U.S. patent application number 11/906388 was filed with the patent office on 2008-02-07 for ball transferring method and apparatus.
This patent application is currently assigned to Nippon Steel Materials Co., Ltd.. Invention is credited to Eiji Hashino, Kenji Shimokawa, Kohei Tatsumi.
Application Number | 20080032495 11/906388 |
Document ID | / |
Family ID | 34826446 |
Filed Date | 2008-02-07 |
United States Patent
Application |
20080032495 |
Kind Code |
A1 |
Shimokawa; Kenji ; et
al. |
February 7, 2008 |
Ball transferring method and apparatus
Abstract
Balls are sucked onto a carrier board so as to be temporarily
arranged in a ball arrangement region of the board, and then the
balls are transferred and bonded onto an objective substance with
their positions being adjusted. Gas blow is applied to the
temporarily arranged balls or alternatively the temporarily
arranged balls are sucked, so as to remove excess balls other than
balls that have been exactly sucked onto the ball arrangement
region. Cooperation with application of fine vibration to the
carrier board makes the removal of the excess balls more
efficient.
Inventors: |
Shimokawa; Kenji; (Chiba,
JP) ; Hashino; Eiji; (Chiba, JP) ; Tatsumi;
Kohei; (Chiba, JP) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Assignee: |
Nippon Steel Materials Co.,
Ltd.
Tokyo
JP
|
Family ID: |
34826446 |
Appl. No.: |
11/906388 |
Filed: |
October 1, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11094051 |
Mar 30, 2005 |
7285486 |
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11906388 |
Oct 1, 2007 |
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09760107 |
Jan 12, 2001 |
6916731 |
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11094051 |
Mar 30, 2005 |
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Current U.S.
Class: |
438/613 ;
257/E21.508; 438/616 |
Current CPC
Class: |
H01L 2924/014 20130101;
H01L 2924/01051 20130101; H01L 2924/01005 20130101; H01L 2924/01023
20130101; H01L 2924/01074 20130101; H05K 2203/082 20130101; H05K
2203/041 20130101; H01L 2224/13099 20130101; H01L 2924/01087
20130101; H01L 2924/01037 20130101; H01L 2224/05573 20130101; H01L
2924/04953 20130101; H01L 2924/01006 20130101; B23K 2101/40
20180801; B23K 3/0623 20130101; H05K 3/3478 20130101; H01L
2924/01018 20130101; H01L 21/4853 20130101; H01L 2924/01079
20130101; H01L 2924/01088 20130101; H01L 2924/01033 20130101; H01L
24/11 20130101; H01L 21/6838 20130101 |
Class at
Publication: |
438/613 ;
438/616 |
International
Class: |
H01L 21/441 20060101
H01L021/441 |
Claims
1-5. (canceled)
6. A ball transferring apparatus comprising: a carrier board onto
which balls are sucked, said carrier board including a ball
arrangement region in which said balls sucked are temporarily
arranged; a gas nozzle disposed near said carrier board for
applying gas blow to said ball arrangement region so as to remove
excess balls other than balls that have been exactly sucked onto
said ball arrangement region; and means for transferring and
bonding the remaining balls onto an objective substance with
positional adjustment being made.
7. The apparatus according to claim 6, wherein said gas nozzle can
be moved relatively to said carrier board and applies said gas blow
with being moved relatively to said ball arrangement region.
8. The apparatus according to claim 6, wherein said gas nozzle is
inclined in relation to the ball arrangement plane on said carrier
board.
9. The apparatus according to claim 6, wherein said gas nozzle has
its gas outlet whose width is broader than a ball arrangement width
in said ball arrangement region.
10. The apparatus according to claim 6, further comprising
vibrating means for applying fine vibration to said carrier
board.
11-14. (canceled)
15. A ball transferring apparatus comprising: a carrier board onto
which balls are sucked, said carrier board including a ball
arrangement region in which said balls sucked are temporarily
arranged; a suction nozzle disposed near said carrier board for
sucking said ball arrangement plane, so as to remove excess balls
other than balls that have been exactly sucked onto said ball
arrangement region; and means for transferring and bonding the
remaining balls onto an objective substance with positional
adjustment being made.
16. The apparatus according to claim 15, wherein said suction
nozzle can be moved relatively to said carrier board and sucks said
plane with being moved relatively to said ball arrangement
region.
17. The apparatus according to claim 15, wherein said suction
nozzle is inclined in relation to the ball arrangement plane on
said carrier board.
18. The apparatus according to claim 15, further comprising
vibrating means for applying fine vibration to said carrier
board.
19. The apparatus according to claim 6, further comprising
collecting means for collecting said excess balls that have been
removed from said carrier board.
20. The apparatus according to claim 19, wherein said collecting
means comprises a vessel for collecting said excess balls.
21. (canceled)
22. The apparatus according to claim 8, wherein the angle of said
gas nozzle to said ball arrangement plane is within the range of
5.degree. to 175.degree..
23. The apparatus according to claim 17, wherein the angle of said
suction nozzle to said ball arrangement plane is within the range
of 5.degree. to 175.degree..
24-26. (canceled)
27. The apparatus according to claim 6, further comprises a ball
arranging unit including a ball stocking tray; a carrier board
conveying mechanism; and ball inspection means.
28. The apparatus according to claim 15, further comprises a ball
arranging unit including a ball stocking tray; a carrier board
conveying mechanism; and ball inspection means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is based upon Japanese Patent Application
Nos. 10-131356, filed on Apr. 24, 1998 and 11-116396, filed on Apr.
23, 1999, the contents being incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to ball transferring methods
and apparatus for transferring balls to form spherical bumps on
electrodes of a semiconductor device, a printed circuit board, or
the like. In particular provided are techniques for removing excess
balls from a ball carrier on which balls being transferred are
temporarily arranged.
[0004] 2. Description of the Related Art
[0005] Japanese Patent Application Laid-open No. 7-153765 discloses
spherical bump bonding method and apparatus for easily and surely
bonding spherical bumps onto electrodes of a semiconductor device,
a printed circuit board, or the like.
[0006] Japanese Patent Application Laid-open No. 8-112671 discloses
a feature that vibration is applied to a suction head with solder
balls being carried thereon in order to allow the solder balls to
drop off.
[0007] In the method disclosed in the former Japanese Patent
Application Laid-open No. 7-153765, as shown in FIGS. 1A and 1B for
example, an apparatus is used which comprises a ball arranging unit
1, a carrier board conveying mechanism 2, ball inspection means 3,
and a bonding stage 4.
[0008] In the ball arranging unit 1, as shown in FIG. 2, fine
metallic balls B are put in a ball stocking tray 11, which is
vibrated with a vibrator 12. The balls B are thereby made to jump
effectively and sucked onto ball suction means 13. The ball suction
means 13 is provided with a ball carrier board 15 where suction
holes 14 each having a diameter smaller than the ball diameter are
arranged into a predetermined pattern. The pattern preferably
corresponds to the area of two or more semiconductor chips.
[0009] The ball suction means 13 is lowered to the vicinity of the
ball stocking tray 11 and balls B are sucked onto the respective
suction holes 14 of the carrier board 15 by vacuum.
[0010] The ball suction means 13 is then lifted up and excess balls
B' other than balls B that have been exactly sucked onto the
respective suction holes 14 are removed and collected for reuse.
The exactly sucked balls may be referred to as normal balls
hereinafter. In the prior art apparatus, a vibrator 16 is used as
means for removing the excess balls. The vibrator 16 applies fine
vibration to the ball suction means 13 in order that only the
excess balls B' may be removed without removing the normal balls
B.
[0011] In this manner, the excess balls B' can be removed so that
only one ball B is sucked onto each suction hole 14 of the carrier
board 15. This brings about an exact arrangement of the balls B on
the carrier board 15 and so shortening of the mass production tact
time.
[0012] However, if the carrier board 15 has a soil and a excess
ball B' has adhered to the carrier board 15 through the soil, the
soil may serve as a buffer between the excess ball B' and the
carrier board 15, so that the vibration is not properly transmitted
to the excess ball B' and the excess ball B' can not be removed. In
this case, application of more intense vibration may result in
removal of normal balls B.
[0013] For this reason, the carrier board 15 has been cleaned in
general. In case of a ball size of less than 300 .mu.m,
particularly less than 150 .mu.m, however, even a very small soil
or dirt may cause such adhesion of a excess ball B'.
[0014] Besides, if too intense vibration is applied upon sucking
balls in order to avoid excess ball adhesion, a normal ball B
exactly sucked onto a suction hole of the carrier board 15 may
rotate as it is being sucked. This may cause damage on the ball
surface, which damage leads to an erroneous detection upon optical
inspection of the ball arrangement. Besides, if removed excess
balls are scattered in the ball transferring apparatus, then it
mostly results in a machine trouble.
SUMMARY OF THE INVENTION
[0015] It is an object of the present invention to provide ball
transferring method and apparatus capable of an exact and proper
ball arrangement with very high accuracy.
[0016] According to an aspect of the present invention, a ball
transferring method comprises the steps of: sucking balls onto a
carrier board so as to arrange temporarily said balls in a ball
arrangement region of said carrier board; applying gas blow to said
ball arrangement region so as to remove excess balls other than
balls that have been exactly sucked onto said ball arrangement
region; and transferring and bonding the remaining balls onto an
objective substance with positional adjustment being made.
[0017] According to another aspect of the present invention, a ball
transferring apparatus comprises: a carrier board onto which balls
are sucked, said carrier board including a ball arrangement region
in which said balls sucked are temporarily arranged; a gas nozzle
disposed near said carrier board for applying gas blow to said ball
arrangement region so as to remove excess balls other than balls
that have been exactly sucked onto said ball arrangement region;
and means for transferring and bonding the remaining balls onto an
objective substance with positional adjustment being made.
[0018] According to still another aspect of the present invention,
a ball transferring method comprises the steps of: sucking balls
onto a carrier board so as to arrange temporarily said balls in a
ball arrangement region of said carrier board; sucking said ball
arrangement plane, so as to remove excess balls other than balls
that have been exactly sucked onto said ball arrangement region;
and transferring and bonding the remaining balls onto an objective
substance with positional adjustment being made.
[0019] According to still another aspect of the present invention,
a ball transferring apparatus comprises: a carrier board onto which
balls are sucked, said carrier board including a ball arrangement
region in which said balls sucked are temporarily arranged; a
suction nozzle disposed near said carrier board for sucking said
ball arrangement plane, so as to remove excess balls other than
balls that have been exactly sucked onto said ball arrangement
region; and means for transferring and bonding the remaining balls
onto an objective substance with positional adjustment being
made.
[0020] According to still another aspect of the present invention,
a ball transferring method comprises the steps of: sucking balls
onto a carrier board so as to arrange temporarily said balls in a
ball arrangement region of said carrier board; in a state that said
balls are fully firmly fixed to said ball arrangement region,
applying gas blow through a nozzle to said ball arrangement region
or sucking said balls through a nozzle, and optionally applying
fine vibration to said carrier board, so as to remove excess balls
other than balls that have been exactly sucked onto said ball
arrangement region; and when transferring the remaining balls onto
an objective substance with positional adjustment being made,
applying vibration to said carrier board so that said balls which
have been sucked to be in contact with said ball arrangement region
may be allowed to drop off.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIGS. 1A and 1B are schematic side and plane views showing
the whole configuration of a prior art apparatus;
[0022] FIG. 2 is a representation showing a process for making a
temporary ball arrangement in the prior art apparatus;
[0023] FIG. 3 is a schematic enlarged sectional view for explaining
the principle of the present invention;
[0024] FIG. 4 is a partially sectional schematic side view of a
principal part of an apparatus according to an embodiment of the
present invention;
[0025] FIGS. 5A to 5E are perspective partial views showing
examples of gas nozzles usable in the embodiment;
[0026] FIGS. 6A to 6C are partial sectional views showing examples
of gas nozzles usable in the embodiment;
[0027] FIG. 7 is a schematic plane view showing examples of
temporary ball arrangement pattern according to the embodiment;
and
[0028] FIGS. 8A and 8B are schematic side and plane views showing
the whole configuration of an apparatus with excess ball collecting
means according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] According to the present invention, bumps are formed on
electrodes of a semiconductor device, a printed circuit board, or
the like, by transferring and bonding fine metallic balls onto the
electrodes. The balls to be transferred are sucked onto and
temporarily arranged in a ball arrangement region of a ball carrier
board.
[0030] The temporary ball arrangement process according to the
present invention comprises several stages from a ball suction
stage to a ball bonding stage. More specifically, in the temporary
ball arrangement process, the ball suction head of a ball
transferring apparatus according to the present invention is
lowered for sucking balls, then raised with sucked balls, and then
lowered again for transferring and bonding the balls onto the
electrodes. In the temporary ball arrangement process, gas is blown
against the balls temporarily arranged on the carrier board to
remove excess balls other than the normal balls exactly sucked onto
the carrier board.
[0031] At this time, the gas is blown against the balls with a
proper intensity that does not exceed the suction force for sucking
each normal ball onto the carrier board. Only the excess balls can
surely be removed thereby. The principle of the excess ball
removing action according to the present invention will be
described below with reference to FIG. 3.
[0032] In FIG. 3, F.sub.R represents the suction force for sucking
a ball onto a suction hole of the ball suction head; F.sub.g does
the force that the ball receives from the gas blow; F.sub.o does
the drag of the point O onto the ball; r.sub.a does the radius of
the suction hole; r.sub.b does the radius of the ball; .theta. does
the angle between the carrier board and the drag F.sub.o; and X
does the vertical distance between the ball arrangement plane
(including the point O) and the center of the ball. In FIG. 3, a
model is discussed in which the gas blow acts on the ball sucked by
the suction force F.sub.R and the ball is going to move around the
point O and come off the ball arrangement plane. Either of the
force F.sub.g and the suction force F.sub.R acts on the centroid of
the ball (that coincides with the geometric center of the ball in
this example).
[0033] At the time when the ball is going to be moved by the force
F.sub.g, the resultant force of the force F.sub.g, the suction
force F.sub.R, and the drag F.sub.o becomes zero so that these
three forces balance. This state gives the following conditions:
F.sub.R=F.sub.o sin .theta.; and F.sub.g=F.sub.o cos .theta.. From
the above conditions, F.sub.g/cos .theta.=F.sub.R/sin .theta..
Hence, F.sub.g=F.sub.R/tan .theta. (1).
[0034] From the relation between the radius r.sub.a of the suction
hole and the radius r.sub.b of the ball,
r.sub.b.sup.2=X.sup.2+r.sub.a.sup.2.
[0035] From the above expression,
X=(r.sub.b.sup.2-r.sub.a.sup.2).sup.1/2.
Hence, tan .theta.=(r.sub.b.sup.2-r.sub.a.sup.2).sup.1/2/r.sub.a
(2).
[0036] From the above expressions (1) and (2),
F.sub.g=F.sub.Rr.sub.a/(r.sub.b.sup.2-r.sub.a.sup.2).sup.1/2 (3).
Actually, because there is a gap between the suction hole and the
ball, F.sub.R has a smaller value than the value calculated with
the expression (3). Thus the expression (3) should be modified
using a coefficient Q as follows:
F.sub.g=QF.sub.Rr.sub.a/(r.sub.b.sup.2-r.sub.a.sup.2).sup.1/2 (4).
The intensity of the gas blow is regulated with this expression (4)
so that only excess balls may be fully removed while the normal
balls exactly sucked onto the respective suction holes remain
intact.
[0037] The coefficient Q is determined within a certain range in
consideration of some conditions for implementation of the present
invention such as the radius of the suction hole and the radius of
the ball. Some experimental results indicate that the coefficient Q
is preferably 0.8 or less, more preferably, 0.6 or less.
[0038] The force F.sub.g that is applied to the ball by the gas
blow is also given by the following expression:
F.sub.g=(1/2).rho.v.sup.2S.sub.b (5) where .rho. represents the gas
density, v does the gas velocity, and S.sub.b does the vertical
sectional area of the ball portion protruding beyond the ball
arrangement plane. From the expressions (4) and (5),
(1/2).rho.v.sup.2S.sub.b=QF.sub.Rr.sub.a/(r.sub.b-r.sub.a.sup.2-
).sup.1/2. Hence,
v=(2QF.sub.Rr.sub.a/(.rho.S.sub.b(r.sub.b.sup.2-r.sub.a.sup.2).sup.1/2)).-
sup.1/2 (6) It was found that gas blow having its velocity more
than the value v calculated with the expression (6) might blow some
normal balls off. Contrastingly, gas blow having its velocity less
than the value v calculated with the expression (6) never blows any
normal ball off.
[0039] Besides, a gas nozzle whose width or inclination angle to
the ball arrangement plane has been properly set brings about very
effective removal of excess balls. In addition, cooperation with a
vibrator for applying fine vibration to the carrier board can more
improve the removal efficiency.
[0040] According to the present invention, removed excess balls are
collected without being scattered. Thus the machine trouble due to
scattered balls can be avoided.
[0041] According to another aspect of the present invention, balls
that have been temporarily arranged in the ball arrangement region
of the carrier board by being sucked onto the carrier board by the
above suction force F.sub.g are further sucked in a different
direction by a suction force less than the suction force F.sub.g.
Also by this manner, excess balls other than the normal balls
exactly sucked onto the carrier board can be removed.
[0042] An embodiment of the present invention will be described
below with reference to FIGS. 4 to 7. In this embodiment,
components corresponding to those of the above prior art are
denoted by the same reference numerals as those of the prior
art.
[0043] This embodiment is for transferring and bonding spherical
bumps onto electrodes of a semiconductor device, a printed circuit
board, or the like. Thus the apparatus according to this embodiment
comprises a ball arranging unit 1, a carrier board conveying
mechanism 2, ball inspection means 3, and a bonding stage 4, like
the prior art apparatus shown in FIGS. 1A and 1B.
[0044] In this embodiment, balls are sucked onto a carrier board
and temporarily arranged in a ball arrangement region of the
carrier board. The balls are then transported to the bonding stage
4 where the balls are transferred onto an objective substance with
their positions being adjusted. FIG. 4 shows a state that fine
metallic balls B are temporarily arranged on the carrier board 15.
The balls B picked up from a ball stocking tray 11 (see FIG. 2) are
sucked onto suction holes 14 of the carrier board 15. Each suction
hole 14 communicates with a reduced pressure space 13a of ball
suction means 13, which is connected to a vacuum pump 17 through a
pressure regulator 18. Although not shown in FIG. 4, such a
vibrator 16 as described before (see FIG. 2) is provided for
applying fine vibration to the ball suction means 13.
[0045] The apparatus of this embodiment is provided with a gas
nozzle 20 disposed near the carrier board 15. The gas nozzle 20 is
for applying gas blow to the ball arrangement region of the carrier
board 15 so as to remove excess balls other than the normal balls
exactly sucked onto the respective suction holes 14 in the ball
arrangement region, as described later. The gas nozzle 20 is
connected to a gas source 21 through a gas flow rate or pressure
regulator 22. Gas used in this embodiment is preferably air or
inert gas such as argon or nitrogen gas.
[0046] When air is used, the humidity is preferably 60% or less,
more preferably, 50% or less. In particular, dry air whose humidity
is 20% or less is most preferable. The humidity of 20% or less can
prevent a excess ball from adhering through the moisture on the
surface of the carrier board. If gas blow is applied when balls are
sucked onto the carrier board, balls in the ball stocking tray 11
may be blown off. Thus gas blow is preferably applied after balls
have been sucked onto the carrier board.
[0047] The gas nozzle 20 can be moved relatively to the carrier
board 15. For this purpose, a nozzle support system (not shown) is
provided which supports the gas nozzle 20 so as to be movable. The
gas nozzle 20 can be moved as shown by a broken arrow in FIG. 4.
Alternatively, the gas nozzle 20 may be fixed at a certain position
and the carrier board 15 may move over the gas nozzle 20 while the
carrier board 15 is conveyed from the ball arranging unit 1 to the
ball inspection means 3 by the carrier board conveying mechanism 2
as shown in FIG. 1. In either case, by the gas nozzle 20 being
moved relatively to the carrier board 15, gas blow can be applied
thoroughly and evenly to the ball arrangement region of the carrier
board 15.
[0048] The gas nozzle 20 is preferably inclined in relation to the
ball arrangement plane on the carrier board 15 as shown in FIG. 4.
The inclination angle .theta. of the gas nozzle 20 is preferably
within the range of 5.degree. to 175.degree., more preferably,
within the range of 20.degree. to 160.degree.. The inclination
angle .theta. can freely be set through the nozzle support system,
i.e., the direction of gas blow from the gas nozzle 20 can freely
be controlled. The above range of the inclination angle .theta.
contains the case that the gas nozzle 20 is perpendicular to the
ball arrangement plane. In case of .theta.=0.degree., i.e., in case
that gas blow is applied just laterally, however, setting of the
gas nozzle 20 may become difficult because the ball size is very
small in general. For this reason, the above range of 5.degree. to
175.degree. is practical.
[0049] As shown in FIG. 5A, the gas nozzle 20 preferably has its
gas outlet 20a whose width W is broader than the ball arrangement
width w on the carrier board 15. In the example of FIG. 5A, while
the gas nozzle 20 is moved perpendicularly to the drawing paper
surface, it can apply gas blow all over the ball arrangement region
of the carrier board 15. In this example, W is larger than w by
about 10 to 20 mm. Alternatively, W.ltoreq.w, i.e., the width of
the gas nozzle 20 may be not more than the ball arrangement
width.
[0050] In this embodiment also usable are gas nozzles of various
other shapes, e.g., as shown in FIGS. 5B to 5E. Further, a slender
pipe gas nozzle can also be used. In case of the gas nozzle of FIG.
5B, when one of the vertical and lateral slits is put along the
relative movement direction of the gas nozzle, removal efficiency
perpendicular to the movement direction is improved. In case of the
gas nozzle of FIG. 5C, gas blow can be concentrated at the position
corresponding to each nozzle opening. In case of the gas nozzle of
FIG. 5D or 5E, gas blow can be applied to a broader region. From
among various gas nozzle shapes including the above examples, the
most effective one can be selected in accordance with the ball
arrangement pattern used.
[0051] As shown in FIG. 6A, the gas nozzle 20 is preferably a slit
nozzle whose gas outlet is formed into a slit. This makes the
control of gas blow easy. The slit width of the gas outlet 20a of
the gas nozzle 20 is preferably within the range of about 0.1 to 10
mm. The gas outlet portion may have a tapered section toward the
front end (FIG. 6B) or vice versa (FIG. 6C).
[0052] Not a single gas nozzle but two or more separate gas nozzles
may be used. If two or more separate gas nozzles different in
nozzle shape, attachment angle or direction, applying gas blow, or
the like, are used, then effect to various forms of excess balls
may be improved.
[0053] In this embodiment, balls B may be temporarily arranged on
the carrier board 15 into an arrangement pattern as shown by solid
lines in FIG. 7, which pattern corresponds to a rectangular outline
along the periphery of the carrier board 15. Alternatively, the
pattern may include the positions as shown by broken lines.
[0054] In this embodiment, balls are sucked onto the respective
suction holes 14 of the carrier board 15 and temporarily arranged
thereon. Gas blow is then applied from the gas nozzle 20 to the
ball arrangement region of the carrier board 15 as shown in FIG. 4
so that normal balls B exactly sucked onto the respective suction
holes 14 remain intact and excess balls other than the normal balls
are removed. At this time, by having properly regulated the
inclination angle .theta. of the gas nozzle 20 and the flow rate or
pressure of the gas blow, only the excess balls can surely be
removed.
[0055] In this manner, application of gas blow from the gas nozzle
20 brings about high efficiency of excess ball removal. However,
cooperation with the vibrator 16 that applies vibration to the
carrier board 15 is more effective. By applying supersonic
vibration to the suction means 13 through the vibrator 16, the
carrier board 15 is finely vibrated and excess balls are surely
removed. When both of gas blow and fine vibration are used, the gas
blow may be applied before or after the fine vibration. Of course,
the gas blow and the fine vibration may be applied at once.
[0056] FIGS. 8A and 8B show another embodiment of the present
invention including excess ball collecting means. After sucking
balls, a suction head is stopped at a position over a gas nozzle
and lowered into a collecting vessel 5, in which gas blow is
applied so as to remove excess balls. Removed excess balls are
collected in the collecting vessel 5 with which the gas nozzle is
integrated. Thus the removed excess balls are never scattered in
the other portions of the apparatus. If cut-off portions for
allowing the suction head to pass are provided in the collecting
vessel 5 of FIGS. 8A and 8B, excess balls can be removed with gas
blow and collected into the collecting vessel 5 without stopping
the suction head. Of course, the collecting vessel 5 may be
provided separately from the gas nozzle. Besides, such collecting
means is not a vessel but an adhesive tape or the like to which
excess balls adhere.
[0057] As described before in connection with the prior art, there
is a case that excess balls can not fully be removed only by fine
vibration through the vibrator 16 due to soils or the like.
According to the present invention, however, since gas blow is
applied in addition to such fine vibration, excess balls can
completely and surely be removed. In this case, because not so
intense vibration through the vibrator 16 is required for full
removal, each ball surface is prevented from being damaged.
[0058] According to another aspect of the present invention, balls
temporarily arranged on the carrier board 15 are further sucked in
a direction different from the suction holes so as to remove excess
balls other than the normal balls exactly sucked onto the
respective suction holes. An embodiment of the present invention in
which excess balls are removed by suction will be described
below.
[0059] In this embodiment, in place of the gas nozzle 20 as
described above, a suction nozzle is disposed near the carrier
board 15. Balls temporarily arranged on the carrier board 15 are
sucked by the suction nozzle in a direction different from the
suction holes of the carrier board 15. The suction nozzle may have
substantially the same basic structure as the gas nozzle 20. The
suction nozzle is designed to be movable relatively to the carrier
board 15. The inclination angle or the like of the suction nozzle
in relation to the ball arrangement plane can be set properly.
[0060] In this embodiment, the suction nozzle is connected to a
vacuum source (pump), a pressure regulator, or the like, and its
suction force is controllable. The suction nozzle may be a slit
nozzle but it must have an inner diameter allowing excess balls to
be sucked into the nozzle.
[0061] In this embodiment, while the suction nozzle is moved
relatively to the carrier board 15, balls temporarily arranged on
the carrier board 15 are sucked by the suction nozzle in a
direction different from the suction holes of the carrier board 15
so as to remove excess balls. Because the excess balls are sucked
into the nozzle, the removed excess balls are never scattered in
the other portions of the apparatus. This embodiment is thus
convenient because separate excess ball collecting means is not
required.
[0062] Also in this embodiment, cooperation with the vibrator 16
that applies vibration to the carrier board 15 is more effective.
Like the above-described embodiment, by applying supersonic
vibration to the carrier board 15 through the vibrator 16, the
carrier board 15 is finely vibrated and excess balls are surely and
efficiently removed by suction. When both of suction for removal
and fine vibration are used, the suction for removal may be
performed before or after applying the fine vibration. Of course,
the suction for removal may be performed simultaneously with
application of the fine vibration.
[0063] Excess balls are preferably removed in a state that balls
are fully firmly fixed to the ball arrangement region of the
carrier board. When excess balls are removed by gas blow or
suction, for ensuring that the normal balls exactly sucked onto the
respective suction holes are left intact, the suction force at each
suction hole must be sufficiently high. Besides, it is also
effective that each suction hole has not a tapered shape but such a
shape that the edge portion of the outlet opening comes into
contact with the ball being sucked so as to obtain high adhesion.
If the suction force is too high, however, the ball too strongly
adheres to the edge portion of the suction hole and the ball may
become difficult to drop off when it should be transferred onto the
objective substance. Therefore, when the ball is to be transferred,
it is effective that the vacuum for sucking the ball onto the
suction hole is broken or the pressure is increased beyond the
atmospheric pressure and further vibration is applied to the
carrier board. The vibration to be applied may be either vertical
or lateral, though it is preferable to use both at once. The
vibration frequency is preferably within the range of 5 to 500 kHz,
more preferably, within the range of 20 to 200 kHz. Supersonic
vibration is preferable. Too low vibration frequency results in
little dropping-off effect while too high vibration frequency may
cause local deformation of or damage on the ball surface. The
timing of applying vibration is preferable when balls are brought
into contact with flux applied on the objective substance onto
which the balls are to be transferred. The thickness of the flux is
preferably within the range of 1/8 to 2/3 of the ball diameter. A
thickness less than 1/8 results in little adhesion so it little
contributes the ball transference while a thickness more than 2/3
may contaminate the carrier board.
Experimental Results
[0064] Experimental results according to the present invention will
be described below. In this experiment, gas blow was applied
through the gas nozzle 20 as described above.
[0065] In this experiment, nitrogen gas was used as gas to be blown
against the ball arrangement region of the carrier board 15. The
N.sub.2 gas flow rate was within the range of 20 to 40 l/min. The
inclination angle .theta. of the gas nozzle 20 was set within the
range of 45.degree. to 135.degree.. Balls B having a diameter of 30
to 300 .mu.m were used. The balls B were sucked by a suction
pressure of -350 to -750 mmHg. The distance of the gas nozzle 20
from the ball arrangement plane on the carrier board 15 was about
0.1 to 10.0 mm.
[0066] Balls B were sucked onto the carrier board 15 under the
above conditions and then supersonic fine vibration was applied to
the carrier board 15. In 50 times of examination, one to ten excess
balls remained. The carrier board 15 under the same conditions was
passed over the gas nozzle 20 and N.sub.2 gas blow was applied to
the carrier board under the above conditions. As a result, the
number of excess balls remaining was zero, i.e., excess balls could
be fully removed.
[0067] The following tables 1 to 4 show results of various
experiments for the above-described Q value. It was found that the
Q value is preferably 0.8 or less, more preferably, 0.6 or less.
TABLE-US-00001 TABLE 1 r.sub.b (.mu.m) r.sub.a (.mu.m) Q value
normal ball held 50 > r.sub.b .gtoreq. 10 1/10- 9/10 .gtoreq.0.
9 X of r.sub.b 0.9 .gtoreq. Q > 0.8 .DELTA. 0.8 .gtoreq. Q >
0.7 .largecircle. 0.7 .gtoreq. Q > 0.6 .largecircle. 0.6
.gtoreq. Q > 0.5 .circleincircle. 0.5 .gtoreq. Q > 0.4
.circleincircle. 0.4 .gtoreq. Q > 0.3 .circleincircle. 0.3
.gtoreq. Q > 0.2 .circleincircle. 0.2 .gtoreq. Q > 0.1
.circleincircle. 0.1 .gtoreq. Q > 0.0 .circleincircle.
[0068] TABLE-US-00002 TABLE 2 r.sub.b (.mu.m) r.sub.a (.mu.m) Q
value normal ball held 100 > r.sub.b .gtoreq. 50 1/10- 9/10
.gtoreq. 0.9 X of r.sub.b 0.9 .gtoreq. Q > 0.8 X 0.8 .gtoreq. Q
> 0.7 .largecircle. 0.7 .gtoreq. Q > 0.6 .largecircle. 0.6
.gtoreq. Q > 0.5 .circleincircle. 0.5 .gtoreq. Q > 0.4
.circleincircle. 0.4 .gtoreq. Q > 0.3 .circleincircle. 0.3
.gtoreq. Q > 0.2 .circleincircle. 0.2 .gtoreq. Q > 0.1
.circleincircle. 0.1 .gtoreq. Q > 0.0 .circleincircle.
[0069] TABLE-US-00003 TABLE 3 r.sub.b (.mu.m) r.sub.a (.mu.m) Q
value normal ball held 200 > r.sub.b .gtoreq. 100 1/10- 9/10
.gtoreq.0.9 X of r.sub.b 0.9 .gtoreq. Q > 0.8 X 0.8 .gtoreq. Q
> 0.7 .largecircle. 0.7 .gtoreq. Q > 0.6 .largecircle. 0.6
.gtoreq. Q > 0.5 .circleincircle. 0.5 .gtoreq. Q > 0.4
.circleincircle. 0.4 .gtoreq. Q > 0.3 .circleincircle. 0.3
.gtoreq. Q > 0.2 .circleincircle. 0.2 .gtoreq. Q > 0.1
.circleincircle. 0.1 .gtoreq. Q > 0.0 .circleincircle.
[0070] TABLE-US-00004 TABLE 4 r.sub.b (.mu.m) r.sub.a (.mu.m) Q
value normal ball held 300 > r.sub.b .gtoreq. 200 1/10- 9/10
.gtoreq.0.9 X of r.sub.b 0.9 .gtoreq. Q > 0.8 .DELTA. 0.8
.gtoreq. Q > 0.7 .largecircle. 0.7 .gtoreq. Q > 0.6
.largecircle. 0.6 .gtoreq. Q > 0.5 .circleincircle. 0.5 .gtoreq.
Q > 0.4 .circleincircle. 0.4 .gtoreq. Q > 0.3
.circleincircle. 0.3 .gtoreq. Q > 0.2 .circleincircle. 0.2
.gtoreq. Q > 0.1 .circleincircle. 0.1 .gtoreq. Q > 0.0
.circleincircle.
[0071] Each experiment in relation to the tables 1 to 4 was done
using a carrier board with 300 suction holes. Inspection was done
n=100 times per experiment. The respective symbols used in the
tables represent the following experimental results:
[0072] X: removal of 20 or more normal balls occurs five or more
times
[0073] .DELTA.: removal of 10 or more normal balls occurs five or
more times
[0074] .largecircle.: removal of one or more normal balls occurs
one or more times
[0075] .circleincircle.: no normal ball was removed
[0076] Gas blow through the gas nozzle 20 may be applied not only
with the direction, the flow rate, etc., being fixed but also with
those being changed at predetermined timings or cycles.
[0077] The balls B to be arranged on the carrier board 15 can be
made of various materials such as gold or solder. The present
invention is effective to balls of any material.
[0078] As described above, according to the present invention,
balls are sucked onto a carrier board and they are temporarily
arranged in a ball arrangement region of the board. Gas blow is
applied to the balls or the balls are sucked in a direction
opposite to the carrier board so that only excess balls other than
the normal balls exactly sucked onto the ball arrangement region
are fully removed. According to the present invention, there is
little possibility that the surface of each normal ball is damaged,
so the quality is improved.
[0079] Besides, by using gas blow in cooperation with vibrating
means, even excess balls that can not be removed only by vibration
can be removed. Thus, more effective removal of excess balls is
realized. As a result, the yield in mass production of spherical
bumps is improved. Besides, since the ball surface is not damaged,
erroneous detection in the subsequent inspection process is
prevented. This improves the yield of products onto which balls
have been transferred.
* * * * *