Power conversion device

Abstract

A power conversion device 100 comprises: a plurality of semiconductor packages 10 arranged in a row; a metal cooler 50A; an insulating plate 30A disposed between the plurality of semiconductor packages 10 and the cooler 50A; and a heat conductive material 40A in contact with the cooler 50A and the insulating plate 30A. The linear expansion coefficient of the cooler 50A is larger than the linear expansion coefficient of the semiconductor packages 10. The insulating plate 30A and the heat conductive material 40A continuously cover the plurality of semiconductor packages 10 along the arrangement direction of the semiconductor packages 10. The thickness t1 of an outer portion 40A1 connected to an intermediate portion 40A3 of the heat conductive material 40A is larger than the thickness t2 of an inner portion 40A2 of the heat conductive material 40A.

Description

Power conversion device

[0001] The present invention relates to a power conversion device.

[0002] Patent Document 1 (Abstract) describes that "the semiconductor device includes a top plate having a heat dissipation surface formed on one surface, a plurality of fins provided on the heat dissipation surface, a peripheral wall portion surrounding the outer periphery of the plurality of fins, and a bottom plate joined to the tips of the peripheral wall portion and the plurality of fins, and a cooler in which a flow path for cooling water is formed by a space defined by the top plate, the plurality of fins, the peripheral wall portion, and the bottom plate, and a semiconductor element disposed on the other surface of the top plate via an insulating substrate." The center of the upper surface of the bottom plate is warped upward. The lower surface of the bottom plate is machined flat.

[0003] Japanese Patent Application Laid-Open No. 2022-050058

[0004] In the technology described in Patent Document 1, in the arrangement of a plurality of semiconductor elements (semiconductor packages), the shear stress of the heat conductive material facing the outer semiconductor element is not considered to be larger than the shear stress of the heat conductive material facing the inner semiconductor element. Therefore, there is a risk that the reliability of the heat conductive material may decrease due to peeling of the heat conductive material facing the outer semiconductor element.

[0005] An object of the present invention is to provide a power conversion device capable of improving the reliability of a heat conductive material.

[0006] To achieve the above objective, the power conversion device of the present invention comprises a plurality of semiconductor packages arranged in a row, a first cooler made of metal, a first insulating plate disposed between the plurality of semiconductor packages and the first cooler, and a first thermal conductive material in contact with the first cooler and the first insulating plate, wherein the coefficient of linear expansion of the first cooler is greater than the coefficient of linear expansion of the semiconductor packages, and the first insulating plate and the first thermal conductive material continuously cover the plurality of semiconductor packages along the arrangement direction of the semiconductor packages, and the thickness of the outer portion connecting to the intermediate portion of the first thermal conductive material is greater than the thickness of the inner portion of the first thermal conductive material, with respect to an outer portion showing the portion of the first thermal conductive material facing the outer semiconductor package which is the outermost semiconductor package, an inner portion showing the portion of the first thermal conductive material facing the inner semiconductor package which is the semiconductor package which is located inside the outer semiconductor package, and an intermediate portion showing the portion of the first thermal conductive material between the outer portion and the inner portion.

[0007] According to the present invention, the reliability of thermal conductive materials can be improved. Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

[0008] This is an example of a circuit diagram of a power converter according to Embodiments 1 and 2. This is an example of a cross-sectional view of a semiconductor package used in Embodiments 1 and 2. This is a cross-sectional view of the power converter of Embodiment 1. This is a cross-sectional view of the power converter of Embodiment 2.

[0009] The configuration of the power conversion device according to Embodiments 1 and 2 will be described below with reference to the drawings. In each figure, the same reference numerals indicate the same part.

[0010] (Circuit Diagram of Power Converter) Figure 1 is an example of a circuit diagram of a power converter (inverter) according to Embodiments 1 and 2. In the example in Figure 1, a circuit is shown with 3 phases (U phase, V phase, W phase) and 4 parallel elements. The number of parallel elements may be 3 or 5 or more.

[0011] The upper arm semiconductor element 1A and the lower arm semiconductor element 1B are, for example, IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The upper arm semiconductor element 1A and the lower arm semiconductor element 1B are equipped with a main terminal and a signal terminal (a terminal to which the gate potential is applied). The main terminal consists of a high-voltage electrode for the main circuit (a terminal to which the collector potential is applied in the case of an IGBT, or the drain potential in the case of a MOSFET) and a low-voltage electrode for the main circuit (a terminal to which the emitter potential is applied in the case of an IGBT, or the source potential in the case of a MOSFET).

[0012] The output current of the power converter can be increased by connecting multiple upper arm semiconductor elements 1A and lower arm semiconductor elements 1B in parallel. A power converter circuit for one phase consists of a pair of upper arm semiconductor elements 1A and lower arm semiconductor elements 1B connected in series, and a capacitor (ceramic capacitor 2B in the example in Figure 1). The output wiring 5Y for each phase is connected to a load such as a motor.

[0013] By placing capacitors such as a large capacitance film capacitor 2A or a small ceramic capacitor 2B near the upper arm semiconductor element 1A and the lower arm semiconductor element 1B, the wiring inductance of the positive electrode wiring 5P and the negative electrode wiring 5N can be reduced.

[0014] The signal terminals of the upper arm semiconductor element 1A and the lower arm semiconductor element 1B are connected to a control circuit (e.g., a gate drive circuit) not shown, and are switched on or off based on a signal (e.g., a PWM signal) input from a higher-level control device such as a microcontroller, thereby outputting an AC voltage to a load such as a motor.

[0015] (Cross-sectional view of semiconductor package) Figure 2 is an example of a cross-sectional view of a semiconductor package 10 used in embodiments 1 and 2.

[0016] The front-side wiring 5A, back-side wiring 5B, and inner layer wiring 5C are electrically connected to other layers by through-holes (not shown). By providing a large number of through-holes, the cross-sectional area of ​​the current flowing in the cross-sectional direction of the printed circuit board 20 can be increased. This reduces electrical resistance and decreases heat generation in the wiring. Furthermore, the heat transfer performance in the cross-sectional direction of the printed circuit board 20 is improved by the through-holes, thereby improving the heat dissipation performance of the wiring package.

[0017] The front wiring 5A, the back wiring 5B, and the inner layer wiring 5C are connected by wiring (not shown) to wiring at a different potential than the main circuit wiring 5M to which the main terminal 4M is connected. This allows the main circuit wiring 5M to be formed without using separate components such as busbars, thus enabling miniaturization of the power conversion device.

[0018] The semiconductor element 1 is connected to the signal terminal 4S by wire bonding 3 or the like. The terminal connection portion 6 is formed by a bonding material such as solder. The semiconductor element 1 is joined to the lead frame 7 (for example, made of copper) by a bonding material such as solder. The main terminal 4M is connected to the same main circuit wiring 5M. The signal terminals 4S are each connected to different signal wirings 5S. The semiconductor package 10 is connected to the printed circuit board 20 by a bonding material such as solder 8.

[0019] [Embodiment 1] (Cross-sectional view of power converter) Figure 3 is a cross-sectional view of the power converter 100 of Embodiment 1.

[0020] Coolers 50A and 50B are installed above and below the semiconductor package 10, respectively. This enables cooling of the semiconductor package 10 from both sides, improving heat dissipation performance. The upper and lower coolers 50A and 50B are fixed together by bolts or the like (not shown).

[0021] For example, the protrusions 51A and 51B of the coolers 50A and 50B are formed by grinding or otherwise removing material from both ends of the coolers 50A and 50B.

[0022] An insulating plate 30A is provided between the semiconductor package 10 and the cooler 50A. This enables insulation between the semiconductor package 10 and the cooler 50A. The insulating plate 30A is connected to the cooler 50A and the semiconductor package 10 via thermal conductive materials 40A and 60A.

[0023] An insulating plate 30B is provided between the printed circuit board 20 and the cooler 50B. This allows for insulation between the printed circuit board 20 and the cooler 50B. The insulating plate 30B is connected to the cooler 50B and the printed circuit board 20 via thermal conductive materials 40B and 60B.

[0024] Multiple semiconductor packages 10 are mounted in a row on a printed circuit board 20 to form an upper or lower arm of a power converter 100. A three-phase power converter 100 is formed by providing multiple arms on the same printed circuit board 20.

[0025] The coolers 50A and 50B may be cooled with a refrigerant such as water, or with a gas such as air. The coolers 50A and 50B are made of metal such as aluminum. The insulating plates 30A and 30B are made of ceramics such as silicon nitride. The thermal conductive materials 40A and 60A are made of resin and a thermally conductive filler, for example. In this embodiment, a curable thermal conductive material is used.

[0026] The main features of Embodiment 1 are as follows:

[0027] As shown in Figure 3, the power converter 100 comprises a plurality of semiconductor packages 10 arranged in a row, a first metal cooler (cooler 50A), a first insulating plate (insulating plate 30A) positioned between the plurality of semiconductor packages 10 and the first cooler (cooler 50A), and a first thermal conductive material (thermal conductive material 40A) in contact with the first cooler (cooler 50A) and the first insulating plate (insulating plate 30A). The linear expansion coefficient of the first cooler (cooler 50A) is greater than that of the semiconductor packages 10. The first insulating plate (insulating plate 30A) and the first thermal conductive material (thermal conductive material 40A) continuously cover the plurality of semiconductor packages 10 along the arrangement direction of the semiconductor packages 10.

[0028] The outer portion 40A1 represents the portion of the first thermal conductive material (thermal conductive material 40A) that faces the outer semiconductor package 10, which is the outermost semiconductor package. The inner portion 40A2 represents the portion of the first thermal conductive material (thermal conductive material 40A) that faces the inner semiconductor package, which is a semiconductor package 10 that is located inside the outer semiconductor package. The intermediate portion 40A3 represents the portion of the first thermal conductive material (thermal conductive material 40A) between the outer portion 40A1 and the inner portion 40A2. The thickness t1 of the outer portion 40A1 that connects to the intermediate portion 40A3 of the first thermal conductive material (thermal conductive material 40A) is greater than the thickness t2 of the inner portion 40A2 of the first thermal conductive material (thermal conductive material 40A).

[0029] By increasing the thickness of the outer portion 40A1 of the first thermal conductive material (thermal conductive material 40A), the shear stress of the outer portion 40A1 is reduced. This suppresses the delamination of the first thermal conductive material (thermal conductive material 40A) from the outer portion 40A1 to the intermediate portion 40A3. As a result, the reliability of the thermal conductive material can be improved.

[0030] The first insulating plate (insulating plate 30A) and the first thermal conductive material (thermal conductive material 40A) continuously cover multiple semiconductor packages 10 along the arrangement direction of the semiconductor packages 10, thereby preventing an increase in size due to the need to secure insulation distance, and enabling higher density and thinner designs. The coefficient of linear expansion of the first cooler (cooler 50A) is, for example, 23 ppm (Al: aluminum), and the coefficient of linear expansion of the semiconductor package 10 is, for example, 17 ppm (Cu: copper).

[0031] Of the surface of the first cooler (cooler 50A) that is in contact with the first thermal conductive material (thermal conductive material 40A), the region facing the inner semiconductor package has a protrusion 51A that protrudes more than the region facing the outer semiconductor package. As a result, the outer portion 40A1 of the first thermal conductive material (thermal conductive material 40A) is made thicker.

[0032] The power converter 100 includes a first insulating plate (insulating plate 30A) and a second thermal conductive material (thermal conductive material 60A) that is in contact with a plurality of semiconductor packages 10. The thickness t2 of the second thermal conductive material (thermal conductive material 60A) is the same as the thickness t2 of the inner portion 40A2 of the first thermal conductive material (thermal conductive material 40A).

[0033] The difference between the linear expansion coefficient of the first insulating plate (insulating plate 30A) and the linear expansion coefficient of the semiconductor package 10 is smaller than the difference between the linear expansion coefficient of the first cooler (cooler 50A) and the linear expansion coefficient of the first insulating plate (insulating plate 30A), so there is no need to make the second thermal conductor (thermal conductor 60A) thicker. By making the thickness of the second thermal conductor (thermal conductor 60A) the same as the thickness of the inner portion 40A2 of the first thermal conductor (thermal conductor 40A), thermal resistance is suppressed.

[0034] The power converter 100 includes a substrate (printed circuit board 20) on which a plurality of semiconductor packages 10 arranged in a row are mounted, a second cooler (cooler 50B) positioned on the side opposite to the side on which the semiconductor packages 10 are mounted, a second insulating plate (insulating plate 30B) positioned between the substrate (printed circuit board 20) and the second cooler (cooler 50B), and a third thermal conductive material (thermal conductive material 40B) in contact with the second cooler (cooler 50B) and the second insulating plate (insulating plate 30B). The thickness t3 of the portion of the third thermal conductive material (thermal conductive material 40B) facing the outer semiconductor package is the same as the thickness t1 of the outer portion 40A1 of the first thermal conductive material (thermal conductive material 40A). This reduces the shear stress in the portion of the third thermal conductive material (thermal conductive material 40B) facing the outer semiconductor package.

[0035] The protrusion 51A of the first cooler (cooler 50A) is planar. This prevents the first cooler (cooler 50A) from tilting when the first heat conductive material (heat conductive material 40A) is molded. As a result, assembly is improved.

[0036] In this embodiment, the first cooler (cooler 50A) is formed in a planar shape in the region facing the outer semiconductor package. Since it can be formed in a planar shape by simple processing such as polishing, manufacturability is improved.

[0037] The thickness t1 of the outer portion 40A1 of the first heat conductive material (heat conductive material 40A) exposed to the atmosphere is greater than the thickness t2 of the inner portion 40A2 of the first heat conductive material (heat conductive material 40A). This makes it possible to suppress the peeling of the first heat conductive material (heat conductive material 40A) from the outer portion 40A1 exposed to the atmosphere.

[0038] The coefficient of thermal expansion of the semiconductor package 10 is greater than that of the first insulating plate (insulating plate 30A). As a result, the semiconductor package 10 is more susceptible to thermal deformation than the first insulating plate (insulating plate 30A). For example, the coefficient of thermal expansion of the semiconductor package 10 is 17 ppm (Cu: copper), while the coefficient of thermal expansion of the first insulating plate (insulating plate 30A) is 2.6 ppm (SiN: silicon nitride).

[0039] The thickness t3 of the portion of the third thermal conductive material (thermal conductive material 40B) facing the outer semiconductor package is greater than the thickness t4 of the portion of the third thermal conductive material (thermal conductive material 40B) facing the inner semiconductor package. By increasing the thickness of the portion of the third thermal conductive material (thermal conductive material 40B) facing the outer semiconductor package, the shear stress in this portion is reduced. This suppresses delamination of the third thermal conductive material (thermal conductive material 40B). As a result, the reliability of the thermal conductive material can be improved.

[0040] [Embodiment 2] (Cross-sectional view of power converter) Figure 4 is a cross-sectional view of the power converter 100 of Embodiment 2.

[0041] The coolers 50A and 50B are tapered by grinding or other processes. This allows the heat conductive material 40A and 40B to be constructed in a tapered shape. As a result, it is possible to reduce thermal resistance compared to when the heat conductive material is uniformly thick.

[0042] The main features of Embodiment 2 are as follows:

[0043] As shown in Figure 4, the first cooler (cooler 50A) is tapered in the region facing the outer semiconductor package. This results in the outer portion 40A1 of the first thermal conductive material (thermal conductive material 40A) being tapered. As a result, the shear stress of the outer portion 40A1 can be reduced while suppressing thermal resistance.

[0044] Note that the present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described. Also, a part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Further, for a part of the configuration of each embodiment, addition, deletion, or replacement with another configuration is possible.

[0045] The embodiments of the present invention may also be as follows.

[0046] (1). A semiconductor device including: a plurality of semiconductor packages arranged in a row and having at least three or more; a metal cooler arranged to face the plurality of semiconductor packages; an insulating plate arranged between the plurality of semiconductor packages and the cooler; and a curable heat conductive material for joining between the facing surfaces of the cooler and the insulating plate, wherein the linear expansion coefficient of the cooler is larger than the linear expansion coefficients of the plurality of semiconductor packages, the insulating plate and the heat conductive material are arranged to continuously cover along the arrangement direction of the plurality of semiconductor packages, and the thickness of the heat conductive material in a region facing an outer semiconductor package arranged on the outside among the plurality of semiconductor packages is larger than the thickness of the heat conductive material in a region facing an inner semiconductor package arranged more inward than the outer semiconductor package among the plurality of semiconductor packages.

[0047] In a multi-parallel structure, by increasing the thickness of the heat conductive material on the outer semiconductor package, the stress of the heat conductive material is reduced. Thereby, the reliability of the heat conductive material is improved.

[0048] (2). The power conversion device according to (1), wherein a surface of the cooler on the side facing the insulating plate has a convex portion where a region facing the inner semiconductor package protrudes more than a region facing the outer semiconductor package.

[0049] One way to vary the thickness of the thermal conductive material is to create protrusions on the insulating plate. However, due to the material properties, creating protrusions on the insulating plate is difficult in terms of productivity and cost, so the protrusions are provided on the cooler instead. This ensures the correct thickness of the thermal conductive material on the outer semiconductor package and reduces stress.

[0050] (3) A power conversion device as described in (1), wherein a semiconductor package-side thermal conductive material is provided between the insulating plate and the semiconductor package, and the semiconductor package-side thermal conductive material is configured to have the same thickness as the thermal conductive material in the region facing the inner semiconductor package.

[0051] The thermal conductive material on the semiconductor package side does not need to be thickened because the stress due to the difference in coefficient of linear expansion is small. Increasing the thickness leads to a deterioration of thermal resistance, so the thickness of the thermal conductive material is kept to a minimum. This reduces (suppresses) thermal resistance.

[0052] (4) A power conversion device as described in (1), wherein the semiconductor package is mounted on a printed circuit board, a bottom cooler is positioned on the lower surface of the printed circuit board, a bottom insulating plate is provided between the printed circuit board and the bottom cooler, a bottom cooler-side thermal conductive material is provided between the bottom insulating plate and the bottom cooler, and the thickness of the bottom cooler-side thermal conductive material is the same as the thickness of the thermal conductive material facing the outer semiconductor package.

[0053] A cooler is also provided on the underside of the semiconductor package. On the underside, the difference in the coefficient of linear expansion between the insulating plate and the cooler increases the stress on the thermal conductive material, so stress is reduced by ensuring sufficient thickness of the thermal conductive material. This improves the reliability of the thermal conductive material.

[0054] (5) A power conversion device as described in (2), wherein the protrusion of the cooler is configured in a planar shape.

[0055] The heat conductive material needs to be assembled under pressure. By making the protruding parts of the cooler flat, tilting during pressurization is suppressed. This improves the ease of assembly.

[0056] (6) A power conversion device as described in (2), wherein the cooler is formed in a planar shape in the region facing the outer semiconductor package.

[0057] Since the protrusions on the cooler can be formed by polishing, manufacturability is improved.

[0058] (7) A power conversion device according to (2), wherein the cooler is formed in a tapered shape on the outer semiconductor package.

[0059] By forming the thermal conductive material in a tapered shape, it is possible to reduce thermal resistance compared to making it uniformly thick.

[0060] According to (1)-(7), increasing the thickness of the thermal conductive material reduces the shear stress of the thermal conductive material, thereby improving the reliability of the thermal conductive material. The outer semiconductor package experiences less thermal shock than the inner semiconductor package which has semiconductor packages on both sides. Therefore, by increasing the thickness of the thermal conductive material in the outer semiconductor package, the effect of increased thermal resistance is minimized.

[0061] 1...Semiconductor element 1A...Upper arm semiconductor element 1B...Lower arm semiconductor element 2A...Film capacitor 2B...Ceramic capacitor 3...Wire bonding 4M...Main terminal 4S...Signal terminal 5A...Front wiring 5B...Back wiring 5C...Inner layer wiring 5M...Main circuit wiring 5N...Negative electrode wiring 5P...Positive electrode wiring 5S...Signal wiring 5Y...Output wiring 6...Terminal connection part 7...Lead frame 8...Bonding material 10...Semiconductor package 20...Printed circuit board 30A, 30B...Insulating board 40A, 40B...Thermal conductive material 40A1...Outer part 40A2...Inner part 40A3...Intermediate part 50A, 50B...Cooler 51A, 51B...Protrusion 60A, 60B...Thermal conductive material 100...Power converter

Claims

1. A power conversion device comprising: a plurality of semiconductor packages arranged in a row; a first cooler made of metal; a first insulating plate disposed between the plurality of semiconductor packages and the first cooler; and a first thermal conductive material in contact with the first cooler and the first insulating plate, wherein the coefficient of linear expansion of the first cooler is greater than the coefficient of linear expansion of the semiconductor packages; the first insulating plate and the first thermal conductive material continuously cover the plurality of semiconductor packages along the arrangement direction of the semiconductor packages; and the first thermal conductive material comprises an outer portion showing the portion of the first thermal conductive material facing the outer semiconductor package which is the outermost semiconductor package, an inner portion showing the portion of the first thermal conductive material facing the inner semiconductor package which is the semiconductor package located inside the outer semiconductor package, and an intermediate portion showing the portion of the first thermal conductive material between the outer portion and the inner portion, wherein the thickness of the outer portion connecting to the intermediate portion of the first thermal conductive material is greater than the thickness of the inner portion of the first thermal conductive material.

2. A power conversion device according to claim 1, characterized in that, of the surface of the first cooler that is in contact with the first heat conductive material, the region facing the inner semiconductor package has a protrusion that protrudes more than the region facing the outer semiconductor package.

3. A power conversion device according to claim 1, comprising a second thermal conductive material in contact with the first insulating plate and a plurality of semiconductor packages, wherein the thickness of the second thermal conductive material is the same as the thickness of the inner portion of the first thermal conductive material.

4. A power conversion device according to claim 1, comprising: a substrate on which a plurality of semiconductor packages arranged in a row are mounted; a second cooler disposed on the side opposite to the side on which the semiconductor packages are mounted; a second insulating plate disposed between the substrate and the second cooler; and a third thermal conductive material in contact with the second cooler and the second insulating plate, wherein the thickness of the portion of the third thermal conductive material facing the outer semiconductor packages is the same as the thickness of the outer portion of the first thermal conductive material.

5. A power conversion device according to claim 2, characterized in that the protrusion of the first cooler is planar.

6. A power conversion device according to claim 2, characterized in that the first cooler is formed in a planar shape in the region facing the outer semiconductor package.

7. A power conversion device according to claim 2, wherein the first cooler is tapered in the region facing the outer semiconductor package.

8. A power conversion device according to claim 1, characterized in that the thickness of the outer portion of the first heat conductive material exposed to the atmosphere is greater than the thickness of the inner portion of the first heat conductive material.

9. A power conversion device according to claim 1, characterized in that the coefficient of linear expansion of the semiconductor package is greater than the coefficient of linear expansion of the first insulating plate.

10. A power conversion device according to claim 4, characterized in that the thickness of the portion of the third thermal conductive material facing the outer semiconductor package is greater than the thickness of the portion of the third thermal conductive material facing the inner semiconductor package.

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