Metal fusion bonding – Process – Plural joints
Reexamination Certificate
1999-12-13
2001-06-12
Dunn, Tom (Department: 1725)
Metal fusion bonding
Process
Plural joints
Reexamination Certificate
active
06244499
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
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.
2. Description of the Related Art
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.
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
.
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
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.
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.
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.
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.
Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description and the accompanying drawings.
REFERENCES:
patent: 4415115 (1983-11-01), James
patent: 5172851 (1992-12-01), Matsushita et al.
patent: 5364004 (1994-11-01), Davidson
patent: 5485949 (1996-01-01), Tomura et al.
patent: 5559054 (1996-09-01), Adamjee
patent: 5858149 (1999-01-01), Seo et al.
patent: 5871141 (1999-02-01), Hadar et al.
patent: 6017812 (2000-01-01), Yonezawa et al.
patent: 409097794A (1997-04-01), None
patent: 409106988A (1997-04-01), None
patent: 410107036A (1998-04-01), None
patent: 410135222A (1998-05-01), None
patent: WO97/39480 (1997-10-01), None
Hsieh Jaw-Shiun
Tsai Yu-Fang
Advanced Semiconductor Engineering Inc.
Bacon & Thomas
Dunn Tom
Stoner Kiley
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