JP4126582B2

JP4126582B2 - Multilayer printed wiring board and manufacturing method thereof

Info

Publication number: JP4126582B2
Application number: JP20878599A
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: 2008-07-30
Anticipated expiration: 2019-07-23
Also published as: JP2001036252A

Description

【０００１】
【発明の属する技術分野】
この発明は、多層プリント配線板およびその製造方法に関し、より詳しくは熱可塑性樹脂からなる絶縁層を有する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】
近年の電子機器の小型・軽量・高速・高機能化の要求に応えるため、プリント配線板に実装する半導体の集積度が高まり、ピン数の増加および各半導体同士の配置間隔（ピッチ）も減少し、多層プリント配線板への高機能化の要望は日々に高まっている。
【０００３】
このような状況の中で使用されている多層プリント配線板は、エポキシ樹脂等を繊維に含浸したプリプレグを絶縁材料とする樹脂多層基板からなるものであり、銅張積層板に形成した電気回路の各層間の接続を可能とするために、層厚方向にビアホール（部品を挿入しないメッキされたスルーホール）またはスルーホールと呼ばれる穴径０．３〜１．２ｍｍ程度の貫通穴を有するものである。
【０００４】
多層プリント配線板のスルーホールの形成密度は、前述のような高機能化の要望に伴って高まり、配線ピッチが例えば５０〜１５０μｍという高配線密度に対応するために、ドリル穴開け加工によってスルーホールを形成することが多層プリント配線板の回路を高密度化するという要望に対する障害になった。
このような問題に対処するために、ミクロン単位の微小な穴径のビアホール（微小径ビアホール）等のスルーホールを形成したビルドアップ層を有する多層プリント配線板が開発されている。
【０００５】
ビルドアップ層を有する多層プリント配線板は、予め所要数のスルーホールを形成した通常の配線板をベース（基板）とし、レーザー加工またはエッチングによって微小径ビアホールを形成した銅箔付き樹脂フィルム（ビルドアップ層）を前記のベースに重ねて接着一体化するか、または全層のすべてを微小径のビアホールを形成したビルドアップ層を積層して形成される。
【０００６】
図２（ａ）、（ｂ）、（ｃ）に製造工程を示すように、全６層がすべてビルドアップ層で形成された多層プリント配線板は、先ず、不織布にエポキシ樹脂を含浸させたプリプレグにレーザー加工で両面に貫通する下穴１１を開け、これに導電性ペースト１２を印刷の手法で充填して真空熱プレスにより銅箔と積層し、プリプレグおよび導電性ペーストを硬化させる。
【０００７】
次いで、銅箔をエッチングして回路パターン１３を形成することにより、両面配線基板１４を形成したものをコア層とし、別途、下穴１１を開けて導電性ペースト１２を充填したプリプレグ１５および銅箔１６を前記コア層の両面に整合させて重ね、これに再度の熱プレスとパターニング（エッチングして回路パターンを形成すること）処理を施して、図２（ｂ）に示すような４層の基板１７を製造する。
【０００８】
そして、図２（ｃ）に示すように、４層基板１７の表面の銅箔をエッチングして両面に回路パターン１３を形成した後、さらにプリプレグ１８および銅箔１９の熱プレスとパターニングの工程を繰り返すことにより、６層のプリント配線板を製造していた。因みに、８層のプリント配線板についても前記６層配線板に対して、さらにプリプレグおよび銅箔の熱プレスとパターニングの工程を繰り返すことにより２層を追加して製造できる。
【０００９】
【発明が解決しようとする課題】
しかしながら、上記した内容の従来の多層プリント配線板は、コア層とプリント配線されたビルドアップ層の接着状態を確実にすることが容易でなく、回路パターンがミクロン単位の配線ピッチで形成されている高密度配線のものは配線間に絶縁材料が完全に充填されない場合があり、絶縁材料のいわゆる「内層回路の埋め込み性」が悪くなり易いという問題がある。
このような問題は、絶縁性などの特性が不均一な製品が製造されることに関連し、プリント配線板の信頼性や不良品の発生による製品の歩留り低下（製造効率の低下）を招くことにもなる。
【００１０】
このように絶縁材料による高配線密度の内層回路の埋め込み性が不確実であるため、４層を越える多層プリント配線板の材料を一括して積層し、熱融着によって確実に一体化して絶縁の信頼性の高い製品を製造することはできなかった。
なお、液状の絶縁材料を使用すれば、内層回路の埋め込み性の問題はかなり改善されるが、絶縁材料の塗布・乾燥工程に長時間を要し、乾燥工程では薄肉の基板が変形しやすくなるといった種々の問題も生じる。
そこで、多層プリント配線板に係る発明の課題は、上記した問題点を解決し、熱融着性のフィルム状絶縁体を用いて積層一体化された多層プリント配線板について、配線が高密度化した内層回路を有する場合でも絶縁材料による配線の埋め込みが確実であるものを提供することである。
【００１１】
また、多層プリント配線板の製造方法に係る発明の課題は、フィルム状絶縁体を用いた多層プリント配線板のビルドアップによる製造方法を改善し、絶縁材料の内層回路の埋め込み性が良好であって高配線密度の回路の絶縁信頼性が高く、しかも積層材料を多層に重ねた際に一度の加熱加圧工程で一括して一度の熱融着により積層一体化できる効率のよい製造方法を提供することである。
【００１２】
【課題を解決するための手段】
上記の課題を解決するため、本発明では、シンジオタクチック構造を有するスチレン系樹脂と、当該スチレン系樹脂組成物と相溶性のある熱可塑性樹脂、すなわち、変性ポリフェニレンエーテルを主成分とし、上記スチレン系樹脂の含有率が３５重量％以上のフィルム状絶縁体であって、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片面または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、このフィルム状配線基板および前記層間接続用熱融着性フィルムからなる積層材料を交互に複数枚重ねて熱融着により一体化してなる多層プリント配線板としたのである。
【００１３】
そして、上記多層プリント配線板におけるフィルム状絶縁体を形成する熱可塑性樹脂組成物が、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Ｈｃ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である多層プリント配線板としたのである。
【００１４】
式（Ｉ）：〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．４
または、上記多層プリント配線板におけるフィルム状配線基板を形成する熱可塑性樹脂組成物が、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（ＩＩ）で示される関係を満たす熱可塑性樹脂組成物である多層プリント配線板としたのである。
【００１５】
式（ＩＩ）：〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．６
または、上記多層プリント配線板における多層プリント配線板を形成する熱可塑性樹脂組成物が、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（ＩＩＩ）で示される関係を満たす熱可塑性樹脂組成物である多層プリント配線板としたのである。
【００１６】
式（ＩＩＩ）：〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≧０．７
また、前述した製造方法に係わる課題を解決するため、本発明では、シンジオタクチック構造を有するスチレン系樹脂と、当該スチレン系樹脂と相溶性のある熱可塑性樹脂、すなわち、変性ポリフェニレンエーテルを主成分とし、上記スチレン系樹脂の含有率が３５重量％以上の熱可塑性樹脂組成物からなるフィルム状絶縁体であって、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で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片面または両面に導体箔を重ねて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、この導体箔に回路を形成してフィルム状配線基板を設け、このフィルム状配線基板および前記層間接続用熱融着性フィルムからなる積層材料を交互に複数枚重ね、各層を構成する熱可塑性樹脂組成物が下記の式（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多層プリント配線板の製造方法としたのである。
【００１７】
式（Ｉ）：〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．４
式（ＩＩ）：〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．６
式（ＩＩＩ）：〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≧０．７
上記したように構成される本発明の多層プリント配線板は、シンジオタクチック構造を有するスチレン系樹脂と、当該スチレン系樹脂組成物と相溶性のある熱可塑性樹脂、すなわち、変性ポリフェニレンエーテル主成分とするフィルム状絶縁体を有するものであり、プリント基板用絶縁材料に要求される導体箔との接着性、耐熱性、機械的強度および電気絶縁性を充分に満足する。
【００１８】
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。
このようなフィルム状絶縁体またはフィルム状配線基板を形成する熱可塑性樹脂は、結晶融解ピーク温度が２６０℃以上のものであり、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（Ｉ）または式（ＩＩ）で示される関係を満たすものであるから、結晶化の進行状態が適当な範囲に調整されたものであり、例えば２５０℃未満という比較的低温での熱融着により優れた接着強度を発揮する。そのため、４層を越えるようなビルドアップ層を有する多層プリント配線板を一括して加熱加圧により積層一体化することができる。導体箔として、表面が粗化されている導体箔を使用すると、接着強度はより大きくなる。
【００１９】
また、式（Ｉ）、（ＩＩ）で示される関係を満たす熱可塑性樹脂組成物は、導体箔との接着温度領域で弾性率が低下するので、微細な配線ピッチにも充填される。そのため、層間接続用熱融着性フィルムおよびフィルム状絶縁体を使用した多層プリント配線板の内層回路の埋め込み性、すなわち絶縁性が良好になる。
本発明の多層プリント配線板の製造方法は、フィルム状配線基板および前記層間接続用熱融着性フィルムからなる積層材料を交互に複数枚重ね、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、かつ導体箔との接着強度も大きくなり、導体箔をエッチングして形成された導電性回路もフィルム状絶縁体に強固に接着して層間剥離を起こし難いものになる。
【００２０】
上記多層プリント配線板の製造方法において、層間接続用熱融着性フィルムの片面または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方法では、その熱融着後に再びフィルム状配線基板および前記層間接続用熱融着性フィルムからなる積層材料を交互に複数枚重ね、一括して加熱加圧による熱融着を行なう時にも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するので、微細な配線ピッチにも適当な低粘度の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ものが製造できる。
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となる。
【００２１】
【発明の実施の形態】
本発明の多層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。
【００２２】
図１（ａ1 ）と（ｂ）、または同図（ａ2 ）と（ｂ）にそれぞれ２系統の製造工程を示すように、この発明に係る多層プリント配線板は、所定の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１に、レーザー加工により両面に貫通する孔２を形成し、この孔２内に導電性ペースト３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４を形成し、さらにこの層間接続用熱融着性フィルム４の両面（図１のａ１）または片面（同図ａ2 ）に導体箔を真空熱プレス機で熱融着すると共に、サブトラクティブ法によって導体箔の不要部分を除いて導電性回路５を形成し、得られたフィルム状配線基板６、７および層間接続用熱融着性フィルム４から選ばれる積層材料を複数枚重ねて、熱融着により積層一体化して得られる。
【００２３】
図１（ｂ）には実線で導電性回路５が４層に形成された多層プリント配線板を示したが、図１（ａ1 ）と同図（ｂ）に鎖線で示された部分を付加して、６層またはそれ以上に多層化された多層プリント配線板を製造することもできる。なお、フィルム状絶縁体を製造するには、シンジオタクチック構造を有するスチレン系樹脂と、当該スチレン系樹脂組成物と相溶性のある熱可塑性樹脂とを配合し、式（Ｉ）で示される所定の結晶性のものを調製する。
【００２４】
式（Ｉ）：〔（ΔＨｍ−ΔＨｃ）／ΔＨｍ〕≦０．４
フィルム状絶縁体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。
【００２５】
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。
フィルム状配線基板および前記層間接続用熱融着性フィルムからなる積層材料を複数枚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。
上記スチレン系樹脂の含有量はフィルム状絶縁体の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。
【００２８】
また、フィルム状絶縁体を構成する第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が、これに限定されるものではない。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フィルム状絶縁体の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。
【００２９】
フィルム状絶縁体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。ゴム状弾性体はフィルム状絶縁体の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。
【００３０】
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。
【００３１】
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。
【００３２】
（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。
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少なくとも一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。
【００３３】
前記式（ＩＩ）で示される値が、０．６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、多層化後の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。
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。
【００３４】
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。
【００３５】
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。
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。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。
【００３６】
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。
なお、ここで、多層化にあっては、フィルム上絶縁体の層厚みが、導体箔の総厚みの２倍以上あることが望ましい。２倍未満では多層時に導体回路部分への樹脂の埋め込み性が不十分となりやすい。
【００３７】
【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。
【００３８】
〔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テレン系樹脂（出光石油化学（株）製：ザレック）（以下の文中または表１、２において、ＳＰＳと略記する。）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−ス）４０重量％をドライブレンドした。この混合組成物を押出成形し、厚さ２５μｍのフィルム状絶縁体を製造した。
【００３９】
〔フィルム状絶縁体の製造例２〕
上記の製造例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。
【００４０】
〔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。
【００４１】
〔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。
【００４２】
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。
【００４３】
（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。
【００４４】
（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。
【００４５】
【表１】

【００４６】
〔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。
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。
【００４７】
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挟んで図１（ａ1 ）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。
得られた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。
【００４８】
（３）接着強度
ＪＩＳＣ６４８１の常態の引き剥がし強さに準拠して、ＦＰＣ素板の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。
【００４９】
（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。
【００５０】
（５）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。
【００５１】
【表２】

【００５２】
〔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。
【００５３】
〔実施例３〕
実施例１において、両面銅張積層板から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５枚取り揃え、この配線基板の間に製造例１で得られたフィルム状絶縁体を挟んで積み重ねてピンラミネーション方式により一括して熱融着したこと以外は、実施例１と同様にして１０層の多層プリント配線板を製造した。
【００５４】
〔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。
【００５５】
〔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。
【００５６】
〔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。
【００５７】
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。４層の多層プリント配線板積層時の（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、さらに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。
【００５８】
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、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。
【００５９】
また、実施例３でも接着強度は良好な値であり、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、１０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。従来のビルドアップ式の多層プリント配線板の製造方法に比べて工程数はかなり少なく、製造日数および製造コストも低減できるものであった。さらに多層プレス前の両面銅張積層板の段階で基板の良否判定を行なえるので、歩留りが大幅に向上した。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。
【００６０】
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。
【００６１】
【発明の効果】
本発明の多層プリント配線板は、以上説明したように、所定のシンジオタクチック構造を有するスチレン系樹脂と該スチレン系樹脂と相溶性のある熱可塑性樹脂、すなわち変性ポリフェニレンエーテルとを所定量配合し、所定の熱的特性の結晶性熱可塑性樹脂組成物でフィルム状絶縁体を形成し、このフィルム状絶縁体でもって積層電気回路の層間接続用熱融着性フィルムを形成すると共に、これに回路形成したフィルム状配線基板を形成し、これらを複数枚重ねて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加熱融解時に優れた接着強度を発揮し、４層を越えるような多層プリント配線板でも層間の剥離がなく、前記熱可塑性樹脂組成物の耐熱性によって所要のハンダ耐熱性を示すものになる。
【００６２】
また、式（Ｉ）で示される関係を満たす熱可塑性樹脂組成物は、導体箔との接着温度領域で弾性率が低下するので、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多層プリント配線板となる。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、しかも積層材料を多層に重ねた際に一度の加熱加圧工程で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】多層プリント配線板の製造工程を示す模式図
【図２】従来の多層プリント配線板の製造工程を示す模式図
【符号の説明】
１フィルム状絶縁体
２孔
３、１２導電性ペースト
４層間接続用熱融着性フィルム
５導電性回路
６、７フィルム状配線基板
１１下孔
１３回路パターン
１４両面配線基板
１５、１８プリプレグ
１６、１９銅箔
１７４層の基板[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multilayer printed wiring board and a method for manufacturing the same, and more particularly to a multilayer printed wiring board having an insulating layer made of a thermoplastic resin and a method for manufacturing the same.
[0002]
[Prior art]
In order to meet the recent demands for smaller, lighter, faster, and more advanced electronic devices, the degree of integration of semiconductors mounted on printed wiring boards has increased, the number of pins has increased, and the spacing (pitch) between semiconductors has also decreased. The demand for higher functionality for multilayer printed wiring boards is increasing day by day.
[0003]
A multilayer printed wiring board used in such a situation is composed of a resin multilayer substrate using a prepreg impregnated with fibers of epoxy resin or the like as an insulating material, and is an electric circuit formed on a copper-clad laminate. In order to enable connection between the layers, a through hole having a hole diameter of about 0.3 to 1.2 mm called a via hole (plated through hole in which no part is inserted) or a through hole is provided in the layer thickness direction. .
[0004]
The formation density of through-holes in multilayer printed wiring boards increases with the demand for higher functionality as described above, and in order to cope with the high wiring density of, for example, 50 to 150 μm, through-holes are formed by drilling. This has become an obstacle to the desire to increase the circuit density of multilayer printed wiring boards.
In order to cope with such a problem, a multilayer printed wiring board having a build-up layer in which a through hole such as a via hole having a minute hole diameter (micro diameter via hole) of a micron unit has been developed.
[0005]
A multilayer printed wiring board with a build-up layer is a resin film with copper foil (build-up) in which a normal wiring board in which a required number of through-holes are formed in advance is used as a base (substrate), and a micro via hole is formed by laser processing or etching. Layer) is laminated and integrated on the base, or all layers are formed by laminating build-up layers in which minute diameter via holes are formed.
[0006]
As shown in FIGS. 2 (a), (b), and (c), the multilayer printed wiring board in which all six layers are formed by build-up layers is first a prepreg in which a nonwoven fabric is impregnated with an epoxy resin. A pilot hole 11 penetrating both sides is formed by laser processing, and the conductive paste 12 is filled in by a printing method and laminated with a copper foil by a vacuum hot press to cure the prepreg and the conductive paste.
[0007]
Next, the copper foil is etched to form the circuit pattern 13, and the prepreg 15 and the copper foil in which the double-sided wiring substrate 14 is formed as a core layer, the pilot hole 11 is separately opened, and the conductive paste 12 is filled. 16 is aligned with both surfaces of the core layer, and is subjected to a second heat press and patterning (etching to form a circuit pattern), and a four-layer substrate as shown in FIG. 17 is manufactured.
[0008]
Then, as shown in FIG. 2C, after the copper foil on the surface of the four-layer substrate 17 is etched to form the circuit pattern 13 on both sides, the steps of hot pressing and patterning of the prepreg 18 and the copper foil 19 are further performed. By repeating, a 6-layer printed wiring board was manufactured. Incidentally, an 8-layer printed wiring board can also be produced by adding two layers to the 6-layer wiring board by further repeating the steps of hot pressing and patterning of the prepreg and copper foil.
[0009]
[Problems to be solved by the invention]
However, the conventional multilayer printed wiring board having the above contents is not easy to ensure the adhesion state between the core layer and the printed wiring build-up layer, and the circuit pattern is formed with a wiring pitch in micron units. In the case of high-density wiring, there are cases where the insulating material is not completely filled between the wirings, and there is a problem that the so-called “embeddability of the inner layer circuit” of the insulating material tends to deteriorate.
Such problems are related to the production of products with non-uniform characteristics such as insulation, and lead to a decrease in product yield (decrease in production efficiency) due to the reliability of printed wiring boards and the occurrence of defective products. It also becomes.
[0010]
As described above, since the embedding property of the inner layer circuit having a high wiring density by the insulating material is uncertain, the materials of the multilayer printed wiring board exceeding four layers are laminated at once and surely integrated by heat-sealing. A reliable product could not be manufactured.
If a liquid insulating material is used, the problem of embedding of the inner layer circuit is considerably improved, but a long time is required for the coating and drying process of the insulating material, and the thin substrate is likely to be deformed in the drying process. Various problems such as these also occur.
Therefore, the problem of the invention related to the multilayer printed wiring board is that the above-mentioned problems are solved, and the wiring density is increased in the multilayer printed wiring board laminated and integrated using the heat-sealable film-like insulator. An object of the present invention is to provide a semiconductor device in which the wiring is reliably embedded with an insulating material even when the inner layer circuit is provided.
[0011]
Further, an object of the invention relating to a method for producing a multilayer printed wiring board is to improve the production method by build-up of a multilayer printed wiring board using a film-like insulator, and the embedding property of an inner layer circuit of an insulating material is good. To provide an efficient manufacturing method in which insulation reliability of a circuit having a high wiring density is high, and when laminated materials are stacked in multiple layers, the layers can be integrated and integrated by one-time heat fusion in one heating and pressing step. That is.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention has a syndiotactic structure. Styrenic resin And a thermoplastic resin compatible with the styrenic resin composition, That is, modified polyphenylene ether And the above Styrenic resin A film-like insulator having a content of 35% by weight or more, in which double-sided through-holes are formed in the film-like insulator and a conductive paste is filled in the through-holes, and heat fusion for interlayer connection of a laminated electric circuit is performed. An adhesive film is formed, a conductive foil is heat-sealed on one or both sides of the interlaminar connection heat-fusible film, and a circuit is formed to provide a film-like wiring board. A multilayer printed wiring board is formed by alternately laminating a plurality of laminated materials composed of heat-fusible films and integrating them by heat-sealing.
[0013]
And Thermoplastic resin for forming a film-like insulator in the multilayer printed wiring board Composition However, the crystal melting peak temperature measured when the temperature is raised by differential scanning calorimetry is 260 ° C. or higher, and the relationship between the crystal melting heat amount ΔHm and the crystallization heat amount Hc generated by crystallization during the temperature rise is as follows: The multilayer printed wiring board is a thermoplastic resin composition that satisfies the relationship represented by the formula (I).
[0014]
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4
Or a thermoplastic resin for forming a film-like wiring board in the multilayer printed wiring board Composition However, since the multilayer printed wiring board is a thermoplastic resin composition in which the relationship between the heat of crystal fusion ΔHm and the heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the following formula (II): is there.
[0015]
Formula (II): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Or a thermoplastic resin for forming a multilayer printed wiring board in the multilayer printed wiring board Composition However, since the multilayer printed wiring board is a thermoplastic resin composition in which the relationship between the heat of crystal fusion ΔHm and the heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the following formula (III): is there.
[0016]
Formula (III): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7
Further, in order to solve the problems related to the manufacturing method described above, the present invention has a syndiotactic structure. Styrenic resin And the relevant Styrenic resin Thermoplastic resin compatible with That is, modified polyphenylene ether And the content of the styrene resin is 35% by weight or more. Consisting of a thermoplastic resin composition A film-like insulator having a crystal melting peak temperature of 260 ° C. or higher measured when the temperature is raised by differential scanning calorimetry, and a crystal melting heat amount ΔHm and a crystallization heat amount ΔHc generated by crystallization during the temperature rise A film-like insulator is formed from a thermoplastic resin composition satisfying the relationship represented by the following formula (I), and a double-sided through-hole is formed in the film-like insulator and a conductive paste is formed in the through-hole. To form a heat-fusible film for interlayer connection of a laminated electric circuit, and a thermoplastic resin composition is formed by the following formula (II) by superimposing a conductor foil on one or both sides of the heat-fusible film for interlayer connection. ), And a film-like wiring board is formed by forming a circuit on this conductor foil, and a laminated material comprising this film-like wiring board and the above-mentioned interlayer-connecting heat-fusible film Exchange A method for producing a multilayer printed wiring board comprising stacking a plurality of sheets and heat-sealing so that the thermoplastic resin composition constituting each layer satisfies the relationship represented by the following formula (III).
[0017]
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4
Formula (II): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (III): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7
The multilayer printed wiring board of the present invention configured as described above has a syndiotactic structure. Styrenic resin And a thermoplastic resin compatible with the styrenic resin composition, That is, modified polyphenylene ether It has a film-like insulator as a main component, and sufficiently satisfies the adhesiveness, heat resistance, mechanical strength, and electrical insulation with a conductor foil required for an insulating material for printed circuit boards.
[0018]
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 becomes 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.
The thermoplastic resin forming such a film-like insulator or film-like wiring board has a crystal melting peak temperature of 260 ° C. or higher, and a crystallization caused by crystallization during heating and ΔHm. Since the relationship with the amount of heat ΔHc satisfies the relationship represented by the above formula (I) or (II), the progress of crystallization is adjusted to an appropriate range. Excellent adhesion strength by thermal fusion at low temperatures. Therefore, multilayer printed wiring boards having build-up layers exceeding 4 layers can be laminated and integrated together by heating and pressing. When a conductor foil whose surface is roughened is used as the conductor foil, the adhesive strength is further increased.
[0019]
In addition, since the thermoplastic resin composition satisfying the relationship represented by the formulas (I) and (II) has a lower elastic modulus in the bonding temperature region with the conductor foil, it is filled into a fine wiring pitch. Therefore, the embedding property of the inner layer circuit of the multilayer printed wiring board using the interlaminar connection heat-fusible film and the film-like insulator, that is, the insulating property is improved.
The method for producing a multilayer printed wiring board according to the present invention comprises a plurality of laminated materials composed of a film-like wiring board and the above-mentioned interlayer-welding heat-fusible film, and the heat of crystal melting of the thermoplastic resin composition constituting each layer. Heat fusion is performed so that the relationship between ΔHm and the amount of heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the above formula (III). In this way, the thermoplastic resin composition after heat-sealing has an appropriate insulation of solder heat resistance that can withstand 260 ° C. since the crystallinity of the styrenic resin having a syndiotactic structure is appropriately advanced. It becomes a layer, and the adhesive strength with the conductor foil is increased, and the conductive circuit formed by etching the conductor foil is firmly adhered to the film-like insulator and hardly causes delamination.
[0020]
In the method for producing a multilayer printed wiring board, when the conductor foil is overlapped and heat-sealed on one or both sides of the heat-fusible film for interlayer connection, the heat of crystal fusion ΔHm after the heat-sealing of the thermoplastic resin composition In the method of heat-sealing so that the relationship between the crystallization heat amount ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the above formula (II), the film-like wiring board and the above-mentioned Even when a plurality of laminated materials composed of heat-fusible films for interlayer connection are stacked alternately and heat fusion is performed by heating and pressing at once, the elastic modulus of the thermoplastic resin decreases in the bonding temperature range with the conductor foil. Therefore, an appropriate low-viscosity resin is surely filled even in a fine wiring pitch, and a good one with extremely high embedding of the inner layer circuit, that is, insulation reliability can be manufactured.
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 laminated material during the manufacturing process, the manufacturing method of a multilayer printed wiring board with high manufacturing efficiency is achieved.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of a multilayer wiring board and a method for manufacturing the same according to the present invention will be described below with reference to the accompanying drawings.
[0022]
As shown in FIGS. 1 (a1) and (b), or FIGS. (A2) and (b), respectively, two production processes are shown, and the multilayer printed wiring board according to the present invention has a heat of a predetermined composition and thermal characteristics. A hole 2 penetrating both surfaces is formed in a film-like insulator 1 made of a plastic resin composition by laser processing, and the hole 2 is filled with a conductive paste 3 so as to be thermally fused for interlayer connection of a laminated electric circuit. A film 4 is formed, and a conductive foil is further heat-sealed with a vacuum hot press on both surfaces (a1 in FIG. 1) or one surface (a2 in FIG. 1) of the heat-bonding film 4 for interlayer connection. The conductive circuit 5 is formed by removing unnecessary portions of the conductive foil, and a plurality of laminated materials selected from the obtained film-

like wiring boards

6 and 7 and the heat-bonding film 4 for interlayer connection are stacked and heat-fused. It is obtained by stacking and integration by wearing.
[0023]
FIG. 1B shows a multilayer printed wiring board in which conductive circuits 5 are formed in four layers by solid lines, but the portion indicated by the chain line in FIG. 1A and FIG. Thus, a multilayer printed wiring board having six or more layers can be manufactured. In order to produce a film-like insulator, a styrenic resin having a syndiotactic structure and a thermoplastic resin compatible with the styrenic resin composition are blended, and the prescribed formula (I) shows. A crystalline one is prepared.
[0024]
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4
When the conductor foil is heat-sealed to the film-like insulator, the glass transition point (Tg) of the thermoplastic resin composition is exceeded, but the crystal melting peak temperature (Tc) is not exceeded, that is, amorphousness 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) was heat-seal | fused is preferably produced.
[0025]
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.
When a plurality of laminated materials composed of a film-like wiring board and the above-mentioned interlayer-bonding heat-fusible film are stacked and heat-sealed together, the crystal melting heat amount ΔHm of the thermoplastic resin composition constituting each layer is increased. Heat fusion is performed so that the relationship with the crystallization heat amount ΔHc generated by crystallization during warming 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 a thermoplastic resin composition of Crystallization proceeds and a multilayer printed wiring board having 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.
The content of the styrenic resin is preferably in the range of 35% by weight or more and 35 to 70% by weight of the film-like insulator. When the content is less than 35% by weight, the solder heat resistance is inferior. It tends to be inferior to the adhesiveness.
[0028]
The thermoplastic resin compatible with the styrene resin as the second component constituting the film-like insulator may be any resin that can be uniformly dispersed during melt molding. , Polyester-based, polyamide-based, polyphenylene ether-based, polyphenylene sulfide-based resins, and the like, but are not limited thereto. In the present invention, modified polyphenylene ether (modified PPE) is preferably used. The content of the thermoplastic resin compatible with the styrenic resin is preferably in the range of 30 to 65% by weight of the film insulator, 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.
[0029]
For the purpose of improving mechanical strength in addition to the above components, the film-like insulator may further contain a rubber-like elastic body. As the rubber-like elastic body, a styrene-butadiene block copolymer (SBR), Examples include, but are not limited to, 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 rubber-like elastic body is preferably contained in the range of 10 to 20% by weight of the film-like insulator, 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.
[0030]
The thermal characteristic of the film insulator, which is an important control factor in the present invention, is the relationship represented by the following formula (I) between the heat of crystal fusion ΔHm and the heat of crystallization ΔHc generated by crystallization during the temperature rise. Is to satisfy.
[0031]
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).
[0032]
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.
The relationship represented by the formula (II) is based on a measurement after heat-sealing in a copper-clad laminate in which a conductor foil is heat-sealed to at least one surface of a film-like insulator in the process of manufacturing a multilayer printed wiring board. It is.
[0033]
When the value represented by the above formula (II) exceeds 0.6, the crystallinity is already high, and the crystallization further proceeds at the time of heat fusion in multi-layering 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.
And the thermal characteristic of the film-like insulator after the heat fusion after the multilayering satisfies the relationship of the following formula (III).
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 crystallization of the insulating layer is insufficient and solder heat resistance (usually 260 ° C.) cannot be maintained.
[0034]
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.
[0035]
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.
Examples of the conductor 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 bonding 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. Specific examples of the conductor foil that has been subjected to surface roughening treatment include a roughened copper foil that has been electrochemically treated when an electrolytic copper foil is produced.
[0036]
When the 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.
Here, in multilayering, it is desirable that the layer thickness of the on-film insulator is at least twice the total thickness of the conductor foil. If it is less than 2 times, the embedding property of the resin in the conductor circuit portion tends to be insufficient in the case of multiple layers.
[0037]
【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.
[0038]
[Production Example 1 of Film Insulator]
A stellenic resin having a syndiotactic structure (produced by Idemitsu Petrochemical Co., Ltd .: Zarek) (abbreviated as SPS in the following text or in Tables 1 and 2) and 60% by weight of modified PPE (Mitsubishi Engineering Plastics ( Co., Ltd .: Iupiace) 40% by weight was dry blended. This mixed composition was extruded to produce a film insulator having a thickness of 25 μm.
[0039]
[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.
[0040]
[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.
[0041]
[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).
[0042]
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.
[0043]
(1) Glass transition temperature (° C.), crystallization temperature (° C.), crystal melting peak temperature (° C.) According to JIS K7121, 10 mg of sample was used, and the heating rate was 10 using DSC-7 manufactured by Perkin Elmer. Each temperature described above when the temperature was raised at ° C./min was determined from a thermogram.
[0044]
(2) (ΔHm−ΔHc) / ΔHm
According to JIS K7122, using 10 mg of sample, manufactured by Perkin Elmer: DSC-7, DSC-7 and heating rate at 10 ° C./min from thermogram ΔHm (J / g) of crystal melting and crystallization The amount of heat ΔHc (J / g) was obtained, and the value of the above formula was calculated.
[0045]
[Table 1]

[0046]
[Example 1]
The film-like insulator having a thickness of 25 μm obtained in Production Example 1 was subjected to perforation processing for inner via holes with a laser, and a conductive paste agent was filled in the holes using a screen printer. 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 manufactured by heat-sealing under conditions of a pressing time of 10 minutes.
The measurement test of (2) (ΔHm−ΔHc) / ΔHm was carried out on the film-like insulator of the produced double-sided copper-clad laminate by the same method, and the formula values are shown in Table 2.
Moreover, the adhesive strength was investigated by the method of (3) mentioned later with respect to the obtained double-sided copper-clad laminate, and the results are also shown in Table 2.
[0047]
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. The film-like insulator having a thickness of 25 μm obtained in Production Example 1 is sandwiched between two wiring boards and stacked in the state shown in FIG. 1 (a1). The press temperature is 220 ° C. at 760 mmHg in a vacuum atmosphere. Pressure 30kg / 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.
The above-mentioned multilayer printed wiring board is subjected to the measurement test (2) (ΔHm−ΔHc) / ΔHm, and the adhesion strength between the copper foil circuit and the film-like insulator at room temperature is as follows: Further, the presence or absence of delamination was observed with a scanning electron microscope (the method (5) below), the solder heat resistance was examined with the test method (4) below, and these results are shown in Table 2. Indicated.
[0048]
(3) Adhesive strength
Based on the normal peel strength of JIS C6481, the peel strength of the copper foil of the FPC base plate was measured, and the average value was expressed in kgf / cm.
[0049]
(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.
[0050]
(5) The 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 the film-like insulator and copper foil are made. The presence or absence of delamination with the conductive circuit was evaluated.
[0051]
[Table 2]

[0052]
[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.
[0053]
Example 3
In Example 1, five circuit boards in which a circuit pattern was formed from a double-sided copper-clad laminate and conductive circuits were formed by etching were prepared, and the film-like insulator obtained in Production Example 1 was placed between the circuit boards. A 10-layer multilayer printed wiring board was produced in the same manner as in Example 1 except that the layers were stacked and heat-sealed together by the pin lamination method.
[0054]
[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 for producing the double-sided copper-clad laminate was 215 ° C., and tests (3) to (3) to this The evaluation of (5) is also shown in Table 2.
[0055]
[Comparative Example 2]
In Example 2, a four-layer multilayer printed wiring board was produced 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 evaluations of 3) to (5) are shown in Table 2.
[0056]
[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.
[0057]
As is clear 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. The value of (ΔHm−ΔHc) / ΔHm when the four-layer multilayer printed wiring board was laminated 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 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.
[0058]
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 even with SEM observation after four-layer heat fusion, there is no delamination It was not observed, and the resin wraps around the circuit pattern.
[0059]
Further, even in Example 3, the adhesive strength is a good value, and 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 10-layer multilayer printed wiring board. In addition, the wraparound (filling amount) of the resin in the vicinity of the circuit pattern was good, and no generation of voids was observed. Compared to the conventional manufacturing method of a build-up type multilayer printed wiring board, the number of steps is considerably smaller, and the manufacturing days and manufacturing costs can be reduced. Furthermore, since the quality of the substrate can be judged at the stage of the double-sided copper clad laminate before the multilayer press, the yield is greatly improved. 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.
[0060]
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.
[0061]
【The invention's effect】
As described above, the multilayer printed wiring board of the present invention has a predetermined syndiotactic structure. Styrenic resin And the Styrenic resin Compatible thermoplastic resin Ie modified polyphenylene ether A film-like insulator is formed with a crystalline thermoplastic resin composition having a predetermined thermal characteristic, and a heat-fusible film for interlayer connection of laminated electric circuits is formed with this film-like insulator. In addition, since a film-like wiring board having a circuit formed thereon is formed, and a plurality of these are laminated and integrated by heat fusion, the thermoplastic resin composition of each layer has excellent adhesive strength when heated and melted. Even when a multilayer printed wiring board having more than four layers is used, there is no delamination between layers, and the heat resistance of the thermoplastic resin composition exhibits the required solder heat resistance.
[0062]
In addition, since the thermoplastic resin composition satisfying the relationship represented by the formula (I) has a lower elastic modulus in the bonding temperature region with the conductor foil, an insulating material can be used even between fine wiring pitches during thermal fusion of each layer. Thus, a multilayer printed wiring board having good insulation of the inner layer circuit formed with a high wiring density is obtained. The method for producing a multilayer printed wiring board of the present invention is a method for producing a multilayer printed wiring board using a film-like insulator made of a crystalline thermoplastic resin having a predetermined thermal characteristic. Efficient embedding into the inner layer circuit and high insulation reliability of the circuit can be manufactured, and when laminated materials are stacked in multiple layers, it can be laminated and integrated by heat fusion in a single heating and pressing process, so efficiency There is an advantage that it is a good manufacturing method.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a manufacturing process of a multilayer printed wiring board.
FIG. 2 is a schematic diagram showing a manufacturing process of a conventional multilayer printed wiring board.
[Explanation of symbols]
1 Film insulator
2 holes
3, 12 Conductive paste
4 Heat-sealable film for interlayer connection
5 Conductive circuit
6, 7 Film-like wiring board
11 Pilot hole
13 Circuit pattern
14 Double-sided wiring board
15, 18 prepreg
16, 19 Copper foil
17 Four-layer substrate

Claims

Double-sided through-holes are formed in a film-like insulator composed of a styrene resin having a syndiotactic structure and a modified polyphenylene ether as a main component and a thermoplastic resin composition having a styrene resin content of 35% by weight or more. At the same time, a conductive paste is filled into the through hole to form a heat-fusible film for interlayer connection of the laminated electric circuit, and a conductive foil is heat-sealed on one or both sides of the heat-fusible film for interlayer connection. In addition, a multilayer printed wiring board is provided by providing a film-like wiring board by forming a circuit, and laminating a plurality of laminated materials composed of the film-like wiring board and the interlayer fusion-bonding film alternately and integrating them by heat-sealing The thermoplastic resin composition forming the film-like insulator has a crystal melting peak temperature of 260 ° C. or higher measured when the temperature is raised by differential scanning calorimetry. And a multilayer printed wiring board and satisfies the relationship the relationship between the crystallization heat ΔHc generated by crystallization in the heat of crystal fusion ΔHm and heated is indicated by the following formula (I).
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4

The multilayer printed wiring board according to claim 1, wherein the conductor foil is a conductor foil having a roughened surface.

The thermoplastic resin composition forming the film-like wiring board is such that the relationship between the heat of crystal fusion ΔHm and the heat of crystallization ΔHc generated by crystallization during temperature rise satisfies the relationship represented by the following formula (II): The multilayer printed wiring board according to claim 1 or 2, characterized in that
Formula (II): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6

The thermoplastic resin composition that forms the multilayer printed wiring board is such that the relationship between the heat of crystal fusion ΔHm and the heat of crystallization ΔHc generated by crystallization during the temperature rise satisfies the relationship represented by the following formula (III): The multilayer printed wiring board according to any one of claims 1 to 3, wherein
Formula (III): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7

A film-like insulator comprising a styrenic resin having a syndiotactic structure and a modified polyphenylene ether as a main component and a content of the styrenic resin of 35% by weight or more, comprising a differential scanning calorific value The crystal melting peak temperature measured when the temperature is raised by measurement is 260 ° C. or higher, and the relationship between the crystal melting heat quantity ΔHm and the crystallization heat quantity ΔHc generated by crystallization during the temperature rise is expressed by the following formula (I): A film-like insulator is formed from a thermoplastic resin composition that satisfies the relationship shown, and a double-sided through-hole is formed in the film-like insulator and a conductive paste is filled in the through-hole for interlayer connection of laminated electric circuits. A thermoplastic resin composition is formed by the following formula (II) by forming a heat-fusible film and superposing a conductor foil on one or both sides of the interlayer-welding heat-fusible film. After heat-sealing so as to satisfy the relationship, a circuit is formed on the conductor foil to provide a film-like wiring board, and a plurality of laminated materials composed of the film-like wiring board and the heat-bonding film for interlayer connection are alternately provided. A method for producing a multilayer printed wiring board comprising stacking sheets and heat-sealing so that a thermoplastic resin composition constituting each layer satisfies a relationship represented by the following formula (III).
Formula (I): [(ΔHm−ΔHc) / ΔHm] ≦ 0.4
Formula (II): [(ΔHm−ΔHc) / ΔHm] ≦ 0.6
Formula (III): [(ΔHm−ΔHc) / ΔHm] ≧ 0.7

6. The method for producing a multilayer printed wiring board according to claim 5, wherein the conductive foil laminated on one side or both sides of the heat-fusible film for interlayer connection is a conductive foil whose surface is roughened.