JP2017037833A - Composite insulation sheet and manufacturing method of composite insulation sheet - Google Patents
Composite insulation sheet and manufacturing method of composite insulation sheet Download PDFInfo
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本発明は熱伝導性材料の充填材と樹脂とを含む複合絶縁板およびその製造方法において、良好な熱伝導性と十分な絶縁性を併せ持つ複合絶縁板とその製造方法に関するものである。 The present invention relates to a composite insulating plate containing a filler of a heat conductive material and a resin, and a method for manufacturing the same, and a composite insulating plate having both good thermal conductivity and sufficient insulation and a method for manufacturing the same.
ハイブリッド自動車、電気自動車、燃料電池車などの新型パワートレインでは、蓄電池の直流電源で駆動用モータを動かすためにインバータによって直流を交流に変換する。また、回生エネルギを回収するため、コンバータで交流を直流変換して蓄電している。このような交直変換器には、IGBTなどのパワーモジュールが使われている。パワーモジュールは半導体のオン抵抗による発熱があり、半導体素子のジャンクション温度以下に抑えるために空冷または水冷による冷却が必要となる。ジャンクション温度はシリコン半導体の場合１５０℃程度であるが、素子の熱劣化を考慮して運転時の素子の温度が通常７５〜８５℃程度に抑えられるような放熱設計が行われている。空冷の場合には金属性の放熱フィンが用いられ、絶縁基板を介してパワーモジュールと接合されている。また、水冷の場合は放熱フィンの代わりに絶縁基板を介して冷却媒体を通す導管を備えた水冷ジャケットがパワーモジュールと接合されている。このため、絶縁基板には厚さ方向への良好な熱伝導性と十分な絶縁性と熱伝導性が要求される。絶縁破壊強度が高いほど、必要となる耐電圧に対して絶縁基板の肉厚を薄くすることができ、伝熱性が向上する。汎用的に用いられている絶縁基板は、簡単に曲がることなく、かつ破損することがない剛直な基板であり、例えば１００μｍから１ｍｍ程度の厚さのものである。この絶縁基板には、現在、比較的高い熱伝導率をもつ窒化ケイ素などのセラミクス板が使用されているが、低コスト化の観点から基板厚さをより薄くすることが求められている。 In new powertrains such as hybrid vehicles, electric vehicles, and fuel cell vehicles, an inverter converts direct current into alternating current in order to drive a drive motor with a direct current power source of a storage battery. Moreover, in order to collect | regenerate regenerative energy, alternating current is converted into direct current with a converter, and it accumulates | stores. Such an AC / DC converter uses a power module such as an IGBT. The power module generates heat due to the on-resistance of the semiconductor and needs to be cooled by air cooling or water cooling in order to keep it below the junction temperature of the semiconductor element. The junction temperature is about 150 ° C. in the case of a silicon semiconductor, but heat dissipation design is performed so that the temperature of the element during operation is normally suppressed to about 75 to 85 ° C. in consideration of thermal degradation of the element. In the case of air cooling, a metal heat radiation fin is used and joined to the power module through an insulating substrate. In the case of water cooling, a water cooling jacket provided with a conduit for passing a cooling medium through an insulating substrate instead of the radiation fin is joined to the power module. For this reason, the insulating substrate is required to have good thermal conductivity in the thickness direction and sufficient insulation and thermal conductivity. The higher the dielectric breakdown strength, the thinner the insulating substrate can be with respect to the required withstand voltage, thereby improving the heat conductivity. The insulating substrate used for general purposes is a rigid substrate that is not easily bent and is not damaged, and has a thickness of, for example, about 100 μm to 1 mm. Currently, a ceramic plate such as silicon nitride having a relatively high thermal conductivity is used for this insulating substrate, but it is required to reduce the thickness of the substrate from the viewpoint of cost reduction.
ところが、製造の困難性および機械的強度の問題から、セラミックス板の更なる薄肉化には限界がある。そこで、これに代わるものとして高分子絶縁材料と充填材から構成される複合絶縁材料を用いた絶縁基板（複合絶縁板）の研究開発が各所で進められている。 However, there is a limit to the further thinning of the ceramic plate due to the difficulty of manufacturing and the problem of mechanical strength. Therefore, as an alternative, research and development of an insulating substrate (composite insulating plate) using a composite insulating material composed of a polymer insulating material and a filler has been promoted in various places.
開発が進められている複合絶縁材料の多くは熱硬化性樹脂であるエポキシ樹脂等の母材と樹脂に比べ高い熱伝導率を持つアルミナ等の無機充填材とを、機械的に混合して作製される。 Many of the composite insulating materials under development are made by mechanically mixing a base material such as epoxy resin, which is a thermosetting resin, and an inorganic filler such as alumina, which has a higher thermal conductivity than the resin. Is done.
かかる充填材としては、熱伝導率および熱拡散率が高いことほど良く、電気的特性としては体積固有抵抗率および、絶縁破壊強度が高いほど良い。かかる性質を有し、更に安価であることから、アルミナが一般的に選択されている。 As such a filler, the higher the thermal conductivity and the thermal diffusivity, the better, and the higher the electrical resistivity, the better the volume resistivity and dielectric breakdown strength. Alumina is generally selected because it has such properties and is inexpensive.
かかる複合絶縁板では、アルミナ充填材粒子どうしの接触による粒子間の空隙部分が電気絶縁上の弱点であり、アルミナ充填材粒子の偏在により樹脂との誘電率の違いによる電界集中が発生し、絶縁性能を低下させるため、セラミック板に置き換わる性能のものはない。このような問題点を解決するため、充填材粒子の分散性を改善するような研究や、ナノ粒子を用いた研究も行われており、６〜１２Ｗ／ｍ・Ｋ程度の熱伝導率をもつ複合絶縁板が開発されている（非特許文献１）。 In such a composite insulating plate, voids between particles due to contact between alumina filler particles are weak points in electrical insulation, and due to uneven distribution of alumina filler particles, electric field concentration occurs due to a difference in dielectric constant from the resin, resulting in insulation. There is no replacement for the ceramic plate to reduce the performance. In order to solve such problems, research for improving the dispersibility of filler particles and research using nanoparticles have been conducted, and the thermal conductivity is about 6 to 12 W / m · K. A composite insulating plate has been developed (Non-Patent Document 1).
更には、アルミナ以外にも、無機充填材としては、窒化アルミ（AlN）、窒化ケイ素（SiC）、窒化ホウ素（BN）、などが知られており、この中でBNは六方晶系のもので体積抵抗率はアルミナ同等であるが、その熱伝導率はアルミナの１５〜３０Ｗ／ｍ・Ｋに比べ、結晶方向によって異方性はあるものの２〜１０倍（６０〜２００Ｗ／ｍ・Ｋ）の高い値を示している。窒化アルミは熱伝導率が１５０〜２００Ｗ／ｍ・Ｋで良好な熱伝導性を有しているが、極めて高コストである。このため、熱伝導性に異方性をもっているが、BNを複合絶縁板の充填材として使いこなす研究が各所で行われている（非特許文献２）。 Furthermore, in addition to alumina, as the inorganic filler, aluminum nitride (AlN), silicon nitride (SiC), boron nitride (BN), and the like are known. Among them, BN is a hexagonal system. Although the volume resistivity is equivalent to alumina, its thermal conductivity is 2 to 10 times (60 to 200 W / m · K) of anisotropy depending on the crystal direction compared to 15 to 30 W / m · K of alumina. It shows a high value. Aluminum nitride has a thermal conductivity of 150 to 200 W / m · K and good thermal conductivity, but is extremely expensive. For this reason, although it has anisotropy in thermal conductivity, studies have been conducted in various places to make full use of BN as a filler for composite insulating plates (Non-patent Document 2).
例えば、特許文献１および非特許文献３に開示される技術は、エポキシ樹脂のような熱硬化性樹脂を用いて硬化前の液体状態でBNを混合し、混錬した上で硬化して複合絶縁板を作製するに際し、硬化前の液体状態で、電界によってBNを電気力線に沿って配向させる方法を示している。 For example, the technology disclosed in Patent Document 1 and Non-Patent Document 3 uses a thermosetting resin such as an epoxy resin to mix BN in a liquid state before curing, knead and then cure to composite insulation. It shows a method of orienting BN along lines of electric force by an electric field in a liquid state before curing when producing a plate.
また、前掲の非特許文献４では熱可塑性樹脂を絶縁母材として用いて複合絶縁板を作ることも試みられている。 Further, in the aforementioned Non-Patent Document 4, an attempt is made to make a composite insulating plate using a thermoplastic resin as an insulating base material.
しかしながら、前掲の特許文献１および非特許文献３の方法では、エポキシ樹脂の常温動粘度は最低でも１０センチストークス程度で粘性が高く電界によってBNをほとんど配向できない。更に、前掲の非特許文献１でもエポキシ樹脂の硬化前の液体状態のものにBNを混ぜ、遠心によって粒子を配向させる方法が開示されているが、液の粘性のため、配向させることができない。 However, in the methods of Patent Document 1 and Non-Patent Document 3 described above, the normal temperature kinematic viscosity of the epoxy resin is at least about 10 centistokes, and the viscosity is so high that BN cannot be oriented almost by an electric field. Further, the above-mentioned Non-Patent Document 1 discloses a method in which BN is mixed in a liquid state before curing of the epoxy resin and particles are oriented by centrifugation, but cannot be oriented due to the viscosity of the liquid.
非特許文献1および２に開示された複合絶縁板では、絶縁破壊強度は市場の要求する１００ｋV／ｍｍ超えるものは、熱伝導率が１Ｗ／ｍ・Ｋ程度以下で市場の要求する１０Ｗ／ｍ・Ｋに比べ極めて低い値である。一方、熱伝導率が１０Ｗ／ｍ・Ｋを超えるものは、絶縁破壊強度は６０ｋV／ｍｍで市場の要求値に比べ低い値に留まっており、熱伝導率と絶縁破壊強度との両者を満足するものは得られていない。 In the composite insulating plates disclosed in Non-Patent Documents 1 and 2, if the dielectric breakdown strength exceeds 100 kV / mm as required by the market, the thermal conductivity is about 1 W / m · K or less and 10 W / m · as required by the market. It is a very low value compared with K. On the other hand, when the thermal conductivity exceeds 10 W / m · K, the dielectric breakdown strength is 60 kV / mm, which is lower than the market requirement, and satisfies both the thermal conductivity and the dielectric breakdown strength. Nothing has been obtained.
更に、前掲の非特許文献４では熱可塑性樹脂を絶縁母材として用いて複合絶縁板を作ることも試みられている。熱可塑性樹脂としてポリプロピレンを用い、熱可塑温度以上に加熱した後にBNを溶融混錬して射出成形による方法が示されているが、溶融状態の熱可塑性樹脂では、前述の電界や遠心力による配向が困難な程、粘性が高い上、BNを均一分散する高度な製造技術が必要である。 Further, in the aforementioned Non-Patent Document 4, an attempt is made to make a composite insulating plate using a thermoplastic resin as an insulating base material. Polypropylene is used as the thermoplastic resin, and BN is melt-kneaded after being heated to a temperature above the thermoplastic temperature, and injection molding has been shown. The more difficult it is, the higher the viscosity and the advanced manufacturing technology that uniformly disperses BN is required.
このような先行技術文献に示されているように、良好な熱伝導性と十分な絶縁性を共に有する複合絶縁板は、未だ提供されていない。 As shown in such prior art documents, a composite insulating plate having both good thermal conductivity and sufficient insulation has not been provided yet.
本発明は上記問題点に鑑みてなされたものであって、その目的とするところは、母材の絶縁性樹脂の中で熱伝導性充填材の配向度を適性に制御し、更に充填密度を改善することで、良好な熱伝導率と十分な絶縁破壊強度を有する複合絶縁板およびその製造方法を提供するところにある。 The present invention has been made in view of the above problems, and its object is to appropriately control the degree of orientation of the heat conductive filler in the insulating resin of the base material, and to further reduce the packing density. The improvement is to provide a composite insulating plate having good thermal conductivity and sufficient dielectric breakdown strength and a method for manufacturing the same.
この目的を達成するために請求項１記載の複合絶縁板は、熱可塑性樹脂とその熱可塑性樹脂よりも熱伝導性の高い板状の熱伝導性充填材粒子とを含む複合絶縁板において、前記複合絶縁板の密度が１．８ｇ／ｃｍ３以上で、かつ板の厚み方向の熱伝導率が１５Ｗ／ｍ・Ｋ以上で、３５Ｗ／ｍ・Ｋ以下となるように熱伝導性充填材粒子が配向しているものであって、前記厚み方向に対する絶縁破壊強度が９５ｋV/ｍｍ以上であるものである。 In order to achieve this object, the composite insulating plate according to claim 1 is a composite insulating plate comprising a thermoplastic resin and plate-like thermally conductive filler particles having higher thermal conductivity than the thermoplastic resin. The thermally conductive filler particles are such that the density of the composite insulating plate is 1.8 g / cm 3 or more and the thermal conductivity in the thickness direction of the plate is 15 W / m · K or more and 35 W / m · K or less. It is oriented and has a dielectric breakdown strength of 95 kV / mm or more in the thickness direction.
請求項２記載の複合絶縁板は、請求項１に記載の複合絶縁板において、前記熱伝導性充填材粒子が六方晶窒化ホウ素粒子であるものである。 A composite insulating plate according to claim 2 is the composite insulating plate according to claim 1, wherein the thermally conductive filler particles are hexagonal boron nitride particles.
請求項３記載の複合絶縁板は、請求項１または２に記載の複合絶縁板において、前記熱可塑性樹脂がポリ（メタ）アクリル酸エステル系高分子化合物であるものである。 A composite insulating plate according to claim 3 is the composite insulating plate according to claim 1 or 2, wherein the thermoplastic resin is a poly (meth) acrylate polymer compound.
請求項４記載の複合絶縁板の製造方法は、 熱伝導性充填材粒子を主粒子とし、その主粒子表面に熱可塑性樹脂粒子を吸着させてなる複合粒子が液体中に含まれたものであって、該熱可塑性樹脂の溶融粘度よりも低い粘性のスラリーを作製するスラリー作製工程と、所定の容積を有するキャビティ内に前記スラリー作製工程により作製したスラリーを導入する導入工程と、前記導入工程でキャビティ内に導入したスラリーに対し所定方向へ遠心力を作用させることにより、固液分離により複合粒子を前記液体から分離させつつキャビティの遠心力の作用方向に対して交差する面へ堆積させる遠心分離工程と、前記遠心分離工程によりキャビティに堆積させた前記複合粒子の堆積物に対し、前記遠心力の作用方向と同じ方向へ押圧して成形体を形成する押圧工程と、前記押圧工程により作られた前記成形体をキャビティから取り出し、前記熱可塑性樹脂粒子を構成する樹脂の融点温度以上の環境下にて、前記押圧工程での押圧方向と交差する方向へプレスするホットプレス工程と、を含むものである。 According to a fourth aspect of the present invention, there is provided a method for producing a composite insulating plate, comprising: heat conductive filler particles as main particles; and composite particles formed by adsorbing thermoplastic resin particles on the surfaces of the main particles. A slurry preparation step of preparing a slurry having a viscosity lower than the melt viscosity of the thermoplastic resin, an introduction step of introducing the slurry prepared by the slurry preparation step into a cavity having a predetermined volume, and the introduction step Centrifugation in which composite particles are separated from the liquid by solid-liquid separation and deposited on a surface that intersects the direction of centrifugal force action by applying a centrifugal force to the slurry introduced into the cavity in a predetermined direction. Pressing the composite particles deposited in the cavities in the process and the centrifugal separation process in the same direction as the direction of the centrifugal force. The pressing step to be formed and the molded body made by the pressing step are taken out from the cavity, and intersect the pressing direction in the pressing step in an environment equal to or higher than the melting point temperature of the resin constituting the thermoplastic resin particles. A hot pressing step of pressing in the direction.
請求項５の複合絶縁板の製造方法は、請求項４に記載の複合絶縁物の製造方法において、前記複合粒子が、板状の熱伝導性充填材粒子に熱可塑性樹脂粒子を吸着させたものであって、熱伝導性充填材粒子の平均粒径に対して熱可塑性樹脂粒子の平均粒径が１／９から１／１５であるものである。 The method for manufacturing a composite insulating plate according to claim 5 is the method for manufacturing a composite insulating material according to claim 4, wherein the composite particles are obtained by adsorbing thermoplastic resin particles to plate-like thermally conductive filler particles. The average particle size of the thermoplastic resin particles is 1/9 to 1/15 with respect to the average particle size of the thermally conductive filler particles.
請求項６の複合絶縁板の製造方法は、請求項４または５に記載の複合絶縁板の製造方法において、前記複合粒子は、液体中で、表面の電荷を正または負に帯電させた熱伝導性充填材粒子と該熱伝導性充填材粒子とは逆の電荷を表面に帯電させた熱可塑性樹脂粒子とを混合し、前記熱伝導性充填材粒子の表面に前記熱可塑性樹脂粒子を吸着させてなるものである。 The method of manufacturing a composite insulating plate according to claim 6 is the method of manufacturing a composite insulating plate according to claim 4 or 5, wherein the composite particles are heat conduction in which a surface charge is positively or negatively charged in a liquid. The conductive filler particles and the thermoplastic resin particles charged on the surface with a charge opposite to that of the thermally conductive filler particles are mixed, and the thermoplastic resin particles are adsorbed on the surface of the thermally conductive filler particles. It will be.
本発明の複合絶縁板によれば、その密度が１．８ｇ／ｃｍ３以上であるため、基板内に密に充填された熱伝導性充填材粒子によって、熱伝導性充填材粒子相互の接点を多く形成することができ、熱伝導性の向上を実現できる。また、複合絶縁板の厚み方向の熱伝導率が１５Ｗ／ｍ・Ｋ以上から３５Ｗ／ｍ・Ｋ以下となるように熱伝導性充填材料粒子が熱の伝達方向に配向している。ここで、配向度の向上は、厚み方向への熱伝導性を向上させることができ、また、その配向度が熱伝導率で３５Ｗ／ｍ・Ｋ以下となる状態とすることで絶縁破壊強度の低下を抑制できる。よって、厚み方向に対する良好な熱伝導性を備えつつ、９５kV/ｍｍ以上となる絶縁破壊強度を有する複合絶縁板を提供できるという効果がある。 According to the composite insulating plate of the present invention, since the density thereof is 1.8 g / cm 3 or more, the heat conductive filler particles closely packed in the substrate can be used to provide contact between the heat conductive filler particles. Many can be formed, and an improvement in thermal conductivity can be realized. Further, the heat conductive filler particles are oriented in the heat transfer direction so that the thermal conductivity in the thickness direction of the composite insulating plate is 15 W / m · K or more and 35 W / m · K or less. Here, the improvement of the degree of orientation can improve the thermal conductivity in the thickness direction, and the dielectric breakdown strength can be improved by setting the degree of orientation to 35 W / m · K or less in terms of thermal conductivity. Reduction can be suppressed. Therefore, there is an effect that it is possible to provide a composite insulating plate having a dielectric breakdown strength of 95 kV / mm or more while having good thermal conductivity in the thickness direction.
本発明の複合絶縁板の製造方法によれば、複合粒子が液体中に含まれたスラリーを所定の容積を有するキャビティ内に導入し、所定の方向に遠心力を作用させることにより、固液分離により複合粒子を前記液体から分離しつつキャビティ内の遠心力の作用方向に対して交差する面に配向した状態で堆積、その後に遠心力の作用方向に押圧することで複合粒子が配向した緻密な成形体を作る効果がある。次に熱可塑性樹脂の融点温度以上の環境温度下で、成形体を遠心力の作用方向と交差する方向にプレスすることで複合絶縁板の厚さ方向に個々の熱伝導性充填材粒子の距離が短縮化されて、粒子の外表面にボイドがなく、かつ熱可塑性樹脂で被覆させ、良好な熱伝導性と十分な絶縁破壊強度とを兼ね備えた複合絶縁板を提供できるという効果がある。 According to the method for producing a composite insulating plate of the present invention, solid-liquid separation is performed by introducing slurry containing composite particles in a liquid into a cavity having a predetermined volume and applying a centrifugal force in a predetermined direction. The composite particles are deposited in a state where the composite particles are separated from the liquid while being oriented in a plane that intersects the direction of the centrifugal force in the cavity, and then pressed in the direction of the centrifugal force. There is an effect of making a molded body. Next, the distance between the individual thermally conductive filler particles in the thickness direction of the composite insulating plate by pressing the molded body in a direction crossing the direction of the centrifugal force at an environmental temperature equal to or higher than the melting point temperature of the thermoplastic resin. Thus, there is an effect that it is possible to provide a composite insulating plate which has no voids on the outer surface of the particles and is coated with a thermoplastic resin and has both good thermal conductivity and sufficient dielectric breakdown strength.
以下に本発明の実施形態について詳細に説明する。 Hereinafter, embodiments of the present invention will be described in detail.
複合絶縁板の一実施形態は、熱可塑性樹脂の母材の中に板状の熱伝導性充填材粒子が分散されたものである。 In one embodiment of the composite insulating plate, plate-like thermally conductive filler particles are dispersed in a thermoplastic resin base material.
複合絶縁板に含まれる熱可塑性樹脂は、絶縁性を有し、その体積固有抵抗は１０１５Ωｃｍ程度である。具体的にはかかる熱可塑性樹脂としては、たとえば、ポリエチレン(PE)、エチレン酢酸ビニル共重合体（EVA）,ポリプロピレン（PP）、ポリスチレン（PS）、ABS樹脂、ポリメタクリル酸メチル（PMMA）、ポリ塩化ビニル（PVC）、ポリエチレンテレフタレート、ポリエチレンナフタレート（PEN）、ポリフェニレンスルファイド（PPS）、ポリアミドイミド（PAI）、ポリテトラフルオロエチレン（PTFE）、ポリエーテルエーテルケトン樹脂（PEEK）などが例示できる。これらの熱可塑性樹脂は、放熱設計の前提となる使用最高温度を勘案して選定される。なお、熱可塑性樹脂として1種類のものを用いても良く、複数種類のものを混合して用いても良い。更には、ホモポリマーであっても良く、共重合体であってもよい。 The thermoplastic resin contained in the composite insulating plate has an insulating property, and its volume resistivity is about 10 15 Ωcm. Specifically, such thermoplastic resins include, for example, polyethylene (PE), ethylene vinyl acetate copolymer (EVA), polypropylene (PP), polystyrene (PS), ABS resin, polymethyl methacrylate (PMMA), poly Examples include vinyl chloride (PVC), polyethylene terephthalate, polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyamideimide (PAI), polytetrafluoroethylene (PTFE), and polyether ether ketone resin (PEEK). These thermoplastic resins are selected in consideration of the maximum operating temperature, which is a precondition for heat dissipation design. One type of thermoplastic resin may be used, or a plurality of types may be mixed and used. Furthermore, it may be a homopolymer or a copolymer.
一般に製造時の成形工程での加熱温度が高い程、冷却に伴い熱可塑性樹脂と充填材との界面に応力が発生した状態となり、界面での剥離を誘発しやすい。一方、ガラス転移点が高いほど耐熱性が優れているため、より高温下での使用に好適に用いることができる。 Generally, the higher the heating temperature in the molding process at the time of manufacture, the more stress is generated at the interface between the thermoplastic resin and the filler with cooling, and the peeling at the interface tends to be induced. On the other hand, since the higher the glass transition point, the better the heat resistance, it can be suitably used for use at higher temperatures.
例えば、自動車用Si系パワーモジュールの最高使用温度１００〜１２０℃に近いが、実際のモジュールでは、熱劣化を考慮し、熱設計温度は６０〜７０℃となる。好適には熱可塑性樹脂はポリ（メタ）アクリル酸エステルである。ポリ（メタ）アクリル酸エステルはアクリル酸エステルまたはメタクリル酸エステルの重合体で、絶縁特性として体積固有抵抗率は１０１６Ωｃｍで良好な値である。 For example, although the maximum operating temperature of the Si-based power module for automobiles is close to 100 to 120 ° C., the actual module has a thermal design temperature of 60 to 70 ° C. in consideration of thermal degradation. Preferably the thermoplastic resin is a poly (meth) acrylic ester. Poly (meth) acrylic acid ester is a polymer of acrylic acid ester or methacrylic acid ester, and has a good volume resistivity of 10 16 Ωcm as an insulating property.
SiC系パワーモジュールでは、運転最高温度が２００℃程度で、熱設計温度は１００℃を超えることになるため、耐熱温度が２００℃を超える熱可塑性樹脂が選択され、好適には耐熱温度が２５０℃であるPTFEやPAIがその候補である。 For SiC power modules, the maximum operating temperature is about 200 ° C and the thermal design temperature exceeds 100 ° C. Therefore, a thermoplastic resin having a heat-resistant temperature exceeding 200 ° C is selected, and preferably the heat-resistant temperature is 250 ° C. These are PTFE and PAI.
複合絶縁板に含まれる熱伝導性充填材粒子は、熱伝導率および熱拡散率が高いほど好ましく、電気的には体積固有抵抗率および絶縁破壊強度が高いほど良い。 The thermally conductive filler particles contained in the composite insulating plate are preferably as the thermal conductivity and thermal diffusivity are higher, and are electrically better as the volume resistivity and dielectric breakdown strength are higher.
一般には熱伝導性充填材粒子としては、アルミナ（Al2O3）、シリカ（SiO２）アルミナ水和物（Al２O3・H2O）、酸化チタン（TiO2）、窒化アルミ（AlN）、窒化ホウ素（BN）、窒化ケイ素（SiC）などが例示される。 Generally, the heat conductive filler particles include alumina (Al 2 O 3 ), silica (SiO 2 ) alumina hydrate (Al 2 O 3 .H 2 O), titanium oxide (TiO 2 ), aluminum nitride (AlN ), Boron nitride (BN), silicon nitride (SiC), and the like.
ここで、本実施形態の熱伝導性充填材粒子は、粒子形状が板状であるものが用いられる。「板状」とは、層状で六方晶の結晶構造を有して粒子が板のような形状であることを言う。また、熱伝導性充填材粒子は、熱伝導性に異方性を有していても良い。「熱伝導の異方性」とは板状の熱伝導性充填材粒子の面内方向と厚さ方向で熱伝導率が異なることを言う。熱伝導性充填材粒子は、その平均粒径が、大きくなるにつれ粒子間に隙間ができ絶縁板内の密度が上がらず、母材の樹脂が多くなり、熱伝導性が上がらない。また、平均粒径が小さくなるにつれて、充填密度は上がるが、母材との界面が多くなり、絶縁性能低下要因になる。よって、熱伝導性充填材粒子の平均粒径が、０．５μｍ〜６０μｍのものが用いられ、より好適には、平均粒径が２０μｍ〜５０μｍのものが用いられる。 Here, as the thermally conductive filler particles of this embodiment, those having a particle shape of a plate shape are used. “Plate-like” means that the layer has a hexagonal crystal structure and the particles have a plate-like shape. Further, the heat conductive filler particles may have anisotropy in heat conductivity. “Anisotropy of heat conduction” means that the thermal conductivity is different between the in-plane direction and the thickness direction of the plate-like thermally conductive filler particles. As the average particle size of the thermally conductive filler particles increases, gaps are formed between the particles, the density in the insulating plate does not increase, the resin of the base material increases, and the thermal conductivity does not increase. In addition, as the average particle size decreases, the packing density increases, but the interface with the base material increases, which causes a decrease in insulation performance. Therefore, the heat conductive filler particles having an average particle size of 0.5 μm to 60 μm are used, and more preferably those having an average particle size of 20 μm to 50 μm.
上記した熱伝導性充填材粒子において好適には六方晶系窒化ホウ素（以降BN）が用いられる。BN粒子の結晶は層状結晶であることから結晶面に沿ってヘキカイするため、BN粒子は板状となり、一般的に平均粒径は０．５〜６０μｍで、厚さは０．１〜３μｍ程度である。BNの体積抵抗率は一般的に使用されているアルミナと同等である。BNの熱伝導率はアルミナに比べ厚さ方向で２倍で、面内方向で１０倍である。 In the above-described thermally conductive filler particles, hexagonal boron nitride (hereinafter referred to as BN) is preferably used. Since the BN particle crystal is a layered crystal, it crawls along the crystal plane, so the BN particle is plate-like, generally having an average particle size of 0.5 to 60 μm and a thickness of about 0.1 to 3 μm. It is. The volume resistivity of BN is equivalent to the commonly used alumina. The thermal conductivity of BN is twice that in the thickness direction and 10 times that in the in-plane direction compared to alumina.
本実施形態では、熱伝導性充填材粒子の粒子径は、レーザー回折散乱法によって測定されたものが用いられる。たとえば、レーザー散乱式粒度測定装置（島津製作所製、ＳＡＬＤ−３１００）を用いて粒度分布を測定し、累積分布率５０重量％での粒度（Ｄ５０）を「平均粒径」という。 In the present embodiment, the particle diameter of the thermally conductive filler particles is measured by a laser diffraction scattering method. For example, the particle size distribution is measured using a laser scattering particle size measuring device (SALD-3100, manufactured by Shimadzu Corporation), and the particle size (D50) at a cumulative distribution rate of 50% by weight is referred to as “average particle size”.
特に限定するものでもないが、本発明のBNの具体例としては、「ＰＴ−１１０（商品名）」（モーメンティブパーフォーマンスマテリアルズジャパン合同会社製、平均粒径４５μｍ）があげられる。これに限らず板状の熱伝導性充填材粒子は粉砕・解砕することで所定の平均粒径の粒子を得ることができる。 Although not specifically limited, as a specific example of the BN of the present invention, “PT-110 (trade name)” (manufactured by Momentive Performance Materials Japan GK, average particle size of 45 μm) can be given. Not limited to this, the plate-like thermally conductive filler particles can be crushed and crushed to obtain particles having a predetermined average particle diameter.
複合絶縁板における熱伝導性充填材粒子の配合量は、４０〜８０体積％の範囲である。熱伝導性充填材粒子の配合量が４０体積％以下であると、熱伝導性が十分得られず、配合量が８０体積％以上であると熱伝導性充填材粒子の外表面の熱可塑性樹脂が不足し、絶縁破壊強度が不十分な複合絶縁板となる。好適には配合量が、５５〜７０体積％の範囲である。 The compounding quantity of the heat conductive filler particle in a composite insulating board is the range of 40-80 volume%. When the blending amount of the thermally conductive filler particles is 40% by volume or less, sufficient thermal conductivity cannot be obtained, and when the blending amount is 80% by volume or more, the thermoplastic resin on the outer surface of the thermally conductive filler particles. Becomes a composite insulating plate with insufficient dielectric breakdown strength. The blending amount is preferably in the range of 55 to 70% by volume.
図１は本実施形態の複合絶縁板の断面の模式図である。本複合絶縁板は、上面視矩形上に形成されており、紙面上側が複合絶縁板の表面となるよう表示されている。 FIG. 1 is a schematic diagram of a cross section of the composite insulating plate of the present embodiment. The composite insulating plate is formed on a rectangular shape in a top view, and is displayed so that the upper side of the paper is the surface of the composite insulating plate.
かかる複合絶縁板は、熱伝導性充填材粒子１が熱可塑性樹脂２に分散され、熱伝導性充填材粒子は熱可塑性樹脂が被覆し、相互に接着し熱可塑性樹脂中に存在した状態である。使用状態においてその両面が半導体素子および放熱フィンと接するようにセットされる。使用に際しては、図1中の矢印方向が電界の印加方向となる。本複合絶縁板は、熱を伝播させたい方向（複合絶縁板の厚み方向）に対し、熱伝導性充填材粒子１の面内方向が所定の配向度の範囲で配向している。 In such a composite insulating plate, the thermally conductive filler particles 1 are dispersed in the thermoplastic resin 2, and the thermally conductive filler particles are coated with the thermoplastic resin, adhered to each other, and present in the thermoplastic resin. . In use, it is set so that both surfaces thereof are in contact with the semiconductor element and the heat radiating fins. In use, the direction of the arrow in FIG. 1 is the direction in which the electric field is applied. In the present composite insulating plate, the in-plane direction of the thermally conductive filler particles 1 is oriented within a predetermined orientation range with respect to the direction in which heat is desired to propagate (the thickness direction of the composite insulating plate).
ここで、本実施形態において、複合絶縁板を構成する熱伝導性充填材粒子の「配向度」とは、複合絶縁板の厚み方向（上下方向）を基準とした場合に、板状の熱伝導性充填材粒子１のそれぞれの面内方向が、厚み方向に対しどの程度傾いているか（整列しているか）を示す指標である。すなわち、熱を伝搬させたい方向への熱伝導性充填材粒子１の整列の度合いであり、複合絶縁板が示す熱伝導率で規定する。熱伝導性充填材粒子の面内方向が複合絶縁板の板面に対してつくる角度は、複合絶縁板内に存在する個々の熱伝導性充填材粒子ごとに一定ではない。複合絶縁板の厚さ方向の単位体積当たりの熱抵抗は、その単位体積内に存在する熱伝導性充填材粒子の熱抵抗と熱伝導性充填材粒子の隙間を埋める熱可塑性樹脂の熱抵抗の直列および並列の合成で計算できる。このため、複合絶縁板の熱伝導率は複合絶縁板内の熱伝導性充填材粒子の全体の配向度と一定の関係がある。従って、複合絶縁板の熱伝導性充填材粒子の配向度は、複合絶縁板の熱伝導度で表すことができる。 Here, in this embodiment, the “degree of orientation” of the thermally conductive filler particles constituting the composite insulating plate is a plate-like heat conduction when the thickness direction (vertical direction) of the composite insulating plate is used as a reference. This is an index indicating how much the in-plane direction of each of the filler particles 1 is inclined (aligned) with respect to the thickness direction. That is, it is the degree of alignment of the thermally conductive filler particles 1 in the direction in which heat is desired to be transmitted, and is defined by the thermal conductivity exhibited by the composite insulating plate. The angle formed by the in-plane direction of the thermally conductive filler particles with respect to the plate surface of the composite insulating plate is not constant for each individual thermally conductive filler particle present in the composite insulating plate. The thermal resistance per unit volume in the thickness direction of the composite insulating plate is the thermal resistance of the thermal conductive filler particles existing in the unit volume and the thermal resistance of the thermoplastic resin filling the gap between the thermal conductive filler particles. It can be calculated by serial and parallel synthesis. For this reason, the thermal conductivity of the composite insulating plate has a certain relationship with the overall degree of orientation of the thermally conductive filler particles in the composite insulating plate. Accordingly, the degree of orientation of the thermally conductive filler particles of the composite insulating plate can be expressed by the thermal conductivity of the composite insulating plate.
本実施形態の複合絶縁板内の熱伝導性充填材粒子の配向度は複合絶縁板の熱伝導率が１５Ｗ／ｍ・Ｋ以上から３５Ｗ／ｍ・Ｋ以下となる配向度である。熱伝導率１５Ｗ／ｍ・Ｋ以下となる配向度では、複合絶縁板としての熱伝導性は不十分である。熱伝導率３５Ｗ／ｍ・Ｋ以上となる配向では、複合絶縁板の絶縁破壊強度が急激に悪化する。 The orientation degree of the thermally conductive filler particles in the composite insulating plate of this embodiment is an orientation degree at which the thermal conductivity of the composite insulating plate is from 15 W / m · K to 35 W / m · K. When the degree of orientation is 15 W / m · K or less, the thermal conductivity as a composite insulating plate is insufficient. In the orientation with a thermal conductivity of 35 W / m · K or more, the dielectric breakdown strength of the composite insulating plate is rapidly deteriorated.
本実施形態の複合絶縁板は絶縁破壊強度が９５ｋＶ／ｍｍ以上のものである。好適には絶縁破壊強度の平均値が１１０ｋＶ／ｍｍである。絶縁破壊強度が９５ｋＶ／ｍｍ以下では、複合絶縁板の熱伝導性充填材粒子の配向度が高く、複合絶縁板の厚さ方向に熱伝導性充填材粒子の面内方向がつながり絶縁上の弱点が多くなる。 The composite insulating plate of this embodiment has a dielectric breakdown strength of 95 kV / mm or more. Preferably, the average value of the dielectric breakdown strength is 110 kV / mm. When the dielectric breakdown strength is 95 kV / mm or less, the degree of orientation of the heat conductive filler particles in the composite insulating plate is high, and the in-plane direction of the heat conductive filler particles is connected to the thickness direction of the composite insulating plate, resulting in a weak point in insulation. Will increase.
本実施形態の複合絶縁板の密度は１．８ｇ／ｃｍ３以上である。１．８ｇ／ｃｍ３以下では、複合絶縁板としての熱伝導性は不十分である。 The density of the composite insulating plate of this embodiment is 1.8 g / cm 3 or more. If it is 1.8 g / cm 3 or less, the thermal conductivity as a composite insulating plate is insufficient.
複合絶縁板の熱伝導性充填材粒子と熱可塑性樹脂は、それぞれ材料本来の絶縁破壊強度を有しているが、両者の誘電率の違いから、その界面では電界の変歪があり、電界が高い部分ができ絶縁的な弱点となる。このため、配向度を上げていくこと、すなわち電界方向に熱伝導性充填材粒子の面内方向が配向するため、粒子の界面が電界方向に連続してしまうため、絶縁性能は低下する。一方、配向度を上げることで、熱伝導率は向上する。このように配向度は両特性に対して背反するため、絶縁破壊強度が十分で、かつ熱伝導性の良い適切な配向度が存在し、本発明の製造方法の条件を適切に制御し、使用目的で要求される絶縁破壊強度と熱伝導率を発現する複合絶縁板を提供できる。 The thermally conductive filler particles and the thermoplastic resin of the composite insulating plate each have the inherent dielectric breakdown strength, but due to the difference in dielectric constant between them, there is distortion of the electric field at the interface, and the electric field is A high part is made and becomes an insulating weak point. For this reason, since the orientation degree is increased, that is, the in-plane direction of the thermally conductive filler particles is oriented in the electric field direction, the interface of the particles is continuous in the electric field direction, so that the insulating performance is lowered. On the other hand, increasing the orientation degree improves the thermal conductivity. In this way, the degree of orientation contradicts both characteristics, so there is an appropriate degree of orientation with sufficient dielectric breakdown strength and good thermal conductivity, and the conditions of the manufacturing method of the present invention are appropriately controlled and used. It is possible to provide a composite insulating plate that exhibits the required dielectric breakdown strength and thermal conductivity.
上記の複合絶縁板の製造方法に関しても本発明の範囲内である。 The manufacturing method of the composite insulating plate is also within the scope of the present invention.
図２〜図４を参照して、本発明の一実施形態における複合絶縁板の製造方法について説明する。なお、以下の実施形態は本発明を具体化した一例にすぎず、本発明の主旨を変更しない範囲で、実施形態を適宜変更できることは言うまでもない。 With reference to FIGS. 2-4, the manufacturing method of the composite insulating board in one Embodiment of this invention is demonstrated. In addition, the following embodiment is only an example which actualized this invention, and it cannot be overemphasized that embodiment can be changed suitably in the range which does not change the main point of this invention.
図２は第一実施形態の複合絶縁板の製造方法を示す工程図である。
本製造方法では、熱伝導性充填材粒子の表面に熱可塑性樹脂が吸着して複合化された複合粒子を含むスラリーを作製するスラリー工程（Ｓ１）、複合粒子が分散したスラリーを型枠に導入する導入工程（Ｓ２）、型枠内で遠心力によって複合粒子を沈降させ固液分離する遠心分離工程（Ｓ３）、沈降した堆積物を加圧する押圧工程（Ｓ４）、型枠を外して成形体を取出す離型工程（Ｓ５）、成形体を加熱しながら加圧するホットプレス工程（Ｓ６）を経て製造される。
FIG. 2 is a process diagram showing the method for manufacturing the composite insulating plate of the first embodiment.
In this production method, a slurry step (S1) for producing a slurry containing composite particles obtained by adsorbing a thermoplastic resin on the surface of the thermally conductive filler particles and compounding them, and introducing the slurry in which the composite particles are dispersed into the mold Introducing step (S2), centrifugal separation step (S3) in which the composite particles are settled by centrifugal force in the mold and solid-liquid separation, pressing step (S4) in which the sediment is pressed, and the molded body is removed. It is manufactured through a mold release step (S5) for taking out and a hot press step (S6) in which the compact is heated and heated.
なお、本実施形態の製造方法で用いる複合粒子は、予め製作されたものを使うこともできる。なお、本実施形態においては、その製造工程（複合粒子作製工程（Ｓ０）を備えて、複合絶縁板の製造方法が構成されている。 In addition, the composite particle used with the manufacturing method of this embodiment can also use what was manufactured previously. In addition, in this embodiment, the manufacturing process (composite particle preparation process (S0)) is provided, and the manufacturing method of a composite insulating board is comprised.
本製造工程で使用される複合粒子は、主粒子(粒径が大きい粒子)表面に、主粒子に比べて粒径が小さな吸着粒子が吸着され、全体として１の粒子として一体となった態様を有するものであり、主粒子は、熱伝導性充填材粒子であり、吸着粒子は熱可塑性樹脂粒子である。 The composite particles used in this production process have a mode in which adsorbed particles having a smaller particle size than the main particles are adsorbed on the surface of the main particles (particles having a large particle size), and are integrated as one particle as a whole. The main particles are thermally conductive filler particles, and the adsorbed particles are thermoplastic resin particles.
主粒子は平均粒径０．５μｍから６０μｍの熱伝導性充填材粒子で、その主粒子の平均粒径に対して吸着粒子の平均粒径は１／９〜１／１５の範囲である。好適には１／１０である。 The main particles are thermally conductive filler particles having an average particle size of 0.5 to 60 μm, and the average particle size of the adsorbed particles is in the range of 1/9 to 1/15 with respect to the average particle size of the main particles. It is preferably 1/10.
複合粒子の主粒子である熱伝導性充填材粒子と、吸着粒子である熱可塑性樹脂粒子のそれぞれの平均粒径の関係は、複合絶縁板の絶縁破壊強度および熱伝導率に大きく影響する。ここで、図３を参照して、この主粒子の平均粒径と吸着粒子の平均粒径との関係が、複合絶縁板の絶縁破壊強度および熱伝導率に及ぼす影響について説明する。 The relationship between the average particle diameters of the thermally conductive filler particles as the main particles of the composite particles and the thermoplastic resin particles as the adsorbed particles greatly affects the dielectric breakdown strength and the thermal conductivity of the composite insulating plate. Here, with reference to FIG. 3, the influence of the relationship between the average particle size of the main particles and the average particle size of the adsorbed particles on the dielectric breakdown strength and the thermal conductivity of the composite insulating plate will be described.
図３は一例として、主粒子として平均粒径４５μｍのBN粒子、吸着粒子としてPMMA粒子を用い、PMMA粒子の平均粒径を１〜１２μｍまで変化させた場合の絶縁破壊強度および熱伝導率の関係を示した図である。 As an example, Fig. 3 shows the relationship between dielectric breakdown strength and thermal conductivity when BN particles with an average particle size of 45 μm are used as the main particles, PMMA particles are used as the adsorbed particles, and the average particle size of the PMMA particles is varied from 1 to 12 μm. FIG.
図３において、横軸はPMMA粒子の平均粒径、左の縦軸は絶縁破壊強度（ｋＶ／ｍｍ）、右の縦軸は熱伝導率（Ｗ／ｍ・Ｋ）である。また、図３中において、破線にて絶縁破壊強度の変化を示し、実線にて熱伝導率の変化を示している。図３からもわかるように、絶縁破壊強度は、PMMA粒子の粒径の増加に伴い向上し、平均粒径４μｍの場合の絶縁破壊強度は平均粒径１μｍに対して２倍程度に達する。しかし、更に、PMMA粒子の平均粒径を８μｍ、１２μｍと粒径を増加しても絶縁破壊強度は比例して増加しない上、ばらつきも増大する。一方、熱伝導率はPMMA粒径が４μｍ程度までは変わらないが、粒径が大きくなるにつれて低下する傾向を示している。８μｍの場合の熱伝導率では１μｍに比べ１／２程度である。このことから、BN粒子の平均粒径が４５μｍの場合には、PMMA粒子４μｍ以上６μｍ以下の間が最適である。これは、主粒子を４５μｍとした例であるが、主粒子の平均粒径が変わっても図３と同様に吸着粒子の粒径は１／９〜１／１５の範囲とされる。 In FIG. 3, the horizontal axis is the average particle size of PMMA particles, the left vertical axis is the dielectric breakdown strength (kV / mm), and the right vertical axis is the thermal conductivity (W / m · K). In FIG. 3, the change in dielectric breakdown strength is indicated by a broken line, and the change in thermal conductivity is indicated by a solid line. As can be seen from FIG. 3, the dielectric breakdown strength increases as the particle size of the PMMA particles increases, and the dielectric breakdown strength in the case of the average particle size of 4 μm reaches about twice the average particle size of 1 μm. However, even if the average particle size of the PMMA particles is increased to 8 μm and 12 μm, the dielectric breakdown strength does not increase in proportion and the variation also increases. On the other hand, the thermal conductivity does not change until the PMMA particle size is about 4 μm, but shows a tendency to decrease as the particle size increases. The thermal conductivity in the case of 8 μm is about ½ compared to 1 μm. Therefore, when the average particle size of the BN particles is 45 μm, the PMMA particles are optimally between 4 μm and 6 μm. This is an example in which the main particles are 45 μm, but even if the average particle size of the main particles changes, the particle size of the adsorbed particles is in the range of 1/9 to 1/15 as in FIG.
図２に戻って説明する。 Returning to FIG.
複合粒子作製工程（Ｓ０）は、粒径の大きい方の主粒子（熱伝導性充填材粒子）の表面に、粒径の小さい方の粒子（熱可塑性樹脂粒子）を吸着粒子として吸着させて複合粒子を作製する工程であり、本実施形態においては、吸着粒子の表面電荷と、熱伝導性充填材粒子の表面電荷とが、反対電荷となるようにそれぞれ調整された後、液中において両粒子を混合することで、静電引力により熱伝導性充填材粒子（主粒子）に熱可塑性樹脂粒子（吸着粒子）が吸着されるようになっている。 In the composite particle preparation step (S0), a composite is obtained by adsorbing the smaller particle (thermoplastic resin particle) as an adsorbed particle on the surface of the main particle (thermal conductive filler particle) having a larger particle size. In this embodiment, the surface charge of the adsorbed particles and the surface charge of the thermally conductive filler particles are adjusted so as to be opposite charges, and then both particles in the liquid. The thermoplastic resin particles (adsorbed particles) are adsorbed on the thermally conductive filler particles (main particles) by electrostatic attraction.
ここでは、吸着粒子の表面電荷を負に調整し、主粒子の表面電荷を正に調整する場合について説明するが、吸着粒子の表面電荷を正に調整し、主粒子の表面電荷を負に調整しても良い。 Here, the case of adjusting the surface charge of the adsorbed particles to negative and adjusting the surface charge of the main particles to positive will be described, but the surface charge of the adsorbed particles is adjusted to positive and the surface charge of the main particles is adjusted to negative You may do it.
具体的には、親水性を高めると共に負の表面電位を高めさせるため、界面活性剤に吸着粒子を浸漬させた。次に２種類の高分子電解質溶液に順に吸着粒子を浸漬した。これらの濃度は各溶液が吸着粒子表面全体に吸着するために十分な濃度である。なお、各溶液に浸漬する前に吸着粒子はイオン交換水中での洗浄処理を実施した。最終的に吸着粒子の表面電位は負に調整した。一方、同様な方法で熱伝導性充填材粒子の表面電位を最終的に正に調整し、主粒子とした。表面電位を負とした吸着粒子および表面電位を正とした主粒子をイオン交換水中で混合し、静電相互作用により主粒子表面に吸着粒子が吸着した複合粒子を作製した。 Specifically, adsorbed particles were immersed in a surfactant in order to increase hydrophilicity and increase negative surface potential. Next, the adsorbed particles were soaked in order in two types of polymer electrolyte solutions. These concentrations are sufficient for each solution to be adsorbed on the entire surface of the adsorbed particles. The adsorbed particles were washed in ion exchange water before being immersed in each solution. Finally, the surface potential of the adsorbed particles was adjusted to be negative. On the other hand, the surface potential of the thermally conductive filler particles was finally adjusted to be positive by the same method to obtain main particles. Adsorbed particles with negative surface potential and main particles with positive surface potential were mixed in ion-exchanged water to produce composite particles with adsorbed particles adsorbed on the main particle surface by electrostatic interaction.
スラリー工程（Ｓ１）は、複合粒子を低粘度液体と混ぜてスラリー状にする工程である。本工程で、複合粒子を溶解しない低粘度液体を用いてスラリーにすることで低い遠心力で容易に複合粒子を緻密化させることができる。この時の溶媒としてはイオン物質の極力すくない低粘度液体であることが望ましい。低粘度とは、常温の動粘度として１センチストークス程度以下である。好適にはイオン交換水である。 The slurry step (S1) is a step of mixing the composite particles with a low viscosity liquid to form a slurry. In this step, the composite particles can be easily densified with a low centrifugal force by forming a slurry using a low-viscosity liquid that does not dissolve the composite particles. The solvent at this time is preferably a low-viscosity liquid that contains as little ionic material as possible. Low viscosity is about 1 centistokes or less as a kinematic viscosity at normal temperature. Ion exchange water is preferred.
導入工程（Ｓ２）は、Ｓ１の工程で作られたスラリーを型枠に入れる工程である。なお、本実施形態において、型枠には、上面を開口する有底の容器であって、好適には、底部が平面状に形成されたものが用いられる。 The introduction step (S2) is a step of putting the slurry made in the step S1 into a mold. In the present embodiment, the mold is a bottomed container having an open top surface, and preferably has a bottom formed in a flat shape.
遠心分離工程（Ｓ３）は、複合粒子を配向させ、かつ固液分離するために遠心力を加える工程である。遠心力は、遠心力＝（回転数）×（回転中心から複合粒子までの距離）×（複合粒子の重量）で算出する。キャビティ内に導入したスラリーに対して遠心力を作用させることにより、スラリーの複合粒子を液体から分離させつつ、遠心力の作用方向と交差する面に堆積させる。複合粒子を水のような低粘度液体中に分散させスラリーを作ることで、遠心力で複合粒子を容易に沈降させ、得られる複合粒子の堆積物において、複合粒子の配向性を向上させることができる。 The centrifugation step (S3) is a step of applying a centrifugal force to orient the composite particles and separate them into solid and liquid. Centrifugal force is calculated by centrifugal force = (number of rotations) × (distance from center of rotation to composite particle) × (weight of composite particle). By applying a centrifugal force to the slurry introduced into the cavity, the composite particles of the slurry are separated from the liquid and deposited on a surface intersecting with the direction of the centrifugal force. By dispersing the composite particles in a low-viscosity liquid such as water to make a slurry, the composite particles can be easily settled by centrifugal force, and the resulting composite particle deposit can improve the orientation of the composite particles. it can.
低粘度液体中に分散させずに単純にドライな粉体状態で型に入れて機械的圧力のみを加え、複合粒子の密度を高める方法もあるが、複合粒子同士が動き難く、複合粒子が配向出来ない上、粒子間に隙間が出来やすく緻密な構造にならない。 There is also a method to increase the density of composite particles by simply putting them in a mold in a dry powder state without dispersing them in a low-viscosity liquid, and increasing the density of the composite particles. In addition, the gaps between the particles are easily formed and the structure is not dense.
一方、本製造方法によれば、遠心分離工程（S３）の工程では型枠に遠心力を付与することで複合粒子の板面が遠心力の作用方向と交差するように沈降し、複合粒子が配向しつつ沈降して堆積物ができる。 On the other hand, according to this manufacturing method, in the step of the centrifugal separation step (S3), by applying centrifugal force to the formwork, the composite particle is settled so that the plate surface of the composite particle intersects with the direction of action of the centrifugal force. A sediment is formed by sedimentation while being oriented.
押圧工程（Ｓ４）は、遠心分離工程（Ｓ３）の工程で作られた堆積物に遠心力の作用方向と同方向に機械的に面圧を加える工程である。前工程の遠心分離工程（Ｓ３）では、複合粒子の重量で決まる遠心力しか複合粒子に力を与えることが出来ない。このため、前記堆積物の密度を更に上げるため、遠心力の作用方向と同方向に機械的に面圧を加える本工程が設けられている。 The pressing step (S4) is a step of mechanically applying a surface pressure in the same direction as the acting direction of the centrifugal force to the deposit produced in the step of the centrifugal separation step (S3). In the centrifugal step (S3) of the previous step, only the centrifugal force determined by the weight of the composite particle can apply force to the composite particle. For this reason, in order to further increase the density of the deposit, this step of mechanically applying a surface pressure in the same direction as that of the centrifugal force is provided.
離型工程（Ｓ５）は、押圧工程（Ｓ４）でできた成形体を型枠から取り外す工程である。図４は取り出した成形体の模式図である。前記成形体は複合粒子が塊となった状態で、複合粒子を構成する熱伝導性充填材粒子の板面が成形体の底面と整列するように配向した状態である。 The mold release step (S5) is a step of removing the molded body made in the pressing step (S4) from the mold. FIG. 4 is a schematic view of the molded body taken out. The molded body is in a state where the composite particles are in a lump and oriented so that the plate surface of the thermally conductive filler particles constituting the composite particles is aligned with the bottom surface of the molded body.
ホットプレス工程（Ｓ６）は、遠心力と交差する方向（図４に図示）つまり複合粒子の面内方向に熱可塑性樹脂の融点温度以上、耐熱温度以下で加熱しながら、プレスする工程である。ホットプレスの継続時間は熱可塑性樹脂の溶融温度で適宜決められた時間である。この工程により、熱可塑性樹脂は融点温度以上になり、溶融して熱伝導性充填材粒子の界面に流動して隙間をなくすように樹脂層を形成する。ホットプレス時の温度は、熱可塑性樹脂の組成で決まる融点温度以上で設定する。ホットプレスの加熱温度は、高いほうが樹脂の流動性が高まり、充填剤粒子間に流れ込み安くなる。このため、熱伝導率を上げるために充填剤粒子の充填密度を上げ、充填粒子間の隙間が小さくなっても、樹脂が流れ込み安くなるため絶縁破壊強度の低下を抑制することができる。加熱温度の上限は樹脂を構成する高分子が劣化し始める温度より低い温度である。ホットプレスの圧力は高くすることで、熱伝導性充填材粒子間の距離を短くすると共に、熱可塑性樹脂内のボイドを追い出すことができ、複合絶縁板の密度が上がる。配向した熱伝導性充填材粒子同士を面内方向に距離を近づけるように力が加わり、熱伝導性充填材粒子の間に存在する空隙が無くなるか、または距離が近くなり、熱抵抗が低下する。さらに、一部の熱伝導性充填材粒子同士の端部（側面）が直接接触した状態になる。これは、複合粒子において、熱可塑性樹脂粒子は熱伝導性充填材粒子の板面に吸着し、板上の熱伝導性充填材粒子の厚さに比べ熱可塑性樹脂粒子の粒径は十分大きいため、熱伝導性充填材粒子の側面には吸着し難いため、ホットプレス時の圧力で熱伝導性充填材粒子どうしが直接接触する。この工程は、真空中で行えば、樹脂中のボイドを更になくすることができ絶縁破壊強度を向上させることができる。 The hot pressing step (S6) is a step of pressing while heating at a temperature not lower than the melting point temperature of the thermoplastic resin and not higher than the heat resistant temperature in the direction crossing the centrifugal force (shown in FIG. 4), that is, in the in-plane direction of the composite particles. The duration of hot pressing is a time appropriately determined by the melting temperature of the thermoplastic resin. By this step, the thermoplastic resin becomes higher than the melting point temperature, and melts and flows to the interface of the thermally conductive filler particles to form a resin layer so as to eliminate the gap. The temperature at the time of hot pressing is set to be equal to or higher than the melting point temperature determined by the composition of the thermoplastic resin. The higher the heating temperature of the hot press, the higher the fluidity of the resin, and the cheaper it will flow between the filler particles. For this reason, even if the packing density of the filler particles is increased in order to increase the thermal conductivity, and the gap between the filler particles is reduced, the resin flows in and becomes cheaper, so that a decrease in dielectric breakdown strength can be suppressed. The upper limit of the heating temperature is a temperature lower than the temperature at which the polymer constituting the resin starts to deteriorate. By increasing the pressure of the hot press, the distance between the thermally conductive filler particles can be shortened and voids in the thermoplastic resin can be driven out, thereby increasing the density of the composite insulating plate. A force is applied to bring the oriented thermally conductive filler particles closer to each other in the in-plane direction, and voids existing between the thermally conductive filler particles are eliminated or the distance is reduced, resulting in a decrease in thermal resistance. . Furthermore, it will be in the state which the edge part (side surface) of some heat conductive filler particles contacted directly. This is because in the composite particles, the thermoplastic resin particles are adsorbed on the plate surface of the thermally conductive filler particles, and the particle size of the thermoplastic resin particles is sufficiently larger than the thickness of the thermally conductive filler particles on the plate. Since it is difficult to adsorb on the side surfaces of the thermally conductive filler particles, the thermally conductive filler particles are in direct contact with each other at the pressure during hot pressing. If this step is performed in a vacuum, voids in the resin can be further eliminated and the dielectric breakdown strength can be improved.
なお、本発明の製造方法によって作られた複合絶縁板の絶縁性および熱伝導性は、以下の評価方法によって測定された値が用いられる。なお、複合絶縁板は方向によってその特性が大きく違うため、実使用の方向、すなわち厚さ方向での測定値が用いられる。 In addition, the value measured by the following evaluation methods is used for the insulation and thermal conductivity of the composite insulating plate made by the manufacturing method of the present invention. In addition, since the characteristic of the composite insulating plate varies greatly depending on the direction, the measured value in the actual use direction, that is, the thickness direction is used.
絶縁性の評価方法を説明する。本発明の複合絶縁板を研磨紙で厚さ約１ｍｍ程度に研磨したものを試料として、マッケオン型電極の１対の電極の間に挟み、試料表面の気中で絶縁破壊することを防止するため、試料および電極のまわりをエポキシ樹脂でモールドした。 室温にて上昇率1 kV／秒の直流ランプ電圧を印加し、絶縁破壊電圧を測定した。絶縁破壊強度（ｋV／ｍｍ）は絶縁破壊電圧をマッケオン電極系作製後の実際の試料厚さで除することにより算出した。試料を変えて複数回、好適には１０回以上 試験を行い、その平均値を「絶縁破壊強度」とする。 The insulation evaluation method will be described. In order to prevent dielectric breakdown in the air on the surface of the sample by sandwiching the composite insulating plate of the present invention with a polishing paper to a thickness of about 1 mm as a sample and sandwiching it between a pair of Mackeon electrodes The sample and the electrode were molded with epoxy resin. A DC lamp voltage with an increase rate of 1 kV / sec was applied at room temperature, and the dielectric breakdown voltage was measured. The dielectric breakdown strength (kV / mm) was calculated by dividing the dielectric breakdown voltage by the actual sample thickness after fabrication of the McKeon electrode system. The test is performed a plurality of times, preferably 10 times or more by changing the sample, and the average value is defined as “dielectric breakdown strength”.
熱伝導性の評価方法を説明する。本発明の複合絶縁板を直径１０ｍｍ、 厚さ１ｍｍの円盤状に切り出したものを試料とし、レーザフラッシュ法にて室温下における熱拡散率（ｍ２／秒）および比熱容量（J／g・K）とを測定する。熱伝導率（Ｗ／ｍ・Ｋ）は、この測定値とアルキメデス法にて常温で測定した密度から計算した値を「熱伝導率」とする。 A method for evaluating thermal conductivity will be described. The composite insulating plate of the present invention cut into a disk shape having a diameter of 10 mm and a thickness of 1 mm is used as a sample, and the thermal diffusivity (m 2 / sec) and specific heat capacity (J / g · K) at room temperature by laser flash method. ) And measure. The thermal conductivity (W / m · K) is a value calculated from this measured value and the density measured at room temperature by the Archimedes method as “thermal conductivity”.
以下、本発明の製造方法による効果を検証するための実験例を説明する。図５は本発明の製造方法を用いて製造条件を変えたときの絶縁破壊強度と熱伝導率の関係の図である。図の縦軸は絶縁破壊強度（ｋＶ／ｍｍ）、横軸は熱伝導率（Ｗ／ｍ・Ｋ）である。図中×印および＋印のプロットは、前掲の非特許文献１および２で開示された結果である。 Hereinafter, experimental examples for verifying the effects of the manufacturing method of the present invention will be described. FIG. 5 is a graph showing the relationship between the dielectric breakdown strength and the thermal conductivity when the manufacturing conditions are changed using the manufacturing method of the present invention. In the figure, the vertical axis represents dielectric breakdown strength (kV / mm), and the horizontal axis represents thermal conductivity (W / m · K). In the figure, the x and + plots are the results disclosed in Non-Patent Documents 1 and 2 described above.
非特許文献1では、熱伝導性充填材粒子としてのBNとエポキシ樹脂とを用い製造条件を変えて複合絶縁板を作製し、絶縁破壊強度と熱伝導率を測定している。その結果によれば、ここで作製した複合絶縁板の絶縁破壊強度は市場の要求する１００ｋV／ｍｍ超えるものがあるが、熱伝導率は１Ｗ／ｍ・Ｋ程度以下で市場の要求する１０Ｗ／ｍ・Ｋに比べ極めて低い値である。一方、熱伝導率が１０Ｗ／ｍ・Ｋを超えるものは、絶縁破壊強度が６０ｋV／ｍｍで市場の要求値に比べ低い値に留まっており、熱伝導率と絶縁破壊強度との両者を満足するものは得られていない。 In Non-Patent Document 1, composite insulation plates are produced using BN and epoxy resin as thermally conductive filler particles under different production conditions, and dielectric breakdown strength and thermal conductivity are measured. According to the result, the dielectric breakdown strength of the composite insulating plate produced here exceeds 100 kV / mm required by the market, but the thermal conductivity is about 1 W / m · K or less and 10 W / m required by the market. -Extremely low value compared to K. On the other hand, when the thermal conductivity exceeds 10 W / m · K, the dielectric breakdown strength is 60 kV / mm, which is lower than the market requirement, and satisfies both the thermal conductivity and the dielectric breakdown strength. Nothing has been obtained.
同様に特許文献２では、同一の構成の複合絶縁板の絶縁破壊強度は６０ｋV／ｍｍ以下で熱伝導率は１Ｗ／ｍ・Ｋ以下と極めて低い値である。 Similarly, in Patent Document 2, the dielectric breakdown strength of the composite insulating plate having the same configuration is 60 kV / mm or less, and the thermal conductivity is 1 W / m · K or less, which are extremely low values.
（実験例１）
図５中のAのプロットは次の条件で作製した試料Aの熱伝導率と絶縁破壊強度である。熱伝導率は１９±２Ｗ／ｍ・Ｋで、絶縁破壊強度の平均値（Ｘ）は１１０ｋV／ｍｍであった。この時の絶縁破壊電圧のばらつきの標準偏差（σ）は５％であった。ばらつきを考慮した絶縁破壊強度の下限値は、Ｘ（１−２σ）、すなわち９５％の発生確率で計算すると、９９ｋＶ／ｍｍである。
(Experimental example 1)
The plot of A in FIG. 5 is the thermal conductivity and dielectric breakdown strength of Sample A produced under the following conditions. The thermal conductivity was 19 ± 2 W / m · K, and the average value (X) of dielectric breakdown strength was 110 kV / mm. At this time, the standard deviation (σ) of the variation in dielectric breakdown voltage was 5%. The lower limit value of the dielectric breakdown strength in consideration of the variation is 99 kV / mm when calculated with X (1-2σ), that is, with a probability of occurrence of 95%.
試料Aの熱可塑性樹脂としては、ポリメタクリル酸メチル（PMMA）を用いた。自動車用Si系パワーモジュールの使用最高温度１００〜１２０℃で、実際のモジュールの熱設計温度が６０〜７０℃であることから成形性の良いPMMAを選定した。熱伝導性充填材粒子としては前掲の六方晶BN「ＰＴ−１１０（商品名）」（モーメンティブパーフォーマンスマテリアルズジャパン合同会社製）を用いた。BNは黒鉛に似た板状結晶の粒子形状で、面内方向の熱伝導率は２００Ｗ／ｍ・Ｋで厚さ方向の熱伝導率６０Ｗ／ｍ・Ｋに比べ３倍以上となっている。 As the thermoplastic resin of Sample A, polymethyl methacrylate (PMMA) was used. PMMA having a good moldability was selected because the maximum temperature of use of the Si-based power module for automobiles was 100 to 120 ° C. and the actual thermal design temperature of the module was 60 to 70 ° C. As the thermally conductive filler particles, the above-mentioned hexagonal BN “PT-110 (trade name)” (made by Momentive Performance Materials Japan GK) was used. BN has a plate-like crystal particle shape similar to graphite, and the thermal conductivity in the in-plane direction is 200 W / m · K, which is more than three times the thermal conductivity in the thickness direction of 60 W / m · K.
本実施例では熱可塑性樹脂と熱伝導性充填材粒子と用いてＳ０の工程で複合粒子を作製した。複合粒子は、主粒子(粒径が大きい粒子)として面内方向の平均粒径４５μｍのBNを用いた。粒径の大きい主粒子の周りの吸着粒子として熱可塑性樹脂PMMAを用いた。主粒子の平均粒径に対し吸着粒子の平均粒径は好適には１／１０であるので４μｍとした。 In this example, composite particles were produced in the step S0 using thermoplastic resin and thermally conductive filler particles. In the composite particles, BN having an average particle size of 45 μm in the in-plane direction was used as main particles (particles having a large particle size). Thermoplastic resin PMMA was used as the adsorbed particles around the main particles having a large particle size. Since the average particle diameter of the adsorbed particles is preferably 1/10 of the average particle diameter of the main particles, it is set to 4 μm.
次にPMMA粒子表面の親水性を高めると同時に負の表面電位を高めさせるため、濃度5 g/ｌの界面活性剤であるデオキシコール酸ナトリウム(SDC)にPMMA粒子を浸漬した。次に高分子電解質である濃度５０g/ｌ のポリジアリルジメチルアンモニウムクロリド(PDDA)，濃度１０g/ｌのポリスチレンスルホン酸ナトリウム(PSS)の順にPMMA粒子を浸漬した。SDC、PDDAおよびPSSの濃度はそれらがPMMA表面全体に吸着するために十分な濃度とした。各溶液に浸漬する前にPMMA粒子はイオン交換水中での洗浄処理を実施した。最終的にPMMA粒子の表面電位は負に調整した。一方、同様な方法でBN粒子の表面電位を最終的に正に調整し、主粒子とした。表面電位を負としたPMMA吸着粒子および表面電位を正としたBN主粒子をイオン交換水中で混合し、静電相互作用によりBN主粒子表面にPMMA吸着粒子が吸着した複合粒子を作製した。図６はBN単粒子の外表面に平均直径４μｍ程度のPMMA粒子が均一に吸着していることを示した電子顕微鏡写真である。BN単粒子の板面は球形のPMMA粒子で覆われており、板の厚さ方向の端部はPMMA粒子が吸着していない。 Next, PMMA particles were immersed in sodium deoxycholate (SDC), a surfactant having a concentration of 5 g / l, in order to increase the hydrophilicity of the surface of the PMMA particles and at the same time increase the negative surface potential. Next, PMMA particles were immersed in the order of polydiallyldimethylammonium chloride (PDDA) having a concentration of 50 g / l and sodium polystyrene sulfonate (PSS) having a concentration of 10 g / l as polymer electrolytes. The concentrations of SDC, PDDA and PSS were sufficient to allow them to adsorb over the entire PMMA surface. Prior to immersion in each solution, the PMMA particles were washed in ion exchange water. Finally, the surface potential of the PMMA particles was adjusted to be negative. On the other hand, the surface potential of the BN particles was finally adjusted to be positive by the same method to obtain main particles. PMMA adsorbed particles with negative surface potential and BN main particles with positive surface potential were mixed in ion-exchanged water, and composite particles with PMMA adsorbed particles adsorbed on the surface of BN main particles by electrostatic interaction were prepared. FIG. 6 is an electron micrograph showing that PMMA particles having an average diameter of about 4 μm are uniformly adsorbed on the outer surface of BN single particles. The plate surface of BN single particles is covered with spherical PMMA particles, and PMMA particles are not adsorbed at the end of the plate in the thickness direction.
Ｓ０の工程で作製された複合粒子は、Ｓ１の工程で導電率１〜１０μS／ｃｍのイオン交換水の中に溶かしスラリー状にした。 The composite particles produced in the step S0 were dissolved in ion-exchanged water having a conductivity of 1 to 10 μS / cm in the step S1 to form a slurry.
Ｓ２の工程では、Ｓ１の工程で作られたスラリーを１２ｍｍ×４０ｍｍで厚さ３ｍｍの板状キャビティを有する型枠（図７）に導入した。 In the step S2, the slurry produced in the step S1 was introduced into a mold (FIG. 7) having a plate-like cavity of 12 mm × 40 mm and a thickness of 3 mm.
Ｓ３の工程で、Ｓ２の工程でスラリーが入った型枠を図中の矢印の方向に遠心分離機を用いて遠心力を与えた。遠心力は複合粒子１個あたり約５μＮで、１０分間与え、固液分離すると共に複合粒子を沈降させた。粒子１個当たりの遠心力は、遠心力＝（回転数）×（回転中心からの距離）×（複合粒子の重量）で算出した。ここで、回転数：３０００ｒｐｍ、回転中心から複合粒子までの平均距離：１７００ｍｍ、複合粒子の重量：２．８７×１０−９ｇ［＝（PMMA密度：１．２g/cm3）×（PMMA粒子体積：３．３５×１０−１１cm3）＋（BN密度：２．１g/cm3）×（BN体積：１．３５×１０−９cm3）］であった。型枠の低面（A面）と交差する方向に遠心力を作用することで複合粒子の板状面が型枠の底面に向くように沈降し、スラリーの液体が型枠の隙間から逃げることにより１２ｍｍ×１３ｍｍで厚さ３ｍｍの複合粒子の堆積物ができた。 In step S3, centrifugal force was applied to the mold containing slurry in step S2 in the direction of the arrow using a centrifuge. Centrifugal force was applied at about 5 μN per composite particle for 10 minutes, solid-liquid separation was performed and the composite particles were allowed to settle. The centrifugal force per particle was calculated by centrifugal force = (number of rotations) × (distance from the center of rotation) × (weight of composite particles). Here, the number of rotations: 3000 rpm, the average distance from the center of rotation to the composite particles: 1700 mm, the weight of the composite particles: 2.87 × 10 −9 g [= (PMMA density: 1.2 g / cm 3 ) × (PMMA particles Volume: 3.35 × 10 −11 cm 3 ) + (BN density: 2.1 g / cm 3 ) × (BN volume: 1.35 × 10 −9 cm 3 )]. By applying centrifugal force in the direction crossing the lower surface (A surface) of the formwork, the composite particles settle so that the plate-like surface of the composite particles faces the bottom surface of the formwork, and the slurry liquid escapes from the gaps in the formwork. As a result, a composite particle deposit of 12 mm × 13 mm and a thickness of 3 mm was formed.
Ｓ４の工程で遠心力の作用方向と同方向に型枠の開口部３と同一形状の板で機械的圧力を加え１２ｍｍ×１３ｍｍで厚さ３ｍｍの堆積物を１２ｍｍ×１０ｍｍで厚さ３ｍｍまで圧縮し成形体とした。 In step S4, mechanical pressure is applied to the plate 3 having the same shape as the opening 3 of the mold in the same direction as the direction of the centrifugal force, and the deposit of 12 mm × 13 mm and 3 mm thick is compressed to 12 mm × 10 mm to 3 mm thick. A molded body was obtained.
Ｓ５の工程では、Ｓ４の工程で作製した成形体を型枠から取り外した。 In the step S5, the molded body produced in the step S4 was removed from the mold.
Ｓ６の工程ではＳ５の工程で作製した成形体の３ｍｍの厚さ方向にPMMAの融点以上の温度１６０℃でホットプレスを１時間行った。PMMAでは８０〜１００℃で軟化し、１６０〜２６０℃で溶融し熱成形するため、ここでは１６０℃でホットプレスした。ホットプレス圧力はφ１０ｍｍの面で５０ＭＰａの圧力である。 In step S6, hot pressing was performed for 1 hour at a temperature of 160 ° C. above the melting point of PMMA in the thickness direction of 3 mm of the molded body produced in step S5. PMMA was softened at 80 to 100 ° C., melted at 160 to 260 ° C. and thermoformed, and was hot pressed at 160 ° C. here. The hot press pressure is a pressure of 50 MPa on a surface of φ10 mm.
図８は、このような工程で作製した複合絶縁板の断面の電子顕微鏡写真である。複合絶縁板の電界がかかる厚さ方向（写真の上下方向）に板状のBN粒子は面内方向が揃った配向を示している上、BN粒子の外表面はPMMAが被覆した状態であり、一部のBN粒子同士は厚さ方向の面が接触した状態となっている。これは、BN粒子の表面に適正粒径のPMMA粒子が均一に付着した複合粒子が加熱によってそのPMMA粒子が融解してBN粒子の表面を被覆すると同時に複合絶縁板の厚さ方向のプレス圧によってBN粒子端面が接触したためである。 FIG. 8 is an electron micrograph of a cross section of the composite insulating plate produced by such a process. In the thickness direction (up and down direction of the photograph) where the electric field of the composite insulating plate is applied, the plate-like BN particles are aligned in the in-plane direction, and the outer surface of the BN particles is covered with PMMA. Some BN particles are in contact with each other in the thickness direction. This is because the composite particles with PMMA particles of the proper particle size uniformly attached to the surface of the BN particles are heated to melt the PMMA particles and coat the surface of the BN particles, and at the same time, the composite insulating plate is pressed in the thickness direction. This is because the BN particle end faces are in contact.
本実施例の複合絶縁板の密度は１．８４g/cm3、BN粒子の配合量は５９体積％であった。ここで用いたBN粒子の密度は２．１g/cm3、PMMA粒子密度は１．２g/cm3であった。 The density of the composite insulating plate of this example was 1.84 g / cm 3 , and the blending amount of BN particles was 59% by volume. The density of the BN particles used here was 2.1 g / cm 3 and the density of the PMMA particles was 1.2 g / cm 3 .
（実験例２）
図５中のBのプロットの試料Bは、試料Aの製造方法および条件の内、Ｓ４の工程を省略して、Ｓ４の押圧工程の効果を検証した試料である。すなわち、Ｓ３工程で遠心分離機によって複合粒子を配向させ、固液分離で液分を除去した堆積物を作製した後、Ｓ４の工程での遠心力の作用方向の機械的圧力を印加しないでＳ５の工程で型枠から取り外し、Ｓ６の工程でホットプレスした試料である。BはAに比べ絶縁破壊強度は２０％程度高いが、熱伝導率は１／２程度であった。また、試料Bの複合絶縁板の密度は１．８２g/cm3、BN粒子の配合量は５７体積％であった。試料Aの密度は試料Bに比べ０．０２g/cm3増大しており、省略したＳ４の工程は複合粒子の沈降した堆積物の方向と同じ方向に力を加えることで複合絶縁板の密度を高める効果がある。さらに、試料A のBNの配向度はＳ４の工程により増加する。このため、試料Aの厚さ方向熱流抵抗が面全体として試料Bに比べ低くなったため熱伝導率が大幅に下がった。また、試料AのBNの配向度は試料Bに比べ高く、電界方向にBN粒子の面内方向の界面が多くなるため、放電がBN界面の面内方向に進展しやすくなり絶縁破壊強度が低下した。つまり、遠心力および機械力によって配向の程度および密度を制御して所要の絶縁破壊強度、熱伝導率の複合絶縁板を製作することができる。ここでは、述べていないが、配向度と機械強度は密接な関係にあるため、本発明の工程条件を組み合わせて使用用途に応じた機械強度を有し、良好な熱伝導率で十分な絶縁破壊強度の複合絶縁板を製作することができる。
(Experimental example 2)
Sample B in the plot of B in FIG. 5 is a sample in which, in the manufacturing method and conditions of sample A, the step S4 is omitted and the effect of the pressing step S4 is verified. That is, after the composite particles are oriented by a centrifuge in the step S3 and a deposit from which the liquid component has been removed by solid-liquid separation is produced, the mechanical pressure in the direction of the centrifugal force in the step S4 is not applied, and S5 is applied. This sample was removed from the mold in the process of (2) and hot pressed in the process of S6. B had a dielectric breakdown strength about 20% higher than A, but its thermal conductivity was about 1/2. Further, the density of the composite insulating plate of Sample B was 1.82 g / cm 3 , and the blending amount of BN particles was 57% by volume. The density of sample A is 0.02 g / cm 3 higher than that of sample B, and the omitted step S4 increases the density of the composite insulating plate by applying a force in the same direction as the sediment of the composite particles. There is an effect to increase. Further, the degree of orientation of BN in sample A increases by the step S4. For this reason, since the heat flow resistance in the thickness direction of the sample A was lower than that of the sample B as a whole surface, the thermal conductivity was greatly lowered. In addition, the BN orientation of sample A is higher than that of sample B, and there are more interfaces in the in-plane direction of the BN particles in the electric field direction. did. That is, a composite insulating plate having a required dielectric breakdown strength and thermal conductivity can be manufactured by controlling the degree and density of orientation by centrifugal force and mechanical force. Although not stated here, since the degree of orientation and mechanical strength are closely related, the mechanical strength according to the intended use is combined by combining the process conditions of the present invention, and sufficient dielectric breakdown with good thermal conductivity. A strong composite insulating plate can be manufactured.
（実験例３）
図５中のCのプロットの試料Ｃは複合絶縁板の密度の影響を見るために、複合粒子におけるBN粒子表面のPMMA粒子の吸着量を約半分程度にし、試料Aと同一方法、同一条件で作製した試料である。この試料の絶縁破壊強度は試料Aに比べ平均値で１０％程度低下したが、熱伝導率は逆に平均値で１０％程度上昇した。本実施例の複合絶縁板の密度は１．９４g/cm3、BN粒子の配合量は６８体積％であった。複合絶縁板の密度が０．１g/cm3増大した。これは、複合絶縁板のPMMA粒子数の減少によりBN粒子配合量が試料Aの５９体積％から６８体積％と９％も増大したため、熱流パスが増加し熱伝導率が増加した。BN粒子の増加は電気的な弱点の増加となり、試料Cの絶縁破壊強度が試料Aのそれに比べ低下したと考えられる。
(Experimental example 3)
In order to see the influence of the density of the composite insulating plate, the sample C in the plot of C in FIG. 5 has about half the amount of PMMA particles adsorbed on the surface of the BN particles in the composite particles. This is a prepared sample. The dielectric breakdown strength of this sample was about 10% lower than the sample A on the average, but the thermal conductivity was about 10% higher on the contrary. The density of the composite insulating plate of this example was 1.94 g / cm 3 , and the blending amount of BN particles was 68% by volume. The density of the composite insulating plate increased by 0.1 g / cm 3 . This is because the amount of BN particles increased from 59% by volume of Sample A to 68% by volume and 9% due to the decrease in the number of PMMA particles in the composite insulating plate, so the heat flow path increased and the thermal conductivity increased. It is thought that the increase in BN particles resulted in an increase in electrical weakness, and the dielectric breakdown strength of sample C was lower than that of sample A.
（実験例４）
実験例１で説明したＳ１〜Ｓ５の工程で作製した成形体をＳ６の工程で温度を１２０℃、２００℃と変化させて３ｍｍの厚さ方向にホットプレスを１時間行った。ホットプレス圧力はφ１０ｍｍの面で５０ＭＰａの圧力である。図９において、横軸のホットプレス温度に対して、左側縦軸は絶縁破壊強度、右側縦軸は熱伝導率であり、ホットプレス温度が２５０℃で作製した試料の絶縁破壊強度は１６０℃のものに比べ１０％程度低下したが、熱伝導率は１．７倍の３３．４ｗ／ｍ・Kとなった。
(Experimental example 4)
The molded body produced in the steps S1 to S5 described in Experimental Example 1 was hot-pressed for 1 hour in a thickness direction of 3 mm while changing the temperature to 120 ° C. and 200 ° C. in the step S6. The hot press pressure is a pressure of 50 MPa on a surface of φ10 mm. In FIG. 9, with respect to the hot press temperature on the horizontal axis, the left vertical axis represents the dielectric breakdown strength, the right vertical axis represents the thermal conductivity, and the dielectric breakdown strength of a sample manufactured at a hot press temperature of 250 ° C. is 160 ° C. Although it was about 10% lower than that of the product, the thermal conductivity was 1.7 times 33.4 w / m · K.
以上のように製造方法にかかる実施形態によって複合絶縁板を製造することができる。本発明は、かかる製造方法によって製造された複合絶縁板を含むものである。 As described above, the composite insulating plate can be manufactured by the embodiment according to the manufacturing method. The present invention includes a composite insulating plate manufactured by such a manufacturing method.
１ 熱伝導性充填材粒子
２ 熱可塑性樹脂
３ 型枠の開口部（キャビティの開口部）
1 Thermally conductive filler particles 2 Thermoplastic resin 3 Mold frame opening (cavity opening)
Claims (7)
前記複合絶縁板の密度が１．８ｇ／ｃｍ３以上で、かつ板の厚み方向の熱伝導率が１５Ｗ／ｍ・Ｋ以上で３５Ｗ／ｍ・Ｋ以下となるように熱伝導性充填材粒子が配向しているものであって、前記厚み方向に対する絶縁破壊強度が９５ｋV/ｍｍ以上であることを特徴とする複合絶縁板。 In a composite insulating plate comprising a thermoplastic resin and plate-like thermally conductive filler particles having a higher thermal conductivity than the thermoplastic resin,
The thermally conductive filler particles have a density of the composite insulating plate of 1.8 g / cm 3 or more and a thermal conductivity in the thickness direction of the plate of 15 W / m · K to 35 W / m · K. A composite insulating plate that is oriented and has a dielectric breakdown strength of 95 kV / mm or more in the thickness direction.
所定の容積を有するキャビティ内に前記スラリー作製工程により作製したスラリーを導入する導入工程と、
前記導入工程でキャビティ内に導入したスラリーに対し所定方向へ遠心力を作用させることにより、固液分離により複合粒子を前記液体から分離させつつキャビティの遠心力の作用方向に対して交差する面へ堆積させる遠心分離工程と、
前記遠心分離工程によりキャビティに堆積させた前記複合粒子の堆積物に対し、前記遠心力の作用方向と同じ方向へ押圧して成形体を形成する押圧工程と、
前記押圧工程により作られた前記成形体をキャビティから取り出し、前記熱可塑性樹脂粒子を構成する樹脂の融点温度以上の環境下にて、前記押圧工程での押圧方向と交差する方向へプレスするホットプレス工程と、
を含むことを特徴とする複合絶縁板の製造方法。 The heat conductive filler particles are the main particles, and composite particles formed by adsorbing the thermoplastic resin particles on the surface of the main particles are contained in the liquid, and the viscosity is lower than the melt viscosity of the thermoplastic resin. A slurry preparation step of preparing a slurry of
An introducing step of introducing the slurry produced by the slurry producing step into a cavity having a predetermined volume;
By applying centrifugal force to the slurry introduced into the cavity in the introduction step in a predetermined direction, the composite particles are separated from the liquid by solid-liquid separation, and the surface intersects with the centrifugal force acting direction of the cavity. A centrifugation step for deposition;
A pressing step of pressing the composite particles deposited in the cavity by the centrifugal separation step in the same direction as the direction of the centrifugal force to form a molded body;
The hot press that takes out the molded body made by the pressing step from the cavity and presses it in a direction intersecting with the pressing direction in the pressing step in an environment equal to or higher than the melting point temperature of the resin constituting the thermoplastic resin particles. Process,
The manufacturing method of the composite insulating board characterized by including.
7. The method for producing a composite insulating plate according to claim 4, wherein the liquid dynamic clay constituting the slurry is 1 centistokes or less at room temperature.
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| CN116715938A (en) * | 2023-08-07 | 2023-09-08 | 四川大学 | Dielectrophoresis force orientation-based epoxy resin composite insulating material and preparation method thereof |
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| JP7317340B2 (en) | 2018-03-02 | 2023-07-31 | 国立大学法人豊橋技術科学大学 | Heat dissipating composite insulating plate with high heat resistance |
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