Semiconductor device

Abstract

A semiconductor device is provided. The semiconductor device (100) includes a semiconductor module (10), a cooler (30), and a heat conductive sheet (20) disposed between a placement surface of the semiconductor module (10) and the cooler (30). The semiconductor module (10) includes a wiring substrate (2), a semiconductor component (6A, 6B) including a laminated substrate (5A, 5B) on which a semiconductor element (1) is mounted, and a sealing portion (11). The heat conductive sheet (20) is in contact with a bottom surface of the laminated substrate (5A, 5B). The heat conductive sheet (20) has a recess (20a, 20b) corresponding to at least a portion of an outer edge of a second conductive plate (53). The second conductive plate (53) is disposed at a bottom portion of the laminated substrate (5A, 5B).

Description

Technical Field

[0001] The present invention relates to a semiconductor device having a heat-conducting sheet disposed between a semiconductor module and a cooler. Background Technology

[0002] Power semiconductor modules, used as switching devices for power conversion, are sometimes adversely affected by the heat generated by power semiconductor components. To suppress this, heat-conducting layers, coolers, and other heat dissipation devices are used on power semiconductors.

[0003] For example, the heat generated when the power semiconductor in the power semiconductor module is working is transferred to the cooler via the thermally conductive layer between the power semiconductor module and the cooler (heat sink) to cool the heat-generating power semiconductor components.

[0004] Without a thermally conductive layer, the unevenness at the contact surface between the semiconductor module and the cooler creates an air layer with low thermal conductivity, making it impossible to dissipate the heat generated by the chip. Therefore, thermally conductive layers such as grease are typically used. However, as the operating temperature Tjmax of power semiconductor devices increases, grease may leak or be pumped out during ΔTjP / C and ΔTcP / C tests, sometimes increasing the thermal resistance.

[0005] For example, Patent Document 1 discloses a grease that, by changing the viscosity during and after grease application, facilitates grease application and reduces the likelihood of pumping out during reliability testing and actual machine use (paragraph 0019). Figure 3 ).

[0006] In recent years, research has been conducted on using thermally conductive materials such as carbon sheets to conduct the generated heat to a cooler by mounting them on the lower surface of a semiconductor module.

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 5383599 Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] However, since carbon fiber is a relatively hard material, when fixing the semiconductor module to the cooler with carbon fiber screws or during reliability testing, there is a problem that the sealing resin of the semiconductor module may be damaged by applying force in the opposite direction to the warping of the semiconductor module.

[0012] The present invention was made in view of the above-mentioned problems, and its object is to provide a semiconductor device that prevents damage to semiconductor modules and has high heat dissipation performance.

[0013] Methods for solving problems

[0014] To achieve the above objectives, the semiconductor device of the present invention comprises: a semiconductor module having at least one semiconductor component and a sealing portion, the semiconductor component being composed of a laminated substrate having a conductive plate disposed on the bottom surface of an insulating substrate and a semiconductor element mounted on the laminated substrate, the sealing portion sealing at least one of the semiconductor components except for the bottom of the conductive plate; a cooler having a mounting surface for mounting the semiconductor module; and a heat-conducting sheet disposed between the semiconductor module and the mounting surface of the cooler and in contact with the bottom surface of the laminated substrate, the heat-conducting sheet having a recess corresponding to at least a portion of the outer edge of the bottom of the conductive plate.

[0015] In the semiconductor device of the present invention, a heat-conducting sheet is provided between the semiconductor module and the cooler to conduct heat generated by the semiconductor components in the semiconductor module to the cooler for heat dissipation.

[0016] Semiconductor components are sealed by a sealing portion, which can sometimes crack when the semiconductor module warps. To address this, in this invention, a recess corresponding to the outer edge of the bottom of the conductive plate is provided on the heat-conducting sheet. Therefore, when warping occurs, the conductive plate enters this recess, and the heat-conducting sheet does not experience a rebound force. It should be noted that the "recess" here includes a recess that extends to the bottom surface of the heat-conducting sheet in a cut-out state. Thus, the semiconductor device of this invention can prevent the sealing portion from cracking due to rebound force, i.e., prevent damage to the semiconductor module, and can maintain a high level of heat dissipation performance.

[0017] In the semiconductor device of the present invention, preferably, the semiconductor module has M semiconductor components, wherein M is an even number, and the conductive plates of the M semiconductor components each have an edge portion extending along the short side direction of the semiconductor module, and the recess has a shape corresponding to the mutually opposing edge portions of the conductive plates of the semiconductor components.

[0018] Each of the M (M being an even number) semiconductor components has a conductive plate with an edge extending along the short side of the semiconductor module. The recess has a shape corresponding to the opposing edges of the conductive plates (this shape does not need to perfectly correspond to the edges). Therefore, in the semiconductor device of the present invention, when the semiconductor module warps along its length, the conductive plate enters the recess, thereby preventing damage to the semiconductor module.

[0019] Furthermore, in the semiconductor device of the present invention, it is preferable that the opposing edge portions are two adjacent edge portions of the conductive plate of the semiconductor component that is adjacent to each other in the central portion of the semiconductor module.

[0020] For example, in the case where the semiconductor module has two semiconductor components, each conductive plate has two edge portions extending in the short side direction, and a total of four edge portions are provided. The recess is formed in a shape corresponding to the two adjacent edge portions of the conductive plates of the semiconductor components that are adjacent to each other. Therefore, in the semiconductor device of the present invention, the recess can be made into a countermeasure against the positive warping of the two ends of the semiconductor module in the long side direction.

[0021] Furthermore, in the semiconductor device of the present invention, it is preferable that the conductive plates of the M semiconductor components each further have an edge portion extending along the length direction of the semiconductor module, and the recess has a shape corresponding to the edge portion in the length direction.

[0022] Each of the M (M being an even number) semiconductor components has a conductive plate that also has two edge portions extending along the length direction of the semiconductor module. The recesses have shapes corresponding to these edge portions (the recesses do not need to perfectly correspond to these edge portions). Therefore, in the semiconductor device of the present invention, when the semiconductor module warps in the short-side direction or the length direction, the conductive plate enters the recess, thereby preventing damage to the semiconductor module.

[0023] Furthermore, in the semiconductor device of the present invention, it is preferable that the semiconductor module has N semiconductor components arranged along the long side direction of the semiconductor module, wherein N is an odd number, one of the N semiconductor components is arranged on the central region in the long direction, and the heat-conducting sheet has a recess corresponding to the center line extending along the short side direction of the semiconductor module.

[0024] For example, when a semiconductor module has three semiconductor components, the position of the center line of the conductive plate of the semiconductor component disposed in the central region along the length direction, extending along the short side, is the position where the semiconductor module bulges downward when positive warping occurs. Therefore, in the semiconductor device of the present invention, by providing a recess on the heat-conducting sheet corresponding to this center line, the recess can serve as a countermeasure against positive warping of the semiconductor module. It should be noted that when the semiconductor module has only one semiconductor component, it is sufficient to provide a recess corresponding to the center line of the single stacked substrate extending along the short side direction.

[0025] Furthermore, in the semiconductor device of the present invention, it is preferable that the semiconductor module has N semiconductor components, wherein N is an odd number, and the conductive plates of the N semiconductor components each have an edge portion extending along the short side direction of the semiconductor module, and the recess has a shape corresponding to the mutually opposing edge portions of the conductive plates of the semiconductor components.

[0026] Each of the N (N is an odd number) semiconductor components has a conductive plate that has an edge extending along the short side of the semiconductor module. A recess has a shape corresponding to the opposing edges of the conductive plates (the recess does not need to perfectly correspond to the edges). Therefore, in the semiconductor device of the present invention, when the semiconductor module warps along its length, the conductive plate enters the recess, thereby preventing damage to the semiconductor module.

[0027] Furthermore, in the semiconductor device of the present invention, it is preferable that the opposing edge portions are two adjacent edge portions of the conductive plates of the adjacent semiconductor components.

[0028] For example, in a semiconductor module having three semiconductor components, each conductive plate has two edge portions extending in the short-side direction, totaling six edge portions. The recess has a shape corresponding to the four adjacent edge portions of the conductive plates of the semiconductor components that are adjacent to each other among these edge portions. Therefore, in the semiconductor device of the present invention, the recess can be made into a countermeasure against positive warping of the semiconductor module.

[0029] Furthermore, in the semiconductor device of the present invention, it is preferable that each of the conductive plates of the N semiconductor components further has an edge portion extending along the length direction of the semiconductor module, and the recess has a shape corresponding to the edge portion in the length direction.

[0030] Each of the N (N is an odd number) semiconductor components has a conductive plate that also has two edge portions extending along the length direction of the semiconductor module. The recess has a shape corresponding to these edge portions (the recess does not need to perfectly correspond to the edge portions). Therefore, in the semiconductor device of the present invention, when the semiconductor module warps in the short-side direction or the length direction, the conductive plate enters the recess, thereby preventing damage to the seal.

[0031] Alternatively, in the semiconductor device of the present invention, recesses corresponding to each of the two adjacent edge portions may be merged to form a common recess.

[0032] The recesses corresponding to two adjacent edge portions disposed in the region between multiple laminated substrates are configured to be shared. This allows the conductive plates at the bottom of either or both of the laminated substrates to enter the shared recess.

[0033] Furthermore, in the semiconductor device of the present invention, it is preferable that the heat-conducting sheet has an inclined portion in which the thickness of the heat-conducting sheet decreases as it moves toward the recess.

[0034] Semiconductor modules often warp along their length, so a sloping portion is provided, with its thickness decreasing as it faces the recess towards the heat-conducting plate. Consequently, in the event of warping, the laminated substrate tilts along the sloping portion, and the conductive plate at its bottom enters the recess, making the sealing portion less susceptible to rebound forces.

[0035] Furthermore, in the semiconductor device of the present invention, it is preferable that the Young's modulus Y of the heat-conducting sheet satisfies the condition 1Pa≤Y≤200Pa.

[0036] A material that meets the above conditions is used as the heat-conducting sheet. Thus, in the event that the heat-conducting sheet is deformed by being pressed or that warps on the semiconductor module, the heat-conducting sheet can follow the warping and reliably conduct the heat generated on the laminated substrate to the cooler.

[0037] Furthermore, in the semiconductor device of the present invention, it is preferable that the heat-conducting sheet is made of carbon sheet.

[0038] Carbon sheets have high thermal conductivity, resulting in excellent heat dissipation. Furthermore, because carbon sheets are thin and rigid, they are easy to machine with recessed areas.

[0039] Furthermore, in the semiconductor device of the present invention, it is preferable that the thickness of the two end portions other than the central portion of the heat-conducting sheet is greater than the thickness of the central portion of the stacked substrate.

[0040] According to this structure, by making the central portion of the heat-conducting sheet thinner, it can follow the warping of the semiconductor module and maintain heat dissipation performance. On the other hand, by making the ends of the heat-conducting sheet thicker, the stress generated by the semiconductor module as a whole can be reduced.

[0041] Furthermore, in the semiconductor device of the present invention, when the plate thickness of the two ends is set to x and the plate thickness of the central portion is set to y, it is preferable that the relationship 2y < x < 3y holds true.

[0042] Based on this structure, the central portion and both ends of the heat-conducting sheet are designed to meet the aforementioned conditions. This further improves heat dissipation performance and reduces the overall stress on the semiconductor module.

[0043] Brief description of the attached diagram

[0044] Figure 1 This is a cross-sectional view of a semiconductor module according to an embodiment of the present invention.

[0045] Figure 2 yes Figure 1 A cross-sectional view of region R.

[0046] Figure 3 This is a cross-sectional view illustrating the warping of a semiconductor module.

[0047] Figure 4 This is a diagram showing the heatsink of the semiconductor module from above.

[0048] Figure 5 This is a diagram illustrating the names of the edges of two laminated substrates.

[0049] Figure 6A This is a diagram illustrating the concave portion corresponding to the positive warp (side A).

[0050] Figure 6B This is a diagram illustrating the concave portion corresponding to the positive warp (side A + side C).

[0051] Figure 6C This is a diagram illustrating the concave portion corresponding to the positive warp (side A + side B).

[0052] Figure 6D This is a diagram illustrating the concave portion corresponding to the positive warp (side A + side B + side C).

[0053] Figure 7A This is a diagram illustrating the concave portion corresponding to the anti-warping (C-side).

[0054] Figure 7B This is a diagram illustrating the concave portion corresponding to the anti-warping (side C + side A).

[0055] Figure 7C This is a diagram illustrating the concave portion corresponding to the anti-warping (side C + side B).

[0056] Figure 7D This is a diagram illustrating the concave portion corresponding to the anti-warping (side C + side B + side A).

[0057] Figure 8 This is a diagram illustrating the names of the edges and center line of a laminated substrate (one).

[0058] Figure 9A This is a diagram illustrating the concave portion corresponding to the positive warp (F line).

[0059] Figure 9B This is a diagram illustrating the concave portion corresponding to the positive warp (line F + edge E).

[0060] Figure 9CThis is a diagram illustrating the concave portion corresponding to the positive warp (F line + D side).

[0061] Figure 9D This is a diagram illustrating the concave portion corresponding to the positive warp (F line + D side + E side).

[0062] Figure 10A This is a diagram illustrating the concave portion corresponding to the anti-warping (E-side).

[0063] Figure 10B This is a diagram illustrating the concave portion corresponding to the anti-warping (E side + F line).

[0064] Figure 10C This is a diagram illustrating the concave portion corresponding to the anti-warping (side D + side E).

[0065] Figure 10D This is a diagram illustrating the concave portion corresponding to the anti-warping (side D + line F + side E).

[0066] Figure 11 yes Figure 4 AA sectional view.

[0067] Figure 12 This is a view of the heat sink of the semiconductor module from above (modification method 1).

[0068] Figure 13 This is a diagram showing the heatsink of the semiconductor module viewed from above (modification 2).

[0069] Figure 14 yes Figure 13 BB cross-sectional view.

[0070] Symbol Explanation

[0071] 1 Semiconductor element; 2 Wiring substrate; 4 Pins; 5A-5C Stacked substrate; 6A, 6B Semiconductor assembly; 8 Housing; 9 Screw; 10 Semiconductor module; 11 Sealing part; 20, 22, 40, 60 Heat-conducting sheet; 20a, 20b, 26a-28b', 31a-39c, 40a-40c, 60a, 60b Recess; 20s, 20t Inclined part; 24 Air layer; 25a, 25b, 45a, 45b, 65a, 65b Threaded hole; 30 Cooler; 30a Heat sink; 30b Mounting plate; 61a-61c Carbon sheet; 100, 200, 300 Semiconductor device. Detailed Implementation

[0072] Hereinafter, embodiments of the semiconductor device of the present invention will be described with reference to the accompanying drawings.

[0073] Figure 1This is a cross-sectional view showing a semiconductor device 100 according to an embodiment of the present invention. First, the semiconductor module 10 is mainly composed of a semiconductor element 1, a wiring substrate 2, a semiconductor assembly 6A, a semiconductor assembly 6B, a sealing part 11, etc.

[0074] Here, semiconductor component 6A is a portion consisting of a multilayer substrate 5A and at least one semiconductor element 1 (which may also include wiring such as pins 4) mounted on the multilayer substrate 5A. Additionally, semiconductor component 6B is a portion consisting of a multilayer substrate 5B and at least one semiconductor element 1 mounted on the multilayer substrate 5B.

[0075] The semiconductor module 10 has at least one semiconductor component 6A, 6B, which are respectively connected to the wiring substrate 2. The wiring substrate 2, semiconductor component 6A, and semiconductor component 6B are sealed into the housing 8 using resin through a casting or molding process. It should be noted that there is no sealing portion 11 on the lower surface side of the laminated substrates 5A, 5B.

[0076] In addition, the semiconductor module 10 is fixed to the cooler 30, which cools the semiconductor module 10 (layered substrates 5A, 5B), by screws 9 or the like. A heat-conducting plate 20 is disposed between the semiconductor module 10 and the cooler 30 (mounting surface).

[0077] Semiconductor element 1 is a power chip such as an IGBT (Insulated Gate Bipolar Transistor) or a diode chip, and various Si devices, SiC devices, GaN devices, etc., can be used. Furthermore, these devices can be combined. For example, a hybrid module using Si-IGBT and SiC-SBD can be used. The number of semiconductor elements 1 is not limited to the arrangement shown in the diagram; multiple semiconductor elements 1 can be mounted.

[0078] Wiring substrate 2 is a substrate having a wiring layer electrically connected to the electrodes of semiconductor element 1, disposed on the upper surface side of semiconductor element 1. Wiring substrate 2 is constructed by covering both sides of an insulating substrate with metal foil (metal wiring board), with the metal foil on the lower surface facing the semiconductor element 1. Wiring substrate 2 can also be a so-called printed substrate. The insulating substrate is preferably made of a material with low dielectric constant and high thermal conductivity, such as Si3N4, AlN, or Al2O3. Furthermore, the metal foil is preferably made of a material with low electrical resistance and high thermal conductivity, such as Cu.

[0079] One end of pin 4 is soldered to the upper surface of semiconductor element 1, and the other end of pin 4 is used for connection to wiring substrate 2. Pin 4 can be made of a metal with low resistance and high thermal conductivity, such as Cu. When pin 4 is connected to the wiring substrate 2 on the upper surface, it may sometimes be connected to a take-out terminal. Pin 4 may also be connected to a lead frame. In addition to pin 4, wiring extending from the upper surface of semiconductor element 1 may also use a lead frame, wires made of Al, etc.

[0080] The laminated substrate 5A comprises an insulating substrate 52 located in the center, a first conductive plate 51 formed on its upper surface, and a second conductive plate 53 formed on its lower surface. The insulating substrate 52 can be made of a material with excellent electrical insulation and thermal conductivity, such as Al2O3, AlN, or SiN. In particular, for high-voltage applications, a material that balances electrical insulation and thermal conductivity is preferred; AlN and SiN can be used, but the application is not limited to these materials.

[0081] Metal materials (metal foils) such as Cu and Al, which have excellent conductivity and machinability, can be used as the first conductive plate 51 and the second conductive plate 53. It should be noted that in this specification, the second conductive plate 53, made of Cu, is sometimes referred to as the back copper plate. For purposes such as rust prevention, the conductive plates 51 and 53 can also be Cu or Al that have undergone Ni plating or similar treatment.

[0082] Methods for arranging conductive plates 51 and 53 on the surface of insulating substrate 52 include direct copper bonding and active metal brazing. The structure of laminated substrate 5B is also the same as that of laminated substrate 5A. Preferably, the periphery of insulating substrate 52 protrudes further outward than the periphery of conductive plates 51 and 53.

[0083] The lower surface of the semiconductor element 1 is electrically and thermally bonded to the first conductive plate 51 of the laminated substrate 5A via solder. Furthermore, the first conductive plate 51 and the second conductive plate 53 of the laminated substrate 5A are electrically separated. The second conductive plate 53 (back copper plate) is bonded to the upper surface (mounting surface) of the cooler 30 (mounting plate 30b described later) via a thermally conductive sheet 20.

[0084] Furthermore, the lower surface of the semiconductor element 1 is electrically and thermally bonded to the first conductive plate 51 of the laminated substrate 5B via solder. In the laminated substrate 5B, the first conductive plate 51 and the second conductive plate 53 are also electrically separated. The second conductive plate 53 is bonded to the upper surface of the cooler 30 via a heat-conducting sheet 20.

[0085] The heat-conducting sheet 20 is formed of a material with high thermal conductivity. In addition, the heat-conducting sheet 20 is in contact with the laminated substrates 5A and 5B containing the semiconductor element 1 and the cooler 30, respectively, so that the heat generated by the semiconductor element 1 can be conducted to the cooler 30 for heat dissipation.

[0086] The cooler 30 consists of a heat sink 30a made of a material with good thermal conductivity, such as Al or Cu, and a mounting plate 30b on which the semiconductor module 10 is mounted. The side of the mounting plate 30b without the heat sink 30a corresponds to the "mounting surface" of the present invention. Alternatively, a heat sink consisting of multiple flow paths formed by multiple parallel plate-shaped fins can be used as the cooler 30.

[0087] Figure 2 express Figure 1 A magnified view of region R.

[0088] The semiconductor device 100 is used, for example, for power conversion, in which case the semiconductor element 1 (layered substrates 5A, 5B) will generate heat. Therefore, it is necessary to keep the temperature of the semiconductor element 1 below a certain temperature, and a cooler 30 is installed on the back side of the semiconductor module 10.

[0089] Macroscopically, gaps may sometimes form on the surface where the semiconductor module 10 contacts the cooler 30 due to warping or undulation of the semiconductor module 10. Furthermore, microscopically, it has fine irregularities caused by the roughness of the mounting surface of the cooler 30, and is therefore not smooth. It should be noted that "warping" refers to a situation where the semiconductor module 10 deforms as a whole, for example, by the peripheral portion of the semiconductor module 10 tilting upwards or downwards.

[0090] When an air layer 24 with low thermal conductivity is formed between the sealing portion 11 of the semiconductor module 10 and the cooler 30, heat cannot be conducted, and the thermal resistance increases. Therefore, the heat-conducting plate 20 needs to fill this space so that gaps are not created even if the aforementioned warping, undulations, or minor irregularities occur. The heat-conducting plate 20 also needs to follow the thermal deformation (expansion, etc.) of the semiconductor module 10 without creating gaps.

[0091] In this embodiment, a carbon sheet (graphite sheet, etc.) with a thickness of about 25μm to 100μm is used as the heat-conducting sheet 20. The advantages of the carbon sheet can be attributed to the following characteristics: its thermal conductivity is 10 to 40 W / mK (Z direction), which is higher than that of soft heat-conducting layers such as grease (1 to 4 W / mK), and therefore it is easy to process.

[0092] Because the carbon sheet itself is rigid, if used directly, the heat-conducting plate 20 cannot absorb warping or unevenness, sometimes creating gaps between the semiconductor module 10 and the cooler 30, preventing heat conduction. Therefore, by using the fastening screw 9 (see reference...) Figure 1By applying a load between the semiconductor module 10 and the cooler 30, the deformation of the heat-conducting plate 20 can absorb the unevenness of the semiconductor module 10 and the cooler 30, thereby enabling heat conduction without the need for an air layer 24. For the heat-conducting plate 20, a higher heat dissipation effect than that of a soft heat-conducting layer such as lubricating grease can be expected.

[0093] The Young's modulus (Y1) of the carbon sheet preferably satisfies the condition 5GPa≤Y1≤15GPa (unit: GPa).

[0094] Carbon sheets are sheet-like components made by compressing and processing materials primarily composed of carbon, and can also be graphite sheets, etc. It should be noted that "primary component" refers to a carbon content of 90 wt% or more, excluding unavoidable impurities, and can also consist solely of carbon. Furthermore, carbon sheets can also be PAN (Polyacylonitrile) based, pitch-based carbon fibers, or materials in which carbon nanofibers are fixed into sheet form. In these cases, from the viewpoint of density, the preferred diameter of the carbon fibers is 5 μm to 10 μm, and the preferred diameter of the carbon nanofibers is 1 nm to 50 nm.

[0095] Alternatively, the sheet can be composed solely of glassy carbon, or it can be a sheet containing a resin other than carbon. When the resin is present, the carbon content is preferably 80 wt% to 99 wt%, and more preferably 90 wt% to 95 wt% from the viewpoint of thermal conductivity and elasticity. It should be noted that if the carbon content is lower than the aforementioned levels, the formability will be compromised, while if the carbon content is higher, the thermal conductivity will deteriorate, and therefore these are not preferred. Furthermore, epoxy resin, phenolic resin, maleimide resin, etc., can be used as the resin.

[0096] Figure 3 This is a cross-sectional view of the semiconductor device 100 under warping conditions (some parts are omitted). In the semiconductor module 10 of the semiconductor device 100, most of the components exhibit positive warping (downward convexity) with their peripheral portions (both ends in the length direction) bulging upwards.

[0097] When positive warping occurs, screws 9 are used for tightening, applying a load between the semiconductor module 10 and the cooler 30. At this point, the following problem arises: the protrusions on the lower surface of the semiconductor module 10 (such as the ends of the copper plates on the back of the laminated substrates 5A and 5B) press against the heat-conducting sheet 20 due to the load from the screw tightening, resulting in stress concentration. Specifically, the ends of the laminated substrates 5A and 5B come into strong contact with the heat-conducting sheet 20 (see reference). Figure 11 The term "end" here specifically refers to the edge (outer edge) on the back side of the second conductive plate 53.

[0098] Furthermore, when the ends of the laminated substrates 5A and 5B are subjected to a rebound force from the heat-conducting sheet 20, the semiconductor module 10 (sealing portion 11) will be damaged due to this repulsive force. In particular, due to the application of such force to the entire semiconductor module 10... Figure 3 The bending stress shown can cause positive warping to become negative warping, and the seal 11, which has the least rigidity, will develop cracks.

[0099] In the heat-conducting sheet 20 of this embodiment, in order to prevent damage to the semiconductor module 10, a recess 20a corresponding to the laminated substrate 5A and a recess 20b corresponding to the laminated substrate 5B are provided. Specifically, a recess is provided at the portion of the back side (bottom end) of the second conductive plate 53 that contacts the heat-conducting sheet 20.

[0100] Here, refer to Figure 4 The details of the heat-conducting sheet 20 in this embodiment will be described below. Hereinafter, the case where two stacked substrates 5A and 5B are arranged adjacent to each other along the length of the semiconductor module 10 will be described, but there may be one or more stacked substrates. Furthermore, the number and arrangement of the stacked substrates may vary depending on the shape of the semiconductor module 10 when viewed from above (e.g., a square).

[0101] Figure 4 This is a top view of the heat-conducting plate 20, which has recesses 20a and 20b. It should be noted that threaded holes 25a and 25b for fastening the semiconductor module 10 and the cooler 30 with screws 9 are provided on the outer side of the recesses 20a and 20b. Here, "outer side" refers to a position closer to the end in the length direction than the recesses 20a and 20b, when the heat-conducting plate 20 is generally rectangular. Therefore, from the viewpoint of thermal conductivity, it is preferable to also position the heat-conducting plate 20 below the fastening parts such as screws.

[0102] Recesses 20a and 20b are respectively formed to correspond to the outer edges of the two laminated substrates 5A and 5B. Both laminated substrates 5A and 5B have a second conductive plate 53 on their bottom side. Furthermore, the bottom edge of one second conductive plate 53 has two opposing sides extending along the short side direction of the heat-conducting sheet 20. Additionally, the bottom edge of one second conductive plate 53 has two opposing sides extending along the length direction of the heat-conducting sheet 20. Figure 4 As shown, the heat-conducting sheet 20 is mainly rectangular, so the width direction of this rectangle constitutes the short side direction. It should be noted that the "short side direction of the heat-conducting sheet 20" is consistent with the short side direction of the semiconductor module 10.

[0103] The recess 20a has a shape corresponding to the edge portion of the bottom of the second conductive plate 53 of the laminated substrate 5A. The recess 20a has a break in the length direction of the heat-conducting sheet 20; however, the recess 20a can also be a continuous shape. The recess 20a has a shape corresponding to the two opposite sides of the edge portion extending in the short side direction and the two opposite sides of the edge portion extending in the length direction; however, the recess 20a can also have a shape corresponding to a portion of the edge portion.

[0104] Furthermore, the recess 20b has a shape corresponding to the bottom edge of the second conductive plate 53 of the laminated substrate 5B. It should be noted that the line width of the recesses 20a and 20b when viewed from above is preferably 0.5 mm to 3 mm, and more preferably 1 mm to 2 mm from the viewpoint of stress reduction and thermal conductivity relative to the sealing portion 11.

[0105] exist Figure 4 , Figure 5 In the original configuration, the long sides of the laminated substrates 5A and 5B are arranged parallel to the long side of the semiconductor module 10. However, they can also be arranged with the short sides of the laminated substrates 5A and 5B parallel to the long side of the semiconductor module 10.

[0106] In this embodiment, when a positive warping occurs in the length direction of the semiconductor module 10, the semiconductor module 10 bulges downward. Furthermore, the central portion of the semiconductor module 10, i.e., the end of the bottom of the second conductive plate 53 of the stacked substrates 5A and 5B, enters the recesses 20a and 20b (see reference). Figure 3 Since the bottom end of the second conductive plate 53 does not directly contact the surface of the heat-conducting sheet 20, it is possible to suppress the rebound force from the heat-conducting sheet 20 on the semiconductor module 10 (sealing part 11).

[0107] The recesses 20a and 20b can be cutouts extending to the bottom surface of the heat-conducting sheet 20. However, it is preferable that the recesses 20a and 20b do not extend to the bottom surface of the heat-conducting sheet 20, and that they can be arranged continuously and in a manner that surrounds the outer periphery of the second conductive plate 53 exposed from the sealing portion 11. Here, "arranged in a manner that surrounds..." means that, when viewed from above, the recesses 20a and 20b are arranged across the outer edge of the bottom of the second conductive plate 53. The carbon sheet having at least one recess can be processed into a predetermined shape by molding, stamping, cutting, or the like.

[0108] On the other hand, if the recess extends to the bottom surface of the heat-conducting plate 20, such as Figure 4As shown, to prevent the heat-conducting sheet 20 from separating, discontinuous portions (breaks) need to be provided on the recesses 20a and 20b. When the recesses 20a and 20b are not continuous, the depth of the recesses 20a and 20b is preferably 40% or more relative to the thickness of the heat-conducting sheet 20. By providing the recesses to a depth within the aforementioned range, the bottom end of the second conductive plate 53 can be embedded in the recesses 20a and 20b, thereby reducing the stress acting on the heat-conducting sheet 20.

[0109] The configuration of the recess varies depending on the countermeasures taken against either positive or negative warping of the semiconductor module 10. Therefore, the following refers to... Figures 5 to 10D This section explains the various models.

[0110] like Figure 5 As shown, when viewed from above, the two adjacent and opposing sides of the second conductive plate 53 of the two stacked substrates 5A and 5B disposed on the heat-conducting sheet 20 are designated as sides A; the two sides that extend in the short side direction and are opposite to sides A are designated as sides C; and the two sides that extend in the long side direction and are opposite to each other (two sets) are designated as sides B.

[0111] When the semiconductor module 10 is rectangular, it often exhibits positive or negative warping along its long side. As a countermeasure against positive warping, such as... Figures 6A to 6D As shown, preferably, (1) recesses 26a and 26b corresponding to side A are provided on the heat-conducting sheet 20 (refer to...). Figure 6A (2) Set recesses 26a, 26a', 26b, and 26b' on the heat-conducting sheet 20 corresponding to sides A and C (refer to...). Figure 6B (3) Set recesses 27a and 27b on the heat-conducting sheet 20 corresponding to sides A and B (refer to...). Figure 6C (4) Set recesses 28a, 28a', 28b, and 28b' on the heat-conducting sheet 20 corresponding to sides A, B, and C (refer to...). Figure 6D ).

[0112] On the other hand, as a countermeasure against the warping of the semiconductor module 10, such as Figures 7A to 7D As shown, preferably, (1) recesses 31a and 31b corresponding to side C are provided on the heat-conducting sheet 20 (refer to...). Figure 7A (2) Set recesses 31a, 31a', 31b, and 31b' on the heat-conducting sheet 20 corresponding to side C and side A (refer to...). Figure 7B (3) Set recesses 32a and 32b on the heat-conducting sheet 20 corresponding to sides C and B (refer to...). Figure 7C(4) Set recesses 33a, 33a', 33b, and 33b' on the heat-conducting sheet 20 corresponding to sides C, B, and A (refer to...). Figure 7D The above-described arrangement of recesses as a method of positive or negative warping is applicable when there are an even number (e.g., four) of laminated substrates.

[0113] When there is only one laminated substrate, in the event of positive warping, the central portion of the laminated substrate bulges downward and comes into strong contact with the heat-conducting sheet 20, and the bottom of the second conductive plate 53 bears a large rebound force from the heat-conducting sheet 20. Therefore, it is sufficient to form a recess in the heat-conducting sheet 20 at the location corresponding to the bulge in the central portion. Here, "bulge" means protruding in the direction of the heat-conducting sheet 20, and "recess corresponding to the bulge" means a recess provided at a position corresponding to at least a portion of the bulge.

[0114] Furthermore, when three or more stacked substrates are arranged within the semiconductor module 10, the second conductive plate 53 located at the center of the semiconductor module 10 along its length protrudes downward, exerting a significant force on the heat-conducting sheet 20. Therefore, it is sufficient to form a recess on the heat-conducting sheet 20 located at the center of the semiconductor module 10 and corresponding to the portion of the second conductive plate 53 constituting the protrusion.

[0115] like Figure 8 As shown, in a top view of the edges (edge ​​portions) of the second conductive plate 53 of a multilayer substrate 5C disposed on the heat-conducting sheet 22, the two sides extending along the length direction of the semiconductor module 10 and facing each other are designated as edges D. Additionally, the two sides extending in the short side direction and facing each other are designated as edges E, and the center line of the edges D extending in the short side direction is designated as line F.

[0116] When the semiconductor module 10 is rectangular, positive or negative warping usually occurs along the long side of the semiconductor module 10. As a countermeasure against positive warping, such as... Figures 9A to 9D As shown, preferably, (1) a recess 34a corresponding to line F is provided on the heat-conducting sheet 22 (see reference). Figure 9A (2) Set recesses 34a, 34b, and 34c on the heat-conducting plate 22 corresponding to line F and side E (refer to) Figure 9B (3) A recess 35a (including the shape of the recess 34a) corresponding to the F line and the D side is provided on the heat-conducting plate 22 (refer to) Figure 9C (4) Set the F line, E edge and the corresponding recesses 36a, 36b and 36c on the heat-conducting plate 22 (refer to) Figure 9D ).

[0117] As a countermeasure against warping of semiconductor module 10, such as Figures 10A to 10DAs shown, preferably, (1) recesses 37a and 37b corresponding to side E are provided on the heat-conducting sheet 22 (refer to...). Figure 10A (2) Set recesses 37a, 37b, and 37c on the heat-conducting plate 22 corresponding to edge E and line F (refer to) Figure 10B (3) Set recesses 38a, 38b, and 38c on the heat-conducting sheet 22 corresponding to sides D and E (refer to...). Figure 10C (4) Set recesses 39a, 39b, and 39c on the heat-conducting sheet 22 corresponding to the D-side, E-side, and F-line (refer to...). Figure 10D The above-described arrangement of recesses as a method of positive or negative warping is applicable when there is an odd number (e.g., three) of laminated substrates.

[0118] Next, in Figure 11 The middle shows Figure 4 AA sectional view.

[0119] An inclined portion 20s, in which the thickness of the heat-conducting sheet 20 decreases toward the recess 20a, can be provided near the recess 20a of the heat-conducting sheet 20. The inclined portion 20s has an inclination corresponding to the warping of the laminated substrate 5A (approximately 30° to 45° relative to the horizontal plane). As a result, the end of the second conductive plate 53 of the laminated substrate 5A contacts the inclined portion 20s, thereby increasing the contact area between the second conductive plate 53 and the heat-conducting sheet 20 and reducing the stress exerted by the second conductive plate 53 on the heat-conducting sheet 20. Therefore, damage to the semiconductor module 10 (sealing portion 11) can be prevented. It should be noted that a similar inclined portion 20s is provided near the recess 20b.

[0120] Furthermore, an inclined portion 20t is provided in the region between the recesses 20a and 20b of the heat-conducting sheet 20. The inclined portion 20t is inclined (approximately 60° to 80° relative to the horizontal plane) to correspond to the large warpage of the laminated substrates 5A and 5B and the thickness decreases as it moves toward the recesses 20a and 20b. This structure also helps to prevent damage to the semiconductor module 10.

[0121] Next, refer to Figures 12-14 The method of changing the heat-conducting sheet is explained.

[0122] Modification method 1 (semiconductor device 200) includes a semiconductor module 10, a cooler 30, and a heat-conducting sheet 40 disposed between the semiconductor module 10 and the cooler 30 (mounting surface).

[0123] exist Figure 12In this embodiment, the heat-conducting sheet 40 has recesses 40a to 40c. A multilayer substrate 5A of the semiconductor module 10 is disposed in the region between recesses 40a and 40c, and a multilayer substrate 5B of the semiconductor module 10 is disposed in the region between recesses 40b and 40c. It is not necessary for the heat-conducting sheet 40 to have all of the recesses 40a to 40c. For example, considering that positive warping is more likely, at least recess 40c is provided, and recesses 40a or 40b are appropriately provided.

[0124] Here, the recess 40c forms a recess shared by the laminated substrate 5A and the laminated substrate 5B. Threaded holes 45a and 45b are provided on the outer sides of the recesses 40a and 40b.

[0125] When positive warping occurs in the semiconductor device 200, the bottom surface of the second conductive plate 53 at the bottom of the stacked substrates 5A and 5B contacts the inclined portion (see reference). Figure 11 Therefore, the contact area between the second conductive plate 53 and the heat-conducting sheet 40 is increased, and the stress exerted by the second conductive plate 53 on the heat-conducting sheet 40 is reduced. This prevents damage to the semiconductor module 10 (sealing portion 11) and improves heat dissipation performance.

[0126] Next, the modified version 2 (semiconductor device 300) includes a semiconductor module 10, a cooler 30, and a heat-conducting sheet 60 disposed between the semiconductor module 10 and the cooler 30 (mounting surface).

[0127] exist Figure 13 In this embodiment, the heat-conducting sheet 60 has recesses 60a and 60b. A multilayer substrate 5A of the semiconductor module 10 is disposed in the region between the recesses 60a, and a multilayer substrate 5B of the semiconductor module 10 is disposed in the region between the recesses 60b. Here, the heat-conducting sheet 60 does not necessarily have all the recesses 60a and 60b; for example, the recesses can be formed by appropriately combining the elements constituting the recesses 60a and 60b.

[0128] Here, the long-side end (diagonal portion) of the heat-conducting sheet 60 is a fastening portion such as a screw. By making the thickness of this end thicker than the film thickness of the central portion of the heat-conducting sheet 60, the overall strength of the heat-conducting sheet 60 is improved. Furthermore, the film thickness of the central portion of the heat-conducting sheet 60 (the portion where the stacked substrates 5A and 5B are disposed on the upper surface) is thinner than that of its two ends, thus maintaining heat dissipation performance while adapting to the warping of the semiconductor module 10. The central portion of the heat-conducting sheet 60 is composed of a carbon sheet 61c, and the carbon sheets 61a and 61b at the ends can also be stacked on top of the carbon sheet 61c.

[0129] The thicker portion of the heat-conducting plate 60 is preferably the area from the edge of the carbon sheet 61c along its length to the portion having recesses 60a and 60b, and preferably includes fastening parts such as screws. The carbon sheets at both ends (diagonal portions) are not limited to two overlapping sheets, but may also overlap three or more sheets. In addition, the overlapping carbon sheets may each have a different thickness.

[0130] Threaded holes 65a and 65b are provided on the outer sides of the recesses 60a and 60b, but the film thickness at both ends (sloping portions) of the heat-conducting sheet 60 is thicker. Therefore, especially in the event of positive warping of the semiconductor module 10, the stress generated by the semiconductor device 300 as a whole can be reduced. Figure 12 As shown, the area between the laminated substrate 5A and the laminated substrate 5B can also be a recess shared by the two laminated substrates.

[0131] Next, in Figure 14 The middle shows Figure 13 BB cross-sectional view.

[0132] Here, when the thickness of the end portion of the heat-conducting sheet 60 is set to x and the thickness of the central portion of the heat-conducting sheet 60 is set to y, it is preferable that the relationship 2y < x < 3y holds. By designing to meet this condition, heat dissipation performance can be improved and the stress generated by the semiconductor module 10 as a whole can be reduced. It should be noted that the width of the end portion in the longitudinal direction is preferably 5mm to 30mm, and from the viewpoint of fixing and securing the heat-conducting sheet 60, the width of the end portion in the longitudinal direction is more preferably 10mm to 20mm.

[0133] The embodiments for implementing the present invention have been described above, but the present invention is not limited to the above embodiments, and appropriate changes can be made without departing from the spirit of the present invention.

[0134] exist Figure 11 In the heat-conducting sheet 20, there are inclined portions 20s and 20t, but these inclined portions are not a necessary structure. Alternatively, the inclined portions can be omitted, and instead, the ends (bottom ends) of the back copper plates of the laminated substrates 5A and 5B can be cut into an inclined shape so that the bottom ends do not come into contact with the heat-conducting sheet 20.

[0135] In the description of the above embodiments, the main focus is on the case where warping (positive warping) forming a trough occurs in the region between two stacked substrates, and a recess is provided at least in the region between the two stacked substrates. However, the same warping may also occur when there is only one stacked substrate, so it is preferable to provide a recess corresponding to the outer edge of the bottom of the stacked substrate in advance.

[0136] The recess only needs to have a depth sufficient to penetrate at least a portion of the bottom end of the laminated substrate (second conductive plate). Therefore, a recess that does not extend to the bottom surface of the heat-conducting sheet or a recess that extends to the bottom surface (cutout) can be used. Specifically, the depth of the recess is preferably 40% or more relative to the thickness of the heat-conducting sheet 20.

[0137] By providing a recess corresponding to the outer edge of the bottom of the heat-conducting sheet, the bottom end of the conductive plate of the laminated substrate can enter the recess regardless of the warping direction, thereby reducing the rebound force from the heat-conducting sheet on the sealing part. For recesses in the direction prone to warping, it is preferable to form them continuously with a certain width. On the other hand, for recesses in the direction less prone to warping, they can be formed intermittently or the width of the recess can be narrowed.

Claims

1. A semiconductor device, characterized in that, have: A semiconductor module having at least one semiconductor component and a sealing portion, the semiconductor component comprising a laminated substrate having a conductive plate disposed on the bottom side of an insulating substrate and semiconductor elements mounted on the laminated substrate, the sealing portion sealing at least one of the semiconductor components except for the bottom of the conductive plate. A cooler having a mounting surface for mounting the semiconductor module; as well as, A heat-conducting sheet is disposed between the mounting surfaces of the semiconductor module and the cooler and in contact with the bottom surface of the laminated substrate. The heat-conducting sheet has a recess corresponding to at least a portion of the outer edge of the bottom of the conductive plate.

2. The semiconductor device according to claim 1, characterized in that, The semiconductor module has M semiconductor components arranged along the long side of the semiconductor module, where M is an even number. Each of the M semiconductor components has a conductive plate that has an edge extending along the short side of the semiconductor module. The recess has a shape corresponding to the opposing edge portion of the conductive plate of the semiconductor component.

3. The semiconductor device according to claim 2, characterized in that, The opposing edges are the two adjacent edges of the conductive plates of the semiconductor component that are adjacent to each other in the central part of the semiconductor module.

4. The semiconductor device according to claim 2 or 3, characterized in that, Each of the M semiconductor components has a conductive plate that further has an edge extending along the long side of the semiconductor module. The recess has a shape corresponding to the edge portion in the direction of the long side.

5. The semiconductor device according to claim 1, characterized in that, The semiconductor module has N semiconductor components arranged along the long side of the semiconductor module, where N is an odd number. One of the N semiconductor components is disposed in the central region along the long side. The heat-conducting sheet has a recess corresponding to the center line extending along the short side of the semiconductor module.

6. The semiconductor device according to claim 1 or 5, characterized in that, The semiconductor module has N semiconductor components, where N is an odd number. Each of the N semiconductor components has a conductive plate that has an edge extending along the short side of the semiconductor module. The recess has a shape corresponding to the opposing edge portion of the conductive plate of the semiconductor component.

7. The semiconductor device according to claim 6, characterized in that, The opposing edges are two adjacent edges of the conductive plates of the adjacent semiconductor components.

8. The semiconductor device according to claim 6, characterized in that, Each of the N semiconductor components has a conductive plate that further has an edge extending along the long side of the semiconductor module. The recess has a shape corresponding to the edge portion in the direction of the long side.

9. The semiconductor device according to claim 3, characterized in that, The recesses corresponding to each of the two adjacent edge portions are merged to form a shared recess.

10. The semiconductor device according to claim 7, characterized in that, The recesses corresponding to each of the two adjacent edge portions are merged to form a shared recess.

11. The semiconductor device according to any one of claims 1, 2, and 5, characterized in that, The heat-conducting sheet has an inclined portion in which the thickness of the heat-conducting sheet decreases as it moves toward the recess.

12. The semiconductor device according to any one of claims 1, 2, and 5, characterized in that, The Young's modulus Y1 of the heat-conducting sheet satisfies the condition 5GPa≤Y1≤15GPa.

13. The semiconductor device according to any one of claims 1, 2, and 5, characterized in that, The heat-conducting sheet is made of carbon sheet.

14. The semiconductor device according to any one of claims 1, 2, and 5, characterized in that, In the heat-conducting sheet, the thickness of the two ends along the long side is greater than the thickness of the central portion of the stacked substrate.

15. The semiconductor device according to claim 14, characterized in that, When the thickness of the plates at both ends is set to x and the thickness of the plate at the center is set to y, the relationship 2y < x < 3y holds true.

16. A semiconductor device, characterized in that, have: A semiconductor module having at least one semiconductor component and a sealing portion, the semiconductor component comprising a laminated substrate having a conductive plate disposed on the bottom side of an insulating substrate and semiconductor elements mounted on the laminated substrate, the sealing portion sealing at least one of the semiconductor components except for the bottom of the conductive plate. A cooler having a mounting surface for mounting the semiconductor module; as well as, A heat-conducting sheet is disposed between the mounting surfaces of the semiconductor module and the cooler and in contact with the bottom surface of the laminated substrate. The heat-conducting sheet has a recess corresponding to the central portion of the conductive plate.

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