Semiconductor device and power conversion device

Abstract

A semiconductor device according to the present disclosure comprises: a cooler; a semiconductor module provided on the cooler; and a pressing member pressing the semiconductor module toward the cooler. The semiconductor module comprises: a heat dissipation member having a mounting surface and a heat dissipation surface on the reverse side of the mounting surface; a semiconductor chip provided on the mounting surface of the heat dissipation member; and a sealing resin exposing the heat dissipation surface of the heat dissipation member and covering the heat dissipation member and the semiconductor chip. In a state in which the heat dissipation surface of the semiconductor module and the cooler face each other, the pressing member presses a pressing surface of the sealing resin on the reverse side of the heat dissipation surface. The linear expansion coefficient of the sealing resin is greater than the linear expansion coefficient of the heat dissipation member, and the elastic modulus of the pressing member becomes lower as the temperature increases.

Description

Semiconductor device and power conversion device

[0001] The present disclosure relates to a semiconductor device and a power conversion device.

[0002] Japanese Patent Application Laid-Open No. 2003-144999 discloses a method for manufacturing a semiconductor device using a thermally conductive grease that conforms to warpage of the package and substrate and does not increase thermal resistance.

[0003] JP 2012-4468 A

[0004] In a semiconductor device such as that disclosed in Patent Document 1, the semiconductor module warps at high temperatures. Furthermore, the modulus of elasticity of the disc springs and disc spring supports that press the semiconductor module against the heat sink decreases at high temperatures. This can result in unstable contact between the semiconductor module and the heat sink, making it difficult to achieve stable heat dissipation.

[0005] An object of the present disclosure is to provide a semiconductor device and a power conversion device that can ensure stable heat dissipation.

[0006] The semiconductor device according to the present disclosure comprises a cooler, a semiconductor module provided on the cooler, and a pressing member that presses the semiconductor module toward the cooler, wherein the semiconductor module comprises a heat dissipation member having a mounting surface and a heat dissipation surface opposite the mounting surface, a semiconductor chip provided on the mounting surface of the heat dissipation member, and a sealing resin that exposes the heat dissipation surface of the heat dissipation member and covers the heat dissipation member and the semiconductor chip, wherein when the heat dissipation surface of the semiconductor module faces the cooler, the pressing member presses the pressing surface of the sealing resin opposite the heat dissipation surface, the linear expansion coefficient of the sealing resin is greater than the linear expansion coefficient of the heat dissipation member, and the elastic modulus of the pressing member decreases as the temperature increases.

[0007] The semiconductor device according to the present disclosure comprises a cooler, a semiconductor module provided on the cooler, and a pressing member that presses the semiconductor module toward the cooler, wherein the semiconductor module comprises a heat dissipation member having a mounting surface and a heat dissipation surface opposite the mounting surface, a semiconductor chip provided on the mounting surface of the heat dissipation member, and a sealing resin that exposes the heat dissipation surface of the heat dissipation member and covers the heat dissipation member and the semiconductor chip, wherein when the heat dissipation surface of the semiconductor module faces the cooler, the pressing member presses the pressing surface of the sealing resin opposite the heat dissipation surface, and when not pressed against the cooler and at room temperature, the semiconductor module warps so as to be convex toward the heat dissipation surface, and the warping of the semiconductor module is smaller as the temperature is higher, and the modulus of elasticity of the pressing member is lower as the temperature is higher.

[0008] The warpage of the semiconductor module according to the present disclosure decreases as the temperature increases. Furthermore, the elastic modulus of the pressing member decreases as the temperature increases. Therefore, the pressing member can press the semiconductor module with a large force when the warpage is large, and with a small force when the warpage is small. Therefore, stable heat dissipation can be ensured.

[0009] FIG. 1 is a plan view of a semiconductor module according to a first embodiment. FIG. 2 is a cross-sectional view of the semiconductor module according to the first embodiment at room temperature. FIG. 3 is a cross-sectional view of the semiconductor module according to the first embodiment at high temperature. FIG. 4 is a cross-sectional view of the semiconductor device according to the first embodiment. FIG. 5 is a bottom view illustrating an example of a cooler according to the first embodiment. FIG. 6 is a bottom view illustrating an example of a cooler according to the first embodiment. FIG. 7 is a cross-sectional view of the semiconductor module according to the second embodiment at room temperature. FIG. 8 is a cross-sectional view of the semiconductor module according to the second embodiment at high temperature. FIG. 9 is a cross-sectional view of the semiconductor device according to the second embodiment. FIG. 10 is a cross-sectional view of a semiconductor device according to a modified example of the second embodiment. FIG. 11 is a block diagram illustrating a configuration of a power conversion system to which a power conversion device according to a third embodiment is applied.

[0010] A semiconductor device and a power conversion device according to each embodiment will be described with reference to the drawings. The same or corresponding components are designated by the same reference numerals, and repeated description may be omitted.

[0011] First Embodiment. Figure 1 is a plan view of a semiconductor module 50 according to a first embodiment. Figure 2 is a cross-sectional view of the semiconductor module 50 according to the first embodiment at room temperature. Figure 3 is a cross-sectional view of the semiconductor module 50 according to the first embodiment at a high temperature. The semiconductor module 50 includes a heat dissipation member 10, semiconductor chips 20a and 20b, and a sealing resin 40. The heat dissipation member 10 has a mounting surface and a heat dissipation surface opposite the mounting surface. The semiconductor chips 20a and 20b are provided on the mounting surface of the heat dissipation member 10. The sealing resin 40 covers the heat dissipation member 10 and the semiconductor chips 20a and 20b, leaving the heat dissipation surface of the heat dissipation member 10 exposed.

[0012] The heat dissipation member 10 has an insulating substrate 11, conductor patterns 12a and 12b formed on one surface of the insulating substrate 11, and a conductor pattern 13 formed on the other surface of the insulating substrate 11. Semiconductor chips 20a and 20b are mounted on the conductor patterns 12a and 12b, respectively. The back surfaces of the semiconductor chips 20a and 20b are bonded to the conductor patterns 12a and 12b with a bonding material 2. The conductor pattern 13 forms a heat dissipation surface.

[0013] The surface of the semiconductor chip 20a is bonded to one end of the wiring member 31a. The other end of the wiring member 31a is bonded to the conductor pattern 12b on which the semiconductor chip 20b is mounted. The surface of the semiconductor chip 20b is bonded to the wiring member 31b. The semiconductor module 50 includes a plurality of main terminals 32a, 32b, and 32c for extracting main current. The main terminal 32a is electrically connected to the conductor pattern 12a, the main terminal 32b is electrically connected to the wiring member 31b, and the main terminal 32c is electrically connected to the conductor pattern 12b. In the example of FIG. 1, the main terminal 32b and the wiring member 31b are integrated.

[0014] The semiconductor chips 20a and 20b each have a signal output portion, which is electrically connected to a signal terminal 34 via a signal wiring 36.

[0015] The sealing resin 40 encloses some or all of the above components and seals them so that at least a portion of the heat dissipation surface of the heat dissipation member 10 is exposed. In the example of Figures 1 to 3, the sealing resin 40 is shown by dashed lines in order to illustrate the interior of the semiconductor module 50.

[0016] The semiconductor chips 20a and 20b may be formed of, for example, silicon (Si) or a wide bandgap semiconductor, such as silicon carbide (SiC), gallium nitride (GaN)-based material, or diamond. Forming the semiconductor chips 20a and 20b from a wide bandgap semiconductor can improve the withstand voltage, heat resistance, and allowable current density, enabling the semiconductor module 50 to be miniaturized.

[0017] The semiconductor chips 20a and 20b may be Si-IGBTs (Insulated Gate Bipolar Transistors), RC (Reverse-Conducting)-IGBTs in which an IGBT and a diode are integrated, etc. Also, instead of Si-IGBTs, MOS-FETs (Metal Oxide Semiconductor Field Effect Transistors) made of SiC or GaN may be mounted.

[0018] The bonding material 2 is made of, for example, lead-free solder containing Sn as its main component, or a sintered material containing Ag or Cu as its main component. In order to dissipate heat from the semiconductor chips 20a and 20b to the back surface side, the thickness of the bonding material 2 on the back surface of the chips is desirably 0.15 mm or less.

[0019] The insulating substrate 11 of the heat dissipation member 10 is made of insulating resin or ceramic. The insulating resin is primarily composed of, for example, epoxy resin. The ceramic is primarily composed of, for example, Al2O3, Si3N4, or AlN. Since the insulating substrate 11 is also required to have heat dissipation properties, it is generally desirable that it have high thermal conductivity and be thin. However, if the insulating substrate 11 is made too thin, there is a concern that it will not be able to ensure sufficient dielectric strength and that the structure will not be able to withstand stresses applied during manufacturing. For this reason, it is desirable that the thickness of the insulating substrate 11 be 100 μm or more.

[0020] The conductor patterns 12a, 12b, and 13 are made of metal, such as aluminum, aluminum alloy, copper, or copper alloy. The conductor patterns 12a and 12b on the side where the semiconductor chips 20a and 20b are mounted also function to dissipate heat from the semiconductor chips 20a and 20b. Therefore, it is desirable that the conductor patterns 12a and 12b have sufficient thickness to ensure sufficient heat dissipation in the planar direction. Although this depends on the planar layout, the thickness of the conductor patterns 12a and 12b is desirably 0.4 mm or greater. The conductor pattern 13 has a smaller impact on heat dissipation than the conductor patterns 12a and 12b. Therefore, the conductor pattern 13 may be thinner than the conductor patterns 12a and 12b. The heat dissipation member 10 of this embodiment is configured with copper layers as conductor patterns on both sides of the insulating substrate 11, which is a Si3N4 substrate. The heat dissipation member 10 may also be a single metal member formed of, for example, Al, Cu, or the like.

[0021] The wiring members 31a, 31b are made of a metal with good conductivity, such as aluminum, aluminum alloy, copper, or copper alloy. Since the wiring members 31a, 31b form the main current path of the semiconductor module 50, it is desirable that they have a large current cross-sectional area. If the wiring members 31a, 31b are metal frames as shown in FIGS. 1-3, connecting materials are required between the wiring members 31a, 31b and the semiconductor chips 20a, 20b. In this case, although it depends on the planar layout, it is desirable that the wiring members 31a, 31b have a thickness of 0.1 mm or more. Furthermore, the wiring members 31a, 31b are not limited to metal frames, and may be wires. In this embodiment, the wiring members 31a, 31b are frame materials made of, for example, copper.

[0022] The main terminals 32a, 32b, and 32c are made of a highly conductive metal, such as aluminum, an aluminum alloy, copper, or a copper alloy. Since the main terminals 32a, 32b, and 32c form the main current path of the semiconductor module 50, it is desirable that they have a large current cross-sectional area. Although it depends on the planar layout, it is desirable that the main terminals 32a, 32b, and 32c have a thickness of 0.1 mm or more.

[0023] The signal wiring 36 is made of wires formed of highly conductive materials such as Al, Cu, Ag, etc., to extract signals from the semiconductor chips 20a and 20b. To ensure strength, the wire diameter is preferably Φ100 μm or more. The signal terminals 34 are made of highly conductive metals such as aluminum, aluminum alloy, copper, and copper alloy. Taking into consideration compatibility with the components contained within, the sealing resin 40 is preferably made of mold resin or the like with a linear expansion coefficient of approximately 5-12 ppm / K.

[0024] Next, a method for manufacturing the semiconductor module 50 will be described. First, the semiconductor chips 20a, 20b are bonded to the heat dissipation member 10 via the bonding material 2. Next, the wiring members 31a, 31b and the main terminals 32a, 32b, 32c are connected to their respective predetermined positions. After that, the signal output portions of the semiconductor chips 20a, 20b are connected to the signal terminals 34 via signal wiring 36. Next, the semiconductor chips 20a, 20b and other components are sealed with sealing resin 40. This completes the manufacturing of the semiconductor module 50.

[0025] During sealing, the temperature of the mold is raised to improve the fluidity of the sealing resin 40, causing the sealing resin 40 to flow at a high temperature. After the flow is complete, the temperature is lowered, and the semiconductor module 50 is removed from the mold when the temperature returns to room temperature. The sealing resin 40 is stress-free at a high temperature before it hardens, and then shrinks when the temperature is lowered.

[0026] In this embodiment, the coefficient of linear expansion of the sealing resin 40 is greater than the coefficient of linear expansion of the heat dissipation member 10. Therefore, due to a mismatch in linear expansion when the temperature drops, the semiconductor module 50 begins to warp convexly toward the heat dissipation surface. That is, as shown in FIG. 2, the semiconductor module 50 of this embodiment warps convexly toward the heat dissipation surface when it is not pressed against a cooler 60 (described later) and at room temperature. On the other hand, as shown in FIG. 3, when the temperature of the semiconductor module 50 is increased, it approaches a stress-free state, and the warping is reduced. In other words, it can be said that the higher the temperature, the smaller the warping of the semiconductor module 50.

[0027] FIG. 4 is a cross-sectional view of a semiconductor device 100 according to the first embodiment. The semiconductor device 100 includes a cooler 60, a semiconductor module 50 provided on the cooler 60, and a presser member 80. The semiconductor module 50 is mounted on one side of the cooler 60 via a thermal interface material 70. The presser member 80 presses the semiconductor module 50 toward the cooler 60 to improve the heat dissipation of the semiconductor module 50. The presser member 80 presses the pressing surface of the sealing resin 40 opposite the heat dissipation surface of the semiconductor module 50, with the heat dissipation surface of the semiconductor module 50 facing the cooler 60. The presser member 80 has an elastic region 81 and is fixed to the cooler 60 by, for example, fastening with bolts 82. This applies a load to the semiconductor module 50, causing the semiconductor module 50 to be pressed against the thermal interface material 70 and the cooler 60.

[0028] The thermal interface material 70 is made of, for example, grease, gap filler, PC-TIM (Phase Change Thermal Interface Material), graphite sheet, etc. To ensure heat dissipation, the thickness of the thermal interface material 70 is preferably 100 μm or less.

[0029] The cooler 60 is made of a metal with good conductivity, such as aluminum, aluminum alloy, copper, or copper alloy. To ensure both heat dissipation and rigidity, the cooler 60 preferably has a thickness of approximately 2 to 4 mm. Furthermore, the surface of the cooler 60 opposite the semiconductor module 50 may be provided with an uneven surface to improve cooling performance. FIGS. 5 and 6 are bottom views illustrating examples of coolers 60a and 60b according to the first embodiment. In the example of FIG. 5, the cooler 60a is provided with cylindrical pin fins 61a. In the example of FIG. 6, the cooler 60b is provided with rectangular pin fins 61b. The cross-sectional shape of the pin fins 61b may be any polygonal shape. The pin fins 61a and 61b improve the cooling performance of the coolers 60a and 60b.

[0030] The elastic modulus of the presser member 80 decreases as the temperature increases. In other words, the presser member 80 is made of a material whose elastic modulus has a negative temperature coefficient. The presser member 80 is made of, for example, a metal, specifically SUS (Steel Use Stainless), particularly spring steel. The presser member 80 has an elastic region 81 that contacts the semiconductor module 50. It is sufficient that at least the elastic region 81 of the presser member 80 is made of a material whose elastic modulus decreases as the temperature increases. Alternatively, the entire presser member 80 may be made of a material whose elastic modulus decreases as the temperature increases.

[0031] The elastic region 81 of the pressing member 80 is flat. However, this is not limiting, and a spring or the like may be provided in the portion of the pressing member 80 that comes into contact with the semiconductor module 50. In this case, the spring that comes into contact with the semiconductor module 50 should be made of a material whose elastic modulus decreases as the temperature increases.

[0032] Next, a method for manufacturing the semiconductor device 100 will be described. First, a thermal interface material 70 is applied to at least one surface of the cooler 60 and the semiconductor module 50. Next, the semiconductor module 50 is mounted on the cooler 60. After that, a pressing member 80 is placed so as to press down on the pressing surface of the semiconductor module 50, and is fixed to the cooler 60 or the like with bolts 82 or the like. The pressing load from the pressing member 80 corrects any warping of the semiconductor module 50 at room temperature. This ensures stable heat dissipation. The pressing load depends on the shape of the semiconductor module 50, but is often set in the range of approximately 100-500 N.

[0033] When the semiconductor device 100 is operated, the temperature of the semiconductor module 50 rises due to heat generation from the semiconductor chips 20a and 20b. At this time, the presser member 80 also receives heat from the contact surface with the semiconductor module 50, causing the temperature to rise. The elastic modulus of the presser member 80 has a negative temperature coefficient. Therefore, as the temperature rises, the rigidity decreases, and the force that suppresses warpage of the semiconductor module 50 decreases. On the other hand, at high temperatures, the sealing resin 40 approaches a stress-free state, so warpage of the semiconductor module 50 is reduced. As a result, it is possible for the presser member 80 to correct warpage of the semiconductor module 50 even at high temperatures. In other words, it is possible to prevent the presser member 80 from exerting insufficient pressure at high temperatures, resulting in insufficient warpage correction.

[0034] In this embodiment, the pressing member 80 can press the semiconductor module 50 with a large force when the warp is large, and can press the semiconductor module 50 with a small force when the warp is small. This stabilizes the contact between the semiconductor module 50 and the cooler 60, ensuring stable heat dissipation. This improves the reliability of the semiconductor device 100.

[0035] Furthermore, by using the insulating substrate 11 with a high elastic modulus as the heat dissipation member 10, the rigidity of the heat dissipation member 10 can be improved. This can suppress warping of the semiconductor module 50 at high temperatures. Therefore, the semiconductor module 50 can be pressed against the cooler 60 stably.

[0036] The structures of the semiconductor module 50 and the semiconductor device 100 described in this embodiment are merely examples and are not limited to these. For example, the semiconductor module 50 may have one or more semiconductor chips. Furthermore, any configuration that can press the semiconductor module 50 against the cooler 60 may be employed as the pressing member 80.

[0037] The above-described modifications can be applied as appropriate to the semiconductor devices and power conversion devices according to the following embodiments. Note that the semiconductor devices and power conversion devices according to the following embodiments have many points in common with the first embodiment, so the following description will focus on the differences from the first embodiment.

[0038] Second Embodiment Fig. 7 is a cross-sectional view of a semiconductor module 250 according to a second embodiment at room temperature. Fig. 8 is a cross-sectional view of a semiconductor module 250 according to the second embodiment at a high temperature. Fig. 9 is a cross-sectional view of a semiconductor device 200 according to the second embodiment. The semiconductor module 250 of this embodiment includes a heat dissipation member 210. The heat dissipation member 210 has an insulating substrate 11, conductor patterns 212a and 212b formed on one surface of the insulating substrate 11, and a conductor pattern 213 formed on the other surface of the insulating substrate 11. The conductor patterns 212a and 212b are thicker than the conductor pattern 13. Although this depends on the planar layout, it is desirable that there be a difference in thickness of 50 µm or more between the conductor patterns 212a and 212b and the conductor pattern 213.

[0039] Furthermore, a recess 242 is formed on the pressing surface of the sealing resin 240. In other words, it can be said that the sealing resin 240 has a thin portion. The glass transition temperature Tg of the sealing resin 240 is equal to or higher than the maximum temperature during operation of the semiconductor module 250. The other configurations are the same as those of the semiconductor module 50. As shown in FIG. 7 , in this embodiment as well, when not pressed against the cooler 60 and at room temperature, the semiconductor module 250 warps so as to be convex toward the heat dissipation surface. Furthermore, as shown in FIGS. 7 and 8 , the warping of the semiconductor module 250 decreases as the temperature increases.

[0040] The pressing member 280 of this embodiment has a spring 284. The spring 284 presses the recess 242 on the pressing surface of the sealing resin 240, for example. The spring 284 may be any member having spring properties, such as a leaf spring or a disc spring. The spring constant of the spring 284 is preferably 100 to 400 N / mm. The pressing member 280 and the spring 284 may be configured as a single member. FIG. 10 is a cross-sectional view of a semiconductor device 300 according to a modification of the second embodiment. In the semiconductor device 300, the pressing member 380 and the spring 384 may be separate members.

[0041] In this embodiment, the thickness of the conductor pattern 213 on the back surface of the heat dissipation member 210 is made thinner than the thickness of the metal of the conductor patterns 212a and 212b on the front surface. This ensures the rigidity of the insulating substrate 11 while reducing warping of the heat dissipation member 210 alone at high temperatures. This allows the semiconductor module 250 to be pressed against the cooler 60 stably.

[0042] Furthermore, by providing the recess 242 on the upper surface of the sealing resin 240 and thinning the sealing resin 240, the bending rigidity of the sealing resin 240 is reduced. This makes it possible to suppress the effect of the sealing resin 240 on warping due to temperature changes. In other words, it is possible to reduce the force that warps the semiconductor module 250 due to a mismatch in linear expansion between the sealing resin 240 and the heat dissipation member 210. Therefore, the semiconductor module 250 can be pressed against the cooler 60 stably.

[0043] Furthermore, the thickness of the outer periphery of the sealing resin 240, from which the main terminals 32a, 32b, 32c and the signal terminals 34 are exposed, is maintained, thereby ensuring the necessary insulation distance between the cooler 60 and the main terminals 32a, 32b, 32c and the signal terminals 34.

[0044] Furthermore, by setting the glass transition temperature Tg of the sealing resin 240 to be equal to or higher than the operating temperature of the semiconductor module 250, the linear expansion of the sealing resin 240 during operation of the semiconductor module 250 is stabilized. Therefore, the warping behavior of the semiconductor module 250 during operation can be stabilized, and the semiconductor module 250 can be pressed against the cooler 60 stably.

[0045] Furthermore, since the pressing member 280 is provided with the spring 284, even if there is variation in the warp of the semiconductor module 250 at room temperature and at high temperature, the variation can be absorbed by the spring 284. Therefore, the warp can be stably corrected and heat dissipation can be ensured.

[0046] Note that only some of the above-described characteristics of the thickness of the conductor patterns 212 a , 212 b , and 213 , the recess 242 of the sealing resin 240 , the glass transition temperature Tg, and the spring 284 may be applied to the semiconductor device 200 .

[0047] Third Embodiment In this embodiment, the semiconductor device according to the first and second embodiments is applied to a power conversion device 400. Although this embodiment is not limited to a specific power conversion device, a three-phase inverter will be described below as the third embodiment.

[0048] FIG. 11 is a block diagram showing the configuration of a power conversion system to which a power conversion device 400 according to the third embodiment is applied. The power conversion system shown in FIG. 11 includes a power supply 600, a power conversion device 400, and a load 500. The power supply 600 is a DC power supply and supplies DC power to the power conversion device 400. The power supply 600 can be configured from a variety of sources. For example, the power supply 600 can be configured from a DC system, a solar cell, or a storage battery, and may also be configured from a rectifier circuit connected to an AC system or an AC / DC converter. Furthermore, the power supply 600 may also be configured from a DC / DC converter that converts DC power output from the DC system into a predetermined power.

[0049] The power conversion device 400 is, for example, a three-phase inverter connected between a power source 600 and a load 500. The power conversion device 400 converts DC power supplied from the power source 600 into AC power and supplies the AC power to the load 500. The power conversion device 400 includes a main conversion circuit 401, a drive circuit 402, and a control circuit 403. The main conversion circuit 401 converts DC power into AC power and outputs it. The drive circuit 402 outputs drive signals that drive each switching element of the main conversion circuit 401. The control circuit 403 outputs control signals to the drive circuit 402 to control the drive circuit 402.

[0050] The load 500 is, for example, a three-phase motor driven by AC power supplied from the power conversion device 400. The load 500 is not limited to a specific application and may be, for example, a motor mounted on various electrical devices. The load 500 is used, for example, as a motor for a hybrid vehicle, an electric vehicle, a railcar, an elevator, or an air conditioning device.

[0051] The power conversion device 400 will be described in detail below. The main conversion circuit 401 includes switching elements and freewheel diodes (not shown). The power conversion device 400 converts DC power supplied from the power source 600 into AC power by switching the switching elements, and supplies the AC power to the load 500. The main conversion circuit 401 may have a variety of specific circuit configurations. The main conversion circuit 401 according to this embodiment is, for example, a two-level three-phase full-bridge circuit. The main conversion circuit 401 can be configured with six switching elements and six freewheel diodes connected in anti-parallel to each switching element.

[0052] The six switching elements are connected in series in pairs to form upper and lower arms. Each upper and lower arm forms a U-phase, V-phase, or W-phase of the full-bridge circuit. The output terminals of each upper and lower arm, i.e., the three output terminals of the main conversion circuit 401, are connected to a load 500. The semiconductor device according to either the first or second embodiment described above can be applied to each switching element or each phase of the main conversion circuit 401, for example.

[0053] The drive circuit 402 generates drive signals for driving the switching elements of the main conversion circuit 401 and supplies them to the control electrodes of the switching elements of the main conversion circuit 401. Specifically, the drive circuit 402 outputs, to the control electrodes of each switching element, a drive signal that turns the switching element on and a drive signal that turns the switching element off, in accordance with a control signal from a control circuit 403 (described later). When maintaining a switching element in the on state, the drive signal is an on signal, which is a voltage signal equal to or higher than the threshold voltage of the switching element. When maintaining a switching element in the off state, the drive signal is an off signal, which is a voltage signal equal to or lower than the threshold voltage of the switching element.

[0054] The control circuit 403 controls the switching elements of the main conversion circuit 401 so that the desired power is supplied to the load 500. Specifically, the control circuit 403 calculates the on-time for which each switching element of the main conversion circuit 401 should be in the on-state based on the power to be supplied to the load 500. For example, the main conversion circuit 401 can be controlled by PWM (Pulse Width Modulation) control, which modulates the on-time of the switching elements according to the voltage to be output. The control circuit 403 outputs control signals to the drive circuit 402 so that an on signal is output to a switching element that should be in the on-state at each point in time, and an off signal is output to a switching element that should be in the off-state at each point in time. In accordance with these control signals, the drive circuit 402 outputs an on signal or an off signal as a drive signal to the control electrode of each switching element.

[0055] In the power conversion device 400 according to this embodiment, the semiconductor device according to embodiments 1 and 2 is applied to the main conversion circuit 401, so that stable heat dissipation can be ensured and reliability can be improved.

[0056] This embodiment is not limited to a two-level three-phase inverter, but can be applied to various power conversion devices. This embodiment may also be applied to a three-level or multi-level power conversion device. When supplying power to a single-phase load, this embodiment may be applied to a single-phase inverter. Furthermore, when supplying power to a DC load or the like, this embodiment may also be applied to a DC / DC converter or an AC / DC converter.

[0057] The load 500 is not limited to an electric motor. The load 500 can also be used as a power supply device for an electric discharge machine, a laser processing machine, an induction heating cooker, or a contactless power supply system. The load 500 can also be used as a power conditioner for a solar power generation system, a power storage system, or the like.

[0058] The technical features described in each embodiment may be used in appropriate combination.

[0059] 2 Bonding material, 10 Heat dissipation member, 11 Insulating substrate, 12a, 12b, 13 Conductive pattern, 20a, 20b Semiconductor chip, 31a, 31b Wiring member, 32a, 32b, 32c Main terminal, 34 Signal terminal, 36 Signal wiring, 40 Sealing resin, 50 Semiconductor module, 60, 60a, 60b Cooler, 61a, 61b Pin fin, 70 Thermal interface material, 80 Pressing member, 81 Elastic region, 82 Bolt, 100, 200 Semiconductor device, 210 Heat dissipation member, 212a, 212b, 213 Conductive pattern, 240 Sealing resin, 242 Recess, 250 Semiconductor module, 280 Pressing member, 284 Spring, 300 Semiconductor device, 380 Pressing member, 384 Spring, 400 Power conversion device, 401 Main conversion circuit, 402 drive circuit, 403 control circuit, 500 load, 600 power supply

Claims

1. A semiconductor device comprising: a cooler; a semiconductor module provided on the cooler; and a pressing member that presses the semiconductor module toward the cooler, wherein the semiconductor module comprises: a heat dissipation member having a mounting surface and a heat dissipation surface opposite the mounting surface; a semiconductor chip provided on the mounting surface of the heat dissipation member; and a sealing resin that exposes the heat dissipation surface of the heat dissipation member and covers the heat dissipation member and the semiconductor chip, wherein when the heat dissipation surface of the semiconductor module faces the cooler, the pressing member presses the pressing surface of the sealing resin opposite the heat dissipation surface, the linear expansion coefficient of the sealing resin is greater than the linear expansion coefficient of the heat dissipation member, and the elastic modulus of the pressing member decreases as the temperature increases.

2. The semiconductor device according to claim 1, characterized in that, when not pressed against the cooler and at room temperature, the semiconductor module warps convexly toward the heat dissipation surface, and the warping of the semiconductor module becomes smaller as the temperature increases.

3. A semiconductor device comprising: a cooler; a semiconductor module provided on the cooler; and a presser member that presses the semiconductor module toward the cooler, wherein the semiconductor module comprises: a heat dissipation member having a mounting surface and a heat dissipation surface opposite the mounting surface; a semiconductor chip provided on the mounting surface of the heat dissipation member; and a sealing resin that exposes the heat dissipation surface of the heat dissipation member and covers the heat dissipation member and the semiconductor chip, wherein when the heat dissipation surface of the semiconductor module is facing the cooler, the presser member presses the pressing surface of the sealing resin opposite the heat dissipation surface, and when not pressed against the cooler and at room temperature, the semiconductor module warps so as to be convex toward the heat dissipation surface, and the warp of the semiconductor module becomes smaller as the temperature increases, and the modulus of elasticity of the presser member becomes lower as the temperature increases.

4. The semiconductor device according to any one of claims 1 to 3, wherein a recess is formed in the pressing surface of the sealing resin.

5. The semiconductor device according to claim 4, wherein the pressing member has a spring, and the spring presses the recessed portion of the pressing surface.

6. A semiconductor device according to any one of claims 1 to 5, characterized in that the heat dissipation member has an insulating substrate, a first conductor pattern formed on one surface of the insulating substrate, and a second conductor pattern formed on the other surface of the insulating substrate, the semiconductor chip being mounted on the first conductor pattern, and the heat dissipation surface being formed on the second conductor pattern.

7. The semiconductor device according to claim 6, wherein the first conductor pattern is thicker than the second conductor pattern.

8. The semiconductor device according to any one of claims 1 to 7, wherein the glass transition temperature of the sealing resin is equal to or higher than the maximum temperature during operation of the semiconductor module.

9. The semiconductor device according to any one of claims 1 to 8, wherein the semiconductor chip is formed of a wide band gap semiconductor.

10. The semiconductor device according to claim 9, wherein the wide band gap semiconductor is silicon carbide, a gallium nitride-based material, or diamond.

11. A power conversion device comprising: a main conversion circuit having a semiconductor device according to any one of claims 1 to 10 and configured to convert and output input power; a drive circuit configured to output a drive signal to the semiconductor device for driving the semiconductor device; and a control circuit configured to output a control signal to the drive circuit for controlling the drive circuit.

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