Power conversion device and method for manufacturing power conversion device

Abstract

Provided is a power conversion device that can achieve both increased output and an improved heat dissipation property. This power conversion device comprises a thermal conduction member having an insulating first resin layer in which an insulating filler is included in a curable base resin, and a thermally conductive second resin layer in which two types of thermal conduction fillers with different particle sizes are included in a curable silicone resin. The power conversion device is characterized in that the thermal conduction fillers that are included in the second resin layer include a first filler that comprises a semiconductor including silicon (Si) as a primary component, and a second filler that has a smaller average particle size than the first filler, and the maximum particle size of the first filler is 80% of the thickness of the second resin layer or greater.

Description

Power Conversion Device and Method for Manufacturing the Same

[0001] The present invention relates to a configuration of a power conversion device and a method for manufacturing the same, and more particularly to a technique effective for application to an in-vehicle power conversion device that requires high output and high reliability.

[0002] Power conversion devices using switching of power semiconductor devices are widely used in consumer applications, in-vehicle applications, railway applications, substation equipment applications, etc. because of their high conversion efficiency. Since this power semiconductor device generates heat when energized, high heat dissipation is required. Particularly in in-vehicle applications, for the purpose of miniaturization and weight reduction, a highly efficient cooling system using water cooling is adopted.

[0003] As a background art in this technical field, for example, there is a technique as disclosed in Patent Document 1. Patent Document 1 discloses "a thermally conductive resin composition for dissipating heat from a heating element such as an LED".

[0004] International Publication No. 2013 / 100174

[0005] By the way, in recent years, power conversion devices are required to have a highly productive and high-output structure. To increase the output, it is effective to improve Tjmax (the maximum rating of the junction temperature of a semiconductor chip) of a power semiconductor device, but since the thermal stress increases, a problem arises in that the reliability of the power conversion device including the power semiconductor device decreases. Therefore, it has become an important issue to achieve both an increase in the output of the power conversion device and an improvement in heat dissipation.

[0006] The above Patent Document 1 relates to a thermally conductive resin composition that is filled in a mold and cured, and does not relate to a thermal interface material that thermally connects a heat radiator such as a power semiconductor device and a cooling body. Therefore, there is room for improvement in order to adopt it as the cooling system of the power conversion device as described above.

[0007] Therefore, an object of the present invention is to provide a power conversion device capable of achieving both an increase in output and an improvement in heat dissipation, and a method for manufacturing the same.

[0008] To solve the above problems, the present invention provides a power conversion device comprising a heat-conducting member having an insulating first resin layer containing an insulating filler in a curable base resin, and a heat-conducting second resin layer containing two types of heat-conducting fillers with different particle sizes in a curable silicone resin, wherein the heat-conducting filler contained in the second resin layer includes a first filler made of a semiconductor containing silicon (Si) as its main component, and a second filler having a smaller average particle size than the first filler, and the maximum particle size of the first filler is 80% or more of the thickness of the second resin layer.

[0009] Furthermore, the present invention relates to a method for manufacturing a power converter, comprising the steps of (a) forming an insulating first resin layer on the front and back surfaces of a semiconductor device, wherein the first resin layer is made of a curable base resin containing an insulating filler; (b) forming a thermally conductive second resin layer on the first resin layer, wherein the second resin layer is made of a curable silicone resin containing two types of thermally conductive fillers with different particle sizes; and (c) applying pressure to the second resin layer from the side opposite to the semiconductor device, wherein the thermally conductive filler contained in the second resin layer comprises a first filler made of a semiconductor containing silicon (Si) as its main component, and a second filler having a smaller average particle size than the first filler, and the maximum particle size of the first filler is 80% or more of the thickness of the second resin layer.

[0010] According to the present invention, it is possible to realize a power conversion device and a method for manufacturing the same that can achieve both high output and improved heat dissipation.

[0011] This can contribute to improving the performance and reliability of power conversion devices.

[0012] Other issues, configurations, and effects not mentioned above will be clarified by the following description of the embodiments.

[0013] This is a plan view (top view) of an electrical circuit body 400 according to Embodiment 1 of the present invention. This is a cross-sectional view of the electrical circuit body 400 in Figure 1 along the line X-X'. This is a cross-sectional perspective view of the electrical circuit body 400 in Figure 1 along the line Y-Y'. This is a cross-sectional perspective view of the semiconductor device 300 in Figure 2. This is a semi-transparent plan view of the semiconductor device 300 in Figure 1. This is an equivalent circuit diagram of the semiconductor device 300 in Figure 5. This is a cross-sectional view showing the manufacturing method of the semiconductor device 300 in Figure 1. This is a cross-sectional view showing the manufacturing method of the electrical circuit body 400 in Figure 1. This is a diagram showing the relationship between the thermal conductivity of the second resin layer 456 and D / L. This is a diagram showing the relationship between the shear stress at the interface of the first filler 460 and D / L. This is a diagram showing the adhesive strength according to the present invention and a comparative example. This is a circuit diagram of a power converter 200 according to Embodiment 2 of the present invention. This is an external perspective view of the power converter 200 in Figure 12. This is a cross-sectional perspective view of the power converter 200 in Figure 13 along the line XV-X'V'.

[0014] Embodiments of the present invention will be described below with reference to the drawings. In each drawing, identical components are denoted by the same reference numerals, and detailed descriptions of overlapping parts are omitted.

[0015] An electrical circuit body according to Embodiment 1 of the present invention will be described with reference to Figures 1 to 11.

[0016] Figure 1 is a plan view (top view) of the electrical circuit body 400 of this embodiment. The electrical circuit body 400 comprises a plurality of semiconductor devices (power semiconductor modules) 300 and a cooling member 340. The semiconductor devices 300 have the function of converting DC current and AC current using semiconductor elements, and generate heat when energized, so they have a structure to be cooled with a refrigerant. Water or an antifreeze solution made by mixing ethylene glycol with water can be used as the refrigerant.

[0017] The semiconductor device 300 is equipped with power terminals that carry large currents, such as the positive terminal 315B and negative terminal 319B connected to the capacitor module 500 of the DC circuit (see Figure 12), and the AC terminal 320B connected to the motor generators 192 and 194 of the AC circuit (see Figure 12). It is also equipped with signal terminals used for controlling the semiconductor device 300, such as the lower arm gate signal terminal 325L, the Miller emitter signal terminal 325M, the Kelvin emitter signal terminal 325K, and the upper arm gate signal terminal 325U.

[0018] Figure 2 shows a cross-sectional view of the electrical circuit 400 in Figure 1 along the line X-X', Figure 3 shows a cross-sectional perspective view of the electrical circuit 400 in Figure 1 along the line Y-Y', and Figure 4 shows a cross-sectional perspective view of the semiconductor device 300 in Figure 2. Figure 5 shows a semi-transparent plan view showing the internal structure of the semiconductor device 300 in Figure 1, and Figure 6 shows an equivalent circuit diagram of the semiconductor device 300 in Figure 5.

[0019] The semiconductor device 300 includes an active element 155 and a diode 156 as first power semiconductor elements forming an upper arm circuit. The semiconductor chip material for the active element 155 can be Si, SiC, GaN, GaO, C, etc. If a body diode is used for the active element 155, the separately attached diode 156 may be omitted. The collector sides of the active element 155 and diode 156 constituting the first power semiconductor element are joined to the second conductor plate 431. Solder or sintered metal may be used for this joining.

[0020] The second conductor plate 431 is not particularly limited as long as it is made of a material with high electrical and thermal conductivity, but copper-based or aluminum-based materials are preferred. The same applies to the first conductor plate 430, third conductor plate 432, and fourth conductor plate 433, which will be described later. These may be used alone, but they may also be plated with Ni, Ag, or the like to improve bonding with solder or sintered metal. The first conductor plate 430 is bonded to the emitter side of the active element 155 and diode 156 that constitute the first power semiconductor element.

[0021] Furthermore, the semiconductor device 300 includes an active element 157 and a diode 158 as second power semiconductor elements that form a lower arm circuit. The collector sides of the active element 157 and diode 158 constituting the second power semiconductor element are bonded to the fourth conductor plate 433. The emitter sides of the active element 157 and diode 158 constituting the second power semiconductor element are bonded to the third conductor plate 432.

[0022] To add functions such as current sensors and lifespan diagnostics, circuit boards with the necessary circuit components mounted on them may be attached to the conductor plates 430, 431, 432, and 433. In addition to conducting current, the conductor plates 430, 431, 432, and 433 also serve as heat transfer members that transfer the heat generated by the active element 155, diode 156, active element 157, and diode 158 to the cooling member 340.

[0023] A highly thermally conductive heat conduction member 453 is placed between the conductive plates 430, 431, 432, 433 and the cooling member 340. The heat transferred to the conductive plates 430, 431, 432, 433 is transferred to the cooling member 340 via the heat conduction member 453. Since the conductive plates 430, 431, 432, 433 and the cooling member 340 have different potentials, the heat conduction member 453 needs to be insulating. Generally, semiconductors and conductors tend to have better thermal conductivity than insulators. In automotive applications, long-term reliability is required, and conductors must be handled with care.

[0024] In this invention, the thermal conductivity of the thermal conductive member 453 is increased by using a semiconductor filler. However, semiconductors have lower insulating properties compared to insulators. Therefore, the thermal conductive member 453 is made into a two-layer structure consisting of a first resin layer 455 using an insulating filler and a second resin layer 456 using a semiconductor filler. By using a two-layer structure, both insulating properties and heat dissipation properties can be achieved. Furthermore, by using a two-layer structure, the semiconductor device 300 equipped with the first resin layer 455 can be manufactured in advance and then brought into close contact with the cooling member 340 using the second resin layer 456, thereby improving productivity.

[0025] As the first resin layer 455, thermal conductive sheets 440 and 441 having resin insulating layers 442 and 443 are used. The thermal conductive sheets 440 and 441 have a two-layer structure with a metal foil 444. The thermal conductive sheets 440 and 441 can be used without the metal foil 444, but when the metal foil 444 is present, as will be described later, the insulating sheet can be bonded to the semiconductor device (power semiconductor module) 300 in the transfer molding process, resulting in superior productivity. In addition, when repeated thermal stress is applied in the operating environment, it has the effect of protecting the first resin layer 455 and improving reliability.

[0026] The active element 155 and diode 156 constituting the first power semiconductor element, the active element 157 and diode 158 constituting the second power semiconductor element, the conductor plates 430, 431, 432, 433, and the thermal conductive sheets 440, 441 are sealed with a sealant 360 by transfer molding. By performing transfer molding including the thermal conductive sheets 440, 441, the edges of the thermal conductive sheets 440, 441 are covered with the sealant 360, which has the effect of improving reliability.

[0027] Conductor plates 430, 431, 432, and 433 are bonded to the active element 155 and diode 156, and the active element 157 and diode 158. The thermal conductive sheets 440 and 441 and the encapsulant 360 are cured simultaneously in the transfer molding process.

[0028] The resin insulating layers 442 and 443 of the thermal conductive sheets 440 and 441 are not particularly limited as long as they have adhesion to the heat sink, but an epoxy resin-based insulating layer with a dispersed high thermal conductivity insulating filler is preferable. This is because it offers a good balance between adhesion and heat dissipation. Although insulating fillers have lower thermal conductivity than semiconductor fillers, the first resin layer 455 does not need to absorb steps, so the filler can be densely packed to improve the thermal conductivity compared to the second resin layer 456.

[0029] The conductive plates 430, 431, 432, and 433 are preferably made of materials with high electrical conductivity and high thermal conductivity. Metallic materials such as copper and aluminum, or composite materials such as diamond, carbon, or ceramics with high thermal conductivity can be used.

[0030] The cooling member 340 is preferably made of a lightweight, aluminum-based metal material with high thermal conductivity. The cooling member 340 is manufactured by extrusion molding, forging, brazing, or the like.

[0031] The second resin layer 456 is based on a silicone resin with a low elastic modulus over a wide temperature range in order to absorb the difference in thermal expansion between the cooling member 340 and the semiconductor device 300. Furthermore, in order to achieve high thermal conductivity, it is desirable to have fillers of at least two different particle sizes, such as a first filler 460 with a relatively large particle size and a second filler 461 with a relatively small particle size. In addition, the first filler 460 and the second filler 461 can be made of semiconductors with high thermal conductivity to achieve high thermal conductivity.

[0032] Since the first filler 460, which has a larger particle size, conducts heat more easily, using a material with higher thermal conductivity than the second filler 461 for the first filler 460 is advantageous for increasing the thermal conductivity of the second resin layer 456. As will be described later using Figure 9, by setting the maximum particle size of the first filler 460 to 80% or more of the film thickness of the second resin layer 456, the thermal conductivity of the first filler 460 can be effectively utilized to improve the thermal conductivity of the second resin layer 456.

[0033] In this invention, the maximum particle size of the first filler 460 refers to the maximum particle size of the first filler 460 located in the second resin layer 456 applied to the heat dissipation surface 347 (see Figure 4) of the semiconductor device 300.

[0034] Specifically, a sample of the second resin layer 456 applied to the heat dissipation surface 347 of the semiconductor device 300 is taken, and the resin components are removed by heating at 550°C for 24 hours. The remaining components, which contain at least the first filler 460, are mixed with water, dispersed by ultrasound, and then measured using a particle size analyzer. The particle size at which the cumulative distribution, calculated from the smallest particle size of 0.2 μm or larger, reaches 98% or more is defined as the maximum particle size of the first filler 460. Alternatively, the maximum particle size may be simply evaluated by the maximum diameter in the longitudinal direction of the first filler 460 observed in an arbitrary cross-section of the second resin layer 456 applied to the heat dissipation surface 347 of the semiconductor device 300. If the maximum particle size obtained by the former method differs from the maximum particle size obtained by the latter method, the maximum particle size obtained by the former method takes precedence.

[0035] The average particle size of the second filler 461 is determined from one image obtained by SEM observation of the second resin layer 456 applied to the heat dissipation surface 347 of the semiconductor device 300 at a magnification that allows the second filler 461 to be clearly identified in any cross-section, and by image processing using the contrast that shows the second filler 461. Furthermore, "the second filler 461 is flattened" as described below means that the longitudinal direction of the second filler 461 is oriented perpendicular to the direction of pressure applied by the pressure mechanism 341. In this invention, "perpendicular" means 90°±30°. These can also be determined from the cross-sectional image.

[0036] In this invention, the manufacturing method is described later using Figure 8, and the second resin layer 456 is applied and cured under pressure. By curing under pressure, the largest particles of the first filler 460 act as pillars, determining the thickness of the second resin layer 456.

[0037] As the thickness of the second resin layer 456 approaches the maximum particle size of the first filler 460, the thermal conductivity of the second resin layer 456 can be improved, as shown in Figure 9. Furthermore, by using a filler with a lower Mohs hardness than the first filler 460 as the second filler 461, the second filler 461 flattens under pressure and adheres closely to the first filler 460, improving heat dissipation.

[0038] Since the second resin layer 456 is applied and then pressurized, the flattened second filler 461 may be sandwiched between the largest particles of the first filler 460, acting as a support that determines the thickness of the second resin layer 456. As shown in Figure 3, when multiple semiconductor devices 300 are sandwiched between a pair of cooling members 340, due to variations in the thickness of the semiconductor devices 300, the largest particles of the first filler 460 act as a support at the heat dissipation surface 347 of the thickest semiconductor device 300, thereby determining the thickness of the second resin layer 456.

[0039] The second resin layer 456 is preferably a curable thermal conductive material that is fluid when uncured and loses its fluidity after curing, in order to ensure workability and long-term reliability. Curable thermal conductive materials have the advantage of low viscosity and excellent workability when applied, and can improve mechanical properties after curing. Thermal curing, moisture curing, ultraviolet curing, etc. can be used to cure the thermal conductive material, but thermal curing is preferable for curing to a deep level. The second resin layer 456, which is the thermal conductive member, is in close contact between the semiconductor device 300 and the cooling member 340, which have different coefficients of thermal expansion, and a Young's modulus of 50 MPa or less is desirable to reduce stress.

[0040] The Young's modulus in this invention is the value measured in a dynamic viscoelasticity test in the tensile or compressive direction at a frequency of 10 Hz, a strain of 0.1%, and a temperature of 25°C. The resin used is a silicone resin that exhibits little change in elastic modulus from around -40°C to around 200°C. The second resin layer 456 uses a silicone resin as the base resin, and the first filler 460 uses a semiconductor containing silicon (Si) as its main component. As the silicon (Si)-containing semiconductor, Si or SiC can be used. SiC, in particular, is desirable due to its high thermal conductivity.

[0041] Silicone resin and silicon (Si)-containing semiconductors exhibit good adhesion, and especially when the silicone resin contains an adhesion promoter such as a coupling agent, a strong covalent bond of -Si-O-Si- is formed. The strong adhesion between the base resin and the filler provides excellent reliability (as will be described later using Figure 11). This effect is particularly important in regions where the maximum particle size of the first filler 460 is 80% or more of the thickness of the second resin layer 456, as in the present invention.

[0042] As shown in FIG. 11 described later, when displacement occurs in the compression direction due to heat generation of the semiconductor element or the like in the resin layer containing the filler with a large particle size, a large shear stress is generated around the filler. In particular, in the region where the particle size of the filler is 80% or more of the thickness of the resin layer, the stress rapidly increases. However, as in the present invention, by using a semiconductor containing silicon (Si) as the main component in the first filler 460 with a silicone resin as the base resin and improving the adhesive force between the base resin and the filler, it is possible to provide excellent reliability even under high stress.

[0043] FIG. 7 is a cross-sectional view showing a method for manufacturing the semiconductor device 300 of FIG. 1. (a) In the temporary attachment process of the structure of the circuit body 310 and the heat conduction sheets 440 and 441, the collector sides of power semiconductor elements such as the active elements 155 and 157 and the diodes 156 and 158 are connected to the conductor plates 431 and 433, the gate electrodes of the active elements 155 and 157 are connected by wire bonding, and the emitter sides of power semiconductor elements such as the active elements 155 and 157 and the diodes 156 and 158 are connected to the conductor plates 430 and 432 to fabricate the circuit body 310.

[0044] Thereafter, the heat conduction sheets 440 and 441 are temporarily attached to the conductor plates 430 and 432 and the conductor plates 431 and 433, respectively. Temporary attachment means that, afterwards, in the transfer molding process, the heat conduction sheets 440 and 441 are attached using the adhesion force of the heat conduction sheets 440 and 441 under the condition that there is room for the heat conduction sheets 440 and 441 to harden and adhere.

[0045] Steps (b) to (d) are the transfer molding process. The transfer molding device 601 has a spring 602 in the mold. By this spring 602, even if the height of the circuit body 310 varies, a predetermined load can be applied by the spring force without applying excessive compression to the power semiconductor element.

[0046] In addition, the transfer molding apparatus 601 includes a vacuum degassing mechanism (not shown). By performing vacuum degassing, even if voids are entrapped, they can be compressed to a small size, improving the insulation performance. Also, a release film (not shown) can be used. By using the release film, it is possible to protect the spring drive unit from resin burrs entering.

[0047] In step (b), the circuit body 310 with the heat conduction sheets 440 and 441 temporarily attached is set in the molds 603 and 604 that have been preheated to a constant temperature of 175°C. Next, in step (c), the upper and lower molds 603 and 604 are clamped. At this time, the heat conduction sheets 440 and 441 and the conductor plates 430, 431, 432, and 433 are pressed and adhered by the spring 602. After that, in step (d), the sealing material 360 is injected into the molds 603 and 604 and pressurized at the molding pressure. The resin-sealed semiconductor device 300 is taken out from the transfer molding apparatus 601 and post-cured at 175°C for 2 hours or more.

[0048] FIG. 8 is a cross-sectional view showing the manufacturing method of the electric circuit body 400 of FIG. 1. In step (a), the second resin layer 456 is applied to the cooling member 340 or the semiconductor device 300, and in step (b), the cooling member 340 and the semiconductor device 300 are brought into close contact by pressurizing with the pressurizing mechanism 341, and the electric circuit body 400 is produced by curing the second resin layer 456.

[0049] By curing the second resin layer 456 in the pressurized state by the pressurizing mechanism 341, the thickness of the second resin layer 456 approaches the maximum particle size of the first filler 460. The second filler 461 sandwiched between the first filler 460 and the cooling member 340 may be deformed and flattened by the pressing force because the second filler 461 has a lower Mohs hardness than the first filler 460. Also, the second filler 461 sandwiched between the first filler 460 and the semiconductor device 300 may be deformed and flattened by the pressing force because the second filler 461 has a lower Mohs hardness than the first filler 460.

[0050] The pressurization mechanism 341 can be made identical in the manufacturing process and the operating environment to improve productivity. By pressurizing in the operating environment, the cooling member 340 and the semiconductor device 300 can be brought into close contact via the second resin layer 456, thereby increasing reliability.

[0051] The effects of the present invention will be explained using Figures 9 to 11.

[0052] Figure 9 shows the relationship between the thermal conductivity of the second resin layer 456 and D / L. Here, L is the thickness of the second resin layer 456 and D is the diameter of the first filler 460. Up to approximately 70% of the ratio D / L (the ratio of the diameter D of the first filler 460 to the thickness L of the second resin layer 456), the thermal conductivity increases almost linearly. However, above 70%, the slope increases, and above 80%, the effect of improving thermal conductivity becomes even greater. This is because the contribution of the thermal conductivity of the first filler 460 becomes larger.

[0053] As in the present invention, by curing the second resin layer 456 under pressure and bringing the thickness of the second resin layer 456 closer to the maximum particle size of the first filler 460, in addition to increased heat dissipation due to reduced thermal resistance resulting from the thinning of the second resin layer 456, an effect of increased heat dissipation due to improved thermal conductivity of the second resin layer 456 is achieved.

[0054] Figure 10 shows the relationship between the shear stress at the interface of the first filler 460 and D / L. L is the thickness of the second resin layer 456, and D is the diameter of the first filler 460. When a semiconductor element generates heat, the nearest conductive plate expands due to thermal expansion, causing a compressive displacement in the second resin layer 456 due to this instantaneous thermal expansion. This compressive displacement generates shear stress at the interface of the first filler 460. This shear stress is hardly generated until the ratio D / L (the ratio of the diameter D of the first filler 460 to the thickness L of the second resin layer 456) reaches around 70%, but the slope increases above 70%, and increases sharply above 80%.

[0055] In other words, when the thickness L of the second resin layer 456 is brought closer to the diameter D of the first filler 460, the thermal conductivity is improved as shown in Figure 9, resulting in a high heat dissipation effect. However, as shown in Figure 10, a problem arises in which the stress at the filler interface increases. Therefore, in this invention, reliability is ensured by improving the adhesive strength between the base resin and the filler.

[0056] Figure 11 shows the adhesive strength of the present invention and a comparative example. Figure 11 shows the adhesive strength between the base resin and the filler when a silicone resin is used as the base resin and a silicon (Si)-containing semiconductor is used as the large-particle first filler 460, as in the present invention, and the adhesive strength when a silicone resin is used as the base resin and Al2O3 is used as the large-particle first filler 460 as a comparative example.

[0057] In the present invention, the adhesive strength is higher than that of the comparative example. This is thought to be because silicone resin and semiconductors containing silicon (Si) have good adhesion, and in particular, by adding an adhesion-enhancing agent such as a coupling agent to the silicone resin, a strong covalent bond of -Si-O-Si- is formed.

[0058] A power conversion device according to Embodiment 2 of the present invention will be described with reference to Figures 12 to 14.

[0059] Figure 12 is a circuit diagram of a power converter 200 using a semiconductor device according to the present invention. The power converter 200 mainly comprises inverter circuit sections 140 and 142, an auxiliary inverter circuit section 43, and a capacitor module 500. Each of the inverter circuit sections 140 and 142 is equipped with multiple semiconductor devices 300, and a three-phase bridge circuit is formed by connecting them. When the current capacity is large, the current capacity can be increased by further connecting the semiconductor devices 300 in parallel and performing these parallel connections corresponding to each phase of the three-phase inverter circuit. In addition, the current capacity can be increased by connecting in parallel the active elements 155 and 157 and diodes 156 and 158, which are power semiconductor elements built into the semiconductor device 300.

[0060] The inverter circuit section 140 and the inverter circuit section 142 have the same basic circuit configuration, and their control methods and operations are also basically the same. Since the general outline of the circuit operation of the inverter circuit section 140, etc., is well known, a detailed explanation will be omitted here.

[0061] The upper arm circuit includes an active element 155 and an upper arm diode 156 as power semiconductor elements for switching, while the lower arm circuit includes an active element 157 and a lower arm diode 158 as power semiconductor elements for switching. The active elements 155 and 157 receive a drive signal output from one or the other of the two driver circuits that constitute the driver circuit 174 and perform switching operations to convert the DC power supplied from the battery 136 into three-phase AC power.

[0062] The active element 155 for the upper arm and the active element 157 for the lower arm are each equipped with a collector electrode, an emitter electrode, and a gate electrode. The diode 156 for the upper arm and the diode 158 for the lower arm are each equipped with two electrodes: a cathode electrode and an anode electrode. As shown in Figure 6, the cathode electrodes of diodes 156 and 158 are electrically connected to the collector electrodes of active elements 155 and 157, and the anode electrodes are electrically connected to the emitter electrodes of active elements 155 and 157. As a result, the current flow from the emitter electrode to the collector electrode of the active element 155 for the upper arm and the active element 157 for the lower arm is in the forward direction.

[0063] Although IGBTs (Insulated Gate Bipolar Transistors) are assumed for the active elements 155 and 157, MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) may also be used. In this case, the diode 156 for the upper arm and the diode 158 for the lower arm would not be necessary.

[0064] The positive terminal 315B and negative terminal 319B of each upper and lower arm series circuit are connected to the DC terminals for capacitor connection of the capacitor module 500, respectively. AC power is generated at the connection points of the upper and lower arm circuits, and the connection points of the upper and lower arm circuits of each upper and lower arm series circuit are connected to the AC terminals 320B of each semiconductor device 300. The AC terminals 320B of each semiconductor device 300 for each phase are connected to the AC output terminals of the power converter 200, and the generated AC power is supplied to the stator windings of the motor generator 192 or 194.

[0065] The control circuit 172 generates timing signals to control the switching timing of the active element 155 for the upper arm and the active element 157 for the lower arm based on input information from the vehicle's control device and sensors (e.g., current sensor 180). The driver circuit 174 generates drive signals to switch the active element 155 for the upper arm and the active element 157 for the lower arm based on the timing signals output from the control circuit 172.

[0066] Reference numerals 138, 181, and 188 are connectors.

[0067] The upper and lower arm series circuit includes a temperature sensor (not shown), and temperature information from the upper and lower arm series circuit is input to a microcontroller (not shown). The microcontroller is also input to voltage information from the DC positive terminal side of the upper and lower arm series circuit. Based on this information, the microcontroller performs over-temperature detection and over-voltage detection. If over-temperature or over-voltage is detected, the microcontroller stops the switching operation of all active elements 155 for the upper arm and 157 for the lower arm, protecting the upper and lower arm series circuit from over-temperature or over-voltage.

[0068] Figure 13 is an external perspective view showing an example of the power converter 200 shown in Figure 12, and Figure 14 is a cross-sectional perspective view of the power converter 200 shown in Figure 13 along the line XV-X'V'.

[0069] The power converter 200 is comprised of a lower case 11 and an upper case 10, and has a housing 12 that is formed in a substantially rectangular parallelepiped shape. Inside the housing 12 are an electrical circuit 400, a capacitor module 500, and the like. The electrical circuit 400 has a cooling channel, and a cooling water inlet pipe 13 and a cooling water outlet pipe 14 that communicate with the cooling channel protrude from one side of the housing 12.

[0070] The lower case 11 has an opening at the top, and the upper case 10 is attached to the lower case 11, closing the opening of the lower case 11. The upper case 10 and the lower case 11 are made of an aluminum alloy or the like, and are sealed and fixed to the outside. The upper case 10 and the lower case 11 may also be constructed as a single unit. By making the housing 12 a simple rectangular parallelepiped shape, it is easy to attach it to vehicles and the like, and it is also easy to manufacture.

[0071] A connector 17 is attached to one longitudinal side of the housing 12, and an AC terminal 18 is connected to this connector 17. In addition, a connector 21 is provided on the side from which the cooling water inlet pipe 13 and cooling water outlet pipe 14 are routed.

[0072] As shown in Figure 14, an electrical circuit body 400 is housed inside the housing 12. A control circuit 172 and a driver circuit 174 are located above the electrical circuit body 400, and a capacitor module 500 is housed on the DC terminal side of the electrical circuit body 400. By positioning the capacitor module 500 at the same height as the electrical circuit body 400, the power converter 200 can be made thinner, improving the flexibility of installation in the vehicle. The AC terminal 320B of the electrical circuit body 400 is connected to the busbar by passing through the current sensor 180. In addition, the DC terminals of the semiconductor device 300, the positive terminal 315B and the negative terminal 319B, are connected to the positive and negative terminals 362A and 362B of the capacitor module 500, respectively.

[0073] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are included. For example, the embodiments described above are described in detail to make the present invention easier to understand, and are not necessarily limited to those having all the configurations described. Furthermore, it is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add configurations from other embodiments to the configuration of one embodiment. In addition, it is possible to add, delete, or replace parts of the configuration of each embodiment with other configurations.

[0074] 10... Upper case, 11... Lower case, 12... Housing, 13... Cooling water inlet pipe, 14... Cooling water outlet pipe, 17, 21, 138, 181, 188... Connectors, 18... AC terminal, 43, 140, 142... Inverter circuit section, 136... Battery, 155... Active element (upper arm circuit active element), 156... Diode (upper arm circuit diode), 157... Active element (lower arm circuit active element), 158... Diode (lower arm circuit diode) 172...control circuit, 174...driver circuit, 180...current sensor, 192, 194...motor generator, 200...power converter, 300...semiconductor device (power semiconductor module), 310...circuit body, 315B...positive terminal, 319B...negative terminal, 320B...AC terminal, 325K...Kelvin emitter signal terminal, 325L...lower arm gate signal terminal, 325M...mirror emitter signal terminal, 325U...upper arm 340...Gate signal terminal, 340...Cooling material, 341...Pressurization mechanism, 347...Heat dissipation surface, 360...Sealing material, 362A, 362B...Positive and negative terminals, 400...Electrical circuit body, 430...First conductor plate (upper arm circuit emitter side), 431...Second conductor plate (upper arm circuit collector side), 432...Third conductor plate (lower arm circuit emitter side), 433...Fourth conductor plate (lower arm circuit collector side), 440...Thermal conductive sheet (emitter side), 441...Thermal conductive sheet T (collector side), 442...First resin insulating layer (emitter side), 443...Second resin insulating layer (collector side), 444...Metal foil, 453...Heat conductive material, 455...First resin layer (insulating layer), 456...Second resin layer (heat conductive layer), 460...First filler, 461...Second filler, 465...Flattened second filler, 500...Capacitor module, 601...Transfer molding device, 602...Spring, 603, 604...Mold.

Claims

1. A power conversion device comprising a heat-conducting member having an insulating first resin layer containing an insulating filler in a curable base resin, and a heat-conducting second resin layer containing two types of heat-conducting fillers with different particle sizes in a curable silicone resin, wherein the heat-conducting filler contained in the second resin layer comprises a first filler made of a semiconductor containing silicon (Si) as its main component, and a second filler having a smaller average particle size than the first filler, and the maximum particle size of the first filler is 80% or more of the thickness of the second resin layer.

2. A power conversion device according to claim 1, characterized in that the second filler has a lower Mohs hardness than the first filler.

3. A power conversion device according to claim 1, characterized in that the maximum particle size of the first filler is greater than the value obtained by subtracting the average particle size of the second filler from the thickness of the second resin layer.

4. A power conversion device according to claim 1, wherein the heat conductive member is disposed between the semiconductor device and the cooling member, and the second filler is flattened so as to be crushed in the direction of the film thickness of the second resin layer between the semiconductor device and the first filler, and between the cooling member and the first filler.

5. A power conversion device according to claim 1, characterized in that it has a metal foil between the first resin layer and the second resin layer.

6. A power conversion device according to claim 1, characterized in that the first filler is Si or SiC.

7. A power conversion device according to claim 1, characterized in that the first resin layer is an epoxy resin.

8. A power conversion device according to claim 1, characterized in that the first resin layer is highly filled with a filler that has a lower thermal conductivity than the first filler.

9. A method for manufacturing a power converter, comprising: (a) forming an insulating first resin layer on the front and back surfaces of a semiconductor device, comprising a curable base resin containing an insulating filler; (b) forming a thermally conductive second resin layer on the first resin layer, comprising a curable silicone resin containing two types of thermally conductive fillers with different particle sizes; and (c) applying pressure to the second resin layer from the side opposite to the semiconductor device, wherein the thermally conductive filler contained in the second resin layer comprises a first filler made of a semiconductor containing silicon (Si) as its main component, and a second filler having a smaller average particle size than the first filler, and the maximum particle size of the first filler is 80% or more of the thickness of the second resin layer.

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