Power conversion device

Abstract

To enable prevention of generation of partial discharge.SOLUTION: A power conversion device includes: a semiconductor module having a semiconductor element; a wiring board having a plurality of conductive wiring layers; and a conductive cooler in thermal contact with one surface of the wiring board via an insulating heat dissipation member. The wiring board includes: a non-conductive wiring layer that is disposed in one or more continuous layers closest to the cooler among the plurality of wiring layers and is not electrically connected to the semiconductor element; a conductive wiring layer electrically connected to the semiconductor element; and an insulating layer disposed between the non-conductive wiring layer and the conductive wiring layer. A projection region of the non-conductive wiring layer when being projected in a thickness direction of the wiring board is formed so as to overlap a region where at least a projection region of the conductive wiring layer and a projection region of the cooler overlap. An electrostatic capacitance formed between the non-conductive wiring layer and the cooler is larger than that formed between the non-conductive wiring layer and the conductive wiring layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, environmental and resource issues on a global scale have come into the spotlight, and power conversion devices using power semiconductor elements are being widely used in various fields, including consumer, automotive, railway, industrial, and infrastructure, in order to make effective use of resources, promote energy conservation, and reduce greenhouse gas emissions. For example, in the automotive field, there are electric vehicles (EVs) that are driven by motors, and hybrid cars (HEVs) that combine motor drive and engine drive. In these EVs and HEVs, the DC voltage of the battery is converted into a pseudo AC voltage by switching power semiconductor elements, which drives the motor with high efficiency.

[0003] A power conversion device is composed of a power module that includes power semiconductor elements such as IGBTs, a printed circuit board, bus bars, and capacitors. The power module generates heat due to the switching of large currents in the power semiconductor elements, and the printed circuit board, bus bars, and capacitors also generate heat in proportion to the product of the square of the current flowing through them due to losses caused by the electrical resistance components of each material. Unlike HEVs, which run on the driving force of the engine supplemented by the driving force of the motor, EVs run purely on the driving force of the motor, which is electrical power, so a power conversion device that can handle larger power is required.

[0004] To increase the power, the voltage must be increased, or the current must be increased, or both. When the current is increased, the loss increases in proportion to the square of the current, and the amount of heat generated increases. To reduce heat generation, it is necessary to increase the amount of conductors used in the power conversion device and reduce the conductor resistance. As a result, the volume and weight of the power conversion device increase, and the vehicle's electric performance (distance that can be driven for a certain amount of power) and driving performance, which is the basic performance of a vehicle, such as running, turning, and stopping, decrease. Increasing the driving range is an issue for EVs, so the capacity of the installed battery must be increased. The size and weight of the battery will increase. For this reason, battery technology development is being promoted to make it smaller, lighter, and larger capacity by increasing the energy density. However, it is necessary to reduce the size and weight of not only the battery but the entire drive system, and there is also a demand for reducing the size and weight of the motor and power conversion device.

[0005] Patent Document 1 discloses a semiconductor device comprising: a heat dissipation member having a flat substrate portion; a bonding member having a first bonding layer provided on the substrate portion of the heat dissipation member and a second bonding layer provided on the first bonding layer; a wiring board having a first metal layer provided on the second bonding layer of the bonding member, an insulating layer provided on the first metal layer, and a second metal layer provided on the insulating layer; and a semiconductor element provided on the second metal layer of the wiring board, wherein the substrate portion of the heat dissipation member and the second bonding layer of the bonding member are formed of Al or an Al alloy, and at least a surface layer of the first metal layer of the wiring board facing the second bonding layer and the first bonding layer of the bonding member are formed of Cu or a Cu alloy, or Ni or a Ni alloy. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2022-029886 Summary of the Invention [Problem to be solved by the invention]

[0007] The invention described in Patent Document 1 does not provide sufficient measures against partial discharge. [Means for solving the problem]

[0008] A power conversion device according to a first aspect of the present invention comprises a semiconductor module having a semiconductor element, a wiring board having a plurality of conductive wiring layers, and a conductive cooler in thermal contact with one side of the wiring board via an insulating heat dissipation member, wherein the wiring board is arranged in one or more consecutive layers of the plurality of wiring layers closest to the cooler, and comprises a non-conductive wiring layer that is not electrically connected to the semiconductor element, a conductive wiring layer that is electrically connected to the semiconductor element, and an insulating layer arranged between the non-conductive wiring layer and the conductive wiring layer, wherein a projected area of ​​the non-conductive wiring layer when projected in the thickness direction of the wiring board is formed to overlap at least an area where a projected area of ​​the conductive wiring layer and a projected area of ​​the cooler overlap, and a capacitance formed between the non-conductive wiring layer and the cooler is greater than a capacitance formed between the non-conductive wiring layer and the conductive wiring layer. Effect of the Invention

[0009] According to the present invention, the occurrence of partial discharge can be prevented. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view of a power conversion device according to a first embodiment. [Diagram 2] A diagram explaining how to manufacture a semiconductor module [Diagram 3] Illustration of a printed wiring board [Figure 4] Cross-sectional view of the first comparative example device [Diagram 5] Enlarged view of part A shown on the right side of Figure 4 [Figure 6] Cross-sectional view of the second comparative example device [Figure 7] FIG. 1 is a diagram showing differences between a power conversion device, a first comparative example device, and a second comparative example device; [Figure 8] 1 is a cross-sectional view of a power conversion device according to a second embodiment. [Figure 9] 11 is a cross-sectional view of a power conversion device according to a third embodiment. [Figure 10] FIG. 1 shows partial discharge test results in the power conversion devices according to the three embodiments. [Figure 11] FIG. 1 shows partial discharge test results for two comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] --First embodiment-- Hereinafter, a first embodiment of a power conversion device will be described with reference to FIGS.

[0012] 1 is a cross-sectional view of a power converter 100A. The power converter 100A includes a printed wiring board 20 having a through hole 26, a semiconductor module 10 including a power semiconductor element 12, and a cooler 36 that sandwiches the semiconductor module 10 from above and below as shown in the figure. The cooler 36 includes an upper cooler 36U and a lower cooler 36L. The semiconductor module 10 including the power semiconductor element 12 generates a large amount of heat, and is therefore cooled using the cooler 36.

[0013] The semiconductor module 10 includes a power semiconductor element 12, a heat spreader 11 that sandwiches the power semiconductor element 12 from above and below as shown in the figure, external terminals 17, and insulating resin 16 that seals the power semiconductor element 12 and the heat spreader 11. Details of the semiconductor module 10 will be described later with reference to FIG.

[0014] The printed wiring board 20 is a five-layer board as indicated by the diagonal hatching. The printed wiring board 20 includes a wiring layer 80, through holes 23, and an insulating layer 24. An insulating layer 24 is provided between each layer of the wiring layer 80, and this insulating layer 24 exists between each of the five layers, making a total of four layers. In this embodiment, for convenience of explanation, only the bottom insulating layer is called the lower insulating layer 24L, and the other insulating layers are called the upper insulating layer 24U. The upper insulating layer 24U and the lower insulating layer 24L have the same composition. The thickness of each layer of the insulating layer 24 is 300 μm.

[0015] Since the power conversion device 100A handles a large current of several hundreds of amperes, the wiring layer 80 is made of a copper foil, for example 200 μm thick, which is thicker than the copper foil used in general electronic devices. The insulating layer 24 is made of a glass fiber reinforced epoxy resin base material with a relative dielectric constant of 4.6. The details of the printed wiring board 20 will be described later with reference to FIG. 3. The printed wiring board 20 contacts the lower cooler 36L via a heat dissipation insulation sheet 35 that has excellent thermal conductivity and insulation properties.

[0016] 2 is a diagram illustrating a method for manufacturing the semiconductor module 10. The lower spreader 11L and the external terminals 17 are integrally molded with a lead frame. First, the power semiconductor element 12 is bonded onto the lower spreader 11L via a bonding material 13 such as solder, and the gate electrode of the power semiconductor element 12 and the external terminals 17 are electrically bonded using wires 14. Next, the upper spreader 11U is bonded via the bonding material 13 to the surface of the power semiconductor element 12 opposite to the surface bonded to the lower spreader 11L, i.e., the upper surface in the figure.

[0017] Thereafter, with the surface of the upper spreader 11U opposite the power semiconductor element 12, i.e., the upper surface in the figure, exposed, the power semiconductor element 12 and the heat spreader 11 are sealed with insulating resin 16 by transfer molding. Finally, unnecessary portions of the lead frame are cut off, and the semiconductor module 10 is completed.

[0018] 3 is an explanatory diagram of the printed wiring board 20. In the wiring layer 80, a circuit required for the power conversion device 100A is formed in advance by etching copper foil. In FIG. 3, the four wiring layers on the upper side of the figure are conductive wiring layers 81 that are electrically connected to the semiconductor device, and each layer of the conductive wiring layer 81 is electrically connected by a through hole 23. The bottom layer of the wiring layer 80 is a non-conductive wiring layer 82 that is insulated from the conductive wiring layer 81 and is not electrically connected to the power semiconductor element 12. A through hole 26 is formed in the printed wiring board 20 at a location where the power semiconductor device is arranged.

[0019] In the following, the end of the conductive wiring layer 81 closest to the non-conductive wiring layer 82 is denoted by the reference symbol "43." As shown in FIG. 3, there are many ends 43. The lower insulating layer 24L insulates and seals the conductive wiring layer 81 so as to entirely cover the conductive wiring layer 81 facing the non-conductive wiring layer 82. In addition, the end of the non-conductive wiring layer 82 is formed so as to be outside the end 43 of the conductive wiring layer 81. Therefore, specifically, partial discharge between the end 43 and the lower cooler 36L is prevented.

[0020] A method for producing the power conversion device 100A will be described with reference to Fig. 1. As shown in Fig. 1, the lower spreader 11L of the semiconductor module 10 is placed on the lower side in the through hole 26 of the printed wiring board 20. Then, the external terminal 17 of the semiconductor module 10 and the electrode portion of the uppermost conductive wiring layer 81 of the printed wiring board 20 are electrically joined using a bonding material 31.

[0021] Next, the heat dissipation material 32 was applied to the upper part of the upper spreader 11U and the lower part of the lower spreader 11L of the semiconductor module 10, and the insulating plate 33 was arranged on the upper part and the lower part. After that, an insulating heat dissipation insulation sheet 35 was formed on the surface of the non-conductive wiring layer 82, which is the lowest layer of the printed wiring board 20, and the insulating heat dissipation material 32 was applied to the surface of the insulating plate 33. The heat dissipation insulation sheet 35 is, for example, an insulating heat dissipation sheet having a relative dielectric constant of 7.8 and a thickness of 200 μm. Finally, an upper cooler 36U and a lower cooler 36L are arranged above and below the printed wiring board 20 on which the semiconductor module 10 is mounted, respectively, to complete the power conversion device 100A.

[0022] The non-conductive wiring layer 82 on the lower surface of the printed wiring board 20 contacts the lower cooler 36L via the heat dissipation insulating sheet 35, and the surface of the lower spreader 11L of the power semiconductor device contacts the cooler 36 via the heat dissipation material 32. In addition, the surface of the upper spreader 11U of the power semiconductor device contacts the cooler 36 via the heat dissipation material 32.

[0023] The non-conductive wiring layer 82 of the printed wiring board 20 is an insulated floating wiring layer that is not electrically connected to the semiconductor module 10. The outer peripheral end of this non-conductive wiring layer 82 is formed wider outside than the end of the conductive wiring layer 81 that is electrically connected to the semiconductor module 10. In addition, the capacitance formed between the non-conductive wiring layer 82 and the cooler 36 is larger than the capacitance formed between the non-conductive wiring layer 82 and the conductive wiring layer 81.

[0024] Comparative Example 1 4 is a cross-sectional view of a first comparative device 100Z1, which is a comparative example. The first comparative device 100Z1 is configured without the non-conductive wiring layer 82 and the lower insulating layer 24L that are included in the printed wiring board 20 of the power conversion device 100A. Furthermore, due to this difference in configuration, a gap 42 occurs during the manufacturing process. This will be described in detail below.

[0025] The first comparative example device 100Z1 includes a first comparative example substrate 20Z1, a semiconductor module 10 including power semiconductor elements 12, and a cooler 36 that sandwiches the semiconductor module 10 from above and below as shown in the figure. The semiconductor module 10 and the cooler 36 included in the first comparative example device 100Z1 are the same as those in the power conversion device 100A, and therefore a description thereof will be omitted.

[0026] The first comparative example substrate 20Z1 includes a comparative wiring layer 80Z, a through hole 23, and a first comparative example insulating layer 24Z1. The comparative wiring layer 80Z is composed of only a conductive wiring layer 81. That is, the comparative wiring layer 80Z does not include a non-conductive wiring layer 82. The conductive wiring layer 81 in the first comparative example device 100Z1 is the same as the conductive wiring layer 81 in the power conversion device 100A. The first comparative example insulating layer 24Z1 is composed of only an upper insulating layer 24U. That is, the first comparative example insulating layer 24Z1 is a three-layer insulating layer that fills the gaps between four wiring layers. The upper insulating layer 24U in the first comparative example device 100Z1 is the same as the upper insulating layer 24U in the power conversion device 100A.

[0027] FIG. 5 is an enlarged view of the portion A shown on the right side of FIG. 4. The comparative wiring layer 80Z has a relatively thick conductor, for example, 200 μm, because a large current flows through it. It is difficult to completely eliminate the warping of the first comparative example substrate 20Z1, so the occurrence of the void 42 is unavoidable. When a large voltage is applied between the conductive wiring layer 81 and the lower cooler 36L, a high electric field is applied to the void 42 due to the relationship between the relative dielectric constants of the heat dissipation insulation sheet 35 and the void 42. When the electric field becomes high, partial discharge occurs in the void 42, partial discharge deterioration progresses in the heat dissipation insulation sheet 35, and in the worst case, insulation breakdown may occur between the first comparative example substrate 20Z1 and the lower cooler 36L. The thicker the conductor layer used in the first comparative example substrate 20Z1, the larger the unevenness of the surface of the first comparative example substrate 20Z1 becomes, so that the heat dissipation insulation sheet 35 is no longer able to follow the unevenness, and the formation of the void 42 becomes more prominent.

[0028] Comparative Example 2 6 is a cross-sectional view of a second comparative device 100Z2. The second comparative device 100Z2 differs from the first comparative device 100Z1 in that a protective insulating film is provided on the surface of the bottom conductive wiring layer 81, that is, a configuration corresponding to the lower insulating layer 24L in the present embodiment. This comparative device 2 also does not have a configuration corresponding to the non-conductive wiring layer 82 in the present embodiment. Therefore, there is a higher possibility of partial discharge occurring than in the configuration of the present embodiment.

[0029] (Differences) 7 is a diagram showing differences between the power conversion device 100A, the first comparative example device 100Z1, and the second comparative example device 100Z2. Specifically, it is an enlarged view of the vicinity of the lower cooler 36L in each configuration. In any configuration, there is a possibility that voids 42 will occur above and below the heat dissipation insulation sheet 35. It should be noted that the printed wiring board 20, the first comparative example board 20Z1, and the second comparative example board 20Z2 can prevent the occurrence of voids 42 inside by vacuum pressing or the like.

[0030] Partial discharge occurs due to the gap 42 and the application of a high voltage. In this embodiment, the occurrence of partial discharge is suppressed by lowering the voltage applied to the heat dissipation insulation sheet 35 as described below. The graph shown at the bottom of Fig. 7 is a schematic diagram of voltage. The potential of the conductive wiring layer 81 at the bottom in the power conversion device 100A, the first comparative device 100Z1, and the second comparative device 100Z2 is V81, the potential of the non-conductive wiring layer 82, and the potential of the lower cooler 36L is V0.

[0031] In Comparative Example 1 and Comparative Example 2, Vz, which is the difference between V81 and V0, is applied to the heat dissipation insulation sheet 35. On the other hand, in the power conversion device 100A, V82 is an intermediate potential between V81 and V0, so the voltage applied to the heat dissipation insulation sheet 35 in the power conversion device 100A is Vy, which is always lower than Vz. Here, Vx can be made larger to reduce Vy. The ratio of Vx to Vy is determined by the capacitance ratio. Therefore, it is desirable that the heat dissipation insulation sheet 35 is thinner than the lower insulating layer 24L, and that the relative dielectric constant of the heat dissipation insulation sheet 35 is larger than that of the lower insulating layer 24L.

[0032] Even if Vx becomes large, the occurrence of partial discharge in the lower insulating layer 24L can be avoided for the following reason: That is, the printed wiring board 20 including the conductive wiring layer 81, the non-conductive wiring layer 82, and the lower insulating layer 24L can be manufactured by vacuum pressing or the like so as not to generate the voids 42.

[0033] According to the above-described first embodiment, the following advantageous effects can be obtained. (1) The power conversion device 100A includes a semiconductor module 10 having a power semiconductor element 12, a printed wiring board 20 having a plurality of conductive wiring layers 80, and a conductive lower cooler 36L in thermal contact with one surface of the printed wiring board 20 via a heat dissipation insulating sheet 35 that is an insulating heat dissipation member. The printed wiring board 20 includes a non-conductive wiring layer 82 that is disposed in one or more continuous layers of the plurality of wiring layers 80 that are closest to the lower cooler 36L and is not electrically connected to the power semiconductor element 12, a conductive wiring layer 81 that is disposed adjacent to the non-conductive wiring layer 82 and is electrically connected to the power semiconductor element 12, and an insulating layer 24 that is disposed between the non-conductive wiring layer 82 and the conductive wiring layer 81. The projected area of ​​the non-conductive wiring layer 82 when projected in the thickness direction of the printed wiring board 20 is formed to overlap at least the area where the projected area of ​​the conductive wiring layer 81 and the projected area of ​​the lower cooler 36L overlap. The capacitance formed between the non-conductive wiring layer 82 and the lower cooler 36L is larger than the capacitance formed between the non-conductive wiring layer 82 and the conductive wiring layer 81.

[0034] (2) The distance between the non-conductive wiring layer 82 and the lower cooler 36L is smaller than the distance between the non-conductive wiring layer 82 and the conductive wiring layer 81.

[0035] (3) The relative dielectric constant of the lower insulating layer 24L, which is the insulating layer 24 disposed between the non-conductive wiring layer 82 and the conductive wiring layer 81, is smaller than the relative dielectric constant of the heat dissipating insulation sheet .

[0036] (4) The heat dissipating insulation sheet 35, which is an insulating heat dissipating member, is made of a mixture of inorganic filler and organic resin.

[0037] (5) The lower insulating layer 24L, which is the insulating layer 24 disposed between the non-conductive wiring layer 82 and the conductive wiring layer 81, insulates and seals the entire conductive wiring layer 81 facing the non-conductive wiring layer 82. This makes it possible to prevent partial discharge between the end of the conductive wiring layer 81 and the lower cooler 36L.

[0038] (Variation 1) In the first embodiment described above, the distance between the non-conductive wiring layer 82 and the lower cooler 36L is smaller than the distance between the non-conductive wiring layer 82 and the conductive wiring layer 81, and the relative dielectric constant of the lower insulating layer 24L, which is the insulating layer 24 disposed between the non-conductive wiring layer 82 and the conductive wiring layer 81, is smaller than the relative dielectric constant of the heat dissipation insulation sheet 35. However, a configuration that satisfies only one of these two requirements may also be used.

[0039] (Variation 2) In the first embodiment described above, the wiring layer 80 includes four conductive wiring layers 81 and one non-conductive wiring layer 82. However, the number of conductive wiring layers 81 and non-conductive wiring layers 82 included in the wiring layer 80 is not limited to this. There may be one or more conductive wiring layers 81 and one or more non-conductive wiring layers 82. The layer of the wiring layer 80 closest to the lower cooler 36L is always the non-conductive wiring layer 82. When there are multiple non-conductive wiring layers 82, it is preferable that all the non-conductive wiring layers 82 are arranged together on the side closer to the lower cooler 36L, but this does not necessarily have to be the case.

[0040] --Second embodiment-- A second embodiment of the power conversion device will be described with reference to FIG. 8. In the following description, the same components as those in the first embodiment are given the same reference numerals, and differences will be mainly described. Points that are not specifically described are the same as those in the first embodiment. This embodiment differs from the first embodiment mainly in that the printed wiring board 20 protrudes outside the cooler 36.

[0041] Fig. 8 is a cross-sectional view of a power conversion device 100B in the second embodiment. The power conversion device 100B differs from the power conversion device 100 in the first embodiment in the configuration in the lateral direction of the figure of the printed wiring board 20. As shown in Fig. 8, the printed wiring board 20 in this embodiment has a through hole 23 formed in a portion protruding outward from the cooler 36.

[0042] The upper insulating layer 24U and the conductive wiring layer 81 may protrude to the outside of the cooler 36. The lower insulating layer 24L and the non-conductive wiring layer 82 are present at least up to the edge of the lower cooler 36L. That is, in the present embodiment as well, the projected area of ​​the non-conductive wiring layer 82 when projected in the thickness direction of the printed wiring board 20 is formed so as to overlap at least the area where the projected area of ​​the conductive wiring layer 81 and the projected area of ​​the lower cooler 36L overlap.

[0043] In this embodiment, the semiconductor module 10, the printed wiring board 20, and the power conversion device 100B are manufactured in the same manner as in the first embodiment 1. That is, in this embodiment, the non-conductive wiring layer 82 is also an insulated floating wiring layer that is not electrically connected to the semiconductor module 10, and the outer periphery end of the non-conductive wiring layer 82 is formed wider than the outer periphery end of the lower cooler 36L. In addition, the capacitance formed between the non-conductive wiring layer 82 and the cooler 36 is larger than the capacitance formed between the non-conductive wiring layer 82 and the conductive wiring layer 81.

[0044] --Third embodiment-- A third embodiment of the power conversion device will be described with reference to FIG. 9. In the following description, the same components as those in the first embodiment are denoted by the same reference numerals, and differences will be mainly described. Points that are not particularly described are the same as those in the first embodiment. The third embodiment differs from the first embodiment mainly in the number of non-conductive wiring layers 82.

[0045] Fig. 9 is a cross-sectional view of a power conversion device 100C in the third embodiment. The power conversion device 100C differs from the power conversion device 100 in the first embodiment in that one non-conductive wiring layer 82 is added. Specifically, the printed wiring board 20 shown in Fig. 9 includes four conductive wiring layers 81 and two non-conductive wiring layers 82. The number of upper insulating layers 24U remains unchanged from three, but the number of lower insulating layers 24L is increased to two.

[0046] In this embodiment, the semiconductor module 10, the printed wiring board 20, and the power conversion device 100B are manufactured in the same manner as in the first embodiment 1. That is, in this embodiment, the non-conductive wiring layer 82 is also an insulated floating wiring layer that is not electrically connected to the semiconductor module 10, and the outer periphery end of the non-conductive wiring layer 82 is formed wider than the outer periphery end of the lower cooler 36L. In addition, the capacitance formed between the non-conductive wiring layer 82 and the lower cooler 36L is larger than the capacitance formed between the non-conductive wiring layer 82 and the conductive wiring layer 81.

[0047] - Testing of power conversion equipment - The results of partial discharge tests using the power conversion device 100A of the first embodiment, the power conversion device 100B of the second embodiment, the power conversion device 100C of the third embodiment, and the first and second comparative example devices 100Z1 and 100Z2 of the first embodiment will now be described.

[0048] In the partial discharge test, the following process is performed using a partial discharge measuring device. First, all input / output terminals of the test target device are short-circuited, and an AC voltage is applied between all input / output terminals and the cooler 36. Then, the AC voltage is gradually increased from 0V, and the partial discharge inception voltage, which is the voltage at which partial discharge occurs, is measured. The input / output terminals of the power conversion device are electrically connected to the external terminals 17 of the semiconductor module 10 and the conductive wiring layer 81 of the printed wiring board 20. Therefore, a voltage is applied between the heat spreader 11 of the semiconductor module 10 and the cooler 36, and between the conductive wiring layer 81 of the printed wiring board 20 and the cooler 36. Here, the threshold value for determining that partial discharge has occurred is set to 10 pC, and the test voltage for partial discharge is set to a maximum of 2.5 kVrms.

[0049] FIG. 10 shows partial discharge test results in the power converters of the three embodiments, and FIG. 11 shows partial discharge test results in the two comparative examples. However, for convenience of description, the power converter 100A in the first embodiment will be called "Example 1", the power converter 100B in the second embodiment will be called "Example 2", and the power converter 100C in the third embodiment will be called "Example 3". Also, the first comparative example device 100Z1 will be called "Comparative Example 1", and the second comparative example device 100Z2 will be called "Comparative Example 2". In both FIG. 10 and FIG. 11, the results during boosting are shown by solid lines, and the results during bucking are shown by dashed lines. However, in FIG. 10, the dashed lines completely overlap the solid lines.

[0050] 10(a) shows the results of Example 1. In Example 1, no partial discharge occurred even at the maximum test voltage of 2.5 kVrms. The test voltage applied between the conductive wiring layer 81 and the lower cooler 36L is divided into the lower insulating layer 24L between the conductive wiring layer 81 and the non-conductive wiring layer 82, and the insulating heat dissipation insulation sheet 35 between the non-conductive wiring layer 82 and the lower cooler 36L. The capacitance of the heat dissipation insulation sheet 35 formed between the non-conductive wiring layer 82 and the lower cooler 36L is larger than the capacitance of the lower insulating layer 24L formed between the non-conductive wiring layer 82 and the conductive wiring layer 81, so that the voltage applied to the lower insulating layer 24L is larger than the voltage applied to the heat dissipation insulation sheet 35. Although there is a possibility that a gap 42 may form between the non-conductive wiring layer 82 and the heat dissipation insulation sheet 35, or between the heat dissipation insulation sheet 35 and the lower cooler 36L, the occurrence of partial discharge in the gap 42 can be suppressed because the voltage applied to the heat dissipation insulation sheet 35 can be reduced.

[0051] In addition, the peripheral end of the non-conductive wiring layer 82 is formed wider than the peripheral end of the conductive wiring layer 81 so that the projected area of ​​the non-conductive wiring layer 82 overlaps at least the area where the projected area of ​​the conductive wiring layer 81 and the projected area of ​​the lower cooler 36L overlap when projected in the thickness direction of the printed wiring board 20. Therefore, the electric field is concentrated at the end 43 of the conductive wiring layer 81, and the electric field at the end of the non-conductive wiring layer 82 where the void 42 may be formed is relaxed. This makes it possible to prevent the occurrence of partial discharge at the end of the non-conductive wiring layer 82. Although the electric field at the end 43 of the conductive wiring layer 81 is high, this portion is covered with the lower insulating layer 24L, so that partial discharge does not occur.

[0052] FIG. 10(b) shows the results of Example 2. In Example 2, no partial discharge occurred even at the maximum test voltage of 2.5 kVrms. As in Example 1, the voltage is divided between the lower insulating layer 24L between the conductive wiring layer 81 and the non-conductive wiring layer 82 and the insulating heat dissipation insulation sheet 35 between the non-conductive wiring layer 82 and the lower cooler 36L. The capacitance of the heat dissipation insulation sheet 35 formed between the non-conductive wiring layer 82 and the lower cooler 36L is larger than the capacitance of the lower insulating layer 24L formed between the non-conductive wiring layer 82 and the conductive wiring layer 81. Therefore, the voltage applied to the lower insulating layer 24L is larger than the voltage applied to the heat dissipation insulation sheet 35. Although there is a possibility that a gap 42 may be formed between the non-conductive wiring layer 82 and the heat dissipation insulation sheet 35 or between the heat dissipation insulation sheet 35 and the lower cooler 36L, the voltage applied to the heat dissipation insulation sheet 35 can be reduced, so that the occurrence of partial discharge in the gap 42 can be suppressed.

[0053] FIG. 10(c) shows the results of Example 3. In Example 3, no partial discharge occurred even at the maximum test voltage of 2.5 kVrms. In Example 3, there are two non-conductive wiring layers 82 between the conductive wiring layer 81 and the lower cooler 36L, and the voltage is divided between the two lower insulating layers 24L and the insulating heat dissipating insulation sheet 35 between the bottom non-conductive wiring layer 82 and the lower cooler 36L. The capacitance of the heat dissipating insulation sheet 35 formed between the non-conductive wiring layer 82 and the lower cooler 36L is larger than the capacitance of the lower insulating layer 24L formed between the non-conductive wiring layer 82 and the conductive wiring layer 81. Therefore, the voltage applied to the lower insulating layer 24L is larger than the voltage applied to the heat dissipating insulation sheet 35.

[0054] Although there is a possibility that gaps 42 may be formed between the non-conductive wiring layer 82 and the heat dissipation insulation sheet 35, or between the heat dissipation insulation sheet 35 and the lower cooler 36L, the voltage applied to the heat dissipation insulation sheet 35 can be reduced, thereby suppressing the occurrence of partial discharge in the gaps 42. In Example 3, there are two non-conductive wiring layers 82 and two lower insulation layers 24L, and therefore the effect of preventing partial discharge is greater than in Example 1.

[0055] 11(a) shows the results of Comparative Example 1. Partial discharge began to occur when the applied voltage exceeded 1.4 kVrms, the partial discharge threshold of 10 pC was exceeded at 1.5 kVrms, and a partial discharge with a charge of 310 pC occurred at 1.7 kVrms. It is believed that the electric field was concentrated at the end 43 of the conductive wiring layer 81, and that a gap 42 was formed around the end of the conductive wiring layer 81, causing a partial discharge to occur at a low voltage of 1.5 kVrms.

[0056] 11(b) shows the results of Comparative Example 2. Partial discharge started to occur when the applied voltage exceeded 1.7 kVrms, and exceeded the partial discharge threshold of 10 pC at 1.8 kVrms. The voltage was then increased to 2.0 kVrms, and the discharge charge amount reached approximately 40 pC at that time. In Comparative Example 2, the outermost conductive wiring layer 81 was covered with a protective insulating film. However, gaps 42 were formed between the printed wiring board 20 and the heat dissipation insulation sheet 35, and between the heat dissipation insulation sheet 35 and the lower cooler 36L, and it is believed that an electric field was concentrated in the gaps 42, causing partial discharge to occur in the gaps 42.

[0057] As described above, the effects of Example 1, Example 2, and Example 3 are that partial discharge does not occur and insulation reliability can be improved. Since partial discharge does not occur, it is also possible to increase the voltage of the power conversion device.

[0058] The above-mentioned embodiments and modifications may be combined with each other. Although various embodiments and modifications have been described above, the present invention is not limited to these. Other aspects that are conceivable within the scope of the technical idea of ​​the present invention are also included in the scope of the present invention. [Explanation of symbols]

[0059] 100A~100C: Power conversion device 10: Semiconductor module 12: Power semiconductor elements 20: Printed wiring board 24U: Upper insulation layer 24L: Lower insulation layer 35: Heat dissipation and insulation sheet 36L: Lower cooler 42: Gap 43: End 80: Wiring layer 81: Conductive wiring layer 82: Non-conductive wiring layer

Claims

1. a semiconductor module having a semiconductor element; A wiring board having a plurality of conductive wiring layers; a conductive cooler that is in thermal contact with one surface of the wiring board via an insulating heat dissipation member; The wiring board includes: a non-conductive wiring layer that is disposed in one or more consecutive layers of the plurality of wiring layers on a side closest to the cooler, the non-conductive wiring layer being not electrically connected to the semiconductor element; A conductive wiring layer electrically connected to the semiconductor element; an insulating layer disposed between the non-conductive wiring layer and the conductive wiring layer; a projection area of ​​the non-conductive wiring layer when projected in a thickness direction of the wiring board is formed to overlap at least an area where a projection area of ​​the conductive wiring layer and a projection area of ​​the cooler overlap, a capacitance formed between the non-conductive wiring layer and the cooler is larger than a capacitance formed between the non-conductive wiring layer and the conductive wiring layer.

2. 2. The power conversion device according to claim 1, a distance between the non-conductive wiring layer and the heat dissipation member is smaller than a distance between the non-conductive wiring layer and the conductive wiring layer.

3. 2. The power conversion device according to claim 1, a dielectric constant of an insulating layer disposed between the non-conductive wiring layer and the conductive wiring layer is smaller than a dielectric constant of the insulating heat dissipation member.

4. In the power conversion device according to any one of claims 1 to 3, The power conversion device, wherein the insulating heat dissipation member is made of a mixture of inorganic filler and organic resin.

5. In the power conversion device according to any one of claims 1 to 3, the insulating layer disposed between the non-conductive wiring layer and the conductive wiring layer insulates and seals the conductive wiring layer so as to entirely cover the conductive wiring layer facing the non-conductive wiring layer.

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