Electric power conversion apparatus

Abstract

The present invention comprises: a semiconductor module that includes a first semiconductor package, a second semiconductor package, and a printed wiring board on which the first semiconductor package and the second semiconductor package are mounted; and a heat dissipation member for dissipating heat transmitted from the semiconductor module. The semiconductor module has a first fixing region and a second fixing region where the heat dissipation member is fixed, and has a low-rigidity member which is provided at a position between the first fixing region and the second fixing region and which is disposed in a manner of being sandwiched between the heat dissipation member and the printed wiring board. The low-rigidity member has a rigidity lower than that of a fixed member disposed in the first fixing region and the second fixing region.

Description

Power Conversion Device

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

[0002] In a power conversion device for a vehicle, the substrate on which the power device, which is the main circuit, is mounted is required to have vibration resistance, heat dissipation properties, and be compact.As an example of a measure to ensure heat dissipation, Patent Document 1 listed below discloses a configuration in which an external force is applied by a base in a direction that narrows the gap between the electronic substrate and the heat dissipation portion, thereby improving the heat dissipation effect of the electronic components and reducing factors that inhibit heat dissipation to the heat dissipation portion, such as multiple electronic components, heat dissipation grease, solder, and warpage of the substrate.

[0003] Patent No. 6789031

[0004] The configuration described in Patent Document 1 ensures heat dissipation, but when miniaturization is required for a main circuit board on which multiple semiconductor packages are mounted, for example, fixing points cannot be easily established, which reduces the number of fixing parts and reduces vibration resistance, resulting in the problem of not being able to ensure reliability.

[0005] a semiconductor module having a first semiconductor package and a second semiconductor package and a printed wiring board on which the first semiconductor package and the second semiconductor package are mounted; and a heat dissipation member that dissipates heat transferred from the semiconductor module, wherein the semiconductor module has a first fixing region and a second fixing region to which the heat dissipation member is fixed, and a low-rigidity member that is provided at a position between the first fixing region and the second fixing region and is sandwiched between the heat dissipation member and the printed wiring board, and the low-rigidity member has lower rigidity than the fixing members that are disposed in the first fixing region and the second fixing region.

[0006] It is possible to provide a power conversion device that is compact, has improved heat dissipation properties, and is improved in vibration resistance.

[0007] FIG. 1 is an overall plan view of a power conversion device according to an embodiment of the present invention. FIG. 2 is an exploded view of a power conversion device according to an embodiment of the present invention. FIG. 3 is a cross-sectional view of a power conversion device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a range fixed by a fixing region according to an embodiment of the present invention. FIG. 5 is an electrical circuit diagram of a power conversion device according to an embodiment of the present invention.

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0009] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0010] (One embodiment and overall configuration) (FIGS. 1 to 3) The power conversion device 1 is a power conversion device used, for example, in a vehicle, and includes a plurality of smoothing capacitors 2, a printed wiring board 5, and a plurality of semiconductor modules 4 having a double-sided cooling structure. The semiconductor module 4 includes a first semiconductor package 4a, a second semiconductor package 4b, and the printed wiring board 5. As will be described later with reference to FIG. 10, the printed wiring board 5 is electrically connected to an EMC circuit 24, a control circuit 23, a current sensor 22, and a motor 17.

[0011] Heat sinks 10a and 10b, which are heat dissipation members that dissipate heat transferred from the semiconductor module 4, are arranged on both sides of the semiconductor module 4. The heat sinks 10a and 10b are fitted into a plurality of openings in a base plate 13, which is also a heat dissipation member, thereby closing the openings.

[0012] The base plate 13 is a member with high thermal conductivity, and even if its thickness is changed, it does not affect the heat dissipation of the semiconductor module 4, and is also more rigid than the semiconductor module 4. By disposing such a base plate 13 near the semiconductor module 4, vibrations occurring in the printed wiring board 5 are suppressed, contributing to improved vibration resistance. Furthermore, by changing the thickness of the base plate 13, the rigidity can be adjusted to match the vibrations of the semiconductor module 4 and the printed wiring board 5.

[0013] In the power conversion device 1, a cover 11 is fastened to a semiconductor module 4 equipped with heat sinks 10a and 10b, and a water channel 10 is formed by the cover 11, the heat sinks 10a and 10b, and the base plate 13. The heat dissipation fins of the heat sinks 10a and 10b come into contact with the refrigerant flowing through the water channel 10, thereby dissipating heat from the semiconductor module 4.

[0014] The first semiconductor package 4a and the second semiconductor package 4b ​​are mounted on the printed wiring board 5 using a solder material or the like (not shown). It is possible to mount a plurality of semiconductor packages on the printed wiring board 5, thereby enabling the power conversion device 1 to handle the large current required. Although not shown, the printed wiring board 5 may also have components other than semiconductors, such as capacitors, resistors, and connectors mounted thereon.

[0015] One surface of each of the first semiconductor package 4a and the second semiconductor package 4b ​​is thermally connected to a heat sink 10a via the printed wiring board 5. In other words, the heat sink 10a, which is a heat dissipation member, is disposed on the surface of the printed wiring board 5 opposite to the surface on which the first semiconductor package 4a and the second semiconductor package 4b ​​are mounted.

[0016] In the semiconductor module 4, the regions where the heat sink 10a is fixed to the first semiconductor package 4a and the second semiconductor package 4b ​​are referred to as a first fixing region 20a and a second fixing region 20b, respectively. Fixing members are provided in the first fixing region 20a and the second fixing region 20b, and the fixing members may be any thermal interface material (TIM) that has high insulation properties, thermal conductivity, and rigidity, such as silicon nitride or aluminum oxide.

[0017] The first low-rigidity member 12 is provided between the first fixing region 20a and the second fixing region 20b, and is disposed on the surface of the printed wiring board 5 opposite the surface on which the semiconductor module 4 is disposed. The first low-rigidity member 12 is disposed sandwiched between the printed wiring board 5 and at least one of the heat sink 10a and the base plate 13, which face the printed wiring board 5. The first low-rigidity member 12 has lower rigidity than the fixing members disposed in the first fixing region 20a and the second fixing region 20b. This ensures heat dissipation while suppressing vibration of the printed wiring board 5 and improving vibration resistance.

[0018] The first low-rigidity member 12 may be made of a heat dissipation sheet, adhesive, epoxy resin, silicon, or an elastomer having thermal conductivity or insulating properties. The first low-rigidity member 12 may have adhesive properties, or may not have adhesive properties because it is held in place by repulsive force.

[0019] Similarly to the first low-rigidity member 12, a second low-rigidity member 12a may be disposed between the first fixing region 20a and the second fixing region 20b so as to contact the terminals 6 connected from the first semiconductor package 4a and the second semiconductor package 4b ​​to the printed wiring board 5. The second low-rigidity member 12a is disposed opposite the position of the first low-rigidity member 12, with the printed wiring board 5 sandwiched therebetween.

[0020] The effects of the present invention can be achieved as long as at least one of the first low-rigidity member 12 and the second low-rigidity member 12a is disposed in the power conversion device 1. The terminal 6 shown in Fig. 3 is, for example, a source terminal or a drain terminal, but may be a gate terminal as will be described later with reference to Fig. 7.

[0021] The liquid gasket 14 is provided between the base plate 13 and the heat sinks 10a and 10b, thereby assembling the heat sinks 10a and 10b to the base plate 13. This ensures close contact between the heat sinks 10a and 10b and the base plate 13, and ensures the sealing of the water channel 10.

[0022] (FIG. 4) Heat generated from each semiconductor package is transferred to the heat sinks 10a, 10b and the base plate 13 via the first and second fixing regions 20a, 20b, and is dissipated. Each fixing region has vibration resistance and heat dissipation properties for multiple semiconductor packages. The power conversion device 1 has the cover 11 fastened and fixed from both sides in the thickness direction, but as shown in the figure, the dashed line regions 25 fixed by each fixing region and the first low-rigidity member 12 do not overlap with each other in the normal direction of the printed wiring board 5.

[0023] In this way, by arranging the first low-rigidity member 12, which has lower rigidity than the fixed region, in a position that does not overlap with the fixed region, the vibration resistance and heat dissipation performance of the fixed region are not reduced. Furthermore, although it is necessary to shorten the intervals between the semiconductor packages in order to meet the demand for miniaturization, the provision of the first low-rigidity member 12 ensures heat dissipation, so that heat dissipation can be ensured even if the area of ​​the printed wiring board 5 is reduced, thereby ensuring both miniaturization and improved heat dissipation.

[0024] Furthermore, when the printed wiring board 5 vibrates, each fixed area becomes a node, and the position of the first low-rigidity member 12 becomes an antinode. In other words, by arranging the first low-rigidity member 12 in the portion of the printed wiring board 5 where the vibration is greatest, it is possible to improve vibration resistance.

[0025] Each fixing region serves as a fixing member to fix each semiconductor package, strengthening the rigidity of the dashed line region 25. By providing heat sinks 10a, 10b on both sides of each semiconductor package in the thickness direction, the rigidity of the dashed line region 25 fixed by the above-mentioned fixing regions is ensured, ensuring stability in the thickness direction. Fixation in the planar direction can be ensured by installing the power conversion device 1 in a housing (not shown). In this way, the configuration of the present invention can achieve miniaturization, improved heat dissipation, and improved vibration resistance.

[0026] (First Modification) (FIG. 5) The printed wiring board 5 has a wiring layer 15, at least a portion of which is formed between the first semiconductor package 4a and the second semiconductor package 4b. The first low-rigidity member 12 is disposed in a position overlapping the wiring layer 15 when viewed from the normal direction of the printed wiring board 5. This allows the terminals 6 of each semiconductor package connected to the wiring layer 15 to contact the first low-rigidity member 12 via the wiring layer 15, thereby enabling heat dissipation from each semiconductor package, thereby achieving miniaturization, improved heat dissipation, and improved vibration resistance.

[0027] (Second Modification) (FIG. 6) In a power converter with a double-sided cooling structure, a heat sink 10b, which is a heat dissipation member, is disposed in a position facing the first semiconductor package 4a and the second semiconductor package 4b. The difference from the heat sink 10a is that no printed wiring board 5 is provided between the semiconductor package 4a and the second semiconductor package 4b.

[0028] The first fixing region 20a is a region where the heat sink 10b is fixed to the first semiconductor package 4a. The second fixing region 20b is a region where the heat sink 10b is fixed to the second semiconductor package. The first low-rigidity member 12 is sandwiched between the printed wiring board 5 and the heat sink 10a facing the printed wiring board 5. Even when fixing members are provided as the first fixing region 20a and the second fixing region 20b on the heat sink 10b side in this way, it is possible to similarly achieve miniaturization, improved heat dissipation, and improved vibration resistance.

[0029] (Third Modification) (FIG. 7) FIG. 7(a) is a cross-sectional view of a printed wiring board 5 on which semiconductor packages are mounted, and FIG. 7(b) is an enlarged view of FIG. 7(a). Each semiconductor package has a drain terminal 6, which is a main terminal through which a main current flows, a gate terminal 8, which is a control terminal, and a source terminal (not shown). Adjacent semiconductor packages are arranged so that the drain terminals 6 face each other and the gate terminals 8 face each other between the adjacent semiconductor packages. The drain terminal 6 is electrically connected to a wiring layer 15 (FIG. 5), which is a main current wiring through which a main current flows.

[0030] The drain terminals 6 electrically connected to the wiring layer 15 are arranged to face each other in order to increase the wiring efficiency on the printed wiring board 5 and secure the required area. Furthermore, the gate terminals 8, which are control terminals through which a small current flows and generate less heat than the drain terminals 6, which have a large current and high voltage, are also arranged to face each other. This configuration ensures heat dissipation and the necessary insulation distance. This also allows the pattern layout of the printed wiring board 5 to be optimized and the printed wiring board 5 to be minimized.

[0031] 3, in this terminal arrangement, the second low-rigidity member 12a is disposed between the terminals of the first semiconductor package 4a and the drain terminals 6 and gate terminals 8 of the second semiconductor package 4b ​​when viewed from the normal direction of the printed wiring board 5. Furthermore, the second low-rigidity member 12a is disposed in contact with the drain terminals 6 or the gate terminals 8, and is sandwiched between the heat sink 10b and the printed wiring board 5. Note that a plurality of second low-rigidity members 12a may be provided so as to contact both the drain terminals 6 and the gate terminals 8.

[0032] This configuration suppresses fatigue damage to the terminals due to increased vibration transmitted from the printed wiring board 5, ensuring the vibration resistance of each terminal. Although the heat dissipation path via the second low-rigidity member 12a is separate from the main heat dissipation path via the heat sinks 10a and 10b, the presence of the first low-rigidity member 12 ensures heat dissipation because the terminals 6 are in direct contact with the first low-rigidity member 12 via the wiring layer 15. This configuration can be applied not only to the drain terminal 6 but also to the gate terminal 8 and source terminal, allowing for efficient heat dissipation and contributing to a reduction in the size of the printed wiring board 5 while ensuring heat dissipation. This allows for miniaturization, improved heat dissipation, and improved vibration resistance.

[0033] (Fourth Modification) (FIG. 8) As shown in the figure, it is not necessary to be limited to a configuration having a cooling structure on both sides, and as long as cooling performance can be ensured, a configuration in which the water channel 10 is provided on only one side is also acceptable. In the case of a power conversion device with a single-sided cooling structure, the water channel 10 is not provided on one side, and a pressing member 16 is provided instead.

[0034] The first semiconductor package 4a and the second semiconductor package 4b ​​are assembled in contact with the pressing member 16 on the surface opposite to the side where the first fixing region 20a and the second fixing region 20b are formed. In this way, the region where the heat dissipation member is fixed on the surface opposite to the side where the first fixing region 20a and the second fixing region 20b are formed is referred to as the other fixing region 20c.

[0035] The other fixing region 20c is provided with an insulating fixing member such as a TIM, similar to the fixing members provided in the first fixing region 20a and the second fixing region 20b. The pressing member 16 is, for example, a case or a spring plate. This similarly achieves miniaturization, improved heat dissipation, and improved vibration resistance.

[0036] (Fifth Modification) (FIG. 9) In a power conversion device 1 having a double-sided cooling structure, a semiconductor module 4 is electrically connected to a smoothing capacitor 2 via a printed wiring board 5. The smoothing capacitor 2 has a connection terminal 7. The connection terminal 7 is connected to the printed wiring board 5. The smoothing capacitor 2 is thermally connected to the semiconductor module 4 via a wiring layer in the printed wiring board 5 that has low thermal resistance.

[0037] The printed wiring board 5 has a third fixing region 20d which is a connection portion where the connection terminal 7 is connected and fixed. The printed wiring board 5 also has a third low-rigidity member 12b arranged thereon, which is a low-rigidity member similar to the first low-rigidity member 12 and the second low-rigidity member 12a.

[0038] The third low-rigidity member 12b is disposed between the first fixing region 20a and the third fixing region 20d, or between the second fixing region 20b and the third fixing region 20d. The third low-rigidity member 12b is sandwiched between the printed wiring board 5 and the heat dissipation member 1a, which has low thermal resistance. The heat dissipation member 1a is, for example, an aluminum case or a water channel that is an exterior of the power conversion device 1.

[0039] Between the smoothing capacitor 2 and the semiconductor module 4, a ripple current generated by switching in the semiconductor module 4 flows in both directions. The ripple current fluctuates depending on the load conditions being driven, and heat is transferred between the film of the capacitor 2, the connection terminals 7, the printed wiring board 5, and each semiconductor package via terminals with low thermal resistance and the patterns on the printed wiring board 5. When the power conversion device 1 is under a high load, the heat generated in the printed wiring board 5 is greater than the heat generated in the capacitor 2, so the heat flows to the smoothing capacitor 2. On the other hand, when the load on the power conversion device 1 is low, the heat generated in the capacitor 2 is greater than the heat generated in the printed wiring board 5, so the heat flows to the printed wiring board 5.

[0040] Heat generated by the smoothing capacitor 2 shortens the life of the smoothing capacitor 2. In addition, if the area of ​​the printed wiring board 5 is increased to ensure heat dissipation, not only will the device become larger, but vibration caused by external force will cause fatigue failure of the connection terminals 7, reducing vibration resistance.

[0041] When a main current is applied to the smoothing capacitor 2, the area of ​​the printed wiring board 5 must be secured in order to ensure heat dissipation, but in the present invention, the third low-rigidity member 12b is disposed between the third fixing region 20d and the first fixing region 20a or the second fixing region 20b, and the third low-rigidity member 12b is sandwiched between the printed wiring board 5 and the heat dissipation member 1a. This ensures heat dissipation, and furthermore, the amplitude of the abdominal portion of the printed wiring board 5 is suppressed, improving vibration resistance, which allows the area of ​​the printed wiring board 5 to be reduced and contributes to miniaturization.

[0042] Furthermore, when the third fixing region 20d (connection terminal 7) and the third low-rigidity member 12b are in contact with each other, the heat dissipation performance can be further improved while ensuring the stability of the third fixing region 20d, and the fixation and stability between the power conversion device 1 and the smoothing capacitor 2 can also be ensured. Furthermore, by applying the arrangement configuration of the third low-rigidity member 12b in combination with the first fixing region 20a and the second fixing region 20b, the amplitude of the printed wiring board 5 can be suppressed, and the vibration resistance and lifespan can be improved.

[0043] (FIG. 10) The power conversion device 1 includes a semiconductor module 4 with upper and lower arms for three phases, U, V, and W, and a smoothing capacitor 2. The power conversion device 1 is electrically connected to a battery 26, a vehicle, and a motor 17. An EMC circuit 24 is electrically connected in parallel to the semiconductor module 4, thereby suppressing noise generated from the DC power supplied from the battery 26.

[0044] Based on a control command from the vehicle system, the power conversion device 1 converts DC power supplied from the battery 26 into AC power, outputs the AC power from the three-phase semiconductor module 4 to the motor 17 to drive the motor 17, and sends regenerative power from the motor 17 to the battery 26. Current sensors 22 are provided in the U, V, and W phases of the output wiring that outputs AC power to the motor 17. The values ​​of the three-phase AC power detected by the current sensors 22 are input to a control circuit 23, which transmits a signal to a higher-level control unit of the vehicle and controls the motor 17.

[0045] According to the embodiment of the present invention described above, the following advantageous effects are achieved.

[0046] (1) A power conversion device 1 includes a semiconductor module 4 having a first semiconductor package 4 a, a second semiconductor package 4 b, and a printed wiring board 5 on which the first semiconductor package 4 a and the second semiconductor package 4 b are mounted, and a heat dissipation member that dissipates heat transferred from the semiconductor module 4, wherein the semiconductor module 4 has a first fixing region 20 a and a second fixing region 20 b to which the heat dissipation member is fixed, and a low-rigidity member is provided between the first fixing region 20 a and the second fixing region 20 b and sandwiched between the heat dissipation member and the printed wiring board 5, the low-rigidity member having lower rigidity than the fixing members disposed in the first fixing region 20 a and the second fixing region 20 b. This configuration makes it possible to provide a power conversion device 1 that is compact, has improved heat dissipation, and has improved vibration resistance.

[0047] (2) The printed wiring board 5 has a wiring layer 15, at least a portion of which is formed between the first semiconductor package 4a and the second semiconductor package 4b, and the low-rigidity member is disposed in a position overlapping the wiring layer 15 when viewed from the normal direction of the printed wiring board 5. This makes it possible to reduce the area of ​​the printed wiring board 5 and improve its vibration resistance while ensuring heat dissipation.

[0048] (3) The low-rigidity member includes a first low-rigidity member 12 and a second low-rigidity member 12a, the first low-rigidity member 12 being disposed on the surface of the printed wiring board 5 opposite to the surface on which the semiconductor module 4 is disposed, the second low-rigidity member 12a being disposed opposite to the position of the first low-rigidity member 12 with the printed wiring board 5 interposed therebetween, the first semiconductor package 4a and the second semiconductor package 4b ​​each having a terminal connected to the wiring layer 15, and the second low-rigidity member 12a being disposed between the terminals of the first semiconductor package 4a and the terminals of the second semiconductor package 4b ​​when viewed from the normal direction of the printed wiring board 5. This arrangement makes it possible to achieve both a reduction in the area of ​​the printed wiring board 5 and improved vibration resistance while ensuring heat dissipation.

[0049] (4) The wiring layer 15 is a main current wiring through which a main current flows, the terminal is a main terminal 6 through which a main current flows, and the second low-rigidity member 12a is provided at a position between the main terminal 6 of the first semiconductor package 4a and the main terminal 6 of the second semiconductor package 4b ​​when viewed from the normal direction of the printed wiring board 5. In this way, it is possible to achieve both a reduction in the area of ​​the printed wiring board 5 and an improvement in vibration resistance while ensuring heat dissipation.

[0050] (5) The second low-rigidity member 12a is in contact with the terminals of the first semiconductor package 4a and the terminals of the second semiconductor package 4b, and is sandwiched between the heat dissipation member and the printed wiring board 5. This arrangement makes it possible to achieve both improved heat dissipation and improved vibration resistance.

[0051] (6) The heat dissipation member has a base plate 13 having a plurality of openings and a heat sink 10a fitted into the openings, and the first low-rigidity member 12 is sandwiched and disposed between the printed wiring board 5 and the base plate 13. This arrangement makes it possible to achieve improved heat dissipation and vibration resistance.

[0052] (7) The heat dissipation member is disposed on the surface of the printed wiring board 5 opposite to the surface on which the first semiconductor package 4a and the second semiconductor package 4b ​​are mounted, and in the first fixing region 20a and the second fixing region 20b, the heat dissipation member is fixed to the printed wiring board 5 and to the semiconductor module 4 via the printed wiring board 5, and the first low-rigidity member 12 is disposed sandwiched between the printed wiring board 5 and the heat dissipation member facing the printed wiring board 5. This arrangement makes it possible to achieve miniaturization, improved heat dissipation, and improved vibration resistance.

[0053] (8) The heat dissipation member faces the first semiconductor package 4a and the second semiconductor package 4b, the first fixing region 20a is the region where the heat dissipation member is fixed to the first semiconductor package 4a, the second fixing region 20b is the region where the heat dissipation member is fixed to the second semiconductor package 4b, and the first low-rigidity member 12 is sandwiched and disposed between the printed wiring board 5 and the heat dissipation member facing the printed wiring board 5. This makes it possible to achieve miniaturization, improved heat dissipation, and improved vibration resistance.

[0054] (9) The heat dissipation member faces the printed wiring board 5, and is fixed to the printed wiring board 5 and to the semiconductor module 4 via the printed wiring board 5 in the first fixing region 20a and the second fixing region 20b, and a pressing member is disposed on the surface of the first semiconductor package 4a and the second semiconductor package 4b ​​opposite to the surface facing the printed wiring board. This makes it possible to achieve miniaturization, improved heat dissipation, and improved vibration resistance.

[0055] (10) The smoothing capacitor 2 is connected to the semiconductor module 4, the printed wiring board 5 has a third fixing region 20d to which the connection terminal 7 of the smoothing capacitor 2 is connected and fixed, and the third low-rigidity member 12b is disposed between the first fixing region 20a and the third fixing region 20d or between the second fixing region 20b and the third fixing region 20d. This arrangement makes it possible to achieve a smaller size, improved heat dissipation, and improved vibration resistance.

[0056] The present invention is not limited to the above-described embodiments, and various modifications and combinations of other configurations are possible without departing from the spirit of the present invention. Furthermore, the present invention is not limited to those having all of the configurations described in the above-described embodiments, and includes those in which some of the configurations are omitted.

[0057] REFERENCE SIGNS LIST 1 power conversion device 1a heat dissipation member 2 smoothing capacitor 4 semiconductor module 4a first semiconductor package 4b ​​second semiconductor package 5 printed wiring board 6 drain terminal 7 connection terminal 8 gate terminal 10 water channel 10a heat sink 10b heat sink 11 cover 12 first low-rigidity member 12a second low-rigidity member 12b third low-rigidity member 13 base plate 14 liquid gasket 15 wiring layer 16 pressing member 17 motor 20 fixing region 20a first fixing region 20b second fixing region 20c other fixing region 20d third fixing region 22 current sensor 23 control circuit 24 EMC circuit 25 dashed line region fixed by fixing region 26 battery

Claims

1. A power conversion device comprising: a semiconductor module having a first semiconductor package and a second semiconductor package, and a printed wiring board on which the first semiconductor package and the second semiconductor package are mounted; and a heat dissipation member that dissipates heat transferred from the semiconductor module, wherein the semiconductor module has a first fixing region and a second fixing region to which the heat dissipation member is fixed, and a low-rigidity member is provided at a position between the first fixing region and the second fixing region and is sandwiched between the heat dissipation member and the printed wiring board, and the low-rigidity member has lower rigidity than the fixing members disposed in the first fixing region and the second fixing region.

2. The power conversion device according to claim 1, wherein the printed wiring board has a wiring layer at least a portion of which is formed between the first semiconductor package and the second semiconductor package, and the low-rigidity member is positioned so as to overlap the wiring layer when viewed from the normal direction of the printed wiring board.

3. The power conversion device according to claim 2, wherein the low-rigidity member comprises a first low-rigidity member and a second low-rigidity member, the first low-rigidity member being arranged on a surface of the printed wiring board opposite to the surface on which the semiconductor module is arranged, the second low-rigidity member being arranged opposite to the arrangement position of the first low-rigidity member with the printed wiring board sandwiched therebetween, the first semiconductor package and the second semiconductor package each having a terminal connected to the wiring layer, and the second low-rigidity member being arranged in a position between the terminal of the first semiconductor package and the terminal of the second semiconductor package when viewed from the normal direction of the printed wiring board.

4. A power conversion device as described in claim 3, wherein the wiring layer is a main current wiring through which a main current flows, the terminal is a main terminal through which the main current flows, and the second low-rigidity member is provided at a position between the main terminal of the first semiconductor package and the main terminal of the second semiconductor package when viewed from the normal direction of the printed wiring board.

5. A power conversion device as described in claim 3, wherein the second low-rigidity member is in contact with the terminals of the first semiconductor package and the terminals of the second semiconductor package, and is sandwiched between the heat dissipation member and the printed wiring board.

6. The power conversion device according to claim 1, wherein the heat dissipation member has a base plate having a plurality of openings and a heat sink fitted into the openings, and the first low-rigidity member is sandwiched and arranged between the printed wiring board and the base plate.

7. A power conversion device as claimed in any one of claims 1 to 6, wherein the heat dissipation member is arranged on the surface of the printed wiring board opposite to the surface on which the first semiconductor package and the second semiconductor package are mounted, the heat dissipation member is fixed to the printed wiring board and to the semiconductor module via the printed wiring board in the first fixing region and the second fixing region, and the first low-rigidity member is sandwiched and arranged between the printed wiring board and the heat dissipation member facing the printed wiring board.

8. A power conversion device as described in claim 1, wherein the heat dissipation member faces the first semiconductor package and the second semiconductor package, the first fixing region is a region where the heat dissipation member is fixed to the first semiconductor package, the second fixing region is a region where the heat dissipation member is fixed to the second semiconductor package, and the first low-rigidity member is sandwiched and arranged between the printed wiring board and the heat dissipation member facing the printed wiring board.

9. A power conversion device as described in claim 1, wherein the heat dissipation member faces the printed wiring board, and is fixed to the printed wiring board and to the semiconductor module via the printed wiring board in the first fixing region and the second fixing region, and a pressing member is arranged on the surface of the first semiconductor package and the second semiconductor package opposite to the surface facing the printed wiring board.

10. A power conversion device as described in claim 1, further comprising a smoothing capacitor connected to the semiconductor module, wherein the printed wiring board has a third fixing region to which a connection terminal of the smoothing capacitor is connected and fixed, and a third low-rigidity member is disposed between the first fixing region and the third fixing region or between the second fixing region and the third fixing region.

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