Active solid-state devices (e.g. – transistors – solid-state diode – Lead frame
Reexamination Certificate
2001-12-28
2003-03-25
Clark, Jasmine J B (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Lead frame
C257S692000, C257S694000, C257S676000
Reexamination Certificate
active
06538306
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an electronic component made of an electrically conductive plate and including a plurality of leads formed with an island for mounting of a semiconductor chip or formed with a connecting portion for connection with a wire. Such an electronic component serves as e.g. a diode, a transistor, or a combination of these.
BACKGROUND ART
As an example of the electronic component, FIG.
17
and
FIG. 18
show a two-terminal electronic component Y, which serves as a diode. The electronic component Y includes a first lead
7
formed with an island
70
, and a second lead
8
formed with a connecting portion
80
. These leads
7
,
8
are opposed to each other so that their respective end surfaces
70
a,
80
a
face in parallel to each other. The island
70
is mounted with a semiconductor chip
9
. The semiconductor chip
9
has an upper surface electrode
90
electrically connected with the connecting portion
80
via a wire
91
. With the above structure, the semiconductor chip
9
, the wire
91
, the island
70
and the connecting portion
80
are entirely sealed in a resin package
92
. Each of the leads
7
,
8
extends out of the resin package
92
. These extensions
71
,
81
serve as outer connection terminals. More specifically, as shown in
FIG. 18
, the extensions
71
,
81
are respectively bent into crank-like shapes, so that their respective tips
71
a,
81
a
are flush with a bottom surface
92
a of the resin package
92
. Alternatively, the extensions
71
,
81
are bent as shown in phantom lines in the figure. In each case, the tips
71
a,
81
a
of the extensions
71
,
81
serve as connecting portions with e.g. a circuit substrate.
Now, with such a structure of the electronic component Y, in view of miniaturizing the electronic component Y, it is necessary to decrease the area of the island
70
and the connecting portion
80
. On the other hand, the size of the semiconductor chip
9
mounted on the island
70
is largely determined by the kind of electronic component Y to be manufactured, which substantially limits the extent of area reduction of the island
70
. Likewise, the connecting portion
80
to which the wire
91
is connected has to allow for a certain minimum area, which substantially limits the extent of area reduction. As a result, in order to reduce the size of the electronic component Y, it is necessary to decrease a distance between the island
70
and the connecting portion
80
, i.e. a distance between the end surfaces
70
a,
80
a
of the leads
7
,
8
.
However, according to the electronic component Y, the leads
7
,
8
are electrically connected with each other, and their respective end surfaces
70
a,
80
a
are faced in parallel to each other. Thus, if the distance between the end surfaces
70
a,
80
a
is decreased, the gap between these end surfaces
70
a,
80
a
functions as a capacitor. Moreover, the smaller the distance between the end surfaces
70
a,
80
a,
the greater is the electric charge held in the gap, leading to a problem that the electronic component Y cannot be used in a high frequency circuit.
There is another problem. Specifically, each of the leads
7
,
8
of the electronic component Y shown in FIG.
17
and
FIG. 18
is made from a leadframe. This leadframe is formed, as shown in
FIG. 19A
for example, by first punching the first and the second lead
7
,
8
as a mutually connected single piece, using a metal die P
1
of a predetermined punching pattern. Next, as shown in
FIG. 19B
, another metal die (blade) P
2
is used to punch out the gap between the leads
7
,
8
. Therefore, in order to decrease the gap between the end surfaces
70
a,
80
a
of the leads
7
,
8
, the blade P
2
must have a decreased thickness. However, if the distance between the leads
7
,
8
is to be decreased, the blade P
2
for forming the leadframe becomes susceptible to fracture or chipping, reducing the life of the blade P
2
and resulting in disadvantage not only in cost but also in manufacturing efficiency in that the blade P
2
must be replaced frequently.
The present invention is made under the above circumstances, and it is therefore an object of the present invention to provide an electronic component which can be made advantageously not only in terms of manufacturing cost but also in terms of manufacturing efficiency, and which is miniaturized yet appropriate for use in a high frequency circuit.
DISCLOSURE OF THE INVENTION
An electronic component provided by the present invention is formed of an electrically conductive plate, includes a plurality of leads each including an island for mounting of a semiconductor chip or including a connecting portion for connection with a wire, and is characterized in that at least a set of mutually adjacent leads have their respective mutually facing side surfaces made non-parallel to each other.
According to this arrangement, the mutually facing side surfaces of the above set of leads are non-parallel to each other, which means the distance between the side surfaces is larger at a certain location and smaller at a certain location. Therefore, even if the leads are brought closer to each other as a whole for the sake of size reduction of the electronic component, the distance between the side surfaces is larger for a certain length. Thus, it becomes possible to accordingly reduce electrostatic capacity between the leads. As a result, the electronic component according to the present invention can be used appropriately even in a high frequency circuit.
Further, even if each lead is formed by punching out an electrically conductive plate, if there is a region having the large distance between the mutually adjacent leads, then the punch (blade) can be given a large thickness in a portion corresponding to the region having the large distance. This enables to reduce fracture and chipping of the blade, leading to an increased life of the blade and improved cost of manufacture.
In order to make a non-parallel arrangement between the mutually facing side surfaces in the set of mutually adjacent leads, at least one side surface of the set of leads can be at least partially curved, folded and/or slanted. Further, as anticipated from that the mutually facing side surfaces may include a folded surface, the term “side surface” implies that the side surface may include not only one surface but also a plurality of continuous surfaces.
According to a preferred embodiment, one lead of the set has the island and the other lead of the set has the connecting portion. Further, the mutually facing side surfaces in the set of leads maybe crossed by a wire which bridges these leads.
The problem that the gap between mutually facing side surfaces functions as a capacitor is not unique to an electronic component including one lead having an island and another lead having a connecting portion. Rather, the problem is common to other electronic components having three or more terminals in which there is a plurality of leads of one or both kinds. In this type of electronic component, the electric charge tends to accumulate between mutually adjacent leads which are electrically connected together. Therefore, the non-parallel arrangement should be provided between leads where the island and the connecting portion are adjacent to each other, or between leads which are connected with each other via a wire, in order to avoid the above-described problem more effectively.
The technical concept of the present invention is applicable to a variety of electronic components having leads made from a leadframe, and particularly applied suitably to an electronic component serving as a diode, a transistor or a combination of these.
According to a preferred embodiment, the set of leads includes at least three leads, and the side surface of one of the leads faces the respective side surfaces of the other leads.
REFERENCES:
patent: 4794431 (1988-12-01), Park
patent: 5298768 (1994-03-01), Okazaki et al.
patent: 5438021 (1995-08-01), Tagawa et al.
patent: 5479050 (1995-12-01), Pritchard et al.
patent:
Inada Shinichi
Maeda Masahide
Clark Jasmine J B
Merchant & Gould P.C.
Rohm & Co., Ltd.
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