Semiconductor module

Abstract

To prevent damage to a wiring board due to deformation during fastening of the heat dissipation base while ensuring heat dissipation in a semiconductor module.SOLUTION: In an energy conversion device 100, a plurality of wiring boards 10 on which semiconductor elements 14 and 15 are mounted and a heat dissipation base 20 are joined by a first bonding material S1. The heat dissipation base is warped so that a second surface 22, which is located on the opposite side of a first surface 21 to which the plurality of wiring boards is bonded, is a convex curved surface. At least several corners of the heat dissipation base are provided with fastening holes 23. A bonding surface 16 facing the heat dissipation base of each of the plurality of wiring boards includes a first corner 16a that is bonded to the heat dissipation base by the first bonding material and a second corner 16b that is not bonded to the heat dissipation base by the first bonding material. The first bonding material joins the plurality of wiring boards and the heat dissipation base, so that the second corner of the wiring board is located at the four corners A1 of the wiring board area A, which includes the entire plurality of wiring boards.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a semiconductor module including a plurality of wiring boards on which semiconductor elements are mounted, and a heat dissipation base to which the plurality of wiring boards are joined. [Background technology]

[0002] Semiconductor modules used in power conversion devices such as inverter devices include those in which a heat dissipation base joined to a wiring board is attached to a cooler (see, for example, Patent Documents 1 to 7). Some heat dissipation bases used in this type of semiconductor module have a second surface, opposite to a first surface to which the wiring board is joined, that faces the cooler and is shaped to be a convex curved surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-141023 A [Patent Document 2] JP 2015-72958 A [Patent Document 3] JP 2015-72957 A [Patent Document 4] JP 2004-134746 A [Patent Document 5] Patent Publication No. 2021-90030 [Patent Document 6] JP 2017-79217 A [Patent Document 7] JP 2017-120888 A Summary of the Invention [Problem to be solved by the invention]

[0004] A wiring board is bonded to the first surface of the heat dissipation base with a bonding material. The heat dissipation base, whose second surface is a convex curved surface, deforms in a direction that changes the second surface from a convex curved surface to a flat surface when it is attached to a cooler. This deformation of the heat dissipation base causes stress to concentrate on the wiring board, which may damage the wiring board. One way to alleviate the stress on the wiring board is to reduce the bonding area of ​​the bonding material, but this would result in a deterioration of heat dissipation.

[0005] In one aspect, an object of the present invention is to provide a semiconductor module capable of preventing damage to a wiring board due to deformation when a heat dissipation base is fastened, while ensuring heat dissipation performance. [Means for solving the problem]

[0006] A semiconductor module according to one embodiment comprises a plurality of wiring boards on which semiconductor elements are mounted, a heat dissipation base having a first surface to which the plurality of wiring boards are joined and a second surface located opposite the first surface, and a first bonding material that bonds the plurality of wiring boards to the heat dissipation base, the heat dissipation base being warped so that the second surface is a convex curved surface, and at least a plurality of corners of the heat dissipation base are provided with fastening holes, and the bonding surface of each of the plurality of wiring boards facing the heat dissipation base includes a first corner that is joined to the heat dissipation base by the first bonding material and a second corner that is not joined to the heat dissipation base by the first bonding material, and the first bonding material bonds the plurality of wiring boards to the heat dissipation base such that the second corners of the wiring boards are located at four corners of a wiring board area that includes the entirety of the plurality of wiring boards. Effect of the Invention

[0007] According to the above-described aspect, it is possible to prevent damage to the wiring board due to deformation when the heat dissipation base is fastened, while ensuring heat dissipation properties. [Brief description of the drawings]

[0008] [Figure 1] 1 is a plan view showing a semiconductor module according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view taken along line II-II of FIG. [Diagram 3] 5 is an explanatory diagram for explaining a warped shape of a second surface (lower surface) of the heat dissipation base in the first embodiment. FIG. [Figure 4] 5 is an explanatory diagram for explaining a local convex portion of a second surface of the heat dissipation base in the first embodiment. FIG. [Diagram 5] 1 is a first example of a circuit diagram of a semiconductor module according to a first embodiment. [Figure 6] 2 is a second example of a circuit diagram of the semiconductor module according to the first embodiment. [Figure 7A] 2 is a cross-sectional view (part 1) showing a semiconductor module in a comparative example and corresponding to the cross-sectional view taken along line II-II in FIG. [Figure 7B] 2 is a second cross-sectional view showing a semiconductor module in a comparative example and corresponding to the cross-sectional view taken along line II-II in FIG. 1; [Figure 7C] 2 is a cross-sectional view (part 3) showing a semiconductor module in a comparative example and corresponding to the cross-sectional view taken along line II-II in FIG. 1; [Figure 8] FIG. 11 is a plan view showing a semiconductor module according to a modified example of the first embodiment. [Figure 9] 10 is a plan view showing in a see-through manner a first bonding material of a wiring board in a modified example of the first embodiment. FIG. [Figure 10A] 1. FIG. 4 is a first cross-sectional view showing a semiconductor module according to a second embodiment, and corresponds to the cross-sectional view taken along line II-II in FIG. [Figure 10B] 1. FIG. 4 is a second cross-sectional view showing a semiconductor module according to a second embodiment, the second cross-sectional view corresponding to the cross-sectional view taken along line II-II in FIG. [Figure 11A] 1. FIG. 4 is a first cross-sectional view showing a semiconductor module according to a third embodiment, and corresponds to the cross-sectional view taken along line II-II in FIG. [Figure 11B] 1. FIG. 4 is a second cross-sectional view showing a semiconductor module according to a third embodiment, and corresponds to the cross-sectional view taken along line II-II in FIG. [Figure 12A] 1. FIG. 1 is a cross-sectional view (part 1) showing a semiconductor module according to a fourth embodiment, the cross-sectional view corresponding to the II-II cross-sectional view of FIG. [Figure 12B] 1. FIG. 1 is a second cross-sectional view showing a semiconductor module according to a fourth embodiment, the second cross-sectional view corresponding to the cross-sectional view taken along line II-II in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, the semiconductor modules according to the first to fourth embodiments of the present invention will be described in detail with reference to the drawings. The X, Y, and Z axes in each of the drawings are shown for the purpose of defining the directions and each surface of the semiconductor module to be illustrated. The X, Y, and Z axes are mutually orthogonal and form a right-handed system. In the following description, the Z direction may be referred to as the up-down direction. Furthermore, the surface including the X and Y axes may be referred to as the upper surface or the lower surface. These directions and surfaces are terms used for convenience of explanation, and the corresponding relationship with each of the X, Y, and Z directions may change depending on the mounting posture of the semiconductor module, etc. For example, in this specification, the surface facing the positive side of the Z direction (+Z direction) of the member constituting the semiconductor module is referred to as the upper surface, and the surface facing the negative side of the Z direction (-Z direction) is referred to as the lower surface, but the surface facing the negative side of the Z direction may be referred to as the upper surface, and the surface facing the positive side of the Z direction may be referred to as the lower surface. Furthermore, in this specification, a plan view means a case where the upper surface (XY surface) of the semiconductor module, etc. is viewed from the positive side of the Z direction toward the negative side of the Z direction.

[0010] The aspect ratios and the size relationships between the components in each drawing are merely schematic and do not necessarily correspond to the relationships in the semiconductor modules that are actually manufactured. For the sake of convenience, the size relationships between the components may be exaggerated. Also, the shapes of the same components may differ between different drawings.

[0011] In the following description, as an example of a semiconductor module according to the embodiment and an energy conversion device including the semiconductor module, a device applied to a power conversion device such as an inverter device for an industrial or vehicle-mounted motor will be given. Therefore, in the following description, detailed descriptions of configurations, functions, operations, assembly methods, etc. that are the same as or similar to those of known semiconductor modules and energy conversion devices will be omitted.

[0012] First Embodiment FIG. 1 is a plan view showing the semiconductor module 1. FIG. 2 is a cross-sectional view taken along line II-II of FIG. 1. FIG. 3 is an explanatory diagram for explaining the warped shape of the second surface (lower surface) 22 of the heat dissipation base 20. FIG. 4 is an explanatory diagram for explaining a local convex portion P4 of the second surface 22. FIGS. 5 and 6 are example circuit diagrams of the semiconductor module 1. In FIGS. 1 and 3, the first bonding material S1 is indicated by a dashed line (hidden line), and the wiring board area A is indicated by a two-dot chain line (imaginary line).

[0013] 1 and 2 includes a plurality of wiring boards 10, a heat dissipation base 20, and a first bonding material S1. The energy conversion device 100 shown in FIG.

[0014] 2, the semiconductor module 1 is attached to the cooler 110 by a screw 120 inserted into a fastening hole 23 of the heat dissipation base 20. The screw 120 has a male thread that screws into a screw hole (female thread) of the cooler 110. The cooler 110 is, for example, a water jacket integrated type having fins, a water jacket, etc., or an open fin type in which the fins are exposed to the outside. The heat dissipation base 20 of the semiconductor module 1 and the cooler 110 are connected via a thermal conductive material C such as thermal grease or thermal compound.

[0015] A plurality of (e.g., four) wiring boards 10 are joined at joining surface 16, which is the lower surface, to a first surface 21 (upper surface) of a common single heat dissipation base 20. Wiring board 10 includes a first conductor layer 11, a second conductor layer 12, and an insulating layer 13. Wiring board 10 may be, for example, a DCB (Direct Copper Bonding) board or an AMB (Active Metal Brazing) board. Wiring board 10 may also be called a laminated board, an insulating circuit board, an insulating heat dissipation circuit board, or the like.

[0016] The insulating layer 13 is, for example, a ceramic substrate. The insulating layer 13 is not limited to a specific substrate, but may be, for example, aluminum nitride (AlN), aluminum oxide (Al 2 O 3 ), silicon nitride (Si 3 N 4 ), and aluminum oxide (Al 2 O 3 ) and zirconium oxide (ZrO 2 The insulating layer 13 may be, for example, a substrate formed of an insulating resin such as an epoxy resin, a substrate formed by impregnating a base material such as glass fiber with an insulating resin, or a substrate formed by coating the surface of a flat metal core with an insulating resin.

[0017] The second conductor layer 12 is a member that functions as a heat conducting member that conducts heat generated in the inverter circuit to the heat dissipation base 20, and is formed, for example, from a metal plate or metal foil such as copper or aluminum. The second conductor layer 12 (wiring board 10) is joined to the heat dissipation base 20 by a first bonding material S1 such as solder. The second conductor layer 12 may be called a heat dissipation layer, a heat dissipation plate, a heat dissipation pattern, a conductor pattern, or the like.

[0018] The first conductor layer 11 is a member that functions as a wiring member in the inverter circuit, and is formed of, for example, a metal plate or metal foil of copper, aluminum, etc. The first conductor layer 11 may be called a conductor plate, a conductor pattern, a conductive layer, a wiring pattern, etc.

[0019] As an example, as shown in FIG. 1, four semiconductor elements 14 and four semiconductor elements 15 are mounted on the first conductor layer 11 in a line of four each in the X direction using a bonding material S such as solder (see FIG. 2).

[0020] The semiconductor element 14 is, for example, an IGBT (Insulated Gate Bipolar Transistor) which is a switching element, and the semiconductor element 15 is, for example, an FWD (Free Wheeling Diode) which is a diode element. As the semiconductor element 14 and the semiconductor element 15, other semiconductor elements such as an RC (Reverse Conducting)-IGBT element which integrates a switching element and a diode element connected in reverse parallel to the switching element may be arranged. The switching element and the diode element in the semiconductor elements 14 and 15 may be formed on a semiconductor substrate using a wide band gap semiconductor such as SiC (Silicon Carbide) or GaN (Gallium Nitride) without being limited to a Si substrate. In addition, the switching element of the semiconductor element 14 may be, for example, a SiC-MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a BJT (Bipolar Junction Transistor), or the like. Furthermore, the diode element of the semiconductor element 15 may be composed of, for example, a SiC-SBD (Schottky Barrier Diode), a JBS (Junction Barrier Schottky) diode, an MPS (Merged PN Schottky) diode, a PN diode, or the like.

[0021] The four wiring boards 10 may be identical or symmetrical. For example, the upper left wiring board 10 in Fig. 1 (positive side in the Y direction and negative side in the X direction) may be identical to or symmetrical with the upper right wiring board 10 (positive side in the Y direction and positive side in the X direction). The upper left wiring board 10 in Fig. 1 may be identical to or symmetrical with the lower left wiring board 10 in Fig. 1 (negative side in the Y direction and negative side in the X direction) and the lower right wiring board 10 in Fig. 1 (negative side in the Y direction and positive side in the X direction) rotated 180 degrees in a plan view.

[0022] The main electrodes provided on the upper surfaces of the semiconductor elements 14 and 15 are connected to the other semiconductor elements 14 and 15, the first conductor layer 11, or an input terminal (not shown) by the main current wiring W1. For example, the semiconductor module 1 has two first input terminals (E terminals), two second input terminals (C terminals), and an auxiliary input terminal (C terminal, E terminal), and these terminals may function as terminals (C, E) constituting a common set of circuits as shown in the circuit diagram of FIG. 5, or may function as terminals (C1, C2, E1, E2) constituting two sets of circuits as shown in the circuit diagram of FIG. 6. In addition, the control electrodes (e.g., gate electrodes) provided on the upper surfaces of the semiconductor elements 14 and 15 are indirectly or directly connected to a control terminal (G) (not shown) via the first conductor layer 11 by the control wiring W2. The input terminals and the control terminals may be fixed integrally to a case (not shown) that covers the periphery of the four wiring boards 10, for example. 1, at four corners A1 of wiring board area A (i.e., the smallest rectangular area surrounding all of wiring boards 10 in a plan view) consisting of four wiring boards 10, first conductor layer 11 (connected to the control terminal) is connected only to control wiring W2 out of main current wiring W1 and control wiring W2. And, at four corners A1, no main current flows through first conductor layer 11.

[0023] 1, heat dissipation base 20 has a rectangular shape in plan view, and has fastening holes 23 for inserting screws 120 at a total of six locations, including four locations at the four corners and two locations at the center in the X direction and both ends in the Y direction. It is preferable that the corners of heat dissipation base 20 in plan view are R-chamfered. It is preferable that the corners of wiring board 10 in plan view are C-chamfered.

[0024] The heat dissipation base 20 is a member that functions as a heat conductive member that conducts heat generated by the semiconductor elements 14 and 15 to the cooler 110, and is formed of a metal plate such as a copper plate or an aluminum plate. The heat dissipation base 20 is formed by warping the entire second surface 22 of a flat metal plate by, for example, pressing so that the second surface 22 is a convex curved surface. As a result, the vertical distance between the heat dissipation base 20 and the cooler 110 shown in FIG. 2 is greater in the peripheral portion G2 in a plan view than the central portion G1 in a plan view, particularly before the heat dissipation base 20 is attached to the cooler 110 by the screws 120. Note that the above-mentioned heat conductive material C is interposed between the heat dissipation base 20 and the cooler 110.

[0025] The shape, number, and location of the wiring board 10 of the semiconductor elements 14, 15, etc. in the semiconductor module 1 can be changed as appropriate. For example, the number of wiring boards 10 is not limited to four, and can be any number equal to or greater than two. The multiple wiring boards 10 may be arranged in only one direction (X direction or Y direction). The layout of the first conductor layer 11 as a wiring member provided on the upper surface side of the wiring board 10 is changed according to the type, shape, number, and location of the semiconductor elements 14, 15 to be mounted. The main current wiring W1 and the control wiring W2 in the above-mentioned semiconductor module 1 are, for example, metallic bonding wires, but may be replaced in part or in whole with leads formed by processing a metal plate such as a copper plate.

[0026] 7A to 7C, a semiconductor module in a comparative example in which wiring board 10 is damaged when heat dissipation base 20 is attached to cooler 110 will be described. Figures 7A to 7C are cross-sectional views at positions corresponding to the II-II cross-sectional view of Figure 1.

[0027] In order to improve the adhesion between the heat dissipation base 20 and the cooler 110 by using a thermally conductive material C such as thermal grease, for example, as shown in Fig. 7A, a plurality of thermally conductive materials C are dotted and arranged on the second surface 22 of the heat dissipation base 20 before it is attached to the cooler 110. Note that before the heat dissipation base 20 is attached to the cooler 110, the four wiring boards 10 are sealed with a sealing resin (gel) not shown.

[0028] The second surface 22 of the heat dissipation base 20 is curved in a convex shape, that is, the position in the vertical direction is up at the periphery and down at the center. Therefore, when the heat dissipation base 20 is placed on the cooler 110, the thermally conductive material C arranged at the center of the second surface 22 of the heat dissipation base 20 first comes into contact with the upper surface of the cooler 110. Then, when the heat dissipation base 20 is pressed against the cooler 110 when the screw 120 is fastened, the thermally conductive material C is integrated between the second surface 22 of the heat dissipation base 20 and the upper surface of the cooler 110 while spreading radially from the center of the second surface 22, as shown in FIG. 7B. At this time, by making the second surface 22 of the heat dissipation base 20 a convex curved surface, the thermally conductive material C is easily spread radially from the center of the second surface 22 of the heat dissipation base 20, and voids are less likely to occur in the integrated thermally conductive material C.

[0029] When the heat dissipation base 20 is attached to the cooler 110, a plurality of wiring boards 10 are joined to the heat dissipation base 20. When the heat dissipation base 20 is attached to the cooler 110, the heat conductive material C is spread between the heat dissipation base 20 and the cooler 110 as described above, and then the heat dissipation base 20 is fixed to the cooler 110 by using the screws 120.

[0030] Therefore, the heat dissipation base 20 is deformed so that the convex curved surface of the second surface 22 becomes a curved surface close to flat. That is, when the heat dissipation base 20 is attached to the cooler 110 by the screw 120, the heat dissipation base 20 is deformed in a direction in which the warping becomes smaller than before the attachment. When the heat dissipation base 20 is deformed in a direction in which the warping becomes smaller, a deformation stress is applied to the wiring board 10 joined to the first surface 21 of the heat dissipation base 20, and for example, the stress is concentrated in the slits between the first conductor layers 11 (or the periphery of the first conductor layer 11) in the vicinity of the screw 120 (stress concentrated portion 13a shown in FIG. 7C), causing damage to the wiring board 10, such as cracking of the insulating layer 13.

[0031] In the above-described comparative example, bonding surface 16 of wiring board 10 with heat dissipation base 20 has only first corners 16a that are bonded to heat dissipation base 20 by first bonding material S11. That is, all four corners of bonding surface 16 are first corners 16a that are bonded to heat dissipation base 20.

[0032] In contrast, in the first embodiment, as shown by the dashed lines in FIG. 1, the first bonding material S1 does not reach the four corners A1 of the wiring board region A, and the bonding surface 16 of the wiring board 10 has second corners 16b that are not bonded to the heat dissipation base 20 by the first bonding material S1 only at the four corners A1 of the wiring board region A. In the second corners 16b shown in FIG. 2, not only the first bonding material S1 but also the second conductor layer 12 is missing. The above-mentioned sealing resin that seals the wiring board 10 penetrates into this missing portion. The missing portion of the second conductor layer 12 can be formed by, for example, etching. The remaining three corners of the bonding surface 16 of the wiring board 10 may be first corners 16a that are bonded to the heat dissipation base 20 by the first bonding material S1. In addition, at the corners of bonding surface 16, if there is a relative difference in size between the areas not bonded to heat dissipation base 20, the corners with the larger unbonded areas may be regarded as second corners 16b, and the corners with the smaller unbonded areas may be regarded as first corners 16a. Also, second corners 16b do not have to be provided at all of the four corners A1 of wiring board area A, and it is sufficient that second corners 16b of one or more wiring boards 10 are located at four corners A1.

[0033] Here, the local convex portion (position of the local convex shape) P4 of the second surface 22 of the heat dissipation base 20 will be described. As shown in FIG. 3, which shows the change in the warpage shape by shading, the positions where the diagonal line D connecting the fastening holes 23 (centers of the fastening holes 23) intersects both ends of the area corresponding to the wiring board area A (the area at the same position as the wiring board area A in a plan view) on the second surface 22, which is the lower surface of the heat dissipation base 20, are defined as reference positions P1 and P2. The intermediate position between the two reference positions P1 and P2 on the second surface 22 is defined as a central position P3. Since the second surface 22 of the heat dissipation base 20 is aligned so as to form a convex curved surface, the diagonal line D can be said to be a line along this curved surface. Also, the reference positions P1 and P2 can be called positions at a predetermined distance L from the center of the fastening holes 23.

[0034] 4, the warpage shape of the second surface 22 (lower surface) of the heat dissipation base 20 along the diagonal line D is shown by a solid black line. The position in the up-down direction (convex and concave) at the reference position P1 (P2) is taken as the origin, and the upper side in FIG. 4 is taken as the larger protrusion amount (convex) and the lower side is taken as the smaller protrusion amount (concave).

[0035] Then, an auxiliary line (gray dotted line) is drawn connecting the position of the warped shape at the central position P3 and the reference positions P1 and P2. The difference between the warped shape and the auxiliary line is the auxiliary height curve (gray solid line). The position (convex peak position) on the diagonal line D where the protrusion amount of this auxiliary height curve is the largest is the local protrusion P4. Note that the local protrusion P4 may also be obtained on another diagonal line intersecting with the diagonal line D, and both may be the local protrusion P4, or only the one with the larger protrusion amount may be the local protrusion P4. In FIG. 1, this local protrusion P4 is shown on the wiring board 10 at the upper right in FIG. 1. The first bonding material S1 is preferably located closer to the central position P3 than the local protrusion P4. That is, the first bonding material S1 is preferably located at a distance from the local protrusion P4 of the heat dissipation base 20 toward the central position P3. The closer the local convex portion P4 is to the slit between the first conductor layers 11 (or the periphery of the first conductor layer 11) in the vicinity of the screw 120 where stress is likely to concentrate, the stronger the stress acting on this slit.

[0036] In the first embodiment described above, the semiconductor module 1 includes a plurality of wiring boards 10 on which semiconductor elements 14 and 15 are mounted, a heat dissipation base 20, and a first bonding material S1. The heat dissipation base 20 has a first surface 21 to which the plurality of wiring boards 10 are bonded, and a second surface 22 located on the opposite side to the first surface 21. The first bonding material S1 bonds the plurality of wiring boards 10 to the heat dissipation base 20. The heat dissipation base 20 is warped so that the second surface 22 is a convex curved surface. At least a plurality of corners of the heat dissipation base 20 are provided with fastening holes 23. The bonding surface 16 of each of the plurality of wiring boards 10 facing the heat dissipation base 20 includes a first corner 16a bonded to the heat dissipation base 20 by the first bonding material S1, and a second corner 16b not bonded to the heat dissipation base 20 by the first bonding material S1. First bonding material S1 bonds multiple wiring boards 10 to heat dissipation base 20 such that second corners 16b of wiring boards 10 are located at four corners A1 of wiring board area A including the entirety of multiple wiring boards 10.

[0037] As a result, even if the second surface 22 of the heat dissipation base 20 is deformed in a direction changing from a convex curved surface to a flat surface when the heat dissipation base 20 is attached to the cooler 110 or the like, the wiring board 10 is not joined to the heat dissipation base 20 at the second corners 16b of the four corners A1 of the wiring board area A, so that the wiring board 10 does not follow the deformation of the heat dissipation base 20 in the vicinity of the fastening holes 23, and stress concentration on the wiring board 10 can be suppressed. Also, compared to a mode in which the wiring board 10 has the second corners 16b at all corners other than the four corners A1 of the wiring board area A, the heat dissipation from the wiring board 10 to the heat dissipation base 20 at the first corners 16a can be ensured. Therefore, according to the first embodiment, damage to the wiring board 10 due to deformation during fastening of the heat dissipation base 20 can be prevented while ensuring heat dissipation. Incidentally, if all corners of bonding surface 16 of wiring board 10 were made into first corners 16a, there was a 5% probability that horizontal cracks would occur in insulating layer 13 of wiring board 10 in a direction intersecting diagonal D when heat dissipation base 20 was attached (fastened) to cooler 110, causing failure (damage) of wiring board 10. However, by providing second corners 16b only at the four corners A1 of wiring board area A as in this first embodiment, the failure rate of semiconductor module 1 was reduced to 0%.

[0038] In the first embodiment, wiring board 10 includes insulating layer 13, first conductor layer 11 provided on the surface of insulating layer 13 facing semiconductor elements 14, 15, and second conductor layer 12 provided on the surface of insulating layer 13 facing heat dissipation base 20. Second conductor layer 12 is missing at second corner portion 16b.

[0039] This makes it possible to more reliably prevent damage to wiring board 10, even if first bonding material S1 protrudes into second corner portion 16b, and therefore to more reliably prevent damage to wiring board 10. In addition, the amount of material used for second conductor layer 12 can be reduced.

[0040] Furthermore, in this first embodiment, the semiconductor module 1 is provided with a main current wiring W1 and a control wiring W2, and the first conductor layer 11 is connected to only the control wiring W2 of the main current wiring W1 and the control wiring W2 at the four corners A1 of the wiring board area A, and no main current flows.

[0041] This prevents wiring board 10 from becoming too hot at second corners 16b (four corners A1 of wiring board area A) of bonding surface 16 where wiring board 10 and heat dissipation base 20 are not bonded, thereby preventing loss of heat dissipation performance.

[0042] In the first embodiment, the heat dissipation base 20 has a local convex portion P4 on the second surface (lower surface) 22, which is the position where the protrusion amount of the convex curved surface from the auxiliary line connecting the two reference positions P1, P2 and the central position P3 is the largest, when the positions where the diagonal line D connecting the fastening holes 23 intersects with both ends of the area corresponding to the wiring board area A are defined as reference positions P1, P2 and the central position P3 is defined as the intermediate position between the two reference positions P1, P2. The first bonding material S1 is located at a distance from the local convex portion P4 of the heat dissipation base 20 toward the central position P3.

[0043] As a result, at local convex portion P4 where stress is likely to concentrate on wiring board 10, wiring board 10 does not follow the deformation of heat dissipation base 20, so that stress concentration on wiring board 10 can be more reliably suppressed.

[0044] <Modification of the first embodiment> Fig. 8 is a plan view showing a semiconductor module 1A according to a modified example of the first embodiment. Fig. 9 is a plan view showing in perspective a first bonding material S1A of a wiring board 10.

[0045] In semiconductor module 1A according to this modification, second corners 16b where wiring board 10 and heat dissipation base 20 are not joined by first bonding material S1A are provided not only at four corners A1 of wiring board area A but also near two fastening holes 23 at the center in the X direction. Other matters can be similar to those described above, and therefore description thereof will be omitted.

[0046] 8 and 9, bonding surface 16 of wiring board 10 has second corners 16b (see FIG. 9) at four corners A1 of wiring board area A, where wiring board 10 and heat dissipation base 20 are not bonded. Bonding surface 16 also has second corner 16b at one corner adjacent (adjacent across one side) to second corner 16b at four corners A1 of wiring board area A. Meanwhile, bonding surface 16 has first corners 16a at the remaining two adjacent corners where wiring board 10 and heat dissipation base 20 are bonded.

[0047] Second corner portion 16b at a position different from the four corners A1 of wiring board region A may be provided at a corner near two fastening holes 23 at the center in the X direction. Also, in second corner portion 16b in this modified example, not only first bonding material S1A but also second conductor layer 12 may be missing. Also, first bonding material S1A may be located at a distance closer to central position P3 (see FIG. 3) than local convex portion P4.

[0048] The first bonding material S1A may be missing symmetrically at the two second corner portions 16b (symmetrically in all four wiring boards 10 in FIG. 8). In the example of FIG. 9, the first bonding material S1A is provided so as to be missing symmetrically at the center in the X direction and on either side of a center line (dotted chain line) extending in the Y direction.

[0049] In the modified example of the first embodiment described above, the same effects as those of the first embodiment described above can be obtained in terms of the same points, namely, the effect of preventing damage to wiring board 10 due to deformation when fastening heat dissipation base 20 while ensuring heat dissipation performance.

[0050] In addition, in this modified example, bonding surface 16 of each of the multiple wiring boards 10 includes two adjacent first corner portions 16a and two adjacent second corner portions 16b, and first bonding material S1A is missing in a symmetrical shape at the two second corner portions 16b.

[0051] This allows not only the wiring boards 10 but also the first bonding material S1A to be formed in the same or symmetrical shape when, for example, four (plural) wiring boards 10 have the same shape or when the wiring boards 10 have symmetrical shapes, etc. Also, compared to a mode in which the first bonding material S1A is missing in an asymmetrical shape at the two second corners 16b, the arrangement of the first bonding material S1A is made easier.

[0052] <Second embodiment> 10A and 10B are cross-sectional views showing a semiconductor module 2 according to the second embodiment, taken along a line corresponding to the cross-sectional view of FIG. 1 taken along the line II-II.

[0053] In semiconductor module 2 according to the second embodiment, second conductor layer 52 of wiring board 50 has solder resist 52a provided at second corner portion 16b. Other matters can be similar to those in the above-described first embodiment, and therefore the same reference numerals as those in the above-described first embodiment are assigned to Figs. 10A and 10B except for wiring board 50, second conductor layer 52, solder resist 52a, and first bonding material S21, and description thereof will be omitted.

[0054] 10A, the second conductor layer 52 has a solder resist 52a at a second corner 16b where the wiring board 50 and the heat dissipation base 20 are not joined by the first bonding material S21. This solder resist 52a is an example of a non-joining processed portion applied to the second conductor layer 52. This non-joining processed portion is not limited to the solder resist 52a as long as it is a processed portion that prevents the second conductor layer 52 (wiring board 50) and the heat dissipation base 20 from being joined by the first bonding material S21.

[0055] The solder resist 52a has a property of repelling the first bonding material S21 even when it comes into contact with the first bonding material S21, and is therefore not bonded to the heat dissipation base 20. Therefore, when the heat dissipation base 20 is attached to the cooler 110 by the screws 120 as shown in Fig. 10B, even if the second surface 22 of the heat dissipation base 20 is deformed in a direction changing from a convex curved surface to a flat surface, the wiring board 50 does not follow the deformation of the heat dissipation base 20 at the second corner portion 16b near the fastening hole 23. Therefore, a vertical gap is generated between the solder resist 52a and the first bonding material S21.

[0056] In this second embodiment, as in the modified example of the first embodiment, the bonding surface 16 of each of the multiple wiring boards 50 includes two adjacent first corner portions 16a and two adjacent second corner portions 16b, and the first bonding material S21 may be missing in a symmetrical shape at the two second corner portions 16b.

[0057] In the second embodiment described above, the same effects as those of the first embodiment described above can be obtained in terms of the same points, namely, the effect of preventing damage to the wiring board 50 due to deformation when the heat dissipation base 20 is fastened while ensuring heat dissipation.

[0058] In the second embodiment, the second conductor layer 52 of the wiring board 50 has a solder resist 52a (an example of a non-bonded portion) applied to the second corner portion 16b that is not bonded to the heat dissipation base 20 by the first bonding material S21.

[0059] 1, solder resist 52a (wiring board 50) is not bonded to heat dissipation base 20, and therefore wiring board 50 does not follow deformation of heat dissipation base 20 in the vicinity of fastening holes 23. Therefore, by a simple process using solder resist 52a without removing second conductor layer 52 at second corner 16b, even if first bonding material S21 is located at second corner 16b, wiring board 50 and heat dissipation base 20 are not bonded, and damage to wiring board 50 can be more reliably prevented.

[0060] The solder resist 52a may be disposed so as to surround the second conductor layer 52 over the entire area of ​​the back surface of the wiring board 50 where the second conductor layer 52 is not present. In this case, the area to be bonded to the first bonding material S21 can be reliably controlled. In particular, when the solder resist 52a is disposed only at the boundary between the second corner portion 16b and the area to be bonded to the first bonding material S21, the first bonding material S21 may be disposed at the second corner portion 16b over the solder resist 52a, thereby bonding the second corner portion 16b to the heat dissipation base 20. It is preferable to cover the entire vicinity of the second corner portion 16b with the solder resist 52a so that the first bonding material S21 does not come to the vicinity of the second corner portion 16b over the solder resist 52a.

[0061] <Third embodiment> 11A and 11B are cross-sectional views showing a semiconductor module 3 according to the third embodiment, taken along a line corresponding to the cross-sectional view of FIG. 1 taken along the line II-II.

[0062] In the semiconductor module 3 according to the third embodiment, the heat dissipation base 60 has a solder resist 61a in an area facing the second corner portion 16b of the first surface 61. Other matters can be similar to those in the above-described first embodiment, so the same reference numerals as those in the above-described first embodiment are assigned to Figs. 11A and 11B except for the heat dissipation base 60, the first surface 61, the solder resist 61a, and the first bonding material S31, and description thereof will be omitted.

[0063] As shown in FIG. 11A, the first surface 61 has a solder resist 61a in an area facing the second corner 16b where the wiring board 10 and the heat dissipation base 60 are not joined by the first bonding material S31. The solder resist 61a is an example of a non-bonding processed portion applied to the first surface 61 of the heat dissipation base 60. The non-bonding processed portion is not limited to the solder resist 61a as long as it is a processed portion that prevents the heat dissipation base 60 and the heat dissipation base 20 from being joined by the first bonding material S31. For example, since the first bonding material S31 is less likely to enter the portion of the first surface 61 of the heat dissipation base 60 that is filled in with a pencil, if a pencil filling process is performed to prevent the first bonding material S31 from entering the second corner 16b, this processed portion functions as a non-bonding processed portion.

[0064] Even if solder resist 61a is in contact with first bonding material S31, it is not bonded to wiring board 10. Therefore, when heat dissipation base 20 is attached to cooler 110 by screws 120 as shown in FIG. 11B, even if second surface 22 of heat dissipation base 60 is deformed in a direction changing from a convex curved surface to a flat surface, wiring board 10 does not follow the deformation of heat dissipation base 60 at second corner portion 16b near fastening hole 23, and a vertical gap is generated between solder resist 61a and wiring board 10.

[0065] In the third embodiment, similarly to the modified example of the first embodiment, bonding surface 16 of each of multiple wiring boards 10 may include two adjacent first corners 16a and two adjacent second corners 16b, and first bonding material S31 may be missing symmetrically at two second corners 16b. Also, in the third embodiment, similarly to the second embodiment, second conductor layer 12 may be provided with a non-bonded portion (solder resist 52a of second conductor layer 52 shown in FIGS. 10A and 10B).

[0066] In the third embodiment described above, the same effects as those of the first embodiment described above can be obtained in terms of the same points, namely, the effect of preventing damage to the wiring board 10 due to deformation when the heat dissipation base 60 is fastened while ensuring heat dissipation.

[0067] In the third embodiment, the heat dissipation base 60 has a solder resist 61a (an example of a non-bonding processed portion) applied to an area of ​​the first surface 61 facing the second corner portion 16b.

[0068] 1, solder resist 61a (heat dissipation base 60) is not bonded to wiring board 10, so that wiring board 10 does not follow the deformation of heat dissipation base 60 in the vicinity of fastening hole 23. Therefore, by a simple process using solder resist 61a without removing second conductor layer 12 at second corner 16b, even if first bonding material S31 is located at second corner 16b, wiring board 10 and heat dissipation base 60 are not bonded, and damage to wiring board 10 can be more reliably prevented.

[0069] Similarly, the solder resist 61a may be arranged on the heat dissipation base 60 facing the portion of the back surface of the wiring board 10 where the second conductor layer 12 is not present, so as to surround the second conductor layer 12. In this case, the portion to be bonded to the first bonding material S31 can be reliably controlled. In particular, when the solder resist 61a is arranged only on the boundary between the second corner portion 16b and the region to be bonded to the first bonding material S31, the second corner portion 16b may be bonded to the heat dissipation base 60 by the first bonding material S31 being arranged on the second corner portion 16b over the solder resist 61a. It is preferable to cover the entire vicinity of the second corner portion 16b with the solder resist 61a so that the first bonding material S31 does not come to the vicinity of the second corner portion 16b over the solder resist 61a. The same can be done with the solder resist 61a by filling in with a pencil (applying graphite).

[0070] <Fourth embodiment> 12A and 12B are cross-sectional views showing a semiconductor module 4 according to the fourth embodiment, taken along a line corresponding to the cross-sectional view of FIG. 1 taken along the line II-II.

[0071] In the semiconductor module 4 according to the fourth embodiment, at second corners 16b where the wiring boards 70 and the heat dissipation base 80 are not joined by the first bonding material S41, the multiple wiring boards 70 and the heat dissipation base 80 are joined by a second bonding material S2 having greater elasticity than the first bonding material S41. Other matters can be similar to those in the above-described first embodiment, and therefore the same reference numerals as those in the above-described first embodiment are assigned to Figs. 12A and 12B except for the wiring boards 70, the second conductor layer 72, the solder resist 72a, the heat dissipation base 80, the first surface 81, the solder resist 81a, and the first bonding material S41, and description thereof will be omitted.

[0072] 12A, in the second corner portion 16b where the wiring board 70 and the heat dissipation base 80 are not joined by the first bonding material S41, solder resists 72a and 81a are provided on the second conductor layer 72 and the first surface 81 of the heat dissipation base 80, respectively, as an example of a non-jointed processed portion. Then, the second bonding material S2 is disposed between these solder resists 72a and 81a.

[0073] The solder resists 72a and 81a are not bonded to the first bonding material S41, and the first bonding material S41 is unlikely to penetrate between the solder resists 72a and 81a. Therefore, after the first bonding material S41 is placed and before the sealing resin is injected, the second bonding material S2 is preferably inserted between the solder resists 72a and 81a. This second bonding material S2 has more elasticity than the first bonding material S41 so that the wiring board 70 does not follow the deformation of the heat dissipation base 80. The second bonding material S2 preferably has a higher thermal conductivity than the sealing resin.

[0074] As shown in FIG. 12B, when the heat dissipation base 80 is attached to the cooler 110 by the screw 120, even if the second surface 22 of the heat dissipation base 80 is deformed in a direction changing from a convex curved surface to a flat surface, the second bonding material S2 stretches at the second corner portion 16b, and the wiring board 70 is less likely to follow the deformation of the heat dissipation base 80 in the vicinity of the fastening hole 23.

[0075] In the fourth embodiment, similarly to the modified example of the first embodiment, the bonding surface 16 of each of the wiring boards 70 includes two adjacent first corners 16a and two adjacent second corners 16b, and the first bonding material S41 may be missing symmetrically at the two second corners 16b. In this case, the second bonding material S2 may be provided at least at the second corners 16b of the four corners A1 of the wiring board area A. In the fourth embodiment, the solder resists 72a and 81a are provided on the wiring board 70 and the heat dissipation base 80, but if the first bonding material S41 can be arranged so as not to enter the second corners 16b, the solder resists 72a and 81a can be omitted.

[0076] In the fourth embodiment described above, the same effects as those of the first embodiment described above can be obtained in terms of the same points, namely, the effect of preventing damage to the wiring board 70 due to deformation when the heat dissipation base 80 is fastened while ensuring heat dissipation.

[0077] In the fourth embodiment, the semiconductor module 4 further includes a second bonding material S2 that bonds the multiple wiring boards 70 and the heat dissipation base 80 at the second corner portion 16b and has greater elasticity than the first bonding material S41.

[0078] This makes it difficult for wiring board 70 to follow the deformation of heat dissipation base 80 at second corners 16b near fastening holes 23 of wiring board 70 located at four corners A1 of wiring board area A shown in Fig. 1. Therefore, damage to wiring board 70 can be prevented with a simple configuration that does not cause loss of second conductor layer 12. Furthermore, if second bonding material S2 has a higher thermal conductivity than the sealing resin, heat dissipation from wiring board 70 to heat dissipation base 80 can be improved at second corners 16b.

[0079] The semiconductor modules 1 to 4 according to the first to fourth embodiments described above are not limited to the above description, and may be modified, substituted, or altered in various ways without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological progress or a derived technology, the semiconductor modules may be implemented using that method. Therefore, the claims cover all embodiments that may be included within the scope of the technical idea.

[0080] Some of the inventions described in the specification and drawings of this application are described below.

[0081] <Appendix 1> A plurality of wiring boards on which semiconductor elements are mounted; a heat dissipation base having a first surface to which the plurality of wiring boards are joined and a second surface located on the opposite side to the first surface; a first bonding material that bonds the plurality of wiring boards and the heat dissipation base; the heat dissipation base is warped so that the second surface is a convex curved surface, At least a plurality of corners of the heat dissipation base are provided with fastening holes; a bonding surface of each of the plurality of wiring boards facing the heat dissipation base includes a first corner portion bonded to the heat dissipation base by the first bonding material and a second corner portion not bonded to the heat dissipation base by the first bonding material; The first bonding material bonds the plurality of wiring boards to the heat dissipation base such that the second corner portions of the wiring boards are positioned at four corners of a wiring board region including the entirety of the plurality of wiring boards. A semiconductor module comprising:

[0082] <Appendix 2> the wiring board includes an insulating layer, a first conductor layer provided on a surface of the insulating layer facing the semiconductor element, and a second conductor layer provided on a surface of the insulating layer facing the heat dissipation base, The second conductor layer is missing at the second corner portion. 2. The semiconductor module according to claim 1 .

[0083] <Appendix 3> the bonding surface of each of the plurality of wiring boards includes two of the first corner portions adjacent to each other and two of the second corner portions adjacent to each other, The first bonding material is missing symmetrically at the two second corners. 3. The semiconductor module according to claim 2.

[0084] <Appendix 4> the wiring board includes an insulating layer, a first conductor layer provided on a surface of the insulating layer facing the semiconductor element, and a second conductor layer provided on a surface of the insulating layer facing the heat dissipation base, The second conductor layer has a non-bonded portion provided at the second corner portion. 2. The semiconductor module according to claim 1 .

[0085] <Appendix 5> The heat dissipation base has a non-bonded portion in a region of the first surface facing the second corner portion. 5. The semiconductor module according to claim 1 or 4.

[0086] <Appendix 6> a second bonding material that bonds the plurality of wiring boards and the heat dissipation base at the second corner portion and has greater elasticity than the first bonding material. 6. The semiconductor module according to claim 1,

[0087] <Appendix 7> Further comprising a main current wiring and a control wiring, the wiring board includes an insulating layer, a first conductor layer provided on a surface of the insulating layer facing the semiconductor element, and a second conductor layer provided on a surface of the insulating layer facing the heat dissipation base, The first conductor layer is connected to only the control wiring among the main current wiring and the control wiring at the four corners of the wiring board region, and a main current does not flow. 7. The semiconductor module according to claim 1,

[0088] <Appendix 8> the heat dissipation base has a local convex portion on the second surface, the local convex portion being a position where the amount of protrusion of the convex curved surface from an auxiliary line connecting the two reference positions and the central position is the largest when a position where a diagonal line connecting the fastening holes intersects both ends of a region corresponding to the wiring board region is defined as a reference position and a middle position between the two reference positions is defined as a central position; The first bonding material is located at a distance from the local convex portion of the heat dissipation base toward the central position. 8. The semiconductor module according to claim 1, [Industrial Applicability]

[0089] As described above, the present invention has the effect of preventing damage to the wiring board due to deformation when the heat dissipation base is fastened while ensuring heat dissipation, and is particularly useful for inverter devices for industrial or electrical equipment. [Explanation of symbols]

[0090] 1,1A,2,3,4 Semiconductor Module 10 Wiring board 11 First conductor layer 12 Second conductor layer 13 Insulating layer 13a Stress concentration area 14,15 Semiconductor elements 16 Joint surface 16a 1st corner 16b 2nd corner 20 Heat dissipation base 21 Page 1 22 Side 2 23 Fastening hole 50 Wiring board 52 Second conductor layer 52a Solder resist 60 Heat dissipation base 61 Page 1 61a Solder resist 70 Wiring board 72 Second conductor layer 72a Solder resist 80 Heat dissipation base 81 Page 1 81a Solder resist 100 Energy Conversion Device 110 Cooler 120 Screw A Wiring board area A1 Four corners D Diagonal C Thermal Conductive Material P1,P2 reference position P3 center position P4 Local convexity S Bonding material S1 (S1A, S11, S21, S31, S41) First bonding material S2 2nd bonding material W1 Main current wiring W2 Control wiring

Claims

1. A plurality of wiring boards on which semiconductor elements are mounted; a heat dissipation base having a first surface to which the plurality of wiring boards are joined and a second surface located on the opposite side to the first surface; a first bonding material that bonds the plurality of wiring boards and the heat dissipation base; the heat dissipation base is warped such that the second surface is a convex curved surface, At least a plurality of corners of the heat dissipation base are provided with fastening holes; a bonding surface of each of the plurality of wiring boards facing the heat dissipation base includes a first corner portion bonded to the heat dissipation base by the first bonding material and a second corner portion not bonded to the heat dissipation base by the first bonding material, The first bonding material bonds the plurality of wiring boards to the heat dissipation base such that the second corners of the wiring boards are positioned at four corners of a wiring board region including the entirety of the plurality of wiring boards. A semiconductor module comprising:

2. the wiring board includes an insulating layer, a first conductor layer provided on a surface of the insulating layer facing the semiconductor element, and a second conductor layer provided on a surface of the insulating layer facing the heat dissipation base, The second conductor layer is missing at the second corner portion.

2. The semiconductor module according to claim 1.

3. the bonding surface of each of the plurality of wiring boards includes two of the first corner portions adjacent to each other and two of the second corner portions adjacent to each other, The first bonding material is missing symmetrically at the two second corners.

3. The semiconductor module according to claim 2.

4. the wiring board includes an insulating layer, a first conductor layer provided on a surface of the insulating layer facing the semiconductor element, and a second conductor layer provided on a surface of the insulating layer facing the heat dissipation base, The second conductor layer has a non-bonded portion provided at the second corner portion.

2. The semiconductor module according to claim 1.

5. The heat dissipation base has a non-jointed portion in a region of the first surface facing the second corner portion.

2. The semiconductor module according to claim 1.

6. a second bonding material that bonds the plurality of wiring boards and the heat dissipation base at the second corner portion and has a greater elasticity than the first bonding material; 2. The semiconductor module according to claim 1.

7. Further comprising a main current wiring and a control wiring, the wiring board includes an insulating layer, a first conductor layer provided on a surface of the insulating layer facing the semiconductor element, and a second conductor layer provided on a surface of the insulating layer facing the heat dissipation base, The first conductor layer is connected to only the control wiring among the main current wiring and the control wiring at the four corners of the wiring board region, and a main current does not flow through the first conductor layer.

2. The semiconductor module according to claim 1.

8. the heat dissipation base has a local convex portion on the second surface, the local convex portion being a position where the amount of protrusion of the convex curved surface from an auxiliary line connecting the two reference positions and the central position is the largest when a position where a diagonal line connecting the fastening holes intersects both ends of a region corresponding to the wiring board region is defined as a reference position and a middle position between the two reference positions is defined as a central position; The first bonding material is located at a distance from the local convex portion of the heat dissipation base toward the central position.

2. The semiconductor module according to claim 1.

Images