Plastic and nonmetallic article shaping or treating: processes – Mechanical shaping or molding to form or reform shaped article – To produce composite – plural part or multilayered article
Reexamination Certificate
2001-02-14
2003-03-04
Pham, Long (Department: 2823)
Plastic and nonmetallic article shaping or treating: processes
Mechanical shaping or molding to form or reform shaped article
To produce composite, plural part or multilayered article
C425S543000
Reexamination Certificate
active
06528000
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims the priority benefit of Japanese Patent Application No. 2000-044478, filed Feb. 22, 2000, the entire disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a molding apparatus for a resin shielding semiconductor device, a lead frame for the device from which surplus resin can be detached without burrs, and a method for removing without burrs surplus resin attached to a semiconductor device formed using the molding apparatus.
2. Description of the Related Art
A conventional process for encapsulating a semiconductor device with a resin material is shown in
FIGS. 6A through 6D
. Referring to
FIG. 6A
, a semiconductor chip
100
mounted on a lead frame
102
is set in a molding apparatus
500
. The molding apparatus
500
includes an upper platen
201
and a lower platen
211
. The upper platen
201
has a cull
202
, an upper resin passage
213
a
and an upper cavity
203
, and the lower platen
211
has a transfer pot
212
, a lower resin passage
213
b,
a gate
214
and a lower cavity
215
. The lower resin passage
213
b
has a rearward region
213
b′
and forward region
213
b″,
which is thinner than the rearward region
213
b′.
The lead frame
102
is placed between the lower platen
211
and the upper platen
201
as the semiconductor chip is located in the center of the lower cavity
215
and the upper cavity
203
. A tablet
301
of the resin material is placed in the transfer pot
212
.
Referring to
FIG. 6B
, the lead frame
102
is placed on the lower cavity wherein one end of the lead frame
102
is sandwiched by the upper and lower cavities
203
and
215
, and other end is extended to the gate
214
and the runner
213
, which are formed in the lower platen
211
. Then, the upper platen
201
is moved toward the lower platen
211
until the upper platen
201
contacts the lower platen
211
so that a space
217
is formed by the upper and lower cavities
203
and
215
, and a runner
213
is formed by contacting the upper resin passage
213
a
to the lower resin passage
213
b.
As a result, the semiconductor chip
100
is located in a center of the space
217
, and the lead frame
102
is sandwiched by the upper and lower platen
201
and
211
. Then, the tablet
301
in the transfer pot
212
is heated until it melts completely. Then, the melted resin is pushed out from the bottom with an unillustrated plunger to the cull
202
and the runner
213
and it reaches, to the gate
214
as shown in FIG.
6
C.
Referring to
FIG. 6D
, the melted resin passes through an opening
300
of the lead frame
102
and the gate
214
, and enters the space
217
. As descried above, since the semiconductor chip
100
has been placed in the space
217
, it is encapsulated with the melted resin. Then, the melted resin is further heated for a particular period and solidifies as it cools down to room temperature.
After the melted resin is solidified, surplus resin remaining in the runner
213
and the cull
202
, is detached from the resin solidified in the space
217
at the gate
214
so as to complete the semiconductor device
101
.
However, residual burrs of the surplus resin sometimes remain in the opening
300
of the lead frame
102
, because of a requirement of the gate shape. That is, since the surplus resin remained in the runner
213
should be detached from the gate to complete the semiconductor device, the size of the gate
214
should as be small as possible to permit the surplus resin to be broken easily. For this purpose, the forward region
213
b″
of the lower resin passage
213
b
is formed thinner than other region.
As a result of this configuration, residual burrs may remain, as illustrated in reference to
FIGS. 7A through 7D
. For example, a residual burr
111
of the surplus resin may remain at one side of the runner
213
(FIG.
7
A), or a residual burr
112
of the surplus resin may remain in the runner
213
(FIG.
7
B). Also, a residual burr
113
of the surplus resin may remain at both sides of the runner
213
(FIG.
7
C). A further possibility is that a residual burr
114
of the surplus resin may remain at the gate
214
(FIG.
7
D).
Therefore, a deflashing process for removing the residual burrs is required when the resin shielding semiconductor device is manufactured by the molding apparatus described above.
SUMMARY OF THE INVENTION
An objective of the invention is to resolve the issue described above, and to provide a molding apparatus for a resin shielding semiconductor device including a lower platen having a lower cavity, a lower resin passage and a gate to connect the lower resin passage to the lower cavity, the lower passage having a region of reduced thickness adjacent to the gate, and an upper platen having an upper cavity, an upper resin passage and a recess, the upper resin passage being connected to the lower resin passage to form a runner when the one of the platens is moved toward the other until they contact, the recess being formed adjacent to the upper cavity at the location that corresponds to the region when the lower and upper platens are contacted.
A further objective of the invention is to provide a lead frame including a first region in which a semiconductor chip can be encapsulated with resin, and a second region in which an opening is formed, the opening having one end, which extends to the first region, and opposite end being rounded.
Another objective of the invention is to provide a method for removing surplus resin from a semiconductor device without leaving burrs including providing a molding apparatus including a lower platen having a pot, a lower cavity, a lower resin passage and a gate to connect the lower resin passage to the lower cavity, the lower passage having a region of reduced thickness adjacent to the gate, and an upper platen having a cull, an upper cavity, an upper resin passage which is connected to the cull and a recess, the recess being formed adjacent to the upper cavity at the location that corresponds to the region when the lower and upper platens are contacted, placing a lead frame on which a semiconductor chip is mounted, on the lower platen, the lead frame having an opening, moving one of the platens toward the other until they contact to connect the upper resin passage to the lower resin passage to form a runner, and whereby the semiconductor chip is enclosed in a space which is formed by the cavities, placing a resin tablet in the pot, and heating the tablet until it melts, transferring the melted resin to the runner via the cull and the recess, and injecting the melted resin from the gate through the opening of the lead frame, solidifying the melted resin in the space, the runner, the cull and the recess, providing a degating apparatus including a movable plate, a binder, a revolved shaft and a lifting device, placing the lead frame having the solidified resin, on the plate, and fixing the solidified resin formed in the cull by the binder and lifting the plate, and turning the plate on the shaft to break the solidified resin which was formed at a location corresponding to the gate.
REFERENCES:
patent: 5275546 (1994-01-01), Fierkens
patent: 5326243 (1994-07-01), Fierkens
patent: 5349136 (1994-09-01), Abe et al.
patent: 5635220 (1997-06-01), Izumi et al.
Mimura Junichi
Oki Electric Industry Co. Ltd.
Pham Long
Pham Thanh V
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