Method of fabricating semiconductor device

Details Method of fabricating semiconductor device Method of fabricating semiconductor device

2001-10-12

2004-08-31

Nelms, David (Department: 2818)

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

Lead frame

C257S734000

Reexamination Certificate

active

06784523

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of fabricating a semiconductor device, and more particularly to a method of fabricating a semiconductor device having a reduced package contour, a reduced mounting area, and a reduced cost.
2. Description of the Related Art
In the fabrication of semiconductor devices, it has been customary to separate semiconductor chips from a wafer by cutting, fixing the semiconductor chips to a lead frame, sealing the semiconductor chips fixed to the lead frame with a mold and a synthetic resin according to a transfer molding process, and dividing the sealed semiconductor chips into individual semiconductor devices. The lead frame comprises a rectangular or hooped frame. A plurality of semiconductor devices are simultaneously sealed in one sealing process.
FIG. 1
of the accompanying drawings illustrates a conventional transfer molding process. In the conventional transfer molding process, a lead frame
2
to which semiconductor chips
1
are fixed by die bonding and wire bonding is placed in a cavity
4
defined by upper and lower molds
3
A,
3
B. Epoxy resin is then poured into the cavity
4
to seal the semiconductor chips
1
. After the transfer molding process, the lead frame
2
is cut off into segments containing the respective semiconductor chips
1
, thus producing individual semiconductor devices. For more details, reference should be made to Japanese laid-open patent publication No. 05-129473, for example.
Actually, as shown in
FIG. 2
of the accompanying drawings, the lower mold
3
B has a number of cavities
4
a
-
4
f,
a source
5
of synthetic resin, a runner
6
connected to the source
5
of synthetic resin, and gates
7
for pouring the synthetic resin from the runner
6
into the cavities
4
a
-
4
f.
The cavities
4
a
-
4
f,
the source
5
of synthetic resin, the runner
6
, and the gates
7
are all in the form of recesses and grooves defined in the surface of the lower mold
3
B. If the lead frame
2
is of a rectangular shape, then ten semiconductor chips
1
are mounted on one lead frame, and the lower mold
3
B has ten cavities
4
, ten gates
7
, and one runner
6
per lead frame. The entire lower mold
3
B has as many cavities
4
as necessary for twenty lead frames
2
, for example.
FIG. 3
of the accompanying drawings shows a semiconductor device fabricated by the conventional transfer molding process. As shown in
FIG. 3
, a semiconductor chip
1
containing components such as transistors is fixedly mounted on an island
8
of a lead frame by a bonding material
9
such as solder. The semiconductor chip
1
has electrode pads connected to leads
10
by wires
11
, and has its peripheral portions covered with a molded body
12
of synthetic resin which is complementary in shape to the cavity
4
. The leads
10
have respective distal ends projecting out of the molded body
12
of synthetic resin.
In the conventional semiconductor package shown in
FIG. 3
, since the leads
10
for connection to external circuits projects from the molded body
12
of synthetic resin, dimensions of the package that extends up to the projecting distal ends of the leads
10
need to be considered as covering a mounting area of the package. Therefore, the mounting area of the package is much larger than the contour of the molded body
12
of synthetic resin.
Furthermore, according to the conventional transfer molding process, since the molded body
12
of synthetic resin is hardened while it is being placed under pressure, the synthetic resin is also hardened in the runner
6
and the gates
7
, and the hardened synthetic resin in the runner
6
and the gates
7
has to be thrown away. Because the gates
7
are required for respective individual semiconductor devices to be fabricated, the synthetic resin is not utilized highly efficiently, and the number of semiconductor devices that can be fabricated is small relative to the amount of synthetic resin used.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method of fabricating a semiconductor device having a relatively small package structure and hence a relatively small mounting area.
Another object of the present invention is to provide a method of fabricating a semiconductor device relatively inexpensively.
According to the present invention, there is provided a method of fabricating a semiconductor device, comprising the steps of preparing an insulating board with a plurality of device carrier areas thereon, fixing semiconductor chips respectively to the device carrier areas, placing an electrode pattern serving as external electrodes of the semiconductor chips on a back of the insulating board, covering the semiconductor chips with a resin layer, and separating the resin layer and the insulating board into segments including the device carrier areas thereby to produce individual semiconductor devices, the electrode pattern being spaced inwardly from edges of the segments.
The above and other objects, features, and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate a preferred embodiment of the present invention by way of example.


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