Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – With contact or lead
Reexamination Certificate
2001-04-17
2002-05-14
Wilson, Allan R. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
With contact or lead
C257S692000, C257S723000
Reexamination Certificate
active
06388316
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor module, and more particularly, a semiconductor module comprising a plurality of semiconductor elements connected in parallel to each other.
FIG. 7A
is a plan view of a conventional semiconductor module (a lid portion is not shown), and
FIG. 7B
is a cross sectional view along lines IV—IV in FIG.
7
B.
As shown in
FIGS. 7A and 7B
, in the conventional semiconductor module generally denoted at
200
, an insulation substrate
71
is placed on a base plate
1
. In a front surface of the insulation substrate
71
, a gate wire pattern
14
, a collector wire pattern
72
, and an emitter wire pattern
73
are formed. On the collector wire pattern
72
, a plurality of insulated gate bipolar transistors
31
(hereinafter referred to as “IGBTs”) and free wheel diodes
32
(hereinafter referred to as “diodes”) are disposed. Collectors of the IGBTs
31
and cathodes of the diodes
32
are connected with the collector wire pattern
72
.
As shown in
FIG. 7A
, the emitter wire pattern
73
is formed in the shape of the letter “L” along two sides of the collector wire pattern
72
. Meanwhile, the gate wire pattern
14
is formed along other one side of the collector wire pattern
72
. This is for the ease of work at a bonding step for connecting the respective wire patterns with the IGBTs
31
and the like.
A back surface pattern
74
is formed in a back surface of the insulation substrate
71
, and fixed on the base plate
1
by a solder layer
2
.
The IGBTs
31
and the diodes
32
are connected respectively with the gate wire pattern
14
and the emitter wire pattern
73
by bonding wires
35
and
34
. Further, the gate wire pattern
14
, the emitter wire pattern
73
and the collector wire pattern
72
are connected respectively with gate electrodes
41
, collector electrodes
42
and emitter electrodes
43
by bonding wires
36
,
37
and
38
.
A case portion
6
is formed on the base plate
1
so as to surround the insulation substrate
71
. After wire bonding of the IGBTs
31
and the like, a gel material
7
for sealing is injected inside the case portion
6
, and a lid portion
8
is put on.
In the semiconductor module
200
with the conventional structure, since wiring distances from the emitter electrodes
43
to the diodes
32
arranged in parallel to each other are different from each other, loads (such as impedance, capacitance) of the wires are different from each other among the diodes
32
. Hence, even when the semiconductor module is applied with a constant voltage, for example, voltages applied to the diodes
32
arranged in parallel to each other are different from each other, which may destroy some of the diodes. This also applies to the IGBTs
31
.
In addition, to allow the semiconductor module to carry a large current, it is necessary that a cross section of the wire patterns has a large size. In contradiction to this, if the wire patterns are thick, there is a problem that the insulation substrate
71
cracks due to a difference in expansion coefficient between the insulation substrate
71
of a ceramic material and the wire pattern
73
of metal. Further, if the width of the wire pattern
73
is large, there is a problem that it is difficult to complete the semiconductor module in a small size.
SUMMARY OF THE INVENTION
In view of this, a first object of the present invention is to provide a semiconductor module in which wiring lengths of semiconductor elements arranged in parallel to each other are approximately the same.
A second object of the present invention is to provide a semiconductor module in which a cross section of wire patterns has a large size without increasing a module size.
The present invention is directed to a semiconductor module in which at least two semiconductor elements arranged along a certain direction, and at least two electrode pad regions arranged along a direction approximately perpendicular to said certain direction, are respectively connected in parallel to each other, characterized in comprising:
a) a base plate;
b) a lower layer substrate comprising: a first insulation substrate in approximately rectangular shape with the back surface fixed on said base plate; a first and a second electrode pads in approximately identical shapes disposed on a front surface of said first insulation substrate along one side of said first insulation substrate so as to be juxtaposed to each other in this order from a corner portion of said one side; and first and second wires which are juxtaposed to each other along other side of said first insulation substrate approximately perpendicular to said one side and including said corner portion of said one side, said second wire extending by the side of said first and said second electrode pads, and said first wire extending by the side of said first electrode pad with said second wire interposed;
c) an upper layer substrate disposed on said lower layer substrate, comprising: a second insulation substrate in approximately rectangular shape; and a first bridge wire connecting said first wire with said first electrode pad and a second bridge wire connecting said second wire with said second electrode pad, which are formed in a back surface of said second insulation substrate;
d) a first semiconductor element electrically connected with said first wire and a second semiconductor element electrically connected with said second wire, which are formed in a front surface of said second insulation substrate; and
e) a cap disposed on said base plate so as to cover said lower layer substrate, said upper layer substrate, and said first and said second semiconductor elements.
In this semiconductor module, wiring lengths from the semiconductor elements to emitter electrodes are approximately uniform between the semiconductor elements arranged in parallel to each other.
This allows achieving approximately the same loads, such as impedances, between the wires arranged in parallel to each other.
As a result, it is possible to prevent overload-induced malfunction of some semiconductor elements occurring in a conventional semiconductor module, and hence, to improve the reliability of the semiconductor module.
Since a semiconductor module herein described comprises two semiconductor elements, a semiconductor module comprising three or more semiconductor elements is also within the scope of the present invention. Further, the cap portion is formed by a case portion and a lid portion.
The present invention is also directed to a semiconductor module further comprising a solder resist layer coating a front surface of said lower layer substrate, characterized in that said first bridge wire and both of said first wire and said first electrode pad are connected with each other by solder layers buried in holes formed in said solder resist layer, while said second bridge wire and both of said second wire and said second electrode pad are connected with each other by solder layers buried in holes formed in said solder resist layer.
Use of the solder resist layer makes it easy to use a structure in which wire layers intersect each other.
A surface area of said lower layer substrate is preferably larger than a surface area of said upper layer substrate, and said first and said second wires and said first and said second electrode pads extend preferably beyond said upper layer substrate covering said lower layer substrate.
With this structure, it is easy to perform wire bonding.
The first and said second semiconductor elements and said first and said second wires may be connected with each other by bonding wires and said first and said second electrode pads and an external electrode may be connected with each other by bonding wires.
The present invention is directed further to a semiconductor module in which at least two semiconductor elements juxtaposed to each other along a certain direction, and an electrode pad region arranged along a direction approximately perpendicular to said certain direction, are connected with each other, characterized in comprising:
a
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Wilson Allan R.
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