JP3995836B2

JP3995836B2 - Metal-based printed wiring board, metal-based multilayer printed wiring board, and manufacturing method thereof

Info

Publication number: JP3995836B2
Application number: JP20910999A
Authority: JP
Inventors: 紳月山田; 礼郎黒崎; 雄二中村
Original assignee: Mitsubishi Plastics Inc
Current assignee: Mitsubishi Plastics Inc
Priority date: 1999-07-23
Filing date: 1999-07-23
Publication date: 2007-10-24
Anticipated expiration: 2019-07-23
Also published as: JP2001036205A

Description

【０００１】
【発明の属する技術分野】
この発明は、金属ベースプリント配線基板、金属ベース多層プリント配線板およびその製造方法に関する。
【０００２】
【従来の技術】
金属ベースプリント配線板として、アルミニウム、鉄、銅、亜鉛などの金属ベース（基材またはコア）の片面または両面に、絶縁層を介して導体箔を重ねて接着一体化し、導体箔をエッチングしてプリント回路を形成したものが知られている。
【０００３】
金属ベースプリント配線板は、金属ベースの特性によって耐熱性、難燃性、シールド効果、機械的強度等が優れたものであり、特に熱放散性が良好であるという特性を有する。すなわち、金属ベースプリント配線板は、ベースの金属が高い熱伝導率を有することから、伝導による熱分散性が良く、基板温度の局部的な上昇が抑えられ、放熱効果が高いものである。金属ベースプリント配線板の絶縁層を形成する素材としては、アルミナなどの放熱性の良いフィラーを含有したエポキシ樹脂が一般的である。
【０００４】
しかしながら、プレス加工前の半硬化状態であるエポキシプリプレグの保存安定性の問題や、プレス加工に２時間程度の長時間を要するなど、作業性の面で不具合がある。
【０００５】
【発明が解決しようとする課題】
そこで、本発明の課題は上記した問題点を解決し、ハンダ耐熱性を有する熱可塑性の絶縁層を用いて導体箔および金属ベースに対して比較的低温で短時間で熱融着することができ、しかも確実に接着一体化された金属ベースプリント配線板または金属ベース多層プリント配線板にすることである。
【０００６】
また、本発明の製造方法に係る発明の課題としては、導体箔および金属ベースとを熱可塑性の絶縁層で簡単な工程により確実に熱融着して金属ベース多層プリント配線板を効率良く製造することである。
【０００７】
【課題を解決するための手段】
本発明の金属ベースプリント配線板に係る発明においては、上記の課題を解決するために、金属板の片面または両面に熱可塑性樹脂組成物からなる絶縁層を介して導体箔を熱融着し、この導体箔でプリント回路を形成した金属ベースプリント配線板において、前記絶縁層が、シンジオタクチック構造を有するスチレン系樹脂組成物と、該スチレン系樹脂組成物と相溶性のあるポリオレフィン系、ポリスチレン系、ポリエステル系、ポリアミド系、ポリフェニレンエーテル系、ポリフェニレンスルフィド系の樹脂から選ばれる熱可塑性樹脂（以下、スチレン系樹脂組成物と相溶性のある熱可塑性樹脂ということがある）を主成分とし上記スチレン系樹脂組成物の含有率が３５〜７０重量％、及び上記スチレン系樹脂組成物と相溶性のある熱可塑性樹脂の含有率が３０〜６５重量％からなり、この熱可塑性樹脂組成物は、示差走査熱量測定で昇温した時に測定される結晶融解ピーク温度が２６０℃以上であり、結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとの関係が下記の式(A) で示される関係を満たす特性のものを下記の式(B) で示される関係を満たすように熱融着したものであることを特徴とする金属ベースプリント配線板としたのである。
【０００８】
式(A): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．６
式(B): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≧０．７
前記導体箔としては、表面粗化されている導体箔を採用することが好ましく、前記金属板としては、表面粗化されている金属板を採用することが好ましい。
【０００９】
また、本願の金属ベース多層プリント配線板に係る発明においては、前記の課題を解決するために、熱可塑性樹脂組成物からなるフィルム状絶縁体に両面貫通孔を形成すると共に貫通孔内に導電性ペーストを充填して積層電気回路の層間接続用熱融着性フィルムを設け、この層間接続用熱融着用フィルムの両面に導体箔を熱融着しかつ回路形成してフィルム状配線基板を設け、金属板の片面または両面に前記熱可塑性樹脂組成物からなる絶縁層を介してフィルム状配線基板を熱融着した金属ベース多層プリント配線板において、前記熱融着された絶縁層および熱融着されたフィルム状配線基板を構成する熱可塑性樹脂組成物が、シンジオタクチック構造を有するスチレン系樹脂組成物と、該スチレン系樹脂組成物と相溶性のある熱可塑性樹脂を主成分とし上記スチレン系樹脂組成物の含有率が３５〜７０重量％、及び上記スチレン系樹脂組成物と相溶性のある熱可塑性樹脂の含有率が３０〜６５重量％からなり、前記熱可塑性樹脂組成物は、示差走査熱量測定で昇温した時に測定される結晶融解ピーク温度が２６０℃以上であり、結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとの関係が下記の式(A) で示される関係を満たす特性のものを加熱して下記の式(B) で示される関係を満たすように熱融着されたものであることを特徴とする金属ベースプリント配線板としたのである。
【００１０】
式(A): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．６
式(B): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≧０．７
前記導体箔としては、表面粗化されている導体箔を採用することが好ましく、前記金属板としては、表面粗化されている金属板を採用することが好ましい。
【００１１】
上記したように構成されるこの発明の金属ベースプリント配線板または金属ベース多層プリント配線板は、結晶性のシンジオタクチック構造を有するスチレン系樹脂を所定量配合した絶縁層を有する。
【００１２】
絶縁層は、示差走査熱量測定で昇温した時に測定される結晶融解ピーク温度が２６０℃以上であり、かつ結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとの関係が前記式(A) で示される関係を満たすものを所定条件で加熱し、熱融着後に前記式(B) で示される関係を満たすようにしたものであって、熱融着時の加熱により上記スチレン系樹脂の結晶性が適当に進行しているので、２６０℃に耐えるハンダ耐熱性を確実に有する絶縁層になり、機械的強度および電気的絶縁性にも優れたものである。
【００１３】
そして、この絶縁層は、導体箔との接着強度も大きく、導体箔をエッチングして形成した電気回路は絶縁層に強固に接着して剥離し難い。通常、表面が粗化されている導体箔もしくは表面粗化されている金属板を採用するか、または何れも粗化された導体箔および金属板を使用して接着強度をより大きくする。
また、フィルム状絶縁体と導体箔の接着は、層間にエポキシ樹脂などの接着剤を介在させないで熱融着するので、金属ベースプリント配線板または金属ベース多層プリント配線板の耐熱性、耐薬品性、電気特性などの諸特性は接着剤の特性に支配されることがなく、絶縁層の優れた諸特性が充分に活かされる。
【００１４】
なお、積層電気回路の層間接続用熱融着性フィルムは、絶縁性の前記熱可塑性樹脂成物で形成されており、両面貫通孔内の導電性ペーストによって両面貫通孔の開口部が電気的接点となって、フィルムの片面または両面に配置形成された電気回路の要所を層厚方向に導通する。金属ベース多層プリント配線板の製造方法に係る発明においては、前記の課題を解決するため、シンジオタクチック構造を有するスチレン系樹脂組成物と、該スチレン系樹脂組成物と相溶性のある熱可塑性樹脂を主成分とし上記スチレン系樹脂組成物の含有率が３５〜７０重量％、及び上記スチレン系樹脂組成物と相溶性のある熱可塑性樹脂の含有率が３０〜６５重量％からなり、前記熱可塑性樹脂組成物は、示差走査熱量測定で昇温した時に測定される結晶融解ピーク温度が２６０℃以上であり、結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとの関係が下記の式(I) で示される関係を満たす熱可塑性樹脂組成物からなるフィルム状絶縁体を形成し、このフィルム状絶縁体に両面貫通孔を形成すると共に貫通孔内に導電性ペーストを充填して積層電気回路の層間接続用熱融着性フィルムを形成し、この層間接続用熱融着性フィルムの両面に導体箔を重ねて前記熱可塑性樹脂組成物が下記の式(II)で示される関係を満たすように熱融着した後、前記導体箔に回路を形成してフィルム状配線基板を設け、金属板の片面または両面に前記フィルム状絶縁体を介して前記フィルム状配線基板を重ね、各層を構成する熱可塑性樹脂組成物が下記の(III) で示される関係を満たすように熱融着することからなる金属ベース多層プリント配線板の製造方法としたのである。
【００１５】
式(I): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．４
式(II): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．６
式(III): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≧０．７
上記多層プリント配線板の製造方法においては、層間接続用熱融着性フィルムの両面に導体箔を重ねて熱融着する際に、熱可塑性樹脂組成物の熱融着後の結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとの関係が前記式(II)で示される関係を満たすように熱融着する。
【００１６】
そして、金属板の片面または両面にフィルム状絶縁体を重ね、その上に前述した層間接続用熱融着性フィルムの両面に導体箔で回路形成したフィルム状配線基板を重ね、前記式(II)で示される関係を有する熱可塑性樹脂組成物が前記式(III) で示される関係を満たすように熱融着する。このようにすると、熱融着後の熱可塑性樹脂組成物は、シンジオタクチック構造を有するスチレン系樹脂の結晶性が適当に進行し、２６０℃に耐えるハンダ耐熱性を確実に有する絶縁層になり、かつ導体箔との接着強度も大きくなる。
【００１７】
そして、加熱加圧による熱融着を行なう時には熱可塑性樹脂が導体箔との接着温度領域で弾性率が低下し、微細な配線ピッチにも適当な低粘度の熱可塑性樹脂が確実に充填されて、内層回路の埋め込み性、すなわち絶縁の信頼性が極めて高い良好な金属ベース多層プリント配線板を製造できる。
【００１８】
なお、フィルム状絶縁体と導体箔の接着は、層間にエポキシ樹脂などの接着剤を介在させずに熱融着するため、耐熱性、耐薬品性、電気特性などの諸特性は接着剤の特性に支配されることがなく、絶縁層の優れた諸特性が充分に生かされる。また、製造工程中に接着剤その他の液状積層材料の塗布・乾燥の工程がないので、製造効率の良い多層プリント配線板の製造方法の製造方法となる。
【００１９】
【発明の実施の形態】
この発明の金属ベースプリント配線板、金属ベース多層プリント配線板およびその製造方法の実施形態を、以下に添付図面に基づいて説明する。図１に示す第１の実施形態は、金属ベースプリント配線板に関し、表面粗化されているアルミニウム板などの金属板１の片面にシンジオタクチック構造を有するスチレン系樹脂組成物と、該スチレン系樹脂組成物と相溶性のあるポリオレフィン系、ポリスチレン系、ポリエステル系、ポリアミド系、ポリフェニレンエーテル系、ポリフェニレンスルフィド系の樹脂から選ばれる熱可塑性樹脂を主成分とし上記スチレン系樹脂組成物の含有率が３５〜７０重量％、及び上記スチレン系樹脂組成物と相溶性のある熱可塑性樹脂の含有率が３０〜６５重量％からなる絶縁層２を介して粗化銅箔等の表面粗化されている導体箔を熱融着し、この導体箔をサブトラクティブ法によってプリント回路３を形成した金属ベースプリント配線板であり、プリント回路３を接着固定している熱融着後の絶縁層２は、示差走査熱量測定で昇温した時に測定される結晶融解ピーク温度が２６０℃以上であり、結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとの関係が下記の式(A) で示される関係を満たす特性のものを加熱して下記の式(B) で示される関係を満たすように熱融着されたものである。
【００２０】
式(A): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．６
式(B): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≧０．７
図１の鎖線に示すように、金属ベースプリント配線板は、例えば、厚さ１．０〜１．６ｍｍ程度の金属板１の両面に対して、熱可塑性樹脂組成物からなる２５〜５０μｍ厚の絶縁層２を介して導体箔を熱融着し、この導体箔でプリント回路３を形成した２層（両面）構造の金属ベースプリント配線板であってもよい。
【００２１】
図２（ｃ）の実線に示す第２の実施形態は、金属板４の片面に熱可塑性樹脂組成物からなる絶縁層５を介してフィルム状配線基板６を熱融着した金属ベース多層プリント配線板である。図２（ａ）、（ｂ）に示すように、層間接続用熱融着性フィルム１０は、熱可塑性樹脂組成物からなるフィルム状絶縁体７の両面貫通孔８に導電性ペースト９を充填したものであり、その両面に導体箔を熱融着しかつサブトラクティブ法によってプリント回路１１を形成したものがフィルム状配線基板６である。
【００２２】
第２の実施形態の金属ベース多層プリント配線板の製造方法を詳細に説明すると、先ず、前記した所定組成および熱特性の熱可塑性樹脂組成物からなるフィルム状絶縁体７に、レーザー加工により両面貫通孔８を形成し、この内部に導電性ペースト９を充填して積層電気回路の層間接続用熱融着性フィルム１０を形成し、さらにこの層間接続用熱融着性フィルム１０の両面に粗化銅箔等の導体箔を真空熱プレス機で熱融着し、これをサブトラクティブ法によって不要部分を除いてプリント回路１１を形成し、金属板の片面（または図２（ｃ）の鎖線に示すように両面）にフィルム状絶縁体７を介してフィルム状配線基板６を重ね、熱融着により積層一体化して得られる。
【００２３】
絶縁層５の材料となるフィルム状絶縁体７を製造するには、式(I) で示される所定の結晶性のものを後述する手法で調製する。
式(I): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．４
フィルム状絶縁体７に導体箔を熱融着する際には、熱可塑性樹脂組成物のガラス転移点（Ｔg ) は越えるが、結晶融解ピーク温度（Ｔc ) は越えず、すなわち非晶性が維持される所定温度範囲に加熱し、好ましくは熱可塑性樹脂組成物が前記式(II)で示される特性を維持する導体箔が熱融着されたフィルム状基板を作製する。
【００２４】
式(II): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．６
導体箔に対する導電性回路の形成方法は、周知のサブトラクティブ法を採用できるが、アディティブ法を採用することもできる。因みに、サブトラクティブ法の具体例としては、銅箔に紫外線硬化性樹脂からなるドライフィルムをラミネートし、次に導電性回路の切り抜き型を形成したパターンフィルムをドライフィルムに密着させた状態で紫外線に露光させ、その後、パターンフィルムおよび未硬化のドライフィルムを取り除いて塩化第二鉄溶液でエッチングを行ない、導電性回路の不要部分の銅箔を除去し、次に、水酸化ナトリム溶液に浸漬して残った銅箔上のドライフィルムを除去して導電性回路を形成する。
【００２５】
金属板４の片面または両面に絶縁層５（フィルム状絶縁体７）を重ね、さらにフィルム状配線基板６を重ねて一括して熱融着する際には、各層を構成する熱可塑性樹脂組成物の結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとの関係が式(III) で示される関係を満たすように熱融着する。
【００２６】
式(III): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≧０．７
このようにすると、熱可塑性樹脂組成物の結晶融解ピーク温度（Ｔc ) 付近（例えば２３０〜２５０℃）まで加熱することになって、確実な熱融着が可能になると共に熱可塑性樹脂組成物の結晶化が進み、ハンダ耐熱性に優れた金属ベース多層プリント配線板を製造できる。
【００２７】
本発明においてフィルム状絶縁体を構成する第１の成分であるシンジオタクチック構造を有するスチレン系樹脂は、立体化学構造がシンジオタクチック構造、すなわちＣ−Ｃ結合から形成される主鎖に対して、側鎖であるフェニル基や置換フェニル基が交互に反対方向に位置する立体構造を有するものである。
【００２８】
上記スチレン系樹脂の含有量は耐熱絶縁性フィルムの３５重量％以上、３５〜７０重量％の範囲が好適であり、３５重量％未満でははんだ耐熱性に劣り、７０重量％を越えると導体箔との接着性に劣り易い傾向がある。
【００２９】
また、耐熱絶縁性フィルムを構成する第２の成分である上記スチレン系樹脂と相溶性のある熱可塑性樹脂としては、溶融成形時に均一な分散が可能な樹脂であればよく、ポリオレフィン系、ポリスチレン系、ポリエステル系、ポリアミド系、ポリフェニレンエーテル系、ポリフェニレンスルフィド系の樹脂などが挙げられる。本発明においては、変性ポリフェニレンエーテル（変性ＰＰＥ）が好適に使用される。このスチレン系樹脂と相溶性のある熱可塑性樹脂の含有量は耐熱絶縁性フィルムの３０〜６５重量％の範囲が好適であり、３０重量％未満では導体箔との接着性に劣り易い傾向があり、６５重量％を越えるとはんだ耐熱性に劣り易い傾向がある。
【００３０】
耐熱絶縁性フィルムには上記成分以外に機械的強度を向上する目的で、さらに、ゴム状弾性体を含有させてもよく、ゴム状弾性体としては、スチレン−ブタジエンブロック共重合体（ＳＢＲ）、水素添加スチレン−ブタジエンブロック共重合体（ＳＥＢ）、スチレン−ブタジエン−スチレンブロック共重合体（ＳＢＳ）、水素添加スチレン−ブタジエン−スチレンブロック共重合体（ＳＥＢＳ）などが挙げられるが、これに限定されるものではない。本発明においては、上記ゴム状弾性体のうちＳＥＢＳが好適に使用される。ゴム状弾性体は耐熱絶縁性フィルムの１０〜２０重量％の範囲で含有するのが好ましく、１０重量％未満では強度の改良効果が少なく、２０重量％を越えるものでは耐熱性が低下する傾向がある。
【００３１】
本発明における重要な制御因子であるフィルム状絶縁体の熱融着前の熱特性は、結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとの関係が下記の式(I) で示される関係を満たすことである。
【００３２】
式(I): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．４
（ΔＨｍ−ΔＨｃ）／ΔＨｍで示される熱特性は、ＪＩＳＫ７１２１、ＪＩＳＫ７１２２に準じた示差走査熱量測定で昇温したときのＤＳＣ曲線に現れる２つの転移熱の測定値、結晶融解熱量ΔＨｍ（Ｊ／ｇ）と結晶化熱量ΔＨｃ（Ｊ／ｇ）の値から算出される。
【００３３】
（ΔＨｍ−ΔＨｃ）／ΔＨｍで示される式の値は、原料ポリマーの種類や分子量、組成物の配合比率にも依存しているが、フィルム状絶縁体の成形・加工条件に大きく影響する。すなわち、フィルム状に製膜する際に、原料ポリマーを溶融させた後、速やかに冷却することにより、前記式の値を小さくすることができる。また、これらの数値は、各工程でかかる熱履歴を調整することにより、制御することができる。ここでいう熱履歴とは、フィルム状絶縁体の温度と、その温度になっていた時間を指し、温度が高いほど、この数値は大きくなる傾向がある。導体箔と熱融着前のフィルム状絶縁体の熱特性については、前記式(I) で示される値ができるだけ小さいほうが好ましい。導体箔との熱融着前に０．４を越えていると、すでに結晶性が高く、多層化の熱融着時には結晶化がさらに進行して接着強度が低下するので好ましくない。
【００３４】
前記式(II)で示される関係は、多層プリント配線板を製造する過程において、フィルム状絶縁体の表面に導体箔を熱融着した銅張積層基板における熱融着後の測定に基づくものである。
【００３５】
前記式(II)で示される値が、０．５を越えると、すでに結晶性が高く、多層化の熱融着時に結晶化がさらに進行して接着強度が低下する。また、導体箔との熱融着を高温で行なう必要があり製造効率の面からも好ましくない。
そして、多層化後における熱融着後のフィルム状絶縁体の熱特性は、下記式(III) の関係を満たすことになる。
【００３６】
式(III): 〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≧０．７
なぜなら、上記式(III) の値が、０．７未満の低い値では、絶縁層の結晶化が不充分であり、ハンダ耐熱性（通常２６０℃）を保てないからである。
【００３７】
本発明に用いるフィルム状絶縁体は、通常２５〜３００μｍの膜厚のものであり、その製造方法は、例えばＴダイを用いた押出キャスト法やカレンダー法などの周知の製膜方法を採用すればよく、特に限定された製造方法を採る必要はない。なお、製膜性や安定生産性の面からＴダイを用いた押出キャスト法を採用することが好ましい。押出キャスト法の成形温度は、組成物の流動特性や製膜特性によって適宜に調節するが、概ね組成物の融点以上、４３０℃以下である。
【００３８】
本発明に用いるフィルム状絶縁体を構成する樹脂組成物には、この発明の効果を阻害しない程度に、他の樹脂その他の添加剤を配合してもよく、その具体例としては、熱安定剤、紫外線吸収剤、光安定剤、着色剤、滑剤、難燃剤、無機フィラーなどが挙げられる。また、フィルム状絶縁体の表面に、ハンドリング性改良等のためのエンボス化工やコロナ処理などを施してもよい。
【００３９】
この発明に用いる金属板としては、金属ベースプリント配線板または金属ベース多層プリント配線板の熱放散性や機械的強度の向上などの目的に応じて選択される周知の金属板であり、例えばアルミニウム、鉄、銅、亜鉛等が挙げられる。板厚は、０．１〜３．０ｍｍ程度のものが好適に使用でき、通例１．０〜１．６ｍｍである。
【００４０】
また、金属板として、表面粗化された金属板を使用する場合の粗化（粗面化）の方法としては、サンドブラスト法、ショットブラスト法、ドライホーニング法、化学エッチング法、電解エッチング法等の方法が例示できる。
【００４１】
本発明に用いる導体箔としては、例えば銅、金、銀、アルミニウム、ニッケル、錫などのように厚さ８〜７０μｍ程度の金属箔が挙げられる。このうち、適用される金属箔としては、その表面を黒色酸化処理などの化成処理した銅箔が特に好ましい。導体箔は、接着効果を高めるために、フィルム状絶縁体との接触面（重ねる面）側を予め化学的または機械的に粗化したものを用いることが好ましい。粗化方法は、前述の金属板の場合と同様であり、表面粗化処理された導体箔の具体例としては、電解銅箔を製造する際に電気化学的に処理された粗化銅箔などが挙げられる。
【００４２】
導体箔をフィルム状絶縁体の片面または両面に重ねて加熱・加圧条件で熱融着する際には、例えば熱プレス法もしくは熱ラミネートロール法またはこれらを組み合わせた方法、その他の周知の加熱圧着方法を採用することができる。
【００４３】
【実施例】
まず、この発明のフィルム状絶縁体の条件を満足するフィルム状絶縁体の製造例１〜３およびこれに対比する参考例１、２の製造方法およびこれらの物性について以下に説明する。〔フィルム状絶縁体の製造例１〕
シンジオタクチック構造を有するスチレン系樹脂［出光石油化学（株）製、ザレック］（以下、単にＳＰＳと略記することがある）６０重量％と、変性ＰＰＥ［三菱エンジニアリングプラスチックス（株）製、ユピエース］４０重量％とからなる混合組成物を、Ｔダイを備えた三菱重工（株）製４０ｍｍφ二軸混練押出機（Ｌ／Ｄ＝３５）を用いて押し出し、調温機能を備えたキャストロールに直ちに接触させて固化させて、厚さ２５μｍのフィルム状絶縁体を製造した。
【００４４】
〔フィルム状絶縁体の製造例２〕
製造例１において、混合組成物の配合割合をＳＰＳ４０重量％、変性ＰＰＥ６０重量％としたこと以外は、同様にしてフィルム状絶縁体を製造した。
【００４５】
〔フィルム状絶縁体の製造例３〕
製造例１において、混合組成物の配合割合をＳＰＳ３０重量％、変性ＰＰＥ７０重量％としたこと以外は、同様にしてフィルム状絶縁体を製造した。
【００４６】
〔フィルム状絶縁体の参考例１、２〕
製造例１において、混合組成物の配合割合をＳＰＳ１００重量％（参考例１）、または変性ＰＰＥ１００重量％（参考例２）としたこと以外は、同様にしてそれぞれのフィルム状絶縁体を製造した。
【００４７】
上記製造例および参考例で得られたフィルム状絶縁体の物性を調べるため、以下の(1) および(2) に示す項目を測定または測定値から計算値を算出した。これらの結果は、表１にまとめて示した。
【００４８】
(1) ガラス転移温度（℃）、結晶化温度（℃）、結晶融解ピーク温度（℃）
ＪＩＳＫ７１２１に準じ、試料１０ｍｇを使用し、パーキンエルマー社製：ＤＳＣ−７を用いて加熱速度を１０℃／分で昇温した時の上記各温度をサーモグラムから求めた。
【００４９】
(2) （ΔＨｍ−ΔＨｃ）／ΔＨｍ
ＪＩＳＫ７１２２に準じ、試料１０ｍｇを使用し、パーキンエルマー社製：ＤＳＣ−７を用いて加熱速度を１０℃／分で昇温した時のサーモグラムから結晶融解熱量ΔＨｍ（Ｊ／ｇ）と結晶化熱量ΔＨｃ（Ｊ／ｇ）を求め、上記式の値を算出した。
【００５０】
【表１】

【００５１】
〔実施例１〕
製造例１で得られた厚さ２５μｍのフィルム状絶縁体に、レーザーでインナーバイアホール（inner via hole) 用の孔開け加工を施し、スクリーン印刷機を用いて孔内に導電性ペースト剤を充填した。この導電性ペーストを充分に乾燥させた後、フィルム状絶縁体の両面に厚さ１２μｍの電気化学的に表面を粗面化した電解銅箔を積層し、真空雰囲気下７６０ｍｍＨｇでプレス温度２００℃、プレス圧力３０ｋｇ／ｃｍ²、プレス時間１０分の条件で熱融着させ両面銅張積層板を作製した。
【００５２】
作製した両面銅張積層板のフィルム状絶縁体に対し、前記 (2)（ΔＨｍ−ΔＨｃ）／ΔＨｍの測定試験を前記同じ方法で行ない、式値を表２に示した。
また、上記得られた両面銅張積層板に対して、後述する(3) の方法で接着強度を調べ、この結果を表２中に併記した。
【００５３】
上記得られた両面銅張積層板にサブトラクティブ法によって回路パターンを形成し、導電性回路をエッチングにより形成した配線基板を２枚製造した。そして、２枚の配線基板の間に製造例１で得られた厚さ２５μｍのフィルム状絶縁体を２枚挟んでさらに芯板として５０５２系（ＪＩＳＨ−００１２）のアルミニウム板（厚さ１．５ｍｍ）を図２（ｃ）に示す状態に積み重ね、真空雰囲気下７６０ｍｍＨｇでプレス温度２２０℃、プレス圧力３０ｋｇ／ｃｍ²、プレス時間２０分の条件でピンラミネーション方式によって熱融着し、４層の多層プリント配線板を製造した。
【００５４】
得られたアルミニウムベース多層プリント配線板に対して前記 (2)（ΔＨｍ−ΔＨｃ）／ΔＨｍの測定試験を行なうと共に、室温における銅箔回路とフィルム状絶縁体との接着強度を以下の(3) の試験方法で調べ、さらに層間剥離の有無を走査型電子顕微鏡（下記の(5) の方法）で観察し、ハンダ耐熱性を下記の(4) の試験方法で調べ、これらの結果を表２中に示した。
(3) 接着強度ＪＩＳＣ６４８１の常態の引剥し強さに準拠して、銅箔の引き剥がし強さを測定し、その平均値をｋｇｆ／ｃｍで示した。
【００５５】
(4) ハンダ耐熱性
ＪＩＳＣ６４８１の常態のハンダ耐熱性に準拠し、２６０℃のハンダ浴に試験片の銅箔側がハンダ浴に接触する状態で１０秒間浮かべた後、浴から取り出して室温まで放冷し、その膨れや剥がれ箇所の有無を目視観察し、その良否を評価した。
【００５６】
(5) 層間剥離有無
多層プリント配線板をエポキシ樹脂に包埋し、精密切断機で断面観察用サンプルを作製し、走査型電子顕微鏡（ＳＥＭ）で切断面を観察し、フィルム状絶縁体と銅箔製の導電性回路との層間剥離の有無を評価した。
【００５７】
【表２】

【００５８】
〔実施例２〕
実施例１において、フィルム状絶縁体として製造例２を使用し、両面銅張積層板を作製する際のプレス温度を２２５℃、４層基板を作製する際の熱プレス条件を温度２４０℃、ブレス時間を３０分に変更したこと以外は実施例１と同様にして４層のプリント配線板を作製し、試験(3) 〜(5) の評価を表２中に併記した。
〔比較例１〕
実施例１において、両面銅張積層板を作製する際のプレス温度を２１５℃としたこと以外は実施例１と同様にして４層の多層プリント配線板を作製し、これに対する試験(3) 〜(5) の評価を表２中に併記した。
【００５９】
〔比較例２〕実施例２において、４層の多層プリント配線板のプレス温度を２３０℃、プレス時間を１０分に変更したこと以外は実施例２と同様にして４層の多層プリント配線板を作製し、試験(3) 〜(5) の評価を表２中に併記した。
【００６０】
〔比較例３〕
実施例１において、フィルム状絶縁体として製造例３を使用し、両面銅張積層板を作製する際のプレス温度を２４０℃、プレス時間を２０分に変更したこと以外は実施例１と同様にして４層の多層プリント配線板を作製し、これに対する試験(3) 〜(5) の評価を表２中に併記した。
【００６１】
表２の結果からも明らかなように、実施例１の両面銅張積層板の接着強度は、０．７ｋｇｆ／１０ｃｍという良好な値であり、（ΔＨｍ−ΔＨｃ）／ΔＨｍの値も０．３１と適正値であった。また、４層の多層プリント配線板積層時における（ΔＨｍ−ΔＨｃ）／ΔＨｍの値も０．９６と適正値であり、接着強度は、１．５ｋｇｆ／１０ｃｍという良好な値であった。また、ハンダ耐熱性試験の結果は基板に膨れや剥がれが一切観察されず、また４層の多層プリント配線板のＳＥＭ観察でも層間剥離は全く観察されず、回路パターン近傍への樹脂の回り込み（充填量）は良好でありボイドの発生は全く見受けられなかった。
【００６２】
実施例２の両面銅張積層板の接着強度も１．３ｋｇｆ／１０ｃｍという良好な値であり、ハンダ耐熱性試験の結果も良好であり、また４層熱融着後のＳＥＭ観察でも層間剥離は全く観察されず、回路パターン近傍への樹脂の回り込みも良好であった。これに対して、比較例１の４層プリント配線板は、層間の密着性が不十分であり、ハンダ耐熱性も膨れや剥がれが観察されて不良であった。
【００６３】
また、比較例２の４層プリント配線板は、層間の密着性はあったが、ハンダ耐熱性は不良であった。比較例３は、両面銅張積層板の銅箔とフィルムの接着強度は０．２ｋｇｆ／１０ｃｍという低い値であり、エッチング工程において回路が剥離した。
【００６４】
【発明の効果】
本発明の金属ベースプリント配線板は、以上説明したように、金属板の片面または両面に所定の熱特性を有する熱可塑性樹脂組成物からなる絶縁層を介して導体箔を熱融着し、この導体箔でプリント回路を形成したので、導体箔および金属ベースに対して比較的低温で熱融着することができ、しかも確実に接着一体化されかつハンダ耐熱性を有する金属ベースプリント配線基板であるという利点がある。
【００６５】
また、本発明の金属ベース多層プリント配線板は、所定の熱的特性の結晶性熱可塑性樹脂組成物を絶縁層とするフィルム状配線基板を形成し、金属板の片面または両面に前記熱可塑性樹脂組成物からなる絶縁層を介して前記フィルム状配線基板を熱融着により一体化したものであるので、各層の熱可塑性樹脂成物は優れた接着強度を発揮し、４層以上の金属ベース多層プリント配線板でも層間の剥離がなく、所要のハンダ耐熱性を示すものになる。
【００６６】
また、各層の熱融着時に微細な配線ピッチ間にも絶縁性材料が充填され、高配線密度に形成された内層回路の絶縁性が良好な金属ベース多層プリント配線板となる。
【００６７】
本発明の多層プリント配線板の製造方法は、所定の熱特性を有する結晶性熱可塑性樹脂からなるフィルム状絶縁体を用いた金属ベース多層プリント配線板の製造方法であるので、絶縁材料の高配線密度の内層回路に対する埋め込み性が良好になって回路の絶縁信頼性が高いものが製造でき、しかも絶縁層を介して多層に重ねた導体箔および金属ベースとを一度の加熱加圧工程で確実に熱融着により積層一体化できるので、効率のよい製造方法であるという利点がある。
【図面の簡単な説明】
【図１】金属ベースプリント配線板の要部の拡大断面図
【図２】金属ベース多層プリント配線板の製造工程を示す要部の拡大断面図
【符号の説明】
１、４金属板
２、５絶縁層
３、１１プリント回路
６フィルム状配線基板
７フィルム状絶縁体
８両面貫通孔
９導電性ペースト
１０層間接続用熱融着性フィルム[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a metal-based printed wiring board, a metal-based multilayer printed wiring board, and a method for manufacturing the same.
[0002]
[Prior art]
As a metal-based printed wiring board, conductor foil is laminated and integrated with one side or both sides of a metal base (base or core) such as aluminum, iron, copper, or zinc via an insulating layer, and then the conductor foil is etched. What formed the printed circuit is known.
[0003]
The metal-based printed wiring board has excellent heat resistance, flame retardancy, shielding effect, mechanical strength, and the like due to the characteristics of the metal base, and particularly has good heat dissipation properties. That is, in the metal base printed wiring board, since the base metal has high thermal conductivity, the heat dispersibility by conduction is good, the local rise in the substrate temperature is suppressed, and the heat dissipation effect is high. As a material for forming the insulating layer of the metal-based printed wiring board, an epoxy resin containing a filler with good heat dissipation such as alumina is generally used.
[0004]
However, there are problems in terms of workability, such as a storage stability problem of an epoxy prepreg that is in a semi-cured state before press processing and a long time of about 2 hours for press processing.
[0005]
[Problems to be solved by the invention]
Therefore, the object of the present invention is to solve the above-mentioned problems and to heat-seal the conductor foil and the metal base at a relatively low temperature in a short time using a thermoplastic insulating layer having solder heat resistance. In addition, a metal base printed wiring board or a metal base multilayer printed wiring board that is securely bonded and integrated is used.
[0006]
Further, as an object of the invention relating to the manufacturing method of the present invention, a metal base multilayer printed wiring board is efficiently manufactured by reliably heat-sealing a conductor foil and a metal base with a thermoplastic insulating layer by a simple process. That is.
[0007]
[Means for Solving the Problems]
In the invention related to the metal-based printed wiring board of the present invention, in order to solve the above problems, the conductor foil is heat-sealed via an insulating layer made of a thermoplastic resin composition on one side or both sides of the metal plate, In the metal-based printed wiring board in which a printed circuit is formed with this conductive foil, the insulating layer is a styrene resin composition having a syndiotactic structure, and a polyolefin or polystyrene system compatible with the styrene resin composition. The above-mentioned styrenic resin mainly composed of a thermoplastic resin selected from polyester-based, polyamide-based, polyphenylene ether-based, and polyphenylene sulfide-based resins (hereinafter also referred to as a thermoplastic resin compatible with the styrene-based resin composition). Thermoplastic having a resin composition content of 35 to 70% by weight and compatibility with the styrenic resin composition The thermoplastic resin composition has a resin content of 30 to 65% by weight, and this thermoplastic resin composition has a crystal melting peak temperature of 260 ° C. or higher measured when the temperature is raised by differential scanning calorimetry. A material having a characteristic that satisfies the relationship represented by the following formula (A) with the crystallization heat amount ΔHc generated by crystallization in the warm condition was heat-sealed so as to satisfy the relationship represented by the following formula (B). This is a metal-based printed wiring board characterized by being a thing.
[0008]
Formula (A): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (B): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7
As the conductor foil, a conductor foil having a roughened surface is preferably employed, and as the metal plate, a metal plate having a roughened surface is preferably employed.
[0009]
Further, in the invention relating to the metal-based multilayer printed wiring board of the present application, in order to solve the above-mentioned problems, both-side through-holes are formed in the film-like insulator made of the thermoplastic resin composition, and the through-holes are electrically conductive. Filling the paste to provide a heat-sealable film for interlayer connection of the laminated electrical circuit, heat-sealing the conductive foil on both sides of this interlayer connection heat-sealing film and forming a circuit to provide a film-like wiring board, In a metal-based multilayer printed wiring board in which a film-like wiring board is heat-sealed via an insulating layer made of the thermoplastic resin composition on one or both surfaces of a metal plate, the heat-sealed insulating layer and the heat-fused The styrene resin composition having a syndiotactic structure, and the thermoplastic resin that is compatible with the styrene resin composition Main component and the content of the styrene-based resin composition is 35 to 70 wt%, and the content of the thermoplastic resin with the styrene-based resin composition and compatibility consists 30 to 65 wt%, Said The thermoplastic resin composition has a crystal melting peak temperature measured at 260 ° C. or higher when the temperature is raised by differential scanning calorimetry, and the crystal melting heat amount ΔHm and the crystallization heat amount ΔHc generated by crystallization during the temperature rise. A metal base characterized by being heat-sealed so that the relationship satisfying the relationship represented by the following formula (A) is heated and satisfying the relationship represented by the following formula (B): It was a printed wiring board.
[0010]
Formula (A): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (B): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7
As the conductor foil, a conductor foil having a roughened surface is preferably employed, and as the metal plate, a metal plate having a roughened surface is preferably employed.
[0011]
The metal-based printed wiring board or metal-based multilayer printed wiring board of the present invention configured as described above has an insulating layer containing a predetermined amount of a styrene resin having a crystalline syndiotactic structure.
[0012]
The insulating layer has a crystal melting peak temperature measured at 260 ° C. or higher when the temperature is raised by differential scanning calorimetry, and the relationship between the crystal melting heat amount ΔHm and the crystallization heat amount ΔHc generated by crystallization during the temperature rise is The one satisfying the relationship represented by the formula (A) is heated under a predetermined condition so as to satisfy the relationship represented by the formula (B) after heat fusion, Since the crystallinity of the styrenic resin proceeds appropriately, it becomes an insulating layer having solder heat resistance that can withstand 260 ° C., and has excellent mechanical strength and electrical insulation.
[0013]
This insulating layer also has a high adhesive strength with the conductor foil, and an electric circuit formed by etching the conductor foil is firmly adhered to the insulating layer and hardly peeled off. Usually, a conductor foil having a roughened surface or a metal plate having a roughened surface is adopted, or a roughened conductor foil and a metal plate are used to increase the adhesive strength.
In addition, the film-like insulator and conductor foil are heat-sealed without interposing an adhesive such as epoxy resin between the layers, so the heat resistance and chemical resistance of the metal-based printed wiring board or metal-based multilayer printed wiring board The various characteristics such as electrical characteristics are not governed by the characteristics of the adhesive, and the excellent characteristics of the insulating layer are fully utilized.
[0014]
The heat-sealable film for interlayer connection of the laminated electric circuit is formed of the insulating thermoplastic resin composition, and the opening of the double-sided through hole is an electrical contact by the conductive paste in the double-sided through-hole. Thus, the electrical circuit disposed on one or both sides of the film is electrically connected in the layer thickness direction. In the invention relating to the method for producing a metal-based multilayer printed wiring board, in order to solve the above-mentioned problems, a styrene resin composition having a syndiotactic structure, and a thermoplastic resin compatible with the styrene resin composition The content of the styrenic resin composition is 35 to 70% by weight, and the content of the thermoplastic resin compatible with the styrenic resin composition is 30 to 65% by weight, Said The thermoplastic resin composition has a crystal melting peak temperature measured at 260 ° C. or higher when the temperature is raised by differential scanning calorimetry, and the crystal melting heat amount ΔHm and the crystallization heat amount ΔHc generated by crystallization during the temperature rise. A film-like insulator made of a thermoplastic resin composition satisfying the relationship represented by the following formula (I) is formed, and a double-sided through hole is formed in the film-like insulator and a conductive paste is formed in the through-hole. Filled to form a heat-fusible film for interlayer connection of the laminated electrical circuit, and the thermoplastic resin composition is represented by the following formula (II) by overlaying a conductor foil on both sides of the heat-fusible film for interlayer connection After heat-sealing so as to satisfy the relationship shown, a circuit is formed on the conductor foil to provide a film-like wiring board, and the film-like wiring board is disposed on one or both sides of a metal plate via the film-like insulator. Stack and configure each layer The thermoplastic resin composition is to that a method for producing a metal base multilayer printed circuit board comprising a heat sealing so as to satisfy the relationship represented by the following (III).
[0015]
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4
Formula (II): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (III): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7
In the manufacturing method of the multilayer printed wiring board, when the conductor foil is overlapped on both sides of the heat-fusible film for interlayer connection and heat-sealed, the heat of crystal melting ΔHm after heat-sealing of the thermoplastic resin composition and Heat fusion is performed so that the relationship with the amount of heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the above formula (II).
[0016]
Then, a film-like insulator is laminated on one side or both sides of the metal plate, and a film-like wiring board formed with a conductive foil on both sides of the above-described heat-fusible film for interlayer connection is overlaid thereon, and the formula (II) The thermoplastic resin composition having the relationship represented by the above is thermally fused so as to satisfy the relationship represented by the formula (III). In this way, the thermoplastic resin composition after heat-sealing becomes an insulating layer in which the crystallinity of the styrenic resin having a syndiotactic structure is appropriately advanced and solder heat resistance that can withstand 260 ° C. is ensured. In addition, the adhesive strength with the conductor foil is increased.
[0017]
When performing heat fusion by heating and pressing, the elastic modulus of the thermoplastic resin decreases in the bonding temperature range with the conductor foil, and an appropriate low-viscosity thermoplastic resin is reliably filled even in a fine wiring pitch. It is possible to manufacture a good metal-based multilayer printed wiring board in which the embedding property of the inner layer circuit, ie, the insulation reliability is extremely high.
[0018]
In addition, since the film-like insulator and conductor foil are heat-sealed without interposing an adhesive such as epoxy resin between the layers, various characteristics such as heat resistance, chemical resistance, and electrical characteristics are characteristic of the adhesive. Therefore, the excellent characteristics of the insulating layer are fully utilized. In addition, since there is no step of applying and drying an adhesive or other liquid laminate material during the manufacturing process, the manufacturing method is a manufacturing method of a multilayer printed wiring board with high manufacturing efficiency.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a metal-based printed wiring board, a metal-based multilayer printed wiring board, and a manufacturing method thereof according to the present invention will be described below with reference to the accompanying drawings. The first embodiment shown in FIG. 1 relates to a metal-based printed wiring board, a styrene-based resin composition having a syndiotactic structure on one surface of a metal plate 1 such as a surface-roughened aluminum plate, and the styrenic resin A thermoplastic resin selected from polyolefin, polystyrene, polyester, polyamide, polyphenylene ether, and polyphenylene sulfide resins that are compatible with the resin composition, and the content of the styrene resin composition is 35. Conductor whose surface is roughened, such as roughened copper foil, through an insulating layer 2 having a content of thermoplastic resin compatible with the styrene-based resin composition of 30 to 65% by weight of 70% by weight A metal-based printed wiring board in which a foil is heat-sealed and a printed circuit 3 is formed on the conductive foil by a subtractive method. The insulating layer 2 after heat fusion to which the circuit 3 is bonded and fixed has a crystal melting peak temperature of 260 ° C. or higher measured when the temperature is raised by differential scanning calorimetry, It is heat-sealed so as to satisfy the relationship represented by the following equation (B) by heating a material having a relationship with the crystallization heat amount ΔHc generated by crystallization that satisfies the relationship represented by the following equation (A). It is a thing.
[0020]
Formula (A): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (B): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7
As shown by the chain line in FIG. 1, the metal base printed wiring board has a thickness of 25 to 50 μm made of a thermoplastic resin composition, for example, on both sides of the metal plate 1 having a thickness of about 1.0 to 1.6 mm. A metal-based printed wiring board having a two-layer (double-sided) structure in which a conductive foil is thermally fused via the insulating layer 2 and a printed circuit 3 is formed using the conductive foil may be used.
[0021]
The second embodiment shown by the solid line in FIG. 2 (c) is a metal-based multilayer printed wiring in which a film-like wiring board 6 is thermally fused to one side of a metal plate 4 with an insulating layer 5 made of a thermoplastic resin composition. It is a board. As shown in FIGS. 2 (a) and 2 (b), the heat-fusible film 10 for interlayer connection has a conductive paste 9 filled in the double-sided through-holes 8 of the film-like insulator 7 made of a thermoplastic resin composition. The film-like wiring board 6 is obtained by thermally fusing conductor foils on both sides and forming the printed circuit 11 by the subtractive method.
[0022]
The manufacturing method of the metal-based multilayer printed wiring board according to the second embodiment will be described in detail. First, the film-like insulator 7 made of the thermoplastic resin composition having the predetermined composition and thermal characteristics described above is penetrated by laser processing. A hole 8 is formed, and the inside thereof is filled with a conductive paste 9 to form a heat-sealable film 10 for interlayer connection of a laminated electric circuit, and further roughened on both surfaces of this heat-sealable film 10 for interlayer connection. A conductive foil such as a copper foil is heat-sealed with a vacuum heat press machine, and the printed circuit 11 is formed by removing unnecessary portions by a subtractive method, and is shown on one side of a metal plate (or a chain line in FIG. 2C). Thus, the film-like wiring board 6 is laminated on both surfaces) via the film-like insulator 7 and laminated and integrated by heat fusion.
[0023]
In order to manufacture the film-like insulator 7 as a material of the insulating layer 5, a predetermined crystalline material represented by the formula (I) is prepared by a method described later.
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4
When the conductor foil is thermally fused to the film-like insulator 7, the glass transition point (Tg) of the thermoplastic resin composition is exceeded, but the crystal melting peak temperature (Tc) is not exceeded, that is, the amorphous property is maintained. The film-like board | substrate with which the conductor foil in which the thermoplastic resin composition maintains the characteristic shown by said Formula (II) is preferably heat-sealed is produced.
[0024]
Formula (II): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
As a method for forming the conductive circuit on the conductor foil, a well-known subtractive method can be adopted, but an additive method can also be adopted. Incidentally, as a specific example of the subtractive method, a dry film made of an ultraviolet curable resin is laminated on a copper foil, and then a pattern film in which a conductive circuit cut-out mold is formed is adhered to the dry film in an ultraviolet ray. After exposure, remove the pattern film and uncured dry film and etch with ferric chloride solution to remove the copper foil of the unnecessary part of the conductive circuit, then immerse in sodium hydroxide solution The dry film on the remaining copper foil is removed to form a conductive circuit.
[0025]
When the insulating layer 5 (film insulator 7) is overlapped on one or both surfaces of the metal plate 4, and the film-like wiring board 6 is overlapped and heat-sealed together, the thermoplastic resin composition constituting each layer The heat fusion is performed so that the relationship between the amount of heat of crystal fusion ΔHm and the amount of heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the formula (III).
[0026]
Formula (III): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7
If it does in this way, it will heat to the crystal-melting peak temperature (Tc) vicinity (for example, 230-250 degreeC) of a thermoplastic resin composition, reliable heat fusion is attained, and while the thermoplastic resin composition of Crystallization progresses and a metal-based multilayer printed wiring board with excellent solder heat resistance can be manufactured.
[0027]
In the present invention, the styrenic resin having a syndiotactic structure, which is the first component constituting the film-like insulator, has a stereochemical structure with respect to a main chain formed from a syndiotactic structure, that is, a C—C bond. These have a three-dimensional structure in which phenyl groups and substituted phenyl groups as side chains are alternately positioned in opposite directions.
[0028]
The content of the styrenic resin is preferably in the range of 35% by weight to 35% by weight of the heat-resistant insulating film. When the content is less than 35% by weight, the solder heat resistance is inferior. It tends to be inferior to the adhesiveness.
[0029]
The thermoplastic resin that is compatible with the styrene resin as the second component constituting the heat-resistant insulating film may be any resin that can be uniformly dispersed during melt molding. , Polyester-based, polyamide-based, polyphenylene ether-based, and polyphenylene sulfide-based resins. In the present invention, modified polyphenylene ether (modified PPE) is preferably used. The content of the thermoplastic resin compatible with the styrene resin is preferably in the range of 30 to 65% by weight of the heat-resistant insulating film, and if it is less than 30% by weight, the adhesiveness to the conductor foil tends to be inferior. If it exceeds 65% by weight, the solder heat resistance tends to be inferior.
[0030]
For the purpose of improving mechanical strength in addition to the above components, the heat-resistant insulating film may further contain a rubber-like elastic body. As the rubber-like elastic body, a styrene-butadiene block copolymer (SBR), Examples include hydrogenated styrene-butadiene block copolymer (SEB), styrene-butadiene-styrene block copolymer (SBS), and hydrogenated styrene-butadiene-styrene block copolymer (SEBS). It is not something. In the present invention, among the rubber-like elastic bodies, SEBS is preferably used. The rubbery elastic body is preferably contained in the range of 10 to 20% by weight of the heat-resistant insulating film, and if it is less than 10% by weight, the effect of improving the strength is small, and if it exceeds 20% by weight, the heat resistance tends to decrease. is there.
[0031]
The thermal characteristics before thermal fusion of the film-like insulator, which is an important control factor in the present invention, is the relationship between the heat of crystal fusion ΔHm and the amount of heat of crystallization ΔHc generated by crystallization during the temperature rise: ) Is satisfied.
[0032]
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4
The thermal characteristics indicated by (ΔHm−ΔHc) / ΔHm are two measured values of transition heat appearing in the DSC curve when the temperature is raised by differential scanning calorimetry according to JIS K7121, JIS K7122, and the heat of crystal melting ΔHm ( J / g) and the value of crystallization heat quantity ΔHc (J / g).
[0033]
Although the value of the equation represented by (ΔHm−ΔHc) / ΔHm depends on the type and molecular weight of the starting polymer and the blending ratio of the composition, it greatly affects the molding and processing conditions of the film-like insulator. That is, when the film is formed into a film, the value of the above formula can be reduced by melting the raw material polymer and then quickly cooling it. Moreover, these numerical values can be controlled by adjusting the thermal history applied in each step. The heat history here refers to the temperature of the film-like insulator and the time during which the temperature has been reached, and this value tends to increase as the temperature increases. Regarding the thermal characteristics of the conductor foil and the film-like insulator before heat sealing, it is preferable that the value represented by the formula (I) is as small as possible. If it exceeds 0.4 before heat-sealing with the conductor foil, the crystallinity is already high, and at the time of multi-layer heat-sealing, crystallization further proceeds and the adhesive strength decreases, which is not preferable.
[0034]
The relationship represented by the above formula (II) is based on the measurement after heat-sealing in a copper-clad laminate in which a conductor foil is heat-sealed to the surface of a film-like insulator in the process of producing a multilayer printed wiring board. is there.
[0035]
When the value represented by the formula (II) exceeds 0.5, the crystallinity is already high, and the crystallization further proceeds at the time of heat fusion for multilayering, and the adhesive strength is lowered. Further, it is necessary to perform heat fusion with the conductor foil at a high temperature, which is not preferable from the viewpoint of manufacturing efficiency.
The thermal characteristics of the film-like insulator after heat fusion after multilayering satisfy the relationship of the following formula (III).
[0036]
Formula (III): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7
This is because if the value of the above formula (III) is a low value of less than 0.7, the insulating layer is insufficiently crystallized and solder heat resistance (usually 260 ° C.) cannot be maintained.
[0037]
The film-like insulator used in the present invention usually has a film thickness of 25 to 300 μm, and the manufacturing method thereof is, for example, a well-known film forming method such as an extrusion casting method using a T die or a calendar method. Well, it is not necessary to take a particularly limited manufacturing method. In addition, it is preferable to employ | adopt the extrusion casting method using T die from the surface of film forming property or stable productivity. The molding temperature of the extrusion casting method is appropriately adjusted depending on the flow characteristics and film forming characteristics of the composition, but is generally not lower than the melting point of the composition and not higher than 430 ° C.
[0038]
The resin composition constituting the film-like insulator used in the present invention may be blended with other resins and other additives to such an extent that the effects of the present invention are not impaired. Specific examples thereof include a heat stabilizer. UV absorbers, light stabilizers, colorants, lubricants, flame retardants, inorganic fillers, and the like. Moreover, you may give the embossing process, corona treatment, etc. for handling property improvement etc. to the surface of a film-form insulator.
[0039]
The metal plate used in the present invention is a well-known metal plate selected according to the purpose such as improvement of heat dissipation and mechanical strength of the metal base printed wiring board or the metal base multilayer printed wiring board, such as aluminum, Examples include iron, copper, and zinc. A plate thickness of about 0.1 to 3.0 mm can be preferably used, and is usually 1.0 to 1.6 mm.
[0040]
In addition, as a metal plate, a roughening (roughening) method in the case of using a roughened metal plate includes a sand blast method, a shot blast method, a dry honing method, a chemical etching method, an electrolytic etching method, and the like. A method can be exemplified.
[0041]
Examples of the conductive foil used in the present invention include a metal foil having a thickness of about 8 to 70 μm, such as copper, gold, silver, aluminum, nickel, and tin. Among these, as the metal foil to be applied, a copper foil whose surface is subjected to chemical conversion treatment such as black oxidation treatment is particularly preferable. In order to enhance the adhesion effect, it is preferable to use a conductor foil that has been chemically or mechanically roughened on the contact surface (surface to be overlapped) side with the film-like insulator. The roughening method is the same as in the case of the metal plate described above, and specific examples of the conductor foil subjected to the surface roughening treatment include a roughened copper foil electrochemically treated when manufacturing an electrolytic copper foil. Is mentioned.
[0042]
When conductor foil is laminated on one or both sides of a film-like insulator and heat-sealed under heating / pressurizing conditions, for example, a hot press method or a heat laminating roll method or a combination thereof, or other well-known thermocompression bonding The method can be adopted.
[0043]
【Example】
First, the production methods 1 to 3 of the film-like insulator satisfying the conditions of the film-like insulator of the present invention, the production methods of Reference Examples 1 and 2 and the physical properties thereof will be described below. [Production Example 1 of Film Insulator]
Styrenic resin having a syndiotactic structure [made by Idemitsu Petrochemical Co., Ltd., Zalec] (hereinafter sometimes simply referred to as SPS) 60% by weight, modified PPE [Mitsubishi Engineering Plastics Co., Ltd., Iupiace The mixture composition consisting of 40% by weight was extruded using a 40 mmφ twin-screw kneading extruder (L / D = 35) manufactured by Mitsubishi Heavy Industries, Ltd. equipped with a T die, and cast into a cast roll having a temperature control function. Immediate contact and solidification produced a film insulator having a thickness of 25 μm.
[0044]
[Production Example 2 of Film Insulator]
A film-like insulator was produced in the same manner as in Production Example 1 except that the blending ratio of the mixed composition was SPS 40% by weight and modified PPE 60% by weight.
[0045]
[Production Example 3 of Film Insulator]
A film-like insulator was produced in the same manner as in Production Example 1 except that the blending ratio of the mixed composition was SPS 30% by weight and modified PPE 70% by weight.
[0046]
[Reference Examples 1 and 2 of film insulator]
The respective film-like insulators were produced in the same manner as in Production Example 1 except that the blending ratio of the mixed composition was SPS 100% by weight (Reference Example 1) or modified PPE 100% by weight (Reference Example 2).
[0047]
In order to examine the physical properties of the film-like insulators obtained in the above production examples and reference examples, the following items (1) and (2) were measured, or calculated values were calculated from the measured values. These results are summarized in Table 1.
[0048]
(1) Glass transition temperature (° C), crystallization temperature (° C), crystal melting peak temperature (° C)
According to JIS K7121, 10 mg of a sample was used, and each temperature described above was measured from a thermogram when the heating rate was increased at 10 ° C./min using DSC-7 manufactured by PerkinElmer.
[0049]
(2) (ΔHm−ΔHc) / ΔHm
In accordance with JIS K7122, 10 mg of sample was used, manufactured by Perkin Elmer: DSC-7, DSC-7 was used to heat the crystal melting heat ΔHm (J / g) and crystallization from the thermogram when the heating rate was raised at 10 ° C./min. The amount of heat ΔHc (J / g) was obtained, and the value of the above formula was calculated.
[0050]
[Table 1]

[0051]
[Example 1]
The film-like insulator having a thickness of 25 μm obtained in Production Example 1 is subjected to drilling for an inner via hole with a laser, and a conductive paste agent is filled in the hole using a screen printer. did. After sufficiently drying this conductive paste, an electrolytic copper foil having a surface roughness of 12 μm and electrochemically roughened is laminated on both sides of the film-like insulator, and a press temperature of 200 ° C. at 760 mmHg in a vacuum atmosphere. Press pressure 30kg / cm ² The double-sided copper-clad laminate was produced by heat-sealing under conditions of a press time of 10 minutes.
[0052]
With respect to the film-like insulator of the produced double-sided copper-clad laminate, the measurement test of (2) (ΔHm−ΔHc) / ΔHm was performed by the same method, and the formula values are shown in Table 2.
Further, the adhesive strength of the obtained double-sided copper-clad laminate was examined by the method (3) described later, and the results are also shown in Table 2.
[0053]
A circuit pattern was formed on the obtained double-sided copper-clad laminate by a subtractive method, and two wiring boards on which conductive circuits were formed by etching were manufactured. Then, two film-like insulators having a thickness of 25 μm obtained in Production Example 1 are sandwiched between two wiring boards, and a 5052 series (JISH-0012) aluminum plate (thickness 1.5 mm) is further used as a core plate. 2) are stacked in the state shown in FIG. 2 (c), in a vacuum atmosphere at 760 mmHg, at a press temperature of 220 ° C., and at a press pressure of 30 kg / cm. ² Then, heat fusion was performed by a pin lamination method under a press time of 20 minutes to produce a four-layer multilayer printed wiring board.
[0054]
The aluminum base multilayer printed wiring board is subjected to the measurement test of (2) (ΔHm−ΔHc) / ΔHm, and the adhesion strength between the copper foil circuit and the film-like insulator at room temperature is as follows: In addition, the presence or absence of delamination was observed with a scanning electron microscope (method (5) below), and the solder heat resistance was examined using the test method (4) below. The results are shown in Table 2. Shown in.
(3) Adhesive strength Based on the normal peel strength of JIS C6481, the peel strength of the copper foil was measured, and the average value was expressed in kgf / cm.
[0055]
(4) Solder heat resistance
According to the normal solder heat resistance of JIS C6481, after floating for 10 seconds in a state where the copper foil side of the test piece is in contact with the solder bath in a 260 ° C. solder bath, the test piece is taken out of the bath and allowed to cool to room temperature. The presence or absence of the peeling part was visually observed and the quality was evaluated.
[0056]
(5) Delamination
A multilayer printed wiring board is embedded in an epoxy resin, a sample for cross-sectional observation is prepared with a precision cutting machine, the cut surface is observed with a scanning electron microscope (SEM), and a film-like insulator and a conductive circuit made of copper foil The presence or absence of delamination was evaluated.
[0057]
[Table 2]

[0058]
[Example 2]
In Example 1, Production Example 2 was used as a film-like insulator, the pressing temperature when producing a double-sided copper-clad laminate was 225 ° C., and the hot pressing conditions when producing a four-layer substrate were 240 ° C. and breathing A four-layer printed wiring board was produced in the same manner as in Example 1 except that the time was changed to 30 minutes, and the evaluations of tests (3) to (5) were also shown in Table 2.
[Comparative Example 1]
In Example 1, a four-layer multilayer printed wiring board was produced in the same manner as in Example 1 except that the pressing temperature at the time of producing the double-sided copper-clad laminate was 215 ° C., and tests (3) to this The evaluation of (5) is also shown in Table 2.
[0059]
[Comparative Example 2] In Example 2, a four-layer multilayer printed wiring board was prepared in the same manner as in Example 2 except that the pressing temperature of the four-layer multilayer printed wiring board was changed to 230 ° C and the pressing time was changed to 10 minutes. The evaluation of tests (3) to (5) is shown in Table 2 together.
[0060]
[Comparative Example 3]
In Example 1, as in Example 1, except that Production Example 3 was used as a film-like insulator, the pressing temperature for producing a double-sided copper-clad laminate was changed to 240 ° C., and the pressing time was changed to 20 minutes. A multilayer printed wiring board having four layers was prepared, and the evaluations of tests (3) to (5) for this were also shown in Table 2.
[0061]
As is apparent from the results in Table 2, the adhesive strength of the double-sided copper clad laminate of Example 1 is a good value of 0.7 kgf / 10 cm, and the value of (ΔHm−ΔHc) / ΔHm is also 0.31. And it was an appropriate value. In addition, the value of (ΔHm−ΔHc) / ΔHm at the time of laminating the four-layer multilayer printed wiring board was also an appropriate value of 0.96, and the adhesive strength was a good value of 1.5 kgf / 10 cm. In addition, as a result of the solder heat resistance test, no swelling or peeling is observed on the substrate, and no delamination is observed even in the SEM observation of the four-layer multilayer printed wiring board, and the resin wraps around the circuit pattern (filling) The amount) was good and no voids were observed.
[0062]
The adhesive strength of the double-sided copper-clad laminate of Example 2 is also a good value of 1.3 kgf / 10 cm, the result of the solder heat resistance test is also good, and delamination is also observed by SEM observation after four-layer heat fusion It was not observed at all, and the resin wraps around the circuit pattern. On the other hand, the four-layer printed wiring board of Comparative Example 1 had poor adhesion between layers, and the solder heat resistance was poor due to swell and peeling.
[0063]
Further, the four-layer printed wiring board of Comparative Example 2 had adhesion between layers, but had poor solder heat resistance. In Comparative Example 3, the adhesive strength between the copper foil and the film of the double-sided copper clad laminate was a low value of 0.2 kgf / 10 cm, and the circuit was peeled off during the etching process.
[0064]
【The invention's effect】
As described above, the metal-based printed wiring board of the present invention is obtained by thermally fusing a conductor foil via an insulating layer made of a thermoplastic resin composition having predetermined thermal characteristics on one or both sides of a metal plate. Since the printed circuit is formed of the conductive foil, it is a metal-based printed wiring board that can be heat-sealed to the conductive foil and the metal base at a relatively low temperature, and is securely bonded and integrated and has solder heat resistance. There is an advantage.
[0065]
Further, the metal-based multilayer printed wiring board of the present invention forms a film-like wiring board having a crystalline thermoplastic resin composition having a predetermined thermal characteristic as an insulating layer, and the thermoplastic resin is formed on one side or both sides of the metal plate. Since the film-like wiring board is integrated by thermal fusion through an insulating layer made of the composition, the thermoplastic resin composition of each layer exhibits excellent adhesive strength, and has a metal base multilayer having four or more layers. Even a printed wiring board has no delamination between layers and exhibits the required solder heat resistance.
[0066]
In addition, an insulating material is filled even between fine wiring pitches at the time of heat-sealing each layer, so that a metal-based multilayer printed wiring board with good insulation of the inner layer circuit formed at a high wiring density is obtained.
[0067]
The method for producing a multilayer printed wiring board according to the present invention is a method for producing a metal-based multilayer printed wiring board using a film-like insulator made of a crystalline thermoplastic resin having predetermined thermal characteristics. It is possible to manufacture a high density insulating layer circuit with high embedding for the inner layer circuit with high density, and to ensure that the conductor foil and metal base stacked in multiple layers via the insulating layer are heated and pressed in one step. Since it can be laminated and integrated by heat fusion, there is an advantage that it is an efficient manufacturing method.
[Brief description of the drawings]
FIG. 1 is an enlarged cross-sectional view of the main part of a metal-based printed wiring board
FIG. 2 is an enlarged cross-sectional view of a main part showing a manufacturing process of a metal-based multilayer printed wiring board
[Explanation of symbols]
1, 4 Metal plate
2, 5 Insulation layer
3, 11 Printed circuit
6 Film-like wiring board
7 Film insulator
8 Double-sided through hole
9 Conductive paste
10 Heat-sealable film for interlayer connection

Claims

In a metal-based printed wiring board in which a conductor foil is heat-fused via an insulating layer made of a thermoplastic resin composition on one or both sides of a metal plate, and a printed circuit is formed with this conductor foil, the insulating layer is a syndiotactic layer. A styrenic resin composition having a tic structure, and a thermoplastic resin selected from polyolefin, polystyrene, polyester, polyamide, polyphenylene ether, and polyphenylene sulfide resins that are compatible with the styrene resin composition. as a main component, the styrene-based content of the resin composition is 35 to 70 wt%, and the content of the thermoplastic resin with the styrene-based resin composition and compatibility consists 30 to 65 wt%, the thermoplastic The resin composition has a crystal melting peak temperature of 260 ° C. or higher measured when the temperature is raised by differential scanning calorimetry, The relationship between the amount of heat release ΔHm and the amount of heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the following equation (A) so as to satisfy the relationship represented by the following equation (B): A metal-based printed wiring board characterized in that it is heat-sealed.
Formula (A): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (B): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7

The metal base printed wiring board according to claim 1, wherein the conductor foil is a conductor foil whose surface is roughened.

The metal base printed wiring board according to claim 1, wherein the metal plate is a metal plate having a roughened surface.

A double-sided through-hole is formed in a film-like insulator made of a thermoplastic resin composition and a conductive paste is filled in the through-hole to provide a heat-bonding film for interlayer connection of a laminated electric circuit. A conductive foil is heat-sealed on both sides of the fusion bonding film and a circuit is formed to provide a film-like wiring board, and a film-like wiring board is provided on one or both sides of a metal plate via an insulating layer made of the thermoplastic resin composition. In the heat-fused metal-based multilayer printed wiring board, the thermoplastic resin composition constituting the heat-fused insulating layer and the heat-fused film-like wiring board is a styrenic resin composition having a syndiotactic structure And polyolefins, polystyrenes, polyesters, polyamides, polyphenylene ethers, polyphenylenes that are compatible with the styrene resin composition The main component is a thermoplastic resin selected from sulfide resins, the content of the styrene resin composition is 35 to 70% by weight, and the content of the thermoplastic resin compatible with the styrene resin composition is consists 30 to 65 wt%, the thermoplastic resin compositions are crystalline melting peak temperature measured when the temperature was raised by differential scanning calorimetry is 260 ° C. or higher, crystallization in the heat of crystal fusion ΔHm and heated Heat-sealed so as to satisfy the relationship represented by the following equation (B) by heating a material whose relationship with the heat of crystallization ΔHc generated by the above satisfies the relationship represented by the following equation (A) A metal-based multilayer printed wiring board characterized by being
Formula (A): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (B): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7

The metal-based multilayer printed wiring board according to claim 4, wherein the conductor foil is a conductor foil whose surface is roughened.

The metal-based multilayer printed wiring board according to claim 4 or 5, wherein the metal plate is a surface-roughened metal plate.

A styrene resin composition having a syndiotactic structure and a thermoplastic resin selected from polyolefin, polystyrene, polyester, polyamide, polyphenylene ether, and polyphenylene sulfide resins that are compatible with the styrene resin composition. the resin as a main component, content of 35 to 70 wt% of the styrene-based resin composition, and the styrene-based resin composition and content of the thermoplastic resin having compatibility consists 30 to 65 wt%, the The thermoplastic resin composition has a crystal melting peak temperature measured at 260 ° C. or higher when the temperature is raised by differential scanning calorimetry, and the crystal melting heat amount ΔHm and the crystallization heat amount ΔHc generated by crystallization during the temperature rise. A film-like insulator composed of a thermoplastic resin composition satisfying the relationship represented by the following formula (I) is formed, and this film A double-sided through hole is formed in the insulating insulator, and a conductive paste is filled in the through hole to form a heat-sealable film for interlayer connection of a laminated electrical circuit. On both sides of this heat-sealable film for interlayer connection After the conductor foil is overlaid and heat-sealed so that the thermoplastic resin composition satisfies the relationship represented by the following formula (II), a circuit is formed on the conductor foil to provide a film-like wiring board, and a metal plate The film-like wiring board is stacked on one or both sides of the film-like insulator, and the thermoplastic resin composition constituting each layer is heat-sealed so as to satisfy the relationship represented by the following (III): The manufacturing method of the metal base multilayer printed wiring board which becomes.
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4
Formula (II): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (III): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7