Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With provision for cooling the housing or its contents
Reexamination Certificate
1998-12-30
2001-05-29
Lee, Eddie C. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With provision for cooling the housing or its contents
C257S666000, C257S783000, C257S793000, C257S722000
Reexamination Certificate
active
06239487
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lead frame with a heat spreader, and a semiconductor package using the same.
2. Background of the Related Art
In general, a semiconductor packaging process is conducted in the manner described below using a lead frame. First, after fabrication of integrated circuits on a wafer, the wafer is separated into individual chips. Next, chip bonding is performed. As shown in
FIG. 1A
, during the chip bonding process each of the separated chips is attached to a die pad
14
of a lead frame with an epoxy
8
. Wire bonding is then performed, during which, bonding pads
5
on the chip
4
and inner leads
2
of the lead frame are electrically connected with a conductive connecting member
6
, which is typically gold wire. Then, a molding process is conducted, and the chip, the connecting members
6
, the die pad
14
and the inner leads
2
are encapsulated for protection with an epoxy molding compound
10
. Then, after the molding, tie bars and dam bars of the lead frame may be trimmed or cut off and the outer leads may be bent into a required form. The result is a semiconductor package as shown in FIG.
1
A. The die pad
14
on the center of the lead frame, which is attached to a semiconductor chip, may also be called a paddle.
FIG. 1B
illustrates a semiconductor package with a heat spreader. The heat spreader
3
is attached under the inner leads
2
with an insulative adhesive
7
. A semiconductor chip
4
is attached to the heat spreader
3
with an epoxy
8
. Conductive connecting members
6
of wire are used to electrically connect bonding pads
5
on the chip
4
to the inner leads
2
. A molding compound
10
encapsulates the chip
4
, the connecting members
6
, the heat spreader
3
and the inner leads
2
.
In the semiconductor package shown in
FIG. 1B
, the heat spreader
3
takes the role of the die pad of a lead frame as shown in FIG.
1
B. However, in the semiconductor package as shown in
FIG. 1B
, the heat spreader
3
extends underneath the inner leads
2
. A maximum size of a chip mountable on the heat spreader
3
is limited to the distance between the inner leads
2
, as shown in FIG.
2
.
When the chip size exceeds the maximum dimension shown in dotted lines in
FIG. 2
, a new lead frame with a larger heat spreader must be developed. Because the development of a new lead frame takes a long time (more than
5
months), and application of the new lead frame to a production line is impossible during the time of development, a deadlock in the production is caused. Also, frequent re-arrangement of a production line to accommodate different size lead frames increases costs and reduces productivity.
SUMMARY OF THE INVENTION
It is an object of the present invention to obviate one or more of the problems, limitations and disadvantages of the background art described above.
It is also an object of the present invention to provide a semiconductor package which allows mounting of various sized chips on a single size lead frame having a heat spreader.
Another object of the present invention is to provide an improved semiconductor package with a heat spreader which has improved heat dissipation properties, and which eliminates or reduces defects in the molding process.
A lead frame embodying the invention includes a plurality of leads having outer portions and inner portions, a heat spreader having a rim portion attached to ends of the inner portions of the leads, wherein a projecting portion of the heat spreader projects between ends of the inner portions of the leads. A lead frame embodying the invention may also include a plurality of recesses or a plurality of projections that are formed on a surface of the heat spreader opposite the projecting portion. An upper surface of the projecting portion of the heat spreader may be located in substantially the same plane as upper surfaces of the inner portions of the leads. Furthermore, a lead frame embodying the invention may include a plurality of aperture or holes that pass through the heat spreader adjacent the rim portion.
A semiconductor package embodying the invention would include a plurality of leads having inner portions and outer portions; a heat spreader having a rim portion attached to the inner portions of the leads and a projecting portion that projects between the ends of the inner portions of the leads; a chip having a plurality of bond pads that is attached to the projecting portion of the heat spreader, a plurality of conductive connecting members that electrically couple bond pads on the chip to respective ones of the inner portions of the leads, and a molded resin body. A semiconductor package embodying the invention may be arranged such that an upper surface of the projecting portion of the heat spreader that is attached to the chip is located in substantially the same plane as upper surfaces of the inner portions of the leads. Also, a semiconductor package embodying the invention may include a heat spreader that has projections or recessed portions on a surface of the heat spreader opposite the projecting portion. Still further, a semiconductor package embodying the invention may include a heat spreader that has apertures or holes passing through the heat spreader adjacent the rim portion.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.
REFERENCES:
patent: 5359222 (1994-10-01), Okumoto et al.
patent: 5402006 (1995-03-01), O'Donley
patent: 5430331 (1995-07-01), Hamzehdoost et al.
patent: 5442234 (1995-08-01), Liang
patent: 5969414 (1999-10-01), Parthasarathi et al.
Cho Dong Whan
Kim Soo Heon
Park Hee Jin
Park Jung Gun
Clark Jhihan B.
Fleshner & Kim LLP
Hyundai Electronics Industries Co,. Ltd.
Lee Eddie C.
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