Semiconductor device

Abstract

To suppress the occurrence of damage at the time of fastening and the deterioration of heat radiation.SOLUTION: The heat dissipation plate 3 has a plate shape and includes an upper surface side 31a and a lower surface side 31b, at least the lower surface side 31b protrudes upward at a central portion C and is inclined downward from the central portion C to a side surface side 32a and a side 32c (a pair of second edges), the insulating circuit substrate 11 is bonded to an inclined region of the upper surface side 31a, and fastening hole side 31a and fastening hole side 31b penetrating the upper surface side and the lower surface side 33a are formed in an outer edge region. 33b. Further, in the 31b portion of the lower surface of the heat sink 3, the outer edge portions of the fastening holes 33a and 33b on the side opposite to the central portion C protrude downward.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a semiconductor device. [Background technology]

[0002] In a semiconductor device, an insulating circuit board to which a semiconductor chip is bonded is disposed on a base plate. Such a base plate is fastened to a cooling unit with screws. In this case, protrusions are provided on the base plate to prevent the base plate, which has a downwardly convex warp on its underside, from being damaged when it is attached to the cooling unit (see, for example, Patent Documents 1 to 4). Furthermore, fastening the base plate to the cooling unit with screws creates a grease escape around the screw holes in the base plate, which is provided between the base plate and the cooling unit (see, for example, Patent Document 5). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-195717 [Patent Document 2] US Patent Application Publication No. 2008 / 0101032 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-058727 [Patent Document 4] U.S. Patent No. 9,929,066 [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-165279 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a semiconductor device that suppresses the occurrence of damage during fastening and the deterioration of heat dissipation. [Means for solving the problem]

[0005] According to one aspect of the invention, there is provided a semiconductor device comprising: an insulating circuit board; and a heat sink that is plate-shaped and includes an upper surface and a lower surface, at least the lower surface having a central portion that protrudes upward and slopes downward from the central portion to an end portion, the insulating circuit board being joined to the sloped region of the upper surface, and fastening holes that penetrate the upper and lower surfaces being formed in outer edge regions, wherein on the lower surface of the heat sink, the outer edge portion opposite the central portion of the fastening hole is positioned lower than the inner portion of the opening edge of the fastening hole on the central portion side. [Effects of the Invention]

[0006] According to the disclosed technology, it is possible to suppress the occurrence of damage during fastening and the deterioration of heat dissipation. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a side cross-sectional view of a semiconductor device according to a first embodiment. [Figure 2] 2 is a plan view (top surface) of a heat sink of the semiconductor device according to the first embodiment; FIG. [Figure 3] 10 is a side cross-sectional view for explaining the attachment of the semiconductor device of the reference example to the cooling device; FIG. [Figure 4] 3 is a side cross-sectional view for explaining the attachment of the semiconductor device of the first embodiment to the cooling device. FIG. [Figure 5] FIG. 10 is a side cross-sectional view of a semiconductor device according to a second embodiment. [Figure 6] 10 is a plan view (bottom surface) of a heat sink of a semiconductor device according to a second embodiment. FIG. [Figure 7] 10 is a side cross-sectional view for explaining the attachment of the semiconductor device to the cooling device according to the second embodiment. FIG. [Figure 8] 10 is a plan view (bottom surface) of a heat sink of a semiconductor device according to a second embodiment (modification 2-1). FIG. [Figure 9] FIG. 10 is a side cross-sectional view of a semiconductor device according to a third embodiment. [Figure 10] 10 is a table showing changes in gaps and stresses in the embodiment compared to the reference example. [Figure 11] 10 is a plan view (top surface) of a heat sink of a semiconductor device according to a fourth embodiment. FIG. [Figure 12] FIG. 10 is a first cross-sectional side view of a semiconductor device according to a fourth embodiment. [Figure 13] FIG. 10 is a second cross-sectional side view of the semiconductor device according to the fourth embodiment. [Figure 14] 13 is a plan view (bottom surface) of a heat sink of a semiconductor device according to a fifth embodiment. FIG. [Figure 15] 13 is a plan view (bottom surface) of a heat sink of a semiconductor device according to a fifth embodiment (modification 5-1). FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, embodiments will be described with reference to the drawings. In the following description, the terms "front surface" and "upper surface" refer to the XY plane facing upward (+Z direction) in the semiconductor device 1 of FIG. 1. Similarly, "up" refers to the upward (+Z direction) direction in the semiconductor device 1 of FIG. 1. The terms "back surface" and "lower surface" refer to the XY plane facing downward (-Z direction) in the semiconductor device 1 of FIG. 1. Similarly, "lower" refers to the downward (-Z direction) direction in the semiconductor device 1 of FIG. 1. Similar directions will be used in other drawings as necessary. The terms "front surface," "upper surface," "upper," "back surface," "lower surface," "lower," and "side surface" are merely convenient expressions for specifying relative positional relationships and do not limit the technical concept of the present invention. For example, "upper" and "lower" do not necessarily refer to the vertical direction relative to the ground. In other words, the "upper" and "lower" directions are not limited to the direction of gravity. In the following description, the term "main component" refers to a component containing 80 vol% or more of a component. In addition, in the drawings, descriptions of the same components may be omitted or simplified. In the reference numerals for components shown in the drawings, reference numerals that have already been used may be omitted. In such cases, reference may be made to the drawings showing the components to which the reference numerals are attached.

[0009] [First embodiment] A semiconductor device 1 according to a first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a side cross-sectional view of the semiconductor device according to the first embodiment. FIG. 2 is a plan view (top) of a heat sink of the semiconductor device according to the first embodiment. Note that FIG. 2 shows the top surface 31a of the heat sink 3 included in the semiconductor device 1. The insulating circuit board 11 on the top surface 31a is indicated by a dashed line. When viewed from the top surface 31a, the locations of the protrusions 34a and 34b on the bottom surface 31b are indicated by a dashed line. Furthermore, although the case 2 is not shown in FIG. 2, the position of the case 2 is indicated by a dashed line. FIG. 1 corresponds to the cross section taken along dashed line II in FIG. 2.

[0010] The semiconductor device 1 includes a heat sink 3, two semiconductor units 10 bonded to an upper surface 31a of the heat sink 3, and a case 2 provided on the upper surface 31a of the heat sink 3 and covering the semiconductor units 10. The semiconductor units 10 within the case 2 are sealed with a sealing member 40.

[0011] The heat sink 3 includes a plate-shaped plate member 30 and protrusions 34a and 34b. The plate member 30 is flat (plate-like) and includes a rectangular upper surface 31a and a lower surface 31b that has the same shape as the upper surface 31a and faces the upper surface 31a. The upper surface 31a and the lower surface 31b may be substantially smooth. The plate member 30 further includes side surfaces 32a, 32b, 32c, and 32d that surround the upper surface 31a and the lower surface 31b on all four sides. The side surfaces 32a, 32b, 32c, and 32d may also be substantially smooth. The plate member 30 may have some inclination or notches in some parts. In other words, the plate member 30 has a small proportion of inclinations and notches in the longitudinal and lateral directions in a plan view (e.g., less than 1%), and can be considered to be substantially flat.

[0012] The side surfaces 32b and 32d extend along the longitudinal direction and are connected to the upper surface 31a and the lower surface 31b at a pair of opposing first edges that extend along the longitudinal direction of the upper surface 31a and the lower surface 31b, respectively. The side surfaces 32a and 32c extend along the lateral direction and are connected to the upper surface 31a and the lower surface 31b at a pair of opposing second edges that extend along the lateral direction of the upper surface 31a and the lower surface 31b, respectively. That is, in FIG. 2, the pair of first edges corresponds to the side surfaces 32b and 32d, respectively, and the pair of second edges corresponds to the side surfaces 32a and 32c, respectively.

[0013] The corners, the pair of first edges, and the pair of second edges of the plate member 30 may be rounded or chamfered. In a plan view, the plate member 30 has a center line CL that is parallel to the side surfaces 32a and 32c. The center of the center line CL is a center portion C.

[0014] The plate member 30 has fastening holes 33a and 33b formed therein. The fastening holes 33a and 33b penetrate vertically through the upper surface 31a and the lower surface 31b, respectively. The fastening holes 33a and 33b are formed in the outer edge regions of the plate member 30 on the side surfaces 32a and 32c sides. That is, the fastening holes 33a and 33b are located at the centers of the side surfaces 32a and 32c (pair of second edges) of the plate member 30 in a plan view, and are spaced a predetermined distance inward (toward the center line CL) from the side surfaces 32a and 32c (pair of second edges). The fastening holes 33a and 33b may be cylindrical in a plan view. In this case, the diameter of the fastening holes 33a and 33b may be selected depending on the diameter of the screw to be used.

[0015] Furthermore, when viewed in the ±Y direction, the center line CL of the plate member 30 is warped upwardly convexly. That is, the center line CL including the central portion C protrudes upward on at least the lower surface 31b of the plate member 30 and is inclined downward from the center line CL to the end portions (side surfaces 32a, 32c (a pair of second edges)). In the plate member 30, the protruding center line CL generates a convex portion P, which is inclined downward from the convex portion P to the side surfaces 32a, 32c (a pair of second edges). The inclination angle of the upper surface 31a sandwiching this convex portion P may be slightly different on the side surfaces 32a, 32c side. Furthermore, the convex portion P in FIG. 2 is generated in a region including the center line CL and is not necessarily generated within the range indicated by the dashed line in FIG. 2.

[0016] The plate member 30 may have a central portion C warped upward in a convex manner when viewed in the ±X direction. However, in the case of the first embodiment, the warping of the convex portion P (when viewed in the ±Y direction) is sufficiently large that the warping of the central portion C when viewed in the ±X direction can be substantially ignored.

[0017] The semiconductor units 10 (insulating circuit boards 11 included therein) are bonded to inclined regions on the upper surface 31a of the plate member 30. In this case, the semiconductor units 10 are bonded to inclined regions on the upper surface 31a of the plate member 30 at positions equidistant from the protrusion P and between the protrusion P and the fastening holes 33a, 33b. Details of the semiconductor units 10 will be described later.

[0018] The protrusions 34a, 34b are provided between the side surfaces 32a, 32c on the opposite side of the center C of the fastening holes 33a, 33b on the underside 31b of the plate member 30. That is, the protrusions 34a, 34b are provided at positions where the centers of the protrusions 34a, 34b and the centers and center C of the fastening holes 33a, 33b are aligned in a straight line. Furthermore, the protrusions 34a, 34b may be provided between the respective side surfaces 32a, 32c and the fastening holes 33a, 33b. The protrusions 34a, 34b may be integrally formed on the underside 31b of the plate member 30. The bottom surfaces of the protrusions 34a, 34b include outer edge portions 31b1, 31b2. This means that the outer edge portions 31b1, 31b2 on the opposite side of the center C of the fastening holes 33a, 33b on the underside 31b of the plate member 30 protrude downward.

[0019] The protrusions 34a, 34b may be columnar. Examples of columnar shapes include a cylindrical shape and a rectangular shape. In FIG. 2, the protrusions 34a, 34b are columnar, and the outer edge portions 31b1, 31b2 are rectangular in plan view. The widths of the outer edge portions 31b1, 31b2 in the ±Y directions may range from approximately the diameter of the fastening holes 33a, 33b to the lengths of the side surfaces 32b, 32d. In FIG. 2, one side of the outer edge portions 31b1, 31b2 is approximately the diameter of the fastening holes 33a, 33b. The maximum widths of the outer edge portions 31b1, 31b2 in the ±X directions are the lengths from the respective side surfaces 32a, 32c to the fastening holes 33a, 33b in plan view, as shown in FIG. 2. Such protrusions 34a and 34b may be formed on the lower surface 31b of the plate member 30 by, for example, die processing or machining.

[0020] Such a heat sink 3 is made of a metal with excellent heat dissipation properties. Such a metal is, for example, copper, aluminum, or an alloy containing at least one of these. The surface of the heat sink 3 may be plated to improve corrosion resistance. Examples of plating materials that can be used in this case include nickel, a nickel-phosphorus alloy, and a nickel-boron alloy.

[0021] The semiconductor unit 10 includes an insulating circuit board 11 and a semiconductor chip 12. The insulating circuit board 11 includes an insulating plate 11a, a conductive circuit pattern 11b formed on the upper surface of the insulating plate 11a, and a metal plate 11c formed on the lower surface of the insulating plate 11a.

[0022] The insulating plate 11a has a rectangular shape in a plan view. The corners of the insulating plate 11a may be rounded or chamfered. The insulating plate 11a is made of ceramics with high thermal conductivity. Such ceramics are made of, for example, a material containing aluminum oxide, silicon nitride, or aluminum nitride as its main component.

[0023] The insulating plate 11a may be made of a resin. The resin may be a material with low thermal resistance and high insulating properties. Examples of such resins include thermosetting resins. Examples of such thermosetting resins include at least one of epoxy resin, cyanate resin, polyimide resin, benzoxazine resin, unsaturated polyester resin, phenol resin, melamine resin, silicone resin, maleimide resin, acrylic resin, and polyamide resin.

[0024] The conductive circuit pattern 11b is formed from a metal with excellent conductivity. Such a metal is, for example, copper, aluminum, or an alloy containing at least one of these. The surface of the circuit pattern may be plated to improve corrosion resistance. In this case, the plating material used is, for example, nickel, a nickel-phosphorus alloy, or a nickel-boron alloy. Note that the conductive circuit pattern 11b may have a shape that realizes a desired circuit, and may include multiple patterns.

[0025] The metal plate 11c is formed mainly from a metal with excellent thermal conductivity. Such metals are, for example, copper, aluminum, or an alloy containing at least one of these. To improve the corrosion resistance of the metal plate, a plating process may be performed. In this case, the plating material used is, for example, nickel, a nickel-phosphorus alloy, or a nickel-boron alloy.

[0026] When the insulating plate 11a is made of ceramic, examples of such an insulating circuit board 11 include a DCB (Direct Copper Bonding) board and an AMB (Active Metal Brazed) board.

[0027] The semiconductor chip 12 may be composed primarily of, for example, silicon carbide, silicon, or gallium nitride. For example, the semiconductor chip 12 may be a power MOSFET (Metal Oxide Semiconductor Field Effect Transistor) composed primarily of silicon carbide. The body diode of the power MOSFET may function as a FWD (Free Wheeling Diode). Such a semiconductor chip 12 has an input electrode (drain electrode) as a main electrode on the back surface, and an output electrode (source electrode) and a control electrode (gate electrode) as main electrodes on the front surface. The control electrode may be provided at the center of one side of the front surface of the semiconductor chip 12 or offset from the center along the side.

[0028] The semiconductor chip 12 may also include a switching element primarily made of silicon. The switching element may be, for example, an RC (Reverse-Conducting)-IGBT (Insulated Gate Bipolar Transistor). An RC-IGBT is a semiconductor element in which an IGBT and an FWD are arranged in anti-parallel within a single chip. Such a semiconductor chip 12 has an input electrode (collector electrode) as a main electrode on the back surface, and an output electrode (emitter electrode) and a control electrode (gate electrode) as main electrodes on the front surface. Note that the control electrode may be provided at the center of one side of the front surface of the semiconductor chip 12 or offset from the center along the side, as in the case of a power MOSFET.

[0029] Alternatively, the semiconductor chip 12 may be a semiconductor chip mainly composed of silicon and including a pair of a switching element and a diode element. Specifically, one semiconductor chip may be a switching element and the other semiconductor chip may be a diode element. The switching element may be, for example, a power MOSFET or an IGBT. The semiconductor chip including the switching element has, for example, an input electrode (a drain electrode in a power MOSFET or a collector electrode in an IGBT) as a main electrode on the back surface, and a gate electrode (a control electrode) and an output electrode (a source electrode in a power MOSFET or an emitter electrode in an IGBT) as a main electrode on the front surface. The diode element may be, for example, an SBD (Schottky Barrier Diode) or a PiN (P-intrinsic-N) diode used as the FWD. The semiconductor chip including the diode element has, for example, an output electrode (a cathode electrode) as a main electrode on the back surface, and an input electrode (anode electrode) as a main electrode on the front surface.

[0030] The lower surface of the semiconductor chip 12 is joined to the conductive circuit pattern 11b of the insulating circuit board 11 by joining member 13b to form the semiconductor unit 10. In addition, the metal plate 11c of the insulating circuit board 11 of the semiconductor unit 10 is joined to the upper surface 31a of the heat sink 3 by joining member 13a.

[0031] The joining members 13a and 13b may be made of the same material, for example, solder. Lead-free solder is used as the solder. Lead-free solder mainly contains at least one of the following alloys: a tin-silver-copper alloy, a tin-zinc-bismuth alloy, a tin-copper alloy, and a tin-silver-indium-bismuth alloy. The solder may also contain additives. Examples of additives include nickel, germanium, cobalt, antimony, and silicon. The addition of additives to the solder improves its wettability, gloss, and bonding strength, thereby improving reliability. The joining members 13a and 13b may be sintered bodies. When joining using a sintered body, the sintered material may be, for example, a powder of silver, iron, copper, aluminum, titanium, nickel, tungsten, or molybdenum.

[0032] The case 2 includes a frame 20 and a lid 24 that covers the upper part of the frame 20. The frame 20 has a generally rectangular frame-like outer shape in plan view that corresponds to the outer shape of the heat sink 3. However, when the frame 20 is placed on the heat sink 3, the portions of the frame 20 that correspond to the fastening holes 33a and 33b in plan view are recessed inward (toward the center line CL). A storage area 25 penetrates the frame 20 at its center. The lower surface of the frame 20 is joined to a continuous annular outer edge region of the upper surface 31a of the heat sink 3 (plate member 30) with an adhesive or the like (not shown).

[0033] Furthermore, the frame portion 20 integrally includes external connection terminals 21 and 22. The external connection terminals 21 and 22 include outer ends 21a and 22a and inner ends 21b and 22b. The outer ends 21a and 22a extend upward from the upper surface of the frame portion 20. The inner ends 21b and 22b are provided in a storage area 25 of the frame portion 20. The lid portion 24 is integrally provided on the upper portion of the frame portion 20 and covers the opening of the frame portion 20.

[0034] Such a case 2 may be formed by insert molding the frame 20 including the external connection terminals 21, 22 and the lid 24 integrally with a thermoplastic resin. Examples of such resins include polyphenylene sulfide resin, polybutylene terephthalate resin, polybutylene succinate resin, polyamide resin, and acrylonitrile butadiene styrene resin.

[0035] Wires 23 electrically connect the inner ends 21b of the external connection terminals 21, the conductive circuit pattern 11b, the electrodes on the front surface of the semiconductor chip 12, the conductive circuit pattern 11b, and the inner ends 22b of the external connection terminals 22 within the case 2 as needed. Note that FIG. 1 merely shows an example of the connection of the wires 23. The wires 23 are made of a material with excellent conductivity. Examples of such materials include gold, silver, copper, aluminum, and alloys containing at least one of these. Alternatively, instead of the wires 23, the inner ends 21b, 22b of the external connection terminals 21, 22 and the conductive circuit pattern 11b may be connected by a lead frame.

[0036] The sealing member 40 is filled in the storage area 25 surrounded by the heat sink 3 and the frame portion 20 of the case 2. The insulating circuit board 11, the semiconductor chip 12, and the wires 23 in the storage area 25 are sealed with the sealing member 40. The sealing member 40 is an insulating polymer gel. Preferably, the main component is silicone gel.

[0037] A cooling device is provided on such semiconductor device 1 (lower surface 31b of heat sink 3) via a bonding member. This improves the heat dissipation performance of the semiconductor device 1. The cooling device may be made of, for example, aluminum, iron, silver, copper, or an alloy containing at least one of these materials, which have excellent thermal conductivity. Examples of the cooling device include a heat sink and a water-cooled cooling device. The heat sink may have multiple fins. The semiconductor device 1 is placed on the cooling surface of such a cooling device via a bonding member, and is fastened to the cooling device by inserting screws into the fastening holes 33a, 33b of the heat sink 3.

[0038] The joining member may be, for example, a thermal interface material (TIM). TIM includes various general terms such as thermally conductive grease, elastomer sheet, RTV (Room Temperature Vulcanization) rubber, gel, and phase change material. The joining member may also contain a filler to improve thermal conductivity. For example, a highly insulating and highly thermally conductive inorganic material is used as the filler. The inorganic material may contain, as a main component, at least one selected from the group including, for example, aluminum oxide, aluminum nitride, silicon nitride, and boron nitride.

[0039] Next, a reference example of the semiconductor device 1 will be described with reference to Fig. 3. Here, the attachment of the semiconductor device of the reference example to a cooling device will be described. Fig. 3 is a side cross-sectional view for explaining the attachment of the semiconductor device of the reference example to a cooling device.

[0040] The semiconductor device of the reference example has a similar configuration to the semiconductor device 1. However, the heat sink 300 included in the semiconductor device of the reference example is the same as the heat sink 3 of the semiconductor device 1, except that the center line CL is warped downwardly convexly. Furthermore, the heat sink 300 of the reference example does not include the protrusions 34a, 34b of the heat sink 3 of the first embodiment. Note that case 2 is not shown in FIG. 3.

[0041] The lower surface 31b of the heat sink 300 of the semiconductor device is set on the cooling surface 4a of the cooling device 4 via a bonding material (not shown) such as a TIM. Then, screws 5a and 5b are inserted into the fastening holes 33a and 33b of the heat sink 300, respectively, and screwed into the cooling surface 4a of the cooling device 4. At this time, the screws 5a and 5b apply stress in the direction of arrow A shown in FIG. 3, causing the heat sink 300 to begin to deform flat around the center line CL of the lower surface 31b. The heat sink 300, which is warped downward and convex, is joined to the insulating circuit board 11 by the bonding material 13a. Therefore, the insulating circuit board 11 is also pulled by the heat sink 300, which is deforming flat, and a stress is applied in the direction of arrow B shown in FIG. 3, which cleaves the insulating circuit board 11. If the stress of arrow B occurs in the insulating circuit board 11, which is joined at an angle, the insulating plate 11a will be damaged. For example, if a crack occurs in insulating plate 11a and the crack propagates to form a crack, the heat dissipation and insulating properties of insulating circuit board 11 will be reduced, and semiconductor chip 12 will not be cooled and its insulating properties will not be maintained, resulting in a breakdown of the semiconductor device.

[0042] Next, the attachment of the semiconductor device 1 to the cooling device 4 will be described with reference to FIG. 4. FIG. 4 is a side cross-sectional view for explaining the attachment of the semiconductor device of the first embodiment to the cooling device. Note that FIG. 4 shows a case in which the semiconductor device 1 is fastened to the cooling device 4 with screws 5a and 5b, similar to the reference example shown in FIG. 3. Also, in FIG. 4, the case 2 is omitted from the semiconductor device 1.

[0043] At this time, as screws 5a and 5b are threaded into heat sink 3, stress is applied in the direction of arrow A shown in Figure 4, and heat sink 3 begins to deform flat with protrusions 34a and 34b as fulcrums. Because heat sink 3 of semiconductor device 1 is warped upward in a convex shape, the stress in the direction of arrow B (see Figure 3) that occurred in insulating circuit board 11 in the reference example is reduced. This prevents damage to insulating circuit board 11.

[0044] Furthermore, when the screws 5a and 5b are screwed into the cooling surface 4a, stress is applied to the heat sink 3 with the outer edge portions 31b1 and 31b2 (reference numbers omitted in FIG. 4 ) of the protrusions 34a and 34b in contact with the cooling surface 4a as fulcrums, flattening the heat sink 3 and bringing the underside 31b closer to the cooling surface 4a. This reduces the gap between the underside 31b of the heat sink 3 and the cooling surface 4a. Reducing this gap also reduces the thickness of the bonding material, such as the TIM, thereby preventing a decrease in heat dissipation performance. It is preferable that this gap be as thin as possible, and for example, it may be approximately the diameter of the filler contained in the bonding material, such as the TIM.

[0045] The semiconductor device 1 includes an insulating circuit board 11 and a heat sink 3. The heat sink 3 is plate-shaped and includes an upper surface 31a and a lower surface 31b. At least the lower surface 31b has a central portion C that protrudes upward and slopes downward from the central portion C to side surfaces 32a, 32c (a pair of second edges). The insulating circuit board 11 is joined to the sloped region of the upper surface 31a, and fastening holes 33a, 33b that penetrate the upper surface 31a and the lower surface 31b are formed in the outer edge regions. Furthermore, outer edge portions 31b1, 31b2 of the lower surface 31b of the heat sink 3 on the opposite side of the central portion C of the fastening holes 33a, 33b protrude downward. Even when such a semiconductor device 1 is fastened to the cooling surface 4a of the cooling device 4 by inserting screws 5a, 5b into fastening holes 33a, 33b of the heat sink 3, the stress generated in the insulating circuit board 11 is reduced and the gap between the lower surface 31b of the heat sink 3 and the cooling surface 4a of the cooling device 4 can be reduced. This makes it possible to prevent damage to the insulating circuit board 11 and a decrease in heat dissipation performance. As a result, a decrease in the reliability of the semiconductor device 1 can be prevented.

[0046] [Second embodiment] The heat sink of the second embodiment will be described with reference to FIGS. 5 and 6. FIG. 5 is a side cross-sectional view of the semiconductor device of the second embodiment. FIG. 6 is a plan view (bottom) of the heat sink of the semiconductor device of the second embodiment. Note that FIG. 5 corresponds to FIG. 1 in which the illustration of case 2 is omitted, and FIG. 6 corresponds to the bottom side of FIG. 2. Also, FIG. 5 corresponds to the cross section taken along dashed line II in FIG. 6. Note that in the side cross-sectional views of the semiconductor device 1 and the attachment of the semiconductor device 1 to the cooling device 4 of the second and subsequent embodiments, the illustration of case 2 is omitted and only the heat sink will be described.

[0047] The semiconductor device of the second embodiment has the same configuration as the semiconductor device 1 of the first embodiment except for the heat sink 3. The heat sink 3a included in the semiconductor device of the second embodiment does not include a protrusion, but includes a plate-shaped plate member 30.

[0048] The plate member 30 has the same configuration as the plate member 30 of the first embodiment except for the fastening holes 33a and 33b. Therefore, the outer edge portions 31b1 and 31b2 of the plate member 30 are flush with the lower surface 31b. The widths of the outer edge portions 31b1 and 31b2 in the ±Y direction correspond to the widths of the notches 35a and 35b (described later) in the same direction.

[0049] In the plate member 30 of the second embodiment, notches 35a, 35b (recesses) are formed on the central C side of the opening edges of the fastening holes 33a, 33b on the underside 31b. That is, in the plate member 30 of the second embodiment, the central C side of the opening edges of the fastening holes 33a, 33b is recessed on the underside 31b of the plate member 30, and inner portions 33a1, 33b1 on the central C side of the opening edges are positioned (recessed) above (in the +Z direction) the underside 31b. The height of the inner portions 33a1, 33b1 from the underside 31b is preferably, for example, 3% or more and 10% or less of the thickness of the plate member 30.

[0050] The cutouts 35a, 35b may be formed to include the central C-side portions of the opening edges of the fastening holes 33a, 33b on the underside 31b. The cutouts 35a, 35b may be formed, for example, across the side surfaces 32b, 32d of the plate member 30, as long as they include the central C-side portions of the opening edges of the fastening holes 33a, 33b on the underside 31b. The cutouts 35a, 35b extend in a rectangular shape toward the central C side, including the inner portions 33a1, 33b1 of the fastening holes 33a, 33b, in a plan view. The cutout edges 35a1, 35b1 of the cutouts 35a, 35b on the central C side may be spaced from the inner portions 33a1, 33b1 of the fastening holes 33a, 33b toward the central C, and may be located between the edges and the side surfaces 32a, 32b of the insulating circuit board 11 in a plan view. If the notch edges 35a1 and 35b1 of the notches 35a and 35b are positioned closer to the center C than the edges of the side surfaces 32a and 32b of the insulating circuit board 11, their function as fulcrums when fastening with the screws 5a and 5b will be weakened, as will be described later.

[0051] 5, the notches 35a, 35b are recessed so as to slope linearly from the inner portions 33a1, 33b1 of the fastening holes 33a, 33b to the notch edges 35a1, 35b1. However, the notches 35a, 35b may be recessed in an L-shape from the inner portions 33a1, 33b1 to the notch edges 35a1, 35b1, and in this case, the corners of the L-shape may be rounded.

[0052] Next, the attachment of the semiconductor device 1 (heat sink 3a) to the cooling device 4 according to the second embodiment will be described with reference to Fig. 7. Fig. 7 is a side cross-sectional view for explaining the attachment of the semiconductor device to the cooling device according to the second embodiment. In the second embodiment, as in the first embodiment, the semiconductor device 1 (heat sink 3a) is fastened to the cooling surface 4a of the cooling device 4 with screws 5a and 5b.

[0053] At this time, the screws 5a, 5b inserted into the fastening holes 33a, 33b of the semiconductor device 1 (heat sink 3a) arranged on the cooling surface 4a of the cooling device 4 are screwed into the cooling surface 4a. As a result, the heat sink 3a becomes flat, and the inner portions 33a1, 33b1 of the fastening holes 33a, 33b come into contact with the cooling surface 4a.

[0054] Furthermore, when screws 5a, 5b are fastened together, stress is applied in the direction of arrow A shown in Fig. 7, and lower surface 31b of center portion C of heat sink 3a moves closer to cooling surface 4a. In this case, too, damage to insulating circuit board 11 is suppressed, as in the first embodiment.

[0055] Furthermore, when the screws 5a and 5b are screwed into the cooling surface 4a, stress is applied to the heat sink 3a with the notched edges 35a1 and 35b1 of the underside 31b in contact with the cooling surface 4a as fulcrums, flattening the heat sink 3a and bringing the underside 31b closer to the cooling surface 4a. Therefore, as in the first embodiment, the gap between the underside 31b of the heat sink 3a and the cooling surface 4a can be reduced. If this gap is reduced, the thickness of the joining member also becomes smaller, preventing a decrease in heat dissipation performance.

[0056] In the case of the heat sink 3 of the first embodiment, when the heat sink 3 is fastened to the cooling surface 4a with the screws 5a, 5b inserted into the fastening holes 33a, 33b, the outer edge portions 31b1, 31b2 of the protrusions 34a, 34b become fulcrums, and the lower surface 31b of the heat sink 3 comes close to the cooling surface 4a.

[0057] In the case of the heat sink 3a of the second embodiment, the outer edge portions 31b1 and 31b2 are flush with the lower surface 31b, and the inner edge portions 33a1 and 33b1 of the opening edges of the fastening holes 33a and 33b are positioned higher. Therefore, when the heat sink 3a is fastened to the cooling surface 4a with the screws 5a and 5b inserted through the fastening holes 33a and 33b, the inner edge portions 33a1 and 33b1 of the lower surface 31b of the heat sink 3a serve as fulcrums, and the lower surface 31b of the heat sink 3a approaches the cooling surface 4a.

[0058] In the heat sinks 3, 3a of the first and second embodiments, outer edge portions 31b1, 31b2 on the lower surface 31b of the heat sink 3, 3a are located lower (in the -Z direction) than inner portions 33a1, 33b1 on the center C side of the opening edges of the fastening holes 33a, 33b. In this case, when the heat sink 3, 3a is fastened to the cooling surface 4a of the cooling device 4 with screws 5a, 5b inserted through the fastening holes 33a, 33b, stress generated in the insulating circuit board 11 joined to the upper surface 31a can be reduced and the gap between the lower surface 31b and the cooling surface 4a can be reduced.

[0059] (Modification 2-1 of the second embodiment) The notches 35a and 35b of the heat sink 3b of the modified example 2-1 are different from those of the heat sink 3a of the second embodiment. The heat sink 3b in this case will be described with reference to Fig. 8. Fig. 8 is a plan view (bottom surface) of the heat sink of the semiconductor device of the second embodiment (modified example 2-1).

[0060] The heat sink 3b has the same configuration as the heat sink 3a of the second embodiment, except for the notches 35a and 35b. The lengths of the notch edges 35a1 and 35b1 of the notches 35a and 35b of the heat sink 3b extend further toward the side surfaces 32b and 32d than the notch edges 35a1 and 35b1 of the heat sink 3a. If the lengths of the notch edges 35a1 and 35b1 of the heat sink 3b are too short, deformation of the heat sink 3b may be suppressed. For this reason, it is preferable that the lengths extend to, for example, the edges of the insulating circuit board 11 on the side surfaces 32b and 32d sides. Similar to heat sink 3a, notch edges 35a1 and 35b1 of notches 35a and 35b may be located between inner portions 33a1 and 33b1 of fastening holes 33a and 33b and the edges of insulating circuit board 11 on the side surfaces 32a and 32b sides. The widths in the ±Y directions of outer edge portions 31b1 and 31b2 of heat sink 3b may also be set to be approximately equal to the widths in the ±Y directions of notches 35a and 35b.

[0061] In this way, by widening the ±Y direction width of the notch edges 35a1, 35b1 of the notches 35a, 35b included in the heat sink 3b, the area over which the notch edges 35a1, 35b1 come into contact with the cooling surface 4a is widened when fastened with the screws 5a, 5b, thereby enabling stable support of the heat sink 3b.

[0062] By using such heat sink 3b, it is possible to reduce stress generated in insulating circuit board 11 bonded to upper surface 31a, just like heat sink 3a. Furthermore, it is possible to reduce the gap between lower surface 31b and cooling surface 4a more reliably than when heat sink 3a is used.

[0063] Note that in Modification 2-1, the cutouts 35a, 35b are shown as having a rectangular shape in plan view that includes the inner portions 33a1, 33b1 of the fastening holes 33a, 33b and extends toward the center C. The shape of the cutouts 35a, 35b in plan view is not limited to this case, and may be, for example, a triangular shape with the center points of the fastening holes 33a, 33b as its apex, with the cutout edges 35a1, 35b1 facing this apex. Alternatively, the shape of the cutouts 35a, 35b in plan view may be a trapezoid with the diameter passing through the centers of the fastening holes 33a, 33b as its upper base and the cutout edges 35a1, 35b1 as its lower base.

[0064] [Third embodiment] The heat sink of the third embodiment has protrusions 34a, 34b on the lower surface 31b, similar to the first embodiment, and notches 35a, 35b formed in the lower surface 31b of the fastening holes 33a, 33b, similar to the second embodiment. Such a heat sink 3c will be described with reference to FIG. 9. FIG. 9 is a side cross-sectional view of the semiconductor device of the third embodiment. Note that FIG. 9 corresponds to the side cross-sectional views of FIGS. 1 and 5 in the third embodiment.

[0065] The heat sink 3c of the third embodiment has cutouts 35a and 35b formed to include inner portions 33a1 and 33b1 of the opening edges on the lower surface 31b side of the fastening holes 33a and 33b of the heat sink 3 of the first embodiment.

[0066] Even when such a heat sink 3c is used, it is fastened to the cooling surface 4a of the cooling device 4 with screws 5a, 5b inserted through fastening holes 33a, 33b, as in the first and second embodiments. This reduces stress generated in the insulating circuit board 11 joined to the upper surface 31a of the heat sink 3c, and also reduces the gap between the lower surface 31b and the cooling surface 4a.

[0067] In this heat sink 3c as well, by widening the notch edges 35a1 and 35b1 of the notches 35a and 35b as in the modified example 2-1, the notch edges 35a1 and 35b1 can stably support the heat sink 3b.

[0068] Here, the changes in the gap between the lower surface 31b and the cooling surface 4a and the stress generated in the insulating circuit board 11 when the heat sinks 3, 3a, and 3c of the first, second, and third embodiments are used compared to the heat sink 300 of the reference example will be described using FIG. 10 . FIG. 10 is a table showing the changes in the gap and stress in the embodiments compared to the reference example. FIG. 10 also shows the improvement in the gap between the lower surface 31b and the cooling surface 4a and the stress generated in the insulating circuit board 11 when the heat sinks 3, 3a, and 3c of the first, second, and third embodiments are used compared to the heat sink 300 of the reference example. Furthermore, "SS" in the table indicates that these gaps and stresses are reduced (improved) by 70% or more compared to when the heat sink 300 of the reference example is used. Similarly, "S" and "A" indicate a reduction of 50% or more and a reduction of less than 50%.

[0069] When the heat sink 3 of the first embodiment is used, the gap between the lower surface 31b and the cooling surface 4a can be reduced by 70% or more compared to the heat sink 300 of the reference example. Also, the stress generated in the insulating circuit board 11 can be reduced by 50% or more.

[0070] When heat sink 3a of the second embodiment is used, the gap between lower surface 31b and cooling surface 4a can be narrowed by less than 50% compared to heat sink 300 of the reference example, and the stress generated in insulating circuit board 11 can be reduced by 70% or more.

[0071] Furthermore, when the heat sink 3c of the third embodiment is used, the gap between the lower surface 31b and the cooling surface 4a and the stress generated in the insulating circuit board 11 can be improved by 70% or more compared to the heat sink 300 of the reference example.

[0072] Based on these results, the heat sinks 3, 3a, and 3c of the first, second, and third embodiments can all improve the gap and stress compared to the reference heat sink 300. In particular, greater improvement can be achieved by using the heat sink 3c of the third embodiment.

[0073] [Fourth embodiment] The heat sink included in the semiconductor device of the fourth embodiment is the heat sink of the first, second, and third embodiments, except that side surfaces 32a and 32c are elongated in the ±Y direction and fastening holes are formed at each of the four corners. A heat sink 3d in this case will be described with reference to FIGS. 11 to 13. FIG. 11 is a plan view (top) of the heat sink of the semiconductor device of the fourth embodiment. FIG. 12 is a first cross-sectional side view of the semiconductor device of the fourth embodiment, and FIG. 13 is a second cross-sectional side view of the semiconductor device of the fourth embodiment. Note that FIGS. 11 to 13 omit the case. FIG. 11 shows the insulating circuit boards 11 with dashed lines, illustrating a case in which three insulating circuit boards 11 are arranged on each side of the center line CL. The number of insulating circuit boards 11 is one example. The positions of the protrusions formed on the bottom surface 31b are indicated by hatching on the top surface 31a. FIGS. 12 and 13 are cross-sectional views taken along dashed lines II and II-II in FIG. 11.

[0074] In the semiconductor device of the fourth embodiment, the semiconductor unit 10 (insulating circuit board 11) and bonding members 13a and 13b are the same as those in the first embodiment. The case may have a configuration according to the number and arrangement of such semiconductor units 10.

[0075] The heat sink 3d of the fourth embodiment includes a plate-shaped plate member 30 and protrusions 34a, 34b, 34c, and 34d. The side surfaces 32a and 32c of the plate member 30 along the short side direction are longer than those of the first embodiment. In a plan view, the plate member 30 has a center line CL that is parallel to the side surfaces 32a and 32c, respectively, and a center line CL2 that is perpendicular to the center line CL and parallel to the side surfaces 32b and 32d, respectively. The area including the intersection of the center lines CL and CL2 is a central portion C.

[0076] The plate member 30 has fastening holes 33a, 33b, 33c, and 33d formed therein. The fastening holes 33a, 33b, 33c, and 33d are formed at corners where the side surfaces 32b and 32d (a pair of first edges) and the side surfaces 32a and 32c (a pair of second edges) intersect. Specifically, the fastening hole 33a is formed at the corner formed by the side surfaces 32d and 32a, and the fastening hole 33b is formed at the corner formed by the side surfaces 32b and 32c. The fastening hole 33c is formed at the corner formed by the side surfaces 32a and 32b, and the fastening hole 33d is formed at the corner formed by the side surfaces 32c and 32d. The fastening holes 33a, 33b, 33c, and 33d vertically penetrate the upper surface 31a and the lower surface 31b, respectively. The fastening holes 33a, 33b, 33c, and 33d are formed in the outer edge regions of the plate member 30. The fastening holes 33a, 33b are formed on a diagonal line passing through the corners where the fastening holes 33a, 33b are formed and the central portion C. The fastening holes 33c, 33d are formed on a diagonal line passing through the corners where the fastening holes 33c, 33d are formed and the central portion C. The fastening holes 33a, 33b, 33c, 33d are formed at a predetermined distance from the corners of the plate member 30 toward the central portion C along the diagonal line. The fastening holes 33a, 33b, 33c, 33d may also be cylindrical in plan view. In this case, the diameter of the fastening holes 33a, 33b, 33c, 33d may be selected depending on the diameter of the screw to be used.

[0077] Furthermore, when viewed in the ±Y and ±X directions, the central portion C of the plate member 30 is warped convexly upward. That is, the central portion C protrudes upward at least on the lower surface 31b of the plate member 30, and is inclined downward from the central portion C to the ends (the side surfaces 32a, 32c (a pair of second edges) and the side surfaces 32b, 32d (a pair of first edges)). The plate member 30 has a protrusion P generated at the central portion C, which is inclined downward from the protrusion P to the side surfaces 32a, 32c (a pair of second edges) and the side surfaces 32b, 32d (a pair of first edges). The protrusion P in FIG. 11 is generated in a region including the central portion C.

[0078] The semiconductor units 10 (or the insulating circuit boards 11 included therein) are joined via joining members 13a to the inclined regions of the upper surface 31a of the plate member 30. In this case, the semiconductor units 10 are joined to the upper surface 31a in two rows of three at equal intervals across the center line CL at positions equidistant from each other across the convex portion P of the upper surface 31a of the plate member 30.

[0079] Protrusions 34a, 34b, 34c, and 34d are provided in the lower surface 31b of plate member 30 between the corners on the opposite side of center C of fastening holes 33a, 33b, 33c, and 33d (hatched areas in FIG. 11). These hatched areas are outer edge portions 31b1, 31b2, 31b3, and 31b4. Outer edge portion 31b1 is, for example, the area from fastening hole 33a to side surfaces 32d and 32a on the opposite side of center C. Outer edge portions 31b2, 31b3, and 31b4 are also in the same area with respect to fastening holes 33b, 33c, and 33d.

[0080] The protrusions 34a, 34b, 34c, and 34d may be integrally formed on the lower surface 31b of the plate member 30. The bottom surfaces of the protrusions 34a, 34b, 34c, and 34d include outer edge portions 31b1, 31b2, 31b3, and 31b4. This can also be said to mean that the outer edge portions 31b1, 31b2, 31b3, and 31b4 on the opposite side from the center portion C of the fastening holes 33a, 33b, 33c, and 33d on the lower surface 31b of the plate member 30 protrude downward.

[0081] The protrusions 34a, 34b, 34c, and 34d may be columnar. Examples of columnar shapes include a cylindrical shape and a rectangular columnar shape. Alternatively, they may be columnar shapes as shown in the hatched shape of FIG. 11. Alternatively, the columnar protrusions 34a, 34b, 34c, and 34d may be formed within this range. In this case, the width of the outer edge portions 31b1, 31b2, 31b3, and 31b4 facing the center portion C may be approximately the diameter of the fastening holes 33a, 33b, 33c, and 33d.

[0082] The heat sink 3d is also made of a metal with excellent heat dissipation properties, similar to the heat sink 3 of the first embodiment. Furthermore, similar to the first embodiment, the surface of the heat sink 3d may also be plated.

[0083] Even when such a semiconductor device is fastened to the cooling surface 4a of the cooling device 4 (not shown) by inserting screws (not shown) into the fastening holes 33a, 33b, 33c, and 33d of the heat sink 3d, the stress generated in the insulating circuit board 11 is reduced. Furthermore, the projections 34a, 34b, 34c, and 34d of the heat sink 3d serve as fulcrums, thereby reducing the gap between the lower surface 31b of the heat sink 3d and the cooling surface 4a of the cooling device 4. This makes it possible to prevent damage to the insulating circuit board 11 and a decrease in heat dissipation performance. As a result, a decrease in the reliability of the semiconductor device can be prevented.

[0084] [Fifth embodiment] The heat sink of the fifth embodiment is the heat sink 3d of the fourth embodiment without the protrusions 34a, 34b, 34c, and 34d, and with notches formed as in the second embodiment. Such a heat sink 3e will be described with reference to Figure 14. Figure 14 is a plan view (bottom surface) of the heat sink of the semiconductor device of the fifth embodiment.

[0085] The heat sink 3e included in the semiconductor device of the fifth embodiment does not include protrusions, but includes a plate-shaped plate member 30. The plate member 30 has the same configuration as the plate member 30 of the fourth embodiment except for the fastening holes 33a, 33b, 33c, and 33d. Therefore, outer edge portions 31b1, 31b2, 31b3, and 31b4 of the plate member 30 are flush with the lower surface 31b. Note that the outer edge portions 31b1, 31b2, 31b3, and 31b4 are not shown in the drawings of the fifth embodiment.

[0086] In the plate member 30 of the fifth embodiment, notches 35a, 35b, 35c, and 35d are formed on the central C side of the opening edges of the fastening holes 33a, 33b, 33c, and 33d on the underside 31b. That is, in the plate member 30 of the fifth embodiment, the central C side of the opening edges of the fastening holes 33a, 33b, 33c, and 33d on the underside 31b of the plate member 30 of the fourth embodiment is recessed, and inner portions 33a1, 33b1, 33c1, and 33d1 on the central C side of the opening edges are positioned above (in the +Z direction) the underside 31b. Note that the notches 35a, 35b, 35c, and 35d are similar to the notches 35a and 35b of the second embodiment and are formed to match the shape of the plate member 30 of the fifth embodiment.

[0087] The heat sink 3e included in the semiconductor device is placed on the cooling surface 4a of the cooling device 4, and screws (not shown) inserted through the fastening holes 33a, 33b, 33c, and 33d are screwed into the cooling surface 4a. As in the second embodiment, stress is applied to the heat sink 3e around the notched edges 35a1, 35b1, 35c1, and 35d1 of the lower surface 31b that contact the cooling surface 4a, causing the heat sink 3e to flatten and move closer to the cooling surface 4a. As in the second embodiment, this reduces stress on the insulating circuit board 11 and reduces the gap between the lower surface 31b of the heat sink 3e and the cooling surface 4a. Reducing this gap reduces the thickness of the joining member, thereby suppressing a decrease in heat dissipation performance. Furthermore, as in the third embodiment, such notches 35a, 35b, 35c, and 35d may be formed in the heat sink 3d of the fourth embodiment.

[0088] (Modification 5-1 of the fifth embodiment) The notches 35a, 35b, 35c, and 35d of the heat sink 3f of the modified example 5-1 are different from those of the heat sink 3e of the fifth embodiment. The heat sink 3f in this case will be described with reference to Fig. 15. Fig. 15 is a plan view (bottom surface) of the heat sink of the semiconductor device of the fifth embodiment (modified example 5-1).

[0089] In the heat sink 3f, the notch edges 35a1, 35b1, 35c1, and 35d1 of the notches 35a, 35b, 35c, and 35d included in the heat sink 3e of the fifth embodiment are wider, so that the notch edges 35a1, 35b1, 35c1, and 35d1 can stably support the heat sink 3f when fastened with screws.

[0090] Similar to heat sink 3e, use of such heat sink 3f can reduce stress generated in insulating circuit board 11 bonded to upper surface 31a. Furthermore, the gap between lower surface 31b and cooling surface 4a can be reduced more reliably than when heat sink 3a is used. [Explanation of symbols]

[0091] 1. Semiconductor device 2 cases 3,3a,3b,3c,3d,3e,3f Heat sink 4 Cooling device (heat sink, etc.) 4a Cooling surface 5a, 5b screws 10 Semiconductor Unit 11 Insulated circuit board 11a Insulating plate 11b Conductive circuit pattern 11c metal plate 12 Semiconductor chips 13a, 13b Joining members 20 Frame 21,22 External connection terminal 21a,22a Outer end 21b,22b Inner end 23 wire 24 Lid 25 Storage area 30 Plate member 31a Upper surface 31b Lower surface 31b1, 31b2, 31b3, 31b4 Outer edge portion 32a, 32b, 32c, 32d Side surfaces 33a, 33b, 33c, 33d Fastening holes 33a1, 33b1, 33c1, 33d1 Inner portions 34a, 34b, 34c, 34d Protrusions 35a, 35b, 35c, 35d Notches 35a1, 35b1, 35c1, 35d1 Notch edges 40 Sealing member CL, CL2 Center lines C Central part P Protruding portion

Claims

1. an insulating circuit board; a plate-shaped heat sink including an upper surface and a lower surface, at least the lower surface having a central portion that protrudes upward and is inclined downward from the central portion to an end portion, the insulating circuit board being bonded to an inclined region of the upper surface, and fastening holes that penetrate the upper surface and the lower surface being formed in an outer edge region; and an outer edge portion of the lower surface of the heat sink opposite to the center portion of the fastening hole is located lower than an inner portion of the opening edge of the fastening hole on the center portion side; Semiconductor device.

2. On the lower surface of the heat sink, the outer edge portion is included in a protrusion that protrudes downward. The semiconductor device according to claim 1 .

3. The protrusion is provided on the lower surface of the heat sink between the fastening hole and the end portion opposite the central portion with respect to the fastening hole. The semiconductor device according to claim 2 .

4. The lower surface of the heat sink is recessed at the center of the opening edge of the fastening hole, and the inner portion is located above the lower surface. The semiconductor device according to claim 1 .

5. On the lower surface of the heat sink, the outer edge portion is included in a protrusion that protrudes downward. The semiconductor device according to claim 4 .

6. the heat sink has, in a plan view, a pair of opposing first edges along a longitudinal direction and a pair of opposing second edges along a lateral direction; The fastening holes are formed at the center of the pair of second edges, a central portion that is parallel to the pair of second edges and passes through the central portion and protrudes upward; The semiconductor device according to claim 1 .

7. The insulating circuit board includes an insulating plate, a conductive circuit pattern formed on an upper surface of the insulating plate, and a metal plate formed on a lower surface of the insulating plate. The semiconductor device according to claim 1 .

8. the heat sink has, in a plan view, a pair of opposing first edges along a longitudinal direction and a pair of opposing second edges along a lateral direction; The fastening holes are formed at corners where the pair of first edges and the pair of second edges intersect, respectively. The semiconductor device according to claim 1 .

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