Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Making plural separate devices
Reexamination Certificate
1998-03-20
2001-06-05
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Making plural separate devices
C438S112000, C438S118000
Reexamination Certificate
active
06242287
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for manufacturing a semiconductor device, and more particularly to a manufacturing method capable of reducing generation of a resin piece, a press die and a guide rail.
2. Description of the Background Art
In general, a semiconductor device has a structure in which an integrated circuit portion (a semiconductor chip) is sealed with an insulating material such as a resin, and includes a lead extending through the insulating material for electrical connection of an integrated circuit to an external portion. In the following description, a quad flat package (QFP) will be taken as an example.
First of all, a process of manufacturing the QFP will be described below. In general, a flat package semiconductor device such as the QFP is formed by mounting a semiconductor chip on a terminal member referred to as a lead frame and sealing the semiconductor chip with a resin.
The semiconductor chip is first fixed (die bonded) to a portion referred to as a die pad of a lead frame
20
and is connected (wire bonded) to a lead by wiring. Then, the semiconductor chip is sealed with a sealing resin
3
. The lead frame
20
is band-shaped and has a structure in which a plurality of semiconductor chips are arranged.
FIG. 30
is a plan view showing the lead frame
20
in a state in which the semiconductor chip is completely sealed with the resin. In
FIG. 30
, a plurality of sealing resins
3
are arranged in a line. At a resin sealing step, the semiconductor chip is enclosed by a die to form a cavity, and a liquid resin is poured into the cavity. Then, the resin is cured to form the sealing resin
3
. A path (gate) for introducing the resin remains on a surface of the lead frame
20
with the resin filled therein. When the lead frame
20
is separated from the die, most of the gate is removed (gate break). A residual portion of the gate makes a remaining gate
3
a.
As shown in
FIG. 31
, the lead frame
20
is divided by press molding for each section corresponding to one semiconductor device (single substance cut). At this step, a divided lead frame
2
is obtained. In this stage, the lead frame
2
has a tie bar TB in a lead LD.
Then, the tie bar TB is removed by the press molding as shown in
FIG. 32
(tie bar cut).
Thereafter, four corners of the lead frame
2
are removed by press molding as shown in
FIG. 33
(pinch cut). At a pinch cut step, the four corners of the lead frame
2
are connected to a die pad (not shown) on which the semiconductor chip is mounted and a pinch portion (not shown) of a suspension lead supporting a die is cut away. At this time, the remaining gate
3
a
is also removed. At this step, the lead frame
2
remains on only a tip of a lead group LG extending from the sealing resin
3
in four directions.
Subsequently, an unnecessary portion of the lead frame
2
remaining on the tip of the lead group LG is removed and the lead LD is subjected to bending. Thus, the QFP is finished.
Since the semiconductor device according to the prior art has been manufactured by the above-mentioned method, it has had the following problems.
FIG. 34
is a detailed diagram showing a structure in FIG.
32
. As shown in
FIG. 34
, a pinch portion
2
b
of the suspension lead extends from four corners of the sealing resin
3
, and is connected to four corners
2
a
of the lead frame
2
. At the pinch cut step, the four corners
2
a
of the lead frame
2
are removed. In this case, the remaining gate
3
a
becomes a problem. The remaining gate
3
a
extends from the corner of the sealing resin
3
to a surface of the corner
2
a
of the lead frame
2
.
FIG. 35
is a perspective view showing an X region in FIG.
34
. At the pinch cut step, the lead frame
2
is cut away along the virtual cutting line CL shown by a broken line in
FIG. 35
so that the corner
2
a
is removed. In this case, the pinch portion
2
b
is torn for removal.
The remaining gate
3
a
is a residual portion of the gate formed by an upper gate method. In the case where the gate is formed by a lower gate method, a remaining gate is formed in a position which is vertically reverse to that of the remaining gate
3
a
. The same remaining gate is indicated at
3
b
.
FIG. 36
corresponds to
FIG. 35
in which the remaining gate
3
b
is formed.
A step of removing the remaining gate
3
b
shown in
FIG. 36
will be described below with reference to
FIGS. 37 and 38
. As shown in
FIG. 37
, the lead frame
2
is mounted on a die
9
.
FIG. 37
is a sectional view showing the corner
2
a
. A punch
8
descends from above the corner
2
a
. The punch
8
presses down the corner
2
a
so that a cutting line CL portion which is not shown is cut away and the pinch portion
2
b
is torn at the same time. At this time, the remaining gate
3
b
is broken off together with the corner
2
a
. In that case, a stress converges on a bottom portion of the remaining gate
3
b
so that the sealing resin
3
is broken off and a resin fracture portion
3
d
is formed or a crack is generated. When the remaining gate
3
b
is broken off, a resin piece is sometimes generated.
In the process of manufacturing a semiconductor device which has been described with reference to
FIGS. 30
to
33
, the lead frame
2
is often slid and carried on a guide rail. However, the remaining gate
3
b
exists on a lower face of the corner
2
a
of the lead frame
2
, that is, on a face on a side which comes in contact with the guide rail as described above with reference to FIG.
36
. As shown in
FIG. 34
, a remaining air vent
3
e
exists in each of the three corners of the sealing resin
3
except the corner where the remaining gate
3
a
(or the remaining gate
3
b
) is formed.
An air vent serves to prevent air accumulation from being generated in the cavity when the liquid resin is poured from the gate into the cavity, and is provided on each of three corners of the cavity. Accordingly, the resin is filled in so that it overflows from the air vent. The overflowing resin is cured so that the remaining air vent
3
e
is formed. The remaining air vent
3
e
is formed on upper and lower faces of the lead frame
2
.
Consequently, the remaining gate
3
b
and the remaining air vent
3
e
rub against the guide rail when the lead frame
2
is slid on the guide rail. At this time, there is a possibility that a resin piece might be generated from the remaining gate
3
b
and the remaining air vent
3
e
and might cut into the sealing resin
3
or stick to the surface of the lead LD.
In the process of manufacturing a semiconductor device which has been described with reference to
FIGS. 30
to
33
, the press molding is performed. During the press molding, the remaining gates
3
a
and
3
b
and the remaining air vent
3
e
might be crushed to generate the resin piece. For example, if a processing proceeds to another press step in a state in which the resin piece adheres to the sealing resin
3
or the lead LD, the resin piece might cut into the sealing resin
3
or stick to the lead LD at the same press step.
Thus, the method for manufacturing a semiconductor device according to the prior art has had a problem that the sealing resin is damaged and the resin piece cuts into the sealing resin and sticks to the lead, thereby causing product failures.
SUMMARY OF THE INVENTION
A first aspect of the present invention is directed to a method for manufacturing a semiconductor device, comprising the steps of (a) forming, on a lead frame, a sealing resin for sealing an integrated circuit by using a resin sealing die, (b) forming a crack in a predetermined position of a remaining gate extending from the sealing resin to the lead frame in a direction perpendicular to a direction of the extension corresponding to a gate of the resin sealing die, and (c) breaking off the remaining gate in a portion where the crack is formed when an unnecessary portion of the lead frame is removed by press molding.
A second aspect of the present invention is directed to the method for manufactur
Aoki Hideji
Katou Kenichirou
Nishitani Hiromu
Sekiya Hidenori
Mitsubishi Denki & Kabushiki Kaisha
Niebling John F.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Pompey Ron
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