JP2007060733A - Power module - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a power module with which the heat generated from a power switching element can be dissipated efficiently, without complicating the mechanism of the apparatus or accompanying increase in the weight of the apparatus, and the apparatus can be miniaturized and facilitates mounting on an HEV. <P>SOLUTION: One end of a thermally conductive sheet 56 is secured to a motor case 55. The other end of the thermally conductive sheet 56 is inserted into a housing 13 from a gap provided in a cover 50 and then is stuck to the back of a substrate 19 through thermally conductive adhesive. Heat generated from power MOSFETs 1a-1c, 2a-2c is conducted to the motor case 55 via the substrate 19 and the thermally conductive sheet 56, and is dissipated by the cooling mechanism of an electric motor 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power module, and more particularly, to a power module including an electric motor and an inverter circuit for driving the electric motor.

  In recent years, attention has been paid to a hybrid vehicle (HEV) using both a gasoline engine and an electric motor as power sources due to an increase in environmental awareness. In HEV, an electric motor is AC-driven by switching a DC power source using an inverter circuit including a plurality of power switching elements. On / off of the switching element is controlled by a control circuit.

  As a configuration example of a conventional power module, there is a power module in which an inverter circuit, a control circuit, and an electric motor are integrated (see Patent Document 1 below). In such a conventional power module, a printed circuit board is fixed to the outer peripheral surface of the peripheral wall of the motor housing, and an inverter circuit and a control circuit are mounted on the printed circuit board.

  As a reference example, technologies relating to a vehicle brushless motor including a ring-shaped bus bar are disclosed in, for example, Patent Documents 2 and 3 below.

JP 2003-324903 A JP 2003-134728 A JP 2003-134756 A

  According to the above-described conventional power module, since the inverter circuit, the control circuit, and the electric motor are all integrated, the apparatus becomes large. Accordingly, considering that such a power module is mounted on the HEV, there is a problem that it is difficult to mount the HEV on the HEV because it is necessary to secure a large space in the vehicle for mounting the large power module.

  In addition, since the power module mounted on the HEV handles a large current, heat generated from the power switching element increases. Here, in order to dissipate heat generated from the power switching element, a heat dissipating mechanism having a cooling fin or the like may be disposed on the back surface of the substrate on which the power switching element is mounted. However, in this case, in order to mechanically support the heat dissipation mechanism disposed on the back surface of the substrate, it is necessary to increase the thickness of the housing in which the substrate is accommodated or to reinforce it with a metal member. Therefore, there is a problem that not only the mechanism of the apparatus becomes complicated, but also the weight of the apparatus increases.

  The present invention has been made to solve such a problem, and can efficiently dissipate heat generated from the power switching element without increasing the complexity of the device mechanism and increasing the weight of the device. It is an object of the present invention to obtain a power module that can be miniaturized and easily mounted on an HEV.

  A power module according to a first invention includes a motor case in which a motor having an electromagnetic coil is housed, a plurality of power elements, an inverter circuit connected to the electromagnetic coil, and a semiconductor chip of each of the plurality of power elements. It is provided with the board | substrate mounted in the main surface, and the heat conductive sheet connected to the motor case and the board | substrate.

  The power module according to the second invention is characterized in that, in the power module according to the first invention, the heat conductive sheet is in contact with the back surface of the substrate.

  According to a third aspect of the present invention, there is provided a power module including a motor case in which a motor having an electromagnetic coil is accommodated, an inverter circuit connected to the electromagnetic coil, and a semiconductor chip for each of the plurality of power elements. It is provided with the mounted board | substrate and the heat conductive sheet connected to the motor case and the semiconductor chip.

  The power module according to a fourth invention is characterized in that, in the power module according to any one of the first to third inventions, the thermal conductive sheet is a highly thermal conductive graphite sheet.

  According to the power module according to the first, second, or fourth invention, the substrate on which the semiconductor chip is mounted is connected to the motor case by the heat conductive sheet. Therefore, the heat generated from the semiconductor chip is conducted to the motor case via the substrate and the heat conductive sheet, and is radiated by the motor cooling mechanism. Therefore, the heat generated from the semiconductor chip can be efficiently radiated.

  Further, since it is not necessary to dispose a heat dissipation mechanism on the back surface of the substrate, the apparatus mechanism can be simplified and the apparatus can be reduced in weight.

  Particularly in the power module according to the second invention, the heat conductive sheet is in contact with the back surface of the substrate. Since a wiring pattern, a bonding wire, or the like is not formed on the back surface of the substrate, a heat conductive sheet serving as a heat conduction path can be easily adhered to the substrate.

  According to the power module of the third or fourth aspect of the invention, the semiconductor chip is connected to the motor case by the heat conductive sheet. Therefore, the heat generated from the semiconductor chip is conducted to the motor case via the heat conductive sheet, and is radiated by the motor cooling mechanism. Therefore, the heat generated from the semiconductor chip can be efficiently radiated. Moreover, since the semiconductor chip is in direct contact with the heat conductive sheet, such a heat dissipation effect is high.

  Further, since it is not necessary to dispose a heat dissipation mechanism on the back surface of the substrate, the apparatus mechanism can be simplified and the apparatus can be reduced in weight.

  In particular, according to the power module according to the fourth aspect of the invention, the use of a highly heat conductive graphite sheet makes it possible to reduce the weight as compared with the case where a heat conductive sheet of metal such as copper is used.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the element which attached | subjected the same or corresponding code | symbol in different drawing shall show the same or corresponding element.

  FIG. 1 is a circuit diagram showing a configuration of a power module according to the present embodiment. FIG. 1 shows an example in which power MOSFETs 1a to 1c and 2a to 2c are used as power switching elements. The power module according to the present embodiment includes a three-phase (U-phase, V-phase, W-phase) electric motor 4, an inverter circuit 8 for driving the electric motor 4, and power MOSFETs 1a to 1c included in the inverter circuit 8. , 2a to 2c.

  The power MOSFETs 1a and 2a are connected in series via a node 6u between a positive DC power supply voltage (first voltage) VH and a negative DC power supply voltage (second voltage) VL. Specifically, the drain electrode of the power MOSFET 1a is connected to the power supply voltage VH, and the source electrode is connected to the node 6u. The drain electrode of the power MOSFET 2a is connected to the node 6u, and the source electrode is connected to the power supply voltage VL. Similarly, power MOSFETs 1b and 2b are connected in series via a node 6v between power supply voltage VH and power supply voltage VL, and power MOSFETs 1c and 2c are connected between power supply voltage VH and power supply voltage VL. 6w is connected in series.

  The gate electrodes of the power MOSFETs 1 a to 1 c and 2 a to 2 c are connected to the control circuit 7. The control circuit 7 drives the power MOSFETs 1a to 1c and 2a to 2c by applying voltage pulses to the gate electrodes of the power MOSFETs 1a to 1c and 2a to 2c, respectively.

  The nodes 6u, 6v, 6w are connected to the electrodes 5u, 5v, 5w of each phase of the electric motor 4, respectively. Depending on which of the power MOSFETs 1a to 1c and the power MOSFETs 2a to 2c is driven by the control circuit 7, the direction of the current flowing in the electromagnetic coil 3 provided in the electric motor 4 can be controlled. The magnitude of the current flowing through the electromagnetic coil 3 can be controlled by the pulse width of the voltage pulse applied from the control circuit 7 to the gate electrodes of the power MOSFETs 1a to 1c and 2a to 2c.

  FIG. 1 shows an example in which power MOSFETs 1a to 1c and 2a to 2c are used as power switching elements, but other power switching elements such as IGBTs may be used instead of the power MOSFETs. Alternatively, a transistor capable of controlling high power and operating at high temperature using a wide band gap semiconductor such as SiC, GaN, or C may be used. When a wide band gap device is used, an inverter circuit that can operate in a high-temperature environment can be realized like the electric motor 4.

  FIG. 1 shows an example in which only one power MOSFET is used for each of the high side and the low side of each of U, V, and W phases. A power MOSFET may be used.

  FIG. 2 is a plan view showing the structure of the inverter circuit 8 shown in FIG. A ring-shaped bus bar 11 is disposed along the outer periphery of the electric motor 4. The bus bar 11 is divided into a bus bar 11u corresponding to the U phase of the electric motor 4, a bus bar 11v corresponding to the V phase, and a bus bar 11w corresponding to the W phase. The bus bars 11u to 11w are configured by performing tin plating on the surface of a punched copper plate. The bus bars 11u to 11w are housed in the housing 10 and connected to electrodes 5u, 5v, 5w (not shown in FIG. 2) of each phase of the motor stator of the electric motor 4.

  The housing 10 is made of a heat resistant resin such as PPS. However, the housing 10 may be reinforced by a metal member in order to increase the strength. A groove is formed inside the housing 10, and bus bars 11u to 11w are fitted in the groove portion (see FIGS. 6 and 7 described later).

  A casing 13 made of the same material as the casing 10 is fixed to the outer peripheral side wall of the casing 10 by fitting or screwing. A substrate 19 is housed and fixed in the housing 13. On the main surface of the substrate 19, the semiconductor chips of the power MOSFETs 1a to 1c and 2a to 2c are mounted. Further, the connector 14 is fixed on the main surface of the substrate 19 by screws or the like. The terminals of the connector 14 are connected to the substrate 19 by soldering or brazing. A connector 15 can be inserted into the connector 14. One end of a connection line 16 is connected to the connector 15, and the other end of the connection line 16 is connected to the control circuit 7 shown in FIG.

  The substrate 19 and the bus bars 11u, 11v, 11w are connected to each other by connection electrodes 12u, 12v, 12w, respectively. The material of the connection electrodes 12u to 12w is the same as the material of the bus bars 11u to 11w. One end of each of the connection electrodes 12u, 12v, and 12w is connected to the bus bars 11u, 11v, and 11w by soldering, brazing, or welding, and the other end of each of the connection electrodes 12u, 12v, and 12w is soldered. Alternatively, it is connected to the substrate 19 by brazing. Accordingly, the connection electrodes 12u to 12w, the bus bars 11u to 11w, and the substrate 19 can be connected with high reliability and simply.

  In order to prevent discharge between the connection electrodes 12u, 12v, and 12w, the distance between the connection electrodes 12u, 12v, and 12w adjacent to each other in a plan view is maintained at a predetermined distance or more.

  Further, one end of the high-voltage connection terminal 17 for supplying the power supply voltage VH and one end of the high-voltage connection terminal 18 for supplying the power supply voltage VL are connected to the substrate 19 by soldering or brazing. . The material of the high-voltage connection terminals 17 and 18 is the same as the material of the bus bars 11u to 11w. The other ends of the high-voltage connection terminals 17 and 18 are connected to a battery or a boost converter by a high-voltage cable for power supply. The other ends of the high-voltage connection terminals 17 and 18 and the high-voltage cable for supplying power are fixed to each other by bolts or the like.

FIG. 3 is a plan view specifically showing the structure of the substrate 19 shown in FIG. On the main surface of the substrate 19, wiring patterns 20, 21, 22a to 22c, 24 _{1 to} 24 ₆ are formed, and metal pads 23a to 23c are attached. The wiring patterns 24 _{1 to} 24 ₆ are made of metal and connected to the terminals of the connector 14. Since the wiring patterns 20, 21, 22a to 22c are made of a thick metal, and can handle a large current, it can be applied to a drive motor for a hybrid vehicle.

  On the wiring pattern 20, vertical power MOSFETs 1a to 1c are bonded. In addition, one end of the high-voltage connection terminal 17 is connected to the wiring pattern 20. One end of the high voltage connection terminal 18 is connected to the wiring pattern 21. Vertical power MOSFETs 2a, 2b, and 2c are bonded to the wiring patterns 22a, 22b, and 22c, respectively. The other ends of the connection electrodes 12u, 12v, and 12w are connected to the pads 23a, 23b, and 23c, respectively.

  Screw holes 25 are formed at the four corners of the substrate 19, and the substrate 19 and the housing 13 shown in FIG. 2 are fixed to each other by screws screwed into the screw holes 25. In addition, bolt holes 26 and 27 are formed at the other ends of the high-voltage connection terminals 17 and 18 for crimping a high-voltage cable for power supply with bolts.

  4 is a plan view showing the structure of the vertical power MOSFET 1a shown in FIG. 3, and FIG. 5 is a cross-sectional view showing a cross-sectional structure relating to the position along the line V-V shown in FIG. 4 and 5, a gate electrode G and a source electrode S are formed on the top surface of the semiconductor chip of the vertical power MOSFET 1a, and a drain electrode D is formed on the bottom surface. The structures of the other power MOSFETs 1b, 1c, 2a to 2c are the same as the structure of the power MOSFET 1a shown in FIGS. Therefore, referring to FIG. 3, each drain electrode D of power MOSFETs 1a to 1c is connected to wiring pattern 20, and each drain electrode D of power MOSFETs 2a, 2b, and 2c is connected to wiring patterns 22a, 22b, and 22c, respectively. Is done.

Referring to FIG. 3, each gate electrode G of power MOSFETs 1a, 1b, 1c, 2a, 2b and 2c is connected to a wiring pattern by bonding wires 30 ₁ , 30 ₂ , 30 ₃ , 30 ₄ , 30 ₅ and 30 ₆ . 24 ₁ , 24 ₂ , 24 ₃ , 24 ₆ , 24 ₅ , 24 ₄ are connected. The source electrodes S of the power MOSFETs 1a, 1b, and 1c are connected to the wiring patterns 22a, 22b, and 22c by bonding wires 31 ₁ , 31 ₂ , and 31 ₃ , respectively. The source electrodes S of the power MOSFETs 2a, 2b, and 2c are connected to the wiring pattern 21 by bonding wires 33 ₁ , 33 ₂ , and 33 ₃ , respectively. The wiring patterns 22a, 22b, and 22c are connected to the pads 23a, 23b, and 23c by bonding wires 32 ₁ , 32 ₂ , and 32 ₃ , respectively. In this way, by using the bonding wires 30 ₁ to 30 ₆ , 31 _{1 to} 31 ₃ , 32 _{1 to} 32 ₃ , 33 _{1 to} 33 ₃ to be connected, the power MOSFETs 1a to 1c and 2a to 2c and the respective wiring patterns are connected. Can be connected with high reliability and simplicity.

  FIG. 3 shows an example in which the vertical power MOSFETs 1a to 1c and 2a to 2c are used. By changing the wiring pattern formed on the main surface of the substrate 19, the horizontal power MOSFET is changed. Can also be used.

FIG. 3 shows an example in which the bonding wires 30 ₁ to 30 ₆ , 31 _{1 to} 31 ₃ , 32 _{1 to} 32 ₃ , and 33 _{1 to} 33 ₃ are each configured by using one wire. However, a plurality of wires may be used depending on the current capacity.

  FIG. 6 is a cross-sectional view showing a cross-sectional structure relating to a position along line VI-VI shown in FIG. The connection electrode 12v for connecting the bus bar 11v and the pad 23b passes above the bus bar 11w by being bent at a plurality of locations. The inside of the housing 10 in which the bus bars 11u to 11w are accommodated is sealed with an insulating sealing material 41 such as resin. Therefore, the discharge between the connection electrodes 12u, 12v, and 12w can be prevented with high reliability. Further, since the distance between the adjacent connection electrodes 12u, 12v, 12w can be shortened, the housing 10 can be reduced in size.

  The inside of the housing 13 in which the substrate 19 is accommodated is sealed with an insulating sealing material 40 such as silicone gel. As a result, electrical insulation between bonding wires and wiring patterns is ensured to prevent electric discharge, and deterioration of the substrate 19 due to external influences (water, oil, dust, etc.) can be prevented. it can. Furthermore, in order to enhance the effect of blocking the influence from the outside, the cover 50 is fixed to the upper surface of the opening of the housing 13 by fitting, bonding, screwing or the like.

  The housing 11 in which the bus bar 11 is housed is fixed to the motor case 55. In the motor case 55, the electric motor 4 shown in FIG. The motor case 55 is provided with a cooling mechanism (not shown) for cooling the electric motor 4, and the motor case 55 itself is also cooled by cooling water or ATF (Automatic Transmission Fluid) of the cooling mechanism. Yes.

  One end of a heat conductive sheet 56 is fixed to the motor case 55. One end of the heat conductive sheet 56 is sandwiched between the motor case 55 and the cover 57 and the cover 57 is screwed to the motor case 55, so that one end of the heat conductive sheet 56 is fixed in contact with the motor case 55. .

  The other end of the heat conductive sheet 56 is inserted into the housing 13 through a gap provided in the cover 50 and then attached to the back surface of the substrate 19 with a heat conductive adhesive. Alternatively, the substrate 19 and the heat conductive sheet 56 are screwed to the housing 13 with the other end of the heat conductive sheet 56 inserted between the back surface of the substrate 19 and the bottom surface of the housing 13. Can also be pressure-bonded. Since the wiring pattern and bonding wires shown in FIG. 3 are not formed on the back surface of the substrate 19, the heat conductive sheet 56 can be easily adhered to the substrate 19.

  As the heat conductive sheet 56, in addition to a heat conductive sheet of metal such as copper or aluminum, a highly heat conductive graphite sheet can be used. While the graphite sheet has a low thermal conductivity in the thickness direction, the graphite sheet has an anisotropic thermal conductivity that is higher in the in-plane direction than the metal. The thermal conductivity in the in-plane direction of the graphite sheet is about 600 to 800 W / (m · K), which is about twice that of copper. Therefore, when the highly heat conductive graphite sheet is used, the thickness of the heat conductive sheet 56 can be reduced as compared with the case where a metal heat conductive sheet is used. Therefore, it is possible to reduce the weight of the entire apparatus while ensuring the same heat radiation effect as that of the metal heat conductive sheet.

  Thus, according to the power module according to the present embodiment, the substrate 19 is fixed to the housing 10 in which the bus bar 11 is housed. The power MOSFETs 1 a to 1 c and 2 a to 2 c are mounted on the substrate 19, and the control circuit 7 shown in FIG. 1 is not mounted on the substrate 19 but is connected to the substrate 19 via the connector 14. Is done. That is, in the power module according to the present embodiment, the inverter circuit 8 and the electric motor 4 are integrally configured, and the control circuit 7 is configured as a separate body. Therefore, as compared with a power module in which the inverter circuit 8, the control circuit 7, and the electric motor 4 are all integrated, the overall size of the apparatus can be reduced.

  In addition, since the inverter circuit 8 and the electric motor 4 are configured integrally, a wiring cable having a large amount of current for connecting the inverter circuit 8 and the electric motor 4 to each other is not necessary, so that the wiring is simplified. Can also be achieved.

  Further, as shown in FIG. 6, the substrate 19 on which the power MOSFETs 1 a to 1 c and 2 a to 2 c are mounted is connected to the motor case 55 by a heat conductive sheet 56. Therefore, heat generated from the power MOSFETs 1 a to 1 c and 2 a to 2 c is conducted to the motor case 55 via the substrate 19 and the heat conductive sheet 56 and is radiated by the cooling mechanism of the electric motor 4. Therefore, heat generated from the power MOSFETs 1a to 1c and 2a to 2c can be efficiently radiated.

  In addition, since it is not necessary to dispose a heat dissipation mechanism on the back surface of the substrate 19, the apparatus mechanism can be simplified and the apparatus can be reduced in weight.

  FIG. 7 is a cross-sectional view showing a modification of the power module according to the present embodiment, corresponding to FIG. In the structure shown in FIG. 6, the other end of the heat conductive sheet 56 is bonded to the back surface of the substrate 19. However, in the structure shown in FIG. 7, the heat conductive sheet 56 is thermally conductive on the main surface side of the substrate 19. The power MOSFETs 1a to 1c and 2a to 2c are bonded to each other by a conductive adhesive. Therefore, heat generated from the power MOSFETs 1 a to 1 c and 2 a to 2 c is conducted to the motor case 55 through the heat conductive sheet 56 and is radiated by the cooling mechanism of the electric motor 4. According to the structure shown in FIG. 7, the power MOSFETs 1 a to 1 c and 2 a to 2 c are in direct contact with the heat conductive sheet 56 without the substrate 19 interposed. Therefore, the power MOSFETs 1a to 1c and 2a to 2c have a higher heat dissipation effect than the structure shown in FIG.

It is a circuit diagram which shows the structure of the power module which concerns on embodiment of this invention. It is a top view which shows the structure of the inverter circuit shown in FIG. FIG. 3 is a plan view specifically showing the structure of the substrate shown in FIG. 2. FIG. 4 is a plan view showing the structure of the vertical power MOSFET shown in FIG. 3. FIG. 5 is a cross-sectional view illustrating a cross-sectional structure related to a position along line V-V illustrated in FIG. 4. FIG. 6 is a cross-sectional view showing a cross-sectional structure related to a position along line VI-VI shown in FIG. 2. It is sectional drawing which shows the modification of the power module which concerns on embodiment of this invention.

Explanation of symbols

1a to 1c, 2a to 2c Power MOSFET
3 electromagnetic coil 4 electric motor 6u~6w node 8 inverter circuit 10, 13 the housing 11u~11w busbar 12u~12w connection electrode 20,21,22a~22c wiring patterns 30 ₁ to 30 _6, 31 ₁ to 31 _3, 32 ₁ 32 ₃ , 33 _{1 to} 33 ₃ Bonding wire 41 Sealing material 56 Thermal conductive sheet

Claims (4)

A motor case containing a motor having an electromagnetic coil;
An inverter circuit comprising a plurality of power elements and connected to the electromagnetic coil;
A substrate on which a semiconductor chip of each of the plurality of power elements is mounted on a main surface;
A power module comprising a heat conductive sheet connected to the motor case and the substrate.   The power module according to claim 1, wherein the heat conductive sheet is in contact with a back surface of the substrate. A motor case containing a motor having an electromagnetic coil;
An inverter circuit comprising a plurality of power elements and connected to the electromagnetic coil;
A substrate on which a semiconductor chip of each of the plurality of power elements is mounted on a main surface;
A power module comprising: a heat conductive sheet connected to the motor case and the semiconductor chip. The power module according to claim 1, wherein the thermal conductive sheet is a highly thermal conductive graphite sheet.

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