Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Bump leads
Reexamination Certificate
2001-05-17
2003-08-19
Tran, Minh Loan (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Bump leads
C257S773000, C257S778000, C257S779000, C257S782000, C257S783000, C257S786000
Reexamination Certificate
active
06608382
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a metal bump. In particular, the present invention relates to a profile-design rule of a metal bump for reducing a diagonal distance between two adjacent metal bumps positioned at adjacent rows.
2. Description of the Related Art
The attachment of a bared die to a glass panel (called COG: chip on glass) is one advanced application for electrically connecting integrated circuits (ICs) achieving lighter weight, smaller size, lower cost and less power consumption demanded in various display products. The quality and reliability of the liquid crystal display (LCD) module depends on the way in which the driver IC is attached to the glass panel. Anisotropic conductive film (ACF) is the most popular material for attaching the chip to the glass panel. ACF is an adhesive film consisting of dispersed, microscopic, electrically conductive particles 3-15 &mgr;m in diameter and an insulating adhesive film 15-35 &mgr;m thick. Various kinds of conductive particles, such as carbon fiber, metal (Ni, solder), and metal (Ni/Au)-coated plastic balls have been proposed, and the uniformity of the conductive particles distribution is considered an influence on the electrical property and reliability of ACF. Also, various types of adhesive materials, such as thermoplastic, thermosetting, and mixed thermoplastic and thermosetting materials have been proposed. In general, ACF is classified into two types. One has conductive particles 5 &mgr;m in diameter covered with a very thin insulating layer, wherein the thin insulating layer is broken when the particles are deformed, the bared conductive particles serving as a bridge for electrically connecting the metal bump on the chip and the bonding pad on the glass panel. However, the breaking of the conductive particles during the fabricating process cannot be ensured; therefore, there is no guarantee of effective contact between the metal bump and the bonding pad. The other type of ACF is a double-layer type, which consists of one layer filled with conductive particles 3 &mgr;m in diameter and the other layer with no conductive particles, so that the functions of conduction and adhesion are separated. This can ensure the effective contact between the metal bump and the bonding pad. Nevertheless, when too many conductive particles exist in the space between two adjacent metal bumps, a lateral connection between the two adjacent metal bumps is easily formed, resulting in an electrical short.
FIG. 1A
to
FIG. 1C
are schematic cross-sectional diagrams of a method of connecting a chip
14
and a glass substrate
10
according to the prior art. The glass substrate
10
of the LCD module comprises a first area for disposing an array of thin film transistors (TFTs), a second area for disposing data IC chips or scan IC chips
14
, and a plurality of bonding pads
12
are formed on the second areas. The chip
14
has a plurality of metal pads
16
and a plurality of metal bumps
18
, wherein each metal bump
18
is patterned on each metal pad
16
and corresponds in position to each bonding pad
12
. In the prior method of connecting the chip
14
and the glass substrate
10
, as shown in
FIG. 1A
, an ACF
20
is attached to the surface of the glass substrate
10
to cover the bonding pad
12
. Then, the surface of the chip
14
is downwardly placed on the predetermined area of the glass substrate
10
, wherein each metal bump
18
corresponds to each bonding pad
12
of the glass substrate
10
. As shown in
FIG. 1B
, by means of the adhesion of the ACF
20
and the downwardly exerted pressure, the chip
14
is tightly attached to the glass substrate
10
. Next, a thermal process is performed to cure the ACF
20
. The conductive particles
22
sandwiched between the top of the metal bump
18
and the surface of the bonding pad
12
now serve as an electrically connecting bridge, as shown in FIG.
1
C. However, the distribution of the conductive particles
22
cannot be controlled in processing, and thereby many conductive particles
22
that exist between adjacent metal bumps
18
may laterally connect with each other to cause electrical shorts.
FIG. 2A
shows a top view of the layout of the metal bumps
18
according to the prior art. For providing great output terminals and avoiding electrical shorts between metal bumps
18
, the metal bumps
18
are generally arranged in two rows. In each row, each metal bump
18
with a transverse width W
2
is spaced out a transverse distance W
1
apart from each other, and the tops of the metal bumps
18
are leveled off. For example, in a first row, a first metal bump
181
and a second metal bump
182
are adjacent and apart from the transverse distance W
1
. In a second row, a third metal bump
183
is disposed between the first metal bump
181
and the second bump
182
. Therefore, the three centers of the three bumps
181
,
182
,
183
respectively are arranged as a triangle. Notice that the transverse distance W
1
is equal to the transverse width W
2
, and a lengthwise distance L between the first row and the second row is smaller than the transverse distance W
1
. However, since the metal bump
18
is shaped into a square or rectangular profile, the shortest distance is found between a point A of the first metal bump
181
and a point B of the third metal bump
183
. A lateral connection between the first metal bump
181
and the third metal bump
183
is easily formed by the conductive particles to result in an electrical short. Similarly, a lateral connection is easily formed between a point C of the second metal bump
182
and a point D of the third metal bump
183
.
In addition, an electrical short is easily caused by an alignment error between the metal bump
18
and the bonding pad
12
. Please refer to
FIG. 2B
, which shows a top view of the metal bump
18
and the bonding pad
12
according to the prior art. In general, the profile of the bonding pad
12
is square or rectangular according to the profile of the metal bump
18
, and the surface area of the bonding pad
12
is larger than the top area of the metal bump
18
. Thereby, a tolerance limitation of an alignment error in COG technique depends on the shorted distance d between the first bonding pad
121
and the third bonding pad
123
. When the chip
14
is inaccurately attached to the glass substrate
10
, the up-left corner or the up-right corner of the third bonding pad
123
is easily contacted with the point A of the first metal bump
181
or the point C of the second metal bump
182
. Similarly, the down-right corner of the first bonding pad
121
or the down-left corner of the second bonding pad
122
is easily contacted with the point B or D of the third metal bump
183
.
From the above-described disadvantages, the square or rectangular profile of the metal bump
18
reduces the diagonal distance between two adjacent metal bumps
18
positioned at adjacent rows. This causes electrical shorts and limits the tolerance of alignment error in COG technique, resulting in lowering quality and reliability of LCD modules.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a cylindrical bump to increase the diagonal distance between metal bumps positioned in adjacent rows.
Another object of the present invention is to provide a polygonal bump to increase the diagonal distance between metal bumps positioned in adjacent rows.
The metal bumps of the present invention include at least a first metal bump having at least one curved face, at least a second metal bump having at least one curved face, and at least a third metal bump having at least a first curved face and a second curved face. The three centers of the first metal bump, the second metal bump and the third metal bump are arranged as a triangle. The first curved face of the third metal bump is adjacent to the curved face of the first metal bump. The second curved face of the third metal bump is adjacent to the curved face of the second metal bump.
Another embodiment of the pre
Chen Hong-Shiung
Liu I-Ming
Yang Chin-Chen
AU Optronics Corporation
Darby & Darby
Tran Minh Loan
Tran Tan
LandOfFree
Metal bump does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Metal bump, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Metal bump will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3130960