Semiconductor module, power conversion device, and method for manufacturing semiconductor module

Abstract

To prevent a resin member from going around to a heat dissipation surface of a sheet-like member.SOLUTION: A semiconductor module includes: a conductor plate on which a semiconductor element is mounted; a sheet-like member which covers the surface of the conductor plate; and a resin member which integrally mold-seals the conductor plate and the sheet-like member. The sheet-like member has the end covered by the resin member in a state where a region overlapping the surface of the conductor plate is exposed. The sheet-like member has an outer peripheral surface formed on the outer periphery, an inner peripheral surface formed on the inner periphery relative to the outer peripheral surface, an outer peripheral step connecting the outer edge of the sheet-like member to the outer peripheral surface, and an inner peripheral step connecting the outer peripheral surface to the inner peripheral surface. The outer peripheral surface is positioned farther from the semiconductor element than the outer edge, and the inner peripheral surface is positioned farther from the semiconductor element than the outer peripheral surface.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a semiconductor module, a power conversion device, and a method for manufacturing a semiconductor module.

Background Art

[0002] Power conversion devices that utilize the switching of power semiconductor elements are widely used in consumer, in-vehicle, railway, and substation equipment because of their high conversion efficiency. Since power semiconductor elements generate heat when energized, high heat dissipation performance is required. Especially in in-vehicle applications, a highly efficient cooling system using water cooling is adopted for the purpose of miniaturization and weight reduction. Patent Document 1 discloses an electric circuit body including a power semiconductor element, a first conductor plate connected to one surface of the power semiconductor element, a first sheet-like member having a first resin insulation layer and at least covering the surface of the first conductor plate, a sealing material for sealing the ends of the power semiconductor element, the first conductor plate, and the first sheet-like member, and a first cooling member in close contact with the first sheet-like member. The first sheet-like member has a buried portion in which the end portion of the first sheet-like member is covered by the sealing material, a heat dissipation surface portion that is a region overlapping the surface of the first conductor plate, and a margin portion that is a region between the buried portion and the heat dissipation surface portion. The margin portion retreats inward from the heat dissipation surface portion, and the buried portion retreats inward from the margin portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the invention described in Patent Document 1, there is room for improvement in the intrusion of the resin member into the heat dissipation surface.

Means for Solving the Problems

[0005] A semiconductor module according to a first aspect of the present invention includes a conductor plate on which a semiconductor element is mounted, a sheet-like member that covers the surface of the conductor plate, and a resin member that integrally molds and seals the conductor plate and the sheet-like member. The sheet-like member has an end portion covered by the resin member in a state where a region overlapping the surface of the conductor plate is exposed. The sheet-like member has an outer peripheral surface formed on the outer periphery, an inner peripheral surface formed on the inner periphery closer to the center than the outer peripheral surface, an outer peripheral step connecting the outer edge of the sheet-like member and the outer peripheral surface, and an inner peripheral step connecting the outer peripheral surface and the inner peripheral surface. The outer peripheral surface is farther from the semiconductor element than the outer edge, and the inner peripheral surface is farther from the semiconductor element than the outer peripheral surface. A power conversion device according to a second aspect of the present invention is a power conversion device including a plurality of the aforementioned semiconductor modules. In the plurality of semiconductor modules, the heights of the outer peripheral steps are the same, and the heights of the inner peripheral steps are not the same. A method for manufacturing a semiconductor module according to a third aspect of the present invention includes a clamping step of arranging the sheet-like member, the conductor plate, and the semiconductor element in a space formed by a mold having a variable step in a central portion and a fixed step on the outer periphery, and a molding step of filling the space with the resin member to integrally mold and seal the conductor plate and the sheet-like member while forming the outer peripheral step and the inner peripheral step.

Advantages of the Invention

[0006] According to the present invention, it is possible to prevent the resin member from creeping onto the heat dissipation surface of the sheet-like member.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Figure 16

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and appropriate omissions and simplifications are made for the sake of clarity of the explanation. The present invention can be implemented in various other forms. Unless otherwise particularly limited, each component may be in a single or plural number. The positions, sizes, shapes, ranges, etc. of the components shown in the drawings may not represent the actual positions, sizes, shapes, ranges, etc. in order to facilitate the understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, ranges, etc. disclosed in the drawings.

[0009] - Embodiment - Hereinafter, embodiments of a semiconductor module and a power conversion device will be described with reference to FIGS. 1 to 15.

[0010] FIG. 1 is a plan view of the electric circuit body 400. In the present embodiment, for the sake of clarity of the correlation between the drawings, the XYZ axes orthogonal to each other are also shown. In FIG. 1, the right direction in the drawing is the plus side of the X axis, the upward direction in the drawing is the plus side of the Y axis, and the front direction in the drawing is the plus side of the Z axis. The electric circuit body 400 includes a semiconductor module 300 and a cooling member 340. As will be described in detail later, the semiconductor module 300 and the cooling member 340 overlap in the Z-axis direction, and in FIG. 1, most of the semiconductor module 300 is hidden by the cooling member 340.

[0011] The semiconductor module 300 converts a direct current and an alternating current into each other using a semiconductor element 150 described later. Since the semiconductor module 300 generates heat when energized, it is cooled by the cooling member 340. As the refrigerant built in the cooling member 340, water or an antifreeze liquid in which ethylene glycol is mixed with water can be used. The semiconductor module 300 includes power terminals through which a large current flows, such as a positive terminal 315B and a negative terminal 319B connected to the capacitor module 500 of the DC circuit, and an AC terminal 320B connected to the motor generators 192 and 194 of the AC circuit. Further, signal terminals used for controlling the semiconductor module, such as a lower arm gate terminal 325L, an upper arm gate terminal 325U, an emitter signal terminal 325E, and a collector signal terminal 325C, are provided.

[0012] FIG. 2 shows a cross-sectional view taken along line II-II of FIG. 1, and FIG. 3 shows a cross-sectional view taken along line III-III of FIG. 1. Further, FIG. 4 shows a cross-sectional perspective view of the semiconductor module 300, FIG. 5 shows a semi-transparent view showing the internal structure of the semiconductor module 300, and FIG. 6 shows a circuit diagram of the semiconductor module 300. As shown in FIG. 5, the semiconductor module 300 includes a first power semiconductor element 155 that constitutes an upper arm circuit and a second power semiconductor element 157 that constitutes a lower arm. Hereinafter, the first power semiconductor element 155 and the second power semiconductor element 157 are collectively referred to as a "semiconductor element" 150. The semiconductor element 150 can be made of, for example, silicon (Si), silicon carbide (SiC), gallium nitride (GaN), gallium oxide (GaO), carbon (C), or the like.

[0013] The semiconductor device 150 can be used in the device structure of an insulated gate bipolar transistor (IGBT), or can also be used in the device structure of a metal oxide semiconductor field effect transistor (MOSFET). IGBTs are suitable for high-power applications because they have high breakdown voltage and low on-resistance, but are not suitable for high-speed switching. On the other hand, MOSFETs are suitable for high-speed switching, but when the breakdown voltage is increased, the drift layer becomes thicker and the on-resistance becomes higher, which poses a problem for increasing the output power. However, as a semiconductor device, if a next-generation device such as SiC with a high breakdown electric field is used, the MOSFET can also increase the output power and achieve low loss due to high-speed switching. However, since the next-generation device is more expensive than Si, it may be realized by connecting a plurality of small-sized power semiconductor devices in parallel.

[0014] In this case, the gate terminals may be provided in common, but it is desirable to provide gate terminals for each element because more precise control can be achieved. Also, in high-voltage applications, a guard ring for relaxing the surface electric field strength is provided on the outer periphery of the chip. The size of the guard ring is determined by the electric field strength, so even if the chip size becomes smaller, the size of the guard ring cannot be made smaller. For this reason, when the chip size becomes smaller, the area ratio of the active region on the source side to the chip area becomes smaller. In the method of simultaneously bonding the sheet-like member 440 and resin-sealing in the transfer molding process, when using a small chip, even if the same pressing force is applied to the chip area, the stress becomes high at the joint where the active region on the source side and the first conductor plate 421 are joined, and the joint is likely to peel off.

[0015] The drain side of the first power semiconductor element 155 is joined to the second conductor plate 422. Hereinafter, the first conductor plate 421 and the second conductor plate 422 are collectively referred to as the "conductor plate" 420. For the joining of the semiconductor element 150 and the conductor plate 420, solder or sintered metal may be used. The conductor plate 420 is not particularly limited as long as it is a material with high electrical conductivity and high thermal conductivity, but a copper-based material or an aluminum-based material is desirable. The copper-based material or the aluminum-based material may be used alone, or may be plated with nickel (Ni), silver (Ag), etc. to enhance the joinability with solder or sintered metal. The conductor plate 420 is joined to the source side of the first power semiconductor element 155.

[0016] The drain side of the second power semiconductor element 157 is joined to the second conductor plate 422. The conductor plate 421 is joined to the source side of the second power semiconductor element 157. In order to add functions such as a current sensor and life diagnosis to the electric circuit body 400, a substrate on which circuit components are mounted may be mounted on the conductor plate 420. In addition to the role of conducting current, the conductor plate 420 serves as a heat transfer member that transfers the heat generated by the first power semiconductor element 155 and the second power semiconductor element 157 to the cooling member 340.

[0017] Since the conductor plate 420 has a different potential from the cooling member 340, a sheet-like member 440 having a resin insulation layer 441 is interposed between the conductor plate 420 and the cooling member 340. A heat conduction member 453 is disposed between the sheet-like member 440 and the cooling member 340 to reduce the contact thermal resistance. The first power semiconductor element 155, the second power semiconductor element 157, the conductor plate 420, the internal connection portion, a part of the insulating resin sheet, a part of the laminated substrate, and a part of the external terminal are sealed with a resin member 360 by transfer molding.

[0018] For the heat conduction member 453, an inorganic high thermal conductivity material such as a carbon-based material can be used. Also, for the heat conduction member 453, members having fluidity at normal temperature or high temperature such as grease, gel grease, and phase change sheets can be used. Further, in order to ensure workability and long-term reliability, a curable heat conduction material that has fluidity when uncured and loses fluidity after curing can be used for the heat conduction member 453. When using a curable material for the heat conduction member 453, there are advantages that the viscosity is low during application and the workability is excellent, and the mechanical properties can be improved by curing. Curing can utilize heat curing, moisture curing, ultraviolet curing, etc., but heat curing is desirable for curing to a deep part. The heat conduction member 453 can be used alone a high thermal conductivity material such as metal, ceramics, carbon-based material, etc., a material obtained by mixing these with resin, or a combination thereof.

[0019] The sheet-like member 440 and the resin member 360 are cured simultaneously in the transfer molding process described later. In the transfer molding process, the adhesion between the conductor plate 420 and the sheet-like member 440 is also performed simultaneously. The heat dissipation surface of the sheet-like member 440 is the adhesion region between the conductor plate 420 connected to the semiconductor element 150 and the sheet-like member 440, and is a region that bears both heat dissipation from the semiconductor element 150 and insulation.

[0020] The resin insulating layer 441 of the sheet-like member 440 may be a material having adhesiveness with the heat sink, and is not limited to a specific material. However, from the viewpoint of the balance between adhesiveness and heat dissipation, it is desirable to use an epoxy resin-based resin insulating layer in which a powdery inorganic filler is dispersed as the resin insulating layer 441. It is desirable to provide a metal foil 444 on the side of the sheet-like member 440 that contacts the heat conducting member 453. In the transfer molding process, in order to prevent adhesion to the mold when mounting the sheet-like member 440 on the mold, a release sheet or a metal foil 444 is provided on the contact surface of the sheet-like member 440 with the mold. Since the release sheet has poor thermal conductivity, a step of peeling it off after transfer molding is required. In the case of a metal foil, by selecting a metal with high thermal conductivity such as copper-based or aluminum-based, it can be used without peeling off after transfer molding. By performing transfer molding including the sheet-like member 440, the end portion of the sheet-like member 440 is covered with the resin member 360, and the effect of improving reliability is achieved.

[0021] As shown in FIG. 4, the sheet-like member 440 has an innermost peripheral surface 461, an inner peripheral surface 462, an outer peripheral surface 463, an innermost peripheral step 431, an inner peripheral step 432, and an outer peripheral step 433. The innermost side is the innermost peripheral surface 461, and toward the outside, they are arranged in the order of the innermost peripheral step 431, the inner peripheral surface 462, the inner peripheral step 432, the outer peripheral surface 463, and the outer peripheral step 433. The innermost peripheral step 431 is a step existing at the boundary between the innermost peripheral surface 461 and the inner peripheral surface 462. The inner peripheral step 432 is a step existing at the boundary between the inner peripheral surface 462 and the outer peripheral surface 463. The outer peripheral step 433 is a step existing at the boundary between the outer peripheral surface 463 and the outer edge of the sheet-like member 440. The distance from the outer peripheral step 433 to the inner peripheral step 432 is farther than the distance from the inner peripheral step 432 to the innermost peripheral step 431.

[0022] The Z-direction positions of the innermost peripheral surface 461, the inner peripheral surface 462, and the outer peripheral surface 463 are such that the innermost peripheral surface 461 is on the most positive Z-axis side, and the outer peripheral surface 463 is on the most negative Z-axis side. Since the semiconductor element 150 is present at the center shown in the figure, among the three surfaces, the innermost peripheral surface 461 is the farthest from the semiconductor element 150. Specifically, it is as follows. The outer peripheral surface 463 is farther from the semiconductor element 150 than the outer edge of the sheet-like member 440. The inner peripheral surface 462 is farther from the semiconductor element 150 than the outer peripheral surface 463. The innermost peripheral surface 461 is farther from the semiconductor element 150 than the inner peripheral surface 462.

[0023] The outer edge of the sheet-like member 440 can also be said to be the "end portion" of the sheet-like member 440. The outer peripheral step 433 is provided in the vicinity of the resin-coated portion at the end of the sheet-like member 440. The outer peripheral step 433 is a step having a height of 100 μm, desirably 150 μm or more. The outer peripheral step 433 prevents the resin member 360 from creeping onto the surface of the sheet-like member 440 due to the molding pressure in the transfer molding process according to the principle shown in FIG. 11 described later.

[0024] Also, the sheet-like member 440 forms the innermost peripheral step 431 according to the principle shown in FIG. 11 described later. Due to the innermost peripheral step 431, the heat dissipation surface that adheres the sheet-like member 440 and the conductor plate 420, that is, the innermost peripheral surface 461, becomes convex. As a result, it effectively adheres to the cooling member 340, and the cooling performance is improved. The inner peripheral step 432 is generated by absorbing the height variation when connecting the power semiconductor element by a pressurizing mechanism using the spring 602 of the transfer molding die. The inner peripheral step 432 absorbs the height variation of the circuit body 310. Since the sheet-like member 440 has the inner peripheral step 432, even if there is a height variation in the circuit body 310, the sheet-like member 440 and the conductor plate 420 can be pressurized with a constant surface pressure. Thereby, the sheet-like member 440 and the conductor plate 420 can be effectively adhered.

[0025] The height of the innermost peripheral step 431, that is, the width in the Z direction, is referred to as the innermost peripheral step height 431H. The height of the inner peripheral step 432, that is, the width in the Z direction, is referred to as the inner peripheral step height 432H. The height of the outer peripheral step 433, that is, the width in the Z direction, is referred to as the outer peripheral step height 433H. Note that the inner peripheral step height 432H and the outer peripheral step height 433H are shown in FIG. 3, but the innermost peripheral step height 431H is not shown due to drawing convenience.

[0026] For the conductor plate 420, a material with high electrical conductivity and high thermal conductivity is desirable. For the conductor plate 420, a metal-based material such as copper or aluminum, or a composite material such as a metal-based material and diamond, carbon, or ceramic with high thermal conductivity can also be used. For the cooling member 340, an aluminum-based or copper-based material with high thermal conductivity and low weight is desirable. The cooling member 340 is manufactured by extrusion molding, forging, brazing, or the like.

[0027] Hereinafter, a method for manufacturing the electric circuit body 400 will be described with reference to FIGS. 7 to 9. FIGS. 7 and 8 show the first to sixth steps of a method for manufacturing the semiconductor module 300, and FIG. 9 shows the manufacturing process of the electric circuit body 400 using the semiconductor module 300 completed at the end of FIG. 8. A method for manufacturing the semiconductor module 300 will be described with reference to FIGS. 7 and 8. FIG. 7 shows the first to third steps, and FIG. 8 shows the fourth to sixth steps. First, FIG. 7 will be described. The first step shown in FIG. 7(a) is a bonding step. First, the drain side of the semiconductor element 150 is connected to the first conductor plate 421, a gate electrode (not shown) is connected by wire bonding, and the source side of the semiconductor element 150 is connected to the second conductor plate 422 to produce the circuit body 310.

[0028] The second step shown in FIG. 7(b) is a temporary attachment step of temporarily attaching the sheet-like member 440 to the conductor plate 420. Temporary attachment means that, thereafter, the sheet-like member 440 is attached using the adhesion force of the sheet-like member 440 under the condition that there is room for the sheet-like member 440 to harden and adhere in the transfer molding step. The third step shown in FIG. 7(c) is a mounting step of mounting the circuit body 310 to which the sheet-like member 440 is temporarily attached on the mold 601 of the transfer molding apparatus. The transfer molding step using the mold 601 will be described with reference to FIG. 8.

[0029] The fourth process shown in Fig. 8(a) is a forming process and a molding process, in which clamping and transfer molding are performed. The transfer molding apparatus includes a spring 602 inside a mold 601. The spring 602 realizes a variable step due to elastic force. By the spring 602, even if the height of the circuit body 310 varies, a predetermined load can be applied by the spring force without applying excessive compression to the semiconductor element 150. Further, the transfer molding apparatus includes a vacuum degassing mechanism (not shown). By performing vacuum degassing, even if voids are entrapped, they can be compressed small, and the insulation can be improved.

[0030] Also, a release film (not shown) can be used. By using the release film, it is possible to protect the driving part of the spring 602 from intrusion of resin burrs. In this clamping process, the upper and lower molds 601 are clamped. At this time, the sheet-like member 440 and the conductor plate 420 are pressed and adhered by the spring 602. After that, a molding process of injecting the resin member 360 by transfer molding is performed. At this time, an inner peripheral step 432 and an outer peripheral step 433 are formed.

[0031] The inner peripheral step 432 varies according to the height of the circuit body 310. On the other hand, since the outer peripheral step 433 has a dimension engraved in the mold 601, it is not affected by the height of the circuit body 310. In other words, the inner peripheral step 432 is formed by a variable step realized by the spring 602, and the outer peripheral step 433 is formed by a fixed step engraved in the mold 601. The height of the outer peripheral step 433 is 50 μm or more, preferably 150 μm or more, and it is possible to prevent the resin transfer molding resin from flowing around the surface of the sheet-like member 440 according to the principle of Fig. 11 described later.

[0032] The fifth step shown in Fig. 8(b) is a releasing step of releasing the mold 601. During the curing process of the resin member 360 and when the mold 601 is released, the innermost peripheral step 431 is formed by cooling. Due to the presence of the innermost peripheral step 431, the heat dissipation surface, that is, the innermost peripheral surface 461, becomes convex, so that the heat dissipation surface can be effectively adhered to the cooling member 340, improving the heat dissipation performance. The sixth step shown in Fig. 8(c) is a post-curing step. The semiconductor module 300 encapsulated with resin is taken out from the mold 601, and post-curing is performed at 175°C for 2 hours or more.

[0033] The manufacturing process of the electric circuit body 400 will be described with reference to Fig. 9. The semiconductor module 300 shown in Fig. 9(a) is obtained after the completion of the sixth step shown in Fig. 8(c). First, as shown in Fig. 9(a), a heat conductive member 453 is applied to the cooling member 340 and the semiconductor module 300. Then, as shown in Fig. 9(b), the cooling member 340 and the semiconductor module 300 are brought into close contact, and the heat conductive member 453 is cured to fabricate the electric circuit body 400. By applying the heat conductive member 453 to the convex portions of the steps of the innermost peripheral step 431 and the inner peripheral step 432, that is, the innermost peripheral surface 461 and the inner peripheral surface 462, the excess heat conductive member 453 can be made to flow out to the outer peripheral step 433. Thereby, it is possible to prevent the heat conductive member 453 from flowing out near the terminals and prevent a decrease in the insulation between the terminals.

[0034] Also, the convex portion of the outer peripheral step 433, that is, the outer peripheral surface 463, is a region where the heat conductive member 453 is not completely applied. Further, since the outer peripheral surface 463 is separated from the conductor plate 420 and has no influence on the insulation, a thin plate can be inserted into this portion to peel off the semiconductor module and the water channel based on the lever principle for repair. During repair, even if the sheet-like member 440 on the outer peripheral surface 463 is damaged, it can be reused because there is no influence on the insulation. Also, when forming the circuit body 310 using a plurality of semiconductor modules 300, the height dimensions of the outer peripheral steps 433 are aligned, which has the effect of facilitating the insertion of the thin plate used for the above-mentioned repair and making it easy to remove a plurality of semiconductor elements 150 collectively.

[0035] FIG. 10 is a diagram showing the characteristics of materials. The horizontal axis of FIG. 10 is temperature, and the vertical axis is the volume per unit mass. T1 is the minimum value of the operating environment temperature of the semiconductor element 150, T2 is the maximum value of the operating environment temperature of the semiconductor element 150, and Tmold is the temperature during mold forming. T1 is, for example, -40 degrees, T2 is, for example, 125 degrees, and Tmold is, for example, 175 degrees. The vertical axis indicates that the volume is larger at the upper part and smaller at the lower part. The four straight lines shown in FIG. 10 are the characteristics of copper, resin A, resin B, and resin C. Resins A to C are provisional resins shown for the sake of convenience of explanation. In FIG. 10, the characteristics of copper are shown by a solid line with the symbol Cu. In FIG. 10, the characteristics of resin A are shown by a dashed line with the symbol Ra. In FIG. 10, the characteristics of resin B are shown by a one-dot chain line with the symbol Rb. In FIG. 10, the characteristics of resin C are shown by a two-dot chain line with the symbol Rc.

[0036] With reference to this FIG. 10, the principle of forming the outer peripheral step 433 will be described. For example, the resin member 360 is injected into the transfer mold at a temperature such as 175°C. Pay attention to the shrinkage in the Z-axis direction of the components of the power module based on the dimensions immediately after injection. When looking at the steel members from the source side towards the drain side, it becomes the sheet-like member 440, the conductor plate 420, the solder, the semiconductor element 150, the solder, the conductor plate 420, and the sheet-like member 440. The sheet-like member 440 is composed of a resin insulating layer with a thickness of 100 μm to 500 μm and a metal foil 444 with a thickness of 30 μm to 200 μm. The conductor plate 420 is composed of a copper-based material with a thickness of 1 mm to 5 mm. The solder is composed of a tin-based material with a thickness of 50 μm to 200 μm. The semiconductor element 150 is composed of a material with a thickness of 80 μm to 200 μm. Although the semiconductor element 150 is composed of various materials, here, since attention is paid to the shrinkage amount in the Z-axis direction, it is represented by the thickest constituent material, the copper-based material, and the thermal shrinkage amount of the semiconductor element 150 will be approximated by the thermal shrinkage amount of pure copper for explanation.

[0037] After the resin member 360 is injected into the mold 601 of the transfer molding apparatus, it cures and shrinks as the curing reaction progresses. The amount of curing shrinkage depends on the composition of the resin member 360 and the amount of temperature change. The greater the proportion of the epoxy resin component that undergoes the curing reaction in the resin member 360, the greater the amount of curing shrinkage. Also, even when the proportion of the epoxy resin component is the same, the greater the proportion of epoxy groups, which are reactive components in the epoxy resin component, the greater the amount of curing shrinkage.

[0038] The semiconductor element 150 taken out from the mold 601 of the transfer molding apparatus is cooled to room temperature. When the glass transition temperature is lower than Tmold, it shrinks at a large shrinkage rate until the glass transition temperature, and when it becomes lower than the glass transition temperature, it shrinks at a smaller shrinkage rate. When the glass transition temperature is higher than Tmold, it shrinks at a constant shrinkage rate. Pay attention to the temperature range of T1 to T2, which is the range of the operating environment temperature of the semiconductor element 150. In this temperature range, when the amount of shrinkage is greater than that of Cu, that is, when the amount of shrinkage of the resin member 360 falls within the hatched area in FIG. 10, the innermost peripheral step 431 is formed in the operating temperature range, and the innermost peripheral surface 461, which is the heat dissipation surface, becomes convex. In other words, by adopting resin B or resin C shown in FIG. 10 for the resin member 360, the innermost peripheral step 431 can be formed. If resin A is adopted for the resin member 360, the innermost peripheral step 431 is not formed.

[0039] Referring to FIG. 11, the principle of preventing the resin from flowing around the surface of the sheet-like member 440 at the outer peripheral step 433 will be described. The surface of the sheet-like member 440 means the side where the sheet-like member 440 and the mold 601 are in contact, that is, the surface on the plus side of the Z axis of the sheet-like member 440 in FIG. 11. Note that the surface of the sheet-like member 440 can also be called a heat dissipation surface for releasing the heat of the semiconductor element 150. By providing a step near the end of the sheet-like member 440, it is possible to prevent the resin burr from entering between the sheet-like member 440 and the mold 601. The resin burr is composed of the resin member 360 filled by transfer molding and the resin components of the resin member 360. The prevention of the intrusion of the resin burr will be described in detail.

[0040] In the process of the resin member 360 flowing into the mold 601, first, the molding pressure generated by the flowing resin member 360 presses the sheet-like member 440 against the mold 601. Next, after the cavity inside the mold 601 is almost filled with the resin member 360, a final molding pressure that is one level greater than before is applied to the resin member 360 as a hydrostatic pressure. At this time, the resin member 360 flows into even the minute gaps, and the resin member 360 and resin burrs flow into the narrow gap between the sheet-like member 440 and the mold 601. However, since the gap is narrow, a loss occurs in the pressure at which the resin member 360 flows in.

[0041] Pay attention to the location where there is a convex step, that is, the location surrounded by the dashed circle in Fig. 11, at the point where the resin member 360 has flowed into the gap between the sheet-like member 440 and the mold 601. Here, the pressure at which the resin member 360 attempts to flow into the narrow gap between the sheet-like member 440 and the mold 601 acts in a direction opposing the molding pressure that attempts to press the sheet-like member 440 against the mold 601. At this time, let the molding pressure that attempts to press the sheet-like member 440 against the mold 601 be Pa. Also, let the molding pressure of the resin member 360 that has flowed through the narrow gap and caused a pressure loss be Pb. In this case, since there is a relationship of Pa > Pb, the resin member 360 that flows between the sheet-like member 440 and the mold 601 stops at this step portion.

[0042] The outer peripheral step 433 is more effective in preventing the resin from overflowing onto the surface of the sheet-like member 440 as the angle approaches a right angle and the height increases. The angle of the outer peripheral step 433 needs to be, for example, 10 degrees or more with respect to the horizontal plane, and preferably 30 degrees or more. Also, the height of the step needs to be, for example, 50 μm or more, and preferably 150 μm or more. Configuration example 1 shown at the bottom of Fig. 11 shows the case where the angle of the outer peripheral step 433 is 10 degrees and the height is 50 μm. Similarly, configuration example 2 shows the case where the angle of the outer peripheral step 433 is 90 degrees and the height is 150 μm. As described above, since the molding pressure that presses the sheet-like member 440 against the mold 601 opposes the pressure at which the resin member 360 attempts to flow into the narrow gap between the sheet-like member 440 and the mold 601, it acts extremely effectively in stopping the overflow of the resin member 360 and resin burrs.

[0043] Refer to FIG. 12 to explain the effects of this embodiment. FIG. 12(a) shows the pressure distribution during molding in this embodiment, and FIG. 12(b) shows the pressure distribution during molding in the comparative example. The comparative example has only one step.

[0044] Let the area of the pressurizing mechanism in this embodiment be S1, and the area of the pressurizing mechanism in the comparative example be S2. Also, let the value obtained by subtracting S1 from S2 be S3, the area of the source-side active region of the semiconductor element 150 be S4, and the molding pressure during transfer molding be P. In this embodiment, the force for pushing up the spring 602 is the value obtained by subtracting S4 from S1 and multiplying by the molding pressure P. On the other hand, in the comparative example, the force for pushing up the spring 602 is the value obtained by subtracting S4 from S2 and multiplying by the molding pressure P. That is, in this embodiment, there is an effect that the molding pressure P can reduce the force for pushing up the spring mechanism by S3, which is the difference between S2 and S1.

[0045] When the force due to the molding pressure exceeds the force for pushing up the spring mechanism, a force in the peeling direction is generated on the semiconductor element 150. The semiconductor element 150 has a structure in which electrodes and elements are laminated, so it is weak against the force in the peeling direction and strong against the force in the compression direction. However, the bonding material for bonding the semiconductor element 150 may plastically deform due to strong compressive stress and peeling may occur.

[0046] That is, in the comparative example, when a force due to the spring mechanism that exceeds the force due to the molding pressure is applied, a strong compressive stress acts on the region of S4 due to the spring mechanism, and the bonding member may peel off. On the other hand, in the example, even when a force due to the spring mechanism that exceeds the force due to the molding pressure is applied, the pressing force due to the spring mechanism can be reduced by the area of S3, so the compressive stress acting on the region of S4 can be reduced and the reliability is improved.

[0047] In addition, in the embodiment, since the outer peripheral step 433 is formed with the dimensions of the mold 601, even if the height of the circuit body 310 changes, the height of the innermost peripheral step 431 does not change, and resin intrusion can be stably prevented. On the other hand, in the comparative example, when the height of the circuit body 310 changes, the height of the step inevitably changes, and there may be a case where the step becomes low and resin intrusion cannot be prevented.

[0048] FIG. 13 is a circuit diagram of the power conversion device 200 using the semiconductor module 300 described above. The power conversion device 200 includes a first inverter circuit section 140, a second inverter circuit 142, an inverter circuit section 43 for auxiliary equipment, and a capacitor module 500. The first inverter circuit section 140 and the second inverter circuit 142 include a plurality of semiconductor modules 300, and a three-phase bridge circuit is configured by connecting the plurality of semiconductor modules 300. When the current capacity is large, the semiconductor modules 300 are further connected in parallel, and these parallel connections are performed corresponding to each phase of the three-phase inverter circuit, so that an increase in the current capacity can be accommodated. Also, an increase in the current capacity can be accommodated by connecting the first power semiconductor element 155 and the second power semiconductor element 157, which are power semiconductor elements built in the semiconductor module 300, in parallel.

[0049] The first inverter circuit section 140 and the second inverter circuit 142 have the same basic circuit configuration, and the control method and operation are also basically the same. Since the outline of the circuit operation of the first inverter circuit section 140 and the like is well known, a detailed description is omitted here.

[0050] As described above, the upper arm circuit includes the upper arm 155 as a power semiconductor element for switching, and the lower arm circuit includes the lower arm 157 as a power semiconductor element for switching. The first power semiconductor element 155 and the second power semiconductor element 157 perform a switching operation in response to a drive signal output from one or the other of the two driver circuits constituting the driver circuit 174, and convert the DC power supplied from the battery 136 into three-phase AC power.

[0051] As described above, the first power semiconductor device 155 and the second power semiconductor device 157 include a drain electrode, a source electrode, and a gate electrode. The positive terminal 315B and the negative terminal 319B of each upper and lower arm series circuit are respectively connected to the DC terminals for capacitor connection of the capacitor module 500. AC power is generated at the connection part between the upper arm circuit and the lower arm circuit, and the connection parts between the upper arm circuit and the lower arm circuit of each upper and lower arm series circuit are connected to the AC side terminals 320B of each semiconductor module 300. The AC side terminals 320B of each semiconductor module 300 of each phase are respectively connected to the AC output terminals of the power conversion device 200, and the generated AC power is supplied to the stator windings of the motor generator 192 or 194.

[0052] The control circuit 172 generates a timing signal for controlling the switching timing of the first power semiconductor device 155 and the second power semiconductor device 157 based on input information from vehicle-side control devices and sensors, such as the current sensor 180. The driver circuit 174 generates a drive signal for causing the first power semiconductor device 155 and the second power semiconductor device 157 to perform a switching operation based on the timing signal output from the control circuit 172. Note that each of the reference numerals 181, 182, and 188 is a connector.

[0053] The upper and lower arm series circuit includes a temperature sensor (not shown), and the temperature information of the upper and lower arm series circuit is input to the microcomputer. Also, the voltage information on the DC positive side of the upper and lower arm series circuit is input to the microcomputer. The microcomputer performs over-temperature detection and over-voltage detection based on that information, and when over-temperature or over-voltage is detected, it stops the switching operations of all the first power semiconductor devices 155 and the second power semiconductor devices 157 to protect the upper and lower arm series circuit from over-temperature or over-voltage.

[0054] FIG. 14 is an external perspective view of the power conversion device 200. FIG. 15 is a cross-sectional view taken along line XV-XV of the power conversion device 200. The power conversion device 200 includes a lower case 11 and an upper case 10, and includes a housing 12 formed in a substantially rectangular parallelepiped shape. Inside the housing 12, an electric circuit body 400, a capacitor module 500, etc. are accommodated. The electric circuit body 400 has a cooling flow path, and from one side surface of the housing 12, a cooling water inflow pipe 13 and a cooling water outflow pipe 14 communicating with the cooling flow path protrude. The lower case 11 has an upper side (Z direction) opened in the cross-sectional view shown in FIG. 15. The upper case 10 is attached to the lower case 11 by closing the opening of the lower case 11. The upper case 10 and the lower case 11 are formed of an aluminum alloy or the like and are sealed and fixed to the outside. The upper case 10 and the lower case 11 may be integrally configured. Since the housing 12 has a simple rectangular parallelepiped shape, it is easy to attach to a vehicle or the like, and production is also easy.

[0055] As shown in FIG. 14, a connector 17 is attached to one side surface in the longitudinal direction of the housing 12. An AC terminal 18 is connected to the connector 17. Also, a connector 21 is provided on the surface of the housing 12 from which the cooling water inflow pipe 13 and the cooling water outflow pipe 14 are led out.

[0056] As shown in FIG. 15, an electric circuit body 400 is accommodated in the housing 12. Above the electric circuit body 400, a control circuit 172 and a driver circuit 174 are arranged, and on the DC terminal side of the electric circuit body 400, a capacitor module 500 is accommodated. By arranging the capacitor module 500 at the same height as the electric circuit body, the power conversion device 200 can be made thinner, and the degree of freedom in installation on a vehicle is improved. The AC side terminal 320B of the electric circuit body 400 passes through a current sensor 180 and is joined to a bus bar 361. Also, the positive electrode side terminal 315B and the negative electrode side terminal 319B, which are the DC terminals of the semiconductor module 300, are joined to the positive electrode terminal 362A and the negative electrode terminal 362B of the capacitor module 500, respectively.

[0057] According to the above-described embodiment, the following operational effects can be obtained. (1) The semiconductor module 300 includes a conductor plate 420 on which a semiconductor element 150 is mounted, a sheet-like member 440 covering the surface of the conductor plate 420, and a resin member 360 that integrally molds and seals the conductor plate 420 and the sheet-like member 440. A region of the sheet-like member 440 that overlaps with the surface of the conductor plate 420 is exposed. As shown in FIG. 11, the end portion of the sheet-like member 440 is covered by the resin member. As shown in FIG. 4, the sheet-like member 440 has an outer peripheral surface 463 formed on the outer periphery, an inner peripheral surface 462 formed on the inner periphery closer to the center than the outer peripheral surface 463, an outer peripheral step 433 connecting the outer edge of the sheet-like member 440 and the outer peripheral surface 463, and an inner peripheral step 432 connecting the outer peripheral surface 463 and the inner peripheral surface 462. The outer peripheral surface 463 is farther from the semiconductor element 150 than the outer edge. The inner peripheral surface 462 is farther from the semiconductor element than the outer peripheral surface 463. Therefore, it is possible to prevent the resin member 360 from overflowing onto the heat dissipation surface of the sheet-like member 440, and it is possible to avoid a decrease in heat dissipation performance due to the resin member 360.

[0058] (2) The sheet-like member 440 has an innermost peripheral surface 461 with an innermost peripheral step 431 formed further inside the inner peripheral surface 462. The innermost peripheral surface 461 is farther from the semiconductor element 150 than the inner peripheral surface 462. Therefore, heat can be dissipated from the conductor plate 420 to the cooling member 340 through the innermost peripheral surface 461 of the sheet-like member 440.

[0059] (3) The distance from the outer peripheral step 433 to the inner peripheral step 432 is farther than the distance from the inner peripheral step 432 to the innermost peripheral step 431. Therefore, the area of S1 shown in FIG. 12 becomes smaller, and the force applied to the semiconductor element 150 can be reduced.

[0060] (4) A heat conduction member 453 that is in close contact with the cooling member 340 is applied to the innermost peripheral surface 461 and the inner peripheral surface 462, and a part of the outer peripheral surface 463 is not coated with the heat conduction member 453. Therefore, this can prevent the heat conduction member 453 from flowing out near the terminals and prevent a decrease in insulation between the terminals.

[0061] (5) The plurality of semiconductor modules 300 included in the power conversion device 200 have the same outer peripheral step height 433H and different inner peripheral step heights 432H. The height variation of the circuit body 310 is absorbed by the inner peripheral step 432, and the outer peripheral step height 433H can be made constant, so that the working efficiency such as repair can be improved.

[0062] (6) The manufacturing method of the semiconductor module 300 includes a clamping step of arranging a sheet-like member 440, a conductor plate 420, and a semiconductor element 150 in a space formed by a mold 601 having a variable step at the center and a fixed step at the outer periphery, and a molding step of filling the space with a resin member 360 to form an outer peripheral step 433 and an inner peripheral step 432 while integrally molding and sealing the conductor plate 420 and the sheet-like member 440.

[0063] (Modification 1) FIG. 16 is a cross-sectional view of the semiconductor module 300 in Modification 1. In the above-described embodiment, two semiconductor elements 150 are stored in the semiconductor module 300. However, only one semiconductor element 150 may be stored in the semiconductor module 300.

[0064] Each of the above-described embodiments and modifications may be combined. Although various embodiments and modifications have been described above, the present invention is not limited to these contents. Other aspects conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention.

Explanation of Reference Numerals

[0065] 150: Semiconductor element 200: Power conversion device 300: Semiconductor module 310: Circuit body 340: Cooling member 360: Resin member 400: Electric circuit body 420: Conductor plate 431: Innermost peripheral step 432: Inner peripheral step 433: Outer peripheral step 440: Sheet-like member 453: Heat-conductive member 601: Mold 602: Spring

Claims

1. A conductor plate on which a semiconductor element is mounted, A sheet-like member covering the surface of the conductor plate, A resin member integrally molding and sealing the conductor plate and the sheet-like member, and comprising: In a state where a region overlapping the surface of the conductor plate of the sheet-like member is exposed, an end portion of the sheet-like member is covered by the resin member, The sheet-like member has an outer peripheral surface formed on the outer periphery, an inner peripheral surface formed on the inner periphery rather than the outer peripheral surface, an outer peripheral step connecting the outer edge of the sheet-like member and the outer peripheral surface, and an inner peripheral step connecting the outer peripheral surface and the inner peripheral surface, The outer peripheral surface is farther from the semiconductor element than the outer edge, The inner peripheral surface is farther from the semiconductor element than the outer peripheral surface, a semiconductor module.

2. The semiconductor module according to claim 1, The sheet-like member has an innermost peripheral surface sandwiching an innermost peripheral step further inside the inner peripheral surface, The innermost peripheral surface is farther from the semiconductor element than the inner peripheral surface, a semiconductor module.

3. The semiconductor module according to claim 2, The distance from the outer peripheral step to the inner peripheral step is farther than the distance from the inner peripheral step to the innermost peripheral step, a semiconductor module.

4. The semiconductor module according to claim 2, A heat conductive member that adheres to a cooling member is applied to the innermost peripheral surface and the inner peripheral surface, and a part of the outer peripheral surface is not coated with the heat conductive member, a semiconductor module.

5. A power conversion device including a plurality of the semiconductor modules according to claim 1, In the plurality of semiconductor modules, the heights of the outer peripheral steps are the same, and the heights of the inner peripheral steps are not the same, a power conversion device.

6. A semiconductor module manufacturing method includes a conductor plate on which a semiconductor element is mounted, a sheet-like member covering the surface of the conductor plate, and a resin member integrally molding and sealing the conductor plate and the sheet-like member. The sheet-like member has an end portion covered by the resin member in a state where a region overlapping the surface of the conductor plate is exposed. The sheet-like member has an outer peripheral surface formed on the outer periphery, an inner peripheral surface formed on the inner periphery closer to the center than the outer peripheral surface, an outer peripheral step connecting the outer edge of the sheet-like member and the outer peripheral surface, and an inner peripheral step connecting the outer peripheral surface and the inner peripheral surface. The outer peripheral surface is farther from the semiconductor element than the outer edge, and the inner peripheral surface is farther from the semiconductor element than the outer peripheral surface. A clamping step of arranging the sheet-like member, the conductor plate, and the semiconductor element in a space formed by a mold having a variable step due to elastic force in a central portion and a fixed step on the outer periphery. A molding step of filling the space with the resin member to integrally mold and seal the conductor plate and the sheet-like member while forming the outer peripheral step and the inner peripheral step. The semiconductor module manufacturing method includes the clamping step and the molding step.

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