Semiconductor device including solid state imaging device

Details Semiconductor device including solid state imaging device Semiconductor device including solid state imaging device

1996-08-13

2002-05-21

Potter, Roy (Department: 2822)

Active solid-state devices (e.g., transistors, solid-state diode

Encapsulated

With heat sink embedded in encapsulant

C257S706000, C257S707000, C257S675000, C257S680000

Reexamination Certificate

active

06392309

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a semiconductor device and a solid state imaging device, having a construction in which a semiconductor chip is mounted on the bottom of a hermetic sealed box-shaped resin-molded package.
2. Description of the Related Art
FIG. 1
shows a existing solid state imaging device in the related art comprising a CCD chip, used as a solid state imaging element
102
, bonded with an adhesive
103
to the bottom surface in a cavity
101
a
of a resin-molded box-shaped package
101
. Integrally extending from the package
101
are outer leads
104
and inner leads
105
. Inner leads
105
are connected to a bonding pad (not shown) of the CCD chip
102
by wires
106
. Thus, the outer leads
104
are electrically connected to the CCD chip
102
. A transparent cap
107
of optical glass, for example, is bonded to the upper end of the package
101
by an adhesive
108
to hermetic seal the interior of the package
101
.
A problem with the solid state imaging device in the related art is a bad moisture resistant property. The package
101
cannot effectively prevent infiltration of moisture into the cavity
101
a
through the bottom wall of the package
101
. There is another solid state imaging device in the related art shown in
FIG. 2
, which has an improved moisture resistance.
In the solid state imaging device of
FIG. 2
, a part (called a depressed portion) of a lead frame used to make outer leads
104
and inner leads
105
is embedded under a cavity
101
a
of a resin-molded box-shaped package
101
to form a moisture resistant plate
109
. In the other respects, the device of
FIG. 2
is the same as the solid state imaging device of FIG.
1
.
In the solid state imaging device of
FIG. 2
, the moisture resistant plate
109
prevents infiltration of moisture through the bottom of the package
101
into the cavity
101
a,
and thus improves the hermetic seal property of the solid state imaging device.
Another problem with the solid state imaging devices shown in
FIGS. 1 and 2
is that the CCD chip
102
is bonded to the bottom in the cavity
101
a
of the package
101
which is made of a resin having a low thermal conductivity (for example, 2.1×10
−3
cal/cm.s.°C.), resulting in that the heat generated from the CCD chip
102
during its operation is shut in the package
101
and increases the temperature of the CCD chip
102
. An increase in temperature of the CCD chip
102
causes an increase in level of defects having a temperature characteristic and hence causes a deterioration in quality of images obtained by the solid state imaging devices.
The high temperature problem of chips during operation explained with reference to solid state imaging devices also applies to semiconductor devices, in general, using a package similar to the package
101
.
OBJECT AND SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a semiconductor device which is alleviated in temperature increase of its semiconductor chip during operation.
It is another object of the invention to provide a solid state imaging device which is alleviated in temperature increase of its solid state imaging element during operation.
According to the invention, there is provided a semiconductor device having a semiconductor chip mounted on a bottom surface of a cavity of an hermetic sealed box-shaped resin-molded package, comprising:
a radiator plate provided in a bottom wall of the package under the cavity or on the bottom surface of the cavity; and
the semiconductor chip and the radiator plate being bonded with an adhesive having a larger thermal conductivity than that of the resin forming the package.
According to the invention, there is also provided a solid state imaging device having a solid state imaging element on a bottom surface of a cavity in a hermetic sealed box-shaped resin-molded package, comprising:
a radiator plate provided in a bottom wall of the package under the cavity or on the bottom surface of the cavity; and
the solid state imaging element and the radiator plate being bonded with an adhesive having a larger thermal conductivity than that of the resin forming the package.
According to the invention, there is further provided a semiconductor device having a semiconductor chip on a bottom surface of a cavity in a hermetic sealed box-shaped resin-molded package, comprising:
a radiator plate which is a part of a lead frame, the radiator plate being provided in the bottom wall of the package under the cavity or on the bottom surface of the cavity; and
the semiconductor chip and the radiator plate being bonded with an adhesive having a larger thermal conductivity than that of the resin forming the package.
According to an aspect of the invention, the radiator plate is embedded in the bottom wall of the package under the cavity, and the semiconductor chip or the solid state imaging element is bonded to the radiator plate with the adhesive through an aperture formed in the bottom wall of the package in the cavity for access to the radiator plate.
According to another aspect of the invention, the radiator plate is provided on the bottom surface of the cavity, and the semiconductor chip or the solid state imaging element is bonded onto the radiator plate with the adhesive.
Usable as the resin forming the package are, for example, thermoset resins including epoxy resin, polyimide, silicone resin, phenolic resin, unsaturated polyester resin, and so forth.
The adhesive having a larger thermal conductivity than the resin of the package may include epoxy resin, imide resin, silicone resin or acrylic resin, for example, as its base material. Typically, the adhesive additionally contains a filler of silver (Ag) or other metal to increase the thermal conductivity.
When the radiator plate is provided on the bottom surface of the cavity in the package and the semiconductor chip or the solid state imaging element is bonded to the radiator plate with the adhesive, reflection of light from the surface of the radiator plate may adversely affect the operation of the semiconductor device or the solid state imaging device. To prevent this, the radiator plate is preferably coated with a light absorptive material such as chromium (Cr). Alternatively, reflection of light by the radiator plate can be prevented by adding a black pigment such as carbon to the adhesive and by applying the light absorptive adhesive to the surface of the radiator plate.
In a typical embodiment of the invention, the resin forming the package is epoxy resin, and the adhesive having a larger thermal conductivity than the resin of the package is epoxy resin containing a metal filler.
The radiator plate is typically a part of the lead frame, but may be a member independent from the lead frame. In the latter case, the radiator plate is bonded onto the bottom surface of the cavity of the package with the adhesive. Here again, the adhesive has a larger thermal conductivity than the resin of the package.
The radiator plate typically has a larger dimension than the semiconductor chip or the solid state imaging element for more effective radiation of heat.
The semiconductor device may be a solid state imaging device incorporating a solid state imaging element chip such as CCD chip, or may be a semiconductor IC device incorporating an IC chip or an LSI chip.
In the semiconductor device according to one or other aspect of the invention, heat from the semiconductor chip or the solid state imaging device during operation is quickly transferred to the radiator plate via the adhesive having a larger thermal conductivity than the package and is effectively radiated from the entirety of the radiator plate. Therefore, the temperature of the semiconductor chip or the solid state imaging element remains moderate during operation.
The above, and other, objects, features and advantage of the present invention will become readily apparent from the following detailed description thereof which is to be read in connection with the accompanying drawings.


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