Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Flip chip
Reexamination Certificate
2000-11-06
2002-10-08
Talbott, David L. (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Flip chip
C257S779000, C257S787000, C257S666000, C257S678000, C257S737000, C257S784000
Reexamination Certificate
active
06462424
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to semiconductor devices, methods of producing semiconductor devices and semiconductor device mounting structures, and more particularly to a semiconductor device which has only a portion of leads exposed at a bottom surface of a package so as to improve the packaging density of the semiconductor device, a method of producing such a semiconductor device, and a semiconductor device mounting structure for mounting such a semiconductor device.
Due to the recent improvements in reducing the size, increasing the operation speed and increasing the functions of electronic equipments, there are demands to realize similar improvements in semiconductor devices. In addition to these demands on the semiconductor devices per se, there are also demands to improve the packaging density of the semiconductor device when packaging the semiconductor device on a substrate.
Accordingly, although the majority of the existing semiconductor devices employ the surface mounting which connects the leads at the surface of the substrate, there are demands to further improve the packaging density of the semiconductor devices.
FIG. 1
shows a perspective view of an example of a conventional semiconductor device
1
.
FIG. 2
is a cross sectional view of this semiconductor device
1
taken along a line A—A in FIG.
1
. For example, this type of semiconductor device was proposed in Japanese Laid-Open Patent Applications No. 63-15453 and No. 63-15451.
In
FIGS. 1 and 2
, the semiconductor device
1
generally includes a semiconductor chip
2
, a resin package
3
which encapsulates the semiconductor chip
2
, a plurality of leads
4
, and a stage
7
on which the semiconductor chip
2
is mounted. One end
4
a
of the lead
4
is connected to the semiconductor chip
2
via a wire
5
, and the other end of the lead
4
is exposed at a bottom surface
3
a
of the package
3
to form an external terminal
6
. In other words, all parts of the semiconductor device
1
excluding the external terminals
6
of the leads
4
are encapsulated within the package
3
.
Because the external terminals
6
of the leads
4
are exposed at the bottom surface
3
a
of the package
3
in this semiconductor device
1
, the projecting length of the leads
4
on the outer side of the package
3
can be made small, thereby making it possible to improve the packaging density. In addition, the external terminals
6
of the leads
4
do not need to be bent as in the case of the conventional leads having the L-shape or gull-wing shape. As a result, no mold is required to bend the external terminals
6
, thereby making it possible to simplify the production process and to reduce the production cost.
On the other hand, another type of semiconductor device was proposed in a Japanese Laid-Open Patent Application No. 4-44347. According to this proposed semiconductor device, the leads are fixed to a circuit forming surface of the semiconductor chip via an insulative adhesive agent. In addition, the size of the package is reduced by encapsulating only the circuit forming surface or only the circuit forming surface and side surfaces of the semiconductor chip.
However, according to the semiconductor device
1
described above, the end
4
a
of the lead
4
is located on both sides of the semiconductor chip
2
. As a result, there is a limit to reducing the size of the package
3
, and there was a problem in that the size of the semiconductor device
1
cannot be reduced to a sufficient extent. In other words, the size of the semiconductor device ideally is approximately the same as the size of the semiconductor chip. However, the size of the semiconductor device
1
is approximately two or more times greater than the size of the semiconductor chip
2
.
In addition, the semiconductor device
1
does not take the heat radiation into any consideration. That is, there was a problem in that the semiconductor device
1
cannot efficiently radiate the heat generated from the semiconductor chip
2
outside the package
3
.
On the other hand, according to the semiconductor device proposed in the Japanese Laid-Open Patent Application No. 4-44347, the leads which are connected to an external substrate are apart from the package, and thus, the transfer mold technique cannot be employed as the package forming technique, and the troublesome potting technique must be employed. As a result, this proposed semiconductor device requires troublesome processes to produce, and there were problems in that the production efficiency of the semiconductor device is poor and the production cost of the semiconductor device is high. It is theoretically possible to produce this semiconductor device by employing the transfer mold technique, however, this would require the mold to be made up of a large number of split molds, and this technique is impractical in that the mold would become extremely expensive.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a novel and useful semiconductor device and a method of producing the same, in which the problems described above are eliminated.
A first particular object of the present invention is to provide a semiconductor device and a method of producing the same, which can sufficiently reduce the size of the semiconductor device.
Another and more specific object of the present invention is to provide a semiconductor device comprising a semiconductor chip having a top surface and a bottom surface, a plurality of leads arranged under the bottom surface of the semiconductor chip, where the leads have first ends electrically coupled to the semiconductor chip and second ends which form external terminals and each of the external terminals have a bottom surface, and a package encapsulating the semiconductor chip and the leads so that the bottom surface of each of the external terminals is exposed at a bottom surface of the package and remaining portions of the leads are embedded within the package, where the package has a size which is approximately the same as that of the semiconductor chip in a plan view viewed from above the top surface of the semiconductor chip. According to the semiconductor device of the present invention, it is possible to considerably reduce the size of the semiconductor device to approximately the same size as the semiconductor chip in the plan view.
Still another object of the present invention is to provide a method of producing a semiconductor device comprising the steps of (a) press-working a lead frame and forming a plurality of leads which extend inwards to a predetermined position where a semiconductor chip is to be mounted, (b) mounting the semiconductor chip at the predetermined position on a stage, where the steps (a) and (b) are carried out in an arbitrary order, (c) wire-bonding first ends of the leads to the semiconductor chip via wires, and (d) encapsulating the semiconductor chip and the leads by a resin package so that a bottom surface of the leads is exposed at second end at a bottom surface of the resin package. According to the method of producing the semiconductor device of the present invention, it is possible to produce the semiconductor device which is considerably small compared to the conventional semiconductor device using simple processes. In addition, since the leads are embedded within the resin package and the second ends (external terminals) of the leads are exposed at the bottom surface of the resin package, it is possible to employ the transfer mold technique as the package forming technique. As a result, it is possible to form the resin package with ease and improve the production yield and also reduce the production cost.
A second particular object of the present invention is to provide a semiconductor device and a semiconductor device mounting structure, which can relieve a stress which is generated due to a difference between coefficients of linear thermal expansion of the semiconductor device and a circuit substrate, so as to improve the mounting characteristic and
Hamano Toshio
Hayashida Katsuhiro
Sato Mitsutaka
Seki Masaaki
Fujitsu Limited
Staas & Halsey , LLP
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