U.S. patent application number 11/411037 was filed with the patent office on 2006-11-02 for conductive ball mounting apparatus.
This patent application is currently assigned to SHIBUYA KOGYO CO., LTD. Invention is credited to Kazuo Niizuma.
Application Number | 20060244155 11/411037 |
Document ID | / |
Family ID | 36589967 |
Filed Date | 2006-11-02 |
United States Patent
Application |
20060244155 |
Kind Code |
A1 |
Niizuma; Kazuo |
November 2, 2006 |
Conductive ball mounting apparatus
Abstract
A conductive ball mounting apparatus for mounting conductive
balls by providing an array mask having through holes, into which
conductive balls are to enter, above a mounting target placed on a
stage, by arranging a ball reservoir having an opening for
reserving a plurality of conductive balls, in the bottom, by moving
the ball reservoir along the array mask, by dropping the conductive
balls into the individual through holes of the array mask, adopts
the following means. Firstly, the conductive ball mounting
apparatus comprises moving means for moving the array mask and the
stage relative to each other in horizontal directions. Secondly,
the positions of the conductive balls in the through holes are
arranged by finely moving at least one of the array mask and the
stage relative to each other in the horizontal directions after the
balls were dropped.
Inventors: |
Niizuma; Kazuo;
(Kanazawa-shi, JP) |
Correspondence
Address: |
SUGHRUE MION, PLLC
2100 PENNSYLVANIA AVENUE, N.W.
SUITE 800
WASHINGTON
DC
20037
US
|
Assignee: |
SHIBUYA KOGYO CO., LTD
|
Family ID: |
36589967 |
Appl. No.: |
11/411037 |
Filed: |
April 26, 2006 |
Current U.S.
Class: |
257/780 ;
257/E21.508 |
Current CPC
Class: |
H05K 2203/0557 20130101;
B23K 3/0623 20130101; B23K 2101/42 20180801; H01L 2924/15787
20130101; H01L 2224/0401 20130101; H01L 2924/00 20130101; H01L
2924/00 20130101; H01L 2224/0401 20130101; H01L 24/11 20130101;
H01L 2924/01005 20130101; H01L 2924/12042 20130101; H01L 2924/00011
20130101; H01L 2924/15787 20130101; H01L 2924/00011 20130101; H01L
2924/01006 20130101; H01L 2924/014 20130101; H01L 2924/30105
20130101; H01L 2924/12042 20130101; H05K 2203/041 20130101; H05K
3/3478 20130101; H01L 2924/00014 20130101; H01L 2224/13099
20130101; H01L 2224/11334 20130101; H01L 21/4853 20130101; H01L
2924/00014 20130101; H01L 2924/01033 20130101 |
Class at
Publication: |
257/780 |
International
Class: |
H01L 23/48 20060101
H01L023/48; H01L 23/52 20060101 H01L023/52; H01L 29/40 20060101
H01L029/40 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 28, 2005 |
JP |
P2005-132062 |
Claims
1. A conductive ball mounting apparatus for mounting a conductive
ball comprising: an array mask having a through hole, into which a
conductive ball is to enter, the array mask being provided above a
mounting target placed on a stage; a ball reservoir having an
opening for reserving a plurality of conductive balls in the bottom
thereof, the ball reservoir moving along the array mask and
dropping the conductive ball into the each through hole of the
array mask; and moving means for moving at least one of the array
mask and the stage relative to each other in a horizontal
direction, wherein a position of the conductive ball in the through
hole is arranged by moving at least one of the array mask and the
stage relative to each other in a horizontal direction after the
ball was dropped.
2. The conductive ball mounting apparatus according to claim 1,
wherein the moving at least one of the array mask and the stage
comprises a straight movement in a horizontal direction.
3. The conductive ball mounting apparatus according to claim 1,
wherein the moving at least one of the array mask and the stage
further comprises a sequential movement in a direction
perpendicular to the horizontal direction.
4. The conductive ball mounting apparatus according to claim 1,
wherein a distance of the moving at least one of the array mask and
the stage is at least a difference between a diameter of the
conductive ball and a diameter of the through hole.
5. The conductive ball mounting apparatus according to claim 4,
wherein the moving at least one of the array mask and the stage
further comprises a movement in another horizontal direction
opposite to the horizontal direction by at least one half of a
difference between the diameter of the conductive ball and the
diameter of the through hole.
6. The conductive ball mounting apparatus according to claim 1,
wherein the moving at least one of the array mask and the stage
comprises a movement to turn in a horizontal plane.
7. The conductive ball mounting apparatus according to claim 1,
wherein, after the moving at least one of the array mask and the
stage, the at least one of the array mask and the stage is so moved
that the conductive ball leaves the inner wall of the through hole.
Description
[0001] This application is based on Japanese Patent Application No.
2005-132062, which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to an improvement in an
apparatus for mounting a number of conductive balls by moving a
ball reservoir for reserving the conductive balls along the upper
face of an array mask and, more particularly, to a conductive ball
mounting apparatus which is improved with a main view to improving
the positional precision of the conductive balls in the through
holes of the array mask.
[0004] 2. Description of the Related Art
[0005] As the conductive ball mounting apparatus for mounting
conductive balls after the adhesive material was applied to
individual electrodes formed in a predetermined array pattern on
the mounting target, there exists in the related art an apparatus
for mounting the conductive balls, after sucked, arrayed and
adsorbed by the ball mounting head having an array plate, on the
individual electrodes on the mounting target, as disclosed in
JP-A-2001-358451. However, as the mounting target product such as a
wafer becomes larger, the number of solder balls to be mounted at
one time exceeds one million. This makes it difficult at present to
reduce the defects in the array of solder balls and the defects at
the mounting time.
[0006] As disclosed in JP-A-2002-538970 and Japanese Patent No.
3177370, therefore, there has been provided an apparatus, in which
an electronic substrate or a mounting target printed with flux is
provided with an array mask and in which solder balls are directly
dropped onto electrodes of the electronic substrate. As compared
with the diameter of the conductive balls, however, the diameter of
the through holes of the array mask is larger. This raises a
problem that the positions of the conductive balls in the through
holes are not arranged merely by dropping the conductive balls into
the through holes of the array mask.
SUMMARY OF THE INVENTION
[0007] The present invention has an object to solve the
aforementioned problem and to provide a conductive ball mounting
apparatus which is enabled by arranging the positions of conductive
balls in through holes to improve the precision even in positions
for mounting a large number of conductive balls.
[0008] In order to solve the aforementioned problem, a first aspect
of the invention adopts the following means in the conductive ball
mounting apparatus for mounting a conductive ball comprising an
array mask having a through hole, into which a conductive ball is
to enter, the array mask being provided above a mounting target
placed on a stage, a ball reservoir having an opening for reserving
a plurality of conductive balls in the bottom thereof, the ball
reservoir moving along the array mask and dropping the conductive
balls into the through hole of the array mask, adopts the following
means.
[0009] Firstly, the conductive ball mounting apparatus comprises
moving means for moving at least one of the array mask and the
stage relative to each other in a horizontal direction.
[0010] Secondly, a position of the conductive ball in the through
hole is arranged by moving at least one of the array mask and the
stage relative to each other in a horizontal direction after the
balls was dropped.
[0011] According to a second aspect of the invention, the moving at
least one of the array mask and the stage comprises a straight
movement in a horizontal direction. According to a third aspect of
the invention, the moving at least on of the array mask and the
stage further comprises a sequential movement in a direction
perpendicular to the horizontal directions. According to a fifth
aspect of the invention, the moving at least one of the array mask
and the stage comprises a movement to turn in a horizontal
plane.
[0012] According to a fourth aspect of the invention, a distance of
the moving at least one of the array mask and the stage is at least
a difference between a diameter of the conductive ball and a
diameter of the through hole. According to a sixth aspect of the
invention, after the moving at least one of the array mask and the
stage, the at least one of the array mask and the stage is so moved
that the conductive ball leaves the inner wall of the through
hole.
[0013] In the first aspect of the invention, the positions of the
conductive balls in the through holes are arranged by finely moving
the array mask and the stage relative to each other in the
horizontal directions after the balls were dropped. As a result,
the conductive ball mounting apparatus can improve the positioning
precision for mounting the conductive balls. Moreover, the
apparatus mounts the conductive balls in position by arranging the
array mask having the through holes for dropping the conductive
balls, above the mounting target, and by moving the ball reservoir
to reserve the numerous conductive balls, by the ball reservoir
moving means, along the array mask. As a result, the apparatus can
precisely mount the numerous conductive balls, the number of which
increases as the mounting target products such as wafers are
large-sized.
[0014] In the second, third or fifth aspect of the invention, the
fine movements of the array mask and the stage are straight
movements in one direction of horizontal directions, sequential
movements in two directions perpendicular in the horizontal
directions, or movements to turn in a horizontal plane. Even at
less steps or by smaller actions, it is possible to improve the
mounting position precision of the conductive balls better. In the
fourth aspect of the invention, moreover, the fine moving distances
of the array mask and the stage in one direction are at least the
difference between the conductive ball diameter and the through
hole diameter. In the sixth aspect of the invention, the array mask
and the stage are finely moved relative to each other and are then
so moved that the conductive balls may leave the inner walls of the
through holes. As a result, it is possible to improve the mounting
position precision of the conductive balls better.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic top plan view showing the entirety of
a solder ball mounting apparatus according to the embodiment;
[0016] FIG. 2 is a schematic top plan view of the case, in which a
wafer feeding unit and a wafer housing unit are disposed in the
same direction;
[0017] FIG. 3 is a partially sectional, explanatory side elevation
showing a ball mounting unit;
[0018] FIG. 4 is a top plan view of the ball mounting unit;
[0019] FIGS. 5A-5C are explanatory views showing a fine moving
procedure of the ball array mask and the wafer transfer stage;
and
[0020] FIG. 6 is a front elevation showing the movement of a wafer
transfer stage.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0021] An embodiment of the invention is described in the following
with reference to the accompanying drawings. In the invention, a
semiconductor wafer (as will be simplified into the wafer), an
electronic circuit substrate or a ceramic substrate is exemplified
as a target for mounting conductive balls, but a wafer 14 is used
in the embodiment. Moreover, electrodes 38 are formed in a
predetermined pattern on the surface of the mounting target. On the
other hand, flux, solder paste or a conductive adhesive is used as
an adhesive material.
[0022] FIG. 1 is a schematic top plan view showing the entirety of
a solder ball mounting apparatus 1. This solder ball mounting
apparatus 1 includes a carry-in wafer transfer unit 2, a flux
printing unit 3, a ball mounting unit 4, and a carry-out wafer
transfer unit 5. A wafer feeding unit 6, a primary alignment unit 7
and a carry-in robot 8 exist at the pre-step of the solder ball
mounting apparatus 1, and an inversion unit 9, a wafer housing unit
10 and a carry-out robot 11 exist at the post-step of the solder
ball mounting apparatus 1.
[0023] The primary alignment unit 7 for the pre-step turns the
wafer 14 in a horizontal plane to detect the position of an
orientation flat or notch of the wafer 14 thereby to correct the
position of the wafer 14 approximately and to direct the wafer 14
to be mounted on the wafer transfer unit 2, in a predetermined
direction. On the other hand, the inversion unit 9 for the
post-step turns the wafer 14 in the horizontal direction so that
the wafer 14 is turned to bring its orientation flat or notch to a
predetermined position and is housed in a magazine 32.
[0024] The solder ball mounting apparatus 1 is equipped with a
wafer transfer stage 12 and a transfer passage 13 for transferring
the wafer 14 from the wafer transfer unit to the flux printing unit
3, the ball mounting unit 4 and the wafer transfer unit 5. The
transfer passage 13 is equipped with an X-axis (longitudinal, as
shown) drive mechanism 40 of the transfer stage 12.
[0025] The flux printing unit 3 is equipped with a flux feeding
device 16, a printing mask 15 for printing flux, or the adhesive
material on the wafer 14, and vertical observation cameras 31 for
observing the alignment marks of the wafer 14 and the printing mask
15 thereby to register the wafer 14 and the printing mask 15. The
printing mask 15 has through holes formed along with the pattern of
the electrodes 38 on the wafer 14. Two (not-shown) alignment marks
are formed at two portions on the lower face of the printing mask
15 in a through hole forming area 36. The printing mask 15 is
applied to a molding box 17 and is held by a fixing unit such as a
frame. The flux feeding device 16 moves the (not-shown) squeezee
along the upper face of the printing mask 15 so that the flux is
printed in the through holes of the printing mask 15 and fed onto
the electrodes 38 of the wafer 14. Here, numeral 33 in the drawing
designates a cleaning unit for cleaning off the flux adhered to the
printing mask 15.
[0026] The ball mounting unit 4 is equipped with a solder ball
feeding device 20, a ball array mask 19 having through holes 18
formed along with the pattern of the electrodes 38 on the wafer 14,
and vertical observation cameras 34 for observing the alignment
marks of the wafer 14 and the ball array mask 19 thereby to
register them.
[0027] The ball array mask 19 has a thickness substantially equal
to the diameter of solder balls 21 to be fed, and the through holes
18 have a diameter slightly larger than that of the solder balls.
Like the printing mask 15, the ball array mask 19 has the
(not-shown) alignment marks formed at two portions on the lower
face of the through hole forming area 36. The ball array mask 19 is
adhered to a molding box 37 and is held by a fixing unit such as
the frame.
[0028] The solder ball feeding device 20 is equipped with a ball
hopper 22 for reserving a number of solder balls 21, a ball cup 23
for dropping the solder balls 21 into the ball array mask 19, a
mask height detecting sensor 27, and a carriage unit 24 not only
for moving the ball cups 23 along an X-axis guide 25 and a Y-axis
guide 26 but also for displacing the same in a Z-axis direction.
Here, the ball hopper 22 is exchanged according to the size and
material of the solder balls 21. Inside of and in the lower portion
of the inner wall face of the ball cup 23, there is formed a recess
35 for causing the solder balls 21 housed therein to circulate, as
indicated by an arrow in the ball cup 23 in FIG. 3.
[0029] The mask height detecting sensor 27 may be of either the
contact type or the non-contact type. Specifically, a laser sensor
or an electrostatic capacity sensor is used as the mask height
detecting sensor 27. The mask height detection is made by bringing
the molding box 37 of the ball array mask 19, when exchanged at an
initial setting time or at a mold exchanging time, into abutment
against a stopper or the like, and by positioning and fixing the
molding box 37 by means of a clamp. Specifically, after the ball
array mask 19 was fixed, the ball cup 23 empty of the solder balls
21 is moved sequentially on a plurality of height detection points
preset outside of the through hole forming area 36, and the height
of the upper face of the ball array mask 19 is measured.
[0030] On the other hand, the height of the upper face of the ball
array mask 19 in the through hole forming area 36 is determined by
calculations. Moreover, the heights at the individual positions are
calculated by considering the weight which is applied when the
solder balls 21 are housed in the ball cup 23. At the ball mounting
time, the ball cup 23 is so moved on the basis of the determined
height, while being controlled by the moving unit 24, that the
clearance between the upper face of the ball array mask 19 and the
lower face of the ball cup 23 may not exceed a predetermined
distance.
[0031] The wafer transfer stage 12 is a stage for placing the wafer
14 thereon and is mounted on the X-axis drive mechanism 40 through
a Y-axis drive mechanism 28 acting as moving means in the direction
(i.e., the Y-axis direction) perpendicular to the transfer passage
13 of the wafer 14, a .theta.-axis drive mechanism 29 acting as
turning means, and a Z-axis drive mechanism 30 acting as vertically
moving means.
[0032] The actions of the solder ball mounting apparatus 1 of the
embodiment are described. At first, the wafer 14 to have the solder
balls 21 mounted thereon is housed in the magazine 32 of the wafer
feeding unit 6. Then, one wafer 14 is extracted from the magazine
32 of the wafer feeding unit 6 and carried in the primary alignment
unit 7. In this primary alignment unit 7, the wafer 14 is turned to
detect the position of the orientation flat or notch thereby to
correct the position of the wafer 14 approximately and to set the
orientation flat or notch at a predetermined position.
Subsequently, the wafer 14 is carried by the carry-in robot 8 from
the primary alignment unit 7 to the wafer transfer stage 12 on
standby at the wafer transfer unit 2.
[0033] The wafer transfer stage 12 having the wafer 14 mounted
thereon is moved by the X-axis drive mechanism 40 along the
transfer passage 13 to the flux printing unit 3 and stops at a
predetermined position. Here, the alignment marks of the wafer 14
and the printing mask 15 are individually observed by the vertical
observation cameras 31, and the wafer transfer stage 12 is so
positioned in the X-axis direction by the X-axis drive mechanism 40
of the transfer passage 13, in the Y-axis direction by the Y-axis
drive mechanism 28 and in the .theta.-axis direction by the
.theta.-axis drive mechanism 29 that the electrodes 38 of the wafer
14 and the through holes of the printing mask 15 may be centrally
aligned. After positioned, the wafer transfer stage 12 is raised by
the Z-axis drive mechanism 30 so that it is stopped at a
predetermined height position with respect to the printing mask 15
having been prepared with the flux. In this state, the printing
mask 15 is fed with the flux at its one end portion in the Y-axis
direction, and the squeezee is moved toward the other end portion
to print the flux on the electrodes 38 of the wafer 14 from the
through holes of the printing mask 15.
[0034] After the flux-printing, the wafer transfer stage 12 is
moved downward by the Z-axis drive mechanism 30 and is moved to the
ball mounting unit 4 by the X-axis drive mechanism 40 so that it is
stopped at a predetermined position. Here, the alignment marks of
the wafer 14 and the ball array mask 19 are also individually
observed by the vertical observation cameras 34, and the wafer
transfer stage 12 is positioned in the X-axis direction by the
X-axis drive mechanism 40 of the transfer passage 13, and in the
Y-axis direction and in the .theta.-axis direction by the Y-axis
drive mechanism 28 and the .theta.-axis drive mechanism 29,
respectively. After this, the wafer transfer stage 12 is moved
upward by the Z-axis drive mechanism 30 so that it is stopped while
leaving the predetermined clearance from the ball array mask
19.
[0035] As shown in FIG. 3, the ball cup 23 moves over the ball
array mask 19 to drop the solder balls 21 into the through holes 18
of the ball array mask 19 so that the solder balls 21 are mounted
on the wafer 14. After this ball dropping operation, the wafer
transfer stage 12 is finely moved straight (in the X-axis
direction) with respect to the ball array mask 19 to correct the
positions of the solder balls 21 in the through holes 18 thereby to
arrange the positions of the solder balls 21. Here, it is preferred
that the fine movement distance of the wafer transfer stage 12 is
at least the distance of the difference between the diameter of the
solder ball 21 and the diameter of the through holes 18.
[0036] FIGS. 5A to 5C are explanatory views showing one example of
a fine moving procedure of the ball array mask 19 and the wafer
transfer stage 12. The centers of the electrodes 38 of the wafer 14
are so positioned that they are deviated in the X-axis direction
from the centers of the through holes 18 of the ball array mask 19
by a half distance of the difference between the diameter of the
solder balls 21 and the diameter of the through holes 18. At first,
FIG. 5A shows the stage immediately after the solder balls 21 were
dropped into the through holes 18 of the ball array mask 19. In
this state, the solder balls 21 are not always mounted in the
centers of the through holes 18. As shown in FIG. 5B, therefore,
the wafer transfer stage 12 is finely moved in the X-axis direction
(leftward of the drawing) by the distance of the difference between
the diameter of the solder balls 21 and the diameter of the through
holes 18. As a result of this fine movement, the solder balls 21
finely move in the X-axis direction together with the wafer
transfer stage 12 thereby to come into abutment against the
lefthand inner walls, as shown, of the through holes 18 so that
their positions in the X-axis direction are corrected.
Simultaneously with this, the solder balls 21 moved along the
lefthand inner walls, as shown in FIG. 5B, of the through holes 18
so that their positions in the Y-axis direction are corrected. In
short, the solder balls 21 come into the state, in which they are
precisely mounted at the central portions of the electrodes 38 of
the wafer 14. As shown in FIG. 5C, the wafer transfer stage 12 is
moved backward of the fine movement from FIG. 5A to FIG. 5B by the
distance of one half of the difference between the diameter of the
solder balls 21 and the diameter of the through holes 18. Then, all
the solder balls 21 in the through holes 18 leave the inner walls
of the through holes 18 and are mounted in the positions
homogeneous in the X-axis direction and in the Y-axis direction. As
a result, the solder balls 21 can leave without any deviation from
the ball array mask 19 when the wafer transfer stage 12 moves
downward. Here, the fine movement distance may be longer than the
difference between the diameter of the solder balls 21 and the
diameter of the through holes 18, but the initial position of the
wafer transfer stage 12 at the ball mounting unit is set according
to that distance.
[0037] In the embodiment thus far described, the fine movements of
the ball array mask 19 and the wafer transfer stage 12 are straight
in one direction, i.e., in the X-axis direction of the horizontal
directions. It is, however, natural that the fine movements may be
one in another direction such as in the Y-axis direction,
sequential ones in two perpendicular directions in the horizontal
directions, or a turning one in a horizontal plane. Here in the
sequential movements in the two directions perpendicular in the
horizontal directions, the wafer transfer stage 12 is finely moved
in the X-axis direction by a distance equal to at least the
difference between the diameter of the solder balls 21 and the
diameter of the through holes 18. After this, the wafer transfer
stage 12 is finely moved in the Y-axis direction perpendicular to
the X-axis direction by the half distance of the difference between
the diameter of the solder balls 21 and the diameter of the through
holes 18, and is then finely moved so that the solder balls 21 may
return to the centers of the through holes 18. In the turning
motions in the horizontal plane, on the other hand, the wafer
transfer stage 12 is turned with a turning radius of one half of
the difference between the diameter of the solder balls 21 and the
diameter of the through holes 18 and is so turned or moved straight
that the solder balls 21 may finally return to the centers of the
through holes 18.
[0038] In this embodiment, as the moving means for that fine
movement, the fine movement in the X-axis direction is caused by
the X-axis drive mechanism 40 of the transfer passage 13, and the
fine movement in the Y-axis direction is caused by the Y-axis drive
mechanism 28 of the wafer transfer stage 12, so that the wafer
transfer stage 12 is finely moved by that moving means. Since the
fine movements may be relative ones, however, the ball array mask
19 may also be provided with a moving device for moving the ball
array mask 19 finely in the X-axis direction and in the Y-axis
direction.
[0039] After the solder balls mounting operation, the wafer
transfer stage 12 is moved downward by the Z-axis drive mechanism
30 so that it is moved to stop at the carry-out wafer transfer
unit. In the wafer housing unit 10, the wafer 14 is transferred
from the wafer transfer stage 12 to the inversion unit 9 by the
carry-out robot 11, and the wafer 14 is turned to bring the
orientation flat or notch to the predetermined position. The wafer
14 is further transferred by the carry-out robot 11 from the
inversion unit 9 to the magazine 32 of the wafer housing unit 10.
When the carry-out robot 11 takes out the wafer 14 from the wafer
transfer stage 12, the wafer transfer stage 12 returns to the
original position or the wafer transfer unit 2, thus completing one
step. The present apparatus repeats the actions thus far
described.
[0040] In the embodiment shown in FIG. 1, the wafer feeding unit 6
is disposed in front of the solder ball mounting apparatus 1, and
the wafer housing unit 10 is disposed at the back. Since the wafer
transfer stage 12 returns to the original position, as described
above, the wafer feeding unit 6 and the wafer housing unit 10 may
also be disposed on one side, as shown in FIG. 2.
[0041] With the structure thus made, the carry-out robot 11 can be
replaced by the carry-in robot 8, and the wafer 14 is held and
housed in the same direction as that of the wafer 14 being carried
in, so that the inversion unit 9 can be omitted. Moreover, one of
the wafer transfer units 2 and 5 can also be omitted so that the
number of structural components can be reduced.
[0042] Moreover, this embodiment employs the vertical observation
cameras 31 and 34 for photographing the alignment marks of the
wafer 14 and the printing mask 15 or the ball array mask 19
simultaneously at the stop time of the wafer transfer stage 12, as
the means for positioning the printing mask 15 and the ball array
mask 19, and the wafer 14. However, the invention should not be
limited thereto but can be conceived to have various
structures.
* * * * *