JP2020066648A - Thermal conductive composite material and heat release sheet - Google Patents
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Abstract
Description
本発明は、樹脂の柔軟性を有しつつシート状成形品の厚み方向への高い熱伝導性を具備した複合材料の製造方法およびこれを用いた放熱シートに関するものである。 TECHNICAL FIELD The present invention relates to a method for producing a composite material having the flexibility of a resin and high thermal conductivity in the thickness direction of a sheet-shaped molded article, and a heat dissipation sheet using the same.
電気自動車やハイブリッド自動車が普及期に入るに伴い、駆動モータの電力制御装置であるパワーモジュールの性能向上が求められている。また世界的な温暖化に伴い、従来比較的温暖とされていた国や地域でもしばしば異常高温（異常気象）となり、人的被害が多発するようになってきた。対策の一つとしてエアーコンディショナーの利用があり、その電力制御にもパワーモジュールが利用されることから、今後の急速な需要拡大が予想される。パワーモジュールには低消費電力、高耐圧が求められ、モジュールの小型化に伴う高温動作への信頼性確保も同時に必要とされている。これら要求特性を満たすため従来のＳｉ系素子に代わりＳｉＣ系素子への置き換えが企図されているが、２００℃以上の高温領域での安定動作を担保するためには、ＳｉＣ系素子が発する熱を効果的に排熱する必要がある（非特許文献１）。このためＳｉＣ系素子そのもの以外に、周辺部品（例えば放熱シート等）にもこれまで以上の高熱伝導や高耐熱性が要求されている。 As electric vehicles and hybrid vehicles enter the popularization period, performance improvement of a power module, which is a power control device for a drive motor, is required. In addition, due to global warming, abnormally high temperatures (abnormal weather) often occur in countries and regions that have been relatively warm in the past, resulting in frequent human damage. One of the countermeasures is the use of air conditioners, and power modules are also used for power control, so it is expected that demand will grow rapidly in the future. The power module is required to have low power consumption and high breakdown voltage, and at the same time, it is necessary to secure reliability for high temperature operation due to miniaturization of the module. In order to satisfy these required characteristics, replacement of the conventional Si-based element with a SiC-based element is planned, but in order to ensure stable operation in a high temperature range of 200 ° C. or higher, heat generated by the SiC-based element is It is necessary to effectively exhaust heat (Non-Patent Document 1). Therefore, in addition to the SiC-based element itself, peripheral components (for example, a heat dissipation sheet) are required to have higher heat conduction and higher heat resistance than ever before.
一方、パワーモジュールに限らず、動作周波数の大きなＣＰＵを用いる高度なデジタルデバイスも小型化／軽量化に伴い排熱が困難となり、Ｓｉ系素子の安定動作環境を逸脱する場合も多くなっている。このため、主として周辺部品に高い熱伝導性が求められる事情は、上記パワーモジュールの場合と同様である。 On the other hand, not only power modules, but also advanced digital devices that use a CPU with a high operating frequency are becoming difficult to exhaust heat due to size reduction / weight reduction, and there are many cases where the stable operation environment of the Si-based element is deviated. For this reason, the situation in which peripheral components are required to have high thermal conductivity is the same as in the case of the power module.
これらの熱伝導性周辺部品は、一般的に賦形性に優れる有機高分子材料を用いて成形された状態で必要な部位に組込まれて使用されるが、有機材料は本質的に熱伝導性に乏しいため、通例、熱伝導性に優れた他素材（熱伝導性フィラー）を分散混合した樹脂組成物として利用される。これは樹脂組成物中に熱伝導性フィラーが連続して存在することで熱伝導パスが形成されることを期待するものである。しかし簡単な計算からも、熱伝導性フィラー同士の界面に僅かな厚さの有機相が介在するだけでも、熱移動には多大な影響を及ぼし、結果として成形品を通過する熱流束は大幅に低減されることが分かる。現実の熱伝導性樹脂組成物成形品の性能も、期待ほどの熱を通過させることができずに当該部品自体が二次的な熱源となってしまう。 These heat conductive peripheral parts are generally molded by using an organic polymer material having excellent shapeability, and are used by incorporating them into necessary parts, but the organic material is essentially heat conductive. Therefore, it is usually used as a resin composition in which another material having excellent thermal conductivity (thermally conductive filler) is dispersed and mixed. This is expected to form a heat conduction path by the continuous presence of the heat conductive filler in the resin composition. However, even from a simple calculation, even a small thickness of organic phase intervening at the interface between the thermally conductive fillers has a great influence on the heat transfer, and as a result, the heat flux passing through the molded article is significantly increased. It can be seen that it is reduced. In the actual performance of the molded product of the heat conductive resin composition, the heat cannot pass as much as expected and the component itself becomes a secondary heat source.
係る不具合を解消するための最も一般的な対策は、熱伝導性フィラーの配合量を増やし、樹脂マトリクス中で熱伝導性フィラー同士が直接コンタクトする確率を高めるというものである。しかし、期待される効果を得るには熱伝導性フィラー配合量は少なくとも５０ｖｏｌ％を超える量は必要であり、熱伝導性フィラーを混合した樹脂組成物の材料物性は樹脂マトリクス本来の性能とは大きく異なるものとなる。特に機械物性や耐衝撃性などが大幅に低下し、賦形性にも影響を及ぼすことは公知である。 The most common measure for solving such a problem is to increase the compounding amount of the heat conductive filler and increase the probability that the heat conductive fillers are in direct contact with each other in the resin matrix. However, in order to obtain the expected effect, the amount of the thermally conductive filler blended must be at least more than 50 vol%, and the material properties of the resin composition mixed with the thermally conductive filler are largely different from the original performance of the resin matrix. It will be different. In particular, it is known that mechanical properties, impact resistance, etc. are significantly reduced and shapeability is also affected.
そこで熱伝導性フィラーの配合量増大を伴わずに、フィラー同士の接触頻度を上げるための考え方として、既製の粒径が異なる熱伝導性フィラーを混合して粒度分布を変えること（特許文献１）、熱伝導性フィラーと樹脂マトリクス成分との濡れ性を上げ両者間の熱抵抗を下げる（特許文献２）、熱伝導性フィラーの凝集構造を崩し樹脂組成物内での分散状態を改変する（特許文献３）や熱伝導性を有する繊維状フィラーと塊状フィラーの混合物を用いて樹脂組成物内にネットワーク構造を形成する（特許文献４）等のフィラー種類や構造面からの改善検討がなされている。 Therefore, as an idea for increasing the frequency of contact between the fillers without increasing the blending amount of the thermally conductive filler, the particle size distribution is changed by mixing ready-made thermally conductive fillers having different particle sizes (Patent Document 1). , Increase the wettability of the thermally conductive filler and the resin matrix component to reduce the thermal resistance between them (Patent Document 2), disrupt the agglomerated structure of the thermally conductive filler, and modify the dispersion state in the resin composition (Patent Improvement studies have been made from the type of filler and structural aspects such as forming a network structure in a resin composition using a mixture of a fibrous filler having thermal conductivity and a bulk filler (Patent document 4). .
一方、熱伝導性フィラーを単一素材から準備するのではなく、熱伝導性フィラー表面に異なる無機化合物を付着させた無機フィラー複合体（特許文献５）や熱伝導性フィラーそのものの形態異方性を低減する方法（特許文献６）等のアプローチも提案されている。しかしながら、前記した数々の改良検討では、成形後の樹脂組成物中での熱伝導パス、特に流動方向と垂直方向での熱伝導パスの再現性に乏しく、必ずしも熱伝導性フィラー配合量を低減できないため良好な対策とは言い難いがないのが現状である。 On the other hand, the morphological anisotropy of the inorganic filler composite (Patent Document 5) in which different inorganic compounds are attached to the surface of the thermally conductive filler or the thermally conductive filler itself, instead of preparing the thermally conductive filler from a single material An approach such as a method of reducing the above (Patent Document 6) is also proposed. However, in the above-described various studies, the reproducibility of the heat conduction path in the resin composition after molding, particularly the heat conduction path in the direction perpendicular to the flow direction is poor, and the amount of the heat conductive filler cannot be necessarily reduced. Therefore, it is difficult to say that this is a good measure.
また、より本質的な対策として、複数の熱伝導性フィラーからなる熱伝導パス形成を指向せず、熱伝導性部品成形体に期待される熱移動方向を１個の熱伝導性素材が貫通することで、フィラー界面の接触の問題を回避するコンセプトも提示されている（特許文献７）。当該文献内に開示されている方向性伝熱基板であれば大きな熱流束が期待されるが、ヒートシンクとの一体構造とは言え、それ自身の容積増大や形状自由度に乏しく、前記した熱伝導性の周辺部品への転用はそのままでは難しい。 Further, as a more essential measure, one heat conductive material penetrates in the heat transfer direction expected for the heat conductive part molded body without directing the formation of the heat conductive path formed of a plurality of heat conductive fillers. Therefore, the concept of avoiding the problem of contact at the filler interface is also proposed (Patent Document 7). A large heat flux is expected if it is a directional heat transfer substrate disclosed in the document, but although it is an integrated structure with a heat sink, its own volume increase and shape flexibility are poor, and the heat conduction described above It is difficult to transfer the property to peripheral parts as it is.
樹脂マトリクスが持つ諸物性を保持しつつ、高い熱伝導性、特に成形品の厚み方向への高い熱伝導性を具備した複合材料およびこれを用いた放熱シートを提供することを目的とする。 An object of the present invention is to provide a composite material having high thermal conductivity, particularly high thermal conductivity in the thickness direction of a molded product, while retaining various physical properties of a resin matrix, and a heat dissipation sheet using the same.
本願発明者等は、上記目的を達成するために鋭意検討した結果、下記に示す発明を完成するに至った。
〔１〕 シート状樹脂マトリクス中に、熱伝導性粒子が分散混合されている複合材料であって、前記複合材料の、表裏２つの表面に前記熱伝導性粒子単体の表面が露出していることを特徴とする複合材料。
〔２〕 前記樹脂マトリクスの厚さが、１０μｍ〜３０ｍｍであることを特徴とする前記〔１〕に記載の複合材料。
〔３〕 前記複合材料に含まれる前記熱伝導性粒子の配合量が、１０ｖｏｌ％以上７４ｖｏｌ％以下の条件を満たす範囲内で分散混合されてなることを特徴とする前記〔１〕又は前記〔２〕に記載の複合材料。
〔４〕 前記熱伝導性粒子が、セルロースナノファイバー、炭素繊維、Ｓｉ、ＳｉＣ、アルミニウム酸化物、窒化アルミニウム、立方晶窒化ホウ素、六方晶窒化ホウ素、酸化亜鉛、酸化マグネシウム、酸化ベリリウム、ダイヤモンドおよび各種金属の粉末やワイヤの単独粒子および／またはこれらの凝集粒子および／または前記熱伝導性粒子が土台となる球状微粒子表面に固定されて被覆層を形成している複合フィラーから選ばることを特徴とする前記〔１〕〜〔４〕のいずれかに記載の複合材料。
〔５〕 前記樹脂マトリクスの樹脂が、アクリル樹脂、エポキシ樹脂、シリコーン樹脂、ポリシルセスキオキサン系樹脂およびこれらの複合組成からなる前記〔１〕〜〔４〕のいずれかに記載の複合材料。
〔６〕 前記〔１〕〜〔５〕のいずれかに記載の複合材料を用いることを特徴とする放熱シート。
〔７〕 前記放熱シートが、異なる最長部長さを有する熱伝導性粒子が分散混合されている少なくとも２種以上の放熱シートを３層以上に重ねたものであって、かつ、熱伝導性粒子の最長部長さが小さい方の熱伝導性粒子を含む放熱シートが、当該積層物の上下方向の最表面に配置されていることを特徴とする前記〔６〕に記載の放熱シート。
The inventors of the present application have conducted extensive studies to achieve the above object, and as a result, have completed the invention described below.
[1] A composite material in which thermally conductive particles are dispersed and mixed in a sheet-shaped resin matrix, and the surface of the single thermally conductive particle is exposed on two front and back surfaces of the composite material. Composite material characterized by.
[2] The composite material according to [1], wherein the resin matrix has a thickness of 10 μm to 30 mm.
[3] The compounding amount of the thermally conductive particles contained in the composite material is dispersed and mixed within a range satisfying a condition of 10 vol% or more and 74 vol% or less, [1] or [2] ] Composite material of description.
[4] The thermally conductive particles are cellulose nanofibers, carbon fibers, Si, SiC, aluminum oxide, aluminum nitride, cubic boron nitride, hexagonal boron nitride, zinc oxide, magnesium oxide, beryllium oxide, diamond and various types. It is characterized by being selected from a composite filler in which individual particles of metal powder or wire and / or their agglomerated particles and / or the heat conductive particles are fixed on the surface of spherical fine particles serving as a base to form a coating layer. The composite material according to any one of [1] to [4] above.
[5] The composite material according to any one of [1] to [4], wherein the resin of the resin matrix is an acrylic resin, an epoxy resin, a silicone resin, a polysilsesquioxane resin, or a composite composition thereof.
[6] A heat dissipation sheet comprising the composite material according to any one of [1] to [5].
[7] The heat-dissipating sheet is obtained by stacking at least two or more heat-dissipating sheets in which heat-conductive particles having different maximum lengths are dispersed and mixed in three or more layers, and The heat dissipation sheet according to the above [6], wherein the heat dissipation sheet containing the thermally conductive particles having the smaller maximum length is arranged on the outermost surface in the vertical direction of the laminate.
ここで、熱伝導性粒子の「最長部長さ」とは、その形状の特徴を最も示す所（長いところ）の距離とする。球状であれば直径、立方体を含む多面体であれば最も大きな頂点間距離、紡錘状であれば長径、板状であれば投影面の長径、繊維状であれば繊維長（厳密には、繊維直径と繊維長からなる三角形の長辺になるが、本願では繊維長で代用できる）となる。 Here, the “longest part length” of the heat conductive particles is the distance at which the characteristic of the shape is the most (long part). If it is spherical, it is the diameter, if it is a polyhedron including a cube, the largest distance between vertices, if it is spindle-shaped, it is the long diameter, if it is plate-shaped, the long diameter of the projection surface, and if it is fibrous, the fiber length (strictly speaking, fiber diameter. And the long side of the triangle consisting of the fiber length, but in the present application, the fiber length can be substituted.
本発明の熱伝導性複合材料では、１個の熱伝導性粒子がシート状成形品の表裏２つの面に露出していることで、当該シート成形品の表側と裏側を貫通する熱伝導パスが既に形成されている。熱伝導性粒子の最長部長さがシート状の樹脂マトリクスの厚みよりもはるかに小さいような通常の熱伝導性樹脂組成物は、成形品の表側と裏側の間に複数個の熱伝導性微粒子が存在し、それら微粒子同士の界面にはマトリクス樹脂による有機層が介在する。この場合、シート成形品の表側と裏側を貫通する熱伝導パスは形成しえない。従って本願発明のシート成形品は、その内部の熱移動に際して有機成分由来の熱抵抗が一切なく、熱伝導性粒子本来の熱伝導率に準じた熱流束が期待できる。 In the heat conductive composite material of the present invention, one heat conductive particle is exposed on the two front and back surfaces of the sheet-shaped molded product, so that the heat conductive path passing through the front side and the back side of the sheet molded product is It has already been formed. A normal heat conductive resin composition in which the longest length of the heat conductive particles is much smaller than the thickness of the sheet-shaped resin matrix, a plurality of heat conductive fine particles are provided between the front side and the back side of the molded product. An organic layer of matrix resin is present at the interface between the fine particles. In this case, a heat conduction path that penetrates the front side and the back side of the sheet molded product cannot be formed. Therefore, the sheet molded article of the present invention has no thermal resistance derived from organic components during heat transfer inside, and a heat flux conforming to the original thermal conductivity of the thermally conductive particles can be expected.
さらに、確実な熱伝導パスがあることにより、想定される熱流束の大きさに応じて熱伝導性粒子の配合量を減ずる方向に調節できるだけの樹脂組成物組成上の自由度を生む。その結果として、従来の複合材料に比べてフィラーが局在化するため、マトリクス樹脂の単独相の体積が大きくなり、樹脂本来の性能を保持しやすい。柔軟性の高いマトリクス樹脂を組み合わせるような場合、特にその柔軟性が損なわれることなく複合材料成形品が得られるメリットがある。 Furthermore, the presence of a reliable heat conduction path gives flexibility in the composition of the resin composition so that the blending amount of the heat conductive particles can be adjusted in the direction of decreasing the expected heat flux. As a result, since the filler is localized as compared with the conventional composite material, the volume of the single phase of the matrix resin is increased, and the original performance of the resin is easily maintained. When a highly flexible matrix resin is combined, there is an advantage that a composite material molded product can be obtained without particularly impairing the flexibility.
本発明の実施形態について詳細に説明する。 Embodiments of the present invention will be described in detail.
（熱伝導性粒子）
本発明に用いる熱伝導性粒子は、熱伝導性がよければ特に制限はないが、その形状から大別して粒子状のものと線状のものに分けることができる。粒子状熱伝導性粒子は、樹脂マトリクスの厚さが比較的薄い場合に適しており、好ましくは厚さ１０μｍ〜５００μｍの場合に用いるのが良く、線状熱伝導性粒子は、樹脂マトリクスの厚さが比較的厚い場合に適しており、好ましくは厚さ１００μｍ〜３０ｍｍの場合に用いるのが良い。
(Thermally conductive particles)
The heat conductive particles used in the present invention are not particularly limited as long as they have good heat conductivity, but they can be roughly classified into particles and linear particles. The particulate thermally conductive particles are suitable when the thickness of the resin matrix is relatively thin, and are preferably used when the thickness is 10 μm to 500 μm. The linear thermally conductive particles have a thickness of the resin matrix. Is suitable when the thickness is relatively thick, and is preferably used when the thickness is 100 μm to 30 mm.
代表的な粒子状の熱伝導性粒子を例示すると、アルミニウム酸化物、窒化アルミニウム、立方晶窒化ホウ素、六方晶窒化ホウ素、酸化亜鉛、酸化マグネシウム、酸化ベリリウム、ダイヤモンドおよび各種金属粉が例示される。これらの一次粒子または凝集粒子が、本発明における微粒子１層を構成する熱伝導性粒子となる。
代表的な線状の熱伝導性粒子を例示すると、セルロースナノファイバー、炭素繊維、金属ワイヤが例示される。
Illustrative examples of thermally conductive particles in the form of particles include aluminum oxide, aluminum nitride, cubic boron nitride, hexagonal boron nitride, zinc oxide, magnesium oxide, beryllium oxide, diamond, and various metal powders. These primary particles or agglomerated particles serve as the heat conductive particles constituting one layer of the fine particles in the present invention.
Examples of typical linear heat conductive particles include cellulose nanofibers, carbon fibers, and metal wires.
さらに、前記した熱伝導性粒子が、熱伝導性粒子とそれとは異なる材質からなる球状微粒子（以下、土台粒子と記す）とからなる複合フィラーであって、熱伝導性粒子が土台粒子表面に固定されて被覆層を形成している構造を有していてもよい。土台粒子としては、サイズに自由度が高いガラスビーズ、シリカビーズや各種ポリマービーズが例示され、中空、多孔体であっても中実であってもよい。これら土台粒子の表面が前記熱伝導性粒子の凝集堆積等によって被覆されてなる複合フィラーであれば、熱伝導性粒子として本発明の複合材料に用いる際に、最長部長さを要求に応じて調節することも可能であり、また耐熱性の点で問題を生じない範囲で材質を選べば、複合材料の低比重化にも貢献しうるので好ましい。これら複合フィラーの作成は、例えば、土台粒子と熱伝導性粒子を所定量混合してえた分散液による噴霧乾燥などにより得ることができる。この際に後述の粒子サイズの制約を受けるのは、複合フィラーとしての最長部長さである。 Furthermore, the heat conductive particles are composite fillers composed of heat conductive particles and spherical fine particles made of a material different from that (hereinafter referred to as base particles), and the heat conductive particles are fixed on the base particle surface. It may have a structure in which it is formed to form a coating layer. Examples of the base particles include glass beads, silica beads, and various polymer beads having a high degree of freedom in size, and may be hollow, porous or solid. When the composite filler is formed by coating the surface of the base particles by cohesive deposition of the heat conductive particles, when used in the composite material of the present invention as the heat conductive particles, the longest part length is adjusted as required. It is also possible to do so, and it is preferable to select a material within a range that does not cause a problem in heat resistance, because it can contribute to lowering the specific gravity of the composite material. These composite fillers can be produced by, for example, spray drying with a dispersion obtained by mixing a predetermined amount of base particles and heat conductive particles. At this time, what is restricted by the particle size described later is the maximum length of the composite filler.
ここまでに述べた熱伝導性粒子の１個の大きさ（最長部長さ）は１０μｍ以上であり、そのバラツキが中心値の±２０％以内入っていることが好ましい。最長部長さは後述する熱伝導性複合材料の放熱シートに要求される厚さに合わせることになるため、上限は本発明を実施する際に利用する熱伝導性粒子あるいは熱伝導性複合フィラーの土台粒子の最長部長さに依存する。一方、熱伝導性粒子あるいは熱伝導性複合フィラーがもつ大きさのバラつきには注意する必要がある。要求される最長部長さの大きさに依存して好ましいバラツキは変わりうるが、最長部長さが１０μｍである場合には、±５％以下であることが望ましく、最長部長さが１００μｍを超える場合には±１０％であっても大きな支障はない。いずれも本発明の実施の形態である放熱シートが取り付けられる発熱体（パワーモジュールやＣＰＵ、ＭＰＵ、ＧＰＵの半導体チップ等）の形状や表面状態に合わせて設定する必要がある。 It is preferable that the size (longest part length) of each of the heat conductive particles described above is 10 μm or more, and the variation thereof is within ± 20% of the central value. Since the longest part length will be adjusted to the thickness required for the heat dissipation sheet of the heat conductive composite material described later, the upper limit is the base of the heat conductive particles or the heat conductive composite filler used when carrying out the present invention. It depends on the longest length of the particle. On the other hand, it is necessary to pay attention to the variation in the size of the heat conductive particles or the heat conductive composite filler. The preferable variation may vary depending on the required maximum length, but when the maximum length is 10 μm, it is preferably ± 5% or less, and when the maximum length exceeds 100 μm. Is ± 10%, there is no big problem. In either case, it is necessary to set the shape according to the shape and surface state of the heating element (power module, semiconductor chip of CPU, MPU, GPU, etc.) to which the heat dissipation sheet according to the embodiment of the present invention is attached.
（複合材料）
本発明の複合材料は、シート状樹脂マトリクス中に、熱伝導性粒子が分散混合されている複合材料であって、前記複合材料の、表裏２つの表面に前記熱伝導性粒子単体の表面が露出していることを特徴とする。
本発明の複合材料は、厚さに比べて面積が大きいシート状の形状であり、その面積の大きさは用途によって決まる。半導体チップそのものの冷却を目的とする場合、そのサイズは２０ｍｍ×２０ｍｍ程度が標準的な大きさとして例示できる。一方でパワーモジュールのようなモジュール化された半導体部品の冷却であれば、より大きな面積が必要になる。
(Composite material)
The composite material of the present invention is a composite material in which thermally conductive particles are dispersed and mixed in a sheet-shaped resin matrix, and the surface of the single thermally conductive particles is exposed on the two front and back surfaces of the composite material. It is characterized by doing.
The composite material of the present invention has a sheet-like shape having an area larger than the thickness, and the size of the area is determined by the application. For the purpose of cooling the semiconductor chip itself, its size can be exemplified as a standard size of about 20 mm × 20 mm. On the other hand, in the case of cooling a modularized semiconductor component such as a power module, a larger area is required.
次に、シートを構成する樹脂マトリクスの厚さは１０μｍ〜３０ｍｍである。樹脂マトリクスの厚さが、１０μｍより薄いと、シート状の複合材料の作成に際して、表裏２面に熱伝導性粒子を露出させる工程が煩雑となり好ましくない。また、樹脂マトリクスの厚さが３０ｍｍより厚くなると、本願発明の実施の形態である放熱シート用途としては実用上厚すぎ、本来、発熱体とヒートシンクを熱的に結合するための部品であることを考慮すると好ましくない。より好ましい、樹脂マトリクスの厚さは、５０μｍ〜１０ｍｍである。これらの範囲内であれば、工業的に入手可能な熱伝導性粒子を好適に用いることができ、それらの露出のための工程も簡便なものとなる。 Next, the thickness of the resin matrix forming the sheet is 10 μm to 30 mm. If the thickness of the resin matrix is less than 10 μm, the step of exposing the thermally conductive particles to the front and back surfaces 2 is complicated when producing the sheet-shaped composite material, which is not preferable. Further, if the thickness of the resin matrix is thicker than 30 mm, it is practically too thick for use as a heat dissipation sheet, which is an embodiment of the present invention, and is originally a component for thermally coupling a heat generating element and a heat sink. It is not preferable in consideration. More preferably, the thickness of the resin matrix is 50 μm to 10 mm. Within the range, industrially available thermally conductive particles can be preferably used, and the process for exposing them can be simplified.
マトリクス樹脂部表面に露出している熱伝導性粒子は、前記複合材料の、表裏２つの表面に前記熱伝導性粒子単体の表面が露出していることが必要である。これにより表裏２面を貫通する形で熱伝導性フィラー（熱伝導性粒子）が配置され、同方向での高い熱伝導性が発現する。一方で表裏２面意外の端面への露出は必須ではなく、むしろ端面での熱伝導性粒子の露出によりマトリクス樹脂から見れば、切欠きが存在することになり、複合材料全体が大きく変形した際の破断開始点になりうることから好ましくない。従って、端面での露出は可能な限り避けるように熱伝導性粒子を分散混合することが望まれる。 The thermally conductive particles exposed on the surface of the matrix resin portion need to have the surfaces of the single thermally conductive particles exposed on the two front and back surfaces of the composite material. As a result, the heat conductive filler (heat conductive particles) is arranged so as to penetrate the front and back surfaces, and high heat conductivity in the same direction is exhibited. On the other hand, it is not essential to expose the two front and back surfaces to the end faces, but rather the exposure of the heat conductive particles on the end faces causes a notch to be seen from the matrix resin, and when the entire composite material is greatly deformed. It is not preferable because it can be a fracture starting point. Therefore, it is desirable to disperse and mix the thermally conductive particles so that the exposure at the end surface is avoided as much as possible.
次に、複合材料に含まれる熱伝導性粒子量は、１０ｖｏｌ％以上７４ｖｏｌ％以下の配合量であることが好ましい。 Next, the amount of the thermally conductive particles contained in the composite material is preferably 10 vol% or more and 74 vol% or less.
複合材料に含まれる熱伝導性粒子量の配合量が、多すぎると複合材料がシートを形成することが困難となるため、７４ｖｏｌ％以下の配合量であることが好ましい。
また、下限値には特別な制約はないが、成形品の一部にしか熱伝導性フィラーが存在しない場合、期待される熱流束は低くなり敢えて本発明の手法を用いずとも既製品を用いて対処すればよい。１０％未満では所望の性能が発揮できず、好ましくは５０％以上の配合が必要である。
配合量は、より好ましくは、２０ｖｏｌ％以上６０ｖｏｌ％以下であり、更に好ましくは、３０ｖｏｌ％以上６０ｖｏｌ％以下である。発熱体からの熱流束を直ちによって、マトリクス樹脂そのものも加熱される一方で、マトリクス部の熱容量が必要以上に大きくなってしまうことは好ましくないことから熱伝導性粒子の配合量は大きい方が望ましいが、最密充填に近い状態に熱伝導性粒子を配列することが必ずしも必要ではないことから、製造工程に大きな負担をもたらさない６０ｖｏｌ％が実質的な配合量の上限として好ましい。
When the amount of the thermally conductive particles contained in the composite material is too large, it becomes difficult for the composite material to form a sheet. Therefore, the amount is preferably 74 vol% or less.
In addition, although there is no particular restriction on the lower limit value, when the heat conductive filler is present only in a part of the molded product, the expected heat flux becomes low and the ready-made product is used without intentionally using the method of the present invention. And deal with it. If it is less than 10%, the desired performance cannot be exhibited, and preferably 50% or more is required.
The blending amount is more preferably 20 vol% or more and 60 vol% or less, and further preferably 30 vol% or more and 60 vol% or less. While the matrix resin itself is also heated by the immediate heat flux from the heating element, it is not preferable that the heat capacity of the matrix portion becomes unnecessarily large. Therefore, it is desirable that the content of the heat conductive particles is large. However, since it is not always necessary to arrange the heat conductive particles in a state close to the closest packing, 60 vol% which does not bring a great burden to the manufacturing process is preferable as the upper limit of the substantial blending amount.
（樹脂マトリクス）
本発明の複合材料を構成するもう一方の成分であるマトリクス樹脂には、硬化性樹脂であるアクリル樹脂、エポキシ樹脂、シリコーン樹脂、ポリシルセスキオキサン系樹脂やこれらの複合組成からなる樹脂および熱可塑性樹脂も用いることができる。これらの選定には、樹脂の耐熱性（熱分解温度）を基準に、本発明の実施の形態である放熱シートが取付られる発熱体の想定温度に応じて選択することになるが、高い熱流束を要求されるパワーモジュール等への接続を前提とする用途であれば、少なくともシリコーン樹脂やポリシルセスキオキサン系樹脂などのケイ素系骨格を有する硬化物であることが求められる。
(Resin matrix)
The matrix resin, which is the other component of the composite material of the present invention, includes a curable resin such as acrylic resin, epoxy resin, silicone resin, polysilsesquioxane resin, a resin having a composite composition of these, and a thermal resin. A plastic resin can also be used. These are selected based on the heat resistance (thermal decomposition temperature) of the resin, according to the assumed temperature of the heat generating element to which the heat dissipation sheet according to the embodiment of the present invention is attached. If the application is intended to be connected to a power module or the like that is required, it is required to be a cured product having at least a silicon skeleton such as a silicone resin or a polysilsesquioxane resin.
シリコーン樹脂は２００℃程度以上の耐熱性を有し、低硬度から高硬度体まで様々に調節が可能、官能基の変更による粘着性付与もでき、多様な成形手法に対応できる等本発明に好適に用いることができる。また、ポリシルセスキオキサン系樹脂であれば、かご型からラダー型構造に至るポリシルセスキオキサン部構造やポリシルセスキオキサン部を連結する架橋部の構造等を制御（ソフトセグメント導入、ハードセグメント導入や両者のバランス化を図る等）することにより、＞２３０℃以上の耐熱性、様々な弾性率への対応等、マトリクスとして本質的な性能をシリコーン系以上に高く設計することができるので好ましい。 Silicone resin has a heat resistance of about 200 ° C. or higher, can be adjusted in various ways from low hardness to high hardness, and can give tackiness by changing the functional group, and is suitable for various molding methods. Suitable for the present invention. Can be used for. If it is a polysilsesquioxane-based resin, it controls the structure of the cross-linking part connecting the polysilsesquioxane part and the polysilsesquioxane part structure from the cage type to the ladder type structure (soft segment introduction, Introducing hard segments and balancing the two) makes it possible to design the matrix's essential performance higher than that of silicones, such as heat resistance> 230 ° C and compatibility with various elastic moduli. Therefore, it is preferable.
一方で、定常状態での排熱量が大きくない場合であれば、耐熱性の点で劣るアクリル樹脂やエポキシ樹脂もしくは熱可塑性樹脂などであっても構わないが、本発明の複合材料の形状を作れる加工方法（例えば、コンプレッション成形とインサート成形の組合せ等）との摺合せが必要である。 On the other hand, if the amount of heat exhausted in the steady state is not large, an acrylic resin, an epoxy resin, or a thermoplastic resin having poor heat resistance may be used, but the shape of the composite material of the present invention can be formed. Sliding with a processing method (for example, a combination of compression molding and insert molding) is required.
以下に、本発明の複合材料の製造方法について説明する。 Below, the manufacturing method of the composite material of this invention is demonstrated.
本発明の複合材料は、熱伝導性粒子が樹脂マトリクスに埋没することなく、当該複合材料の、少なくとも端面以外の表裏２つの表面にその一部がそれぞれ露出していることが必要である。従って、係る構造を再現よく作成する方法も重要となる。樹脂マトリクスの極めて薄い薄膜が熱伝導性粒子表面に存在し、その露出状態が阻害されることでも熱流束の大幅な低下となる。以下の方法はこれを回避するための方法として例示したものである。 In the composite material of the present invention, it is necessary that the heat conductive particles are not buried in the resin matrix and at least a part thereof is exposed on at least two front and back surfaces other than the end surfaces of the composite material. Therefore, a method of reproducibly creating such a structure is also important. An extremely thin thin film of the resin matrix is present on the surface of the heat conductive particles, and the exposed state is hindered, so that the heat flux is significantly reduced. The following method is an example of a method for avoiding this.
本発明の複合材料の製造方法の一つ例示をすると、熱伝導性粒子１個の最長部長さより大きな厚さを有する樹脂マトリクス中に、当該熱伝導性粒子が分散混合され、必要に応じて硬化あるいは冷却されて固化した複合材料成形品を作成後、端面以外の表裏２つの表面を物理的な研磨や電子線等の照射によるエッチング処理により、熱伝導性粒子の一部を露出させる方法がある。熱伝導性粒子の露出に当たっては溶解や融解等の処理も可能であるが、前記したように極めて薄い有機層が残留しても熱伝導性には悪影響を及ぼす場合がある。処理後の熱伝導性粒子表面の残留有機成分の確認が必須となる。 As one example of the method for producing the composite material of the present invention, the heat conductive particles are dispersed and mixed in a resin matrix having a thickness larger than the longest length of one heat conductive particle, and the heat conductive particles are cured if necessary. Alternatively, there is a method of exposing a part of the heat conductive particles by physically polishing the two surfaces other than the end surface and performing an etching treatment by irradiation with an electron beam, etc., after producing a composite material molded product that is cooled and solidified. . When exposing the thermally conductive particles, it is possible to perform processing such as dissolution or melting. However, even if the extremely thin organic layer remains as described above, the thermal conductivity may be adversely affected. It is essential to confirm the residual organic components on the surface of the thermally conductive particles after the treatment.
次に、他の方法として、熱伝導性粒子１個の最長部長さよりも小さい距離を保持した平行平板間に形成された空間に、当該熱伝導性粒子が分散配置された状態で、未硬化の樹脂組成物または適切な熱可塑性樹脂を流入させ、硬化あるいは冷却して固化させた後、平行平板を取り除いて複合材料成形品を得る方法もある。この場合、平行平板にはテフロン（登録商標）やシリコーンゴム等の高硬度シートが好適に用いられ、これらシートの全面に均等に荷重を印加することで、熱伝導性粒子がシートに喰い込んだ状態となり、その最長部長さよりも小さい平行平板間距離を得、結果的に熱伝導性粒子の一部が露出した成形品となる。平行平板の硬度や弾性率および厚さと荷重の組合せによって、得られる露出の程度はある程度調節することができる。
工業的にはコンプレッション成形機の利用が好適である。
Next, as another method, in a state where the thermally conductive particles are dispersed and arranged in a space formed between parallel flat plates holding a distance smaller than the maximum length of one thermally conductive particle, the uncured material is uncured. There is also a method of injecting a resin composition or an appropriate thermoplastic resin, curing or cooling to solidify, and then removing the parallel flat plates to obtain a composite material molded article. In this case, a high hardness sheet such as Teflon (registered trademark) or silicone rubber is preferably used as the parallel plate, and the heat conductive particles are embedded in the sheet by applying a load evenly to the entire surface of the sheet. Then, a distance between the parallel plates smaller than the length of the longest part is obtained, and as a result, a molded product in which a part of the heat conductive particles is exposed is obtained. The degree of exposure obtained can be adjusted to some extent by the hardness and elastic modulus of the parallel plate and the combination of thickness and load.
It is industrially preferable to use a compression molding machine.
一方で、熱伝導性粒子の最長部長さが大きくなり、繊維状に近づく場合には前述の手法では複合材料を作ることが難しい。予め有限長に切断または折り曲げ加工した繊維状熱伝導性粒子を一定量束ねた「部品」を作成し、これを各繊維の長手方向と垂直な面に立てた状態で、樹脂マトリクスとなる硬化性組成物あるいは熱可塑性樹脂に含浸することで作成できる。この時、樹脂マトリクスに含浸される「部品」の数とその分布に制約はない。例えば、直径の大きな「部品」１個（ただしこの「部品」には多数の繊維状熱伝導微粒子が仕込まれている）を所定量の樹脂マトリクスに含浸させて得る構造体でもよいし、直径の小さな「部品」を多数用いて、前記した最長部長さが小さい熱伝導性粒子を配合してなる複合材料を得る際の、配合量の考え方に準じて配置し、所定量の樹脂マトリクスに含浸させている構造体でも良い。いずれにせよ、硬化後あるいは冷却後の樹脂マトリクス成形品の端面以外の表裏２つの表面に前記「部品」が露出していることが必要である。露出面の作成には、前記した手法の利用が考えられる。 On the other hand, when the longest length of the thermally conductive particles becomes large and approaches a fibrous shape, it is difficult to make a composite material by the above method. A "part" is created by bundling a certain amount of fibrous heat conductive particles that have been cut or bent in advance to a finite length, and is placed on a surface perpendicular to the longitudinal direction of each fiber to form a resin matrix It can be prepared by impregnating a composition or a thermoplastic resin. At this time, there is no restriction on the number of “components” impregnated in the resin matrix and their distribution. For example, it may be a structure obtained by impregnating a predetermined amount of resin matrix with one "part" having a large diameter (however, a large number of fibrous heat conductive fine particles are charged in this "part"), or When a large number of small "parts" are used, they are arranged according to the concept of the compounding amount when a composite material is prepared by compounding the above-mentioned thermal conductive particles having a small maximum length, and the resin matrix is impregnated with a predetermined amount. The structure may be In any case, it is necessary that the "components" are exposed on the two front and back surfaces other than the end surfaces of the resin matrix molded product after curing or cooling. The method described above may be used to create the exposed surface.
本発明の構成を満たす複合材料を放熱部品として利用する場合、複合材料シートの厚みが大きくなることが想定され、厚さの増大に伴い熱伝導性粒子や熱伝導性複合フィラーの最長部長さを大きくすることが必要になる。現実的な材料としては線状の熱伝導性粒子を利用することになり、各種金属ワイヤ、セルロースナノファイア―、カーボンファイバー、カーボンナノチューブや土台となる繊維状物質（例えば、グラスファイバーなどを前記した熱伝導性粒子で被覆した複合繊維等）が利用できる、 When a composite material satisfying the constitution of the present invention is used as a heat dissipation component, it is assumed that the thickness of the composite material sheet becomes large, and the maximum length of the heat conductive particles or the heat conductive composite filler is increased as the thickness increases. It needs to be large. As a realistic material, linear thermal conductive particles will be used, and various metal wires, cellulose nanofires, carbon fibers, carbon nanotubes and fibrous substances as a base (for example, glass fiber etc. are mentioned above). Composite fibers coated with heat conductive particles, etc.) can be used,
前記した熱伝導性複合材料シートの厚みが大きくなる場合、そのままでヒートシンク等の機能を具備した方が放熱性の点で効率的である。そこで、係る複合材料の構造を利用したヒートシンク構造の形成が望ましい。当該複合材料の端面以外の表裏２面の内の一方に露出している繊維状の熱伝導性粒子が微粒子１個の表面積の、平均して２０％以上が露出している状態を作ればよい。具体的には複合材料のマトリクス部厚みを繊維長に比して小さく（繊維状熱伝導性粒子の露出の程度を大きく）すればよく、外観上は剣山のような状態となる。ヒートシンクとしての性能を高めるとすれば、この露出の程度は大きいほどよく、少なくとも繊維状熱伝導性粒子の１個当たりの表面積の２０％以上が露出していることが望ましく、５０％以上であってもよい。この数値は２０％未満であれば、ヒートシンクとしての性能が乏しくなり、好ましくない。 When the thickness of the above-mentioned thermally conductive composite material sheet becomes large, it is more efficient in terms of heat dissipation if it is provided with a function such as a heat sink as it is. Therefore, it is desirable to form a heat sink structure using the structure of the composite material. The fibrous thermally conductive particles exposed on one of the two front and back surfaces other than the end surface of the composite material may be exposed in an average of 20% or more of the surface area of one fine particle. . Specifically, the thickness of the matrix portion of the composite material may be made smaller than the fiber length (the degree of exposure of the fibrous heat-conductive particles is large), and the appearance looks like a sword. In order to improve the performance as a heat sink, the greater the degree of this exposure, the better, and it is desirable that at least 20% or more of the surface area of each fibrous thermally conductive particle is exposed, and at least 50%. May be. If this value is less than 20%, the performance as a heat sink becomes poor, which is not preferable.
特に、熱伝導性複合材料シートの厚みが大きくなる場合、樹脂マトリクスが低硬度もしくあは低弾性率の耐熱性樹脂と組み合わせることで、下地の形状追従性を付与することが出来る。繊維状の高熱伝導性粒子を束にして立てる構造は、変形性に乏しく硬くなるが、本発明では柔軟な樹脂マトリクスを繊維状の熱伝導性粒子の間に充填することで、複合材料成形品全体としての柔軟性も確保することが出来る。樹脂マトリクスが低弾性率であれば塑性変形的な挙動、弾性率が大きければ可逆性のある変形挙動となる。さらに、これら束を必要に応じて一つの熱伝導性粒子と見なし、樹脂マトリクス内に分散混合するという考え方を導入することで、複合材料成形品全体の柔軟性を高められ多様なアプリションへの適用が可能となる。 In particular, when the thickness of the heat conductive composite material sheet is large, the shape conformability of the base can be imparted by combining the resin matrix with a heat resistant resin having low hardness or low elastic modulus. The structure in which fibrous high thermal conductive particles are bundled and stiff has poor deformability, but in the present invention, a flexible resin matrix is filled between the fibrous thermal conductive particles to form a composite material molded product. The flexibility as a whole can be secured. If the resin matrix has a low elastic modulus, it behaves like plastic deformation, and if the resin matrix has a large elastic modulus, it has reversible deformation behavior. Furthermore, by introducing the concept that these bundles are regarded as one thermally conductive particle as needed and dispersed and mixed in the resin matrix, the flexibility of the composite material molded article as a whole can be increased and various applications can be realized. Applicable.
（放熱シート）
前述のように、本発明の構成を満たす複合材料はシート状であるので、そのまま利用すれば発熱体とヒートシンク等の間に挟む放熱シートとして利用できる。しかし、フィラーサイズが小さな均一分散体とは異なり、熱伝導性粒子の大きさが大きく、その数が限られている本発明の構成では、放熱シートして十分な下地形状追従性が発揮できず、この部分が熱抵抗となる可能性がある。これを回避するためには、最長部長さの異なる熱伝導性粒子あるいは熱伝導性複合フィラーを用いた複合材料のシートを複数準備し、これらを厚さ方向に積層することで放熱シートとしての厚みを稼ぎ下地形状追従性を確保することが好ましい。
(Heat dissipation sheet)
As described above, since the composite material satisfying the constitution of the present invention is in the form of a sheet, if it is used as it is, it can be used as a heat dissipation sheet to be sandwiched between a heating element and a heat sink or the like. However, unlike a uniform dispersion having a small filler size, the size of the thermally conductive particles is large, and in the configuration of the present invention in which the number is limited, a heat dissipation sheet cannot exhibit sufficient base shape conformability. , This part may become a thermal resistance. In order to avoid this, prepare multiple sheets of composite material using thermally conductive particles or thermally conductive composite fillers having different longest lengths, and stack these in the thickness direction to obtain a thickness as a heat dissipation sheet. It is preferable to secure the base shape conformability.
本発明の熱伝導性複合材料のシートを積層して放熱シートする場合、少なくとも２水準の最長部長さを有する熱伝導性粒子を準備し、それぞれを用いてなるシート状複合材料を積層することが望ましい。その際に、最長部長さの大きさに応じて段階的に、すなわち相対的に小さな最長部長さを有する熱伝導性粒子を含むシート状複合材料が放熱シートの表裏の表面寄りに配置されてなるように表裏対称に積層し、さらに、熱伝導性粒子の配合量も同じ方向に大きくなるように設計することで、シート間の熱伝導パスが確実に形成できるようになる。 When a sheet of the heat conductive composite material of the present invention is laminated to form a heat dissipation sheet, it is possible to prepare heat conductive particles having a longest part length of at least 2 levels and laminate the sheet-shaped composite material using each of them. desirable. At that time, the sheet-shaped composite material containing heat-conductive particles having a relatively small maximum length is arranged stepwise according to the size of the maximum length, and is arranged near the front and back surfaces of the heat dissipation sheet. By thus stacking the sheets symmetrically on the front and back and further designing the compounding amount of the heat conductive particles to increase in the same direction, the heat conduction path between the sheets can be surely formed.
以下に実施例及び比較例を示して本発明を具体的に説明する。但し、本発明は実施例に限定されるものではない。 The present invention will be specifically described below with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.
＜シート状複合材料１（Ｓ−１）＞
市販のｃ−ＢＮ（立方晶窒化ホウ素、グローバルダイヤモンド社製 ＦＢＮ−３００，４２０μｍφ）の所定量を底面積が１００ｍｍ×１００ｍｍ以上あるテフロン（登録商標）トレーの上に拡げ、振とう機（アズワン社製ＭＰＸ−９６Ａ）上に固定し、ゆっくりと振動させながら、シリコーン樹脂製のヘラを併用しながらｃ−ＢＮ微粒子を一層厚さで展開した。その後、５ｍｍ厚さ、外形寸法が前記したテフロン（登録商標）トレーの底面積と同じテフロン（登録商標）シートを展開したｃ−ＢＮ層の上から静かに置き、さらに２ｍｍ厚さ（同形状）のステンレス板を重ねた上に１ｋｇの錘を置いた。これにより、テフロン（登録商標）トレーとテフロン（登録商標）シートの間にｃ−ＢＮが挟まれてなる空間を作った。
次に、マトリクス樹脂としてエポキシ樹脂（三菱ケミカル社製 エピコート８２８）、エポキシ樹脂硬化剤（日立化成社製ＨＮ−２０００）、反応性希釈材（ナガセケムテックス社製 デナコールＥＸ−１４１）および硬化触媒を所定量混合した熱硬化性組成物を前記したテフロン（登録商標）トレーとテフロン（登録商標）シートの間にｃ−ＢＮが挟まれてなる空間に静かに流し込み、必要に応じて、超音波振動を印加しながら脱泡を行った。
その後、８０℃、４時間の硬化処理を行った後、樹脂マトリクス部の厚さが３８０μｍであり、ｃ−ＢＮが露出したシート状複合材料１（Ｓ−１）を得た。
<Sheet-shaped composite material 1 (S-1)>
A predetermined amount of commercially available c-BN (cubic crystal boron nitride, FBN-300, 420 μmφ manufactured by Global Diamond Co., Ltd.) was spread on a Teflon (registered trademark) tray having a bottom area of 100 mm × 100 mm or more, and shaker (As One Co., Ltd.). (Manufactured by MPX-96A), and while slowly vibrating, a c-BN fine particle was developed with a further thickness while using a spatula made of silicone resin. Thereafter, a Teflon (registered trademark) sheet having the same 5 mm thickness and outer dimensions as the above-mentioned bottom area of the Teflon (registered trademark) tray is gently placed on the developed c-BN layer and further 2 mm thick (same shape). A 1 kg weight was placed on the stacked stainless steel plates. This created a space in which the c-BN was sandwiched between the Teflon (registered trademark) tray and the Teflon (registered trademark) sheet.
Next, as a matrix resin, an epoxy resin (Epicoat 828 manufactured by Mitsubishi Chemical Co., Ltd.), an epoxy resin curing agent (HN-2000 manufactured by Hitachi Chemical Co., Ltd.), a reactive diluent (Denacol EX-141 manufactured by Nagase Chemtex Co.) and a curing catalyst are used. The thermosetting composition mixed in a predetermined amount is gently poured into a space in which c-BN is sandwiched between the Teflon (registered trademark) tray and the Teflon (registered trademark) sheet described above, and ultrasonic vibration is applied as necessary. Was applied while applying degassing.
Then, after carrying out a curing treatment at 80 ° C. for 4 hours, a sheet-shaped composite material 1 (S-1) was obtained in which the thickness of the resin matrix portion was 380 μm and c-BN was exposed.
＜シート状複合材料２（Ｓ−２）＞
前記Ｓ−１と同じｃ−ＢＮの所定量を底面積が１００ｍｍ×１００ｍｍ以上あるテフロン（登録商標）トレーの上に拡げ、振とう機（アズワン社製ＭＰＸ−９６Ａ）上に固定し、ゆっくりと振動させながら、シリコーン樹脂製のヘラを併用しながらｃ−ＢＮ微粒子を一層厚さで展開した。その後、５０μｍ厚さ、外形寸法が前記したテフロン（登録商標）トレーの底面積と同じテフロン（登録商標）フィルムを展開したｃ−ＢＮ層の上から静かに置いた。これにより、テフロン（登録商標）トレーとテフロン（登録商標）フィルムの間にｃ−ＢＮが挟まれてなる空間を作った。
次に、マトリクス樹脂としてエポキシ樹脂（三菱ケミカル社製 エピコート８２８）、エポキシ樹脂硬化剤（日立化成社製ＨＮ−２０００）、反応性希釈材（ナガセケムテックス社製 デナコールＥＸ−１４１）および硬化触媒を所定量混合した熱硬化性組成物を前記したテフロン（登録商標）トレーに静かにとテフロン（登録商標）シートの間にｃ−ＢＮが挟まれてなる空間に静かに流し込み、必要に応じて、超音波振動を印加しながら脱泡を行った。
その後、８０℃、４時間の硬化処理を行った後、樹脂マトリクス部の厚さが４５０μｍであり、ｃ−ＢＮが露出していないシート状複合材料２（Ｓ−２）を得た。
<Sheet-like composite material 2 (S-2)>
A predetermined amount of the same c-BN as S-1 was spread on a Teflon (registered trademark) tray having a bottom area of 100 mm × 100 mm or more, fixed on a shaker (MPX-96A manufactured by As One Co.), and slowly. While vibrating, while using a spatula made of a silicone resin together, the c-BN fine particles were developed to a further thickness. Then, a Teflon (registered trademark) film having a thickness of 50 μm and the same external dimensions as the above-mentioned bottom area of the Teflon (registered trademark) tray was gently placed on the developed c-BN layer. This created a space in which the c-BN was sandwiched between the Teflon (registered trademark) tray and the Teflon (registered trademark) film.
Next, as a matrix resin, an epoxy resin (Epicoat 828 manufactured by Mitsubishi Chemical Co., Ltd.), an epoxy resin curing agent (HN-2000 manufactured by Hitachi Chemical Co., Ltd.), a reactive diluent (Denacol EX-141 manufactured by Nagase Chemtex Co.) and a curing catalyst are used. The thermosetting composition mixed in a predetermined amount is gently poured into the above-mentioned Teflon (registered trademark) tray and gently into a space in which c-BN is sandwiched between Teflon (registered trademark) sheets, and if necessary, Defoaming was performed while applying ultrasonic vibration.
Then, after carrying out a curing treatment at 80 ° C. for 4 hours, a sheet-shaped composite material 2 (S-2) was obtained in which the resin matrix portion had a thickness of 450 μm and c-BN was not exposed.
＜シート状複合材料３（Ｓ−３）＞
市販のｃ−ＢＮ（立方晶窒化ホウ素、グローバルダイヤモンド社製 ＦＢＮ−３００，）を用いたほかは、前記した＜シート状複合材料１＞と同様の手順を経て、樹脂マトリクス部の厚さが８０μｍであり、ｃ−ＢＮが露出したシート状複合材料３（Ｓ−３）を得た。
<Sheet-shaped composite material 3 (S-3)>
A commercially available c-BN (cubic boron nitride, FBN-300, manufactured by Global Diamond Co., Ltd.) was used, and the procedure of <Sheet-shaped composite material 1> described above was followed, and the thickness of the resin matrix portion was 80 μm. And a sheet-shaped composite material 3 (S-3) in which c-BN was exposed was obtained.
＜シート状複合材料４（Ｓ−４）＞
市販の銅ワイヤ（Ｃｏｉｎｉｎｇ社製 ＯＷ−２２５，１５０μｍφ）を１８ｍｍずつに切断し、両面粘着テープ（３Ｍ社製 ９４１５ＰＣ，０．０６ｍｍｔ）上に片端の位置を両面粘着テープの端部に一致させるように相互の位置を合わせて横並びに並べた。得られた簾状の銅ワイヤ集合体をロールして巻物状にし、最終手的に直径が１５ｍｍになるまで巻き取った。
次に、マトリクス樹脂としてエポキシ樹脂（三菱ケミカル社製 エピコート８２８）、エポキシ樹脂硬化剤（日立化成社製ＨＮ−２０００）、反応性希釈材（ナガセケムテックス社製 デナコールＥＸ−１４１）および硬化触媒を所定量混合した熱硬化性組成物を準備し、
直径５０ｍｍのテフロン（登録商標）製シャーレに３ｍｍの深さに張り込み、前記した銅ワイヤからなる巻物の両面粘着テープが取りついた側と反対側を当該熱硬化性組成物に浸漬して、倒れないように固定した。必要に応じて超音波振動を印加しながら脱泡を行った。
その後、８０℃、４時間の硬化処理を行った後、樹脂マトリクスのブロックから突出した銅ワイヤからなる巻物のうち両面粘着テープが張付いている端から１０ｍｍの部分を切り落とし、樹脂マトリクス部の厚さが３ｍｍであり、そこから５ｍｍの高さの銅ワイヤが剣山のように突き出たシート状複合材料（Ｓ−４）を得た。
<Sheet-shaped composite material 4 (S-4)>
Commercially available copper wire (Coining OW-225, 150 μmφ) is cut into 18 mm each, and one end position is aligned with the end of the double-sided adhesive tape on the double-sided adhesive tape (3M 9415PC, 0.06 mmt). They were placed side by side with their positions aligned with each other. The obtained blind-shaped copper wire aggregate was rolled into a roll shape, and finally rolled up to a diameter of 15 mm.
Next, as a matrix resin, an epoxy resin (Epicoat 828 manufactured by Mitsubishi Chemical Co., Ltd.), an epoxy resin curing agent (HN-2000 manufactured by Hitachi Chemical Co., Ltd.), a reactive diluent (Denacol EX-141 manufactured by Nagase Chemtex Co.) and a curing catalyst are used. Prepare a thermosetting composition mixed in a predetermined amount,
The Teflon (registered trademark) petri dish with a diameter of 50 mm was stretched to a depth of 3 mm, and the side of the roll made of the copper wire opposite to the side to which the double-sided adhesive tape was attached was immersed in the thermosetting composition, and collapsed. I fixed it so that it wouldn't exist. Defoaming was performed while applying ultrasonic vibration as needed.
Then, after performing a curing treatment at 80 ° C. for 4 hours, a 10 mm portion from the end on which the double-sided adhesive tape is stuck is cut off from the roll made of copper wires protruding from the resin matrix block, and the thickness of the resin matrix portion is cut off. Was 3 mm, from which a sheet-shaped composite material (S-4) was obtained in which a copper wire having a height of 5 mm was projected like a sword.
＜シート状複合材料２（Ｓ−５）＞
市販の銅ワイヤ（Ｃｏｉｎｉｎｇ社製 ＯＷ−２２５，１５０μｍφ）を３ｍｍずつに切断し、両面粘着テープ（３Ｍ社製 ９４１５ＰＣ，０．０６ｍｍｔ）上に、片端の位置を両面粘着テープの端部に一致させるように相互の位置を合わせて横並びに並べた。得られた簾状の銅ワイヤ集合体をロールして巻物状にし、最終手的に直径が１５ｍｍになるまで巻き取った。その後、銅ワイヤが含まれていない粘着テープ部分を切り落とし、厚さが約３ｍｍの巻物を作り、直径５０ｍｍのテフロン（登録商標）製シャーレの底から２ｍｍの位置に浮かせて固定した。
次に、マトリクス樹脂としてエポキシ樹脂（三菱ケミカル社製 エピコート８２８）、エポキシ樹脂硬化剤（日立化成社製ＨＮ−２０００）、反応性希釈材（ナガセケムテックス社製 デナコールＥＸ−１４１）および硬化触媒を所定量混合した熱硬化性組成物を準備し、前記のテフロン（登録商標）製シャーレに８ｍｍの深さに張り込み、前記した銅ワイヤからなる巻物を当該熱硬化性組成物に浸漬した。必要に応じて超音波振動を印加しながら脱泡を行った。
その後、８０℃、４時間の硬化処理を行った後、樹脂マトリクスの中に銅ワイヤの巻物が包埋された構造となるシート状複合材料２（Ｓ−５）を得た。
<Sheet-shaped composite material 2 (S-5)>
A commercially available copper wire (OW-225, 150 μmφ manufactured by Coining) is cut into 3 mm pieces, and one end position is aligned with the end of the double-sided adhesive tape on the double-sided adhesive tape (9415PC, 0.06 mmt manufactured by 3M). As shown in FIG. The obtained blind-shaped copper wire aggregate was rolled into a roll shape, and finally rolled up to a diameter of 15 mm. Then, the adhesive tape portion containing no copper wire was cut off to form a roll having a thickness of about 3 mm, which was fixed by floating it at a position 2 mm from the bottom of a Teflon (registered trademark) petri dish having a diameter of 50 mm.
Next, as a matrix resin, an epoxy resin (Epicoat 828 manufactured by Mitsubishi Chemical Co., Ltd.), an epoxy resin curing agent (HN-2000 manufactured by Hitachi Chemical Co., Ltd.), a reactive diluent (Denacol EX-141 manufactured by Nagase Chemtex Co.) and a curing catalyst are used. A thermosetting composition mixed in a predetermined amount was prepared, and the thermosetting composition was applied to the Teflon (registered trademark) petri dish to a depth of 8 mm, and the roll made of the copper wire was dipped in the thermosetting composition. Defoaming was performed while applying ultrasonic vibration as needed.
Then, after carrying out a curing treatment at 80 ° C. for 4 hours, a sheet-shaped composite material 2 (S-5) having a structure in which a rolled copper wire was embedded in a resin matrix was obtained.
（性能評価）
＜熱特性の評価＞
本願発明の熱伝導性複合材料およびそれを用いた各種の成形体の熱伝導率は、その形状形態面から安定な測定が難しい。そのため簡易的な非接触型温度測定装置を組み立て、非検体を熱源に接触させた後の、熱源と反対側の表面温度の時間変化を計測した。すなわち、ホットプレート（アズワン社製 ＨＰＰ−４１１型）を予め９０℃に設定し、一定温度に到達後に所定のサンプルを所定位置に置く。このとき、サンプル直上６００ｍｍの位置に放射温度計センサ部（ＦＬＩＲ社製 ＦＬＩＲ ＯＮＥ ｆｏｒ ｉＯＳ）を設置し、前記したサンプルがホットプレート上に設置されたと同時、時間計測を開始、３０秒間隔でサンプルの温度変化を追跡した。定常状態に到達後のサンプル表面温度とホットプレート温度の差が小さいほど高い放熱性が発揮できると共に、定常状態に至るまでの時間が短いほど、放熱性が高くかつ温度変化の激しい熱源の放熱への動的な対応能力に優れることを意味する。
(Performance evaluation)
<Evaluation of thermal characteristics>
It is difficult to stably measure the thermal conductivity of the thermally conductive composite material of the present invention and various molded products using the same from the aspect of shape and form. Therefore, a simple non-contact temperature measuring device was assembled, and after the non-specimen was brought into contact with the heat source, the time change of the surface temperature on the side opposite to the heat source was measured. That is, a hot plate (type HPP-411 manufactured by As One Co., Ltd.) is set at 90 ° C. in advance, and a predetermined sample is placed at a predetermined position after reaching a constant temperature. At this time, a radiation thermometer sensor unit (FLIR ONE for iOS made by FLIR) was installed at a position 600 mm directly above the sample, and at the same time when the above-mentioned sample was installed on the hot plate, time measurement was started, and the sample was sampled at intervals of 30 seconds. The temperature change was tracked. The smaller the difference between the sample surface temperature and the hot plate temperature after reaching the steady state, the higher the heat radiation performance can be achieved, and the shorter the time to reach the steady state, the higher the heat radiation performance and the heat radiation of the heat source with drastic temperature changes. It means superior in dynamic response capability.
前記したＳ−１，Ｓ−２，Ｓ−３について、それぞれ熱特性を評価したところ、定常状態までの到達時間はそれぞれ０．２５分以下、４分および０．１分以下と有意な差があった。また定常状態での温度はそれぞれ７７℃、６８℃および８０℃と有意を見出した。表１にまとめて掲げる。 When the thermal characteristics of S-1, S-2, and S-3 described above were evaluated, the arrival times to the steady state were 0.25 minutes or less, 4 minutes, and 0.1 minutes or less, respectively, which showed a significant difference. there were. The temperatures in the steady state were found to be 77 ° C, 68 ° C, and 80 ° C, respectively. They are summarized in Table 1.
〔実施例１〕
Ｓ−１およびＳ−３を用い、Ｓ−１を上下からＳ−３で挟んだ積層シート（Ｓ−３／Ｓ−１／Ｓ−３）準備した。熱特性の評価には、ホットプレート接触面と反対側の放射温度計観測面に厚さ５ｍｍのアルミブロックを積み、これをヒートシンクと見立てた際の温度変化を追跡した。
[Example 1]
Using S-1 and S-3, a laminated sheet (S-3 / S-1 / S-3) was prepared by sandwiching S-1 from above and below with S-3. For the evaluation of thermal characteristics, an aluminum block having a thickness of 5 mm was stacked on the radiation thermometer observation surface on the side opposite to the hot plate contact surface, and the temperature change was traced when this was regarded as a heat sink.
〔実施例２〕
Ｓ−４をそのままホットプレート上に設置し、その後のホットプレート接触面と反対側のヒートシンク様構造部の温度変化を放射温度計によって追跡した。
[Example 2]
The S-4 was placed on the hot plate as it was, and the temperature change of the heat sink-like structure portion on the side opposite to the hot plate contact surface after that was followed by a radiation thermometer.
〔比較例１〕
Ｓ−２およびＳ−３を用い、Ｓ−２を上下からＳ−３で挟んだ積層シート（Ｓ−３／Ｓ−２／Ｓ−３）を準備した。熱特性の評価には、ホットプレート接触面と反対側の放射温度計観測面に厚さ５ｍｍのアルミブロックを積み、これをヒートシンクと見立てた際の温度変化を追跡した。
[Comparative Example 1]
Using S-2 and S-3, a laminated sheet (S-3 / S-2 / S-3) in which S-2 was sandwiched between S-3 from above and below was prepared. For the evaluation of thermal characteristics, an aluminum block having a thickness of 5 mm was stacked on the radiation thermometer observation surface on the side opposite to the hot plate contact surface, and the temperature change was traced when this was regarded as a heat sink.
〔比較例２〕
Ｓ−５をそのままホットプレート上に設置し、その後のホットプレート接触面と反対側のヒートシンク様構造部の温度変化を放射温度計によって追跡した。
[Comparative Example 2]
The S-5 was placed on the hot plate as it was, and the temperature change of the heat sink-like structure portion on the side opposite to the hot plate contact surface after that was traced by a radiation thermometer.
Ｓ−１、Ｓ−２、Ｓ−３，実施例１〜２、比較例１〜２の組成および性能評価結果をまとめて表１に示した。 The compositions and performance evaluation results of S-1, S-2, S-3, Examples 1 and 2 and Comparative Examples 1 and 2 are summarized in Table 1.
表１より、実施例１では短時間（熱源接触後１分）で定常状態に到達し、その温度も熱源温度に近い８０℃近傍を観測したが、比較例１では、定常状態到達にまで６分を要し、かつ到達温度も熱源温度よりも２０℃以上低かった。これは高い熱伝導率を有する熱伝導性フィラーを用いても、十分な熱伝導パスが形成されない場合には熱流束が大きくならず、放熱シートとしての性能も乏しくなることが分かる。 From Table 1, in Example 1, the steady state was reached in a short time (1 minute after contact with the heat source), and the temperature was observed to be near 80 ° C. close to the heat source temperature. It took minutes and the ultimate temperature was lower than the heat source temperature by 20 ° C. or more. It can be seen that even if a heat conductive filler having a high heat conductivity is used, the heat flux does not increase and the performance as a heat dissipation sheet becomes poor if a sufficient heat conduction path is not formed.
表１より、実施例２ではブロック状であるにもかかわらず３分で定常状態に到達し、その時の温度も熱源温度に近いものであった。一方で、比較例２では定常状態にまで長時間を要し（１８分）、さらに到達温度も低かった。連続的な熱伝導パスを予め作っておくことに相当する実施例２でも、熱伝導の阻害要因となる樹脂成分の影響を長距離にわたって受けることなく、熱流束を大きく維持できることが分かる。 According to Table 1, in Example 2, although it was block-shaped, it reached a steady state in 3 minutes, and the temperature at that time was close to the heat source temperature. On the other hand, in Comparative Example 2, it took a long time to reach a steady state (18 minutes), and the reached temperature was low. It can be seen that also in Example 2, which corresponds to making a continuous heat conduction path in advance, a large heat flux can be maintained without being affected by the resin component, which is a factor that inhibits heat conduction, over a long distance.
本発明の熱伝導性複合材料を構成部品とした放熱シートは、高い熱移送能力を有する樹脂製成形品や接着剤等をもたらすことが出来る。今後の利用拡大が期待される自動車や空調用のパワー半導体の封止材や放熱材あるいは放熱フィンとの接着材等への利用が期待される。
The heat dissipation sheet using the heat conductive composite material of the present invention as a component can provide a resin molded product having a high heat transfer ability, an adhesive agent and the like. It is expected to be used as an encapsulating material for power semiconductors for automobiles and air-conditioners, which is expected to expand in the future, and as a heat radiation material or as an adhesive material with heat radiation fins.
Claims (7)
（ The composite amount according to claim 1 or 2, wherein the compounding amount of the thermally conductive particles contained in the composite material is dispersed and mixed within a range satisfying a condition of 10 vol% or more and 74 vol% or less. material.
(
The heat dissipation sheet is obtained by stacking at least two kinds of heat dissipation sheets in which heat conductive particles having different maximum lengths are dispersed and mixed in three or more layers, and the longest length of the heat conductive particles. 7. The heat dissipation sheet according to claim 6, wherein the heat dissipation sheet containing the smaller thermally conductive particles is disposed on the uppermost surface in the vertical direction of the laminate.
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| JP2008270678A (en) * | 2007-04-25 | 2008-11-06 | Mitsubishi Electric Corp | Insulation sheet and semiconductor device |
| JP2008280496A (en) * | 2007-04-11 | 2008-11-20 | Hitachi Chem Co Ltd | Heat-conductive sheet, method for producing the same, and heat radiator using the same |
| JP2015193504A (en) * | 2014-03-31 | 2015-11-05 | ナガセケムテックス株式会社 | Boron nitride particle, resin composition and heat-conductive sheet |
| JP2019071360A (en) * | 2017-10-10 | 2019-05-09 | トヨタ自動車株式会社 | Filler and heat transfer member |
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|---|---|---|---|---|
| JP2008280496A (en) * | 2007-04-11 | 2008-11-20 | Hitachi Chem Co Ltd | Heat-conductive sheet, method for producing the same, and heat radiator using the same |
| JP2008270678A (en) * | 2007-04-25 | 2008-11-06 | Mitsubishi Electric Corp | Insulation sheet and semiconductor device |
| JP2015193504A (en) * | 2014-03-31 | 2015-11-05 | ナガセケムテックス株式会社 | Boron nitride particle, resin composition and heat-conductive sheet |
| JP2019071360A (en) * | 2017-10-10 | 2019-05-09 | トヨタ自動車株式会社 | Filler and heat transfer member |
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