JP2004087548A - Method for manufacturing printed wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printed wiring board on which a high-density circuit can be formed and which has superior adhesive strength and excellent adhesion reliability in a high-temperature and high-humidity environment. <P>SOLUTION: The printed wiring board is manufactured by using a laminate which has metal layers formed on both the surfaces of a polyimide film so that a metal layer formed on at least one surface comprises a 1st metal layer made of nickel or its alloy and a 2nd metal layer made of copper or its alloy, or a 1st layer made of copper or copper alloy formed by an ion plating method and a 2nd metal layer made of copper or copper alloy thereupon. <P>COPYRIGHT: (C)2004,JPO

Description

ただし、ｍは０〜４の整数、Ｘは（化２）で示される置換基から選ばれた一種類、
【００１１】
【化５】

あるいはＣ１からＣ１８の炭化水素残基、またはＣ３からＣ１８のカルボン酸およびそのアンモニュウム残基である。
また（化１）あるいは（化２）中、Ｒ１は水素、またはＣ１からＣ１８の炭化水素残基、Ｒ２、Ｒ３はＣ１からＣ１８の炭化水素残基、Ｒ４はＣ１からＣ１８の炭化水素残基、Ｒ４はＣ１からＣ１８の炭化水素残基または一般式（化３）で表される置換基、
【００１２】
【化６】

Ｒ５，Ｒ６はＣ１からＣ１８の炭化水素残基、Ｒ７はＣ１からＣ１８の炭化水素残基、Ｒ８はＣ１からＣ１８の炭化水素残基である。
（９）前記ポリイミドフィルムが、無水ピロメリット酸、４，４´−ジアミノジフェニルエーテルを主成分とするポリアミド酸を脱水閉環して得られるポリイミドを用いたフィルムである請求項１〜８のいずれか一項に記載のプリント配線板の製造方法。
（１０）前記ポリイミドフィルムが無水ピロメリット酸、４，４´−ジアミノジフェニルエーテル、ｐ−フェニレンジアミンの３成分を主成分とするポリアミド酸を脱水閉環して得られるポリイミドを用いたフィルムである（１）〜（８）いずれか一項に記載のプリント配線板の製造方法。
（１１）前記ポリイミドフィルムが無水ピロメリット酸、４，４´−ジアミノジフェニルエーテル、ｐ−フェニレンジアミン、ｐ−フェニレンビス（トリメリット酸モノエステル酸無水物）の４成分を主成分とするポリアミド酸を脱水閉環して得られるポリイミドを用いたフィルムである（１）〜（８）いずれか一項に記載のプリント配線板の製造方法。
（１２）（１）〜（１１）のいずれか一項に記載のプリント配線板の製造方法において、前記積層体を貫通するビアホールを形成する工程と、第２金属層の表面およびビアホール内部に触媒を塗布する工程と、該触媒を用いて第２金属層表面およびビアホール内部に無電解メッキ銅を施す工程と、無電解メッキ銅上に電解メッキ銅を施す工程、を含むプリント配線板配線板の製造方法。
（１３）さらに、サブトラクティブ法によりエッチングをおこない回路形成を行う工程を含む（１２）に記載のフレキシブルプリント配線板の製造方法
（１４）（１）〜（１１）のいずれか一項に記載のプリント配線板の製造方法において、積層体を貫通するビアホールを形成する工程と、第２金属層の表面およびビアホール内部に触媒を塗布する工程と、該触媒を用いて第２金属層表面およびビアホール内部に無電解メッキ銅を施す工程と、無電解メッキ銅上にレジスト膜を形成する工程と、回路の形成を予定する部分のレジスト被膜を取り除く工程と、無電解メッキ膜が露出する部分を給電電極として使用して電解銅メッキを行い回路を形成する工程と、レジスト被膜を除去する工程と、無電解銅メッキ皮膜、および、該第１金属層、第２金属層をエッチング除去する工程とを含むプリント配線板の製造方法。
【００１３】
【発明の実施の形態】
以下、本発明に係る金属／ポリイミド／金属積層体の実施の形態を具体的に説明する。
【００１４】
まず、本発明に係る金属／ポリイミド／金属積層体及びフレキシブルプリント配線板に用い得るポリイミドフィルムについて説明する。このポリイミドフィルムは、チタンの元素を含むことを必須とする。本発明において使用されるポリイミドフィルムは、「Ｊｏｕｒｎａｌ　　ｏｆ　Ｐｏｌｙｍｅｒ　　Ｓｃｉｅｎｃｅ：ｐａｒｔＡ　　ｖｏｌ．３　　ＰＰ．１３７３−１３９０（１９６５）」等に開示されている公知の方法で製造することができる。即ちポリアミド酸を支持体に流延、塗布し、化学的にあるいは熱的にイミド化することで得られる。好ましくは化学的にイミド化することが、フィルムの靭性、破断強度、及び生産性の観点から好ましい。
【００１５】
本発明に用いられるポリイミドの前駆体であるポリアミド酸は、基本的には、公知のあらゆるポリアミド酸を適用することができる。本発明に用いられるポリアミド酸は、通常、芳香族酸二無水物の少なくとも１種とジアミンの少なくとも１種を、実質的等モル量を有機溶媒中に溶解させて、得られたポリアミド酸有機溶媒溶液を、制御された温度条件下で、上記酸二無水物とジアミンの重合が完了するまで攪拌することによって製造される。また、ポリイミドはポリアミド酸をイミド化して得られるが、イミド化には、熱キュア法及びケミカルキュア法のいずれかを用いる。熱キュア法は、脱水閉環剤等を作用させずに加熱だけでイミド化反応を進行させる方法である。また、ケミカルキュア法は、ポリアミド酸有機溶媒溶液に、無水酢酸等の酸無水物に代表される化学的転化剤（脱水剤）と、イソキノリン、β−ピコリン、ピリジン等の第三級アミン類等に代表される触媒とを作用させる方法である。ケミカルキュア法に熱キュア法を併用してもよい。イミド化の反応条件は、ポリアミド酸の種類、フィルムの厚さ、熱キュア法及び／またはケミカルキュア法の選択等により変動し得る。
【００１６】
ここで、本発明に係るポリイミド前駆体ポリアミド酸組成物に用いられる材料について説明する。本ポリイミドにおける使用のための適当な酸無水物は、ピロメリット酸二無水物、２，３，６，７−ナフタレンテトラカルボン酸二無水物、３，３’，４，４’−ビフェニルテトラカルボン酸二無水物、１，２，５，６−ナフタレンテトラカルボン酸二無水物、２，２’，３，３’−ビフェニルテトラカルボン酸二無水物、３，３’，４，４’−ベンゾフェノンテトラカルボン酸二無水物、２，２−ビス（３，４−ジカルボキシフェニル）プロパン二無水物、３，４，９，１０−ペリレンテトラカルボン酸二無水物、ビス（３，４−ジカルボキシフェニル）プロパン二無水物、１，１−ビス（２，３−ジカルボキシフェニル）エタン二無水物、１，１−ビス（３，４−ジカルボキシフェニル）エタン二無水物、ビス（２，３−ジカルボキシフェニル）メタン二無水物、ビス（３，４−ジカルボキシフェニル）エタン二無水物、オキシジフタル酸二無水物、ビス（３，４−ジカルボキシフェニル）スルホン二無水物、ｐ−フェニレンビス（トリメリット酸モノエステル酸無水物）、エチレンビス（トリメリット酸モノエステル酸無水物　　）、ビスフェノールＡビス（トリメリット酸モノエステル酸無水物）、及びそれらの類似物を含む。
【００１７】
これらのうち、本発明に係る金属／ポリイミド／金属積層体における使用のための最も適当な酸二無水物はピロメリット酸二無水物、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’−ビフェニルテトラカルボン酸二無水物、ｐ−フェニレンビス（トリメリット酸モノエステル酸無水物）であり、これらを単独または、任意の割合の混合物が好ましく用いられる。本発明に係るポリイミド組成物において使用し得る適当なジアミンは、４，４’−ジアミノジフェニルプロパン、４，４’−ジアミノジフェニルメタン、ベンジジン、３，３’−ジクロロベンジジン、４，４’−ジアミノジフェニルスルフィド、３，３’−ジアミノジフェニルスルホン、４，４’−ジアミノジフェニルスルホン、４，４’−ジアミノジフェニルエーテル、３，３’−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、１，５−ジアミノナフタレン、４，４’−ジアミノジフェニルジエチルシラン、４，４’−ジアミノジフェニルシラン、４，４’−ジアミノジフェニルエチルホスフィンオキシド、４，４’−ジアミノジフェニルＮ−メチルアミン、４，４’−ジアミノジフェニルＮ−フェニルアミン、１，４−ジアミノベンゼン（ｐ−フェニレンジアミン）、１，３−ジアミノベンゼン、１，２−ジアミノベンゼン、及びそれらの類似物を含む。これらポリイミドフィルムに用いられるジアミンにおいて、４，４’−ジアミノジフェニルエーテル及びｐ−フェニレンジアミンが特に好ましく、また、これらをモル比で１００：０から０：１００、好ましくは１００：０から１０：９０の割合で混合した混合物が好ましく用い得る。
【００１８】
本発明に好ましい酸二無水物とジアミン類の組み合わせは、ピロメリット酸二無水物と４，４’−ジアミノジフェニルエーテル、ピロメリット酸二無水物と４，４’−ジアミノジフェニルエーテル及びｐ−フェニレンジアミンの組み合わせ、あるいはピロメリット酸二無水物、ｐ−フェニレンビス（トリメリット酸モノエステル酸無水物）と４，４’−ジアミノジフェニルエーテル及びｐ−フェニレンジアミンの組み合わせである。これらのモノマーを組み合わせて合成したポリイミドは適度な弾性率、寸法安定性、低吸水率等の優れた特性を発現し、本発明のポリイミド／金属積層体に用いるのに好適である。ポリアミド酸を合成するための好ましい溶媒は、アミド系溶媒すなわちＮ，Ｎ−ジメチルフォルムアミド、Ｎ，Ｎ−ジメチルアセトアミド、Ｎ−メチル−２−ピロリドンなどであり、Ｎ，Ｎ−ジメチルフォルムアミドが特に好ましく用いられる。
【００１９】
また、イミド化をケミカルキュア法により行なう場合、本発明に係るポリアミド酸組成物に添加する化学的転化剤は、例えば脂肪族酸無水物、芳香族酸無水物、Ｎ，Ｎ　’　−　ジアルキルカルボジイミド、低級脂肪族ハロゲン化物、ハロゲン化低級脂肪族ハロゲン化物、ハロゲン化低級脂肪酸無水物、アリールホスホン酸ジハロゲン化物、チオニルハロゲン化物またはそれら２種以上の混合物が挙げられる。それらのうち、無水酢酸、無水プロピオン酸、無水ラク酸等の脂肪族無水物またはそれらの２種以上の混合物が、好ましく用い得る。これらの化学的転化剤はポリアミド酸溶液中のポリアミド酸部位のモル数に対して１〜１０倍量、好ましくは１〜７倍量、より好ましくは２〜５倍量を添加するのが好ましい。　また、イミド化を効果的に行うためには、化学的転化剤に触媒を同時に用いることが好ましい。触媒としては脂肪族第三級アミン、芳香族第三級アミン、複素環式第三級アミン等が用いられる。それらのうち複素環式第三級アミンから選択されるものが特に好ましく用い得る。具体的にはキノリン、イソキノリン、β−ピコリン、ピリジン等が好ましく用いられる。これらの触媒は化学的転化剤のモル数に対して１／２０〜１０倍量、好ましくは１／１５〜５倍量、より好ましくは１／１０〜２倍量のモル数を添加する。これらの、化学的転化剤及び触媒は、量が少ないとイミド化が効果的に進行せず、逆に多すぎるとイミド化が早くなり取り扱いが困難となる。
【００２０】
本発明に用いられる、チタン化合物は、有機または無機化合物であれば限定されないが、例えば塩化物、臭化物等のハロゲン化物、酸化物、水酸化物、炭酸塩、硝酸塩、亜硝酸塩、リン酸塩、硫酸塩、珪酸塩、ホウ酸塩、縮合リン酸塩等が挙げられる。また、チタン原子との配位結合を形成し得る有機化合物を有する有機チタン化合物であり得る。たとえば、ジアミン、ジホスフィン等の中性分子やアセチルアセトナートイオン、カルボン酸イオン、ジチオカルバミン酸イオン等を有する有機化合物、またポリフィリン等の環状配位子等が挙げられる。これらの化合物はカップリング剤、あるいは金属塩の形で与えられる。これらの化合物は熱重量分析による熱分解温度が１００℃から２５０℃の範囲にあるものが好ましく、この範囲を外れるものは所定の効果を発現しにくい。また、一般式（化７）で示されるものが好ましい。
【００２１】
【化７】

ただし、ｍは０〜４の整数、Ｘは（化８）で示される置換基から選ばれた一種類、
【００２２】
【化８】

あるいはＣ１からＣ１８の炭化水素残基、またはＣ３からＣ１８のカルボン酸およびそのアンモニュウム残基である。
また（化７）あるいは（化８）中、Ｒ１は水素、またはＣ１からＣ１８の炭化水素残基、Ｒ２、Ｒ３はＣ１からＣ１８の炭化水素残基、Ｒ４はＣ１からＣ１８の炭化水素残基、Ｒ４はＣ１からＣ１８の炭化水素残基または一般式（化９）で表される置換基、
【００２３】
【化９】

Ｒ５，Ｒ６はＣ１からＣ１８の炭化水素残基、Ｒ７はＣ１からＣ１８の炭化水素残基、Ｒ８はＣ１からＣ１８の炭化水素残基である。
【００２４】
なお、（化７）中ＸはＣ８からＣ１８の炭化水素残基である事がより好ましく、Ｒ１は水素またはＣ３からＣ１８の炭化水素残基であることがより好ましく、Ｒ２はＣ３からＣ１８の炭化水素残基である事がより好ましく、Ｒ３はＣ３からＣ１８の炭化水素残基である事がより好ましく、Ｒ４はＣ３からＣ１８の炭化水素残基、または一般式（化９）であらわされる置換基である事がより好ましく、Ｒ５はＣ３からＣ１８の炭化水素基である事がより好ましく、Ｒ６はＣ３からＣ１８の炭化水素残基である事がより好ましく、Ｒ７はＣ２からＣ１８の炭化水素残基である事がより好ましい。
【００２５】
中でも、Ｒ１として最も好ましくは−Ｃ３Ｈ７、−Ｃ４Ｈ７を表し、Ｒ２として最も好ましくは−Ｃ１７Ｈ３５を表し、Ｒ３として最も好ましくは−Ｃ１２Ｈ２５を表し、Ｒ４として最も好ましくは−Ｏ−Ｐ（Ｏ）−（ＯＣ８Ｈ１７）２を表し、Ｒ５として最も好ましくは−Ｃ２Ｈ４−を表し、Ｒ６、Ｒ７として最も好ましくは−Ｃ２Ｈ４ＯＨを表す。
【００２６】
具体的にはトリ−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、テトラノルマルブチルチタネート、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などが例示される他、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等も使用可能である。最も好ましいのはトリ−ｎ−ブトキシチタンモノステアレートあるいはジヒドロキシチタンビスラクテートである。上記のチタン元素を含むポリイミドフィルムを用いることにより、優れた接着性を持ち、耐久性に優れた接着信頼性を実現できる。
【００２７】
次にチタン元素をポリイミドフィルムに含有させる方法についてのべる。具体的な方法としては、例えば、ポリイミドの前駆体のポリアミド酸溶液に、チタン元素を含む化合物を混合した後に、ポリアミド酸をポリイミドに転化する方法がある。しかし、この方法ではチタン元素がポリイミドフィルム全体に均一に分散する事になり、フィルム中のチタン元素濃度が低い場合には有効に使用できるが、チタン元素濃度が高い場合にはフィルムが脆くなり好ましくない。好ましい濃度は０．５％以下０．００１％以上であり、０．２％以下、０．００２％以上である事はより好ましく、０．１％以下、０．０１％以上である事は最も好ましい。
【００２８】
チタン元素をポリイミドフィルムに含有させる他の方法として、部分的に硬化または部分的に乾燥されたポリアミド酸フィルムまたはポリイミドフィルムに該元素を含む化合物の溶液を塗布した後、該フィルムを加熱乾燥し、完全にイミド化する方法が、本目的にはより好ましく用いられる。上記元素をポリイミドフィルムに含有させるさらに他の方法としては、部分的に硬化または部分的に乾燥されたポリアミド酸フィルムまたはポリイミドフィルムを、該元素を含む化合物の溶液に浸漬した後、該フィルムを加熱乾燥し、完全にイミド化する方法である。
【００２９】
これらの方法の特徴はポリイミドフィルム表面に存在するチタン元素の原子数濃度がフィルム内部における原子数濃度よりも大きくなる事である。この方法によってチタン元素添加によるポリイミドフィルムの脆弱化を防止する事が出来る。表面とフィルム内部のチタン元素濃度の差は２倍以上、より好ましくは５倍以上、最も好ましくは１０倍以上異なる事が好ましい。これらの濃度差は浸漬時間の選択で制御する事ができる。
【００３０】
以下にさらに詳しくチタン元素の添加法について述べる。最初にチタン元素をポリアミド酸溶液に混合した後、ポリアミド酸をポリイミドに転化する方法について説明する。上記の手法で得られたポリアミド酸溶液は、通常ポリアミド酸固形分として１５〜２５ｗｔ％の濃度で得られる。この範囲の濃度である場合に適当な分子量と溶液粘度を得る。即ち、ポリアミド酸の平均分子量は１０，０００〜１，０００，０００であることが望ましい。平均分子量が１０，０００未満ではできあがったフィルムが脆くなり、一方、１，０００，０００以上を越えるとポリアミド酸ワニスの粘性が高くなりすぎるため、取扱いが困難となる。また、溶液の粘度は１，０００〜１０，０００ポイズ、好ましくは２，０００〜５，０００ポイズが溶液の取り扱い性などの点から好ましい。ポリアミド酸溶液に、チタン化合物を混合する場合の形状は、液状、コロイド状、スラリー状、あるいは固形状のものが可能であり、適当な溶媒に希釈した溶液で混合することは作業性、混合の均一性等の観点から好ましい。
【００３１】
具体的に、例えばケミカルキュア法について説明する。上記得られたチタン元素を含有するポリアミド酸組成物に化学的転化剤と触媒を混合した後、キャスティング面にフィルム状にキャスティングする。次に、例えば１００℃程度で緩やかに加熱し、化学的転化剤と触媒を活性化させて、キャストフィルムをポリアミド酸−ポリイミドゲルフィルム（以下ゲルフィルムという）に転移させる。続いて、得られたゲルフィルムを加熱し、水分や残留する溶媒及び化学的転化剤を除去するとともに、ポリアミド酸をポリイミドに変換する。この加熱によるフィルムの収縮を回避するため、例えば、連続製造法においては、テンター工程においてゲルフィルムをテンダークリップまたピンを用いてフィルムの両端を保持することが好ましい。また、フィルムを乾燥かつイミド化するためには、常法に従い、段階的、連続的に加熱し、最終的に短時間の高温加熱を用いるのが好ましい。具体的には、最終的に５００〜６００℃の温度で１５〜４００秒加熱するのが好ましい。この温度より高いまたは時間が長いと、フィルムの熱劣化が起こる。逆にこの温度より低いまたは時間が短いと所定の効果が発現しない。
【００３２】
次に、上記元素を、部分的に硬化、または部分的に乾燥されたポリアミド酸フィルムまたはポリイミドフィルムに上記元素を含む化合物の溶液を塗布または浸漬した後、加熱乾燥し、ポリイミドフィルムを得る方法について説明する。部分的に硬化または部分的に乾燥されたポリアミド酸フィルムまたはポリイミドフィルム（以下ゲルフィルムという）は公知の方法で製造することができる。即ち、ポリアミド酸をガラス板などの支持体上に流延または塗布し、熱的にイミド化することによって、または化学的転化剤及び触媒をポリアミド酸溶液中に混合し、引き続いてこのポリアミド酸溶液を支持体上にフィルム状にキャストし、１００℃程度の温度で加熱して化学的転化剤及び触媒を活性化することによって、自己支持性を有する程度に硬化しイミド化したゲルフィルムを製造することができる。
【００３３】
ゲルフィルムは、ポリアミド酸からポリイミドへの硬化の中間段階にあり、自己支持性を有し、式１
（Ａ−Ｂ）×１００／Ｂ　　　　　・・・・・・・・式１
（但し：式１中Ａはゲルフィルムの重量、Ｂはゲルフィルムを４５０℃で２０分間加熱した後の重量である）
から算出される揮発分含量は５〜５００％の範囲、好ましくは５〜１００％、より好ましくは５〜５０％の範囲にある。この範囲のフィルムを用いることが好適であり、この範囲を外れると所定の効果が発現しにくい。
赤外線吸光分析法を用いて、式２
（Ｃ／Ｄ）×１００／（Ｅ／Ｆ）　　・・・・・・・・・式２
（但し：式２中Ｃはゲルフィルムの１３７０ｃｍ−１の吸収ピーク高さ、Ｄはゲルフィルムの１５００ｃｍ−１の吸収ピーク高さ、Ｅはポリイミドフィルムの１３７０ｃｍ−１の吸収ピーク高さ、Ｆはポリイミドフィルムの１５００ｃｍ−１の吸収ピーク高さを表す）
から算出されるイミド化率は５０％以上の範囲、好ましくは８０％以上、より好ましくは８５％以上、最も好ましくは９０％以上の範囲にある。この範囲のフィルムを用いることが好適であり、外れると所定の効果が発現しにくい。
【００３４】
本発明において、ゲルフィルムに塗布又は浸漬する該元素を含む化合物の溶液に使用される溶剤は、該化合物を溶解するものであればよく、水、トルエン、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−ジメチルフォルムアミド、アセチルアセトンなどが使用可能である。これらの溶剤を２種類以上混合して使用しても良い。本発明において、Ｎ，Ｎ−ジメチルフォルムアミド、１−ブタノール、および水が特に好ましく用いられ得る。
【００３５】
Ｘ線光電子分光法で測定したポリイミドフィルム表面のチタンの原子数濃度は好ましくは、０．０１％〜１％である。ポリイミドフィルム表面におけるチタン元素の原子数濃度が０．０１％以下である場合には接着力向上の効果が徐々に低下する傾向にある。チタン元素の原子濃度の下限は分析機器の感度限界の関係で規定するのが困難であるが、０．００１％以下では接着力向上の効果はほとんど無くなるものと考えられる。一方、チタン元素の原子濃度が１％以上であると回路形成をした場合にその絶縁性が低下する傾向があり好ましくない。これは残留チタン元素の影響であろうと考えられる。そのようなフィルムを得るためには、溶液中のチタン化合物の濃度と分子中のチタン元素の積で算出される溶液のチタン元素濃度は、１ｐｐｍ〜５，０００ｐｐｍ、好ましくは１０ｐｐｍ〜２０００ｐｐｍ、より好ましくは３０ｐｐｍ〜１０００ｐｐｍが好適である。これらの溶液のチタン元素濃度と浸漬時間の組合せによりポリイミドフルム表面、および内部のチタン元素濃度を制御できる。
【００３６】
上記の、部分的に硬化または部分的に乾燥されたポリアミド酸フィルムまたはポリイミドフィルムに、上記元素を含む溶液を塗布する方法は、当業者が用い得る公知の方法を用い得るが、例えば、グラビアコート、スプレーコート、ナイフコーター等を用いた塗布方法が利用可能であり、塗布量の制御や均一性の観点より、グラビアコーターが特に好ましく用い得る。塗布量としては０．１ｇ／ｍ２〜１００ｇ／ｍ２好ましくは１ｇ／ｍ２〜１０ｇ／ｍ２が好適であり、この範囲を外れると、効果と、フィルムの外観のバランスを両立しにくい。
【００３７】
また、上記元素を含む溶液を浸漬する場合は、特に制限はなく、一般的なディプコート法が利用し得る。具体的には、上記溶液を入れた槽に上記部分的に硬化または部分的に乾燥されたポリアミド酸フィルムまたはポリイミドフィルムを連続的に、またはバッチで浸すことにより行われる。浸漬時間は１〜１００秒、好ましくは１〜２０秒が好適である。部分的に硬化または部分的に乾燥されたポリアミド酸フィルムまたはポリイミドフィルムは、上記元素を含む化合物の溶液を塗布、又は浸漬した後フィルム表面の余分な液滴を除去する工程を加えることが、フィルム表面にムラのない外観の優れたポリイミドフィルムを得ることが出来るので好ましい。液滴の除去は、ニップロールによる液絞り、エアナイフ、ドクターブレード、拭き取り、吸い取りなどの公知の方法が利用可能であり、フィルムの外観、液切り性、作業性等の観点より、ニップロールが好ましく用いられ得る。
【００３８】
この上記元素を含む溶液を塗布または浸漬したゲルフィルムを加熱し、ポリイミドに転化する。ゲルフィルムをポリイミドに転化しするためには、常法に従い、段階的、連続的に加熱し、最終的に短時間の高温を用いるのが好ましい。具体的には、最終的に５００〜６００℃の温度で１５〜４００秒加熱するのが好ましい。この温度より高いまたは時間が長いとフィルムの熱劣化が起る。逆にこれより温度が低いか、または処理時間が短いと所定の効果が発現しない。
【００３９】
これらのチタン元素を含有したポリイミドフィルムの表面をエックス線光電子分光法で分析すると、フィルム表面から原子数濃度で０．０１〜１％チタン元素が検出される。また、既述の如く、ゲルフィルムにチタン化合物溶液を塗布、または浸漬して製造したポリイミドフィルムを、飛行時間型二次イオン質量分析装置を用いてフィルムの厚み方向でのチタンの濃度分布を分析すると、チタンはフィルム表層部に高濃度で存在し、厚み方向の中央部ではチタンの濃度は表層部の１／２以下であり、浸漬時間を上記の範囲とすると厚み方向の中央部でのチタンの濃度は表層部の濃度の１／１０以下とする事ができた。
【００４０】
上記種々の方法で得られるポリイミドフィルムは、公知の方法で無機あるいは有機物のフィラー、有機リン化合物等の可塑剤や酸化防止剤を添加してもよく、またコロナ放電処理やプラズマ放電処理等の公知の物理的表面処理や、プライマー処理等の化学的表面処理を施し、さらに良好な特性を付与し得る。
【００４１】
ポリイミドフィルムの厚みは、２μｍ以上、１２５μｍ以下であることが好ましく、５μｍ以上、５０μｍ以下であることがより好ましい。この範囲より厚みが薄いと積層体の剛性が不足し取り扱い性が悪くなり、また層間の電気絶縁性が悪くなる等の問題が生じる。一方、フィルムが厚すぎるとプリント配線板の薄型化の傾向に逆行する事になる。また、インピーダンス制御の点から絶縁層厚みが厚くなると回路幅を広くする必要があり、このことはプリント配線板の小型化、高密度化の要請に逆行するものである。
【００４２】
ポリイミド表面の１０点平均粗さ（Ｒｚと言う）で２μｍ以下好ましくは１μｍ以下であることが好ましい。表面が平滑であることはライン／スペース２５／２５μｍ以下の高密度回路を形成するのに好適であり、エッチング工程において樹脂表面の凹凸にエッチング残りが生じない点からも好適である。ＲｚはＪＩＳＢ０６０１等の表面形状に関する規格に規定されており、その測定には、ＪＩＳ　Ｂ０６５１の触針式表面粗さ計やＢ０６５２の光波干渉式表面粗さ計を用いることができる。本発明では、光波干渉式表面粗さ計ＺＹＧＯ社製ＮｅｗＶｉｅｗ５０３０システムを用いて高分子フィルムの１０点平均粗さを測定した。
このポリイミドフィルムの内部には、導体回路や、スルーホール等を有していても良い。また、第一金属被膜との引き剥がし強さを向上するためにポリイミドフィルムの表面に粗化処理や、コロナ放電処理、プラズマ処理、火炎処理、加熱処理、プライマー処理、等の公知の表面処理を施しても良い。
【００４３】
次に本発明にかかる金属層について説明する。
まず、金属層の形成方法としては真空蒸着法、イオンプレーティング法、スパッタリング法等の物理的手法が適用し得る。本発明において金属層の厚みは２０ｎｍ以上５００ｎｍ以下である。特に、設備の簡便さ、生産性、得られる導体層と高分子フィルムの接着性などを総合的に判断するとスパッタリングが好ましい。
【００４４】
スパッタリングを用いる場合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中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を組み合わせて通常６×１０−４Ｐａ以下まで真空引きする。次いでスパッタガスを導入しチャンバー内を０．１Ｐａ〜１０Ｐａ好ましくは０．１Ｐａ〜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で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無いようにしながら、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（プレスパッタという）。プレスパッタの終了後、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う。スパッタ時の放電パワーは好ましくは１００Ｗ〜１０００Ｗの範囲である。また、スパッタするサンプルの形状に従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。
【００４５】
また、高分子フィルムとスパッタ膜との密着性を向上するために前処理としてプラズマ放電処理、コロナ放電処理、加熱処理、イオンボンバード処理、等を適用することができる。通常、これらの処理の後高分子フィルムを大気などに触れさせると改質した表面が失活して処理効果が大幅に減少することがあるため、これらの処理を真空中で行い、そのまま真空中で連続してスパッタすることが好ましい。
【００４６】
以上述べた、スパッタリング法では精度良く均一な薄膜が製造できるが、一般的にスパッタリング法によって形成された銅あるいは銅合金の薄膜は、表面平面性にすぐれた高分子フィルム上では強固な接着を実現する事はできない。我々の検討でも、Ｒｚ値が３μｍ以下の表面性のポリイミドフィルム上では３Ｎ／ｃｍ以上の強度の接着性は実現できなかった。この事は本発明の方法であるチタン元素を含むポリイミドフィルムにおいても同様で、その様なポリイミドフィルムを用いても４Ｎ／ｃｍ以上の強度の接着性は実現できなかった。
【００４７】
その様な状況に鑑み、本発明にかかる金属層の第一の生成法は下地金属層を設け、該金属層を２層構造とする方法である。上記の様な接着性を改善する目的で、樹脂基板とスパッタリング金属膜との間に下地金属を形成する。下地金属としてはニッケル、クロム、チタン、モリブデン、タングステン、亜鉛、スズ、インジウム、あるいはこれらの合金が用いられ、特にニッケル、クロム、チタンを用いる事は有効であり、ニッケルあるいはニッケルとクロムの合金を用いる事は特に好ましい。クロムとニッケルの合金を用いる主な目的はスパッタリング速度を上げることにある。磁性体である純ニッケル金属ではスパッタリング速度をあげる事が難しい。しかし、ニッケルとクロムの合金とする事によりスパッタリング速度を上げる事が出来る。この目的達成のためにクロムとニッケルの比率は特に限定されないが、一般的には２％以上である事が望ましい。
【００４８】
この様な金属下地層を用いる事により５Ｎ／ｃｍ以上の優れた接着性を実現できた、さらにこの様な金属下地層とチタン元素ポリイミドフィルムを用いる事を併用して、７Ｎ／ｃｍ以上の強固な接着性を実現できる事が分かった。特に後者の方法での接着では、プレッシャークッカーテスト（ＰＣＴテスト）後にも６Ｎ／ｃｍの優れた接着強度を有している事が分かった。また、これらの下地金属上にスパッタリング法で形成された銅および銅合金からなる金属層は、化学処理プロセスにつよく、その表面に容易に無電解メッキプロセスを用いて銅メッキの膜を形成してもその接着力が低下する事はなかった。
【００４９】
この場合、ニッケルあるいはニッケルとクロムの合金による下地層の厚みは２ｎｍ以上、１００ｎｍ以下が好ましく、３ｎｍ以上２０ｎｍ以下である事がより好ましい。これよりも薄いと接着性を向上する効果が不十分である。一方、銅層の厚みは１０ｎｍ以上、５００ｎｍ以下である事が望ましく、２０ｎｍ以上、３００ｎｍ以下である事がより好ましく、３０ｎｍ以上、２００ｎｍ以下である事が最も好ましい。これらの金属厚みの合計は経済性とエッチング性の観点から５００ｎｍよりも薄い事が好ましく、３００ｎｍ以下である事はより好ましく、２００ｎｍ以下である事が最も好ましい。５００ｎｍ以上厚いとエッチング性が悪くなり、高密度回路パターンを形成するのに不適当である。２種類以上の金属層を積層、形成する場合はそれぞれのスパッタ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、スパッタリングは真空中で連続して行うことが好ましい。
【００５０】
本発明にかかる金属層の第二の生成法は、二種類の異なった物理的手法で形成された銅あるいは銅の合金層よりなる２層構造とする方法である。ここで言う銅合金とは銅を主成分とした合金を言い、添加される金属としてはニッケル、クロム、チタンなどが挙げられる。前記の異種金属下地層を設ける第一の方法では、作成された金属膜では本質的に２種類以上の金属が用いられるために、セミアディティブ法でのエッチングプロセス（すなわち電解メッキ後の給電層の剥離プロセス）で、銅以外の金属のエッチング工程が余分に必要となると言う問題があった。
【００５１】
そこで我々は銅あるいは銅合金のみからなる金属層の形成法の検討をおこなった。その結果、イオンプレーティング法とスパッタ法の組み合わせで銅あるいは銅合金からなる層を形成する事でこの問題を解決できる事を発見し、金属層の第二の形成法の発明に至った。すなわち、種々検討の結果、イオンプレーティング法で作成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事が分った。特に、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５Ｎ／ｃｍ以上の強固な銅薄膜を形成できる事が分った。
【００５２】
しかしながらさらに検討の結果、イオンプレーティング法で作成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メッキのプロセスを用いて銅薄膜を形成しようとすると、高分子基板から剥離してしまう事が分った。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の上にさらにスパッタ法で銅薄膜を形成する事を試みた。スパッタリング法は特に限定されず、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等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ポリイミド膜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の形成を形成しても変わる事はなかった。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メッキ法でメッキ膜を形成する事が出来た。すなわちスパッタ膜は無電解メッキ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メッキ層との接合の役割を果たすものと考えられる。この様な手法とチタン含有ポリイミドフィルムを併用して用いる事により７Ｎ／ｃｍ以上の強固な接着が可能となった。また、この接着強度はＰＣＴ試験の後にも６Ｎ／ｃｍ以上の優れた接着特性を有していた。
【００５３】
この様なプロセスを実現するためのイオンプレーティング銅層の最適厚さは、２ｎｍ以上、１００ｎｍ以下であった。２ｎｍ以下では基板となる高分子との強固な接着が実現出来なかった。また、１００ｎｍ以上では高分子基板との接着強度が低下する傾向にあり、さらにセミアディティブ工法でのエッチングプロセスで余分にエッチングを行う必要があり、回路形状が劣化すると言う問題が生じる。また、この様なプロセスを実現するためのスパッタ銅層の最適厚さは、１０ｎｍ以上、５００ｎｍ以下であった。１０ｎｍ以下ではイオンプレーティング層との強固な接着が実現出来ず、また無電解メッキプロセスでの保護膜としての役割も十分でない。また５００ｎｍ以上ではセミアディティブ工法のエッチングプロセスで余分にエッチングを行う必要があり、回路形状が劣化すると言う問題が生じる。また、同じ理由から、この方法による金属層の厚さの合計は５００ｎ以下が好ましく、３００ｎｍ以下がより好ましく、２００ｎｍ以下が最も好ましい。
【００５４】
次に、本発明に係る金属層／ポリイミド／金属層積層体について説明する。
【００５５】
本発明の金属層／ポリイミド／金属層積層体の少なくとも片方の面の金属層は上記のいくつかの物理的方法で作製された金属層であるが、他の面の金属層は同じ手法で形成された金属層でも良く、湿式化学法で形成されたものでも良い。
【００５６】
次にこの様な、金属層／ポリイミド／金属層積層体を用いた配線板の製造方法についてのべる。
【００５７】
金属層／ポリイミド／金属層積層体の両面が物理的方法で形成された金属層である場合には以下に示す代表的な二つの方法でプリント配線板の製造が可能である。無論、ここに示した方法は代表的な方法であって、本発明の製造方法がこれに限定されるものではない事は言うまでもない。
【００５８】
第一のプリント配線板の製造方法はでは、まず積層体を貫通するビアホールを形成する。ビアホールの形成は通常の機械的なドリル法、あるいは、炭酸ガスレーザーやＵＶ−ＹＡＧレーザーを用いたレーザーによる穴開け法が可能である。貫通穴を形成後、金属層の表面およびビアホール内部に触媒を塗布する。触媒としてはパラジュウム触媒が用いられる。次に該触媒を用いて両面の金属層表面およびビアホール内部に無電解メッキ銅を施す。次に無電解メッキ銅上にレジスト膜を形成し、露光、エッチング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。次に無電解メッキ膜が露出する部分を給電電極として使用して電解銅メッキを行い、この電解メッキ法により回路を形成する。ついでレジスト部分を取り除き不要部分の無電解メッキ層、物理的方法で形成された金属層をエッチングにより取り除いて回路を形成する。
【００５９】
金属／ポリイミド／金属積層体の両面が物理的方法で形成された金属層である場合、第二のプリント配線板の方法は以下のように行われる。すなわち、まず、金属層／ポリイミド／金属層積層体を貫通するビアホールを形成する。次に上記と同様に金属層の表面に触媒を塗布し、該触媒を用いて金属層表面およびビアホール内部に無電解メッキ銅層を形成する。次に無電解メッキ銅上に電解メッキ銅を施して、二つの金属層がビアホールによって接続された金属層／ポリイミド層／金属層からなる積層体を作製する。次に電解銅メッキ層表面にレジスト膜を形成し、露光、エッチングにより回路の形成しない部分のレジスト被膜を取り除き、次にエッチングにより不要な金属層を取り除き回路を形成する。
【００６０】
本発明で得られたポリイミド／金属積層体はフレキシブルプリント配線板、フレキシブルプリント配線板を積層した多層プリント配線板、フレキシブルプリント配線板と硬質プリント配線板を積層したリジッド・フレックス配線板、ポリイミド／金属積層体をＴＡＢ（Ｔａｐｅ　　Ａｕｔｏｍａｔｅｄ　　Ｂｏｎｄｉｎｇ）に適用したＴＡＢ用テープ、プリント配線板上に直接半導体素子を実装したＣＯＦ（Ｃｈｉｐ　　Ｏｎ　　Ｆｉｌｍ）、ＭＣＭ（Ｍｕｌｔｉ　　Ｃｈｉｐ　　Ｍｏｄｕｌｅ）等の半導体パッケージなどに応用可能であり、これらの用途について公知の方法で加工することができる。
【００６１】
以上述べた様に、本発明に係る金属／ポリイミド／金属積層体を用いることにより、ライン／スペース（Ｌ／Ｓ）が２０μｍ以下であるような高密度回路形成が可能で、優れた接着性と高温・高湿、等の厳しい環境における高い接着信頼性を持つフレキシブルプリント配線板、フレキシブルプリント配線板を積層した多層プリント配線板、フレキシブルプリント配線板と硬質プリント配線板を積層したリジッド・フレックス配線板、ＴＡＢ（Ｔａｐｅ　　Ａｕｔｏｍａｔｅｄ　　Ｂｏｎｄｉｎｇ）に適用したＴＡＢ用テープ、プリント配線板上に直接半導体素子を実装したＣＯＦ（Ｃｈｉｐ　　Ｏｎ　　Ｆｉｌｍ）、ＭＣＭ（Ｍｕｌｔｉ　ＣｈｉｐＭｏｄｕｌｅ）、等の半導体パッケージを得ることができる。
【００６２】
【実施例】
以下に実施例を挙げて、本発明の効果を具体的に説明するが、本発明は以下の実施例に限定されるものではなく、当業者は本発明の範囲を逸脱することなく、種々の変更、修正、及び改変を行い得る。なお、実施例中の種々の分析、測定、評価、ポリイミドフィルムの作製、金属層の形成法、は以下の方法で行った。
（ポリイミドフィルム表面のチタン原子数濃度）
エックス線光電子分光分析装置（アルバックファイ社製、Ｍｏｄｅｌ−５４００）を用い、エックス線源：ＭｇのＫα線、エネルギー７１．５５電子ボルトの条件で分析した。
（接着強度）
ＩＰＣ―ＴＭ−６５０−ｍｅｔｈｏｄ．２．４．９に従い、パターン幅３ｍｍ、剥離角度
９０度、剥離速度５０ｍｍ／ｍｉｎで測定した。
（プレッシャークッカー試験）
１２１℃、１００％ＲＨ、９６時間、の条件下で試験を行った。
（ポリイミドフィルムの作製法−Ａ）
ピロメリット酸二無水物／４，４’−ジアミノジフェニルエーテル／ｐ−フェニレンジアミンをモル比で４／３／１の割合で合成したポリアミド酸の１７ｗｔ％のＤＭＦ溶液９０ｇに無水酢酸１７ｇとイソキノリン２ｇからなる転化剤を混合、攪拌し、遠心分離による脱泡の後、アルミ箔上に厚さ７００μｍで流延塗布した。攪拌から脱泡までは０℃に冷却しながら行った。このアルミ箔とポリアミド酸溶液の積層体を１１０℃、４分間加熱し、自己支持性を有するゲルフィルムを得た。このゲルフィルムの残揮発分含量は３０ｗｔ％であり、イミド化率は９０％であった。このゲルフィルムをアルミ箔から剥がし、フレームに固定した。このゲルフィルムを３００℃、４００℃、５００℃で各１分間加熱して厚さ２５μｍのポリイミドフィルムを製造した。
（ポリイミドフィルムの作製法−Ｂ）
ピロメリット酸二無水物／４，４’−ジアミノジフェニルエーテルモル比で１／１の割合で合成する以外は作製法−Ａと同様の方法でポリイミドフィルムを作製した。
（ポリイミドフィルムの作製法−Ｃ）
３，３’，４，４’−ビフェニルテトラカルボン酸二無水物／ｐ−フェニレンビス（トリメリット酸モノエステル酸無水物）／ｐ−フェニレンジアミン／４，４’−ジアミノジフェニルエーテルをモル比で４／５／７／２の割合で合成したポリアミド酸の１７ｗｔ％のＤＭＡｃ溶液を用い、これに転化剤を混合しないでアルミ箔上に厚さ７００μｍで流延塗布した。このアルミ箔とポリアミド酸溶液の積層体を１１０℃１０分間加熱し、自己支持性を有するゲルフィルムを得た。このゲルフィルムの残揮発分含量は３０ｗｔ％であり、イミド化率は５０％であった。このゲルフィルムを用い作成法−Ｃと同様の方法でポリイミドフィルムを作製した。
（ポリイミドフィルムの作製法−Ｄ）
ピロメリット酸二無水物／ｐ−フェニレンビス（トリメリット酸モノエステル酸無水物）／ｐ−フェニレンジアミン／４，４’−ジアミノジフェニルエーテルをモル比で５／５／４／６の割合で合成する以外は作製例−Ａ同様の方法でポリイミドフィルムを作製した。
（ポリイミドフィルム（チタンを含む）の作成法−Ｅ）
ポリイミドフィルム作製法−Ａ、Ｂ、Ｃ、Ｄと同様の方法で得たゲルフィルムを、チタン元素濃度１００ｐｐｍのジヒドロキシチタンビスラクテート／イソプロピルアルコール溶液に１０秒間浸漬し、圧縮空気を吹き付けて余分な液滴を除去した後、作製法−Ａと同じ条件で加熱し、表面にチタン原子が存在するポリイミドフィルムを製造した。
（ポリイミドフィルム（チタンを含む）の作成法−Ｆ）
ポリイミドフィルムの作成法−Ａ、Ｂ、Ｃ、Ｄと同様の方法で得たゲルフィルムに、チタン元素濃度１０００ｐｐｍのジヒドロキシチタンビスラクテート／イソプロピルアルコール溶液をスプレーコート方式で余分な液がフィルムに付着しないように塗布した後、作製法−Ａと同じ条件で加熱し、表面にチタン原子が存在するポリイミドフィルムを製造した。
（ポリイミドフィルム（チタンを含む）の作成法−Ｇ）
ポリイミドフィルムの作成法−Ａ、Ｂ、Ｃ、Ｄと同様の方法で得たゲルフィルムを、チタン元素濃度１００ｐｐｍのトリ−Ｎ−ブトキシチタンモノステアレート／トルエン溶液に１０秒間浸漬し、ニップロールで余分な液滴を除去した後、作成法−Ａと同じ条件で加熱し、表面にチタン原子が存在するポリイミドフィルムを製造した。
（スパッタリング法による金属層の形成）
ポリイミドフィルムへの金属層の形成は、昭和真空社製スパッタリング装置ＮＳＰ−６を用い、下記の方法で行った。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る。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以下まで真空引きする。その後、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ニッケル、次いで銅をスパッタリングする。ＤＣパワーはどちらも２００Ｗでスパッタリングした。製膜速度は、ニッケルが７ｎｍ／ｍｉｎ、銅が１１ｎｍ／ｍｉｎであり、成膜時間を調整して成膜厚みを制御した。
（イオンプレーティング法とスパッタリング法の組合せによる金属層の形成）ポリイミドフィルムへのイオンプレーティング法による金属層の形成は、神港精機（株）製ＡＩＦ型イオンプレーティング装置を用い、以下の方法を用いて行った。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。５〜１０００ｎｍの範囲で種々の厚さの膜を作成した。
【００６３】
次いで、その様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：２００Ｗ，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成した。
【００６４】
【実施例】
（実施例１）
ポリイミド作製法Ａ，Ｂ，Ｃ，Ｄで作製したポリイミドフィルム、および作製法Ａで作製したフィルムを基に、Ｅ，Ｆ，Ｇの方法で作製したチタン含有ポリイミドフィルムを用い、各ポリイミドフィルムの両面に３分間ニッケルをスパッタし厚み６ｎｍのニッケル膜を形成し、連続して０．９分間銅をスパッタして厚み１００ｎｍの銅膜を形成し、金属／ポリイミド積層体を得た。また、Ｅ、Ｆ、Ｇの方法ではチタン元素濃度、ディップ時間を変えてチタン元素濃度を変えた試料を２つ作製した。（これを例えばＥ−１、Ｅ−２と記している。）得られたスパッタ膜を給電層として用いて電解メッキ法により厚さ５μｍの銅層を形成し、上記、手法でその常温での接着強度および、ＰＴＣ試験後の接着強度を測定した。その結果を表１にしめす。
【００６５】
【表１】

この結果から、ニッケル下地層を設ける事によりいずれのポリイミドでも５Ｎ／ｃｍ以上のすぐれた初期接着強度が実現できた。さらに、ＰＣＴ後の接着強度も４Ｎ／ｃｍ以上を確保できた。さらに、チタン含有ポリイミドとニッケル下地層の形成によりすぐれたＰＣＴ後の接着性が実現できる事がわかった。
（比較例１）
実施例１と同様の方法で、ニッケル下地層のない積層体を作製し、同様の方法で接着性を測定した。その結果を表２にしめす。
【００６６】
【表２】

この結果から、表１との比較を行う事によりニッケル下地層が無い場合には所定の効果が出ず、チタン含有ポリイミドを用いてもＰＣＴ後の接着強度は２Ｎ／ｃｍまで低下した。この事からニッケル下地層の効果が確認できた。
（実施例２）
実施例例１と同じ方法で種々の厚さのニッケル下地層、銅層よりなる金属層を形成しその接着強度を測定した。その結果を表３に示す。
【００６７】
【表３】

この結果から、下地層（第１金属層）の厚さが２ｎｍ以上、１００ｎｍ以下であり、その表面の形成された第２金属の厚層さが１０ｎｍ以上、５００ｎｍ以下であれば特に優れた接着性を有する積層体が得られる事が分った。
（実施例３）
下地層（第１金属層）としてイオンプレーティング法により銅金属層を設けた以外は実施例１と同様の方式で、種々の積層体を作製し、その接着性を測定した。その結果を表４にしめす。この結果から、下地層（第１金属層）の厚さが２ｎｍ以上、１００ｎｍ以下であり、その表面の形成された第２金属の厚層さが１０ｎｍ以上、５００ｎｍ以下であれば優れた接着性を有する積層体が得られる事が分った。
【００６８】
【表４】

（実施例４）
ポリイミドフィルムの製造法Ａ、Ｂ、Ｃ、Ｄをもちいて作製したポリイミドフィルムを用い、作成法Ｆを用いてチタン含有ポリイミドフィルムを作製した。次に実施例１と同じ方法で各ポリイミドフィルムの両面に３分間ニッケルをスパッタし厚み６ｎｍのニッケル膜を形成し、連続して０．９分間銅をスパッタして厚み１００ｎｍの銅膜を形成し、金属／ポリイミド積層体を得た。フィルム表面のチタン濃度は０．０６％、フィルム内部のチタン濃度は０．００２％以下であった。これらの試料では初期接着強度はいずれも７Ｎ／ｃｍであり、ＰＣＴ後の接着強度も６Ｎ／ｃｍ以上であり、ポリイミドの種類によらずすぐれた接着強度を示す事が分った。
（実施例５）
ポリイミドフィルムの製造法−Ｅをもちいて作製したフィルムの両面に、スパッタリング法で５ｎｍの厚さのニッケル下地層（第１金属層）、および１００ｎｍの厚さの銅金属層（第２金属層）を形成した積層体を作製した。この積層体を用いて以下の方法で回路を形成した。
まず、ＵＶ−ＹＡＧレーザーを用いて内径３０μｍの積層体を貫通するビアホールを形成した。次に、無電解メッキ法で金属層表面、およびビアホール内部に銅メッキ層を形成した。無電解メッキ層の形成方法は次の通りである。まずアルカリクリーナー液で積層体を洗浄し、次に酸での短時間プレディップを行った。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。次にアルカリ中での無電解銅メッキを行なった。メッキ温度は室温、メッキ時間は１０分間であり、この方法で３００ｎｍの厚さの無電解銅メッキ層を形成した。　　　　次に、液状感光性めっきレジスト（日本合成ゴム（株）社製、ＴＨＢ３２０Ｐ）をコーティングし、次いで高圧水銀灯を用いてマスク露光を行い、ライン／スペースが１０／１０のレジストパターンを形成した。続いて、電解銅めっきを行って、無電解銅メッキ皮膜が露出する部分の表面に、銅回路を形成した。電解銅めっきは１０％硫酸中で３０秒間予備洗浄し、次に室温中で４０分間メッキを行なった。電流密度は２Ａ／ｄｍ^２である。電解銅膜の厚さは１０μｍとした。次にアルカリ型の剥離液を用いてめっきレジストを剥離し、スパッタニッケル層をニッケルの選択的エッチング液（メック株式会社製エッチング液、ＮＨ−１８６２）で除去してプリント配線板を得た。
【００６９】
得られたプリント配線板は設計値通りのライン／スペースを有しており、また、サイドエッチは無かった。また、給電層剥離部分のオージェ分析、ＥＰＭＡ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無かった。また、回路パターンは６Ｎ／ｃｍの強さで強固に接着していた。
（実施例６）
ポリイミドフィルムの製造法−Ｅをもちいて作製したフィルムの両面に、下地層（第１金属層）としてイオンプレーティング法により厚さ１０ｎｍの銅金属層を設け、次に第２金属層として１００ｎｍの厚さの銅金属層（第２金属層）を形成した積層体を作製した。この積層体を用いて実施例４と同じ方法でライン／スペースが１０／１０μｍの回路を形成した。ただし、回路形成最終段階における、レジスト剥離後の給電層の除去には銅のエッチング液（メック株式会社製、エッチボンドＣＺ−８５００）を用いて行った。
得られたプリント配線板は設計値通りのライン／スペースを有しており、また、サイドエッチは無かった。また、給電層剥離部分のオージェ分析、ＥＰＭＡ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無かった。また、回路パターンは６Ｎ／ｃｍの強さで強固に接着していた。
（実施例７）
ポリイミドフィルムの製造法−Ｅをもちいて作製したフィルムの両面に、スパッタリング法で５ｎｍの厚さのニッケル下地層（第１金属層）、および１００ｎｍの厚さの銅金属層（第２金属層）を形成した積層体を作製した。この積層体を用いて以下の方法で回路を形成した。
まず、ＵＶ−ＹＡＧレーザーを用いて内径３０μｍの積層体を貫通するビアホールを形成した。次に、無電解メッキ法で金属層表面、およびビアホール内部に銅メッキ層を形成した。無電解メッキ層の形成方法は次の通りである。まずアルカリクリーナー液で積層体を洗浄し、次に酸での短時間プレディップを行った。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。次にアルカリ中での化学銅メッキを行った。メッキ温度は室温、メッキ時間は１０分間であり、この方法で３００ｎｍの厚さの無電解銅メッキ層を形成した。続いて、電解銅めっきを行って１０μｍの厚さの銅メッキ層を形成した。電解銅めっきは１０％硫酸中で３０秒間予備洗浄し、次に室温中で４０分間メッキを行った。電流密度は２Ａ／ｄｍ^２である。電解銅膜の厚さは１０μｍとした。
次に、液状感光性めっきレジスト（日本合成ゴム（株）社製、ＴＨＢ３２０Ｐ）をコーティングし、次いで高圧水銀灯を用いてマスク露光を行い、ライン／スペースが１０／１０のレジストパターンを形成した。こうして作製したパターンをもちいて通常のサブトラクティブ法（薬品名：塩化第二鉄）により回路を形成した。次にスパッタニッケル層をニッケルの選択的エッチング液（メック株式会社製エッチング液、ＮＨ−１８６２）で除去し、さらにアルカリ型の剥離液を用いてめっきレジストを剥離してプリント配線板を作製した。
【００７０】
得られたプリント配線板は設計値通りのライン／スペースを有しており、また、サイドエッチは無かった。また、給電層剥離部分のオージェ分析、ＥＰＭＡ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無かった。また、回路パターンは７Ｎ／ｃｍの強度で強固に接着していた。
（実施例８）
ポリイミドフィルムの製造法−Ｅをもちいて作製したフィルムの両面に、イオンプレーティング法で１０ｎｍの厚さの銅下地層（第１金属層）を作製し、次にスパッタリング法により１００ｎｍの厚さの銅金属層（第２金属層）を形成した積層体を作製した。この積層体を用いて実施例８と同じ方法で回路を形成した。ただし、実施例７におけるニッケルの選択的エッチング液（メック株式会社製エッチング液、ＮＨ−１８６２）によるエッチングは実施していない。
得られたプリント配線板は設計値通りのライン／スペースを有しており、また、サイドエッチは無かった。また、給電層剥離部分のオージェ分析、ＥＰＭＡによる残留金属の有無の測定を行ったが残存金属の存在は認められ無かった。また、回路パターンは７Ｎ／ｃｍの強度で強固に接着していた。
【００７１】
【発明の効果】
本発明の金属／ポリイミド／金属積層体を用いて作製したフレキシブルプリント配線板、フレキシブルプリント配線板を積層した多層プリント配線板、フレキシブルプリント配線板と硬質プリント配線板を積層したリジッド・フレックス配線板、該金属／ポリイミド／金属積層体をＴＡＢ（Ｔａｐｅ　ＡｕｔｏｍａｔｅｄＢｏｎｄｉｎｇ）に適用したＴＡＢ用テープ、プリント配線板上に直接半導体素子を実装したＣＯＦ（Ｃｈｉｐ　Ｏｎ　Ｆｉｌｍ）、ＭＣＭ（Ｍｕｌｔｉ　Ｃｈｉｐ　Ｍｏｄｕｌｅ）等は、高密度配線が可能で、接着安定性にすぐれ、さらに高温高湿環境下での高い接着信頼性を持つので広く電子機器のプリント配線板として使用できる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a printed wiring board using a laminate in which a copper metal layer is formed on a polymer film having a smooth flat surface, which is widely used in electric / electronic devices and the like, In particular, the present invention relates to a method of manufacturing a printed wiring board using a three-layered laminate composed of metal / polyimide / metal, which is most suitable for manufacturing a circuit board. More specifically, high-density flexible printed wiring boards with excellent adhesion and environmental stability, multilayer printed wiring boards with laminated flexible printed wiring boards, rigid / flex printed wiring boards with laminated flexible printed wiring boards and rigid printed wiring boards, TAB The present invention relates to a method for producing a tape for (Tape Automated Bonding), a COF (Chip On Film) having a semiconductor element directly mounted on a printed wiring board, an MCM (Multi Chip Module), and the like.
[0002]
[Prior art]
Printed wiring boards with circuits formed on the surface are widely used for mounting electronic components and semiconductor elements, etc., and with the recent demand for miniaturization and high functionality of electronic equipment, such printed wiring boards have There is a strong demand for higher density and thinner circuits. In particular, establishment of a fine circuit forming method in which the line / space interval is 25 μm / 25 μm or less is an important subject in the field of printed wiring boards.
[0003]
Generally, in a printed wiring board, adhesion between a polymer film serving as a substrate and a circuit is achieved by surface irregularities called an anchor effect. Therefore, a step of roughening the film surface is generally provided, and the surface is usually provided with irregularities of about 3 to 5 μm in terms of Rz value. Such irregularities on the surface of the substrate are not a problem when the line / space value of the circuit to be formed is 30/30 μm or more. However, the circuit has a line width of 30/30 μm or less, particularly 25/25 μm or less. Is a serious problem. The reason is that such high-density thin circuit lines are affected by the unevenness of the substrate surface. Therefore, in order to form a circuit having a line / space value of 25/25 μm or less, a circuit forming technique on a polymer substrate having high surface smoothness is required, and the flatness thereof is 2 μm or less in terms of Rz value, and more desirably. It needs to be 1 μm or less. Naturally, in this case, the above-mentioned anchor effect cannot be expected as the adhesive force, so that another adhesive method needs to be developed.
[0004]
On the other hand, circuit boards are required to have higher-density fine wiring and, at the same time, to be more stable under severe environments such as high temperature and high humidity. It is also required to withstand high temperature and high humidity environment. For this reason, a method of strongly bonding to a flat surface must also have excellent environmental resistance.
[0005]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the objects thereof are as follows: (1) A fine circuit wiring firmly adhered to a polyimide polymer substrate having excellent surface smoothness. (2) To provide a method for producing a printed wiring board having excellent adhesion under normal conditions and excellent adhesion stability under high temperature and high humidity. .
[0006]
Various studies have been made to improve the adhesion between the polyimide film and the circuit wiring. For example, Japanese Patent No. 1,948,445 (U.S. Pat. No. 4,742,099) discloses a technique for improving adhesion by adding a titanium-based organic compound to a polyimide film. I have. However, this technique has problems that the film is significantly colored and that the brittleness of the film is reduced due to the high concentration of titanium atoms inside the film. Japanese Patent Application Laid-Open No. 6-73209 (U.S. Pat. No. 5,227,224) discloses an improved surface adhesion coated with a metal salt comprising Sn, Cu, Zn, Fe, Co, Mn or Pd. A polyimide is disclosed. In the present invention, the metal used is titanium, and a metal salt made of Sn, Cu, Zn, Fe, Co, Mn or Pd is not used. U.S. Pat. No. 5,130,192 discloses a method of applying a heat-resistant surface treatment agent to a solidified polyamic acid film and then metallizing the imidized polyimide film. However, in the above technique, there are problems that the film is markedly colored and that the titanium element is present at a high concentration also in the inside of the film and the film is embrittled.
[0007]
In view of such a situation, the present inventors have developed a new method for causing the titanium element to mainly exist on the surface of the polyimide film. The details of the invention are disclosed in JP-A-11-71474. The copper metal layer formed by physical methods such as vapor deposition and the like on the surface of these polyimide films has a much superior adhesive strength as compared with the copper metal layer formed on the normal polyimide film surface containing no titanium element. I was However, these strengths are still insufficient to be applied to fine wiring, and furthermore, there has been a problem that their adhesive strength is reduced in a high-temperature and high-humidity environment.
[0008]
The present inventors have conducted intensive studies to solve the above-mentioned conventional problems, and as a result, have developed a metal / polyimide / metal laminate excellent in adhesiveness under normal conditions and environmental resistance. It has been reached. By using the laminate of the present invention, a flexible printed wiring board having a high density and excellent environmental stability, a multilayer printed wiring board in which flexible printed wiring boards are laminated, and a rigid in which flexible printed wiring boards and rigid printed wiring boards are laminated -Flex wiring boards, TAB (Tape Automated Bonding) tapes, COFs (Chip On Films) in which semiconductor elements are directly mounted on printed wiring boards, MCMs (Multi Chip Modules), and the like can be manufactured.
[0009]
[Means for Solving the Problems]
The present invention can achieve the above object by the following manufacturing method.
(1) A laminate in which a polyimide film and a metal layer are provided on both surfaces thereof, wherein at least one of the metal layers is a first metal layer made of nickel or an alloy thereof in contact with the polyimide film; A method for manufacturing a printed wiring board using a laminate comprising a second metal layer made of copper or an alloy thereof formed on the layer.
(2) A first laminate comprising a polyimide film and a metal layer provided on both surfaces thereof, wherein at least one metal layer is made of copper or a copper alloy formed by an ion plating method in contact with the polyimide film. A method of manufacturing a printed wiring board using a laminate comprising a metal layer and a second metal layer made of copper or a copper alloy formed on the first metal layer.
(3) The method according to (1) or (2), wherein the first metal layer has a thickness of 2 nm to 100 nm, and the second metal layer has a thickness of 10 nm to 500 nm. Manufacturing method of printed wiring board.
(4) The method for producing a printed wiring board according to any one of (1) to (3), wherein the polyimide film is a film containing a titanium element.
(5) The polyimide film according to (1) to (4), wherein the atom number concentration of titanium on the surface of the polyimide film is 0.01% or more and 1% or less as measured by X-ray photoelectron spectroscopy. The method for producing a printed wiring board according to any one of the preceding claims.
(6) The method for producing a printed wiring board according to (5), wherein the polyimide film is a film in which the concentration of a titanium element at the center in the thickness direction of the film is smaller than the concentration of the titanium element on the film surface.
(7) The polyimide film is obtained by casting or coating a polyamic acid on a support and drying to obtain a partially cured or partially dried self-supporting film, and the film is formed of an organic titanium Production of printed wiring board using a laminate according to any one of (1) to (6), which is a polyimide film obtained by applying and / or immersing a solution of the compound in an organic solvent and then converting the polyamic acid into polyimide. Method.
(8) The method for producing a printed wiring board according to any one of (1) to (7), wherein the organic titanium compound is at least one selected from the organic titanium compounds represented by Chemical Formula 1.
[0010]
Embedded image

Here, m is an integer of 0 to 4, X is one selected from substituents represented by (Chemical Formula 2),
[0011]
Embedded image

Alternatively, it is a C1 to C18 hydrocarbon residue, or a C3 to C18 carboxylic acid and its ammonium residue.
In (Chemical Formula 1) or (Chemical Formula 2), R1 is hydrogen, or a C1 to C18 hydrocarbon residue, R2 and R3 are C1 to C18 hydrocarbon residues, R4 is a C1 to C18 hydrocarbon residue, R4 is a C1 to C18 hydrocarbon residue or a substituent represented by the general formula (Formula 3);
[0012]
Embedded image

R5 and R6 are C1 to C18 hydrocarbon residues, R7 is a C1 to C18 hydrocarbon residue, and R8 is a C1 to C18 hydrocarbon residue.
(9) The polyimide film according to any one of claims 1 to 8, wherein the polyimide film is a polyimide film obtained by dehydrating and ring-closing a polyamic acid containing pyromellitic anhydride and 4,4'-diaminodiphenyl ether as main components. Item 13. The method for producing a printed wiring board according to item 9.
(10) The polyimide film is a film using a polyimide obtained by dehydrating and ring-closing a polyamic acid having three main components of pyromellitic anhydride, 4,4'-diaminodiphenyl ether and p-phenylenediamine as main components. The method for producing a printed wiring board according to any one of (1) to (8).
(11) The polyimide film is composed of a polyamic acid mainly composed of four components of pyromellitic anhydride, 4,4′-diaminodiphenyl ether, p-phenylenediamine, and p-phenylenebis (trimellitic acid monoester anhydride). The method for producing a printed wiring board according to any one of (1) to (8), which is a film using a polyimide obtained by dehydration ring closure.
(12) In the method for manufacturing a printed wiring board according to any one of (1) to (11), a step of forming a via hole penetrating the laminate, and a step of forming a catalyst on the surface of the second metal layer and inside the via hole. A step of applying electroless plated copper to the surface of the second metal layer and the inside of the via hole using the catalyst, and a step of applying electrolytic plated copper on the electroless plated copper. Production method.
(13) The method for manufacturing a flexible printed wiring board according to (12), further including a step of forming a circuit by performing etching by a subtractive method.
(14) In the method for manufacturing a printed wiring board according to any one of (1) to (11), a step of forming a via hole penetrating the laminate, and a step of forming a catalyst on the surface of the second metal layer and inside the via hole. A step of applying, a step of applying electroless plated copper to the surface of the second metal layer and the inside of the via hole using the catalyst, a step of forming a resist film on the electroless plated copper, and a step of forming a circuit. A step of removing the resist film, a step of forming a circuit by performing electrolytic copper plating using a portion where the electroless plating film is exposed as a power supply electrode, a step of removing the resist film, and an electroless copper plating film, and Etching the first metal layer and the second metal layer.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the metal / polyimide / metal laminate according to the present invention will be specifically described.
[0014]
First, the polyimide film that can be used for the metal / polyimide / metal laminate and the flexible printed wiring board according to the present invention will be described. This polyimide film must contain a titanium element. The polyimide film used in the present invention can be produced by a known method disclosed in “Journal of Polymer Science: part A vol.3 PP.1373-1390 (1965)” or the like. That is, it can be obtained by casting and coating a polyamic acid on a support and chemically or thermally imidizing it. Preferably, chemically imidization is preferred from the viewpoints of film toughness, breaking strength, and productivity.
[0015]
As the polyamic acid which is a precursor of the polyimide used in the present invention, basically any known polyamic acid can be applied. The polyamic acid used in the present invention is usually a polyamic acid organic solvent obtained by dissolving at least one kind of aromatic dianhydride and at least one kind of diamine in an organic solvent in substantially equimolar amounts. It is produced by stirring the solution under controlled temperature conditions until the polymerization of the dianhydride and diamine is completed. Polyimide is obtained by imidizing a polyamic acid. For the imidization, either a thermal curing method or a chemical curing method is used. The thermal curing method is a method in which the imidization reaction proceeds only by heating without the action of a dehydrating ring-closing agent or the like. In addition, the chemical curing method involves adding a chemical conversion agent (a dehydrating agent) represented by an acid anhydride such as acetic anhydride and a tertiary amine such as isoquinoline, β-picoline and pyridine to a polyamic acid organic solvent solution. This is a method for reacting with a catalyst represented by A thermal cure method may be used in combination with the chemical cure method. The reaction conditions for imidization can vary depending on the type of polyamic acid, the thickness of the film, the selection of the thermal curing method and / or the chemical curing method, and the like.
[0016]
Here, the materials used for the polyimide precursor polyamic acid composition according to the present invention will be described. Suitable acid anhydrides for use in the present polyimide include pyromellitic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic acid Acid dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenone Tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis (3,4-dicarboxy) Phenyl) propane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (2,3 -Dicarboxyphenyl) Tan dianhydride, bis (3,4-dicarboxyphenyl) ethane dianhydride, oxydiphthalic dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, p-phenylenebis (trimellitic acid monohydrate) Ester anhydrides), ethylene bis (trimellitic monoester anhydride), bisphenol A bis (trimellitic monoester anhydride), and the like.
[0017]
Of these, the most suitable acid dianhydrides for use in the metal / polyimide / metal laminates of the present invention are pyromellitic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride. Anhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and p-phenylenebis (trimellitic acid monoester anhydride), and these are preferably used alone or in a mixture at an arbitrary ratio. Used. Suitable diamines that can be used in the polyimide composition according to the present invention are 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenylmethane, benzidine, 3,3'-dichlorobenzidine, 4,4'-diaminodiphenyl Sulfide, 3,3'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylether, 3,3'-diaminodiphenylether, 3,4'-diaminodiphenylether, 1,5-diaminonaphthalene 4,4'-diaminodiphenyldiethylsilane, 4,4'-diaminodiphenylsilane, 4,4'-diaminodiphenylethylphosphine oxide, 4,4'-diaminodiphenyl N-methylamine, 4,4'-diaminodiphenyl N-phenylamine, 1,4-diaminoben Zen (p- phenylene diamine), including 1,3-diaminobenzene, 1,2-diaminobenzene, and their analogs. Among the diamines used for these polyimide films, 4,4′-diaminodiphenyl ether and p-phenylenediamine are particularly preferred, and they are preferably used in a molar ratio of 100: 0 to 0: 100, preferably 100: 0 to 10:90. Mixtures mixed in proportions can be preferably used.
[0018]
Preferred combinations of acid dianhydrides and diamines in the present invention are pyromellitic dianhydride and 4,4′-diaminodiphenyl ether, pyromellitic dianhydride and 4,4′-diaminodiphenyl ether and p-phenylenediamine. A combination or a combination of pyromellitic dianhydride, p-phenylene bis (trimellitic acid monoester anhydride), 4,4′-diaminodiphenyl ether and p-phenylenediamine. Polyimides synthesized by combining these monomers exhibit excellent properties such as moderate elastic modulus, dimensional stability, and low water absorption, and are suitable for use in the polyimide / metal laminate of the present invention. Preferred solvents for synthesizing the polyamic acid are amide solvents, i.e., N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone and the like, and N, N-dimethylformamide is particularly preferred. It is preferably used.
[0019]
When the imidization is carried out by a chemical curing method, the chemical conversion agent added to the polyamic acid composition according to the present invention includes, for example, an aliphatic acid anhydride, an aromatic acid anhydride, N, N′-dialkylcarbodiimide, Examples include lower aliphatic halides, halogenated lower aliphatic halides, halogenated lower fatty acid anhydrides, arylphosphonic dihalides, thionyl halides, and mixtures of two or more thereof. Among them, aliphatic anhydrides such as acetic anhydride, propionic anhydride, and lacnic anhydride or a mixture of two or more thereof can be preferably used. These chemical conversion agents are preferably added in an amount of 1 to 10 times, preferably 1 to 7 times, more preferably 2 to 5 times the molar number of the polyamic acid site in the polyamic acid solution. Further, in order to effectively perform imidization, it is preferable to simultaneously use a catalyst as the chemical conversion agent. As the catalyst, an aliphatic tertiary amine, an aromatic tertiary amine, a heterocyclic tertiary amine or the like is used. Among them, those selected from heterocyclic tertiary amines can be particularly preferably used. Specifically, quinoline, isoquinoline, β-picoline, pyridine and the like are preferably used. These catalysts are added in an amount of 1/20 to 10 times, preferably 1/15 to 5 times, more preferably 1/10 to 2 times the number of moles of the chemical conversion agent. When the amounts of these chemical conversion agents and catalysts are small, imidization does not proceed effectively. On the other hand, when the amounts are too large, imidization is accelerated and handling becomes difficult.
[0020]
The titanium compound used in the present invention is not limited as long as it is an organic or inorganic compound.For example, chlorides, halides such as bromide, oxides, hydroxides, carbonates, nitrates, nitrites, phosphates, Sulfate, silicate, borate, condensed phosphate and the like can be mentioned. Further, an organic titanium compound having an organic compound capable of forming a coordination bond with a titanium atom may be used. Examples thereof include neutral molecules such as diamine and diphosphine, organic compounds having acetylacetonate ion, carboxylate ion, dithiocarbamate ion and the like, and cyclic ligands such as porphyrin. These compounds are provided in the form of a coupling agent or a metal salt. It is preferable that these compounds have a thermal decomposition temperature in the range of 100 ° C. to 250 ° C. by thermogravimetric analysis. Further, those represented by the general formula (Formula 7) are preferable.
[0021]
Embedded image

Here, m is an integer of 0 to 4, X is one kind selected from substituents represented by (Chem. 8),
[0022]
Embedded image

Alternatively, it is a C1 to C18 hydrocarbon residue, or a C3 to C18 carboxylic acid and its ammonium residue.
Further, in (Chemical formula 7) or (Chemical formula 8), R1 is hydrogen, or a C1 to C18 hydrocarbon residue, R2 and R3 are C1 to C18 hydrocarbon residues, R4 is a C1 to C18 hydrocarbon residue, R4 is a C1 to C18 hydrocarbon residue or a substituent represented by the general formula (Formula 9);
[0023]
Embedded image

R5 and R6 are C1 to C18 hydrocarbon residues, R7 is a C1 to C18 hydrocarbon residue, and R8 is a C1 to C18 hydrocarbon residue.
[0024]
In the chemical formula 7, X is more preferably a C8 to C18 hydrocarbon residue, R1 is more preferably hydrogen or a C3 to C18 hydrocarbon residue, and R2 is a C3 to C18 hydrocarbon residue. R3 is more preferably a C3 to C18 hydrocarbon residue, and R4 is a C3 to C18 hydrocarbon residue, or a substituent represented by the general formula (Chemical Formula 9). R5 is more preferably a C3 to C18 hydrocarbon group, R6 is more preferably a C3 to C18 hydrocarbon residue, and R7 is a C2 to C18 hydrocarbon residue. Is more preferable.
[0025]
Among them, R1 most preferably represents -C3H7, -C4H7, R2 most preferably represents -C17H35, R3 most preferably represents -C12H25, and R4 most preferably represents -OP (O)-(OC8H17). ) 2; R5 most preferably represents -C2H4-; and R6 and R7 most preferably represent -C2H4OH.
[0026]
Specific examples include tri-n-butoxytitanium monostearate, diisopropoxytitanium bis (triethanolaminate), butyl titanate dimer, tetra-n-butyl titanate, tetra (2-ethylhexyl) titanate, and titanium octylene glycolate. In addition, dihydroxybis (ammonium lactate) titanium, dihydroxytitanium bislactate and the like can also be used. Most preferred is tri-n-butoxytitanium monostearate or dihydroxytitanium bislactate. By using the above-mentioned polyimide film containing a titanium element, it is possible to realize excellent adhesion and excellent adhesion reliability with excellent durability.
[0027]
Next, a method of including a titanium element in a polyimide film will be described. As a specific method, for example, there is a method in which a compound containing a titanium element is mixed into a polyamic acid solution of a polyimide precursor, and then the polyamic acid is converted into polyimide. However, in this method, the titanium element is uniformly dispersed throughout the polyimide film, and can be used effectively when the titanium element concentration in the film is low.However, when the titanium element concentration is high, the film becomes brittle. Absent. The preferred concentration is 0.5% or less, 0.001% or more, 0.2% or less, more preferably 0.002% or more, and most preferably 0.1% or less, 0.01% or more. preferable.
[0028]
As another method of containing the titanium element in the polyimide film, after applying a solution of a compound containing the element to a partially cured or partially dried polyamic acid film or polyimide film, heat drying the film, A method of completely imidizing is more preferably used for this purpose. As yet another method for incorporating the above elements into a polyimide film, a partially cured or partially dried polyamic acid film or polyimide film is immersed in a solution of a compound containing the element, and then the film is heated. This is a method of drying and completely imidizing.
[0029]
The feature of these methods is that the atomic concentration of the titanium element present on the surface of the polyimide film is larger than the atomic concentration inside the film. This method can prevent the polyimide film from becoming brittle due to the addition of the titanium element. It is preferred that the difference between the titanium element concentration on the surface and the inside of the film be at least two times, more preferably at least five times, and most preferably at least ten times. These differences in concentration can be controlled by selecting the immersion time.
[0030]
Hereinafter, the method of adding the titanium element will be described in more detail. First, a method of converting a polyamic acid into a polyimide after mixing a titanium element with a polyamic acid solution will be described. The polyamic acid solution obtained by the above method is usually obtained at a concentration of 15 to 25 wt% as a solid content of polyamic acid. When the concentration is within this range, an appropriate molecular weight and solution viscosity are obtained. That is, the average molecular weight of the polyamic acid is desirably 10,000 to 1,000,000. If the average molecular weight is less than 10,000, the resulting film becomes brittle. On the other hand, if it exceeds 1,000,000, the viscosity of the polyamic acid varnish becomes too high, and handling becomes difficult. Further, the viscosity of the solution is preferably from 1,000 to 10,000 poise, and more preferably from 2,000 to 5,000 poise from the viewpoint of handleability of the solution. When the titanium compound is mixed with the polyamic acid solution, the liquid, colloidal, slurry, or solid form can be used, and mixing with a solution diluted in an appropriate solvent is not suitable for workability and mixing. It is preferable from the viewpoint of uniformity and the like.
[0031]
Specifically, for example, a chemical cure method will be described. After a chemical conversion agent and a catalyst are mixed with the obtained polyamic acid composition containing a titanium element, the film is cast on a casting surface. Next, the cast film is transferred to a polyamic acid-polyimide gel film (hereinafter referred to as a gel film) by gently heating, for example, at about 100 ° C. to activate the chemical converting agent and the catalyst. Subsequently, the obtained gel film is heated to remove water, remaining solvent and chemical converting agent, and to convert polyamic acid into polyimide. In order to avoid shrinkage of the film due to this heating, for example, in a continuous manufacturing method, it is preferable to hold both ends of the film using a tender clip or a pin in the tenter process. Further, in order to dry and imidize the film, it is preferable to heat the film stepwise and continuously according to a conventional method, and finally to use high-temperature heating for a short time. Specifically, it is preferable to finally heat at a temperature of 500 to 600 ° C. for 15 to 400 seconds. If the temperature is higher or the time is longer, thermal degradation of the film occurs. Conversely, if the temperature is lower than this temperature or the time is short, the predetermined effect is not exhibited.
[0032]
Next, after applying or immersing a solution of a compound containing the above element in a partially cured or partially dried polyamic acid film or polyimide film, heating and drying the above element to obtain a polyimide film explain. The partially cured or partially dried polyamic acid film or polyimide film (hereinafter referred to as a gel film) can be produced by a known method. That is, the polyamic acid is cast or coated on a support such as a glass plate and thermally imidized, or a chemical conversion agent and a catalyst are mixed in the polyamic acid solution, and then the polyamic acid solution is mixed. Is cast into a film on a support and heated at a temperature of about 100 ° C. to activate the chemical conversion agent and the catalyst, thereby producing a gel film which is cured and imidized to a degree having self-supporting properties. be able to.
[0033]
The gel film is in the middle stage of curing from polyamic acid to polyimide, has self-supporting properties, and has the formula 1
(A−B) × 100 / B Equation 1
(However, in Formula 1, A is the weight of the gel film, and B is the weight after heating the gel film at 450 ° C. for 20 minutes.)
The volatiles content calculated from is in the range of 5 to 500%, preferably 5 to 100%, more preferably 5 to 50%. It is preferable to use a film in this range, and if it is out of this range, it is difficult to achieve a predetermined effect.
Using infrared absorption spectroscopy, Equation 2
(C / D) × 100 / (E / F) Equation 2
(However, in Formula 2, C is the absorption peak height of the gel film at 1370 cm -1, D is the absorption peak height of the gel film at 1500 cm -1, E is the absorption peak height of the polyimide film at 1370 cm -1, and F is (Represents the absorption peak height at 1500 cm-1 of the polyimide film.)
Is in the range of 50% or more, preferably 80% or more, more preferably 85% or more, and most preferably 90% or more. It is preferable to use a film in this range.
[0034]
In the present invention, the solvent used for the solution of the compound containing the element to be applied or immersed in the gel film may be any solvent that dissolves the compound, and may be water, toluene, tetrahydrofuran, 2-propanol, 1-butanol, Ethyl acetate, N, N-dimethylformamide, acetylacetone and the like can be used. These solvents may be used as a mixture of two or more kinds. In the present invention, N, N-dimethylformamide, 1-butanol, and water can be particularly preferably used.
[0035]
The atomic number concentration of titanium on the surface of the polyimide film measured by X-ray photoelectron spectroscopy is preferably 0.01% to 1%. When the atomic number concentration of the titanium element on the surface of the polyimide film is 0.01% or less, the effect of improving the adhesive strength tends to gradually decrease. Although it is difficult to define the lower limit of the atomic concentration of the titanium element due to the sensitivity limit of the analytical instrument, it is considered that the effect of improving the adhesive strength is almost eliminated at 0.001% or less. On the other hand, if the atomic concentration of the titanium element is 1% or more, the insulating property tends to decrease when a circuit is formed, which is not preferable. This is thought to be due to the effect of the residual titanium element. To obtain such a film, the titanium element concentration of the solution calculated by the product of the concentration of the titanium compound in the solution and the titanium element in the molecule is 1 ppm to 5,000 ppm, preferably 10 ppm to 2000 ppm, more preferably Is preferably 30 ppm to 1000 ppm. The titanium element concentration on the surface and inside the polyimide film can be controlled by a combination of the titanium element concentration and the immersion time of these solutions.
[0036]
The method of applying a solution containing the above elements to the partially cured or partially dried polyamic acid film or polyimide film may be a known method that can be used by those skilled in the art. A coating method using a spray coat, a knife coater, or the like can be used, and a gravure coater can be particularly preferably used from the viewpoint of control of the coating amount and uniformity. The coating amount is preferably from 0.1 g / m2 to 100 g / m2, preferably from 1 g / m2 to 10 g / m2, and if it is out of this range, it is difficult to achieve a balance between the effect and the appearance of the film.
[0037]
When a solution containing the above element is immersed, there is no particular limitation, and a general dip coating method can be used. Specifically, the step is performed by continuously or batch immersing the partially cured or partially dried polyamic acid film or polyimide film in a bath containing the solution. The immersion time is 1 to 100 seconds, preferably 1 to 20 seconds. A partially cured or partially dried polyamic acid film or polyimide film is coated with a solution of the compound containing the above element, or a step of removing extra droplets on the film surface after immersion is added to the film. This is preferable because a polyimide film having an excellent appearance without unevenness on the surface can be obtained. Known methods such as liquid squeezing with a nip roll, an air knife, a doctor blade, wiping, and sucking can be used to remove the droplets.Nip rolls are preferably used from the viewpoint of film appearance, liquid drainage, workability, and the like. obtain.
[0038]
The gel film coated or dipped with the solution containing the above element is heated to be converted into polyimide. In order to convert the gel film to polyimide, it is preferable to heat the film stepwise and continuously according to a conventional method, and finally to use a high temperature for a short time. Specifically, it is preferable to finally heat at a temperature of 500 to 600 ° C. for 15 to 400 seconds. If the temperature is higher or the time is longer than this temperature, thermal deterioration of the film occurs. Conversely, if the temperature is lower than this or the processing time is short, the predetermined effect is not exhibited.
[0039]
When the surface of the polyimide film containing these titanium elements is analyzed by X-ray photoelectron spectroscopy, 0.01 to 1% of titanium elements are detected from the film surface in terms of atomic number concentration. In addition, as described above, a titanium compound solution is applied to a gel film, or a polyimide film produced by immersion is analyzed using a time-of-flight secondary ion mass spectrometer to analyze the concentration distribution of titanium in the thickness direction of the film. Then, titanium exists at a high concentration in the surface layer portion of the film, and the concentration of titanium in the central portion in the thickness direction is １ ／ or less of the surface layer portion. Could be made 1/10 or less of the concentration of the surface layer.
[0040]
The polyimide film obtained by the above various methods may be a known method such as an inorganic or organic filler, a plasticizer such as an organic phosphorus compound or an antioxidant, or a corona discharge treatment or a plasma discharge treatment. Physical surface treatment or a chemical surface treatment such as a primer treatment to impart more excellent characteristics.
[0041]
The thickness of the polyimide film is preferably 2 μm or more and 125 μm or less, more preferably 5 μm or more and 50 μm or less. If the thickness is smaller than this range, the rigidity of the laminated body is insufficient, the handling property is deteriorated, and the electrical insulation between the layers is deteriorated. On the other hand, if the film is too thick, it will go against the tendency of thinning the printed wiring board. Also, from the point of impedance control, it is necessary to increase the circuit width when the thickness of the insulating layer is increased, which goes against the demands for downsizing and higher density of the printed wiring board.
[0042]
It is preferable that the average roughness (referred to as Rz) of the polyimide surface be 2 μm or less, and more preferably 1 μm or less. A smooth surface is suitable for forming a high-density circuit having a line / space of 25/25 μm or less, and is also preferable from the viewpoint that no etching residue remains on unevenness on 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 was measured using a light interference type surface roughness meter NewView5030 system manufactured by ZYGO.
A conductor circuit, a through hole, and the like may be provided inside the polyimide film. In addition, in order to improve the peel strength with the first metal film, the surface of the polyimide film is subjected to a known surface treatment such as a roughening treatment, a corona discharge treatment, a plasma treatment, a flame treatment, a heat treatment, a primer treatment, and the like. May be applied.
[0043]
Next, the metal layer according to the present invention will be described.
First, as a method for forming a metal layer, a physical method such as a vacuum evaporation method, an ion plating method, and a sputtering method can be applied. In the present invention, the thickness of the metal layer is from 20 nm to 500 nm. In particular, sputtering is preferred in terms of the simplicity of equipment, the productivity, and the adhesiveness between the obtained conductor layer and the polymer film.
[0044]
When using sputtering, a known method can be applied. That is, DC magnetron sputtering, RF sputtering, or a method obtained by variously improving these methods can be appropriately applied according to each requirement. 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 mixing of a sputtering gas in the 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. The vacuum is usually reduced to 6 × 10 −4 Pa or less by a combination of a rough pump using a normal rotary pump and a diffusion pump or a cryopump. Next, a sputtering gas is introduced into the chamber to a pressure of 0.1 Pa to 10 Pa, preferably 0.1 Pa 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 to increase 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 (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 100W to 1000W. 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.
[0045]
In order to improve the adhesion between the polymer film and the sputtered film, a plasma discharge treatment, a corona discharge treatment, a heating treatment, an ion bombardment treatment, or the like can be applied as a pretreatment. Normally, 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 perform sputtering continuously.
[0046]
As described above, a uniform thin film can be produced with high accuracy by the sputtering method, but in general, a thin film of copper or a copper alloy formed by the sputtering method achieves strong adhesion on a polymer film having excellent surface flatness. I can't. According to our study, it was not possible to realize an adhesive strength of 3 N / cm or more on a polyimide film having a surface roughness of 3 μm or less. The same is true for the polyimide film containing a titanium element according to the method of the present invention. Even when such a polyimide film was used, an adhesive property having a strength of 4 N / cm or more could not be realized.
[0047]
In view of such a situation, a first method for forming a metal layer according to the present invention is a method in which a base metal layer is provided and the metal layer has a two-layer structure. For the purpose of improving the adhesion as described above, a base metal is formed between the resin substrate and the sputtered metal film. As the base metal, nickel, chromium, titanium, molybdenum, tungsten, zinc, tin, indium, or an alloy thereof is used.In particular, it is effective to use nickel, chromium, and titanium. Use is particularly preferred. The main purpose of using chromium and nickel alloys is to increase the sputtering rate. It is difficult to increase the sputtering speed with pure nickel metal, which is a magnetic material. However, the sputtering rate can be increased by using an alloy of nickel and chromium. Although the ratio of chromium and nickel is not particularly limited to achieve this purpose, it is generally desirable that the ratio be 2% or more.
[0048]
By using such a metal underlayer, excellent adhesiveness of 5 N / cm or more could be realized. Further, by using such a metal underlayer and using a titanium element polyimide film together, a strong adhesion of 7 N / cm or more was obtained. It was found that a good adhesion could be realized. In particular, it was found that the adhesive by the latter method had an excellent adhesive strength of 6 N / cm even after the pressure cooker test (PCT test). In addition, a metal layer made of copper and a copper alloy formed on these base metals by a sputtering method is suitable for a chemical treatment process, and a copper plating film is easily formed on the surface thereof using an electroless plating process. However, the adhesive strength did not decrease.
[0049]
In this case, the thickness of the underlayer made of nickel or an alloy of nickel and chromium is preferably 2 nm or more and 100 nm or less, more preferably 3 nm or more and 20 nm or less. If the thickness is smaller than this, the effect of improving the adhesiveness is insufficient. On the other hand, the thickness of the copper layer is preferably 10 nm or more and 500 nm or less, more preferably 20 nm or more and 300 nm or less, and most preferably 30 nm or more and 200 nm or less. The total thickness of these metals is preferably smaller than 500 nm, more preferably 300 nm or less, and most preferably 200 nm or less, from the viewpoints of economy and etching properties. If the thickness is 500 nm or more, the etching property deteriorates, which is unsuitable for forming a high-density circuit pattern. When laminating and forming two or more types of metal layers, if an oxide layer is formed on the surface of each sputtered film, the adhesion between the respective metals is reduced. Therefore, it is preferable to perform sputtering continuously in a vacuum.
[0050]
The second method of forming a metal layer according to the present invention is a method of forming a two-layer structure composed of copper or a copper alloy layer formed by two 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. In the first method of providing the dissimilar metal base layer described above, since two or more types of metals are used in the formed metal film, an etching process using a semi-additive method (that is, a power supply layer after electrolytic plating) is used. In the stripping process), there is a problem that an extra step of etching a metal other than copper is required.
[0051]
Therefore, we studied a method for forming a metal layer composed of only copper or a copper alloy. As a result, they have discovered that this problem can be solved by forming a layer made of copper or a copper alloy by a combination of ion plating and sputtering, leading to the invention of a second method for forming a metal layer. That is, as a result of various studies, it was found that the copper thin film prepared by the ion plating method has excellent adhesiveness to the substrate, and can realize strong adhesiveness even to a polymer film having excellent surface smoothness. Was. In particular, it has been found that a strong copper thin film of 5 N / cm or more can be formed even on polyimide, which was difficult by the conventional sputtering method.
[0052]
However, as a result of further investigation, the copper and copper alloy thin film layers created by the ion plating method alone were not easily affected by the chemical treatment process, and a copper thin film was formed on the ion plating film using an electroless plating process. Attempts were made to peel off the polymer substrate. Therefore, we tried to form a copper thin film by sputtering on a copper thin film 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.
Although the copper thin film formed by the ion plating method realizes strong adhesion with the polyimide film, 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 plated layer. By using such a method in combination with a titanium-containing polyimide film, a strong bond of 7 N / cm or more has become possible. This adhesive strength had excellent adhesive properties of 6 N / cm or more even after the PCT test.
[0053]
The optimum thickness of the ion-plated copper layer for realizing such a process was 2 nm or more and 100 nm or less. If it is less than 2 nm, strong adhesion to the polymer as the substrate cannot be realized. On the other hand, if the thickness is 100 nm or more, the adhesive strength to the polymer substrate tends to decrease, and it is necessary to perform extra etching in the etching process by the semi-additive method, which causes a problem that the circuit shape is deteriorated. Further, the optimum thickness of the sputtered copper layer for realizing such a process was 10 nm or more and 500 nm or less. If the thickness is less than 10 nm, strong adhesion to the ion plating layer cannot be realized, and the role as a protective film in the electroless plating process is not sufficient. On the other hand, if the thickness is 500 nm or more, it is necessary to perform extra etching in the etching process of the semi-additive method, which causes a problem that the circuit shape is deteriorated. For the same reason, the total thickness of the metal layers by this method is preferably 500 n or less, more preferably 300 nm or less, and most preferably 200 nm or less.
[0054]
Next, the metal layer / polyimide / metal layer laminate according to the present invention will be described.
[0055]
The metal layer on at least one side of the metal layer / polyimide / metal layer laminate of the present invention is a metal layer prepared by any of the above physical methods, but the metal layer on the other side is formed by the same method. A metal layer may be used, or a layer formed by a wet chemical method may be used.
[0056]
Next, a method for manufacturing a wiring board using such a metal layer / polyimide / metal layer laminate will be described.
[0057]
When both surfaces of the metal layer / polyimide / metal layer laminate are metal layers formed by a physical method, a printed wiring board can be manufactured by the following two typical methods. Of course, the method shown here is a typical method, and it goes without saying that the production method of the present invention is not limited to this method.
[0058]
In the first method for manufacturing a printed wiring board, first, a via hole penetrating through the laminate is formed. The formation of the via hole can be performed by a usual mechanical drilling method or a hole making method using a laser using a carbon dioxide gas laser or a UV-YAG laser. After forming the through holes, a catalyst is applied to the surface of the metal layer and the inside of the via holes. A palladium catalyst is used as the catalyst. Next, electroless plated copper is applied to both surfaces of the metal layer and the inside of the via hole using the catalyst. Next, a resist film is formed on the electroless plated copper, and the resist film in a portion where a circuit is to be formed is removed by exposure and etching. Next, electrolytic copper plating is performed using a portion where the electroless plating film is exposed as a power supply electrode, and a circuit is formed by this electrolytic plating method. Then, the circuit is formed by removing the resist portion and removing the unnecessary portion of the electroless plating layer and the metal layer formed by a physical method by etching.
[0059]
When both sides of the metal / polyimide / metal laminate are metal layers formed by a physical method, the method of the second printed wiring board is performed as follows. That is, first, a via hole penetrating the metal layer / polyimide / metal layer laminate is formed. Next, a catalyst is applied to the surface of the metal layer in the same manner as described above, and an electroless plated copper layer is formed on the surface of the metal layer and inside the via hole using the catalyst. Next, electroplating copper is applied on the electroless plated copper to produce a laminate composed of a metal layer / polyimide layer / metal layer in which two metal layers are connected by via holes. Next, a resist film is formed on the surface of the electrolytic copper plating layer, the resist film on a portion where a circuit is not formed is removed by exposure and etching, and then an unnecessary metal layer is removed by etching to form a circuit.
[0060]
The polyimide / metal laminate obtained by the present invention is a flexible printed wiring board, a multilayer printed wiring board in which flexible printed wiring boards are laminated, a rigid / flex printed wiring board in which flexible printed wiring boards and rigid printed wiring boards are laminated, and polyimide / metal. It can be applied to TAB tape in which the laminate is applied to TAB (Tape Automated Bonding), COF (Chip On Film) in which semiconductor elements are directly mounted on a printed wiring board, and semiconductor packages such as MCM (Multi Chip Module). For these uses, it can be processed by a known method.
[0061]
As described above, by using the metal / polyimide / metal laminate according to the present invention, a high-density circuit having a line / space (L / S) of 20 μm or less can be formed, and excellent adhesiveness and Flexible printed wiring boards with high adhesion reliability in severe environments such as high temperature and high humidity, multilayer printed wiring boards with laminated flexible printed wiring boards, and rigid / flex printed wiring boards with flexible printed wiring boards and rigid printed wiring boards laminated And a semiconductor package such as TAB (Tape Automated Bonding) TAB tape, COF (Chip On Film) having a semiconductor element mounted directly on a printed wiring board, or MCM (Multi Chip Module).
[0062]
【Example】
Hereinafter, the effects of the present invention will be described specifically with reference to Examples. However, the present invention is not limited to the following Examples, and those skilled in the art may make various modifications without departing from the scope of the present invention. Changes, modifications, and alterations may be made. In the examples, various analyzes, measurements, evaluations, preparation of a polyimide film, and a method for forming a metal layer were performed by the following methods.
(Titanium atom number concentration on polyimide film surface)
The analysis was performed using an X-ray photoelectron spectrometer (Model-5400, manufactured by ULVAC-PHI) under the conditions of an X-ray source: Mg Kα ray and an energy of 71.55 eV.
(Adhesive strength)
IPC-TM-650-method. According to 2.4.9, pattern width 3mm, peel angle
The measurement was performed at 90 degrees at a peeling speed of 50 mm / min.
(Pressure cooker test)
The test was performed under the conditions of 121 ° C., 100% RH and 96 hours.
(Preparation method of polyimide film-A)
Pyromellitic dianhydride / 4,4'-diaminodiphenyl ether / p-phenylenediamine was synthesized at a molar ratio of 4/3/1 from a 17 wt% polyamic acid 17 g% DMF solution to 90 g in 17 g of acetic anhydride and 2 g of isoquinoline. The resulting inverting agent was mixed, stirred, defoamed by centrifugation, and then cast on an aluminum foil to a thickness of 700 μm. The process from stirring to defoaming was performed while cooling to 0 ° C. The laminate of the aluminum foil and the polyamic acid solution was heated at 110 ° C. for 4 minutes to obtain a self-supporting gel film. The residual volatile content of this gel film was 30% by weight, and the imidization ratio was 90%. This gel film was peeled off from the aluminum foil and fixed to a frame. The gel film was heated at 300 ° C., 400 ° C., and 500 ° C. for 1 minute each to produce a polyimide film having a thickness of 25 μm.
(Preparation method of polyimide film-B)
A polyimide film was prepared in the same manner as in Preparation Method-A, except that the synthesis was performed at a molar ratio of pyromellitic dianhydride / 4,4'-diaminodiphenyl ether of 1/1.
(Preparation method of polyimide film -C)
3,3 ', 4,4'-biphenyltetracarboxylic dianhydride / p-phenylenebis (trimellitic acid monoester anhydride) / p-phenylenediamine / 4,4'-diaminodiphenyl ether in a molar ratio of 4 A 17 wt% solution of polyamic acid in DMAc synthesized at a rate of / 5/7/2 was used, and a 700 μm-thick film was cast on an aluminum foil without mixing with a conversion agent. The laminate of the aluminum foil and the polyamic acid solution was heated at 110 ° C. for 10 minutes to obtain a self-supporting gel film. The residual volatile matter content of this gel film was 30% by weight, and the imidization ratio was 50%. Using this gel film, a polyimide film was prepared in the same manner as in Preparation Method-C.
(Preparation method of polyimide film-D)
Pyromellitic dianhydride / p-phenylene bis (trimellitic acid monoester anhydride) / p-phenylenediamine / 4,4'-diaminodiphenyl ether is synthesized in a molar ratio of 5/5/4/6. Except for the above, a polyimide film was produced in the same manner as in Production Example-A.
(Preparation method of polyimide film (including titanium) -E)
Polyimide film preparation method-A gel film obtained by the same method as in A, B, C, and D is immersed in a dihydroxytitanium bislactate / isopropyl alcohol solution having a titanium element concentration of 100 ppm for 10 seconds, and compressed air is sprayed thereon to produce extra droplets. Was removed, and heated under the same conditions as in Production Method-A to produce a polyimide film having titanium atoms on the surface.
(Method of preparing polyimide film (including titanium) -F)
Preparation method of polyimide film-To a gel film obtained by the same method as in A, B, C and D, a dihydroxytitanium bislactate / isopropyl alcohol solution having a titanium element concentration of 1000 ppm is spray-coated so that no excess liquid adheres to the film. Then, the mixture was heated under the same conditions as in Preparation Method-A to produce a polyimide film having titanium atoms on the surface.
(Preparation method of polyimide film (including titanium) -G)
Preparation method of polyimide film-A gel film obtained by the same method as in A, B, C, and D is immersed in a tri-N-butoxytitanium monostearate / toluene solution having a titanium element concentration of 100 ppm for 10 seconds, and is then nip rolled. After removing the droplets, the mixture was heated under the same conditions as in Preparation Method-A to produce a polyimide film having titanium atoms on the surface.
(Formation of metal layer by sputtering method)
The formation of the metal layer on the polyimide film was performed by the following method using a sputtering device NSP-6 manufactured by Showa Vacuum Co., Ltd. The polymer film is set on the jig and the vacuum chamber is closed. 6 × 10 with the substrate (polymer film) revolving around its axis and heating with a lamp heater ^-4 Vacuum to Pa or less. Thereafter, nickel gas and then copper are sputtered by DC sputtering by introducing argon gas to 0.35 Pa. The DC power was both sputtered at 200 W. 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.
(Formation of Metal Layer by Combination of Ion Plating Method and Sputtering Method) The metal layer was formed on the polyimide film by the ion plating method using an AIF ion plating apparatus manufactured by Shinko Seiki Co., Ltd. This was performed using Typical ionization conditions are 40 V, bombard conditions are an argon gas pressure of 26 Pa, and a substrate heating temperature of 150 ° C. Films of various thicknesses were formed in the range of 5-1000 nm.
[0063]
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 W and argon gas pressure: 0.35 Pa. Films of various thicknesses were formed in the range of 5-1000 nm.
[0064]
【Example】
(Example 1)
Based on the polyimide films prepared by the methods A, B, C and D, and the films prepared by the method A, titanium-containing polyimide films prepared by the methods E, F and G were used. Was sputtered with nickel for 3 minutes to form a 6-nm-thick nickel film, and copper was sputtered continuously for 0.9 minutes to form a 100-nm-thick copper film, thereby obtaining a metal / polyimide laminate. In the methods E, F, and G, two samples were prepared in which the titanium element concentration and the dipping time were changed to change the titanium element concentration. (These are referred to as, for example, E-1 and E-2.) Using the obtained sputtered film as a power supply layer, a copper layer having a thickness of 5 μm was formed by an electrolytic plating method, and the above-described method at room temperature was used. The adhesive strength and the adhesive strength after the PTC test were measured. Table 1 shows the results.
[0065]
[Table 1]

From these results, by providing the nickel underlayer, excellent initial adhesive strength of 5 N / cm or more could be realized with any of the polyimides. Furthermore, the adhesive strength after PCT was 4 N / cm or more. Furthermore, it was found that excellent adhesion after PCT can be realized by forming the titanium-containing polyimide and the nickel underlayer.
(Comparative Example 1)
A laminate having no nickel underlayer was produced in the same manner as in Example 1, and the adhesion was measured in the same manner. Table 2 shows the results.
[0066]
[Table 2]

From these results, by comparing with Table 1, the predetermined effect was not obtained without the nickel underlayer, and the adhesive strength after PCT was reduced to 2 N / cm even when the titanium-containing polyimide was used. This confirmed the effect of the nickel underlayer.
(Example 2)
Metal layers composed of nickel underlayers and copper layers of various thicknesses were formed in the same manner as in Example 1, and the adhesive strength was measured. Table 3 shows the results.
[0067]
[Table 3]

From this result, particularly excellent adhesion is obtained when the thickness of the underlayer (first metal layer) is 2 nm or more and 100 nm or less, and the thickness of the second metal formed on the surface is 10 nm or more and 500 nm or less. It was found that a laminate having properties was obtained.
(Example 3)
Various laminates were prepared in the same manner as in Example 1 except that a copper metal layer was provided as an underlayer (first metal layer) by an ion plating method, and the adhesion was measured. Table 4 shows the results. From these results, it can be seen that if the thickness of the underlayer (first metal layer) is 2 nm or more and 100 nm or less and the thickness of the second metal layer formed on the surface is 10 nm or more and 500 nm or less, excellent adhesiveness is obtained. It was found that a laminate having the following formula was obtained.
[0068]
[Table 4]

(Example 4)
A titanium-containing polyimide film was produced by using a production method F using a polyimide film produced using the polyimide film production methods A, B, C and D. Next, nickel was sputtered on both sides of each polyimide film for 3 minutes in the same manner as in Example 1 to form a 6-nm thick nickel film, and copper was continuously sputtered for 0.9 minutes to form a 100-nm thick copper film. Thus, a metal / polyimide laminate was obtained. The titanium concentration on the film surface was 0.06%, and the titanium concentration inside the film was 0.002% or less. In each of these samples, the initial adhesive strength was 7 N / cm, and the adhesive strength after PCT was 6 N / cm or more, indicating that excellent adhesive strength was exhibited regardless of the type of polyimide.
(Example 5)
Polyimide film production method-A nickel base layer (first metal layer) having a thickness of 5 nm and a copper metal layer (second metal layer) having a thickness of 100 nm on both sides of a film prepared by using the sputtering method E. Was formed. Using this laminate, a circuit was formed by the following method.
First, via holes were formed using a UV-YAG laser to penetrate the laminate having an inner diameter of 30 μm. Next, a copper plating layer was formed on the surface of the metal layer and inside the via hole 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 solution, 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, electroless copper plating in an alkali was performed. The plating temperature was room temperature and the plating time was 10 minutes. An electroless copper plating layer having a thickness of 300 nm was formed by this method. Next, a liquid photosensitive plating resist (THB320P, manufactured by Japan Synthetic Rubber Co., Ltd.) was coated, and then mask exposure was performed using a high-pressure mercury lamp to form a resist pattern having a line / space ratio of 10/10. Subsequently, electrolytic copper plating was performed to form a copper circuit on the surface where the electroless copper plating film was exposed. The electrolytic copper plating was pre-washed in 10% sulfuric acid for 30 seconds, and then plated at room temperature for 40 minutes. Current density is 2 A / dm ² It is. The thickness of the electrolytic copper film was 10 μm. Next, the plating resist was stripped off using an alkaline stripping solution, and the sputtered nickel layer was removed with a nickel selective etching solution (etching solution, NH-1862 manufactured by MEC Corporation) to obtain a printed wiring board.
[0069]
The obtained printed wiring board had lines / spaces as designed, and there was no side etch. Further, Auger analysis of the power supply layer peeled portion and measurement of the presence / absence of residual metal by EPMA were performed, but no residual metal was found. The circuit pattern was firmly adhered at a strength of 6 N / cm.
(Example 6)
A 10-nm-thick copper metal layer was provided as an underlayer (first metal layer) on both surfaces of a film prepared by using the polyimide film manufacturing method-E by an ion plating method, and then a 100-nm thick second metal layer was formed. A laminate having a copper metal layer (second metal layer) having a thickness formed thereon was produced. Using this laminate, a circuit having a line / space of 10/10 μm was formed in the same manner as in Example 4. However, in the final stage of circuit formation, the removal of the power supply layer after the removal of the resist was performed using a copper etching solution (etch bond CZ-8500, manufactured by MEC Corporation).
The obtained printed wiring board had lines / spaces as designed, and there was no side etch. Auger analysis of the power supply layer peeled portion and measurement of the presence or absence of residual metal by EPMA were performed, but no presence of the residual metal was found. The circuit pattern was firmly adhered at a strength of 6 N / cm.
(Example 7)
Polyimide film production method-A nickel base layer (first metal layer) with a thickness of 5 nm and a copper metal layer (second metal layer) with a thickness of 100 nm on both sides of a film produced using E, by a sputtering method. Was formed. Using this laminate, a circuit was formed by the following method.
First, via holes were formed using a UV-YAG laser to penetrate the laminate having an inner diameter of 30 μm. Next, a copper plating layer was formed on the surface of the metal layer and inside the via hole 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 solution, 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 in alkali was performed. The plating temperature was room temperature and the plating time was 10 minutes. An electroless copper plating layer having a thickness of 300 nm was formed by this method. Subsequently, electrolytic copper plating was performed to form a copper plating layer having a thickness of 10 μm. The electrolytic copper plating was pre-washed in 10% sulfuric acid for 30 seconds, and then plated at room temperature for 40 minutes. Current density is 2 A / dm ² It is. The thickness of the electrolytic copper film was 10 μm.
Next, a liquid photosensitive plating resist (THB320P, manufactured by Nippon Synthetic Rubber Co., Ltd.) was coated, and then mask exposure was performed using a high-pressure mercury lamp to form a resist pattern having a line / space ratio of 10/10. A circuit was formed by the ordinary subtractive method (chemical name: ferric chloride) using the pattern thus produced. Next, the sputtered nickel layer was removed with a nickel selective etching solution (etching solution manufactured by Mec Co., NH-1862), and the plating resist was peeled off using an alkaline stripping solution, thereby producing a printed wiring board.
[0070]
The obtained printed wiring board had lines / spaces as designed, and there was no side etch. In addition, Auger analysis of the peeled portion of the power supply layer and measurement of the presence / absence of residual metal by EPMA were performed, but no residual metal was found. The circuit pattern was firmly adhered at a strength of 7 N / cm.
(Example 8)
Polyimide film production method-A copper base layer (first metal layer) having a thickness of 10 nm was formed on both sides of the film prepared by using the E by an ion plating method, and then a 100 nm-thick copper underlayer was formed by a sputtering method. A laminate on which a copper metal layer (second metal layer) was formed was manufactured. Using this laminate, a circuit was formed in the same manner as in Example 8. However, the etching with the nickel selective etching solution (the etching solution manufactured by MEC Corporation, NH-1862) in Example 7 was not performed.
The obtained printed wiring board had lines / spaces as designed, and there was no side etch. In addition, Auger analysis of the peeled portion of the power supply layer and measurement of the presence or absence of residual metal by EPMA were performed, but no residual metal was found. The circuit pattern was firmly adhered at a strength of 7 N / cm.
[0071]
【The invention's effect】
A flexible printed wiring board prepared by using the metal / polyimide / metal laminate of the present invention, a multilayer printed wiring board obtained by laminating a flexible printed wiring board, a rigid / flex printed wiring board obtained by laminating a flexible printed wiring board and a hard printed wiring board, A TAB tape in which the metal / polyimide / metal laminate is applied to TAB (Tape Automated Bonding), a COF (Chip On Film) in which a semiconductor element is directly mounted on a printed wiring board, an MCM (Multi Chip Module), and the like have a high density. Wiring is possible, it has excellent adhesive stability, and it has high adhesive reliability under high temperature and high humidity environment, so it can be widely used as printed wiring board of electronic equipment.

Claims (14)

A polyimide film and a laminate provided with a metal layer on both surfaces thereof, wherein at least one metal layer is a first metal layer made of nickel or an alloy thereof in contact with the polyimide film, and on the first metal layer A method for manufacturing a printed wiring board using a laminate comprising the formed second metal layer made of copper or an alloy thereof. A polyimide film and a laminate provided with a metal layer on both surfaces thereof, wherein at least one metal layer is a first metal layer made of copper or a copper alloy formed by an ion plating method in contact with the polyimide film. And a second metal layer made of copper or a copper alloy formed on the first metal layer. The printed wiring board according to claim 1, wherein a thickness of the first metal layer is 2 nm or more and 100 nm or less, and a thickness of the second metal layer is 10 nm or more and 500 nm or less. Production method. The method for manufacturing a printed wiring board according to any one of claims 1 to 3, wherein the polyimide film is a film containing a titanium element. 5. The polyimide film according to claim 1, wherein the atom number concentration of titanium on the surface of the polyimide film is 0.01% or more and 1% or less when measured by X-ray photoelectron spectroscopy. 5. A method for manufacturing the printed wiring board according to the above. 6. The method for manufacturing a printed wiring board according to claim 5, wherein the polyimide film is a film in which a concentration of a titanium element in a central portion in a film thickness direction is smaller than a concentration of a titanium element on a film surface. The polyimide film is cast or coated with a polyamic acid on a support and dried to obtain a partially cured or partially dried film having a self-supporting property. A method for producing a printed wiring board using a laminate according to any one of claims 1 to 6, which is a polyimide film obtained by applying and / or immersing a solvent solution and then converting the polyamic acid to polyimide. The method according to claim 1, wherein the organic titanium compound is at least one selected from the organic titanium compounds represented by Chemical Formula 1.

Here, m is an integer of 0 to 4, X is one selected from substituents represented by (Chemical Formula 2),

Alternatively, it is a C1 to C18 hydrocarbon residue, or a C3 to C18 carboxylic acid and its ammonium residue.
In (Chemical Formula 1) or (Chemical Formula 2), R1 is hydrogen, or a C1 to C18 hydrocarbon residue, R2 and R3 are C1 to C18 hydrocarbon residues, R4 is a C1 to C18 hydrocarbon residue, R4 is a C1 to C18 hydrocarbon residue or a substituent represented by the general formula (Formula 3);

R5 and R6 are C1 to C18 hydrocarbon residues, R7 is a C1 to C18 hydrocarbon residue, and R8 is a C1 to C18 hydrocarbon residue. The said polyimide film is a film using the polyimide obtained by dehydrating and ring-closing polyamic acid which has pyromellitic anhydride and 4,4'-diaminodiphenyl ether as main components, The polyimide film is described in any one of Claims 1-8. Manufacturing method of printed wiring board. 9. A film using a polyimide obtained by dehydrating and ring-closing a polyamic acid containing three main components, pyromellitic anhydride, 4,4'-diaminodiphenyl ether, and p-phenylenediamine, as the polyimide film. The method for producing a printed wiring board according to any one of the preceding claims. The polyimide film dehydrates and ring-closes a polyamic acid composed mainly of four components of pyromellitic anhydride, 4,4'-diaminodiphenyl ether, p-phenylenediamine, and p-phenylenebis (trimellitic acid monoester anhydride). The method for producing a printed wiring board according to any one of claims 1 to 8, which is a film using a polyimide obtained by the above method. The method of manufacturing a printed wiring board according to any one of claims 1 to 11, wherein a step of forming a via hole penetrating the laminate, and a step of applying a catalyst to the surface of the second metal layer and the inside of the via hole are performed. And a step of applying electroless plating copper to the surface of the second metal layer and the inside of the via hole using the catalyst, and applying electroplating copper to the electroless plating copper. 13. The method for manufacturing a flexible printed wiring board according to claim 12, further comprising a step of forming a circuit by performing etching by a subtractive method. The method for manufacturing a printed wiring board according to any one of claims 1 to 11, wherein a step of forming a via hole penetrating the laminate, and a step of applying a catalyst to the surface of the second metal layer and the inside of the via hole, A step of applying electroless plating copper to the surface of the second metal layer and the inside of the via hole using the catalyst, a step of forming a resist film on the electroless plating copper, and a step of removing a resist film in a portion where a circuit is to be formed Forming a circuit by performing electrolytic copper plating using a portion where the electroless plating film is exposed as a power supply electrode, removing a resist film, an electroless copper plating film, and the first metal layer. And etching the second metal layer.