balls coated with metal, with a
diameter of 1 mm or less onto a substrate.
[0003] Japanese Laid-Open Patent Publication No. H09-148332
(hereinafter reference publication 1) discloses one example of a
technology that arranges minute particles at desired positions.
This publication discloses moving minute particles on a mask with
apertures for arranging the minute particles by a moving means
called a squeegee that has a predetermined softness to insert the
minute particles into the apertures, with the minute particles
being arranged held on a porous substrate by the suction air.
[0004] The squeegee in the reference publication 1 is used to move
excess particles that have not been inserted into the apertures. In
the reference publication 1, the squeegee is moved by being
attached to a belt that moves in a linear direction above the mask.
The reference publication 1 also states that above the mask in
which a ring-shaped gutter is formed, the squeegee that is attached
to a disc-shaped holding member is moved along the gutter. In
either case, the minute particles are moved by the squeegee in one
predetermined direction. A squeegee that moves back and forth is
also disclosed, but in such case, the movement direction consists
of just two directions, an "out" direction and a "return"
direction.
[0005] In the reference publication 1, by inserting the minute
particles into the apertures using suction air, the minute
particles are appropriately arranged at the necessary positions.
Regardless of the presence or absence of suction air, one condition
for the minute particles, that is, the conductive balls, to fill
the apertures or openings provided in a pattern in the mask without
missing any apertures is for a sufficiently large number of
conductive balls to be supplied relative to the number of apertures
(the density of the apertures). However, if the number of
conductive balls is large relative to the number of apertures, time
(life time) of moving the conductive balls over the surface of the
mask becomes long. During the time, due to a number of factors,
such as contact with the atmosphere, contact between balls, contact
between the balls and the mask, friction and contact between the
balls and the squeegee, abrasion and deformation are caused for the
surfaces of the balls, which reduce the performance of the balls as
electrodes. Accordingly, if a large number of conductive balls are
moved in an attempt to reduce the number of unfilled apertures, or
to reduce arrangement errors or mounting errors for a substrate
(work) due to unfilled apertures, there is an increase in the
probability of problems occurring for the conductive balls disposed
on the substrate. In addition, when a method that moves a large
number of balls is used, since it is necessary to discard a large
number of conductive balls that have not been disposed, there is an
increased rate of loss for the conductive balls that is not
preferable from a cost perspective.
[0006] When the conductive balls are moved in the same direction by
the squeegee, due to the squeegee conditions, the mask conditions,
and the like, variations in density of the conductive balls are
likely to occur in the longitudinal direction of the squeegee,
which can lead to fail of filling of apertures and fail of placing
of balls. When the amount moved by the conductive balls is
increased in an attempt to improve the yield, this results in an
increased loss of balls in the same way as described above. In the
apparatus described in the reference publication 1, the squeegee is
moved back and forth over the mask to reduce failure of filling the
apertures. However, since the number of particles inserted into the
apertures during one time of the movement of the squeegee falls
when the times of the back and forth movement are increased, the
damage to the particles due to such movement proceeds.
DISCLOSURE OF THE INVENTION
[0007] It is a first object of the present invention to provide a
method and apparatus that can highly reliably fill a plurality of
apertures in a mask with conductive balls and can highly reliably
arrange or mount conductive balls at predetermined positions on a
substrate. It is another object of the present invention to provide
a method and apparatus that can reduce a rate of discarded for
conductive balls and can economically mount conductive balls at
predetermined positions on a substrate.
[0008] Instead of moving the conductive balls in one direction or
in back and forth directions using a squeegee that moves across the
entire surface of the mask in one direction or in back and forth
directions, the present invention includes gathering the balls in
an area that is part of the surface of the mask by rotating the
head, holding a group of conductive balls in the area, and moving
the area so that parts of the path taken by the area overlap. In
addition, by moving the area in this way to cover the surface of
the mask, the apertures in the mask are filled with the conductive
balls. That is, one aspect of the present invention is a method of
mounting conductive balls comprising: a step of setting, on a
substrate, a mask that includes a plurality of apertures for
disposing conductive balls on the substrate; and a filling step
that includes using a head that moves along a surface of the mask,
holding a group of conductive balls in an area that is part of the
surface of the mask, and moving the area so that parts of a path
taken by the area overlap. Another aspect of the present invention
is a filling device for filling conductive balls, after setting a
mask on a substrate, in a plurality of apertures in the mask for
disposing conductive balls on the substrate, the device comprising:
a head for holding a group of conductive balls in an area that is
part of a surface of the mask; and a head supporting means for
supporting the head so as to move along the surface of the mask. In
addition, another aspect of the present invention is a mounting
apparatus including the above filling device and a device for
setting the mask on a substrate.
[0009] Here, moving the head and area across or along the surface
of the mask means changing the positions of the head and the area
relative to the substrate on which the mask is set, and includes
moving one or both of the head and the substrate. Here, "substrate"
refers to the object onto which the conductive balls are to be
mounted and includes a semiconductor wafer, a circuit board, a
board used for transferring, and other types of work-piece. The
path taken by the area shows the part or track passed when the area
moves on the surface of the mask. Also, when the area passes, the
openings or apertures in the parts of the mask corresponding to the
track are filled with the conductive balls but there is no need to
leave a clear trace on the surface or the like of the mask to show
that the area has passed.
[0010] According to the present invention, the conductive balls are
not simply moved on the mask but move in a state where the
conductive balls are held in a limited area. By doing so, the
conductive balls are prevented from freely spreading out on the
surface of the mask and the range in which the group of conductive
balls is present is limited. Accordingly, the density of the
conductive balls in the area can be raised using a comparatively
small number of conductive balls and the apertures in the parts of
the mask passed by the area can be efficiently filled with the
conductive balls. For this reason, it is possible to reduce the
occurrence of unfilled apertures. Also, by moving the area with a
high filling ratio so that parts of the path taken by the area
overlap, it is possible to cover the entire surface of the mask
without omissions, and therefore the rate of failure of filling
into the apertures can be made extremely small.
[0011] Also, in the present invention, the number of conductive
balls that should be held in the area that is limited region on the
mask is extremely low compared to the amount of that required for
trying to fill the apertures in the entire mask at once.
Accordingly, the number of conductive balls that may be damaged due
to movement on the mask is reduced and therefore the amount of
conductive balls lost during a filling operation is reduced.
[0012] With a squeegee that merely moves back and forth on a mask,
the squeegee will move with the same region being completely
overlapped, and therefore aside from the first pass of the
squeegee, the subsequent movements of the squeegee will fill only
the apertures that have been failed of filling with balls.
Accordingly, when back and forth movement is carried out, aside
from the first or first few passes, repeatedly moving the balls
with the squeegee for attempting to reduce the number of unfilled
apertures will damage the balls and lead to many balls being
lost.
[0013] In the present invention, an area with a high filling ratio
is moved so that the path taken by the area partially overlaps, and
therefore the entire surface of the mask is covered without
omissions. Accordingly, by moving the area, new apertures to be
filled appear. By providing a means for supplying the conductive
balls inside the area and adding an amount of conductive balls
corresponding to the conductive balls consumed for filling as the
area moves, it is possible to keep the conductive balls held inside
the area in a fresh condition. The lifetime (the time taken for
conductive balls to be consumed) from the supplying of new
conductive balls to the area to the filling of the apertures in the
mask, i.e., the disposing of the conductive balls at predetermined
positions on the substrate can be reduced, and therefore
fluctuations in the lifetimes of the conductive balls that last
until the conductive balls fill the openings of the mask can be
reduced. This means that according to the present invention, it is
possible to dispose conductive balls with uniformly high quality at
predetermined positions on the substrate and therefore the yield of
mounting the conductive balls on a substrate can be improved.
[0014] To have the path taken by the area or head partially overlap
and thereby cover the entire surface of the mask, moving of the
area includes moving tracing a zigzag or a sine curve pattern.
Moving the area in a spiral or whirl pattern is also preferable. By
having adjacent parts of the path overlap by 50% or more, the
surface of the mask can be covered by the area ultimately with an
overlapping ratio of 100% or higher. On the other hand, if the
overlapping ratio of the adjacent parts of the path is too high,
the number of balls that fill apertures as the area moves falls,
the lifetimes of the conductive balls become longer, and the
probability of the balls becoming damaged increases. Accordingly,
the overlapping ratio for the path should preferably be around 50%
to improve the probability of filling the apertures in the mask
with conductive balls of high quality.
[0015] To prevent the quality of the balls from deteriorating due
to interference between the conductive balls and the mask having
apertures and other reasons, the conductive balls should preferably
fill the apertures in the mask by dropping due to gravity, that is,
under their own weight. When the conductive balls are continuously
pushed in one direction, due to a large number of balls gathering,
the balls interfere with one another, resulting in the possibility
of the balls not falling into the apertures. In addition, it is not
preferable to forcibly push the balls in such state into the
apertures using a squeegee. In the present invention, by holding
the conductive balls in the area, it is possible to move the area
in a freely chosen direction. In addition, by appropriately
changing the direction of movement of the area, it is possible to
prevent the conductive balls from becoming distributed extremely
unevenly inside the area. Accordingly, it is possible to encourage
the conductive balls to fill the apertures under their own
weight.
[0016] One method of holding the conductive balls in the area is to
surround the area so that the balls cannot escape from the area.
However, efforts to surround the area so that no balls can escape
from the area have a number of problems. For example, it is
necessary to apply pressure so that a means for moving the balls,
such as a squeegee, is completely in tight contact with the surface
of the mask, but by doing so, there is the possibility of the balls
that have filled apertures jumping out and/or of the mask being
damaged. Also, should a ball somehow escape from the area, the ball
will remain on the mask and become a stray ball, such balls causes
erroneous mounting at an unexpected position on the substrate.
[0017] In the present invention, by gathering the conductive balls
from around the area toward the area using the head, a group of
conductive balls is held in the area. That is, one aspect of the
present invention is a method of mounting including: setting on a
substrate, a mask that includes a plurality of apertures for
disposing conductive balls on the substrate; and a filling step
that includes using a head that is movable along a surface of the
mask, gathering conductive balls into an area that is part of the
surface of the mask from around the area, and moving the area.
Another aspect of the present invention is a filling device that
includes a head for holding a group of conductive balls in an area
that is part of a surface of a mask; and head supporting means for
supporting the head so as to move across the surface of the
mask.
[0018] A circle and a polygon that circumscribes a circle are
examples of shapes for the area where the conductive balls can be
easily gathered toward the area regardless of the direction in
which the area is moving. For example, it is possible to vibrate or
oscillate the head so that the conductive balls in the round or
surrounding of the area are swept together toward the area. Also,
by blowing out gas such as air from the head toward the area for
filling the balls, it is possible to sweep the conductive balls
together. One preferred method for gathering the conductive balls
is rotating the head to move the conductive balls toward an area in
the center of the head and thereby gather the conductive balls. By
causing the head to rotate about an axis of a shaft that is
perpendicular to the mask and moving the perpendicular shaft (axis)
across the surface of the mask to gather the conductive balls in
the area by rotating the head, it is possible to move a group of
conductive balls while keeping the conductive balls in the
area.
[0019] The head supporting means of the filling device included in
the present invention should preferably include a means for
rotating the head about a shaft that is perpendicular to the mask
and a means for moving the perpendicular shaft across the surface
of the mask. The head should also preferably include a means that
gathers the conductive balls by rotating the head to move the
conductive balls toward a concentric circular area (inner circle)
around the center of rotation of the head. If the means that
gathers the conductive balls is a magnetic body or an electret body
(a charged body), a repulsive force of the means may be used. One
preferable means for gathering is a sweeper for sweeping the
surface around the circular area using one or more members that
protrude from the head or by blowing out gas. The sweeper needs to
be disposed or shaped so that the conductive balls are moved toward
the area. Examples are a shape that is curved in a part of spiral,
a shape that is oriented toward the center of the rotation with
respect to the radial direction, and the like.
[0020] One type of member that protrudes from the head is called a
squeegee that achieves a sweeping effect for the surface of the
mask. One example has squeegee with a simple linear shape extend
tangentially from the circular area in which the conductive balls
are gathered, and by rotating a head including a plurality of such
squeegees, it is possible to apply a force in a direction of a
circular area to the conductive balls in around or surroundings of
the circular area. In addition, by disposing the plurality of
squeegees so as to overlap in the direction of movement thereof,
that is, the direction of the movement due to the rotation of the
head, conductive balls that have escaped from other squeegees can
be caught and reliably gathered toward the circular area.
[0021] To gather the conductive balls from the around the area,
members that protrude from the head or gas blown out from the head
also function so as to press the mask in the periphery of the area
onto the substrate. When the substrate on which the conductive
balls are mounted is the wafer of a semiconductor device or a work
(work-piece), the tendency for substrates to be increasingly large
means that the mask also becomes large. On the other hand, there is
a tendency for the conductive balls to become smaller as the
integration of devices progresses, and examples of the conductive
balls are solder balls, gold balls, or copper balls with a diameter
of around 30 to 300 .mu.m. Accordingly, when mounting balls on the
substrate, it is important to minimize the effect of the gaps
produced between the substrate and the mask due to warping and
bending of the mask. Although it is comparatively easy to correct
the surface profile irregularity of the substrate by attaching the
substrate from the rear side thereof using suction, the mask cannot
be reinforced from the front or rear and therefore it is difficult
to correct the profile irregularity of the mask. In particular,
when the mask is large, it is difficult to prevent warping and
bending, and therefore if the balls have a small diameter, there
will be the possibility of the balls getting into minute gaps and
becoming stray balls. In addition, although in order to place the
conductive balls, the mask should preferably be tightly attached to
a substrate, there are cases where flux for mechanically and
electrically connecting the balls is printed on the substrate, and
when this is the case, it may not be preferable to tightly attach
the mask to a substrate.
[0022] According to the present invention, instead of improving the
flatness or correcting profile irregularity of the entire mask, the
flatness of part of the surface of the mask is improved by pressing
the around or periphery of the area. By doing so, since it is
possible to improve the flatness inside the limited area for
filling the conductive balls, it is possible to prevent the
occurrence of stray balls from the outset. Also, by holding the
conductive balls gathered together inside the area, it is possible
to prevent the occurrence of stray balls even if there are gaps in
other regions of the mask. Accordingly, one aspect of mask used by
the mounting apparatus and mounting method in the present invention
is a mask that is flexible so that the mask can be made flatter by
being pressed by members that protrude from the head or by gas
blown out from the head.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] FIG. 1 is a plan view schematically showing a general
arrangement of a ball mounter according to the present
invention.
[0024] FIG. 2 is a side view schematically showing details of a
head.
[0025] FIG. 3 is a view showing details of the head when looking
through the head from above.
[0026] FIG. 4 is a cross-sectional view showing details of the
head.
[0027] FIG. 5 is an enlarged view of a squeegee.
[0028] FIG. 6(a) is a diagram showing one example of a path taken
by a circular area by the head, and FIG. 6(b) is an enlarged view
of part of the path.
[0029] FIG. 7 is a diagram showing another example of a path taken
by a circular area by the head.
[0030] FIG. 8(a) is a diagram showing another example of a path
taken by a circular area by the head, and FIG. 8(b) is an enlarged
view of part of the path.
[0031] FIG. 9(a) is a perspective view showing a different example
of a head, and FIG. 9(b) is a view showing the head when looking
through the head from above.
[0032] FIG. 10(a) is a perspective view showing yet another example
of a head, and FIG. 10(b) is a view showing the head when looking
through the head from above.
[0033] FIG. 11(a) is a perspective view showing yet another example
of a head, and FIG. 11(b) is a view showing the head when looking
through the head from above.
[0034] FIG. 12 is a cross-sectional view where yet another example
of a head is partially enlarged.
[0035] FIG. 13 is a cross-sectional view where yet another example
of a head is partially enlarged.
[0036] FIG. 14 is a view showing the construction of yet another
example of a head when looking through the head from above.
BEST MODE FOR CARRYING OUT THE INVENTION
[0037] FIG. 1 shows the general arrangement of a mounting apparatus
of one example the present invention. This mounting apparatus 1 is
called a ball mounter and disposes conductive balls at
predetermined positions on a semiconductor substrate (wafer or
work-piece) 10. Almost present wafers 10 are around eight inches or
twelve inches in diameter. The conductive balls mounted on the
substrate 10 are refined so that the diameter is 1 mm or below. The
mounting of balls with a diameter of around 10 to 500 .mu.m is
being investigated, with present demand being for the mounting of
balls with a diameter of around 30 to 300 .mu.m. Here, "conductive
balls" includes solder balls, metal balls made of gold, silver, or
the like, and also ceramic balls or plastic balls that have been
subjected to a process such as plating with a conductive
material.
[0038] The ball mounter 1 includes a table 2 for setting the
substrate 10 in a horizontal state where warping is corrected by a
method such as attachment by suction, a mask handler (mask carrier)
3 for setting a mask 11, which includes a plurality of apertures or
openings for disposing the conductive balls at predetermined
positions on the substrate 10, on the substrate 10, and a filling
device 5 for filling the apertures in the mask 11 with the
conductive balls. The mask handler 3 includes a conveying unit 31
for moving the mask 11 between a position above the substrate 10
and a withdrawal position shown by the broken line and an alignment
unit 32 for aligning the substrate 10 and the mask 11. The device
for setting the mask 11 on the substrate 10 may fix the position of
the mask 11 and move the substrate 10 up and down and/or in the
horizontal direction to align the mask 11 and the substrate 10.
[0039] The mask 11 includes a plurality of apertures of a size that
is suited to inserting single conductive balls that are minute. The
substrate 10 normally includes a plurality of semiconductor devices
and the plurality of apertures in the mask 11 are formed with a
repetitive design according to rules for disposing conductive balls
at predetermined positions of such semiconductor devices. Such
openings provided in the mask 11 are referred to as apertures,
pattern holes, a hole pattern or an opening pattern, and the like,
and in the present specification, when referring to a plurality of
apertures, the expression "opening pattern" is used.
[0040] The filling device 5 includes a head 20 that moves across or
along a surface 11a of the mask 11 set on the substrate 10 to fill
the apertures of the mask 11 with the conductive balls and a head
supporting device 50 for supporting the head so as to move in a
freely chosen direction on the surface 11a of the mask 11. The head
supporting device 50 includes a motor 56 that support the head so
as to rotate about an axis (shaft) 55 that is perpendicular to the
mask 11 and a carriage 52 that supports the motor 56 via an arm 53
that is retractable in the Y direction. The carriage 52 moves along
a carriage shaft 51 in the X direction. Accordingly, the head 20
can be set at a freely chosen position in the X-Y direction on the
surface 11a of the mask 11 by the arm 53, the carriage 52, and the
carriage shaft 51 of the supporting device 50. Also, the head 20
can be moved by the supporting device 50 so as to trace a desired
path across the surface 11a of the mask 11.
[0041] The mounting apparatus 1 includes a step of setting the mask
11, which includes the plurality of apertures 12 for arranging the
conductive balls, on the substrate 10 and a filling step process
for filling the apertures 12 of the mask 11 with the conductive
balls using the head 20 that moves along the surface 11a of the
mask 11, and thereby disposes the conductive balls at predetermined
positions on the substrate 10. This filling step of process will
now be described in more detail while describing the details of the
filling device and its operation.
[0042] FIG. 2 shows an enlargement of the head 20 of the filling
device 5 when looking from the side. The head 20 includes a
disc-shaped squeegee support 21 and six sets of squeegees 22 that
protrude toward the surface 11a of the mask 11 from a lower surface
21a of the squeegee support 21. The center of the squeegee support
21 is connected to the shaft 55 that extends perpendicular to the
mask 11. The head 20 is rotated about the axis of the shaft 55 by
the motor 56 in a clockwise direction when looking from above the
squeegee support 21. The motor 56 is a means that rotates the
squeegee support 21 about the shaft 55 on the surface 11a of the
mask 11, and the shaft 55 is moved in a desired direction on the
X-Y plane across the surface 11a of the mask 11 by the arm 53, the
carriage 52, and the carriage shaft 51. Accordingly, by using the
head supporting device 50, the head 20 can be moved so as to trace
a desired path on the surface 11a of the mask 11 while the head 20
is being rotated. A ball supplying device 60, which supplies
conductive balls via an inside of the shaft 55 onto the mask 11
from the center of the squeegee support 21, is mounted on the
carriage 52.
[0043] FIG. 3 shows a state where the arrangement of the six sets
of squeegees 22 attached to the lower surface of the squeegee
support 21 are viewed from above looking through the squeegee
support 21. FIG. 4 shows the construction of the head 20 via a
cross-section where the head 20 is cut in a diameter direction for
the squeegee support 21. The six sets of squeegees 22 include a
plurality of sweep members 23 attached so as to be rectangular when
respectively viewed from above. The sweep members 23 may be any
members that contact the surface 11a of the mask 11 comparatively
softly and can sweep together the conductive balls 15 remaining on
the surface 11a. Wires that are bent so as to contact the surface
11a of the mask 11, elastic members such as rubber plates or
sponges shaped so as to contact the surface 11a of the mask 11, and
a large number of wires that extend far enough to contact the
surface 11a of the mask 11 can be given as examples of the sweep
members 23.
[0044] The squeegees 22 are arranged with a uniform pitch in the
circumferential direction around an inner circle 26 that is
concentric with the rotational shaft 55 and linearly extend
tangentially in a clockwise direction from the inner circle 26
toward an outer circle 27. Accordingly, in a state where the
squeegees 22 contact the surface 11a of the mask 11, when the
squeegee support 21 is rotated in the clockwise direction when
looking from above, the conductive balls 15 present in the movement
direction (rotation direction) of the squeegees 22 are pushed and
swept toward the inner circle 26, as shown by the arrows 18. This
means that the conductive balls 15 remaining on the surface 11a of
the mask 11 are moved toward the inner circle 26 and gathered
inside the inner circle 26.
[0045] In FIG. 3 and the subsequent drawings, areas defined with
the inner circle 26 and the outer circle 27 are virtual areas.
However, when the head 20 moves on the surface 11a of the mask 11
while being rotated by the head supporting device 50, the excess
conductive balls 15 remaining on the mask 11 in the area between
the inner circle 26 and the outer circle 27 are gathered in the
direction of the area in the inner circle 26 located on the center
of the head 20. Since the plurality of squeegees 22 are arranged so
as to overlap in the direction of rotation (the direction of
movement), by moving the head 20, the conductive balls 15 that are
outside the range of the inner circle 26 are successively gathered
in the direction of the inner circle 26 when the inner circle 26 is
moved. Accordingly, the conductive balls 15 are held in a circular
area 26 around the center of rotation of the head 20, the circular
area 26 moves together with the movement of the head 20, and
therefore a group 16 of the plurality of conductive balls 15 held
inside the head 20 also moves. In this way, in the filling device
5, the virtual circular area 26 in the center of the head 20 is
part of the area 26 of the surface 11a of the mask 11 where the
group 16 of conductive balls 15 is held, with the area 26 moving
due to the movement of the head 20.
[0046] In FIG. 5, the state where the front ends of the squeegees
22 contact the surface 11a of the mask 11 is shown by an
enlargement. The respective squeegees 22 include a plurality of
sweep members 23 which are disposed so as to multiple in a
direction of movement of the squeegees 22. The plurality of sweep
members 23 are attached to the squeegee support 21 so that the
front ends that contact the surface 11a of the mask are bent
backward with respect to the direction of movement of the squeegees
22. The sweep members 23 move so as to lightly press or sweep the
conductive balls on the mask 11 towards the circular area 26 that
is the direction of movement A. For this reason, a group 16 of
conductive balls 15 is formed and held in the circular area 26
inside the head 20. The balls 15 gathered in the area 26 fall under
their own weight into the apertures 12 of the mask 11 in the area
26 to fill the apertures 12 with the balls 15. Flux 17 for
soldering purposes is screen-printed in advance on the surface of
the substrate 10 corresponding to the opening pattern 12 of the
mask 11. Accordingly, the conductive balls 15 filled in the
apertures 12 are tightly attached to the flux 17 to temporarily fix
the conductive balls 15 at predetermined positions on the substrate
10. The substrate 10 on which the conductive balls 15 have been
mounted is thereafter subjected to a well-known reflow process to
fix the balls 15 to the substrate 10.
[0047] By the filling device 5, balls 15 are always gathered to the
limited area referred to as the circular area 26 for filling the
apertures. Accordingly, by monitoring the state of the conductive
balls 15 gathered in the area 26, it is possible to control the
condition of filling the apertures 12 of the mask 11 with the balls
15. For example, the conductive balls 15 held in the area 26 are
consumed by filling the apertures 2. Then, balls 15 are introduced
inside the area 26 from the ball supplying device 60 based on the
number of balls that have been consumed. Balls 15 may be supplied
at intervals of a predetermined time based on the number of balls
consumed per unit time (hour). Accordingly, the density of the
group 16 of conductive balls 15 in the area 26 is maintained and a
fall in the probability of the apertures 12 being filled due to a
fall in the ball density is avoided. The head 20 shown in FIG. 4
includes an optical sensor 65 that detects the density of the balls
15 in the area 26, and regardless of whether balls are being
supplied at intervals of a predetermined time, should the ball
density of the area 26 fall for whatever reason, new conductive
balls 15 are supplied to the area 26 from the ball supplying device
60 mounted on the carriage 52. It is also possible to provide a
mechanism for periodically renewing the balls 15. If a state where
the balls are moved without being inserted into the apertures 12 in
the mask 11 continues for a long time, the balls 15 would be
damaged by factors such as contact and abrasion. In this system
following process may be applied that collecting the balls 15 held
in the area 26, discarding the balls whose quality has
deteriorated, and returning only proper balls 15 to the area 26 for
filling.
[0048] An appropriate size for the area 26 for holding and moving
the balls 15 will change depending on conditions such as the
diameter of the conductive balls and the density of the apertures
in the mask 11. If the diameter of the conductive balls 15 is
around 10 to 500 .mu.m, a head 20 that can form the area 26 with a
diameter of 10 to 100 mm on the mask is preferable. If the area 26
for holding the balls is too small, the time required to fill the
openings in the entire mask is increased. Accordingly, the diameter
of the area 26 should preferably be at least 10 mm. On the other
hand, if the area 26 is too large, the movement of the balls 15
inside the area 26 will be insufficient, resulting in increased
unevenness in the density of the balls held inside the area 26.
Accordingly, the diameter of the area 26 should preferably be no
greater than 100 mm. More preferably, the circular area 26 should
be 20 to 60 mm, inclusive.
[0049] If the rotational speed of the head 20 is too low, the
movement of the balls 15 inside the area 26 will be insufficient,
resulting in increased probability of the conductive balls 15
failing to fill the apertures 12. Accordingly, the rotational speed
of the head 20 should be at least 10 rpm. On the other hand, if the
rotational speed is too high, the movement speed of the conductive
balls 15 will become fast, resulting in increased probability of
the balls 15 passing the apertures 12 without falling thereinto and
increased probability of the conductive balls 15 failing to fill
the apertures 12. Accordingly, the rotational speed of the head 20
should be no greater than 120 rpm. A more preferable range for the
rotational speed of the head is 30 to 90 rpm. For example, in the
filling device 5 according to the present embodiment, the diameter
of the circular area 26 formed by the head 20 in which the balls
gather is 40 mm and the rotational speed is 45 rpm.
[0050] FIGS. 6 to 8 show a number of examples of paths for moving
the circular area 26 so as to cover the surface 11a of the mask 11.
When the surface 11a of the mask 11 is an XY plane, the head
supporting device 50 of the filling device 5 can move the head 20
in a freely chosen direction on the XY plane. The direction of
movement of the head 20 can also be freely and dynamically changed.
In addition, the head 20 can gather and hold the conductive balls
15 in the circular area 26 by rotating regardless of the direction
of movement of the head 20. For this reason, in a state where the
conductive balls 15 are held in the circular area 26, the filling
device 5 can move the area 26 in a freely chosen direction on the
surface 11a of the mask 11, with it being possible to freely and
dynamically change the direction of movement.
[0051] FIG. 6(a) schematically shows an example where the head 20
is moved to trace a spiral or whirl-like path on the surface 11a of
the mask 11. By moving the head 20, the circular area 26 for
filling the balls 15 moves across the entire surface of the mask 11
in a spiral or whirl-like path 71 to dispose the conductive balls
15 at predetermined positions on the substrate 10. The spiral or
whirl-like path 71 is suited to cases where the substrate 10 is
circular, the mask 11 is circular, and/or the entire region to be
filled with the conductive balls 15 is circular.
[0052] It should be noted that in FIG. 6(a), the path 71 on which
the area 26 moves is shown by a line representing the path on which
the center of rotation moves. For ease of understanding, the head
20 and the area 26 are shown by the same circle, but as described
above the area 26 is actually formed concentrically with the head
20 and is not the same size. However, since the area 26 is
constructed so as to be concentric with the head 20, the path
traced by the center during movement is the same. Also, in the
present specification, the "path taken by the area 26" does not
represent the movement of the center but represents a wide path,
track or route indicating how the area 26 moves over the surface
11a of the mask 11. Also, even if the path taken by the area 26 can
be said to be a path on which the apertures 12 of the mask are
physically filled by the conductive balls 15, the path does not
need to leave a trace on the surface 11a of the mask 11. As one
specific example relating to the path taken by the area 26, in the
head supporting device 50 of the filling device 5, the detail
profile of the path can be provided by a program or function for
automatically moving the head 20.
[0053] FIG. 6(b) shows an enlargement of part of the path 71. To
cover the entire surface 11a of the mask 11 with the area 26
without omissions, the head 20 is moved by the head supporting
device 50 of the filling device 5 so that parts of the path taken
by the area 26 overlap. In this example, the path 71 is selected so
that adjacent parts T(n) and T(n+1) of the path 71 overlap by
almost 50%. By moving the head 20 on this path 71, the area 26 can
move so as to overlap 100% of the entire surface of the mask 11 and
fill the apertures 12 of the mask 11 with the balls 15.
[0054] FIG. 7 shows a different example of the path taken by the
head 20 and the circular area 26. In this example, by moving the
head 20, the area 26 moves so as to trace a "zigzag", "sine curve",
or "snaking" path 72 so that the area 26 covers the entire surface
11a of the mask 11. When the path 72 is used, in the same way as
described above, the overlapping rate of adjacent parts of the path
72 should preferably be set appropriately.
[0055] FIG. 8(a) shows an example where the conductive balls 15 are
disposed by setting a mask 81 with an overall rectangular filling
region on a rectangular electronic circuit board 80 in place of the
circular substrate 10. In this example, by moving the head 20, the
area 26 moves so as to trace a "zigzag", "sine curve", or "snaking"
path 73, with the area 26 covering the entire surface 81a of the
mask 81. As shown in FIG. 8(b), when the path 73 is used, the
adjacent parts T(n) and T(n+1) of the path 73 should preferably
overlap by around 50%. The zigzag path 73 is one example of a path
that is suited to covering a quadrangular filling region. A spiral
path that traces a route along the outer circumference of a
quadrangle is another path that is suited to covering a
quadrangular filling region.
[0056] To fill the opening pattern 12 of the mask 11 without
omissions, the area 26 should preferably move with a high
overlapping rate. On the other hand, if the overlapping rate of the
path is high, the processing time require to dispose the balls 15
on the entire substrate 10 increases. Also, if the overlapping rate
of the path is high, there is a fall in the consumed number of
balls 15, and since the balls are present in the area 26 for a long
time, the probability of the balls being damaged increases. For
this reason, the area 26 should preferably move so as to trace a
path with the rate of overlapping in a range of 10 to 90%
inclusive. The area 26 should more preferably move so as to trace a
path with the rate of overlapping in a range of 30 to 70%
inclusive. A path with a rate of overlapping of 50% is one example
of an optimal path for moving the area 26.
[0057] If the movement speed of the head 20 is too slow, too much
time will be taken to dispose the balls 15 on the entire substrate
10. On the other hand, if the movement speed of the head 20 is too
fast, the probability of the area 26 moving on before the balls 15
have fallen into the openings 12 increases. Accordingly, the
movement speed of the head 20 should preferably fall in a range of
2 to 60 mm/s, with a speed in a range of 5 to 40 mm/s being more
preferable. For the filling device 5 of the present embodiment, the
movement speed of the head 20 is set at 20 mm/s.
[0058] In this way, in the filling device 5 used in the ball
mounter 1, the conductive balls 15 are held in a limited part, that
is, the circular area 26 of the head 20, out of the surface 11a of
the mask 11. Also, by moving the head 20, the area 26 moves across
or along the surface 11a of the mask with parts of the path 51
taken by the area 26 overlapping to fill the apertures 12 of the
mask 11 with the conductive balls 15, thereby disposing the balls
15 at predetermined positions on the substrate 10 that is the
work-piece. In the filling device 5, since the balls that do not
fill the apertures do not move away from the mask but balls are
gathered on the mask to fill the next apertures, waste is prevented
for the conductive balls 15. Accordingly, unlike a method where the
apertures 12 are filled with the balls 15 by sweeping and removing
the entire surface of the mask 11 at a time with a squeegee, the
limited area can be covered by a group 16 of the balls 15 that is
sufficient (sufficiently excessive) with respect to the apertures
(opening density) of the area to be filled without supplying an
extremely large number of balls at a time. That is, in the small
area 26 that is part of the surface of the mask, by gathering an
excessive number of balls in the around or surrounding of the area
and adding the consumed balls, a sufficient rate of excess is
maintained for the conductive balls 15 with respect to the
apertures 12 in the area 26. By using this method, the rate of loss
for the balls is low relative to the number of apertures 12 in the
entire mask, thereby preventing waste for the balls 15 and
achieving a high fill ratio.
[0059] Also, by moving the area 26 used for filling so that parts
of the path overlap, it is possible to constantly supply new balls
15 as the area 26 moves. Accordingly, the time (referred to as
"lifetime" in the present specification) from the supplying of the
new balls 15 to the disposing of such balls on the substrate 10 can
be reduced, and the lifetimes of the conductive balls 15 disposed
on the substrate 10 can be made fairly uniform. Accordingly, likely
to the as-produced conditions of the conductive balls 15 disposed
on the substrate 10 can be kept uniformly high and conductive balls
15 with little damage can be disposed on the entire substrate.
[0060] In addition, by rotating the squeegee support 21, the head
20 of the filling device 5 can gather the conductive balls 15 in
the internal circular area 26 without being affected by the
direction of movement of the head 20. Accordingly, the function
(ability) of the head 20 to gather the balls in the inner circular
area 26 does not change regardless of the direction of movement of
the head 20 in the X-Y plane on the mask 11. This means that while
the head 20 is moving, the excess balls 15 on the mask 11 in the
area around the inner circular area 26 can be constantly gathered
into the area 26. In addition, the overall distribution of balls 15
in the inner circular area 26 becomes substantially uniform,
unevenly clustered balls in one part of the inner circular area 26
becomes substantially lower, and the entire area 26 that extends in
two dimensions can be useable to fill the opening pattern 12 with
the conductive balls 15. Too much excessive gathering of balls 15
inside the area 26 does not occur, and the excess rate and
distribution of the conductive balls 15 become substantially
constant without becoming excessively unbalanced. For this reason,
by moving the area 26 so that parts of the path overlap, it is
possible to reliably reduce the number of unfilled apertures
without overlapping the entire movement path.
[0061] A head 20 that applies a force to move the conductive balls
15 toward the area 26 by rotating is one of the most preferred
embodiments of the present invention. As another example of the
method of gathering the conductive balls 15 toward the area 26, it
is possible to vibrate or oscillate the head to sweep together the
balls in the direction of the area 26 using the squeegees attached
to the bottom of the head. In this method, depending on the
direction and number of vibrations and the shape of the squeegees,
the shape of the area 26 is not limited to a circle and may be a
polygon that circumscribes a circle. When the area 26 is shaped as
a polygon, the performance for gathering the balls 15 may differ
according to the direction of movement of the head. Therefore, a
circular area 26 is superior in that the direction of movement of
the head 20 can be selected without the performance for gathering
and holding the balls 15 rising or falling according to the
direction of movement of the head 20.
[0062] The squeegees 22 of the head 20 of the filling device 5
collect the balls 15 from around the area 26 used for filling and
also have a function (ability) for flattening a part of the mask 11
corresponding to the area 26 used for filling by pressing. As shown
in FIG. 3, the squeegees 22 are arranged between the inner circle
26 and the outer circle 27 of the head 20, that is, in the
surroundings (the area around) 28 of the circular area 26. The
front ends of the squeegees 22 are pressed with suitable pressure
onto the surface 11a of the mask 11 to gather the balls 15
remaining on the surface 11a of the mask 11 without leaving any
balls. Accordingly, even if the part of the mask 11 corresponding
to the area 26 is warped or bent, by pressing the periphery 28 of
the area 26 using the squeegees 22, it is possible to correct the
part to a flat (horizontal) state.
[0063] To prevent multiple balls from filling the apertures, the
mask 11 is a thin-plate-like member with substantially equal
thickness to the balls 15. Accordingly, although the mask 11 is
susceptible to warping and bending, by pressing the squeegees 22
onto the surface 11a with a suitable pressure, such warping and
bending (distortion) can be corrected. When the mask 11 is warped
or bent, gaps are produced between the substrate 10 and the mask
11. If the substrate 10 is held on the table 2 that is highly flat
by a vacuum suction method, warping and bending can be corrected to
make its surface flat. Accordingly, by correcting warping or
bending of the part corresponding to the area 26 by pressing the
surface 11a of the mask 11 with the squeegees 22, it is possible to
prevent gaps being produced between the mask 11 and the substrate
10 and therefore balls 15 can be prevented from escaping via such
gaps.
[0064] If the diameter of the balls to be mounted on the substrate
is a few mm or larger, the mask will also be a few mm thick,
resulting in the mask having higher strength. Accordingly, the mask
will be resistant to warping and bending, contrary, should such
warping and bending occur, it will not be easy to correct such
warping with the amount of pressure that can be applied by the
squeegees. Also, if the diameter of the balls is a few mm, no balls
would not escape from the gap between the substrate and the mask if
the gap can be adjusted in units of mm. However, if the diameter of
the balls is in units of .mu.m, it will be necessary to adjust the
gap between the substrate and the mask in units of .mu.m. Although
it is preferable to tightly attach the entire mask 11 to the
substrate 10 to prevent gaps from being produced between the mask
11 and the substrate 10, the flux 17 for fixing the balls 15 is
printed on the substrate 10. Accordingly, tightly attaching the
entire mask 11 to the substrate 10 cannot be said to be
preferable.
[0065] When the squeegees move the balls in one direction or simply
back and forth, it may be possible to correct warping and bending
of the mask at a linear part of the mask where the squeegees are in
contact. However, it will not be possible to correct the area part
of the mask where the balls are present by pressing the squeegees
and if there is a gap through which the balls can move between the
substrate and the mask at such positions, the balls that fill the
apertures of the mask will come out of the mask, so that balls
cannot be disposed at the predetermined positions of the substrate.
In addition, the balls that come out of the mask can stray across
the surface of the substrate and be disposed at unintended
positions, become trapped between the mask and the substrate,
and/or become a factor that obstructs balls from filling other
apertures.
[0066] On the other hand, the squeegees 22 of the head 20 of the
filling device 5 according to the present embodiment press the
periphery of the area 26 in which the conductive balls 15 are
present. For this reason, in the area 26 in which the conductive
balls 15 are to be present, the degree to which the mask 11 is
horizontal is corrected, the mask 11 and the substrate 10 are kept
parallel, and the gap between the mask 11 and the substrate 10 can
be set at a value where the balls 15 do not flow out. When the head
200 is passed, parts of the mask 11 that have been passed by the
head 20 may return to a bent or warped state. However, the
conductive balls 15 are gathered in the area 26 and move together
with the head 20. This means that the conductive balls 15 basically
do not remain after the head 20 has moved, so that even if the mask
11 is warped or bent, risk of the conductive balls 15 straying is
prevented. In addition, the conductive balls 15 that have filled
the apertures 12 of the mask 11 are held at predetermined positions
by the flux 17 on the surface of the substrate 10. Accordingly,
even if the mask 11 may float above the surface of the substrate 10
when the head 20 passes, problems may not be occur. In this way, in
the filling device 5 according to the present embodiment, minute
particles can be reliably disposed at predetermined positions on
the work 10 without omissions and without being affected by warping
or bending of the mask 11.
[0067] The members 23 that construct the squeegees 22 need to push
minute particles such as conductive balls that function as
connection terminals of a semiconductor device with a suitable
force and to sweep together the minute particles toward the area
26. Also, the sweep members 23 should preferably have a suitable
elasticity so that the balls 15 that have been inserted into the
apertures 12 are not brushed out. One suitable example of the sweep
members 23 is the resin or metal wires shown in FIGS. 3 to 5 that
extend in the longitudinal direction of the squeegees 22. For
members 23 constructed by bending both ends of wires that extend in
a longitudinal direction along the surface of the mask 11 in a
U-shape and attaching the wires to the squeegee support 21, the
lower central parts of the U-shaped wires contact the mask 11.
Accordingly, the U-shaped wires 23 are pressed onto the mask 11 in
a state where the wires 23 have a suitable elasticity so as to not
damage the mask 11 and the outer parts of the wires do not brush
out the balls 15 inserted into the holes of the mask 11. In
addition, since the U-shaped wires 23 extend in a direction
perpendicular to the direction of movement of the squeegees 22,
such wires 23 are suitable as members for sweeping the balls 15.
The wires 23 disposed in an overlapping state or in many layers on
one squeegee 22 are suited to reliably sweeping together the balls
15 while flexibly contacting the mask 11. Also, the plurality of
squeegees 22 arranged around the circular area 26 of the head 20
evenly gather the balls 15 from the entire surroundings of the area
26, and are also suited to reliably pressing a peripheral of the
area 26.
[0068] FIG. 9 to FIG. 14 show different examples of a head. FIG.
9(a) shows a state where another head 20a is viewed from a base
surface thereof, while FIG. 9(b) shows the head 20a from above when
looking through the squeegee support 21. The head 20a includes the
squeegee support 21 and twelve squeegees 22a that protrude from the
lower surface 21a of the squeegee support 21 toward the surface 11a
of the mask 11. The head 20a can be attached to the head supporting
device 50 of the filling device 5 and used in place of the head 20
described above. The respective squeegees 22a are bundles of a
plurality of superfine wires and are constructed to function as a
single squeegee by crimping both ends 22r of the wires. The
squeegees 22a are formed in overall U-shapes and are attached
around the inner circle 26 of the rear surface 21a of the support
21 so as to extend substantially tangentially to the inner circle
26.
[0069] FIG. 10(a) shows yet another example head 20b when looking
from a base surface thereof, while FIG. 10(b) shows the head 20b
from above when looking through the squeegee support 21. The head
20b includes the squeegee support 21 and seven sets of squeegees
22b that protrude from the lower surface 21a of the squeegee
support 21 toward the surface 11a of the mask 11. This head 20b can
be attached to the head supporting device 50 of the filling device
5 and used in place of the head 20 described above. These squeegees
22b are formed by thin sheets of polyimide of U-shapes laminating
together. As examples of this type of squeegee, it is possible to
use single thin sheets of resin or metal or laminated such sheets.
To avoid the effects of static electricity that may be produced
between the squeegees 22b and the mask 11, one preferable example
is metal squeegees. Also, squeegees made of plastic should
preferably have their surfaces coated with a thin conductive film,
such as copper foil, or be made conductive by including carbon. The
front end parts of the squeegees that contact the mask 11 may also
be edges. When the squeegees are constructed of thin films, the
thin films may be bent back with the bent surfaces contacting the
mask 11.
[0070] FIG. 11(a) shows yet another example head 20c when looking
from a base surface thereof, while FIG. 11(b) shows the head 20c
from above when looking through the squeegee support 21. The head
20c includes the squeegee support 21 and six sets of squeegees 22c
that protrude from the lower surface 21a of the squeegee support 21
toward the surface 11a of the mask 11. These squeegees 22c are
composed of conductive squeegees formed substantially as cuboids.
This head 20c can also be attached to the head supporting device 50
of the filling device 5 and used in place of the head 20 described
above.
[0071] Another example of the squeegees is constructed by attaching
superfine wires made of resin or metal to the squeegee support 21
like the bristles of a brush. Also, the number of sets of squeegees
is not limited to the numbers given above. In addition, although
setting the squeegees in tangential directions for the inner circle
26 is one of favorable arrangements for the present invention, the
present invention is not limited to such arrangement. The
arrangement of squeegees may be any arrangement that functions as a
sweeper to sweep together the balls to the area 26 due to the
rotation of the head 20. For example, the squeegees may be disposed
at angles to tangential directions for the inner circle 26, or the
squeegees themselves may be curved or shaped as a part of
spirals.
[0072] FIG. 12 shows the construction of yet another example head
20d. The head 20d includes air nozzles 92 for blowing out gas 91
onto the surface 11a of the mask 11 to sweep together the balls 15.
This head 20d can also be attached to the head supporting device 50
of the filling device 5 and used in place of the head 20 described
above. The air nozzles 92 are attached to the support 21 in place
of the squeegees. One example of the air nozzles 92 includes linear
nozzle ends 93 that extend tangentially from the inner circle 26 to
the outer circle 27 on the rear surface 21a of the support 21 in
the same way as the various types of squeegees shown in the
drawings described above. Filters 94 made of sintered metal or the
like are attached to nozzle ends 93 and the air 91 is blown out
diagonally downward through the filters 94 toward the surface 11a
of the mask 11. The air 91 that has been blown out flows across and
along the surface 11a of the mask 11 in the direction of the inner
circle 26. It is possible to move the head 20 while having the air
91 blow the conductive balls 15 in the direction to the area 26 of
the inner circle. In addition, the surface 11a of the mask around
the area 26 for filling the balls is pressed due to the pressure of
the air 91 blown onto the surface 11a of the mask and thereby
warping and bending of the mask 11 can be corrected.
[0073] Air expelling parts of the air nozzles 92 may be constructed
of groups of slits or minute cylindrical holes in place of the
filters 94. Also, in place of the air 91, it is effective to use an
inert gas such as nitrogen or argon gas, or an ionized gas for
controlling the charge of the conductive balls.
[0074] In the head 20d that blows out gas such as air, the balls
can be moved by the pressure of the air. Accordingly, by moving the
head 20d in a freely chosen direction using the head supporting
device 50, the filling device 5 can gather the balls 15 in the area
26 for filling without rotating the head 20d. It is also possible
to rotate the head 20d to gather the balls 15 in the area 26 of the
inner circle. This means that with a filling device 5 that uses
only the head 20d that blows out gas for sweeping, it is possible
to omit the motor 56 for rotating the head, and the construction of
the head supporting device 50 can be simplified.
[0075] FIG. 13 shows another example of a head that blows out air.
This head 20e includes a squeegee support 21 and squeegee-type
nozzles 92 that protrude from the lower surface 21a of the squeegee
support 21 toward the surface 11a of the mask 11. As one example,
the nozzles 92 are formed of elastic members such as rubber
members, and contact the surface 11a of the mask 11 to press the
mask. The nozzles 92 include outlets 93 oriented toward the inside
and expel air 91 toward the inside to gather the conductive balls
15 in the area 26. This head 20e can also be attached to the head
supporting device 50 of the filling device 5 and used in place of
the head 20 described above. Since the conductive balls 15 can be
moved by the expelled air 91, the head 20e is also a type where the
conductive balls 15 can be swept together without rotating the
head.
[0076] It should be noted that the substrate 10 shown in FIG. 13
includes a conductive layer 10a on a surface thereof and the
conductive layer 10a is additionally covered by a protective film
13, with the resist 13 in the parts where the conductive balls 15
are mounted being removed by etching or the like. Accordingly, the
mask 11 can be set on the substrate 10 so as to be tightly attached
to the resist layer 13. In addition, the conductive balls 15 that
fill the apertures 12 of the mask 11 are mounted in a state where
there is electrical contact with the concave parts (the exposure
potions 10a) of the substrate with the individual conductive balls
15 functioning as contact terminals.
[0077] FIG. 14 shows a state where yet another example of a head is
viewed from above when looking through the squeegee support. The
head 20f includes a rectangular squeegee support 21 and two sets of
squeegees 22f that extend from the rear surface 21a of the squeegee
support 21 toward the surface 11a of the mask 11, the squeegees 22f
being in V-shapes when viewed from above. The two sets of squeegees
22f that are V-shaped are attached to the squeegee support 21 so as
to face each other with a square area 26 formed in between.
Accordingly, the conductive balls 15 are gathered in the area 26
between the squeegees 22f by oscillating or vibrating the head 20f
in the left-right direction in FIG. 14, and the conductive balls 15
are filled or inserted in the apertures 12 of the mask 11 under
their own weight in the area 26. In addition, since the surface 11a
of the mask 11 in the periphery of the area 26 is pressed by the
squeegees 22f, warping and the like of the mask 11 are corrected.
The head 20f can move in a freely chosen direction in the XY plane
while oscillating and with the conductive balls 15 held inside the
area 26. Since the squeegees 22f vibrate so as to gather the
conductive balls 15, unevenness in the distribution of the
conductive balls 15 inside the area 26 can be reduced.
[0078] In the present invention, since the head rotates or
oscillates (swings) and the head moves in a freely chosen
direction, in most cases, the shape of the area 26 in which the
conductive balls 15 are gathered will not be a geometric shape with
a clear outline. However, in a head type where the balls are
gathered while the head rotates, the area 26 becomes near or
substantially circular. In addition, in a head type where the balls
are gathered while the head vibrates, depending on the shapes of
the squeegees, the area 26 can be circular or a polygon that is
circumscribed on a circle. The polygon for the present invention is
not limited to a square and includes triangles and also polygons
with five or more sides.
[0079] It should be noted that the heads described above are merely
a number of examples included in the present invention which is not
limited to the above description. The head included in the present
invention moves over the surface of the mask while holding
conductive balls for filling in a group in a two-dimensional area
of a limited size, with one favorable aspect of the head sweeping
together the conductive balls from around the area for filling. In
addition, by moving the head over the surface of the mask so that
parts of the path overlap, it is possible to efficiently dispose or
place the conductive balls in the apertures in the entire mask, so
that the possibility of failure of filling balls into the apertures
can be reduced.
[0080] The ball mounter 1 according to the present embodiment
includes the mask handler 3 and the filling device 5 and may
additionally include a device for conveying the substrate 10 and
setting the substrate 10 on the table 2 and a device for applying
flux onto the surface of the substrate 10. By using such devices,
before the process that sets the mask and the process that fills
the balls, processes such as setting the substrate on the table and
applying the flux can be carried out. In addition, a system that
carries out such processes in a series can be provided.
* * * * *