Power conversion device

Abstract

The power conversion device is a semiconductor device provided with: a semiconductor module in which a semiconductor element and the heat transfer plate connected to the semiconductor element are molded and sealed with a resin; and a semi-solid heat conduction material disposed between the semiconductor module and a cooling member for cooling the semiconductor module, the thickness of the resin between the heat conduction material and the heat transfer plate being thicker than the thickness of the heat conduction material.

Description

Technical Field

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

[0002] In a double-sided cooling type power conversion device, during the welding process of the lead frame of the semiconductor module, overmolding is performed in a state where there is a deviation in the size of each component, a deviation in the parallelism of the components when joining, etc. However, since it is necessary to consider the low degree of thermal conductivity of the resin of the overmolding, it is necessary to grind off the resin portion to expose the surface of the heat transfer plate, thereby causing a deviation in the height of the plurality of semiconductor modules arranged on the substrate. Therefore, a device is required to eliminate this height deviation and further improve reliability.

[0003] For example, Patent Document 1 listed below discloses a semiconductor module structure that arranges TIM (Thermal Interface Material) as a heat conductive material to absorb the resulting height variations, thereby achieving both absorption of the variations and improvement of heat dissipation. Prior art literature Patent Literature

[0004] Patent Document 1: International Publication No. 1999 / 16128 Summary of the invention Problem that the invention aims to solve

[0005] Conventionally, if the TIM is thickened to absorb the height variation of the device, pumping of the TIM may occur, which may reduce reliability. In view of this, an object of the present invention is to provide a power conversion device that suppresses pumping and achieves improved productivity, improved reliability, and reduced cost. Technical means of solving problems

[0006] A power conversion device is a semiconductor device, which includes: a semiconductor module, in which a semiconductor element and a heat transfer plate connected to the semiconductor element are molded and sealed with resin; a semi-solid heat conductive material, which is arranged between the semiconductor module and a cooling member for cooling the semiconductor module, and the thickness of the resin between the heat conductive material and the heat transfer plate is thicker than the thickness of the heat conductive material. Effects of the Invention

[0007] The present invention provides a power conversion device which suppresses pumping out and achieves improved productivity, improved reliability and reduced cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 This is an overall cross-sectional view of a power conversion device according to an embodiment of the present invention. Figure 2 It is a diagram showing the thickness of a heat conductive material and a cross-sectional view of an installation of a plurality of power conversion devices. Figure 3 This is the first modification example. DETAILED DESCRIPTION

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. The following description and drawings are examples for illustrating the present invention, and appropriate omissions and simplifications have been made for clarity of the description. The present invention may also be implemented in various other ways. Unless otherwise specified, each component may be single or multiple.

[0010] In order to facilitate understanding of the invention, the position, size, shape, and range of each component shown in the drawings may not represent the actual position, size, shape, and range. Therefore, the present invention is not necessarily limited to the position, size, shape, and range disclosed in the drawings.

[0011] (One embodiment of the present invention and overall structure of the device)

[0012] ( Figure 1 ) The power conversion device has a semiconductor module 1 sandwiched on both sides by a cooling water channel 8 (cooling member 8). The semiconductor module 1 has a semiconductor chip 3 (semiconductor element 3) and a heat transfer plate 4 (lead frame 4) connected to the semiconductor chip 3. The semiconductor chip 3 and the heat transfer plate 4 are molded and sealed with a resin 5.

[0013] Semi-solid heat-conducting materials 6 are disposed between the semiconductor module 1 and the cooling water channels 8 on the upper and lower surfaces. The heat-conducting materials 6 are, for example, TIM. Figure 1 The upper and lower surfaces of the heat conductive material 6 are in contact with the heat conductive material 6. The heat conductive material 6 is in contact with the insulating sheet 7 on the surface opposite to the surface in contact with the semiconductor module 1. The insulating sheet 7 is in contact with the cooling water channel 8 on the surface opposite to the surface in contact with the heat conductive material 6.

[0014] Both surfaces of the semiconductor chip 3 are connected to the heat transfer plate 4 via solder. In addition, the connection between the semiconductor chip 3 and the heat transfer plate 4 is not limited to solder, and for example, a sintered material, a mixed material of metal and resin, etc. can also be used. The gate pad on the upper surface side of the semiconductor chip 3 and the lead terminal 11 are connected by the lead 10.

[0015] The lead terminals 11 of the semiconductor module 1 are connected to the printed circuit board 2 (hereinafter referred to as the substrate 2) by solder. The semiconductor module 1 is mounted on the substrate 2, and the cooling water channel 8 to which the heat conductive material 6 and the insulating sheet 7 are attached is assembled to the semiconductor module 1 in a manner of sandwiching from the upper and lower sides. Figure 1The figure shows a single installation, but in fact, as described later Figure 2 As shown in (b) , a plurality of semiconductor modules 1 are arranged on a substrate 2 , and a semi-solid heat conductive material 6 is arranged between each semiconductor module 1 and a cooling water channel 8 provided on the upper and lower surfaces.

[0016] The semiconductor module 1 is provided with a molded resin 5 having a predetermined thickness between the heat transfer plate 4 and the heat conductive material 6, and is overmolded by the resin 5. The molded resin 5 has high thermal conductivity. The thickness 5b of the resin 5 between the heat conductive material 6 and the heat transfer plate 4 is thicker than the thickness 6a of the heat conductive material 6.

[0017] When TIM containing a commonly used alumina filler is used as the heat conductive material 6, the thickness 6a of the heat conductive material 6 is set within a range of 40 μm to 60 μm or less. This thickness 6a is thinner than the thickness of the conventional heat conductive material 6, thus contributing to cost reduction. In addition, since the thickness 6a of the heat conductive material 6 is thinner than before, the thermal resistivity is improved and the cooling performance is improved.

[0018] Therefore, the reason why TIM used as the heat conductive material 6 is set within a specified range is because TIM is a heat conductive material 6 with a thickness that is difficult to pump out. TIM generally has a region of bond line thickness (BLT: Bond Line Thickness) where the film thickness does not change significantly even if a load greater than a specified value is applied, and the bond line thickness is determined by the size of the filler contained in the TIM. If this property is utilized to reduce the TIM to a bond line thickness that is difficult to pump out to suppress pumping, and the range is set to 40 μm to 60 μm or less, the possibility of pumping out of the heat conductive material 6 can be suppressed. In addition, since TIM is more expensive than the resin 5 that conducts heat, by making such a restriction, cost reduction and improved cooling performance can be achieved at the same time.

[0019] The molding resin 5 is a cured epoxy resin obtained by curing an epoxy compound and a curing agent. In addition, in order to achieve high thermal conductivity of the cured epoxy resin, the resin 5 may use a modified epoxy compound with high thermal conductivity, or may contain one or more fillers with high thermal conductivity to increase the amount of fillers. As a result, the cooling performance of the semiconductor module 1 is improved.

[0020] The filler material contained in the resin 5 is, for example, silica powder such as fused silica, talc, aluminum powder, mica, clay, calcium carbonate, graphite, etc. These filler materials may be used in combination, and the thermal conductivity of the resin 5 may be improved by changing the particle size.

[0021] The molded resin 5 does not need to cover the heat transfer plate 4 over the entire surface, and may be configured such that the heat transfer plate 4 is partially covered by the molded resin 5, such as resin burrs. Generally, when resin burrs are present, thermal resistance increases and cooling performance decreases, so the resin burrs need to be removed by grinding or the like. However, in the present invention, since the molded resin 5 itself has low thermal resistance, the resin burrs can be used directly without grinding.

[0022] ( Figure 2 ) Figure 2 (a) is a diagram showing the difference in thickness of the heat conductive material 6 and the mold resin 5 formed between the insulating sheet 7 and the heat transfer plate 4. Figure 2 (b) is a diagram showing a state where a plurality of semiconductor modules 1 are mounted on a substrate 2 .

[0023] like Figure 2 As shown in (a), in the configuration of the present invention, as described above, the heat conductive material 6 is set within the range of 40 μm to 60 μm or less. In addition, the thermal conductivity of the resin 5 is set to be greater than 55% and less than 260% relative to the heat conductive material 6. The reason for doing so is to maintain the heat conductive material 6 of the present invention at a thermal resistance value equal to or greater than the thickness and thermal conductivity of the heat conductive material 6 used in the past. Therefore, in the present invention, the thickness of the heat conductive material 6 is set to be thinner than before, and the resin 5 is set to be thicker than the heat conductive material 6. For example, when the heat conductive material 6 is 3 W / m·K, the thermal conductivity of the highly thermally conductive molding resin 5 is set to be greater than 3·6 W / m·K.

[0024] like Figure 2 As shown in (b), when a plurality of semiconductor modules 1 are arranged on a substrate 2, even if there is a deviation in the height of each heat transfer plate 4, the resin 5 formed by overmolding can absorb the deviation. As a result, the thickness of the heat conductive material 6 can be made constant and thinner than before, thereby suppressing pumping out.

[0025] Thus, in the power conversion device of the present invention, since the resin 5 overmolded on the heat transfer plate 4 absorbs the height deviation of the heat transfer plate 4, the grinding process of the overmolded resin 5 which is conventionally performed can be omitted, and since the molded resin 5 can be controlled with high precision by mold forming, productivity can be improved and costs can be reduced. In addition, by overmolding and configuring the resin 5 which is thicker than the heat conductive material 6, the height of each heat transfer plate 4 can be prevented from deviating, and the heat conductive material 6 which does not need to absorb the height deviation can be fixed to a thin joint line thickness which is difficult to pump out, so the pumping out of the heat conductive material 6 can be suppressed. In addition, the reliability of the power conversion device is improved by this.

[0026] (First Modification) ( Figure 3 ) like Figure 3 As shown, the heat transfer plate 4 and the heat conductive material 6 may be arranged so that their respective surfaces are not parallel. By applying the present invention, the semiconductor module 1 can be manufactured without being affected by the non-parallelism of their respective surfaces. When the thickness of the molded resin 5 is not constant due to the inclination of the heat transfer plate 4, the length in the vertical direction from the upper surface of the resin 5 overmolded on the heat transfer plate 4 (the surface in contact with the upper heat conductive material 6) to the end 4b of the heat transfer plate 4 at the maximum distance is taken as the thickness 5b of the molded resin 5. As a result, the heat transfer plate 4 and the heat conductive material 6 can achieve the same effect as when their respective surfaces are parallel.

[0027] According to one embodiment of the present invention described above, the following effects are achieved.

[0028] (1) A power conversion device is a semiconductor device, comprising: a semiconductor module 1, in which a semiconductor element 3 and a heat transfer plate 4 connected to the semiconductor element 3 are molded and sealed with a resin 5; and a semi-solid heat conductive material 6, which is arranged between the semiconductor module 1 and a cooling member 8 for cooling the semiconductor module 1, and the thickness of the resin 5 between the heat conductive material 6 and the heat transfer plate 4 is thicker than the thickness of the heat conductive material 6. Thus, a power conversion device can be provided that suppresses pumping, improves productivity, improves reliability, and reduces costs.

[0029] (2) A plurality of semiconductor modules 1 are mounted on a substrate 2, and a semi-solid heat conductive material 6 is disposed between each of the plurality of semiconductor modules 1 and the cooling member 8. Thus, it is possible to eliminate the height deviation of each of the semiconductor modules 1 by resin overmolding, and the amount of the heat conductive material 6 (TIM) disposed relative to the semiconductor module 1 can be made thin and fixed, and pumping out can also be suppressed.

[0030] (3) The thickness of the heat conductive material 6 is within a range of 40 μm to 60 μm. This contributes to cost reduction and improved cooling performance.

[0031] (4) The thermal conductivity of the resin 5 is higher than that of the heat conductive material 6. Thus, the resin 5 is formed thicker than the heat conductive material 6 while making the thermal resistance value equal or higher, and pumping out can be suppressed.

[0032] (5) The thermal conductivity with respect to the heat conductive material 6 is greater than 55% and less than 260%. Thus, the resin 5 is formed thicker than the heat conductive material 6 while making the thermal resistance value equal or greater, and pumping out can be suppressed.

[0033] (6) The resin 5 is an epoxy compound or contains at least one filler material. Thus, the resin 5 having high thermal conductivity is used to improve the cooling performance.

[0034] In addition, the present invention is not limited to the above-mentioned embodiments, and various modifications and other configurations can be combined within the scope of the gist thereof. In addition, the present invention is not limited to a configuration having all the configurations described in the above-mentioned embodiments, and also includes a configuration in which a part of the configuration is deleted. Explanation of symbols

[0035] 1. Semiconductor module, 2. Printed substrate (substrate), 3. Semiconductor chip, 4. Heat transfer plate (lead frame), 4a. Inclined heat transfer plate, 4b. Surface end of the heat transfer plate farthest from the heat conductive material, 5. Molding resin, 5b. Thickness of the molding resin, 6. Heat conductive material, 6a. Thickness of the heat conductive material, 7. Insulating sheet, 8. Cooling water channel, 9. Heat sink, 10. Wire bonding, 11. Lead terminal.

Claims

1. A power conversion device, which is a semiconductor device, comprising: A semiconductor module in which a semiconductor element and the heat transfer plate connected to the semiconductor element are molded and sealed with resin; and a semi-solid heat-conductive material disposed between the semiconductor module and a cooling member for cooling the semiconductor module, The power conversion device is characterized in that: The thickness of the resin between the heat conductive material and the heat transfer plate is thicker than the thickness of the heat conductive material.

2. The power conversion device according to claim 1, characterized in that: A plurality of the semiconductor modules are mounted on a substrate. In each of the plurality of semiconductor modules, the semisolid heat conductive material is disposed between the semiconductor modules and the cooling member.

3. The power conversion device according to claim 1, characterized in that: The thickness of the heat conductive material is in the range of 40 μm to 60 μm.

4. The power conversion device according to claim 1, characterized in that: The thermal conductivity of the resin is higher than that of the heat conductive material.

5. The power conversion device according to claim 4, characterized in that: The thermal conductivity of the resin is greater than 55% and less than 260% of the thermal conductivity of the thermally conductive material.

6. The power conversion device according to any one of claims 1 to 5, characterized in that , The resin is an epoxy compound or contains at least one filler material.

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