Active solid-state devices (e.g. – transistors – solid-state diode – Housing or package – For plural devices
Reexamination Certificate
2000-03-29
2001-05-22
Clark, Sheila V. (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Housing or package
For plural devices
C257S784000
Reexamination Certificate
active
06236110
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a power semiconductor module which is used in power conversion equipment, such as an inverter and a converter.
The power semiconductor module involves a MOSFET module with a plurality of MOSFET (Metal Oxide Semiconductor Field Effect Transistor) devices built therein, a diode module with a plurality of diode devices built therein, an IGBT module with a plurality of IGBT (Insulated Gate Bipolar Transistor) devices and a plurality of diode devices built therein. Now, the internal structure of the power semiconductor module will be explained in the case of an IGBT module with a plurality of IGBT devices and a plurality of diode devices as semiconductor devices coupled in parallel.
In
FIG. 10
is shown a plan view of a semiconductor device section and its vicinities of a conventional IGBT module (hereinbelow, referred to as the module). In
FIG. 11
is shown a cross-sectional view of a pair of IGBT device and diode device, and their vicinities in the module. In the module, four IGBT devices and four diode devices are connected in parallel to provide a single module. An IGBT device and a diode device adjacent thereto are reversely connected in parallel so that the emitter of the IGBT device and the anode of the diode device are at the same potential, and the collector of the IGBT device and the cathode of the diode device are at the same potential.
In
FIGS. 10 and 11
, reference numeral
1
designates a heat dissipating plate made of copper to cool the semiconductor devices, reference numeral
2
designates an aluminum nitride substrate as an insulating substrate, reference numeral
21
designates an electrode pattern provided on each of opposite sides of the aluminum nitride substrate
2
, reference numeral
3
designates an IGBT device, and reference numeral
4
designates a diode device. The IGBT device
3
and the diode device
4
are soldered on the electrode pattern
21
side by side. The aluminum nitride substrate
2
is bonded onto the heat dissipating plate
1
by soldering.
Each of the IGBT devices
3
has an emitter electrode
31
provided thereon by patterning, and each of the diode devices
4
has an anode electrode
41
provided thereon by patterning. The emitter electrode is connected to the anode electrode and further to an emitter trunk substrate
7
by aluminum wires
51
. The electrode pattern
21
on an aluminum nitride substrate
2
, on which an IGBT device
3
and a diode device
4
are soldered, is connected to one of collector trunk substrates
8
by aluminum wires
52
. Reference numeral
25
designates a housing, which is made of resin material and is fixed to the heat dissipating plate
1
. The collector trunk substrates
8
have electrode patterns provided thereon, and the respective electrode patterns are connected to a module collector electrode
9
. To the emitter trunk substrate
7
is connected a module emitter electrode
10
. The module emitter electrode
10
and the module collector electrode
9
are connected to a load or the like outside the module housing
25
.
In order to control a gate potential for on and off operation of the IGBT devices
3
, aluminum wires
53
extend from wiring boards
11
to gate terminals
32
of the IGBT devices
3
. Reference numeral
19
designates a module gate electrode, which is connected to the gate terminals
32
of the respective IGBT devices
3
through the wiring boards
11
in the module. Reference numeral
33
designates a current sensing terminal, which is provided on one of the IGBT devices
3
, and through which a small current flows in proportion to a current flowing through the emitter electrode
31
of the one IGBT device
3
.
In the module with the IGBT devices provided as stated earlier, an overcurrent flows at a value beyond a rated current during operation in some cases, or an excessive current can flow in the module because of short circuit on a load side. When an excessive current flows at a value beyond a rated current in the module, the IGBT devices are heated to be broken, which requires module replacement. In order to prevent the module from being broken due to an overcurrent, it is required that a current flowing through the IGBT devices be detected and that the IGBT devices are turned off immediately before an excessive current flows. A protection circuit is provided in order to prevent the breakage of the IGBT devices, which might cause from the presence of such an overcurrent or on short circuit on a load side.
In
FIG. 12
is shown a block diagram of such a protection circuit. Reference numeral
12
designates the module, and reference numeral
13
designates the one IGBT device
3
with the current sensing terminal
33
. The current sensing terminal
33
is utilized to detect a primary current flowing through the module emitter electrode
10
. The current sensing terminal
33
detects a current flowing through the single IGBT device
13
among the four IGBT devices
3
in the module
12
, and the detected current is inputted into a protection circuit
16
against an overcurrent or a short circuit current. Under the action of the protection circuit, a gate voltage control circuit
17
outputs a gate voltage at such a value to turn off the IGBT devices
3
to protect the entire module
2
as required.
The respective IGBT devices
3
have a large number of fine IGBT cells (not shown) connected in parallel therein. The emitter electrode
31
and the current sensing terminal
33
are connected to a large number of IGBT cells in the corresponding IGBT device
13
, respectively. The ratio of the number of the IGBT cells connected to the emitter electrode
31
and the number of the IGBT cells connected to the current sensing terminal
33
is set at around 1,000 to 1. Both groups of IGBT cells are separated, and the current that flows through the emitter electrode
31
is measured based on the current that flows through the current sensing terminal
33
.
As another prior art, there is a method wherein a resistive element (not shown) is provided at a location in a primary current path and the value of the primary current is detected based on a voltage drop across the resistive element.
A current flowing through the current sensing terminal and the current flowing trough the emitter electrode do not necessarily have the relationship corresponding to the ratio of the numbers of the IGBT cells connected to the respective terminals. The reason is that the IGBT devices are heated during operation to cause a certain temperature distribution on a device surface, and that the temperature of the IGBT cells connected to the current sensing terminal is different from the temperature of the IGBT cells connected to the emitter electrode since the IGBT cells connected to the current sensing terminal is located at a certain position on the device surface. For this reason, the current value detected at the current sensing terminal has not reflected the actual current flowing through the module emitter electrode in accurate fashion in some cases.
In addition, there is provided a problem in that the current flowing through the current sensing terminal varies due to variations in the device production.
In the method to provide a resistive element in a primary current path, the variations in detected values can be minimized since the voltage drop across the resistive element is detected. However, a conventional flat plate shaped resistive element has created a problem in that high-frequency characteristics are not good since the resistive element has large inductance. In the case of a power semiconductor module, such as the IGBT module, a current as large as around 100 A is measured at every IGBT device for instance. In order to reduce power loss caused by the insertion of the resistive element, the resistive element is required to have resistance as low as m&OHgr;. The flat plate shaped resistive element having such resistance has created a problem in that impedance due to inductance is more dominant than impedance due to resis
Horiguchi Takeshi
Kikunaga Toshiyuki
Kinouchi Shin-ichi
Muto Hirotaka
Ohi Takeshi
Clark Sheila V.
Leydig Voit & Mayer Ltd
Mitsubishi Denki & Kabushiki Kaisha
LandOfFree
Power semiconductor module does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Power semiconductor module, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power semiconductor module will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2540262