JP5116001B2 - Method for manufacturing wet-etched insulator and method for manufacturing electronic circuit component - Google Patents

Description

【０００７】
Ｅ１：金属の弾性率
Ｅ２：絶縁層の弾性率
Δα：金属−絶縁層間の熱膨張係数の差
ΔΤ：温度差
ｈ：膜厚ｌ：配線長
この式により、配線の反りを低減させる方法として、
１．絶縁層の弾性率を低減する方法
２．絶縁層と金属配線層の熱膨張率差を低減する方法
の２種が考えられる。
【０００８】
配線を形成する方法において、第１金属層−絶縁層−第２金属層という構成からなる積層体における金属層をエッチングして配線を形成するために用いられる積層体に、積層体の反りを低減する為、金属層と絶縁層との熱膨張率を同じにする必要性がある。そのために、このような積層体の絶縁層として低膨張性のポリイミドを用いることが提案されている（ＵＳＰ４，５４３，２９５、特開昭５５−１８４２６号公報、特開昭５２−２５２６７号公報）。
【０００９】
しかし、低膨張性のポリイミドは一般に熱可塑性ではないため、金属層との接着性に乏しく、実用に耐えうるような密着力を得るのは困難である。そこで、金属層に対して密着性が良好な熱可塑性のポリイミド系樹脂やエポキシ樹脂を、金属層と低膨張性ポリイミドの絶縁層（コア層）の間に接着性絶縁層として用いることが知られている（特開平７−５８４２８号公報）。
【００１０】
該熱可塑性樹脂は一般に熱膨張率が大きく、金属と積層すると反りの発生の原因となる。そこで、金属と熱膨張率が近い低膨張性のコア絶縁層の厚みを、接着層の厚みより厚くすることで積層体全体として反りが表面に現れないようにしている。接着性絶縁層は薄ければ薄いほど反りに対してはいいが、薄すぎると接着性が損なわれる。また少なくとも、コア層の上下の接着層を合わせた厚みがコア層の厚みの半分以下であれば、反りが出ずらい。そのため、市販の電子回路部品用に加工される積層体は、接着性絶縁層の厚みの和がコア絶縁層の厚みの半分以下になっている場合が多く、密着性を保てる最低限の膜厚で形成されていることが理想とされている（特開平０１−２４５５８７）。
【００１１】
現在、パーソナルコンピューターの生産量の急激な伸びに伴い、それに組み込まれているハードディスクドライブもまた生産量が増大している。ハードディスクドライブにおける、磁気を読み取るヘッドを支持しているサスペンションといわれる部品は、ステンレスの板ばねに、銅配線を接続するものから、小型化への対応のためステンレスの板ばねに直接銅配線が形成されているワイヤレスサスペンションといわれるものへと主製品が移り変わりつつある。
【００１２】
該ワイヤレスサスペンションは、第１金属層−接着性絶縁層−コア絶縁層−接着性絶縁層−第２金属層からなる積層体を用いて作製されているものが主流である。該積層体は、例えば、第１金属層を銅の合金箔、第２金属層をステンレス箔とし、絶縁層を、コア絶縁層と該コア絶縁層の両面に積層された接着性絶縁層としたものが挙げられる。該積層体を用いたワイヤレスサスペンションは、高速で回転するディスク上をスキャンすることから細かな振動が加わる部材であるため、配線の密着強度は非常に重要である。したがって、該積層体を用いたワイヤレスサスペンションは、厳しいスペックが求められている。
【００１３】
また、ハードディスクドライブは情報を記録する装置であるので、データの読み書きに対する高度な信頼性が要求され、そのためにはワイヤレスサスペンションから発生する塵などのごみ及びアウトガスを最大限に減らさなければならない。
【００１４】
該ワイヤレスサスペンションと呼ばれる部品は、主にメッキにより配線を形成するアディティブ法と、銅箔をエッチングすることで配線を形成するサブトラクティブ法の２種類の作製法がある。サブトラクティブ法の場合、絶縁層であるポリイミドのパターニングを行うのに、専らドライプロセスによるプラズマエッチング法が用いられている。
【００１５】
【発明が解決しようとする課題】
上記のような厳しいスペックを満たす電子回路部品における低膨張性の絶縁層（コア絶縁層）と金属層との接着に用いられる接着性絶縁層は高度の絶縁信頼性を確保する必要性からポリイミド系樹脂が用いられている。ポリイミド系樹脂に接着性を持たせる為には、熱可塑性を与えるのが一般的ではあるが、熱可塑性を与えるような柔軟な構造をポリイミド骨格内に導入すると耐薬品性が強くなるものが多い。したがって、このような接着性を持たせたポリイミド樹脂はウエットプロセスにおけるエッチング適性が劣る傾向となり、コア絶縁層に比べてウェットプロセスでエッチングしにくいという理由から、プラズマやレーザーを用いたドライプロセスで絶縁層のエッチングを一括して行なっている。
【００１６】
ドライプロセスは被処理物に対して一般的に枚様毎の処理（枚様式）がなされるため、生産性が悪く、また装置も高価なため生産コストが非常に高くなってしまう欠点がある。一方、ウエットプロセスは、長尺物に対して連続処理にてエッチングが可能であるため生産性が高く、装置コストも安いというメリットがあるる。しかしながら、ワイヤレスサスペンションにおいては、コア絶縁層はエッチングされやすいが、接着性絶縁層がエッチングされにくいため、接着性絶縁層が張り出したようになって残り、エッチング形状がきれいにならず、エッチングムラが発生し、ワイヤレスサスペンションの使用中に発塵するという問題がある。したがって、厳しいスペックが求められているワイヤレスサスペンション用の積層体に対してはウエットプロセスが実用化できる程度には実現していない。
【００１７】
そこで、本発明は、第１無機物層−絶縁層−第２無機物層、又は、無機物層−絶縁層からなる層構成の積層体の絶縁層として存在する絶縁体が、ウエットエッチングが施されても、前記した不都合がなく、使用時に発塵が抑制された積層体における絶縁層としての絶縁体、さらに具体的には、該絶縁体が適用された電子回路部品、特に、ワイヤレスサスペンションを提供することを目的とする。
【００１８】
【課題を解決するための手段】
本発明者らは、鋭意検討を重ねた結果、第１無機物層−絶縁層−第２無機物層、又は、無機物層−絶縁層からなる層構成の積層体の絶縁層として存在する絶縁体が、ウエットエッチングが施されても、ウエットエッチング端面に脱水触媒による処理を施せば、該端面が堅固になり、発塵が抑制されることを見出した。
【００１９】
即ち、本発明は、単層構造又は２層以上の積層構造の、少なくとも１層が線熱膨張率３０（ｐｐｍ／℃）以下の低膨張性ポリイミド樹脂である絶縁ユニット層からなる絶縁体に対し、ウエットエッチングによるパターニングを行い、脱水触媒により処理することでエッチング端面を強固にすることを特徴とした絶縁体の製造方法である。
【００２０】
本発明の積層体の製造方法は、第１無機物層−絶縁層−第２無機物層、又は、無機物層−絶縁層からなる層構成の積層体における第１無機物層、第２無機物層及び無機物層の一部が除去されて露出している絶縁層に対して、ウエットエッチングによるパターニングと脱水触媒による処理を行うことを特徴とする積層体の製造方法である。
【００２１】
本発明の絶縁体は、電子回路部品、特に、ハードディスクドライブ用サスペンションの絶縁層として適用されることが有用である。
【００２２】
本発明の絶縁体の製造において、ウエットエッチングした場合に良好なエッチング形状が得られる絶縁体が用いられる。例えば、絶縁体が二層以上の積層構造の絶縁ユニット層である絶縁体では、ウエットエッチング時の各層のエッチングレートの比が６：１〜１：１、好ましくは４：１〜１：１の範囲内にあるものが用いられる。この範囲内のエッチングレートを持つ各絶縁ユニット層を選択すれば、絶縁体が良好なエッチング形状となる。したがって、従来、厳しいスペックが求められているワイヤレスサスペンション用の積層体でもウエットエッチングが精度良く行えるので、ドライエッチングに比べて短時間のエッチングが可能な生産性のよいウエットエッチングの適用が可能になる。
【００２３】
本発明による脱水触媒により処理された絶縁体の発塵が抑制されるメカニズムは次のように考えられる。絶縁体のウエットエッチングについて、アルカリ溶液でのポリイミド系樹脂のエッチングを例にとって説明する。ウエットプロセスは、水酸化物イオンにより絶縁体におけるイミド結合その他の加水分解されやすい結合（例えばエステル結合等）を加水分解するものである。絶縁体がポリイミド樹脂である場合にはポリイミドが加水分解により低分子量化し、または、アミド酸となり溶解性が増しエッチング液に溶出する。
【００２４】
一方、ウエットプロセスによるパターニング後に、エッチング液に溶出しなかったもので長い分子鎖のうち部分的に分解されアミド酸となったり、エッチング液に溶出しないもので分子量が小さくなっているものが、パターンの端面に残存している可能性が高いと考えられる。これら、加水分解によって切断された部位は、活性が低く他の原子との反応はしにくい状態にある為、パターンの端面は、エッチング液にさらされていない部位に比べると、分子量が低く強度的にもろくなっていると考えられ、これが発塵の原因と考えられる。
【００２５】
このようなウエットエッチング処理されてもろくなったエッチング端面に脱水触媒による処理を施すと、堅固に強化される。その理由は、前記加水分解により切断されて生成した低分子量化合物中の分子鎖のアミノ基、ジカルボキシル基及びアミド酸が脱水触媒により比較的反応しやすいので、脱水触媒によりこれらの基が反応して分子鎖同士が結合し、エッチング端面が強固になったものと考えられる。
【００２６】
このようなメカニズムにより、本発明の脱水触媒により処理された絶縁体は、部分的に脱落や剥離が起こりずらくなり、発塵が抑制される効果が生じる。
【００２７】
本発明において、脱水触媒による処理は、特別な装置を必要としないので装置コストが安く、大量処理に適しているので有利である。
【００２８】
【発明の実施の形態】
以下に本発明について具体的に説明する。
【００２９】
本発明の絶縁体において、ウエットエッチング後のエッチング端面に対するプラズマ処理による端面補強効果は、絶縁体が単層でも二層以上でも同様である。
【００３０】
本発明の絶縁体が電気回路部品に適用される場合には、その絶縁体の層構成は、接着性絶縁層−コア絶縁層−接着性絶縁層からなる積層構造が好ましい。本発明の絶縁体が表裏面に接着性絶縁層を計２層有し、内部に低膨張率のコア絶縁層を有するものであるならば、接着性絶縁層の厚みはコア絶縁層の１／４の厚みであることが反りの発生を抑制するので望ましい。
【００３１】
本発明の絶縁体を構成する絶縁ユニット層は、ポリイミド樹脂を含む有機材料を用いて作製される。しかしながら、絶縁体を構成する絶縁ユニット層のうち少なくとも一層に無機材料が配合されていてもよい。該無機材料には、例えば、コロイダルシリカ、ガラス繊維、その他の無機フィラーが挙げられる。
【００３２】
本発明の絶縁体は、耐熱性及び絶縁性が優れるという観点から、絶縁体を構成する絶縁ユニット層の少なくとも一層がポリイミド樹脂であることが好ましく、さらに好ましくは全てがポリイミド樹脂であることが望ましい。
【００３３】
本発明の絶縁体は、導電性を示す無機物層（主として金属層）と積層されて、電子回路部品、特に、ハードディスクドライブ用サスペンションに好適に利用できる。したがって、該電子回路部品の反り防止の観点から、絶縁体は低膨張性の絶縁体、特にポリイミド樹脂の層を有することが好ましく、その熱膨張率は積層される無機物とほぼ同等の値であることが反り防止に好ましい。この場合の低膨張性とは、熱膨張率が３０（ｐｐｍ／℃）以下の物質のことをいう。さらに好ましくは、本発明の絶縁体を構成する少なくとも１つの絶縁ユニット層の線熱膨張率と前記無機物層の線熱膨張率との差異が１５（ｐｐｍ／℃）以内であることが望ましい。該線熱膨張率を持つ樹脂には、例えば、低膨張性ポリイミドが好ましく用いられる。
【００３４】
本発明の絶縁体において、接着性絶縁層として用いられる樹脂には、好ましくは被着体との密着力が１００ｇ／ｃｍ以上の接着性ポリイミドが挙げられるが、同様な接着性、及び耐熱性や絶縁性が良好な樹脂であれば特に限定されず、イミド結合の有無によらない。本発明の絶縁体における接着性絶縁層には主に熱可塑性ポリイミドが用いられるが特に限定されない。また、本発明の絶縁体は被着体との接着性の相性により発現する密着力が異なる場合があるので、被着体の種類が異なる場合や、被着体と接着されてなる積層体に要求される特性に応じて、接着性ポリイミドを適宜選択する必要がある。したがって、絶縁層の表裏面にそれぞれ種類の異なった無機物層が積層される場合には、各無機物層に接する各接着性絶縁層の材料として必ずしも同一の組成の接着性ポリイミドを用いる必要はない。
【００３５】
本発明の絶縁体の各絶縁ユニット層は、実用上問題ない範囲の強度を保てれば、どのような分子量でも良い。特に、重量平均分子量が、その分子構造にもよるが一般に６０００以上５０００００以下が好ましい。特に好ましくは８０００以上１０００００以下である。分子量が５０００００以上であると、均一な塗膜を得難く、６０００以下では成膜性が悪く均一な接着性の塗膜が得られにくい。なおこの分子量の範囲は、もともと高分子の樹脂を用いて絶縁体を構成した場合の分子量の範囲を規定するものであり、低分子材料を用いて層を形成し、その後、熱処理等によって高分子量化させるような手段で作製された絶縁体に関しては、適用されない。
【００３６】
また、本発明の絶縁体は溶液の状態で塗布により成形されてもよいし、別な方法、例えば、独立したフィルム形態のものを用いてもよい。さらに、前駆体やその誘導体の状態で成形後に処理を行うことにより所望の化学構造にしてもよい。
【００３７】
本発明の絶縁体が、電子回路部品に適用される場合には、該電子回路部品の積層材料の層構成は、第１無機物層−絶縁層−第２無機物層、又は、無機物層−絶縁層からなり、本発明の絶縁体は該積層体の絶縁層として主として存在する。その積層体の製造方法は無機物に直接、絶縁体となる材料の溶液を１層以上塗布・積層することにより絶縁層を成形し、さらにもう一方の無機物を積層後、熱圧着することにより作製する方法（キャスト法）でも、予め用意されたコア絶縁フィルムに接着性絶縁層を形成し、その上下に無機物を積層し熱圧着して作製する方法（フィルム法）または、接着性絶縁層をフィルム上に形成後、蒸着やスパッタ・めっき等で無機物層を形成する方法等、最終的な積層体の層構成さえ同じであれば、その作製方法は特に限定するものではない。
【００３８】
本発明の絶縁体が存在する積層体における、無機物層の無機物とは広く有機物ではないものを指し、たとえば、金属や金属酸化物、単結晶シリコンやそれを加工した半導体製品等が挙げられる。特に、本発明の絶縁体がハードディスクドライブ用サスペンションに適用される場合には、バネとしての特性が必要なことからステンレス等の高弾性な金属と配線となる銅箔や合金銅箔との積層が好ましい。
【００３９】
基本的には本発明の絶縁体は積層体におけるウエットエッチングされた絶縁層に関するものであり、積層体としたときにいかなる無機物と積層されていようとも、使用時に発塵が抑制された、積層体における絶縁層であれば、無機物の種類は特に限定されない。
【００４０】
本発明の絶縁体のウエットエッチングは、無機物層と積層体を形成した後に、ウエットエッチングを行っても良いし、積層前にウエットエッチングを行っても良い。本発明のウエットエッチングされた絶縁体には次のような態様が挙げられる。
▲１▼ 絶縁フィルムの両面に対して、配線を形成した基板となる無機物層を接着した後、絶縁フィルムのウエットエッチングを行う。
▲２▼ 無機物層の基板上に配線を形成した後に、絶縁フィルムを接着し、その後、絶縁フィルム表面上に無機物層を貼り付け、無機物層と絶縁フィルムをウエットエッチングする。
▲３▼ 予めウエットエッチングした絶縁フィルムを無機物層へ貼り付ける。
【００４１】
本発明におけるウエットエッチングは、絶縁体がポリイミドである場合には、通常、ｐＨ７．０を超えるエッチング液で行われる。
【００４２】
用いるエッチング液としては、ポリイミドをウエットエッチングする場合を例にとると特開平１０−９７０８１号公報に開示されるようなアルカリ−アミン系エッチング液等が挙げられ、好適に利用できるが、特に限定されない。具体的には、アルカリ性の水溶液であることが望ましく、好ましくはｐＨが９以上、さらに好ましくは１１以上の塩基性薬液を用いることがよい。また、有機系のアルカリでもよいし無機系のアルカリでもよく、更にその２種の混合形でもよい。
【００４３】
本発明者らはワイヤレスサスペンション用等の高精密度電子回路部品用の第１金属層−絶縁層−第２金属層、又は、金属層−絶縁層からなる層構成の積層体における、絶縁層を構成するコア絶縁層と接着性絶縁層各１層の厚みの最大比が４：１であるところに着目し、コア絶縁層のエッチングレートの１／４のエッチングレートを持つ接着性絶縁層であれば、同じ時間でエッチングされる為、良好な形状を得られると仮説を立て、実験によりこれを証明した。絶縁層を構成する各絶縁ユニット層のエッチングレートの大きいものと小さいものとの比が、６：１乃至１：１の範囲内、好ましくは４：１〜１：１の範囲内であれば、ウエットプロセスにおいても絶縁層全体のエッチングが均一に進行しエッチング形状の良好なものが得られる。
【００４４】
ウエットエッチングを行う温度は実質的に何度でも良く、エッチャントがエッチャントとして性能を発揮する温度であればよい。特にエッチャントが水溶液であれば、０℃〜１１０℃の間が好ましく、温度が低いと一般にエッチングレートが遅くなるため、また、温度が高いと沸騰したりして作業性が良くないので、３０℃〜９０℃の範囲であるのがより好ましい。さらに好ましくは成分の蒸発等によるエッチャント組成の変化を押さえ、且つ、エッチング時間を短縮させるために、５０℃〜９０℃でウエットエッチングを行うのが良い。
【００４５】
本発明の絶縁体に適用される脱水触媒による処理とは、絶縁体、又は絶縁体と無機層との積層体になされたウエットエッチングの後に行われる後処理であって、該絶縁体や積層体を脱水触媒の処理液に浸漬したり、スプレー等で噴霧するなどして、該処理液を処理したい絶縁体や積層体の特定部位に接触させることを言い、該接触方法は限定されない。処理するときの処理液の温度は、縮合反応が十分進行する温度であれば実用上不都合がない範囲内の何度でもよいが、作業性の観点から０℃〜１００℃の温度であることが好ましく、１０℃〜４０℃であることがさらに好ましい。処理時間は、０．０１秒以下であると処理の効果が得られにくく、３０分以上だと生産性が悪くなる為好ましくない。
【００４６】
本発明に使用される脱水触媒とは、アミノ基とカルボキシル基、又はアミド基とカルボキシル基の縮合反応を促進する働きのある試薬のことを言い、具体的には、無水酢酸、テトラフルオロ無水酢酸等の酸無水物系の化合物や；ジシクロへキシルカルボジイミド等のカルボジイミド類化合物や；カルボジイミド樹脂や；ＤＢＮ（１，５−ジアザビシクロ［４．３．０］ノン−５‐エン）等の有機化合物や；濃硫酸、塩化ホスホリル、３塩化リン等の無機物が挙げられるが、特に限定されない。コストや扱い易さの面から酸無水物系の化合物や、カルボジイミド系化合物が好ましく、その中でも無水酢酸が最も汎用的であり好ましい。
【００４７】
脱水触媒による処理の際には、反応促進作用を高める働きのある、３級アミンやピリジンのような化合物を添加しても良い。３級アミンの具体例には、トリエチルアミンが挙げられるが、特に限定されない。
【００４８】
また、脱水触媒をそのまま処理液として用いても良いが、脱水作用が十分発揮されるような範囲で、その他の溶媒で希釈して用いても良い。具体的には、アセトンやメチルエチルケトン、等のケトン系溶媒や、トルエン等の芳香族炭化水素、ヘキサンやシクロヘキサン等の炭化水素、ジエチルエーテル等のエーテル類、酢酸エチル等のエステル類などが挙げられるが特に限定されない。
【００４９】
電子回路部品
電子回路部品の形成は、一般的には以下の方法で行うことができる。
【００５０】
回路を形成したい側の積層体（第１無機物層−絶縁層−第２無機物層、又は、無機物層−絶縁層）の導電性無機物層表面に感光性樹脂層を塗布又はラミネートによって形成する。形成された感光性樹脂層上に、所望のパターンの像が描かれたマスクを密着させ感光性樹脂が感度を持つ波長の電磁波を照射する。所定の現像液でポジ型感光性樹脂であれば感光部を、ネガ型感光性樹脂であれば未露光部を溶出させ、所望の回路の像を無機物層上に形成する。この状態のものを塩化第二鉄水溶液のような金属を溶解させる溶液に浸漬又は、溶液を基板に噴霧することで露出している金属を溶出させた後に、所定の剥離液で感光性樹脂を剥離し回路とする。次いで、該金属表面に形成した回路上に同様にして所望のパターンの像が描かれたマスクを密着させウエットプロセスで絶縁層をパターニングする。次いで、パターニングされた絶縁層に対して、脱水触媒による処理を行う。
【００５１】
本発明の積層体が適用できる電子回路部品には、例えば、フレキシブルプリント基板等の配線盤、ＣＳＰ（チップスケールパッケージ）等の半導体関連部品、トナージェットプリンタのノズル等のデバイス、特に、ハードディスクドライブ用サスペンションが挙げられる。
【００５２】
【実施例】
エッチング性試験
銅側の接着性絶縁層に使用する熱可塑性ポリイミドＡ、ＳＵＳ側の接着性絶縁層に使用する熱可塑性ポリイミドＢと、コア絶縁層に使用する低膨張性ポリイミドを用意した。エッチング試験に用いたエッチング液は、東レエンジニアリング株式会社製アルカリ−アミン系ポリイミドエッチング液 ＴＰＥ−３０００（商品名）を用意した。
【００５３】
それらの各樹脂をそれぞれ、１５ｃｍ×１５ｃｍの大きさの膜厚の２０μｍのＳＵＳ３０４箔上にバーコートで膜厚２０μｍ〜４０μｍにコーティングし、熱処理を加えることで、ＳＵＳ上に各ポリイミド膜を作製した。それらの塗布物を長さ約１．５ｃｍ、幅約２ｃｍに切り出し、中心部にカッターナイフで傷をつけた後に、膜厚を触針式膜厚計デックタックにて測定し、初期の膜厚とした。その後、８０℃に調節されたマグネチックスターラーにて渦ができる程度に撹拌されたポリイミドエッチング液を ＴＰＥ−３０００に、浸漬し時間毎に初期膜厚を測定した場所と同じ場所の膜厚をデックタックにて測定し、初期の膜厚から浸漬後の膜厚を差し引いたものを、膜減り量とし、エッチングレートを求めた。その結果を下記の表１に示す。
【００５４】
【表１】

【００５５】
上記各ポリイミドを用いてＳＵＳ３０４ Ｈ−ＴＡ 箔（商品名、新日本製鉄（株）製、厚さ２０μｍ）−熱可塑性ポリイミドＢ（厚み１．５μｍ）−低膨張性ポリイミド（厚み１４．５μｍ）−熱可塑性ポリイミドＡ（厚み１．５μｍ）−圧延銅箔Ｃ７０２５（商品名、オーリン社製、厚さ１８μｍ）からなる層構成の積層体を作製し、以下の実験に用いた。
【００５６】
発塵性評価
前記積層体を、ＳＵＳ側をマスクして、塩化第二鉄溶液に浸積し、銅箔をエッチングした。このようにして露出させた接着層面に厚み５０μｍのアルカリ現像型ドライフィルムレジストを熱ラミネーターにより、６．５ｍ／ｍｉｎの速さで、ロールの表面の温度１０５℃で、２〜４Ｋｇ／ｃｍの線圧でラミネート後、１５分間室温で放置した。その後、所定のマスクを用いて密着露光機で１００ｍＪ／ｃｍ²露光した。室温で１５分間放置後、Ｎａ₂ ＣＯ₃ １重量％水溶液で、３０℃、スプレー圧２Ｋｇで４０秒間ドライフィルムレジストを現像した。その後、乾燥し、７０℃でマグネチックスターラーで渦ができるほど攪拌したポリイミド用エッチング液ＴＰＥ−３０００（商品名、東レエンジニアリング社製）に浸積し、マスクの形状にきれいにポリイミド膜が除去された時点で、取り出し、５０℃の３重量％ＮａＯＨ水溶液で、スプレー圧１Ｋｇでドライフィルムレジストを剥離して絶縁層を作製した。このようにして得られた絶縁層を室温で攪拌した処理液中に３分間浸漬した後、６０℃の水で洗浄を行い、乾燥させた。該処理液は予め無水酢酸５００ｇとトリエチルアミン５ｇを混合し作製したものを使用した。該脱水触媒による処理の前後のサンプル（処理前をサンプルＡ、処理後をサンプルＢとする）について以下の手順で、発塵量を測定した。
【００５７】
予め濾過した蒸留水（以下ブランクとする）及び十分に洗浄したビーカー、ピンセットを準備した。
【００５８】
上記工程で得られた各サンプルから無作為に選んだ絶縁層（各４パターン分）を、ビーカーに入れ、一定量のブランクを注ぎ、超音波照射装置内に置き、超音波を１分間照射した（抽出）。超音波照射後、装置からビーカーを取出し、サンプルをピンセットで取り出した。取り出した後の抽出液３０ｍｌを、ＨＩＡＣ／ＲＯＹＣＯ社製液体用自動微粒子測定装置、吸引方式セミオートサンプリング装置、レーザーダイオード光遮断方式センサを装備した測定装置にセットし、パーティクル量を測定した。サンプルを入れずに同様の測定を行った結果をブランク値とした。測定装置の洗浄は測定毎に行った。測定値からブランク値を差し引いたものをサンプル測定結果とした。測定は、一つのサンプルあたり５回行い、その平均値を最終測定結果とした。上記のようにして得られた脱水触媒による処理前サンプルＡと処理後サンプルＢの測定値を下記の表１に示す。各サンプル欄のパーティクル量は４パターンの平均を示す。
【００５９】
【表２】

【００６０】
表２によれば、脱水触媒による処理を行ったサンプルＢの方が発塵量が少ないことが分かる。
【００６１】
【発明の効果】
本発明の絶縁体によれば、ウエットプロセスによりパターニングされた絶縁層に、脱水触媒による処理が行われているので、エッチング液に接触した絶縁層の端面は超音波照射しても発塵が抑制されており、表面が改質されている。したがって、本発明の絶縁体を電子回路部品に適用した場合には、発塵の少ないものとなり、ウエットプロセスを適用した電子回路部品の信頼性を高める。特に、ハードディスクドライブ用サスペンションは、エッチングにより除去される絶縁層の面積が広く、しかも微細なパターンが必要とされていることから、ウエットエッチングを適用する効果が大であるが、本発明の絶縁体はウエットエッチングの信頼性を高めているので、ハードディスクドライブ用サスペンションの絶縁層に好適である。[0001]
BACKGROUND OF THE INVENTION
The present invention constitutes an insulating layer in a laminate composed of a first inorganic layer (mainly metal layer) -insulating layer-second inorganic layer (mainly metal layer) or inorganic layer (mainly metal layer) -insulating layer. The present invention relates to a laminate suitable for etching a plurality of resin layers by a wet process, and an electronic circuit component obtained by etching the laminate by a wet process, and more particularly to a suspension for a hard disk drive.
[0002]
[Prior art]
In recent years, with the rapid development of semiconductor technology, miniaturization of semiconductor packages, increase in pin count, fine pitch, miniaturization of electronic components, etc. have rapidly progressed, and the era of so-called high-density packaging has been entered. Along with this, printed wiring boards have been made thinner and thinner from single-sided wiring to double-sided wiring (Iwata, Harazoen, Electronic Materials, 35 (10), 53 (1996)).
[0003]
A pattern forming method for forming such wiring / circuits includes etching a metal layer on a substrate in a layer structure of metal layer-insulating layer-metal layer with an acidic solution such as ferric chloride, and wiring. After the formation, the insulating layer is removed in a desired shape in a dry state such as plasma etching or laser etching or a wet state such as hydrazine in order to establish conduction between layers (Japanese Patent Laid-Open No. 6-164084). There is a method of connecting between wirings with a conductive paste or the like. Another pattern forming method is a method in which an insulating layer is provided in a desired shape using photosensitive polyimide (Japanese Patent Laid-Open No. 4-168441) or the like, and then wiring is formed in the gap by plating (electronic packaging) Proceedings of the 7th Research Discussion Meeting of the Society (published in 1999).
[0004]
Due to the downsizing trend of electrical products in recent years, the metal layer and the polymer insulator layer have been made thinner, and each is often used with a thickness of 100 μm or less. Thus, when wiring is produced with a thin film, the wiring is warped due to the difference in thermal expansion coefficient between the metal layer and the polymer insulator layer.
[0005]
Such warpage σ of the substrate can be calculated by the following equation if the thermal properties of the insulating layer and the conductor layer are known (Miyaaki, Miki, Nitto Technical Report, 35 (3), 1, (1997).
[0006]
[Expression 1]

[0007]
E1: Elastic modulus of metal E2: Elastic modulus of insulating layer Δα: Difference in thermal expansion coefficient between metal and insulating layer ΔΤ: Temperature difference h: Film thickness l: Wiring length As a method for reducing warping of wiring by this equation,
1. 1. Method for reducing the elastic modulus of an insulating layer Two methods of reducing the difference in coefficient of thermal expansion between the insulating layer and the metal wiring layer are conceivable.
[0008]
In the method of forming a wiring, the warpage of the stacked body is reduced in the stacked body used for forming the wiring by etching the metal layer in the stacked body having the configuration of the first metal layer-insulating layer-second metal layer. Therefore, it is necessary to make the thermal expansion coefficient of the metal layer and the insulating layer the same. Therefore, it has been proposed to use a low-expansion polyimide as an insulating layer of such a laminate (USP 4,543,295, JP-A-55-18426, JP-A-52-25267). .
[0009]
However, since low-expansion polyimide is generally not thermoplastic, it has poor adhesion to the metal layer and it is difficult to obtain adhesion that can withstand practical use. Therefore, it is known that a thermoplastic polyimide resin or epoxy resin having good adhesion to the metal layer is used as an adhesive insulating layer between the metal layer and the insulating layer (core layer) of the low expansion polyimide. (JP-A-7-58428).
[0010]
The thermoplastic resin generally has a large coefficient of thermal expansion, and if it is laminated with a metal, it causes warpage. Therefore, the thickness of the low-expansion core insulating layer having a thermal expansion coefficient close to that of the metal is made larger than the thickness of the adhesive layer so that no warpage appears on the surface of the entire laminate. The thinner the adhesive insulating layer, the better against warping, but if it is too thin, the adhesiveness is impaired. Further, if at least the combined thickness of the upper and lower adhesive layers of the core layer is less than half the thickness of the core layer, warpage is unlikely to occur. Therefore, laminates processed for commercially available electronic circuit components often have a sum of adhesive insulating layer thicknesses that is less than half the thickness of the core insulating layer, and the minimum film thickness that can maintain adhesion Is ideally formed (Japanese Patent Laid-Open No. 01-245587).
[0011]
Currently, along with the rapid growth of personal computer production, the production of hard disk drives built into it is also increasing. In a hard disk drive, a part called a suspension that supports a magnetic reading head connects a copper wire to a stainless steel leaf spring, and a copper wire is directly formed on the stainless steel leaf spring to cope with downsizing. The main product is changing to what is called wireless suspension.
[0012]
The wireless suspension is mainly manufactured using a laminate including a first metal layer-adhesive insulating layer-core insulating layer-adhesive insulating layer-second metal layer. In the laminate, for example, the first metal layer is a copper alloy foil, the second metal layer is a stainless steel foil, and the insulating layer is a core insulating layer and an adhesive insulating layer laminated on both surfaces of the core insulating layer. Things. Since the wireless suspension using the laminate is a member to which fine vibration is applied because the disk is rotated at a high speed, the adhesion strength of the wiring is very important. Therefore, strict specifications are required for the wireless suspension using the laminate.
[0013]
In addition, since the hard disk drive is a device for recording information, high reliability for reading and writing data is required. For this purpose, dust such as dust generated from the wireless suspension and outgas must be reduced to the maximum.
[0014]
There are two types of parts called wireless suspensions, namely, an additive method in which wiring is mainly formed by plating and a subtractive method in which wiring is formed by etching a copper foil. In the case of the subtractive method, a plasma etching method based on a dry process is exclusively used for patterning the polyimide as an insulating layer.
[0015]
[Problems to be solved by the invention]
Adhesive insulating layers used for bonding low-expansion insulating layers (core insulating layers) and metal layers in electronic circuit components that meet the above strict specifications are polyimide-based due to the need to ensure a high degree of insulation reliability. Resin is used. In order to give adhesion to a polyimide resin, it is common to give thermoplasticity, but there are many chemicals that become stronger when a flexible structure that gives thermoplasticity is introduced into the polyimide skeleton. . Therefore, polyimide resin with such adhesive properties tends to be inferior in etching suitability in the wet process, and it is difficult to etch in the wet process as compared with the core insulating layer. Therefore, it is insulated by a dry process using plasma or laser. Layer etching is performed in a batch.
[0016]
Since the dry process is generally performed for each workpiece (sheet format) on the workpiece, the productivity is poor and the apparatus is expensive, so that the production cost is very high. On the other hand, the wet process is advantageous in that it can be etched in a continuous process for a long object, so that the productivity is high and the apparatus cost is low. However, in the wireless suspension, the core insulating layer is easy to etch, but the adhesive insulating layer is difficult to etch, so the adhesive insulating layer remains protruding, the etching shape is not clean, and etching unevenness occurs However, there is a problem that dust is generated during use of the wireless suspension. Therefore, the wet process has not been realized to the extent that it can be put into practical use for a laminate for a wireless suspension that requires strict specifications.
[0017]
Therefore, the present invention provides a method in which an insulator existing as an insulating layer of a layered structure composed of a first inorganic layer-insulating layer-second inorganic layer or an inorganic layer-insulating layer is subjected to wet etching. To provide an insulator as an insulating layer in a laminate in which dust generation is suppressed during use without the above-described disadvantage, and more specifically, an electronic circuit component to which the insulator is applied, particularly a wireless suspension. With the goal.
[0018]
[Means for Solving the Problems]
As a result of intensive studies, the present inventors have found that an insulator that exists as an insulating layer of a layered structure composed of a first inorganic layer-insulating layer-second inorganic layer, or an inorganic layer-insulating layer, It has been found that even if wet etching is performed, if the wet etching end face is treated with a dehydration catalyst, the end face becomes firm and dust generation is suppressed.
[0019]
That is, the present invention relates to an insulator composed of an insulating unit layer having a single layer structure or a laminated structure of two or more layers, wherein at least one layer is a low expansion polyimide resin having a linear thermal expansion coefficient of 30 (ppm / ° C.) or less. In this method of manufacturing an insulator, patterning is performed by wet etching and the etching end face is strengthened by treatment with a dehydration catalyst.
[0020]
The method for producing a laminate of the present invention includes a first inorganic layer, a second inorganic layer, and an inorganic layer in a laminate having a layer structure composed of a first inorganic layer-insulating layer-second inorganic layer or an inorganic layer-insulating layer. In this method, the insulating layer exposed by removing a part of the substrate is subjected to patterning by wet etching and treatment with a dehydration catalyst.
[0021]
The insulator of the present invention is useful when applied as an insulating layer for electronic circuit components, particularly suspensions for hard disk drives.
[0022]
Te manufacturing smell of insulation of the present invention, insulator excellent etching shape can be obtained when wet etching is used. For example, in an insulator in which the insulator is an insulating unit layer having a laminated structure of two or more layers , the ratio of the etching rate of each layer during wet etching is 6: 1 to 1: 1, preferably 4: 1 to 1: 1. Those within the range are used. If each insulating unit layer having an etching rate within this range is selected, the insulator has a good etching shape. Therefore, since the wet etching can be performed with high precision even in a laminate for wireless suspension, which has conventionally required strict specifications, it is possible to apply wet etching with high productivity capable of etching in a shorter time than dry etching. .
[0023]
The mechanism by which dust generation of the insulator treated by the dehydration catalyst according to the present invention is suppressed is considered as follows. The wet etching of the insulator will be described by taking the etching of polyimide resin with an alkaline solution as an example. The wet process hydrolyzes imide bonds and other bonds that are easily hydrolyzed (for example, ester bonds and the like) in an insulator with hydroxide ions. When the insulator is a polyimide resin, the polyimide has a low molecular weight by hydrolysis, or becomes an amic acid, so that the solubility is increased and the polyimide is eluted in the etching solution.
[0024]
On the other hand, after patterning by the wet process, the pattern that was not eluted into the etchant and partially decomposed into amic acid out of the long molecular chain, or that did not elute into the etchant and the molecular weight was small It is considered that there is a high possibility that it remains on the end face of. Since these sites cleaved by hydrolysis are in a state of low activity and difficult to react with other atoms, the end face of the pattern has a low molecular weight and strength compared to the site not exposed to the etching solution. It is thought that it has become brittle, and this is thought to be the cause of dust generation.
[0025]
When the etching end face that has become brittle after such wet etching is treated with a dehydration catalyst , it is firmly strengthened. This is because the amino groups of the molecular chain of the low molecular weight compound that is generated is cut by the hydrolysis, since dicarboxyl group and an amide acid is relatively easily reacted with a dehydration catalyst, these groups react with a dehydration catalyst It is thought that molecular chains are bonded to each other and the etching end face is strengthened.
[0026]
Due to such a mechanism, the insulator treated with the dehydration catalyst of the present invention is less likely to drop off or peel off partially, and the effect of suppressing dust generation occurs.
[0027]
In the present invention, the treatment with the dehydration catalyst is advantageous because it does not require any special equipment, so that the equipment cost is low and it is suitable for mass treatment.
[0028]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be specifically described below.
[0029]
In the insulator of the present invention, the end face reinforcing effect of the plasma treatment for etching end face after the wet etching, an insulator is also on two layers or more in a single layer.
[0030]
When the insulator of the present invention is applied to an electric circuit component, the layer structure of the insulator is preferably a laminated structure including an adhesive insulating layer, a core insulating layer, and an adhesive insulating layer. If the insulator of the present invention has a total of two adhesive insulating layers on the front and back surfaces and a core insulating layer with a low expansion coefficient inside, the thickness of the adhesive insulating layer is 1 / (the thickness of the core insulating layer). A thickness of 4 is desirable because it suppresses the occurrence of warpage.
[0031]
The insulating unit layer constituting the insulator of the present invention is manufactured using an organic material containing a polyimide resin . However, at least one layer of inorganic material of the insulating unit layers constituting the insulating member may be blended. Examples of the inorganic material include colloidal silica, glass fiber, and other inorganic fillers.
[0032]
In the insulator of the present invention, from the viewpoint of excellent heat resistance and insulation, it is preferable that at least one of the insulating unit layers constituting the insulator is a polyimide resin, and more preferable that all are polyimide resins. .
[0033]
The insulator of the present invention is laminated with a conductive inorganic layer (mainly a metal layer), and can be suitably used for electronic circuit components, in particular, suspensions for hard disk drives. Therefore, from the viewpoint of preventing warpage of the electronic circuit component, the insulator preferably has a low-expansion insulator, in particular, a polyimide resin layer, and the coefficient of thermal expansion is substantially the same value as the inorganic material to be laminated. It is preferable to prevent warping. The low expansibility in this case means a substance having a thermal expansion coefficient of 30 (ppm / ° C.) or less. More preferably, the difference between the linear thermal expansion coefficient of at least one insulating unit layer constituting the insulator of the present invention and the linear thermal expansion coefficient of the inorganic layer is preferably within 15 (ppm / ° C.) . For example, low-expansion polyimide is preferably used for the resin having the linear thermal expansion coefficient.
[0034]
In the insulator of the present invention, the resin used as the adhesive insulating layer is preferably an adhesive polyimide having an adhesion force with an adherend of 100 g / cm or more. The resin is not particularly limited as long as it has a good insulating property, and does not depend on the presence or absence of an imide bond. For the adhesive insulating layer in the insulator of the present invention, thermoplastic polyimide is mainly used, but is not particularly limited. In addition, since the adhesive strength of the insulator of the present invention may be different depending on the compatibility of the adhesion with the adherend, the type of adherend may be different, or the laminate that is bonded to the adherend may be used. It is necessary to appropriately select an adhesive polyimide according to the required characteristics. Therefore, when different types of inorganic layers are laminated on the front and back surfaces of the insulating layer, it is not always necessary to use adhesive polyimide having the same composition as the material of each adhesive insulating layer in contact with each inorganic layer.
[0035]
Each insulation unit layer of the insulator of the present invention may have any molecular weight as long as it can maintain a strength within a range where there is no practical problem. In particular, the weight average molecular weight is generally preferably from 6000 to 500,000, although it depends on the molecular structure. Particularly preferably, it is 8000 or more and 100,000 or less. When the molecular weight is 500,000 or more, it is difficult to obtain a uniform coating film, and when it is 6000 or less, the film formability is poor and it is difficult to obtain a uniform adhesive coating film. This molecular weight range originally defines the molecular weight range when an insulator is formed using a high molecular resin. After the layer is formed using a low molecular material, the high molecular weight is obtained by heat treatment or the like. It does not apply to insulators made by means of making them.
[0036]
Moreover, the insulator of the present invention may be formed by coating in a solution state, or another method, for example, an independent film form may be used. Further, a desired chemical structure may be obtained by performing a treatment after molding in the state of a precursor or a derivative thereof.
[0037]
When the insulator of the present invention is applied to an electronic circuit component, the layer configuration of the laminated material of the electronic circuit component is the first inorganic layer-insulating layer-second inorganic layer or the inorganic layer-insulating layer. The insulator of the present invention mainly exists as an insulating layer of the laminate. The laminated body is manufactured by directly forming an insulating layer by applying and laminating one or more solutions of the material to be an insulator on the inorganic material, and then laminating the other inorganic material, followed by thermocompression bonding. Even in the method (cast method), an adhesive insulating layer is formed on a core insulating film prepared in advance, an inorganic material is laminated on the top and bottom, and thermocompression-bonded (film method), or the adhesive insulating layer is formed on the film. As long as the layer structure of the final laminate is the same, such as a method of forming an inorganic layer by vapor deposition, sputtering, plating, or the like after the formation, the manufacturing method is not particularly limited.
[0038]
In the laminate in which the insulator of the present invention is present, the inorganic material of the inorganic material layer refers to a material that is not an organic material widely, and examples thereof include metals, metal oxides, single crystal silicon, and semiconductor products obtained by processing the same. In particular, when the insulator of the present invention is applied to a suspension for a hard disk drive, since a characteristic as a spring is required, a laminate of a highly elastic metal such as stainless steel and a copper foil or alloy copper foil as a wiring is required. preferable.
[0039]
Basically, the insulator of the present invention relates to a wet-etched insulating layer in a laminated body, and the laminated body in which dust generation is suppressed during use, regardless of what inorganic material is laminated when the laminated body is used. If it is an insulating layer in, the kind of inorganic substance will not be specifically limited.
[0040]
In the wet etching of the insulator of the present invention, the wet etching may be performed after forming the inorganic layer and the laminated body, or the wet etching may be performed before the lamination. Examples of the wet-etched insulator of the present invention include the following modes.
{Circle around (1)} After bonding an inorganic layer to be a substrate on which wiring is formed on both sides of the insulating film, the insulating film is wet etched.
(2) After the wiring is formed on the substrate of the inorganic layer, the insulating film is bonded, and then the inorganic layer is attached on the surface of the insulating film, and the inorganic layer and the insulating film are wet-etched.
(3) A wet-etched insulating film is pasted on the inorganic layer.
[0041]
In the present invention, when the insulator is polyimide, the wet etching is usually performed with an etching solution having a pH exceeding 7.0.
[0042]
Examples of the etching solution to be used include an alkali-amine type etching solution as disclosed in JP-A-10-97081, for example, when wet etching of polyimide is used, but is not particularly limited. . Specifically, an alkaline aqueous solution is desirable, and it is preferable to use a basic chemical solution having a pH of 9 or more, more preferably 11 or more. Moreover, an organic alkali may be sufficient and an inorganic alkali may be sufficient, and also the mixed form of the 2 types may be sufficient.
[0043]
The inventors of the present invention provide an insulating layer in a layered structure composed of a first metal layer-insulating layer-second metal layer or a metal layer-insulating layer for a high-precision electronic circuit component such as a wireless suspension. Paying attention to the fact that the maximum ratio of the thicknesses of the core insulating layer and the adhesive insulating layer constituting each layer is 4: 1, an adhesive insulating layer having an etching rate that is 1/4 of the etching rate of the core insulating layer. For example, it was hypothesized that a good shape could be obtained because it was etched in the same time, and this was proved by experiments. If the ratio between the large etching rate and the small etching rate of each insulating unit layer constituting the insulating layer is in the range of 6: 1 to 1: 1, preferably 4: 1 to 1: 1, Even in the wet process, the etching of the entire insulating layer proceeds uniformly, so that a good etching shape can be obtained.
[0044]
The temperature at which the wet etching is performed may be substantially any number as long as the etchant exhibits performance as an etchant. In particular, when the etchant is an aqueous solution, the temperature is preferably between 0 ° C. and 110 ° C. Since the etching rate is generally slow when the temperature is low, and when the temperature is high, it boils and the workability is not good. More preferably, it is in the range of ˜90 ° C. More preferably, wet etching is performed at 50 ° C. to 90 ° C. in order to suppress the change in the etchant composition due to evaporation of components and shorten the etching time.
[0045]
The treatment with the dehydration catalyst applied to the insulator of the present invention is a post-treatment performed after wet etching performed on the insulator or the laminate of the insulator and the inorganic layer, and the insulator or the laminate Is immersed in a treatment solution of a dehydration catalyst or sprayed with a spray or the like, and the treatment solution is brought into contact with a specific part of an insulator or a laminate to be treated, and the contact method is not limited. The temperature of the treatment liquid during the treatment may be any number within a practically inconvenient range as long as the condensation reaction proceeds sufficiently. However, from the viewpoint of workability, it should be a temperature of 0 ° C to 100 ° C. Preferably, it is 10-40 degreeC. If the treatment time is 0.01 seconds or less, it is difficult to obtain the effect of the treatment, and if it is 30 minutes or more, the productivity deteriorates, which is not preferable.
[0046]
The dehydration catalyst used in the present invention refers to a reagent having a function of promoting the condensation reaction of an amino group and a carboxyl group, or an amide group and a carboxyl group. Specifically, acetic anhydride, tetrafluoroacetic anhydride Such as acid anhydride compounds such as: carbodiimide compounds such as dicyclohexylcarbodiimide; carbodiimide resins; organic compounds such as DBN (1,5-diazabicyclo [4.3.0] non-5-ene); Inorganic substances such as concentrated sulfuric acid, phosphoryl chloride, and phosphorus chloride may be mentioned, but are not particularly limited. From the viewpoint of cost and ease of handling, acid anhydride compounds and carbodiimide compounds are preferred, and among them, acetic anhydride is the most versatile and preferred.
[0047]
In the treatment with the dehydration catalyst, a compound such as a tertiary amine or pyridine having a function of enhancing the reaction promoting action may be added. Specific examples of the tertiary amine include triethylamine, but are not particularly limited.
[0048]
In addition, the dehydration catalyst may be used as the treatment liquid as it is, but may be diluted with another solvent as long as the dehydration action is sufficiently exhibited. Specific examples include ketone solvents such as acetone and methyl ethyl ketone, aromatic hydrocarbons such as toluene, hydrocarbons such as hexane and cyclohexane, ethers such as diethyl ether, and esters such as ethyl acetate. There is no particular limitation.
[0049]
Electronic circuit component The electronic circuit component can be generally formed by the following method.
[0050]
A photosensitive resin layer is formed by coating or laminating on the surface of the conductive inorganic layer of the laminate (first inorganic layer-insulating layer-second inorganic layer or inorganic layer-insulating layer) on the side where the circuit is to be formed. A mask on which an image of a desired pattern is drawn is brought into close contact with the formed photosensitive resin layer, and an electromagnetic wave having a wavelength sensitive to the photosensitive resin is irradiated. If a positive photosensitive resin is used with a predetermined developer, the photosensitive part is eluted, and if it is a negative photosensitive resin, the unexposed part is eluted to form an image of a desired circuit on the inorganic layer. In this state, after immersing the exposed metal in a solution such as ferric chloride aqueous solution or spraying the solution on the substrate to elute the exposed metal, the photosensitive resin is removed with a predetermined stripping solution. Peel off to make a circuit. Next, a mask on which an image of a desired pattern is drawn is brought into close contact with the circuit formed on the metal surface, and the insulating layer is patterned by a wet process. Next, the patterned insulating layer is treated with a dehydration catalyst.
[0051]
Electronic circuit components to which the laminate of the present invention can be applied include, for example, wiring boards such as flexible printed boards, semiconductor related components such as CSP (chip scale package), devices such as nozzles of toner jet printers, particularly for hard disk drives. Suspension.
[0052]
【Example】
Etchability test Thermoplastic polyimide A used for the copper-side adhesive insulating layer, thermoplastic polyimide B used for the SUS-side adhesive insulating layer, and low expansion polyimide used for the core insulating layer did. The etching liquid used for the etching test prepared Toray Engineering Co., Ltd. alkali-amine type polyimide etching liquid TPE-3000 (brand name).
[0053]
Each of these resins was coated on a 20 μm SUS304 foil having a thickness of 15 cm × 15 cm by bar coating to a thickness of 20 μm to 40 μm, and heat treatment was performed to prepare each polyimide film on SUS. . After cutting these coated materials into a length of about 1.5 cm and a width of about 2 cm and scratching the center with a cutter knife, the film thickness was measured with a stylus type film thickness meter deck tack, did. Then, the polyimide etching solution stirred to such an extent that the vortex can be generated with a magnetic stirrer adjusted to 80 ° C. is immersed in TPE-3000, and the film thickness at the same place where the initial film thickness is measured every time is determined. The etching rate was obtained by subtracting the film thickness after immersion from the initial film thickness as the amount of film reduction. The results are shown in Table 1 below.
[0054]
[Table 1]

[0055]
Using each of the above polyimides, SUS304 H-TA foil (trade name, manufactured by Nippon Steel Corporation, thickness 20 μm) -thermoplastic polyimide B (thickness 1.5 μm) -low expansion polyimide (thickness 14.5 μm)- A laminate having a layer structure composed of thermoplastic polyimide A (thickness 1.5 μm) -rolled copper foil C7025 (trade name, manufactured by Olin, thickness 18 μm) was produced and used in the following experiments.
[0056]
Dust generation evaluation The laminate was immersed in a ferric chloride solution with the SUS side masked, and the copper foil was etched. An alkali development type dry film resist having a thickness of 50 μm is applied to the surface of the exposed adhesive layer in this way by a thermal laminator at a speed of 6.5 m / min at a temperature of the roll surface of 105 ° C. and a line of 2 to 4 kg / cm. After laminating with pressure, it was left at room temperature for 15 minutes. Then, 100 mJ / cm < ² > exposure was carried out with the contact | attachment exposure machine using the predetermined mask. After standing at room temperature for 15 minutes, the dry film resist was developed with a 1% by weight aqueous solution of Na ₂ CO ₃ at 30 ° C. and a spray pressure of 2 kg for 40 seconds. Then, it was immersed in a polyimide etching solution TPE-3000 (trade name, manufactured by Toray Engineering Co., Ltd.) that was dried and stirred with a magnetic stirrer at 70 ° C. to remove the polyimide film cleanly in the shape of the mask. At that time, the dry film resist was peeled off with a 3 wt% NaOH aqueous solution at 50 ° C. and a spray pressure of 1 kg to produce an insulating layer. The insulating layer thus obtained was immersed in a processing solution stirred at room temperature for 3 minutes, washed with water at 60 ° C., and dried. The treatment solution used was prepared by previously mixing 500 g of acetic anhydride and 5 g of triethylamine. The amount of dust generation was measured for the samples before and after the treatment with the dehydration catalyst (sample A before treatment and sample B after treatment) according to the following procedure.
[0057]
Pre-filtered distilled water (hereinafter referred to as “blank”), a thoroughly washed beaker and tweezers were prepared.
[0058]
Insulating layers (4 patterns each) randomly selected from each sample obtained in the above process were placed in a beaker, a certain amount of blank was poured, placed in an ultrasonic irradiation apparatus, and irradiated with ultrasonic waves for 1 minute. (Extraction). After the ultrasonic irradiation, the beaker was taken out from the apparatus, and the sample was taken out with tweezers. 30 ml of the extracted liquid after taking out was set in a measuring device equipped with an automatic particle measuring device for liquid manufactured by HIAC / ROYCO, a suction semi-auto sampling device, and a laser diode light blocking sensor, and the amount of particles was measured. The result of the same measurement without a sample was taken as a blank value. The measuring device was washed for each measurement. The sample measurement result was obtained by subtracting the blank value from the measurement value. The measurement was performed 5 times per sample, and the average value was used as the final measurement result. The measured values of the sample A before treatment and the sample B after treatment with the dehydration catalyst obtained as described above are shown in Table 1 below. The amount of particles in each sample column shows the average of four patterns.
[0059]
[Table 2]

[0060]
According to Table 2, it can be seen that Sample B subjected to the treatment with the dehydration catalyst has less dust generation.
[0061]
【Effect of the invention】
According to the insulator of the present invention, since the insulating layer patterned by the wet process is treated with a dehydration catalyst, dust generation is suppressed even when the end surface of the insulating layer in contact with the etching solution is irradiated with ultrasonic waves. And the surface is modified. Therefore, when the insulator of the present invention is applied to an electronic circuit component, it generates less dust and increases the reliability of the electronic circuit component to which a wet process is applied. In particular, since the hard disk drive suspension has a large area of the insulating layer removed by etching and requires a fine pattern, the effect of applying wet etching is great. Since this improves the reliability of wet etching, it is suitable for an insulating layer of a hard disk drive suspension.

Claims (18)

Patterning by wet etching is applied to an insulator composed of an insulating unit layer of a single layer structure or a laminated structure of two or more layers, wherein at least one layer is a low expansion polyimide resin having a linear thermal expansion coefficient of 30 (ppm / ° C.) or less. A method of manufacturing an insulator, characterized in that the etching end face is strengthened by performing the treatment with a dehydration catalyst. The method for manufacturing an insulator according to claim 1, wherein the dehydration catalyst is an acid anhydride or an acid anhydride diluted with a solvent. The method for manufacturing an insulator according to claim 1, wherein the dehydration catalyst is carbodiimide or carbodiimide diluted with a solvent. The dehydration catalyst is selected from acetic anhydride, tetrafluoroacetic anhydride, dicyclohexylcarbodiimide, carbodiimide resin, 1,5-diazabicyclo [4.3.0] non-5-ene, concentrated sulfuric acid, phosphoryl chloride, phosphorus trichloride. The method for producing an insulator according to claim 1, wherein the compound is obtained by diluting the compound with a solvent. The method for producing an insulator according to claim 2, 3 or 4, wherein the dehydration catalyst is further a tertiary amine, pyridine, or both a tertiary amine and pyridine added as a reaction accelerator. The method for producing an insulator according to claim 5, wherein the tertiary amine is triethylamine. The method for manufacturing an insulator according to claim 1, wherein all layers of the insulating unit layer include a polyimide resin. The method for manufacturing an insulator according to any one of claims 1 to 6, wherein all of the insulating unit layers include a polyimide resin, and at least one of the unit layers further includes an inorganic material. The insulating unit layer, adhesive polyimide - coefficient of linear thermal expansion 30 (ppm / ℃) less low expansion polyimide - insulator according to any one of the adhesive according to claim 1 to 6 is a layer structure comprising a polyimide Manufacturing method . The method of manufacturing an insulator according to any one of claims 1 to 9, wherein the wet etching is performed with an etching solution having a pH of greater than 7.0. A part of the first inorganic layer, the second inorganic layer, and the inorganic layer in the layered structure of the first inorganic layer-insulating layer-second inorganic layer or the inorganic layer-insulating layer is removed and exposed. A method for manufacturing a laminate, comprising performing patterning by wet etching and treatment with a dehydration catalyst according to any one of claims 1 to 10 on the insulating layer. The method for producing a laminate according to claim 11, wherein all of the first inorganic layer, the second inorganic layer, and the inorganic layer are copper or a material obtained by subjecting copper to a surface treatment . The method for producing a laminate according to claim 11, wherein all of the first inorganic layer, the second inorganic layer, and the inorganic layer are alloy copper or a material obtained by subjecting the alloy copper to a surface treatment . The method for producing a laminate according to claim 11, wherein all of the first inorganic layer, the second inorganic layer, and the inorganic layer are stainless steel or a material obtained by subjecting stainless steel to surface treatment . 12. One of the first inorganic layer, the second inorganic layer, and the inorganic layer is stainless steel or a material obtained by subjecting stainless steel to a surface treatment, and the other layer is copper or a material obtained by subjecting copper to a surface treatment. The manufacturing method of the laminated body of description . One of the first inorganic layer, the second inorganic layer, and the inorganic layer is stainless steel or a material obtained by subjecting stainless steel to surface treatment, and the other layer is alloy copper or a material obtained by subjecting alloy copper to a surface treatment. The manufacturing method of the laminated body of 11 . The manufacturing method of the electronic circuit component by which the manufacturing method of the laminated body of any one of Claims 11 thru | or 16 is applied . A method for manufacturing a suspension for a hard disk drive, to which the method for manufacturing a laminate according to any one of claims 11 to 16 is applied .