Semiconductor module

Abstract

A semiconductor module (1) comprises: semiconductor elements (10); wiring boards (20) on which the semiconductor elements (10) are mounted; and a heat dissipation base (30) having a first surface (31) to which the wiring boards (20) are joined and a second surface (32) located on the opposite side from the first surface (31). The heat dissipation base (30) is warped such that the second surface (32) becomes a convex curved surface. The heat dissipation base (30) has a plurality of fastening holes (33) provided therein to span between the first surface (31) and the second surface (32). The heat dissipation base (30) has a thin portion (34) that is spaced a distance (length L1) from a joining region (A) where the wiring board (20) is joined on the first surface (31), and that is provided along the peripheral edge of the first surface (31).

Description

Semiconductor Module

[0001] The present invention relates to a semiconductor module including a wiring board on which a semiconductor element is mounted and a heat dissipation base to which the wiring board is joined.

[0002] Conventionally, various configurations of semiconductor modules used in power conversion devices and the like have been known, such as a heat dissipation base bonded to a wiring board and attached to a cooler (see, for example, Patent Documents 1 to 5). In some heat dissipation bases of this type of semiconductor module, the second surface facing the cooler, opposite the first surface to which the wiring board is bonded, is processed into a convex curved surface to wet and spread thermal grease between the cooler and the heat dissipation base.

[0003] Japanese Patent Laid-Open No. 07-202088 Japanese Patent Laid-Open No. 2017-135144 International Publication No. 2013 / 141154 Japanese Patent Laid-Open No. 2012-044140 Japanese Patent Laid-Open No. 2020-017702

[0004] When the heat dissipation base is attached to the cooler, the second surface, which is machined to a convex curved surface, is deformed to a flat surface. If this deformation of the heat dissipation base applies a deformation stress to the wiring board that exceeds its flexural strength, the wiring board may be damaged and insulation may be impaired. One possible way to alleviate the stress on the wiring board is to reduce the thickness of the heat dissipation base, but this would result in a deterioration of heat dissipation performance.

[0005] In one aspect, an object of the present invention is to provide a semiconductor module that can prevent damage to a wiring board due to deformation when a heat dissipation base is fastened, while ensuring heat dissipation.

[0006] According to one aspect, a semiconductor module includes a semiconductor element, a wiring board on which the semiconductor element is mounted, and a heat dissipation base having a first surface to which the wiring board is bonded and a second surface opposite the first surface, the second surface of the heat dissipation base being warped so as to form a convex curve, the heat dissipation base having a plurality of fastening holes extending from the first surface to the second surface, and the first surface of the heat dissipation base having a thin portion spaced apart from a bonding area to which the wiring board is bonded and extending along a periphery of the first surface.

[0007] According to this aspect, it is possible to prevent damage to the wiring board due to deformation when fastening the heat dissipation base while ensuring heat dissipation properties.

[0008] FIG. 1 is a cross-sectional view showing an energy conversion device including a semiconductor module according to an embodiment; FIG. 2 is a plan view showing a heat dissipation base according to an embodiment; FIG. 3 is a front view showing a heat dissipation base according to an embodiment; FIG. 4 is a plan view showing a heat dissipation base according to a first modified example of an embodiment; FIG. 5 is a front view showing a heat dissipation base according to a first modified example of an embodiment; FIG. 6 is a plan view showing a heat dissipation base according to a second modified example of an embodiment; FIG. 7 is a front view showing a heat dissipation base according to a second modified example of an embodiment; FIG. 8 is a front view showing a heat dissipation base according to a third modified example of an embodiment; FIG. 9 is a front view showing a heat dissipation base according to a third modified example of an embodiment; FIG. 10 is a diagram (part 1) explaining how a thermally conductive material spreads when a heat dissipation base according to a comparative example is attached to a cooler; FIG. 11 is a diagram (part 2) explaining how a thermally conductive material spreads when a heat dissipation base according to a comparative example is attached to a cooler; FIG. 12 is a diagram (part 3) explaining how a thermally conductive material spreads when a heat dissipation base according to a comparative example is attached to a cooler; FIG. 13 is a diagram explaining an example of a problem that occurs when a heat dissipation base according to a comparative example is attached to a cooler; FIG. 14 is a diagram of an embodiment for explaining a difference in tensile stress applied to a wiring board between an embodiment and a comparative example; FIG. 15 is a diagram of a comparative example for explaining a difference in tensile stress applied to a wiring board between an embodiment and a comparative example.

[0009] A semiconductor module 1 according to an embodiment of the present invention will be described in detail below with reference to the drawings. The X, Y, and Z axes in each of the referenced figures are shown for the purpose of defining directions and surfaces of the illustrated semiconductor module 1, etc. The X, Y, and Z axes are orthogonal to each other and form a right-handed system. In the following description, the Z direction may be referred to as the up-down direction. Furthermore, a plane including the X and Y axes may be referred to as the top or bottom surface. These directions and surfaces are used for convenience of explanation, and their correspondence with the X, Y, and Z directions may change depending on the mounting orientation of the semiconductor module 1, etc. For example, in this specification, the surface of a component constituting the semiconductor module 1 facing the positive side of the Z direction (+Z direction) is referred to as the top surface, and the surface facing the negative side of the Z direction (-Z direction) is referred to as the bottom surface. However, the surface facing the negative side of the Z direction may also be referred to as the top surface, and the surface facing the positive side of the Z direction may also be referred to as the bottom surface. Furthermore, in this specification, a plan view refers to the top surface (XY plane) of the semiconductor module 1, etc., viewed from the positive side of the Z direction toward the negative side of the Z direction.

[0010] The aspect ratios and size relationships between components in each drawing are merely schematic representations and do not necessarily correspond to the relationships in the semiconductor module 1 that is actually manufactured. For ease of explanation, the size relationships between components may be exaggerated. Also, the shapes of the same components may differ between different drawings.

[0011] In the following description, a device applied to a power conversion device such as an inverter device for an industrial or automotive motor will be given as an example of a semiconductor module 1 according to one embodiment and an energy conversion device 100 including this semiconductor module 1. For this reason, 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] FIG. 1 is a cross-sectional view showing an energy conversion device 100 including a semiconductor module 1 according to an embodiment.

[0013] 1 includes a semiconductor module 1 and a cooler 110. The semiconductor module 1 includes a semiconductor element 10, a wiring board 20, and a heat dissipation base 30. The cooler 110 is, for example, a water jacket-integrated cooler having fins, a water jacket, etc., or an open fin-type cooler with fins exposed to the outside. A thermally conductive material T, such as thermal grease or a thermal compound, is disposed between the heat dissipation base 30 of the semiconductor module 1 and the cooler 110.

[0014] The semiconductor module 1 is attached to the cooler 110 by screws S that are inserted into the fastening holes 33 of the heat dissipation base 30 and the fastened portions 51 of the case 50. The screws S have male threads that screw into female threaded holes in the cooler 110.

[0015] The semiconductor elements 10 are mounted on the wiring boards 20 by a bonding material J1 such as solder. In the example of Fig. 1, the semiconductor module 1 includes two wiring boards 20 and four semiconductor elements 10 (see the two-dot chain lines in Fig. 2A) arranged on each of the two wiring boards 20.

[0016] For example, the semiconductor element 10 may be an IGBT (Insulated Gate Bipolar Transistor) which is a switching element, or an FWD (Free Wheeling Diode) which is a diode element. Other semiconductor elements, such as an RC (Reverse Conducting)-IGBT element which integrates a switching element and a diode element connected in antiparallel to the switching element, may also be disposed as the semiconductor element 10. The switching element and the diode element in the semiconductor element 10 are not limited to being formed on a Si substrate, and may be formed on a semiconductor substrate using a wide bandgap semiconductor such as SiC (silicon carbide) or GaN (gallium nitride). The switching element may be configured, for example, by a SiC-MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a BJT (Bipolar Junction Transistor), etc. The diode element may be configured, for example, by a SiC-SBD (Schottky Barrier Diode), a JBS (Junction Barrier Schottky) diode, an MPS (Merged PN Schottky) diode, a PN diode, etc.

[0017] The lower surface (second conductor layer 22) of each of the two wiring boards 20 is joined to the first surface 31 (upper surface) of a common single heat dissipation base 30 by a bonding material J2 such as solder. The wiring board 20 includes a first conductor layer 21, a second conductor layer 22, and an insulating layer 23. The wiring board 20 may be, for example, a DCB (Direct Copper Bonding) substrate or an AMB (Active Metal Brazing) substrate. The wiring board 20 may also be called a laminated substrate, an insulating circuit board, an insulating heat dissipation circuit board, or the like.

[0018] The first conductor layer 21 is a member that functions as a wiring member in, for example, an inverter circuit, and is formed on the insulating layer 23 in multiple separated pieces using a metal plate or metal foil such as copper or aluminum. The first conductor layer 21 is electrically connected to other first conductor layers 21, main electrodes provided on the upper surface of the semiconductor element 10, main terminals 41 and 42, and control terminals (not shown) via wiring W. The first conductor layer 21 may also be called a conductor plate, conductor pattern, conductive layer, wiring pattern, etc. The wiring W is, for example, a metallic bonding wire, but some or all of the wiring W may be replaced with other wiring such as leads formed by processing a metal plate such as a copper plate.

[0019] The second conductor layer 22 is, for example, a member that functions as a heat-conducting member that conducts heat generated in the inverter circuit to the heat dissipation base 30, and is formed on the lower surface of the insulating layer 23 using a metal plate or metal foil such as copper or aluminum. The second conductor layer 22 (wiring board 20) is joined to the heat dissipation base 30 with a joining material J2 such as solder. The second conductor layer 22 may also be called a heat dissipation layer, a heat dissipation plate, a heat dissipation pattern, a conductor pattern, or the like.

[0020] The insulating layer 23 is, for example, a ceramic substrate. The insulating layer 23 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 23 may be, for example, a substrate formed of an insulating resin such as an epoxy resin, a substrate in which a base material such as glass fiber is impregnated with an insulating resin, or a substrate in which the surface of a flat metal core is coated with an insulating resin.

[0021] Note that two wiring boards 20 constitute one semiconductor unit, and for example, three sets of semiconductor units may be arranged to form a three-phase inverter circuit. Furthermore, the shapes, number, and locations of the semiconductor elements 10 and wiring boards 20 can be changed as appropriate. Therefore, the number of semiconductor elements 10 and wiring boards 20 can each be any number equal to or greater than one.

[0022] 2A and 2B are a plan view and a front view showing the heat dissipation base 30. FIG.

[0023] As shown in Fig. 2A, the heat dissipation base 30 has a rectangular shape when viewed in a plan view in the thickness direction (Z direction) of the heat dissipation base 30. The corners of the heat dissipation base 30 in a plan view are preferably rounded. Here, since Fig. 2A is a plan view of the heat dissipation base 30, the wiring board 20 bonded to the first surface 31 of the heat dissipation base 30, the bonding area A (i.e., bonding material J2) to which the wiring board 20 is bonded, and the semiconductor element 10 mounted on the wiring board 20 are shown by imaginary two-dot chain lines.

[0024] The heat dissipation base 30 functions as a thermally conductive member that conducts heat generated by the semiconductor device 10 to the cooler 110. The heat dissipation base 30 is formed of a metal plate, such as a copper plate or an aluminum plate. As shown in FIG. 2B , the heat dissipation base 30 is formed by warping the entire second surface 32 of a flat metal plate, for example, by pressing, so that the second surface 32 has a convex curve. As a result, the vertical distance between the heat dissipation base 30 and the cooler 110 shown in FIG. 1 is larger at the periphery than at the center before the heat dissipation base 30 is attached to the cooler 110 with the screws S. The convex curve of the second surface 32 has a larger curvature at the center and periphery of the second surface 32, for example. After the heat dissipation base 30 is fastened to the cooler 110, the heat dissipation base 30 approaches a flat plate shape, as shown in FIG. 1 .

[0025] The heat dissipation base 30 has fastening holes 33 formed at four locations, for example, at four corners, across the first surface 31 and the second surface 32, into which screws S shown in FIG. 1 are inserted.

[0026] The heat dissipation base 30 has a thin-walled portion 34 on the first surface 31, spaced a distance (length L1) from the bonding area A where the wiring board 20 is bonded, and disposed along the periphery of the first surface 31. Because two wiring boards 20 are bonded to the first surface 31 of the heat dissipation base 30, the thin-walled portion 34 is disposed a distance (length L1) from the two bonding areas A. The distance (length L1) between the thin-walled portion 34 and the bonding area A is preferably longer than the thickness t (see FIG. 1 ) of the heat dissipation base 30 (thick portion 35) in the bonding area A. Furthermore, when the thickness t of the heat dissipation base 30 is divided into a thickness t2 of the area where the thin-walled portion 34 is provided and a remaining thickness t1, the thickness t1 is preferably thicker than the thickness t2. In other words, the thickness t2 of the thin-walled portion 34 is less than half the thickness t1 + t2 of the thick-walled portion 35. The distance between the thin portion 34 and the joining area A varies depending on the position, but is shown in FIG. 2A as the shortest length L1 in the Y direction.

[0027] The thin-walled portion 34 may be provided with a plurality of fastening holes 33. The thin-walled portion 34 continuously surrounds the wiring board 20 on the first surface 31 in a plan view in the thickness direction (Z direction) of the heat dissipation base 30 shown in FIG. 2A . The thin-walled portion 34 also continuously surrounds a central portion C of the heat dissipation base 30 on the first surface 31 in a plan view. This central portion C of the heat dissipation base 30 is the center of the heat dissipation base 30 in the X and Z directions. The thin-walled portion 34 may be provided integrally along the entire periphery of the first surface 31. As a result, in a plan view of the heat dissipation base 30, a portion (e.g., the thick-walled portion 35) where the thin-walled portion 34 is not provided becomes a rectangular region including two bonding regions A.

[0028] Thin-walled portion 34 is provided at a position spaced a distance (L2) from wiring board 20 in a plan view seen in the thickness direction (Z direction) of heat dissipation base 30 shown in Fig. 2A . In the example of Fig. 1 , wiring board 20 has the largest size in the XY plane at insulating layer 23, and therefore thin-walled portion 34 is provided at a position spaced a distance from insulating layer 23 in a plan view. Note that even if thin-walled portion 34 is provided outside bonding region A and extending to the inside of heat dissipation base 30 in a plan view, thin-walled portion 34 can be said to continuously surround wiring board 20 along the periphery of first surface 31.

[0029] The thin-walled portion 34 is preferably located at a distance (L3) from the semiconductor element 10 in the plan view of the heat dissipation base 30 shown in Fig. 2A that is longer than the distance between the semiconductor element 10 and the heat dissipation base 30 in the thickness direction (Z direction) of the heat dissipation base 30 (i.e., the length D, which is the total thickness of the bonding material J1, the wiring board 20, and the bonding material J2 shown in Fig. 1 ) (L3>D). Note that the length L3 is preferably longer than the sum of the length D and the thickness t of the heat dissipation base 30 (L3>D+t).

[0030] The thin-walled portion 34 (the end portion of the thin-walled portion 34 on the first surface 31 closest to the center) is preferably located closer to the periphery of the first surface 31 than the midpoint between the joining area A and the fastening hole 33. In other words, when the length L4 between the joining area A and the fastening hole 33 is divided into a length L4a between the joining area A and the thin-walled portion 34 and the remaining length L4b, the length L4a is preferably longer than the length L4b.

[0031] 1 include, for example, two main terminals 41 that are input terminals (P terminal and N terminal) and two main terminals 42 that are output terminals, and are electrically connected to the first conductor layer 21 of the wiring board 20 by the wiring W as described above. The main terminals 41, 42 are integrated with the case 50 by, for example, insert molding so that both ends are exposed to the outside from the case 50. The main terminals 41, 42 may be connected to external terminals by fastening screws in the through holes 41 a, 42 a.

[0032] The case 50 has, for example, a rectangular cylindrical shape with a central axis in the Z direction, and houses the semiconductor element 10 and the wiring board 20. The case 50 is fixed to the periphery of the first surface 31 of the heat dissipation base 30 by, for example, adhesive, and is fastened to the cooler 110 together with the heat dissipation base 30 by screws S at fastening portions 51 at the four corners, which are relatively thin in the Z direction. Note that the portion of the case 50 that holds the main terminals 41, 42 protrudes further toward the negative Y direction than the fastening portion 51 on the negative Y direction side, and protrudes further toward the positive Y direction than the fastening portion 51 on the positive Y direction side.

[0033] The sealing material 60 seals the semiconductor element 10 and the wiring board 20 inside the case 50. The sealing material 60 is, for example, an epoxy resin, a silicone gel, or the like.

[0034] 6A to 6C are diagrams illustrating the spreading of the thermally conductive material T when the heat dissipation base 530 in the comparative example is attached to the cooler 110. FIG.

[0035] FIG. 7 is a diagram illustrating an example of a problem that occurs when the heat dissipation base 530 is attached to the cooler 110. In FIG.

[0036] 6A to 6C and 7, the same reference numerals as those used in the above description are used to denote the various components of wiring board 20 and the like, excluding heat dissipation base 530. Heat dissipation base 530 of the comparative example has a first surface 531 to which wiring board 20 is joined, a second surface 532 located on the opposite side of first surface 531, and a plurality of fastening holes 533 (see FIG. 7), but first surface 531 of heat dissipation base 530 does not have thin-walled portion 34 shown in FIGS. 2A and 2B.

[0037] When using a thermally conductive material T such as thermal grease to improve adhesion between the heat dissipation base 530 and the cooler 110, for example, as illustrated in FIG. 6A , a plurality of thermally conductive materials T are arranged in a predetermined pattern on the second surface 532 of the heat dissipation base 530. The heat dissipation base 530 has a rectangular shape in plan view with rounded corners, and fastening holes 533 for inserting screws S (see FIG. 7 ) are formed in the corners. The heat dissipation base 530 is formed, for example, by warping a flat metal plate by press working or the like so that the second surface 532 has a convex curve. The second surface 532 of the heat dissipation base 530 shown in FIGS. 6A to 6C has a central portion of the second surface 532 as the apex in plan view.

[0038] The plurality of thermally conductive materials T are arranged on the second surface 532 of the heat dissipation base 530 excluding the areas around the fastening holes 533. The arrangement pattern of the plurality of thermally conductive materials T is, for example, a pattern in which materials of the same shape and the same dimensions are aligned. The plurality of thermally conductive materials T arranged on the second surface 532 of the heat dissipation base 530 may have, for example, a plurality of shapes, or may have the same shape and a plurality of dimensions. The arrangement pattern of the plurality of thermally conductive materials T may change depending on, for example, the distance from the center of the second surface 532 of the heat dissipation base 530 in a plan view.

[0039] When the second surface 532 of the heat dissipation base 530 is placed on the cooler 110 facing the cooler 110, the thermally conductive material T arranged at the center and periphery of the second surface 532 first comes into contact with the cooler 110, as shown in Fig. 6A. Then, for example, when the heat dissipation base 530 is pressed against the cooler 110, the thermally conductive material T that has come into contact with the cooler 110 is integrated between the second surface 532 of the heat dissipation base 530 and the cooler 110 while spreading radially from the center of the second surface 532, as shown in Figs. 6B and 6C. In this case, if the second surface 532 of the heat dissipation base 530 is formed into a convex curved surface, the thermally conductive material T can easily spread radially from the center of the second surface 532 of the heat dissipation base 530, and voids are less likely to occur within the integrated thermally conductive material T.

[0040] 6A to 6C, when the heat dissipation base 530 is attached to the cooler 110, the wiring board 20 is joined to the first surface 531 of the heat dissipation base 530. When the heat dissipation base 530 is attached to the cooler 110, the heat conductive material T is spread between the heat dissipation base 530 and the cooler 110, and then the heat dissipation base 530 is fixed to the cooler 110 using the screws S.

[0041] If fastening holes 533 for screwing are provided at the corners of the second surface 532 of the heat dissipation base 530, when a screw S inserted through the fastening hole 533 is threaded into a screw hole in the cooler 110, the heat dissipation base 530 deforms from the convex curved surface of the second surface 532 (a curved surface represented by the curve shown by the solid line) to a nearly flat curved surface with a small curvature (a curved surface represented by the curve shown by the two-dot chain line), as shown in Fig. 7. In other words, when the heat dissipation base 530 is attached to the cooler 110 with the screw S, the heat dissipation base 530 deforms in a direction that reduces warping compared to before attachment. When the heat dissipation base 530 is deformed in a direction that reduces the warping, a deformation stress greater than the flexural strength (e.g., the ceramic strength of the insulating layer 23) is applied to the wiring board 20 joined to the first surface 531 of the heat dissipation base 530, resulting in damage to the wiring board 20, such as the insulating layer 23 cracking or the first conductor layer 21 and the second conductor layer 22 peeling off from the insulating layer 23.

[0042] While the attachment of heat dissipation base 530 of the comparative example to cooler 110 has been described above, heat dissipation base 30 of the present embodiment is also attached to cooler 110 in a similar manner. Note that, before attaching heat dissipation base 30 to cooler 110, wiring board 20, with semiconductor element 10 mounted thereon, is housed in case 50 and sealed with sealing material 60, as shown in FIG.

[0043] 8A and 8B are diagrams illustrating the difference in tensile stress applied to wiring board 20 between the present embodiment (FIG. 8A) and the comparative example (FIG. 8B). FIG. 8A ((a-1) to (a-4)) shows heat dissipation base 30 according to the present embodiment, which has thin-walled portion 34, and FIG. 8B ((b-1) to (b-4)) shows heat dissipation base 530 according to the comparative example, which does not have thin-walled portion 34. Note that screws S fasten case 50 to cooler 110 along with heat dissipation base 30, but illustration of case 50 is omitted in FIGS. 8A and 8B.

[0044] As shown in an exaggerated manner in FIG. 8A (a-1) and FIG. 8B (b-1), the heat dissipation base 30, 530 is configured so that the second surface 32, 532 forms a convex curved surface, as described above.

[0045] 8A(a-2) and 8B(b-2), in the process of fastening the heat dissipation base 30, 530 to the cooler 110 (see FIGS. 1 and 6A to 6C) through the fastening holes 33, 533 with the screws S, the heat dissipation base 30, 530 is pressed downward by the screws S, and deforms so as to reduce the warpage of the second surfaces 32, 532. At this time, a tensile stress indicated by the double-headed arrow is applied to the wiring board 20.

[0046] As shown in Figures 8A(a-3) and 8B(b-3), as the screw S is tightened, in the comparative example shown in Figure 8B(b-3), the tensile stress applied to the wiring board 20 increases as the warping of the second surface 532 is almost eliminated due to local deformation near the fastening hole 533. On the other hand, in the present embodiment shown in Figure 8A(a-3), the thickness of the heat dissipation base 30 is reduced at the thin-walled portion 34, making it difficult for the deformation of the heat dissipation base 30 on the screw S side to be transmitted to the wiring board 20, and therefore the tensile stress applied to the wiring board 20 is unlikely to increase. This difference in tensile stress increases until the screw S is tightened, as shown in Figures 8A(a-4) and 8B(b-4).

[0047] In this manner, in the present embodiment, by providing a thin portion 34 on the first surface 31 of the heat dissipation base 30, it is possible to reduce distortion of the heat dissipation base 30 at each of the positions P1 on the first surface 31 corresponding to the corner of the wiring board 20 shown in FIG. 2A, the position P2 corresponding to the center of one side of the wiring board 20 where the two wiring boards 20 face each other, and the position P3 corresponding to the center of one side of the two wiring boards 20 where they do not face each other.

[0048] 3A and 3B are a plan view and a front view showing a heat dissipation base 130 according to a first modification of the present embodiment.

[0049] In the heat dissipation base 130 of this first modified example shown in FIGS. 3A and 3B , the thin-walled portion 134 is provided across two bonding areas A. That is, the thin-walled portion 134 integrally includes an intermediate portion 134a that passes between the two bonding areas A. As a result, the thin-walled portion 134 continuously surrounds each of the wiring boards 20 on the first surface 131 in a plan view. Other details can be the same as those described above. That is, the heat dissipation base 130, like the heat dissipation base 30, has a first surface 131, a second surface 132, fastening holes 133, a thin-walled portion 134, and a thick-walled portion 135. The thin-walled portion 134 is provided along the periphery of the first surface 131, spaced apart from the bonding area A to which the wiring board 20 is bonded. The positional relationship of the remaining thin-walled portions 134 (the positional relationship of lengths L1 to L4) may be the same as the positional relationship of the thin-walled portion 34 described above.

[0050] Furthermore, the thin-walled portion 134 is also provided in the intermediate portion 134a at a distance (length L11) from the bonding area A to which the wiring board 20 is bonded. This length L11 is also preferably longer than the thickness t (see FIG. 1 ) of the heat dissipation base 30 in the bonding area A. The thin-walled portion 134 is also provided in the intermediate portion 134a at a distance (L12) from the wiring board 20 in a plan view in the thickness direction (Z direction) of the heat dissipation base 30 shown in FIG. 3A . The thin-walled portion 134 is also provided in the intermediate portion 134a at a distance (L13) longer from the semiconductor element 10 in the plan view shown in FIG. 3A than the distance between the semiconductor element 10 and the heat dissipation base 130 in the thickness direction (Z direction) of the heat dissipation base 130 (i.e., the length D, which is the total thickness of the bonding material J1, the wiring board 20, and the bonding material J2 shown in FIG. 1 ). When three or more wiring boards 20 are joined to the heat dissipation base 30 , the thin-walled portions 134 may be provided across each of the three or more wiring boards 20 .

[0051] Here, the thin-walled portion 134 continuously surrounds the wiring board 20 in a planar view, but does not necessarily surround the entire periphery of the wiring board 20 in a planar view. However, as shown in FIG. 3A , when considering a loop Lo (an example of the periphery of the first surface 131) on the heat dissipation base 130 that surrounds the multiple fastening holes 133, the thin-walled portion 134 preferably occupies 70% or more of the loop Lo. Thus, the thin-walled portion 134 preferably occupies 70% or more of the periphery of the heat dissipation base 130 (first surface 131). In other words, the thin-walled portion 134 may be omitted in an area that is less than 30% of the periphery of the heat dissipation base 130. The loop Lo may simply pass between the multiple fastening holes 133 and the periphery of the first surface 131, and may be, for example, rectangular and surround the fastening holes 133. When a portion (e.g., a thick portion 135) where the thin portion 134 is not formed in the loop Lo is provided, the portion should be away from the fastening hole 133 that is the starting point of deformation, and therefore should be near the middle of two adjacent fastening holes 133 in the loop Lo (e.g., a middle Lo1 in the X direction on the negative Y-direction side, a middle Lo2 in the X direction on the positive Y-direction side, a middle Lo3 in the Y direction on the negative X-direction side, and a middle Lo4 in the Y direction on the positive X-direction side). Note that in the first modified example, in a configuration in which the thin portion 134 is provided across two joining regions A, it has been explained that the thin portion 134 desirably occupies 70% or more of the loop Lo. However, this explanation also applies to a configuration in which the thin portion 134 is not provided across two joining regions A, such as the heat dissipation base 30 shown in FIGS. 2A and 2B , and to the second and third modified examples described below.

[0052] 4A and 4B are a plan view and a front view showing a heat dissipation base 230 according to a second modification of the present embodiment.

[0053] 4A and 4B , the heat dissipation base 230 of the second modified example has a thin portion 234 located closer to the periphery of the first surface 231 than the multiple fastening holes 233. Other details can be the same as the heat dissipation base 30 shown in FIGS. 2A and 2B described above. That is, like the heat dissipation base 30, the heat dissipation base 230 has a first surface 231, a second surface 232, fastening holes 233, a thin portion 234, and a thick portion 235, and the thin portion 234 is provided along the periphery of the first surface 231 at a distance (length L21) from the bonding area A where the wiring board 20 is bonded.

[0054] The positional relationship of the other thin-walled portions 234 may be similar to that of the thin-walled portion 34 described above. That is, the distance (length L21) between the thin-walled portion 234 and the bonding area A may be longer than the thickness of the heat dissipation base 230 in the bonding area A (see thickness t shown in FIG. 1 ). Furthermore, the thin-walled portion 234 may be located at a distance (L22) from the wiring board 20 in a plan view of the heat dissipation base 230 in the thickness direction (Z direction) of the heat dissipation base 230 shown in FIG. 4A . Furthermore, the thin-walled portion 234 may be located at a longer distance (L23) from the semiconductor element 10 in a plan view of the heat dissipation base 230 in the thickness direction (Z direction) of the heat dissipation base 230 than the distance between the semiconductor element 10 and the heat dissipation base 230 in the thickness direction (Z direction) of the heat dissipation base 230 (i.e., the length D, which is the total thickness of the bonding material J1, the wiring board 20, and the bonding material J2 shown in FIG. 1 ).

[0055] 5A and 5B are a plan view and a front view showing a heat dissipation base 330 according to a third modification of the present embodiment.

[0056] In the heat dissipation base 330 of the third modified example shown in Figures 5A and 5B, the thin-walled portion 334 is located closer to the periphery of the first surface 331 than the multiple fastening holes 333, and the thin-walled portion 334 is provided across an intermediate portion 334a between two bonding areas A. Other details can be the same as those described for the heat dissipation bases 30, 130, and 230 above. That is, like the heat dissipation base 30, the heat dissipation base 330 has a first surface 331, a second surface 332, fastening holes 333, a thin-walled portion 334, and a thick-walled portion 335, and the thin-walled portion 334 is provided along the periphery of the first surface 331 at a distance from the bonding area A to which the wiring board 20 is bonded. The positional relationship of the remaining thin-walled portions 334 (lengths L11 to L13 and lengths L21 to L23) may be the same as that of the thin-walled portions 134 and 234 described above.

[0057] In the present embodiment described above, the semiconductor module 1 includes a semiconductor element 10, a wiring board 20 on which the semiconductor element 10 is mounted, and a heat dissipation base 30 having a first surface 31 to which the wiring board 20 is bonded and a second surface 32 located opposite the first surface 31. The second surface 32 of the heat dissipation base 30 is warped so that it is a convex curved surface, and the heat dissipation base 30 has a plurality of fastening holes 33 formed across the first surface 31 and the second surface 32. The heat dissipation base 30 has a thin-walled portion 34 on the first surface 31 that is spaced a distance (length L1) from a bonding area A to which the wiring board 20 is bonded and that is provided along the periphery of the first surface 31. Preferably, the thin-walled portion 34 continuously surrounds a central portion C of the heat dissipation base 30 on the first surface 31 in a plan view. 3A , the thin-walled portion 134 preferably occupies 70% or more of the peripheral distance of the heat dissipation base 130 at the periphery (e.g., loop Lo) of the heat dissipation base 130 surrounding the multiple fastening holes 133. If there is a portion (thick portion 135) at the periphery of the heat dissipation base 130 where the thin-walled portion 134 is not formed, this portion should be near the middles Lo1, Lo2, Lo3, and Lo4 of the multiple adjacent fastening holes 133 at the periphery (loop Lo) of the heat dissipation base 130.

[0058] When the heat dissipation base 30 is attached to the cooler 110, the second surface 32 of the heat dissipation base 30 deforms from a convex curved surface to a flat surface. During this deformation, the thin-walled portion 34, which is thin around the periphery of the first surface 31, absorbs the stress of the deformation. This prevents excessive stress from being applied to the wiring board 20. Furthermore, because the thin-walled portion 34 is located a distance (length L1) from the bonding area A, heat dissipation from the semiconductor element 10 and the wiring board 20 to the cooler 110 is ensured in the relatively thick portion (e.g., thick portion 35) of the heat dissipation base 30 where the thin-walled portion 34 is not provided (thickness t shown in FIG. 1 ). Therefore, according to this embodiment, heat dissipation is ensured while preventing damage to the wiring board 20 due to deformation during fastening of the heat dissipation base 30. Furthermore, in this embodiment, because the thin-walled portion 34 is located a distance (length L1) from the joining area A, it is easier to join the wiring board 20 to the heat dissipation base 30 with the bonding material J2 compared to when the thin-walled portion 34 is not located a distance from the joining area A (for example, when the thin-walled portion 34 is provided on the entire first surface 31 except for the joining area A). Furthermore, because the thickness of the heat dissipation base 30 is reduced at the thin-walled portion 34 provided on the periphery of the first surface 31, the case 50 can be thickened at the thin-walled portion 34, thereby improving the mechanical strength of the case 50 at the fastened portion 51, etc. Furthermore, when the curvature of the heat dissipation base 30 is relatively large at the periphery of the first surface 31, the thin-walled portion 34 located on the periphery of the first surface 31 can more effectively absorb stress.

[0059] In this embodiment, a plurality of fastening holes 33 are provided in the thin portion 34 .

[0060] As a result, deformation of the heat dissipation base 30 caused by fastening the screws S in the fastening holes 33 can be absorbed by the thin-walled portions 34 from the part of the fastening holes 33 where the deformation originates. Therefore, damage to the wiring board 20 due to deformation when the heat dissipation base 30 is fastened can be further prevented.

[0061] In this embodiment, the heat dissipation base 30 has a thick portion 35 including the bonding area A, and the thickness t2 of the thin portion 34 is less than half the thickness t1+t2 of the thick portion 35.

[0062] By reducing the thickness t2 of the thin portion 34 at the periphery of the first surface 31 of the heat sink base 30 in this manner, the stress of deformation can be absorbed even more effectively.

[0063] In addition, in this embodiment, the semiconductor module 1 includes a plurality of wiring boards 20, and the heat dissipation base 30 has a thick portion 35 including a bonding area A, the thickness t1+t2 of the thick portion 35 is thicker than the thickness t2 of the thin portion 34, and the thin portion 34 is located at a distance (length L1) from the plurality of bonding areas A to which the plurality of wiring boards 20 are bonded.

[0064] Therefore, thin portion 34 absorbs stress when heat dissipation base 30 is attached to cooler 110, thereby preventing damage to multiple wiring boards 20. Furthermore, because thin portion 34 is located at a distance (length L1) from multiple bonding areas A, heat dissipation from multiple wiring boards 20 to cooler 110 can be ensured in relatively thick portion 35 of heat dissipation base 30 where thin portion 34 is not provided. Therefore, damage to multiple wiring boards 20 can be prevented while ensuring even better heat dissipation.

[0065] In the first and third modified examples of the present embodiment, thin-walled portions 134, 334 are provided across the spaces (intermediate portions 134 a, 334 a) between a plurality of bonding regions A. Desirably, thin-walled portions 134, 334 continuously surround each of wiring boards 20 on first surfaces 131, 331 in a plan view.

[0066] This allows thin-walled portions 134, 334 to absorb the stress between multiple wiring boards 20 when heat dissipation base 130, 330 is attached to cooler 110, thereby further preventing damage to multiple wiring boards 20. Furthermore, when the curvature of heat dissipation base 130, 330 is relatively large at the center of first surface 131, 331, positioning intermediate portion 134a, 334a at the center of first surface 131, 331 allows for more effective stress absorption.

[0067] In this embodiment, thin portion 34 is provided at a distance (length L2) from wiring board 20 in a plan view seen in the thickness direction of heat dissipation base 30 .

[0068] This makes it possible to further ensure heat dissipation from the semiconductor element 10 and the wiring board 20 to the cooler 110 .

[0069] In this embodiment, the thin portion 34 is provided at a position away from the joining region A by a distance (length L1) that is longer than the thickness t of the heat sink base 30 in this joining region A.

[0070] This makes it possible to further ensure heat dissipation from the semiconductor element 10 and the wiring board 20 to the cooler 110 .

[0071] In addition, in this embodiment, the thin-walled portion 34 is located at a longer distance (length L3) from the semiconductor element 10 in a planar view in the thickness direction of the heat dissipation base 30 than the distance (length D) between the semiconductor element 10 and the heat dissipation base 30 in the thickness direction (Z direction) of the heat dissipation base 30.

[0072] This makes it possible to further ensure heat dissipation from the semiconductor element 10 and the wiring board 20 to the cooler 110 .

[0073] In addition, in this embodiment, the thin portion 34 is located closer to the peripheral edge of the first surface 31 than the intermediate position between the joining area A and the fastening hole 33 (length L4a>length L4b).

[0074] This makes it possible to further ensure heat dissipation from the semiconductor element 10 and the wiring board 20 to the cooler 110 .

[0075] The embodiments of the semiconductor module 1 according to the present invention are not limited to the above-described embodiments, and may be variously changed, substituted, or modified without departing from the spirit of the technical idea. Furthermore, if the technical idea can be realized in a different way due to technological advances or other derived technologies, it may be implemented using that method. Therefore, the claims cover all embodiments that may fall within the scope of the technical idea.

[0076] For example, the heat dissipation base 30 according to the above-described embodiment is formed by warping a flat base plate by press working or the like, so that the second surface 32 is curved convexly, and the first surface 31 to which the wiring board 20 is bonded is curved concavely. However, the heat dissipation base 30 according to the present invention is not limited to such a shape. For example, the heat dissipation base 30 according to the present invention may have a convexly curved second surface 32 facing the cooler 110, and a flat first surface 31 to which the wiring board 20 is bonded. Furthermore, the apex of the convexly curved second surface 32 of the heat dissipation base 30 does not have to be at the center of the second surface 32 in a plan view, but may be off-center. Furthermore, the thin-walled portion 34 may be provided along the entire periphery of the first surface 31, but may also be interrupted in part and separated into multiple portions. The position and shape of the thin-walled portion 34 may be arbitrarily changed. Furthermore, the fastening holes 33 for screw fastening of the heat dissipation base 30 may be provided in other portions, such as the center of the longitudinal edge of the first surface 31, in addition to the corners of the first surface 31. Furthermore, the shape of the heat dissipation base 30 in plan view is not limited to the roughly rectangular planar shape in which the sides extending in the X direction and the sides extending in the Y direction are of different lengths as described above with reference to Fig. 2A etc., but may also be a roughly square planar shape in which the sides extending in the X direction and the sides extending in the Y direction are of approximately the same length.

[0077] Below, some of the inventions described in the specification and drawings of this application will be additionally noted.

[0078] <Supplementary Note 1> A semiconductor module comprising: a semiconductor element; a wiring board on which the semiconductor element is mounted; and a heat dissipation base having a first surface to which the wiring board is bonded and a second surface located on the opposite side to the first surface, wherein the heat dissipation base is warped so that the second surface is a convex curved surface, the heat dissipation base has a plurality of fastening holes formed across the first surface and the second surface, and the heat dissipation base has a thin portion on the first surface that is spaced a distance from a bonding area to which the wiring board is bonded and that is formed along the periphery of the first surface.

[0079] <Supplementary Note 2> The semiconductor module according to Supplementary Note 1, wherein the plurality of fastening holes are provided in the thin-walled portion.

[0080] <Supplementary Note 3> The semiconductor module according to Supplementary Note 1, wherein the heat dissipation base has a thick portion including the bonding area, and the thickness of the thin portion is less than half the thickness of the thick portion.

[0081] <Appendix 4> A semiconductor module according to appendix 1, comprising a plurality of the wiring boards, wherein the heat dissipation base has a thick portion including the bonding area, the thickness of the thick portion is greater than the thickness of the thin portion, and the thin portion is provided at a position spaced apart from the bonding areas to which the plurality of wiring boards are bonded.

[0082] <Supplementary Note 5> The semiconductor module according to Supplementary Note 4, wherein the thin portion is provided across the plurality of bonding regions.

[0083] <Supplementary Note 6> The semiconductor module according to Supplementary Note 1, wherein the thin portion is provided at a position spaced apart from the wiring board in a plan view.

[0084] <Supplementary Note 7> The semiconductor module according to Supplementary Note 1, wherein the thin portion is provided at a position separated from the bonding region by a distance longer than the thickness of the heat dissipation base at the bonding region.

[0085] <Appendix 8> The semiconductor module according to appendix 1, wherein the thin-walled portion is provided at a position that is a longer distance from the semiconductor element in a planar view than the distance between the semiconductor element and the heat dissipation base in the thickness direction of the heat dissipation base.

[0086] <Supplementary Note 9> The semiconductor module according to Supplementary Note 1, wherein the thin-walled portion is located closer to the periphery of the first surface than an intermediate position between the joining region and the fastening hole.

[0087] <Supplementary Note 10> The semiconductor module according to Supplementary Note 1, wherein the thin portion continuously surrounds the center portion of the heat dissipation base on the first surface in a plan view.

[0088] <Supplementary Note 11> The semiconductor module according to Supplementary Note 4, wherein the thin portion continuously surrounds each of the wiring boards on the first surface in a plan view.

[0089] <Supplementary Note 12> A semiconductor module comprising: a semiconductor element; a wiring board on which the semiconductor element is mounted; and a heat dissipation base having a first surface to which the wiring board is bonded and a second surface located opposite the first surface, wherein the heat dissipation base is warped so that the second surface is a convex curved surface, the heat dissipation base is provided with a plurality of fastening holes across the first surface and the second surface, the heat dissipation base has a thin-walled portion on the first surface that is spaced a distance from a bonding area to which the wiring board is bonded and that is provided along a periphery of the first surface, and the thin-walled portion occupies 70% or more of the distance of the periphery of the heat dissipation base at the periphery surrounding the plurality of fastening holes.

[0090] <Supplementary Note 13> The semiconductor module according to Supplementary Note 12, wherein the heat dissipation base has a periphery where the thin-walled portion is not formed near the middle of the plurality of adjacent fastening holes.

[0091] 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.

[0092] This application is based on Japanese Patent Application No. 2024-125807, filed August 1, 2024, the contents of which are incorporated herein in their entirety.

[0093] REFERENCE SIGNS LIST 1 semiconductor module 10 semiconductor element 20 wiring board 21 first conductor layer 22 second conductor layer 23 insulating layer 30 heat dissipation base 31 first surface 32 second surface 33 fastening hole 34 thin-walled portion 35 thick-walled portion 41, 42 main terminal 41a, 42a through hole 50 case 51 fastened portion 60 sealing material 100 energy conversion device 110 cooler 130, 230, 330 heat dissipation base 131, 231, 331 first surface 132, 232, 332 second surface 133, 233, 333 fastening hole 134, 234, 334 thin-walled portion 134a, 334a middle portion 135, 235, 335 thin-walled portion A bonding area C central portion J1, J2 Bonding material Lo Loop Lo1, Lo2, Lo3, Lo4 Intermediate S Screw T Thermal conductive material W Wiring

Claims

1. A semiconductor module comprising: a semiconductor element; a wiring board on which the semiconductor element is mounted; and a heat dissipation base having a first surface to which the wiring board is bonded and a second surface located on the opposite side to the first surface, wherein the heat dissipation base is warped so that the second surface is a convex curved surface, the heat dissipation base has a plurality of fastening holes formed across the first surface and the second surface, and the heat dissipation base has a thin portion on the first surface that is spaced a distance from the bonding area to which the wiring board is bonded and that is formed along the periphery of the first surface.

2. The semiconductor module according to claim 1, wherein the plurality of fastening holes are provided in the thin-walled portion.

3. The semiconductor module according to claim 1, wherein the heat dissipation base has a thick portion including the bonding area, and the thickness of the thin portion is less than half the thickness of the thick portion.

4. A semiconductor module as described in claim 1, characterized in that it comprises a plurality of the wiring boards, the heat dissipation base has a thick portion including the bonding area, the thickness of the thick portion is greater than the thickness of the thin portion, and the thin portion is located at a distance from the bonding areas to which the plurality of wiring boards are bonded.

5. The semiconductor module according to claim 4, wherein the thin portion is provided across the plurality of bonding regions.

6. The semiconductor module according to claim 1, wherein the thin portion is provided at a position spaced apart from the wiring board in a plan view.

7. The semiconductor module according to claim 1, wherein the thin portion is provided at a position spaced from the bonding area by a distance greater than the thickness of the heat sink base at the bonding area.

8. A semiconductor module according to claim 1, characterized in that the thin-walled portion is located at a position that is a longer distance from the semiconductor element in a planar view than the distance between the semiconductor element and the heat dissipation base in the thickness direction of the heat dissipation base.

9. The semiconductor module according to claim 1, wherein the thin-walled portion is located closer to the periphery of the first surface than the intermediate position between the joining region and the fastening hole.

10. The semiconductor module according to claim 1, wherein the thin portion continuously surrounds the center of the heat dissipation base on the first surface in a plan view.

11. The semiconductor module according to claim 4, wherein the thin portion continuously surrounds each of the wiring boards on the first surface in a plan view.

12. A semiconductor module comprising: a semiconductor element; a wiring board on which the semiconductor element is mounted; and a heat dissipation base having a first surface to which the wiring board is bonded and a second surface located opposite the first surface, wherein the heat dissipation base is warped so that the second surface is a convex curved surface, the heat dissipation base has a plurality of fastening holes formed across the first and second surfaces, the heat dissipation base has a thin-walled portion on the first surface that is spaced apart from a bonding area to which the wiring board is bonded and that is formed along the periphery of the first surface, and the thin-walled portion occupies 70% or more of the distance of the periphery of the heat dissipation base at the periphery surrounding the plurality of fastening holes.

13. The semiconductor module according to claim 12, wherein there are areas on the periphery of the heat dissipation base where the thin-walled portions are not formed near the middle of the plurality of adjacent fastening holes.

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