Metal fusion bonding – With means to juxtapose and bond plural workpieces – Plural discrete workpieces
Reexamination Certificate
2000-02-16
2002-06-11
Lee, Eddie (Department: 2815)
Metal fusion bonding
With means to juxtapose and bond plural workpieces
Plural discrete workpieces
C257S667000, C257S669000, C257S674000, C257S666000, C228S173100, C228S173200, C228S173600, C228S174000, C228S180210, C228S004500
Reexamination Certificate
active
06402009
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus and method for shaping a lead frame of a semiconductor device which are used to provide a step portion on a lead frame for a semiconductor device such as IC (Integrated Circuit), LSI (Large Scale Integrated circuit) so that a plate-shaped semiconductor element mount portion of the lead frame on which a semiconductor element is mounted is depressed from the surrounding horizontal portion, for example, and a lead frame for a semiconductor device.
2. Description of the Related Art
There are generally known various types of lead frames for semiconductor devices (hereinafter merely referred to as “lead frame”) which are different from one another in constituent material, shape, etc. Of these lead frames, a lead frame
12
used for a resin-sealed type semiconductor device
10
as shown in
FIG. 1
is well known.
The lead frame
12
is formed of a conductive metal thin plate
13
having a thickness of 0.1 to 0.2 mm, and a step portion is formed on the lead frame so as to be more deeply depressed as compared with the surrounding horizontal portion
14
thereof. The lead frame
12
has a plate-shaped semiconductor element mount portion
18
on which a semiconductor element
16
formed of silicon-based material is mounted, and the semiconductor element
16
is mounted through adhesive agent
20
on the semiconductor element mount portion
18
.
The tip end portions of bonding wires
22
extending from the semiconductor element
16
are electrically connected to internal draw-out leads
24
of the lead frame
12
, and the respective parts are sealed by sealing resin
26
such as epoxy resin as shown in FIG.
1
. External draw-out leads
28
of the lead frame
12
are projected from the sealing resin
26
under the state that they are subjected to outer-sheath plating, shape working, etc.
When such a resin-sealed type semiconductor device
10
as described above is constructed by using a lead frame
12
as described above, it is required to make equal the thickness of the upper portion of the sealing resin
26
located at the upside from the semiconductor element
16
to the thickness of the lower portion of the sealing resin
26
at the downside from the semiconductor element mount portion
18
. Therefore, a press working must be carried out to set a depression amount D so that the semiconductor element
16
and the semiconductor element mount portion
18
are located at the center in the height direction of the resin-sealed type semiconductor device
10
and make a step portion on the lead frame so that the semiconductor element mount portion
18
is depressed from the surrounding horizontal portion thereof by the depression amount D thus set.
Here, the process of manufacturing the semiconductor device lead frame
12
as described above will be described with reference to
FIGS. 2A
to
2
C.
First, etching and stamping are applied to the plate-shaped conductive metal thin plate
13
as shown in
FIG. 2A
so that a shape which is approximately similar to the lead frame
12
is formed on the conductive metal thin plate
13
as shown in FIG.
2
B.
Subsequently, plating is applied to the conductive metal thin plate
13
having the internal draw-out leads
24
, the semiconductor element mount portion
18
, etc. Thereafter, press working is applied to the conductive metal thin plate
13
thus plated as shown in
FIG. 2C
so that the semiconductor element mount portion
18
is depressed from the surrounding horizontal portion thereof as shown in
FIG. 2C
, thereby substantially completing the lead frame
12
with leaving the final stamping step.
A die instrument
30
as shown in
FIG. 3
is used to perform the press working for depressing the semiconductor element mount portion
18
at the center portion of the lead frame
12
. That is, a concave shape
32
is formed on a die
31
serving as a lower die by electric discharge machining or the like, and the overall body of the die
31
is designed as an integrated body which is continuous in the horizontal direction.
A convex shape
36
is formed on a punch
34
serving as an upper die through a finishing treatment using cutting work or the like, and the length of the punch
34
is set to be smaller than the die
31
in the horizontal direction. Further, a cavity
34
a
is formed at the center of the punch
34
, and a stopper
38
for pressing the conductive metal thin plate
13
in the shaping process is provided around the punch
34
so as to be upwardly and downwardly movable independently of the punch
34
.
The procedure of the press working for depressing the semiconductor element mount portion
18
of the lead frame
12
by using the die instrument
30
will be described hereunder with reference to
FIGS. 4A
to
4
C. That is, as shown in
FIG. 4A
, the conductive metal thin plate
13
is positioned and mounted on the die
31
.
Subsequently, as shown in
FIG. 4B
, the stopper
38
is downwardly moved to press and fix the conductive metal thin plate
13
. Finally, as shown in
FIG. 4C
, the punch
34
is downwardly moved to sandwich the conductive metal thin plate
13
between the convex shape
36
of the punch
34
and the concave shape
32
of the die
31
and press and properly crush the sandwiched portion, thereby completing the working.
However, the conventional shaping method of depressing the semiconductor element mount portion
18
of the lead frame
12
has such a problem that it is very difficult to adjust the depression amount D in
FIG. 1
after the working is completed.
That is, even when the punch
34
and the die
31
are manufactured under the condition that the projection amount of the convex shape
36
of the punch
34
and the recess amount of the concave shape
32
of the die
31
are coincident with the depression amount D or slightly different from the depression amount D, the depression amount D of the lead frame
12
after the press working is completed is not necessarily coincident with an expected dimensional value. This is because the depression amount D is effected by various factors such as the material, thickness and shape of the lead frame
12
.
Therefore, in a case where the actual depression amount D of the lead frame
12
is larger than an expected value, if the press force of the punch
34
is reduced in order to adjust the depression amount D to a smaller value, the depression amount D of the lead frame
12
is excessively reduced, so that the shaping is insufficiently carried out or the depression amount D is greatly dispersed.
On the other hand, in a case where the actual depression amount D of the lead frame
12
is smaller than an expected value, if the press force of the punch
34
is increased in order to adjust the depression amount D to a larger value, the conductive metal thin plate
13
is excessively compressed, so that the compressed portion is crushed and thus the mechanical strength of the lead frame is insufficient or the depression amount D is greatly dispersed.
In order to perfectly solve these problems, the punch
34
and the die
31
must be remade while slightly varying the projection amount of the convex shape
36
and the recess amount of the concave shape
32
, resulting in remarkable increase of the manufacturing time and the manufacturing cost. In addition, even when the above manner is adopted, an expected result cannot be necessarily obtained.
SUMMARY OF THE INVENTION
Therefore, the present invention has been implemented in view of the foregoing problems, and has an object to provide apparatus and method for shaping a lead frame for a semiconductor device and a lead frame for a semiconductor device, which can broad the adjustment range of the depression amount of a semiconductor element mount portion and easily adjust the depression amount to be equal to an expected value with inducing neither insufficient shaping nor insufficient strength.
In order to attain the above object, according to a first aspect of the present invention, an apparatus for shaping a lead frame for a semiconduc
Sonnenschein Nath & Rosenthal
Sony Corporation
Warren Matthew E.
LandOfFree
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