WO2014045758A1 - Power semiconductor module - Google Patents

Power semiconductor module Download PDF

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Publication number
WO2014045758A1
WO2014045758A1 PCT/JP2013/071762 JP2013071762W WO2014045758A1 WO 2014045758 A1 WO2014045758 A1 WO 2014045758A1 JP 2013071762 W JP2013071762 W JP 2013071762W WO 2014045758 A1 WO2014045758 A1 WO 2014045758A1
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WO
WIPO (PCT)
Prior art keywords
substrate
heat dissipation
power semiconductor
semiconductor module
fin
Prior art date
Application number
PCT/JP2013/071762
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French (fr)
Japanese (ja)
Inventor
教文 山田
広道 郷原
Original Assignee
富士電機株式会社
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Publication of WO2014045758A1 publication Critical patent/WO2014045758A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/34—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements
    • H01L23/46—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids
    • H01L23/473—Arrangements for cooling, heating, ventilating or temperature compensation ; Temperature sensing arrangements involving the transfer of heat by flowing fluids by flowing liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/26—Layer connectors, e.g. plate connectors, solder or adhesive layers; Manufacturing methods related thereto
    • H01L2224/31—Structure, shape, material or disposition of the layer connectors after the connecting process
    • H01L2224/32—Structure, shape, material or disposition of the layer connectors after the connecting process of an individual layer connector
    • H01L2224/321—Disposition
    • H01L2224/32151—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive
    • H01L2224/32221—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked
    • H01L2224/32225—Disposition the layer connector connecting between a semiconductor or solid-state body and an item not being a semiconductor or solid-state body, e.g. chip-to-substrate, chip-to-passive the body and the item being stacked the item being non-metallic, e.g. insulating substrate with or without metallisation
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/01—Means for bonding being attached to, or being formed on, the surface to be connected, e.g. chip-to-package, die-attach, "first-level" interconnects; Manufacturing methods related thereto
    • H01L2224/42—Wire connectors; Manufacturing methods related thereto
    • H01L2224/47—Structure, shape, material or disposition of the wire connectors after the connecting process
    • H01L2224/48—Structure, shape, material or disposition of the wire connectors after the connecting process of an individual wire connector
    • H01L2224/4805—Shape
    • H01L2224/4809—Loop shape
    • H01L2224/48091—Arched
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2224/00—Indexing scheme for arrangements for connecting or disconnecting semiconductor or solid-state bodies and methods related thereto as covered by H01L24/00
    • H01L2224/73—Means for bonding being of different types provided for in two or more of groups H01L2224/10, H01L2224/18, H01L2224/26, H01L2224/34, H01L2224/42, H01L2224/50, H01L2224/63, H01L2224/71
    • H01L2224/732—Location after the connecting process
    • H01L2224/73251—Location after the connecting process on different surfaces
    • H01L2224/73265—Layer and wire connectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/11—Device type
    • H01L2924/13—Discrete devices, e.g. 3 terminal devices
    • H01L2924/1304—Transistor
    • H01L2924/1305—Bipolar Junction Transistor [BJT]
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2924/00—Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10—Details of semiconductor or other solid state devices to be connected
    • H01L2924/11—Device type
    • H01L2924/13—Discrete devices, e.g. 3 terminal devices
    • H01L2924/1304—Transistor
    • H01L2924/1305—Bipolar Junction Transistor [BJT]
    • H01L2924/13055—Insulated gate bipolar transistor [IGBT]

Definitions

  • the present invention relates to a power semiconductor module used in a semiconductor device that controls a large current and a high voltage.
  • Power conversion devices are used for energy saving in devices that use motors such as hybrid vehicles and electric vehicles.
  • a power semiconductor module including a power semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) is widely used in this power conversion device. Since a power semiconductor element generates heat when controlling a large current, a power semiconductor module including a plurality of fins for cooling the power semiconductor element is known.
  • IGBT Insulated Gate Bipolar Transistor
  • solder is applied to the surface of the circuit layer of the insulating substrate having an insulating layer made of a thin plate of ceramic material, a circuit layer formed on one surface of the insulating layer, and a metal layer formed on the other surface.
  • a power semiconductor module that includes a bonded semiconductor element, a heat dissipation substrate that contacts the metal layer of the insulating substrate, and fins integrated with the heat dissipation substrate (Patent Document 1).
  • the heat dissipation board is generally manufactured from a material mainly composed of aluminum or copper.
  • a power semiconductor module having such a configuration is configured so that a metal substrate for holding fins or heat radiation grease is not interposed between the heat radiation substrate and the fins, that is, an insulating substrate on which a semiconductor element is mounted is used as a cooling body.
  • a metal substrate for holding fins or heat radiation grease is not interposed between the heat radiation substrate and the fins, that is, an insulating substrate on which a semiconductor element is mounted is used as a cooling body.
  • the insulating layer of the insulating substrate is made of a ceramic material, and this ceramic material generally has a linear expansion coefficient of about 3 to 8 ( ⁇ 10 ⁇ 6 / ° C.).
  • the metal layer is copper, it is about 16.5 ( ⁇ 10 ⁇ 6 / ° C.)
  • the thermal expansion substrate (aluminum or aluminum alloy) has a linear expansion coefficient of 22 to 24 ( ⁇ 10 ⁇ 6 / ° C.). )
  • Due to these linear expansion coefficient differences there is a problem in that thermal stress is generated during the thermal cycle, and breakage occurs at the joint between the metal layer and the heat dissipation substrate.
  • the present invention has an object to provide a power semiconductor module that relieves stress concentration generated in the solder layer and hardly generates cracks.
  • the power semiconductor module includes an insulating substrate, a semiconductor element mounted on the insulating substrate, a heat dissipation substrate bonded to a surface of the insulating substrate opposite to the surface on which the semiconductor element is mounted, and the heat dissipation A plurality of fins provided on the substrate and extending, and a metal plate different from a case housing the fins is joined to a tip of the fin extending from the heat dissipation substrate.
  • the metal plate is bonded to the tip portion of the fin extending from the heat dissipation board, warpage of the heat dissipation board is suppressed, thereby causing a crack in the solder layer between the heat dissipation board and the insulating substrate. Can be prevented.
  • FIG. 1 is a schematic cross-sectional view of an embodiment of a power semiconductor module of the present invention.
  • FIG. 2 is a schematic top view of an embodiment of the power semiconductor module of the present invention.
  • FIG. 3 is a schematic cross-sectional view of a conventional fin base integrated power module.
  • FIG. 4 is a graph showing the results of thermal stress simulation in Example 1.
  • FIG. 5 is a graph showing the results of thermal stress simulation in Example 2.
  • a power semiconductor module 10 according to an embodiment of the present invention shown in a sectional view in FIG. 1 has a plurality of circuit element portions 11A and 11B in the illustrated embodiment.
  • the power semiconductor module 10 includes, for example, a three-phase inverter circuit by these circuit element units 11A and 11B and other circuit element units not shown in the drawing.
  • the circuit element portions 11A and 11B each have an insulating substrate 12.
  • the insulating substrate 12 includes an insulating layer 12a made of a thin plate of an electrically insulating material, a circuit layer 12b formed on one surface of the insulating layer 12a, and a metal formed on the other surface of the insulating layer 12a.
  • Layer 12c for the insulating layer 12a of the insulating substrate 12, for example, a ceramic substrate such as aluminum nitride, aluminum oxide, or silicon nitride can be used. More preferably, silicon nitride can be used.
  • the circuit layer 12b and the metal layer 12c of the insulating substrate 12 can be formed using a conductive metal foil (eg, copper foil, aluminum foil) such as copper or aluminum.
  • a circuit pattern is formed on the circuit layer 12b of the insulating substrate 12, and the semiconductor elements 13 and 14 are bonded to the circuit layer 12b via a bonding layer 15 such as solder.
  • the semiconductor elements 13 and 14 are electrically connected directly by the circuit pattern of the circuit layer 12 b or via the wire 16.
  • the exposed surface of the circuit layer 12b and the metal layer 12c of the insulating substrate 12 and the surface of the wire 16 that electrically connects the semiconductor elements 13 and 14 and the circuit layer 12b are stained by nickel plating or the like.
  • a protective layer may be formed for protection from corrosion, external force, and the like.
  • the semiconductor elements 13 and 14 mounted on such an insulating substrate 12 power semiconductor elements are used in the illustrated embodiment.
  • the semiconductor element 13 can be a free wheeling diode (FWD)
  • the other semiconductor element 14 can be an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor: IGBT). 1 shows the semiconductor elements 13 and 14, the power semiconductor module of the present invention is not limited to the case where there are two semiconductor elements, and may be one or three or more.
  • the power semiconductor module of the present invention is not limited to the case where there are two circuit element units.
  • the number of circuit element units can be appropriately changed according to the circuit, application, or function in which the power semiconductor module 10 is used.
  • the power semiconductor module 10 is provided with a resin case 17 so as to surround the circuit element portions 11A and 11B.
  • the insulating substrate 12 on which the semiconductor elements 13 and 14 are mounted is bonded to the heat dissipation substrate 19 via the bonding layer 18 on the metal layer 12c side. In this way, the insulating substrate 12 and the semiconductor elements 13 and 14 are connected to the heat dissipation substrate 19 so as to be able to conduct heat.
  • the heat dissipation substrate 19 is provided with a plurality of fins 20 extending from the heat dissipation substrate 19 on the side opposite to the side bonded to the insulating substrate 12.
  • the fin 20 is used as a heat radiating plate for heat generated from the semiconductor elements 13, 14, in other words, as a heat sink.
  • the fin 20 is, for example, a blade fin in which a plurality of blade-shaped fins are provided in parallel to each other, a corrugated fin formed by folding a single plate at a certain distance, or a plurality of cylindrical or prismatic pins. Pin fins arranged at intervals can also be used.
  • the fin shape of the fin 20 is not limited to a blade fin, a corrugated fin, or a pin fin, and various shapes can be used. However, since the fin 20 has resistance when a coolant as a cooling medium flows through the gaps between the fins 20, it is desirable that the fin 20 has a shape with a small pressure loss with respect to the coolant.
  • the shape and dimensions of the fins 20 are preferably set as appropriate in consideration of the flow conditions of the coolant, the type and nature of the coolant (particularly viscosity), the intended heat removal amount, and the like.
  • the illustrated plurality of fins 20 are integrated with the heat dissipation substrate 19.
  • the means for integrating can be formed, for example, by casting the fin 20 integrally with the heat dissipation substrate 19 by die casting.
  • the fin 20 can also be integrally formed with the heat radiating substrate 19 by brazing the fin 20 or directly joining the heat radiating substrate 19 by various welding methods.
  • the fin base may be bonded to the heat radiating board 19 so that the heat radiating board 19 and the fin 20 are integrated.
  • the convex portion which is a rough outer shape of the fin by die casting or press forging, at the same time as the heat dissipation substrate 19, the convex portion is processed into a desired fin shape by cutting or wire cutting method. It can also be formed. Further, it is possible to integrally form the heat dissipation substrate 19 and the fins 20 only by the press forging method.
  • the outer shape of the heat sink composed of the fins 20 is a substantially rectangular parallelepiped, preferably a rectangular parallelepiped, and may be chamfered or deformed as long as the effects of the present invention are not impaired.
  • the metal plate 21 is bonded to the tip of the fin 20 extending from the heat dissipation board 19.
  • the plane size of the metal plate 21 is approximately the same as the size of the heat sink composed of the fins 20 and is joined to the tips of the fins. But it does not exclude that the fin 20 which is not joined to the metal plate 21 exists partially.
  • the heat dissipation substrate 19 can be deformed relatively freely while the deformation amount is suppressed, and the deformation state becomes gradual. It is possible to prevent cracks from occurring in the bonding layer 18 that bonds the two. If the metal plate 21 is bonded to the tip of the fin 20, the deformation of the heat radiating substrate 19 can be controlled regardless of the thickness of the metal plate 21. In particular, since the thickness of the metal plate 21 is 1.2 mm or more, heat dissipation The deformation of the substrate 19 can be effectively controlled.
  • the heat dissipation substrate 19, the fins 20, and the metal plate 21 are preferably made of a material having high thermal conductivity, and a metal material is particularly preferable. For example, it can be formed using a metal material such as aluminum, aluminum alloy, copper, or copper alloy. More preferably, aluminum or an aluminum alloy can be used.
  • the heat dissipation substrate 19, the fins 20, and the metal plate 21 may be the same type of metal material or different types of metal materials. The same kind of metal material is easy to manufacture.
  • FIG. 2 is a schematic top view of the heat dissipation board 19.
  • the wire 16 and the resin case 17 are not shown for easy understanding of the present invention.
  • the same members as those in FIG. 1 are denoted by the same reference numerals, and description of the members already described is omitted in the following description.
  • a plurality of circuit element portions 11A to 11F are formed on the upper surface of the heat dissipation substrate 19. Further, as indicated by a broken line in FIG. 2, fins 20 are provided on the lower surface of the heat dissipation substrate 19.
  • the region where the fins 20 are provided on the heat dissipation substrate 19 is preferably a planar region of the insulating substrate 12 parallel to the thickness direction of the heat dissipation substrate 19.
  • the projected area is the same as or wider than this projected area.
  • the region where the fins 20 are provided on the heat dissipation substrate 19 includes the region where the insulating substrate 12 is provided on the heat dissipation substrate 19 and this region. It is an area wider than or equal to.
  • the distance L between the contour line of the projected area of the insulating substrate 12 and the contour line of the area where the fins 20 are provided on the heat dissipation substrate 19 is preferably 2 mm or more. The greater the distance between the two contour lines, the wider the fin region than the projection region, so that the stress strain concentration can be effectively alleviated.
  • the fin 20 is accommodated in the case 22.
  • the case 22 has a bottom wall 22a and a side wall 22b provided on the periphery of the bottom wall 22a, and has an opening at the top.
  • the case 22 has a substantially rectangular parallelepiped shape, but is not limited to a substantially rectangular parallelepiped shape.
  • the upper end of the side wall 22b of the case 22 is joined to the heat dissipation board 19 so that the coolant does not leak.
  • the case 22 is provided with an inlet and an outlet for the coolant not shown in the figure.
  • the coolant is introduced from the inlet, and the coolant passes through the gap between the fins 20 accommodated in the case 22. And discharged from the outlet.
  • the fins 20 are cooled by the coolant by the flow of the coolant in the case 22.
  • the discharged cooling liquid is collected, led to the introduction port by a pump, and circulated.
  • the case 22 is preferably made of a material having a high thermal conductivity, like the fins 20 and the heat radiating substrate 19, and a metal material is particularly preferable.
  • a metal material such as aluminum, aluminum alloy, copper, or copper alloy.
  • the case 22 can also use a material containing a carbon filler as a metal material.
  • a ceramic material, a resin material, or the like can be used depending on the type of the coolant, the temperature of the coolant flowing in the case 22, and the like. It is.
  • the coolant water, long life coolant (LLC), or the like can be used.
  • the tips of the fins 20 are joined to the metal plate 21 as described above.
  • the metal plate 21 is a member different from the bottom wall 22 a of the case 22. That is, the fin 20 is not joined to the bottom wall 22 a of the case 22. As shown in FIG. 1, the metal plate 21 is provided at a position in the case 22 that is separated from the bottom wall 22 a by a predetermined distance.
  • the heat dissipation substrate 19 and the fin 20 can be deformed relatively freely while the deformation amount is suppressed by the metal plate 21 in the environment of the thermal cycle. The deformation state is gradual. Since the heat dissipation substrate 19 hardly bends suddenly, the stress on the bonding layer 18 is also small.
  • the heat dissipation board 19 is strongly restrained by the case 22 as compared to the case where the fins 20 are joined to the metal plate 21. If the fin 20 is joined to the bottom wall 22a, the heat dissipation substrate 19 is integrated with the case 22 including the side wall 22b via the fin 20, and cannot be freely deformed. Under a thermal cycle environment, a sharp bent portion is generated in the heat dissipation substrate 19 due to the stress concentrated in the vicinity of the region where the bonding layer 18 is formed, and the stress on the bonding layer 18 increases. Further, as shown in FIG.
  • the tip of the fin 20 is joined to the metal plate 21, so that the surface area of the heat sink is increased by the surface area of the metal plate 21 compared to the case where the fins 20 are joined to the bottom wall 22 a of the case 22. Therefore, the cooling efficiency is high.
  • FIG. 3 shows a schematic cross-sectional view of a conventional power semiconductor module.
  • the power semiconductor module 110 shown in FIG. 3 is different from the power semiconductor module 10 shown in FIG.
  • Such a conventional power semiconductor module 110 may cause deformation of the heat dissipation substrate 19, specifically, warpage, which may cause cracks in the bonding layer 18 that joins the heat dissipation substrate 19 and the insulating substrate 12. there were. Since the deformation of the heat dissipation substrate 19 can be suppressed and cracking of the bonding layer 18 can be prevented, the effect of the power semiconductor module 10 of the present embodiment shown in FIG. 1 is great.
  • the insulating layer 12a of the insulating substrate 12 was made of silicon nitride having a thickness of 0.32 mm.
  • the circuit layer 12b and the metal layer 12c were made of 0.4 mm thick copper.
  • the heat dissipation substrate 19 was made of an aluminum alloy having a thickness of 5 mm.
  • the inside of the resin case 17 was sealed with a sealing resin such as silicone gel or epoxy resin.
  • the clearance between the metal plate 21 and the bottom wall 22a of the case 22 was 1 mm.
  • the relationship between the plastic strain amplitude generated in the bonding layer 18 (Sn—Sb solder) under the insulating substrate 12 and the thickness of the metal plate 21 was analyzed by thermal stress simulation. .
  • FIG. 4 shows the analysis results when the thickness of the metal plate 21 at the tip of the fin was changed to 0 mm (comparative example), 1.2 mm (example), and 1.8 mm (example).
  • the metal plate 21 By installing the metal plate 21, the plastic strain amplitude can be reduced.
  • the metal plate 21 it is considered that the deformation of the heat dissipation substrate 19 is suppressed.
  • the thickness of the metal plate 21 is almost saturated when the thickness is 1.2 mm or more.
  • the plastic strain amplitude can be reduced by about 30%.
  • FIG. 5 shows the thermal stress simulation results.
  • the plastic strain amplitude decreases. It is expected that stress due to warping of the heat dissipation substrate 19 is concentrated at the boundary of the fin region (broken line in FIG. 2), and the plastic strain amplitude can be reduced by separating such a stress concentration location from the bonding layer 18. Conceivable. In particular, when the fin region is expanded to 2 mm or more, it is saturated, and it can be said that the effect of reducing the plastic strain amplitude can be enjoyed more remarkably at 2 mm or more.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)

Abstract

The present invention provides a power semiconductor module in which deformation of a heat dissipating substrate under thermal stress is suppressed and cracking in a joining layer between the heat dissipating substrate and an insulating substrate is prevented. A power semiconductor module (10) is provided with an insulating substrate (12), a semiconductor element (13, 14) mounted on the insulating substrate (12), a heat dissipating substrate (19) joined to the insulating substrate (12), and a plurality of fins (20) that are provided extending from the heat dissipating substrate (19). In the power semiconductor module (10), a metal plate (21) that is separate from a case (22) that accommodates the fins (20) is joined to the distal ends of the fins (20) that extend from the heat dissipating substrate (19).

Description

パワー半導体モジュールPower semiconductor module
　本発明は、大電流、高電圧を制御する半導体装置に用いられるパワー半導体モジュールに関するものである。 The present invention relates to a power semiconductor module used in a semiconductor device that controls a large current and a high voltage.
　ハイブリッド自動車や電気自動車等に代表される、モータを使用する機器には、省エネルギーのために電力変換装置が利用されている。この電力変換装置には、ＩＧＢＴ（Ｉｎｓｕｌａｔｅｄ　Ｇａｔｅ　Ｂｉｐｏｌａｒ　Ｔｒａｎｓｉｓｔｏｒ）等のパワー半導体素子を含むパワー半導体モジュールが広く用いられている。パワー半導体素子は、大電流を制御する際に発熱するため、このパワー半導体素子を冷却するための複数のフィンを備えるパワー半導体モジュールが知られている。 Power conversion devices are used for energy saving in devices that use motors such as hybrid vehicles and electric vehicles. A power semiconductor module including a power semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) is widely used in this power conversion device. Since a power semiconductor element generates heat when controlling a large current, a power semiconductor module including a plurality of fins for cooling the power semiconductor element is known.
　例えば、セラミックス材の薄板よりなる絶縁層と、この絶縁層の一方の面に形成された回路層と、他方の面に形成された金属層とを有する絶縁基板の上記回路層の表面に、はんだ接合された半導体素子を備えるとともに、絶縁基板の上記金属層に接触する放熱基板を備え、この放熱基板にフィンが一体化されているパワー半導体モジュールがある（特許文献１）。放熱基板は一般的にアルミニウム又は銅を主成分とした材料で製造される。 For example, solder is applied to the surface of the circuit layer of the insulating substrate having an insulating layer made of a thin plate of ceramic material, a circuit layer formed on one surface of the insulating layer, and a metal layer formed on the other surface. There is a power semiconductor module that includes a bonded semiconductor element, a heat dissipation substrate that contacts the metal layer of the insulating substrate, and fins integrated with the heat dissipation substrate (Patent Document 1). The heat dissipation board is generally manufactured from a material mainly composed of aluminum or copper.
　このような構成を備えるパワー半導体モジュールは、フィン保持用の金属基板や放熱グリースを、放熱基板とフィンとの間に介在させないようにして、つまり、半導体素子を搭載した絶縁基板を、冷却体としてのフィンを備える放熱基板に直接に接合することにより、半導体素子と冷却体との間の熱抵抗を大幅に低減して、放熱性の改善、製品の信頼性向上が図られる。 A power semiconductor module having such a configuration is configured so that a metal substrate for holding fins or heat radiation grease is not interposed between the heat radiation substrate and the fins, that is, an insulating substrate on which a semiconductor element is mounted is used as a cooling body. By directly joining to the heat dissipation substrate having the fins, the thermal resistance between the semiconductor element and the cooling body can be greatly reduced, improving the heat dissipation and improving the reliability of the product.
特開２０１０－１０５０５号公報JP 2010-10505 A
　上述したフィンを備えるパワー半導体モジュールにおいては、絶縁基板の絶縁層が、セラミックス材料よりなり、このセラミックス材料は絶縁基板の線膨張係数が一般的に３～８（×１０－６／℃）程度であり、金属層が銅の場合は１６．５（×１０－６／℃）程度であるのに対し、放熱基板（アルミニウム又はアルミニウム合金）の線膨張係数が２２～２４（×１０－６／℃）程度と大きい。これらの線膨張係数差によって、熱サイクル時の熱応力が発生し、金属層と放熱基板との接合部で破断が生じてしまう問題があった。 In the power semiconductor module including the fins described above, the insulating layer of the insulating substrate is made of a ceramic material, and this ceramic material generally has a linear expansion coefficient of about 3 to 8 (× 10 −6 / ° C.). Yes, when the metal layer is copper, it is about 16.5 (× 10 −6 / ° C.), whereas the thermal expansion substrate (aluminum or aluminum alloy) has a linear expansion coefficient of 22 to 24 (× 10 −6 / ° C.). ) About big. Due to these linear expansion coefficient differences, there is a problem in that thermal stress is generated during the thermal cycle, and breakage occurs at the joint between the metal layer and the heat dissipation substrate.
　さらに近年、パワー半導体モジュールは、小型化や高耐熱化の要求が厳しいものがある。これらの要求に対応する一つの方策として、フィンが設けられた放熱基板の薄型化がある。放熱基板を薄くすると、熱抵抗を低下することができ、パワー半導体モジュールの半導体素子の温度Ｔｊを下げることが可能となる。しかし一方で、放熱基板を薄くすると放熱基板が容易に変形するようになり、絶縁基板と放熱基板とを接合しているはんだ層にクラックが発生する問題があった。 In recent years, power semiconductor modules have strict requirements for miniaturization and high heat resistance. One way to meet these requirements is to reduce the thickness of the heat dissipation substrate provided with fins. If the heat dissipation substrate is made thin, the thermal resistance can be lowered, and the temperature Tj of the semiconductor element of the power semiconductor module can be lowered. On the other hand, however, if the heat dissipation board is made thin, the heat dissipation board is easily deformed, and there is a problem that a crack is generated in the solder layer joining the insulating substrate and the heat dissipation board.
　そこで、本発明は上述の問題点を鑑み、前記はんだ層に生じる応力集中を緩和しクラックが発生し難いパワー半導体モジュールの提供を目的とする。 Therefore, in view of the above-described problems, the present invention has an object to provide a power semiconductor module that relieves stress concentration generated in the solder layer and hardly generates cracks.
　上記目的を達成するために以下のようなパワー半導体モジュールが提供される。
　このパワー半導体モジュールは、絶縁基板と、該絶縁基板上に搭載された半導体素子と、該絶縁基板における該半導体素子が搭載された面とは反対側の面に接合された放熱基板と、該放熱基板に設けられて延在する複数のフィンと、を備え、前記フィンにおける前記放熱基板から延びた先端に、前記フィンを収容するケースとは別の金属板が接合されていることを特徴とする。 In order to achieve the above object, the following power semiconductor module is provided.
The power semiconductor module includes an insulating substrate, a semiconductor element mounted on the insulating substrate, a heat dissipation substrate bonded to a surface of the insulating substrate opposite to the surface on which the semiconductor element is mounted, and the heat dissipation A plurality of fins provided on the substrate and extending, and a metal plate different from a case housing the fins is joined to a tip of the fin extending from the heat dissipation substrate. .
　本発明によれば、放熱基板から延びるフィンの先端部に金属板が接合されていることから、放熱基板の反りを抑制し、これにより放熱基板と絶縁基板との間のはんだ層にクラックが生じることを防ぐことができる。 According to the present invention, since the metal plate is bonded to the tip portion of the fin extending from the heat dissipation board, warpage of the heat dissipation board is suppressed, thereby causing a crack in the solder layer between the heat dissipation board and the insulating substrate. Can be prevented.
図１は、本発明のパワー半導体モジュールの一実施形態の断面模式図である。FIG. 1 is a schematic cross-sectional view of an embodiment of a power semiconductor module of the present invention. 図２は、本発明のパワー半導体モジュールの一実施形態の上面模式図である。FIG. 2 is a schematic top view of an embodiment of the power semiconductor module of the present invention. 図３は、従来のフィンベース一体型パワーモジュールの断面模式図である。FIG. 3 is a schematic cross-sectional view of a conventional fin base integrated power module. 図４は、実施例１における熱応力シミュレーションの結果を示すグラフである。FIG. 4 is a graph showing the results of thermal stress simulation in Example 1. 図５は、実施例２における熱応力シミュレーションの結果を示すグラフである。FIG. 5 is a graph showing the results of thermal stress simulation in Example 2.
　本発明のパワー半導体モジュールの実施形態を、図面を用いて具体的に説明する。
　図１に断面図で示す本発明の一実施形態のパワー半導体モジュール１０は、図示した本実施形態では、複数の回路素子部１１Ａおよび１１Ｂを有している。これらの回路素子部１１Ａ、１１Ｂ及び図に表れない他の回路素子部により、パワー半導体モジュール１０は、例えば三相インバータ回路が構成されている。 An embodiment of a power semiconductor module of the present invention will be specifically described with reference to the drawings.
A power semiconductor module 10 according to an embodiment of the present invention shown in a sectional view in FIG. 1 has a plurality of circuit element portions 11A and 11B in the illustrated embodiment. The power semiconductor module 10 includes, for example, a three-phase inverter circuit by these circuit element units 11A and 11B and other circuit element units not shown in the drawing.
　回路素子部１１Ａ、１１Ｂは、それぞれ絶縁基板１２を有している。この絶縁基板１２は、電気絶縁性の材料の薄板よりなる絶縁層１２ａと、この絶縁層１２ａの一方の面に形成された回路層１２ｂと、この絶縁層１２ａの他方の面に形成された金属層１２ｃとを有する。絶縁基板１２の絶縁層１２ａには、例えば窒化アルミニウム、酸化アルミニウム、窒化ケイ素等のセラミック基板を用いることができる。より好ましくは、窒化ケイ素を用いることができる。絶縁基板１２の回路層１２ｂ、金属層１２ｃは、銅やアルミニウム等の導電性の金属箔（例えば、銅箔、アルミニウム箔）を用いて形成することができる。 The circuit element portions 11A and 11B each have an insulating substrate 12. The insulating substrate 12 includes an insulating layer 12a made of a thin plate of an electrically insulating material, a circuit layer 12b formed on one surface of the insulating layer 12a, and a metal formed on the other surface of the insulating layer 12a. Layer 12c. For the insulating layer 12a of the insulating substrate 12, for example, a ceramic substrate such as aluminum nitride, aluminum oxide, or silicon nitride can be used. More preferably, silicon nitride can be used. The circuit layer 12b and the metal layer 12c of the insulating substrate 12 can be formed using a conductive metal foil (eg, copper foil, aluminum foil) such as copper or aluminum.
　絶縁基板１２の回路層１２ｂは、回路パターンが形成されていて、この回路層１２ｂ上に、半導体素子１３、１４が、はんだ等の接合層１５を介して接合されている。半導体素子１３、１４は、回路層１２ｂの回路パターンにより直接に、又はワイヤ１６を介して、電気的に接続される。なお、絶縁基板１２の回路層１２ｂ、金属層１２ｃの露出表面や、半導体素子１３、１４と回路層１２ｂとを電気的に接続するワイヤ１６表面には、ニッケルめっき等により、それらの表面を汚れ、腐食、外力等から保護するための保護層を形成するようにしてもよい。 A circuit pattern is formed on the circuit layer 12b of the insulating substrate 12, and the semiconductor elements 13 and 14 are bonded to the circuit layer 12b via a bonding layer 15 such as solder. The semiconductor elements 13 and 14 are electrically connected directly by the circuit pattern of the circuit layer 12 b or via the wire 16. The exposed surface of the circuit layer 12b and the metal layer 12c of the insulating substrate 12 and the surface of the wire 16 that electrically connects the semiconductor elements 13 and 14 and the circuit layer 12b are stained by nickel plating or the like. Further, a protective layer may be formed for protection from corrosion, external force, and the like.
　このような絶縁基板１２上に搭載される半導体素子１３、１４として、図示した本実施形態ではパワー半導体素子を用いている。例えば半導体素子１３をフリーホイールダイオード（Ｆｒｅｅ　Ｗｈｅｅｌｉｎｇ　Ｄｉｏｄｅ：ＦＷＤ）とし、他方の半導体素子１４を絶縁ゲートバイポーラトランジスタ（Ｉｎｓｕｌａｔｅｄ　Ｇａｔｅ　Ｂｉｐｏｌａｒ　Ｔｒａｎｓｉｓｔｏｒ：ＩＧＢＴ）とすることができる。なお、図１では半導体素子１３、１４を図示しているが、本発明のパワー半導体モジュールは、半導体素子が２個である場合に限られず、１個でもよいし、３個以上でもよい。 As the semiconductor elements 13 and 14 mounted on such an insulating substrate 12, power semiconductor elements are used in the illustrated embodiment. For example, the semiconductor element 13 can be a free wheeling diode (FWD), and the other semiconductor element 14 can be an insulated gate bipolar transistor (Insulated Gate Bipolar Transistor: IGBT). 1 shows the semiconductor elements 13 and 14, the power semiconductor module of the present invention is not limited to the case where there are two semiconductor elements, and may be one or three or more.
　図１のパワー半導体モジュール１０は、回路素子部１１Ａ及び回路素子部１１Ｂが示されているが、本発明のパワー半導体モジュールは、回路素子部が２個である場合に限られない。回路素子部の個数は、パワー半導体モジュール１０が用いられる回路、用途、又は機能に応じて、適宜に変更可能である。パワー半導体モジュール１０は、回路素子部１１Ａ、１１Ｂを囲うように樹脂ケース１７が設けられている。 1 shows the circuit element unit 11A and the circuit element unit 11B, the power semiconductor module of the present invention is not limited to the case where there are two circuit element units. The number of circuit element units can be appropriately changed according to the circuit, application, or function in which the power semiconductor module 10 is used. The power semiconductor module 10 is provided with a resin case 17 so as to surround the circuit element portions 11A and 11B.
　半導体素子１３、１４が搭載された絶縁基板１２は、金属層１２ｃ側で、接合層１８を介して放熱基板１９が接合される。こうして、絶縁基板１２及び半導体素子１３、１４は、放熱基板１９と熱伝導可能に接続された状態になる。 The insulating substrate 12 on which the semiconductor elements 13 and 14 are mounted is bonded to the heat dissipation substrate 19 via the bonding layer 18 on the metal layer 12c side. In this way, the insulating substrate 12 and the semiconductor elements 13 and 14 are connected to the heat dissipation substrate 19 so as to be able to conduct heat.
　放熱基板１９は、絶縁基板１２と接合された側と反対側に、この放熱基板１９から延びる複数のフィン２０が設けられている。フィン２０は、半導体素子１３、１４から発生した熱の放熱板、換言すればヒートシンク（ｈｅａｔ　ｓｉｎｋ）として用いられる。 The heat dissipation substrate 19 is provided with a plurality of fins 20 extending from the heat dissipation substrate 19 on the side opposite to the side bonded to the insulating substrate 12. The fin 20 is used as a heat radiating plate for heat generated from the semiconductor elements 13, 14, in other words, as a heat sink.
　フィン２０は、例えばブレード（ｂｌａｄｅ）形状の複数のフィンが互いに平行に設けられたブレードフィン、一枚の板を一定の距離で折り畳んで形成されたコルゲートフィン又は円柱又は角柱形状のピンを複数個、間隔を空けて配列させたピンフィンを用いることもできる。フィン２０のフィン形状については、ブレードフィン、コルゲートフィン又はピンフィンに限られず、様々な形状のものを用いることが可能である。もっとも、フィン２０は、冷却媒体としての冷却液をフィン２０の間隙に流したときの抵抗になるので、冷却液に対する圧力損失が小さい形状を有するものが望ましい。 The fin 20 is, for example, a blade fin in which a plurality of blade-shaped fins are provided in parallel to each other, a corrugated fin formed by folding a single plate at a certain distance, or a plurality of cylindrical or prismatic pins. Pin fins arranged at intervals can also be used. The fin shape of the fin 20 is not limited to a blade fin, a corrugated fin, or a pin fin, and various shapes can be used. However, since the fin 20 has resistance when a coolant as a cooling medium flows through the gaps between the fins 20, it is desirable that the fin 20 has a shape with a small pressure loss with respect to the coolant.
　フィン２０の形状及び寸法は、冷却液の流動条件、冷却液の種類と性質（特に粘性等）、目的とする除熱量等を考慮して、適宜設定することが好ましい。 The shape and dimensions of the fins 20 are preferably set as appropriate in consideration of the flow conditions of the coolant, the type and nature of the coolant (particularly viscosity), the intended heat removal amount, and the like.
　図示した複数のフィン２０は、放熱基板１９と一体化されている。一体化する手段は、例えばフィン２０をダイキャストにより放熱基板１９と一体的に鋳造することにより形成することができる。また、フィン２０をロウ付け、又は各種の溶接法により、放熱基板１９に直接的に接合することにより、フィン２０を放熱基板１９と一体的に形成することもできる。更に、フィンをあらかじめ板状のフィン基材に接合した後、そのフィン基材を放熱基板１９に接合することにより、放熱基板１９とフィン２０とを一体化してしてもよい。また更に、ダイキャストやプレス鍛造によって、フィンの概略的な外形となる凸部を、放熱基板１９と同時に形成した後、この凸部を切削やワイヤーカット法によって所望するフィン形状に加工することによって形成することもできる。また、プレス鍛造法のみで放熱基板１９とフィン２０とを一体的に形成することも可能である。 The illustrated plurality of fins 20 are integrated with the heat dissipation substrate 19. The means for integrating can be formed, for example, by casting the fin 20 integrally with the heat dissipation substrate 19 by die casting. Moreover, the fin 20 can also be integrally formed with the heat radiating substrate 19 by brazing the fin 20 or directly joining the heat radiating substrate 19 by various welding methods. Further, after the fin is bonded to the plate-shaped fin base in advance, the fin base may be bonded to the heat radiating board 19 so that the heat radiating board 19 and the fin 20 are integrated. Furthermore, by forming a convex portion, which is a rough outer shape of the fin by die casting or press forging, at the same time as the heat dissipation substrate 19, the convex portion is processed into a desired fin shape by cutting or wire cutting method. It can also be formed. Further, it is possible to integrally form the heat dissipation substrate 19 and the fins 20 only by the press forging method.
　フィン２０からなるヒートシンクの外形は略直方体であり、好ましくは直方体であり、本発明の効果を損ねない範囲で面取りや変形された形状であってもよい。 The outer shape of the heat sink composed of the fins 20 is a substantially rectangular parallelepiped, preferably a rectangular parallelepiped, and may be chamfered or deformed as long as the effects of the present invention are not impaired.
　そして、放熱基板１９から延びたフィン２０の先端に、金属板２１が接合されている。金属板２１の平面の寸法は、フィン２０からなるヒートシンクの大きさとほぼ同じ大きさとし、各々のフィンの先端に接合されるものとする。もっとも、金属板２１に接合されていないフィン２０が部分的に存在することを排除するものではない。 The metal plate 21 is bonded to the tip of the fin 20 extending from the heat dissipation board 19. The plane size of the metal plate 21 is approximately the same as the size of the heat sink composed of the fins 20 and is joined to the tips of the fins. But it does not exclude that the fin 20 which is not joined to the metal plate 21 exists partially.
　フィン２０の先端に金属板２１が接合されていることにより、放熱基板１９は変形量を抑制されつつも比較的自由に変形でき、その変形状態は緩やかとなるため、放熱基板１９と絶縁基板１２とを接合する接合層１８にクラックが生じるのを防ぐことができる。フィン２０の先端に金属板２１が接合されていれば金属板２１の厚みにかかわらず放熱基板１９の変形を制御できるが、特に、金属板２１の厚みが１．２ｍｍ以上であることにより、放熱基板１９の変形を効果的に制御することができる。 Since the metal plate 21 is bonded to the tip of the fin 20, the heat dissipation substrate 19 can be deformed relatively freely while the deformation amount is suppressed, and the deformation state becomes gradual. It is possible to prevent cracks from occurring in the bonding layer 18 that bonds the two. If the metal plate 21 is bonded to the tip of the fin 20, the deformation of the heat radiating substrate 19 can be controlled regardless of the thickness of the metal plate 21. In particular, since the thickness of the metal plate 21 is 1.2 mm or more, heat dissipation The deformation of the substrate 19 can be effectively controlled.
　放熱基板１９、フィン２０及び金属板２１は、熱伝導率の高い材料よりなることが好ましく、特に金属材料が好ましい。例えばアルミニウム、アルミニウム合金、銅、銅合金等の金属材料を用いて形成することができる。より好ましくは、アルミニウム又はアルミニウム合金を用いることができる。放熱基板１９、フィン２０及び金属板２１は、同種の金属材料であってもよいし、異種の金属材料であってもよい。同種の金属材料であることが、製造が容易である。 The heat dissipation substrate 19, the fins 20, and the metal plate 21 are preferably made of a material having high thermal conductivity, and a metal material is particularly preferable. For example, it can be formed using a metal material such as aluminum, aluminum alloy, copper, or copper alloy. More preferably, aluminum or an aluminum alloy can be used. The heat dissipation substrate 19, the fins 20, and the metal plate 21 may be the same type of metal material or different types of metal materials. The same kind of metal material is easy to manufacture.
　図２に、放熱基板１９の上面模式図を示す。図２は、本発明の理解を容易にするためにワイヤ１６や樹脂ケース１７の記載を省略している。また、図２では、図１と同じ部材については同じ符号を付しており、以下の説明では既に述べた部材についての説明を省略する。図２から分かるように、放熱基板１９の上面には、複数の回路素子部１１Ａ～１１Ｆが形成されている。また、図２に破線で示すように、放熱基板１９の下面にはフィン２０が設けられている。 FIG. 2 is a schematic top view of the heat dissipation board 19. In FIG. 2, the wire 16 and the resin case 17 are not shown for easy understanding of the present invention. In FIG. 2, the same members as those in FIG. 1 are denoted by the same reference numerals, and description of the members already described is omitted in the following description. As can be seen from FIG. 2, a plurality of circuit element portions 11A to 11F are formed on the upper surface of the heat dissipation substrate 19. Further, as indicated by a broken line in FIG. 2, fins 20 are provided on the lower surface of the heat dissipation substrate 19.
　放熱基板１９にフィン２０が設けられる領域（以下、「フィン領域」ともいう。）は、好ましくは、絶縁基板１２の平面の領域を、放熱基板１９の厚み方向と平行に該放熱基板１９の表面に投影したときの投影領域を包含し、かつ、この投影領域と同じか、それよりも広い領域である。分かり易くいうと、絶縁基板１２及び放熱基板１９を上から見たときに、フィン２０が放熱基板１９に設けられる領域は、絶縁基板１２が放熱基板１９に設けられる領域を含み、かつ、この領域と同等以上に広い領域である。このようにフィンが設けられる領域を同等以上に広くすることにより、外周に位置する絶縁基板１２に発生する応力集中を緩和することができる。 The region where the fins 20 are provided on the heat dissipation substrate 19 (hereinafter also referred to as “fin region”) is preferably a planar region of the insulating substrate 12 parallel to the thickness direction of the heat dissipation substrate 19. The projected area is the same as or wider than this projected area. In other words, when the insulating substrate 12 and the heat dissipation substrate 19 are viewed from above, the region where the fins 20 are provided on the heat dissipation substrate 19 includes the region where the insulating substrate 12 is provided on the heat dissipation substrate 19 and this region. It is an area wider than or equal to. Thus, by making the area where the fins are provided equal to or larger than that, stress concentration generated in the insulating substrate 12 located on the outer periphery can be alleviated.
　上記絶縁基板１２の投影領域の輪郭線と、フィン２０が放熱基板１９に設けられる領域の輪郭線との距離Ｌは、２ｍｍ以上離れていることが好ましい。両者の輪郭線が２ｍｍ以上離れるほどに、投影領域よりもフィン領域のほうが広くなることにより、応力歪の集中を効果的に緩和することができる。 The distance L between the contour line of the projected area of the insulating substrate 12 and the contour line of the area where the fins 20 are provided on the heat dissipation substrate 19 is preferably 2 mm or more. The greater the distance between the two contour lines, the wider the fin region than the projection region, so that the stress strain concentration can be effectively alleviated.
　図１に示したように、フィン２０は、ケース２２内に収容される。ケース２２は、底壁２２ａとこの底壁２２ａの周縁に設けられた側壁２２ｂを有し、上部が開口となっている形状である。ケース２２は、外形が略直方体形状であるが、略直方体形状に限定されるものではない。このケース２２の側壁２２ｂの上端が放熱基板１９に冷却液が漏れないように接合される。また、ケース２２に図に表れない冷却液の導入口及び排出口が設けられて、この導入口から冷却液が導入され、冷却液が、このケース２２内に収容されたフィン２０の間隙を通過して排出口から排出される。このようなケース２２内での冷却液の流動によりフィン２０は冷却液で冷却される。排出された冷却液は回収され、ポンプにより上記導入口に導かれて循環する。 As shown in FIG. 1, the fin 20 is accommodated in the case 22. The case 22 has a bottom wall 22a and a side wall 22b provided on the periphery of the bottom wall 22a, and has an opening at the top. The case 22 has a substantially rectangular parallelepiped shape, but is not limited to a substantially rectangular parallelepiped shape. The upper end of the side wall 22b of the case 22 is joined to the heat dissipation board 19 so that the coolant does not leak. The case 22 is provided with an inlet and an outlet for the coolant not shown in the figure. The coolant is introduced from the inlet, and the coolant passes through the gap between the fins 20 accommodated in the case 22. And discharged from the outlet. The fins 20 are cooled by the coolant by the flow of the coolant in the case 22. The discharged cooling liquid is collected, led to the introduction port by a pump, and circulated.
　ケース２２は、フィン２０や放熱基板１９と同様に、熱伝導率の高い材料よりなることが好ましく、特に金属材料が好ましい。例えばアルミニウム、アルミニウム合金、銅、銅合金等の金属材料を用いて形成することができる。このような金属材料を用いてケース２２を形成する場合、例えばダイキャストによって、上記のような導入口や排出口や、ケース２２内の流路を形成することができる。ケース２２は、金属材料にカーボンフィラーを含有する材料を用いることもできる。また、冷却液の種類やケース２２内に流れる冷却液の温度等によっては、セラミック材料や樹脂材料等を用いることも可能である。
れる。冷却液は、水やロングライフクーラント（ＬＬＣ）等を用いることができる。 The case 22 is preferably made of a material having a high thermal conductivity, like the fins 20 and the heat radiating substrate 19, and a metal material is particularly preferable. For example, it can be formed using a metal material such as aluminum, aluminum alloy, copper, or copper alloy. When the case 22 is formed using such a metal material, the above-described inlet and outlet and the flow path in the case 22 can be formed by die casting, for example. The case 22 can also use a material containing a carbon filler as a metal material. Further, a ceramic material, a resin material, or the like can be used depending on the type of the coolant, the temperature of the coolant flowing in the case 22, and the like.
It is. As the coolant, water, long life coolant (LLC), or the like can be used.
　フィン２０の先端は、上述したように金属板２１と接合される。この金属板２１は、ケース２２の底壁２２ａとは別の部材である。つまり、フィン２０がケース２２の底壁２２ａと接合されるものではない。図１に示したように、金属板２１は、ケース２２内で底壁２２ａとは所定の距離が離れるような位置に設けられている。この場合、フィン２０が底壁２２ａに接合されていないので、熱サイクルの環境下において、放熱基板１９およびフィン２０は金属板２１により変形量を抑制されながらも、比較的自由に変形できるため、その変形状態は緩やかである。放熱基板１９が急に屈曲することがほとんどないので、接合層１８への応力も小さい。一方、フィン２０の先端がケース２２の底壁２２ａに接合された場合は、金属板２１に接合された場合と比べて、放熱基板１９はケース２２に強く拘束される。フィン２０が底壁２２ａに接合されていると、放熱基板１９がフィン２０を介して側壁２２ｂを含むケース２２と一体となり、自由に変形できない。熱サイクルの環境下では、放熱基板１９が、接合層１８を形成した領域近傍に集中する応力により急な屈曲箇所が生じてしまい、接合層１８への応力が大きくなる。
　また、図１のようにフィン２０の先端が金属板２１に接合されることにより、ケース２２の底壁２２ａに接合された場合に比べてヒートシンクの表面積が金属板２１の表面積の分で増えているので、冷却効率が高い。 The tips of the fins 20 are joined to the metal plate 21 as described above. The metal plate 21 is a member different from the bottom wall 22 a of the case 22. That is, the fin 20 is not joined to the bottom wall 22 a of the case 22. As shown in FIG. 1, the metal plate 21 is provided at a position in the case 22 that is separated from the bottom wall 22 a by a predetermined distance. In this case, since the fin 20 is not joined to the bottom wall 22a, the heat dissipation substrate 19 and the fin 20 can be deformed relatively freely while the deformation amount is suppressed by the metal plate 21 in the environment of the thermal cycle. The deformation state is gradual. Since the heat dissipation substrate 19 hardly bends suddenly, the stress on the bonding layer 18 is also small. On the other hand, when the tips of the fins 20 are joined to the bottom wall 22 a of the case 22, the heat dissipation board 19 is strongly restrained by the case 22 as compared to the case where the fins 20 are joined to the metal plate 21. If the fin 20 is joined to the bottom wall 22a, the heat dissipation substrate 19 is integrated with the case 22 including the side wall 22b via the fin 20, and cannot be freely deformed. Under a thermal cycle environment, a sharp bent portion is generated in the heat dissipation substrate 19 due to the stress concentrated in the vicinity of the region where the bonding layer 18 is formed, and the stress on the bonding layer 18 increases.
Further, as shown in FIG. 1, the tip of the fin 20 is joined to the metal plate 21, so that the surface area of the heat sink is increased by the surface area of the metal plate 21 compared to the case where the fins 20 are joined to the bottom wall 22 a of the case 22. Therefore, the cooling efficiency is high.
　図３に、従来のパワー半導体モジュールの断面模式図を示す。なお、図３において、図１に示した部材と同一部材については同一符号を付しており、以下では重複する説明を省略する。図３のパワー半導体モジュール１１０は、図１に示すパワー半導体モジュール１０とは、金属板２１を有しない点で相違している。このような従来のパワー半導体モジュール１１０は、放熱基板１９の変形、具体的には反りを生じることがあり、これにより放熱基板１９と絶縁基板１２とを接合する接合層１８にクラックが生じることがあった。このような放熱基板１９の変形を抑制し接合層１８のクラックを防止することができるので、図１に示す本実施形態のパワー半導体モジュール１０の効果は大きい。 FIG. 3 shows a schematic cross-sectional view of a conventional power semiconductor module. In FIG. 3, the same members as those shown in FIG. 1 are denoted by the same reference numerals, and redundant description will be omitted below. The power semiconductor module 110 shown in FIG. 3 is different from the power semiconductor module 10 shown in FIG. Such a conventional power semiconductor module 110 may cause deformation of the heat dissipation substrate 19, specifically, warpage, which may cause cracks in the bonding layer 18 that joins the heat dissipation substrate 19 and the insulating substrate 12. there were. Since the deformation of the heat dissipation substrate 19 can be suppressed and cracking of the bonding layer 18 can be prevented, the effect of the power semiconductor module 10 of the present embodiment shown in FIG. 1 is great.
（実施例１）
　次に、本発明のパワー半導体モジュールの実施例を、比較例と対比させて説明する。
　絶縁基板１２の絶縁層１２ａは、０．３２ｍｍ厚の窒化ケイ素にて構成した。回路層１２ｂと金属層１２ｃは０．４ｍｍ厚の銅で構成した。放熱基板１９は５ｍｍ厚のアルミニウム合金で構成した。そして、樹脂ケース１７内部はシリコーンゲルやエポキシ樹脂等の封止樹脂で封止された。金属板２１とケース２２の底壁２２ａとの間のクリアランスは１ｍｍとした。 (Example 1)
Next, examples of the power semiconductor module of the present invention will be described in comparison with comparative examples.
The insulating layer 12a of the insulating substrate 12 was made of silicon nitride having a thickness of 0.32 mm. The circuit layer 12b and the metal layer 12c were made of 0.4 mm thick copper. The heat dissipation substrate 19 was made of an aluminum alloy having a thickness of 5 mm. The inside of the resin case 17 was sealed with a sealing resin such as silicone gel or epoxy resin. The clearance between the metal plate 21 and the bottom wall 22a of the case 22 was 1 mm.
　このような構成を持つパワー半導体モジュールについて、熱応力シミュレーションにより、絶縁基板１２下の接合層１８（Ｓｎ－Ｓｂ系はんだ）に発生する塑性ひずみ振幅と、金属板２１の厚みとの関係を解析した。 For the power semiconductor module having such a configuration, the relationship between the plastic strain amplitude generated in the bonding layer 18 (Sn—Sb solder) under the insulating substrate 12 and the thickness of the metal plate 21 was analyzed by thermal stress simulation. .
　ここで、塑性ひずみ振幅について説明する。一般的にはんだの低サイクル疲労寿命は、下式のマンソン－コフィン則に従うとされる。
ΔεｐＮｆ ｂ＝Ｃ
（Δεｐ：塑性ひずみ振幅、Ｎｆ：疲労寿命、ｂ、Ｃ：材料による定数）
　したがって、疲労寿命を延ばすためには、塑性ひずみ振幅を小さくすれば良いことが分かる。 Here, the plastic strain amplitude will be described. Generally, the low cycle fatigue life of solder is assumed to follow the following Manson-Coffin rule.
Δε p N f b = C
(Δε p : plastic strain amplitude, N f : fatigue life, b, C: constants depending on the material)
Therefore, it can be seen that the plastic strain amplitude should be reduced in order to extend the fatigue life.
　フィン先端の金属板２１の厚みを、０ｍｍ（比較例）、１．２ｍｍ（実施例）、１．８ｍｍ（実施例）と変化させた解析結果を図４に示す。金属板２１の設置により、塑性ひずみ振幅が低減できている。金属板２１を設置することにより、放熱基板１９の変形が抑制された効果であると考えられる。特に、金属板２１の厚みが１．２ｍｍ以上にてほぼ飽和しており、１．２ｍｍ以上にすることで塑性ひずみ振幅を約３０％低減することができる。 FIG. 4 shows the analysis results when the thickness of the metal plate 21 at the tip of the fin was changed to 0 mm (comparative example), 1.2 mm (example), and 1.8 mm (example). By installing the metal plate 21, the plastic strain amplitude can be reduced. By installing the metal plate 21, it is considered that the deformation of the heat dissipation substrate 19 is suppressed. In particular, the thickness of the metal plate 21 is almost saturated when the thickness is 1.2 mm or more. By setting the thickness to 1.2 mm or more, the plastic strain amplitude can be reduced by about 30%.
（実施例２）
　実施例２では、実施例１で説明した金属板２１の設置に加えて、フィン領域の広さを調整したものである。図５に熱応力シミュレーション結果を示す。フィン領域を広くしていくと、塑性ひずみ振幅が小さくなっていく。フィン領域の境界（図２の破線）には、放熱基板１９の反りによる応力が集中することが予想され、このような応力集中箇所を、接合層１８と離すことで塑性ひずみ振幅が低減できたと考えられる。特に、フィン領域を２ｍｍ以上に広げると飽和しており、２ｍｍ以上にて塑性ひずみ振幅を低減させる効果をより顕著に享受することができるといえる。 (Example 2)
In the second embodiment, in addition to the installation of the metal plate 21 described in the first embodiment, the width of the fin region is adjusted. FIG. 5 shows the thermal stress simulation results. As the fin region is increased, the plastic strain amplitude decreases. It is expected that stress due to warping of the heat dissipation substrate 19 is concentrated at the boundary of the fin region (broken line in FIG. 2), and the plastic strain amplitude can be reduced by separating such a stress concentration location from the bonding layer 18. Conceivable. In particular, when the fin region is expanded to 2 mm or more, it is saturated, and it can be said that the effect of reducing the plastic strain amplitude can be enjoyed more remarkably at 2 mm or more.
　１０　パワー半導体モジュール
　１１Ａ～１１Ｆ　　回路素子部
　１２　絶縁基板
　１２ａ　絶縁層
　１２ｂ　回路層
　１２ｃ　金属層
　１３、１４　半導体素子
　１５　接合層
　１６　ワイヤ
　１７　樹脂ケース
　１８　接合層
　１９　放熱基板
　２０　フィン
　２１　金属板
　２２　ケース
　２２ａ　底壁
　２２ｂ　側壁 DESCRIPTION OF SYMBOLS 10 Power semiconductor module 11A-11F Circuit element part 12 Insulation board 12a Insulation layer 12b Circuit layer 12c Metal layer 13, 14 Semiconductor element 15 Bonding layer 16 Wire 17 Resin case 18 Bonding layer 19 Heat sink 20 Fin 21 Metal plate 22 Case 22a Bottom Wall 22b side wall

Claims (5)

  1. 　絶縁基板と、該絶縁基板上に搭載された半導体素子と、該絶縁基板における該半導体素子が搭載された面とは反対側の面に接合された放熱基板と、該放熱基板に設けられて延在する複数のフィンと、を備え、
    　前記フィンにおける前記放熱基板から延びた先端に、前記フィンを収容するケースとは別の金属板が接合されていることを特徴とするパワー半導体モジュール。     An insulating substrate; a semiconductor element mounted on the insulating substrate; a heat dissipating substrate bonded to a surface of the insulating substrate opposite to the surface on which the semiconductor element is mounted; and a heat dissipating substrate provided on the heat dissipating substrate. A plurality of existing fins,
    A power semiconductor module, wherein a metal plate different from a case for housing the fin is joined to a tip of the fin extending from the heat dissipation substrate.
  2. 　前記金属板の厚みが１．２ｍｍ以上である請求項１記載のパワー半導体モジュール。 The power semiconductor module according to claim 1, wherein the metal plate has a thickness of 1.2 mm or more.
  3. 　前記フィンが前記放熱基板に設けられる領域は、前記絶縁基板の平面の領域を、前記放熱基板の厚み方向と平行に、該該放熱基板の表面に投影したときの投影領域を包含し、かつ、該投影領域と同じ又はそれ以上に広い請求項１記載のパワー半導体モジュール。 The region where the fins are provided on the heat dissipation substrate includes a projection region when a planar region of the insulating substrate is projected on the surface of the heat dissipation substrate in parallel with the thickness direction of the heat dissipation substrate, and 2. The power semiconductor module according to claim 1, wherein the power semiconductor module is wider than the projection area.
  4. 　前記投影領域の輪郭線と前記フィンが前記放熱基板に設けられる領域の輪郭線とが、２ｍｍ以上離れている請求項３記載のパワー半導体モジュール。 The power semiconductor module according to claim 3, wherein a contour line of the projection region and a contour line of the region where the fin is provided on the heat dissipation substrate are separated by 2 mm or more.
  5. 　前記放熱基板がアルミニウム又はアルミニウム合金からなり、前記絶縁基板に含まれる絶縁層が窒化ケイ素からなる請求項１記載のパワー半導体モジュール。 The power semiconductor module according to claim 1, wherein the heat dissipation substrate is made of aluminum or an aluminum alloy, and the insulating layer included in the insulating substrate is made of silicon nitride.
PCT/JP2013/071762 2012-09-19 2013-08-12 Power semiconductor module WO2014045758A1 (en)

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