POWER CONVERSION DEVICE

Abstract

A power conversion device is a semiconductor device comprising: a semiconductor module in which a semiconductor element and the heat exchanger plate associated with the semiconductor element are formed and sealed with resin; and a thermally conductive material of a semi-solid form arranged between the semiconductor module and a cooling element that cools the semiconductor module, wherein a thickness of the resin between the thermally conductive material and the heat exchanger plate is greater than a thickness of the thermally conductive material.

Description

Technical area

[0001] The present invention relates to a power conversion device. State of the art

[0002] In a double-sided cooling type power conversion device, during the soldering process of a lead frame of a semiconductor module, overmolding is performed in a state where dimensional variations of elements, variations in parallelism between elements at the time of bonding, and the like occur. However, since it is necessary to consider the low thermal conductivity of this overmolded resin, it is necessary to grind the resin part to expose the surface of a heat exchanger plate, and this causes a variation in the height of a plurality of semiconductor modules arranged on the board. Therefore, there is a need for an apparatus that eliminates such variation in height and further improves reliability.

[0003] For example, PTL 1 described below discloses a configuration of a semiconductor module in which a thermal interface material (TIM) is arranged as a thermally conductive material to absorb such a variation in height, thereby achieving both the absorption of the variation and the improvement of heat dissipation. Citation listPatent literature

[0004] PTL 1: WO 1999 / 16128 A Summary of the inventionTechnical problem

[0005] Conventionally, when the TIM is thickened to absorb the height variation of the device, pumping out of the TIM occurs, and thus there is a concern about a reduction in reliability. In view of this, an object of the present invention is to provide a power conversion device that suppresses pumping out and achieves improved productivity, improved reliability, and reduced cost. Solution to the problem

[0006] A power conversion device is a semiconductor device including: a semiconductor module in which a semiconductor element and the heat exchanger plate connected to the semiconductor element are molded and sealed with resin; and a thermally conductive material having a semi-solid shape disposed between the semiconductor module and a cooling member that cools the semiconductor module, wherein a thickness of the resin between the thermally conductive material and the heat exchanger plate is greater than a thickness of the thermally conductive material. Advantageous effects of the invention

[0007] It is possible to provide a power conversion device that suppresses pumping out and achieves improvement in productivity, improvement in reliability, and cost reduction. Short description of the drawings Fig. 1 is an overall cross-sectional view of a power conversion device according to an embodiment of the present invention. Fig. 2 is a view illustrating a thickness of a thermally conductive material and an assembly cross-sectional view of a plurality of power conversion devices. Fig. 3 is a first modification.

[0008] An embodiment of the present invention will be described below with reference to the drawings. The following description and drawings are examples for describing the present invention and are omitted and simplified for clarity. The present invention may be embodied in various other forms. Unless otherwise stated, each constituent element may be singular or plural.

[0009] The positions, sizes, shapes, areas, and the like of the constituent elements illustrated in the drawings do not always represent actual positions, sizes, shapes, areas, and the like for easier understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, areas, and the like disclosed in the drawings. (An embodiment of the present invention and overall configuration of the device) (FIG. 1)

[0010] A power conversion device includes a semiconductor module 1 whose two surfaces are sandwiched by cooling water channels 8 (cooling elements 8). The semiconductor module 1 includes a semiconductor chip 3 (semiconductor element 3) and a heat exchanger plate 4 (lead frame 4) connected to the semiconductor chip 3. The semiconductor chip 3 and the heat exchanger plate 4 are molded and sealed by a resin 5.

[0011] A thermally conductive material 6 having a semi-solid form is arranged between the semiconductor module 1 and each of the cooling water channels 8 on the upper and lower surfaces. The thermally conductive material 6 is, for example, a TIM. The semiconductor module 1 is in contact with the thermally conductive material 6 on the upper and lower surfaces. Fig. 1. Each of the thermally conductive materials 6 is in contact with an insulating film 7 on a surface opposite a surface in contact with the semiconductor module 1. The insulating film 7 is in contact with the cooling water channel 8 on a surface opposite a surface in contact with the thermally conductive material 6.

[0012] Both surfaces of the semiconductor chip 3 are connected to the heat exchanger plate 4 via solder. Note that the connection between the semiconductor chip 3 and the heat exchanger plate 4 is not limited to solder, and a sintered material, a metal-resin hybrid material, or the like can be used. A gate pad on the upper surface side of the semiconductor chip 3 and a lead terminal 11 are connected by a wire 10.

[0013] The lead terminal 11 of the semiconductor module 1 is connected to a printed circuit board 2 (hereinafter, circuit board 2) by solder. The circuit board 2 is mounted with the semiconductor module 1 and is assembled by sandwiching the cooling water channel 8, in which the heat-conductive material 6 and then the insulating film 7 are applied to this semiconductor module 1 from both the upper and lower sides. It should be noted that although a single semiconductor module 1 mounted on the circuit board 2 Fig. 1 is illustrated, in fact, as in Fig. 2(b) which will be described later, a plurality of semiconductor modules 1 are arranged side by side on the board 2, and the heat-conductive material 6 having a semi-solid shape is arranged between each semiconductor module 1 and the cooling water channel 8 installed on the upper and lower surfaces.

[0014] The semiconductor module 1 is provided with overmolding by the resin 5, so that the molded resin 5 is arranged with a predetermined thickness between the heat exchanger plate 4 and the thermally conductive material 6. The molded resin 5 has high thermal conductivity. A thickness 5b of the resin 5 between the thermally conductive material 6 and the heat exchanger plate 4 is greater than a thickness 6a of the thermally conductive material 6.

[0015] The layer 6a of the thermally conductive material 6 is set in a range of 40 µm to 60 µm inclusive when using a TIM containing an alumina filler, which is commonly used for the thermally conductive material 6. This layer 6a is thinner than the layer of the conventional thermally conductive material 6, thus contributing to cost reduction. Since the layer 6a of the thermally conductive material 6 is thinner than the conventional one, the specific thermal resistance is improved, and the cooling performance is enhanced.

[0016] The reason why the TIM used as the thermally conductive material 6 is set within a limited range as described above is that it is a layer of the thermally conductive material 6 in which the TIM is difficult to pump out. The TIM generally has a range called the bond line thickness (BLT), in which the thickness of a film layer does not change significantly even when applied with a certain load or more, and the bond line thickness is determined by the size of a filler contained in the TIM. By using this method, it is possible to suppress the possibility of the thermally conductive material 6 pumping out, to thin the TIM to a bond line thickness that is difficult to pump out, and to suppress pumping out when the thickness is in the range of 40 μm to 60 μm or less.Since the TIM is more expensive than the resin 5, which is thermally conductive, it is possible to achieve both cost reduction and improvement of cooling performance by performing such limitation.

[0017] The molding resin 5 is a cured epoxy resin obtained by curing an epoxy compound together with a curing agent. Note that to achieve high thermal conductivity of the cured epoxy resin, the resin 5 may be a modified epoxy compound with high thermal conductivity or may contain one or more types of high thermal conductivity fillers to increase the amount of filler. This improves the cooling performance of the semiconductor module 1.

[0018] Examples of the filler material contained in the resin 5 include silica powders such as quartz glass, talc, aluminum powder, mica, clay, calcium carbonate, and graphite. These filler materials can be used in combination, and the thermal conductivity of the resin 5 can be improved by changing the particle size.

[0019] The molding resin 5 does not need to cover the entire surface of the heat exchanger plate 4 and may be arranged to partially cover the heat exchanger plate 4 with the molding resin 5, for example, like a resin burr. When a resin burr is present, the thermal resistance generally increases and the cooling performance decreases, and thus, it is necessary to remove the resin burr by grinding or the like. However, since the thermal resistance of the molding resin 5 itself is low, the resin burr can be applied as it is without grinding in the present invention. (FIG. 2)

[0020] Fig. Fig. 2(a) is a view illustrating a difference in thickness between the heat-conducting material 6 and the molding resin 5 formed between the insulating film 7 and the heat exchanger plate 4, and Fig. 2(b) is a view illustrating the plurality of semiconductor modules 1 mounted on the board 2.

[0021] As in Fig. As illustrated in Figure 2(a), in the configuration of the present invention as described above, the thermally conductive material 6 is set in a range of 40 μm to 60 μm or less. The resin 5 is set to be more than 55% and 260% or less of the thermal conductivity of the thermally conductive material 6. The reason for this is to maintain the thermally conductive material 6 of the present invention at a thermal resistance value equal to or higher than the layer and thermal conductivity of the thermally conductive material 6 conventionally deposited. Therefore, in the present invention, the layer of the thermally conductive material 6 is set to be thinner than the conventional one, and the resin 5 is set to be thicker than the thermally conductive material 6. For example, when the thermally conductive material 6 is 3W / m·K, the thermal conductivity of the molding resin 5 with a high thermal conductivity is set to 3·6W / m·K or more.

[0022] As in Fig. As illustrated in Figure 2(b), when the plurality of semiconductor modules 1 are arranged on the board 2, even if there is a variation in the height of each heat exchanger plate 4, the resin 5 formed by insert molding can absorb the variation. Due to this, the thermally conductive material 6 can be formed to have a constant layer and be thinner than the conventional one, and therefore, pumping out can be suppressed.

[0023] In this way, in the power conversion device of the present invention, since the resin 5 obtained by overmolding the heat exchanger plate 4 absorbs the variation in the height of the heat exchanger plate 4, it is possible to omit the grinding process of the resin 5 for overmolding, which has been conventionally performed, and it is also possible to control the molding resin 5 with high precision by molding, and therefore, productivity is improved and costs can be reduced. By disposing the resin 5 thicker than the thermally conductive material 6 by overmolding, the height of each heat exchanger plate 4 does not vary, and the thermally conductive material 6, which does not need to absorb the height variation, can be made thin and constant to the bond line thickness, which is less likely to pump out, and therefore, pumping out of the thermally conductive material 6 can be suppressed. This improves the reliability of the power conversion device. (First modification)(FIG. 3)

[0024] As in Fig.As illustrated in FIG. 3, the surfaces of the heat exchanger plate 4 and the heat-conducting material 6 do not need to be arranged in parallel, and by applying the present invention, the semiconductor module 1 can be manufactured without being affected by the fact that the respective surfaces are not parallel. When the thickness of the molding resin 5 is not constant depending on the degree of inclination of the heat exchanger plate 4, the length in the vertical direction from the upper surface (surface in contact with the heat-conducting material 6 on the upper side) of the resin 5 overmolded with the heat exchanger plate 4 to an end portion 4b of the maximum clearance in the heat exchanger plate 4 is defined as the thickness 5b of the molding resin 5. Thereby, the heat exchanger plate 4 and the heat-conducting material 6 can achieve the same effects as in the case where the respective surfaces are parallel.

[0025] According to an embodiment of the present invention described above, the following operational effects are achieved.

[0026] A semiconductor device includes: the semiconductor module 1 in which the semiconductor element 3 and the heat exchanger plate 4 connected to the semiconductor element 3 are molded and sealed with the resin 5; and the thermally conductive material 6 having a semi-rigid shape is disposed between the semiconductor module 1 and the cooling member 8 that cools the semiconductor module 1, wherein the thickness of the resin 5 between the thermally conductive material 6 and the heat exchanger plate 4 is greater than the thickness of the thermally conductive material 6. This can provide a power conversion device that suppresses pumping out and achieves productivity improvement, reliability improvement, and cost reduction.

[0027] The plurality of semiconductor modules 1 are mounted on the board 2, and the thermally conductive material 6 having a semi-rigid shape is disposed between each of the plurality of semiconductor modules 1 and the cooling member 8. This eliminates height variation due to resin overmolding, makes the amount of thermally conductive material 6 (TIM) disposed on the semiconductor module 1 thin and constant, and also suppresses pumping out.

[0028] (3) The thickness of the thermally conductive material 6 is in the range of 40 µm to 60 µm. This contributes to cost reduction and improves cooling performance.

[0029] (4) The thermal conductivity of the resin 5 is higher than the thermal conductivity of the thermally conductive material 6. As a result, the resin 5 can be formed thicker than the thermally conductive material 6 while keeping the thermal resistance value equal to or larger, and pumping out can be suppressed.

[0030] (5) The thermal conductivity of the resin 5 is more than 55% and 260% or less of the thermal conductivity of the thermally conductive material 6. Thereby, the resin 5 can be formed thicker than the thermally conductive material 6 while keeping the thermal resistance value equal to or greater, and pumping out can be suppressed.

[0031] (6) Resin 5 is an epoxy compound or contains at least one type of filler material. This allows resin 5 to be used with high thermal conductivity and improve cooling performance.

[0032] Note that the present invention is not limited to the above embodiment, and various modifications and other configurations can be combined without departing from the gist of the present invention. The present invention is not limited to one that includes all the configurations described in the above embodiment, and includes one in which part of the configuration is deleted. List of reference symbols 1 semiconductor module 2 Printed circuit board (PCB) 3 semiconductor chip 4 Heat exchanger plate (ladder frame) 4a inclined heat exchanger plate 4b Surface end section of the heat exchanger plate, the is furthest away from the heat-conducting material 5 mold resin 5b Thickness of the mold resin 6 heat-conducting material 6a Thickness of the heat-conducting material 7 Insulating foil 8 Cooling water channel 9 Heat dissipation foil 10 wire bonding 11 Conductor connection QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 1999 / 16128 A

[0004]

Claims

[1] A power conversion device which is a semiconductor device comprising: a semiconductor module in which a semiconductor element and the heat exchanger plate connected to the semiconductor element are molded and sealed with resin; and a thermally conductive material having a semi-solid form arranged between the semiconductor module and a cooling element that cools the semiconductor module, wherein a thickness of the resin between the heat-conducting material and the heat exchanger plate is greater than a thickness of the heat-conducting material. [2] Power conversion device according to claim 1, wherein a large number of semiconductor modules are mounted on a circuit board and the thermally conductive material having the semi-solid form is arranged between each of the plurality of semiconductor modules and the cooling element. [3] Power conversion device according to claim 1, wherein the thickness of the thermally conductive material is in a range of 40 µm to 60 µm. [4] The power conversion device according to claim 1, wherein the thermal conductivity of the resin is higher than the thermal conductivity of the thermally conductive material. [5] The power conversion device according to claim 4, wherein the thermal conductivity of the resin is more than 55% and 260% or less of the thermal conductivity of the thermally conductive material. [6] The power conversion device according to any one of claims 1 to 5, wherein the resin is an epoxy compound or contains at least one kind of filler material.

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