Heat dissipation base, semiconductor module, and energy conversion device

Abstract

The present invention prevents damage to a wiring board caused by deformation of a heat dissipation base to which the wiring board is joined. A second surface of a heat dissipation base (3), which has a first surface to which a wiring board (4) is joined and a second surface facing a cooler (10), is a convex curved surface, and has a substantially rectangular shape having a side extending in a first direction and a side extending in a second direction in plan view. A first curve indicating the shape of the second surface on a first straight line that passes through the center of the second surface and extends in the first direction, and a second curve indicating the shape of the second surface on a second straight line that passes through the center of the second surface and extends in the second direction are provided. In a third curve representing the shape of the second surface on a straight line in the diagonal direction, a change in shape in the direction from the end toward the center, including the end, is represented by a curve protruding downward, and in a third curve representing the shape of the second surface on a straight line in the diagonal direction, a change in shape in the direction from the end toward the center, including the end, is represented by a curve protruding upward. And a change in shape in a direction from the center toward the end portion, including the center, is represented by a curve protruding downward.

Description

Technical Field

[0001] The invention relates to a heat dissipation base, a semiconductor module and an energy conversion device. Background Art

[0002] Among semiconductor devices used in power conversion devices such as inverter devices, there are semiconductor devices in which a heat sink base on which a wiring board and semiconductor elements are arranged is mounted on a cooler. Among the heat sink bases used in such semiconductor devices, there are heat sink bases formed in a manner such that a second surface opposite to a first surface on which a wiring board and semiconductor elements are arranged and facing the cooler is convex (for example, refer to Patent Documents 1 to 7).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2018-195717

[0006] Patent Document 2: Japanese Patent Application Publication No. 2020-188152

[0007] Patent Document 3: Japanese Patent Application Publication No. 2016-167548

[0008] Patent Document 4: International Publication No. 2012 / 108073

[0009] Patent Document 5: Japanese Patent Application Publication No. 2007-88045

[0010] Patent Document 6: Japanese Patent Application Publication No. 2005-39081

[0011] Patent Document 7: U.S. Patent No. 7511961 Summary of the invention

[0012] Problem that the invention aims to solve

[0013] A wiring board is bonded to the first surface of the heat dissipation base by a bonding material. The heat dissipation base formed in such a way that the second surface becomes convex deforms in the direction that the second surface changes from a convex curved surface to a flat surface when mounted on the cooler. Therefore, due to the deformation of the heat dissipation base, deformation stress is applied to the wiring board bonded to the first surface of the heat dissipation base by the bonding material, and the wiring board may be damaged.

[0014] In one aspect, an object of the present invention is to prevent damage to a wiring board caused by deformation of a heat dissipation base to which the wiring board is bonded.

[0015] Solutions for solving problems

[0016] A heat dissipation base of a technical solution comprises a first surface for bonding a wiring board and a second surface located on the opposite side of the first surface and opposite to the cooler, wherein the second surface of the heat dissipation base is a convex curved surface, and its shape when viewed from above is a roughly rectangular shape having sides extending in the first direction and sides extending in the second direction. When the second surface is facing downward, in each of a first curve representing the shape of the second surface on a first straight line passing through the center of the second surface and extending in the first direction, and a second curve representing the shape of the second surface on a second straight line passing through the center of the second surface and extending in the second direction, a change in shape in a direction from the end toward the center including the end is represented by a curve convex downward, and in a third curve representing the shape of the second surface on a straight line in a diagonal direction of the heat dissipation base, a change in shape in a direction from the end toward the center including the end is represented by a curve convex upward, and a change in shape in a direction from the center toward the end including the center is represented by a curve convex downward.

[0017] Effects of the Invention

[0018] According to the above-described technical solution, it is possible to prevent damage to the wiring board due to deformation of the heat dissipation base to which the wiring board is bonded. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a plan view showing a configuration example of an energy conversion device according to an embodiment.

[0020] Figure 2 It means in Figure 1 A sectional side view of an example of the structure inside the energy conversion device cut along the line AA'.

[0021] Figure 3 It means in Figure 1 A sectional side view of the energy conversion device cut along the BB' line.

[0022] Figure 4 It is a diagram showing a configuration example of a circuit of a semiconductor module.

[0023] Figure 5 This is a bottom view for explaining an example of a coating pattern of a thermally conductive material when a heat dissipating base is mounted on a cooler.

[0024] Figure 6 This is a diagram for explaining how the heat conductive material spreads when the heat dissipation base is attached to the cooler.

[0025] Figure 7 This is a diagram for explaining an example of a problem that occurs when a heat dissipation base is mounted on a cooler.

[0026] Figure 8This is a plan view for explaining an example of the shape of a heat dissipation base according to one embodiment.

[0027] Fig. 9 Yes Description Figure 8 Graph showing the warping tendency of the heat dissipation base in three directions as an example.

[0028] Fig.10 Yes Description Figure 8 Graph showing a specific example of the warpage of the heat dissipation base in the diagonal direction as illustrated in FIG.

[0029] Fig.11 It means Figure 8 FIG. 4 is a diagram illustrating deformation of the heat dissipation base when the heat dissipation base is mounted on a cooler.

[0030] Fig.12 This is a diagram for supplementing the shape of the convex curved surface of the heat dissipation base according to one embodiment. DETAILED DESCRIPTION

[0031] Hereinafter, the embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the X, Y, and Z axes in the referenced figures are shown for the purpose of defining the planes and directions in the energy conversion device, semiconductor module, etc. exemplified. The X, Y, and Z axes are orthogonal to each other and constitute a right-hand system. In the following description, the Z direction is sometimes referred to as the up and down direction. In addition, sometimes the surface including the X-axis and the Y-axis is referred to as the XY surface, the surface including the Y-axis and the Z-axis is referred to as the YZ surface, and the surface including the Z-axis and the X-axis is referred to as the ZX surface. These directions and surfaces are terms used for the convenience of explanation, and the corresponding relationship with each of the XYZ directions may sometimes change depending on the different installation postures of the energy conversion device, etc. For example, in this specification, the surface facing the positive side (+Z direction) of the Z direction in the component constituting the energy conversion device is referred to as the upper surface, and the surface facing the negative side (-Z direction) of the Z direction is referred to as the lower surface, but the surface facing the negative side of the Z direction may also 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. In this specification, the planar viewing angle refers to the case where the upper surface or the lower surface (XY plane) of the energy conversion device or the like is viewed from the Z direction.

[0032] The aspect ratios and the size relationships of the components in the drawings are only schematic representations and may not be consistent with the relationships in the energy conversion device actually manufactured. For the sake of convenience, it is also assumed that the size relationships of the components are exaggerated. In addition, there are also cases where the shapes of the same components are different between different drawings.

[0033] In the following description, as an example of the energy conversion device of the present disclosure, an inverter device such as an electric power conversion device applied to an industrial or vehicle-mounted motor is cited. Therefore, in the following description, detailed descriptions of the structure, function, operation, assembly method, etc. that are the same or similar to the known energy conversion device are omitted.

[0034] Figure 1 It is a plan view showing a configuration example of an energy conversion device according to an embodiment. Figure 2 It means in Figure 1 A sectional side view of an example of the structure inside the energy conversion device taken along the line AA'. Figure 3 is Figure 1 A sectional side view of the energy conversion device taken along line BB'. Figure 4 FIG. 1 is a diagram showing a configuration example of a circuit of a semiconductor module. Figure 1 In the embodiment, the sealing material for sealing the wiring board and semiconductor elements is omitted. Figure 2 The diagram schematically shows the Figure 1 An example of a structure of a portion of an energy conversion device cut along the line AA' of the left side of the energy conversion device. Figure 2 In FIG. 1 , the hatching lines representing the cross-section of the sealing material are omitted. Figure 3 The diagram schematically shows the Figure 1 An example of a structure of a portion of an energy conversion device cut along line BB' located on the left side of line BB'.

[0035] Figure 1 to Figure 3 The energy conversion device 1 illustrated includes a semiconductor module 2 as a semiconductor device and a cooler 10. The semiconductor module 2 includes a heat sink 3, a wiring board 4, semiconductor elements 5A, 5B, a plurality of bonding wires 7A to 7F, a housing 8, and a sealing material 9. The cooler 10 includes a heat sink 11 and a water cooling jacket 12. The semiconductor module 2 is mounted on the cooler 10 using a screw member 13, which has an external thread, passes through a through hole of the heat sink 3, and is threadedly engaged with a threaded hole (internal thread) provided on the upper surface 1110 of the heat sink 11 of the cooler 10. The heat sink 3 of the semiconductor module 2 is connected to the heat sink 11 of the cooler 10 via a heat conductive material 14 such as thermal grease or a heat conductive compound.

[0036] Figure 1 to Figure 3 The semiconductor module 2 shown in the example is composed of Figure 4The illustrated single-phase voltage type half-bridge inverter circuit. A wiring board 4 is arranged on the upper surface of the heat dissipation base 3 of the semiconductor module 2. The wiring board 4 includes an insulating substrate 400, a first conductor pattern 401 and a second conductor pattern 402 provided on the upper surface (first surface) of the insulating substrate 400, and a third conductor pattern 403 provided on the lower surface (second surface) of the insulating substrate 400. The wiring board 4 can be, for example, a DCB (Direct Copper Bonding) substrate or an AMB (Active Metal Brazing) substrate. The wiring board 4 can also be called a laminated substrate or an insulating circuit substrate.

[0037] The insulating substrate 400 is not limited to a specific substrate. The insulating substrate 400 may be made of, for example, aluminum oxide (Al 2 O 3 ), aluminum nitride (AlN), silicon nitride (Si 3 N 4 ) and aluminum oxide (Al 2 O 3 ) and zirconium oxide (ZrO 2 ) or a ceramic substrate formed of a composite material such as a ceramic substrate of a composite material of a 2- or 3-dimensional ceramic substrate. The insulating substrate 400 may be, for example, a substrate formed by molding an insulating resin such as 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.

[0038] The third conductor pattern 403 is a member that functions as a heat conducting member that conducts heat generated by the inverter circuit to the heat dissipation base 3, and is formed of, for example, a metal plate or metal foil such as copper or aluminum. The third conductor pattern 403 is bonded to the heat dissipation base 3 using a bonding material 21 such as solder. The third conductor pattern 403 may also be referred to as a heat dissipation layer or a heat dissipation pattern.

[0039] The first conductor pattern 401 and the second conductor pattern 402 function as wiring members in the inverter circuit and are formed of, for example, a metal plate or metal foil such as copper or aluminum. The first conductor pattern 401 and the second conductor pattern 402 may also be referred to as a conductor layer, a conductor plate, a conductive layer, or a wiring pattern.

[0040] A first semiconductor element 5A is arranged on the first conductor pattern 401 and is bonded to the first conductor pattern 401 by a bonding material (not shown). A second semiconductor element 5B is arranged on the second conductor pattern 402 and is bonded to the second conductor pattern 402 by a bonding material 2122. The first semiconductor element 5A and the second semiconductor element 5B are bonded to the first conductor pattern 401 and the second conductor pattern 402, respectively, by a conductive bonding material such as solder.

[0041] The first semiconductor element 5A and the second semiconductor element 5B are each composed of, for example, an RC (Reverse Conducting: reverse conducting)-IGBT element formed by integrating an IGBT (Insulated Gate Bipolar Transistor) element as a switching element and a diode element such as a FWD (Free Wheeling Diode) element connected in reverse parallel to the switching element. The switching element and the diode element in the semiconductor elements 5A and 5B are not limited to being formed on a Si substrate, and can also be formed on a semiconductor substrate using a wide bandgap semiconductor such as SiC (silicon carbide) and GaN (gallium nitride). Such semiconductor elements 5A and 5B are respectively provided with a first main electrode not shown in the figure on the lower surface, and a second main electrode and a control electrode (gate) not shown in the figure on the upper surface. That is, the first conductor pattern 401 is electrically connected to the first main electrode of the first semiconductor element 5A by a conductive bonding material, and the second conductor pattern 402 is electrically connected to the first main electrode of the second semiconductor element 5B by a conductive bonding material 22.

[0042] The second main electrode provided on the upper surface of the first semiconductor element 5A is electrically connected to an output terminal 803 provided on the housing 8 by means of a bonding wire 7A. The control electrode provided on the upper surface of the first semiconductor element 5A is electrically connected to a first control terminal 804 provided on the housing 8 by means of a bonding wire 7C. The first conductor pattern 401 electrically connected to the first main electrode provided on the lower surface of the first semiconductor element 5A is electrically connected to a first input terminal (P terminal) 801 provided on the housing 8 by means of a bonding wire 7B. That is, the first main electrode of the first semiconductor element 5A is electrically connected to the first input terminal 801 provided on the housing 8 via the bonding material, the first conductor pattern 401, and the bonding wire 7B.

[0043] The second main electrode provided on the upper surface of the second semiconductor element 5B is electrically connected to the second input terminal (N terminal) 802 provided on the housing 8 by means of a bonding wire 7D. The control electrode provided on the upper surface of the second semiconductor element 5B is electrically connected to the second control terminal 805 provided on the housing 8 by means of a bonding wire 7F. The second conductor pattern 402 electrically connected to the first main electrode provided on the lower surface of the second semiconductor element 5B is electrically connected to the output terminal 803 provided on the housing 8 by means of a bonding wire 7E. That is, the first main electrode of the second semiconductor element 5B is electrically connected to the output terminal 803 provided on the housing 8 via the bonding material 22, the second conductor pattern 402, and the bonding wire 7E.

[0044] The first input terminal 801, the second input terminal 802, the output terminal 803, the first control terminal 804, and the second control terminal 805 are provided integrally with the insulating member 800 of the housing 8. The upper and lower surfaces of the insulating member 800 are open, and have a hollow portion capable of accommodating the wiring board 4, the semiconductor elements 5A, 5B, the bonding wires 7A to 7F, etc. arranged on the upper surface of the heat dissipation base 3. The insulating member 800 is formed of an insulating resin material such as PPS (Poly Phenylene Sulfide) and PA (Poly Amide). The first input terminal 801, the second input terminal 802, the output terminal 803, the first control terminal 804, and the second control terminal 805 are formed of a metal plate such as a copper plate, and are integrated with the insulating member 800 by, for example, insert molding.

[0045] The first input terminal 801, the second input terminal 802, and the output terminal 803 are bent in such a manner that the portion protruding from the upper surface of the insulating member 800 extends along the upper surface of the insulating member 800. In the upper surface of the insulating member 800, in the region overlapping with the first input terminal 801, in the region overlapping with the second input terminal 802, and in the region overlapping with the output terminal 803, there are respectively provided a receiving portion (not shown) that can receive the nut 15 in a direction that the axial direction of the threaded hole becomes the up-down direction. The first input terminal 801, the second input terminal 802, and the output terminal 803 are provided with a through hole (not shown) that can threadably engage a threaded component such as a bolt with the nut 15 received in the receiving portion of the insulating member 800.

[0046] One end of each of the first input terminal 801, the second input terminal 802, the output terminal 803, the first control terminal 804, and the second control terminal 805 is exposed to the inner peripheral surface of the hollow portion defined by the insulating member 800. One end of the bonding wires 7A to 7F is electrically connected to the portion of the corresponding terminal exposed to the inner peripheral surface of the insulating member 800.

[0047] The housing 8 is mounted on the heat dissipation base 3 by bonding the lower surface of the insulating member 800 to the upper surface of the heat dissipation base 3. The adhesive 16 bonding the insulating member 800 to the heat dissipation base 3 can be, for example, an epoxy-based adhesive or a silicone-based adhesive. The wiring board 4, the semiconductor elements 5A and 5B, and the bonding wires 7A to 7F arranged on the upper surface of the heat dissipation base 3 are located in a recessed space defined by the heat dissipation base 3 and the insulating member 800 of the housing 8, and are sealed by a sealing material 9 filled in the recessed space. The sealing material 9 can be, for example, an epoxy resin, a silicone gel, or the like.

[0048] like Figure 1As shown in the example, the heat sink 3 is a plate-like member having a substantially rectangular shape with rounded corners when viewed from above and having a through hole (not shown) formed at the corner for the rod of the screw 13 to pass through. The heat sink 3 is a member that functions as a heat-conducting member that conducts the heat generated by the semiconductor elements 5A and 5B to the cooler 10, and is formed of a metal plate such as a copper plate or an aluminum plate. The heat sink 3 is warped, for example, by stamping a flat metal plate so that the lower surface 301 becomes a convex curved surface. The insulating member 800 of the housing 8 is shaped such that the corners on the outer peripheral side are cut off in a manner that does not overlap with the through hole of the heat sink 3 when viewed from above (more specifically, in a manner that enables the screw 13 to be threadedly connected to the threaded hole of the heat sink 11).

[0049] As mentioned above, the above reference Figure 1 to Figure 3 The semiconductor module 2 described above is composed of Figure 4 The illustrated single-phase voltage type half-bridge inverter circuit (hereinafter referred to as "half-bridge inverter circuit") is a circuit diagram of a single-phase voltage type half-bridge inverter circuit. The half-bridge inverter circuit includes a switch element 503 and a diode element 504 connected between a first input terminal IN(P) and an output terminal OUT, and a switch element 505 and a diode element 506 connected between a second input terminal IN(N) and an output terminal OUT. The first input terminal IN(P) and the output terminal OUT are sometimes referred to as an upper arm, and the second input terminal IN(N) and the output terminal OUT are sometimes referred to as a lower arm. Figure 1 to Figure 3 In the semiconductor module 2 described above, the switch element 503 and the diode element 504 of the upper arm are formed in the first semiconductor element 5A, and the switch element 505 and the diode element 506 of the lower arm are formed in the second semiconductor element 5B.

[0050] When the switch elements 503 and 505 are IGBT elements, the first main electrode on the lower surface side of the first semiconductor element 5A and the second semiconductor element 5B is called a collector, and the second main electrode on the upper surface side is called an emitter. The collector of the switch element 503 of the upper arm is connected to the first input terminal IN(P) which can be the first input terminal 801, and the emitter of the switch element 505 of the lower arm is connected to the second input terminal IN(N) which can be the second input terminal 802. The first input terminal IN(P) and the second input terminal IN(N) are connected to the positive electrode and the negative electrode of the DC power supply, respectively. The emitter of the switch element 503 of the upper arm and the collector of the switch element 505 of the lower arm are connected to the output terminal OUT which can be the output terminal 803. In addition, the gate of the switch element 503 and the gate of the switch element 505 are connected to a control circuit (not shown) via the first control terminal 804 and the second control terminal 805, respectively.

[0051] Figure 4The illustrated half-bridge inverter circuit can convert the DC between the first input terminal IN(P) and the second input terminal IN(N) into AC and output it from the output terminal OUT by using the control signal applied to the gate of the switching element 503 of the upper arm and the control signal applied to the gate of the switching element 505 of the lower arm. In addition, three ACs can be connected in parallel between the first input terminal IN(P) and the second input terminal IN(N). Figure 4 The illustrated half-bridge inverter circuit is configured as a three-phase AC inverter circuit by controlling control signals applied to each circuit.

[0052] With the above reference Figure 4 The semiconductor module 2 of the half-bridge inverter circuit described above is not limited to the semiconductor module 2 of the half-bridge inverter circuit described above. Figure 1 to Figure 3 The structure described. The switch elements 503 and 505 may be composed of, for example, a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a BJT (Bipolar Junction Transistor), etc. In the case where the switch element is a MOSFET element, the main electrode on the lower surface side of the semiconductor element 5A and 5B may also be called a drain, and the main electrode on the upper surface side may also be called a source. In addition, the diode elements 504 and 506 may also be composed of, for example, an SBD (Schottky Barrier Diode), a JBS (Junction Barrier Schottky) diode, an MPS (Merged PN Schottky) diode, a PN diode, etc. In addition, the substrate forming the switch elements 503 and 505 and the diode elements 504 and 506 is not limited to a Si substrate, and may be, for example, a substrate using a wide bandgap semiconductor such as SiC (silicon carbide) or GaN (gallium nitride).

[0053] In addition, for the semiconductor module 2, for example, each element such as the switch element 503 and the diode element 504 of the upper arm and the switch element 505 and the diode element 506 of the lower arm may be an independent semiconductor element. For example, the switch element 503 and the diode element 504 of the upper arm are not limited to one semiconductor element 5A (one semiconductor chip) formed with these elements on one semiconductor substrate, and may be composed of one or more semiconductor elements (one or more semiconductor chips) formed with the switch element 503 and one or more semiconductor elements (one or more semiconductor chips) formed with the diode element 504. The shape, number of arrangements, arrangement position, etc. of the semiconductor element can be changed appropriately. The layout of the conductor pattern as a wiring member provided on the upper surface side of the wiring board 4 is changed according to the type, shape, number of arrangements, arrangement position, etc. of the semiconductor element mounted. In addition, some or all of the bonding wires 7A to 7F of the semiconductor module 2 described above may be replaced by leads formed by processing a metal plate such as a copper plate, for example.

[0054] In addition, the control electrode provided on the upper surface of the semiconductor elements 5A and 5B may also include a gate and an auxiliary electrode. For example, the auxiliary electrode may be an auxiliary emitter or an auxiliary source that is electrically connected to the main electrode on the upper surface side and serves as a reference potential relative to the gate potential. In addition, the auxiliary electrode may be a temperature sensing electrode that is electrically connected to a temperature sensing portion that is sometimes included in an inverter device having the semiconductor module 2 and measures the temperature of the semiconductor elements 5A and 5B. These electrodes (main electrodes and control electrodes including gates and auxiliary electrodes) formed on the upper surfaces of the semiconductor elements 5A and 5B may also be collectively referred to as upper surface electrodes.

[0055] The circuit structure of the semiconductor module 2 is not limited to the above reference Figure 4 The inverter circuit of the semiconductor module 2 may be, for example, a single-phase full-bridge inverter circuit. In addition, the inverter circuit in one semiconductor module 2 is not limited to a single-phase inverter circuit, and may be, for example, a three-phase AC inverter circuit as described above.

[0056] Installed as mentioned above Figure 1 to Figure 3The cooler 10 of the semiconductor module 2 described includes a heat sink 11 and a water cooling jacket 12. The heat sink 11 includes a base 1101 having an upper surface 1110 on which the semiconductor module 2 is mounted and a plurality of heat sink portions 1102 extending downward from the lower surface of the base 1101. The water cooling jacket 12 is configured to have a shape that divides a flow path of a refrigerant provided with the heat sink portions 1102 when mounted on the heat sink 11. The energy conversion device 1 of the present embodiment conducts part of the heat generated by the semiconductor elements 5A and 5B during the operation of the semiconductor module 2 to the cooler 10 via the wiring board 4 and the heat sink base 3 to dissipate the heat. In this energy conversion device 1, a heat conductive material 14 such as thermal grease is used to improve the adhesion between the heat sink base 3 and the heat sink 11, so that heat can be efficiently conducted from the heat sink base 3 to the cooler 10 (heat sink 11).

[0057] Figure 5 This is a bottom view for explaining an example of a coating pattern of a thermally conductive material when a heat dissipating base is mounted on a cooler. Figure 6 This is a diagram for explaining how the heat conductive material spreads when the heat dissipation base is attached to the cooler. Figure 7 1 is a diagram illustrating an example of a problem that occurs when a heat dissipation base is mounted on a cooler. Figure 6 and Figure 7 In the figure, the heat sink portion 1102 of the heat sink 11 is omitted.

[0058] When the heat conductive material 14 such as thermal grease is used to improve the adhesion between the heat dissipation base 3 and the heat sink 11, for example, Figure 5 and Figure 6 As shown in FIG. 1A, a plurality of heat conductive materials 14 are arranged in a predetermined pattern on the lower surface 301 of the heat dissipation base 3. The shape of the heat dissipation base 3 when viewed from above is a rectangular shape with rounded corners, and a through hole 303 is formed at the corner for the screw 13 to pass through. In addition, the heat dissipation base 3 is set to a shape in which a flat metal plate is warped in a manner such that the lower surface 301 becomes a convex curved surface by, for example, stamping. Figure 6 The lower surface 301 of the heat dissipation base 3 illustrated in A to C is a curved surface in which the center portion of the lower surface 301 is the top in a plan view and the change in the relative position of each point of the lower surface 301 in the Z direction with respect to the center portion is represented by a downwardly convex curve.

[0059] The plurality of thermally conductive materials 14 are arranged on the lower surface 301 of the heat dissipation base 3 except for the periphery of the through hole 303. The arrangement pattern of the plurality of thermally conductive materials 14 is not limited to Figure 5The illustrated pattern is a pattern of arranging heat-conducting materials of the same shape and the same size. The plurality of heat-conducting materials 14 arranged on the lower surface 301 of the heat dissipation base 3 may be, for example, of various shapes, or of the same shape but of various sizes. The arrangement pattern of the plurality of heat-conducting materials 14 may also vary, for example, depending on the distance from the center of the lower surface 301 of the heat dissipation base 3 when viewed from above.

[0060] If the lower surface 301 of the heat dissipation base 3 and the upper surface 1110 of the heat dissipation sheet 11 are arranged on the heat dissipation sheet 11 opposite to each other, Figure 6 As shown in A of FIG. 1 , the heat conductive material 14 disposed at the center and the periphery of the lower surface 301 first contacts the upper surface 1110 of the heat sink 11. Then, for example, if the heat sink base 3 is pressed against the upper surface 1110 of the heat sink 11, Figure 6 As shown in B and C, the thermal conductive material 14 in contact with the heat sink 11 expands radially outward from the center of the lower surface 301 and integrates between the lower surface 301 of the heat sink 3 and the upper surface 1110 of the heat sink 11. At this time, if the lower surface 301 of the heat sink 3 is set as a convex curved surface in advance, the thermal conductive material 14 can easily expand radially outward from the center of the lower surface 301 of the heat sink 3, and it is not easy to generate gaps in the thermal conductive material 14 after integration.

[0061] However, when the heat dissipation base 3 is mounted on the heat sink 11 of the cooler 10, Figure 6 As shown in A to C of , the wiring board 4 is joined to the upper surface 302 of the heat sink 3. When the heat sink 3 is mounted on the heat sink 11 of the cooler 10, the heat sink 3 is fixed to the heat sink 11 by the screw 13 after the heat conductive material 14 is extended between the heat sink 3 and the heat sink 11.

[0062] Figure 7 Schematically shows the deformation of the heat sink 30 used in the conventional semiconductor device (semiconductor module) when the heat sink 30 is mounted on the heat sink 11 of the cooler 10. For the conventional heat sink 30, when the lower surface 301 is facing downward, for example, the shape of the lower surface 301 observed on a straight line in a diagonal direction passing through the through hole 303 for screw fastening is represented by a downward convex curve.

[0063] In the case where there is a through hole 303 for screw fastening at the corner of the lower surface 301 of the heat dissipation base 30, if the screw 13 passing through the through hole 303 is screwed into the screw hole 1111 on the upper surface 1110 of the heat dissipation fin 11, Figure 7As shown in the example, the heat dissipation base 30 is deformed in a manner that the convex curved surface of the lower surface 301 (the curved surface represented by the solid line) is changed into a nearly flat curved surface with a smaller curvature (the curved surface represented by the double-dashed line). That is, when the heat dissipation base 30 is mounted on the heat sink 11 by the screw 13, the heat dissipation base 30 is deformed in a direction in which the warping becomes smaller than before the mounting. If the heat dissipation base 30 is deformed in a direction in which the warping becomes smaller, a deformation stress is applied to the wiring board 4 bonded to the upper surface 302 of the heat dissipation base 30, and damage to the wiring board 4 such as cracking of the insulating substrate 400 and peeling of the conductor patterns 401 to 403 from the insulating substrate 400 may occur. Such damage to the wiring board 4 is likely to occur in the following cases: the area of ​​the lower surface 301 of the heat dissipation base 30 is large, the wiring board 4 is arranged near the through hole 303, and the through hole 303 for the screw 13 to penetrate is formed at the corner of the lower surface 301.

[0064] Figure 8 This is a plan view for explaining an example of the shape of a heat dissipation base according to one embodiment. Fig. 9 Yes Description Figure 8 A graph showing the warping tendency of the heat sink in three directions. Fig.10 Yes Description Figure 8 A graph showing a specific example of the warpage of the heat dissipation base in the diagonal direction. Fig.11 It means Figure 8 A diagram illustrating deformation of the heat dissipation base when the heat dissipation base is attached to a cooler.

[0065] Figure 8 A diagram illustrating the definition of parameters used in the description of the shape of the heat dissipation base 3 of the present embodiment. The shape of the convex curved surface of the lower surface 301 in the heat dissipation base 3 of the present embodiment is described using a curve representing the shape of the lower surface 301 observed on a straight line S1 in the long side direction (X direction) passing through the center P of the lower surface 301 when viewed from above, a curve representing the shape of the lower surface 301 observed on a straight line S2 in the short side direction (Y direction), and a curve representing the shape of the lower surface 301 observed on a straight line S3 in the diagonal direction (D direction). Figure 8 The illustrated heat dissipation base 3 has a dimension in the long side direction of Lx (mm), a dimension in the short side direction of Ly (mm), and a dimension in the diagonal direction of Ld (mm). In addition, for the sake of simplicity, the lower surface 301 of the heat dissipation base 3 is a convex curved surface with the center P as the vertex when viewed from above.

[0066] exist Fig. 9 In the graph, curve R1 represents Figure 8 The shape of the lower surface 301 observed on the straight line S1 in the long side direction (X direction) of the heat dissipation base 3 is shown in FIG. Figure 8 The shape of the lower surface 301 viewed from the straight line S2 in the short side direction (Y direction) of the heat dissipation base 3 is shown as an example. Fig. 9 In the graph of Figure 8 The shape of the lower surface 301 as viewed from the straight line S3 in the diagonal direction (direction D) of the heat dissipation base 3 shown in the example. The shape of the lower surface 301 indicated by the straight line S3 includes a portion of the opening end of the lower surface 301 side of the through hole 303. Fig. 9 In the graph of , the horizontal axis is the distance from the center P of the lower surface 301, and the distance to the portion located on the positive side of the center P in each direction of the X direction, the Y direction, and the D direction is represented by a positive value, and the distance to the portion located on the negative side of the center P is represented by a negative value. Fig. 9 In the graph of , the vertical axis represents the relative position in the Z direction of each point with respect to the position of the center P in the Z direction when the lower surface 301 of the heat dissipation base 3 is directed downward (to the negative side in the Z direction).

[0067] For the lower surface 301 of the heat dissipation base 3 of the present embodiment, the relative position in the Z direction of each point on the straight line S1 passing through the long side direction (X direction) of the center P is shown as a curve R1, and the whole is represented by a downward convex curve. On the straight line S1, the relative position in the Z direction in the direction from the end point toward the center P including the end point (end) of the straight line S1 and the relative position in the Z direction in the direction from the center P toward the end point including the center P are both changed as represented by a downward convex curve. Similarly, for the lower surface 301 of the heat dissipation base 3 of the present embodiment, the relative position in the Z direction of each point on the straight line S2 passing through the short side direction (Y direction) of the center P is shown as a curve R2, and the whole is represented by a downward convex curve. On the straight line S2, the relative position in the Z direction in the direction from the end point toward the center P including the end point (end) of the straight line S2 and the relative position in the Z direction in the direction from the center P toward the end point including the center P are both changed as represented by a downward convex curve.

[0068] In contrast, for the lower surface 301 of the heat dissipation base 3 of the present embodiment, the relative positions in the Z direction of each point on the straight line S3 passing through the diagonal direction (D direction) of the center P have a section in which the change is represented by a downward convex curve and a section in which the change is represented by an upward convex curve, as shown by the curve R3. On the straight line S3, the relative position in the Z direction in the direction from the end point toward the center P including the end point (end) of the straight line S3 changes as represented by an upward convex curve, and the relative position in the Z direction in the direction from the center P toward the end point including the center P changes as represented by a downward convex curve. Specifically, the section where the distance Lp from the center is Li>Lp>-Li changes as represented by a downward convex curve, and the section where Lp>Li changes as represented by an upward convex curve. That is, the curve R3 has an inflection point Q at the distances from the center P of -Li and Li.

[0069] The distances -Li and Li related to the position of the inflection point Q are set, for example, between the minimum value Lk1 and the maximum value Lk2 of the distance from the center of the through hole 303 for screw fastening formed at the corner of the heat dissipation base 3. The minimum value Lk1 and the maximum value Lk2 of the distance are set, for example, based on the dimension Lx in the long side direction and the dimension Ly in the short side direction of the heat dissipation base 3 and the hole diameter of the through hole 303 for screw fastening. When the dimension Lx in the long side direction and the dimension Ly in the short side direction of the heat dissipation base 3 are Lx = about 120 mm and Ly = about 60 mm, and the hole diameter of the through hole 303 for screw fastening is about 5 mm, the minimum value Lk1 and the maximum value Lk2 of the distance can be set, for example, to Lk1 = 5 mm and Lk2 = 20 mm.

[0070] exist Fig. 9 The curve R3 shown in the example has a downward convex curve and an upward convex curve bounded by the inflection point Q, for example. Fig.10 As shown, the tangent line of the upward convex curve at the position of the desired inflection point Q is consistent with the tangent line T of the downward convex curve. As a result, the relative position in the Z direction of each point in the end section from the end point to the nearest inflection point Q on the diagonal straight line S3 can be made smaller than the relative position in the case where the change in the relative position in the Z direction in the central section between the two inflection points Q is extended to the end section ( Fig.10 The relative positions are shown by dashed lines in the figure).

[0071] When the change of the convex curved surface in the diagonal direction (D direction) of the heat dissipation base 3 satisfies the above-mentioned conditions (conditions of the curve R3) and the distance Li from the center is about 48 mm and the relative position in the Z direction at the position of the distance Li is 160 μm, the relative position in the Z direction of the end portion in the diagonal direction can be set to about 240 μm, for example. On the other hand, when only the change of the relative position in the Z direction in the diagonal direction is set to the change represented by the downward convex curve without the inflection point Q in the same manner as the change in the long side direction and the change in the short side direction, the change of the relative position in the Z direction in the end portion section becomes Fig.10 The change is shown by the dotted line in FIG. 1. In this case, the relative position of the end in the diagonal direction in the Z direction is, for example, about 310 μm.

[0072] Thus, by setting the convex curved surface of the lower surface 301 of the heat dissipation base 3 as the above reference Figure 8 to Figure 10 By adopting the above-described shape, it is possible to reduce the amount of deformation of the heat dissipation base 3 in the direction of reducing the warpage, which occurs when the heat dissipation base 3 is attached to the cooler 10 (heat sink 11 ).

[0073] That is, when the heat dissipation base 3 of the present embodiment is mounted on the heat dissipation fin 11 of the cooler 10, as shown in FIG. Fig.11 As shown, the shape of the curved surface is represented by the curve protruding downward to the end of the heat dissipation base 30 shown by the dotted line (refer to Figure 7 ), the distance in the Z direction from the corner of the heat sink 3 to the upper surface 1110 of the heat sink 11 can be shortened. Therefore, the deformation of the heat sink 3 generated when the screw 13 is inserted into the through hole 303 of the heat sink 3 and screwed into the screw hole 1111 of the heat sink 11 can be made smaller than that described above with reference to Figure 7 Therefore, by using the heat dissipation base 3 of the present embodiment, the deformation stress generated on the wiring board 4 due to the deformation of the heat dissipation base 3 when the heat dissipation base 3 is mounted on the heat sink 11 can be reduced, and the damage of the wiring board 4 caused by the deformation stress can be prevented.

[0074] In addition, as mentioned above Fig.10 As described above, the heat dissipation base 3 of the present embodiment can smoothly change the lower surface 301 from a downwardly convex curved surface to an upwardly convex curved surface at the inflection point Q generated when viewed on the straight line S3 in the diagonal direction. In this way, by smoothly changing the curved surface of the lower surface 301 at the inflection point Q, it is less likely to cause stress concentration at the inflection point Q, compared with the case of performing a bending process such that the tangent line changes discontinuously around the inflection point Q, and it is easy to reduce the deformation stress of the wiring board 4 caused by the deformation of the heat dissipation base 3.

[0075] Fig.12This is a diagram for supplementing the shape of the convex curved surface in the heat dissipation base according to one embodiment.

[0076] As an example of the shape of the lower surface 301 on the straight line S3 in the diagonal direction of the heat dissipation base 3 in this embodiment, Fig. 9 and Fig.10 The curve R3 shown in FIG. 1 shows the shape of the lower surface 301 before the wiring board 4 is bonded to the upper surface 302 of the heat dissipation base 3. When the wiring board 4 is bonded to the upper surface of the heat dissipation base 3 of the present embodiment described above, the relative positions of the points on the diagonal straight line S3 in the Z direction may be changed by, for example, Fig.12 The curve R4 shown in FIG. 1 shows a change in the relative position in the Z direction. The curve R4, like the curve R3, has a section where the relative position in the Z direction changes as indicated by the downward convex curve and a section where the relative position changes as indicated by the upward convex curve. The curve R4 has two end sections divided at the distance -Li and the distance Li and a central section located between the two end sections, and the two end sections include the end points of the curve R4 and the relative position in the Z direction in the direction from the end points toward the center P changes only as indicated by the upward convex curve. The change in the relative position in the Z direction in the central section of the curve R4 is different from the change in the central section of the curve R3, and includes a section indicated by the downward convex curve and a section indicated by the upward convex curve.

[0077] In addition, although the description with reference to the accompanying drawings is omitted, when the wiring board 4 is joined to the heat dissipation base 3, the relative positions in the Z direction of each point on the straight line in the long side direction passing through the center of the lower surface 301 and the relative positions in the Z direction of each point on the straight line in the short side direction are sometimes represented by a curve having an interval represented by a curve convex downward and an interval represented by a curve convex upward, as in the central interval of the curve R4.

[0078] However, when there are intervals represented by downward convex curves and intervals represented by upward convex curves in the central interval, the change in the relative position in the Z direction from the end point toward the center including the end point (end point) also becomes a reference. Fig. 9 and Fig.10 Therefore, even when there are sections represented by downward convex curves and sections represented by upward convex curves in the central section, the amount of deformation generated when the heat dissipation base 3 is attached to the cooler 10 (heat dissipation fins 11) can be reduced.

[0079] As described above, the lower surface 301 of the heat dissipation base 3 of the present embodiment, which is opposite to the heat dissipation fin 11 of the cooler 10, is a convex curved surface, and the shape of the lower surface 301 on the straight line S1 in the long-side direction passing through the center P of the lower surface 301 and the shape of the lower surface on the straight line S2 in the short-side direction, including the end portion, in the direction from the end portion toward the center P, is represented by a downward convex curve, and the shape of the lower surface 301 on the straight line S3 in the diagonal direction, including the end portion, in the direction from the end portion toward the center P, including the end portion, is represented by an upward convex curve. Therefore, the heat dissipation base 30 (see FIG. 1 ) is also represented by a downward convex curve. Figure 7 ), the heat sink 3 of this embodiment can reduce the amount of deformation when mounted on the heat sink 11, and can reduce the deformation stress generated in the wiring board 4 bonded to the upper surface of the heat sink 3. Therefore, in the energy conversion device 1 using the heat sink 3 of this embodiment, it is possible to prevent damage to the wiring board 4 caused by the deformation stress, and to prevent failure of the energy conversion device 1 (semiconductor module 2).

[0080] The embodiments of the heat dissipation base 3 and the energy conversion device 1 of the present invention are not limited to the above-mentioned embodiments, and various changes, substitutions, and deformations can be made within the scope of the main purpose of the technical idea. Moreover, if the technical idea can be realized in other ways due to technological progress or other derived technologies, the method can also be used for implementation. Therefore, the claims cover all embodiments that can be included in the scope of the technical idea.

[0081] For example, the heat dissipation base 3 of the above-mentioned embodiment uses stamping or the like to warp the flat base plate so that the lower surface 301 becomes a convex curved surface, and the upper surface 302 joined to the wiring board 4 becomes a concave curved surface. However, the heat dissipation base 3 of the present invention is not limited to such a shape. The heat dissipation base 3 of the present invention may be, for example, a convex curved surface in the lower surface 301 opposite to the heat sink 11 of the cooler 10, and a flat surface in the upper surface 302 joined to the wiring board 4. In addition, the position of the vertex when the lower surface 301 of the heat dissipation base 3 is set as a convex curved surface is not limited to the position that becomes the center of the lower surface 301 when viewed from above, and may also be a position deviated from the center. In addition, the number of wiring boards 4 joined to one heat dissipation base 3 may be more than two. In addition, for example, from the viewpoint of preventing the wiring board 4 from breaking with the inflection point Q as the starting point when the screw is tightened, the inflection point Q in the heat dissipation base 3 is expected to exist outside the area where the wiring board 4 is joined when viewed from above. However, for example, as Figure 8As shown in the example, a part of the inflection point Q distributed in a curved shape on the lower surface 301 of the heat dissipation base 3 may also exist inside the area of ​​the heat dissipation base 3 that is bonded to the wiring board 4. In addition, the through hole 303 for screw fastening of the heat dissipation base 3 may be formed in the middle part of the end side in the longitudinal direction in addition to the corner part of the lower surface 301. In addition, the shape of the heat dissipation base 3 when viewed from above is not limited to the shape described above with reference to FIG. Figure 8 The substantially rectangular planar shape in which the sides extending in the X direction and the sides extending in the Y direction have different lengths may be a substantially square planar shape in which the sides extending in the X direction and the sides extending in the Y direction have substantially the same lengths.

[0082] The characteristic points of the above-mentioned embodiment are summarized below.

[0083] The heat dissipation base of the above-mentioned embodiment has a first surface for bonding a wiring board and a second surface located on the opposite side of the first surface and opposite to the cooler, wherein the second surface of the heat dissipation base is a convex curved surface, and its shape when viewed from above is a roughly rectangular shape having sides extending in the first direction and sides extending in the second direction. When the second surface is facing downward, in each of the first curve representing the shape of the second surface on the first straight line passing through the center of the second surface and extending in the first direction, and the second curve representing the shape of the second surface on the second straight line passing through the center of the second surface and extending in the second direction, a change in shape in a direction from the end toward the center including the end is represented by a downwardly convex curve, and in the third curve representing the shape of the second surface on the straight line in the diagonal direction, a change in shape in a direction from the end toward the center including the end is represented by an upwardly convex curve, and a change in shape in a direction from the center toward the end including the center is represented by a downwardly convex curve.

[0084] In the heat dissipation base of the above embodiment, a through hole is formed at a position which is a corner of the second surface in a plan view, and a male screw for attaching the heat dissipation base to the cooler can pass through the through hole.

[0085] In the heat dissipation base of the above embodiment, the third curve representing the shape of the second surface on the straight line in the diagonal direction has an inflection point at a position closer to the center than the through hole, and the section between the end and the inflection point in the third curve is an upwardly convex curve.

[0086] In the heat dissipation base of the above embodiment, the inflection point is located outside the region to which the wiring board is bonded.

[0087] In the heat dissipation base of the above embodiment, the inflection point is located within a range of 5 mm to 20 mm from the center of the through hole.

[0088] In the heat dissipation base of the above embodiment, the first surface is a concave curved surface corresponding to the convex curved surface of the second surface.

[0089] In the heat dissipation base of the above-mentioned embodiment, the third curve representing the shape of the second surface on the straight line in the diagonal direction has two end intervals represented by the upwardly convex curve and a central interval located between the two end intervals in which the shape change in the direction from the end toward the center including the end is represented by the upwardly convex curve, and the central interval has a partial interval represented by the upwardly convex curve.

[0090] In the heat dissipation base of the above embodiment, the length of the side extending along the first direction is different from the length of the side extending along the second direction.

[0091] The semiconductor module of the above embodiment includes: the heat dissipation base of the above embodiment; a wiring board bonded to the first surface of the heat dissipation base; and a semiconductor element arranged on the upper surface of the wiring board.

[0092] The energy conversion device of the above embodiment comprises: the semiconductor module of the above embodiment; the cooler arranged opposite to the second surface of the heat dissipation base and mounted on the heat dissipation base; and a thermally conductive material filled between the heat dissipation base and the cooler.

[0093] Industrial Applicability

[0094] As described above, the present invention has the effect of preventing the wiring board from being damaged due to deformation of the heat dissipation base when the heat dissipation base to which the wiring board is joined is attached to a cooler, and is particularly useful for industrial or electrical inverter devices.

[0095] This application is based on Japanese Patent Application No. 2023-038214 filed on March 13, 2023. The entire contents are incorporated herein.

[0096] Description of Reference Numerals

[0097] 1. Energy conversion device; 2. Semiconductor module; 3. Heat dissipation base; 301. Lower surface; 302. Upper surface; 303. Through hole; 4. Wiring board; 400. Insulating substrate; 401, 402, 403. Conductor pattern; 5A, 5B. Semiconductor element; 7A to 7F. Bonding wire; 8. Housing; 800. Insulating member; 801, 802. Input terminal; 803. Output terminal; 804, 805. Control terminal; 9. Sealing material; 10. Cooler; 11. Heat sink; 1110. Upper surface; 1111. Threaded hole; 12. Water cooling jacket; 13. Threaded member; 14. Thermal conductive material; 15. Nut; 16. Adhesive.

Claims

1. A heat dissipation base having a first surface bonded to a wiring board and a second surface located on the opposite side of the first surface and facing a cooler, wherein: The second surface of the heat dissipation base is a convex curved surface, and has a substantially rectangular shape when viewed from above, with a side extending in the first direction and a side extending in the second direction. When the second surface is facing downward, In each of a first curve representing the shape of the second surface on a first straight line passing through the center of the second surface and extending along the first direction, and a second curve representing the shape of the second surface on a second straight line passing through the center of the second surface and extending along the second direction, a change in shape in a direction from the end toward the center including the end is represented by a curve that bulges downward, In the third curve representing the shape of the second surface on the straight line in the diagonal direction of the heat dissipation base, the change in shape in the direction from the end toward the center including the end is represented by a curve convex upward, and the change in shape in the direction from the center toward the end including the center is represented by a curve convex downward.

2. The heat dissipation base according to claim 1, wherein: A through hole is formed at a position which becomes a corner of the second surface in a plan view, and a male screw for attaching the heat dissipation base to the cooler can pass through the through hole.

3. The heat dissipation base according to claim 2, wherein: The third curve representing the shape of the second surface on the straight line in the diagonal direction has an inflection point at a position closer to the center than the through hole, and a section between the end portion and the inflection point in the third curve is an upwardly convex curve.

4. The heat dissipation base according to claim 3, wherein: The inflection point is located outside a region where the wiring board is bonded.

5. The heat dissipation base according to claim 3, wherein: The inflection point is located within a range of 5 mm to 20 mm inclusive from the center of the through hole.

6. The heat dissipation base according to claim 1, wherein: The first surface is a concave curved surface corresponding to the convex curved surface of the second surface when the second surface is directed downward.

7. The heat dissipation base according to claim 1, wherein: The third curve representing the shape of the second surface on the straight line in the diagonal direction has two end intervals represented by the upwardly convex curve and a central interval located between the two end intervals, in which the shape change in the direction from the end toward the center including the end is represented by the upwardly convex curve, and a partial interval is included in the central interval and represented by the upwardly convex curve.

8. The heat dissipation base according to claim 1, wherein: The length of the side extending along the first direction is different from the length of the side extending along the second direction.

9. A semiconductor module, wherein: The semiconductor module has: The heat dissipation base according to any one of claims 1 to 8; a wiring board bonded to the first surface of the heat dissipation base; and The semiconductor element is arranged on the upper surface of the wiring board.

10. An energy conversion device, wherein: The energy conversion device has: The semiconductor module according to claim 9; The cooler is arranged opposite to the second surface of the heat dissipation base and is mounted on the heat dissipation base; and The heat conducting material is filled between the heat dissipation base and the cooler.

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