Capacitor and method for manufacturing capacitor

Abstract

This invention provides a capacitor capable of easily improving the contact property of a heat sink to a housing. A capacitor (1) is provided with: a plurality of capacitor elements (10); a housing (20) provided with a pair of side surface plates (21a, 21b); and a heat sink (30). In a condition in which the pair of side surface plates are disposed so as to form at least a portion of the housing and the heat sink is disposed so as to partition the space inside the housing, the pair of side surface plates and the heat sink are welded together.

Description

Capacitor and method for manufacturing the same

[0001] The present invention relates to a capacitor and a method for manufacturing a capacitor.

[0002] Conventionally, capacitors have been known in which capacitor elements (electrodes and dielectrics) are housed in a metal housing, and the interior of the housing is filled with an insulator such as resin. In such capacitors, it is necessary to deal with the heat generated in the capacitor elements. Patent Document 1 discloses a configuration in which heat sinks are inserted between multiple capacitor elements, and the heat generated in the capacitor elements is dissipated by the heat sinks.

[0003] Japanese Patent Application Publication No. 2000-277377

[0004] However, in Patent Document 1, the heat sink is not directly connected to the housing, meaning that the contact between the heat sink and the housing is not good, leaving room for improvement in terms of heat dissipation.

[0005] Therefore, as described below, it is possible to improve the contact between the heat sink and the housing by welding the heat sink to the housing. For example, by welding a side panel (U-shaped) made up of three connected flat plates, a flat plate connecting both ends of the side panel, and a heat sink placed inside the space formed by the side panel and the flat plate, the heat sink is directly connected to the housing to form a capacitor housing. Here, if the flat plate is welded to the side panel first, there is no working space in the space to weld the heat sink. Therefore, it is necessary to weld the heat sink to the side panel first. However, if the heat sink is welded to the side panel first, the side panel will be distorted by the welding, making it difficult to weld the flat panel.

[0006] An object of one aspect of the present invention is to provide a capacitor that can easily improve the contact of a heat sink with a housing.

[0007] In order to solve the above problem, a capacitor according to one embodiment of the present invention comprises a plurality of capacitor elements, a housing that houses the plurality of capacitor elements, and a heat sink that dissipates heat generated by the plurality of capacitor elements, wherein the housing has a pair of side plates, each of which has a first flat plate, a second flat plate connected to the first flat plate, and a third flat plate that is connected to the first flat plate and faces the second flat plate, and the pair of side plates are arranged to form at least a portion of the housing, and the heat sink is arranged to divide the space inside the housing, and the pair of side plates and the heat sink are welded together.

[0008] In order to solve the above-mentioned problems, one embodiment of the present invention provides a method for manufacturing a capacitor comprising a plurality of capacitor elements, a housing that houses the plurality of capacitor elements, and a heat sink that dissipates heat generated by the plurality of capacitor elements, wherein the housing comprises a pair of side panels, each of which has a first flat plate, a second flat plate connected to the first flat plate, and a third flat plate that is connected to the first flat plate and faces the second flat plate, and the method includes an arrangement step of arranging the pair of side panels to form at least a portion of the housing and arranging the heat sink to divide the space inside the housing, and a welding step of welding the pair of side panels to the heat sink.

[0009] According to one aspect of the present invention, the contact of the heat sink with the housing can be easily improved.

[0010] It is a cross-sectional view showing a schematic configuration of a capacitor according to a first embodiment of the present invention. It is an exploded perspective view showing a housing of the capacitor. It is an enlarged cross-sectional view showing a welded portion ... a capacitor according to a second embodiment of the present invention.

[0011] [Embodiment 1] Hereinafter, an embodiment of the present invention will be described in detail. For the sake of convenience, components having the same functions as those shown in each embodiment will be denoted by the same reference numerals, and their description will be omitted as appropriate. Furthermore, directions are identified using X, Y, and Z shown in the drawings.

[0012] (Schematic Configuration of Capacitor 1) Fig. 1 is a cross-sectional view (cross-sectional view cut along the XY plane) showing the schematic configuration of a capacitor 1 according to one embodiment of the present invention. As shown in Fig. 1, capacitor 1 includes a plurality of capacitor elements 10, a housing 20, and a heat sink 30. In this embodiment, capacitor 1 is a metallized film capacitor.

[0013] The capacitor element 10 is an element portion that exhibits the electrical performance of a capacitor. In this embodiment, the capacitor element 10 is an element having a structure in which electrodes are wound around a winding core. Specifically, the capacitor element 10 has a structure in which two metallized films are stacked and wound around a winding core. The metallized film is formed by vapor-depositing a metal (electrode) as a surface electrode on one side of a dielectric substrate film. The capacitor element 10 has a substantially cylindrical shape and has a pair of electrodes 12 at both ends in the axial direction. The surface electrode of one metallized film is connected to one of the pair of electrodes 12, and the surface electrode of the other metallized film is connected to the other of the pair of electrodes 12.

[0014] The housing 20 accommodates a plurality of capacitor elements 10. The housing 20 has a substantially rectangular parallelepiped shape. Hereinafter, the direction perpendicular to the side surfaces extending in the longitudinal direction of the housing 20 will be referred to as the left-right direction (X-axis direction), the direction perpendicular to the side surfaces extending in the lateral direction of the housing 20 will be referred to as the front-rear direction (Y-axis direction), and the direction perpendicular to the XY plane will be referred to as the up-down direction (Z-axis direction). The dimensions of the housing 20 are, for example, approximately 600 mm in the front-rear direction, approximately 250 mm in the left-right direction, and approximately 800 mm in the up-down direction. The housing 20 may be made of any metal, such as stainless steel (SUS). The detailed structure of the housing 20 will be described later with reference to FIG. 2.

[0015] The capacitor element 10, which has a substantially cylindrical shape, is arranged in the housing 20 with its axis aligned in the left-right direction. In the example shown in Fig. 1, two capacitor elements 10 are arranged in the left-right direction, and five capacitor elements 10 are arranged in the front-rear direction. Although not shown in Fig. 1, a plurality of capacitor elements 10 may be stacked in the vertical direction.

[0016] The electrodes 12 of the plurality of capacitor elements 10 are drawn out to the outside of the housing 20 by wiring. For example, the electrodes 12 of the plurality of capacitor elements 10 are connected in parallel to external terminals (not shown) outside the housing 20 by wiring. The external terminals function as terminals of the capacitor 1.

[0017] An insulator is filled between the housing 20 and the capacitor element 10. The insulator may be, for example, a resin such as an epoxy resin.

[0018] The heat sink 30 is provided at least inside the housing 20 so as to dissipate heat generated by the capacitor element 10. As shown in FIG. 1, the heat sink 30 is preferably contained within the space inside the housing 20. This reduces the area occupied by the capacitor 1 and improves the appearance. The heat sink 30 may also extend to the outside of the housing 20. The heat sink 30 may be made of any metal, such as SUS (stainless steel).

[0019] Furthermore, the heat sink 30 is arranged so as to separate the space inside the housing 20. From the viewpoint of heat dissipation, it is preferable that the heat sink 30 is arranged inside the housing 20 so as to completely block the space between a pair of capacitor elements 10. However, it is sufficient that the heat sink 30 is located between at least a pair of capacitor elements 10. In other words, the two spaces separated by the heat sink 30 may be connected. In the example shown in FIG. 1 , the heat sink 30 extends in the front-to-rear direction so as to be located between the five capacitor elements 10 arranged on the left side and the five capacitor elements 10 arranged on the right side.

[0020] Specifically, the heat sink 30 is preferably provided inside the housing 20 so that one electrode 12 of the capacitor element 10 faces the heat sink 30. This allows the heat sink 30 to be provided near the electrode 12, which is particularly susceptible to heat generation in the capacitor element 10, and allows the heat generated in the capacitor element 10 to be efficiently dissipated. Furthermore, because the heat sink 30 faces the axial end face of the capacitor element 10, which is substantially cylindrical, the area in close proximity to the capacitor element 10 can be increased compared to when the heat sink 30 faces the side face of the capacitor element 10. In other words, the heat generated in the capacitor element 10 can be efficiently dissipated. The heat sink 30 preferably faces the entire axial end face of the capacitor element 10, but it is sufficient if it faces at least a portion of the axial end face of the capacitor element 10.

[0021] The housing 20 and the heat sink 30 are connected by welding. Specifically, the side surfaces of the housing 20 extending in the left-right direction (X direction) are welded to the front-rear end portions of the heat sink 30. In FIG. 1 , the portion where the housing 20 and the heat sink 30 are welded is shown as a weld 40. By connecting the housing 20 and the heat sink 30 by welding, the contact of the heat sink with the housing can be improved. Therefore, the heat dissipation performance of the capacitor 1 can be improved.

[0022] 2 is an exploded perspective view showing the housing 20 of the capacitor 1. The housing 20 includes a pair of side plates 21 a, 21 b, a bottom plate 22, and a top plate 23. The housing 20 is formed by welding the pair of side plates 21 a, 21 b, the bottom plate 22, and the top plate 23 together.

[0023] The pair of side plates 21a, 21b form the side surfaces of the housing 20. Each of the pair of side plates 21a, 21b includes a first flat plate 211a, 211b, a second flat plate 212a, 212b connected to the first flat plate 211a, 211b, and a third flat plate 213a, 213b connected to the first flat plate 211a, 211b and facing the second flat plate 212a, 212b. The first flat plates 211a, 211b form the side surfaces extending in the front-to-rear direction (Y direction) of the housing 20. The second flat plate 212a and the second flat plate 212b are welded to each other to form one side surface extending in the left-to-right direction of the housing 20. The third flat plate 213a and the third flat plate 213b are welded to each other to form the other side surface extending in the left-to-right direction of the housing 20. Hereinafter, unless there is a need to particularly distinguish between them, the pair of side plates 21a and 21b will be simply referred to as side plates 21. The same applies to the first flat plates 211a and 211b, the second flat plates 212a and 212b, and the third flat plates 213a and 213b.

[0024] 2 , the second flat plate 212 is a flat plate extending from a first side of the first flat plate 211 in a direction perpendicular to the first flat plate 211. The third flat plate 213 is a flat plate extending from a second side opposite the first side of the first flat plate 211 in a direction perpendicular to the first flat plate 211. In other words, the side plate 21 has a U-shape. The pair of U-shaped side plates 21 a, 21 b are butted together to form the side surfaces of the housing 20.

[0025] The bottom plate 22 forms the bottom surface of the housing 20. The top plate 23 forms the top surface of the housing 20. The heat sink 30 is connected to the second flat plates 212a and 212b at one end in the front-rear direction and to the third flat plates 213a and 213b at the other end in the front-rear direction.

[0026] The side panel 21 may form part of the side, bottom, and top of the housing 20. In this case, the housing 20 is composed of the side panel 21 and two flat plates that form the rest of the side of the housing 20.

[0027] 3 is an enlarged cross-sectional view showing the weld 40 of the capacitor 1. Hereinafter, the terms "inner surface" and "outer surface" refer to the surface of the flat plate facing the inside of the housing 20 and the surface facing the outside of the housing 20, respectively.

[0028] As shown in Figure 3, the pair of side panels 21a, 21b are arranged to form at least a part of the housing 20 (in this embodiment, the side surfaces), and the heat sink 30 is arranged to divide the space inside the housing 20, and the pair of side panels 21a, 21b and the heat sink 30 are welded together.

[0029] In the example shown in FIG. 3 , the pair of side plates 21a, 21b have the same dimensions. One end of the heat sink 30 is interposed between the second flat plate 212a and the second flat plate 212b. In this case, the pair of side plates 21a, 21b and the heat sink 30 are welded from the outside of the housing 20 (from the outside of the space formed by the pair of side plates 21a, 21b). Specifically, the pair of side plates 21a, 21b and the heat sink 30 are welded over one end of the outer surface of the second flat plate 212a, one end face of the heat sink 30, and one end of the outer surface of the second flat plate 212b. In other words, the contact portion between the second flat plate 212a and the heat sink 30 and the contact portion between the second flat plate 212b and the heat sink 30 are welded at a single weld 40.

[0030] Although not shown in FIG. 3, the pair of side plates 21 a and 21 b and the heat sink 30 are welded to each other at the other end of the heat sink 30 as well.

[0031] (Method of Manufacturing Capacitor 1) Hereinafter, an example of a method of manufacturing the capacitor 1 will be described with reference to FIG.

[0032] First, the pair of side plates 21a, 21b and the heat sink 30 are arranged as shown in Fig. 3 (arrangement step). Specifically, the pair of side plates 21a, 21b are arranged so as to form at least a portion (in this embodiment, the side surfaces) of the housing 20. The heat sink 30 is also arranged so as to partition the internal space of the housing 20 and so that one end of the heat sink 30 is interposed between the second flat plates 212a and 212b.

[0033] Next, the pair of side plates 21a, 21b are welded to the heat sink 30 (welding step). Specifically, the pair of side plates 21a, 21b are welded to the heat sink 30 across one end of the outer surface of the second flat plate 212a, one end face of the heat sink 30, and one end of the outer surface of the second flat plate 212b. In addition, the pair of side plates 21a, 21b are welded to the heat sink 30 across one end of the outer surface of the third flat plate 213a, the other end face of the heat sink 30, and one end of the outer surface of the third flat plate 213b.

[0034] Next, the bottom plate 22 is welded to the pair of side plates 21a, 21b and the heat sink 30. Next, the plurality of capacitor elements 10 are arranged in the space partitioned by the pair of side plates 21a, 21b and the heat sink 30. The plurality of capacitor elements 10 may be positioned, for example, by a positioning structure provided on the bottom plate 22. Next, the wiring connected to the electrodes 12 of the plurality of capacitor elements 10 is drawn to the outside. Next, an insulator is filled between the housing 20 and the capacitor elements 10. Next, the top plate 23 is welded to the pair of side plates 21a, 21b and the heat sink 30. In this manner, the capacitor 1 is manufactured.

[0035] (Effects of Capacitor 1) The welding method (hereinafter referred to as the welding method according to the comparative example) for welding a side panel made up of three connected flat plates, a flat plate connecting both ends of the side panel, and a heat sink placed inside the space formed by the side panel and the flat plate has the following problems: If the flat plate is welded to the side panel first, there is no working space in the space to weld the heat sink plate. If the heat sink plate is welded to the side panel first, the center of the side panel will be distorted by the welding, which will change the distance between both ends of the side panel, making it difficult to weld the flat plate.

[0036] On the other hand, in the capacitor 1 according to this embodiment, the pair of side plates 21 a, 21 b are arranged so as to form at least a part of the housing 20, and the pair of side plates 21 a, 21 b are welded to the heat sink 30. Therefore, compared to the welding method according to the comparative example, there is no need to consider distortion of the pair of side plates 21 a, 21 b due to welding, and welding can be performed easily and accurately. Therefore, good contact between the heat sink 30 and the housing 20 can be easily achieved.

[0037] The heat sink 30 also functions as a partition plate that separates the plurality of capacitor elements 10. Specifically, when arranging the plurality of capacitor elements 10 in the space inside the housing 20, the positioning of the plurality of capacitor elements 10 can be facilitated by allocating the plurality of capacitor elements 10 to the left or right side of the heat sink 30. The heat sink 30 also ensures that the right electrode 12 of the capacitor element 10 on the left side of the heat sink 30 and the left electrode 12 of the capacitor element 10 on the right side of the heat sink 30 are spaced apart from each other.

[0038] 3, the pair of side panels 21 a, 21 b and the heat sink 30 are welded from the outside of the housing 20. This makes it possible to ensure a working space for welding the pair of side panels 21 a, 21 b and the heat sink 30 together, facilitating welding.

[0039] Furthermore, the pair of side plates 21a, 21b and the heat sink 30 are welded to one end of the outer surface of the second flat plate 212a, one end face of the heat sink 30, and one end of the outer surface of the second flat plate 212b. That is, the pair of side plates 21a, 21b and the heat sink 30 are welded near their ends. This makes it difficult for the ends to shift position. This is possible because both of the pair of side plates 21a, 21b are U-shaped.

[0040] Furthermore, in the welding method according to the comparative example, the flat plate, the side plate, and the heat sink plate were connected by two welding operations. Therefore, after the first welding operation, time was required to allow sufficient heat to dissipate. In contrast, in the capacitor 1, the pair of side plates 21a, 21b and the heat sink plate 30 can be connected by a single welding operation. Therefore, the time required for the welding operation can be reduced compared to the welding method according to the comparative example.

[0041] [Embodiment 2] Another embodiment of the present invention will be described below. For ease of explanation, the same reference numerals will be used to designate components having the same functions as those described in the above embodiment, and the description thereof will not be repeated.

[0042] Fig. 4 is an enlarged cross-sectional view showing welds 40A and 40B of capacitor 1A. Capacitor 1A shown in Fig. 4 differs from capacitor 1 shown in Fig. 3 in that the pair of side plates 21a, 21b and heat sink 30 are welded by welds 40A and 40B instead of weld 40.

[0043] As shown in Figure 4, the pair of side panels 21a, 21b are arranged to form at least a part of the housing 20 (in this embodiment, the side surfaces), and the heat sink 30 is arranged to divide the space inside the housing 20, and the pair of side panels 21a, 21b and the heat sink 30 are welded together.

[0044] In the example shown in Figure 4, in capacitor 1A, the second flat plate 212b of the right-side side plate 21b is formed longer in the left-right direction than the second flat plate 212a of the left-side side plate 21a. One end of the heat sink 30 abuts against the inner surface of the second flat plate 212b. In this case, the side plate 21b and the heat sink 30 are welded from outside the space formed by the side plate 21b and the heat sink 30. Specifically, the side plate 21b and the heat sink 30 are welded over one end of the inner surface of the second flat plate 212b and one end of the left surface of the heat sink 30. In addition, the side plate 21a and the side plate 21b are welded from outside the housing 20 (outside the space formed by the pair of side plates 21a, 21b). Specifically, side plate 21 a and side plate 21 b are welded to one end of the outer surface of second flat plate 212 a and one end of the outer surface of second flat plate 212 b. In other words, the contact portion between second flat plate 212 a and heat sink 30 and the contact portion between second flat plate 212 b and heat sink 30 are welded at weld 40A and weld 40B, respectively.

[0045] Although not shown in FIG. 4, the pair of side plates 21a, 21b and the heat sink 30 are welded to each other at the other end of the heat sink 30 as well.

[0046] (Method of Manufacturing Capacitor 1A) Hereinafter, an example of a method of manufacturing the capacitor 1A will be described with reference to FIG.

[0047] First, the side panel 21b and the heat sink 30 are arranged as shown in Fig. 4 (arrangement step). Specifically, the heat sink 30 is arranged relative to the side panel 21b so that one end of the heat sink 30 abuts against the inner surface of the second flat plate 212b and the other end of the heat sink 30 abuts against the inner surface of the third flat plate 213b.

[0048] Next, the side panel 21b and the heat sink 30 are welded together (welding step). Specifically, the side panel 21b and the heat sink 30 are welded together over one end of the inner surface of the second flat plate 212b and one end of the left surface of the heat sink 30. The side panel 21b and the heat sink 30 are also welded together over one end of the inner surface of the third flat plate 213b and the other end of the left surface of the heat sink 30.

[0049] Next, the side panel 21a is disposed relative to the side panel 21b and the heat sink 30 as shown in Fig. 4 (disposing step). Specifically, the pair of side panels 21a, 21b are disposed so as to form at least a part of the housing 20.

[0050] Next, the side plate 21a and the side plate 21b are welded together (welding step). Specifically, the side plate 21a and the side plate 21b are welded together along one end of the outer surface of the second flat plate 212a and one end of the outer surface of the second flat plate 212b. In addition, the side plate 21a and the side plate 21b are welded together along one end of the outer surface of the third flat plate 213a and one end of the outer surface of the third flat plate 213b.

[0051] The steps after the arrangement step and welding step in the method for manufacturing the capacitor 1A are the same as those in the method for manufacturing the capacitor 1 described above.

[0052] (Operations and Effects of Capacitor 1A) The capacitor 1A according to this embodiment has the same effects as the capacitor 1.

[0053] 4, in the first welding step, side panel 21b and heat sink 30 are welded from outside the space formed by side panel 21b and heat sink 30. In addition, in the second welding step, side panel 21a and side panel 21b are welded from outside casing 20. This makes it possible to ensure a working space for welding the pair of side panels 21a, 21b and heat sink 30 together, facilitating welding.

[0054] Furthermore, the side panel 21b and the heat sink 30 are welded to one end of the inner surface of the second flat panel 212b and one end of the left surface of the heat sink 30, and the side panel 21a and the side panel 21b are welded to one end of the outer surface of the second flat panel 212a and one end of the outer surface of the second flat panel 212b. In other words, the ends of the pair of side panels 21a, 21b and the heat sink 30 are welded together. This makes it difficult for the ends to shift position. This is possible because both of the pair of side panels 21a, 21b are U-shaped.

[0055] [Summary] A capacitor according to aspect 1 of the present invention comprises a plurality of capacitor elements, a housing that houses the plurality of capacitor elements, and a heat sink that dissipates heat generated by the plurality of capacitor elements, wherein the housing comprises a pair of side plates, each of which has a first flat plate, a second flat plate connected to the first flat plate, and a third flat plate that is connected to the first flat plate and faces the second flat plate, and the pair of side plates are arranged to form at least a portion of the housing, and the heat sink is arranged to divide the space inside the housing, and the pair of side plates and the heat sink are welded together.

[0056] According to the above configuration, the pair of side plates are welded together while being arranged so as to form at least a part of the housing. Therefore, there is no need to consider distortion of the pair of side plates due to welding, and welding can be performed easily and accurately. Therefore, good contact between the heat sink and the housing can be easily achieved.

[0057] In a capacitor according to Aspect 2 of the present invention, in the capacitor according to Aspect 1, the pair of side plates and the heat sink may be welded from the outside of the housing.

[0058] According to the above configuration, a working space for welding the heat sink plate to the pair of side plates can be secured, and the welding can be easily performed.

[0059] In the capacitor according to Aspect 3 of the present invention, in Aspect 1 or 2, one electrode of the capacitor element may face the heat sink.

[0060] According to the above configuration, the heat sink can be provided near the electrodes of the capacitor element, which are particularly prone to heat generation, and the heat generated in the capacitor element can be efficiently dissipated. Furthermore, because the heat sink faces the axial end face of the capacitor element, the area in which the heat sink is close to the capacitor element can be increased compared to when the heat sink faces the side face of the capacitor element. In other words, the heat generated in the capacitor element can be efficiently dissipated.

[0061] In a capacitor according to Aspect 4 of the present invention, in any one of Aspects 1 to 3, the heat sink may be contained within the space.

[0062] According to the above configuration, the area occupied by the capacitor is reduced and the external appearance is improved.

[0063] A capacitor manufacturing method according to aspect 5 of the present invention comprises a plurality of capacitor elements, a housing that houses the plurality of capacitor elements, and a heat sink that dissipates heat generated by the plurality of capacitor elements, wherein the housing comprises a pair of side panels, each of which has a first flat plate, a second flat plate connected to the first flat plate, and a third flat plate that is connected to the first flat plate and faces the second flat plate, and includes an arrangement step of arranging the pair of side panels to form at least a portion of the housing and arranging the heat sink to divide the space inside the housing, and a welding step of welding the pair of side panels to the heat sink.

[0064] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0065] REFERENCE SIGNS LIST 1, 1A Capacitor 10 Capacitor element 12 Electrode 20 Housing 21, 21a, 21b Side plate 22 Bottom plate 23 Top plate 30 Heat sink 40, 40A, 40B Welded portion 211, 211a, 211b First flat plate 212, 212a, 212b Second flat plate 213, 213a, 213b Third flat plate

Claims

1. A capacitor comprising: a plurality of capacitor elements; a housing that houses the plurality of capacitor elements; and a heat sink that dissipates heat generated by the plurality of capacitor elements, wherein the housing has a pair of side plates, each of the side plates having a first flat plate, a second flat plate connected to the first flat plate, and a third flat plate connected to the first flat plate and facing the second flat plate, the pair of side plates being arranged to form at least a part of the housing, and the heat sink being arranged to divide the space inside the housing, and the pair of side plates and the heat sink being welded to each other.

2. The capacitor according to claim 1, wherein the pair of side panels and the heat sink are welded from the outside of the housing.

3. The capacitor according to claim 1 or 2, wherein one electrode of said capacitor element faces said heat sink.

4. The capacitor according to claim 1 or 2, wherein the heat sink is contained within the space.

5. A method for manufacturing a capacitor comprising: a plurality of capacitor elements; a housing that houses the plurality of capacitor elements; and a heat sink that dissipates heat generated by the plurality of capacitor elements, wherein the housing comprises a pair of side plates, each of the side plates having a first flat plate, a second flat plate connected to the first flat plate, and a third flat plate connected to the first flat plate and facing the second flat plate, the method including: an arrangement step of arranging the pair of side plates to form at least a portion of the housing and arranging the heat sink to divide an internal space of the housing; and a welding step of welding the pair of side plates to the heat sink.

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