U.S. patent application number 09/839144 was filed with the patent office on 2001-09-20 for structure of a ball bump for wire bonding and the formation thereof.
This patent application is currently assigned to Advanced Semiconductor Engineering, Inc.. Invention is credited to Hsieh, Jaw-Shiun, Tsai, Yu-Fang.
Application Number | 20010022315 09/839144 |
Document ID | / |
Family ID | 23827363 |
Filed Date | 2001-09-20 |
United States Patent
Application |
20010022315 |
Kind Code |
A1 |
Tsai, Yu-Fang ; et
al. |
September 20, 2001 |
Structure of a ball bump for wire bonding and the formation
thereof
Abstract
The ball bump mainly includes a body and a protrusion. The
protrusion is located at the upper of the body and essentially
consists of a flat upper surface with an annular inclination. The
flat upper surface and the annular inclination together define the
area for wire bonding. The method of the formation of the ball bump
of wire bonding mainly comprises steps of: an end of a wire held by
a bonding machine is melted to form a ball; the bonding machine
bonds the ball onto the bonding pad to form a ball bump; the
bonding tool moves upward a predetermined vertical distance and the
clamp of the bonding tool is then opened; the bonding tool is moved
a predetermined horizontal distance to reduce the connection part
of wire connecting to the upper of the ball bump for the
convenience of wire cutting, and this forms a protrusion on the
ball bump consisting of a flat upper surface with an annular
inclination; the bonding tool is again moved upward a predetermined
vertical distance, and the clamp releases the wire for the ball
bump process which follows; the clamp is closed to hold the wire
and is moved upward to pull the wire, and the wire is cut along the
heat affected zone and leaves a smaller tip on the ball bump.
Inventors: |
Tsai, Yu-Fang; (Kaohsiung,
TW) ; Hsieh, Jaw-Shiun; (Kaohsiung, TW) |
Correspondence
Address: |
BACON & THOMAS, PLLC
625 Slaters Lane, 4th Floor
Alexandria
VA
22314-1176
US
|
Assignee: |
Advanced Semiconductor Engineering,
Inc.
|
Family ID: |
23827363 |
Appl. No.: |
09/839144 |
Filed: |
April 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09839144 |
Apr 23, 2001 |
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09460093 |
Dec 13, 1999 |
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6244499 |
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Current U.S.
Class: |
228/180.5 ;
228/4.5; 257/737; 257/738; 257/E21.508; 438/613 |
Current CPC
Class: |
H01L 2224/78302
20130101; H01L 2924/00014 20130101; H01L 2224/05568 20130101; H01L
2924/01013 20130101; H01L 2924/01033 20130101; H01L 2924/00013
20130101; H01L 24/11 20130101; H01L 2224/48511 20130101; H01L 24/12
20130101; H01L 2224/13099 20130101; H01L 2224/48463 20130101; B23K
20/007 20130101; H01L 2224/1134 20130101; H01L 2224/78301 20130101;
H01L 2924/01075 20130101; H01L 2224/13019 20130101; H01L 2224/05573
20130101; H01L 2224/13099 20130101; H01L 2924/00014 20130101; H01L
2924/00013 20130101; H01L 2224/13099 20130101; H01L 2224/48511
20130101; H01L 2924/00 20130101; H01L 2924/00014 20130101; H01L
2224/05599 20130101; H01L 2224/1134 20130101; H01L 2924/00012
20130101 |
Class at
Publication: |
228/180.5 ;
228/4.5; 438/613; 257/737; 257/738 |
International
Class: |
B23K 031/02; H01L
023/48 |
Claims
What is claimed is:
1. A method of formation of a ball bond of wire bonding comprising
steps of: an end of a wire held by a bonding machine is melted to
form a ball; the bonding machine which bonds the ball onto a
bonding pad to form a ball bump; the bonding tool which is moved
upward a predetermined vertical distance to form an annular
inclination on a top of the ball bump, and a clamp of the bonding
tool is then opened; the bonding tool which is moved a
predetermined horizontal distance to reduce the connection part of
wire for the convenience of wire cutting, and this forms a
protrusion on the ball bump consisting of a flat upper surface and
an annular inclination; the bonding tool which is again moved
upward a predetermined vertical distance, and the clamp releases
the wire for the ball bump process which follows; and the clamp
which is closed to hold the wire and moved upward to pull the wire,
and the wire is cut along the heat-affected zone.
2. The method of formation of the ball bond of wire bonding as
defined in claim 1, wherein the bonding tool is moved upward in
vertical direction to a specified height to form the annular
inclination on a upper of the ball bump; the height should be equal
to the height of an inclination of an opening in the bonding
tool.
3. The method of formation of the ball bond of wire bonding as
defined in claim 1, wherein the bonding tool is moved a
predetermined horizontal distance to form a protrusion on the ball
bump, whose width is preferably 2/3 - 7/8 of the diameter of the
wire.
4. A structure of a ball bump of wire bonding comprising: a body,
and a protrusion located at the upper of the body and essentially
consisting of a flat upper surface with an annular inclination
which together define an area for wire bonding. whereas the flat
upper surface and the annular inclination provide a regular
structure of the ball bump and thus reduce the variability of wire
bonding.
5. The structure of a ball bump of wire bonding as defined in claim
4, wherein the height of the protrusion of the ball bump is equal
to a height of an opening of the bonding tool.
6. The structure of a ball bump of wire bonding as defined in claim
4, wherein the width of the protrusion is equal to 2/3-7/8 of the
diameter of a wire.
7. The structure of a ball bump of wire bonding as defined in claim
4, wherein the protrusion further has a smaller tip at the edge of
the flat upper surface of the protrusion.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention is related to the structure of a ball
bump of wire bonding and the formation thereof and more
particularly to the formation of the ball bump with a bonding
portion that provides a flat upper surface for wire bonding.
[0003] 2. Description of the Related Art
[0004] To avoid the destruction of the bonding pads during wire
bonding onto the bonding pad of the semiconductor device, the ball
bump is arranged on the bonding pad in such a way as to protect it.
Although the ball bump protects the bonding pad directly from being
struck, wire bonding on an irregular upper surface of the ball bump
increases the variability of results. Providing that a bonding
machine uses the same set of wire bonding parameters, an irregular
upper surface reduces the quality and reliability of wire bonding
of the semiconductor device.
[0005] The prior art of the U.S. Pat. No. 5,858,149, issued on Jan.
12, 1999 to Seo et al., discloses the structure of a ball bump and
the formation thereof. As shown in FIG. 1, the chip 100 has a
bonding pad 101. A bonding tool 110, located above the chip 100,
holds a wire 120 which is melted to form a ball 121. As shown in
FIG. 2, the bonding tool 110 strike the ball onto the bonding pad
101 of the chip 100 such that the bottom of the ball adheres to the
bonding pad 101. Then, the clamp 111 of the bonding tool 110 is
opened and the bonding tool 110 presses the ball bump 130. As shown
in FIG. 3, the bonding tool 110 is moved upward a predetermined
distance so as to reserve an appropriate distance of wire 120. The
clamp 111 is then closed to hold the wire 120, and the bonding tool
110 is moved upward to pull the wire 120. The ball bump 130 and the
wire 120 are cut along the heat-affected zone and leave the ball
bump 130 on the bonding pad 101. However, the upper of the ball
bump 130 forms a tip 131 whose height is determined by the heat
affected-zone of the wire 120; so tip 131 varies in accordance with
the heat-affected zone and increases the variability of wire
bonding. When the bonding tool 110 directly pushes the tip 131 in a
horizontal direction, this results in the collapse and shift of tip
131, and the irregular upper surface of the tip 131 increases the
variability of the ball bump 130.
[0006] The present invention intends to provide a structure for the
ball bump which includes a bonding portion on which a flat upper
surface of uniform height is formed so as to reduce the variability
of wire bonding in such a way as to mitigate and overcome the above
problem.
SUMMARY OF THE INVENTION
[0007] The primary objective of this invention is to provide a
structure of the ball bump for wire bonding and the formation
thereof, to form a flat upper surface on the bonding portion of the
ball bump for wire bonding. By eliminating the irregularities in
the structure of the ball bump, the quality and reliability of wire
bonding is increased.
[0008] The secondary objective of this invention is to provide a
structure for the ball bump of wire bonding and the formation
thereof, such that the tip of the ball bump on the flat upper
surface of the bonding portion is smaller and more uniform in
structure thus the regular structure of the ball bump increase the
quality and the reliability of the wire bonding.
[0009] The present invention defines the structure of the ball bump
of wire bonding. The ball bump mainly includes a body and a
protrusion. The protrusion is located at the upper of the body and
essentially consists of a flat upper surface with an annular
inclination. The flat upper surface and the annular inclination
together define the wire bonding area.
[0010] The present invention is a method for the formation of the
ball bump for wire bonding. The formation of the ball bump for wire
bonding mainly comprises steps of: the end of a wire held by a
bonding machine is melted to form a ball; the bonding machine bonds
the ball onto the bonding pad to form a ball bump; the bonding tool
is moved upward a predetermined vertical distance and the clamp of
the bonding tool is then opened; the bonding tool moves a
predetermined horizontal distance to decrease the connection part
of wire connecting to the top of the ball bump for the convenience
of wire cutting, this creates a protrusion from the ball bump
consisting of a flat upper surface with an annular inclination; the
bonding tool is again moved upward a predetermined vertical
distance, and the clamp is opened to release the wire for the ball
bump process which follows; the clamp is then closed to hold the
wire and moved upward to pull the wire; the wire is cut in the
heat-affected zone therefore leaving a smaller tip on the ball
bump.
[0011] Other objectives, advantages and novel features of the
invention will become more apparent from the following detailed
description and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The present invention will now be described in detail with
reference to the accompanying drawings herein;
[0013] FIG. 1 is a side view of the first step of ball bump
formation in accordance with the prior art;
[0014] FIG. 2 is a side view of the second step of ball bump
formation in accordance with the prior art;
[0015] FIG. 3 is a side view of the third step of ball bump
formation in accordance with the prior art;
[0016] FIG. 4 is a side view of the first step of ball bump
formation in accordance with the embodiment of the present
invention;
[0017] FIG. 5 is a side view of the second step of ball bump
formation in accordance with the embodiment of the present
invention;
[0018] FIG. 6 is an enlarged view of the bonding tool of FIG. 5 in
accordance with the embodiment of the present invention;
[0019] FIG. 7 is an enlarged view of the bonding tool of FIG. 5 in
accordance with the embodiment of the present invention;
[0020] FIG. 8 is a side view of the third step of ball bump
formation in accordance with the embodiment of the present
invention;
[0021] FIG. 9 is a side view of the fourth step of ball bump
formation in accordance with the embodiment of the present
invention;
[0022] FIG. 10 is a side view of the fifth step of ball bump
formation in accordance with the embodiment of the present
invention; and
[0023] FIG. 11 is a side view of the sixth step of ball bump
formation in accordance with the embodiment of the present
invention.
DETAILED DESCRIPTION OF THE INVENTION
[0024] The formation of the ball bump of wire bonding mainly
comprises steps of: the end of a wire held by a bonding machine is
melted to form a ball; the bonding machine bonds the ball onto the
bonding pad to form a ball bump; the bonding tool is moved a
predetermined vertical distance and the clamp of the bonding tool
is opened; the bonding tool is then moved a predetermined
horizontal distance to reduce the connection part of the wire
connecting to the upper of the ball bump for the convenience of
wire cutting, thus forming a protrusion of the ball bump which
consists of a flat upper surface with an annular inclination; the
bonding tool is again moved a predetermined vertical distance, the
clamp releases the wire for the ball bump process which follows;
the clamp is closed to hold the wire and moves upward to pull the
wire, so the wire is cut along the heat affected zone of the
connection part and therefore the wire leaves a smaller tip on the
ball bump.
[0025] Referring to FIG. 4, a capillary 210 of the bonding tool
holds the wire 220 at an appropriate length and the end of the wire
220 is melted to form a ball 221 for ball bump bonding. Then the
clamp 211 is opened.
[0026] Referring to FIGS. 4, 5, 6 and 7, the capillary 210 of the
bonding tool moves downward onto a bonding pad 201 of the chip 200
to form a ball bump 230. Because the capillary 210 has an annular
inclination, the ball 221 is mechanically pressed to form the ball
bump 230, and the wire 220 remains connected to the ball bump
230.
[0027] Referring to FIG. 6, the method of formation of the ball
bump 230, in accordance with the embodiment of the present
invention, applies a capillary 210 which has an opening with the
height "h" and the diameter "d". The height "h" is 0.3-1.0 mil and
the diameter "d" is 1.3-1.5 mil.
[0028] Referring to FIGS. 6 and 8, the capillary 210 is moved
vertically a height "H" leaving an annular inclination on a upper
of the ball bump 230. When the height "H" is equal to the height of
the ball bump 230, the clamp 211 of the capillary 210 is
opened.
[0029] Referring to FIGS. 6 and 9, after the capillary 210 moved
vertically a height "H" and stopped, the capillary 210 is moved a
distance "D", called smooth distance, in a horizontal direction
thus formation a protrusion with a flat upper surface for wire
bonding. The wire 220 is pushed to the side by the capillary 210 to
reduce the connection part of the wire 220 for the convenience of
wire cutting. The distance "D", as well as the width of the
protrusion, is preferably 2/3-7/8 of the diameter of the wire 220
and can be adjusted according to the gap between the wire 220 and
the opening of the capillary 210.
[0030] Referring to FIGS. 10 and 11, the capillary 210 is again
moved vertically upward a predetermined distance from the ball bump
230. The clamp releases the wire 220 for the ball bump process
which follow. When the wire 220 is cut off from the ball bump 230,
a length of the wire 220 is reserved on the capillary 210 and is
melted to form a ball. The capillary 210 is moved upward in a
vertical direction from ball bump 230. The wire 220 is cut off
along the heat-affected zone so as to provide a smaller tip on the
flat upper surface 233.
[0031] Referring to FIG. 11, the ball bump 230 of the present
invention mainly includes a body 231 and a protrusion 232. The
protrusion 232 is located at the upper of the body 231 and
essentially consists of a flat upper surface 233 with an annular
inclination 234. The flat upper surface 233 and the annular
inclination 234 form the upper surface and side surface of the
protrusion 232, respectively. The smooth surface and the uniform
level of the protrusion 232 together provide a regular structure
for wire bonding, and a tip 235 is left between the flat upper
surface 233 and the annular inclination 234. Even though the
smaller tip 235 is left on the protrusion 232, the variability of
wire bonding on the protrusion 232 is less than usual.
[0032] Comparing FIG. 3 with FIG. 11, the ball bump 130 of the
prior art with the tip 131 reduces the bondability and reliability
of the wire bonding; but the ball bump 230 of the present invention
with its flat upper surface 233 and the annular inclination
increases the bondability and reliability of wire bonding.
Therefore, the wire bonding of the present invention increases the
bondability and reliability by using a set of parameters.
[0033] The body and protrusion of the ball bump of the present
invention have a uniform total height, under proper controls. Thus
the present invention provides a uniform height of balls on a
substrate. Therefore, the present invention can be applied to flip
chip bonding in such a way that the protrusions of the ball bump
are aimed and attached to the corresponding bonding pad of the chip
and then reflow to electrically connect to the corresponding
bonding pad.
[0034] Although the invention has been described in detail with
reference to its presently preferred embodiment, it will be
understood by one of ordinary skill in the art that various
modifications can be made without departing from the spirit and the
scope of the invention, as set forth in the appended claims.
* * * * *