JPWO2003004262A1 - Laminate and manufacturing method thereof - Google Patents

Abstract

The metal layer A is formed on one surface of the polymer film by a dry plating method. When a circuit is formed by a semi-additive method using this laminate, a high-density printed wiring board excellent in the shape of circuit wiring, insulation between circuits, and adhesion to a substrate can be obtained. Further, by forming an adhesive layer on the other surface of the polymer film of the laminate, an interlayer adhesive film can be obtained. After attaching the interlayer adhesive film to the inner layer circuit board, the adhesive layer is heat-sealed or cured, whereby a multilayer printed wiring board can be manufactured. When manufacturing the circuit board, it is preferable to use an etchant that selectively etches the first metal film when etching the first metal film.

Description

または、炭素数３〜１８のカルボン酸またはそのアンモニウム塩を含む残基を示し、Ｒ^２は炭素数３〜１８の炭化水素残基を示し、Ｒ^３は炭素数３〜１８の炭化水素残基を示し、Ｒ^４は炭素数３〜１８の炭化水素残基を示し、Ｒ^５、Ｒ^６は独立して炭素数３〜１８の炭化水素残基を示し、Ｒ^７は炭素数３〜１８の炭化水素残基、または、

を示し、Ｒ^８は炭素数２〜１８の炭化水素残基を示す）
で表される化合物がより好ましいが、とくに限定されるものではない。式（Ｉ）で表される化合物としては、具体的には、たとえば、トリ−ｎ−ブトキシチタンモノステアレート、ジイソプロポキシチタンビス（トリエタノールアミネート）、ブチルチタネートダイマー、テトラ−ｎ−ブチルチタネート、テトラ（２−エチルヘキシル）チタネート、チタンオクチレングリコレート、ジヒドロキシビス（アンモニウムラクテート）チタニウム、ジヒドロキシチタンビスラクテートなどがあげられる。前記例示の化合物のうち、トリ−ｎ−ブトキシチタンモノステアレート、ジヒドロキシチタンビスラクテートがとくに好ましい。
前記化合物の溶液を調製するのに好適な溶媒としては、具体的には、たとえば、水、トルエン、キシレン、テトラヒドロフラン、２−プロパノール、１−ブタノール、酢酸エチル、Ｎ，Ｎ−ジメチルホルムアミド、アセチルアセトンなどがあげられるが、とくに限定されるものではなく、前記化合物を溶解することができる溶媒であればよい。これらの溶媒は、１種類のみを用いてもよく、また、２種類以上を適宜混合して用いてもよい。前記例示の溶媒のうち、水、２−プロパノール、１−ブタノール、Ｎ，Ｎ−ジメチルホルムアミドがとくに好ましい。前記化合物の溶液には、さらに、ケミカルキュア剤を添加してもよい。
溶液における前記元素群の濃度は、１〜１０００００ｐｐｍの範囲内がより好ましく、１０〜５００００ｐｐｍの範囲内がさらに好ましい。したがって、溶液における前記元素群を含む化合物の濃度は、該化合物の種類（分子量）にもよるが、概ね、好ましくは０．００１〜１００重量％、より好ましくは０．０１〜１０重量％、とくに好ましくは０．１〜５重量％である。
ゲルフィルムを前記化合物の溶液に浸漬するか、もしくは、ゲルフィルムに該溶液を塗布したのち、該ゲルフィルム表面に付着した余分な液滴を除去することにより、接着性がより向上され、かつ、表面にムラのない外観により優れたポリイミドフィルムを得ることができる。液滴の除去方法としては、たとえば、ニップロールやエアナイフ、ドクターブレードなどを用いた公知の方法があげられる。このうち、液切り性や作業性、あるいは得られるポリイミドフィルムの外観などの観点から、ニップロールを用いた方法がより好ましい。
本発明におけるポリイミドフィルムの厚さは、とくに限定されるものではないが、５〜１２５μｍの範囲内であることがより好ましく、とくに多層プリント配線板用途としては１０〜７５μｍの範囲内であることがさらに好ましく、１０〜５０μｍの範囲内であることがとくに好ましい。また、ポリイミドフィルムの引張り弾性率は４ＧＰａ以上であることが好ましく、６ＧＰａ以上であることがより好ましく、１０ＧＰａ以上であることがさらに好ましい。ポリイミドフィルムの線膨張係数は１７ｐｐｍ以下であることが好ましく、１２ｐｐｍ以下であることがより好ましく、１０ｐｐｍ以下であることがさらに好ましい。ポリイミドフィルムの吸水率は２％以下であることが好ましく、１．５％以下であることがより好ましく、１％以下であることがさらに好ましい。
＜金属層Ａ＞
つぎに、本発明に係る金属層Ａに関して説明する。金属層Ａは、高分子フィルムの少なくとも一方の表面に形成されており、パネルめっき工程により形成される無電解めっきが形成される場合には、無電解めっき層と強固に接着する機能を有している。このとき、高分子フィルムと金属層Ａが強固に接着している必要があることは言うまでもない。
金属層Ａを形成する方法としては、乾式めっき法が好ましい。乾式めっき法によれば、金属層Ａを形成するために高分子フィルムにめっき触媒を付与する必要はなく、高分子フィルム上にめっき触媒が残ることがないので好ましい。例えば、無電解めっきを行う場合でも、金属層Ａ上に無電解めっき触媒が存在しており、その後のエッチング工程においては、金属層Ａとともに触媒が洗い流されるため、従来の樹脂材料上に直接無電解めっき触媒を付与し、無電解めっきを行う場合に比較して、電気絶縁性が優れたものが得られる。また、湿式無電解めっきのように密着性向上のために表面粗化処理（デスミア処理）を行なう必要がなく、金属皮膜と絶縁基板の界面が平滑となり、狭間隔の回路形成や、電気特性に良い影響を与える。乾式めっき法による金属層Ａの形成方法としては、真空蒸着法、スパッタリング法、イオンプレーティング法、ＣＶＤ法などが適用できる。
これらの中でも、良好な接着性が得られる点で、物理的蒸着法により形成する金属層が好ましい。ここで、物理的蒸着法とは、真空蒸着法として、抵抗加熱蒸着、ＥＢ蒸着、クラスタイオンビーム蒸着、イオンプレーティング蒸着など、また、スパッタリング法として、ＲＦスパッタリング、ＤＣスパッタリング、マグネトロンスパッタリング、イオンビームスパッタリングなどをあげることができ、また、これらを組み合わせた方法も含め、いずれも本発明に適用可能である。
さらに、これらの中でも、高分子フィルムと金属層Ａとの密着強度の観点、設備の簡便さ、生産性、コスト的な観点などより、スパッタリング法が好ましく、中でもＤＣスパッタリングがとくに好ましい。また、イオンプレーティング蒸着も製膜速度が速く、工業的に有利であり、また良好な密着性を有するので好ましく使用できる。
とくにスパッタリングを用いる場合について詳しく説明する。スパッタリングは公知の方法を適用できる。すなわちＤＣマグネトロンスパッタやＲＦスパッタあるいはそれらの方法に種々改善を加えたものが、それぞれの要求に応じて適宜適用し得る。たとえばニッケルや銅などの導体を効率よくスパッタするためにはＤＣマグネトロンスパッタが好ましい。一方、薄膜中のスパッタガスの混入を防ぐなどの目的で高真空でスパッタする場合には、ＲＦスパッタが適している。
ＤＣマグネトロンスパッタについて詳しく説明すると、まず、高分子フィルムを基板として真空チャンバー内にセットし、真空引きをする。通常回転ポンプによる粗引きと拡散ポンプまたはクライオポンプあるいはターボポンプを組み合わせて通常６×１０^−４Ｐａ以下まで真空引きする。ついでスパッタガスを導入しチャンバー内を０．１〜１０Ｐａ好ましくは０．１〜１Ｐａの圧力とし、金属ターゲットにＤＣ電圧を印可してプラズマ放電を起こさせる。この際、ターゲット上に磁場を形成し、生成したプラズマを磁場内に閉じこめることにより、プラズマ粒子のターゲットへのスパッタ効率を高める。高分子フィルムにプラズマやスパッタの影響がないようにしながら、プラズマが生成した状態で数分間から数時間保持して金属ターゲットの表面酸化層を除去する（プレスパッターという）。プレスパッター終了後、シャッターを開けるなどして高分子フィルムにスパッタを行なう。スパッタ時の放電パワーは、好ましくは１００〜１０００ワットの範囲である。また、スパッタするサンプルの形状にしたがってバッチ方式のスパッタやロールスパッタが適用される。導入スパッタガスは通常アルゴンなどの不活性ガスを用いるが、少量の酸素を含んだ混合ガスやその他のガスを用いることもできる。
金属層Ａに用いられる金属の種類としては、高分子フィルム、および後の配線板の製造工程において金属層Ａ上に形成される回路パターンとの密着強度が高く、かつ、本発明のプリント配線板の製造方法におけるエッチング工程において、きれいに除去できる金属種であることが重要である。
たとえば、銅、ニッケル、クロム、チタン、ニクロム、モリブデン、タングステン、亜鉛、錫、インジウムおよびアルミニウムなどの金属またはこれらの合金を用いることができ、これらの単層または２層以上で金属層Ａを構成することも可能である。
本発明における金属層Ａの一実施の形態では、金属層Ａを構成する金属材料として、銅が好適であるが、ニッケル、クロム、銀、アルミニウム、チタンおよびシリコンからなる群より選ばれる少なくとも１種の金属と、銅とを用いる。すなわち、金属層Ａは、（ｉ）銅からなっていてもよく、（ｉｉ）前記群より選ばれる少なくとも１種の金属と、銅とを含む合金（複合体）からなっていてもよく、（ｉｉｉ）前記群より選ばれる少なくとも１種の金属からなる層と、銅からなる層との２層構造となっていてもよい。
金属層Ａの厚さは、必要に応じて設定すればよいが、１０００ｎｍ以下であるが、２〜１０００ｎｍ、さらには２〜５００ｎｍの範囲内であることが好ましい。金属層Ａの厚さを２ｎｍ未満に設定すると、安定したピール強度が得られない傾向にある。金属層の厚さを１０００ｎｍよりも厚く設定すると、従来技術である接着剤付き銅箔と同様に、ファインパターンが形成された多層プリント配線板を製造するのに適さない。とくに、セミアディティブ法による回路パターンが形成された多層プリント配線板を製造する場合には、金属層の厚さを１０００ｎｍ以下に設定することが最も好ましい。
本発明における金属層Ａの別の実施の形態では、金属層Ａを、２種の金属層からなる２層構成とし、それぞれの厚さを適切な厚さに制御する。ここで高分子フィルム上に直接形成される金属層を金属層Ａ１と呼び、その上に形成される金属層を金属層Ａ２と呼ぶことにする。２種類の金属層で構成することにより、エッチング特性、高分子フィルムとの接着性、無電解めっき皮膜や電気めっき皮膜との引き剥がし強さなどを向上することができる。すなわち、高分子フィルム上に直接形成される金属層Ａ１には、高分子フィルムとの密着性を良好に保つのに有効な金属を選択する。一方、その上に形成される金属層Ａ２には、直接Ａ２上に形成される電気めっき層または、パネルめっき工程により形成される無電解めっき層と強固に接着できる金属を選択することが有効である。
金属層Ａ１に用いられる金属としては、銅、ニッケル、クロム、スズ、チタン、アルミニウムなどが好ましく、ニッケルがとくに好ましい。この金属層Ａ１の厚さは、２〜２００ｎｍ、さらには３〜１００ｎｍ、とくには３〜３０ｎｍの範囲にすることが好ましい。２ｎｍ未満の厚さでは充分な接着強度を得ることができず、好ましくない。また、高分子上に均一に成膜することが困難となる。一方、２００ｎｍをこえる厚さでは、プリント配線板を製造する際にエッチング工程で余分にエッチングを行なう必要があり、回路設計値よりも回路厚さが薄くなる、回路幅が狭くなる、アンダーカットなどが発生する、回路形状が劣化するなどして好ましくない。また、金属層Ａ２との間で、膜中の応力や温度により寸法変化の違いから膜が剥がれる、カールするなどの問題が生じる。
一方、金属層Ａ２に用いる金属は、プリント配線板の製造工程においてＡ２に直接形成される電気めっきまたは無電解めっきの種類に応じて決めるべきであるが、後述の通り、無電解めっきとして無電解銅めっき、無電解ニッケルめっきが好ましく、とくに好ましくは無電解銅めっきであることを考慮すると、金属層Ａ２に用いる金属は銅、ニッケルが好ましく、とくに銅が好ましい。プリント配線板の製造に用いる無電解めっきにより形成される金属層の主成分を金属層Ａ２が含んでいることが、接着強度に有効である。この金属層Ａ２の最適な厚さは、１０〜３００ｎｍ、さらには２０〜２００ｎｍ、好ましくは５０〜１５０ｎｍである。１０ｎｍ未満では、つぎの工程で形成される無電解めっき層との十分な接着性を保つ事が困難である。一方、２００ｎｍ以上の厚さは必要がないばかりでなく、のちのエッチング工程を考慮すると２００ｎｍ以下であることが望ましい。
金属層Ａ１と金属層Ａ２を合わせた金属層Ａの厚さは、好ましくは２０〜４００ｎｍ、より好ましくは５０〜２００ｎｍである。また、ピール強度が高くなるという点から、高分子フィルムに直接形成される金属層Ａ１の方がＡ２より小さくなることが好ましい。この範囲の厚さとすることで、セミアディティブ法を適用した際のエッチング特性と、無電解めっきおよび／または電気めっきによって形成した金属層の引き剥がし強度を両立することが可能となる。すなわち、金属層が薄すぎると、無電解めっきおよび電気めっきで形成した金属層の引き剥がし強度が小さく、パターン剥がれの原因となる。一方、金属層が厚すぎると、エッチング工程で余分にエッチングを行なう必要が生じ、スペース部分のエッチングの際に回路も大きくエッチングされ、回路設計値よりも回路厚さが薄くなる、回路幅が狭くなる、アンダーカットなどが発生する、あるいは本来長方形であるべき回路断面の形状が崩れるなどして設計の回路幅に対して充分な断面積が得られないなど、回路形状が劣化し好ましくない。回路形状の劣化は、ひいては回路の伝道度が設計値よりも低下して回路の誤動作の原因となる。
たとえば、高分子フィルムにポリイミドを用い、無電解めっきに無電解銅めっきを用いた場合、金属層Ａ１の厚さが、１０〜１００ｎｍのニッケル、クロム、チタンなどの金属またはそれらを主成分とする合金を用い、金属層Ａ２の厚さが２０〜２００ｎｍの銅または銅合金を用い、両層併せた金属層の総厚さを３０〜２００ｎｍにした場合には、何れも６Ｎ／ｃｍ以上の強固な薄膜を形成することができる。
２種類以上の金属層を積層、形成する場合も、それぞれの膜表面に酸化層ができると、それぞれの金属間の密着性が低下するため、乾式めっきは、真空中で連続して行なうことが好ましい。この場合の乾式めっきは、蒸着、スパッタリングが好ましく、なかでもスパッタリング、とくにはＤＣスパッタリングが好ましい。
本発明における金属層Ａのまた別の実施の形態では、金属層Ａは、イオンプレーティング法によって形成された銅または銅合金よりなる層である。この方法によっても、高分子フィルムおよびのちの配線板の製造工程において、金属層Ａ上に形成される回路パターンとの密着強度を向上させることができる。
イオンプレーティング法により作製された銅薄膜は基板との接着性にすぐれ、表面平滑性に優れた高分子フィルムに対しても強固な接着性を実現できることを発見した。なお、ここで言う銅の合金とは、銅を主たる成分とし他の金属を添加した合金であって、添加される金属としてはニッケル、クロム、チタンなどの金属をあげることができる。とくに、従来のスパッタリング法では困難であったポリイミドに対しても、６Ｎ／ｃｍ以上の強固な銅薄膜を形成できることが分った。
本発明における金属層Ａのさらに別の実施の形態では、金属層Ａは、２種以上の異なる物理的手法で形成された銅または銅の合金層よりなる２層構造を有する。ここで、銅合金とは銅を主成分とする合金をいい、添加される金属としては、ニッケル、クロム、チタンなどがあげられる。
前述のように、イオンプレーティング法によって作製された銅薄膜は基板との接着性にすぐれ、表面平滑性に優れた高分子フィルムに対しても強固な接着性を実現できる。
しかしながら、イオンプレーティング法で作製された銅および銅合金の薄膜層のみでは、化学的な処理プロセスに弱く、イオンプレーティング膜の上に無電解めっきのプロセスを用いて銅薄膜を形成しようとすると、高分子フィルムから剥離してしまう。
そこで、我々はイオンプレーティング法で形成した銅薄膜（金属層Ａ１）の上に、さらにスパッタ法で銅薄膜を形成することを試みた。スパッタリング法は、とくに限定されず、ＤＣマグネトロンスパッタリング、高周波マグネトロンスパッタリング、イオンビームスパッタリングなどの方法が有効に利用できる。
イオンプレーティング法で形成した銅薄膜は、高分子フィルムとの間に強固な接着を実現するが、この接着性はスパッタ法でその上に銅膜を形成しても変わることはなかった。さらにスパッタ膜は化学的なプロセスに強いため、容易にその上に無電解めっき法でめっき膜を形成することができた。すなわちスパッタ膜は、無電解めっきプロセスでイオンプレーティング膜を保護する役割と無電解めっき層との接合の役割を果たすものと考えられる。
＜接着層＞
接着層に関しては、とくに種類を制限されるものでなく、接着剤に適用できる公知の樹脂が適用可能である。大きくは、（Ａ）熱可塑性樹脂を用いた熱融着性の接着剤と、（Ｂ）熱硬化樹脂の硬化反応を利用した硬化型の接着剤とに分けることができる。これらについて以下に説明する。
（Ａ）接着剤に熱融着性を与える熱可塑性樹脂としては、ポリイミド樹脂、ポリアミドイミド樹脂、ポリエーテルイミド樹脂、ポリアミド樹脂、ポリエステル樹脂、ポリカーボネート樹脂、ポリケトン系樹脂、ポリスルホン系樹脂、ポリフェニレンエーテル樹脂、ポリオレフィン樹脂、ポリフェニレンスルフィド樹脂、フッ素樹脂、ポリアリレート樹脂、液晶ポリマー樹脂などがあげられる。これらは、１種で、または２種以上を適宜組合わせて本発明の積層体の接着層として用いることができる。なかでも優れた耐熱性、電気信頼性などの観点より、熱可塑性ポリイミド樹脂を用いることが好ましい。
ここで熱可塑性ポリイミド樹脂の製造方法について説明する。ポリイミド樹脂はその前駆体であるポリアミド酸重合体溶液から得られるが、このポリアミド酸重合体溶液は、前述のごとき公知の方法で製造することができる。すなわち、テトラカルボン酸２無水物成分とジアミン成分を実質等モル使用し、有機極性溶媒中で重合して得られる。
この熱可塑性ポリイミド樹脂に用いられる酸２無水物は、酸２無水物であればとくに限定されない。酸２無水物成分の例としては、ブタンテトラカルボン酸２無水物、１，２，３，４−シクロブタンテトラカルボン酸２無水物、１，３−ジメチル−１，２，３，４−シクロブタンテトラカルボン酸、１，２，３，４−シクロペンタンテトラカルボン酸２無水物、２，３，５−トリカルボキシシクロペンチル酢酸２無水物、３，５，６−トリカルボキシノルボナン−２−酢酸２無水物、２，３，４，５−テトラヒドロフランテトラカルボン酸２無水物、５−（２，５−ジオキソテトラヒドロフラル）−３−メチル−３−シクロヘキセン−１，２−ジカルボン酸２無水物、ビシクロ［２，２，２］−オクト−７−エン−２，３，５，６−テトラカルボン酸２無水物などの脂肪族または脂環式テトラカルボン酸２無水物；ピロメリット酸２無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、３，３’，４，４’−ジフェニルスルホンテトラカルボン酸２無水物、１，４，５，８−ナフタレンテトラカルボン酸２無水物、２，３，６，７−ナフタレンテトラカルボン酸２無水物、４，４’−オキシフタル酸無水物、３，３’，４，４’−ジメチルジフェニルシランテトラカルボン酸２無水物、３，３‘，４，４’−テトラフェニルシランテトラカルボン酸２無水物、１，２，３，４−フランテトラカルボン酸２無水物、４，４‘−ビス（３，４−ジカルボキシフェノキシ）ジフェニルスルフィド２無水物、４，４‘−ビス（３，４−ジカルボキシフェノキシ）ジフェニルスルホン２無水物、４，４‘−ビス（３，４−ジカルボキシフェノキシ）ジフェニルプロパン２無水物、４，４‘−ヘキサフルオロイソプロピリデンジフタル酸無水物、３，３’，４，４‘−ビフェニルテトラカルボン酸２無水物、２，３，３’，４‘−ビフェニルテトラカルボン酸２無水物、ビス（フタル酸）フェニルホスフィンオキサイド２無水物、ｐ−フェニレン−ビス（トリフェニルフタル酸）２無水物、ｍ−フェニレン−ビス（トリフェニルフタル酸）２無水物、ビス（トリフェニルフタル酸）−４，４’−ジフェニルエーテル２無水物、ビス（トリフェニルフタル酸）−４，４’−ジフェニルメタン二無水物などの芳香族テトラカルボン酸２無水物；２，２−ビス（４−ヒドロキシフェニル）プロパンジベンゾエート−３，３’，４，４’−テトラカルボン酸２無水物、ｐ−フェニレンビス（トリメリット酸モノエステル無水物）、４，４’−ビフェニレンビス（トリメリット酸モノエステル無水物）、１，４−ナフタレンビス（トリメリット酸モノエステル無水物）、１，２−エチレンビス（トリメリット酸モノエステル無水物）、１，３−トリメチレンビス（トリメリット酸モノエステル無水物）、１，４−テトラメチレンビス（トリメリット酸モノエステル無水物）、１，５−ペンタメチレンビス（トリメリット酸モノエステル無水物）、１，６−ヘキサメチレンビス（トリメリット酸モノエステル無水物）、４，４’−（４，４’−イソプロピリデンジフェノキシ）ビス（無水フタル酸）などが好ましく、これらの１種を、または２種以上を組み合わせて、酸２無水物成分の一部または全部として用いることができる。
優れた熱融着性の発現のためには、２，２−ビス（４−ヒドロキシフェニル）プロパンジベンゾエート−３，３’，４，４’−テトラカルボン酸２無水物、１，２−エチレンビス（トリメリット酸モノエステル無水物）、４，４’−ヘキサフルオロイソプロピリデンジフタル酸無水物、２，３，３’，４‘−ビフェニルテトラカルボン酸二無水物、４，４’−オキシジフタル酸無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸２無水物、４，４’−（４，４’−イソプロピリデンジフェノキシ）ビス（無水フタル酸）を用いることが好ましい。
また、ジアミン成分としては４，４’−ジアミノジフェニルエーテル、３，４’−ジアミノジフェニルエーテル、２，２−ビス［４−（４−アミノフェノキシ）フェニル］プロパン、２，２，−ビス［３−（３−アミノフェノキシ）フェニル］プロパン、１，４−ビス（４−アミノフェノキシ）ベンゼン、１，３−ビス（４−アミノフェノキシ）ベンゼン、１，３−ビス（３−アミノフェノキシ）ベンゼン、ビス（４−（４−アミノフェノキシ）フェニル）スルフォン、ビス（４−（３−アミノフェノキシ）フェニル）スルフォン、４，４’−ビス（４−アミノフェノキシ）ビフェニル、２，２−ビス（４−アミノフェノキシフェニル）ヘキサフルオロプロパン、４、４’−ジアミノジフェニルスルフォン、３、３’−ジアミノジフェニルスルフォン、９、９−ビス（４−アミノフェニル）フルオレン、ビスアミノフェノキシケトン、４、４’−（１，４−フェニレンビス（１−メチルエチリデン））ビスアニリン、４、４’−（１，３−フェニレンビス（１−メチルエチリデン））ビスアニリン、３，３’−ジメチルベンジジン、３，３’−ジヒドロキシベンジジンなどをあげることができ、これらを単独で、または２種以上を組合わせて用いることができる。
本発明の積層体に用いる熱可塑性ポリイミド樹脂の原料としては、１，３−ビス（３−アミノフェノキシ）ベンゼン、３，３’−ジヒドロキシベンジジン、ビス（４−（３−アミノフェノキシ）フェニル）スルフォンをそれぞれ単独または任意の割合で混合して用いることが好ましい。
ポリアミド酸重合体溶液を得る反応の代表的な手順として、１種以上のジアミン成分を有機極性溶剤に溶解または拡散させ、そののち１種以上の酸２無水物成分を添加してポリアミド酸溶液を得る方法があげられる。各モノマーの添加順序はとくに限定されず、酸２無水物成分を有機極性溶媒に先に加えておき、ジアミン成分を添加し、ポリアミド酸重合体の溶液としてもよいし、ジアミン成分を有機極性溶媒中に先に適量加えて、つぎに過剰の酸２無水物成分を加え、過剰量に相当するジアミン成分を加えて、ポリアミド酸重合体の溶液としてもよい。このほかにも、当業者に公知の様々な添加方法がある。なお、ここでいう「溶解」とは、溶媒が溶質を完全に溶解する場合のほかに、溶質が溶媒中に均一に分散または拡散されて実質的に溶解しているのと同様の状態になる場合を含む。
ポリアミド酸溶液の生成反応に用いられる有機極性溶媒としては、たとえば、ジメチルスルホキシド、ジエチルスルホキシドなどのスルホキシド系溶媒；Ｎ，Ｎ−ジメチルホルムアミド、Ｎ，Ｎ−ジエチルホルムアミドなどのホルムアミド系溶媒；Ｎ，Ｎ−ジメチルアセトアミド、Ｎ，Ｎ−ジエチルアセトアミドなどのアセトアミド系溶媒；Ｎ−メチル−２−ピロリドン、Ｎ−ビニル−２−ピロリドンなどのピロリドン系溶媒；フェノール、ｏ−、ｍ−、またはｐ−クレゾール、キシレノール、ハロゲン化フェノール、カテコールなどのフェノール系溶媒；あるいはヘキサメチルホスホルアミド、γ−ブチロラクトンなどをあげることができる。さらに必要に応じて、これらの有機極性溶媒と、キシレン、トルエンのような芳香族炭化水素とを組み合わせて用いることもできる。
つぎに、ポリアミド酸をイミド化する方法について説明する。ポリアミド酸のイミド化反応はポリアミド酸の脱水閉環反応であり、反応によって水を生成する。この生成した水は、ポリアミド酸を容易に加水分解し分子量の低下を引き起こす。この水を除去しながらイミド化する方法として、通常、１）トルエン・キシレンなどの共沸溶媒を加えて共沸により除去する方法、２）無水酢酸などの脂肪族酸２無水物とトリエチルアミン、ピリジン、ピコリン、イソキノリンなどの３級アミンを加える化学的イミド化法、３）減圧下で加熱してイミド化する方法がある。
本発明の熱可塑性ポリイミド樹脂のイミド化の方法は、減圧下で加熱してイミド化する方法が好ましい。このイミド化の方法によれば、イミド化によって生成する水を積極的に系外に除去できるので、ポリアミド酸の加水分解を抑えることが可能であり、高分子量のポリイミドが得られる。また、この方法によれば、原料の酸２無水物中に不純物として存在する片側または両側開環物が再閉環するので、より一層の分子量の向上効果が期待できる。
減圧下で加熱イミド化する方法の加熱条件は８０〜４００℃が好ましいが、イミド化が効率よく行なわれ、しかも水が効率よく除かれる１００℃以上がより好ましく、さらに好ましくは１２０℃以上である。最高温度は、目的とするポリイミドの熱分解温度以下が好ましく、通常のイミド化の完結温度、すなわち２５０〜３５０℃程度が通常適用される。減圧する圧力の条件は、小さいほうが好ましいが、具体的には９００ｈＰａ以下、好ましくは８００ｈＰａ以下、より好ましくは７００ｈＰａ以下である。
また、熱可塑性ポリイミド樹脂を得るための別の方法として、前期の熱的または化学的に脱水閉環する方法において、溶媒の蒸発を行なわない方法もある。具体的には、熱的イミド化処理または脱水剤による化学的イミド化処理を行なって得られるポリイミド樹脂溶液を貧溶媒中に投入して、ポリイミド樹脂を析出させ、未反応モノマーを取り除いて精製、乾燥させ、固形のポリイミド樹脂を得る方法である。貧溶媒としては、溶媒とは良好に混合するがポリイミドは溶解しにくい性質を有するものを選択する。例示すると、アセトン、メタノール、エタノール、イソプロパノール、ベンゼン、メチルセロソルブ、メチルエチルケトンなどが挙げられるが、これらに限定されない。これらの方法により熱可塑性ポリイミド樹脂を得ることができ、本発明の積層体の接着層として用いることができる。
つぎに、（Ｂ）熱硬化樹脂の硬化反応を利用した硬化型の接着剤に関して説明する。熱硬化型樹脂としては、ビスマレイミド樹脂、ビスアリルナジイミド樹脂、フェノール樹脂、シアナート樹脂、エポキシ樹脂、アクリル樹脂、メタクリル樹脂、トリアジン樹脂、ヒドロシリル硬化樹脂、アリル硬化樹脂、不飽和ポリエステル樹脂などをあげることができ、これらを単独で、または適宜組み合わせて用いることができる。また、前記熱硬化性樹脂以外に、高分子鎖の側鎖または末端に、エポキシ基、アリル基、ビニル基、アルコキシシリル基、ヒドロシリル基，水酸基などの反応性基を有する側鎖反応性基型熱硬化性高分子を熱硬化成分として使用することも可能である。
以下に側鎖反応性基型熱硬化性ポリイミド樹脂について説明する。具体的製法例としては、（１）すでに述べた熱可塑性ポリイミド樹脂に準じた方法で製造され、この際に、エポキシ基、ビニル基、アリル基、メタクリル基、アクリル基、アルコキシシリル基、ヒドロシリル基、カルボキシ基、水酸基、シアノ基などの官能基を有するジアミン成分、あるいは酸２無水物成分をモノマー成分として用い、熱硬化型ポリイミドを得る方法、また、（２）水酸基、カルボキシ基、芳香族ハロゲン基などを有する溶媒可溶性ポリイミドを、すでに述べた熱可塑性ポリイミド樹脂の製法に準じて製造したのち、エポキシ基、ビニル基、アクリル基、メタクリル基、アリル基、メタクリル基、アクリル基、アルコキシシリル基、ヒドロシリル基、カルボキシ基、水酸基、シアノ基などの官能基を化学反応により付与する方法などにより、熱硬化性ポリイミド樹脂を得ることも可能である。
熱硬化性樹脂に対し、さらに有機過酸化物などのラジカル反応開始剤、反応促進剤、トリアリルシアヌレート、トリアリルイソシアヌレートなどの架橋助剤、耐熱性、接着性などの向上のために、必要に応じて、酸２無水物系、アミン系、イミダゾール系などの一般に用いられるエポキシ硬化剤、種々のカップリング剤などを適宜添加することも可能である。
加熱接着時の接着剤の流れ性を制御する目的で、前記熱可塑性樹脂に熱硬化性樹脂を混合することも可能である。このためには、熱可塑性樹脂１００重量部に対して、熱硬化性樹脂を１〜１００００重量部、好ましくは５〜２０００重量部加えるのが望ましい。熱硬化性樹脂が多すぎると接着層が脆くなるおそれがあり、逆に少なすぎると接着剤のはみ出しが生じたり、接着性が低下するおそれがある。
本発明の積層体に用いる接着剤として、接着性、加工性、耐熱性、柔軟性、寸法安定性、誘電率、価格などの観点から熱可塑性ポリイミド樹脂、熱硬化性ポリイミド樹脂系、エポキシ樹脂系、シアナートエステル樹脂系あるいはこれらをブレンドしたものは、とくに好ましく、熱可塑性ポリイミド樹脂とエポキシ樹脂、熱可塑性ポリイミド樹脂とシアナートエステル樹脂、側鎖反応性基型熱硬化性ポリイミド樹脂とエポキシ樹脂、側鎖反応性基型熱硬化性ポリイミド樹脂とシアナートエステル樹脂などのブレンドが、とくに好ましい。なかでも、熱可塑性ポリイミド樹脂とエポキシ樹脂を混合したものが、接着性、加工性、耐熱性などのバランスがよく好適である。
熱可塑性樹脂を用いた接着剤または熱硬化性樹脂を用いた接着剤を、たとえば、バーコーター、スピンコーター、グラビアコーターなどを用いてポリイミドフィルムに塗布することにより、接着層が形成される。
接着層の厚さは、とくに限定されるものではないが、５〜１２５μｍ以下、さらには５〜５０μｍ、とくには５〜３５μｍが好適である。接着剤層は、積層する際の内層回路パターンを埋め込むために、充分な量、厚さが必要である。内層回路のパターン率にもよるが、通常内層回路厚さの１／２〜１倍程度の厚さが必要である。すなわち、実用上有効な最小回路厚さとして９μｍ程度を想定した場合、パターン率を５０％と仮定すると、接着層の厚さは最小５μｍ程度が必要となる。一方、接着層が厚すぎると、高分子フィルムの場合と同様に、プリント配線板の薄型化、小型化の要請に逆行するばかりでなく、積層工程中に接着剤が基板から流れ出て基板製品や加工設備を汚染する、接着剤中に溶媒などの揮発成分が残留し発泡その他の原因となるなどの問題が生じる。
金属層Ａ／高分子フィルム／接着層からなる構成を有する積層体を製造するには、高分子フィルムの片面に、すでに述べた方法で金属層Ａを形成したのち、接着層２を形成しても、また、逆の手順でも本発明の効果を損ねるものではない。接着層の形成方法としては、既に述べた接着層となる樹脂材料を溶液状にして塗布乾燥する方法、樹脂材料を溶融塗布する方法などが考えられる。
本発明の積層体は、前記高分子フィルム、金属層Ａ、接着層のほかに、金属層Ａ上に、必要に応じてプロテクトフィルムなどの保護フィルムを有することができる。以下に保護フィルムについて説明する。
＜保護フィルム＞
保護フィルムを設ける目的は、イオンプレーティング法で作製した銅薄膜を回路形成プロセスに適用するまでの間、その物性を変化させないための工夫である。イオンプレーティング膜は、長期間空気中にさらしておくと無電解銅めっき層との接着性が落ちる傾向にある。おそらく銅表面の酸化の進行やごみの付着などが原因であると考えられる。また、多層プリント配線板の製造においては、積層体に接着剤を塗布・乾燥する際に加熱することが少なくない。さらに、積層体を内層基板に積層する場合も加熱および加圧することが一般的である。それらの際に金属層が熱の影響を受けて酸化劣化することがある。一方、内層基板に積層回路基板に積層後、基板表面に新たな回路を形成するために、この保護フィルムは容易に剥離できるものでなければならない。
また、接着剤を塗布乾燥した積層体においては、接着剤の収縮により著しくカールする場合がある。これについても、保護フィルムを貼り合わせ、積層体全体の剛性を高めることでカールを低減することができる。
保護フィルムは、金属層と弱い接着力を持つものであれば材料の種類はとくに制限されない。該保護フィルムの形成方法は、とくに限定されるものではない。たとえば、金属層に、イミダゾール系の化合物を用いた有機被膜形成処理、または、クロメート処理やジンケート処理などの公知の防錆処理を施してもよい。これにより、長期保存安定性を付与することができる。
つぎに、本発明の積層体を用いた回路基板の製造方法を説明する。
＜回路基板の製造方法＞
本発明の積層体を用いた回路基板の製造方法を図１に示す。
まず、高分子フィルム１の表面に乾式めっき法によって金属層Ａを形成する（図１（ａ））。
つぎに、金属層Ａの表面にパラジウム化合物などのめっき触媒を付与したのち、そのめっき触媒を核として無電解銅めっきを行ない、銅膜の表面に無電解銅めっき層４を形成する（ｂ）。
無電解銅めっきのほかにも、無電解ニッケルめっき、無電解金めっき、無電解銀めっき、無電解錫めっきなどをあげることができ、本発明に使用可能であるが、工業的観点および耐マイグレーション性などの電気特性の観点より、無電解銅めっき、無電解ニッケルめっきが好ましく、とくに無電解銅めっきが好ましい。
無電解めっき工程としては、公知の無電解めっき処理が適用可能である。通常、基板表面の粗化、基板表面の洗浄、プレディップ、めっき触媒付与、めっき触媒の活性化、無電解めっき膜の形成の工程を経る。通常、２００〜３００ｎｍ、条件によっては８００〜１０００ｎｍのめっき皮膜を形成できる。
また、無電解めっき層は、レーザードリリングなどの方法により形成されたビアの内面および／または貫通スルーホールの内面にめっき皮膜を形成し、給電電極となる必要がある。したがって、その厚さは１００〜１０００ｎｍであることが好ましく、さらには１００〜５００ｎｍ、とくには２００〜８００ｎｍであることが好ましい。１００ｎｍより薄いと給電電極とした際に面内の電気めっきの厚さがばらつき、逆に１０００ｎｍをこえる場合、エッチング工程で余分にエッチングを行なう必要があり、回路設計値よりも回路厚さが薄くなったり、回路幅が狭くなったりする。さらに、アンダーカットなどが発生し、回路形状が劣化するという問題が生じる。また、無電解めっきのプロセス時間があまり長時間になると、金属層Ａとの接着強度が低下する傾向にあり、この意味から無電解銅めっき層の厚さは８００ｎｍ以下であることが好ましい。
つぎに、そのようにして形成された無電解銅めっき層の表面にレジスト被膜５を塗布し（ｃ）、回路の形成を予定する部分のレジスト被膜を取り除く（ｄ）。
本発明に用いるレジスト被膜としては、第２金属皮膜を形成するめっき液に耐え、このめっきを行なったときに、その表面に第２金属皮膜が形成されにくいものであれば、とくに限定するものではない。たとえば、液状の樹脂をスクリーン印刷法で回路の形成を予定する部分を除く部分に塗布したのち、固化して形成したものや、液状またはシート状の感光性樹脂を第１金属皮膜の表面全体に形成したのち、回路形状に露光し、ついで、回路の形成を予定する部分の感光性樹脂を除去して形成したものなどがあげられる。狭ピッチ化に対応するためには、５０μｍ以下の解像度を有する感光性めっきレジストを用いることが好ましい。もちろん、５０μｍ以下のピッチを有する回路とそれ以上のピッチを有する回路が混在してもよい。
レジスト被膜を形成したのち、無電解めっき膜が露出する部分を給電電極として使用して電解銅めっきを行ない、その表面に電解銅めっき層６（第２金属皮膜）を形成する（ｅ）。電解銅めっきのほかにも、電解はんだめっき、電解錫めっき、電解ニッケルめっき、電解金めっきなどの公知の電解銅めっきなどの電気めっきを適用することができるが、工業的観点、耐マイグレーション性などの電気特性の観点から、電解銅めっき、電解ニッケルめっきが好ましく、電解銅めっきがとくに好ましい。
電気めっきは公知の方法が適用できる。具体的には硫酸銅めっき、青化銅めっき、ピロリン酸銅めっきなどが知られているが、めっき液の取り扱い性、生産性、皮膜の特性などから、硫酸銅めっきが好ましい。硫酸銅めっきについてのめっき液組成とめっき条件を、以下に例示する。
＜硫酸銅めっき条件＞
（めっき液組成）
硫酸銅 ：７０ｇ／Ｌ
硫酸 ：２００ｇ／Ｌ
塩素イオン：５０ｍｇ／Ｌ
添加剤 ：適量
（めっき条件）
液温 ：室温
空気攪拌 ：有り
陰極基板の揺動：有り
陰極電流密度 ：２Ａ／ｄｍ^２
なお、このとき形成する第２金属皮膜の厚さは、レジスト被膜の厚さより厚くてもよく、薄くてもよい。また、電解めっきにかえて、無電解めっきにより第２金属皮膜を形成するようにしてもよい。
電解銅めっきののち、ついで、レジスト被膜を除去する（ｆ）。レジスト剥離液は、用いるレジスト被膜によって適宜決められるものである。
つぎに、金属層Ａおよび無電解銅めっき層よりなる給電層をエッチング除去し、回路を形成する（ｇ）。
なお、この際、第２金属皮膜をほとんど浸食せず、第１金属皮膜のみを選択的にエッチングするエッチャントを用いる。すなわち、レジストパターン剥離により露出した無電解銅めっき層と金属層Ａをエッチングにより除去する工程において、無電解銅めっき層および金属層Ａを除去するのに必要な時間あたりの電気銅めっき層のエッチング厚さをＴ１、無電解銅めっき層および金属層Ａの厚さの和をＴ２としたとき、Ｔ１／Ｔ２＜１となるエッチング液を用いる。Ｔ１／Ｔ２はできるだけ小さいことが好ましく、Ｔ１／Ｔ２が０．１〜１であることが好ましく、より好ましくは０．１〜０．５である。このような条件を満足するエッチング液としては、硝酸と硫酸を主成分とするエッチング液がとくに有効であり、さらに過酸化水素、塩化ナトリウムなどを添加したエッチング液がより有効である。ここでの主成分とは、エッチング液を構成する水以外の成分に対する主成分を意味する。
さらに好ましくは、第１金属皮膜に対するエッチング速度が第２金属皮膜にたいするエッチング速度の１０倍以上であるエッチャントを用いる。これにより、第２金属皮膜はエッチングされず、形成したときの状態がほぼ保たれる。そのため、回路形状はほぼ矩形を保つことができ、形状が優れた回路を得ることが可能になる。エッチャントの例としては、たとえば第１金属皮膜にニッケルを、第２金属皮膜に銅を用いた場合には、特開２００１−１４００８４公報に開示されているエッチャントが好適に用いられる。
ここで、エッチング速度は、４０ｍｍ×４０ｍｍ×０．３ｍｍ（厚さ）の金属板をエッチング液中に３分間浸漬し、静置した際の重量減少から次式により算出する。
エッチング速度（μｍ／分）＝（重量減少）×１００００
／（表面積×金属板の密度×浸漬時間） 式（３）
ここで、金属板の密度は、ニッケルでは８．８４５ｇ／ｃｍ^３、銅では８．９２ｇ／ｃｍ^３である。表面積は、４ｃｍ×４ｃｍ×２＋４ｃｍ×０．０３ｃｍ×４＝３２．４８ｃｍ^２、浸漬時間は３分である。
エッチング液の具体例として、メック（株）製のエッチング液（商品名、メックリムーバーＮＨ−１８６２）をあげることができるが、前記特長を有するものであれば、本発明に適用可能である。このエッチング液の各種金属に対するエッチング速度は、電解銅めっき層に対する速度を１としたとき、無電解銅めっき層に対する速度が５〜１０、スパッタリング銅層に対する速度が５〜１０、スパッタリングニッケル層に対する速度が１０〜２０である。たとえば、金属層Ａをニッケル層と銅層の２層構造で構成し、厚さの合計を２００ｎｍとし、さらに無電解銅めっきを２００ｎｍ行なった場合、金属層Ａと無電解銅めっき層の合計の厚さ４００ｎｍをエッチングにより完全に除去するのに必要な時間は、約４分であり、その間にエッチングされる電解銅めっき層の厚さは８０ｎｍであった。前記のプリント配線板の製造方法にしたがい、ライン／スペースが１０μｍ／１０μｍの回路パターンを製造した場合、得られた回路の幅は、エッチング前１０．０μｍであったものがエッチング後に９．８μｍとなり、ほぼ設計どおりの形状を有していた。なお、エッチング速度は各種金属をエッチング液に浸漬した際のエッチング厚さの変化を観察することにより求めた。
ところで、標準的な銅のエッチング液によるエッチング速度を測定した場合、そのエッチング速度は銅層の形成方法によって大きく異なる。イオンプレーティング法で形成された銅薄膜はセミアディティブ法におけるエッチング過程において非常に簡易にエッチングすることができる。
イオンプレーティング法、スパッタ法、無電解めっき法、電解めっき法によって形成された銅層のなかで、エッチング速度の最も速いのは、イオンプレーティング法によって作製した銅層である。つぎにエッチングされやすいのは、スパッタ法による銅層と無電解銅めっき層である。最もエッチングされ難いのは、電解法で形成された銅層である。イオンプレーティング法による銅層のエッチング速度はスパッタ法による銅層、あるいは無電解法による銅層の約３倍である。また、スパッタ法による銅層、あるいは無電解法による銅層のエッチング速度は電解法による銅層の約５〜１０倍である。すなわち、イオンプレーティング法で形成された銅層は、電解法による銅層の３０倍〜１５倍ものエッチング速度を有する。
したがって、イオンプレーティング法、スパッタ法、無電解めっき法によって形成された電解めっき用の給電層として用いられる銅層は、セミアディティブ法におけるエッチングプロセスで非常に容易にエッチング除去することができる。
また、生産性をあげる目的で、エッチング時間を短くするために、外部と導通をとりながらエッチングすることが有効であり、好ましく実施される。
最後に、必要に応じて無電解ニッケルめっきや無電解金めっきなどの仕上げ加工を行なって、プリント配線板を製造する。
なお、ライン／スペースが２５μｍ／２５μｍ以下の高密度回路を形成する際には、金属層と絶縁基板が強固に接着していることが極めて重要である。とくに、セミアディティブ法のみでなく、両面プリント配線板や多層プリント配線板の製造工程においても、貫通スルーホールやＩＶＨ（インターステーシャルビアホール）に伝導性を持たせるために無電解めっき、電気めっきは必須である。しかし、これらの工程は、強酸、強アルカリなど絶縁樹脂に対して少なからずダメージを与える性質の薬液処理を種々用いるため、これらの回路パターンの引き剥がし強度を確保することが実用上重要である。
前記回路基板の製造方法により、たとえば、無電解めっき法および電気めっき法によって形成した金属層の引き剥がし強度は、５Ｎ／ｃｍ以上とすることができる。従来、とくに表面のＲｚが１μｍ以下の高分子フィルムにおいて、無電解銅めっきがこのような高い引き剥がし強度を示すものは知られていない。金属層の引き剥がし強度は、金属層上に無電解めっき後、レジストパターンを形成せず硫酸銅めっきによって全面に２Ａ／ｄｍ^２の条件で４０分間電気めっきを施し、厚さ２０μｍの銅めっき層を形成し、ＪＩＳ Ｃ６４７１（引き剥がし強さ：Ｂ法）に準拠し、測定パターンの幅３ｍｍ、クロスヘッドスピード５０ｍｍ／分、剥離角度１８０度の条件で、高分子フィルムと金属層の引き剥がし強さを測定して求められる。
つぎに、本発明の多層プリント配線板の製造方法を説明する。
＜多層プリント配線板の製造方法＞
本発明にかかるビルドアップ多層プリント配線板の製造方法を、図２および図３に示す。ここでは、高分子フィルム１の片面に接着層３を有する積層体を用いる。まず、高分子フィルムの表面に、乾式めっき法によって金属層Ａを形成する（図２（ａ））。
つぎに、積層体の接着層面を、絶縁基板７に内層回路８を形成したプリント配線板９の回路面と張り合わせ、接着層を熱融着または硬化させる（図２（ｂ））。層間接着フィルムを構成する高分子フィルムが、多層プリント配線板を構成する樹脂絶縁層となる。
貼着は、加熱および／または加圧を伴う方法によって行なわれる。具体的には、加熱器を備えた真空プレス機や、加熱器および圧着ロールを備えた圧着装置を使用して加熱・加圧すればよい。プレス加工としては、油圧プレス、単板プレスのほか、真空プレス、真空ラミネートも適用できる。貼着時の泡の絞込み、内層回路の埋め込み性の観点、また金属層Ａの加熱による金属酸化を抑える観点から、真空プレス、真空ラミネートが好ましく使用される。貼着時の泡の咬み込み、内層回路の埋め込み性から真空プレスが好ましい。
貼着時の温度・圧力条件は、層間接着フィルムの組成、内層回路板の金属層ａの厚さなどに応じた最適な条件となるように設定すればよいが、貼着温度は３００℃以下、さらには２５０℃以下、さらには２２０℃以下、とくには２００℃以下が好適である。また、１００℃以上、１６０℃以上、１８０℃以上が好適である。貼着時間は１分〜３間程度、とくには１分〜２時間が好適である。圧力は０．０１〜１００ＭＰａが好適である。真空プレス、真空ラミネートの場合は、チャンバー内圧力は１０ｋＰａ以下、さらに好ましくは１ｋＰａ以下である。
貼着したのち、熱風オーブンなどの硬化炉に投入することも可能である。これにより接着層の熱硬化反応を硬化炉中で促進させることができる。とくに貼着時間を短くした場合、たとえば２０分以下にした場合には、貼着後に硬化炉で処理することが、生産性向上の観点から好ましい。
なお、前記貼着工程を行なう前に、内層回路上に接着層と同様の組成を有する接着層ワニスを塗布したのち、乾燥することによって、該内層回路板の表面を予め平坦化しておくことがより望ましい。
本発明の多層プリント配線板の製造方法では、高分子フィルムを用いているため、内層配線板との貼着の際に内層回路が接着層に埋め込まれ、高分子フィルムに内層回路が近接した状態で内層回路の接着層への埋め込みが終わる。その結果、層間の絶縁層厚さが高分子フィルム厚さとほぼ同一の厚さとなり、面内の絶縁層厚さを均一に保つ効果がある。また、本発明に係る高分子フィルムは層間の絶縁性を高める効果もある。
貼着工程を行なったのち、めっき層形成工程を行なう前に、必要に応じて、層間接着フィルムにおける所定位置に、ドリルやレーザ光を用いた穴開け操作を行なってスルーホールやビアホール１０などを形成する（図２（ｃ））。加工方法としては、公知のドルマリン、ドライプラズマ装置、炭酸ガスレーザー、ＵＶレーザー、エキシマレーザーなどを用いることができる。ビアホールの穴開けは、レーザードリリングが小径ビアのブラインドビア形成に有効であり、第１金属皮膜ごと穴開けするためには、ＵＶ−ＹＡＧレーザーが好適である。
必要に応じて公知の方法によるデスミア処理によりビアホールのクリーニングを行なうことが好ましい。デスミア処理は広く一般に行われている過マンガン酸塩を用いる湿式プロセスまたはプラズマなどを用いるドライデスミアにより行うことが好ましい。とくに、ドライデスミアは本発明の積層体の金属層Ａに対するダメージを低く抑えつつ、ビア底部のスミアを除去する効果があるため、好ましく用いられる。デスミア条件は、ビア穴開け条件により適宜修正されうる。金属層上に保護フィルムが積層されている場合には、上記穴開け操作を行なう前に、保護フィルムを金属層から剥離する。
無電解銅めっきなどにより該スルーホール部やビアホール部などを介して、内層回路板の金属層ａと層間接着フィルムの金属層とを導通させる工程を行なう。具体的には、銅膜の表面およびビアホール内部にパラジウム化合物などのめっき触媒１１を付与し（図２（ｄ））、そのめっき触媒を核として無電解銅めっきを行ない、銅膜の表面およびビアホール内部に無電解銅めっき層４を形成する（図２（ｅ））。
さらにその様にして形成された無電解銅めっき層の表面にレジスト膜５を塗布またはラミネートする（図２（ｆ））。必要に応じてフィルム状のもの、液状のものが使用可能である。取り扱い性や、その後のめっきによる回路形成の際のレジストの厚さの均一性から、フィルムレジストをラミネートする方法が好ましい。
フォトリソグラフィーにより、回路の形成を予定する部分のレジスト被膜を取り除く（図３（ａ））。高密度回路の形成には、感光材料のレジストに対して平行光源で露光、現像する方法が好ましい。また、マスクは基材と密着させる方法が高解像度実現には好ましい。一方、基材に密着させる場合、マスクに傷や汚れが問題となる場合があり、使用において適宜選択されうる。
そののち、無電解銅めっき層が露出する部分を給電電極として使用して電解銅めっきを行ない、その表面およびビアホール内に電解銅めっき層６を形成する（図３（ｂ））。このとき、ビアホールは電解銅めっき皮膜で充填されるようにする。めっきの方法としては、めっき液添加剤の調整やパルス状の電流を印加するなどの方法が適用できる。これらの方法を組み合わせることによって、用途に応じためっき皮膜を付けることができる。
ついで、レジスト被膜を除去する（図３（ｃ））。通常アルカリ性溶液によってレジスト被膜を剥離する。
金属層Ａおよび無電解銅めっき層よりなる給電層をソフトエッチングなどによって除去し、回路を形成する（図３（ｄ））。
以上の工程を経ることで、本発明の積層体の特徴を充分に生かして多層プリント配線板を製造することができる。とくにビアホールの導通のためには無電解めっきの触媒付与が必要となるが、ビアホール部以外は第１金属皮膜上に触媒が付与しているため、第１金属皮膜のエッチングによって不要部の触媒は容易に除去できる。
なお、前記の説明においては、内層回路板に層間接着フィルムを１枚貼着することによって多層プリント配線板を製造する方法を例にあげたが、たとえば、多層プリント配線板は、内層回路板の両面に層間接着フィルム２枚を貼着することによって製造されていてもよく、内層回路板に貼着された層間接着フィルムの上に、さらに別の層間接着フィルムを貼着することによって製造されていてもよい。つまり、前記各工程図２（ｂ）〜図３（ｄ）を繰り返し行なうことによって、内層回路板の片面もしくは両面に、複数枚の層間接着フィルムが積層された多層プリント配線板を製造することができる。
本発明の積層体は、金属層が、樹脂絶縁層である高分子フィルムに、乾式めっき法、より具体的には、真空蒸着法、スパッタリング法、イオンプレーティング法などの成膜法によって直接形成された金属薄膜を下地として形成されているので、金属層と樹脂絶縁層との密着性に優れている。つまり、高分子フィルムの表面を粗化する工程を行わなくとも、該高分子フィルムに金属層を密着させることができ、電気特性を向上させることができる。したがって、層間接着フィルムや多層プリント配線板の製造工程を従来と比較して簡略化することができるため、製造コストを低減することができると共に、製品の歩留りを向上させることができる。
また、前述した回路基板形成プロセス、およびビルドアップ多層基板形成プロセスのいずれにおいても、エッチングプロセスを非常に効果的に行なうことができる。
さらに、本発明の積層体を用いたプリント配線板の製造方法では、金属層Ａおよび無電解めっき層は、表面が平滑な高分子フィルム上に形成されるため、従来技術である粗化された樹脂表面に形成された無電解めっき層よりも迅速にエッチングを行なうことができる。このことは工業的に有利であるばかりでなく、粗化表面の奥深くまでエッチングを行なう必要もないことが、設計通りの良好な回路形状を得ることに寄与していると考えられる。
また、得られた回路パターン間にエッチング残渣が非常に少なく、回路形成時のイオンマイグレーションなどの問題をなくすることができる。従来技術によるセミアディテイブ法では、絶縁基板の表面に無電解銅めっき皮膜や無電解銅めっき触媒が残留しやすいため、得られるプリント配線板の絶縁性が低下しやすく、さらに最終工程で回路にニッケルめっきや金めっきを行なうため、これらの残留しているめっき触媒の触媒作用で絶縁基板の表面にニッケル、金がめっきされ、回路が形成できないという問題点があった。しかし、本発明では、無電解めっき層形成のための触媒処理は、乾式めっき法などにより形成された金属層Ａの上に行なわれるので、触媒はエッチング処理によって完全に取り除くことができる。したがって、本発明によれば、基板との密着性に優れ、かつ絶縁性にも優れた高密度回路の形成が可能となる。
以下に実施例に基づいて本発明の積層体を用いた回路基板の製造方法を示す。
＜回路基板の製造＞
実施例１
厚さ２５μｍのポリイミドフィルム（鐘淵化学工業（株）製アピカルＨＰ）の片方の面に、ニッケル３００ｎｍをＤＣスパッタリングして第１金属皮膜を形成した。
ついで、感光性ドライフィルムレジスト（旭化成工業（株）製サンフォート）を熱ラミネートしたのち、回路形状に露光した。なお、回路形状は、１５μｍの絶縁間隔を設けて形成した回路幅１５μｍの櫛型電極の形状に露光した。
ついで、回路の形成を予定する部分の感光性樹脂を除去して、第１金属皮膜の表面のうち、回路の形成を予定する部分を除く部分にレジスト被膜を形成したのち、電気銅めっきを行なって、第１金属皮膜が露出する部分の表面に、厚さ１０μｍの銅の第２金属皮膜を形成した。
ついで、アルカリ型の剥離液を用いてレジスト被膜を除去したのち、表１に示される組成のエッチング液を基板にスプレーしてニッケルの第１金属皮膜をエッチングし、回路幅１５μｍ、絶縁間隔１５μｍのパターンを作製した。ついで、仕上げ工程として、無電解ニッケルめっきを行なって、第２金属皮膜の表面に厚さ２μｍのニッケルの金属皮膜を形成したのち、無電解金めっきを行なって、ニッケルの金属皮膜の表面に厚さ０．１μｍの金の金属皮膜を形成してプリント配線板を得た。なお、用いたエッチャントのエッチング速度は、ニッケルに対するエッチング速度が５．３８μｍ／分、銅に対するエッチング速度が０．０４μｍ／分であった。

得られたプリント配線板の回路形状および絶縁性を評価した。回路形状は、形成した櫛型電極の形状の回路のうち、回路幅１５μｍに露光した部分の回路幅を顕微鏡で観察して、回路形状が矩形のものを合格、矩形の頂点がつぶれているものを不合格とした。絶縁性は、形成した櫛型電極の形状の回路のうち、１５μｍの絶縁間隔を有して導通しない回路間の絶縁抵抗を求めた。その結果、回路形状は合格であり、１×１０^１１Ω以上の絶縁抵抗を有していた。このように、実施例１では、回路形状、絶縁特性が優れているプリント配線板を簡便に製造できることが確認された。
実施例２
厚さ１２．５μｍのポリイミドフィルム（鐘淵化学工業（株）製アピカルＨＰ）の片方の面にイオンプレーティング法により銅薄膜を形成した。実験に用いたポリイミドフィルムの表面平滑度はＲｚ値換算で１μｍであった。また、代表的なイオン化の条件は４０Ｖ、ボンバード条件はアルゴンガス圧２６Ｐａ、基板加熱温度１５０℃である。この方法で５〜１０００ｎｍの範囲で種々の厚さの膜を作成した。
つぎに、ポリイミドフィルム／イオンプレーティング銅層よりなる積層体に、無電解めっき法で銅めっき層を形成した。無電解めっき層の形成方法はつぎの通りである。まず、アルカリクリーナー液で積層体を洗浄し、つぎに酸での短時間プレディップを行なった。さらに、アルカリ溶液中で白金付加とアルカリによる還元を行なった。つぎにアルカリ中での化学銅めっきを行なった。めっき温度は室温、めっき時間は１０分間であり、この方法で３００ｎｍの厚さの無電解銅めっき層を形成した。
こうして形成した銅薄膜層の接着強度をピール強度の値で評価した。接着性の評価において、剥離面は常にポリイミドフィルムとイオンプレーティング銅層の界面であり、イオンプレーティングの条件はあまりピール強度に影響を与えなかったが、厚さは強度に影響があった。すなわち、イオンプレーティング層が２０ｎｍ以下の場合には接着強度が１〜４Ｎ／ｃｍであり、場所によっての強度のばらつきが大きかった。これは、２０ｎｍ以下の厚さでは部分的にポリイミド膜の露出した部分が存在するためであろうと考えられる。これに対して、イオンプレーティング層の厚さが１０〜４００ｎｍの間では６〜８Ｎ／ｃｍであり、接着強度が安定して得られた。一方、厚さが４００ｎｍ以上では接着強度が低下し、６〜４Ｎ／ｃｍの値となった。
前記の方法により作製したポリイミドフィルム（１２．５μｍ）／イオンプレーティング銅層（５０ｎｍ）／無電解銅めっき層（３００ｎｍ）よりなる積層体に電解銅めっき層を形成した。電解銅めっきは、前記積層体を１０％硫酸中で３０秒間予備洗浄し、つぎに室温中で４０分間めっきを行なった。電流密度は２Ａ／ｄｍ^２であり、膜厚は１０μｍとした。
この積層体のピール強度を測定した。無電解めっき層と電解めっき層、イオンプレーティング銅層／無電解めっき層との間の接着強度は良好で、剥離はポリイミドとイオンプレーティング銅層の間で生じた。しかし、その強度は６〜７Ｎ／ｃｍであり、電解銅層の形成が各層の間の接着性に悪影響を与えていないことが分った。
前記の方法により作製したポリイミドフィルム（１２．５μｍ）／イオンプレーティング銅層（５０ｎｍ）／無電解銅めっき層（３００ｎｍ）よりなる積層体の表面に、レジスト液（ジェイ エス アール（株）製、ＴＨＢ３２０Ｐ）を１０μｍの厚さでスピンコートした。ついで高圧水銀灯を用いてマスク露光、レジスト膜剥離を行ない、ライン／スペースが１０μｍ／１０μｍのパターンを形成した。
つぎに、イオンプレーティング銅層（５０ｎｍ）／無電解銅めっき層（３００ｎｍ）よりなる銅層を給電体として用いて、レジスト膜の剥離された部分に電解銅めっきを行なった。電解銅めっきの厚さは１０μｍとした。
つぎに、アルカリ型の剥離液を用いてレジスト膜の剥離を行ない、さらにフラッシュエッチを行ない、給電体層を取り除いた。フラッシュエッチは、硫酸／過酸化水素／水の系で実施した。これにより、線幅が１０μｍ、線間隔が１０μｍのパターンを形成した。
つぎに、作製した回路の断面を電子顕微鏡を用いて観察した。イオンプレーティング銅層の厚さが４００ｎｍ以下の場合にはフラッシュエッチングの時間を適当に制御することにより、回路のアンダーエッチングがほとんどない状態で、完全に給電体層を取り除くことができた。しかし、イオンプレーティング銅層が４００ｎｍより厚い場合には、給電体層を完全に取り除こうとすると回路線のアンダーエッチングが生じることが分った。
つぎに、作製した回路パターンの絶縁特性を測定した。絶縁特性の測定はスペース間距離１０μｍの櫛型電極を用い、既知の方法（ＩＰＣ−ＴＭ−６５０−２．５．１７）で行なったが、１０^１６Ωｃｍの良好な線間抵抗を有していた。
さらに、給電層剥離部分のオージェ分析による残留金属の有無の測定を行なったが、残存金属の存在は認められなかった。
実施例３
実施例２と同様の方法で、ポリイミドフィルムの片方の面に、イオンプレーティング法により銅薄膜を形成した。
ついで、そのようにして形成した銅薄膜上にＤＣスパッタリング法で銅薄膜の形成を行なった。代表的なスパッタの条件は、ＤＣパワー：２００ワット、アルゴンガス圧：０．３５Ｐａである。５〜１０００ｎｍの範囲で種々の厚さの膜を作製した。
このようにして形成した銅薄膜層の接着強度をピール強度の値で評価した。接着性の評価で剥離面は常にポリイミドとイオンプレーティング銅層の界面であり、イオンプレーティングの条件はあまりピール強度に影響を与えなかったが、厚さは強度に影響があった。すなわち、イオンプレーティングの層が１０ｎｍ以下の場合には接着強度が１〜４Ｎ／ｃｍであり場所によっての強度のばらつきが大きかった。これは１０ｎｍ以下の厚さでは部分的にポリイミド膜の露出した部分が存在するためであると考えられる。これに対して、イオンプレーティング層の厚さが１０〜２００ｎｍの間では６〜８Ｎ／ｃｍであり、接着強度が安定して得られた。一方、厚さが２００ｎｍ以上では接着強度が低下し、６〜４Ｎ／ｃｍの値となった。
前記の方法で作製したポリイミドフィルム／イオンプレーティング銅層／スパッタリング銅層よりなる積層体に、実施例２と同様の方法で、無電解めっき法により銅めっき層を形成した。実験はイオンプレーティング銅層を５０ｎｍに固定し、種々の厚さのスパッタ銅層を形成した試料について実施した。スパッタリング銅層がない場合には、イオンプレーティング銅層が無電解銅めっき中にポリイミド基板から剥離した。また、スパッタリング銅層の厚さが１０ｎｍ以下の場合でも同様に剥離が生じた。
スパッタリング銅層が１０ｎｍ以上の場合は、無電解めっきプロセスにおけるイオンプレーティング銅層の保護膜としての役割を果たし、剥離は生じなかった。また、スパッタリング銅と無電解銅めっき層との接着強度は良好であり、その間が剥離することはなかった。ピール強度試験における剥離は、イオンプレーティング銅層とポリイミドフィルムの間で生じ、その場合のピール強度も６Ｎ／ｃｍ以上の良好な特性を示した。スパッタ銅の厚さは１０ｎｍ以上であれば良いが、２００ｎｍ以上の厚さはとくに必要でなく、むしろピール強度は２００ｎｍ以上の厚さでは低下する傾向にあった。
前記の方法で作製したポリイミドフィルム（１２．５μｍ）／イオンプレーティング銅層（５０ｎｍ）／スパッタリング銅層（１００ｎｍ）／無電解銅めっき層（３００ｎｍ）よりなる積層体に、実施例２と同様の方法で電解銅めっき層を形成した。
この積層体のピール強度を測定した。無電解めっき層と電解めっき層との間の接着強度は良好で、剥離はポリイミドとイオンプレーティング銅層の間で生じた。しかし、その強度は６〜７Ｎ／ｃｍであり、電解銅層の形成が各層の間の接着性に悪影響を与えていないことが分った。
前記の方法で作製したポリイミドフィルム（１２．５μｍ）／イオンプレーティング銅層（５０ｎｍ）／スパッタリング銅層（１００ｎｍ）／無電解銅めっき層（３００ｎｍ）よりなる積層体の表面に、実施例２と同様の方法により、レジストパターンを形成し、つぎに、レジストの剥離された部分に電解銅めっきを行ない、さらに、レジスト膜の剥離、フラッシュエッチを行なって、線幅が１０μｍ、線間隔が１０μｍのパターンを形成した。
つぎに、作製した回路の断面を電子顕微鏡を用いて観察した。スパッタリング銅層の厚さが２００ｎｍ以下の場合には、フラッシュエッチングの時間を適当に制御することにより、回路のアンダーエッチングがほとんどない状態であり、完全に給電体層を取り除くことができた。しかし、スパッタリング銅層が２００ｎｍより厚い場合には、給電体層を完全に取り除こうとすると回路線のアンダーエッチングが生じることが分った。
つぎに、実施例２と同様の方法で作製した回路パターンの絶縁特性を測定したところ、１０^１６Ωｃｍの良好な線間抵抗を有していた。
さらに給電層剥離部分のオージェ分析による残留金属の有無の測定を行なったが、残存金属の存在は認められなかった。
実施例４
厚さ１２．５μｍのポリイミドフィルム（鐘淵化学工業（株）製アピカルＨＰ）の片方の面にスパッタ法により直接銅薄膜を形成した。ＤＣスパッタリングの条件は実施例３と同じである。５〜１０００ｎｍの範囲で種々の厚さの膜を作製し、その接着強度を測定したが、いずれの膜厚でもピール強度は１Ｎ／ｃｍ以下であった。
比較例１
エポキシ樹脂両面銅張り積層板の表面の銅箔を全面エッチングした板の表面に、エポキシ樹脂をカーテンコーター法で塗布したのち、１５０℃で１時間加熱して、表面樹脂層が半硬化状態である絶縁基板を得た。
ついで、前記絶縁基板を、過マンガン酸カリウム溶液に浸漬して、樹脂層の表面を粗面化し、無電解めっきの密着性を向上させる処理を行なった。ついで、その樹脂層の表面に、パラジウム−スズコロイド型のめっき触媒を付与したのち、無電解銅めっきを行ない、絶縁基板の表面に、厚さ０．５μｍの銅の第１金属皮膜を形成した。
ついで、第１金属皮膜の表面に、実施例１と同様の方法で回路の形成を予定する部分を除く部分にレジスト被膜を形成し、第１金属皮膜が露出する部分の表面に、厚さ１０μｍの銅製第２金属皮膜を形成した。
ついで、ハンダめっきを行なって、第２金属皮膜の表面に、厚さ３μｍのハンダの金属皮膜（第３金属皮膜）を形成した。
ついで、アルカリ型の剥離液を用いてレジスト被膜を除去したのち、アルカリエッチング液を絶縁基板の表面にスプレーして第１金属皮膜をエッチングし、ついで、ハンダ剥離液を用いて、第２金属皮膜の表面に形成したハンダの第３金属皮膜を除去して、第２金属皮膜を露出させた。
ついで、過マンガン酸カリウム溶液に絶縁基板を浸漬して、絶縁基板の表面の半硬化状態の樹脂層を除去すると共に、絶縁基板の表面に残留するめっき触媒を除去したのち、１７０℃で２時間加熱して、半硬化状態の樹脂層を完全に硬化させた。
得られたプリント配線板の回路形状および絶縁性を、実施例１と同様の方法で評価した。その結果、回路形状は合格であり、１×１０^９Ω以上の絶縁抵抗を有していた。このように、比較例１では、実施例１と比較して絶縁特性に劣ることが確認された。さらに、比較例１では、実施例１と比較して第２金属皮膜の表面にさらに金属皮膜を形成および除去すること、めっき触媒を除去することが必要であり、工程が複雑であるという問題も有している。
比較例２
第２金属皮膜の表面に、ハンダの金属皮膜（第３金属皮膜）を形成せずに、レジスト被膜および第１金属皮膜の除去を行なったことほかは、比較例１と同様にしてプリント配線板を得た。
得られたプリント配線板の回路形状および絶縁性を、実施例１と同様の方法で評価した。その結果、回路形状は不合格であり、１×１０^９Ω以上の絶縁抵抗を有していた。このように、比較例２では、実施例１と比較して回路形状および絶縁特性に劣ることが確認された。さらに、比較例２では、実施例１と比較して、めっき触媒を除去することが必要であり、工程がやや複雑であるという問題も有している。
つぎに、実施例に基づいて本発明の積層体を用いたビルトアップ多層プリント配線板の製造方法を示す。なお、以下に示す実施例および比較例では、接着剤層に、以下の方法により調整した接着剤溶液を用いた。
容量２０００ｍｌのガラス製フラスコに入れたＮ，Ｎ−ジメチルホルムアミドに、チッ素雰囲気下、１当量のビス｛４−（３−アミノフェノキシ）フェニル｝スルホンを溶解した。この溶液を氷水で冷却しながら攪拌し、該溶液に１当量の４，４’−（４，４’−イソプロピリデンジフェノキシ）ビス無水フタル酸を溶解すると共に重合させた。これにより、固形分濃度が３０重量％のポリアミド酸重合体溶液を得た。このポリアミド酸重合体溶液を、２００℃（常圧）で３時間加熱したのち、さらに２００℃、６６５Ｐａで３時間、減圧加熱した。これにより、固形の熱可塑性ポリイミド樹脂を得た。
この熱可塑性ポリイミド樹脂と、熱硬化性樹脂としてのノボラック型のエポキシ樹脂（商品名・エピコート１０３２Ｈ６０、油化シェルエポキシ（株）製）と、硬化剤として４，４’−ジアミノジフェニルスルホンとを、重量比が７０／３０／９となるように混合すると共に、該混合物をジオキソラン（有機極性溶媒）に、固形分濃度が２０重量％となるように溶解することにより、接着剤溶液を得た。
＜ビルトアップ多層プリント配線板の製造＞
実施例５
厚さ１２．５μｍのポリイミドフィルム（商品名・アピカルＮＰＩ、鐘淵化学工業（株）製）の一方の面に、ＤＣマグネトロンスパッタを用いたスパッタリング法によって厚さ３００ｎｍの銅薄膜（金属層）を形成した。また、該ポリイミドフィルムの他方の面に、前記接着剤溶液を、乾燥後の厚さが９μｍとなるようにグラビアコーターを用いて塗布し、１７０℃で２分間、乾燥することにより接着層を形成した。これにより、層間接着フィルムを製造した。
一方、厚さ９μｍの銅箔が貼着されたガラスエポキシ銅張積層板から内層回路板を作製した。そして、該内層回路板の銅箔（金属層ａ）に前記層間接着フィルムを貼着したのち、真空プレス機を用いて２００℃で２時間、加熱・加圧することにより、接着層である熱可塑性ポリイミド樹脂を銅箔に熱融着させた。
つぎに、層間接着フィルムにレーザ光を用いて穴開け操作を行なったのち、無電解銅めっきにより銅薄膜の厚さを３μｍにすると共に、内層回路板の銅箔と層間接着フィルムの銅薄膜とを導通させた。ついで、層間接着フィルムの銅薄膜上に、感光性ドライフィルムレジスト（商品名・サンフォートＡＱ−２５３６、旭化成工業（株）製）によってめっきレジストパターンを形成したのち、該銅薄膜上における回路パターンとなるべき部位に、電解銅めっきにより厚さ２０μｍの銅膜（めっき層）を積層した。そののち、めっきレジストを剥離し、ソフトエッチングによって銅薄膜を除去した。これにより、ライン／スペースが３０μｍ／３０μｍの微細な回路パターンが形成された多層プリント配線板を得た。
実施例６
スパッタリング法を採用する代わりに、ポリイミドフィルムの一方の面に、イオンプレーティング法によって厚さ３００ｎｍの銅薄膜（金属層）を形成したほかは、実施例５と同様の工程を行なって多層プリント配線板を形成した。該多層プリント配線板には、ライン／スペースが３０μｍ／３０μｍの微細な回路パターンを形成することができた。
実施例７
スパッタリング法を採用する代わりに、ポリイミドフィルムの一方の面に、真空蒸着法によって厚さ３００ｎｍの銅薄膜（金属層）を形成したほかは、実施例５と同様の工程を行なって多層プリント配線板を形成した。該多層プリント配線板には、ライン／スペースが３０μｍ／３０μｍの微細な回路パターンを形成することができた。
実施例８
スパッタリング法を採用して、ポリイミドフィルムの一方の面に、厚さ３０ｎｍのニッケル薄膜を形成したのち、該ニッケル薄膜上に厚さ３００ｎｍの銅薄膜を積層することにより、二層構造の金属層を形成したほかは、実施例５と同様の工程を行なって多層プリント配線板を形成した。該多層プリント配線板には、ライン／スペースが３０μｍ／３０μｍの微細な回路パターンを形成することができた。
実施例９
実施例１と同様に第１金属皮膜を形成した積層体の該ポリイミドフィルムの他方の面に、接着剤溶液を乾燥後の厚さが９μｍになるように塗布し、１７０℃で２分間乾燥して接着層を形成して、ビルドアップ多層プリント配線板用積層体を作製した。一方、銅箔９μｍのガラスエポキシ銅張積層板から内層回路板を作製し、ついでビルドアップ多層プリント配線板用積層体を真空プレスにより２００℃２時間の条件でプリント配線板表面に積層、硬化した。
ＵＶ−ＹＡＧレーザーによりビアホールの穴開けを行ない、基板全面に無電解めっきの触媒を付与したのち、実施例１と同様の方法で回路およびビアホールの形成を予定する部分を除く部分にレジスト被膜を形成した。そののち、無電解銅めっきでレーザー穴の導通を採り、さらに電気銅めっきを行なって、第１金属皮膜が露出する部分の表面に、厚さ１０μｍの銅製第２金属皮膜を形成した。ついで、実施例１と同様の方法でめっきレジストを剥離し、第１金属皮膜をエッチングして回路幅１５μｍ、絶縁間隔１５μｍの微細回路の多層プリント配線板を得た。
得られたプリント配線板の回路形状および絶縁性を実施例１と同様の方法で評価した。その結果、実施例１と同様の結果が得られた。
実施例１０
接着剤溶液をポリイミドフィルム（鐘淵化学工業（株）製、アピカル、１２．５μｍ）の片面に乾燥後の厚さが９μｍになるように塗布し、１７０℃で２分間乾燥して接着層を形成した。
次に、ポリイミドの他方の面に実施例２と同様の方法でイオンプレーティング銅層（５０ｎｍ）を形成し、ビルドアップ多層プリント配線板用積層体を作製した。
一方、銅箔９μｍのガラスエポキシ銅張積層板から内層回路板を作製し、ついで、上記のビルドアップ多層プリント配線板用積層体を真空プレスにより２００℃、２時間の条件でガラスエポキシ積層板表面に積層し、硬化させた。
つぎに、イオンプレーティング銅層の表面に、実施例２と同様の方法でフォトレジストを用いて回路パターンを形成した。ＵＶ−ＹＡＧレーザーによりビアホールの穴開けを行ない、基板全面およびビアホール内部に触媒を付与したのち、無電解めっきを行なった。無電解銅めっきでレーザー穴の導通を採り、さらに電気銅めっきを行なって、厚さ１０μｍの銅めっき層を形成した。ついで、実施例２と同様の方法でめっきレジストを剥離し、給電体層をエッチングして回路幅１０μｍ、絶縁間隔１０μｍの微細回路のビルドアップ多層プリント配線板を得た。
得られたプリント配線板の回路形状および絶縁性を評価した。回路形状は、形成した櫛型電極形状の回路のうち、回路幅１０μｍに露光した部分の回路幅を顕微鏡で観察して、回路形状が矩形のものを合格、矩形の頂点がつぶれているものを不合格とした。絶縁性は、形成した櫛型電極形状の回路のうち、１０μｍの絶縁間隔を有して導通しない回路間の絶縁抵抗を求めた。その結果、実施例１０では、比較例２と比べて、回路形状、絶縁特性が優れているプリント配線板を簡便に製造できることが確認された。
実施例１１
接着剤溶液をポリイミドフィルム（鐘淵化学工業（株）製、アピカル、１２．５μｍ）の片面に乾燥後の厚さが９μｍになるように塗布し、１７０℃で２分間乾燥して接着層を形成した。
つぎに、ポリイミドの他方の面に、実施例３の方法でイオンプレーティング銅層（２０ｎｍ）／スパッタリング銅層（１００ｎｍ）を形成し、ビルドアップ多層プリント配線板用積層体を作製した。
一方、銅箔９μｍのガラスエポキシ銅張積層板から内層回路板を作製し、ついで、前記のビルドアップ多層プリント配線板用積層体を真空プレスにより２００℃、２時間の条件でガラスエポキシ積層板表面に積層し、硬化させた。
つぎに、スパッタリング銅層の表面に、実施例３と同様の方法でフォトレジストを用いて回路パターンを形成した。ＵＶ−ＹＡＧレーザーによりビアホールの穴開けを行ない、基板全面およびビアホール内部に触媒を付与した後、無電解めっきを行った。無電解銅めっきでビアホール内部を導電化し、さらに電気銅めっきを行なって、厚さ１０μｍの銅めっき層を形成すると同時にビアホール内部を銅で充填した。ついで、実施例３と同様の方法でめっきレジストを剥離し、給電体層をエッチングして回路幅１０μｍ、絶縁間隔１０μｍの微細回路のビルドアップ多層プリント配線板を得た。
得られたプリント配線板の回路形状および絶縁性を実施例１０と同様の方法で評価した。その結果、実施例１１では、比較例２と比べて、回路形状、絶縁特性が優れているプリント配線板を簡便に製造できることが確認された。
実施例１２
まず、以下の方法によりポリイミドフィルムを合成した。
セパラブルフラスコ中でパラフェニレンジアミン（以下ＰＤＡ）と４，４’−ジアミノジフェニルエーテル（以下ＯＤＡ）各１当量をＮ，Ｎ−ジメチルホルムアミド（以下ＤＭＦ）に溶解した。そののち、ｐ−フェニレンビス（トリメリット酸モノエステル無水物）（以下ＴＭＨＱ）１当量を加え、３０分間攪拌した。そののち、ピロメリット酸２無水物（以下ＰＭＤＡ）０．９当量を加え、３０分間攪拌した。ついで粘度上昇に注意しながらＰＭＤＡのＤＭＦ溶液（濃度７％）を加え、２３℃での粘度が２０００〜３０００ポイズになるように調整し、ポリアミド酸重合体のＤＭＦ溶液を得た。なお、ＤＭＦの使用量はジアミン成分およびテトラカルボン酸２無水物成分のモノマー仕込濃度が、１８重量％となるようにした。また、重合は４０℃で行なった。
前記ポリアミド酸溶液１００ｇに対して、無水酢酸１０ｇとイソキノリン１０ｇを添加し、均一に攪拌したのち、脱泡を行ない、ガラス板上に流延塗布し、約１１０℃で約５分間乾燥後、ポリアミド酸塗膜をガラス板より剥し、自己支持性を持つゲルフィルムを得た。このゲルフィルムをチタン濃度１００ｐｐｍに調整したＴＢＳＴＡの１−ブタノール溶液に１分間浸漬し、フィルム表面の液滴を除去したのち、フレームに固定して、その後約２００℃で約１分間、約３００℃で約１分間、約４００℃で約１分間、約５００℃で約１分間加熱し、脱水閉環乾燥し、厚さ約２５μｍのポリイミドフィルムを得た。このポリイミドフィルムは、引張り弾性率６ＧＰａ、引張り伸び率５０％、吸水率１．２％、誘電率３．４、誘電正接０．０１、１０点平均粗さＲｚは０．２μｍであった。
つぎに、昭和真空社製スパッタリング装置ＮＳＰ−６を用い、以下の方法により、前記方法により製造したポリイミドフィルムへの金属層の形成を行なった。
高分子フィルムを冶具にセットして、真空チャンバーを閉じた。基板（高分子フィルム）を自公転させながら、ランプヒーターで加熱しながら、６×１０^−４Ｐａ以下まで真空引きした。そののち、アルゴンガスを導入し、０．３５ＰａにしてＤＣスパッタリングにより厚さ２０ｎｍのニッケル、ついで厚さ１０ｎｍの銅をスパッタリングした。ＤＣパワーはどちらも２００ワットでスパッタリングした。成膜速度は、ニッケルが７ｎｍ／分、銅が１１ｎｍ／分であり、成膜時間を調整して成膜厚さを制御した。
つぎに、接着剤溶液をコンマコーターを用いて高分子フィルムの金属層を形成した面と反対の面に、乾燥後の厚さが９μｍになるように塗布し、１７０℃で２分間乾燥して接着剤層を形成して、ビルドアップ多層プリント配線板用積層体を作製した。
得られた層間接着フィルムを用いて、下記方法により多層プリント配線板を作製した。
まず、内層回路（厚さ９μｍのＦＲ４基板）に、前記層間接着フィルムを、温度２００℃、圧力３ＭＰａ、真空度１０Ｐａの条件で１時間プレスして積層した。必要な位置に、ＵＶ−ＹＡＧレーザーで直径３０μｍのビアホールを穴開けし、アトテック（株）製無電解銅めっきのプロセスにしたがい、クリーナーコンディショナー（商品名クリーナーセキュリガント９０２）５分、プレディップ（商品名プリディップネオガントＢ）１分、アクチーベーター（商品名、アクチベーターネオガント８３４コンク）５分、還元（商品名リデュサーネオガント）２分、無電解銅めっき（ノビガントＭＳＫ−ＤＫ）１５分の条件でめっきした。
無電解銅めっき皮膜をアセトンで洗浄したのち、ジェイ エス アール（株）製の液状ホトレジスト（商品名ＴＨＢ−３２０Ｐ）をスピンコート法で１０００ＲＰＭで１０秒間塗布し、１１０℃で１０分間乾燥して１０μｍの厚さのレジスト層を形成した。つぎに、レジスト層にライン／スペースが１０／１０μｍのガラスマスクを密着して超高圧水銀灯の紫外線露光機で１分間露光したのち、ジェイ エス アール（株）製の現像液（ＰＤ５２３ＡＤ）に３分間浸漬して感光した部分を除去し、ライン／スペースが１０／１０μｍのパターンを形成した。
得られた積層基板を硫酸銅めっき液によって電流密度２Ａ／ｄｍ^２で２０分間電気めっきを施し、レジストを除去した部分に厚さ１０μｍのパターンを形成した。得られた回路基板をアセトンで洗浄して基板上に残ったレジスト層を剥離した。さらに、メック（株）製のエッチング液（商品名、メックリムーバーＮＨ−１８６２）に５分間浸漬した。このエッチング液は銅と比較してニッケルに対するエッチング速度が大きく、回路以外の部分のニッケルを除去する際に回路部分の銅のダメージを最小限に抑えることができる。
得られた多層プリント配線板の回路を走査型電子線顕微鏡で観察し、設計通りライン／スペース＝１０／１０μｍの回路を形成していることを確認した。また、スペース部分は平滑でニッケルあるいは銅のエッチング残りは観察されなかった。さらに、本来長方形となるべき銅の導体回路の断面形状はエッチング工程での回路細りが見られず、設計通りの長方形の形状を維持していた。
また、金属層の厚さが２０μｍのときの高分子フィルムとの引き剥がし強さは６．８Ｎ／ｃｍであり、高密度配線を形成する上で充分な引き剥がし強さを示した。
実施例１３
ニッケルのスパッタ層を１０ｎｍ、銅スパッタ層を５０ｎｍとしたほかは、実施例１２と同様の方法でプリント配線板を作製・評価した。結果、ライン／スペースが１０／１０μｍの回路が良好に作製されていることを確認した。また、金属層と高分子フィルムとの引き剥がし強さは８．２Ｎ／ｃｍであり、高密度配線を形成する上で充分な引き剥がし強さを示した。
実施例１４
ニッケルスパッタ層を１０ｎｍ、銅スパッタ層を１００ｎｍとしたほかは、実施例１２と同様の方法でプリント配線板を作製・評価した。結果、ライン／スペースが１０／１０μｍの回路が良好に作製されていることを確認した。また、金属層と高分子フィルムとの引き剥がし強さは９．６Ｎ／ｃｍであり、高密度配線を形成する上で充分な引き剥がし強さを示した。
実施例１５
ニッケル／クロム合金のスパッタ層を１０ｎｍ、銅スパッタ層を１００ｎｍとしたほかは、実施例１２と同様の方法でプリント配線板を作製・評価した。結果、ライン／スペースが１０／１０μｍの回路が良好に作製されていることを確認した。また、金属層と高分子フィルムとの引き剥がし強さは１０．６Ｎ／ｃｍであり、高密度配線を形成する上で充分な引き剥がし強さを示した。
実施例１６
ニッケルスパッタ層を１０ｎｍ、銅スパッタ層を２００ｎｍとしたほかは、実施例１２と同様の方法でプリント配線板を作製・評価した。目視による回路観察の結果、スペース部分のエッチングが不充分であった。スペース部分を充分にエッチングするためには３０分のエッチングが必要であった。得られた配線板の回路はエッチングにより幅が減少し、とくに回路の上部は丸みを帯びて細くなっていた。
実施例１７
厚さ１２．５μｍのポリイミドフィルム（鐘淵化学工業（株）製アピカルＨＰ）の片方の面に、マグネトロンＤＣスパッタ法によりニッケルを２０ｎｍ、引きつづき銅を１０ｎｍの薄膜を形成し、積層体を得た。つぎに、接着剤溶液を前記積層体のポリイミドフィルム面に乾燥後の厚さが９μｍになるように塗布し、１７０℃で２分間乾燥して接着層を形成し、層間接着フィルムを得た。
銅箔９μｍのガラスエポキシ銅張積層板から内層回路板を作製し、ついで前記層間接着フィルムを真空プレスにより温度２００℃、熱板圧力３ＭＰａ、プレス時間２時間、真空条件１ＫＰａの条件で内層回路板に積層し、硬化した。
ＵＶ−ＹＡＧレーザーにより内層板の電極直上に該電極に至る内径３０μｍのビアホールを開けた。つづいて、基板全面に無電解銅めっきを行なった。無電解めっき層の形成方法は、実施例２と同様である。液状感光性めっきレジスト（ジェイ エス アール（株）製、ＴＨＢ３２０Ｐ）をコーティングし、１１０℃で１０分間乾燥して１０μｍの厚さのレジスト層を形成した。レジスト層にライン／スペースが１０／１０μｍのガラスマスクを密着して超高圧水銀灯の紫外線露光機で１分間露光したのち、現像液（ジェイ エス アール（株）製、ＰＤ５２３ＡＤ）に３分間浸漬して感光した部分を除去し、ライン／スペースが１０／１０μｍのめっきレジストパターンを形成した。
つづいて、硫酸銅めっき液によって無電解銅めっき皮膜が露出する部分の表面に、厚さ１０μｍの銅のパターンを形成した。電解銅めっきは、１０％硫酸中で３０秒間予備洗浄し、つぎに室温中で２０分間めっきを行なった。電流密度は２Ａ／ｄｍ^２であり、膜厚は１０μｍとした。
つぎに、アセトンを用いてめっきレジストを剥離した。さらに、メック（株）製エッチング液（メックリムーバーＮＨ−１８６２）に５分間浸漬し、回路以外の部分の無電解銅めっき層／銅薄膜／ニッケル薄膜を除去してプリント配線板を得た。
得られたプリント配線板はほぼ設計値通りのライン／スペースを有しており、また、サイドエッチはなかった。また、給電層剥離部分のオージェ分析による残留金属の有無の測定を行なったが、残存金属の存在は認められなかった。また、回路パターンは強固に接着していた。
さらに、本実施例のエッチング工程において、外部に導通を取りながらエッチングを行なった。この場合には、給電層剥離部分のオージェ分析による残留金属の有無の測定により、約２分のエッチング液への浸漬で残存金属の存在は認められなくなっていた。
実施例１８
マグネトロンＤＣスパッタ法によりニッケルを１０ｎｍ、引きつづき銅を５０ｎｍの薄膜を形成したほかは、実施例１７と同様にしてプリント配線板を得た。得られたプリント配線板はほぼ設計値通りのライン／スペースを有しており、また、サイドエッチはなかった。また、給電層剥離部分のオージェ分析による残留金属の有無の測定を行なったが、残存金属の存在は認められなかった。また、回路パターンは強固に接着していた。
実施例１９
マグネトロンＤＣスパッタ法によりニッケルを１０ｎｍ、引きつづき銅を１００ｎｍの薄膜を形成したほかは、実施例１７と同様にしてプリント配線板を得た。得られたプリント配線板はほぼ設計値通りのライン／スペースを有しており、また、サイドエッチはなかった。また、給電層剥離部分のオージェ分析による残留金属の有無の測定を行なったが、残存金属の存在は認められなかった。また、回路パターンは強固に接着していた。
実施例２０
マグネトロンＤＣスパッタ法によりニッケル−クロム合金を１０ｎｍ、引きつづき銅を１０ｎｍの薄膜を形成したほかは、実施例１７と同様にしてプリント配線板を得た。得られたプリント配線板は、ほぼ設計値通りのライン／スペースを有しており、また、サイドエッチはなかった。また、給電層剥離部分のオージェ分析による残留金属の有無の測定を行なったが、残存金属の存在は認められなかった。また、回路パターンは強固に接着していた。
実施例２１
マグネトロンＤＣスパッタ法によりニッケル−クロム合金を１０ｎｍ、引きつづき銅を５０ｎｍの薄膜を形成したほかは、実施例１７と同様にしてプリント配線板を得た。得られたプリント配線板は、ほぼ設計値通りのライン／スペースを有しており、また、サイドエッチはなかった。また、給電層剥離部分のオージェ分析による残留金属の有無の測定を行なったが、残存金属の存在は認められなかった。また、回路パターンは強固に接着していた。
比較例３
厚さ１２．５μｍのポリイミドフィルム（商品名・アピカルＮＰＩ、鐘淵化学工業（株）製）の一方の面に、エポキシ系接着剤を介して厚さ１８μｍの電解銅箔を貼着した。また、該ポリイミドフィルムの他方の面に、熱可塑性ポリイミド樹脂からなる接着剤溶液を、乾燥後の厚さが９μｍとなるようにグラビアコーターを用いて塗布し、乾燥することにより接着層を形成した。これにより、層間接着フィルムを製造した。
一方、厚さ９μｍの銅箔が貼着されたガラスエポキシ銅張積層板から内層回路板を作製した。そして、該内層回路板の銅箔に前記層間接着フィルムを貼着したのち、真空プレス機を用いて２００℃で２時間、加熱・加圧することにより、接着層である熱可塑性ポリイミド樹脂を銅箔に熱融着させた。
つぎに、層間接着フィルムにレーザ光を用いて穴開け操作を行なったのち、無電解銅めっきおよび電解銅めっきにより電解銅箔の厚さを３３μｍにすると共に、内層回路板の銅箔と層間接着フィルムの電解銅箔とを導通させた。ついで、層間接着フィルムの電解銅箔上に、感光性ドライフィルムレジスト（商品名・サンフォートＡＱ−２５３６、旭化成工業（株）製）によってめっきレジストパターンを形成したのち、該電解銅箔上における回路パターンとなるべき部位に、電解銅めっきにより厚さ２０μｍの銅膜（めっき層）を積層した。そののち、めっきレジストを剥離し、ソフトエッチングによって電解銅箔を除去した。しかしながら、サイドエッチングの影響によって回路パターンの幅（ライン）にばらつきが生じると共に、短絡箇所や断線箇所が多数、発生した。したがって、ライン／スペースが３０μｍ／３０μｍの微細な回路パターンが形成された多層プリント配線板を得ることはできなかった。
比較例４
スパッタリング法を採用する代わりに、ポリイミドフィルムの一方の面に、無電解銅めっきによって厚さ２μｍの銅薄膜を形成したほかは、実施例５と同様の工程を行なって多層プリント配線板を形成した。しかしながら、銅薄膜のポリイミドフィルムへの密着性が劣っているため、該銅薄膜がポリイミドフィルムから剥離し、回路パターンを形成することができなかった。
比較例５
エポキシ樹脂製の層間絶縁材料（味の素ファインテクノ（株）製ＡＢＦ−ＳＨ−９Ｋ）を、回路厚さ９μｍのＦＲ４基板に、温度９０℃でラミネートし、１７０℃で３０分間硬化した。
得られた積層体を過マンガン酸法でデスミア処理による表面粗化を行なったのち、実施例１２の無電解めっきプロセス以降の工程を経て多層プリント配線板を製造し、評価した。
表面粗化後の樹脂表面の１０点平均粗さは３．０μｍであった。得られた多層プリント配線板は、樹脂表面の凹凸が大きいために回路幅が安定しなかった。また、スペース部分をＳＥＭ観察したところ、凹凸にニッケルのエッチングのこりが見られた。樹脂層と金属層の密着強度は７．４Ｎ／ｃｍであった。
産業上の利用可能性
本発明によれば、高分子フィルムに乾式めっき法による金属層Ａを形成することにより、表面平滑性に優れた高分子表面においても、強固に接着した配線回路を形成することができる。また、密着性に優れているので、電気特性を向上させることができる。さらに、絶縁層となる高分子フィルムの厚さを薄く均一にすることができる。したがって、この積層体を用いてプリント配線板を製造すると、接着強度および形状に優れた配線回路の製造が可能となり、さらに絶縁抵抗性にも優れたプリント配線板を得ることが可能になる。とくに、ライン／スペースが２５μｍ以下の高密度回路を形成するのに好適である。
また、本発明によれば、前記積層体の高分子フィルムのもう一方に接着層を有することにより、ファインパターンを形成するのに好適な多層プリント配線板用層間接着フィルムを提供することができる。該積層体を用いて多層プリント配線板を製造すると、従来と比較して製造工程を簡略化することができるので、製造コストを低減することができるとともに、製品の歩留まりを向上させることができる。これにより、たとえば、ファインパターン、とくにセミアディティブ法による回路パターンが形成された多層プリント配線板を、簡単にかつ安価に製造することができる。
さらに、本発明によれば、第１金属皮膜を除去する際に、第１金属皮膜を選択的にエッチングするエッチャントを用いることにより、第２金属皮膜の回路形状が優れたプリント配線板を得ることができる。
【図面の簡単な説明】
図１は、本発明の積層体を用いた回路基板の製造方法を説明するための図である。
図２は、本発明のビルトアップ多層プリント配線板の製造方法を説明するための図である。
図３は、本発明のビルトアップ多層プリント配線板の製造方法を説明するための図である。Technical field
The present invention relates to a laminate in which a copper metal layer is formed on a polymer film having a smooth flat surface widely used in electric / electronic devices and the like, and a method for producing the same, and particularly, it is suitable for producing a circuit board. The present invention relates to a laminate and a method for producing the laminate. More specifically, the present invention relates to a high-density printed wiring board manufactured by a semi-additive method and a method for manufacturing the same.
The present invention also relates to a laminate for a build-up multilayer printed wiring board to which a semi-additive method can be applied, a build-up multilayer printed wiring board manufactured by using the laminate and applying the method, and a method of manufacturing the same. More specifically, an interlayer adhesive film for a multilayer printed wiring board in which an insulating resin layer and a metal layer having a circuit pattern formed thereon are sequentially laminated on a metal layer of a wiring board having a circuit pattern (inner circuit board). The present invention relates to a build-up multilayer printed wiring board obtained by using a film, and a method for manufacturing the same.
Background art
A printed wiring board having a circuit formed on the surface of an insulating substrate is widely used for mounting electronic components, semiconductor elements, and the like. 2. Description of the Related Art With the recent demand for smaller and more sophisticated electronic devices, printed wiring boards are strongly demanded to have higher density and thinner circuits. In particular, establishment of a method for forming a fine circuit having a line / space interval of 25 μm / 25 μm or less is an important issue in the field of printed wiring boards.
As a method of manufacturing such a high-density printed wiring board, a method called a semi-additive method has been studied. As a typical example, a printed wiring board is manufactured by the following steps.
After roughening the surface of the insulating substrate and applying a plating catalyst such as a palladium compound, electroless copper plating is performed using the plating catalyst as a nucleus to form a thin metal film on the entire surface of the polymer film.
Next, a resist film is applied or laminated on the surface of the electroless copper plating film, and the portion of the resist film where a circuit is to be formed is removed by a method such as photolithography. Thereafter, electrolytic copper plating is performed using a portion where the electroless copper plating film is exposed as a power supply electrode, and a second metal film is formed in a portion where a circuit is to be formed.
Next, after removing the resist film, the exposed unnecessary electroless copper plating film is removed by etching. At this time, the surface of the electrolytic copper plating film is also slightly etched, and the thickness and width of the circuit pattern decrease.
Further, if necessary, the surface of the formed circuit pattern is subjected to nickel plating and gold plating to manufacture a printed wiring board.
As described above, in the semi-additive method, since a thin electroless copper plating film (first metal film) is manufactured by etching, a thin metal foil is etched to form a circuit, which is called a subtractive method. Compared with the method, a fine circuit can be formed with high accuracy.
However, it has been found that the semi-additive method has the following problems.
The first is the problem of adhesion between the circuit pattern to be formed and the substrate. As described above, the space between the substrate and the circuit pattern is an electroless copper plating layer. Since the electroless copper plating layer is formed therefrom using the catalyst as an active point, it should be considered that there is essentially no adhesion to the substrate. When the unevenness of the substrate surface is large, the adhesion during this period is favorably maintained by the anchor effect. However, as the surface of the substrate becomes smoother, the adhesiveness naturally tends to weaken.
For this reason, the semi-additive method requires a step of roughening the surface of the insulating substrate, and usually has irregularities of about 3 to 5 μm in terms of 10-point average roughness (Rz). Such unevenness on the surface of the substrate does not pose a practical problem when the line / space value of the circuit to be formed is 30 μm / 30 μm or more. It is a serious problem in circuit formation. This is because such a high-density circuit line width is affected by irregularities on the substrate surface.
Therefore, in order to form a circuit having a line / space value of 25 μm / 25 μm or less, a circuit forming technique on an insulating substrate having a smooth surface is required, and its flatness is 1 μm or less in terms of Rz value, and further 0.5 μm. The following is preferred. Naturally, in this case, the adhesive force due to the anchor effect is weakened, and it is necessary to develop another adhesive method.
The second problem of the semi-additive method lies in its etching process. Since the electroless copper plating layer used as a power supply layer for electroplating is an unnecessary layer for a circuit, it must be removed by etching after forming the electroplating layer. However, when the electroless plated copper layer (first metal film) is removed by etching, the electroplated layer (second metal film) is also etched, and the width and thickness of the circuit pattern are reduced. It is difficult to manufacture well. In particular, when the surface of the insulating substrate has large irregularities, metal such as electroless copper plating remains in the concaves of the irregularities. Therefore, it is necessary to take a sufficient etching time to completely remove the metal, which should be etched. The metal (the second metal film) that forms a non-circuit is etched more than necessary, and the width of the circuit pattern is reduced, the cross-sectional shape of the circuit is deformed, and in severe cases, the circuit pattern is broken.
Also, as a third problem, since the plating catalyst tends to remain on the surface of the polymer film, the insulating property of the obtained printed wiring board tends to decrease, and further, when nickel plating or gold plating is performed on the circuit in the final step, Another effect is that nickel and gold are plated on the surface of the polymer film by the action of these remaining plating catalysts, and a circuit cannot be formed.
Therefore, the plating catalyst on the surface of the polymer film is simultaneously removed by etching away the first metal film using an etching solution having a high etching ability.
However, when the electroless copper plating layer is removed by etching using this etching solution having a high etching ability, the circuit is excessively etched, and the same problem as described above occurs.
On the other hand, conventionally, a method for manufacturing a multilayer printed wiring board includes a plurality of wiring boards (inner circuit boards) on which a circuit pattern is formed, and a plurality of prepregs obtained by impregnating a glass cloth with an epoxy resin and forming a B stage. A method is known in which sheets (insulating adhesive layers) are alternately laminated, pressed, heated and pressed, and then through-holes are formed to allow electrical connection between wiring boards. However, in this method, since heating and pressure molding are performed, a long time is required for the production and large-scale equipment is required, so that the production cost is increased. In addition, since a glass cloth having a relatively high dielectric constant is used for the prepreg sheet, there is a problem in that there is a limitation in reducing the thickness of the prepreg sheet and there is a concern about insulation properties.
In order to solve the above-mentioned problem, a method of manufacturing a build-up type multilayer printed wiring board in which an organic insulating layer and a metal layer having a circuit pattern are sequentially laminated on a metal layer of an inner circuit board has recently been proposed. Is attracting attention.
For example, JP-A-7-202418 and JP-A-7-202426 disclose a method in which a copper foil with an adhesive is attached (laminated) to an inner layer circuit board and the adhesive is cured. JP-A-6-108016 discloses a method using an adhesive film containing a plating catalyst in an additive method. JP-A-7-304933 discloses a method using an adhesive layer formed on an inner circuit board. Discloses a method for forming a metal layer by electroless plating or electrolytic copper plating.
Further, Japanese Patent Application Laid-Open No. 9-296156 discloses that a thin metal layer having a thickness of 0.05 to 5 μm is formed on an adhesive film layer having thermal fluidity by a vacuum evaporation method, a sputtering method, or an ion plating method. A method for manufacturing a multilayer printed wiring board using an interlayer adhesive film for a multilayer printed wiring board is disclosed.
However, the above-mentioned conventional method has the following problems. That is, in the methods disclosed in JP-A-7-202418 and JP-A-7-202426, there is a restriction on the thinning of the copper foil in order to maintain the strength because the copper foil is used, When plating through holes, the thickness of the copper foil further increases. Therefore, it has a problem that it is not suitable for manufacturing a multilayer printed wiring board on which a fine pattern (fine circuit pattern) is formed. According to the methods disclosed in JP-A-6-108016 and JP-A-7-304933, in order to form a metal layer having excellent adhesion that can withstand practical use, an adhesive layer is required as a preceding step. Requires a step of roughening the surface. However, the process is difficult to manage. In addition, since the interface between the metal layer and the adhesive layer is not smooth and the adhesive layer contains an organic or inorganic roughening component, various physical properties required for the insulating adhesive layer, such as heat resistance and electric characteristics, are not obtained. It has problems such as difficulty in satisfying.
Furthermore, in the method disclosed in Japanese Patent Application Laid-Open No. 9-296156, since a single-layer adhesive film having thermal fluidity is used as the insulating layer, the thickness of the layer can be controlled to be thin and uniform. There is a problem that it is difficult.
In other words, in the above-mentioned conventional method, there are restrictions on the thinning of the metal layer, problems with the adhesion of the metal layer, or problems with the thinning and uniformity of the insulating layer. In particular, it is difficult to manufacture a multilayer printed wiring board having a circuit pattern formed by a semi-additive method.
Disclosure of the invention
The present invention has been made to solve the above problems, and an object of the present invention is to provide a method for manufacturing a printed wiring board by a semi-additive method, in which a polymer film having excellent surface smoothness is solidified. To form a fine metal circuit layer adhered to the substrate. Furthermore, such fine metal wiring can be formed while minimizing the deterioration of the circuit shape in the etching step, and the power supply electrode layer can be removed in the etching step, so that the insulation properties between the layers can be reduced. It is an object of the present invention to provide a method for manufacturing a printed wiring board which can ensure the above.
Another object of the present invention is, for example, a method capable of easily and inexpensively manufacturing a multilayer printed wiring board having a fine pattern, particularly a circuit pattern formed by a semi-additive method, and a method obtained by the method. For example, it is an object of the present invention to provide a multilayer printed wiring board of a build-up type and an interlayer adhesive film for a multilayer printed wiring board which is suitably used for the multilayer printed wiring board and has excellent adhesion between an insulating layer and a metal layer.
That is, the first laminate of the present invention relates to a laminate having a metal layer A having a thickness of 1000 nm or less on at least one surface of a polymer film.
The second laminate of the present invention relates to a laminate having a metal layer A having a thickness of 1000 nm or less on one surface of a polymer film and an adhesive layer on the other surface.
The third laminate of the present invention relates to the first or second laminate, wherein the metal layer A is formed by a dry plating method.
The fourth laminate of the present invention relates to the laminate in which the metal layer A is copper or a copper alloy formed by an ion plating method in the first or second laminate.
In the fifth laminate of the present invention, in the first or second laminate, the metal layer A includes a metal layer A1 in contact with the polymer film and a metal layer A2 formed on the metal layer A1. And a laminate having the same.
The sixth laminate of the present invention relates to the fifth laminate, wherein the metal layer A1 has a thickness of 2 to 200 nm.
The seventh laminate of the present invention relates to the fifth laminate, wherein the thickness of the metal layer A2 is 10 to 300 nm.
The eighth laminate of the present invention relates to the fifth laminate, wherein the metal layers A1 and A2 are made of copper or a copper alloy formed by two different physical methods.
The ninth laminate of the present invention relates to the eighth laminate, wherein the metal layer A1 in contact with the polymer film is copper or a copper alloy formed by an ion plating method.
The tenth laminate of the present invention relates to the eighth laminate, wherein the metal layer A2 is copper or a copper alloy formed by a sputtering method.
The eleventh laminate of the present invention relates to the fifth laminate, wherein the metal layer A1 and the metal layer A2 are made of two kinds of different metals.
The twelfth laminate of the present invention relates to the eleventh laminate, wherein the metal layer A1 is made of nickel or an alloy thereof, and the metal layer A2 is made of copper or an alloy thereof.
The thirteenth laminate of the present invention relates to the eleventh laminate, wherein the metal layer A is formed by a sputtering method.
The fourteenth laminate of the present invention relates to the eleventh laminate, in which an oxide layer does not exist at the interface between the metal layer A1 and the metal layer A2.
The fifteenth laminate of the present invention relates to the first or second laminate, wherein the 10-point average roughness of the polymer film surface is 3 μm or less.
The sixteenth laminate of the present invention relates to the first or second laminate, wherein the dielectric constant of the polymer film surface is 3.5 or less and the dielectric loss tangent is 0.02 or less.
The seventeenth laminate of the present invention relates to the first or second laminate, wherein the polymer film contains a non-thermoplastic polyimide resin component.
The eighteenth laminate of the present invention relates to the laminate of the second laminate, wherein the adhesive layer is made of an adhesive containing a thermoplastic polyimide resin.
The nineteenth laminate of the present invention relates to the laminate of the second laminate, wherein the adhesive layer is made of a polyimide resin and a thermosetting resin.
The twentieth laminate of the present invention relates to the first or second laminate, which has a protective film on the metal layer A.
The twenty-first laminate of the present invention relates to the first or second laminate, wherein the peel strength of the metal layer A is 5 N / cm or more.
A first method for manufacturing a printed wiring board according to the present invention is a method for manufacturing a printed wiring board, wherein a printed wiring board having a pattern formed by a first metal film and a second metal film formed on a polymer film is formed by a semi-additive method. The present invention relates to a method for manufacturing a printed wiring board, characterized by using an etchant having an etching rate for the first metal film that is 10 times or more the etching rate for the second metal film.
In a second method for manufacturing a printed wiring board according to the present invention, in the first method for manufacturing a printed wiring board, the first metal film is at least one selected from the group consisting of nickel, chromium, titanium, aluminum and tin. The present invention relates to a method for manufacturing a printed wiring board, wherein the second metal film is copper or an alloy thereof.
The first method for manufacturing a printed wiring board of the present invention relates to a method for manufacturing a printed wiring board for forming a circuit using the first or second laminate.
The second method of manufacturing a printed wiring board according to the present invention relates to a method of manufacturing a printed wiring board in which a through hole is formed in a first laminate and then electroless plating is performed.
A third method of manufacturing a printed wiring board according to the present invention is directed to a method of manufacturing a printed wiring board, comprising: attaching a conductive foil to an adhesive layer of a laminate according to claim 2; forming a through hole; and performing electroless plating. It relates to a manufacturing method.
According to the fourth method of manufacturing a multilayer printed wiring board of the present invention, the adhesive layer of the second laminate is opposed to the circuit surface of the inner wiring board on which the circuit pattern is formed, and involves heating and / or pressing. The present invention relates to a method for manufacturing a multilayer printed wiring board in which a laminate is laminated with an inner wiring board by a method.
The method for manufacturing a multilayer printed wiring board according to the fifth aspect of the present invention is the method for manufacturing a multilayer printed wiring board according to the fourth aspect, further comprising: a drilling step from a surface of the metal layer A of the laminate to an electrode of the inner wiring board; The present invention relates to a method for manufacturing a multilayer printed wiring board including a panel plating step by electroless plating.
The sixth method for manufacturing a multilayer printed wiring board according to the present invention is the second, third or fifth method for manufacturing a multilayer printed wiring board, further comprising forming a through hole, and further including a desmear process. The present invention relates to a method for manufacturing a plate.
The seventh method of manufacturing a multilayer printed wiring board according to the present invention relates to the method of manufacturing a sixth multilayer printed wiring board, wherein the desmear processing is dry desmear processing.
The eighth method for manufacturing a multilayer printed wiring board according to the present invention is the method for manufacturing a multilayer printed wiring board according to the fifth aspect, further comprising: a resist pattern forming step using a photosensitive plating resist; a circuit pattern forming step using electroplating; The present invention relates to a method for manufacturing a multilayer printed wiring board, comprising a step of removing an electroless plating layer and a metal layer A exposed by stripping a resist pattern by etching.
A ninth multilayer printed wiring board manufacturing method according to the present invention relates to the eighth multilayer printed wiring board manufacturing method, wherein the resist pattern forming step is performed using a dry film resist.
The tenth method for manufacturing a multilayer printed wiring board according to the present invention is the method for manufacturing a multilayer printed wiring board according to the fourth method for manufacturing a multilayer printed wiring board, wherein the laminate and the inner layer wiring board are laminated under reduced pressure of 10 kPa or less. About.
An eleventh multilayer printed wiring board manufacturing method according to the present invention relates to the fifth multilayer printed wiring board manufacturing method, wherein the drilling step is performed by a laser drilling device.
The twelfth multilayer printed wiring board manufacturing method according to the present invention is the eighth multilayer printed wiring board manufacturing method according to the eighth embodiment, wherein the electroless plating layer and the metal layer A exposed by peeling off the resist pattern by electroplating used for forming the circuit. The present invention relates to a method for producing a multilayer printed wiring board using an electroless plating and an etching solution that makes the etching thickness of the electroplated layer per unit time necessary for removing the metal layer A smaller than the sum of the thicknesses of the metal layers A.
BEST MODE FOR CARRYING OUT THE INVENTION
The laminate of the present invention has a metal layer A having a thickness of 1000 nm or less on at least one surface of the polymer film.
Further, the laminate of the present invention may have a metal layer A formed by dry plating on one surface of the polymer film and an adhesive layer on the other surface. The laminate having such a configuration is suitable for manufacturing a multilayer printed wiring board by laminating an adhesive layer on an inner substrate on which a circuit is formed so as to face the laminate.
Hereinafter, the polymer film, the metal layer A, and the adhesive layer constituting the laminate of the present invention will be described in detail.
<Polymer film>
The polymer film used in the present invention has a 10-point average roughness (Rz) of the surface of preferably 3 μm or less, more preferably 1 μm or less, and particularly preferably 0.5 μm or less. Of course, the present invention can be effectively applied to a polymer film having an Rz value of 3 μm or less, but there is a problem that it becomes difficult to remove a supply electrode in an etching process in a semi-additive process. In other words, in order to completely remove the supply electrode, it is necessary to remove the supply electrode adhered to the inside of the surface irregularities. The etched circuit pattern layer is also etched. Therefore, the circuit width and thickness become smaller than the design values, and in extreme cases, the circuit may even disappear. The smooth surface is suitable for forming a high-density circuit having a line / space of 25 μm / 25 μm or less, and is also preferable from the viewpoint that no etching residue remains on the unevenness of the resin surface in the etching step. Rz is defined in a standard relating to the surface shape such as JIS B0601, and a stylus type surface roughness meter of JIS B0651 or a light wave interference type surface roughness meter of B0652 can be used for the measurement. In the present invention, a 10-point average roughness of a polymer film is measured using a light interference type surface roughness meter NewView5030 system manufactured by ZYGO.
The dielectric constant of the polymer film is preferably 3.5 or less, more preferably 3.2 or less, particularly preferably 3.0 or less, and the dielectric loss tangent is preferably 0.02 or less, more preferably 0.015 or less. The value is particularly preferably 0.01 or less. This is required from the viewpoint of increasing the frequency and speed of the transmission signal and reducing transmission loss. The dielectric characteristics have frequency dependence, and the present invention considers the dielectric constant and the dielectric loss tangent in a high frequency band from a MHz band to a GHz band. Various methods have been proposed as measurement methods, but the cavity resonator method is superior in terms of measurement stability and reproducibility. In the present invention, measurement is performed at a measurement frequency of 12.5 GHz using a MOA2012 (manufactured by KS Systems) using a cavity resonator method.
The thickness of the polymer film is preferably 5 to 125 µm, more preferably 10 to 50 µm, and particularly preferably 10 to 25 µm. If the thickness is smaller than this range, the rigidity of the laminated body is insufficient, handling becomes poor, and problems such as poor electrical insulation between layers arise. On the other hand, if the film is too thick, it not only goes against the trend of thinning the printed wiring board, but also when controlling the characteristic impedance of the circuit, it is necessary to widen the circuit width when the insulating layer thickness is large, which means that It is not acceptable due to the demand for smaller and higher density printed wiring boards.
As the polymer film used in the present invention, an insulating plate, sheet or film is used. For example, thermosetting resins such as epoxy resin, phenol resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene ether resin, and polyphenylene sulfide can be used. In addition, a polyester resin, a cyanate ester resin, a benzocyclobutene, a liquid crystal polymer and the like are effectively used. In addition, a board, a sheet, a film, and the like, in which a board in which an inorganic filler such as glass is blended with a resin, a cloth of inorganic fibers such as glass, or an organic fiber such as polyester, polyamide, and cotton, and a paper or the like, which is bonded with the resin, are used. Can also be used effectively. Among these, from the viewpoint of heat resistance, chemical resistance, flexibility, dimensional stability, dielectric constant, electrical properties, workability, price, etc., polyimide resin-based or epoxy resin-based or a blend thereof is preferable, and polyimide Film is most preferred.
The inside of the polymer film may have a conductor circuit, a through hole, and the like. In addition, in order to improve the peel strength with the metal layer A, the surface of the polymer film is subjected to a known treatment such as a roughening treatment, a corona discharge treatment, a plasma treatment, a flame treatment, a heating treatment, a primer treatment, and an ion bombardment treatment. May be subjected to various surface treatments. Usually, if the polymer film is exposed to the atmosphere after these treatments, the modified surface may be deactivated and the treatment effect may be greatly reduced. It is preferable to provide the metal layer A continuously in the inside. It is also effective and preferable to add a known adhesion-imparting agent to the resin constituting the polymer film or perform a surface treatment.
Here, the case where polyimide is used as the polymer film will be described in detail.
The polyimide film is not particularly limited, and polyimide films manufactured by various known methods can be used. For example, a polyimide film is obtained by forming a polyamic acid film (hereinafter referred to as a gel film) partially imidized or partially dried to a degree having self-supporting property from a polyamic acid polymer solution, and then forming the gel film. Is heated to completely imidize the polyamic acid. The polyamic acid polymer solution uses substantially equimolar amounts of a tetracarboxylic dianhydride component composed of at least one type of tetracarboxylic dianhydride and a diamine component composed of at least one type of diamine. It is obtained by polymerization in a solvent. The obtained polyimide film does not have thermal fluidity.
Examples of tetracarboxylic dianhydride suitable for obtaining a polyamic acid polymer for producing a polyimide film include, for example, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone Carboxylic acid dianhydride, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalene Tetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,3 ', 4,4'-dimethyldiphenylsilanetetracarboxylic dianhydride, 3,3', 4,4'-tetraphenylsilane Tetracarboxylic dianhydride, 2,3,4,5-furan tetracarboxylic dianhydride, 4,4′-bis (3,4-dicarboxyphenoxy) diphenylpropane dianhydride, 4, '-Hexafluoroisopropylidene diphthalic anhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride, p- Examples include aromatic tetracarboxylic dianhydrides such as phenylenediphthalic anhydride and p-phenylenebis (trimellitic acid monoester anhydride), but are not particularly limited thereto. One of these tetracarboxylic dianhydrides may be used alone, or two or more thereof may be used in combination. Among the tetracarboxylic dianhydrides exemplified above, pyromellitic dianhydride and p-phenylene bis (trimellitic acid monoester anhydride) are used in an optional ratio, that is, tetracarboxylic dianhydride It is more preferable to use these tetracarboxylic dianhydrides as components at an arbitrary ratio.
As the diamine suitable for obtaining a polyamic acid polymer for producing a polyimide film, specifically, for example, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 2,2-bis (4- Aminophenoxyphenyl) propane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, bis {4- ( 4-aminophenoxy) phenyl} sulfone, bis {4- (3-aminophenoxy) phenyl} sulfone, 4,4′-bis (4-aminophenoxy) biphenyl, 2,2-bis {4- (4-aminophenoxy) ) Phenyl @ hexafluoropropane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenyl Sulfone, 9,9-bis (4-aminophenyl) fluorene, bisaminophenoxyketone, 4,4 '-{1,4-phenylenebis (1-methylethylidene)} bisaniline, 4,4'-{1,3 -Phenylenebis (1-methylethylidene)｝ bisaniline, m-phenylenediamine, p-phenylenediamine, 4,4′-diaminobenzanilide, 3,3′-dimethyl-4,4′-diaminobiphenyl, 3,3 ′ Examples include aromatic diamines such as -dimethoxy-4,4'-diaminobiphenyl, 3,3'-dimethylbenzidine, and 3,3'-dihydroxybenzidine, or aliphatic diamines, but are not particularly limited. These diamines may be used alone or in combination of two or more. Of the above-described diamines, p-phenylenediamine, 4,4′-diaminobenzanilide, and 4,4′-diaminodiphenyl ether are used in an arbitrary ratio, that is, these diamines are optionally used as a diamine component. It is more preferable to use them together in the ratio of
Specific combinations and compounding ratios when using two or more kinds of tetracarboxylic dianhydrides, specific combinations and mixing ratios when using two or more kinds of diamines, and tetracarboxylic dianhydride component The specific combination of and the diamine component is not particularly limited. In other words, the above-described examples are preferred examples, and these combinations and compounding ratios may be selected so as to be optimal according to the desired characteristics of the polyimide film.
Specific examples of the organic polar solvent suitable for obtaining a polyamic acid polymer for producing a polyimide film include, for example, sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide; N, N-dimethylformamide, N, N- Formamide solvents such as diethylformamide; acetamide solvents such as N, N-dimethylacetamide and N, N-diethylacetamide; pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; phenol; Phenolic solvents such as o-cresol, m-cresol, p-cresol, xylenol, halogenated phenol, catechol; hexamethylphosphoramide, γ-butyrolactone, dioxolane and the like. These organic polar solvents may be used alone, or two or more of them may be appropriately mixed and used. Further, an aromatic hydrocarbon such as toluene or xylene may be used as a mixture with an organic polar solvent as long as polymerization is not hindered.
The addition method (order) and polymerization method when adding the tetracarboxylic dianhydride component and the diamine component to the organic polar solvent are not particularly limited, and various known methods can be employed. For example, a polyamic acid polymer solution may be obtained by gradually adding and polymerizing a tetracarboxylic dianhydride component to an organic polar solvent in which a diamine component is dissolved, and a tetracarboxylic dianhydride component and a diamine component may be obtained. A polyamic acid polymer solution may be obtained by simultaneously adding to an organic polar solvent and polymerizing, and a polyamic acid is obtained by alternately adding a tetracarboxylic dianhydride component and a diamine component to an organic polar solvent and polymerizing. A polymer solution may be obtained. The polymerization conditions are not particularly limited. When two or more kinds of tetracarboxylic dianhydrides and / or diamines are used in combination, that is, when three or more kinds of monomers are copolymerized, the polyamide obtained by appropriately changing the order of addition of each monomer is used. The molecular structure of the acid polymer (the sequence of the monomers) can be controlled. Examples of the polymerization method for copolymerizing three or more types of monomers include random copolymerization, block copolymerization, partial block copolymerization, and sequential copolymerization.
Also, when obtaining a polyamic acid polymer solution, before polymerization, during polymerization, at any stage after polymerization, that is, at any time until the gel film forming step, foreign matter and high molecular weight in the solution An operation such as filtration may be performed to remove substances and the like. Further, in order to shorten the time required for the polymerization step, the polymerization step is performed by a first polymerization step of obtaining a so-called prepolymer having a low degree of polymerization, and a second polymerization step of obtaining a high-molecular-weight polyamic acid polymer having a higher degree of polymerization. And the polymerization step. In particular, in order to improve the polymerization efficiency and the filtration efficiency, it is more preferable to perform an operation such as filtration at the stage of the prepolymer obtained in the first polymerization step, and then perform the second polymerization step.
Further, at any time before performing the step of forming a gel film, by adding various organic additives, inorganic fillers, or various reinforcing materials to the polyamic acid polymer solution, a composite polyimide film is formed. It is also possible to manufacture.
The proportion (concentration) of the polyamic acid polymer in the solution is not particularly limited, but is preferably in the range of 5 to 40% by weight, more preferably in the range of 10 to 30% by weight from the viewpoint of handling. Is more preferred.
The average molecular weight of the polyamic acid polymer is preferably in the range of 10,000 to 1,000,000. If the average molecular weight is less than 10,000, the resulting polyimide film may be brittle. On the other hand, if the average molecular weight exceeds 1,000,000, the viscosity of the polyamic acid polymer solution may be too high, and handling may be difficult.
The method for forming a gel film from the polyamic acid polymer solution obtained by the above method and the method for producing a polyimide film from the gel film are not particularly limited. Therefore, a polyimide film can be manufactured by various known methods. Specifically, for example, a polyamic acid polymer solution is cast and coated on a support such as a glass plate or a stainless steel belt to form a gel film, and then the polyimide film is heated by heating the gel film. Obtainable. When heating the gel film, the gel film may be peeled off from the support, and its end may be fixed using a pin or a clip.
Examples of the method for imidizing the polyamic acid polymer include a so-called chemical curing method and a thermal curing method.In consideration of the productivity of the polyimide film and the physical properties desired for the polyimide film, the chemical curing method, or the chemical curing method is used. A method using a combination of a curing method and a heat curing method is more preferable. When employing the chemical curing method, at any time before performing the step of forming a gel film, the polyamic acid polymer solution, a dehydrating agent and a catalyst that promote the imidization reaction, and a solvent such as an organic polar solvent Is added, and the mixture is mixed and stirred.
Since the gel film is located in the middle of drying, it contains a solvent such as an organic polar solvent. The volatile component content (solvent content) of the gel film is calculated from the following equation (1).
Volatile component content (% by weight) = {(AB) / B} × 100 (1)
(In the formula (1), A represents the weight of the gel film, and B represents the weight after heating the gel film at 450 ° C. for 20 minutes.)
The volatile component content is preferably in the range of 5 to 300% by weight, more preferably in the range of 5 to 100% by weight, and still more preferably in the range of 5 to 50% by weight.
In addition, the gel film is located in the middle of the imidization reaction from the polyamic acid polymer to the polyimide, the imidation rate indicating the degree of progress of the reaction, based on the measurement results using infrared absorption spectroscopy, It is calculated from equation (2).
Imidation ratio (%) = {(C / D) / (E / F)} × 100 (2)
(In the formula (2), C is 1370 cm of the gel film.^-1Absorption peak height of D is 1500 cm of gel film^-1E is 1370 cm of the polyimide film^-1Absorption peak height, F is 1500 cm of polyimide film^-1Shows the absorption peak height. )
The imidation ratio is preferably 50% or more, more preferably 70% or more, further preferably 80% or more, and most preferably 85% or more.
According to the above method, the thickness of the polyimide film can be controlled to be thin and uniform. The polyimide film obtained by the above method may be subjected to various treatments such as known surface treatment and post-treatment, if necessary. As the treatment, specifically, for example, emboss treatment, sand blast treatment, corona discharge treatment, plasma discharge treatment, electron beam irradiation treatment, UV treatment, heat treatment, flame treatment, solvent cleaning treatment, primer treatment, chemical etching treatment And the like. These processes may be performed in combination as necessary. Further, after performing one or more of the above treatments on a gel film, a polyimide film can be produced from the gel film.
In particular, in order to further improve the adhesion between the polyimide film and the metal layer or the adhesive layer, the gel film is made of Al, Si, Ti, Mn, Fe, Co, Cu, Zn, Sn, Sb, Pb, Bi, Pd After immersing in a solution of a compound containing at least one element selected from the group consisting of (hereinafter, referred to as an element group) or applying the solution to a gel film, the gel film is completely dried and It is more preferable to perform a treatment for imidizing the polyamic acid polymer. Among the above elements, Si and Ti are more preferable.
Examples of the compound containing the element group include an inorganic compound and an organic compound. Examples of the inorganic compound include halides such as chlorides and bromides, oxides, hydroxides, carbonates, nitrates, nitrites, phosphates, sulfates, silicates, borates, condensed phosphates, and the like. Is mentioned. Examples of the organic compound include neutral molecules such as alkoxide, acylate, chelate, diamine and diphosphine; ionic molecules having acetylacetonate ion, carboxylate ion, dithiocarbamate ion and the like; cyclic ligands such as porphyrin; Complex salts and the like. Among the compounds exemplified above, alkoxides, acylates, chelates, and metal complexes are more preferable, and these compounds containing Si and Ti are more preferable.
Specific examples of the compound containing Si (silicon compound) include, for example, NB (aminoethyl) -γ-aminopropyltrimethoxysilane, N-β (aminoethyl) -γ-aminopropylmethyldimethoxysilane, Aminosilane compounds such as N-phenyl-γ-aminopropyltrimethoxysilane and γ-aminopropyltriethoxysilane; β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane And epoxysilane-based compounds such as γ-glycidoxypropylmethyldimethoxysilane; and the like, but are not particularly limited thereto.
As the compound containing Ti (titanium compound), the following formula (I)
(R¹O)_m-Ti- (OX)_4-m      (I)
(Wherein, m is an integer of 0 or more and 4 or less;¹Independently represents a hydrogen atom or a hydrocarbon residue having 3 to 18 carbon atoms;

Or a residue containing a carboxylic acid having 3 to 18 carbon atoms or an ammonium salt thereof,²Represents a hydrocarbon residue having 3 to 18 carbon atoms;³Represents a hydrocarbon residue having 3 to 18 carbon atoms;⁴Represents a hydrocarbon residue having 3 to 18 carbon atoms;⁵, R⁶Independently represents a hydrocarbon residue having 3 to 18 carbon atoms;⁷Is a hydrocarbon residue having 3 to 18 carbon atoms, or

And R⁸Represents a hydrocarbon residue having 2 to 18 carbon atoms)
The compound represented by is more preferable, but is not particularly limited. Specific examples of the compound represented by the formula (I) include, for example, tri-n-butoxytitanium monostearate, diisopropoxytitanium bis (triethanolaminate), butyl titanate dimer, and tetra-n-butyl titanate , Tetra (2-ethylhexyl) titanate, titanium octylene glycolate, dihydroxybis (ammonium lactate) titanium, dihydroxytitanium bislactate and the like. Among the compounds exemplified above, tri-n-butoxytitanium monostearate and dihydroxytitanium bislactate are particularly preferred.
As a solvent suitable for preparing a solution of the compound, specifically, for example, water, toluene, xylene, tetrahydrofuran, 2-propanol, 1-butanol, ethyl acetate, N, N-dimethylformamide, acetylacetone and the like However, the solvent is not particularly limited, and may be any solvent that can dissolve the compound. One of these solvents may be used alone, or two or more of them may be appropriately mixed and used. Among the solvents exemplified above, water, 2-propanol, 1-butanol and N, N-dimethylformamide are particularly preferred. A chemical curing agent may be further added to the solution of the compound.
The concentration of the element group in the solution is more preferably in the range of 1 to 100,000 ppm, and further preferably in the range of 10 to 50,000 ppm. Therefore, the concentration of the compound containing the element group in the solution depends on the type (molecular weight) of the compound, but is generally preferably 0.001 to 100% by weight, more preferably 0.01 to 10% by weight, particularly preferably 0.01 to 10% by weight. Preferably it is 0.1 to 5% by weight.
By immersing the gel film in the solution of the compound, or after applying the solution to the gel film, by removing excess droplets attached to the surface of the gel film, the adhesiveness is further improved, and An excellent polyimide film having an appearance with no unevenness on the surface can be obtained. As a method for removing the droplet, for example, a known method using a nip roll, an air knife, a doctor blade, or the like can be used. Among these, a method using a nip roll is more preferable from the viewpoints of drainage property, workability, and appearance of the obtained polyimide film.
The thickness of the polyimide film in the present invention is not particularly limited, but is more preferably in the range of 5 to 125 μm, and particularly in the range of 10 to 75 μm as a multilayer printed wiring board application. More preferably, it is particularly preferably within the range of 10 to 50 μm. The tensile modulus of the polyimide film is preferably 4 GPa or more, more preferably 6 GPa or more, and even more preferably 10 GPa or more. The linear expansion coefficient of the polyimide film is preferably 17 ppm or less, more preferably 12 ppm or less, and even more preferably 10 ppm or less. The water absorption of the polyimide film is preferably 2% or less, more preferably 1.5% or less, and even more preferably 1% or less.
<Metal layer A>
Next, the metal layer A according to the present invention will be described. The metal layer A is formed on at least one surface of the polymer film, and has a function of firmly adhering to the electroless plating layer when electroless plating is formed by a panel plating process. ing. At this time, it is needless to say that the polymer film and the metal layer A need to be firmly bonded.
As a method for forming the metal layer A, a dry plating method is preferable. Dry plating is preferred because it is not necessary to apply a plating catalyst to the polymer film to form the metal layer A, and the plating catalyst does not remain on the polymer film. For example, even when performing electroless plating, an electroless plating catalyst is present on the metal layer A, and in the subsequent etching step, the catalyst is washed away together with the metal layer A. As compared with a case where an electroplating catalyst is applied and electroless plating is performed, a material having excellent electrical insulation properties can be obtained. Also, unlike the wet electroless plating, it is not necessary to perform a surface roughening treatment (desmear treatment) to improve the adhesion, and the interface between the metal film and the insulating substrate becomes smooth, thereby forming a circuit at a narrow interval and improving electrical characteristics. Have a good effect. As a method for forming the metal layer A by the dry plating method, a vacuum evaporation method, a sputtering method, an ion plating method, a CVD method, or the like can be applied.
Among these, a metal layer formed by a physical vapor deposition method is preferable in that good adhesiveness can be obtained. Here, the physical vapor deposition method includes resistance heating vapor deposition, EB vapor deposition, cluster ion beam vapor deposition, ion plating vapor deposition, etc. as a vacuum vapor deposition method, and RF sputtering, DC sputtering, magnetron sputtering, ion beam vaporization as a sputtering method. Sputtering and the like can be given, and all of them can be applied to the present invention, including a method combining these.
Further, among these, the sputtering method is preferable from the viewpoint of the adhesion strength between the polymer film and the metal layer A, the simplicity of equipment, the productivity, the cost, and the like, and DC sputtering is particularly preferable. In addition, ion plating deposition can be preferably used because it has a high film-forming speed, is industrially advantageous, and has good adhesion.
In particular, a case where sputtering is used will be described in detail. A known method can be applied to sputtering. That is, DC magnetron sputtering, RF sputtering, or those obtained by variously improving these methods can be appropriately applied according to the respective requirements. For example, DC magnetron sputtering is preferable for efficiently sputtering a conductor such as nickel or copper. On the other hand, when sputtering is performed in a high vacuum for the purpose of preventing a sputtering gas from being mixed in a thin film, RF sputtering is suitable.
Describing DC magnetron sputtering in detail, first, a polymer film is set in a vacuum chamber as a substrate, and vacuum is evacuated. Usually 6 × 10 by combining a rough pump with a rotary pump and a diffusion pump or a cryopump or a turbo pump.^-4Vacuum to Pa or less. Next, a sputtering gas is introduced, the inside of the chamber is set to a pressure of 0.1 to 10 Pa, preferably 0.1 to 1 Pa, and a DC voltage is applied to the metal target to cause plasma discharge. At this time, a magnetic field is formed on the target, and the generated plasma is confined within the magnetic field, thereby increasing the efficiency of sputtering the plasma particles on the target. The surface oxide layer of the metal target is removed by holding the polymer film in a state where the plasma is generated for several minutes to several hours while preventing the polymer film from being affected by plasma or sputtering (referred to as pre-sputtering). After the pre-sputtering, the polymer film is sputtered by opening a shutter or the like. The discharge power during sputtering is preferably in the range of 100 to 1000 watts. Further, batch-type sputtering or roll sputtering is applied according to the shape of the sample to be sputtered. As the introduced sputtering gas, an inert gas such as argon is usually used, but a mixed gas containing a small amount of oxygen or another gas can also be used.
As the kind of metal used for the metal layer A, the adhesion strength between the polymer film and a circuit pattern formed on the metal layer A in a later manufacturing process of the wiring board is high, and the printed wiring board of the present invention is used. It is important that the metal species be able to be removed cleanly in the etching step in the manufacturing method of (1).
For example, metals such as copper, nickel, chromium, titanium, nichrome, molybdenum, tungsten, zinc, tin, indium and aluminum or alloys thereof can be used, and the metal layer A is composed of a single layer or two or more layers. It is also possible.
In one embodiment of the metal layer A according to the present invention, copper is suitable as the metal material forming the metal layer A, but at least one selected from the group consisting of nickel, chromium, silver, aluminum, titanium and silicon. Metal and copper. That is, the metal layer A may be composed of (i) copper, or (ii) an alloy (composite) containing at least one metal selected from the group and copper, iii) It may have a two-layer structure of a layer made of at least one metal selected from the above group and a layer made of copper.
The thickness of the metal layer A may be set as needed, but is not more than 1000 nm, but is preferably in the range of 2 to 1000 nm, more preferably 2 to 500 nm. When the thickness of the metal layer A is set to less than 2 nm, a stable peel strength tends to not be obtained. If the thickness of the metal layer is set to be thicker than 1000 nm, it is not suitable for manufacturing a multilayer printed wiring board on which a fine pattern is formed, as in the case of the conventional copper foil with an adhesive. In particular, when manufacturing a multilayer printed wiring board on which a circuit pattern is formed by the semi-additive method, it is most preferable to set the thickness of the metal layer to 1000 nm or less.
In another embodiment of the metal layer A in the present invention, the metal layer A has a two-layer structure composed of two types of metal layers, and the thickness of each layer is controlled to an appropriate thickness. Here, the metal layer formed directly on the polymer film is referred to as a metal layer A1, and the metal layer formed thereon is referred to as a metal layer A2. By being composed of two types of metal layers, it is possible to improve etching characteristics, adhesion to a polymer film, peeling strength from an electroless plating film or an electroplating film, and the like. That is, for the metal layer A1 formed directly on the polymer film, a metal effective to maintain good adhesion to the polymer film is selected. On the other hand, for the metal layer A2 formed thereon, it is effective to select a metal that can firmly adhere to an electroplating layer formed directly on A2 or an electroless plating layer formed by a panel plating process. is there.
As a metal used for the metal layer A1, copper, nickel, chromium, tin, titanium, aluminum and the like are preferable, and nickel is particularly preferable. The thickness of the metal layer A1 is preferably in the range of 2 to 200 nm, more preferably 3 to 100 nm, and particularly preferably 3 to 30 nm. If the thickness is less than 2 nm, sufficient adhesive strength cannot be obtained, which is not preferable. Further, it is difficult to form a uniform film on the polymer. On the other hand, if the thickness exceeds 200 nm, it is necessary to perform extra etching in the etching step when manufacturing a printed wiring board, so that the circuit thickness becomes smaller than the circuit design value, the circuit width becomes narrower, undercut, etc. Occurs, and the circuit shape is deteriorated. In addition, a problem such as peeling or curling of the film occurs due to a difference in dimensional change due to stress or temperature in the film between the film and the metal layer A2.
On the other hand, the metal used for the metal layer A2 should be determined according to the type of electroplating or electroless plating formed directly on A2 in the manufacturing process of the printed wiring board. Considering that copper plating and electroless nickel plating are preferred, and particularly preferred is electroless copper plating, the metal used for the metal layer A2 is preferably copper or nickel, and particularly preferably copper. The fact that the metal layer A2 contains the main component of the metal layer formed by electroless plating used in the manufacture of the printed wiring board is effective for the adhesive strength. The optimum thickness of the metal layer A2 is 10 to 300 nm, more preferably 20 to 200 nm, and preferably 50 to 150 nm. If it is less than 10 nm, it is difficult to maintain sufficient adhesiveness with the electroless plating layer formed in the next step. On the other hand, a thickness of 200 nm or more is not necessary, and is preferably 200 nm or less in consideration of a later etching process.
The thickness of the metal layer A including the metal layer A1 and the metal layer A2 is preferably 20 to 400 nm, more preferably 50 to 200 nm. In addition, it is preferable that the metal layer A1 formed directly on the polymer film is smaller than A2 in that the peel strength is increased. By setting the thickness in this range, it is possible to achieve both the etching characteristics when the semi-additive method is applied and the peel strength of the metal layer formed by electroless plating and / or electroplating. That is, if the metal layer is too thin, the peeling strength of the metal layer formed by electroless plating and electroplating is low, which causes pattern peeling. On the other hand, if the metal layer is too thick, it becomes necessary to perform extra etching in the etching step, the circuit is also etched largely when etching the space portion, the circuit thickness is smaller than the circuit design value, and the circuit width is narrow. The circuit shape deteriorates, for example, an undercut or the like occurs, or a sufficient cross-sectional area with respect to a designed circuit width cannot be obtained due to a collapse of a circuit cross-section which should be originally a rectangle. Deterioration of the circuit shape eventually causes the circuit to have a lower degree of conduction than the designed value, causing a malfunction of the circuit.
For example, when polyimide is used for the polymer film and electroless copper plating is used for the electroless plating, the thickness of the metal layer A1 is 10 to 100 nm, such as nickel, chromium, or a metal such as titanium or a main component thereof. When an alloy is used and copper or a copper alloy having a thickness of the metal layer A2 of 20 to 200 nm is used, and the total thickness of both metal layers is set to 30 to 200 nm, the rigidity of each is 6 N / cm or more. A thin film can be formed.
Even when two or more types of metal layers are stacked and formed, if an oxide layer is formed on each film surface, the adhesion between the respective metals is reduced. Therefore, dry plating can be continuously performed in a vacuum. preferable. In this case, the dry plating is preferably performed by vapor deposition or sputtering, and particularly preferably performed by DC sputtering.
In another embodiment of the metal layer A in the present invention, the metal layer A is a layer made of copper or a copper alloy formed by an ion plating method. According to this method as well, the adhesion strength to the circuit pattern formed on the metal layer A can be improved in the process of manufacturing the polymer film and the wiring board later.
It has been discovered that a copper thin film prepared by an ion plating method has excellent adhesiveness to a substrate and can realize strong adhesiveness even to a polymer film having excellent surface smoothness. The copper alloy referred to here is an alloy in which copper is a main component and another metal is added, and examples of the added metal include metals such as nickel, chromium, and titanium. In particular, it has been found that a strong copper thin film of 6 N / cm or more can be formed even on polyimide, which has been difficult by the conventional sputtering method.
In still another embodiment of the metal layer A in the present invention, the metal layer A has a two-layer structure composed of copper or a copper alloy layer formed by two or more different physical methods. Here, the copper alloy refers to an alloy containing copper as a main component, and examples of the added metal include nickel, chromium, and titanium.
As described above, the copper thin film produced by the ion plating method has excellent adhesiveness to a substrate, and can realize strong adhesiveness to a polymer film having excellent surface smoothness.
However, the copper and copper alloy thin film layers produced by the ion plating method alone are vulnerable to the chemical treatment process, and when the copper thin film is formed on the ion plating film by using the electroless plating process. , Peels off from the polymer film.
Therefore, we tried to form a copper thin film by sputtering on a copper thin film (metal layer A1) formed by ion plating. The sputtering method is not particularly limited, and methods such as DC magnetron sputtering, high-frequency magnetron sputtering, and ion beam sputtering can be effectively used.
The copper thin film formed by the ion plating method realizes strong adhesion to the polymer film, but this adhesiveness did not change even if the copper film was formed thereon by the sputtering method. Further, since the sputtered film is resistant to a chemical process, a plated film could be easily formed thereon by an electroless plating method. That is, it is considered that the sputtered film plays a role of protecting the ion plating film in the electroless plating process and a role of bonding with the electroless plating layer.
<Adhesive layer>
The type of the adhesive layer is not particularly limited, and a known resin applicable to the adhesive can be used. It can be broadly classified into (A) a heat-fusible adhesive using a thermoplastic resin and (B) a curable adhesive using a curing reaction of a thermosetting resin. These will be described below.
(A) Examples of the thermoplastic resin that imparts heat-fusibility to the adhesive include polyimide resin, polyamideimide resin, polyetherimide resin, polyamide resin, polyester resin, polycarbonate resin, polyketone resin, polysulfone resin, and polyphenylene ether resin. , Polyolefin resin, polyphenylene sulfide resin, fluorine resin, polyarylate resin, liquid crystal polymer resin and the like. These can be used alone or in an appropriate combination of two or more as the adhesive layer of the laminate of the present invention. Among them, it is preferable to use a thermoplastic polyimide resin from the viewpoint of excellent heat resistance, electric reliability and the like.
Here, a method for producing a thermoplastic polyimide resin will be described. The polyimide resin is obtained from a polyamic acid polymer solution that is a precursor thereof, and the polyamic acid polymer solution can be produced by a known method as described above. That is, it is obtained by using substantially equimolar amounts of the tetracarboxylic dianhydride component and the diamine component and polymerizing in an organic polar solvent.
The acid dianhydride used in this thermoplastic polyimide resin is not particularly limited as long as it is an acid dianhydride. Examples of the acid dianhydride component include butanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and 1,3-dimethyl-1,2,3,4-cyclobutanetetraanhydride. Carboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 2,3,5-tricarboxycyclopentylacetic dianhydride, 3,5,6-tricarboxynorbonane-2-acetic dianhydride Compound, 2,3,4,5-tetrahydrofurantetracarboxylic dianhydride, 5- (2,5-dioxotetrahydrofural) -3-methyl-3-cyclohexene-1,2-dicarboxylic dianhydride, bicyclo Aliphatic or alicyclic tetracarboxylic dianhydrides such as [2,2,2] -oct-7-ene-2,3,5,6-tetracarboxylic dianhydride; pyromellitic dianhydride; , 3 ', 4,4'-Benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride 2,3,6,7-naphthalenetetracarboxylic dianhydride, 4,4′-oxyphthalic anhydride, 3,3 ′, 4,4′-dimethyldiphenylsilanetetracarboxylic dianhydride, 3 ', 4,4'-tetraphenylsilanetetracarboxylic dianhydride, 1,2,3,4-furantetracarboxylic dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenyl Sulfide dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylsulfone dianhydride, 4,4'-bis (3,4-dicarboxyphenoxy) diphenylpropane 2 Hydrate, 4,4'-hexafluoroisopropylidene diphthalic anhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,3,3', 4'-biphenyltetracarboxylic acid Dianhydride, bis (phthalic acid) phenylphosphine oxide dianhydride, p-phenylene-bis (triphenylphthalic acid) dianhydride, m-phenylene-bis (triphenylphthalic acid) dianhydride, bis (triphenyl) 2,4-bis (4-phthalic acid) -4,4'-diphenyl ether dianhydride, aromatic tetracarboxylic dianhydride such as bis (triphenylphthalic acid) -4,4'-diphenylmethane dianhydride; (Hydroxyphenyl) propanedibenzoate-3,3 ′, 4,4′-tetracarboxylic dianhydride, p-phenylenebis (trimellitic acid monoester anhydride) ), 4,4'-biphenylenebis (trimellitic acid monoester anhydride), 1,4-naphthalenebis (trimellitic acid monoester anhydride), 1,2-ethylenebis (trimellitic acid monoester anhydride) ), 1,3-trimethylene bis (trimellitic acid monoester anhydride), 1,4-tetramethylene bis (trimellitic acid monoester anhydride), 1,5-pentamethylene bis (trimellitic acid monoester anhydride) ), 1,6-hexamethylenebis (trimellitic acid monoester anhydride), 4,4 ′-(4,4′-isopropylidene diphenoxy) bis (phthalic anhydride), and the like. Or a combination of two or more of them can be used as part or all of the acid dianhydride component.
In order to exhibit excellent heat-fusibility, 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3 ′, 4,4′-tetracarboxylic dianhydride, 1,2-ethylene Bis (trimellitic acid monoester anhydride), 4,4'-hexafluoroisopropylidene diphthalic anhydride, 2,3,3 ', 4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthal It is preferable to use an acid anhydride, 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride and 4,4 ′-(4,4′-isopropylidene diphenoxy) bis (phthalic anhydride).
As the diamine component, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2, -bis [3- ( 3-aminophenoxy) phenyl] propane, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, bis ( 4- (4-aminophenoxy) phenyl) sulfone, bis (4- (3-aminophenoxy) phenyl) sulfone, 4,4'-bis (4-aminophenoxy) biphenyl, 2,2-bis (4-aminophenoxy Phenyl) hexafluoropropane, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenyls Von, 9,9-bis (4-aminophenyl) fluorene, bisaminophenoxyketone, 4,4 ′-(1,4-phenylenebis (1-methylethylidene)) bisaniline, 4,4 ′-(1,3 -Phenylenebis (1-methylethylidene)) bisaniline, 3,3′-dimethylbenzidine, 3,3′-dihydroxybenzidine and the like, and these can be used alone or in combination of two or more. it can.
The raw materials of the thermoplastic polyimide resin used for the laminate of the present invention include 1,3-bis (3-aminophenoxy) benzene, 3,3′-dihydroxybenzidine, and bis (4- (3-aminophenoxy) phenyl) sulfone Are preferably used alone or in a mixture at an arbitrary ratio.
As a typical procedure of a reaction for obtaining a polyamic acid polymer solution, one or more diamine components are dissolved or diffused in an organic polar solvent, and then one or more acid dianhydride components are added to form a polyamic acid solution. There is a way to get it. The order of addition of each monomer is not particularly limited, and an acid dianhydride component may be added to an organic polar solvent first, and a diamine component may be added to form a polyamic acid polymer solution. The polyamic acid polymer solution may be added by first adding an appropriate amount thereof, then adding an excess acid dianhydride component, and then adding an excess amount of a diamine component. In addition, there are various addition methods known to those skilled in the art. In addition, the term “dissolve” as used herein means, in addition to the case where the solvent completely dissolves the solute, a state in which the solute is uniformly dispersed or diffused in the solvent and substantially dissolved. Including cases.
Examples of the organic polar solvent used in the polyamic acid solution forming reaction include, for example, sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide; formamide solvents such as N, N-dimethylformamide and N, N-diethylformamide; Acetamide solvents such as -dimethylacetamide, N, N-diethylacetamide; pyrrolidone solvents such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone; phenol, o-, m-, or p-cresol; Phenolic solvents such as xylenol, halogenated phenols and catechol; and hexamethylphosphoramide, γ-butyrolactone and the like. Further, if necessary, these organic polar solvents can be used in combination with an aromatic hydrocarbon such as xylene or toluene.
Next, a method for imidizing polyamic acid will be described. The imidization reaction of polyamic acid is a dehydration ring-closing reaction of polyamic acid, and water is generated by the reaction. The generated water easily hydrolyzes the polyamic acid and causes a decrease in molecular weight. As a method for imidation while removing water, usually, 1) a method of adding an azeotropic solvent such as toluene and xylene to remove by azeotropic distillation, 2) an aliphatic acid dianhydride such as acetic anhydride, triethylamine, and pyridine , A tertiary amine such as picoline and isoquinoline, and 3) a method of imidation by heating under reduced pressure.
The method for imidizing the thermoplastic polyimide resin of the present invention is preferably a method of imidizing by heating under reduced pressure. According to this imidization method, water generated by the imidization can be positively removed from the system, so that hydrolysis of the polyamic acid can be suppressed, and a high-molecular-weight polyimide can be obtained. Further, according to this method, one or both ring-opened products present as impurities in the raw acid dianhydride are re-closed, so that a further improvement in molecular weight can be expected.
The heating condition of the method of heating and imidizing under reduced pressure is preferably 80 to 400 ° C, more preferably 100 ° C or more, at which imidization is efficiently performed, and water is efficiently removed, and still more preferably 120 ° C or more. . The maximum temperature is preferably equal to or lower than the thermal decomposition temperature of the target polyimide, and a normal completion temperature of imidization, that is, about 250 to 350 ° C. is usually applied. The condition of the pressure for reducing the pressure is preferably smaller, but specifically, 900 hPa or less, preferably 800 hPa or less, and more preferably 700 hPa or less.
Further, as another method for obtaining a thermoplastic polyimide resin, there is a method in which the solvent is not evaporated in the above-mentioned thermal or chemical dehydration ring closure method. Specifically, a polyimide resin solution obtained by performing a thermal imidization treatment or a chemical imidization treatment with a dehydrating agent is poured into a poor solvent, a polyimide resin is precipitated, and purified by removing unreacted monomers, This is a method of drying to obtain a solid polyimide resin. As the poor solvent, a solvent that is mixed well with the solvent but has a property that the polyimide is hardly dissolved is selected. Illustrative examples include, but are not limited to, acetone, methanol, ethanol, isopropanol, benzene, methyl cellosolve, methyl ethyl ketone, and the like. A thermoplastic polyimide resin can be obtained by these methods, and can be used as an adhesive layer of the laminate of the present invention.
Next, (B) a curable adhesive utilizing a curing reaction of a thermosetting resin will be described. Examples of the thermosetting resin include a bismaleimide resin, a bisallylnadiimide resin, a phenol resin, a cyanate resin, an epoxy resin, an acrylic resin, a methacrylic resin, a triazine resin, a hydrosilyl cured resin, an allyl cured resin, and an unsaturated polyester resin. And these can be used alone or in an appropriate combination. Further, in addition to the thermosetting resin, a side chain reactive group type having a reactive group such as an epoxy group, an allyl group, a vinyl group, an alkoxysilyl group, a hydrosilyl group, or a hydroxyl group on a side chain or at a terminal of a polymer chain. It is also possible to use thermosetting polymers as thermosetting components.
Hereinafter, the side chain reactive group type thermosetting polyimide resin will be described. Specific examples of the production method include (1) a method according to the thermoplastic polyimide resin described above, in which case an epoxy group, vinyl group, allyl group, methacryl group, acrylic group, alkoxysilyl group, hydrosilyl group is used. A method of obtaining a thermosetting polyimide by using a diamine component having a functional group such as a carboxy group, a hydroxyl group, a cyano group, or an acid dianhydride component as a monomer component; and (2) a hydroxyl group, a carboxy group, or an aromatic halogen atom. After producing a solvent-soluble polyimide having a group or the like in accordance with the thermoplastic polyimide resin production method described above, an epoxy group, a vinyl group, an acrylic group, a methacryl group, an allyl group, a methacryl group, an acrylic group, an alkoxysilyl group, Add functional groups such as hydrosilyl, carboxy, hydroxyl, and cyano groups by chemical reaction Due law, it is also possible to obtain a thermosetting polyimide resin.
For the thermosetting resin, furthermore a radical reaction initiator such as an organic peroxide, a reaction accelerator, triallyl cyanurate, a crosslinking auxiliary such as triallyl isocyanurate, heat resistance, for improving the adhesiveness, etc. If necessary, commonly used epoxy curing agents such as acid dianhydrides, amines, and imidazoles, and various coupling agents can be appropriately added.
It is also possible to mix a thermosetting resin with the thermoplastic resin for the purpose of controlling the flowability of the adhesive during the heat bonding. For this purpose, it is desirable to add the thermosetting resin in an amount of 1 to 10000 parts by weight, preferably 5 to 2000 parts by weight, based on 100 parts by weight of the thermoplastic resin. If the amount of the thermosetting resin is too large, the adhesive layer may become brittle. On the other hand, if the amount is too small, the adhesive may protrude or the adhesiveness may decrease.
As the adhesive used for the laminate of the present invention, thermoplastic polyimide resin, thermosetting polyimide resin type, epoxy resin type from the viewpoint of adhesiveness, processability, heat resistance, flexibility, dimensional stability, dielectric constant, price, etc. , A cyanate ester resin or a blend thereof are particularly preferable, thermoplastic polyimide resin and epoxy resin, thermoplastic polyimide resin and cyanate ester resin, side chain reactive group type thermosetting polyimide resin and epoxy resin, A blend of a side-chain reactive group type thermosetting polyimide resin and a cyanate ester resin is particularly preferred. Among them, a mixture of a thermoplastic polyimide resin and an epoxy resin is preferable because of good balance of adhesiveness, workability, heat resistance and the like.
An adhesive layer is formed by applying an adhesive using a thermoplastic resin or an adhesive using a thermosetting resin to a polyimide film using, for example, a bar coater, a spin coater, a gravure coater, or the like.
The thickness of the adhesive layer is not particularly limited, but is preferably 5 to 125 μm or less, more preferably 5 to 50 μm, and particularly preferably 5 to 35 μm. The adhesive layer needs to have a sufficient amount and thickness to embed the inner layer circuit pattern at the time of lamination. Although it depends on the pattern ratio of the inner layer circuit, the thickness is usually required to be about 1/2 to 1 times the thickness of the inner layer circuit. That is, assuming that the practically effective minimum circuit thickness is about 9 μm, assuming a pattern ratio of 50%, the adhesive layer needs to have a minimum thickness of about 5 μm. On the other hand, if the adhesive layer is too thick, as in the case of the polymer film, not only does it go against the demand for thinner and smaller printed wiring boards, but also the adhesive flows out of the substrate during the laminating process and the substrate product or There are problems such as contamination of processing equipment, and volatile components such as solvents remaining in the adhesive and causing foaming and other causes.
In order to manufacture a laminate having a structure of metal layer A / polymer film / adhesive layer, a metal layer A is formed on one surface of the polymer film by the method described above, and then an adhesive layer 2 is formed. Also, the reverse procedure does not impair the effects of the present invention. Examples of the method for forming the adhesive layer include a method in which the resin material to be the adhesive layer described above is formed into a solution and applied and dried, and a method in which the resin material is melt-coated.
The laminate of the present invention may have a protective film such as a protective film on the metal layer A, if necessary, in addition to the polymer film, the metal layer A, and the adhesive layer. Hereinafter, the protective film will be described.
<Protective film>
The purpose of providing the protective film is to keep the physical properties of the copper thin film prepared by the ion plating method unchanged until the copper thin film is applied to a circuit forming process. If the ion plating film is exposed to air for a long time, the adhesiveness to the electroless copper plating layer tends to decrease. Probably due to progress of oxidation of copper surface and adhesion of dust. In addition, in the production of a multilayer printed wiring board, heating is often used when applying and drying an adhesive on a laminate. Further, when the laminate is laminated on the inner substrate, it is general to apply heat and pressure. At that time, the metal layer may be oxidatively deteriorated under the influence of heat. On the other hand, in order to form a new circuit on the substrate surface after lamination on the multilayer circuit board on the inner layer substrate, the protective film must be easily peelable.
In addition, in the laminate obtained by applying and drying the adhesive, the curl may be remarkably curled due to the contraction of the adhesive. Also in this case, curling can be reduced by bonding a protective film and increasing the rigidity of the entire laminate.
The material of the protective film is not particularly limited as long as it has a weak adhesive force to the metal layer. The method for forming the protective film is not particularly limited. For example, the metal layer may be subjected to an organic film forming treatment using an imidazole-based compound, or a known rust preventive treatment such as a chromate treatment or a zincate treatment. Thereby, long-term storage stability can be imparted.
Next, a method for manufacturing a circuit board using the laminate of the present invention will be described.
<Circuit board manufacturing method>
FIG. 1 shows a method for manufacturing a circuit board using the laminate of the present invention.
First, a metal layer A is formed on the surface of the polymer film 1 by a dry plating method (FIG. 1A).
Next, after applying a plating catalyst such as a palladium compound to the surface of the metal layer A, electroless copper plating is performed using the plating catalyst as a nucleus to form an electroless copper plating layer 4 on the surface of the copper film (b). .
In addition to electroless copper plating, electroless nickel plating, electroless gold plating, electroless silver plating, electroless tin plating and the like can be mentioned, and can be used in the present invention. From the viewpoint of electrical characteristics such as properties, electroless copper plating and electroless nickel plating are preferable, and electroless copper plating is particularly preferable.
As the electroless plating process, a known electroless plating process can be applied. Usually, the steps of roughening the substrate surface, cleaning the substrate surface, pre-dipping, applying a plating catalyst, activating the plating catalyst, and forming an electroless plating film are performed. Usually, a plating film having a thickness of 200 to 300 nm and, depending on the conditions, 800 to 1000 nm can be formed.
In addition, the electroless plating layer needs to form a plating film on the inner surface of the via and / or the inner surface of the through-hole formed by a method such as laser drilling and to serve as a power supply electrode. Therefore, the thickness is preferably 100 to 1000 nm, more preferably 100 to 500 nm, particularly preferably 200 to 800 nm. If the thickness is less than 100 nm, the thickness of the in-plane electroplating varies when the power supply electrode is used. Conversely, if the thickness exceeds 1000 nm, it is necessary to perform extra etching in the etching process, and the circuit thickness is smaller than the circuit design value. Or the circuit width becomes narrower. Further, there arises a problem that an undercut or the like occurs and a circuit shape is deteriorated. If the process time of the electroless plating is too long, the adhesive strength to the metal layer A tends to decrease. In this sense, the thickness of the electroless copper plating layer is preferably 800 nm or less.
Next, a resist film 5 is applied to the surface of the electroless copper plating layer thus formed (c), and the resist film at a portion where a circuit is to be formed is removed (d).
The resist film used in the present invention is not particularly limited as long as it resists the plating solution for forming the second metal film, and when the plating is performed, the second metal film is not easily formed on the surface. Absent. For example, a liquid resin is applied to a portion except a portion where a circuit is to be formed by a screen printing method, and then solidified or formed, or a liquid or sheet-shaped photosensitive resin is applied to the entire surface of the first metal film. After forming, a circuit shape is exposed, and then, a photosensitive resin is removed from a portion where a circuit is to be formed to form a circuit. In order to cope with the narrow pitch, it is preferable to use a photosensitive plating resist having a resolution of 50 μm or less. Of course, a circuit having a pitch of 50 μm or less and a circuit having a pitch of more than 50 μm may coexist.
After forming the resist film, electrolytic copper plating is performed using a portion where the electroless plating film is exposed as a power supply electrode, and an electrolytic copper plating layer 6 (second metal film) is formed on the surface (e). In addition to electrolytic copper plating, known electroplating such as electrolytic solder plating, electrolytic tin plating, electrolytic nickel plating, and electrolytic gold plating can be applied, but from an industrial viewpoint, migration resistance, etc. From the viewpoint of the electrical characteristics of the above, electrolytic copper plating and electrolytic nickel plating are preferred, and electrolytic copper plating is particularly preferred.
A known method can be applied to the electroplating. Specifically, copper sulfate plating, copper cyanide plating, copper pyrophosphate plating and the like are known, but copper sulfate plating is preferred from the viewpoint of handling properties of a plating solution, productivity, and film properties. The plating solution composition and plating conditions for copper sulfate plating are exemplified below.
<Copper sulfate plating conditions>
(Plating solution composition)
Copper sulfate: 70 g / L
Sulfuric acid: 200 g / L
Chloride ion: 50mg / L
Additives: appropriate amount
(Plating conditions)
Liquid temperature: room temperature
Air stirring: Yes
Oscillation of cathode substrate: Yes
Cathode current density: 2 A / dm²
Note that the thickness of the second metal film formed at this time may be larger or smaller than the thickness of the resist film. Further, the second metal film may be formed by electroless plating instead of electrolytic plating.
After the electrolytic copper plating, the resist film is removed (f). The resist stripping solution is appropriately determined depending on the resist film used.
Next, the power supply layer composed of the metal layer A and the electroless copper plating layer is removed by etching to form a circuit (g).
At this time, an etchant that selectively etches only the first metal film without substantially eroding the second metal film is used. That is, in the step of removing the electroless copper plating layer and the metal layer A exposed by the resist pattern peeling by etching, the etching of the electrolytic copper plating layer per time required to remove the electroless copper plating layer and the metal layer A is performed. When the thickness is T1, and the sum of the thicknesses of the electroless copper plating layer and the metal layer A is T2, an etchant satisfying T1 / T2 <1 is used. T1 / T2 is preferably as small as possible, T1 / T2 is preferably from 0.1 to 1, and more preferably from 0.1 to 0.5. As an etchant satisfying such conditions, an etchant containing nitric acid and sulfuric acid as main components is particularly effective, and an etchant further added with hydrogen peroxide, sodium chloride, or the like is more effective. Here, the main component means a main component with respect to components other than water constituting the etching solution.
More preferably, an etchant having an etching rate for the first metal film that is 10 times or more the etching rate for the second metal film is used. As a result, the second metal film is not etched, and the state when formed is substantially maintained. Therefore, the circuit shape can be kept substantially rectangular, and a circuit having an excellent shape can be obtained. As an example of the etchant, for example, when nickel is used for the first metal film and copper is used for the second metal film, the etchant disclosed in JP-A-2001-140084 is preferably used.
Here, the etching rate is calculated by the following equation from the weight loss when a metal plate of 40 mm × 40 mm × 0.3 mm (thickness) is immersed in an etchant for 3 minutes and left standing.
Etching rate (μm / min) = (weight loss) × 10000
/ (Surface area × density of metal plate × immersion time) Equation (3)
Here, the density of the metal plate is 8.845 g / cm for nickel.³, For copper 8.92 g / cm³It is. The surface area is 4cm × 4cm × 2 + 4cm × 0.03cm × 4 = 32.48cm²The immersion time is 3 minutes.
Specific examples of the etchant include an etchant manufactured by Mec Co., Ltd. (trade name, Meckri Remover NH-1862). Any etchant having the above-mentioned features can be applied to the present invention. The etching rate of this etchant for various metals is 5 to 10 for an electroless copper plating layer, 5 to 10 for a sputtered copper layer, and 5% for a sputtering nickel layer, when the rate of the electrolytic copper plating layer is 1. Is 10 to 20. For example, when the metal layer A is constituted by a two-layer structure of a nickel layer and a copper layer, the total thickness is 200 nm, and the electroless copper plating is further performed at 200 nm, the total of the metal layer A and the electroless copper plating layer The time required to completely remove the thickness of 400 nm by etching was about 4 minutes, during which the thickness of the electrolytic copper plating layer etched was 80 nm. When a circuit pattern having a line / space of 10 μm / 10 μm is manufactured according to the above-described method for manufacturing a printed wiring board, the width of the obtained circuit is changed from 10.0 μm before etching to 9.8 μm after etching. Had a shape almost as designed. The etching rate was determined by observing a change in etching thickness when various metals were immersed in an etching solution.
When the etching rate of a standard copper etchant is measured, the etching rate varies greatly depending on the method of forming the copper layer. The copper thin film formed by the ion plating method can be very easily etched in the etching process in the semi-additive method.
Among the copper layers formed by the ion plating method, the sputtering method, the electroless plating method, and the electrolytic plating method, the copper layer formed by the ion plating method has the highest etching rate. Next, the copper layer and the electroless copper plating layer which are easily etched are formed by the sputtering method. The most difficult to etch is the copper layer formed by the electrolytic method. The etching rate of the copper layer by the ion plating method is about three times that of the copper layer by the sputtering method or the copper layer by the electroless method. The etching rate of the copper layer formed by the sputtering method or the copper layer formed by the electroless method is about 5 to 10 times that of the copper layer formed by the electrolytic method. That is, the copper layer formed by the ion plating method has an etching rate of 30 to 15 times that of the copper layer formed by the electrolytic method.
Therefore, the copper layer used as the power supply layer for electrolytic plating formed by the ion plating method, the sputtering method, or the electroless plating method can be very easily removed by etching in the etching process in the semi-additive method.
Further, for the purpose of improving productivity, in order to shorten the etching time, it is effective and preferable to carry out the etching while maintaining conduction with the outside.
Finally, if necessary, finish processing such as electroless nickel plating and electroless gold plating is performed to manufacture a printed wiring board.
When forming a high-density circuit having a line / space of 25 μm / 25 μm or less, it is extremely important that the metal layer and the insulating substrate are firmly bonded. In particular, not only in the semi-additive method, but also in the manufacturing process of double-sided printed wiring boards and multilayer printed wiring boards, electroless plating and electroplating are required to impart conductivity to through-holes and IVH (interstitial via holes). Required. However, since these processes use various chemical treatments such as strong acids and strong alkalis that cause considerable damage to the insulating resin, it is practically important to ensure the peel strength of these circuit patterns.
According to the circuit board manufacturing method, for example, the peel strength of the metal layer formed by the electroless plating method and the electroplating method can be 5 N / cm or more. Heretofore, it has not been known that electroless copper plating exhibits such high peel strength, particularly in a polymer film having a surface Rz of 1 μm or less. The peel strength of the metal layer is 2 A / dm2 by copper sulfate plating without forming a resist pattern after electroless plating on the metal layer.²Electroplating for 40 minutes under the conditions described above to form a copper plating layer having a thickness of 20 μm, and conforming to JIS C6471 (peeling strength: method B), measuring pattern width 3 mm, crosshead speed 50 mm / min, peeling It is determined by measuring the peel strength between the polymer film and the metal layer under the condition of an angle of 180 degrees.
Next, a method for manufacturing a multilayer printed wiring board according to the present invention will be described.
<Manufacturing method of multilayer printed wiring board>
2 and 3 show a method for manufacturing a build-up multilayer printed wiring board according to the present invention. Here, a laminate having the adhesive layer 3 on one side of the polymer film 1 is used. First, a metal layer A is formed on the surface of a polymer film by a dry plating method (FIG. 2A).
Next, the adhesive layer surface of the laminate is bonded to the circuit surface of the printed wiring board 9 having the inner circuit 8 formed on the insulating substrate 7, and the adhesive layer is thermally fused or cured (FIG. 2B). The polymer film constituting the interlayer adhesive film becomes the resin insulating layer constituting the multilayer printed wiring board.
The application is performed by a method involving heating and / or pressurization. Specifically, heating and pressurization may be performed using a vacuum press equipped with a heater or a crimping device equipped with a heater and a press roll. As the press working, in addition to a hydraulic press and a single plate press, a vacuum press and a vacuum lamination can be applied. A vacuum press and a vacuum laminator are preferably used from the viewpoint of narrowing bubbles at the time of sticking, embedding of an inner layer circuit, and suppressing metal oxidation due to heating of the metal layer A. Vacuum pressing is preferred from the viewpoint of the biting of bubbles at the time of sticking and the embedding of the inner layer circuit.
The temperature and pressure conditions at the time of sticking may be set so as to be optimal conditions according to the composition of the interlayer adhesive film, the thickness of the metal layer a of the inner layer circuit board, etc., but the sticking temperature is 300 ° C. or less. The temperature is preferably 250 ° C. or less, more preferably 220 ° C. or less, and particularly preferably 200 ° C. or less. Further, the temperature is preferably 100 ° C. or higher, 160 ° C. or higher, and 180 ° C. or higher. The sticking time is preferably between about 1 minute and 3 hours, particularly preferably between 1 minute and 2 hours. The pressure is preferably 0.01 to 100 MPa. In the case of vacuum pressing and vacuum lamination, the pressure in the chamber is 10 kPa or less, more preferably 1 kPa or less.
After sticking, it can be put into a curing oven such as a hot air oven. Thereby, the thermosetting reaction of the adhesive layer can be promoted in the curing furnace. In particular, when the sticking time is shortened, for example, when the sticking time is set to 20 minutes or less, it is preferable to perform a treatment in a curing furnace after sticking from the viewpoint of improving productivity.
Before performing the attaching step, after applying an adhesive layer varnish having the same composition as the adhesive layer on the inner layer circuit, by drying, the surface of the inner layer circuit board may be flattened in advance. More desirable.
In the method for manufacturing a multilayer printed wiring board according to the present invention, since the polymer film is used, the inner layer circuit is embedded in the adhesive layer when sticking to the inner layer wiring board, and the inner layer circuit is close to the polymer film. This completes the embedding of the inner circuit into the adhesive layer. As a result, the thickness of the insulating layer between the layers becomes substantially the same as the thickness of the polymer film, and there is an effect that the thickness of the insulating layer in the plane is kept uniform. Further, the polymer film according to the present invention also has the effect of increasing the insulation between layers.
After performing the attaching step and before performing the plating layer forming step, if necessary, a drilling operation using a drill or a laser beam is performed at a predetermined position in the interlayer adhesive film to form a through hole or a via hole 10. It is formed (FIG. 2C). As a processing method, a known dolmarin, dry plasma device, carbon dioxide laser, UV laser, excimer laser, or the like can be used. For drilling a via hole, laser drilling is effective for forming a blind via of a small diameter via, and a UV-YAG laser is suitable for drilling the entire first metal film.
It is preferable to clean the via holes by desmearing according to a known method, if necessary. The desmear treatment is preferably performed by a wet process using permanganate, which is widely performed, or by dry desmear using plasma or the like. In particular, dry desmear is preferably used because it has an effect of removing smear at the bottom of the via while suppressing damage to the metal layer A of the laminate of the present invention. The desmear condition can be appropriately modified depending on the via hole forming condition. When the protective film is laminated on the metal layer, the protective film is peeled off from the metal layer before performing the above-described punching operation.
A step of conducting between the metal layer a of the inner circuit board and the metal layer of the interlayer adhesive film through the through-holes and via-holes by electroless copper plating or the like is performed. Specifically, a plating catalyst 11 such as a palladium compound is applied to the surface of the copper film and the inside of the via hole (FIG. 2 (d)), and electroless copper plating is performed using the plating catalyst as a nucleus. An electroless copper plating layer 4 is formed inside (FIG. 2E).
Further, a resist film 5 is applied or laminated on the surface of the electroless copper plating layer thus formed (FIG. 2 (f)). If necessary, a film-like material or a liquid-like material can be used. A method of laminating a film resist is preferred from the viewpoint of handleability and uniformity of the thickness of the resist at the time of forming a circuit by plating thereafter.
A portion of the resist film where a circuit is to be formed is removed by photolithography (FIG. 3A). For forming a high-density circuit, a method of exposing and developing a resist of a photosensitive material with a parallel light source is preferable. In addition, a method of bringing the mask into close contact with the base material is preferable for achieving high resolution. On the other hand, when the mask is brought into close contact with the substrate, scratches and stains may be a problem in the mask, and may be appropriately selected in use.
Thereafter, electrolytic copper plating is performed using the portion where the electroless copper plating layer is exposed as a power supply electrode, and an electrolytic copper plating layer 6 is formed on the surface and in the via hole (FIG. 3B). At this time, the via hole is filled with an electrolytic copper plating film. As a plating method, a method such as adjustment of a plating solution additive or application of a pulsed current can be applied. By combining these methods, a plating film according to the application can be provided.
Next, the resist film is removed (FIG. 3C). Usually, the resist film is peeled off with an alkaline solution.
The power supply layer including the metal layer A and the electroless copper plating layer is removed by soft etching or the like to form a circuit (FIG. 3D).
Through the above steps, a multilayer printed wiring board can be manufactured by fully utilizing the features of the laminate of the present invention. In particular, for the conduction of the via hole, it is necessary to provide a catalyst for electroless plating. However, since the catalyst is provided on the first metal film except for the via hole portion, the catalyst of the unnecessary portion is not etched by etching the first metal film. Can be easily removed.
In the above description, a method of manufacturing a multilayer printed wiring board by attaching one interlayer adhesive film to an inner circuit board has been described as an example. It may be manufactured by attaching two interlayer adhesive films on both sides, and is further manufactured by attaching another interlayer adhesive film on the interlayer adhesive film attached to the inner circuit board. You may. That is, it is possible to manufacture a multilayer printed wiring board in which a plurality of interlayer adhesive films are laminated on one or both sides of the inner circuit board by repeatedly performing each of the steps shown in FIGS. 2 (b) to 3 (d). it can.
In the laminate of the present invention, the metal layer is directly formed on a polymer film, which is a resin insulating layer, by a dry plating method, more specifically, a film forming method such as a vacuum evaporation method, a sputtering method, or an ion plating method. Since the formed metal thin film is used as a base, the adhesion between the metal layer and the resin insulating layer is excellent. That is, even without performing the step of roughening the surface of the polymer film, the metal layer can be adhered to the polymer film, and the electrical characteristics can be improved. Therefore, the manufacturing process of the interlayer adhesive film or the multilayer printed wiring board can be simplified as compared with the related art, so that the manufacturing cost can be reduced and the product yield can be improved.
In both the circuit board forming process and the build-up multilayer substrate forming process described above, the etching process can be performed very effectively.
Furthermore, in the method for manufacturing a printed wiring board using the laminate of the present invention, the metal layer A and the electroless plating layer are formed on a polymer film having a smooth surface, and thus are roughened, which is a conventional technique. Etching can be performed more quickly than the electroless plating layer formed on the resin surface. This is not only industrially advantageous but also does not require etching deep into the roughened surface, which is believed to contribute to obtaining a good circuit shape as designed.
Further, there is very little etching residue between the obtained circuit patterns, so that problems such as ion migration during circuit formation can be eliminated. In the semi-additive method according to the prior art, the electroless copper plating film and the electroless copper plating catalyst easily remain on the surface of the insulating substrate. Since nickel plating or gold plating is performed, there is a problem that nickel or gold is plated on the surface of the insulating substrate by the catalytic action of the remaining plating catalyst, and a circuit cannot be formed. However, in the present invention, since the catalyst treatment for forming the electroless plating layer is performed on the metal layer A formed by the dry plating method or the like, the catalyst can be completely removed by the etching treatment. Therefore, according to the present invention, it is possible to form a high-density circuit having excellent adhesion to a substrate and excellent insulation.
Hereinafter, a method for manufacturing a circuit board using the laminate of the present invention will be described based on examples.
<Manufacture of circuit boards>
Example 1
On one surface of a 25 μm-thick polyimide film (Apical HP, manufactured by Kaneka Chemical Industry Co., Ltd.), 300 nm of nickel was DC-sputtered to form a first metal film.
Subsequently, a photosensitive dry film resist (Sunfort manufactured by Asahi Kasei Kogyo Co., Ltd.) was heat-laminated, and then exposed to a circuit shape. The circuit was exposed to the shape of a comb-shaped electrode having a circuit width of 15 μm and having an insulating interval of 15 μm.
Next, the photosensitive resin is removed from the portion where the circuit is to be formed, and a resist film is formed on the surface of the first metal film except for the portion where the circuit is to be formed. Thus, a second metal film of copper having a thickness of 10 μm was formed on the surface of the portion where the first metal film was exposed.
Next, after removing the resist film using an alkaline stripping solution, an etching solution having a composition shown in Table 1 was sprayed on the substrate to etch the first metal film of nickel, and a circuit width of 15 μm and an insulation interval of 15 μm were used. A pattern was made. Next, as a finishing step, electroless nickel plating is performed to form a nickel metal film having a thickness of 2 μm on the surface of the second metal film, and then electroless gold plating is performed to form a thick metal film on the surface of the nickel metal film. A 0.1 μm thick gold metal film was formed to obtain a printed wiring board. The etch rate of the used etchant was 5.38 μm / min for nickel and 0.04 μm / min for copper.

The circuit shape and insulation of the obtained printed wiring board were evaluated. For the circuit shape, the circuit width of a portion exposed to a circuit width of 15 μm was observed with a microscope among circuits formed in the shape of a comb-shaped electrode, and a circuit having a rectangular circuit shape was accepted, and a rectangular vertex was crushed. Was rejected. The insulation property was determined by measuring the insulation resistance between circuits that had a 15 μm insulation interval and did not conduct, among the circuits having the shape of the comb electrodes formed. As a result, the circuit shape passed, and 1 × 10¹¹It had an insulation resistance of Ω or more. Thus, in Example 1, it was confirmed that a printed wiring board having an excellent circuit shape and excellent insulating properties could be easily manufactured.
Example 2
A copper thin film was formed on one surface of a 12.5 μm-thick polyimide film (Apical HP, manufactured by Kaneka Chemical Industry Co., Ltd.) by an ion plating method. The surface smoothness of the polyimide film used in the experiment was 1 μm in terms of Rz value. Typical ionization conditions are 40 V, bombard conditions are an argon gas pressure of 26 Pa, and a substrate heating temperature of 150 ° C. In this way, films having various thicknesses in the range of 5 to 1000 nm were formed.
Next, a copper plating layer was formed on the laminate composed of the polyimide film and the ion-plated copper layer by an electroless plating method. The method of forming the electroless plating layer is as follows. First, the laminate was washed with an alkaline cleaner, and then subjected to a short pre-dip with an acid. Further, platinum addition and reduction with alkali were performed in an alkali solution. Next, chemical copper plating was performed in an alkali. The plating temperature was room temperature and the plating time was 10 minutes, and an electroless copper plating layer having a thickness of 300 nm was formed by this method.
The adhesive strength of the copper thin film layer thus formed was evaluated by the value of the peel strength. In the evaluation of adhesiveness, the peeled surface was always the interface between the polyimide film and the ion-plated copper layer, and the condition of ion plating did not affect the peel strength much, but the thickness did affect the strength. That is, when the ion plating layer had a thickness of 20 nm or less, the adhesive strength was 1 to 4 N / cm, and the strength varied depending on the location. This is presumably because the polyimide film has a partially exposed portion at a thickness of 20 nm or less. On the other hand, when the thickness of the ion plating layer was between 10 and 400 nm, it was 6 to 8 N / cm, and the adhesive strength was stably obtained. On the other hand, when the thickness was 400 nm or more, the adhesive strength was reduced to a value of 6 to 4 N / cm.
An electrolytic copper plating layer was formed on a laminate composed of the polyimide film (12.5 μm) / ion plating copper layer (50 nm) / electroless copper plating layer (300 nm) produced by the above method. In electrolytic copper plating, the laminate was preliminarily washed in 10% sulfuric acid for 30 seconds, and then plated at room temperature for 40 minutes. Current density is 2 A / dm²And the film thickness was 10 μm.
The peel strength of this laminate was measured. The adhesion strength between the electroless plating layer and the electrolytic plating layer, and between the ion plating copper layer and the electroless plating layer was good, and peeling occurred between the polyimide and the ion plating copper layer. However, the strength was 6-7 N / cm, and it was found that the formation of the electrolytic copper layer did not adversely affect the adhesion between the layers.
A resist solution (manufactured by JSR Co., Ltd., on the surface of the laminate composed of the polyimide film (12.5 μm) / ion-plated copper layer (50 nm) / electroless copper plating layer (300 nm) produced by the above method) THB320P) was spin-coated to a thickness of 10 μm. Next, mask exposure and resist film peeling were performed using a high-pressure mercury lamp to form a pattern having a line / space of 10 μm / 10 μm.
Next, using a copper layer composed of an ion-plated copper layer (50 nm) and an electroless copper plating layer (300 nm) as a power feeder, electrolytic copper plating was performed on the stripped portion of the resist film. The thickness of the electrolytic copper plating was 10 μm.
Next, the resist film was stripped off using an alkaline stripping solution, flash etching was further performed, and the power supply layer was removed. The flash etch was performed in a sulfuric acid / hydrogen peroxide / water system. Thus, a pattern having a line width of 10 μm and a line interval of 10 μm was formed.
Next, a cross section of the manufactured circuit was observed using an electron microscope. When the thickness of the ion-plated copper layer was 400 nm or less, the power supply layer could be completely removed with little under-etching of the circuit by appropriately controlling the flash etching time. However, it has been found that when the ion-plated copper layer is thicker than 400 nm, undercutting of the circuit line occurs when the feeder layer is completely removed.
Next, the insulation characteristics of the produced circuit pattern were measured. The measurement of the insulation characteristics was performed by a known method (IPC-TM-650-2.5.17) using a comb-shaped electrode having a space distance of 10 μm.¹⁶It had a good line resistance of Ωcm.
Further, the presence or absence of residual metal was measured by Auger analysis of the power supply layer peeled portion, but no residual metal was found.
Example 3
In the same manner as in Example 2, a copper thin film was formed on one surface of the polyimide film by an ion plating method.
Next, a copper thin film was formed on the copper thin film thus formed by a DC sputtering method. Typical sputtering conditions are DC power: 200 watts and argon gas pressure: 0.35 Pa. Films of various thicknesses in the range of 5 to 1000 nm were produced.
The adhesive strength of the copper thin film layer thus formed was evaluated by the peel strength. In the evaluation of the adhesiveness, the peeled surface was always the interface between the polyimide and the ion-plated copper layer, and the conditions of the ion plating did not significantly affect the peel strength, but the thickness did affect the strength. That is, when the thickness of the ion plating layer was 10 nm or less, the adhesive strength was 1 to 4 N / cm, and the strength varied depending on the location. This is considered to be due to the presence of a partially exposed polyimide film at a thickness of 10 nm or less. On the other hand, when the thickness of the ion plating layer was 10 to 200 nm, it was 6 to 8 N / cm, and the adhesive strength was stably obtained. On the other hand, when the thickness was 200 nm or more, the adhesive strength was reduced to a value of 6 to 4 N / cm.
A copper plating layer was formed on the laminate made of the polyimide film / ion plating copper layer / sputtered copper layer produced by the above method by an electroless plating method in the same manner as in Example 2. The experiment was conducted on samples in which the ion-plated copper layer was fixed at 50 nm and sputtered copper layers of various thicknesses were formed. If there was no sputtered copper layer, the ion plated copper layer peeled off the polyimide substrate during electroless copper plating. Also, peeling occurred when the thickness of the sputtered copper layer was 10 nm or less.
When the thickness of the sputtered copper layer was 10 nm or more, it served as a protective film for the ion-plated copper layer in the electroless plating process, and no peeling occurred. Further, the adhesion strength between the sputtered copper and the electroless copper plating layer was good, and there was no separation between them. Peeling in the peel strength test occurred between the ion-plated copper layer and the polyimide film, and in this case, the peel strength also showed good characteristics of 6 N / cm or more. The thickness of the sputtered copper may be 10 nm or more, but a thickness of 200 nm or more is not particularly necessary, and the peel strength tends to decrease at a thickness of 200 nm or more.
In the same manner as in Example 2, a laminate consisting of the polyimide film (12.5 μm) / ion-plated copper layer (50 nm) / sputtered copper layer (100 nm) / electroless copper plating layer (300 nm) produced by the above method was used. An electrolytic copper plating layer was formed by the method.
The peel strength of this laminate was measured. The adhesive strength between the electroless plating layer and the electrolytic plating layer was good, and peeling occurred between the polyimide and the ion-plated copper layer. However, the strength was 6-7 N / cm, and it was found that the formation of the electrolytic copper layer did not adversely affect the adhesion between the layers.
On the surface of the laminate composed of the polyimide film (12.5 μm) / ion plated copper layer (50 nm) / sputtered copper layer (100 nm) / electroless copper plating layer (300 nm) produced by the above method, By the same method, a resist pattern is formed, and then, a portion where the resist has been stripped is subjected to electrolytic copper plating, and further, a resist film is stripped and flash-etched, so that the line width is 10 μm and the line interval is 10 μm. A pattern was formed.
Next, a cross section of the manufactured circuit was observed using an electron microscope. When the thickness of the sputtered copper layer was 200 nm or less, under-etching of the circuit was hardly performed by appropriately controlling the flash etching time, and the power supply layer could be completely removed. However, when the sputtered copper layer was thicker than 200 nm, it was found that undercutting of the circuit line would occur if the feeder layer was to be completely removed.
Next, the insulation characteristics of the circuit pattern manufactured in the same manner as in Example 2 were measured.¹⁶It had a good line resistance of Ωcm.
Further, the presence or absence of residual metal was measured by Auger analysis of the power supply layer peeled portion, but no residual metal was found.
Example 4
A copper thin film was directly formed on one surface of a 12.5 μm-thick polyimide film (Apical HP, manufactured by Kanegafuchi Chemical Industry Co., Ltd.) by a sputtering method. The conditions of DC sputtering are the same as in the third embodiment. Films of various thicknesses were prepared in the range of 5 to 1000 nm, and the adhesive strength was measured. The peel strength was 1 N / cm or less at any film thickness.
Comparative Example 1
An epoxy resin is applied by a curtain coater method on the surface of the copper resin double-sided copper-clad laminate obtained by etching the entire surface of the copper foil, and then heated at 150 ° C. for 1 hour, so that the surface resin layer is in a semi-cured state. An insulating substrate was obtained.
Next, the insulating substrate was immersed in a potassium permanganate solution to roughen the surface of the resin layer and perform a treatment for improving the adhesion of electroless plating. Then, after applying a palladium-tin colloid type plating catalyst to the surface of the resin layer, electroless copper plating was performed to form a 0.5 μm-thick first metal film of copper on the surface of the insulating substrate.
Next, a resist film is formed on the surface of the first metal film except for the portion where a circuit is to be formed in the same manner as in Example 1, and a thickness of 10 μm is formed on the surface where the first metal film is exposed. Was formed.
Then, solder plating was performed to form a 3 μm-thick solder metal film (third metal film) on the surface of the second metal film.
Then, after removing the resist film using an alkaline stripping solution, the first metal film is etched by spraying an alkali etching solution on the surface of the insulating substrate. Then, the second metal film is etched using a solder stripping solution. The third metal film of the solder formed on the surface was removed to expose the second metal film.
Then, the insulating substrate is immersed in a potassium permanganate solution to remove the semi-cured resin layer on the surface of the insulating substrate and to remove the plating catalyst remaining on the surface of the insulating substrate, and then at 170 ° C. for 2 hours. By heating, the semi-cured resin layer was completely cured.
The circuit shape and insulation of the obtained printed wiring board were evaluated by the same method as in Example 1. As a result, the circuit shape passed, and 1 × 10⁹It had an insulation resistance of Ω or more. Thus, it was confirmed that Comparative Example 1 was inferior to Example 1 in insulation properties. Furthermore, in Comparative Example 1, it is necessary to further form and remove the metal film on the surface of the second metal film and to remove the plating catalyst, as compared with Example 1, and the process is complicated. Have.
Comparative Example 2
A printed wiring board was manufactured in the same manner as in Comparative Example 1, except that the resist film and the first metal film were removed without forming a solder metal film (third metal film) on the surface of the second metal film. Got.
The circuit shape and insulation of the obtained printed wiring board were evaluated by the same method as in Example 1. As a result, the circuit shape was rejected and 1 × 10⁹It had an insulation resistance of Ω or more. Thus, it was confirmed that Comparative Example 2 was inferior in the circuit shape and the insulating characteristics as compared with Example 1. Furthermore, in Comparative Example 2, it is necessary to remove the plating catalyst as compared with Example 1, and there is also a problem that the process is slightly complicated.
Next, a method for manufacturing a built-up multilayer printed wiring board using the laminate of the present invention will be described based on examples. In the following examples and comparative examples, an adhesive solution prepared by the following method was used for the adhesive layer.
One equivalent of bis {4- (3-aminophenoxy) phenyl} sulfone was dissolved in N, N-dimethylformamide in a 2000 ml glass flask in a nitrogen atmosphere. The solution was stirred while being cooled with ice water, and 1 equivalent of 4,4 '-(4,4'-isopropylidenediphenoxy) bisphthalic anhydride was dissolved and polymerized in the solution. Thus, a polyamic acid polymer solution having a solid content of 30% by weight was obtained. After heating the polyamic acid polymer solution at 200 ° C. (normal pressure) for 3 hours, it was further heated under reduced pressure at 200 ° C. and 665 Pa for 3 hours. Thus, a solid thermoplastic polyimide resin was obtained.
This thermoplastic polyimide resin, a novolak type epoxy resin as a thermosetting resin (trade name: Epicoat 1032H60, manufactured by Yuka Shell Epoxy Co., Ltd.), and 4,4′-diaminodiphenyl sulfone as a curing agent, The mixture was mixed so that the weight ratio became 70/30/9, and the mixture was dissolved in dioxolane (organic polar solvent) so that the solid content concentration became 20% by weight to obtain an adhesive solution.
<Manufacture of built-up multilayer printed wiring boards>
Example 5
A copper thin film (metal layer) having a thickness of 300 nm was formed on one surface of a 12.5 μm-thick polyimide film (trade name: Apical NPI, manufactured by Kaneka Chemical Industry Co., Ltd.) by a sputtering method using DC magnetron sputtering. Formed. On the other surface of the polyimide film, the adhesive solution was applied using a gravure coater so that the thickness after drying was 9 μm, and dried at 170 ° C. for 2 minutes to form an adhesive layer. did. Thus, an interlayer adhesive film was manufactured.
On the other hand, an inner circuit board was manufactured from a glass epoxy copper-clad laminate on which a 9-μm-thick copper foil was adhered. Then, after the interlayer adhesive film is adhered to the copper foil (metal layer a) of the inner circuit board, it is heated and pressed at 200 ° C. for 2 hours using a vacuum press machine, so that the thermoplastic layer as the adhesive layer is formed. The polyimide resin was thermally fused to the copper foil.
Next, after performing a drilling operation using laser light on the interlayer adhesive film, the thickness of the copper thin film was reduced to 3 μm by electroless copper plating, and the copper foil of the inner circuit board and the copper thin film of the interlayer adhesive film were removed. Was turned on. Then, a plating resist pattern is formed on the copper thin film of the interlayer adhesive film using a photosensitive dry film resist (trade name: Sanfort AQ-2536, manufactured by Asahi Kasei Corporation), and a circuit pattern on the copper thin film is formed. A copper film (plating layer) having a thickness of 20 μm was laminated on a portion to be formed by electrolytic copper plating. After that, the plating resist was peeled off, and the copper thin film was removed by soft etching. Thus, a multilayer printed wiring board on which a fine circuit pattern having a line / space of 30 μm / 30 μm was formed.
Example 6
Instead of employing the sputtering method, a 300 nm thick copper thin film (metal layer) was formed on one surface of the polyimide film by an ion plating method. A plate was formed. A fine circuit pattern having a line / space of 30 μm / 30 μm could be formed on the multilayer printed wiring board.
Example 7
Instead of employing the sputtering method, a 300 nm thick copper thin film (metal layer) was formed on one surface of the polyimide film by a vacuum evaporation method, except that the same process as in Example 5 was performed to perform the multilayer printed wiring board. Was formed. A fine circuit pattern having a line / space of 30 μm / 30 μm could be formed on the multilayer printed wiring board.
Example 8
A sputtering method is used to form a 30 nm thick nickel thin film on one side of the polyimide film, and then a 300 nm thick copper thin film is laminated on the nickel thin film to form a two-layer metal layer. A multilayer printed wiring board was formed by performing the same steps as in Example 5 except for the formation. A fine circuit pattern having a line / space of 30 μm / 30 μm could be formed on the multilayer printed wiring board.
Example 9
An adhesive solution was applied to the other surface of the polyimide film of the laminate having the first metal film formed thereon in the same manner as in Example 1 so that the thickness after drying became 9 μm, and dried at 170 ° C. for 2 minutes. To form a laminate for a build-up multilayer printed wiring board. On the other hand, an inner circuit board was prepared from a glass epoxy copper-clad laminate having a copper foil of 9 μm, and a laminate for a build-up multilayer printed wiring board was laminated and cured on the surface of the printed wiring board by vacuum pressing at 200 ° C. for 2 hours. .
After forming a via hole with a UV-YAG laser and applying a catalyst for electroless plating to the entire surface of the substrate, a resist film is formed in a portion other than a portion where a circuit and a via hole are to be formed in the same manner as in Example 1. did. Thereafter, conduction of the laser hole was obtained by electroless copper plating, and further, electrolytic copper plating was performed to form a 10 μm thick copper second metal film on the surface where the first metal film was exposed. Subsequently, the plating resist was peeled off in the same manner as in Example 1, and the first metal film was etched to obtain a multilayer printed wiring board of a fine circuit having a circuit width of 15 μm and an insulating interval of 15 μm.
The circuit shape and insulation of the obtained printed wiring board were evaluated in the same manner as in Example 1. As a result, the same result as in Example 1 was obtained.
Example 10
The adhesive solution was applied to one side of a polyimide film (Kanebuchi Chemical Industry Co., Ltd., Apical, 12.5 μm) so that the thickness after drying was 9 μm, and dried at 170 ° C. for 2 minutes to form an adhesive layer. Formed.
Next, an ion-plated copper layer (50 nm) was formed on the other surface of the polyimide in the same manner as in Example 2 to produce a laminate for a build-up multilayer printed wiring board.
On the other hand, an inner layer circuit board was prepared from a glass epoxy copper-clad laminate having a copper foil of 9 μm, and then the above-mentioned laminate for a build-up multilayer printed wiring board was subjected to vacuum pressing at 200 ° C. for 2 hours at a surface of the glass epoxy laminate. And cured.
Next, a circuit pattern was formed on the surface of the ion-plated copper layer using a photoresist in the same manner as in Example 2. A via-hole was formed by a UV-YAG laser, and a catalyst was applied to the entire surface of the substrate and the inside of the via-hole, and then electroless plating was performed. The conduction of the laser holes was obtained by electroless copper plating, and further, electrolytic copper plating was performed to form a copper plating layer having a thickness of 10 μm. Then, the plating resist was peeled off in the same manner as in Example 2, and the power supply layer was etched to obtain a build-up multilayer printed wiring board of a fine circuit having a circuit width of 10 μm and an insulating interval of 10 μm.
The circuit shape and insulation of the obtained printed wiring board were evaluated. As for the circuit shape, among the formed comb-shaped electrode-shaped circuits, the circuit width of a portion exposed to a circuit width of 10 μm is observed with a microscope, and a circuit having a rectangular circuit shape is accepted, and a circuit whose rectangular apex is crushed. Rejected. The insulation property was obtained by measuring the insulation resistance between the non-conductive circuits having an insulation interval of 10 μm among the formed comb-shaped electrode-shaped circuits. As a result, it was confirmed that, in Example 10, compared to Comparative Example 2, a printed wiring board having an excellent circuit shape and excellent insulating properties could be easily manufactured.
Example 11
The adhesive solution was applied to one side of a polyimide film (Kanebuchi Chemical Industry Co., Ltd., Apical, 12.5 μm) so that the thickness after drying was 9 μm, and dried at 170 ° C. for 2 minutes to form an adhesive layer. Formed.
Next, an ion-plated copper layer (20 nm) / sputtered copper layer (100 nm) was formed on the other surface of the polyimide by the method of Example 3 to produce a laminate for a build-up multilayer printed wiring board.
On the other hand, an inner layer circuit board was prepared from a glass epoxy copper-clad laminate having a copper foil of 9 μm. And cured.
Next, a circuit pattern was formed on the surface of the sputtered copper layer using a photoresist in the same manner as in Example 3. A via-hole was formed by a UV-YAG laser, a catalyst was applied to the entire surface of the substrate and the inside of the via-hole, and then electroless plating was performed. The inside of the via hole was made conductive by electroless copper plating, and further, electrolytic copper plating was performed to form a copper plating layer having a thickness of 10 μm, and at the same time, the inside of the via hole was filled with copper. Next, the plating resist was peeled off in the same manner as in Example 3, and the power supply layer was etched to obtain a build-up multilayer printed wiring board of a fine circuit having a circuit width of 10 μm and an insulating interval of 10 μm.
The circuit shape and insulating properties of the obtained printed wiring board were evaluated in the same manner as in Example 10. As a result, in Example 11, it was confirmed that compared to Comparative Example 2, a printed wiring board having excellent circuit shape and insulation properties could be easily manufactured.
Example 12
First, a polyimide film was synthesized by the following method.
One equivalent of each of paraphenylenediamine (hereinafter, PDA) and 4,4'-diaminodiphenyl ether (hereinafter, ODA) was dissolved in N, N-dimethylformamide (hereinafter, DMF) in a separable flask. Thereafter, 1 equivalent of p-phenylenebis (trimellitic acid monoester anhydride) (hereinafter referred to as TMHQ) was added, and the mixture was stirred for 30 minutes. Thereafter, 0.9 equivalent of pyromellitic dianhydride (hereinafter referred to as PMDA) was added, and the mixture was stirred for 30 minutes. Then, a DMF solution of PMDA (concentration: 7%) was added while paying attention to the increase in viscosity, and the viscosity at 23 ° C. was adjusted to 2000 to 3000 poise to obtain a DMF solution of a polyamic acid polymer. The amount of DMF used was such that the concentration of charged monomers in the diamine component and the tetracarboxylic dianhydride component was 18% by weight. The polymerization was carried out at 40 ° C.
10 g of acetic anhydride and 10 g of isoquinoline were added to 100 g of the polyamic acid solution, and after uniformly stirring, defoaming was performed, cast and applied on a glass plate, and dried at about 110 ° C. for about 5 minutes. The acid coating film was peeled off from the glass plate to obtain a self-supporting gel film. This gel film was immersed in a 1-butanol solution of TBSTA adjusted to a titanium concentration of 100 ppm for 1 minute to remove droplets on the surface of the film, and then fixed to a frame, and then at about 200 ° C. for about 1 minute at about 300 ° C. For about 1 minute, about 400 ° C. for about 1 minute, and about 500 ° C. for about 1 minute, and dehydrated and ring-closed to obtain a polyimide film having a thickness of about 25 μm. This polyimide film had a tensile elasticity of 6 GPa, a tensile elongation of 50%, a water absorption of 1.2%, a dielectric constant of 3.4, a dielectric loss tangent of 0.01, and a ten-point average roughness Rz of 0.2 μm.
Next, a metal layer was formed on the polyimide film produced by the above method using a sputtering apparatus NSP-6 manufactured by Showa Vacuum Co., Ltd. by the following method.
The polymer film was set on a jig, and the vacuum chamber was closed. While rotating the substrate (polymer film) on its own, heating it with a lamp heater, 6 × 10^-4It was evacuated to Pa or less. After that, argon gas was introduced, the pressure was set to 0.35 Pa, and nickel having a thickness of 20 nm and then copper having a thickness of 10 nm were sputtered by DC sputtering. DC power was both sputtered at 200 watts. The film forming speed was 7 nm / min for nickel and 11 nm / min for copper, and the film forming time was adjusted to control the film forming thickness.
Next, the adhesive solution was applied using a comma coater on the surface opposite to the surface on which the metal layer of the polymer film was formed so that the thickness after drying was 9 μm, and dried at 170 ° C. for 2 minutes. An adhesive layer was formed to produce a laminate for a build-up multilayer printed wiring board.
Using the obtained interlayer adhesive film, a multilayer printed wiring board was produced by the following method.
First, the interlayer adhesive film was laminated on an inner layer circuit (FR4 substrate having a thickness of 9 μm) at a temperature of 200 ° C., a pressure of 3 MPa, and a degree of vacuum of 10 Pa for 1 hour. A via hole having a diameter of 30 μm was formed at a required position with a UV-YAG laser, and a cleaner conditioner (trade name: Cleaner Securigant 902) was used for 5 minutes according to the process of electroless copper plating manufactured by Atotech Co., Ltd. 1 minute, activator (brand name, activator neogant 834 conc) 5 minutes, reduction (brand name Reducer neogant) 2 minutes, electroless copper plating (Noviganto MSK-DK) 15 The plating was performed under the conditions of minutes.
After washing the electroless copper plating film with acetone, a liquid photoresist (trade name: THB-320P) manufactured by JSR Co., Ltd. is applied by spin coating at 1000 RPM for 10 seconds, dried at 110 ° C. for 10 minutes, and dried at 10 ° C. for 10 minutes. Was formed. Next, a glass mask having a line / space of 10/10 μm is adhered to the resist layer and exposed for 1 minute with an ultraviolet light exposure device of an ultra-high pressure mercury lamp, and then is applied to a developer (PD523AD) manufactured by JSR Corporation for 3 minutes. The portion exposed by immersion was removed to form a pattern having a line / space of 10/10 μm.
The obtained laminated substrate was subjected to a current density of 2 A / dm by a copper sulfate plating solution.²For 20 minutes to form a pattern having a thickness of 10 μm in the portion where the resist was removed. The obtained circuit board was washed with acetone to remove the resist layer remaining on the board. Furthermore, it was immersed in an etching solution (trade name, Meckri Remover NH-1862) manufactured by Mec Corporation for 5 minutes. This etching solution has a higher etching rate with respect to nickel than copper, and can minimize damage to copper in a circuit portion when removing nickel in a portion other than the circuit.
The circuit of the obtained multilayer printed wiring board was observed with a scanning electron microscope, and it was confirmed that a circuit having a line / space = 10/10 μm was formed as designed. The space was smooth and no nickel or copper etching residue was observed. Further, the cross-sectional shape of the copper conductor circuit, which should be originally rectangular, did not show circuit narrowing in the etching step, and maintained a rectangular shape as designed.
The peel strength with the polymer film when the thickness of the metal layer was 20 μm was 6.8 N / cm, which was sufficient for forming a high-density wiring.
Example 13
A printed wiring board was prepared and evaluated in the same manner as in Example 12, except that the nickel sputter layer was 10 nm and the copper sputter layer was 50 nm. As a result, it was confirmed that a circuit having a line / space of 10/10 μm was successfully manufactured. The peel strength between the metal layer and the polymer film was 8.2 N / cm, indicating a sufficient peel strength for forming a high-density wiring.
Example 14
A printed wiring board was prepared and evaluated in the same manner as in Example 12, except that the nickel sputtered layer was 10 nm and the copper sputtered layer was 100 nm. As a result, it was confirmed that a circuit having a line / space of 10/10 μm was successfully manufactured. Further, the peel strength between the metal layer and the polymer film was 9.6 N / cm, which was sufficient peel strength for forming a high-density wiring.
Example 15
A printed wiring board was produced and evaluated in the same manner as in Example 12, except that the nickel / chromium alloy sputtered layer was 10 nm and the copper sputtered layer was 100 nm. As a result, it was confirmed that a circuit having a line / space of 10/10 μm was successfully manufactured. Further, the peel strength between the metal layer and the polymer film was 10.6 N / cm, which was sufficient for forming a high-density wiring.
Example 16
A printed wiring board was prepared and evaluated in the same manner as in Example 12, except that the nickel sputter layer was 10 nm and the copper sputter layer was 200 nm. As a result of visual circuit observation, etching of the space portion was insufficient. In order to sufficiently etch the space, etching for 30 minutes was necessary. The width of the circuit of the obtained wiring board was reduced by etching, and the top of the circuit was particularly rounded and thin.
Example 17
On one surface of a 12.5 μm-thick polyimide film (Apical HP, manufactured by Kaneka Chemical Industry Co., Ltd.), a thin film of 20 nm of nickel and 10 nm of copper was formed by magnetron DC sputtering to obtain a laminate. Was. Next, an adhesive solution was applied on the polyimide film surface of the laminate so that the thickness after drying was 9 μm, and dried at 170 ° C. for 2 minutes to form an adhesive layer, thereby obtaining an interlayer adhesive film.
An inner layer circuit board was prepared from a glass epoxy copper-clad laminate having a copper foil of 9 μm, and then the interlayer adhesive film was vacuum-pressed at a temperature of 200 ° C., a hot plate pressure of 3 MPa, a pressing time of 2 hours, and a vacuum condition of 1 KPa. And cured.
A via hole having an inner diameter of 30 μm reaching the electrode was formed directly above the electrode on the inner layer plate by a UV-YAG laser. Subsequently, electroless copper plating was performed on the entire surface of the substrate. The method of forming the electroless plating layer is the same as that of the second embodiment. A liquid photosensitive plating resist (THB320P, manufactured by JSR Co., Ltd.) was coated and dried at 110 ° C. for 10 minutes to form a resist layer having a thickness of 10 μm. A glass mask having a line / space of 10/10 μm was adhered to the resist layer and exposed for 1 minute with an ultraviolet exposure machine of an ultra-high pressure mercury lamp, and then immersed in a developing solution (PD523AD, manufactured by JSR Corporation) for 3 minutes. The exposed portion was removed to form a plating resist pattern having a line / space of 10/10 μm.
Subsequently, a 10 μm-thick copper pattern was formed on the surface of the portion where the electroless copper plating film was exposed by the copper sulfate plating solution. The electrolytic copper plating was preliminarily washed in 10% sulfuric acid for 30 seconds, and then plated at room temperature for 20 minutes. Current density is 2 A / dm²And the film thickness was 10 μm.
Next, the plating resist was peeled off using acetone. Further, the printed wiring board was obtained by immersing in an etching solution (Mech Remover NH-1862) manufactured by Mec Co., Ltd. for 5 minutes to remove the electroless copper plating layer / copper thin film / nickel thin film other than the circuit.
The resulting printed wiring board had lines / spaces substantially as designed, and had no side etch. Further, the presence or absence of the residual metal was measured by Auger analysis of the power supply layer peeled portion, but the presence of the residual metal was not recognized. The circuit pattern was firmly adhered.
Further, in the etching step of the present example, the etching was performed while the external conduction was maintained. In this case, by measuring the presence or absence of the residual metal by Auger analysis of the power supply layer peeled portion, the presence of the residual metal was not recognized by the immersion in the etching solution for about 2 minutes.
Example 18
A printed wiring board was obtained in the same manner as in Example 17, except that a thin film of 10 nm of nickel and 50 nm of copper were formed by magnetron DC sputtering. The resulting printed wiring board had lines / spaces substantially as designed, and had no side etch. Further, the presence or absence of the residual metal was measured by Auger analysis of the power supply layer peeled portion, but the presence of the residual metal was not recognized. The circuit pattern was firmly adhered.
Example 19
A printed wiring board was obtained in the same manner as in Example 17, except that a thin film of 10 nm of nickel and 100 nm of copper were formed by magnetron DC sputtering. The resulting printed wiring board had lines / spaces substantially as designed, and had no side etch. Further, the presence or absence of the residual metal was measured by Auger analysis of the power supply layer peeled portion, but the presence of the residual metal was not recognized. The circuit pattern was firmly adhered.
Example 20
A printed wiring board was obtained in the same manner as in Example 17 except that a thin film of nickel-chromium alloy was formed to a thickness of 10 nm and copper was formed to a thickness of 10 nm by magnetron DC sputtering. The obtained printed wiring board had lines / spaces almost as designed, and had no side etch. Further, the presence or absence of the residual metal was measured by Auger analysis of the power supply layer peeled portion, but the presence of the residual metal was not recognized. The circuit pattern was firmly adhered.
Example 21
A printed wiring board was obtained in the same manner as in Example 17, except that a thin film of nickel-chromium alloy was formed to a thickness of 10 nm and copper was subsequently formed to a thickness of 50 nm by magnetron DC sputtering. The obtained printed wiring board had a line / space almost as designed, and had no side etch. Further, the presence or absence of the residual metal was measured by Auger analysis of the power supply layer peeled portion, but the presence of the residual metal was not recognized. The circuit pattern was firmly adhered.
Comparative Example 3
An 18 μm-thick electrolytic copper foil was adhered to one surface of a 12.5 μm-thick polyimide film (trade name: Apical NPI, manufactured by Kanegabuchi Chemical Industry Co., Ltd.) via an epoxy-based adhesive. Further, on the other surface of the polyimide film, an adhesive solution made of a thermoplastic polyimide resin was applied using a gravure coater so that the thickness after drying was 9 μm, and an adhesive layer was formed by drying. . Thus, an interlayer adhesive film was manufactured.
On the other hand, an inner circuit board was manufactured from a glass epoxy copper-clad laminate on which a 9-μm-thick copper foil was adhered. Then, after the interlayer adhesive film is adhered to the copper foil of the inner layer circuit board, the thermoplastic polyimide resin as an adhesive layer is heated and pressed at 200 ° C. for 2 hours using a vacuum press machine so that the thermoplastic polyimide resin as the adhesive layer is coated on the copper foil. Was heat-sealed.
Next, after performing an opening operation using a laser beam on the interlayer adhesive film, the thickness of the electrolytic copper foil is reduced to 33 μm by electroless copper plating and electrolytic copper plating, and the interlayer adhesive film is bonded to the copper foil of the inner circuit board. The film was made conductive with the electrolytic copper foil. Then, a plating resist pattern is formed on the electrolytic copper foil of the interlayer adhesive film using a photosensitive dry film resist (trade name: Sanfort AQ-2536, manufactured by Asahi Kasei Corporation), and a circuit on the electrolytic copper foil is formed. A copper film (plating layer) having a thickness of 20 μm was laminated on a portion to be a pattern by electrolytic copper plating. After that, the plating resist was peeled off, and the electrolytic copper foil was removed by soft etching. However, the width (line) of the circuit pattern varied due to the influence of the side etching, and a large number of short-circuited portions and disconnected portions occurred. Therefore, it was not possible to obtain a multilayer printed wiring board on which a fine circuit pattern having a line / space of 30 μm / 30 μm was formed.
Comparative Example 4
A multilayer printed wiring board was formed by performing the same steps as in Example 5 except that a copper thin film having a thickness of 2 μm was formed on one surface of a polyimide film by electroless copper plating instead of employing the sputtering method. . However, since the adhesion of the copper thin film to the polyimide film was poor, the copper thin film was peeled off from the polyimide film, and a circuit pattern could not be formed.
Comparative Example 5
An epoxy resin interlayer insulating material (ABF-SH-9K manufactured by Ajinomoto Fine Techno Co., Ltd.) was laminated on a FR4 substrate having a circuit thickness of 9 μm at a temperature of 90 ° C. and cured at 170 ° C. for 30 minutes.
After the obtained laminate was subjected to surface roughening by desmear treatment using a permanganate method, a multilayer printed wiring board was manufactured and evaluated through the steps following the electroless plating process of Example 12.
The 10-point average roughness of the resin surface after the surface roughening was 3.0 μm. The circuit width of the obtained multilayer printed wiring board was not stable due to large irregularities on the resin surface. Further, when the space was observed by SEM, nickel etching residue was found on the irregularities. The adhesion strength between the resin layer and the metal layer was 7.4 N / cm.
Industrial applicability
According to the present invention, by forming the metal layer A on the polymer film by the dry plating method, it is possible to form a strongly bonded wiring circuit even on a polymer surface having excellent surface smoothness. In addition, since the adhesiveness is excellent, the electrical characteristics can be improved. Further, the thickness of the polymer film serving as the insulating layer can be made thin and uniform. Therefore, when a printed wiring board is manufactured using this laminate, a wiring circuit having excellent adhesive strength and shape can be manufactured, and a printed wiring board having excellent insulation resistance can be obtained. In particular, it is suitable for forming a high-density circuit having a line / space of 25 μm or less.
Further, according to the present invention, it is possible to provide an interlayer adhesive film for a multilayer printed wiring board suitable for forming a fine pattern by having an adhesive layer on the other side of the polymer film of the laminate. When a multilayer printed wiring board is manufactured using the laminate, the manufacturing process can be simplified as compared with the related art, so that the manufacturing cost can be reduced and the product yield can be improved. Thus, for example, a multilayer printed wiring board on which a fine pattern, particularly a circuit pattern formed by a semi-additive method is formed, can be easily and inexpensively manufactured.
Further, according to the present invention, it is possible to obtain a printed wiring board having an excellent circuit shape of the second metal film by using an etchant for selectively etching the first metal film when removing the first metal film. Can be.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a method for manufacturing a circuit board using the laminate of the present invention.
FIG. 2 is a diagram for explaining a method of manufacturing a built-up multilayer printed wiring board according to the present invention.
FIG. 3 is a diagram for explaining a method of manufacturing a built-up multilayer printed wiring board according to the present invention.

Claims (35)

A laminate having a metal layer A having a thickness of 1000 nm or less on at least one surface of a polymer film. A laminate having a metal layer A having a thickness of 1000 nm or less on one surface of a polymer film and an adhesive layer on the other surface. 3. The laminate according to claim 1, wherein the metal layer A is formed by a dry plating method. The laminate according to claim 1 or 2, wherein the metal layer A is copper or a copper alloy formed by an ion plating method. 3. The laminate according to claim 1, wherein the metal layer A has a metal layer A1 in contact with the polymer film and a metal layer A2 formed on the metal layer A1. The laminate according to claim 5, wherein the thickness of the metal layer A1 is 2 to 200 nm. The laminate according to claim 5, wherein the thickness of the metal layer A2 is 10 to 300 nm. 6. The laminate according to claim 5, wherein the metal layers A1 and A2 are made of copper or a copper alloy formed by two different physical methods. 9. The laminate according to claim 8, wherein the metal layer A1 is copper or a copper alloy formed by an ion plating method. 9. The laminate according to claim 8, wherein the metal layer A2 is copper or a copper alloy formed by a sputtering method. The laminate according to claim 5, wherein the metal layer A1 and the metal layer A2 are made of two different metals. The laminate according to claim 11, wherein the metal layer A1 is made of nickel or an alloy thereof, and the metal layer A2 is made of copper or an alloy thereof. The laminate according to claim 11, wherein the metal layer A1 and the metal layer A2 are formed by a sputtering method. The laminate according to claim 11, wherein no oxide layer exists at the interface between the metal layer A1 and the metal layer A2. The laminate according to claim 1 or 2, wherein a 10-point average roughness of the polymer film surface is 3 µm or less. 3. The laminate according to claim 1, wherein the dielectric constant of the polymer film surface is 3.5 or less, and the dielectric loss tangent is 0.02 or less. 3. The laminate according to claim 1, wherein the polymer film contains a non-thermoplastic polyimide resin component. 3. The laminate according to claim 2, wherein the adhesive layer is made of an adhesive containing a thermoplastic polyimide resin. 3. The laminate according to claim 2, wherein the adhesive layer comprises a polyimide resin and a thermosetting resin. The laminate according to claim 1 or 2, further comprising a protective film on the metal layer (A). The laminate according to claim 1 or 2, wherein the peel strength of the metal layer A is 5 N / cm or more. A method for manufacturing a printed wiring board, wherein a printed wiring board having a pattern formed by a first metal film and a second metal film on a polymer film is formed by a semi-additive method, wherein the etching rate for the first metal film is the second. A method for manufacturing a printed wiring board, comprising using an etchant having an etching rate of 10 times or more of a metal film. 23. The method according to claim 22, wherein the first metal film is at least one selected from the group consisting of nickel, chromium, titanium, aluminum and tin, or an alloy thereof, and the second metal film is copper or an alloy thereof. The method for producing a printed wiring board according to the above item. A method for manufacturing a printed wiring board, wherein a circuit is formed using the laminate according to claim 1 or 2. A method for manufacturing a printed wiring board, comprising: forming a through hole in the laminate according to claim 1 and performing electroless plating. 3. A method for manufacturing a printed wiring board, comprising: attaching a conductive foil to an adhesive layer of the laminate according to claim 2, forming a through hole, and performing electroless plating. The adhesive layer of the laminate according to claim 2 is opposed to the circuit surface of the inner wiring board on which the circuit pattern is formed, and the laminate is connected to the inner wiring board by a method involving heating and / or pressing. A method for manufacturing a multilayer printed wiring board to be laminated. 28. The method for manufacturing a multilayer printed wiring board according to claim 27, further comprising a step of forming a hole from a surface of the metal layer A of the laminate to an electrode of the inner layer wiring board, and a panel plating step of electroless plating. 29. The method of manufacturing a multilayer printed wiring board according to claim 25, further comprising a desmearing step after forming the through hole. 30. The method for manufacturing a multilayer printed wiring board according to claim 29, wherein the desmearing is a dry desmearing. The method further includes a step of forming a resist pattern using a photosensitive plating resist, a step of forming a circuit pattern by electroplating, a step of removing a resist pattern, and a step of etching and removing the electroless plating layer and the metal layer A exposed by removing the resist pattern. 29. The method for producing a multilayer printed wiring board according to item 28. 32. The method for manufacturing a multilayer printed wiring board according to claim 31, wherein the resist pattern forming step is performed using a dry film resist. 28. The method for manufacturing a multilayer printed wiring board according to claim 27, wherein the laminate and the inner wiring board are laminated under a reduced pressure of 10 kPa or less. 29. The method for manufacturing a multilayer printed wiring board according to claim 28, wherein the drilling step is performed by a laser drilling device. The etching thickness of the electroplated layer per unit time required to remove the electroless plating layer and the metal layer A exposed by the resist pattern peeling by the electroplating used for the circuit formation is the thickness of the electroless plating and the metal layer A. 32. The method for manufacturing a multilayer printed wiring board according to claim 31, wherein an etching solution thinner than the sum of the above is used.

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