Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – On insulating carrier other than a printed circuit board
Reexamination Certificate
2000-11-22
2004-03-30
Fahmy, Wael (Department: 2814)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
On insulating carrier other than a printed circuit board
C257S667000, C257S787000, C257S670000, C257S669000, C257S674000, C257S671000, C438S123000, C438S124000, C438S613000
Reexamination Certificate
active
06713850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to integrated circuit packaging technology, and more particularly, to a tape carrier package (TCP) structure with dummy pads and dummy leads for reinforcement of the package construction.
2. Description of Related Art
TCP (Tape Carrier Package) is an advanced type of integrated circuit packaging technology which is characterized in the use of a tape carrier, rather than a leadframe or a substrate, as the chip-mounting base, and also in the use of TAB (Tape Automated Bonding) technology to implement the overall packaging process. The tape carrier is typically formed with a device hole for accommodating the packaged semiconductor chip, and a plurality of inner leads bonded to the I/O pads of the packaged semiconductor chip to serve as external connecting means for the packaged semiconductor chip. A conventional TCP structure is illustratively depicted in the following with reference to
FIGS. 1A-1D
.
Referring to
FIG. 1A
, the conventional TCP structure is used to pack a semicon-ductor chip
110
having a plurality of I/O pads
111
arranged along the four sides thereof (note that
FIGS. 1A-1C
are simplified to show only a small number of bond pads and those parts that are related to the invention for demonstration purpose, the actual circuit layout of the TCP structure may be much more complex).
By the conventional TCP technology, however, no I/O pads are arranged on the four corners
110
a
,
110
b
,
110
c
,
110
d
of the semiconductor chip
110
(the four corners
110
a
,
110
b
,
110
c
,
110
d
are indicated by the dotted circles in FIG.
1
A).
Referring further to
FIG. 1B
, the semiconductor chip
110
of
FIG. 1A
is to be mounted on a tape carrier
120
, such as a TAB tape, which is formed with a centrally-located device hole
120
a
and is predefined with a plurality of lead-bonding areas
121
surrounding the device hole
120
a
the areas indicated by the dotted rectangular boxes in
FIG. 1B
)
Referring further to
FIG. 1C
, during assembly, the fist step is to mount the semicon-ductor chip
110
of
FIG. 1A
in the device hole
120
a
of the tape carrier
120
of FIG.
1
B. As the semiconductor chip
110
is mounted in position, an ILB (Inner Lead Bonding) process is performed to bond a set of electrically-conductive inner leads
130
between the respective I/O pads
111
on the semiconductor chip
110
and the lead-bonding areas
121
on the tape carrier
120
to serve as external connecting means for the packaged semiconductor chip
110
.
Referring further to
FIG. 1C
, in the next step, an encapsulation process is performed to dispense an encapsulation material, such as resin, through the gaps between the inner leads
130
into the device hole
120
a
so as to form an encapsulation body
140
to encapsulate the semiconductor chip
110
.
In practical realization, however, the foregoing conventional TCP technology has the following drawbacks.
First, since the four corners
110
a
,
110
b
,
110
c
,
110
d
of the semiconductor chip
110
are provided with no bond pads and unconnected to any leads, these four corners
110
a
,
110
b
,
110
c
,
110
d
of the semiconductor chip
110
would be nearly unsupported. As a result, during the ILB process, it would easily cause cracking of the inner leads
130
. In addition, during the movement of the tape carrier
120
, it would easily cause the package construction to be subjected to deformation.
Second, during the potting process, since the comer-situated lead gap width (denoted by W in
FIG. 1B
) is considerably greater than the pitch of the side-situated inner leads
130
(denoted by P in FIG.
1
B), it would cause the potting of the encapsulation material through these inner leads
130
during the encapsulation process to be unevenly distributed to the back side of the semiconductor chip
110
, which would easily cause undesired forming of voids that would be easily subjected to popcorn effect and delamination, thus degrading the quality and reliability of the finished TCP product.
SUMMARY OF THE INVENTION
It is therefore an objective of this invention to provide an improved TCP technology which allows the corners of the packaged semiconductor chip to be firmly supported.
It is another objective of this invention to provide an improved TCP technology which allows the encapsulation material to be substantially evenly distributed to the back side of the packaged semiconductor chip, so as to allow the resulted encapsulation body to be substantially free of voids for prevention of undesired popcorn effect and delamination.
It is still another objective of this invention to provide an improved TCP technology which would prevent the package construction from being deformed during movement of the tape carrier.
In accordance with the foregoing and other objectives, the invention proposes an improved TCP structure.
Broadly recited, the TCP structure of the invention comprises the following constituent components: (a) a semiconductor chip having: (a
1
) a plurality of I/O pads arranged along the sides thereof; and (a
2
) a plurality of dummy pads arranged on the corners thereof; (b) a tape carrier having a device hole and a plurality of side-situated lead-bonding areas and comer-situated lead-bonding areas surrounding the device hole, (c) a set of inner leads, including: (c
1
) a group of I/O leads, which are bonded between the respective I/O pads on the semiconductor chip and the side-situated lead-bonding areas on the tape carrier; and (c
2
) group of dummy leads, which are bonded between the respective dummy pads on the semiconductor chip and the comer-situated lead-bonding areas on the tape carrier.
During assembly, since dummy leads are bonded between the dummy pads and the corner-situated lead-bonding areas, the corners of the semiconductor chip can be firmly supported in addition to the lateral support of the semiconductor chip by the functional I/O leads, thus reinforcing the package construction During the inner-lead bonding (ILB) process, such reinforcement can help prevent the cracking of any of the I/O leads. More-over, during encapsulation process, since the provision of the dummy leads can help reduce the lead gap width at the four corners of the device hole, it can help the encapsulation material to be more evenly distributed to the back side of the semiconductor chip, thus preventing the undesired forming of voids in the resulted encapsulation body making the resulted encapsulation body less likely to be subjected to popcorn effect and delamination. In addition, it can help provide a uniform package height (UPH) to the overall package construction. These advantages allow the finished TCP product to be more assured in quality and reliability than prior art.
REFERENCES:
patent: 6060770 (2000-05-01), Nakamura et al.
patent: 6265762 (2001-07-01), Tanaka et al.
patent: 6268644 (2001-07-01), Umehara et al.
Chen Chih-Shun
Wu Chi-Chuan
Yuan Po-Hao
Corless Peter F.
Edwards & Angell LLP
Fahmy Wael
Jensen Steven M.
Nguyen DiLinh
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