Power module and method for manufacturing the same

Abstract

To provide a method for manufacturing a power module that allows the dispersion medium, which volatilizes when sintering metal particles in a sintering material paste, to escape to the outside. [Solution] A method for manufacturing a power module, comprising the steps of: applying a sintered material paste containing metal particles and a dispersion medium to a sintered material paste application area on one surface of a substrate; mounting a semiconductor element on the sintered material paste; and electrically connecting the semiconductor element to the substrate by volatilizing the dispersion medium in the sintered material paste and sintering the metal particles together, wherein the sintered material paste application area has a liquid-repellent portion that is liquid-repellent to the sintered material paste, and the liquid-repellent portion extends from within the sintered material paste application area to the outer edge.

Description

Technical Field

[0001] The present disclosure relates to a power module and a method for manufacturing the same.

Background Art

[0002] Power modules are used in various fields such as automobiles, railways, power supply equipment, and industrial equipment. In a power module, semiconductor elements are mounted on a substrate having a metal layer. The semiconductor elements are electrically connected to the metal layer using a sintering material paste such as copper paste or silver paste (see, for example, Patent Document 1 below).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of connection using a sintering material paste, when the dispersion medium (and a reducing agent used as necessary; the same applies hereinafter) in the sintering material paste is volatilized by heating, metal particles such as copper particles and silver particles are sintered to form a sintered layer. At this time, the volatilized dispersion medium may remain in the sintered layer to form voids, which may cause problems in the connection of the semiconductor elements.

[0005] An object of the present disclosure is to provide a method for manufacturing a power module capable of discharging to the outside a dispersion medium that volatilizes when metal particles of a sintering material paste are sintered.

Means for Solving the Problems

[0006] The present disclosure includes the following aspects. [1] A method for manufacturing a power module, comprising the steps of: applying a sintered material paste containing metal particles and a dispersion medium to a sintered material paste coating area on one surface of a substrate; mounting a semiconductor element on the sintered material paste; and electrically connecting the semiconductor element to the substrate by volatilizing the dispersion medium in the sintered material paste and sintering the metal particles together, wherein the sintered material paste coating area has a liquid-repellent portion that is liquid-repellent to the sintered material paste, and the liquid-repellent portion extends from within the sintered material paste coating area to the outer edge. [2] The liquid-repellent portion is made of a material such that the contact angle of the sintered paste with the liquid-repellent portion is 50° or more, as described in [1]. [3] The liquid-repellent portion has irregularities such that the contact angle of the sintered material paste with the liquid-repellent portion is 50° or more. The method for manufacturing a power module according to [1]. [4] A method for manufacturing a power module according to any one of [1] to [3], wherein the liquid-repellent portion extends within the sintered material paste application area from one outer edge to the other outer edge of the sintered material paste application area. [5] A method for manufacturing a power module according to any one of [1] to [4], wherein the liquid-repellent portion extends in a grid or honeycomb pattern within the sintered material paste application area.

[0007] [6] A power module comprising a substrate, a sintered layer of metal particles provided on one surface of the substrate, and a semiconductor element electrically connected to the substrate via the sintered layer, wherein a cavity is formed in the sintered layer, extending along the one surface of the substrate so as to communicate the inside and outside of the sintered layer. [7] The power module according to [6], wherein the cavity extends along the one surface of the substrate so as to penetrate the sintered layer. [8] The power module according to [6] or [7], wherein the cavity extends in a grid or honeycomb pattern along the one surface of the substrate.

[0008] [9] A method for manufacturing a power module, comprising the steps of: applying a sintered material paste containing metal particles and a dispersion medium to a sintered material paste application area on one surface of a heat sink; mounting a semiconductor package on the sintered material paste; and connecting the semiconductor package to the heat sink by volatilizing the dispersion medium in the sintered material paste and sintering the metal particles together, wherein the sintered material paste application area has a liquid-repellent portion that is liquid-repellent to the sintered material paste, and the liquid-repellent portion extends from within the sintered material paste application area to the outer edge.

[10] The liquid-repellent portion is made of a material such that the contact angle of the sintered paste with the liquid-repellent portion is 50° or more, as described in [9], for manufacturing a power module.

[11] The liquid-repellent portion has irregularities such that the contact angle of the sintered material paste with the liquid-repellent portion is 50° or more. The method for manufacturing a power module according to [9].

[12] A method for manufacturing a power module according to any one of [9] to

[11] , wherein the liquid-repellent portion extends within the sintered material paste application area from one outer edge to the other outer edge of the sintered material paste application area.

[13] A method for manufacturing a power module according to any one of [9] to

[12] , wherein the liquid-repellent portion extends in a grid or honeycomb pattern within the sintered material paste application area.

[0009]

[14] A power module comprising a heat sink, a sintered layer of metal particles provided on one surface of the heat sink, and a semiconductor package connected to the heat sink via the sintered layer, wherein a cavity is formed in the sintered layer, extending along the one surface of the heat sink so as to communicate the inside and outside of the sintered layer.

[15] The power module according to

[14] , wherein the cavity extends along the one surface of the heat sink so as to penetrate the sintered layer.

[16] The power module according to

[14] or

[15] , wherein the cavity extends in a grid or honeycomb pattern along the one surface of the heat sink. [Effects of the Invention]

[0010] From one perspective, this method provides a power module manufacturing method that allows the dispersion medium, which volatilizes when sintering metal particles in a sintering paste, to escape to the outside. This manufacturing method can suppress the generation of unexpected (undesirable) voids caused by the dispersion medium. Furthermore, having a path to release the dispersion medium to the outside allows the time required for the dispersion medium to volatilize (drying time) to be shortened. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a schematic plan view showing the coating process in one embodiment. [Figure 2] Figure 2(a) is a schematic plan view showing the mounting and connection processes in one embodiment, and Figure 2(b) is a schematic cross-sectional view along the line IIb-IIb in Figure 2(a). [Figure 3] Figure 3 is a schematic plan view showing examples of other shapes of the liquid-repellent area. [Figure 4] Figure 4 is a schematic plan view showing examples of other shapes of the liquid-repellent area. [Figure 5] Figure 5 is a schematic plan view showing examples of other shapes of the liquid-repellent area. [Figure 6] Figure 6 is a schematic plan view showing the coating process in another embodiment. [Figure 7] Figure 7(a) is a schematic plan view showing the mounting and connection processes in another embodiment, and Figure 7(b) is a schematic cross-sectional view along the line VIIb-VIIb in Figure 7(a). [Modes for carrying out the invention]

[0012] One embodiment includes a step of applying a sintering material paste containing metal particles and a dispersion medium to a sintering material paste application region on one surface of a substrate (application step), a step of mounting a semiconductor element on the sintering material paste (mounting step), and a step of volatilizing the dispersion medium in the sintering material paste and sintering the metal particles together to electrically connect the semiconductor element to the substrate (connection step), which is a method for manufacturing a power module.

[0013] FIG. 1 is a schematic plan view showing an application step in one embodiment. The substrate 1 used in the application step may have an insulating member (insulating substrate) 2 and a metal member (metal layer) 3 provided on the insulating member. The substrate 1 may have a plurality of metal members (metal layers) arranged at intervals from each other. As the constituent material of the insulating member 2, ceramic can be used. Examples of the constituent material of the insulating member 2 include aluminum oxide, aluminum nitride, silicon nitride, etc. Examples of the metal constituting the metal member 3 include copper, aluminum, etc.

[0014] As shown in FIG. 1(a), the substrate 1 may have a sintering material paste application region (application surface) R1 on which the sintering material paste is applied within the plane of the metal member 3. The substrate 1 may have one sintering material paste application region R1, or may have two or more. When the substrate 1 has a plurality of metal members 3, the substrate 1 may have a sintering material paste application region R1 within the plane of a part or all of the plurality of metal members 3.

[0015] In this sintering material paste application region R1, a liquid-repellent portion 4 having liquid repellency with respect to the sintering material paste is formed. Having liquid repellency with respect to the sintering material paste means that when the sintering material paste is applied to the sintering material paste application region R1, the contact angle of the sintering material paste with respect to the liquid-repellent portion 4 becomes 50° or more. The liquid-repellent portion 4 may be a liquid-repellent portion such that the contact angle is preferably 60° or more, 70° or more, 80° or more, or 90° or more.

[0016] In one embodiment, the liquid-repellent portion 4 may be formed of a material having liquid repellency (low affinity) with respect to the sintering material paste, that is, a material having a contact angle of 50° or more (preferably 60° or more, 70° or more, 80° or more, or 90° or more) with respect to the liquid-repellent portion 4 of the sintering material paste. Specifically, the liquid-repellent portion 4 may be formed of at least one selected from the group consisting of graphite, graphene, and polytetrafluoroethylene. In another embodiment, the liquid-repellent portion 4 may have irregularities (fine irregularities) that exhibit liquid repellency with respect to the sintering material paste, that is, irregularities (fine irregularities) having a contact angle of 50° or more (preferably 60° or more, 70° or more, 80° or more, or 90° or more) with respect to the liquid-repellent portion 4 of the sintering material paste. In one embodiment, as shown in FIG. 1(a), the liquid-repellent portion 4 extends in a lattice pattern within the sintering material paste application region R1.

[0017] The ratio of the liquid-repellent portion 4 in the sintering material paste application region R1 may be set in consideration of the balance between ensuring the degassing path and ensuring the adhesion to the substrate of the semiconductor element. The larger the ratio, the easier it is to ensure the degassing path, and the smaller the ratio, the easier it is to ensure the adhesion. The ratio may be 5 area % or more, 10 area % or more, or 20 area % or more, and may be 60 area % or less, 40 area % or less, or 30 area % or less.

[0018] In the application step, as shown in FIG. 1(b), a sintering material paste 5 containing metal particles and a dispersion medium is applied to the sintering material paste application region R1. The sintering material paste application region R1 may be a region wider than the semiconductor element mounting region, including the semiconductor element mounting region where the semiconductor element is mounted in a subsequent mounting step and its periphery.

[0019] The metal particles may be particles of a single metal, particles of an alloy, or the like. The surface of the metal particles may be coated with an organic compound. Examples of the metal element contained in the metal particles include copper, silver, gold, titanium, nickel, palladium, aluminum, and the like. The metal particles may preferably be copper particles or silver particles. The dispersion medium may be a known dispersion medium used in a sintering material paste (copper paste, silver paste, etc.).

[0020] The viscosity of the sintered material paste is preferably as low as possible from the viewpoint of improving workability (ease of application, etc.). The viscosity of the sintered material paste at 25°C may be 10 Pa·s or more or 20 Pa·s or more, and may be 40 Pa·s or less or 30 Pa·s or less. In the manufacturing method according to this embodiment, since the liquid-repellent portion 4 described above is formed, even when the viscosity of the sintered material paste is low, the liquid-repellent portion 4 appropriately repels the sintered material paste, and the shape of the sintered material paste after application is suitably maintained.

[0021] Figure 2(a) is a schematic plan view showing the mounting process and connection process in one embodiment, and Figure 2(b) is a schematic cross-sectional view along the line IIb-IIb in Figure 2(a). In the mounting process following the coating process, as shown in Figures 2(a) and (b), a semiconductor element 6 is mounted on the sintered material paste 5 applied in the sintered material paste coating area (semiconductor element mounting area). The semiconductor element 6 may be a known semiconductor element used in a power module.

[0022] In the connection process following the mounting process, heating is performed to volatilize the dispersion medium in the sintered material paste 5 and to sinter the metal particles together. As a result, as shown in Figures 2(a) and (b), a sintered layer 7 is formed where the metal particles are sintered together in the area where the sintered material paste 5 is applied, and the semiconductor element 6 is electrically connected to the metal member 3 of the substrate 1 via this sintered layer 7. The heating temperature and heating time in the connection process may be set appropriately according to the composition of the sintered material paste 5 (type of metal particles, etc.). The heating in the connection process may be a one-stage or two-stage heating. In the case of two-stage heating, a portion of the dispersion medium may be volatilized in the first stage of heating (preheating), and the remainder of the dispersion medium may be volatilized in the second stage of heating.

[0023] In the manufacturing method described above, since the liquid-repellent portion 4 is formed in the sintered material paste application area R1, the volatile dispersion medium can be released to the outside when the metal particles of the sintered material paste 5 are sintered together during the connection process. More specifically, as shown in Figure 2(b), since the sintered material paste 5 is not easily applied to the liquid-repellent portion 4, the sintering of the metal particles and the volatilization of the dispersion medium proceed with a space S1 secured on the liquid-repellent portion 4. As a result, this space S1 functions as a degassing path for the volatilized dispersion medium to escape to the outside.

[0024] As shown in Figures 2(a) and (b), another embodiment of the present disclosure is a power module 10 comprising a substrate 1, a sintered layer 7 of metal particles provided on one surface of the substrate 1, and a semiconductor element 6 electrically connected to the substrate 1 via the sintered layer 7. Details of the substrate 1 and the semiconductor element 6 are the same as those described in the manufacturing method described above.

[0025] The sintered layer 7 is a layer formed by sintering the metal particles described above. The details of the metal particles are the same as those described in the manufacturing method described above. The sintered layer 7 has cavities S1 that extend along one surface (metal member surface) of the substrate 1 so as to connect the inside and outside of the sintered layer 7. The cavities S1 may extend linearly, and may extend in shapes such as straight lines, curves, or bent lines. In one embodiment, the cavities S1 may extend along one surface (metal member surface) of the substrate 1 so as to penetrate the sintered layer 7. In another embodiment, the cavities S1 may extend in a grid or honeycomb pattern along one surface (metal member surface) of the substrate 1. In each embodiment, the cavities S1 may extend substantially parallel to one surface (metal member surface) of the substrate 1. The cavities S1 may correspond to the degassing paths described in the manufacturing method described above.

[0026] In the above embodiment, the liquid-repellent portion 4 (cavity S1) extends in a grid pattern, but the shape of the liquid-repellent portion is not limited to a grid pattern. The liquid-repellent portion may be any portion that extends from within the sintered material paste application area R1 to the outer edge so that the dispersion medium that volatilizes during the connection process can escape to the outside. In another embodiment, the liquid-repellent portion may extend in a linear shape, and may extend in a straight line, curved line, bent line, or the like. Specific examples of other shapes of the liquid-repellent portion will be described below.

[0027] Figures 3-5 are schematic plan views showing examples of other shapes of the liquid-repellent portion. In another embodiment, as shown in Figure 3(a), the liquid-repellent portion 4A may be a straight line extending from a point within the sintered material paste application area R1 to a point on the outer edge. In yet another embodiment, as shown in Figure 3(b), the liquid-repellent portion 4B may be a straight line extending from a point within the sintered material paste application area R1 to two opposing points on the outer edge (in other words, extending from one outer edge to the other outer edge). In these embodiments as well, compared to cases where the liquid-repellent portions 4A and 4B are not formed, the dispersion medium that volatilizes during the connection process can be released to the outside. In the embodiments shown in Figures 3(a) and (b), the liquid-repellent portions 4A and 4B may extend in a curved shape or in a bent shape, respectively.

[0028] In another embodiment, as shown in Figures 4(a) and (b), the liquid-repellent portion may be composed of a plurality of liquid-repellent portions extending in a straight line parallel to each other. In such an embodiment, for example, each of the plurality of liquid-repellent portions 4C may start from a point within the sintered material paste application area R1 and extend from that starting point to a point on the outer edge, as shown in Figure 4(a). Alternatively, for example, each of the plurality of liquid-repellent portions 4D may start from a point within the sintered material paste application area R1 and extend from that starting point to two opposing points on the outer edge (in other words, they may extend from one outer edge to another), as shown in Figure 4(b). In these embodiments as well, compared to cases where the liquid-repellent portions 4C and 4D are not formed, the dispersion medium that volatilizes during the connection process can be released to the outside.

[0029] In another embodiment, as shown in Figure 5, the liquid-repellent portion 4E may extend in a honeycomb pattern within the sintered material paste application area R1. In this case, the sintered material paste is applied to the hexagonal portion within the sintered material paste application area R1 where the liquid-repellent portion 4E is not formed. In this embodiment, since the liquid-repellent portion 4E is comprehensively formed throughout the entire sintered material paste application area R1, the dispersion medium that volatilizes during the connection process can be more effectively released to the outside.

[0030] Another embodiment of the present disclosure is a method for manufacturing a power module, comprising the steps of: applying a sintered material paste containing metal particles and a dispersion medium to a sintered material paste application area on one surface of a heat sink (application step); mounting a semiconductor package on the sintered material paste (mounting step); and connecting the semiconductor package to the heat sink by volatilizing the dispersion medium in the sintered material paste and sintering the metal particles together (connection step).

[0031] Figure 6 is a schematic plan view showing the coating process in another embodiment. The heat sink 11 used in the coating process may be a known heat sink. Examples of constituent materials for the heat sink 11 include copper and aluminum. The heat sink 11 has a sintered material paste coating area (coated surface) R2 on a part of the surface on which the semiconductor package is mounted, where the sintered material paste is applied. The heat sink may have a sintered material paste coating area (coated surface) on the entire surface on which the semiconductor package is mounted.

[0032] In this sintered material paste application region R2, a liquid-repellent portion 14 is formed that is liquid-repellent to the sintered material paste. The details of the liquid-repellent portion 14 are the same as those described in the above embodiment.

[0033] In the coating process, as shown in Figure 6(b), a sintered material paste 15 containing metal particles and a dispersion medium is applied to the sintered material paste coating area R2. The sintered material paste coating area R2 may be a wider area than the semiconductor package mounting area, including the semiconductor package mounting area and its surroundings where the semiconductor package will be mounted in the subsequent mounting process. The details of the sintered material paste are the same as those described in the above embodiment.

[0034] Figure 7(a) is a schematic plan view showing the mounting and connection processes in another embodiment, and Figure 7(b) is a schematic cross-sectional view along the line VIIb-VIIb in Figure 7(a). In the mounting process following the coating process, a semiconductor package is mounted on the sintered material paste 15 applied to the sintered material paste coating area (semiconductor package mounting area) R2. The semiconductor package 16 may be a known semiconductor package used in a power module. The semiconductor package 16 may, for example, include a base plate, a substrate bonded to the base plate, a semiconductor element bonded to the substrate, a case arranged on the base plate so as to cover the substrate and the semiconductor element, and a sealing material that fills the space inside the case. Details of the substrate and semiconductor element are the same as those described in the above embodiment.

[0035] In the connection process following the mounting process, heating is performed to volatilize the dispersion medium in the sintered material paste 15 and to sinter the metal particles together. This forms a sintered layer 17, through which the sintered metal particles are connected to the heat sink 11. The heating temperature and heating time in the connection process may be set appropriately according to the composition of the sintered material paste 15 (type of metal particles, etc.).

[0036] In the manufacturing method described above, since the liquid-repellent portion 14 is formed in the sintered material paste application area R2, the volatile dispersion medium can be released to the outside when the metal particles of the sintered material paste 15 are sintered together during the connection process. More specifically, as shown in Figure 7(b), since the sintered material paste 15 is not easily applied to the liquid-repellent portion 14, the sintering of the metal particles and the volatilization of the dispersion medium proceed with a space S2 secured on the liquid-repellent portion 14. As a result, this space S2 functions as a degassing path for the volatilized dispersion medium to escape to the outside.

[0037] The heat sink 11 and the semiconductor package 16 are connected over a large area, which increases the amount of sintering paste 15 required for connection, and also increases the amount of dispersion medium that volatilizes when sintering the metal particles together, making it easy for voids to form due to the volatilized dispersion medium. In contrast, with the manufacturing method described above, the liquid-repellent portion 14 is formed, and the space S2 on the liquid-repellent portion 14 functions as a degassing path for the volatilized dispersion medium to escape to the outside, thus effectively suppressing the generation of voids.

[0038] As shown in Figures 7(a) and (b), another embodiment of the present disclosure is a power module 20 comprising a heat sink 11, a sintered layer 17 of metal particles provided on one surface of the heat sink 11, and a semiconductor package 16 connected to the heat sink 11 via the sintered layer 17. Details of the heat sink 11 and the semiconductor package 16 are the same as those described in the manufacturing method described above.

[0039] The sintered layer 17 is a layer formed by sintering the metal particles described above. The details of the metal particles are the same as those described in the manufacturing method described above. A cavity S2 is formed in the sintered layer 17, extending along one surface of the heat sink 11 (the surface on which the semiconductor package 16 is mounted) so as to connect the inside and outside of the sintered layer 17. The cavity S2 may extend linearly, and may extend in a straight line, curved line, bent line, or other shape. In one embodiment, the cavity S2 may extend along one surface of the heat sink 11 (the surface on which the semiconductor package 16 is mounted) so as to penetrate the sintered layer 17. In another embodiment, the cavity S2 may extend in a grid or honeycomb shape along one surface of the heat sink 11 (the surface on which the semiconductor package 16 is mounted). In each embodiment, the cavity S2 may extend substantially parallel to one surface of the heat sink 11 (the surface on which the semiconductor package is mounted). The cavity S2 may be a cavity corresponding to the degassing path described in the manufacturing method described above. [Explanation of Symbols]

[0040] 1...Substrate, 2...Insulating material, 3...Metal material, 4, 4A, 4B, 4C, 4D, 4E, 14...Liquid-repellent area, 5, 15...Sintered material paste, 6...Semiconductor element, 7, 17...Sintered layer, 10, 20...Power module, 11...Heat sink, 16...Semiconductor package, R1, R2...Sintered material paste application area, S1, S2...Space (cavity).

Claims

1. A step of applying a sintered material paste containing metal particles and a dispersion medium to a sintered material paste coating area on one surface of a substrate, A step of mounting a semiconductor element on the sintered material paste, The process includes a step of volatilizing the dispersion medium in the sintered paste and sintering the metal particles together to electrically connect the semiconductor element to the substrate, A method for manufacturing a power module, wherein the sintered material paste application area has a liquid-repellent portion that is liquid-repellent to the sintered material paste, and the liquid-repellent portion extends from within the sintered material paste application area to the outer edge.

2. The method for manufacturing a power module according to claim 1, wherein the liquid-repellent portion is formed of a material such that the contact angle of the sintered material paste with respect to the liquid-repellent portion is 50° or more.

3. The method for manufacturing a power module according to claim 1, wherein the liquid-repellent portion has irregularities such that the contact angle of the sintered material paste with the liquid-repellent portion is 50° or more.

4. The method for manufacturing a power module according to any one of claims 1 to 3, wherein the liquid-repellent portion extends within the sintered material paste application area from one outer edge to the other outer edge of the sintered material paste application area.

5. The method for manufacturing a power module according to any one of claims 1 to 3, wherein the liquid-repellent portion extends in a grid or honeycomb pattern within the sintered material paste application area.

6. circuit board and A sintered layer of metal particles is provided on one surface of the substrate, A semiconductor element electrically connected to the substrate via the sintered layer, Equipped with, A power module in which a cavity is formed in the sintered layer, extending along one surface of the substrate so as to connect the inside and outside of the sintered layer.

7. The power module according to claim 6, wherein the cavity extends along the one surface of the substrate so as to penetrate the sintered layer.

8. The power module according to claim 6 or 7, wherein the cavity extends in a grid or honeycomb pattern along one surface of the substrate.

9. A step of applying a sintered material paste containing metal particles and a dispersion medium to a sintered material paste application area on one surface of a heat sink, A step of mounting a semiconductor package on the sintered material paste, The process includes volatilizing the dispersion medium in the sintered paste and sintering the metal particles together to connect the semiconductor package to the heat sink, A method for manufacturing a power module, wherein the sintered material paste application area has a liquid-repellent portion that is liquid-repellent to the sintered material paste, and the liquid-repellent portion extends from within the sintered material paste application area to the outer edge.

10. The method for manufacturing a power module according to claim 9, wherein the liquid-repellent portion is formed of a material such that the contact angle of the sintered material paste with respect to the liquid-repellent portion is 50° or more.

11. The method for manufacturing a power module according to claim 9, wherein the liquid-repellent portion has irregularities such that the contact angle of the sintered material paste with the liquid-repellent portion is 50° or more.

12. The method for manufacturing a power module according to any one of claims 9 to 11, wherein the liquid-repellent portion extends within the sintered material paste application area from one outer edge to the other outer edge of the sintered material paste application area.

13. The method for manufacturing a power module according to any one of claims 9 to 11, wherein the liquid-repellent portion extends in a grid or honeycomb pattern within the sintered material paste application area.

14. heatsink and A sintered layer of metal particles is provided on one surface of the heat sink, A semiconductor package connected to the heat sink via the sintered layer, Equipped with, A power module in which a cavity is formed in the sintered layer, extending along one surface of the heat sink so as to connect the inside and outside of the sintered layer.

15. The power module according to claim 14, wherein the cavity extends along the one surface of the heat sink so as to penetrate the sintered layer.

16. The power module according to claim 14 or 15, wherein the cavity extends in a grid or honeycomb pattern along one surface of the heat sink.

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