JP5926654B2 - Power semiconductor module and method of manufacturing power semiconductor module - Google Patents

Description

  The present invention relates to a power semiconductor module used for a power converter and the like, and a method for manufacturing the power semiconductor module.

  From the viewpoint of energy saving, automobiles are required to have high fuel efficiency, and electric cars driven by motors and hybrid cars combining motor driving and engine driving are attracting attention. A large-capacity on-vehicle motor used in an automobile is difficult to drive or control with a DC voltage of a battery, and a power conversion device using switching of a power semiconductor chip is indispensable for boosting and AC control. In addition, since the power semiconductor chip generates heat when energized, a power module on which the power semiconductor chip is mounted is required to have a high heat dissipation capability.

  Therefore, in order to enhance the heat dissipation performance, for example, a power module having a configuration in which a power semiconductor chip and a conductor plate on which the power semiconductor chip is mounted are in close contact with a metal heat dissipation base via an electrical insulating layer is disclosed in Patent Literature 1. In the power module described in Patent Document 1, a ceramic coating composed of aluminum nitride particles and aluminum oxide particles is obtained by spraying a fine powder obtained by mixing aluminum nitride particles and aluminum oxide particles onto a substrate at room temperature by an aerosol deposition method. Is used as an insulating layer.

  Further, Patent Document 2 describes a technique for forming an insulating layer containing aluminum nitride and aluminum oxide by spraying particles with an aluminum nitride core material covered with an aluminum oxide clothing material by plasma spraying. Has been.

JP 2006-278558 A JP 2006-66559 A

  However, since the aerosol deposition method described in Patent Document 1 is a method of forming an insulating layer by depositing a mixed powder of aluminum nitride particles and aluminum oxide particles, the porosity of the insulating layer becomes a problem. If the porosity is high, the thermal resistance of the insulating layer increases and the heat dissipation performance decreases. In addition, the plasma spraying method described in Patent Document 2 uses a special spraying material called a granule in which an aluminum nitride core material is covered with a clothing material made of aluminum oxide, which increases costs.

The power semiconductor module according to the invention includes a semiconductor chip, a conductor plate in which the semiconductor chip is electrically connected to one surface of the front and back surfaces, and a heat radiation surface formed on the other surface, and a conductor so that the heat radiation surface is exposed. A sealing resin that seals the plate and the semiconductor chip, and a metal base that is in thermal contact with the heat dissipation surface of the conductor plate via the insulating layer, and the insulating layer is formed of a metal base that faces the heat dissipation surface. A ceramic sprayed coating formed on a surface or a heat radiating surface by spraying a mixture of aluminum nitride particles , α-aluminum oxide particles, and ceramic particles having higher thermal conductivity than γ-aluminum oxide. The film is characterized in that the sum of the volume ratio of aluminum nitride and the volume ratio of α-aluminum oxide is 30% or more and the cross-sectional porosity is 10% or less.
The method for manufacturing a power semiconductor module according to the present invention includes a semiconductor chip, a conductor plate in which the semiconductor chip is electrically connected to one surface of the front and back surfaces, and a heat dissipation surface formed on the other surface, and the heat dissipation surface is exposed. A sealing resin for sealing the conductor plate and the semiconductor chip, and a can-like housing having a metal base that is in thermal contact with the heat dissipation surface through an insulating layer having a ceramic sprayed film. A method for manufacturing a power semiconductor module, in which a ceramic sprayed film having a total volume ratio of aluminum nitride and α-aluminum oxide of 30% or more and a cross-sectional porosity of 10% or less is formed. The first process of spraying a mixture of aluminum nitride particles and α-aluminum oxide particles on the surface of the metal base facing the heat radiating surface or the heat radiating surface by adjusting the thermal spraying conditions as described above. A degree, a second step of flattening by machining the surface of the ceramics sprayed film, a third step of impregnating the resin into the pores formed in the ceramics sprayed film from the planarized surface, the And a fourth step in which a resin is disposed between the metal base and the heat radiating surface, and the metal base is pressed against the heat radiating surface so as to deform the housing and is thermocompression bonded .

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductor power module excellent in heat dissipation can be manufactured at low cost.

It is an external appearance perspective view of a power module. It is a figure explaining the electric circuit structure of a power converter device. It is EE sectional drawing of FIG. It is a figure which shows the power module structure 3000. FIG. FIG. 5 is a view showing a state in which the first sealing resin 348 and the wiring insulating portion 608 are further removed from the state shown in FIG. 4. It is a disassembled perspective view of the primary sealing body 302. FIG. It is a figure explaining enclosure with the module case 304 of the power module structure 3000. FIG. 3 is a circuit diagram of a primary sealing body 302. FIG. FIG. 10 illustrates a structure of an insulating layer 333. It is a figure explaining the planarization process of the ceramic spraying film 333A. It is a figure explaining the formation method of resin layer 333B. It is sectional drawing of the power module 300 in which the ceramic sprayed film 333A was formed in the thermal radiation part 307A, 307B side. It is a figure explaining the formation procedure of ceramic spraying film 333A to radiating part 307A. It is a figure explaining the heat-transfer performance of the ceramic sprayed film 333A. It is a figure explaining the relationship between the insulation performance of ceramic spraying film 333A, and heat transfer performance. It is a figure which shows the insulation performance at the time of impregnating the ceramic sprayed film 333A with resin. It is a figure explaining the 1st example of the method of impregnating resin to ceramic spraying film 333A. It is a figure explaining the 2nd example of the method of impregnating resin to ceramic spraying film 333A. 3 is a plan view of a single-sided cooling power module 300. FIG. It is a figure explaining adhesion | attachment to the thermal radiation part 307. FIG. It is a figure which shows the power module 300 of the structure which clamps the primary sealing body 302 with a pair of thermal radiation part 307D. It is a figure explaining the concept of plasma spraying.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
-First embodiment-
FIG. 1 is an external perspective view of a power module. The power module 300 is a module in which a power semiconductor unit in which an electronic component including a switching element is transfer molded is housed in a module case 304. The power module 300 is used in, for example, a power conversion device mounted on an electric vehicle such as an electric vehicle or a hybrid vehicle.

  FIG. 2 is a diagram illustrating an electric circuit configuration of the power conversion device. The power conversion device 140 converts the direct current of the battery 136 into an alternating current and supplies it to the motor generator 192. Inverter circuit 144 of power converter 140 is provided with upper and lower arm series circuits 150 for three phases (U phase, V phase, W phase) corresponding to each phase winding of the armature winding of motor generator 192. ing. The power module 300 shown in FIG. 1 is provided with the semiconductor element of the upper and lower arm series circuit 150 for one phase.

  The upper and lower arm series circuit 150 includes an IGBT 328 and a diode 156 that operate as an upper arm, and an IGBT 330 and a diode 166 that operate as a lower arm. A middle point portion (intermediate electrode 169) of each upper and lower arm series circuit 150 is connected to an AC power line (AC bus bar) 186 to motor generator 192 via AC terminal 159 and AC connector 188. The collector electrode 153 of the IGBT 328 of the upper arm is electrically connected to the capacitor electrode on the positive electrode side of the capacitor module 500 via the positive electrode terminal (P terminal) 167. The emitter electrode of the IGBT 330 of the lower arm is electrically connected to the capacitor electrode on the negative electrode side of the capacitor module 500 via a negative electrode terminal (N terminal) 168.

  The control unit 170 includes a driver circuit 174 that drives and controls the inverter circuit 144, and a control circuit 172 that supplies a control signal to the driver circuit 174 via the signal line 176. The IGBT 328 and the IGBT 330 operate in response to the drive signal output from the control unit 170, and convert DC power supplied from the battery 136 into three-phase AC power. The converted electric power is supplied to the armature winding of the motor generator 192.

  The IGBT 328 includes a collector electrode 153, a signal emitter electrode 151, and a gate electrode 154. The IGBT 330 includes a collector electrode 163, a signal emitter electrode 165, and a gate electrode 164. A diode 156 is electrically connected in parallel to the IGBT 328, and a diode 158 is electrically connected in parallel to the IGBT 330. A MOSFET (metal oxide semiconductor field effect transistor) may be used as the switching power semiconductor element. In this case, the diode 156 and the diode 158 are not required.

  The positive electrode side capacitor terminal 506 and the negative electrode side capacitor terminal 504 of the capacitor module 500 are electrically connected to the battery 136 via the DC connector 138. The power converter 140 is connected to the positive capacitor terminal 506 via the DC positive terminal 314 and is connected to the negative capacitor terminal 504 via the DC negative terminal 316.

  The control circuit 172 includes a microcomputer (hereinafter referred to as “microcomputer”) for calculating the switching timing of the IGBTs 328 and 330. The microcomputer has a target torque value required for the motor generator 192, a current value supplied to the armature winding of the motor generator 192 from the upper and lower arm series circuit 150, and a magnetic pole position of the rotor of the motor generator 192. Input as input information.

  The target torque value is based on a command signal output from a host controller (not shown). The current value is detected based on the detection signal output from the current sensor 180 via the signal line 182. The magnetic pole position is detected based on a detection signal output from a rotating magnetic pole sensor (not shown) provided in the motor generator 192. In the present embodiment, the case where the current values of three phases are detected will be described as an example, but the current values for two phases may be detected.

  The microcomputer in the control circuit 172 calculates the d and q axis current command values of the motor generator 192 based on the target torque value, and the calculated d and q axis current command values and the detected d and q The voltage command values for the d and q axes are calculated based on the difference from the current value of the shaft, and the calculated voltage command values for the d and q axes are calculated based on the detected magnetic pole position. Convert to W phase voltage command value. Then, the microcomputer generates a pulse-like modulated wave based on a comparison between the fundamental wave (sine wave) and the carrier wave (triangular wave) based on the voltage command values of the U phase, V phase, and W phase, and the generated modulation wave The wave is output to the driver circuit 174 via the signal line 176 as a PWM (pulse width modulation) signal.

  When driving the lower arm, the driver circuit 174 outputs a drive signal obtained by amplifying the PWM signal to the gate electrode of the corresponding IGBT 330 of the lower arm. Further, when driving the upper arm, the driver circuit 174 amplifies the PWM signal after shifting the level of the reference potential of the PWM signal to the level of the reference potential of the upper arm, and uses this as a drive signal as a corresponding upper arm. Are output to the gate electrodes of the IGBTs 328 respectively.

  In addition, the control unit 170 performs abnormality detection (overcurrent, overvoltage, overtemperature, etc.) to protect the upper and lower arm series circuit 150. For this reason, sensing information is input to the control unit 170. For example, information on the current flowing through the emitter electrodes of the IGBTs 328 and 330 is input from the signal emitter electrode 151 and the signal emitter electrode 165 of each arm to the corresponding driver (IC). Thereby, each drive part (IC) detects overcurrent, and when overcurrent is detected, it stops the switching operation of corresponding IGBT328,330, and protects corresponding IGBT328,330 from overcurrent.

  The temperature information of the upper and lower arm series circuit 150 is input to the microcomputer from a temperature sensor (not shown) provided in the upper and lower arm series circuit 150. Further, voltage information on the DC positive side of the upper and lower arm series circuit 150 is input to the microcomputer. The microcomputer performs overtemperature detection and overvoltage detection based on the information, and stops switching operations of all the IGBTs 328 and 330 when an overtemperature or overvoltage is detected.

  3 to 8 are diagrams for explaining the configuration of the power module 300. FIG. 3 shows an EE cross section of FIG. The power module 300 is obtained by housing the power module structure 3000 shown in FIG. 4 in a module case 304 that functions as a CAN-type cooler. FIG. 4 is a view showing the power module structure 3000, FIG. 4 (a) is a perspective view, and FIG. 4 (b) is an EE cross-sectional view of FIG. 4 (a). The EE cross section in FIG. 4 represents the same cross section as the EE cross section in FIG.

  As shown in FIG. 3, the CAN-type cooler is a cylindrical cooler having an insertion port 306 on one surface and a bottom on the other surface. The module case 304 is formed of a member having excellent thermal conductivity, such as a composite material such as Cu, Cu alloy, Cu-C, or Cu-CuO, or a composite material such as Al, Al alloy, AlSiC, or Al-C. ing. Further, it is integrally formed in a case shape without a joint by a highly waterproof joining method such as welding or by forging or casting.

  The module case 304 is a flat case having no opening other than the insertion port 306, and the insertion port 306 is provided with a flange 304B. A heat radiating portion 307A is provided on one of the two opposing surfaces with a large area of the flat case, and a heat radiating portion 307B is provided on the other surface. The heat dissipating part 307A and the heat dissipating part 307B function as heat dissipating walls of the module case 304, and a plurality of fins 305 are uniformly formed on the outer peripheral surface thereof. The peripheral surface surrounding the heat radiation part 307A and the heat radiation part 307B is a thin part 304A that is extremely thin and can be easily plastically deformed. By making the thin portion 304A extremely thin, the heat dissipation portion 307A and the heat dissipation portion 307B can be easily deformed when pressurized in the case inner direction. The shape of the module case 304 need not be an accurate rectangular parallelepiped, and the corners may form curved surfaces as shown in FIG.

  As shown in FIG. 4, the power module structure 3000 includes a primary sealing body 302 and an auxiliary mold body 600. The primary sealing body 302 and the auxiliary mold body 600 are connected at the connection portion 370. For example, TIG welding or the like can be used for metal bonding in the connection portion 370. As shown in FIG. 1, the power module structure 3000 is positioned in the module case 304 by fixing the wiring insulating portion 608 provided in the auxiliary mold body 600 to the flange 304 </ b> B of the module case 304 with screws 309.

  First, the structure of the primary sealing body 302 is demonstrated using FIG. 6 and FIG. FIG. 6 is an exploded perspective view showing the configuration of the primary sealing body 302. FIG. 8 is a circuit diagram of the primary sealing body 302. FIG. 6 shows a process before the state shown in FIG. 5, that is, a state before connection by the bonding wire 371 is performed, and the tie bar 372 is in an undeleted state.

  As shown in FIG. 8, the collector electrode of the upper arm IGBT 328 and the cathode electrode of the upper arm diode 156 are connected to the conductor plate 315, and the emitter electrode of the IGBT 328 and the anode electrode of the diode 156 are connected to the conductor plate 318. . The collector electrode of the lower arm IGBT 330 and the cathode electrode of the lower arm diode 166 are connected to the conductor plate 320, and the emitter electrode of the IGBT 330 and the anode electrode of the diode 166 are connected to the conductor plate 319. The conductor plate 318 and the conductor plate 320 are connected via an intermediate electrode 159. The upper arm circuit and the lower arm circuit are electrically connected by the intermediate electrode 159, and the upper and lower arm series circuit as shown in FIG. 4 is formed. As the conductor plates 315, 318, 319, and 320, metals such as Cu, Al, Ni, Au, Ag, Mo, Fe, and Co, alloys thereof, and composites are used.

  In the state shown in FIG. 6, the DC positive electrode side conductor plate 315 and the AC output side conductor plate 320, and the upper arm signal connection terminal 327 </ b> U and the lower arm signal connection terminal 327 </ b> L are connected to a common tie bar 372. It is in a state. These are integrally processed so as to have a substantially coplanar arrangement. The control electrode 328A of the IGBT 328 is connected to the upper arm signal connection terminal 327U by a bonding wire. The control electrode 330A of the IGBT 330 is connected to the lower arm signal connection terminal 327L by a bonding wire. Convex chip fixing portions 322 are respectively formed on the portions of the conductor plates 315 and 320 where the semiconductor chips (IGBTs 328 and 330, diodes 156 and 166) are joined. Each semiconductor chip is bonded onto the chip fixing portion 322 by a metal bonding material 160. As the metal bonding material 160, for example, a solder material, a silver sheet, and a low-temperature sintered bonding material containing fine metal particles are used. In addition, it is desirable to use solder containing tin as a main component for the metal bonding material 160, but it is also possible to use a solder containing one of gold, silver, and copper as a main component, a brazing material, a paste, or the like.

  On the IGBTs 328 and 330 and the diodes 155 and 166, the conductor plate 318 and the conductor plate 319 are arranged in substantially the same plane via the metal bonding material 160 and are metal-bonded. As shown in FIG. 4, the conductor plate 318 is joined to the emitter electrode of the IGBT 328 on the upper arm side and the anode electrode of the diode 156 on the upper arm side. The conductor plate 319 is joined to the emitter electrode of the IGBT 330 on the lower arm side and the anode electrode of the diode 166 on the lower arm side. A direct current positive electrode connection terminal 315D is formed on the conductor plate 315. An AC connection terminal 320D is formed on the conductor plate 320. A DC negative connection terminal 319D is formed on the conductor plate 319.

  As described above, the IGBT 328 and the diode 156 are sandwiched between the conductor plate 315 and the conductor plate 318, and the IGBT 330 and the diode 166 are sandwiched between the conductor plate 320 and the conductor plate 319, so that the conductor plate 320 and the conductor plate 318 are intermediate. Connection is made by the electrode 329. Further, the control electrode 328A of the IGBT 328 and the signal connection terminal 327U are connected by the bonding wire 371, and the control electrode 330A of the IGBT 330 and the signal connection terminal 327L are connected by the bonding wire 371.

  Thereafter, a portion including the semiconductor chips (IGBTs 328 and 330, diodes 156 and 166) and the bonding wire 371 is sealed with a sealing resin 348. This sealing is performed by transfer molding. As the sealing resin 348, for example, a resin based on a novolac-based, polyfunctional, or biphenyl-based epoxy resin can be used, and ceramics such as SiO2, Al2O3, AlN, and BN, gel, rubber, and the like are included. The thermal expansion coefficient is brought close to the conductor plates 315, 320, 318, and 319. As a result, the difference in thermal expansion coefficient between the members can be reduced, and the thermal stress generated as the temperature rises in the use environment is significantly reduced, so that the life of the power module can be extended.

  The tie bar 372 shown in FIG. 6 is cut off after being sealed with the sealing resin 348. And each edge part of DC positive electrode connection terminal 315D, DC negative electrode connection terminal 319D, AC connection terminal 320D, and signal connection terminals 327U and 327L arranged in a line on one side of the primary sealing body 302 is as shown in FIG. Are bent in the same direction.

  As shown in FIGS. 4 and 1, the auxiliary mold body 600 is provided with a DC positive electrode wiring 315A, a DC negative electrode wiring 319A, an AC wiring 320A, a signal wiring 324U, and a signal wiring 324L, which are made of a resin material. They are integrally molded in a state where they are insulated from each other by the molded wiring insulating portion 608. The wiring insulating portion 608 also functions as a support member for supporting each wiring, and an insulating thermosetting resin or thermoplastic resin is suitable for the resin material used for the wiring insulating portion 608. Thereby, it is possible to secure insulation between the DC positive electrode wiring 315A, the DC negative electrode wiring 319A, the AC wiring 320A, the signal wiring 324U, and the signal wiring 324L, and high-density wiring is possible.

  A DC positive electrode terminal 315B is formed at the upper end of the DC positive electrode wiring 315A, and a DC positive electrode connection terminal 315C is formed at the lower end so as to be bent at a right angle. A DC negative electrode terminal 319B is formed at the upper end of the DC negative electrode wiring 319A, and a DC negative electrode connection terminal 319C is formed at the lower end so as to be bent in the same direction as the DC positive electrode connection terminal 315C. An AC terminal 320B is formed at the upper end of the AC wiring 320A, and an AC connection terminal 320C is formed at the lower end so as to be bent in the same direction as the DC positive connection terminal 315C. Signal terminals 325U and 325L are formed at the upper ends of the signal wirings 324U and 324L, respectively. On the other hand, the signal connection terminal 326U and the signal connection terminal 326L are formed at the lower ends of the signal wirings 324U and 324L so as to be bent in the same direction as the DC positive electrode connection terminal 315C.

  The direct current positive electrode connection terminal 315C is connected to the direct current positive electrode connection terminal 315D on the primary sealing body 302 side. The DC negative electrode connection terminal 319C is connected to the DC negative electrode connection terminal 319D on the primary sealing body 302 side. The AC connection terminal 320C is connected to the AC connection terminal 320D on the primary sealing body 302 side. The signal connection terminal 326U is connected to the signal connection terminal 327U on the primary sealing body 302 side. The signal connection terminal 326L is connected to the signal connection terminal 327L on the primary sealing body 302 side.

  8 corresponds to the gate electrode 154 and the signal emitter electrode 155 in FIG. 2, and the signal connection terminal 327L in FIG. 8 corresponds to the gate electrode 164 and the emitter electrode 165 in FIG. 8 corresponds to the positive electrode terminal 157 in FIG. 2, and the DC negative branch terminal 319D in FIG. 8 corresponds to the negative electrode terminal 158 in FIG.

  When the power module structure 3000 as shown in FIG. 4 is completed, the power module structure 3000 is inserted into the module case 304 as shown in FIG. 7A, and the wiring insulating portion 608 of the auxiliary mold body 600 is connected to the module. The case 304 is fixed to the flange 304B. At the time of the insertion, an insulating layer 333 for providing electrical insulation is provided between the primary sealing body 302 and the heat radiating portions 307A and 307B. Details of the insulating layer 333 will be described later.

  Then, as shown by the arrows in FIG. 7B, the heat radiating portions 307A and 307B are pressed inside the case to deform the thin portion 304A, and the heat radiating portions 307A and 307B and the primary sealing body 302 are heated by the insulating layer 333. Crimp. After that, by filling the module case 304 with the sealing resin 351 and sealing it, a necessary insulation distance between the connection portion 370 and the module case 304 can be stably secured. As the sealing resin 351, for example, a resin based on a novolak-based, polyfunctional, or biphenyl-based epoxy resin can be used.

(Description of insulating layer 333)
FIG. 9 is a diagram illustrating the structure of the insulating layer 333. FIG. 9A is a cross-sectional view of the primary sealing body 302, and FIG. 9B schematically shows a cross-sectional structure of a portion indicated by reference numeral B in FIG. 9A. The insulating layer 333 includes two layers, and includes a ceramic sprayed film 333A formed by plasma spraying ceramic powder and a resin layer 333B made of an insulating resin.

  When the ceramic sprayed film 333A is formed by the plasma spraying method, since the temperature rise of the primary sealing body 302 is about 100 to 180 ° C., the sealing resin 348, the IGBTs 328 and 330, and the diodes 156 and 166 are not thermally deteriorated. Therefore, chip bonding performed in a temperature range of 220 to 300 ° C. can be performed first. As a result, the thermal stress generated in the laminated portion of the thermal spray film having a small thermal expansion coefficient and the conductor plate having a large thermal expansion coefficient can be reduced as compared with the case of chip joining after thermal spraying on the lead frame (conductor plate). it can.

  Further, when the surface of the conductor plates 315, 318, 319, 320 on which the ceramic spray film 333A is formed, that is, the heat radiation surface of the conductor plates 315, 318, 319, 320 is roughened by sandblasting or etching before spraying, The bonding strength of the ceramic sprayed film 333A can be improved. If these are sealed with the sealing resin 348 during these processes, physical and chemical damage to the IGBTs 328 and 330 and the bonding wires 371 can be prevented, so that complicated masking is unnecessary and productivity is improved. To do. After the transfer molding, the conductive plates 315, 318, 319, and 320 may be covered with the sealing resin 348, but may be removed by a sandblasting process that is a pretreatment for thermal spraying. Since the sealing resin 348 has a lower thermal conductivity than the conductor plate, it can be removed from the heat radiating surface, thereby improving the heat dissipation.

  As shown in FIG. 9B, the ceramic sprayed film 333A of the present embodiment has a configuration in which aluminum nitride particles are dispersed in an aluminum oxide sprayed film. In general, a sprayed film of aluminum oxide is used as a sprayed film having good thermal conductivity. Aluminum nitride is a ceramic material that has better heat transfer characteristics than aluminum oxide. Since aluminum nitride is a substance that sublimes, it vaporizes without passing through a liquid state as the temperature rises, and aluminum nitride cannot be sprayed.

  As will be described in detail later, aluminum oxide particles are formed in a molten or semi-molten state by mixing aluminum oxide (AlN) powder with aluminum oxide (Al2O3) powder and plasma spraying under predetermined spraying conditions. The present inventor has found that a sprayed film that is incident on the film surface and in which flat aluminum oxide flat bodies 3331 are laminated can be obtained. On the other hand, the aluminum nitride particles are incident on the film formation surface without melting, but the aluminum oxide particles 3332 are deposited on the film formation surface because the molten aluminum oxide serves as a binder. As shown in FIG. 9, the ceramic sprayed film 333A is formed on the exposed surfaces of the conductor plates 315 and 318 and the surface of the sealing resin 348 around the exposed surfaces. Reference numeral 3330 denotes pores formed in the sprayed film.

  FIG. 10A shows a ceramic sprayed film 333A formed on the conductor plate 315, and the surface of the ceramic sprayed film 333A formed by plasma spraying is an uneven surface. Therefore, as shown in FIG. 10B, planarization is performed by machining or the like so that the thickness of the ceramic sprayed film 333A is made uniform. The heat of the conductor plate 315 is transmitted in the thickness direction of the ceramic sprayed film 333A, and the heat transfer performance can be made uniform by making the thickness of the ceramic sprayed film 333A uniform.

  If the ceramic sprayed film 333A is formed on both surfaces of the primary sealing body 302 as shown in FIG. 10B, a resin layer 333B is formed on the ceramic sprayed film 333A. FIG. 11 is a diagram illustrating a method for forming the resin layer 333B. Here, a resin layer 333B formed in the form of a sheet is pasted on the ceramic sprayed film 333A as shown in FIG. By this temporary pressure bonding, a part of the resin layer 333B enters the pores near the surface of the ceramic sprayed film 333A.

  Note that the temporarily press-bonded resin layer 333B is used for the adhesion between the resin layer 333B and the heat radiation portions 307A and 307B after the primary sealing body 302 is accommodated in the module case 304 in the process shown in FIG. Crimping operation is performed. Therefore, in the temporary pressure bonding shown in FIG. 11B, the temperature condition and the pressure condition during pressure bonding so that the resin component is in a semi-cured state (for example, a state where the degree of cure of the resin component is about 80% or less). Set.

  A protective film 352 is provided on the opposite surface of the resin layer 333B so as to facilitate the work. The protective film 352 is removed when the primary sealing body 302 is stored in the module case 304 in the step shown in FIG. For the protective film 352, polyethylene terephthalate, polyethylene, polypropylene, polybutylene terephthalate, or the like is used.

  The resin layer 333B is required to have sufficient adhesiveness and high thermal conductivity for the resin layer 333B. Therefore, the resin constituting the resin layer 333B includes adhesive resins such as phenolic, acrylic, polyimide, polyamideimide, epoxy, silicon, bismaleimide triazine, and cyanate esthel. Used. In particular, it is preferable to use a resin based on bismaleimide triazine, polyamideimide, polyimide, cyanate esthel, epoxy, or phenol, which has high adhesiveness, and it is difficult to peel off after adhesion, thus increasing the life of the power module.

  Generally, in order to improve the thermal conductivity of the resin layer 333B, a good thermal conductive filler is mixed into the resin layer 333B. The filler mixed in the resin layer 333B is preferably an insulating material, and has high thermal conductivity such as oxides such as alumina, silica, magnesia, and beryllia, nitrides such as aluminum nitride, silicon nitride, and boron nitride, and carbides such as silicon carbide. More preferable are ceramic fillers.

  In the example described above, the case where the ceramic sprayed film 333A is formed on the conductor plates 315 and 318 of the primary sealing body 302 has been described. However, as shown in FIGS. 12 and 13, the heat radiating portions 307A and 307B of the module case 304 are formed. A ceramic sprayed film 333A may be formed on the inner peripheral surface of the film.

  A module case 304 shown in FIG. 12 includes a case frame and a pair of case side surfaces. The case frame includes a thick flange 304B and a frame portion 304D. One of the pair of case side surface portions 304C (the left side in the drawing) includes a heat radiating portion 307A in which the fins 305 are formed, and a thin portion 304A surrounding the periphery thereof. The other case side surface portion 304C includes a heat radiation portion 307A in which the fins 305 are formed and a thin portion 304A surrounding the periphery thereof. The module case 304 is formed by metal-bonding the thin portion 304A to the case frame.

  In the insulating layer 333, the ceramic sprayed film 333A is formed on the inner peripheral surface side of the heat radiation portions 307A and 307B, and the resin layer 333B is formed on the conductor plates 315 and 318 side. As shown in FIG. 13A, a case side surface portion 304C having a heat radiation portion 307A and a thin portion 304A in which fins 305 are formed is prepared, and the inner peripheral surface side of the heat radiation portion 307A, that is, the fin 305 is formed. A ceramic sprayed film 333A is formed on the surface opposite to the surface on which it is present. Note that a masking process is performed so that the sprayed film 333A is not formed on the thin portion 304A.

  Thereafter, a resin layer 333B is formed as shown in FIG. In addition to the method using the resin sheet 3332 described above, a method of applying, spraying, or dipping a resin mixed with a liquid filler may be used as a method for forming the resin layer 333B. Then, the module case 304 is formed by joining the case side surface portion 304C on which the insulating layer 333 is formed to the frame portion 304D.

(Explanation of spraying conditions)
As described above, since aluminum nitride is a sublimating substance, it vaporizes without passing through a liquid state as the temperature rises, and aluminum nitride cannot be sprayed. However, a state in which aluminum nitride particles are embedded in an aluminum oxide film by mixing aluminum oxide (Al2O3) powder with aluminum nitride (AlN) powder and plasma spraying under predetermined spraying conditions. That is, as shown in FIG. 9B, the ceramic sprayed film 333A in which aluminum nitride particles 3332 are dispersed in the aluminum oxide sprayed film is formed.

  FIG. 22 is a diagram for explaining the concept of plasma spraying. Power is supplied from a power supply device 401 to the plasma spray gun 400 for generating the plasma jet P. Thermal spray material powder 402 (mixed powder of aluminum oxide particles and aluminum nitride particles) is put into plasma jet P. The thermal spray material powder 402 put into the plasma jet P is accelerated and heated by the high-temperature and high-speed plasma jet P to become flying particles. The flying particles can be molten particles or solid particles. The flying particles are incident on the surface of the base material 403 at a high speed, and a sprayed film 404 is formed on the surface of the base material. At the time of thermal spraying, the plasma spray gun 400 is traversed in the T direction parallel to the base material 403.

  The main conditions for plasma spraying include the conditions shown in FIG. The construction conditions are mainly those relating to the plasma spray gun 400, such as voltage, current, traverse speed, spray distance, spray material powder 402 supply speed, and the like. The powder conditions are conditions relating to the thermal spray material powder 402, and include a mixing ratio, a mixing method, a particle size, purity, and the like. The flying particle condition is a condition related to material particles (flying particles) accelerated and heated by a plasma jet, and here, the temperature of the flying particles is given as a condition. The substrate conditions include the temperature of the substrate 403 during thermal spraying, pretreatment conditions before thermal spraying, and the like.

  Among these conditions, in order to prevent the sublimation of the aluminum nitride particles and form the ceramic sprayed film 333A containing aluminum nitride and aluminum oxide as shown in FIG. 9B, at least the temperature of the flying particles is set. It is necessary to set it as 2000-2200 degreeC. In practice, the construction conditions (the plasma spray gun 400, which is a heating source, and the power supply device 401) are adjusted so that such temperature conditions are satisfied. In particular, in order to form the ceramic sprayed film 333A, it is important to set the spraying distance to be shorter than a general spraying distance (for example, about 50 mm).

(Explanation regarding the structure of the ceramic sprayed film 333A)
14 and 15 are diagrams illustrating the characteristics of the ceramic sprayed film 333A. FIG. 14 shows the relationship between the amount of aluminum oxide (Al2O3) added to aluminum nitride (AlN) and the cross-sectional porosity, and the ratio of the amount added and (AlN + α-Al2O3) in the ceramic sprayed film. It is.

  The characteristics shown in FIG. 14 are obtained for the following samples. Here, as shown in FIG. 13, a case where a ceramic sprayed film 333A is formed on an Al heat radiation portion 307A will be considered. First, a square Al plate having a thickness of 2 mm and a length and width of 150 mm is prepared, and the surface of the Al plate is subjected to sand blasting treatment with aluminum oxide (pretreatment). Thereafter, atmospheric plasma spraying (APS) was performed at an output of 40 kW using a mixed powder of aluminum nitride particles having a particle size of about 10 to 30 μm and aluminum oxide particles (α-aluminum oxide particles). At this time, the Al plate was preheated to 180 ° C. in order to suppress the porosity of the sprayed coating formed on the Al plate and prevent cracking of the sprayed coating during cooling.

  In this embodiment, the APS spraying method is used. However, a low pressure plasma spraying method (LPPS, VPS), a high-speed flame spraying (HVOF), a warm spraying method or the like may be used.

  The cross-sectional porosity was measured and the phase was identified by X-ray diffraction with respect to the ceramic sprayed film manufactured through such processes. In FIG. 14, the horizontal axis indicates the amount of aluminum oxide powder added (mass%), which is the ratio of aluminum oxide in the raw powder. For example, in the case of 0% at the left end, the raw powder is all aluminum nitride, and in the case of 100% at the right end, the raw powder is all aluminum oxide. In addition, when spraying only with the aluminum nitride powder, the sprayed film could not be formed.

  In FIG. 14, the white rhombus is data regarding the cross-sectional porosity, and the black rectangle is data regarding the volume ratio. The vertical axis on the left side of FIG. 14 shows the cross-sectional porosity (%), and the vertical axis on the right side shows the volume ratio (Vol%) of aluminum nitride and the volume ratio (Vol%) of α-aluminum oxide in the sprayed film. Shows the total. Note that the vertical axis of the cross-sectional porosity is set to 0 on the upper side in the figure with an emphasis on ease of understanding. The cross-sectional porosity was calculated by binarizing the tissue density using image analysis software.

  By the way, aluminum oxide has α-aluminum oxide with high thermal conductivity and γ-aluminum oxide with low thermal conductivity, and when the temperature rises, it transforms from α phase to γ phase. The aluminum oxide particles used as the thermal spray material are α-aluminum oxide. Aluminum nitride is superior to α-aluminum oxide in terms of thermal conductivity. That is, the greater the value on the right vertical axis, the greater the thermal conductivity of the ceramic sprayed film 333A. In addition, the volume ratio of each phase includes a method of converting to volume from observation of a cross-sectional structure, a method of estimating from a peak intensity ratio of X-ray diffraction, and the like. When identifying phases by X-ray diffraction, the crystal plane of aluminum nitride is the (100) plane, the crystal plane of α-aluminum oxide is the (113) plane, and the crystal plane of γ-aluminum oxide is the (400) plane.

(Cross section porosity)
Looking at the cross-sectional porosity data (white rhombus) in FIG. 14, when the amount of aluminum oxide (α-aluminum oxide) added was increased from 0%, the cross-sectional porosity rapidly increased when the amount added exceeded a certain range. descend. Furthermore, when the addition amount of aluminum oxide was made larger than the addition amount shown by line L1, the cross-sectional porosity was less than 10%.

  In the region on the left side of the line L1 (the region indicated by solid phase rich in FIG. 14), the proportion of aluminum oxide present in a particle state (solid state) is large, and it is deposited on the substrate without being sufficiently flattened during the thermal spraying process. It is thought that. As a result, the pores remained without being sufficiently filled, and the cross-sectional porosity became larger than 10%. That is, the thermal conductivity is not good.

  On the other hand, when the amount of aluminum oxide powder added is increased to the region on the right side of the line L1 (region that is rich in liquid phase), the aluminum oxide undergoes transformation from solid (particle state) to liquid, and the aluminum oxide particles undergo thermal spraying. And was deposited on the substrate in that state. As a result, the pores were filled and the porosity became 10% or less. Looking at the cross-sectional porosity data in FIG. 14, if the addition amount is larger than the position of the line L1, the cross-sectional porosity changes in a range of 5 to 10%, which is a region having a small influence on the thermal conductivity. . That is, the numerical value of 5 to 10% indicates an optimum range as the cross-sectional porosity of the ceramic sprayed film 333A. On the contrary, when the added amount is smaller than the position of the line L1, the cross-sectional porosity is greatly changed in a stepped manner and becomes a value of about 16 to 17%. When the cross-sectional porosity is as large as 16 to 17%, the influence on the decrease in thermal conductivity becomes significant.

(Volume ratio)
As described above, when the temperature increases, α-aluminum oxide is transformed into γ-aluminum oxide. Furthermore, as can be seen from the data on the volume ratio in FIG. 14 (black rectangle), when the amount of aluminum oxide powder added is increased, the aluminum oxide tends to transform from the α phase to the γ phase. This can be grasped by identifying the phase by X-ray diffraction with respect to the sprayed film. Therefore, as shown in FIG. 14, in the region where the amount of aluminum oxide (α-aluminum oxide) powder added is small, the volume ratio greatly exceeds 30%, but when the amount of aluminum oxide powder added increases, the volume ratio increases. It gradually decreases and decreases rapidly from the vicinity of the addition amount indicated by the line L2. Line L2 indicates the amount of addition at a volume ratio of 30%.

  As described above, the transition of the volume ratio is significantly different between the right side and the left side of the line L2, and the volume ratio of 30% or more is shifted on the left side of the line L2. On the other hand, on the right side of the line L2, the volume ratio decreases rapidly and greatly falls below 30%. Since there is a transformation from α phase to γ phase, the ceramic sprayed film 333A is composed of α-aluminum oxide, γ-aluminum oxide and aluminum nitride. Therefore, the thermal conductivity of the ceramic sprayed film 333A depends on these ratios, and the thermal conductivity increases as the total volume ratio of α-aluminum oxide and aluminum nitride, which are high thermal conductivity phases, increases. That is, in the ceramic sprayed film 333A obtained by spraying aluminum nitride and α-aluminum oxide, the region where the volume ratio is 30% or more shows an optimum range from the viewpoint of thermal conductivity.

  As described above, both the cross-sectional porosity and the volume ratio affect the thermal conductivity of the ceramic sprayed film 333A. And in the area | region on the left side of the line L1 of FIG. 14, thermal conductivity deteriorates by the influence of a cross-sectional porosity, and thermal conductivity deteriorates by the influence of a volume ratio in the right side of the line L2. Therefore, in order for the ceramic sprayed film 333A to have a suitable thermal conductivity, the cross-sectional porosity of the ceramic sprayed film 333A is 10% or less, and the total volume ratio of aluminum nitride and α-aluminum oxide is 30% or more. It is preferable that

  The cross-sectional porosity is affected by the molten state of the aluminum oxide particles, and the volume ratio is affected by transformation due to the temperature of the aluminum oxide particles. For this reason, the above-mentioned flying particle condition (temperature of flying particles) affects the cross-sectional porosity and volume ratio, but basically, the formation of the ceramic sprayed film 333A has the highest priority. Temperature 2000-2200 degreeC is set from such a viewpoint.

  As described above, the cross-sectional porosity and volume ratio are influenced by the thermal spraying conditions such as temperature, but are mainly determined by the addition amount (mixing ratio) of aluminum oxide as shown in FIG. Therefore, the addition amount with a cross-sectional porosity of less than 10% and the addition amount with a volume ratio of more than 30% are determined by performing thermal spraying in advance on a trial basis. As an example, the suitable mixing ratio in the sample preparation conditions mentioned above was 40-62 mass%.

  Thus, when performing thermal spraying using the mixture of an aluminum oxide powder and an aluminum nitride powder, by making the addition amount of an aluminum oxide powder into the value between the line L1 and the line L2 of FIG. 14, cross-sectional porosity Is 10% or less, and the ceramic sprayed film 333A in which the total of the volume ratio of aluminum nitride and the volume ratio of α-aluminum oxide is 30% or more can be formed. That is, as the ceramic sprayed film 333A made of aluminum oxide and aluminum nitride, an optimum sprayed film with respect to heat transfer characteristics can be obtained.

  It can be measured from the X-ray diffraction peak intensity that the total of the volume ratio of aluminum nitride and the volume ratio of α-aluminum oxide is 30% or more. The peak intensity of the (100) plane of aluminum nitride, α-oxidation The peak intensity of (100) plane of aluminum nitride and the peak intensity of (113) plane of α-aluminum oxide with respect to the total value of the peak intensity of (113) plane of aluminum and the peak intensity of (400) plane of γ-aluminum oxide The ratio of the total value is 30% or more. X-ray diffraction makes it possible to grasp the abundance ratio of each phase with good reproducibility, so that variations in mass production and characteristics can be guaranteed.

  In the above-described example, the ceramic sprayed film 333A made of aluminum nitride, α-aluminum oxide and γ-aluminum oxide is formed by using a mixed powder of aluminum nitride and aluminum oxide, but an additive other than aluminum oxide is further added. You may do it. However, it is desirable that the additive forms a higher thermal conductivity phase than γ-aluminum oxide. For example, when at least one kind of yttrium oxide (Y2O3), zirconia oxide (Zr2O3), silicon carbide (SiC), silicon nitride or the like (Si3N4) is added, the same effect as when α-aluminum oxide is added is obtained. Demonstrate and contribute to increase of high thermal conductivity phase and reduction of porosity.

  FIG. 15 is a view for explaining the relationship between the insulating performance and the heat transfer performance of the ceramic sprayed film 333A. Also in this case, as in the case of FIG. 14, a 150 mm square Al plate having a thickness of 2 mm as a base material was sandblasted using aluminum oxide, and then a mixed powder of aluminum nitride particles and aluminum oxide particles was used. Plasma spraying was performed at an output of 40 kW. The cross-sectional porosity of the sprayed film at this time was 4%. The cross-sectional porosity was calculated by binarizing the tissue density using image analysis software.

  The horizontal axis in FIG. 15 is the film thickness of the sprayed film, and the vertical axis on the left is when the breakdown voltage of the single sprayed film having a thickness of 80 μm (minimum breakdown voltage required in this embodiment) is 1. Normalized dielectric breakdown voltage, the vertical axis on the right side is the normalized thermal conductivity when the thermal conductivity of the sprayed film alone having a thickness of 200 μm (minimum required thermal conductivity in this embodiment) is 1. is there. Since the ceramic sprayed film 333A is a film in which an aluminum oxide flat body 3331 and aluminum nitride particles 3332 are laminated as shown in FIG. 9, the surface of the sprayed film has an uneven shape. Therefore, the thickness of the ceramic sprayed film 333A in the present embodiment means a thickness after flattening by grinding or the like.

  In FIG. 15, the white triangle is data on the dielectric breakdown voltage, and the black circle is data on the thermal conductivity. As the thickness of the ceramic sprayed film 333A increases, the dielectric breakdown voltage also increases and the insulation performance improves. On the other hand, the thermal conductivity decreases as the thickness increases, and the heat transfer performance decreases. Therefore, in order to achieve both insulation performance and heat transfer performance, for example, the thickness of the ceramic sprayed film 333A is preferably set to 80 μm or more and 200 μm or less.

  14 and 15, the ceramic sprayed film was formed on the Al plate which is the same material as the heat dissipating parts 307A and 307B, and the characteristics were measured. However, the conductive plates 315 and 318 and the sealing resin 348 side were measured. In the case where a ceramic sprayed film was formed on, a sample corresponding to that was also produced and the characteristics were examined. In this case, a 150 mm square Cu plate having a thickness of 2 mm as a substrate and a resin plate were subjected to a sandblast treatment using aluminum oxide, and then a mixed powder of aluminum nitride and aluminum oxide particles was plasma sprayed at an output of 40 kW. When the ceramic sprayed film is actually formed on the conductor plates 315 and 318 and the sealing resin 348 side, the heat deformation capacity, the melting point, etc. are different between the conductor plate and the resin, but the amount of heat input is adjusted. Thus, thermal spraying can be performed in a series of scans without masking. Of course, you may make it spray individually using masking.

  By the way, in the process of laminating the spray particles, the first layer in which the base material and the particles first contact each other affects the heat transfer characteristics, and thus largely governs the characteristics of the entire sprayed film. As a method for improving the contact state, the temperature of the base material may be increased in order to improve wettability. Thereby, the adsorbed substance on the substrate surface is desorbed, and the contact state is improved due to the effect of improving the wettability.

  However, on the other hand, the thermal deformation of the base material is accelerated by increasing the base material temperature, and the deformation of the base material affects the dimensional tolerance when the module is assembled. Furthermore, when the substrate is a resin, aluminum nitride particles that collide with the solid may grind the surface of the resin substrate and cause a blast treatment.

  Regarding the fact that aluminum nitride particles grind the surface of the resin base material, by adding aluminum oxide, liquid phase aluminum oxide particles are laminated on the resin base material during spraying, and serve as a buffer for solid particles. Demonstrate the effect. This effect makes it possible to form the ceramic sprayed film 333A on the resin base material.

  As described above, in the present embodiment, the power module 300 includes the semiconductor chip (IGBTs 328 and 330, the diodes 156 and 166), the semiconductor chip electrically connected to one surface of the front and back surfaces, and the heat dissipation to the other surface. Conductive plates 315, 318, 319, and 320 having surfaces formed thereon, sealing resin 348 that seals the conductive plate and the semiconductor element so that the heat radiating surface is exposed, and a heat radiating surface of the conductive plate via the insulating layer 333 And metal bases 307A and 307B that are in thermal contact. The insulating layer 333 is a ceramic sprayed film 333A formed by spraying a mixture of aluminum nitride particles and α-aluminum oxide particles on the surface of the metal bases 307A and 307B facing the heat radiating surface or the heat radiating surface of the conductor plate. The ceramic sprayed film 333A has a total volume ratio of aluminum nitride and α-aluminum oxide of 30% or more and a cross-sectional porosity of 10% or less.

  As described above, since aluminum nitride is a substance that sublimates from a solid to a gas without passing through a liquid, a sprayed coating of aluminum nitride could not be formed. However, by using a mixed powder in which aluminum nitride particles and sprayable α-aluminum oxide particles are mixed, it was possible to form a ceramic sprayed film having high thermal conductivity composed of aluminum nitride and α-aluminum oxide. . The insulating layer 333 of the present invention enables the formation of a ceramic sprayed film containing aluminum nitride. The ceramic sprayed film has better thermal conductivity than a sprayed film using aluminum oxide powder alone, and when applied to a power module, the thermal resistance of the insulating layer is reduced, and the heat dissipation of the power module can be improved.

  In the ceramic sprayed film, aluminum nitride is in the form of particles, but the α-aluminum oxide particles are incident on the deposition surface in a molten state, so the porosity is smaller than when aluminum nitride particles are simply deposited. We were able to. Furthermore, suitable thermal conductivity was obtained by setting the porosity to 10% or less. In addition, α-aluminum oxide changes to γ-aluminum oxide as the temperature rises. Therefore, increasing the mixing ratio of α-aluminum oxide particles changes α-aluminum oxide to γ-aluminum oxide. It was found that the volume ratio combined with aluminum decreased. And when the volume ratio was 30% or more, suitable thermal conductivity was obtained.

  That is, the porosity of the ceramic sprayed film formed by spraying a mixture of aluminum nitride particles and α-aluminum oxide particles is set to 10% or more, and the sum of the volume ratio of aluminum nitride and the volume ratio of α-aluminum oxide is defined as By setting it to 30% or more, a ceramic sprayed film having high thermal conductivity can be obtained. Furthermore, the heat dissipation performance of the power module can be improved by using it for the insulating layer of the power module. Moreover, when it applies to a power module, it can construct continuously with an adjacent conductor board, and can aim at reduction of a manufacturing man-hour and manufacturing cost reduction.

  That is, the spraying conditions were adjusted so that a ceramic sprayed film having a total volume fraction of aluminum nitride and α-aluminum oxide of 30% or more and a cross-sectional porosity of 10% or less was formed. Then, a mixture of aluminum nitride particles and α-aluminum oxide particles is sprayed onto the surface of the metal base or the heat dissipation surface facing the heat dissipation surface. The spraying conditions include the mixing ratio of α-aluminum oxide particles in the mixture of aluminum nitride particles and α-aluminum oxide particles and the heating temperature of the mixture during spraying. In the example described above, the mixing ratio is set to 40 to 62 mass%. Further, the heating temperature is 2000 to 2200 ° C., and the thermal spraying conditions of the heating source (spray gun 400, power supply device 401) are adjusted so that the temperature of the flying particles shown in FIG. 22 is 2000 to 2200 ° C.

  Furthermore, as shown in FIG. 15, by setting the thickness of the ceramic sprayed film 333A to 80 μm or more and 200 μm or less, both insulation performance and heat transfer performance can be achieved.

-Second Embodiment-
In the first embodiment described above, the insulating layer 333 has a structure in which the resin layer 333B is laminated on the ceramic sprayed film 333A. In this case, the resin enters the pores 3330 in the vicinity of the surface of the ceramic sprayed film 333A, but overall, the heat transfer performance of the ceramic sprayed film 333A and the heat transfer performance of the resin layer 333B cause the heat transfer of the insulating layer 333. Thermal performance is determined.

  By the way, the pores 3330 in the sprayed film cause a decrease in the heat transfer performance of the ceramic sprayed film 333A. As shown in FIG. 14, about 4% of the pores 3330 in the ceramic sprayed film 333A remain as much as possible, and the influence of the pores 3330 on the heat transfer performance cannot be ignored. Further, since the three-dimensional through-hole is formed in the sprayed film 333A by the pore 3330, there is a problem that the crack sensitivity due to the thermal stress accompanying the temperature rise and fall is high as it is.

  Therefore, in the second embodiment, the resin is impregnated in the pores 3330 of the ceramic sprayed film 333A. FIG. 16 is a diagram showing the insulation performance when the ceramic sprayed film 333A is impregnated with resin. The black triangle indicates data when impregnated, and the white triangle indicates data when not impregnated. The vertical axis represents the normalized breakdown voltage when the breakdown voltage of the ceramic sprayed film 333A having a film thickness of 100 μm and not impregnated is 1.

  Also in this case, as in the case of FIG. 14, a 150 mm square Al plate having a thickness of 2 mm as a substrate was sandblasted using aluminum oxide, and then a mixed powder of aluminum nitride and aluminum oxide particles was used. Plasma spraying was performed at an output of 40 kW. The cross-sectional porosity of the sprayed film at this time was 4%. When the produced ceramic sprayed film 333A was impregnated with an epoxy resin, the cross-sectional porosity decreased to 1.0% or less. As a result, the dielectric breakdown voltage of the ceramic sprayed film 333A was larger than that without impregnation. For example, in the case of a film thickness of 100 μm, when impregnated, the dielectric breakdown voltage increases to about three times.

  Thus, since the cross-sectional porosity is lowered by impregnating the resin, the dielectric breakdown voltage of the ceramic sprayed film 333A is improved. Therefore, when applying to a power module, the thickness of the insulating layer 333 can be made thinner, and as a result, the thermal resistance can be reduced and the heat dissipation of the power module can be improved.

  17 and 18 illustrate a method of impregnating a ceramic sprayed film 333A with a resin. FIG. 17 is a diagram illustrating a first example. FIG. 17A and FIG. 17B show the part indicated by the symbol F in FIG. 9A regarding the procedure for forming the resin layer 333B shown in FIG. 11A and FIG. 11B. It is. FIG. 17C shows the state after resin impregnation.

  The formation region of the ceramic sprayed film 333A is set larger than the formation region of the resin layer 333B, and the ceramic sprayed film 333A is exposed at the edge portion of the insulating layer 333 indicated by the symbol F. Then, the resin 333C is impregnated from the exposed region Y. For the resin 333C used for impregnation, for example, the same resin as the resin component constituting the resin layer 333B is used. In addition, by performing the impregnation operation in a reduced pressure state, it is possible to prevent the residual gas in the pores 3330 from being entrained in the impregnation resin 333C and generating voids or unfilled regions. . Further, the resin 333C may be injected from the exposed region Y using a dispenser or the like.

  FIG. 18 is a diagram illustrating a second example. First, as shown in FIG. 18A, a ceramic sprayed film 333A is formed on the heat radiation part 307A, and a resin sheet 3334 for forming a resin layer 333B is disposed on the ceramic sprayed film 333A. The resin sheet 3334 is obtained by mixing a filler into the resin 333C, and the amount of the resin sheet 3334 is set larger than the amount of the resin layer 333B to be formed.

  Next, as shown in FIG. 18B, the heat radiation portion 307A is pressurized in the direction of the primary sealing body 302, and the resin sheet 3334 is pressure-bonded to the primary sealing body 302 to form the resin layer 333B. During the pressure bonding, the resin sheet 3334 is pressurized to the thickness of the resin layer 333B, so that the resin component (resin 333C) of the resin sheet 3334 is impregnated in the pores 3330 of the ceramic sprayed film 333A and the ceramic sprayed film 333A. Overflowing around.

  In this case, the resin component of the resin sheet 3334 is impregnated into the pores 3330 in the ceramic sprayed film 333A, and the resin component flows out to the periphery as shown in FIG. It becomes larger than the filler mixing rate of the sheet 3334.

  In the first and second embodiments described above, the power module in which the primary sealing body 302 is inserted into the CAN-type module case 304 and sealed with resin has been described. As shown in 20, it can be similarly applied to a single-sided cooling power module. FIG. 19 is a plan view of the single-sided cooling power module 300, and shows the arrangement of the semiconductor chip and the conductor plate sealed in the sealing resin 348 of the power module 300.

  In the arrangement shown in FIG. 19, the conductor plates 318 and 320 have the same potential and can be formed by a single conductor plate (hereinafter referred to as the conductor plate 318). The main surface electrodes of IGBTs 328 and 330 and diodes 156 and 166 are connected by a plurality of metal wires or metal ribbons, and further connected to conductor plates 318 and 319. The material of the wire or ribbon is a single or composite material of Al, Al alloy, Cu, Cu alloy. The back electrodes of IGBT 328 and diode 156 are metal bonded to conductor plate 315 by metal bonding material 160. The conductor plates 315 and 318 and the heat radiating portion 307 are joined via the insulating layer 333. The back electrodes of the IGBT 330 and the diode 166 are metal bonded to the conductor plate 318 by the metal bonding material 160. The conductor plates 315, 318, 319 and the heat radiating portion 307 are joined via the insulating layer 333.

  FIG. 20A is a cross-sectional view of a portion indicated by a broken line in FIG. The heat generated from the semiconductor chip is efficiently radiated to the outside through the conductor plate 315, the insulating layer 333, and the heat radiation portion 307. Here, an example in which the ceramic sprayed film 333A is provided on the heat radiating portion 307 side and the conductor plates 315, 318, 319 are joined by the resin layer 333B is shown, but the sprayed film 333A is provided on the conductor plates 315, 318, 319 side. The resin layer 333B may be provided on the heat dissipation portion 307.

  As shown in FIG. 20B, the resin layer 333B in which the highly thermally conductive filler is dispersed is larger than the bottom area of the conductor plates 315, 318, and 319 in contact with the insulating layer 333, and is larger than the area of the ceramic sprayed film 333A. The area is small, and is temporarily attached to the heat dissipation unit 307. Thereafter, the resin is impregnated using a blank portion of the ceramic sprayed film 333A to which the resin layer 333B is not temporarily attached. The resin is impregnated so that a portion of the resin 333C is formed at the circumferential end of the laminate. After impregnation, as shown by the arrow in FIG.

  FIG. 21 is a diagram showing a power module 300 configured to sandwich the primary sealing body 302 with a pair of heat radiation portions 307D. The insulating layer 333 having the above-described structure can also be applied to the power module having such a configuration. A refrigerant flow path 3070 is formed in the heat radiating portion 307D, and the refrigerant flows therethrough. A ceramic sprayed film 333A impregnated with resin is formed on one surface of the heat radiating portion 307D, and a resin layer 333B is formed so as to be laminated on the ceramic sprayed film 333A. A resin portion 333C is provided at the circumferential end of the laminated body. The ceramic sprayed film 333A may be formed on the primary sealing body 302 side.

  As described above, in the second embodiment, in addition to the function and effect of the first embodiment described above, the pore 3330 of the ceramic sprayed film 333A is impregnated with resin, so that the thermal conductivity of the insulating layer 333 is increased. Further improvement can be achieved.

  Each of the embodiments described above may be used alone or in combination. This is because the effects of the respective embodiments can be achieved independently or synergistically. In addition, the present invention is not limited to the above embodiment as long as the characteristics of the present invention are not impaired.

  156, 166: Diode, 300: Power module, 302: Primary sealing body, 304: Module case, 307A, 307B: Heat radiation part, 315, 318, 319, 320: Conductor plate, 328, 330: IGBT, 333: Insulation Layer, 333A: ceramic sprayed film, 333B: resin layer, 348: sealing resin, 3330: pores, 3331: flat aluminum oxide, 3332: aluminum nitride particles, 400: plasma spray gun, 401: power supply device

Claims (5)

A semiconductor chip;
A conductor plate in which the semiconductor chip is electrically connected to one surface of the front and back surfaces, and a heat dissipation surface is formed on the other surface;
A sealing resin for sealing the conductor plate and the semiconductor chip so that the heat dissipation surface is exposed;
A metal base that is in thermal contact with the heat dissipation surface of the conductor plate via an insulating layer, and
The insulating layer is a mixture of aluminum nitride particles , α-aluminum oxide particles, and ceramic particles having higher thermal conductivity than γ- aluminum oxide on the surface of the metal base facing the heat dissipation surface or the heat dissipation surface. Has a ceramic spray coating formed by thermal spraying
The ceramic sprayed coating is a power semiconductor module in which the total volume ratio of aluminum nitride and α-aluminum oxide is 30% or more and the cross-sectional porosity is 10% or less. The power semiconductor module according to claim 1,
A power semiconductor module, wherein pores of the ceramic sprayed film are impregnated with a resin. The power semiconductor module according to claim 2,
A power semiconductor module, wherein the ceramic sprayed film has a thickness of 80 μm to 200 μm. In the power semiconductor module according to any one of claims 1 to 3 ,
The power semiconductor module, wherein the ceramic particles include at least one of yttrium oxide (Y2O3) particles, zirconia oxide (Zr2O3) particles, silicon carbide (SiC) particles, and silicon nitride (Si3N4) particles. A semiconductor chip; a conductive plate electrically connected to one surface of the front and back surfaces; a conductive plate having a heat radiating surface formed on the other surface; and the conductive plate and the semiconductor chip so that the heat radiating surface is exposed. And a can-shaped housing having a metal base that is in thermal contact with the heat dissipation surface via an insulating layer having a ceramic sprayed film. There,
Adjusting the thermal spraying conditions so that a ceramic sprayed film having a volume fraction of aluminum nitride and a volume fraction of α-aluminum oxide of 30% or more and a cross-sectional porosity of 10% or less is formed, A first step of spraying a mixture of aluminum nitride particles and α-aluminum oxide particles on the surface of the metal base facing the heat dissipation surface or the heat dissipation surface;
A second step of flattening the surface of the ceramic sprayed film by machining;
A third step of impregnating the pores formed in the ceramic sprayed film from the flattened surface with a resin;
A power semiconductor module comprising: a fourth step of arranging a resin between the metal base and the heat radiating surface, and pressing the metal base against the heat radiating surface so as to deform the housing and thermocompression-bonding. Method.

Images