Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame – With separate tie bar element or plural tie bars
Reexamination Certificate
1999-04-27
2001-10-16
Williams, Alexander O. (Department: 2826)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
With separate tie bar element or plural tie bars
C257S673000, C257S788000, C257S787000, C257S790000, C257S666000, C257S920000, C257S713000, C257S775000, C438S414000, C438S942000, C438S946000
Reexamination Certificate
active
06303983
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a resin-encapsulated semiconductor device such as a molded flat package, and a semiconductor device manufacturing method and apparatus.
A conventional resin-encapsulated semiconductor device of this type has an arrangement as shown in FIG.
7
A. This will be described in brief. This resin-encapsulated semiconductor device
1
has a semiconductor chip
3
mounted on a die pad
2
, and a large number of leads
4
disposed around the die pad
2
. The semiconductor chip
3
and the inner lead portions of the respective leads
4
are connected to each other through thin metal wires
5
bonded to them and formed of Au wires or the like.
The die pad
2
, the semiconductor chip
3
, and the inner lead portions of the leads
4
described above are encapsulated with a molding resin to form a resin-encapsulated portion
6
. Hence, the package type semiconductor device
1
is formed.
The outer lead portions of the respective leads
4
are bent into required shapes.
Resin-encapsulated semiconductor devices
1
of this type are manufactured by using a large number of die pads
2
and a lead frame (not shown) formed around the die pads
2
to have portions that form the leads
4
. Of the lead frame forming portions of this lead frame, portions of the outer lead portions corresponding to extending portions of the resin-encapsulated portion
6
form tie bars
7
for preventing resin leakage during resin encapsulation. These tie bars
7
are cut in a finishing step after a resin encapsulating step, thus forming tie bar sectional surfaces
7
a
as shown in FIG.
7
B.
The manufacturing process for these conventional resin-encapsulated semiconductor devices
1
includes a mounting bonding step, a resin molding step, a runner/gate removing step, a thermal aging step, a trimming and plating step, a tie bar cutting step, a lead cutting, forming, marking, and cutting/separating step, and a screening step.
In a semiconductor device resin-encapsulating apparatus which performs the resin encapsulating step of the manufacturing process described above, as shown in
FIGS. 8A and 8B
, a structure obtained by connecting the semiconductor chip
3
mounted on the die pad
2
of a lead frame and the leads
4
of the lead frame to each other by bonding is prepared at a supply unit.
This structure is conveyed from the supply unit to a molding unit, and is resin-molded by the molding unit, to encapsulate the semiconductor chip
3
portion with a resin.
The semiconductor device resin-encapsulated by the molding unit is conveyed to a runner/gate removing unit that removes a runner and gates formed during resin encapsulation. After its runner and gates are removed, the semiconductor device is stored in a storing unit.
After that, the process advances to the finishing step of the resin-encapsulating step. After thermal aging, trimming, and plating are performed, the process advances to the tie bar cutting step to cut tie bars. Lead bending is also performed.
In the tie bar cutting step described above, the tie bars are cut, and simultaneously a resin dammed by the tie bars (to be referred to as a not required by the tie bars hereinafter) is also removed.
In the conventional semiconductor device resin-encapsulating apparatus described above, although the runner/gate removing unit is provided, a tie bar cutting/removing unit is not provided. Accordingly, the tie bars must be removed by a separate apparatus.
With the conventional semiconductor device resin-encapsulating apparatus described above, since tie bar cutting (including removal of the resin not required by the tie bars) is performed after trimming and plating, the semiconductor device undergoes the lead forming, cutting, marking, and cutting/separating step and then the screening step described above while the removed resin scrap and metal scrap attach to the package. The following inconveniences arise.
More specifically, the scrap generated during tie bar cutting and removal as described above may induce punching marks on the surfaces of the leads during, e.g., forming the leads, to result in defective leads. In the process described above, a lead cutting failure, a marking failure, and a screening failure (a situation wherein a product that should be particularly nondefective causes an adhesion failure due to the attaching scrap described above and is undesirably determined as a defective product) are caused to decrease the yield.
It is cumbersome to screen a shape failure caused by small damages formed by such resin scrap and metal scrap. A semiconductor device which cannot be screened as one having an outer appearance failure may be shipped as a nondefective product.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above situation, and has as its object to provide a semiconductor device in which trimmed scrap formed of resin scrap or metal scrap generated in the tie bar cutting step of the finishing step after the resin-encapsulating step for a resin-encapsulated semiconductor device causes no trouble in the following manufacturing steps, and a method and apparatus for manufacturing this semiconductor device.
In order to achieve the above object, according to the present invention, there is provided a semiconductor device comprising a lead frame, a semiconductor chip mounted on a die pad of the lead frame, a resin-encapsulated portion for resin-encapsulating the semiconductor chip, and tie bars which are provided to outer lead portions of the lead frame to prevent resin leakage during resin encapsulation and which are cut and removed in a finishing step of resin encapsulation, wherein a plating surface is formed on a sectional surface of each of the tie bars.
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patent: 4942454 (1990-07-01), Mori et al.
patent: 5619065 (1997-04-01), Kim
patent: 5767527 (1998-06-01), Yoneda et al.
patent: 5874783 (1999-02-01), Yamada
patent: 5909053 (1999-06-01), Fukase et al.
patent: 5929511 (1999-07-01), Nakazawa et al.
patent: 5945731 (1999-08-01), Iino
patent: 5955778 (1999-09-01), Shingai
patent: S63-96947 (1988-04-01), None
patent: S63-180119 (1988-11-01), None
patent: H7-22447 (1995-01-01), None
patent: 9-153504 (1997-06-01), None
patent: H9-312368 (1997-12-01), None
Hayes, Soloway, Hennessey Grossman & Hage, P.C.
NEC Corporation
Williams Alexander O.
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