Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With provision for cooling the housing or its contents
Reexamination Certificate
2002-08-26
2004-03-30
Potter, Roy (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With provision for cooling the housing or its contents
C257S706000, C257S730000
Reexamination Certificate
active
06713865
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a semiconductor device, and more particularly to a semiconductor device in which semiconductor element or elements are housed in a package including a heat sink.
BACKGROUND OF THE INVENTION
FIG. 4
is a partially cutaway perspective view illustrating a conventional semiconductor device. The semiconductor device shown in
FIG. 4
comprises a heat sink
41
, and a semiconductor element
42
such as an integrated circuit device and the like mounted on the surface of the heat sink
41
. The semiconductor device of
FIG. 4
further comprises a sidewall
43
which is attached to the surface of the heat sink
41
and which surrounds the semiconductor element
42
, and a cap not shown in the drawing which closes the opening portion of the sidewall
43
and covers the semiconductor element
42
. In other words, the semiconductor element
42
is housed within a container having the heat sink
41
, the sidewall
43
and the cap.
In the sidewall
43
, a plurality of leads
44
are provided such that the leads
44
are partially buried in the sidewall
43
and penetrate the sidewall
43
. One end of each of the leads
44
is coupled with a coupling pad
46
of the semiconductor element
42
via a bonding wire
45
and the like.
Fixing of the semiconductor element
42
to the heat sink
41
, fixing of the sidewall
43
to the heat sink
41
and fixing of the cap to the sidewall
43
are respectively done by using thermosetting resin.
Japanese patent laid-open publication No. 11-238838 discloses another conventional semiconductor device. The semiconductor device disclosed in this publication has a similar structure to that of the semiconductor device shown in
FIG. 4
, except for the following. That is, the heat sink has projections at the peripheral portion thereof and the projections fit into concave portions formed in the sidewall, or the frame shaped sidewall is fit inside the projections formed in the heat sink. Thereby, an influence of the thermal expansion can be suppressed and disconnection of the bonding wires can be avoided.
According to the recent development in mobile communications, the size of a semiconductor device for use in a transmitter has become larger and larger, and an output power thereof has become higher and higher. Therefore, heat generation of such semiconductor device has become larger and larger. As a result, it is required that the package of the semiconductor device has far superior heat dissipating performance.
However, the conventional semiconductor devices mentioned above have a problem that, because of an increase in the size thereof and an increase in thermal expansion caused by an increase in heat generation, there arises a warp in the heat sink. Even in the semiconductor device disclosed in the Japanese patent laid-open publication No. 11-238838 in which thermal expansion of the frame member is suppressed by the heat sink, this problem arises when the size of such semiconductor device becomes large.
Also, the conventional semiconductor devices have a problem that, according to an increase in the size thereof and an increase in the thermal expansion caused by an increase in heat generation, an adhesive which joins the sidewall to the heat sink can not withstand the stress caused by the difference of thermal expansion between the sidewall and the heat sink, and junction between the sidewall and the heat sink becomes broken. Especially, this disjunction often occurs between the heat sink and the adhesive, because of the materials of the heat sink and the adhesive.
In the semiconductor device disclosed in the Japanese patent laid-open publication No. 11-238838 in which thermal expansion of the frame member is suppressed by the heat sink, gas which is produced when the adhesive is thermally cured and which causes voids can not escape effectively. Therefore, airtightness of the semiconductor package is deteriorated.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a semiconductor device in which a warp in a heat sink does not occur even when a temperature of the semiconductor device has changed largely and thereby a high heat dissipating efficiency can be realized.
It is another object of the present invention to provide a semiconductor device in which junction between a heat sink and a sidewall of a semiconductor package is not broken even when a temperature of the semiconductor device has changed largely and thereby high airtightness can be maintained.
It is still another object of the present invention to provide a semiconductor device which has high reliability and uniform quality.
It is still another object of the present invention to obviate the disadvantages of the conventional semiconductor device having a heat sink.
According to an aspect of the present invention, there is provided a semiconductor device comprising: a heat sink on which a semiconductor element is mounted; a sidewall which is attached onto the heat sink and which surrounds the semiconductor element; wherein one of the heat sink and the sidewall has a plurality of projections formed on a joining surface thereof to be joined to an opposing surface of the other one of the heat sink and the sidewall; wherein a gap is formed by the projections between the sidewall and the heat sink when the sidewall is disposed on the heat sink; and wherein the sidewall and the heat sink are joined together by using low elasticity liquid resin which fills at least the gap formed by the projections between the sidewall and the heat sink.
In this case, it is preferable that the projections are formed on the heat sink.
It is also preferable that each of the projections have a height of 200 &mgr;m or larger.
It is further preferable that the low elasticity liquid resin is thermosetting epoxy resin, and the sidewall and the heat sink are joined by thermally curing the low elasticity liquid resin.
It is advantageous that the modulus of elasticity of the low elasticity liquid resin becomes 1000 kgf/mm
2
or smaller after thermally curing the low elasticity liquid resin.
According to another aspect of the present invention, there is procided a method of manufacturing a semiconductor device having a heat sink on which a semiconductor element is mounted and a sidewall which is attached onto the heat sink and which surrounds the semiconductor element, the method comprising: forming a plurality of projections on a joining surface of one of the heat sink and the sidewall, the joining surface is a surface to be joined to an opposing surface of the other one of the heat sink and the sidewall; disposing the sidewall on the heat sink; filling a gap formed by the projections between the heat sink and the sidewall with low elasticity liquid resin; and joining the heat sink and the sidewall by curing the low elasticity liquid resin.
In this case, it is preferable that the low elasticity liquid resin is cured in the condition the sidewall is pressed onto the heat sink.
It is also preferable that the projections are formed on the heat sink.
It is further preferable that the low elasticity liquid resin is thermosetting epoxy resin, and the sidewall and the heat sink are joined by thermally curing the low elasticity liquid resin.
It is advantageous that the modulus of elasticity of the low elasticity liquid resin becomes 1000 kgf/mm
2
or smaller after thermally curing the low elasticity liquid resin.
NEC Compound Semiconductor Devices Ltd.
Potter Roy
Sughrue & Mion, PLLC
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