Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For plural devices
Reexamination Certificate
1999-09-03
2003-05-20
Zarabian, Amir (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For plural devices
C257S724000
Reexamination Certificate
active
06566750
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor module, and in particular it relates to a non-insulated power semiconductor module.
2. Description of the Related Art
Lately, semiconductor modules are being widely used not only to process control signals, but also to control large electric currents. For example, a power semiconductor module with a large current capacity is used in a control device for driving the motor for running an electromotive vehicle, such as a battery-powered forklift, etc., as a switching device installed between a battery and the motor.
For such semiconductor modules, semiconductor modules with a variety of structures, such as, a semiconductor in which the current capacity is enlarged by connecting power semiconductor chips of the same kind in parallel, a semiconductor module which is constituted as a simple circuit with several kinds of semiconductor chips, a semiconductor module which has an embedded driving circuit composed of semiconductor chips, etc., are known.
A semiconductor module, in particular a power semiconductor module, is usually formed by building one of the semiconductor chips described above in a resin package. The package is usually made of plastics, and the semiconductor chip is insulated using ceramics, etc. The space inside the package is filled up with gel, epoxy resin, etc.
A power semiconductor module generates a large amount of heat, since a large current flows through the module. Therefore, measures must be taken to radiate the heat. A method for installing a semiconductor module on a base substrate which has both a large heat capacity and a high heat radiation effect is often used to radiate the heat of semiconductor modules. In this case, the heat generated by a semiconductor module is radiated through the base substrate.
FIG. 1A
shows the internal structure of a conventional semiconductor module. A MOSFET is used as an example here.
A semiconductor module
100
includes a plurality of semiconductor chips
101
which are connected to each other in parallel (three semiconductor modules
101
a
,
101
b
and
101
c
in FIG.
1
A). A plurality of semiconductor chips
101
are arranged in a straight line with the respective drain region connected to the conductive base substrate
102
. Semiconductors with such a structure are often termed “non-insulated”.
A source electrode
103
and a gate electrode
104
are formed in parallel with the arranging direction of the plurality of semiconductor chips
101
. The source electrode
103
and gate electrode
104
are connected to a source region and a gate region, respectively, of each semiconductor chip
101
using bonding wires
105
. The source electrode
103
and gate electrode
104
are electrically insulated from the base substrate
102
using an insulation sheet
106
.
A drain terminal
107
, a source terminal
108
and a gate terminal
109
are connected to the base substrate
102
, source electrode
103
and gate electrode
104
, respectively. The drain terminal
107
and source terminal
108
are an input point and an output point of the main current of this semiconductor module, respectively.
Each of the semiconductor chips
101
are turned on, when a control voltage is applied between the gate and source. In this case, the main current which is supplied through the drain terminal
103
reaches the source terminal
108
through the base substrate
102
, each of the semiconductor chips
101
, bonding wires
105
and source electrode
103
in this order. Here, the base substrate
102
functions as a drain electrode.
However, as shown in
FIG. 1A
, in a conventional semiconductor module
100
, only one drain terminal
107
and only one source terminal
108
are usually provided in either end of the module. For this reason, as shown in
FIG. 1B
, the lengths of the path through which the main current flows are different depending on the position of the respective semiconductor chip
101
. In the example shown in
FIG. 1B
, a path Ic through the semiconductor chip
101
c
is substantially longer than a path Ia through the semiconductor chip
101
a
. Here, inductance in a current path is nearly proportional to the length of the path. Thus, in this example, the inductance of the path Ic becomes larger than the inductance of the path Ia.
The influence of this inductance occurs at the time the semiconductor chip
101
is switched (especially, at the time the MOSFET is turned off). Specifically, the larger the inductance is, the larger the surge voltage that is generated at the time the semiconductor chip
101
is turned off is. Sometimes the semiconductor chip
101
is damaged since this surge voltage is applied to the semiconductor chip
101
.
In a case that the length of a current path is different in each semiconductor chip, all the semiconductor chips do not operate in the same way even if the characteristics of all the semiconductor chips are the same. As a result, some of the particular semiconductor chips are easily damaged.
SUMMARY OF THE INVENTION
An object of the present invention is to suppress the surge voltage of a semiconductor module including a plurality of semiconductor elements.
In a semiconductor module of the present invention, a plurality of semiconductor chips are arranged in a straight line on a conductive substrate which functions as an electrode for inputting the main current. This semiconductor module comprises a terminal for inputting the main current, which is connected to the conductive substrate and is formed in parallel with the arranging direction of the plurality of semiconductor chips, and a terminal which is connected to the respective region for outputting the main current of the plurality of semiconductor chips and is formed in parallel with the arranging direction of the plurality of semiconductor chips. The end portion of at least one of the terminal for inputting the main current and terminal for outputting the main current is divided in parallel in the flowing direction of the main current.
If the terminal for inputting the main current is divided into two or more parts, the main current supplied to the respective semiconductor chip is to be inputted through the nearest divided part. If the terminal for outputting the main current is divided into two or more parts, the main current which flows through the respective semiconductor chip is to be outputted to the nearest divided part. In addition, the terminal for inputting the main current and terminal for outputting the main current are formed in parallel with the arranging direction of the plurality of semiconductor chips, respectively. Therefore, the main current of the respective semiconductor chip flows through the shortest path, and the lengths of all the paths are almost the same each other. As a result, the wiring inductances of all the semiconductor chips become uniform and small, and thus the surge voltages which are applied to the semiconductor chips also become uniform and small.
REFERENCES:
patent: 5233235 (1993-08-01), Ramacher
patent: 5822191 (1998-10-01), Tagusa et al.
patent: 0 588 094 (1994-03-01), None
patent: 61-139051 (1986-06-01), None
patent: 10-84078 (1998-03-01), None
Fukatsu Toshinari
Nagase Toshiaki
Sofue Kenichi
Yoshiyama Hiromitsu
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
Rose Kiesha
Zarabian Amir
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