Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Making plural separate devices
Reexamination Certificate
1999-07-13
2001-07-10
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Making plural separate devices
C438S113000, C438S123000, C438S124000, C438S127000, C438S907000, C438S908000
Reexamination Certificate
active
06258628
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to methods of processing lead frames in which an electronic part such as an IC (Integrated Circuit) is sealed with resin, hereinafter simply referred to as a resin sealed lead frame, and apparatuses therefor. More specifically, the present invention relates to a method of processing resin sealed lead frames for cutting a prescribed portion of the resin sealed lead frame or separating each electronic section forming a product, on the resin sealed lead frame and an improvement of the apparatus for performing the method.
2. Description of the Background Art
A first type of prior art related to the present invention will now be described with reference to
FIGS. 11 and 12A
to
12
C.
FIG. 11
generally shows a processing apparatus for a resin sealed lead frame according to the first type of prior art.
FIGS. 12A
to
12
C schematically show an arrangement of a so-called QFP (Quad Flat Package) type resin sealed lead frame A in which outer leads
3
protrude from four sides of a resin sealed molding or mold package
2
in which an electronic part
1
is sealed.
In a resin sealed lead frame A shown in
FIGS. 12A
to
12
C, a lead frame body
4
and a die pad
6
for mounting an electronic part
1
are connected by a pinch lead
5
. A dam bar
7
is provided for preventing melted resin material from flowing out of a mold cavity at the time of sealing the electronic part
1
with resin. A cavity
8
serves as a resin pool. Four electronic parts
1
are mounted to the lead frame body
4
and each part
1
is electrically connected to a prescribed outer lead.
For separating each electronic section or product from the resin sealed lead frame A, for example, various cutting steps, such as cutting of the cavity
8
, cutting of the resin at the dam bar
7
, cutting of the dam bar
7
itself, cutting of a tip connecting portion of the outer lead
3
and cutting of the pinch lead
5
, must be performed.
A plurality of such cutting steps, for example, the above mentioned resin cutting step and the dam bar cutting step can be performed almost simultaneously, depending on the thickness, shape or the like of the lead frame body
4
. At the same time, any unnecessary step should be eliminated. The above mentioned separation of each electronic section is performed by a lead processing apparatus having an upper mold or tool
9
and a lower mold or tool
10
, for example as shown in FIG.
11
.
The lead processing apparatus illustrated in
FIG. 11
is structured to perform only the above mentioned cavity cutting step, the dam bar cutting step and the pinch lead cutting step. More specifically, the lead processing apparatus shown in
FIG. 11
is provided with a structure of a so-called sequentially feeding mold and includes: an upper mold base
11
; a punch holder
12
fixed to the upper mold base
11
; a punch blade
13
fixed to the punch holder
12
; a stripper blade
14
suspended from the punch blade
13
, a cavity cutting punch
15
for cutting the cavity
8
; a dam bar cutting punch
16
for cutting the resin at the dam bar
7
; and a pinch lead cutting punch
17
for cutting the pinch lead
5
.
Base portions of punches
15
,
16
and
17
are fixed to the same punch holder
12
through the punch blade
13
, and their tip blades are fitted onto a punch guide
18
. Dies
19
,
20
and
21
are arranged on the lower mold
10
, respectively corresponding to punches
15
,
16
and
17
.
As shown in
FIG. 11
, the resin sealed lead frame A is fed to a prescribed position between the upper and lower molds
9
and
10
, and the cutting steps are sequentially performed by the punches
15
,
16
,
17
, and the dies
19
,
20
,
21
while sequentially feeding each electronic section on the resin sealed lead frame A. Thus, each electronic section is sequentially separated.
As described above, in the conventional lead processing apparatus, each punch used for cutting and separating the electronic sections or product from the resin sealed lead frame A, is integrally fixed to one mold base, and the die corresponding to the punch is integrally fixed to the other mold base.
When the leads of a different type of resin sealed lead frame are to be processed, the above described conventional lead processing apparatus cannot be directly used. Then, a different lead processing apparatus for the resin sealed lead frame must be provided, or any unnecessary punches and dies fixed to the mold base
11
must be removed so that different punches and different dies required for the lead processing can be integrally fixed to the mold base.
Providing a dedicated separate lead processing apparatus for every kind of resin sealed lead frame is very uneconomical, and changing of the punches and dies for every kind of resin sealed lead frame requires not only a laborious operation but also skill for the fine adjusting after the tool and die change.
A second type of prior art related to the present invention will now be described with reference to
FIGS. 13A and 13B
. It is noted that elements corresponding to those of the above described first type of prior art shown in
FIGS. 12A
to
12
C are denoted by the same reference numerals.
FIGS. 13A and 13B
schematically show an exemplary arrangement of a resin sealed lead frame in which outer leads
3
protrude from two sides of a resin sealed molding
2
including an electronic part
1
.
In the resin sealed lead frame according to the second type of prior art shown in
FIGS. 13A and 13B
, a cradle
4
and a die pad
6
for mounting the electronic part
1
are connected by a pinch lead
5
. A dam bar
7
is further provided to prevent melted resin from flowing out of a mold cavity at the time of sealing the electronic part
1
with resin. A prescribed number of electronic parts
1
are mounted on a cradle
4
and each part is electrically connected to a prescribed inner lead
28
.
For the step of separating each electronic section or product from the resin sealed lead frame, a lead processing apparatus having a so-called sequentially feeding mold is used. The sequentially feeding mold includes a punch and die for cutting and thereby performs each cutting step while sequentially feeding the resin sealed lead frame to a prescribed position between the punch and die. For example, the mold sequentially performs cutting of resin and removal of resin at the dam bar
7
, cutting of the dam bar
7
, cutting of a tip connecting portion of an outer lead
3
, and cutting of the pinch lead
5
or the like.
It is noted that if a mold for bending the outer lead
3
is provided along with the above described mold for cutting, a step of bending the outer lead can be simultaneously or separately performed. However, as the bending of the lead is performed in a manner substantially similar to that of the above mentioned cutting steps, a further description thereof is not necessary.
In the conventional method of processing the lead or leads described with reference to
FIGS. 13A and 13B
, the products are pressed by cutting molds which are spaced by one pitch along the feeding path while sequentially feeding the products on the lead frame by a distance equal to one pitch. One pitch is defined as the on-center spacing between two neighboring products along the feeding path. In the final processing step, each product is sequentially cut and separated from the resin sealed lead frame to produce separate products. For increasing the production volume per period of time, the number of lead processing apparatuses having similar functions and structures must be increased. For example, to double the production volume in the same period of time, two lead processing apparatuses having similar structures must be provided, whereby the equipment costs, and the required space for the equipment is doubled.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for processing a resin sealed lead frame capable of accommodating a change in the processing operation and a change in the production volume for pro
Hidaka Tetsuo
Horiuchi Kazuo
Osada Michio
Fasse W. F.
Fasse W. G.
Niebling John F.
Towa Corporation
Zarneke David A.
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