Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame
Reissue Patent
2000-03-03
2003-03-25
Potter, Roy (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
C257S670000, C257S671000
Reissue Patent
active
RE038043
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a leadframe included is a resin-sealed semiconductor device.
2. Description of the Background Art
When a resin-sealed semiconductor device, for example, fabricated, a leadframe is prepared to mount a semiconductor element (chip) thereon.
FIG. 18
is a perspective view showing a configuration of a background-art leadframe
100
. A metal sheet is processed to form the leadframe
100
. The leadframe
100
has a pad
2
for mounting the semiconductor element
3
at its center portion, which is supported by suspension leads
6
a to
6
d from four directions. Inner leads
5
radially extend from the periphery towards the pad
2
. The inner leads
5
are connected b electrode portions of the semiconductor element
3
with metal thin wires
4
.
After the leadframe
100
in the state of
FIG. 18
is obtained, the semiconductor element
3
is sealed in resin such as epoxy resin and the inner leads
5
and the suspension leads
6
a to
6
d are cut off from the leadframe
100
.
In a case of a semiconductor package which includes a larger number of inner leads
5
, such as a multiple pin QFP (Quad Flat Package), each inner lead
5
becomes narrower sad longer and its rigidity becomes lower. To prevent deformation of such inner lead
5
in a fabricating process, a support tape is applied to the inner leads
5
and the suspension leads
6
a to
6
d. As to the support tape, a variety of forms are proposed as below.
FIG. 18
shows a rectangular ring-shaped support tape
201
. The rectangular ring-shaped support tape
201
is applied to the inner leads
5
and the suspension leads
6
a to
6
d around the pad
2
. Since the support tape is rectangular, the inner leads
5
and the suspension leads
6
a to
6
d are not deformed or displaced even if the support tape
201
contracts.
FIG. 19
is a plan view illustrating a manner of taking the support tape
201
out of its material. The material
200
for the support tape
201
is generally supplied in tape form, and a rectangular ring-shaped support tape
201
is punched and applied to the inner leads
5
. In this case, there are remaining portions
202
and
203
, and the material
200
is disadvantageously utilized with low efficiency. In general, the material
200
is expensive, and therefore inefficient use of the material
200
leads to a costly leadframe
100
.
To solve the problem of the structure of
FIG. 18
, use of strip shaped support tapes, instead of rectangular ring-shaped support tapes, is proposed.
FIG. 20A
is a plan view showing a configuration of a leadframe
101
and
FIG. 20B
is a section taken along the line
20
B—
20
B and viewed from the direction of the arrow of FIG.
20
A.
The support tapes
211
and
221
are of strip-shape and applied to all of the inner leads and suspension leads
6
a to
6
d.
FIG. 21
is a plan view illustrating a manner of taking the support tapes
211
and
221
out of their materials
210
and
220
in tape form. The support tapes
211
and
221
can be taken out of the materials
210
and
220
with higher efficiency than in the structure of
FIG. 18
since those support tapes are rectangular.
With this type of support tapes, however, the inner leads
5
are deformed at the suspension leads
6
a to
6
d and their vicinities, e.g., in an area A including the suspension lead
66
and its vicinity.
FIG. 22
is as enlarged plan view of an area A and its vicinity of FIG.
20
A. Among the inner leads
5
, an inner lead
501
adjacent to the suspension lead
6
b to which both the support tapes
211
and
221
are applied is pulled in the directions of the arrows by contractions of the support tapes
211
and
221
. The inner lead
501
is thereby deformed and comes into contact with an adjacent inner lead
502
at a point B. Then, the suspension lead
6
b and the inner lead
502
are also deformed.
To solve the problems of the structure of
FIGS. 18 and 20A
, it is also proposed that the strip-shaped support tapes
211
and
221
should be applied to the inner leads
5
and the suspension leads
6
a to
6
d with their end portions over-lapped.
FIG. 23A
is plan view showing a configuration of a leadframe
102
and
FIG. 23B
is a section taken along the line
23
B—
23
B of FIG.
23
A and viewed from the direction of the arrow.
The end portions of the strip-shaped support tapes
211
and
221
are overlapped to form a rectangular ring-shaped support tape on the whole and further their materials
210
and
220
can be utilized with higher efficiency. Moreover, at their overlapped end portions, stresses generated by contraction along the directions of the respective lengths of the support tapes
211
and
221
are balanced and the suspension leads
6
a to
6
d are given stresses only in a direction towards the pad
2
. That avoids deformation of the suspension leads
6
a to
6
b.
It is not desirable, however, that many portions are each given stresses in different directions at an angle of 90° when the support tapes contract. The reason is the alignment of their end portions to be overlapped should be accurately made in order to balance the stresses applied to the support tapes
211
and
221
along the directions of their lengths.
SUMMARY OF THE INVENTION
The present invention is directed to a leadframe. According to a first aspect of the present invention, the leadframe comprises: a plurality of inner leads provided radially; and a group of support tapes applied to the plurality of inner leads in a ring shape, in which inner end portions of the plurality of inner leads expose on inner peripheral side of the group of support tapes, and in which the group of support tapes includes a plurality of first support tapes of L-shape, and both and portions of one of the plurality of first support tapes are overlapped with end portions of at least one of the plurality of first support tapes which is different from said one of the plurality of first support tapes.
According to a second aspect of the present invention, in the leadframe of the first aspect, the group of support tapes includes two first support tapes.
According to a third aspect of the present invention, the leadframe of the fast aspect further comprises: a pad of substantially rectangular surrounded by the plurality of inner leads, in which the respective center portions of the plurality of first support tapes are located on two opposed ones of four suspension leads which are inner leads for supporting the pad at its four corners.
According to a fourth aspect of the present invention, in the leadframe of the third aspect, one of the plurality of first support tapes is applied to a front surface of the inner leads and the other is applied to a back surface of the inner leads, and the respective end portions are overlapped with each other through the inner leads.
According to a fifth aspect of the present invention, in the leadframe of the second aspect, each of the end portions of the plurality of first support tapes has a chipped portion having an angle of almost 45° in its extending direction.
According to a sixth aspect of the present invention, in the leadframe of the first aspect, the group of support tapes includes four first support tapes.
According to a seventh aspect of the present invention, the leadframe of the sixth aspect further comprises: a pad of substantially rectangular surrounded by the plurality of inner leads, in which the respective center portions of the plurality of first support tapes are located on four suspension leads which are inner leads for supporting the pad at its four corners.
According to an eighth aspect of the present invention, in the leadframe of the seventh aspect, a first pair of the plurality of first support tapes are opposed to each other and a second pair of the plurality of first support tapes are opposed to each other, the first pair and the second pair are different from each other, the first pair is applied to a front surface of the inner leads and the second pair is applied to a back surface of the inner leads, and
Shinohara Toshiaki
Takahashi Yoshiharu
Mitsubishi Denki & Kabushiki Kaisha
Potter Roy
LandOfFree
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