JP3978056B2

JP3978056B2 - Heat dissipation member and connection structure

Info

Publication number: JP3978056B2
Application number: JP2002074512A
Authority: JP
Inventors: 賢一東; 淳長谷川; 俊司俵頭
Original assignee: Sekisui Chemical Co Ltd
Current assignee: Sekisui Chemical Co Ltd
Priority date: 2002-03-18
Filing date: 2002-03-18
Publication date: 2007-09-19
Anticipated expiration: 2022-03-18
Also published as: JP2003273296A

Description

【０００１】
【発明の属する技術分野】
本発明は、発熱体と放熱体との間に介在し、高い柔軟性を有することにより発熱体及び放熱体に密着して効率よく発熱体から発生した熱を放熱体に伝導することができ、かつ、常温においては優れた取り扱い性を有する放熱用部材、及び、該放熱用部材により発熱体と放熱体とを接続してなる接続構造体に関する。
【０００２】
【従来の技術】
電気・電子部品等の発熱体と放熱体の間に介在させ、発熱体から発生する熱を放散させる目的で、放熱シート等の放熱用部材が利用されている。しかし、電気・電子部品に限らず、多くの発熱体や放熱体の表面は平滑でないため放熱用部材が発熱体及び放熱体に密着できず、発熱体や放熱体と放熱用部材との間の接触面積が減少すると、発熱体から放熱体への熱伝達効率が低下し、放熱用部材が有する放熱性能が充分に発揮できない。
【０００３】
発熱体と放熱体の間の熱的な抵抗は熱抵抗と呼ばれ、熱抵抗が小さいほど、発熱体から放熱体への熱伝達が優れ、高い放熱効果が得られる。そのため熱抵抗を小さくするためには、放熱用部材に対して優れた柔軟性が要求されている。そこで、従来は、放熱用部材として熱伝導性徴粒子を含有した放熱グリース；シリコンゴムやアクリル酸エステル系樹脂等の柔軟かつ復元力のある樹脂に熱伝導性徴粒子を分散させた放熱シート等が用いられていた。
【０００４】
放熱グリースとしては、例えば、特公平６−３９５９１号公報にシリコンオイルをベースとし、亜鉛華、アルミナ、窒化アルミニウム等の熱伝導性徴粒子を含有させたものが開示されている。このような放熱グリースは流動性のある粘ちょうな物質であるため、発熱体と放熱体の間に介在させた際に大きな接触面積が得られることから優れた熱伝導性能を発現可能である。しかしながら、発熱体や放熱体に塗布する際に、周辺部位の汚れなどが生じて作業性が低下することや、作業のばらつきにより熱伝導性能が変化する可能性が高い等の問題があった。
【０００５】
放熱シートとしては、例えば、特開平６−８８０６１号公報にアクリル酸エステル系樹脂に熱伝導性徴粒子をランダムに分散させた熱伝導テープが開示されている。このような放熱シートは定形のシートであるため、発熱体や放熱体に容易に貼り付けることができ、発熱体と放熱体の間に介在させる際に一定の間隙にすることができるため、安定した熱伝導性能を発現することができる。しかしながら、流動性がないため、放熱グリースほどの高い柔軟性が得られず、高い熱伝導性能を発現することが困難であった。
【０００６】
これに対し、特表２０００−５０９２０９号公報にはアクリル系感圧性粘着成分に対し、約５０〜６０℃に融解温度を有するαオレフィン系熱可塑性成分や約６０〜７０℃の融解温度を有するパラフィン系ロウ成分等の化合物を混合した放熱用部材が開示されている。これらは、電圧を印加することで発熱体の温度が上がり、混合しているαオレフィン系熱可塑性成分やパラフィン系ロウ成分の融解温度に達すると急激に放熱用部材が軟化し、柔軟性が向上して熱伝導性能が向上するというものである。
【０００７】
しかしながら、このような融解温度を持つ化合物は、発熱体や放熱体への貼付作業を行う２３℃付近の温度では接着性のない固体であるため、これを含有するアクリル系感圧性粘着成分の粘着性が損なわれ、貼付作業性か低下する。また、発熱体の温度が上がって融解温度を超える際に、化合物がすべて融解するまでに若干の時間がかかることから、発熱体の温度がいったんは急上昇する。そして、融解温度を有する化合物が溶けて放熱用部材の柔軟性が向上し、発熱体と放熱体の間が密着して熱伝達率が向上すると発熱体の温度は急降下する。そのため短時間ではあるが、発熱体に温度負荷がかかるという問題があった。
【０００８】
【発明が解決しようとする課題】
本発明は、上記現状に鑑み、発熱体と放熱体との間に介在し、高温では高い柔軟性を有することにより発熱体及び放熱体に密着して効率よく発熱体から発生した熱を放熱体に伝導することができ、かつ、常温においては優れた取り扱い性を有する放熱用部材、及び、該放熱用部材により発熱体と放熱体とを接続してなる接続構造体を提供することを目的とするものである。
【０００９】
【課題を解決するための手段】
本発明は、熱可塑性樹脂と熱伝導性微粒子とを含有し、４０〜１００℃に融解温度を有する化合物を含有しない熱可塑性樹脂組成物からなる放熱用部材であって、２３℃においては、０．１Ｈｚ時の貯蔵弾性率が５０００Ｐａ以上であり、かつ、定形を保持しており、８０℃においては、０．１Ｈｚ時の貯蔵弾性率が１０００Ｐａ以下であり、かつ、不定形である放熱用部材である。
以下に本発明を詳述する。
【００１０】
本発明の放熱部材は、２３℃においては、０．１Ｈｚ時の貯蔵弾性率が５０００Ｐａ以上であり、かつ、定形を保持しており、８０℃においては、０．１Ｈｚ時の貯蔵弾性率が１０００Ｐａ以下であり、かつ、不定形である。これにより、発熱体や放熱体への貼付作業を行う２３℃付近の温度では定形のシート状にして用いることができ優れた貼付作業性を示し、一方で、電圧を印加することにより発熱体の温度が上がると放熱用部材は急速に軟化し、８０℃以上の温度に達すると柔軟性が更に向上するため発熱体と放熱体に対する接触面積が向上し、優れた熱伝導性能を発現することができる。
なお、貯蔵弾性率は、例えばレオメトリックス社製のダイナミック・アナライザーＲＤＡII等の動的粘弾性測定装置で測定することができる。
【００１１】
２３℃の温度における０．１Ｈｚ時の貯蔵弾性率が５０００Ｐａ未満であると、柔らかすぎて取り扱いにくくなり、貼付作業も行いにくくなる。また、８０℃の温度における０．１Ｈｚ時の貯蔵弾性率が１０００Ｐａを超えると、放熱用部材の柔軟性が低く発熱体や放熱体に密着できず、充分な熱伝導性能が得られない。
【００１２】
２３℃と８０℃との間に、相転移現象を伴わずにかかる急速な貯蔵弾性率の変化が起こることから、発熱体の温度の上昇にあわせて放熱用部材がしだいに密着していく。すると、発熱体の温度の上昇と、放熱用部材が軟化して発熱体と放熱体に対する接触面積が向上し優れた熱伝導性能を発現するまでの間に時間の遅れが生じないため、発熱体の温度が急上昇してしまうことがなく、発熱体に温度負荷がかかることがない。
また、相転移現象を伴わない熱可塑性樹脂組成物では、室温や室温よりわずかに加熱しただけで柔らかくなったり、樹脂表面に粘着性が現れることがあり放熱用部材として取り扱いにくいことが多いが、低温において定形を保持することができ取扱い性にも優れる。
【００１３】
なお、上記熱可塑性樹脂組成物に４０〜１００℃に融解温度を有する化合物が添加されると、融解という相転移現象に伴う潜熱吸収が起こるため、融解が充分に進むまで放熱用部材が軟化しない。すると、発熱体の温度の上昇と、放熱用部材が軟化して発熱体と放熱体に対する接触面積が向上し優れた熱伝導性能を発現するまでの間に時間の遅れが生じてしまい、発熱体に温度負荷がかかってしまう。したがって、上記熱可塑性樹脂組成物は、４０〜１００℃に融解温度を有する化合物を含有しない。
【００１４】
本発明の放熱用部材は、２３℃における対アルミニウム接着力が０．５Ｎ／ｃｍ²以上であることが好ましい。これにより、発熱体及び放熱体に対して高い接着性を有することとなり、発熱体及び放熱体に放熱用部材を貼り付ける際の貼付作業性が向上する。
【００１５】
本発明の放熱用部材は、特に限定されないが、シート状に加工して用いることが好ましい。シート状にすることにより、貼付作業性が著しく向上する。
シート状にして用いる場合、シートが薄くなりすぎると取り扱い性が低下するとともに、発熱体と放熱体との間に介在させた際に、隙間を充分に埋めることが難しくなり、また、シートが厚すぎると熱伝導性能が低下する傾向にある。したがって、本発明の放熱用部材の厚さは下限が２０μｍ、上限が４００μｍであることが好ましい。
【００１６】
本発明の放熱用部材は、熱可塑性樹脂と熱伝導性微粒子とを含有する熱可塑性樹脂組成物からなる。
上記熱可塑性樹脂としては、（メタ）アクリル酸エステル系共重合体；スチレン−ブタジエン−スチレンブロック共重合体、スチレン−イソプレン−スチレンブロック共重合体等およびこれらの水素添加樹脂等のスチレン系ブロック共重合体；エチレン−酢酸ビニル樹脂、ブタジエン系樹脂、イソブチレン系樹脂、オレフィン系樹脂、ウレタン系樹脂、エポキシ系樹脂、酢酸ビニル系樹脂、スチレン系樹脂、ブチラ−ル系樹脂、ポリビニルアルコール系樹脂、シリコン系樹脂；これらの変性樹脂等が挙げられる。これらは単独で用いられてもよいし、２種類以上を併用してもよい。なかでも、上述の貯蔵弾性率を実現できる設計が比較的容易であることから、アクリル酸エステル系共重合体、スチレン系ブロック共重合体、ブチルゴム系樹脂が好適である。例えば、アクリル酸エステル系共重合体であれば、共重合体の重量平均分子量を２０万以下にすれば、上述の貯蔵弾性率を発現することができる。
【００１７】
なお、上記熱可塑性樹脂はＩＣ等の電子部品の高温側の動作限界温度付近に融点を有する樹脂ではないことが好ましい。また、ガラス転移温度を有する樹脂の場合においても、示差熱量計を用いて測定されるガラス転移温度がＩＣ等の電子部品の高温側の動作限界温度付近にないことが好ましい。これらの樹脂の融解やガラス転移現象における潜熱吸収もまた、発熱体や放熱体と放熱用部材との間が密着するまでに時間の遅れを生じさせる原因となることがある。また、流動性が高い樹脂の場合は放熱用部材が発熱体と放熱体の間から流れ出してしまう恐れもある。例えば、ガラス転移温度を有する樹脂の場合は、示差熱量計を用いて測定されるガラス転移温度が４０℃以下又は６０℃以上であることが好ましい。なお、低い温度ではより好ましくは３０℃以下、更に好ましくは２０℃以下であり、高い温度ではより好ましくは７０℃以上、更に好ましくは８０℃以上である。
【００１８】
また、上記熱可塑性樹脂として、スチレン系ブロック共重合体、ブチルゴム等の２３℃において固形状の芳香族熱可塑性樹脂を用いる場合には、更に２３℃において液状の芳香族化合物を含有することが好ましい。
例えば、スチレン系ブロック共重合体であればアルキルベンゼン等を添加することによって、ブチルゴムであればプロセスオイル等を添加することによって、上述の貯蔵弾性率の挙動においてより急激な変化を発現させることができる。これは、２３℃において固形状の芳香族熱可塑性樹脂と２３℃において液状の芳香族化合物とを混合して使用すると、それぞれの芳香環同士の相互作用によって２３℃では固形状態を保つが、温度を上昇させるとしだいに相互作用が弱まり、ある温度領域で相転移現象を伴うことなく相互作用が急激に弱まり軟化するためである。ただし、熱伝導性微粒子の配合量が増えると、種類によっては高温での弾性率が低下する傾向にあるので、本発明の放熱用部材の弾性率挙動は、熱可塑性樹脂の種類、液状の芳香族化合物の種類及び配合量により適当に調整する必要がある。
【００１９】
上記熱伝導性微粒子としては、例えば、窒化ホウ素、窒化アルミニウム、アルミナ、アルミニウム、炭化珪素、酸化亜鉛、銅、金属水酸化物から選ばれる少なくとも１種類以上の熱伝導性微粒子が挙げられる。
上記金属水酸化物としては、例えば、水酸化マグネシウム、水酸化アルミニウム等が挙げられる。
また、これらの熱伝導性微粒子は、高い配合割合で均一に混合できるように表面処理されていることが好ましい。
【００２０】
上記熱可塑性樹脂組成物における上記熱伝導性微粒子の配合量の好ましい下限は１０体積％、上限は９０体積％である。１０体積％未満であると、充分な熱伝導率が得られないことがあり、９０体積％を超えると、得られる放熱用部材の対アルミニウム接着力が低下して貼付作業性が低下することがある。
【００２１】
上記熱可塑性樹脂組成物は、所望の弾性率と対アルミニウム接着力を損なわない鞄囲であれば、必要に応じて、ハロゲン系化合物、リン酸エステル系化合物、金属水酸化物、酸化チタン等の難燃材；カーボンブラック、ホワイトカーボン等の着色剤；シラン系、チタネート系カップリング剤等の粉体表面改質剤；ビスフェノール系、ヒンダード・フェノール系等の酸化防止剤；クロマン樹脂、テルペンフェノール樹脂、フェノール樹脂、ロジン、テルペン樹脂、脂肪族炭化水素、脂環式炭化水素等の粘着付与剤等を含有してもよい。
【００２２】
本発明の放熱用部材の製造方法としては特に限定されず、例えば、所定量の熱可塑性樹脂と熱伝導性徴粒子とを、２本ロール、３本ロール、プラストミル、ニーダー、プラネタリーミキサー、バンバリーミキサー等を用いて混合し、それをコーティング成形、押し出し成形、プレス成形等によって所望の厚さのシート状に成形する方法等が挙げられる。
【００２３】
本発明の放熱用部材は、２３℃付近の常温においては定形であり極めて取り扱い性に優れ、効率よく発熱体と放熱体とを接続した接続構造体を作製することができる。
この接続構造体の発熱体の温度を上昇させると、一定温度以上になった時点で、ガラス転移現象や融解等の潜熱吸収を伴う相転移現象を伴うことなく急速に本発明の放熱用部材が軟化して発熱体及び放熱体との接触面積が大きくなり、更にそれに伴って放熱用部材の厚みが減少して、優れた熱抵抗性能を発現することができる。しかも、かかる放熱用部材の変化は急速であり、発熱体の温度が発熱体にとって負荷となる温度に達するまで上昇してしまう前に起こることから、発熱体に温度負荷がかかることがない。
かかる、本発明の放熱用部材により発熱体と放熱体とを接続してなる接続構造体であって、上記放熱用部材は、発熱体の発熱により、上記発熱前よりも厚みが減少することが可能である接続構造体もまた、本発明の１つである。
また、本発明の放熱用部材により発熱体と放熱体とを接続してなる接続構造体であって、上記放熱用部材は、発熱体が発熱したことにより、上記発熱前よりも既に厚みが減少しているものである接続構造体もまた、本発明の１つである。
【００２４】
【実施例】
以下に実施例を掲げて本発明を更に詳しく説明するが、本発明はこれら実施例のみに限定されるものではない。
【００２５】
（実施例１）
希釈溶剤を予め乾燥により除去した粘稠なアクリル酸エステル系共重合体（根上工業社製、商品名「Ｓ−２０２２改３」：重量平均分子量１７万）１００重量部、窒化アルミニウム（トクヤマ社製、商品名「グレードＦ」）１４０重量部をプラストミルで混合しスラリー状物を得た。このスラリー状物において窒化アルミニウムの体積比率は３０％であった。
次いで、プレス板の上に離型ＰＥＴフィルムを敷き、その上に厚みが１００μｍの金属枠を載せ、金属枠内に得られたスラリー状物を流し込んだ。次いで、離型ＰＥＴフィルムをその上に載せ上下からプレス板で挟み込み、室温下でプレス成形を行った。これにより、両面に離型ＰＥＴフィルムが付いた厚さ１００μｍのシート状の放熱用部材を得た。
【００２６】
（実施例２）
スチレン含量２２重量％のスチレン−イソプレンブロック共重合体２０重量部、ドデシルベンゼン８０重量部、及び、窒化アルミニウム（トクヤマ社製、商品名「グレードＦ」）３３０重量部をプラストミルで混合しスラリー状物を得た。このスラリー状物において窒化アルミニウムの体積比率は５０％であった。
このスラリー状物を用いて、実施例１と同様にして両面に離型ＰＥＴフィルムが付いた厚さ１００μｍのシート状の放熱用部材を得た。
【００２７】
（比較例１）
スチレン含量２２重量％のスチレン−イソプレンブロック共重合体３０重量部、ドデシルベンゼン７０重量部、及び、窒化アルミニウム（トクヤマ社製、商品名「グレードＦ」）７６０重量部をプラストミルで混合しスラリー状物を得た。このスラリー状物において窒化アルミニウムの体積比率は７０％であった。
このスラリー状物を用いて、実施例１と同様にして両面に離型ＰＥＴフィルムが付いた厚さ１００μｍのシート状の放熱用部材を得た。
【００２８】
（比較例２）
スチレン含量２２重量％のスチレン−イソプレンブロック共重合体５０重量部、ドデシルベンゼン５０重量部、及び、窒化ホウ素（電気化学工業社製、商品名「グレードＳＧＰ」）２２６重量部をプラストミルで混合しスラリー状物を得た。このスラリー状物において窒化ホウ素の体積比率は５０％であった。
このスラリー状物を用いて、実施例１と同様にして両面に離型ＰＥＴフィルムが付いた厚さ１００μｍのシート状の放熱用部材を得た。
【００２９】
（比較例３）
アクリル酸エステル系共重合体（根上工業社製、商品名「Ｓ−２０２２改３」：重量平均分子量１７万）１００重量部の代わりにアクリル酸エステル系共重合体（根上工業社製、商品名「Ｓ−２０２２改２」：重量平均分子量２７万）１００重量部を、窒化アルミニウム（トクヤマ社製、商品名「グレードＦ」）１４０重量部の代わりに窒化ホウ素（電気化学工業社製、商品名「グレードＳＧＰ」）２２６重量部を用いたこと以外は実施例１と同様にして両面に離型ＰＥＴフィルムが付いた厚さ１００μｍのシート状の放熱用部材を得た。
【００３０】
＜評価＞
実施例１〜２及び比較例１〜３で得られた放熱用部材について、以下の方法により、熱抵抗及び貯蔵弾性率を測定した。
【００３１】
（熱抵抗の測定）
熱抵抗は、図１に示す測定装置により測定した。すなわち、アルミニウム製の冷却器１の上に離型ＰＥＴフィルムを剥がした放熱用部材２を貼り付け、更にその上に熱源となるＩＣを積層し、ボルト３により締め付けトルク１Ｎ・ｍで締め付けた。
ＩＣに電源を入れて８０Ｗ／ｈの電力を供給し、６０分後に、ＩＣの温度Ｔ１と、冷却器１の放熱用部材の近傍温度Ｔ２を測定した。なお、冷却器１は、内部に恒温水槽４から２３℃の水が供給循環されるようになっている。測定結果から熱抵抗を下記式で求めた。
【００３２】
【数１】

【００３３】
（貯蔵弾性率の測定）
ダイナミック・アナライザーＲＤＡII（レオメトリックス社製）を用い、０．１Ｈｚの条件で、２３℃及び８０℃における放熱用部材の貯蔵弾性率を測定した。
【００３４】
【表１】

【００３５】
【発明の効果】
本発明によれば、発熱体と放熱体との間に介在し、高温では高い柔軟性を有することにより発熱体及び放熱体に密着して効率よく発熱体から発生した熱を放熱体に伝導することができ、かつ、常温においては優れた取り扱い性を有する放熱用部材、及び、該放熱用部材により発熱体と放熱体とを接続してなる接続構造体を提供できる。
【図面の簡単な説明】
【図１】放熱用部材の熱抵抗の測定に用いた測定装置を示す模式図である。
【符号の説明】
１冷却器
２放熱用部材
３ボルト
４恒温水槽[0001]
BACKGROUND OF THE INVENTION
The present invention is interposed between the heat generating body and the heat radiating body and has high flexibility so that the heat generated from the heat generating body can be efficiently conducted in close contact with the heat generating body and the heat radiating body, In addition, the present invention relates to a heat dissipating member having excellent handleability at room temperature, and a connection structure in which a heat generator and a heat dissipator are connected by the heat dissipating member.
[0002]
[Prior art]
A heat radiating member such as a heat radiating sheet is used for the purpose of dissipating the heat generated from the heat generating element by being interposed between the heat generating element such as an electric / electronic component and the heat radiating element. However, the surface of many heating elements and radiators, not limited to electrical and electronic parts, is not smooth, so the heat radiating member cannot be in close contact with the heating element and the radiating member. When the contact area decreases, the heat transfer efficiency from the heat generating element to the heat dissipating body decreases, and the heat dissipating performance of the heat dissipating member cannot be sufficiently exhibited.
[0003]
The thermal resistance between the heating element and the heat radiating body is called thermal resistance. The smaller the thermal resistance, the better the heat transfer from the heating element to the heat radiating body, and the higher the heat dissipation effect can be obtained. Therefore, in order to reduce the thermal resistance, excellent flexibility is required for the heat radiating member. Therefore, conventionally, a heat-dissipating grease containing heat-conducting particles as a heat-dissipating member; a heat-dissipating sheet in which heat-conducting particles are dispersed in a flexible and resilient resin such as silicon rubber or acrylate resin is used. It was done.
[0004]
For example, Japanese Patent Publication No. 6-39591 discloses a heat dissipating grease based on silicon oil and containing heat conductive particles such as zinc white, alumina and aluminum nitride. Since such a heat dissipating grease is a fluid and viscous substance, a large contact area can be obtained when it is interposed between the heat generating element and the heat dissipating element, so that excellent heat conduction performance can be expressed. However, when applied to a heat generator or a heat radiating body, there are problems such as contamination of peripheral parts and the like, resulting in a decrease in workability, and a high possibility that the heat conduction performance is changed due to variations in work.
[0005]
As a heat-dissipating sheet, for example, JP-A-6-88061 discloses a heat conductive tape in which heat conductive particles are randomly dispersed in an acrylate resin. Since such a heat dissipation sheet is a regular sheet, it can be easily affixed to a heating element or a heat dissipation body, and can be a constant gap when interposed between the heating element and the heat dissipation element, so that it is stable. Heat conduction performance can be exhibited. However, since there is no fluidity, the flexibility as high as that of the heat-dissipating grease cannot be obtained, and it has been difficult to express high heat conduction performance.
[0006]
In contrast, JP 2000-509209 A discloses an α-olefin thermoplastic component having a melting temperature of about 50 to 60 ° C. and a paraffin having a melting temperature of about 60 to 70 ° C. with respect to the acrylic pressure-sensitive adhesive component. A heat dissipation member in which a compound such as a system wax component is mixed is disclosed. When applying a voltage, the temperature of the heating element increases, and when the melting temperature of the mixed α-olefin thermoplastic component or paraffin wax component is reached, the heat dissipation member suddenly softens and the flexibility is improved. As a result, the heat conduction performance is improved.
[0007]
However, since a compound having such a melting temperature is a solid having no adhesiveness at a temperature of about 23 ° C. at which a heating operation or a heat radiating operation is performed, the adhesion of an acrylic pressure-sensitive adhesive component containing the same The applicability is impaired, and the workability of application is reduced. In addition, when the temperature of the heating element rises and exceeds the melting temperature, it takes some time for all the compounds to melt, so the temperature of the heating element rises rapidly. Then, the compound having the melting temperature is melted to improve the flexibility of the heat dissipating member, and when the heat generating member and the heat dissipating member are brought into close contact with each other and the heat transfer coefficient is improved, the temperature of the heat generating member is rapidly lowered. For this reason, there is a problem that a temperature load is applied to the heating element for a short time.
[0008]
[Problems to be solved by the invention]
In view of the above situation, the present invention is interposed between a heat generating body and a heat radiating body, and has high flexibility at high temperatures so that the heat generated from the heat generating body is efficiently adhered to the heat generating body and the heat radiating body. It is an object of the present invention to provide a heat dissipating member that can be conducted to room temperature and has excellent handleability at room temperature, and a connection structure in which the heat generating member and the heat dissipating member are connected by the heat dissipating member. To do.
[0009]
[Means for Solving the Problems]
The present invention is a heat dissipating member comprising a thermoplastic resin composition containing a thermoplastic resin and thermally conductive fine particles and not containing a compound having a melting temperature of 40 to 100 ° C. A heat-dissipating member having a storage elastic modulus at 1 Hz of 5000 Pa or more and having a fixed shape, and having a storage elastic modulus of 0.1 Pa or less at 0.1 Hz at 80 ° C. and being indefinite. It is.
The present invention is described in detail below.
[0010]
The heat-dissipating member of the present invention has a storage elastic modulus of 5000 Pa or more at 0.1 Hz at 23 ° C. and maintains a fixed shape, and has a storage elastic modulus of 1000 Pa at 0.1 Hz at 80 ° C. It is the following and is indefinite. As a result, it can be used in the form of a regular sheet at a temperature of around 23 ° C. where the heating work or the heat sink is applied, and exhibits excellent workability while applying a voltage to the heating element. When the temperature rises, the heat-dissipating member softens rapidly, and when it reaches a temperature of 80 ° C. or higher, the flexibility is further improved, so that the contact area between the heating element and the heat-dissipating element is improved, and excellent heat conduction performance is exhibited. it can.
The storage elastic modulus can be measured by a dynamic viscoelasticity measuring device such as a dynamic analyzer RDAII manufactured by Rheometrics.
[0011]
If the storage elastic modulus at 0.1 Hz at a temperature of 23 ° C. is less than 5000 Pa, it is too soft and difficult to handle, and it is difficult to perform the pasting operation. On the other hand, if the storage elastic modulus at 0.1 Hz at a temperature of 80 ° C. exceeds 1000 Pa, the flexibility of the heat dissipating member is so low that the heat dissipating member or the heat dissipating member cannot be adhered, and sufficient heat conduction performance cannot be obtained.
[0012]
Since a rapid change in storage elastic modulus takes place between 23 ° C. and 80 ° C. without causing a phase transition phenomenon, the heat radiating member gradually adheres as the temperature of the heating element rises. Then, since there is no time delay until the temperature of the heating element rises and the heat dissipation member softens and the contact area between the heating element and the heat dissipation element improves and exhibits excellent heat conduction performance, the heating element The temperature of the heating element does not rise rapidly, and the heating element is not subjected to a temperature load.
In addition, the thermoplastic resin composition that does not involve a phase transition phenomenon is often difficult to handle as a heat-dissipating member because it becomes soft just by heating at room temperature or slightly from room temperature, and adhesiveness may appear on the resin surface. It can hold a fixed shape at low temperature and is easy to handle.
[0013]
When a compound having a melting temperature of 40 to 100 ° C. is added to the thermoplastic resin composition, latent heat absorption accompanying a phase transition phenomenon called melting occurs, so that the heat radiating member does not soften until melting sufficiently proceeds. . Then, there is a time lag between the temperature rise of the heating element and the heat dissipation member softening to improve the contact area between the heating element and the radiator and exhibit excellent heat conduction performance. Temperature load. Therefore, the said thermoplastic resin composition does not contain the compound which has a melting temperature in 40-100 degreeC.
[0014]
The heat radiating member of the present invention preferably has an adhesive strength to aluminum at 23 ° C. of 0.5 N / cm ² or more. Thereby, it has high adhesiveness with respect to a heat generating body and a heat radiator, and the sticking workability | operativity at the time of affixing the heat radiating member on a heat generating body and a heat radiator improves.
[0015]
Although the heat radiating member of the present invention is not particularly limited, it is preferably processed into a sheet shape. By making it into a sheet, the workability of attaching is remarkably improved.
When used in the form of a sheet, if the sheet becomes too thin, the handleability deteriorates, and when it is interposed between the heating element and the radiator, it becomes difficult to sufficiently fill the gap, and the sheet is thick. If it is too high, the heat conduction performance tends to decrease. Therefore, the thickness of the heat radiating member of the present invention is preferably 20 μm at the lower limit and 400 μm at the upper limit.
[0016]
The heat radiating member of the present invention comprises a thermoplastic resin composition containing a thermoplastic resin and thermally conductive fine particles.
Examples of the thermoplastic resin include (meth) acrylic acid ester copolymers; styrene-butadiene-styrene block copolymers, styrene-isoprene-styrene block copolymers, and styrene block copolymers such as hydrogenated resins thereof. Polymer: ethylene-vinyl acetate resin, butadiene resin, isobutylene resin, olefin resin, urethane resin, epoxy resin, vinyl acetate resin, styrene resin, butyral resin, polyvinyl alcohol resin, silicon System resins; these modified resins and the like. These may be used alone or in combination of two or more. Especially, since the design which can implement | achieve the above-mentioned storage elastic modulus is comparatively easy, an acrylate-type copolymer, a styrene-type block copolymer, and a butyl rubber-type resin are suitable. For example, in the case of an acrylic ester copolymer, the above storage elastic modulus can be expressed by setting the weight average molecular weight of the copolymer to 200,000 or less.
[0017]
The thermoplastic resin is preferably not a resin having a melting point near the operating limit temperature on the high temperature side of an electronic component such as an IC. Even in the case of a resin having a glass transition temperature, it is preferable that the glass transition temperature measured using a differential calorimeter is not in the vicinity of the operating limit temperature on the high temperature side of an electronic component such as an IC. The melting of these resins and the absorption of latent heat in the glass transition phenomenon may also cause a time delay until the heat generating member or the heat radiating member and the heat radiating member come into close contact with each other. Moreover, in the case of resin with high fluidity, the heat radiating member may flow out between the heat generating body and the heat radiating body. For example, in the case of a resin having a glass transition temperature, the glass transition temperature measured using a differential calorimeter is preferably 40 ° C. or lower or 60 ° C. or higher. In addition, it is 30 degrees C or less more preferably at low temperature, More preferably, it is 20 degrees C or less, More preferably, it is 70 degreeC or more, More preferably, it is 80 degreeC or more.
[0018]
Moreover, when using a solid aromatic thermoplastic resin at 23 ° C., such as a styrene block copolymer and butyl rubber, as the thermoplastic resin, it is preferable to further contain a liquid aromatic compound at 23 ° C. .
For example, by adding alkylbenzene or the like for a styrene-based block copolymer, or by adding process oil or the like for a butyl rubber, a more rapid change in the behavior of the storage elastic modulus can be expressed. . This is because when a solid aromatic thermoplastic resin at 23 ° C. and a liquid aromatic compound at 23 ° C. are mixed and used, the solid state is maintained at 23 ° C. due to the interaction between the aromatic rings. This is because the interaction weakens as soon as the value of R is increased, and the interaction suddenly weakens and softens without causing a phase transition phenomenon in a certain temperature range. However, since the elastic modulus at high temperatures tends to decrease depending on the type as the blending amount of the heat conductive fine particles increases, the elastic modulus behavior of the heat dissipating member of the present invention depends on the type of thermoplastic resin, the liquid fragrance. It is necessary to adjust appropriately according to the kind and compounding quantity of a group compound.
[0019]
Examples of the heat conductive fine particles include at least one kind of heat conductive fine particles selected from boron nitride, aluminum nitride, alumina, aluminum, silicon carbide, zinc oxide, copper, and metal hydroxide.
Examples of the metal hydroxide include magnesium hydroxide and aluminum hydroxide.
Moreover, it is preferable that these heat conductive fine particles are surface-treated so that it can mix uniformly with a high compounding ratio.
[0020]
The minimum with the preferable compounding quantity of the said heat conductive microparticles | fine-particles in the said thermoplastic resin composition is 10 volume%, and an upper limit is 90 volume%. If it is less than 10% by volume, sufficient thermal conductivity may not be obtained, and if it exceeds 90% by volume, the adhesion of the obtained heat-dissipating member to aluminum may be reduced, and the pasting workability may be reduced. is there.
[0021]
The thermoplastic resin composition may be a halogen compound, a phosphate compound, a metal hydroxide, titanium oxide, etc. Flame retardants; Colorants such as carbon black and white carbon; Powder surface modifiers such as silane and titanate coupling agents; Antioxidants such as bisphenols and hindered phenols; Chroman resins and terpene phenol resins Further, it may contain tackifiers such as phenol resin, rosin, terpene resin, aliphatic hydrocarbon and alicyclic hydrocarbon.
[0022]
The method for producing the heat radiating member of the present invention is not particularly limited. For example, a predetermined amount of thermoplastic resin and thermally conductive particles are used in two rolls, three rolls, a plast mill, a kneader, a planetary mixer, and a Banbury mixer. Etc., and a method of forming it into a sheet having a desired thickness by coating molding, extrusion molding, press molding, or the like.
[0023]
The heat dissipating member of the present invention has a fixed shape at a room temperature around 23 ° C., is extremely excellent in handleability, and can efficiently produce a connection structure in which a heat generator and a heat dissipator are connected.
When the temperature of the heating element of this connection structure is raised, when the temperature rises above a certain temperature, the heat radiating member of the present invention is rapidly produced without a glass transition phenomenon or a phase transition phenomenon accompanied by latent heat absorption such as melting. Softening increases the contact area between the heat generating element and the heat radiating body, and accordingly, the thickness of the heat radiating member is reduced, and excellent thermal resistance performance can be exhibited. In addition, the change of the heat radiating member is rapid and occurs before the temperature of the heating element rises until it reaches a temperature that is a load for the heating element, so that no temperature load is applied to the heating element.
Such a connection structure in which the heat generating member and the heat dissipating member are connected by the heat dissipating member of the present invention, wherein the heat dissipating member may be reduced in thickness than before the heat generation due to heat generation of the heat generating member. Connection structures that are possible are also one aspect of the present invention.
Further, the present invention is a connection structure in which a heat generating member and a heat dissipating member are connected by the heat dissipating member of the present invention, and the heat dissipating member is already reduced in thickness than before the heat generation because the heat generating member generates heat. The connecting structure which is the same is also one aspect of the present invention.
[0024]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.
[0025]
Example 1
100 parts by weight of viscous acrylic acid ester copolymer (manufactured by Negami Kogyo Co., Ltd., trade name “S-2022 modified 3”: weight average molecular weight 170,000) from which diluted solvent has been removed by drying in advance, aluminum nitride (manufactured by Tokuyama Co., Ltd.) , 140 parts by weight of a product name “Grade F”) was mixed with a plast mill to obtain a slurry. In this slurry, the volume ratio of aluminum nitride was 30%.
Next, a release PET film was laid on the press plate, a metal frame having a thickness of 100 μm was placed thereon, and the resulting slurry was poured into the metal frame. Next, a release PET film was placed thereon and sandwiched between press plates from above and below, and press molding was performed at room temperature. As a result, a sheet-like heat radiation member having a thickness of 100 μm with a release PET film on both sides was obtained.
[0026]
(Example 2)
20 parts by weight of a styrene-isoprene block copolymer having a styrene content of 22% by weight, 80 parts by weight of dodecylbenzene, and 330 parts by weight of aluminum nitride (trade name “Grade F” manufactured by Tokuyama Co., Ltd.) are mixed with a plastmill to form a slurry. Got. In this slurry, the volume ratio of aluminum nitride was 50%.
Using this slurry-like material, a sheet-like heat-dissipating member having a thickness of 100 μm with a release PET film on both sides was obtained in the same manner as in Example 1.
[0027]
(Comparative Example 1)
30 parts by weight of a styrene-isoprene block copolymer having a styrene content of 22% by weight, 70 parts by weight of dodecylbenzene, and 760 parts by weight of aluminum nitride (trade name “Grade F”, manufactured by Tokuyama Co., Ltd.) are mixed with a plastmill to form a slurry. Got. In this slurry, the volume ratio of aluminum nitride was 70%.
Using this slurry-like material, a sheet-like heat-dissipating member having a thickness of 100 μm with a release PET film on both sides was obtained in the same manner as in Example 1.
[0028]
(Comparative Example 2)
A slurry obtained by mixing 50 parts by weight of a styrene-isoprene block copolymer having a styrene content of 22% by weight, 50 parts by weight of dodecylbenzene, and 226 parts by weight of boron nitride (trade name “Grade SGP” manufactured by Denki Kagaku Kogyo Co., Ltd.) using a plastmill. A product was obtained. In this slurry, the volume ratio of boron nitride was 50%.
Using this slurry-like material, a sheet-like heat-dissipating member having a thickness of 100 μm with a release PET film on both sides was obtained in the same manner as in Example 1.
[0029]
(Comparative Example 3)
Acrylate ester-based copolymer (manufactured by Negami Kogyo Co., Ltd., trade name “S-2022 Rev. 3”: weight average molecular weight 170,000) 100 parts by weight of acrylic ester copolymer (manufactured by Negami Kogyo Co., Ltd., trade name) "S-2022 modified 2": 100 parts by weight of weight average molecular weight 270,000), boron nitride (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name) instead of 140 parts by weight of aluminum nitride (made by Tokuyama, trade name "Grade F") “Grade SGP”) A sheet-like heat radiation member having a thickness of 100 μm with a release PET film on both sides was obtained in the same manner as in Example 1 except that 226 parts by weight were used.
[0030]
<Evaluation>
About the heat radiating member obtained in Examples 1-2 and Comparative Examples 1-3, the thermal resistance and the storage elastic modulus were measured with the following method.
[0031]
(Measurement of thermal resistance)
The thermal resistance was measured with the measuring apparatus shown in FIG. That is, the heat radiating member 2 from which the release PET film was peeled off was pasted on the aluminum cooler 1, an IC serving as a heat source was further laminated thereon, and the bolt 3 was tightened with a tightening torque of 1 N · m.
The IC was powered on and supplied with 80 W / h of power. After 60 minutes, the IC temperature T1 and the temperature T2 near the heat dissipating member of the cooler 1 were measured. The cooler 1 is supplied and circulated with water at 23 ° C. from the constant temperature water tank 4. From the measurement results, the thermal resistance was determined by the following formula.
[0032]
[Expression 1]

[0033]
(Measurement of storage modulus)
Using a dynamic analyzer RDAII (manufactured by Rheometrics), the storage elastic modulus of the heat radiating member at 23 ° C. and 80 ° C. was measured under the condition of 0.1 Hz.
[0034]
[Table 1]

[0035]
【The invention's effect】
According to the present invention, it is interposed between the heating element and the radiator, and has high flexibility at a high temperature so that the heat generated from the heating element can be efficiently conducted in close contact with the heating element and the radiator. It is possible to provide a heat dissipating member having excellent handleability at room temperature, and a connection structure in which the heat generating member and the heat dissipating member are connected by the heat dissipating member.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a measuring apparatus used for measuring the thermal resistance of a heat radiating member.
[Explanation of symbols]
1 Cooler 2 Heat Dissipating Member 3 Bolt 4 Constant Temperature Water Tank

Claims

A heat radiating member comprising a thermoplastic resin composition containing an acrylic acid ester copolymer having a weight average molecular weight of 200,000 or less and thermally conductive fine particles and not containing a compound having a melting temperature of 40 to 100 ° C. ,
At 23 ° C., the storage elastic modulus at 0.1 Hz is 5000 Pa or more, and retains a fixed shape,
A heat radiating member having a storage elastic modulus at 0.1 Hz of 1000 Pa or less and an indefinite shape at 80 ° C.

It consists of a thermoplastic resin composition containing a solid styrene block copolymer at 23 ° C., a liquid aromatic compound and heat conductive fine particles at 23 ° C., and no compound having a melting temperature at 40 to 100 ° C. A heat dissipating member,
At 23 ° C., the storage elastic modulus at 0.1 Hz is 5000 Pa or more, and retains a fixed shape,
At 80 ° C., the storage elastic modulus at 0.1 Hz is 1000 Pa or less and is indefinite.
A member for heat dissipation.

The heat radiating member according to claim 2, wherein the aromatic compound that is liquid at 23 ° C. is alkylbenzene.

It is a connection structure which connects a heat generating body and a heat radiator with the heat radiating member of Claim 1, 2, or 3, Comprising: The said heat radiating member is thicker than the said before heat_generation | fever by heat_generation | fever of a heat generating body. Connection structure characterized in that it can be reduced.

It is a connection structure which connects a heat generating body and a heat radiator by the heat radiating member of Claim 1, 2, or 3, Comprising: The said heat radiating member is more than before the said heat_generation | fever when the heat generating body heat | fever-generated. A connection structure characterized in that the thickness has already been reduced.