Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Metallic housing or support
Reexamination Certificate
2001-12-11
2003-11-11
Fahmy, Wael (Department: 2814)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Metallic housing or support
C438S111000, C438S112000, C438S118000, C438S124000
Reexamination Certificate
active
06645792
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for fabricating a resin-encapsulated semiconductor device using a surface-mounted lead frame in which leads are exposed on the bottom surface of a resin-encapsulated portion (package).
In recent years, there is an increasing demand for high-density mounting of semiconductor elements on electronic devices in order to realize smaller electronic devices with higher functionalities. Accordingly, the overall size and the thickness of a semiconductor element such as a resin-encapsulated semiconductor device (a device obtained by integrally encapsulating a semiconductor chip and leads in an encapsulation resin) have been quickly reduced. Therefore, various techniques have been developed for the fabrication of semiconductor elements such as resin-encapsulated semiconductor devices in order to reduce the production cost and to increase the productivity. For example, a molding method has been developed in the art, in which a plurality of semiconductor chips are individually encapsulated in an encapsulation resin after the die bonding step and the wire bonding step. A process of resin encapsulation according to a conventional molding method will now be described with reference to
FIG. 7A
to
FIG. 7C
, FIG.
8
A and FIG.
8
B.
FIG. 7A
to
FIG. 7C
are perspective views schematically illustrating a resin encapsulation apparatus used in a conventional molding method and a process of resin encapsulation with such an apparatus. FIG.
8
A and
FIG. 8B
are cross-sectional views illustrating the inside of an encapsulation mold set during the resin encapsulation process.
As illustrated in
FIG. 7A
, the resin encapsulation apparatus is capable of holding an encapsulation tape
1015
under a constant tension.
As illustrated in
FIG. 7B
, a lead frame
1000
carrying a number of semiconductor chips thereon is set on a lower mold
1052
, and resin tablets
1062
are placed in encapsulation resin supply sections
1061
of the lower mold
1052
.
Then, as illustrated in
FIG. 8A
, the lead frame
1000
is clamped between an upper mold
1051
and the lower mold
1052
. At this time, a melted encapsulation resin is supplied by a plunger
1058
from below into semiconductor product molding sections
1060
, whereby a resin-encapsulated semiconductor device
1055
is injection-molded in each die cavity. Upon completing the injection molding and opening the lower mold
1052
, the encapsulation tape
1015
is separated from a resin cull
1063
and the resin-encapsulated semiconductor device
1055
illustrated in FIG.
7
C.
However, in the conventional molding method, when the lead frame
1000
is clamped between the upper mold
1051
and the lower mold
1052
, a gas (e.g., an air left therein due to warping of the lead frame
1000
, etc., a vapor generated from the encapsulation tape
1015
due to a temperature increase, or an organic material gas) may be entrapped in the slight gap between the encapsulation tape
1015
and the opposing upper mold
1051
. If the lead frame
1000
is clamped between the upper mold
1051
and the lower mold
1052
with such a gas being entrapped, the gas will not be discharged out of the gap between the upper and lower molds. Moreover, subsequent injection of an encapsulation resin into the cavity may push the entrapped gas away from a resin injection gate
1070
, as illustrated in
FIG. 8B
, thereby deforming the lead frame
1000
by the pressure of the gas being pushed. An excessive deformation of the lead frame
1000
may cause a semiconductor chip
1021
and/or a thin metal wire
1022
to come into contact with the lower mold
1052
, thereby damaging or deforming the semiconductor chip
1021
and/or the thin metal wire
1022
.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve this problem in the prior art, and has an object to suppress the deformation of a lead frame during the resin encapsulation step.
A lead frame of the present invention is a lead frame used in resin encapsulation of a semiconductor chip using an encapsulation mold that includes a die cavity to be filled with an encapsulation resin, the lead frame including: a first region exposed to the die cavity; a second region that is surrounding the first region and to be clamped by the encapsulation mold; a third region exposed to an ambient air with the die cavity being filled with the encapsulation resin; and at least one groove formed on a surface of the lead frame that is opposite to another surface of the lead frame on which the first region is present, the at least one groove extending from an area corresponding to the first region across another area corresponding to the second region so as to reach the third region.
When a resin-encapsulated semiconductor device is fabricated with a resin creepage preventing member being attached to one surface of the lead frame of the present invention that is opposite to the surface thereof on which the first region is present, the air entrapped between the resin creepage preventing member and the encapsulation mold is pushed into the second region clamped by the encapsulation mold due to the pressure from the resin being injected into the die cavity in the resin encapsulation process. The air being pushed lifts the resin creepage preventing member covering at least one groove toward the lead frame, i.e., into the at least one groove. The at least one groove extends from an area corresponding to the first region across another area corresponding to the second region so as to reach the third region that is exposed to the ambient air, whereby the air lifting the resin creepage preventing member into the at least one groove is discharged to the outside of the encapsulation mold. Therefore, in the fabrication of a resin-encapsulated semiconductor device, it is possible to suppress/prevent the lead frame from being deformed, and to suppress/prevent a damage to semiconductor chips, a deformation and disruption of thin metal wires, etc., which may otherwise occur due to the deformation of the lead frame.
The at least one groove may be a U-shaped groove; and the third region may be a side edge of the lead frame surrounding the second region.
The at least one groove may be a U-shaped groove that includes a through hole connecting the at least one groove to the third region.
A method for fabricating a resin-encapsulated semiconductor device of the present invention includes the steps of: (a) preparing a lead frame, including: a first region; a second region surrounding the first region; a third region located outside the second region; and at least one groove formed on a surface of the lead frame that is opposite to another surface of the lead frame on which the first region is present, the at least one groove extending from an area corresponding to the first region across another area corresponding to the second region so as to reach the third region; (b) providing a resin creepage preventing member on the area corresponding to the first region; (c) mounting a semiconductor chip on the first region of the lead frame; and (d) clamping the second region by an encapsulation mold that includes a die cavity so as to place the semiconductor chip into the die cavity, and filling the die cavity with a resin.
With this fabrication method, in the resin filling step, the air entrapped between the resin creepage preventing member and the encapsulation mold is pushed into the second region clamped by the encapsulation mold due to the pressure from the resin being injected into the die cavity. The air being pushed lifts the resin creepage preventing member covering at least one groove toward the lead frame, i.e., into the at least one groove. The at least one groove extends from an area corresponding to the first region across another area corresponding to the second region so as to reach the third region that is located outside the second region and is not clamped by the encapsulation mold, whereby the air lifting the resin creepage preventing member into the at least one groove is discharg
Hidaka Hiroshi
Inao Hisaho
Oga Akira
Fahmy Wael
Matsushita Electric - Industrial Co., Ltd.
Nguyen DiLinh
LandOfFree
Lead frame and method for fabricating resin-encapsulated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Lead frame and method for fabricating resin-encapsulated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Lead frame and method for fabricating resin-encapsulated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3137757