Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With housing mount
Reexamination Certificate
1997-01-02
2001-06-05
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With housing mount
C257S646000, C257S672000, C257S676000, C257S724000, C257S691000, C257S084000, C257S080000, C257S784000
Reexamination Certificate
active
06242801
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a semiconductor device in which a semiconductor element is mounted on an island, and especially to a semiconductor device in which an island has a characteristic shape.
BACKGROUND ART
Conventionally, a semiconductor device has a structure as described below. Here, a photodetector device having a semiconductor element such as a photodiode is taken as an example.
As shown in
FIG. 4
, the photodetector device is composed of a common lead
31
having at one end an approximately square-shaped island
31
a
, specific leads
32
and
33
formed on both sides of and approximately parallel with the common lead
31
, a semiconductor element
34
die-bonded on the island
31
a
, a plurality of wires
35
made of gold or other for electrically connecting the semiconductor element
34
to the top surface of the island
31
a
and to the specific leads
32
and
33
by wire bonding, and an approximately square-shaped resin seal
36
made of epoxy resin for sealing in the semiconductor element
34
and the wires
35
(the resin seal
36
actually is opaque, though it is shown as transparent in FIG.
4
). On the top surface of the above semiconductor element
34
are formed a plurality of projection-like electrode pads (not shown) made of aluminum or other. On these electrode pads are bonded wires
35
, of which four are, at the other end, bonded on the top surface of the island
31
a
and two are, at the other end, bonded on the specific leads
32
and
33
, respectively. The first four wires are electrically connected to the island
31
a
so as to be grounded, and thus serve to adjust the resistance against a current flowing between the specific leads
32
and
33
.
The resin seal
36
is so formed as to seal in the semiconductor element
34
and the wires
35
as shown in
FIG. 5
by use of a resin-forming mold (not shown). The resin seal
36
has, at its portion approximately above the semiconductor device
34
, a hemispherical condenser lens
37
for leading light from outside to the semiconductor element
34
.
However, this photodetector has been suffering from a following problem.
The above resin seal
36
is heated to seal in the semiconductor element
34
and the wires
35
, and thereafter, as the resin seal
36
cools down, it develops contraction stress inside itself. This causes the wires
35
to be pulled together with the resin, of which the resin seal
36
is made, in the direction of the inward contraction of the resin. On the other hand, the island
31
a
, on which one end of each wire
35
is stitch-bonded, contracts far less than the resin seal
36
because of their different thermal expansion coefficients.
As a result, the wires
35
are subjected to force that pulls them in the direction of the contraction of the resin and that tends to tear the ends of the wires
35
off the island
31
a
, and eventually the wires
35
are broken as shown in FIG.
6
. Moreover, the same can be caused even by variations in ambient temperature.
An object of the present invention is to provide a highly reliable semiconductor device that is substantially free from wire breakage.
DISCLOSURE OF THE INVENTION
According to the present invention, in a semiconductor device comprising a lead terminal having an island at one end, a semiconductor element whose bottom surface is connected to the island, one or more wires that connect the top surface of the semiconductor element to the island, and a resin seal that seals in the semiconductor element and the wires, said island has a cut formed between a section on which said semiconductor element is mounted and a section on which said wires are bonded.
Moreover, according to the present invention, in a semiconductor device as described above, the cut is so formed as to extend below all the wires.
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Arent Fox Kintner & Plotkin & Kahn, PLLC
Rohm & Co., Ltd.
Williams Alexander O.
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