Power conversion device

Abstract

This power conversion device comprises: a semiconductor package that embeds a power semiconductor element and constitutes a power conversion circuit; a smoothing capacitor that is electrically connected to the semiconductor package; a first cooler that is thermally connected to one surface of the semiconductor package by a first thermal path having a first thermal resistance and has a first flow path through which a refrigerant flows; and a second cooler that is thermally connected to the other surface of the semiconductor package by a second thermal path having a second thermal resistance larger than the first thermal resistance and has a second flow path through which the refrigerant flows, wherein the smoothing capacitor is disposed facing the other surface of the semiconductor package with the second cooler interposed therebetween, and the height of the second flow path is smaller than the height of the first flow path.

Description

Power conversion device

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

[0002] For example, Patent Document 1 below discloses a configuration of a power conversion device that can be reduced in height while suppressing an increase in pressure loss.

[0003] Japanese Patent Application Laid-Open No. 2023-059830

[0004] In view of the configuration of Patent Document 1, an object of the present invention is to provide a power conversion device that realizes miniaturization, cost reduction, and low inductance.

[0005] The power conversion device includes a semiconductor package that incorporates a power semiconductor element and constitutes a power conversion circuit, a smoothing capacitor electrically connected to the semiconductor package, a first cooler that is thermally connected to one surface of the semiconductor package by a first heat path having a first thermal resistance and has a first flow path through which a refrigerant flows, and a second cooler that is thermally connected to the other surface of the semiconductor package by a second heat path having a second thermal resistance greater than the first thermal resistance and has a second flow path through which a refrigerant flows. The smoothing capacitor is disposed to face the other surface of the semiconductor package via the second cooler, and the height of the second flow path is smaller than the height of the first flow path.

[0006] A power conversion device that realizes miniaturization, cost reduction, and low inductance can be provided.

[0007] FIG. for explaining the structure of the first cooler of the power conversion device according to an embodiment of the present invention. Cross-sectional view for explaining the configuration of the power conversion device according to an embodiment of the present invention. First modification example. Second modification example. Third modification example. Fourth modification example.

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

[0009] The positions, sizes, shapes, and ranges of the components shown in the drawings may not represent their actual positions, sizes, shapes, and ranges in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, and ranges disclosed in the drawings.

[0010] (An Embodiment and Overall Configuration) (Figures 1 and 2) Figure 1 illustrates the configuration of the first cooler 11 in the power converter 1 shown in Figure 2. Figure 2 shows a cross-sectional view of the power converter 1 as seen along the Y-Y line in Figure 1. Figure 6, described later, is a cross-sectional view of the power converter 1 as seen along the X-X line in Figure 1.

[0011] The power converter 1 comprises a plurality of semiconductor packages 10. Each semiconductor package 10 incorporates a power semiconductor element to form a power conversion circuit. Coolers are provided on both sides of the semiconductor package 10 in the vertical direction (stacking direction), each forming a channel through which a coolant flows. In Figure 2, the cooler provided on the upper side of the semiconductor package 10 is referred to as the first cooler 11, and the cooler provided on the lower side of the semiconductor package 10 via the wiring board 6 is referred to as the second cooler 12. The wiring board 6 has a wiring layer through which DC current flows and is made up of printed circuit boards, ceramic substrates, etc. The semiconductor package 10 is mounted on one side of the wiring board 6, and the second cooler 12 is thermally connected to the other side of the wiring board 6.

[0012] The first cooler 11 has a heat dissipation fin 2, a first channel cover 3, and a frame 4. The heat dissipation fin 2 has a structure in which a plurality of fins are formed on a fin base 2a. The fin base 2a is thermally connected to the semiconductor package 10 via a heat dissipation member 7, thereby cooling the heat generated from the semiconductor package 10. The heat dissipation member 7 is made of a material such as ceramics or resin. The semiconductor package 10 and the heat dissipation member 7 may be directly joined to each other, or they may be indirectly joined using adhesive, soldering, brazing, sintering, TIM (Thermal Interface Material), etc. The first channel cover 3 is made of aluminum, copper, stainless steel, etc. The frame 4 is joined to the first channel cover 3 by brazing, laser welding, adhesive, etc.

[0013] The first cooler 11 has a first flow path 11a through which a refrigerant flows. The fin base 2a is connected to the frame 4 via a sealing member 4a, thereby ensuring the airtightness of the first flow path 11a in the first cooler 11. The first flow path cover 3 is provided so as to cover the fin tips of the heat dissipation fins 2, thereby forming the flow path wall of the first flow path 11a. The first flow path cover 3 may be in the shape of a single plate, or it may be composed of multiple divided members. The sealing member 4a may be any flexible material such as an adhesive or rubber elastic material that can ensure the airtightness of the first flow path 11a. The first cooler 11 is thermally connected to one side of the semiconductor package 10, and the heat path through which heat generated from the semiconductor package 10 moves to the first cooler 11 side is called the first heat path. The first thermal path is, for example, a thermal path through which heat generated from the collector and drain electrodes in the semiconductor package 10 is transferred. Because it directly cools the semiconductor package 10, it has a high heat transfer coefficient and a first thermal resistance that is smaller than the second resistance of the second thermal path described later.

[0014] The second cooler 12 has a second flow path 12a through which the refrigerant flows. The height 12b of the second flow path 12a is smaller than the height 11b of the first flow path 11a, and the second cooler 12 does not have heat dissipation fins 2 in the second flow path 12a, which contributes to cost reduction. The second cooler 12 is thermally connected to the wiring board 6 on one side via a heat dissipation member 7, and thermally connected to the smoothing capacitor 5 on the other side. The second cooler 12 is thermally connected to the other side of the semiconductor package 10, and the heat path through which heat generated from the semiconductor package 10 moves to the second cooler 12 side is called the second thermal path. The second thermal path is the heat path through which heat generated from the emitter and source electrode side of the semiconductor package 10 moves, and because it indirectly cools the semiconductor package 10 via the wiring board 6, it has a high heat transfer coefficient and a second thermal resistance that is greater than the first resistance of the first thermal path described above.

[0015] The smoothing capacitor 5 is positioned opposite the other side of the semiconductor package 10 and the wiring board 6 via the second cooler 12. On the smoothing capacitor 5, a pressure plate 8 is provided on the side opposite to the side that is thermally connected to the second cooler 12. Fastening members 9 (screws, etc.) inserted from both ends of the first flow path cover 3 in the cross section shown in Figure 2 fasten the pressure plate 8. By fastening the fastening members 9 from the first flow path cover 3 to the pressure plate 8 via the frame 4 and the wiring board 6, the first flow path cover 3 is in close contact with the frame 4, ensuring the airtightness of the first flow path 11a, and at the same time, the pressure plate 8 pressurizes the smoothing capacitor 5, thereby ensuring surface pressure of the heat dissipation member 7 on the smoothing capacitor 5 and the wiring board 6.

[0016] To improve the heat dissipation of the power converter 1, it is necessary to ensure sufficient height for the first channel 11a to directly cool the semiconductor package 10 and to ensure sufficient flow velocity of the refrigerant flowing through the first channel 11a. Therefore, the height 12b of the channel of the second cooler 12, which has high thermal resistance, is made smaller than the height 11b of the channel of the first cooler 11, without providing a configuration such as the heat dissipation fins 2 provided on the first cooler 11, thereby increasing the pressure loss of the second cooler 12. This balances the pressure loss between the first cooler 11 and the second cooler 12 while suppressing an increase in the overall thermal resistance, thus ensuring heat dissipation. Furthermore, by reducing the height 12b of the channel of the second cooler 12, the smoothing capacitor 5 can be positioned closer to the wiring board 6. As a result, the length required for the capacitor terminals 5a of the smoothing capacitor 5 to be electrically connected to the wiring board 6 and the semiconductor package 10 via the wiring board 6 can be shortened compared to conventional designs. This enables miniaturization and reduction of inductance.

[0017] (First Modification) (Figure 3) As a modification of the present invention, the power conversion device 1 may be such that the entire semiconductor package 10 is covered and sealed with resin 13. Unlike the above-described embodiment, the semiconductor package 10 is directly thermally connected to the second cooler 12 via the heat dissipation member 7. Since the resin 13 has high thermal conductivity, heat transfer from the semiconductor package 10 to the first cooler 11 and the second cooler 12 is ensured even when the semiconductor package 10 is sealed with resin. By using such a resin 13, it is not necessary to provide an insulating layer such as a ceramic plate, so costs can be reduced and the process can be simplified.

[0018] The semiconductor package 10 is provided with leads that electrically conduct to the power semiconductor element 20 on both sides of the power semiconductor element 20. The leads include a first lead 10a electrically connected to one side of the power semiconductor element 20 and a second lead 10b electrically connected to the other side of the power semiconductor element 20. The second lead 10b has a terminal 10c for electrically connecting to the capacitor terminal 5a of the smoothing capacitor 5. The semiconductor package 10 is resin-sealed such that the surface of the first lead 10a that is thermally connected to the first cooler 11 side is exposed to the outside of the resin 13. As a result, a portion of the first lead 10a is exposed from the resin 13, while the second lead 10b is not exposed from the resin 13. This configuration makes the thermal resistance on the second lead 10b side greater than the thermal resistance on the first lead 10a side, thus achieving the same effects as in the embodiment described above.

[0019] (Second Modification) (Figure 4) As a modification of the present invention, the second cooler 12 described above may be formed as a capacitor-integrated cooler 12c integrated with the smoothing capacitor 5. The capacitor-integrated cooler 12c includes a fastening portion with the fastening member 9 and a contact portion with the smoothing capacitor 5 that is formed by extending in the planar direction. The capacitor-integrated cooler 12c has a contact surface 12d in the portion that contacts the smoothing capacitor 5. The thickness of the fastening portion with the fastening member 9 of the capacitor-integrated cooler 12c is greater than the thickness formed in the contact surface 12d. In this way, the capacitor-integrated cooler 12c can realize a simpler water channel structure than the first cooler 11, and the warping of the entire capacitor-integrated cooler 12c can be reduced, ensuring rigidity even when the capacitor-integrated cooler 12c is made thinner.

[0020] Furthermore, since the capacitor-integrated cooler 12c is formed by methods such as die casting or casting, costs can be reduced. Also, because the thickness of the part of the capacitor-integrated cooler 12c that contacts the smoothing capacitor 5 is small, a pressure loss balance with the first cooler 11 and inductance reduction can be achieved, similar to the embodiment described above.

[0021] (Third Modification) (Figure 5) As a modification of the present invention, the capacitor-integrated cooler 12c described above may include a second channel cover 12e formed to cover the second channel 12a. The second channel cover 12e is formed by a manufacturing method such as pressing, die casting, or casting. The smoothing capacitor 5 may also be provided with a simpler heat dissipation fin 5b in the second channel 12a than the heat dissipation fin 2 provided on the first cooler 11. With this configuration, the capacitor-integrated cooler 12c can be integrated with the smoothing capacitor 5 while reducing thickness, reducing costs, and improving the heat dissipation of the smoothing capacitor 5, and furthermore, it becomes easier to mount the heat dissipation fin 5b on the second channel 12a.

[0022] (Fourth Modification) (Figure 6) As a modification of the present invention, the power converter 1 may have a cooling structure that is divided in accordance with the semiconductor package 10. Although not shown, a smoothing capacitor 5 is provided on the lower side of the second cooler 12 as described above, and as with the above embodiments and modifications, the smoothing capacitor 5 is cooled by contact with the second cooler 12. The heat dissipation fins 2 of the first cooler 11 are formed by being divided in accordance with each upper and lower arm of the semiconductor package 10. The fin base 2a is displaceable in the stacking direction (up and down direction) relative to the frame 4 and the first flow channel cover 3. The first flow channel cover 3 has a pressing portion 3a formed in a convex shape, and when the fastening member 9 (Figure 2, etc.) is fastened, the pressing portion 3a is pressed against the heat dissipation fins 2 and deforms. As a result, even if the heights of the arms of the semiconductor package 10 vary, the heat dissipation fins 2 can follow each semiconductor package 10. In addition, the heat dissipation member 7 that is thermally connected to the semiconductor package 10 can be made as thin as possible, and the thermal resistance can be reduced.

[0023] The embodiments and modifications of the present invention described above provide the following advantages. Conventionally, in power conversion devices, movable fins or the like have been used in the water channel structure to absorb variations in the height of each semiconductor package. However, in this case, the thickness of the cooling channel becomes large, resulting in increased costs. Furthermore, regarding the arrangement of smoothing capacitors in power conversion devices, if they are to be placed outside the channel structure to avoid the aforementioned variations, the terminals for connecting the smoothing capacitors to the semiconductor packages must be made longer, resulting in increased inductance. In addition, the heat dissipation performance of the main cooling channel (first cooler 11 side) decreases, making it necessary to consider the pressure loss balance between the channels formed on both sides of the semiconductor package 10.

[0024] Therefore, in embodiments and modifications of the present invention, in the semiconductor package 10, by making the first flow path 11a of the first cooler 11 as large as possible and making the second flow path 12a of the second cooler 12, which has high thermal resistance, small, a cooling structure that improves heat dissipation while considering the pressure loss balance can be provided. Furthermore, the step-following ability of the semiconductor package 10 enables the securing of surface pressure of the heat dissipation member and the securing of cooling performance. In addition, miniaturization, cost reduction, and low inductance can be achieved.

[0025] According to the embodiments of the present invention described above, the following effects and advantages are achieved.

[0026] (1) The power converter 1 comprises a semiconductor package 10 that incorporates a power semiconductor element 20 to constitute a power conversion circuit, a smoothing capacitor 5 electrically connected to the semiconductor package 10, a first cooler 11 thermally connected to one side of the semiconductor package 10 by a first thermal path having a first thermal resistance and having a first flow path 11a through which a coolant flows, and a second cooler 12 thermally connected to the other side of the semiconductor package 10 by a second thermal path having a second thermal resistance greater than the first thermal resistance and having a second flow path 12a through which a coolant flows, the smoothing capacitor 5 is positioned facing the other side of the semiconductor package 10 via the second cooler 12, and the height 12b of the second flow path is smaller than the height of the first flow path 11a. In this way, a power converter 1 that is miniaturized, low-cost and has low inductance can be provided.

[0027] (2) The power converter 1 is equipped with a wiring board 6 having a DC wiring layer, the semiconductor package 10 is mounted on one side of the wiring board 6, the second cooler 12 is thermally connected to the other side of the wiring board 6, and the smoothing capacitor 5 is positioned facing the other side of the wiring board 6 via the second cooler 12. This configuration contributes to miniaturization, cost reduction, and low inductance of the power converter 1.

[0028] (3) The semiconductor package 10 is provided with leads that electrically conduct to the power semiconductor element 20 on both sides of the power semiconductor element 20, and the leads include a first lead 10a electrically connected to one side of the power semiconductor element 20 and a second lead 10b electrically connected to the other side of the power semiconductor element 20, and the semiconductor package 10 is resin-sealed so that a part of the first lead 10a is exposed. In this way, even when the wiring board 6 is not used, it is possible to similarly contribute to miniaturization, cost reduction and low inductance of the power conversion device 1.

[0029] (4) The second cooler 12 is formed integrally with the smoothing capacitor 5, and in the second cooler 12 (12c), the thickness of the fastening portion with the fastening member 9 is greater than the thickness of the contact portion with the smoothing capacitor 5 which is formed by extending in the planar direction. This reduces the cost of the power converter 1.

[0030] (5) The second cooler 12 is provided with a second channel cover 12e that covers the second channel 12a, and the smoothing capacitor 5 is provided with heat dissipation fins 5b that are placed in the second channel 12a. This makes it possible to improve the mountability of the heat dissipation fins 5b to the second cooler 12.

[0031] (6) The first cooler 11 is equipped with heat dissipation fins 2 provided on each of the upper and lower arms of the semiconductor package 10. This makes it possible to achieve similar miniaturization, cost reduction, and low inductance for multiple semiconductor packages 10.

[0032] It should be noted that the present invention is not limited to the embodiments described above, and various modifications and combinations of other configurations can be made without departing from the spirit of the invention. Furthermore, the present invention is not limited to having all the configurations described in the embodiments described above, and may also include configurations in which some of those configurations are omitted.

[0033] 1 Power converter 2 Heat dissipation fin 2a Fin base 3 First channel cover 3a Pressing part 4 Frame 4a Sealing member 5 Smoothing capacitor 5a Capacitor terminal 5b Heat dissipation fin 6 Wiring board 7 Heat dissipation member 8 Pressure plate 9 Fastening member 10 Semiconductor package 10a First lead 10b Second lead 10c Terminal 11 First cooler 11a First channel 11b Height of the first channel 12 Second cooler 12a Second channel 12b Height of the second channel 12c Capacitor-integrated cooler 12d Contact surface with smoothing capacitor 12e Second channel cover 13 Resin 20 Power semiconductor element

Claims

1. A power conversion device comprising: a semiconductor package that incorporates a power semiconductor element to constitute a power conversion circuit; a smoothing capacitor electrically connected to the semiconductor package; a first cooler thermally connected to one side of the semiconductor package by a first thermal path having a first thermal resistance and having a first flow path through which a coolant flows; and a second cooler thermally connected to the other side of the semiconductor package by a second thermal path having a second thermal resistance greater than the first thermal resistance and having a second flow path through which a coolant flows, wherein the smoothing capacitor is positioned opposite the other side of the semiconductor package via the second cooler, and the height of the second flow path is smaller than the height of the first flow path.

2. A power conversion device according to claim 1, comprising a wiring board having a DC wiring layer, wherein the semiconductor package is mounted on one side of the wiring board, the second cooler is thermally connected to the other side of the wiring board, and the smoothing capacitor is arranged opposite the other side of the wiring board via the second cooler.

3. A power conversion device according to claim 1, wherein the semiconductor package comprises leads that electrically conduct to the power semiconductor element on both sides of the power semiconductor element, the leads include a first lead electrically connected to one side of the power semiconductor element and a second lead electrically connected to the other side of the power semiconductor element, and the semiconductor package is resin-sealed such that a portion of the first lead is exposed.

4. A power conversion device according to claim 1, wherein the second cooler is formed integrally with the smoothing capacitor, and in the second cooler, the thickness of the fastening portion with the fastening member is greater than the thickness of the contact portion with the smoothing capacitor, which is formed by extending in the planar direction.

5. A power conversion device according to claim 1, wherein the second cooler comprises a second flow path cover that covers the second flow path, and the smoothing capacitor comprises heat dissipation fins disposed within the second flow path.

6. A power conversion device according to claim 1, wherein the first cooler comprises heat dissipation fins provided for each upper and lower arm of the semiconductor package.

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