JP2010073769A - Transistor, circuit board, and motor drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To use MOSFETs even in the case of a short circuit fault without changing the size of a substrate. <P>SOLUTION: The circuit board has a plurality of power MOSFETs including a plurality of cells 50, an MOSFET 10u incudes two source pads 53a and 53b which are not connected to each other, and wire-bonded to predetermined wiring conductors by two aluminum wires. When one cell 50 is short-circuited, the MOSFET 10u is turned off to make a short circuit current to flow, and then an excessive current flows through only the two aluminum wires connected to the source pad connected with the cell 50 having short-circuited so that the aluminum wires are blown. Furthermore, the respective cells 50 connected to the source pad which is not connected with the cell 50 having a short-circuited function even after the aluminum wires are blown, therefore the MOSFETs are continuously usable (while a maximum current is limited to a half of the current in normal operation). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a transistor, a circuit board, and a motor driving apparatus including the transistor, and more particularly to a motor driving apparatus used in an electric power steering apparatus using the circuit board.

  The electric power steering device for a vehicle drives a steering assist motor so that a suitable steering assist force is obtained in accordance with a steering torque applied to a steering wheel by a driver, a vehicle speed, or the like. The steering assist motor is driven by a motor drive circuit built in an electronic control unit (hereinafter referred to as ECU). The motor drive circuit controls a large electric power of about 500 W to 2000 W when driving the steering assist motor.

  In order to control such a large electric power, a motor drive circuit is generally equipped with a plurality of power MOSFETs, and these power MOSFETs are appropriately turned on / off by signals from known control units. The steering assist motor is driven.

The following prior arts are known in relation to the present invention. Patent Document 1 discloses a configuration of a multilayer circuit board in which a conductive layer is formed on the inner surface by copper plating or the like and a heat radiating via filled with resin is provided for heat dissipation of an electronic component such as a power MOSFET. Patent Document 2 discloses a configuration of a multi-chip IC in which a plurality of bare chips are arranged using a positioning substrate and a housing is molded. Further, Patent Document 3 discloses a configuration of a semiconductor chip in which four rectangular bare chip forming portions are continuously arranged in the short side direction. Furthermore, Patent Document 4 discloses a structure for mounting a polymer actuator on a substrate. Further, Patent Document 5 discloses a configuration in which a drive gear connected to a motor shaft is biased in the direction of a driven gear fitted to a steering shaft by controlling a polymer actuator.
International Publication No. 2008/078739 Pamphlet JP-A-7-86502 JP 2002-373958 A JP 2008-84957 A JP 2006-8049 A

  As described above, the power MOSFET has a particularly large current and generates a large amount of heat. Therefore, the power MOSFET may break down due to a short circuit inside the element. Such a failure of the power MOSFET occurs only in one of the plurality provided on the substrate, and causes a function stop or abnormal operation of the entire substrate.

  Here, when the above-described failure occurs in the motor drive circuit board provided in the electric power steering device, the steering assist operation must be stopped to prevent abnormal operation. However, when the circuit board is mounted on an automobile having a large front axle load, the steering operation becomes particularly heavy when the steering assist operation is stopped, and steering becomes difficult.

  In order to prevent the steering from becoming difficult in this way, a circuit configuration in which another new power MOSFET is immediately switched in place of the failed power MOSFET is used, or instead of the failed circuit board itself. A configuration in which another new circuit board is used is also conceivable. However, such a configuration not only increases the manufacturing cost of the device, but also increases the size of the substrate, so that it may be difficult to mount the device on an electric power steering device that has been downsized in recent years.

  Accordingly, an object of the present invention is to provide a circuit board that can use the semiconductor even when a short circuit failure occurs in a semiconductor element such as a power MOSFET to be mounted without changing the size of the board. .

A first invention is a transistor including a plurality of cells,
The plurality of cells included in the transistor are divided into a plurality of cell groups, and each cell group has a connection terminal.

A second invention is a circuit board in which a conductor layer including a wiring conductor forming a circuit and an insulating layer are laminated,
A plurality of transistors according to the first invention;
A plurality of wires connecting the cell groups of the plurality of transistors and the wiring conductors;
The plurality of wires are divided into a plurality of wire groups so as to correspond to each of a plurality of cell groups in the transistor, the cell groups are not connected by the wire groups, and the cell groups correspond to each other. The wire group is connected to the wiring conductor.

According to a third invention, in the second invention,
When the short-circuit fault occurs in one of the cell groups included in the transistor, the plurality of wires have an excessive current that flows only by the wire group connected to the cell group in which the short-circuit fault has occurred. It consists of the raw material, diameter, and number which were chosen so that it may melt | fuse by.

A fourth invention is the circuit board according to the second or third invention,
A control unit that drives and controls an n-phase (n is a natural number of 3 or more) electric motor provided outside the device by turning on and off the plurality of transistors provided on the circuit board;
When a short circuit failure occurs in one of the cell groups included in the transistor, the control unit instructs the transistor including the cell group in which the short circuit failure has occurred to turn off the current due to the short circuit failure. It is a motor control apparatus characterized by controlling so that may flow.

According to a fifth invention, in the first invention,
It is used for a circuit board for driving a motor, and is characterized in that the same number as the number of phases of an electric motor provided outside is connected.

  According to the first aspect of the invention, when the connection terminals of the transistors are connected to the wiring conductors of the substrate, for example, by corresponding wire groups, the cell group including the cell in which the short-circuit failure occurs even when a short-circuit failure occurs Since only the wire group connected to the fuse is blown, the transistor can be used continuously (typically with the maximum current limited from the normal time) even when a short circuit failure occurs.

  According to the second aspect, each cell group in the transistor is not connected to each other by the wire group, and is connected to the wiring conductor by the corresponding wire group. Only the wire group connected to each cell of the group including the cell in which the short-circuit failure has occurred is fused. Therefore, even when a short circuit failure occurs without changing the size of the substrate, the transistor can be used continuously (typically with the maximum current limited from the normal time).

  According to the third aspect of the invention, since the current flowing through the wire group connected to the short-circuited cell at the time of the short-circuit failure is determined in advance, when current flows through all the wire groups connected to the failed transistor, When the short-circuit current flows only in the wire group connected to the short-circuited cell without fusing, the material, diameter, and number of wires that can be blown out are selected in the design, so that it is ensured in the event of a short-circuit fault. The wire group can be fused.

  According to the fourth aspect of the present invention, when a short-circuit failure occurs, the transistor including the cell group in which the short-circuit failure has occurred is turned off by an instruction from the control unit, and current due to the short-circuit failure flows through the transistor (in some cases Since the other transistors are controlled), the wire group can be surely blown in the event of a short circuit failure.

  According to the fifth aspect, since the same number of phases as the number of electric motors provided outside is connected, the temperature rise of each transistor becomes uniform and the peak temperature of each transistor decreases, so that the output of the transistor is stabilized. And reliability can be improved.

<1. Circuit board configuration>
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
The multilayer circuit board according to the present embodiment is a motor drive circuit board for an electric power steering apparatus, and this motor drive circuit board is used by being incorporated in an ECU (electronic control unit) for the electric power steering apparatus.

  The ECU includes a motor control circuit including a control unit that calculates the amount of drive current supplied to the steering assist motor, and a motor drive circuit that controls the large current to drive the steering assist motor. The motor control circuit generates a small amount of heat during operation, and the flowing current is small. The motor drive circuit generates a large amount of heat generated during operation, and the current flowing through the motor control circuit is large. Such a motor drive circuit is mounted on a motor drive circuit board, and the motor control circuit is mounted on a separate circuit board. These two circuit boards are arranged side by side in the ECU or stacked in two stages. Hereinafter, the structure of a circuit board which is a motor drive circuit board will be described with reference to FIGS.

  FIG. 1 is an external perspective view showing a structure of a circuit board according to an embodiment of the present invention, and FIG. 2 is a circuit diagram of the circuit board. The circuit board shown in FIG. 1 is formed by thermocompression bonding a single layer circuit unit 100 and a metal base 102. In addition, you may form these by adhere | attaching these with the adhesive agent which consists of epoxy resins, for example, and you may form by fixing these by well-known methods, such as screwing.

  The metal base 102 is formed of a metal having good thermal conductivity such as aluminum and functions as a heat sink. The metal base 102 is provided so that the upper surface thereof is in contact with the insulating layer on the lower surface of the single-layer circuit unit 100 and is thermocompression bonded to the insulating layer.

  The single-layer circuit unit 100 has a layer structure in which a conductor layer and an insulating layer immediately below the conductor layer are thermocompression bonded. This conductor layer is made of a highly conductive metal such as copper, and the insulating layer is made of a synthetic material (so-called prepreg) in which glass fiber is impregnated with an insulating resin material. Electronic components such as a power MOSFET, which will be described later, and a shunt resistor (not shown in FIG. 1) are mounted on the single-layer circuit unit 100, and a predetermined conductive layer for electrically connecting these electronic components to the surface of the conductor layer. Wiring is provided.

  More specifically, on the surface of the single-layer circuit portion 100 of this circuit board, a shunt resistor 12 shown in FIG. 2 and six MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) 10u, 10v, 10w, 11u , 11v, and 11w are placed. Then, three of these MOSFETs 10u, 10v, 10w corresponding motor wiring conductors 110u, 110v, 110w provided at predetermined positions on the source connection terminal (source pad) on the surface (upper surface) and the single-layer circuit unit 100 (surface layer). Are wire-bonded by four aluminum wires 161-164. These may be connected by a known method other than bonding. The drain electrodes on the back surfaces (lower surfaces) of the MOSFETs 10u, 10v, and 10w are connected to a power supply wiring conductor 120 provided at a predetermined position of the single-layer circuit unit 100 (surface layer) with the heat spreader 150 interposed therebetween. In addition, although solder is used and die-bonded for these connections, they may be connected by other known methods.

  Further, the source connection terminal (source pad) on the surface (upper surface) of the other three MOSFETs 11u, 11v, and 11w and the ground wiring conductor 130 provided at a predetermined position of the single-layer circuit unit 100 (surface layer) are each composed of four aluminum wires. Wire bonded. These may be connected by a known method other than bonding. The ground wiring conductors 130 are connected by these aluminum wires. Further, the drain electrodes on the back surfaces (lower surfaces) of the MOSFETs 11u, 11v, and 11w are connected to the corresponding motor wiring conductors 110u, 110v, and 110w with the heat spreader 150 interposed therebetween.

  The motor wiring conductors 110u, 110v, and 110w are connected to the input terminals of each phase of the electric motor (not shown) to be controlled, the power wiring conductor 120 is connected to the positive pole of the power supply unit (not shown), and the ground wiring conductor 130 is shown. Not connected to the negative pole (grounding pole) of the power supply. Next, a characteristic structure of the power MOSFET in the present embodiment that can be used even when a short circuit failure occurs will be described with reference to FIGS. 3 and 4 and a comparison with a conventional structure example.

<2. Power MOSFET structure>
FIG. 3 is a plan view showing a schematic structural example of a conventional power MOSFET, and FIG. 4 is a plan view showing a schematic structural example of the power MOSFET in the present embodiment. First, as shown in FIG. 3, a conventional power MOSFET typically includes a plurality of cells 50 arranged in a matrix (indicated by hatching in the drawing). All of the gate electrode films (not shown) arranged on a part of the lower surface side of each of the cells 50 are connected to a gate line 51, and the gate line 51 is connected to a wiring outside the substrate (here, a gate pad 52). Wiring for transmitting a PWM signal for control). This PWM signal is generated by a PWM modulator controlled by a control unit described later. The source electrode film (not shown) disposed on the upper surface side of the cell 50 is all connected to the source pad 93, and the source pad 93 is connected to another wiring conductor in the circuit board by wire bonding. Thus, it is possible to control a large electric power by forming a plurality of cells.

  On the other hand, the MOSFET 10u of the present embodiment shown in FIG. 4 is basically provided with a plurality of cells 50 (indicated by hatching in the drawing) arranged in a matrix as in the prior art. A gate electrode film (not shown) is formed on a part of the lower surface side of the cell 50, and a source electrode film (not shown) is formed on the upper surface side of the cell 50. Here, the laminated structure including such an electrode film is, for example, an N channel type power MOSFET in which an N + type silicon substrate, a drain region made of an N− type epitaxial layer, and a p type body part are laminated. The p-type body portion is composed of a semiconductor substrate. The p-type body portion includes a channel region composed of an impurity diffusion region implanted with p + -type ions, a source region composed of an n + impurity diffusion region implanted with phosphorus, arsenic, etc., aluminum, and its It includes a source electrode formed by sputtering an alloy, a gate oxide film formed by thermal oxidation, and a gate electrode formed by doping polysilicon with impurities. Since these structures are well known, detailed description thereof is omitted. For convenience of explanation, the MOSFET 10u is described as an example, but other MOSFETs have the same structure.

  As can be seen from a comparison with FIG. 3, the power MOSFET of this embodiment shown in FIG. 4 is different from the conventional configuration in that the cells 50 included in the group on the left half of the figure among all the cells 50. The gate electrode film is connected to the gate line 51a, and the source electrode film is connected to the source pad 53a, and the gate electrode film of the cell 50 included in the group on the right half of the remaining figure is connected to the gate line 51b. The electrode film is connected to the source pad 53b.

  Each of the gate lines 51a and 51b is connected to a gate pad 52. The gate pad 52 is connected to a wiring (not shown) for transmitting a PWM signal outside the substrate. This PWM signal is given from a PWM modulator described later. The source pad 53a is connected to the two aluminum wires 161 and 162, and the source pad 53b is connected to the two aluminum wires 163 and 164. Although the gate lines 51a and 51b may be connected to each other, the source pad 53a and the source pad 53b are not electrically connected, and the two aluminum lines 161 and 162 and the two aluminum lines 163 are not connected. 164 and 164 are spaced apart from each other so as not to contact each other. An insulating film may be formed on these surfaces.

  In this way, it is the same as the conventional configuration in that large power can be controlled by forming a plurality of cells, but in the conventional configuration, when one of the plurality of cells 50 has a short circuit fault Even so (because of the short circuit), the entire element is in a short circuit failure state. In this regard, in the present embodiment, when a short circuit failure occurs in one of the plurality of cells 50, the following on / off control is performed, thereby avoiding the short circuit failure state as a whole. Can do. The control operation at the time of such a short circuit failure will be described in detail with reference to FIG.

<3. Control action when short-circuit failure occurs>
FIG. 5 is a block diagram showing a schematic configuration of a motor control device that controls the motor drive circuit shown in FIG. 2 by giving a PWM signal. As shown in FIG. 5, the motor control device generates a PWM signal based on the control unit 61 that calculates the level of the three-phase voltage for driving the motor according to the target value, and the calculated level. And a PWM modulator 62. This PWM modulator 62 has three types of PWM signals (U, V, W and their negative signals shown in FIGS. 2 and 5) having a duty ratio corresponding to the three-phase voltage level calculated by the control unit 61. Is generated from the control unit 61, and three types of PWM signals having the duty ratio are generated. The motor driving circuit configured by the single-layer circuit unit 100 is a PWM voltage source inverter circuit, and the six MOSFETs included therein are controlled by three types of PWM signals and their negative signals. . By controlling on / off of the conduction state of the MOSFET using the PWM signal, three-phase drive current (U-phase current, V-phase current and W-phase current) is supplied to the brushless motor outside the apparatus, and the motor is driven. The

  Here, when a short circuit fault occurs in any of the six MOSFETs 10u, 10v, 10w, 11u, 11v, and 11w shown in FIG. 2, a control signal for applying a PWM signal to the gate pads of these six MOSFETs. The control unit 61 that generates the signal gives a PWM signal for temporarily turning off all the six MOSFETs by the PWM modulator 62. Although it is well known to determine which of these six MOSFETs has a short-circuit fault, for example, it is easily determined by referring to each detected current value flowing in each phase of the motor and the control state of each MOSFET. be able to.

  Thereafter, the control unit 61 turns off the MOSFET in which the short-circuit failure has occurred, and controls the motor phase (U-phase, V-phase, or W-phase) controlled by the MOSFET in which the short-circuit failure has occurred. Turn on. For example, when it is determined that the MOSFET 10u has a short circuit failure, the control unit 61 controls to turn off the MOSFET 10u and turn on the MOSFET 11u. In this case, as can be seen with reference to FIG. 2, a power supply voltage is almost applied to the MOSFET 10u, so that a large current flows through the MOSFET 10u in which a short circuit failure has occurred.

  Here, in the MOSFET 10u in which a short circuit failure has occurred, usually only one of all the cells included in the MOSFET 10u has a short circuit failure. Therefore, among all the cells 50 included in the MOSFET 10u, the cell 50 is connected to any cell included in the group of cells 50 connected to the source pad 53a (hereinafter referred to as “first group”), or to the source pad 53b. It can be said that one of the cells included in the group of the cells 50 (hereinafter referred to as “second group”) has a short-circuit fault.

  Therefore, for example, if one of the cells 50 of the first group connected to the source pad 53a has a short-circuit fault, the MOSFET 10u is controlled to be turned off, so that it is connected to the source pad 53b. No current flows through the second group of cells 50, and a large current flows only through the first group of cells 50 connected to the shorted source pad 53a. Since only two aluminum wires 161 and 162 are connected to the source pad 53a and the aluminum wires 163 and 164 are not connected, the current flows only through the two aluminum wires 161 and 162. Become. Therefore, during normal operation, the current flowing through the four aluminum wires flows only through the two aluminum wires 161 and 162, so that the value of the current flowing through the one aluminum wire becomes excessive and the fusing occurs. Of course, it is possible to thicken or increase the number of aluminum wires so that they do not melt, but here the diameter, number, material, etc. of the aluminum wires that do not melt during normal operation and that melt in such cases Is selected by design. In other words, since the currents flowing through these two aluminum wires at the time of a short circuit failure are determined in advance, they do not melt when flowing through four aluminum wires, but are blown when flowing through two aluminum wires. The diameter is determined within a predetermined range in design. The diameter, number, and material of the aluminum wire are selected for design. Note that the control operation is continued for a time that does not adversely affect the MOSFETs (cells) that are not short-circuited and that the aluminum wire is surely blown.

  If the aluminum wire is melted in this way, the first group of cells 50 connected to the source pad 53a to which the two melted aluminum wires 161 and 162 are connected are not affected by the control state of the MOSFET 10u. Since no current flows and the current of the MOSFET 10u flows in the second group of cells 50 connected to the source pad 53b according to the control state as usual, the number of cells of the MOSFET 10u in which the short-circuit fault has occurred is halved. As a MOSFET, the maximum current is limited to half of that in the normal state, and the on / off operation is continued.

<4. Effect>
As described above, in the circuit board according to the above-described embodiment, a plurality of cells included in the MOSFET are grouped, the source pads divided for each group are connected, and a different aluminum wire is connected to each of these source pads (typically (Wire bonding). According to such a configuration, even when a short circuit failure occurs, only the aluminum wire connected to the source pad connected to each cell of the (first or second) group including the cell in which the short circuit failure has occurred is blown out. Therefore, the MOSFET can be continuously used even when a short-circuit failure occurs without changing the size of the substrate (with the maximum current limited to half that of the normal state).

<5. Modification>
<5.1 Main Modification>
FIG. 6 is an external perspective view showing a structure of a circuit board according to a modification of the embodiment of the present invention. The circuit board shown in FIG. 6 has substantially the same configuration as the circuit board in the above-described embodiment shown in FIG. 1, except that three MOSFETs 10u, 10v, and 10w are integrally formed. That is, the three MOSFETs 10u, 10v, and 10w are formed in an integral three-unit shape that is not cut, and this integral element is die-bonded (soldered on the entire surface) to the power wiring conductor 120 with one heat spreader 150 interposed therebetween. Attached).

  With the configuration of such a modification, heat is diffused throughout the three MOSFETs 10u, 10v, and 10w, so that the temperature rise is uniform and the peak temperature is lowered, so that the reliability of the element is improved. That is, when the temperature rise timing for each element is different, such as the three MOSFETs 10u, 10v, and 10w mounted on the circuit board in the embodiment shown in FIG. 1, the output characteristics of each element according to the temperature. Changes, the output of the entire circuit decreases. Also, the higher the peak temperature, the lower the output of the device and the greater the risk of thermal destruction. On the other hand, in the configuration of the modified example, the temperature rise is uniform and the peak temperature is lowered, so that the output of the element can be stabilized and the reliability can be improved.

<5.2 Other Modifications>
FIG. 7 is a sectional view showing a conventional bolted substrate and housing. A substrate 301 shown in FIG. 7 is a motor drive circuit substrate on which a power MOSFET as described in the above embodiment is mounted. The substrate 301 is sandwiched between resin housings 305 with respect to a housing 302 that functions as a heat mass and is fixed by fastening bolts 304. It is fixed by tightening with the force of. Further, a high thermal conductive grease 303 is applied between the substrate 301 and the housing 302. With such a configuration, heat generated from the power MOSFET mounted on the substrate 301 is efficiently transmitted to the housing 302.

  However, since the amount of heat changes depending on the use environment and use state, a gap is formed between the substrate 301 and the housing 302 due to heat shrinkage, which may reduce the heat conduction efficiency. In addition, there is a problem that parts are deteriorated (for example, cracked) due to thermal expansion (specifically, due to repeated stress caused by a difference in thermal expansion coefficient).

  Therefore, unlike the conventional configuration, a configuration of a circuit board that can solve the above problem by appropriately adjusting the tightening force while using the fastening bolt 304 will be described with reference to FIG.

  FIG. 8 is a cross-sectional view showing a substrate and a housing capable of appropriately adjusting the tightening force of the fastening bolt according to the modification of the embodiment. A substrate 301 shown in FIG. 8 is fixed by being clamped by a fastening bolt 304 and a polymer actuator 310 with a resin housing 305 sandwiched between a housing 302 similar to FIG. This polymer actuator 310 is an actuator made of a polymer whose volume changes by applying a voltage (here, the volume decreases as a high voltage is applied). It is a structure provided with the well-known ion exchange resin base material containing a polar molecule, and two electrodes formed so that the surface might be opposed by methods, such as electroless plating. Such a polymer actuator has a well-known configuration having various uses such as an artificial muscle, and is described in detail in, for example, Patent Document 4 and Patent Document 5 described above.

  Here, an appropriate voltage is applied to the polymer actuator 310 in accordance with the temperature of the substrate 301 or the fastening bolt 304 detected by a temperature sensor (not shown). For example, when a high voltage is applied, the polymer actuator 310 contracts. Therefore, when the temperature rises and the fastening force of the fastening bolt 304 increases due to thermal expansion, a high voltage is applied to the polymer actuator 310. This is contracted to control the tightening force. In addition, when the temperature decreases and the tightening force of the fastening bolt 304 decreases due to thermal contraction, control is performed to increase the tightening force by applying a low voltage to the polymer actuator 310.

  In this way, by controlling the voltage applied to the polymer actuator 310 so that there is no gap between the substrate 301 and the housing 302 due to thermal contraction (typically, tightening at a constant pressure), the voltage from the substrate 301 is controlled. A decrease in the efficiency of heat conduction to the housing 302 can be prevented. In addition, by controlling the voltage applied to the polymer actuator 310 so that the component is not deteriorated (or mechanically / physically damaged) due to thermal expansion (specifically, due to repeated stress caused by the difference in thermal expansion coefficient). Deterioration of parts can be prevented.

  In addition, although it demonstrated that said control was performed according to the temperature detected by a temperature sensor, the pressure sensor which detects a clamping force, the distance of the board | substrate 301 and the housing 302, or the fastening bolt 304 (the head) and the board | substrate 301. The configuration may be such that the tightening force of the fastening bolt 304 is controlled to be substantially constant in accordance with the detection result of a gap sensor or the like that detects the distance to. In such a configuration, not only the tightening force changes due to thermal expansion or contraction of the substrate 301 or the like according to the temperature change, but also the tightening force due to the loosening of the fastening bolt 304 due to vibration in a place where there is a lot of vibration. It is possible to perform control corresponding to a change or a change in tightening force in a short cycle due to vibration itself.

It is an appearance perspective view showing the structure in the circuit board concerning one embodiment of the present invention. It is a circuit diagram of the circuit board in the embodiment. It is a top view which shows the schematic structural example of the conventional power MOSFET. It is a top view which shows the schematic structural example of power MOSFET in the said embodiment. It is a block diagram which shows the schematic structure of the motor control apparatus in the said embodiment. It is an external appearance perspective view which shows the structure in the circuit board which concerns on the modification of the said embodiment. It is sectional drawing which shows the board | substrate and housing which were conventional bolted. It is sectional drawing which shows the board | substrate and housing which can adjust suitably the fastening force of the fastening bolt which concerns on the modification of the said embodiment.

Explanation of symbols

  10u, 10v, 10w, 11u, 11v, 11w ... MOSFET, 12 ... shunt resistor, 50 ... cell, 51 ... gate line, 52 ... gate pad, 53a, 53b ... source pad, 100 ... single layer circuit section, 102 ... metal 110u, 110v, 110w ... motor wiring conductor, 120 ... power wiring conductor, 130 ... ground wiring conductor, 150 ... heat spreader, 161-164 ... aluminum wire, 301 ... substrate, 302 ... housing (heat mass), 303 ... high heat conduction Grease, 304 ... fastening bolt, 305 ... resin housing, 310 ... polymer actuator

Claims (5)

A transistor comprising a plurality of cells,
2. The transistor according to claim 1, wherein the plurality of cells included in the transistor are divided into a plurality of cell groups, and each of the cell groups has a connection terminal. A circuit board in which a conductor layer including a wiring conductor forming a circuit and an insulating layer are laminated,
A plurality of the transistors according to claim 1;
A plurality of wires connecting the cell groups of the plurality of transistors and the wiring conductors;
The plurality of wires are divided into a plurality of wire groups so as to correspond to each of a plurality of cell groups in the transistor, the cell groups are not connected by the wire groups, and the cell groups correspond to each other. A circuit board, wherein the circuit board is connected to the wiring conductor by a wire group.   When the short-circuit fault occurs in one of the cell groups included in the transistor, the plurality of wires have an excessive current that flows only by the wire group connected to the cell group in which the short-circuit fault has occurred. The circuit board according to claim 2, wherein the circuit board is made of a material, a diameter, and a number selected so as to be melted. The circuit board according to claim 2 or claim 3,
A control unit that drives and controls an n-phase (n is a natural number of 3 or more) electric motor provided outside the device by turning on and off the plurality of transistors provided on the circuit board;
When a short circuit failure occurs in one of the cell groups included in the transistor, the control unit instructs the transistor including the cell group in which the short circuit failure has occurred to turn off the current due to the short circuit failure. The motor drive device is characterized in that it is controlled to flow.   2. The transistor according to claim 1, wherein the transistor is used in a circuit board for driving a motor and is connected in the same number as the number of phases of an electric motor provided outside.

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