JP3766263B2 - Heat resistant film and flexible printed wiring board based on the heat resistant film - Google Patents

Description

【式４】

【０００８】
【発明の実施の形態】
以下、本発明を詳しく説明する。
本発明のフィルムは、その樹脂組成が結晶性ポリアリールケトン樹脂と非晶性ポリエーテルイミド樹脂とからなるフィルムである。
ここで、本発明を構成する結晶性ポリアリールケトン樹脂は、その構造単位に芳香核結合、エーテル結合及びケトン結合を含む熱可塑性樹脂であり、その代表例としては、ポリエーテルケトン、ポリエーテルエーテルケトン、ポリエーテルケトンケトン等があるが、本発明においては、下記構造式（１）に示すポリエーテルエーテルケトンが好適に使用される。
【０００９】
【式５】

【００１０】
また、非晶性ポリエーテルイミド樹脂は、その構造単位に芳香核結合、エーテル結合及びイミド結合を含む非晶性熱可塑性樹脂であり、本発明においては、下記構造式（２）に示すポリエーテルイミドが好適に使用される。
【式６】

【００１１】
本発明のフィルムは、結晶融解ピーク温度が２６０℃以上である結晶性ポリアリールケトン樹脂７０〜３０重量％と非晶性ポリエーテルイミド樹脂３０〜７０重量％とからなるフィルムを結晶化処理したフィルムであって、透過型電子顕微鏡で観察した際に、最大結晶粒径が０．３μｍ以下、好ましくは０．１μｍ以下であることが必要であり、このことが最も重要である。
【００１２】
すなわち、本発明の実施例においても説明するが、特許公報に記載された実施例（例えば、特開昭５９−１８７０５４号公報、特表昭６１−５０００２３号公報、特開昭５９−１１５３５３号公報、米国特許第５１１０８８０号公報など）や、文献（例えば、（ａ）：Ｊ．Ｅ．Ｈａｒｒｉｓ ａｎｄＬ．Ｍ．Ｒｏｂｅｓｏｎ，Ｊ．Ａｐｐｌ．Ｐｏｌｙｍ．Ｓｃｉ．，３５，１８７７−１８９１（１９８８）、（ｂ）：Ｇ．Ｃｒｅｖｅｃｏｅｕｒ ａｎｄ Ｇ．Ｇｒｏｅｎｉｎｃｋｘ，Ｍａｃｒｏｎｏｌｅｃｕｌｅｓ，２４，１１９０−１１９５（１９９０）、（ｃ）：Ｂｅｎｊａｍｉｎ Ｓ．Ｈｓｉａｏ ａｎｄ Ｂｒｙａｎ Ｂ．Ｓａｕｅｒ，Ｊ．Ｐｏｌｙｍ．Ｓｃｉ．，Ｐｏｌｙｍ．Ｐｈｙｓ．Ｅｄ．，３１，９０１−９１５（１９９３）など）で検討されているポリアリールケトン樹脂として上記構造式（１）を有するポリエーテルエーテルケトン（ＶＩＣＴＲＥＸ社製、商品名「ＰＥＥＫ１５１Ｇ」「ＰＥＥＫ３８１Ｇ」「ＰＥＥＫ４５０Ｇ」等として市販されている）と
【００１３】
非晶性ポリエーテルイミド樹脂として下記構造式（３）を有するポリエーテルイミド樹脂（ゼネラルエレクトリック社製、商品名「Ｕｌｔｅｍ１０００」として市販されている）との混合組成物においては、相溶性が非常に良好なため、結晶化処理を行うとポリアリールケトン樹脂の結晶成分に由来する球晶成長が起こり（図２参照）、球晶界面が主な欠陥となり機械的強度、特に端裂強度が低下し易いことを見出した。
【００１４】
【式７】

【００１５】
ところが驚くべきことに上記の非晶性ポリエーテルイミド樹脂の替わりに上記構造式（２）を有するポリエーテルイミド樹脂（ゼネラルエレクトリック社製、商品名「Ｕｌｔｅｍ ＣＲＳ５００１」として市販されている）を用いると結晶化処理を行っても球晶成長がほとんど見られず、縞状のモルホロジーを形成し（図１参照）、機械的強度、特に端裂強度が向上することを見出し、本発明を完成するに至ったのである。この理由は明確ではないが、上記構造式（１）を有するポリエーテルエーテルケトンと上記構造式（２）を有するポリエーテルイミド樹脂との混合組成物では、分子間の電子的な相互作用が異なり、相溶性が劣るため特有の高次構造を形成し、このことから端裂強度が向上したものと思われる。
【００１６】
非晶性ポリエーテルイミド樹脂の製造方法は特に限定されるものではないが、通常、上記構造式（２）を有する非晶性ポリエーテルイミド樹脂は、４,４´−[イソプロピリデンビス（ｐ−フェニレンオキシ）ジフタル酸二無水物とｐ−フェニレンジアミンとの重縮合物として、また上記構造式（３）を有する非晶性ポリエーテルイミド樹脂は、４,４´−[イソプロピリデンビス（ｐ−フェニレンオキシ）ジフタル酸二無水物とｍ−フェニレンジアミンとの重縮合物として公知の方法によって合成される。また、上述した非晶性ポリエーテルイミド樹脂には、本発明の趣旨を超えない範囲で共重合可能な他の単量体単位を導入してもよい。
【００１７】
なお、本発明において透過型電子顕微鏡による観察は次の条件で行ったものである。得られたフィルムの中央部分（製膜時の樹脂の流れ方向に平行方向）から、厚さ７００オングストローム程度の薄片を採取して、それを四酸化ルテニウムで球晶構造などの高次構造が識別できるように染色した試料を作製し、透過型電子顕微鏡（日本電子(株）製透過型電子顕微鏡 ＪＥＭ−１２００ＥＸ）を用いて、加速電圧８０Ｋｖで２万倍まで拡大し観察した。なお、本発明でいう最大結晶粒径とは、球晶やトランスクリスタルあるいは束状結晶などの最大径のことである。
【００１８】
ここで、結晶性ポリアリールケトン樹脂が７０重量％を越えたり、非晶性ポリエーテルイミド樹脂が３０重量％未満では、組成物全体としてのガラス転移温度を向上させる効果が少ないため耐熱性が不充分となり易かったり、結晶性が高いため結晶化処理を行うと球晶などの結晶構造が高度に成長、発達するため機械的強度、特に端裂強度が低下し易く、また、結晶化に伴う体積収縮（寸法変化）が大きくなり回路基板としての信頼性が低下する為好ましくない。また、結晶性ポリアリールケトン樹脂が３０重量％未満であったり、非晶性ポリエーテルイミド樹脂が７０重量％を越えると組成物全体としての結晶性自体が低く、また結晶化速度も遅くなり過ぎ結晶融解ピーク温度が２６０℃以上であってもはんだ耐熱性が低下するため好ましくない。このことから本発明においては、上記ポリアリールケトン樹脂６５〜３５重量％と非晶性ポリエーテルイミド樹脂３５〜６５重量％とからなる混合組成物が好適に用いられる。
【００１９】
また、上述した結晶化処理したフィルムとは、示差走査熱量測定で昇温した時に測定される結晶融解熱量ΔＨｍと昇温中の結晶化により発生する結晶化熱量ΔＨｃとが、下記の関係式を満たす
［（ΔＨｍ−ΔＨｃ）／ΔＨｍ］≧０．９０
ことをいう。なお、本発明において使用する結晶融解熱量ΔＨｍ（Ｊ／ｇ）と結晶化熱量ΔＨｃ（Ｊ／ｇ）は、次のようにして求めた値である。すなわち、パーキンエルマー社製ＤＳＣ−７を用いて、試料１０ｍｇをＪＩＳ−Ｋ７１２２に準じて、加熱速度１０℃／分で４００℃まで昇温したときのサーモグラムから求めた。
【００２０】
この関係式［（ΔＨｍ−ΔＨｃ）／ΔＨｍ］の値は、原料ポリマーの種類・分子量・組成物の比率等にも依存するが、フィルムの成形・加工条件、特に結晶化処理条件に大きく依存する。すなわち、フィルムを製膜する際に、原料ポリマーを溶融させた後、速やかに冷却すれば該数値は小さくなる。また、結晶化処理条件において、処理温度及び処理時間を長くすれば、該数値を大きくすることができる。該数値の最大値は１．０であり、数値が大きいほど結晶化が進行していることを意味している。
ここで該数値が、０．９０未満では、充分に結晶化が進行しておらず、寸法安定性が低下したり、はんだ耐熱性が不充分となり好ましくない。
【００２１】
本発明フィルムは、フレキシブルプリント配線基板の基材として有用であるが、このような用途に用いる場合には、寸法安定性を向上させる目的から上述した結晶性ポリアリールケトン樹脂と非晶性ポリエーテルイミド樹脂からなる樹脂組成物１００重量部に対し、無機充填材を３０重量部以下、好適には１０〜３０重量部の範囲で混合することが好ましい。ここで無機充填材が３０重量部を超えると、フィルムの可とう性、引き裂き強度などの機械的強度が低下するため好ましくない。また一般に１０重量部未満では、線膨張係数を低下し寸法安定性を向上させる効果が少ない。用いる無機充填材としては、特に制限はなく、公知のものを使用することができる。例えば、タルク、マイカ、クレー、ガラス、アルミナ、シリカ、窒化アルミニウム、窒化珪素などが挙げられ、これらは１種類を単独で、２種類以上を組み合わせて用いることができる。特に、平均粒径が１〜２０μｍ程度、平均アスペクト比（粒径／厚み）が２０〜５０程度の無機充填材が、低添加量（１０〜２５重量部程度）で、機械的強度を低下させることなく寸法安定性を向上させる効果が高く好ましい。
【００２２】
本発明フィルムを構成する樹脂組成物には、その性質を損なわない程度に、他の樹脂や無機充填材以外の各種添加剤、例えば、熱安定剤、紫外線吸収剤、光安定剤、核剤、着色剤、滑剤、難燃剤等を適宜配合しても良い。また無機充填材を含めた各種添加剤の混合方法は、公知の方法を用いることができる。例えば、（a）各種添加剤をポリアリールケトン樹脂及び／または非晶性ポリエーテルイミド樹脂などの適当なベース樹脂に高濃度（代表的な含有量としては１０〜６０重量％）に混合したマスターバッチを別途作製しておき、これを使用する樹脂に濃度を調整して混合し、ニーダーや押出機等を用いて機械的にブレンドする方法、（b）使用する樹脂に直接各種添加剤をニーダーや押出機等を用いて機械的にブレンドする方法などが挙げられる。上記混合方法の中では、（a）のマスターバッチを作製し、混合する方法が分散性や作業性の点から好ましい。さらに、フィルムの表面にはハンドリング性の改良等のために、エンボス加工やコロナ処理等を適宜施しても良い。
【００２３】
本発明フィルム製膜方法としては、公知の方法、例えばＴダイを用いる押出キャスト法やカレンダー法等を採用することができ、特に限定されるものではないが、シートの製膜性や安定生産性等の面から、Ｔダイを用いる押出キャスト法が好ましい。Ｔダイを用いる押出キャスト法での成形温度は、組成物の流動特性や製膜性等によって適宜調整されるが、概ね融点以上、４３０℃以下である。また、該フィルムの厚みは、通常２５〜３００μｍ程度である。
さらに、本発明フィルムの結晶化処理方法は、特に限定されるものではないが、例えば、押出キャスト時に結晶化させる方法（キャスト結晶化法）や製膜ライン内で、熱処理ロールや熱風炉等により結晶化させる方法（インライン結晶化法）及び製膜ライン外で、熱風炉や熱プレス等により結晶化させる方法（アウトライン結晶化法）などを挙げることができる。
【００２４】
次に、本発明フィルムを用いたフレキシブルプリント配線基板の製造方法について説明する。
プリント配線基板の製造方法においては、接着層を介することなく熱融着方法として加熱、加圧できる方法であれば公知の方法を採用することができ、特に限定されるものではないが、例えば、熱プレス法や熱ラミネートロール法、又はこれらを組み合わせた方法を好適に採用することができる。
本発明に使用される導体箔としては、例えば銅、金、銀、アルミニウム、ニッケル、錫等の、厚さ５〜７０μｍ程度の金属箔が挙げられる。金属箔としては、通常銅箔が使用され、さらに表面を黒色酸化処理等の化成処理を施したものが好適に使用される。導体箔は、接着効果を高めるために、フィルムとの接触面（重ねる面）側を予め化学的または機械的に粗化したものを用いることが好ましい。表面粗化処理された導体箔の具体例としては、電解銅箔を製造する際に電気化学的に処理された粗化銅箔などが挙げられる。
【００２５】
また、導体箔に導電性回路を形成させる方法についても、公知の方法を採用することができ、特に限定されるものではない。例えば，サブトラクティブ法（エッチング）、アディティブ法（メッキ），ダイスタンプ法（金型）、導体印刷法（導電ペースト）などの公知の方法が適用でき、多層基板とした場合の層間接続の方法としては、例えば、スルーホールに銅メッキする方法やスルーホール、インナーバイアホール中へ導電性ペーストや半田ボールを充填する方法、微細な導電粒子を含有した絶縁層による異方導電性材料を応用する方法などが挙げられる。
【００２６】
【実施例】
以下に本発明を実施例でさらに詳しく説明するが、これらにより本発明は何ら制限を受けるものではない。なお、本明細書中に表示されるフィルムについての種々の測定値及び評価は次のようにして行った。ここで、フィルムの押出機からの流れ方向を縦方向、その直交方向を横方向とよぶ。
【００２７】
（１）ガラス転移温度（Ｔｇ）、結晶融解ピーク温度（Ｔｍ）
パーキンエルマー（株）製ＤＳＣ−７を用いて、試料１０ｍｇをＪＩＳ Ｋ７１２１に準じて、加熱速度を１０℃／分で昇温した時のサーモグラムから求めた。
【００２８】
（２）（ΔＨｍ−ΔＨｃ）／ΔＨｍ
パーキンエルマー（株）製ＤＳＣ−７を用いて、試料１０ｍｇをＪＩＳ Ｋ７１２２に準じて、加熱速度を１０℃／分で昇温した時のサーモグラムから、結晶融解熱量ΔＨｍ（Ｊ／ｇ）と結晶化熱量ΔＨｃ（Ｊ／ｇ）を求め、算出した。
【００２９】
（３）接着強度
ＪＩＳ Ｃ６４８１の常態の引き剥がし強さに準拠して測定した。
【００３０】
（４）はんだ耐熱性
ＪＩＳ Ｃ６４８１の常態のはんだ耐熱性に準拠し、２６０℃のはんだ浴に試験片を銅箔側とはんだ浴とが接触するように１０秒間浮かべ、室温まで冷却した後、膨れやはがれ等の有無を目視によって調べ、良否を判定した。
【００３１】
（５）透過型電子顕微鏡観察
得られたフィルムの中央部分（樹脂流動方向に平行方向）から、厚さ７００オングストローム程度の薄片を採取して、それを四酸化ルテニウムで染色した試料を作製し、透過型電子顕微鏡（日本電子（株）製 ＪＥＭ−１２００ＥＸ）を用いて、加速電圧８０Ｋｖで２万倍まで拡大し観察した。
【００３２】
（６）端裂強度
ＪＩＳ Ｃ２１５１の端裂抵抗試験に準拠して、厚さ７５μｍのフィルムから幅１５ｍｍ、長さ３００ｍｍの試験片を切り出し、試験金具Ｂを用いて、引張速度５００ｍｍ／分の条件で縦方向および横方向を測定した。
【００３３】
（実施例１）
表１に示すようにポリエーテルエーテルケトン樹脂［ビクトレックス社製、ＰＥＥＫ３８１Ｇ、Ｔｇ：１４３℃、Ｔｍ：３３４℃］（以下、単にＰＥＥＫと略記することがある）６０重量部と、非晶性ポリエーテルイミド樹脂［ゼネラルエレクトリック社製、Ｕｌｔｅｍ−ＣＲＳ５００１、Ｔｇ：２２６℃］（以下、単にＰＥＩ−１と略記することがある）４０重量部及び市販のマイカ（平均粒径：１０μｍ、平均アスペクト比：３０）２０重量部とからなる混合組成物を、Ｔダイを備えた押出機を用いて設定温度３８０℃で厚さ７５μｍのフィルムに押出し、同時に銅箔（厚さ：１８μｍ、表面粗面化）をラミネートすることにより銅張基板を得た。さらに得られた銅張基板を２４０℃の恒温槽で６０分間結晶化処理することにより目的とする結晶化処理済銅張基板を得た。
【００３４】
得られた結晶化処理済銅張基板を用いて、評価した熱特性や機械的強度などの評価結果を表１に示す。また図１には得られた結晶化処理済銅張基板の基材フィルムを透過型電子顕微鏡を用いて高次構造を観察した写真（図中の矢印はフィルムの押出機からの流れ方向を示している。）を示す。写真（寸法：８．３×１２．５ｃｍ）は２万倍に拡大した写真であり実物寸法では、４．１５×６．２５μｍの範囲が写っており、１ｃｍの長さ（図中のスケール）は０．５μｍに相当する。写真で針状に見えている部分が使用したマイカであり、また、白黒の縞状のモルホロジーが観察されるが、球晶構造は全く観察されないことが分かる。表１に示すように、得られた結晶化処理済銅張基板は銅箔との接着強度やはんだ耐熱性及び機械的強度（端裂強度）にも優れているものであった。
【００３５】
（実施例２）
実施例１において、使用するＰＥＥＫとＰＥＩ−１の混合比を表１に示すようにそれぞれ３５重量部及び６５重量部に変更した以外は、実施例１と同様に結晶化処理済銅張基板を得た。得られた結晶化処理済銅張基板を用いて、評価した熱特性や機械的強度などの評価結果を表１に示す。
【００３６】
（実施例３）
実施例１において、使用するＰＥＥＫとＰＥＩ−１の混合比を表１に示すようにそれぞれ５０重量部及び５０重量部に変更した以外は、実施例１と同様に結晶化処理済銅張基板を得た。得られた結晶化処理済銅張基板を用いて、評価した熱特性や機械的強度などの評価結果を表１に示す。
【００３７】
（比較例１）
実施例１において、ＰＥＩの種類を表１に示すようにポリエーテルイミド樹脂［ゼネラルエレクトリック社製、Ｕｌｔｅｍ−１０００、Ｔｇ：２１６℃］（以下、単にＰＥＩ−２と略記することがある）に変更した以外は、実施例１と同様に結晶化処理済銅張基板を得た。得られた結晶化処理済銅張基板を用いて、評価した熱特性や機械的強度などの評価結果を表１に示す。また図２には得られた結晶化処理済銅張基板の基材フィルムを透過型電子顕微鏡を用いて高次構造を観察した写真を示す。写真で針状に見えている部分が使用したマイカであり、また、黒く樹木状に見える部分がポリアリールケトン樹脂の結晶成分に由来する球晶あるいは束状結晶構造である。表１に示すように、得られた結晶化処理済銅張基板は銅箔との接着強度やはんだ耐熱性は良好なものの、端裂強度に劣るものであった。
【００３８】
（比較例２）
実施例１において、得られた銅張基板に２４０℃×６０分間の結晶化処理を行わなかった以外は、実施例１と同様に結晶化処理済銅張基板を得た。得られた結晶化処理済銅張基板を用いて、評価した熱特性や機械的強度などの評価結果を表１に示す。結晶化処理を行っていない銅張基板は、結晶化の進行が不充分であり、はんだ耐熱性が不良であり、プリント配線基板としての基本的特性に欠けるものであった。
【００３９】
（比較例３）
実施例１において、使用するマイカの混合重量比を４５重量部に変更した以外は、実施例１と同様に結晶化処理済銅張基板を得た。得られた結晶化処理済銅張基板を用いて、評価した熱特性や機械的強度などの評価結果を表１に示す。得られた結晶化処理済銅張基板は銅箔との接着強度やはんだ耐熱性は良好なものの、可とう性や端裂強度に劣るものであった。
【００４０】
【表１】

【００４１】
表１から本発明で規定する成分を有し、かつ規定する範囲にある実施例１乃至３のフィルムは、いずれも球晶構造が観察されず縞状のモルホロジーを有しており、接着強度，はんだ耐熱性及びフレキシブルプリント配線基板用フィルムとしての端裂強度に総合的に優れていることが分かる。端裂強度は縦、横方向ともに６０Ｎ以上である。これに対して、成分が異なるか（比較例１）、本発明で規定する範囲外（比較例２、３）のフィルムは、端裂強度やはんだ耐熱性のいずれかの特性に劣ることが分かる。
【００４２】
【発明の効果】
本発明によれば、結晶性ポリアリールケトン樹脂と非晶性ポリエーテルイミド樹脂からなるフィルムを用いて、寸法安定性、耐熱性などを保持しつつ端裂強度を向上させたフレキシブルプリント配線基板が提供できる。
【図面の簡単な説明】
【図１】実施例１の結晶化処理済銅張基板の基材フィルムを透過型電子顕微鏡を用いて高次構造を観察した写真である。図中の矢印は、フィルムの押出機からの流れ方向（縦方向）を示している。
【図２】比較例１の結晶化処理済銅張基板の基材フィルムを透過型電子顕微鏡を用いて高次構造を観察した写真である。図中の矢印は、フィルムの押出機からの流れ方向（縦方向）を示している。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heat-resistant film having improved mechanical strength suitable as a member for electronics, and a flexible printed wiring board using the heat-resistant film as a base material.
[0002]
[Prior art]
Crystalline polyarylketone resins represented by polyetheretherketone resins are excellent in heat resistance, flame retardancy, hydrolysis resistance, chemical resistance, etc., and are mainly used in aircraft parts and electrical / electronic parts. It has been adopted. However, since the polyaryl ketone resin is very expensive, and the glass transition temperature of the resin itself is relatively low at about 140 to 170 ° C., various studies for improving heat resistance have been conducted. Among them, a blend with an amorphous polyetherimide resin has attracted attention as a system exhibiting good compatibility.
For example, Japanese Patent Application Laid-Open Nos. 59-187054 and 61-500023 disclose a mixed composition of a polyaryl ketone resin and an amorphous polyetherimide resin. 59-115353 also discloses that these compositions are useful for circuit board substrates.
Furthermore, the present inventors have also proposed a printed wiring board using the above mixed composition and a method for producing the same in Japanese Patent Application Laid-Open Nos. 2000-38464 and 2000-200150.
[0003]
However, a flexible printed wiring board is produced using a film made of a mixed composition of a crystalline polyaryl ketone resin and an amorphous polyetherimide resin (usually including an inorganic filler for improving dimensional stability). Then, although the dimensional stability, heat resistance, etc. are good, the mechanical strength, especially the edge tear strength, is not necessarily at a sufficient level, and the folding resistance and bending resistance are impaired, so that the connection reliability of the board can be secured. However, there is a problem that the application range is limited, and an improvement thereof has been desired. In addition, the above-mentioned patent gazette has no technical disclosure or suggestion regarding this cause or improvement method.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a flexible printed wiring board having improved end tear strength while maintaining dimensional stability, heat resistance, etc., using a film comprising a crystalline polyaryl ketone resin and an amorphous polyetherimide resin. It is to provide.
[0005]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found a flexible printed wiring board that can solve the above problems by controlling the higher-order structure (morphology) of a film used as a base material, and completed the present invention. It came to do.
That is, the gist of the present invention is that a film comprising 70 to 30% by weight of a crystalline polyaryl ketone resin having a crystal melting peak temperature of 260 ° C. or higher and 30 to 70% by weight of an amorphous polyetherimide resin. A crystallization-treated film having a maximum crystal grain size of 0.3 μm or less when observed with a transmission electron microscope.
[0006]
The present invention also includes a flexible printed wiring board in which a conductive foil is provided on at least one surface of the heat-resistant film by thermal fusion without using an adhesive layer, and a conductive circuit is formed on the conductive foil. . The crystalline polyaryl ketone resin is a polyether ether ketone resin having a repeating unit of the following structural formula (1), and the amorphous polyetherimide resin is a polyether having a repeating unit of the following structural formula (2). An imide resin is used.
[0007]
[Formula 3]

[Formula 4]

[0008]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
The film of the present invention is a film whose resin composition is composed of a crystalline polyaryl ketone resin and an amorphous polyetherimide resin.
Here, the crystalline polyaryl ketone resin constituting the present invention is a thermoplastic resin containing an aromatic nucleus bond, an ether bond and a ketone bond in its structural unit, and representative examples thereof include polyether ketone and polyether ether. In the present invention, a polyether ether ketone represented by the following structural formula (1) is preferably used.
[0009]
[Formula 5]

[0010]
The amorphous polyetherimide resin is an amorphous thermoplastic resin containing an aromatic nucleus bond, an ether bond and an imide bond in its structural unit. In the present invention, the polyether represented by the following structural formula (2) is used. Imides are preferably used.
[Formula 6]

[0011]
The film of the present invention is a film obtained by crystallizing a film comprising 70 to 30% by weight of a crystalline polyaryl ketone resin having a crystal melting peak temperature of 260 ° C. or higher and 30 to 70% by weight of an amorphous polyetherimide resin. When observed with a transmission electron microscope, it is necessary that the maximum crystal grain size is 0.3 μm or less, preferably 0.1 μm or less, and this is most important.
[0012]
That is, although the embodiments of the present invention will be described, the embodiments described in the patent gazettes (for example, Japanese Patent Application Laid-Open Nos. 59-187054, 61-500023, and 59-115353) are disclosed. U.S. Pat. No. 5,110,880) and literature (for example, (a): JE Harris and LM Robeson, J. Appl. Polym. Sci., 35, 1877-1891 (1988), (b). ): G. Crevecoeur and G. Groeninckx, Macronouleles, 24, 1190-1195 (1990), (c): Benjamin S. Hsiao and Bryan B. Sauer, J. Polym. Sci., PolyE. , 901-915 (1993) etc.) Polyetheretherketone having the above structural formula (1) as a polyaryl ketone resin being studied (commercially available under the trade names “PEEK151G”, “PEEK381G”, “PEEK450G”, etc., manufactured by VICTREX)
In a mixed composition with a polyetherimide resin having the following structural formula (3) as an amorphous polyetherimide resin (commercially available under the trade name “Ultem1000” manufactured by General Electric Co., Ltd.), the compatibility is very high. Because it is good, crystallization treatment causes spherulite growth derived from the crystal components of the polyarylketone resin (see FIG. 2), and the spherulite interface becomes the main defect, resulting in a decrease in mechanical strength, in particular the edge crack strength. I found it easy.
[0014]
[Formula 7]

[0015]
However, surprisingly, instead of the amorphous polyetherimide resin, a polyetherimide resin having the above structural formula (2) (manufactured by General Electric Co., Ltd., commercially available under the trade name “Ultem CRS5001”) is used. In order to complete the present invention, it was found that spherulite growth was hardly observed even when crystallization treatment was performed, a striped morphology was formed (see FIG. 1), and mechanical strength, particularly edge strength was improved. It has come. The reason for this is not clear, but in the mixed composition of the polyetheretherketone having the structural formula (1) and the polyetherimide resin having the structural formula (2), the electronic interaction between molecules is different. Since the compatibility is inferior, a unique higher order structure is formed, which is considered to have improved the end crack strength.
[0016]
The method for producing the amorphous polyetherimide resin is not particularly limited. Usually, the amorphous polyetherimide resin having the structural formula (2) is 4,4 ′-[isopropylidenebis (p As the polycondensate of -phenyleneoxy) diphthalic dianhydride and p-phenylenediamine, and the amorphous polyetherimide resin having the above structural formula (3), 4,4 '-[isopropylidenebis (p It is synthesized by a known method as a polycondensation product of -phenyleneoxy) diphthalic dianhydride and m-phenylenediamine. Moreover, you may introduce | transduce into the amorphous polyetherimide resin mentioned above the other monomer unit which can be copolymerized in the range which does not exceed the meaning of this invention.
[0017]
In the present invention, observation with a transmission electron microscope was performed under the following conditions. From the central part of the film (parallel to the flow direction of the resin during film formation), a thin piece having a thickness of about 700 angstroms is collected, and the higher-order structure such as a spherulite structure is identified with ruthenium tetroxide. The sample dye | stained so that it could be produced was produced, and it expanded and observed to 20,000 times with the accelerating voltage of 80 Kv using the transmission electron microscope (JEOL Co., Ltd. transmission electron microscope JEM-1200EX). The maximum crystal grain size as used in the present invention is the maximum diameter of a spherulite, transcrystal, or bundle crystal.
[0018]
Here, if the crystalline polyaryl ketone resin exceeds 70% by weight or the amorphous polyetherimide resin is less than 30% by weight, the effect of improving the glass transition temperature of the entire composition is small, and heat resistance is poor. Since crystal structure such as spherulites grows and develops to a high degree due to high crystallinity due to its high crystallinity, mechanical strength, especially edge strength, tends to decrease, and volume associated with crystallization. This is not preferable because shrinkage (dimensional change) increases and the reliability of the circuit board decreases. When the crystalline polyaryl ketone resin is less than 30% by weight or the amorphous polyetherimide resin exceeds 70% by weight, the crystallinity of the composition as a whole is low and the crystallization rate is too slow. Even if the crystal melting peak temperature is 260 ° C. or higher, the solder heat resistance is lowered, which is not preferable. Therefore, in the present invention, a mixed composition comprising 65 to 35% by weight of the polyaryl ketone resin and 35 to 65% by weight of an amorphous polyetherimide resin is preferably used.
[0019]
In addition, the above-mentioned crystallized film has the following relational expression: the amount of heat of crystal fusion ΔHm measured when the temperature is raised by differential scanning calorimetry and the amount of heat of crystallization ΔHc generated by crystallization during the temperature rise. Satisfies [(ΔHm−ΔHc) / ΔHm] ≧ 0.90
That means. The heat of crystal fusion ΔHm (J / g) and the heat of crystallization ΔHc (J / g) used in the present invention are values obtained as follows. That is, it calculated | required from the thermogram when it heated up to 400 degreeC by heating rate 10 degree-C / min according to JIS-K7122 using DSC-7 by Perkin Elmer.
[0020]
Although the value of this relational expression [(ΔHm−ΔHc) / ΔHm] depends on the type, molecular weight, composition ratio, etc. of the starting polymer, it greatly depends on the film forming / processing conditions, particularly the crystallization treatment conditions. . That is, when the film is formed, the numerical value becomes small if the raw material polymer is melted and then cooled quickly. In addition, when the treatment temperature and the treatment time are increased under the crystallization treatment conditions, the numerical values can be increased. The maximum value is 1.0, and the larger the value, the more crystallization is progressing.
If the numerical value is less than 0.90, crystallization is not sufficiently progressed, so that the dimensional stability is lowered or the solder heat resistance is insufficient, which is not preferable.
[0021]
The film of the present invention is useful as a base material for flexible printed wiring boards, but when used in such applications, the crystalline polyaryl ketone resin and amorphous polyether described above are used for the purpose of improving dimensional stability. It is preferable to mix the inorganic filler in an amount of 30 parts by weight or less, preferably 10 to 30 parts by weight with respect to 100 parts by weight of the resin composition made of an imide resin. Here, if the inorganic filler exceeds 30 parts by weight, it is not preferable because mechanical strength such as flexibility and tear strength of the film is lowered. Moreover, generally less than 10 weight part has few effects which reduce a linear expansion coefficient and improve dimensional stability. There is no restriction | limiting in particular as an inorganic filler to be used, A well-known thing can be used. For example, talc, mica, clay, glass, alumina, silica, aluminum nitride, silicon nitride, and the like can be mentioned. These can be used alone or in combination of two or more. In particular, an inorganic filler having an average particle size of about 1 to 20 μm and an average aspect ratio (particle size / thickness) of about 20 to 50 reduces the mechanical strength with a low addition amount (about 10 to 25 parts by weight). The effect of improving the dimensional stability without increasing is preferable.
[0022]
In the resin composition constituting the film of the present invention, various additives other than other resins and inorganic fillers, such as heat stabilizers, ultraviolet absorbers, light stabilizers, nucleating agents, to the extent that the properties are not impaired. Colorants, lubricants, flame retardants and the like may be appropriately blended. Moreover, a well-known method can be used for the mixing method of various additives including an inorganic filler. For example, (a) a master in which various additives are mixed at a high concentration (typically 10 to 60% by weight) with an appropriate base resin such as a polyaryl ketone resin and / or an amorphous polyetherimide resin. Separately preparing a batch, adjusting the concentration to the resin to be used, mixing it, and mechanically blending using a kneader or extruder, etc. (b) Kneader with various additives directly to the resin to be used Or a mechanical blending method using an extruder or the like. Among the above mixing methods, the method of preparing and mixing the master batch (a) is preferable from the viewpoint of dispersibility and workability. Furthermore, the surface of the film may be appropriately subjected to embossing, corona treatment or the like for improving handling properties.
[0023]
As the method for forming a film of the present invention, a known method such as an extrusion casting method using a T-die or a calender method can be adopted, and the film forming property and stable productivity of the sheet are not particularly limited. From such a viewpoint, an extrusion casting method using a T die is preferable. The molding temperature in the extrusion casting method using a T-die is appropriately adjusted depending on the flow characteristics and film forming properties of the composition, but is generally about the melting point or higher and 430 ° C. or lower. Moreover, the thickness of this film is about 25-300 micrometers normally.
Furthermore, the crystallization treatment method of the film of the present invention is not particularly limited. For example, in a method of crystallization at the time of extrusion casting (cast crystallization method) or in a film production line, by a heat treatment roll, a hot air oven, or the like. Examples thereof include a crystallization method (in-line crystallization method) and a crystallization method (outline crystallization method) by a hot air furnace or hot press outside the film production line.
[0024]
Next, the manufacturing method of the flexible printed wiring board using this invention film is demonstrated.
In the method for producing a printed wiring board, a known method can be adopted as long as it can be heated and pressurized as a thermal fusion method without using an adhesive layer, and is not particularly limited. A hot pressing method, a hot laminating roll method, or a combination of these methods can be suitably employed.
Examples of the conductive foil used in the present invention include a metal foil having a thickness of about 5 to 70 μm, such as copper, gold, silver, aluminum, nickel, and tin. As the metal foil, a copper foil is usually used, and a metal foil having a surface subjected to chemical conversion treatment such as black oxidation treatment is preferably used. In order to enhance the adhesion effect, it is preferable to use a conductor foil that has been chemically or mechanically roughened in advance on the contact surface (surface to be overlapped) side with the film. Specific examples of the conductor foil that has been subjected to surface roughening treatment include a roughened copper foil that has been electrochemically treated when an electrolytic copper foil is produced.
[0025]
Moreover, a well-known method can be employ | adopted also about the method of forming a conductive circuit in conductor foil, It does not specifically limit. For example, a known method such as a subtractive method (etching), an additive method (plating), a die stamp method (mold), or a conductor printing method (conductive paste) can be applied. For example, a method of plating a through hole with copper, a method of filling a through hole, an inner via hole with a conductive paste or a solder ball, a method of applying an anisotropic conductive material with an insulating layer containing fine conductive particles Etc.
[0026]
【Example】
The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In addition, the various measured values and evaluation about the film displayed in this specification were performed as follows. Here, the flow direction from the extruder of the film is called the vertical direction, and the orthogonal direction is called the horizontal direction.
[0027]
(1) Glass transition temperature (Tg), crystal melting peak temperature (Tm)
Using DSC-7 manufactured by PerkinElmer Co., Ltd., a 10 mg sample was obtained from a thermogram when the heating rate was raised at 10 ° C./min according to JIS K7121.
[0028]
(2) (ΔHm−ΔHc) / ΔHm
Using DSC-7 manufactured by PerkinElmer Co., Ltd., from a thermogram when heating a sample at a heating rate of 10 ° C./min according to JIS K7122, the crystal melting heat amount ΔHm (J / g) and the crystal The amount of heat of formation ΔHc (J / g) was determined and calculated.
[0029]
(3) Adhesive strength Measured according to the normal peel strength of JIS C6481.
[0030]
(4) Solder heat resistance In accordance with the normal solder heat resistance of JIS C6481, the test piece is floated in a 260 ° C. solder bath for 10 seconds so that the copper foil side and the solder bath are in contact with each other. The presence or absence of peeling or the like was examined visually to determine whether it was good or bad.
[0031]
(5) Transmission electron microscope observation From the central portion of the film obtained (parallel to the resin flow direction), a thin piece having a thickness of about 700 angstroms was collected, and a sample dyed with ruthenium tetroxide was prepared. Using a transmission electron microscope (JEM-1200EX, manufactured by JEOL Ltd.), the observation was performed at an acceleration voltage of 80 Kv and enlarged up to 20,000 times.
[0032]
(6) End tear strength In accordance with the end tear resistance test of JIS C2151, a test piece having a width of 15 mm and a length of 300 mm was cut out from a 75 μm-thick film, and using a test fitting B, a condition of a tensile speed of 500 mm / min. The vertical direction and the horizontal direction were measured.
[0033]
Example 1
As shown in Table 1, 60 parts by weight of polyetheretherketone resin [manufactured by Victrex, PEEK381G, Tg: 143 ° C., Tm: 334 ° C.] (hereinafter sometimes simply abbreviated as PEEK), 40 parts by weight of etherimide resin [General Electric Co., Ultem-CRS5001, Tg: 226 ° C.] (hereinafter sometimes simply referred to as PEI-1) and commercially available mica (average particle size: 10 μm, average aspect ratio: 30) A mixed composition consisting of 20 parts by weight was extruded into a film having a thickness of 75 μm at a set temperature of 380 ° C. using an extruder equipped with a T die, and simultaneously a copper foil (thickness: 18 μm, surface roughening). Was laminated to obtain a copper-clad substrate. Further, the obtained copper-clad substrate was crystallized in a constant temperature bath at 240 ° C. for 60 minutes to obtain a target crystallized copper-clad substrate.
[0034]
Table 1 shows evaluation results such as thermal characteristics and mechanical strength evaluated using the obtained crystallized copper-clad substrate. Also, FIG. 1 is a photograph of the obtained base film of the crystallized copper-clad substrate observed with a higher-order structure using a transmission electron microscope (the arrows in the figure indicate the flow direction of the film from the extruder). ). The photograph (dimension: 8.3 x 12.5 cm) is a photograph magnified 20,000 times, and the actual size shows a range of 4.15 x 6.25 μm, and the length is 1 cm (scale in the figure) Corresponds to 0.5 μm. It can be seen that the mica used in the photograph is the mica used, and black and white striped morphology is observed, but no spherulite structure is observed. As shown in Table 1, the obtained crystallized copper-clad substrate was excellent in adhesion strength with copper foil, solder heat resistance and mechanical strength (end tear strength).
[0035]
(Example 2)
In Example 1, except that the mixing ratio of PEEK and PEI-1 to be used was changed to 35 parts by weight and 65 parts by weight, respectively, as shown in Table 1, the crystallized copper-clad substrate was the same as in Example 1. Obtained. Table 1 shows evaluation results such as thermal characteristics and mechanical strength evaluated using the obtained crystallized copper-clad substrate.
[0036]
Example 3
In Example 1, except that the mixing ratio of PEEK and PEI-1 to be used was changed to 50 parts by weight and 50 parts by weight as shown in Table 1, respectively, the crystallization-treated copper-clad substrate was prepared in the same manner as in Example 1. Obtained. Table 1 shows evaluation results such as thermal characteristics and mechanical strength evaluated using the obtained crystallized copper-clad substrate.
[0037]
(Comparative Example 1)
In Example 1, as shown in Table 1, the type of PEI was changed to polyetherimide resin [General Electric Co., Ultem-1000, Tg: 216 ° C.] (hereinafter sometimes simply referred to as PEI-2). A crystallized copper-clad substrate was obtained in the same manner as in Example 1 except that. Table 1 shows evaluation results such as thermal characteristics and mechanical strength evaluated using the obtained crystallized copper-clad substrate. FIG. 2 shows a photograph of the obtained crystallized copper-clad base material film with a higher-order structure observed using a transmission electron microscope. The part that looks like a needle in the photograph is the mica used, and the part that looks like a black tree is a spherulite or bundle crystal structure derived from the crystal component of the polyaryl ketone resin. As shown in Table 1, the obtained crystallized copper-clad substrate was inferior in end tear strength although it had good adhesive strength with the copper foil and solder heat resistance.
[0038]
(Comparative Example 2)
In Example 1, a crystallized copper-clad substrate was obtained in the same manner as in Example 1 except that the obtained copper-clad substrate was not subjected to crystallization treatment at 240 ° C. for 60 minutes. Table 1 shows evaluation results such as thermal characteristics and mechanical strength evaluated using the obtained crystallized copper-clad substrate. A copper-clad substrate that has not been crystallized has insufficient progress of crystallization, has poor solder heat resistance, and lacks basic characteristics as a printed wiring board.
[0039]
(Comparative Example 3)
In Example 1, a crystallized copper-clad substrate was obtained in the same manner as in Example 1 except that the mixing weight ratio of mica used was changed to 45 parts by weight. Table 1 shows evaluation results such as thermal characteristics and mechanical strength evaluated using the obtained crystallized copper-clad substrate. The obtained crystallized copper-clad substrate was inferior in flexibility and end tear strength, although it had good adhesive strength with copper foil and solder heat resistance.
[0040]
[Table 1]

[0041]
The films of Examples 1 to 3 having the components specified in the present invention from Table 1 and in the specified range have no spherulite structure and have a striped morphology, adhesive strength, It turns out that it is excellent in the endurance strength as a solder heat resistance and a film for flexible printed wiring boards. The end crack strength is 60 N or more in both the vertical and horizontal directions. On the other hand, it can be seen that films having different components (Comparative Example 1) or out of the range defined in the present invention (Comparative Examples 2 and 3) are inferior in either end tear strength or solder heat resistance. .
[0042]
【The invention's effect】
According to the present invention, there is provided a flexible printed wiring board using a film made of a crystalline polyarylketone resin and an amorphous polyetherimide resin and having improved end tear strength while maintaining dimensional stability, heat resistance and the like. Can be provided.
[Brief description of the drawings]
FIG. 1 is a photograph of a higher order structure of a base film of a crystallized copper-clad substrate of Example 1 observed using a transmission electron microscope. The arrows in the figure indicate the flow direction (longitudinal direction) of the film from the extruder.
2 is a photograph of a higher-order structure of a base film of a crystallized copper-clad substrate of Comparative Example 1 observed using a transmission electron microscope. FIG. The arrows in the figure indicate the flow direction (longitudinal direction) of the film from the extruder.

Claims (7)

A film obtained by crystallizing a film comprising 70 to 30% by weight of a crystalline polyaryl ketone resin having a crystal melting peak temperature of 260 ° C. or higher and 30 to 70% by weight of an amorphous polyetherimide resin. The polyaryl ketone resin is a polyether ether ketone resin having the following structural formula (1), the amorphous polyether imide resin is a polyether imide resin having the following structural formula (2), and a transmission electron microscope. A heat-resistant film having a maximum crystal grain size of 0.3 μm or less when observed.
[Formula 1]

[Formula 2]

When a section taken from a direction parallel to the film flow direction with a transmission electron microscope is stained with ruthenium tetroxide and observed, the maximum crystal grain size is 0.1 μm or less and has a striped morphology. The heat resistant film according to claim 1 . The resin composition 100 parts by weight of a crystalline polyaryl ketone resin and amorphous polyether imide resin, according to claim 1, characterized in that the inorganic filler by mixing with 10 to 30 parts by weight or 2. The heat resistant film according to 2 . The heat of crystal fusion ΔHm measured when the temperature is raised by differential scanning calorimetry of the heat-resistant film and the amount of heat of crystallization ΔHc generated by crystallization during the temperature rise satisfy the following relational expression: 4. The heat resistant film according to any one of 1 to 3 .
[(ΔHm−ΔHc) / ΔHm] ≧ 0.90 End tear strength of the heat-resistant film (based on edge-cracking resistance test of JIS C2151) is longitudinal and heat resistance according to any one of claims 1 to 4, characterized in that in the transverse direction both at least 60N the film. A flexible printed wiring formed by providing a conductive foil on at least one surface of the heat-resistant film according to any one of claims 1 to 5 by thermal fusion without using an adhesive layer, and forming a conductive circuit on the conductive foil. substrate. The flexible printed wiring board according to claim 6, wherein the surface of the conductive foil is roughened.

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