JP2011040565A - Thermal conductive sheet, semiconductor device using the same, and method of manufacturing the same - Google Patents

Thermal conductive sheet, semiconductor device using the same, and method of manufacturing the same Download PDF

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JP2011040565A
JP2011040565A JP2009186549A JP2009186549A JP2011040565A JP 2011040565 A JP2011040565 A JP 2011040565A JP 2009186549 A JP2009186549 A JP 2009186549A JP 2009186549 A JP2009186549 A JP 2009186549A JP 2011040565 A JP2011040565 A JP 2011040565A
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heat conductive
heat
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semiconductor device
particle size
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Katsuhiko Yanagawa
克彦 柳川
Yoshinari Ikeda
良成 池田
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Fuji Electric Co Ltd
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Fuji Electric Systems Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L24/00—Arrangements for connecting or disconnecting semiconductor or solid-state bodies; Methods or apparatus related thereto
    • H01L24/01—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
    • 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]

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  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Adhesive Tapes (AREA)
  • Adhesives Or Adhesive Processes (AREA)
  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal conductive sheet capable of preventing peeling off between a copper-based substrate and a cooling fin, and also of preventing increase in thermal resistance; and a high-reliability power semiconductor device using the same. <P>SOLUTION: At least on one side of the thermal conductive layer, wherein a first thermal conductive filler with particle sizes of no smaller than 10 μm and no larger than 30 μm and of no smaller than 40 wt.% and no larger than 60 wt.% and a second thermal conductive filler with particle sizes of no smaller than 0.1 μm and no larger than 10 μm and of no smaller than 20 wt.% and no greater than 30 wt.% are filled in heat-resistant epoxy resin, an adhesive layer, wherein a third thermal conductive filler with particle sizes of no smaller than 0.1 μm and no larger than 10 μm and of no smaller than 20 wt.% and no larger 30 wt.% is filled in heat-resistant epoxy resin, is laminated. Then, that is heat-molded and the thermal conductive sheet is fabricated. Using the thermal conductive layer, the copper-based substrate and the cooling fin are bonded and fixed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

本発明は、熱伝導シートおよびこれを用いた半導体装置等に関し、特にはパワー半導体素子が収容される半導体装置(以下、パワーモジュールと称す)に関する。   The present invention relates to a heat conductive sheet and a semiconductor device using the same, and more particularly to a semiconductor device (hereinafter referred to as a power module) in which a power semiconductor element is accommodated.

図４に従来のパワーモジュールの模式的断面図を示す。パワーモジュール２００は、半導体素子１０を搭載した略方形の銅ベース基板２０と冷却フィン３０とからなる。銅ベース基板２０は絶縁層２１と回路パターン２２および銅板２３を有し、回路パターン２２には半田層ａ１１によりパワー半導体素子１０が半田付けされる。半導体素子１０には半田層ｂ１２によりリードフレーム１３が半田付けされ、主端子１４が取り付けられる。この状態で、銅ベース基板２０には箱型のケース４０が取り付けられ、両者の接合部が接着剤（図示せず）でシールされ、封止材層４１が充填され、ケース４０の上部に板状の蓋４２が取り付けられる。この状態で、銅ベース基板２０は、熱伝導ペースト６０が塗布された冷却フィン３０に、取付ボルト４３で締付トルクを管理し取付けられパワーモジュール２００は完成される。   FIG. 4 shows a schematic cross-sectional view of a conventional power module. The power module 200 includes a substantially rectangular copper base substrate 20 on which the semiconductor element 10 is mounted and cooling fins 30. The copper base substrate 20 includes an insulating layer 21, a circuit pattern 22, and a copper plate 23, and the power semiconductor element 10 is soldered to the circuit pattern 22 by a solder layer a11. A lead frame 13 is soldered to the semiconductor element 10 by a solder layer b12, and a main terminal 14 is attached. In this state, a box-shaped case 40 is attached to the copper base substrate 20, a joint portion between the two is sealed with an adhesive (not shown), a sealing material layer 41 is filled, and a plate is placed on the upper portion of the case 40. A lid 42 is attached. In this state, the copper base substrate 20 is attached to the cooling fins 30 to which the heat conductive paste 60 is applied by managing the tightening torque with the attachment bolts 43, and the power module 200 is completed.

パワーモジュールの動作時はパワー半導体素子１０や回路パターン２２に大電流が流れるため、パワー半導体素子１０で発生した熱を銅ベース基板２０から熱伝導ペースト６０を介して冷却フィン３０に伝熱し、冷却することが重要である。   Since a large current flows through the power semiconductor element 10 and the circuit pattern 22 during the operation of the power module, the heat generated in the power semiconductor element 10 is transferred from the copper base substrate 20 to the cooling fins 30 via the heat conductive paste 60 to be cooled. It is important to.

特開２００４−８７７３５号公報JP 200487735 A

従来のパワーモジュールでは、熱伝導ペースト６０としてグリース状の材料を使用するが、グリース状のため、パワーモジュールの使用中に起こる温度変化により銅ベース基板２０と冷却フィン３０の間に剥離空間（ボイド）が発生したり、グリース材のため材料が長期間の使用において劣化し熱抵抗が増加する問題点がある。   In the conventional power module, a grease-like material is used as the heat conductive paste 60. However, because of the grease-like shape, a peeling space (void) is formed between the copper base substrate 20 and the cooling fin 30 due to a temperature change that occurs during use of the power module. ), Or because of the grease material, the material deteriorates during long-term use and the thermal resistance increases.

例えば、ΔＴｊ＝１００℃、運転１秒、休止９秒の条件を１サイクルとしてパワーサイクル試験を実施すると、サイクル数の増加にしたがい銅ベース基板２０と冷却フィン３０の間に剥離空間が発生し、パワーモジュールの熱抵抗が増加する傾向が顕著になる。また、−４０℃（３０分間)〜＋１２５℃（３０分間）の条件を１サイクルとしてヒートショック試験を実施すると、パワーサイクル試験と同様にサイクル数の増加とともに銅ベース基板２０と冷却フィン３０の間に剥離空間が発生が増加し、熱抵抗が増加する傾向が顕著になる。   For example, when a power cycle test is performed with ΔTj = 100 ° C., 1 second of operation, and 9 seconds of rest as one cycle, a separation space is generated between the copper base substrate 20 and the cooling fin 30 as the number of cycles increases. The tendency for the thermal resistance of the power module to increase becomes prominent. Moreover, when the heat shock test is performed with the condition of −40 ° C. (30 minutes) to + 125 ° C. (30 minutes) as one cycle, the number of cycles increases with the increase in the number of cycles as in the power cycle test. In particular, the tendency for the separation space to increase and the thermal resistance to increase increases.

本発明は、上述の問題点を解決するため銅ベース基板２０と冷却フィン３０の間の剥離を防止し、かつ熱抵抗の増加を防止することができる熱伝導シート、およびこれを用いた信頼性の高いパワー半導体装置を提供するものである。   In order to solve the above-described problems, the present invention prevents a separation between the copper base substrate 20 and the cooling fin 30 and prevents an increase in thermal resistance, and reliability using the same. A high power semiconductor device is provided.

なお、上記特許文献１には、熱伝導ペーストに代えて熱伝導シートを用いる半導体装置が開示されているが、銅ベース基板および冷却フィンとの接着性、熱抵抗がともに優れる熱伝導シートは開示されていない。   The above Patent Document 1 discloses a semiconductor device that uses a heat conductive sheet instead of the heat conductive paste, but discloses a heat conductive sheet that has both excellent adhesion and heat resistance to the copper base substrate and the cooling fin. It has not been.

上記の課題を解決するため、本発明の熱伝導シートは、熱伝導層の少なくとも片面に接着層を積層し、加熱、成型したものである。熱伝導層は粒径１０μｍ以上３０μｍ以下の第１の熱伝導フィラーを４０ｗｔ％以上６０ｗｔ％以下、粒径０．１μｍ以上１０μｍ以下の第２の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、夫々耐熱性エポキシ樹脂に充填したものである。接着層は粒径０．１μｍ以上１０μｍ以下の第３の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、耐熱性エポキシ樹脂に充填したものである。ここで熱伝導層および接着層の厚さは夫々５０〜１６０μｍ、１０〜２０μｍであることが好ましい。   In order to solve the above problems, the heat conductive sheet of the present invention is obtained by laminating an adhesive layer on at least one surface of a heat conductive layer, heating and molding. The heat conductive layer is 40 wt% or more and 60 wt% or less of the first heat conductive filler having a particle diameter of 10 μm or more and 30 μm or less, and the second heat conductive filler having a particle diameter of 0.1 μm or more and 10 μm or less is 20 wt% or more and 30 wt% or less. It is filled with a conductive epoxy resin. The adhesive layer is formed by filling a heat-resistant epoxy resin with a third heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less and 20 wt% or more and 30 wt% or less. Here, the thicknesses of the heat conductive layer and the adhesive layer are preferably 50 to 160 μm and 10 to 20 μm, respectively.

また、本発明の半導体装置は、半導体素子を搭載した銅ベース基板および冷却フィンを少なくとも含む半導体装置であって、銅ベースと冷却フィンを接着固定する熱伝導シートを備えることを特徴とする。ここで熱伝導シートは、熱伝導層と、その両面に配置された接着層とからなる３層構造であることが好ましい。さらに熱伝導層は、粒径１０μｍ以上３０μｍ以下の第１の熱伝導フィラーを４０ｗｔ％以上６０ｗｔ％以下、粒径０．１μｍ以上１０μｍ以下の第２の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、夫々耐熱性エポキシ樹脂に充填したものであることが好ましく、また、接着層は、粒径０．１μｍ以上１０μｍ以下の第３の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、耐熱性エポキシ樹脂に充填したものであることが好ましい。加えて熱伝導フィラーは、窒化ホウ素粉末、窒化ケイ素粉末、アルミナ粉末および石英粉末からなる群より選ばれた少なくとも１種のフィラーを含むことが好ましい。   The semiconductor device according to the present invention is a semiconductor device including at least a copper base substrate on which a semiconductor element is mounted and a cooling fin, and includes a heat conductive sheet for bonding and fixing the copper base and the cooling fin. Here, the heat conductive sheet preferably has a three-layer structure including a heat conductive layer and adhesive layers disposed on both sides thereof. Furthermore, the heat conductive layer has a first heat conductive filler having a particle size of 10 μm or more and 30 μm or less, 40 wt% or more and 60 wt% or less, a second heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less, 20 wt% or more and 30 wt% or less, Each is preferably filled with a heat-resistant epoxy resin, and the adhesive layer is filled with a third heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less in a heat resistant epoxy resin of 20 wt% or more and 30 wt% or less. It is preferable that In addition, the heat conductive filler preferably contains at least one filler selected from the group consisting of boron nitride powder, silicon nitride powder, alumina powder, and quartz powder.

また、本発明の半導体装置の製造方法は、半導体素子を搭載した銅ベース基板および冷却フィンを少なくとも含む半導体装置の製造方法であって、上記の熱伝導シートを用意する工程と、この熱伝導シートを銅ベース基板および冷却フィンの間に挟み、加圧、硬化させる工程とを有することを特徴とする。   Also, a method for manufacturing a semiconductor device according to the present invention is a method for manufacturing a semiconductor device including at least a copper base substrate on which semiconductor elements are mounted and a cooling fin, the step of preparing the above-described heat conductive sheet, and the heat conductive sheet. Between the copper base substrate and the cooling fin, and pressurizing and curing.

本発明の熱伝導シートは、上記構成により加圧、硬化された場合の接着性、熱抵抗がともに優れるものである。
また、本発明の半導体装置は、銅ベース基板および冷却フィンの間に上記の熱伝導シートを挟んで加圧、硬化させたことにより、銅ベース基板および冷却フィンの間の接着性が優れ、剥離がなく、かつ熱抵抗が優れるものである。 The heat conductive sheet of the present invention is excellent in both adhesiveness and heat resistance when pressed and cured by the above configuration.
Further, the semiconductor device of the present invention has excellent adhesion between the copper base substrate and the cooling fin by peeling and pressing the above heat conductive sheet between the copper base substrate and the cooling fin. There is no thermal resistance.

本発明の第１の実施の形態に係る半導体装置の模式的断面図である。1 is a schematic cross-sectional view of a semiconductor device according to a first embodiment of the present invention. 本発明の第１の実施の形態に係る熱伝導シートの模式的断面図である。It is a typical sectional view of the heat conduction sheet concerning a 1st embodiment of the present invention. 本発明の第２の実施の形態に係る半導体装置の模式的断面図である。It is a typical sectional view of a semiconductor device concerning a 2nd embodiment of the present invention. 従来の半導体装置の模式的断面図である。It is typical sectional drawing of the conventional semiconductor device.

以下、本発明の実施の形態について、図１〜３を参照して説明する。なお、以下の図面において、同じ機能を有する部材には同一の符号を付した。
（第１の実施の形態）
図１は、本発明の第１の実施の形態に係るパワーモジュールの模式的断面図である。 Hereinafter, embodiments of the present invention will be described with reference to FIGS. In addition, in the following drawings, the same code | symbol was attached | subjected to the member which has the same function.
(First embodiment)
FIG. 1 is a schematic cross-sectional view of a power module according to a first embodiment of the present invention.

パワーモジュール１００は、半導体素子１０を搭載した略方形の銅ベース基板２０と冷却フィン３０とから主に構成される。銅ベース基板２０は絶縁層２１、回路パターン２２および銅板２３を有し、回路パターン２２には半田層ａ１１によりパワー半導体素子１０が半田付けされる。銅板２３は、腐食防止および電腐防止のためにニッケルなどの金属膜が被覆されている。半導体素子１０は、例えばＩＧＢＴ（絶縁ゲートバイポーラトランジスタ：Insulated Gate Bipolar Transistor）およびＦＷＤ（フリーホイーリングダイオード：Free Wheeling Diode）とすることができる。半導体素子１０には半田層ｂ１２によりリードフレーム１３が半田付けされ、主端子１４が取り付けられる。この状態で、銅ベース基板２０の周囲には箱型のケース４０が取り付けられ、両者の接合部が接着剤（図示せず）でシールされ、封止材層４１が充填されている。   The power module 100 mainly includes a substantially square copper base substrate 20 on which the semiconductor element 10 is mounted and cooling fins 30. The copper base substrate 20 has an insulating layer 21, a circuit pattern 22, and a copper plate 23. The power semiconductor element 10 is soldered to the circuit pattern 22 by a solder layer a11. The copper plate 23 is coated with a metal film such as nickel to prevent corrosion and electrocorrosion. The semiconductor element 10 can be, for example, an IGBT (Insulated Gate Bipolar Transistor) and an FWD (Free Wheeling Diode). A lead frame 13 is soldered to the semiconductor element 10 by a solder layer b12, and a main terminal 14 is attached. In this state, a box-shaped case 40 is attached around the copper base substrate 20, and a joint portion between the two is sealed with an adhesive (not shown) and filled with a sealing material layer 41.

封止材層４１として好適に使用されるのはシリコーンゲル材料で、２液混合型の反応材料である。所定量計量したのち混合し０．１Ｔｏｒｒの真空状態で１０分間一次脱泡したのちにケース４０内に注型される。その後、０．１Ｔｏｒｒの真空状態で１０分間２次脱泡し１２０℃、２時間加熱硬化され、続いてケース４０の上部に板状の蓋４２が取り付けられる。この状態で、銅ベース基板２０を熱伝導シート５０を介して冷却フィン３０上に設置し、取付ボルト４３で締付トルクを管理しケース４０を冷却フィン３０に固定し、熱伝導シート５０を１５０℃、１時間加熱硬化することによりパワーモジュール１００が完成する。   A silicone gel material is preferably used as the sealing material layer 41, and a two-component mixed reaction material. A predetermined amount is weighed, mixed, and subjected to primary degassing for 10 minutes in a vacuum state of 0.1 Torr, and then cast into the case 40. After that, secondary defoaming is performed for 10 minutes in a vacuum state of 0.1 Torr, heat curing is performed at 120 ° C. for 2 hours, and then a plate-like lid 42 is attached to the top of the case 40. In this state, the copper base substrate 20 is installed on the cooling fin 30 via the heat conductive sheet 50, the tightening torque is managed by the mounting bolt 43, the case 40 is fixed to the cooling fin 30, and the heat conductive sheet 50 is fixed to 150. The power module 100 is completed by heating and curing at 1 ° C. for 1 hour.

熱伝導シート５０は、図２に示すように、熱伝導層５１と、その両面に配置された接着層５２とからなる３層構造であり、熱伝導層５１および接着層５２を積層したものを加熱、成型したものである。各層は、窒化ホウ素粉末、窒化ケイ素粉末、アルミナ粉末および石英粉末からなる群より選ばれた少なくとも１種の熱伝導フィラー（充填剤）を、耐熱性エポキシ樹脂に充填したものである。   As shown in FIG. 2, the heat conductive sheet 50 has a three-layer structure including a heat conductive layer 51 and an adhesive layer 52 disposed on both sides thereof, and is a laminate of the heat conductive layer 51 and the adhesive layer 52. Heated and molded. Each layer is obtained by filling a heat-resistant epoxy resin with at least one heat conductive filler (filler) selected from the group consisting of boron nitride powder, silicon nitride powder, alumina powder, and quartz powder.

熱伝導層５１は、好ましくは、粒径１０μｍ以上３０μｍ以下の熱伝導フィラーを４０ｗｔ％以上６０ｗｔ％以下、粒径０．１μｍ以上１０μｍ以下のものを２０ｗｔ％以上３０ｗｔ％以下、夫々耐熱性エポキシ樹脂に充填、混合し、加熱、成型したものである。熱伝導層５１に粒径の異なる２種類の熱伝導フィラーを充填することにより熱伝導率の向上と絶縁距離の確保を同時に実現することができる。すなわち、粒径１０μｍ以上３０μｍ以下の大きな熱伝導フィラーを配合することにより、銅ベース基板２０と冷却フィン３０の間で加圧硬化された後においても絶縁距離（厚さ）を確保できるとともに、これらの大きな熱伝導フィラーの隙間を、粒径０．１μｍ以上１０μｍ以下の小さな熱伝導フィラーで埋めることにより熱伝導性も良好となる。大きな熱伝導フィラーおよび小さな熱伝導フィラーの粒径は、夫々さらに２０μｍ以上３０μｍ以下、０．１μｍ以上５μｍ以下の範囲とすることが好ましい。なお、熱伝導フィラーの含有率は硬化前のエポキシ樹脂に対するものである。   The heat conductive layer 51 is preferably a heat conductive epoxy resin having a particle size of 10 μm or more and 30 μm or less, 40 wt% or more and 60 wt% or less, and a particle size of 0.1 μm or more and 10 μm or less, 20 wt% or more and 30 wt% or less, respectively. Filled, mixed, heated and molded. By filling the heat conductive layer 51 with two kinds of heat conductive fillers having different particle diameters, it is possible to simultaneously improve the thermal conductivity and secure the insulation distance. That is, by blending a large heat conductive filler having a particle size of 10 μm or more and 30 μm or less, an insulation distance (thickness) can be secured even after being pressure-cured between the copper base substrate 20 and the cooling fin 30, and these The thermal conductivity is also improved by filling the gap between the large thermal conductive fillers with a small thermal conductive filler having a particle size of 0.1 μm or more and 10 μm or less. The particle sizes of the large heat conductive filler and the small heat conductive filler are preferably in the range of 20 μm to 30 μm and 0.1 μm to 5 μm, respectively. In addition, the content rate of a heat conductive filler is with respect to the epoxy resin before hardening.

また、接着層５２は、好ましくは、粒径０．１μｍ以上１０μｍ以下の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、耐熱性エポキシ樹脂に充填し、加熱、成型したものである。接着層５２は、大きな接着強さを有するとともに高い熱伝導性を備える必要がある。すなわち、熱伝導層５１とは異なり、粒径０．１μｍ以上１０μｍ以下の熱伝導フィラーのみを使用し、接着層５２の厚さを１０μｍ以下することにより、１０ＭＰａ以上の接着強さを達成することができるとともに、最大粒径１０μｍ以下のものを３０ｗｔ％以下添加することにより高い熱伝導性をも達成できる。   The adhesive layer 52 is preferably formed by filling a heat-resistant epoxy resin with a heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less into a heat resistant epoxy resin, heating, and molding. The adhesive layer 52 needs to have high adhesive strength and high thermal conductivity. That is, unlike the heat conductive layer 51, only a heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less is used, and the adhesive layer 52 has a thickness of 10 μm or less to achieve an adhesive strength of 10 MPa or more. In addition, a high thermal conductivity can be achieved by adding 30 wt% or less of a material having a maximum particle size of 10 μm or less.

なお、熱伝導層５１、接着層５２ともに、０．１μｍより小さい粒径の熱伝導フィラーの含有は不可避な量にとどめるべきである。小さなフィラーを多く含むと樹脂の粘度が上がって、シートとしての成形性、加工性が劣るからである。   It should be noted that both the heat conductive layer 51 and the adhesive layer 52 should contain an inevitable amount of heat conductive filler having a particle size of less than 0.1 μm. This is because when a large amount of small fillers are contained, the viscosity of the resin increases and the formability and workability as a sheet are poor.

上記熱伝導層５１および接着層５２の厚さはそれぞれ５０〜１６０μｍ、１０〜２０μｍが好ましく、合計（熱伝導シート５０）の膜厚は７０〜２００μｍが好ましい。また、銅ベース基板２０と冷却フィン３０の間で加圧、硬化した熱伝導シート５０の膜厚は４０〜１８０μｍが好ましい。   The thicknesses of the heat conductive layer 51 and the adhesive layer 52 are preferably 50 to 160 μm and 10 to 20 μm, respectively, and the total film thickness (heat conductive sheet 50) is preferably 70 to 200 μm. Moreover, the film thickness of the heat conductive sheet 50 pressed and cured between the copper base substrate 20 and the cooling fins 30 is preferably 40 to 180 μm.

なお、上記の所定粒径の熱伝導フィラーは、例えば、平均粒径１０〜３０μｍの熱伝導フィラを公知の方法により分級し得ることができる。
以下、熱伝導シート５０の製作方法を具体的に説明する。 In addition, the heat conductive filler of said predetermined particle diameter can classify | categorize the heat conductive filler with an average particle diameter of 10-30 micrometers by a well-known method, for example.
Hereinafter, the manufacturing method of the heat conductive sheet 50 is demonstrated concretely.

先ず熱伝導層５１を形成する。ノボラック型の１液性エポキシ樹脂に熱伝導フィラーとして粒径１０μｍ以上で粒径３０μｍ以下の窒化ホウ素粉末（ＢＮ、昭和電工（株）製）を添加量６０ｗｔ％、粒径０．１μｍ以上で粒径１０μｍ以下の窒化ホウ素粉末を添加量３０ｗｔ％配合し、充分な混合を行った後、６０℃に加熱されたロール型ラミネーターで厚さ１００μｍのシートに成型し、熱伝導層５１が形成される。   First, the heat conductive layer 51 is formed. Boron nitride powder (BN, manufactured by Showa Denko Co., Ltd.) having a particle size of 10 μm or more and a particle size of 30 μm or less as a heat conductive filler is added to a novolac type one-part epoxy resin with an addition amount of 60 wt% and a particle size of 0.1 μm or more. A boron nitride powder having a diameter of 10 μm or less is blended in an addition amount of 30 wt%, and after sufficient mixing, it is molded into a sheet having a thickness of 100 μm by a roll laminator heated to 60 ° C., and the heat conduction layer 51 is formed. .

次に接着層５２を形成する。ノボラック型の１液性エポキシ樹脂に熱伝導フィラーとして粒径０．１μｍで粒径１０μｍ以下の窒化ホウ素粉末（ＢＮ、昭和電工（株）製）を添加量３０ｗｔ％配合し、充分な混合を行った後、６０℃に加熱されたロール型ラミネーターで厚さ２０μｍのシートに成型し、接着層５２が形成される。   Next, the adhesive layer 52 is formed. A novolac type one-part epoxy resin is mixed with 30 wt% of boron nitride powder (BN, Showa Denko KK) having a particle size of 0.1 μm and a particle size of 10 μm or less as a heat conductive filler, and mixed thoroughly. After that, it is molded into a sheet having a thickness of 20 μm by a roll type laminator heated to 60 ° C., and the adhesive layer 52 is formed.

さらに、このように形成した熱伝導層５１の両面にそれぞれ接着層５２を積層、配置し、６０℃に加熱されたロール型ラミネーターで厚さ１４０μｍに成型して熱伝導シート５０が製作される。   Further, the adhesive layers 52 are laminated and arranged on both surfaces of the heat conductive layer 51 formed as described above, and are molded into a thickness of 140 μm with a roll-type laminator heated to 60 ° C., whereby the heat conductive sheet 50 is manufactured.

上記の方法により製作した熱伝導シート５０は、樹脂の硬化反応状態がＢステージ状態であるため、冷蔵保管することにより可使時間を長くとることが可能となる。
熱伝導シート５０を銅ベース基板２０と冷却フィン３０に挟み、接着時に１ＭＰａの加圧力を加えることで熱伝導シート５０は厚さ１２０μｍに潰れた状態となる。これは加圧力により接着層５２が約５０％潰れる状態となるためである。この状態で熱伝導シート５０は、銅ベース基板２０と冷却フィン３０の表面に対して充分にぬれる状態となり、良好な接着状態が得られる。また、接着層５２が潰れることにより、潰れる前より熱伝導フィラーの体積密度が大きくなり、熱伝導率が高くなる。この状態で１５０℃、１時間加熱し、熱伝導シート５０を硬化させる。 In the heat conductive sheet 50 manufactured by the above method, the curing reaction state of the resin is in the B stage state, so that the pot life can be increased by refrigeration storage.
The thermal conductive sheet 50 is sandwiched between the copper base substrate 20 and the cooling fins 30 and a pressure of 1 MPa is applied at the time of bonding so that the thermal conductive sheet 50 is crushed to a thickness of 120 μm. This is because the adhesive layer 52 is crushed by about 50% by the applied pressure. In this state, the heat conductive sheet 50 is sufficiently wetted with respect to the surfaces of the copper base substrate 20 and the cooling fins 30, and a good adhesion state is obtained. Moreover, when the adhesive layer 52 is crushed, the volume density of the heat conductive filler is larger than before the crushed, and the thermal conductivity is increased. In this state, the heat conductive sheet 50 is cured by heating at 150 ° C. for 1 hour.

接着、硬化後の熱伝導シート５０を評価したところ、熱伝導率は３．８Ｗ／ｍ・Ｋで厚さ１２０μｍでの熱抵抗は０．３Ｋ／Ｗであった。これに対し、従来技術として熱伝導ペースト６０にグリース状材料（信越化学製：Ｇ−７４７（商品名））を使用したところ、熱伝導率１．０Ｗ／ｍ・Ｋで厚さ６０μｍでの熱抵抗は０．６Ｋ／Ｗであった。熱伝導シート５０を使用した場合、熱抵抗は、従来の１／２と良好な性能となる。また、熱伝導ペースト６０のグリース状材料の接着強さは、ほとんどない状態であるが、さらに、ノボラック型エポキシ樹脂を使用することにより熱伝導シート５０の硬化後の熱変形温度が１８０℃となり、低温域の−３０℃から高温域の１７５℃まで１０ＭＰａ以上の接着強さ示し、特に高温域での接着強度の性能維持が図られ、銅ベース基板２０と冷却フィン３０の間の熱伝導機能が高温域において長期の信頼性が得られるパワーモジュール構造となる。
（第２の実施の形態）
図３は、本発明の第２の実施の形態に係るパワーモジュールの模式的断面図である。 When the heat conductive sheet 50 after bonding and curing was evaluated, the heat conductivity was 3.8 W / m · K, and the heat resistance at a thickness of 120 μm was 0.3 K / W. In contrast, when a grease-like material (manufactured by Shin-Etsu Chemical Co., Ltd .: G-747 (trade name)) is used for the heat conductive paste 60 as a conventional technique, heat with a heat conductivity of 1.0 W / m · K and a thickness of 60 μm is obtained. The resistance was 0.6 K / W. When the heat conductive sheet 50 is used, the thermal resistance is as good as 1/2 of the conventional one. Moreover, although the adhesive strength of the grease-like material of the heat conductive paste 60 is almost absent, the heat deformation temperature after the heat conductive sheet 50 is cured becomes 180 ° C. by using a novolac type epoxy resin. Adhesion strength of 10 MPa or more is shown from −30 ° C. in the low temperature range to 175 ° C. in the high temperature range, and particularly the performance of the adhesive strength in the high temperature range is maintained, and the heat conduction function between the copper base substrate 20 and the cooling fin 30 is achieved. It becomes a power module structure which can obtain long-term reliability in a high temperature range.
(Second Embodiment)
FIG. 3 is a schematic cross-sectional view of a power module according to the second embodiment of the present invention.

パワーモジュール１００は、半導体素子１０を搭載した略方形の銅ベース基板２０と冷却フィン３０ａとから主に構成される。銅ベース基板２０は絶縁層２１、回路パターン２２および銅板２３を有し、回路パターン２２には半田層ａ１１によりパワー半導体素子１０が半田付けされる。半導体素子１０には半田層ｂ１２によりリードフレーム１３が半田付けされ、主端子１４が取り付けられる。この状態で、銅ベース基板２０の周囲には箱型のケース４０ａが取り付けられ、両者の接合部を接着剤（図示せず）でシールされ、封止材層４１が充填される。   The power module 100 is mainly composed of a substantially rectangular copper base substrate 20 on which the semiconductor element 10 is mounted and cooling fins 30a. The copper base substrate 20 has an insulating layer 21, a circuit pattern 22, and a copper plate 23. The power semiconductor element 10 is soldered to the circuit pattern 22 by a solder layer a11. A lead frame 13 is soldered to the semiconductor element 10 by a solder layer b12, and a main terminal 14 is attached. In this state, a box-shaped case 40 a is attached around the copper base substrate 20, the joint between the two is sealed with an adhesive (not shown), and the sealing material layer 41 is filled.

封止材層４１として好適に使用されるのはシリコーンゲル材料で、２液混合型の反応材料である。所定量計量したのち混合し０．１Ｔｏｒｒの真空状態で１０分間一次脱泡したのちにケース４０ａ内に注型される。その後、０．１Ｔｏｒｒの真空状態で１０分間２次脱泡し１２０℃、２時間加熱硬化され、続いてケース４０ａの上部に板状の蓋４２が取り付けられる。さらに熱伝導シート５０を銅ベース基板２０と冷却フィン３０ａの間に設置し熱プレス（図示せず）により１ＭＰａの加圧力で１５０℃、１時間の加熱硬化を行うことによりパワーモジュール１００が完成する。   A silicone gel material is preferably used as the sealing material layer 41, and a two-component mixed reaction material. A predetermined amount is weighed, mixed, and subjected to primary degassing for 10 minutes in a vacuum state of 0.1 Torr, and then cast into the case 40a. After that, secondary defoaming is performed for 10 minutes in a vacuum state of 0.1 Torr, followed by heat curing at 120 ° C. for 2 hours. Furthermore, the power module 100 is completed by installing the heat conductive sheet 50 between the copper base substrate 20 and the cooling fin 30a and performing heat curing at 150 ° C. for 1 hour with a pressure of 1 MPa by a hot press (not shown). .

１０ パワー半導体素子
１１ 半田層ａ
１２ 半田層ｂ
１３ リードフレーム
１４ 主端子
２０ 銅ベース基板
２１ 絶縁層
２２ 回路パターン
２３ 銅板
３０、３０ａ 冷却フィン
４０、４０ａ ケース
４１ 封止材層
４２ 蓋
４３ 取付ボルト
５０ 熱伝導シート
５１ 熱伝導層
５２ 接着層
１００ パワーモジュール 10 Power Semiconductor Element 11 Solder Layer a
12 Solder layer b
DESCRIPTION OF SYMBOLS 13 Lead frame 14 Main terminal 20 Copper base board 21 Insulating layer 22 Circuit pattern 23 Copper plate 30, 30a Cooling fin 40, 40a Case 41 Sealing material layer 42 Lid 43 Mounting bolt 50 Thermal conductive sheet 51 Thermal conductive layer 52 Adhesive layer 100 Power module

Claims (8)

粒径１０μｍ以上３０μｍ以下の第１の熱伝導フィラーを４０ｗｔ％以上６０ｗｔ％以下、粒径０．１μｍ以上１０μｍ以下の第２の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、夫々耐熱性エポキシ樹脂に充填した熱伝導層の少なくとも片面に、粒径０．１μｍ以上１０μｍ以下の第３の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、耐熱性エポキシ樹脂に充填した接着層を積層し、加熱成型されたことを特徴とする熱伝導シート。 The first heat conductive filler having a particle size of 10 μm or more and 30 μm or less is 40 wt% or more and 60 wt% or less, and the second heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less is 20 wt% or more and 30 wt% or less, respectively. An adhesive layer filled with a heat-resistant epoxy resin with a third heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less and a heat resistant epoxy resin was laminated on at least one side of the filled heat conductive layer, and was heat molded. A heat conductive sheet characterized by that. 前記熱伝導層および接着層の厚さが夫々５０〜１６０μｍ、１０〜２０μｍであることを特徴とする請求項１記載の熱伝導シート。 2. The heat conductive sheet according to claim 1, wherein the heat conductive layer and the adhesive layer have a thickness of 50 to 160 [mu] m and 10 to 20 [mu] m, respectively. 半導体素子を搭載した銅ベース基板および冷却フィンを少なくとも含む半導体装置であって、前記銅ベース基板と冷却フィンを接着固定する熱伝導シートを備えることを特徴とする半導体装置。 A semiconductor device comprising at least a copper base substrate on which a semiconductor element is mounted and a cooling fin, comprising a heat conductive sheet for bonding and fixing the copper base substrate and the cooling fin. 前記熱伝導シートが、熱伝導層と、その両面に配置された接着層とからなる３層構造であることを特徴とする請求項３記載の半導体装置。 4. The semiconductor device according to claim 3, wherein the heat conductive sheet has a three-layer structure including a heat conductive layer and adhesive layers disposed on both sides thereof. 前記熱伝導層は、粒径１０μｍ以上３０μｍ以下の第１の熱伝導フィラーを４０ｗｔ％以上６０ｗｔ％以下、粒径０．１μｍ以上１０μｍ以下の第２の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、夫々耐熱性エポキシ樹脂に充填したものであることを特徴とする請求項４記載の半導体装置。 The heat conductive layer includes a first heat conductive filler having a particle size of 10 μm or more and 30 μm or less, 40 wt% or more and 60 wt% or less, a second heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less, 20 wt% or more and 30 wt% or less, 5. The semiconductor device according to claim 4, wherein each of the semiconductor devices is filled with a heat-resistant epoxy resin. 前記接着層は、粒径０．１μｍ以上１０μｍ以下の第３の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、耐熱性エポキシ樹脂に充填したものであることを特徴とする請求項４記載の半導体装置。 5. The semiconductor device according to claim 4, wherein the adhesive layer is formed by filling a heat-resistant epoxy resin with a third heat conductive filler having a particle diameter of 0.1 μm to 10 μm in a range of 20 wt% to 30 wt%. . 前記の各熱伝導フィラーが、窒化ホウ素粉末、窒化ケイ素粉末、アルミナ粉末および石英粉末からなる群より選ばれた少なくとも１種のフィラーを含むことを特徴とする請求項５または６記載の半導体装置。 7. The semiconductor device according to claim 5, wherein each of the heat conductive fillers includes at least one filler selected from the group consisting of boron nitride powder, silicon nitride powder, alumina powder, and quartz powder. 半導体素子を搭載した銅ベース基板および冷却フィンを少なくとも含む半導体装置の製造方法であって、
粒径１０μｍ以上３０μｍ以下の第１の熱伝導フィラーを４０ｗｔ％以上６０ｗｔ％以下、粒径０．１μｍ以上１０μｍ以下の第２の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、夫々耐熱性エポキシ樹脂に充填した熱伝導層の少なくとも片面に、粒径０．１μｍ以上１０μｍ以下の第３の熱伝導フィラーを２０ｗｔ％以上３０ｗｔ％以下、耐熱性エポキシ樹脂に充填した接着層を積層し、加熱成型された熱伝導シートを用意する工程と、
当該熱伝導シートを銅ベース基板および冷却フィンの間に挟み、加圧、硬化させる工程とを有することを特徴とする半導体装置の製造方法。 A method of manufacturing a semiconductor device including at least a copper base substrate on which a semiconductor element is mounted and a cooling fin,
40 wt% or more and 60 wt% or less of the first heat conductive filler having a particle size of 10 to 30 µm, and 20 wt% or more and 30 wt% or less of the second heat conductive filler having a particle size of 0.1 to 10 µm, respectively. An adhesive layer filled with a heat-resistant epoxy resin with a third heat conductive filler having a particle size of 0.1 μm or more and 10 μm or less and a heat resistant epoxy resin was laminated on at least one side of the filled heat conductive layer, and was heat molded. Preparing a heat conductive sheet;
And a step of sandwiching the heat conductive sheet between the copper base substrate and the cooling fin, pressurizing and curing the semiconductor device.
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