JP3588428B2 - Laminate base material and prepreg and electric circuit laminate using the same - Google Patents

Description

【００２１】
【化２】

【００２２】
上記芳香族ポリアミド繊維の基本的な製造方法や繊維特性については、例えば、英国特許第１５０１９４８号公報、米国特許第３７３３９６４号公報、第３７６７７５６号公報、第３８６９４２９号公報、日本国特許の特開昭４９−１００３２２号公報、特開昭４７−１０８６３号公報、特開昭５８−１４４１５２号公報、特開平４−６５５１３号公報などに記載されており、特に耐熱性の優れたものとしてパラ型芳香族ポリアミド繊維があげられるが、これは前記Ａｒ₁、Ａｒ₂の５０モル％以上がパラ配位の芳香族基である繊維であり、具体的には、ポリパラフェニレンテレフタルアミド短繊維（デュポン（株）製「ケブラー」）や、コポリパラフェニレン・３，４’−オキシジフェニレン・テレフタルアミド短繊維（帝人（株）製「テクノーラ」）等が例示される。
【００２３】
特に後者は、不純イオンの含有量が少ないので電気絶縁性に優れ、より好ましい。また、繊維表面上に固体状のカチオン変換性で且つ非イオン吸着性の無機化合物が固着されているコポリパラフェニレン・３，４’−オキシジフェニレン・テレフタルアミド繊維は、配合ワニスの含浸性も良く、また、該無機化合物を介して配合ワニスとの接着性も向上するため、電気絶縁材料や電気回路用積層板等の製造工程における変形量が少なくなる効果や、高湿下における電気絶縁性、熱寸法安定性などを向上させる効果も有しているのでより好ましい。
【００２４】
ここでカチオン変換性で且つ非イオン吸着性の無機化合物とは、カチオンとの変換能を有し、さらに非イオンの吸着能をも有する化合物であり、具体例としてはシリカ・アルミナ、シリカ・マグネシア、カオリン、酸性白土、活性白土、タルク、ベントナイト、オスモス等があげられる。
【００２５】
これらの無機化合物は、特に固体粒子として繊維表面に固着されていると接着効果が更に向上するので好ましい。粒子の大きさとしては、０．０１〜５．００μｍ程度のものが用いられる。また、繊維表面に該無機化合物を固着させるには、例えば、繊維表面が軟化した状態で該無機化合物粒子を繊維表面に押し付けて繊維の極表層部に食い込ませたものでよい。
【００２６】
なお、本発明の積層板用基材が、電気絶縁材料や電気回路用積層板等に適用される場合には、繊維内部に含有される抽出ナトリウムイオンや抽出カリウムイオン、抽出塩素イオンなどの不純イオンが絶縁不良を誘発して問題となるため、その製造工程中やその後の後工程等で、該不純イオンの含有量が下記（１）〜（３）を、好ましくは下記（４）〜（６）を満足するように充分洗浄処理する必要がある。
（１）抽出ナトリウムイオンの量≦４０ｍｇ／リットル
（２）抽出カリウムイオンの量≦３．０ｍｇ／リットル
（３）抽出塩素イオンの量≦７．５ｍｇ／リットル
（４）抽出ナトリウムイオンの量≦３５ｍｇ／リットル
（５）抽出カリウムイオンの量≦２．５ｍｇ／リットル
（６）抽出塩素イオンの量≦６．５ｍｇ／リットル
該不純イオンの含有量が上記（１）〜（３）を超えると絶縁不良を誘発し易くなって電気絶縁材料分野では使用出来なくなる。
【００２７】
また、本発明において使用する芳香族ポリアミド短繊維の１部は、破断時の伸度が、５．３％以上（高伸度）、且つ、破断時の強度が１５．４４ｃＮ／ｄｔｅｘ（１７．５ｇ／ｄｅ）以下（低強度）であり、且つ、比重が１．３８０以下（低比重）のパラ型芳香族ポリアミド繊維からなる短繊維（市販されていない）である必要がある。このような高伸度で低強度、低比重のパラ型芳香族ポリアミド繊維からなる短繊維とは、例えば、前記のコポリパラフェニレン・３，４’−オキシジフェニレン・テレフタルアミド繊維の製造工程において、結晶化が促進されないように未延伸のままで使用したり、延伸倍率を低く押さえたものや、熱履歴を少なくしたりするなどの製造条件により得ることが出来る。
【００２８】
このような未延伸、若しくは、低倍率延伸の芳香族ポリアミド繊維は、低温で軟化、変形、溶融（半溶融も含む）、切断し易いなどの特性を有するために、これを少量混合して抄造したものは、カレンダー加工等による加熱加圧加工時に該未延伸、若しくは、低倍率延伸の芳香族ポリアミド繊維が軟化、変形、部分溶融、部分切断して紙を形成している他の短繊維（他の芳香族ポリアミド短繊維やフェノール樹脂短繊維など）との交絡性や密着性、接着性、接着面積などを高めて短繊維相互間の固定度や固着度を向上せしめ、得られる混抄紙の引張り強度や層間剥離強度、熱寸法安定性を高める効果が発現されるので、この混抄紙を用いて作成された電気回路用積層板は、その製造工程における変形量や熱寸法変化量も減少し、得られる積層板も熱寸法安定性に優れたものとなる。
【００２９】
本発明で使用するメタ型芳香族ポリアミドからなる短繊維とは、前述の芳香族ポリアミドのうち、延鎖結合の５０モル％以上が非共軸で非平行の芳香族ポリアミド、例えば、ジカルボン酸として、テレフタル酸、イソフタル酸等の一種又は二種以上と、ジアミンとしてメタフェニレンジアミン、４，４−ジアミノフェニルエーテル、４，４’−ジアミノジフェニルメタン、キシリレンジアミン等の一種又は二種以上を使用したホモポリマー又は共重合ポリマーからなる短繊維をあげることができ、その代表的な例としては、ポリメタフェニレンイソフタルアミド、ポリメタキシレンテレフタルアミド、あるいはイソフタル酸クロライド、テレフタル酸クロライド、メタフェニレンジアミン等を共重合せしめた共重合ポリマーからなる繊維等がある。
【００３０】
一般に、メタ型芳香族ポリアミド繊維は、パラ型芳香族ポリアミド繊維に比べて、平衡水分率（含水率）が高く、且つ、不純イオン含有量も多いために、電気絶縁性、特に高湿度下における電気絶縁性を低下せしめ、長期に渡って高信頼性が要求される電気材料用基材や電気回路用積層板の基材に使用する場合には、充分な洗浄処理を行って不純イオン含有量を低下させたり、上記のパラ型芳香族ポリアミド繊維よりもさらに過酷な熱履歴を付与するなどの工夫が必要である。
【００３１】
なお、この場合においても前述の如く、該芳香族ポリアミド繊維表面に固体状のカチオン変換性及び非イオン吸着性の無機化合物が固着されている方が配合ワニスの含浸性も良く、また、当該無機化合物を介して配合ワニスとの接着性も向上するため、電気絶縁材料や電気回路用積層板等の製造工程における変形量減少や高湿下における電気絶縁性、熱寸法安定性向上などの観点からより好ましい。
なお、本発明に使用される芳香族ポリアミド繊維は、単繊維繊度が０．３３〜１１．１１ｄｔｅｘ（０．３〜１０．０ｄｅ）、繊維長が０．５〜６０ｍｍの範囲にあるものが好ましい。
【００３２】
次に、本発明の積層板基材に使用するフェノール樹脂繊維からなる短繊維には、吸湿性が比較的少ないノボラック型フェノール樹脂繊維が好適であるが、これに限定されるものではない。しかし、未硬化若しくは半硬化のフェノール樹脂繊維を使用したものは、耐熱性がなく、１１０〜２５０℃の温度範囲での平均熱膨張係数が測定できないばかりでなく、混抄後に行う加熱加圧加工処理により該フェノール樹脂繊維が切断されたり、不均一な太さに変形し、又は、塊状になるために紙全体中での熱膨張率の均一化や調節機能の発現が不十分となり好ましくない。
【００３３】
そこで特に、本発明では、該フェノール樹脂繊維は予め熱硬化処理されたものを使用することが重要である。すなわち、全フェノール樹脂繊維の少なくとも９０重量％が予め熱硬化処理をされたものを使用する必要があり、混合抄造に先立って硬化剤（ヘキサメチレンテトラミン、レゾール型フェノール樹脂等）を使用して熱硬化処理を施したものか、又は、該フェノール樹脂繊維の製造工程で既に熱硬化処理されたものを短繊維にカットして使用する。従って、前記芳香族ポリアミド短繊維とフェノール樹脂短繊維とを混合抄造した後はフェノール樹脂繊維用の硬化剤等は不要である。このように熱硬化処理されたフェノール樹脂繊維を使用することにより、フェノール樹脂繊維をバインダーとして機能させることは出来なくなるが、得られる耐熱性繊維紙の熱寸法安定性や熱膨張率を調節することが可能となる。なお、該フェノール樹脂短繊維は、単繊維繊度が０．５６〜１１．１１ｄｔｅｘ（０．５〜１０．０ｄｅ）、繊維長が０．５〜１０ｍｍの範囲にあるものが好ましく使用される。
【００３４】
かかる芳香族ポリアミド短繊維とフェノール樹脂短繊維とを使用する際の両者の使用比率としては、全短繊維に対して芳香族ポリアミド短繊維：９５〜６０重量％、フェノール樹脂短繊維：５〜４０重量％の範囲で使用するものが好ましい。該芳香族ポリアミド短繊維の使用比率が、９５重量％を超える場合には、フェノール樹脂短繊維の使用効果が充分に発揮されず、得られる積層板用基材の特性、特に、熱膨張係数を調節することが困難になるので好ましくない。また、該フェノール樹脂短繊維の使用比率が、４０重量％を超える場合には、芳香族ポリアミド短繊維を使用することにより得られる優れた特性が損なわれるようになり、特に、耐熱性が低下し、平衡水分率が高くなり電気絶縁性や高湿度下における電気絶縁特性の信頼性が損なわれるので好ましくない。
【００３５】
また、本発明では該芳香族ポリアミド短繊維の１１０〜２５０℃の温度範囲における長さ方向の平均熱膨張係数が、−１．０×１０^-6／℃以下であり、且つ、フェノール樹脂繊維からなる短繊維の前記と同一温度範囲における長さ方向の平均熱膨張係数が、＋１．０×１０^-6／℃以上であるものを使用することにより得られる耐熱性繊維紙の熱膨張係数を用途に対応して制御することが可能となる。すなわち、このような芳香族ポリアミド短繊維とフェノール樹脂短繊維とを組合わせて用いることにより、得られる耐熱性繊維紙の面方向の前記と同一温度範囲における平均熱膨張係数が＋１０×１０^-6／℃〜−１０×１０^-6／℃の範囲になるように調節することが出来、このような耐熱性繊維紙を使用して用途やその使用温度に応じて最適な熱寸法変化をする積層板用基材を得ることが出来る。
【００３６】
一般に、芳香族ポリアミドからなる短繊維の長さ方向の熱膨張係数は、通常はマイナス（収縮方向）であり、その値は製造条件や組成（ホモタイプ、コポリマータイプなど）等により異なるが、市販されているものでは、１１０〜２５０℃の温度範囲における平均熱膨張係数は、−１．５〜−１５×１０^-6／℃である。
【００３７】
一方、熱硬化処理されたフェノール樹脂繊維の長さ方向の熱膨張係数は、逆に、プラス（伸張方向）であり、その値は、製造条件や硬化度、組成により異なるが、同じく１１０〜２５０℃の温度範囲における平均熱膨張係数は、＋４．５〜＋３０×１０^-6／℃であるために、両繊維の混合比率を上手くコントロールすることにより積層板用基材の面方向の平均熱膨張係数を前記の範囲に調節することが可能となり、さらに、該積層板用基材の面方向の平均熱膨張係数を限りなく０に近づけることも出来る。
【００３８】
このように芳香族ポリアミドからなる短繊維に対してフェノール樹脂からなる短繊維は、該芳香族ポリアミド繊維とは逆方向に約２〜２０倍の熱膨張係数（長さ方向）を有しているので、フェノール樹脂繊維の芳香族ポリアミド繊維に対する混合比率は、１／２〜１／２０の範囲内で調節するのが好適である。該フェノール樹脂繊維の混合比率を高くすると、混抄紙の耐熱性が低下し、平衡公水分率も高くなるために前記のように該フェノール樹脂繊維の混合比率は、５〜４０重量％の範囲内で使用するものが好ましい。
【００３９】
さらに、このような予め熱硬化処理を施されたフェノール樹脂短繊維を混抄した耐熱性繊維紙（基材）は、カレンダー加工工程等で加熱加圧処理された後に、再度、高温度雰囲気下で加熱処理を行った場合でも、驚くべきことに、厚さ方向における基材の寸法変化量（厚さ変化量）が、従来の芳香族ポリアミド紙と比較して小さくなる。すなわち、温度：３３５℃、５分間の熱処理後の該耐熱性繊維紙の厚さ方向の寸法変化率は７％以下、実質的には０．５〜５％の範囲にあり、市販の芳香族ポリアミド紙（８〜３５％）と比較して著しく低い値を示すものである。
【００４０】
この理由は、該フェノール樹脂繊維が、塊状となるなどの不均一部分を形成することなく均一分布を形成し、耐熱性繊維紙を構成する短繊維が加熱加圧下で圧縮変形、熱セットされるので均一分布の状態がそのまま固定化され、継続維持されるためと推測される。このように厚さ方向における寸法変化が少ないことは、電気回路積層板用基材に用いた場合に好適である。一般に、電気回路用積層板は、製造工程で２５０℃以上、ハンダ耐熱性モデルテストでは３００℃以上の高温付与がなされるばかりでなく、部品実装後の製品でも、使用条件によっては常温から１００℃以上の高温度までの昇降温を繰返す状況で使用される。そのため、それらの昇降温過程における該電気回路用積層板の厚さ方向の寸法変化量が小さい程、該積層板層間のスルーホールやビアを経由する電気回路接続の信頼性を高
めることができる。
【００４１】
次に、本発明で用いる有機系樹脂バインダー及び／又は耐熱性の有機高分子重合体からなるフィブリッドのうち、有機系樹脂バインダーとしては、熱硬化性の有機系樹脂、例えば、エポキシ樹脂、フェノール樹脂、ポリウレタン樹脂、メラミン樹脂などであるが、中でも分子内にエポキシ官能基を有する水分散可能なエポキシ系の樹脂が、プリプレグ作成工程で含浸させる配合ワニスとの相溶性も良く好適である。
【００４２】
また、本発明で使用する有機高分子重合体からなるフィブリッドは、その平衡水分率が７．５％以下であることが好ましく、湿式抄造工程において、バインダー性能を呈する微小フィブリルを有する薄葉状、鱗片状の小片、又は、ランダムにフィブリル化した微小短繊維の総称であり、例えば、特公昭３５−１１８５１号公報、特公昭３７−５７３２号公報等に記載の如く、有機高分子重合体溶液を該高分子重合体溶液の沈澱剤及び剪断力が存在する系において混合することにより製造されるフィブリッドや、特公昭５９−６０３号公報に記載の如く、光学的異方性を示す高分子重合体溶液から成形した分子配向性を有する成形物に叩解等の機械的剪断力を与えてランダムにフィブリル化させたフィブリッドが例示され、なかでも前者の方法によるものが最適である。
【００４３】
また、このようなフィブリッドを形成する有機高分子重合体としては、繊維、若しくは、フィルム形成能を有する耐熱性高分子重合体であって熱分解開始温度が、２６０℃以上、好ましくは、３１０℃以上のものであればどれでも使用できる。
【００４４】
例えば、芳香族ポリアミド、溶融液晶性全芳香族ポリエステル、ヘテロ環含有芳香族ポリマー等を用いることが出来るが、それらの中でも、特に、不純イオン含有量の少ないコポリパラフェニレン・３，４’−オキシジフェニレン・テレフタルアミド（帝人（株）製「テクノーラ」）や、平衡水分率の小さいｐ−ヒドロキシ安息香酸と２，６−ヒドロキシナフトエ酸の共重合体からなる溶融液晶性全芳香族ポリエステル（（株）クラレ製「ベクトラン」）が好ましく使用され、また、耐熱性が要求される場合には、前述のポリパラフェニレンベンズビスオキサゾール（東洋紡績（株）製「ＰＢＯ」）を使用するものが好ましい。
【００４５】
このような有機系樹脂バインダー及び／又は耐熱性の有機高分子重合体からなるフィブリッドの耐熱性繊維紙中に占める比率は、３〜４０重量％の範囲であり、好ましくは４〜３０重量％、さらに好ましくは、５〜２５重量％の範囲にあるものである。このような有機系樹脂バインダー及び／又は耐熱性の有機高分子重合体からなるフィブリッドの耐熱性繊維紙中に占める比率が、３重量％未満の場合には、短繊維の同士の結着が充分でなく、得られる耐熱性繊維紙の嵩密度が、０．４６ｇ／ｃｍ³未満となり、逆に該比率が、４０重量％を超える場合には、嵩密度が０．９０ｇ／ｃｍ³を超えるものとなり後で述べる理由により好ましくない。
【００４６】
また、本発明に使用する耐熱性繊維紙は、従来から公知の方法で製造することが出来、例えば、未延伸若しくは低倍率延伸のパラ型芳香族ポリアミド繊維を含むパラ型芳香族ポリアミド短繊維やメタ型芳香族ポリアミド短繊維及びフェノール樹脂短繊維を所定の混合比率になるように秤量し、繊維濃度が０．１５〜０．４０重量％の範囲になるようにして水中に投入して均一分散させ、調整した水性スラリー中に、必要に応じて、前記のバインダー成分であるフィブリッド及び／又は有機系樹脂バインダーを加え、さらに必要ならば、分散剤や粘度調整剤を加えた後に、長網式や傾斜短網、丸網式等の抄紙機による湿式抄造法で湿紙を形成し、さらに必要に応じて該湿紙に再度該有機系樹脂バインダーをスプレー方式、含浸方式等により所定の固形分比率になるように付与した後に乾燥して乾燥紙として得られる。また、該乾燥紙は、再度加熱加圧加工して、所定の坪量、嵩密度、引張り強力等を有する耐熱性繊維紙として得ることが必要である。
【００４７】
該加熱加圧加工は、例えば、カレンダー機を用いて加熱加圧するものが例示される。カレンダー機を用いて加熱加圧する場合には、直径約１５〜８０ｃｍからなる１ケの硬質表面ロールと、直径約３０〜１００ｃｍからなる１ケの表面変形可能な弾性ロールとの間で、又は、直径約２０〜８０ｃｍからなる２ケの硬質表面ロール同士の間で行えばよく、その際の加熱加圧の温度は２２０〜３５０℃とし、線圧力は１４７０〜３９２０Ｎ／ｃｍ（１５０〜４００ｋｇ／ｃｍ）の範囲で行うことが必要である。
【００４８】
このような加熱加圧加工により得られる耐熱性繊維紙は、その嵩密度が０．４６〜０．９０ｇ／ｃｍ³、好ましくは、０．５０〜０．８０ｇ／ｃｍ³の範囲内にあるものがよく、従って前記の加熱加圧加工の条件は、このような紙密度が得られるように前記の範囲内で行えばよい。
【００４９】
該嵩密度が０．４６ｇ／ｃｍ³未満の場合は、紙の中層部における短繊維相互間の接着力が低下して配合ワニスの紙内部への含浸量が多くなりすぎ、プリプレグ製造工程や電気回路用積層板の製造工程、特に、積層プレス工程で含浸ワニスの流れに起因する単繊維の部分的な移動が生じ、得られる電気回路板用積層物内部で繊維の密度ムラが発生して、耐熱寸法安定性や耐変形性の低下を招くことがある。一方、該嵩密度が０．９０ｇ／ｃｍ³を超える場合は、配合ワニスの紙内部への含浸が少なくなり、得られる電気回路板用積層物の電気絶縁性、耐熱寸法安定性、耐変形性が低下することがあるのでこれも好ましくない。
【００５０】
【発明の作用】
このような耐熱性繊維紙からなる積層板用基材は、高温時にマイナス（長さ方向で収縮）の熱膨張係数を有する芳香族ポリアミド短繊維とプラス（長さ方向で伸張）の熱膨張係数を有するフェノール樹脂短繊維とを組合わせて構成されているので積層板用基材全体の熱膨張率を設定した範囲とすることができ、従来の耐熱性繊維紙とは異なり優れた熱寸法安定性を有するものである。
【００５１】
さらに、該フェノール樹脂短繊維として、混合抄造する前に予め熱硬化処理されたものを使用するために、耐熱性繊維紙を製造する際にはより高い温度での処理が可能であり、従って得られる耐熱性繊維紙に優れた耐熱性を付与することができ、また、加熱加圧加工時の収縮による皺の発生もなく、短繊維の分布密度の斑もなく均一な耐熱性繊維紙が得られるために優れた積層板用基材を提供できるものである。
【００５２】
特に、本発明の積層板用基材は、製造工程において加熱加圧加工処理された後は、再度、高温度雰囲気下での加熱処理を行っても、厚さ方向における基材の寸法変化量（厚さ変化量）が、従来の芳香族ポリアミド紙と比較して小さくなり電気回路用積層板の基材として優れたものである。このような積層板用基材を用い、プリプレグとし、さらに該プリプレグを積層して加熱加圧成形して得られる積層板の厚さ方向の平均熱膨張係数（温度範囲：５０〜２５０℃）は、２６０×１０^-6／℃以下とすることが出来、熱変化に対して厚さ方向の寸法変化の極めて少ない優れた電気回路用積層板が得られる。
【００５３】
また、一般にフェノール樹脂繊維は、パラ型芳香族ポリアミドからなる繊維に比べて平衡水分率が高く、電気絶縁材料や電気回路用積層板の用途に使用するには制限があるが、本発明の構成とすることにより、平衡水分率も許容される範囲にあるため優れた積層板用基材を得ることが出来る。
【００５４】
【実施例】
以下、実施例により本発明をさらに詳細に説明する。なお、実施例で用いた物性の測定値は下記の測定法及び積層物（電気回路用積層板）の製造方法は以下の通りである。
【００５５】
（１）嵩密度
ＪＩＳ Ｃ−２１１１の６．１に準拠する方法で測定した。
【００５６】
（２）引張強力と伸度
Ａ；繊維の引張強力と伸度
定速伸長型引張試験機を用い、ＪＩＳ Ｌ−１０１３の７に準じて測定した。
Ｂ；紙の引張強力と伸度
定速伸長型引張試験機を用い、ＪＩＳ Ｃ−２１１１の７に準じて測定した。
【００５７】
（３）比重
密度勾配管法（Ｎ―ヘプタン／四塩化炭素、２５℃）により求めた。
【００５８】
（４）平衡水分率
ＪＩＳ Ｌ―１０１３に準拠し、以下の方法で測定した。
Ａ；繊維の平衡水分率
使用する繊維を温度１０５℃の雰囲気中で２４時間乾燥（絶乾）した後、温度：２０℃、且つ、相対湿度：６５％ＲＨにおいて７２時間調整し、該繊維中に含まれる水分率を求めて、該繊維中の絶乾状態での重量に対する割合を算出し、これを百分率（％）にて表した。但し、２種類以上の繊維を混合して用いる場合には、各繊維の平衡水分率を独立に測定し、混合比に従って重量平均にて表すものとする。
Ｂ；繊維紙（混抄紙）の平衡水分率
抄造し、加熱加圧加工後の耐熱性混抄紙を温度：１０５℃の雰囲気中で２４時間絶乾した後、温度：２０℃、且つ、相対湿度：６５％ＲＨにおいて７２時間調整し、該耐熱性混抄紙中に含まれる水分率を求め、該耐熱性混抄紙の絶乾状態での重量に対する割合を算出し、これを百分率（％）にて表した。
【００５９】
（５）繊維と混抄紙の平均熱膨張係数
（繊維の長さ方向と混抄紙の面方向の平均熱膨張係数）
Ａ；繊維の平均熱膨張係数（繊維の長さ方向の平均熱膨張係数）
熱分析装置（ＴＭＡ；理学電機（株）製サーモフレックス型）を用い、チャック間初期サンプル長：２００ｍｍ、昇降温速度：２０℃／分で、常温から２８０℃まで昇温（１回目）後、該サンプルを取り付け治具とともに五酸化リン（Ｐ₂０₅）入りのデシケーター中で冷却した後に、再度、常温から２８０℃まで昇温（２回目）した場合の２回目の１１０〜２５０℃範囲内における寸法変化量から熱膨張係数を算出し、ｎ＝５以上の測定値により平均熱膨張係数を求め表した。なお、測定に用いるサンプルは予め、１０５℃で約２４時間乾燥後、五酸化リン（Ｐ₂Ｏ₅）中で４８時間冷却調整したものを用いた。
Ｂ；混抄紙の平均熱膨張係数（混抄紙の面方向の平均熱膨張係数）
測定用サンプルとして、５ｍｍ幅の試料を用いた以外は上記繊維の場合と同様に行って、平均熱膨張係数を求めた。
【００６０】
（６）繊維紙（混抄紙）の厚さ変化率
加熱加圧加工後の耐熱性混抄紙を温度：２０℃、且つ、相対湿度：６５％ＲＨにおいて４８時間調整した後に、該耐熱性混抄紙の５ヶ所（印をつける）について厚さを測定し、その平均厚さ（Ａ）を求め、次に、該耐熱性混抄紙を温度：３３５℃の高温雰囲気中にて５分間熱処理した後、該熱処理後の耐熱性混抄紙を温度：２０℃、且つ、相対湿度：６５％ＲＨにおいて４８時間冷却調整後、前記と同一場所（印をつけた５ヶ所）について厚さを測定してその平均厚さ（Ｂ）を求め、熱処理の前後における平均厚さの変化量（Ｃ＝Ｂ−Ａ）を算出し、熱処理前の該耐熱性混抄紙の平均厚さ（Ａ）に対する割合（Ｃ÷Ａ）を計算して、これを百分率（％）にて表した。
【００６１】
（７）電気回路用積層板の作成方法
高純度のブロム化ビスフェノールＡ型エポキシ樹脂及びオルソクレゾールノボラック型エポキシ樹脂に硬化剤としてジシアンジアミド、硬化促進剤として２−エチル−４メチルイミダゾールを配合してなるエポキシ樹脂組成物をメチルエチルケトンとメチルセルソルブの混合溶液に溶解して得た配合ワニスを芳香族ポリアミド繊維紙に含浸させた後、１１０〜１２０℃の温度で５〜１０分間乾燥して、樹脂分の体積含有率が５５％であるＢステージのプリプレグ紙を作成した。該プリプレグ紙を１５枚積層した後、ホットプレスにより、減圧下で温度：１７０℃、圧力：３９２Ｎ／ｃｍ（４０ｋｇ／ｃｍ）の条件で５０分間、加熱加圧処理して樹脂を硬化せしめ、電気回路用積層板を得て、さらに温度：２００℃の熱風乾燥機内で約２０分間後硬化処理を行って目的とする電気回路用積層物を作成する。
【００６２】
（８）電気回路用積層板の面方向と厚さ方向の平均熱膨張係数
Ａ；積層板の面方向の平均熱膨張係数
熱分析装置（セイコー電子工業（株）製「ＴＭＡ（１２０）ＳＳＣ／５２００」）を用い、厚さが約１．５ｍｍの電気回路用積層板を５ｍｍ×７ｍｍ角に裁断し、その面方向（＝７ｍｍ長さの方向）について熱膨張係数を測定した。その測定方法は、常温〜２００℃まで昇温速度：１０℃／分で昇温した後、続いて常温まで冷却し、さらに引き続いて同条件で２５０℃まで昇温し、２回目の昇温過程における５０℃〜２５０℃範囲内における面方向の長さの変化から熱膨張係数を算出し、ｎ＝５以上の測定値により平均熱膨張係数（面方向）を求め表した。
Ｂ；積層板の厚さ方向の平均熱膨張係数
熱分析装置（セイコー電子工業（株）製「ＴＭＡ（１２０）ＳＳＣ／５２００」）を用い、厚さが約１．５ｍｍの電気回路用積層板を５ｍｍ×５ｍｍ角に裁断し、その厚さ方向（約１．５ｍｍの厚さの方向）について熱膨張係数を測定した。その測定方法は、常温〜２００℃まで昇温速度：１０℃／分で昇温した後、続いて常温まで冷却し、さらに引き続いて同条件で２５０℃まで昇温し、２回目の昇温過程における５０℃〜２５０℃範囲内における厚さの変化から熱膨張係数（厚さ方向）を算出し、ｎ＝５以上の測定値により平均熱膨張係数を求め表した。
【００６３】
［実施例１］
芳香族ポリアミドからなる低伸度、高強度、高比重の短繊維として、コポリパラフェニレン・３，４’―オキシジフェニレン・テレフタルアミドからなり、その繊維表面にタルクが０．５重量％、オスモスが０．１重量％固着した破断時の伸度が４．６％で破断時の強度が２５．９３ｃＮ／ｄｔｅｘ（２９．４ｇ／ｄｅ）、比重が１．３９８である単繊維繊度：１．６７ｄｔｅｘ（１．５ｄｅ）、繊維長：３ｍｍ、長さ方向の平均熱膨張係数が−９．２×１０^-6／℃、平衡水分率：１．８％の短繊維（帝人（株）製「テクノーラ」）：７３重量％及び芳香族ポリアミドからなる高伸度で低強度、低比重の短繊維として、コポリパラフェニレン・３，４’―オキシジフェニレン・テレフタルアミドからなり、その繊維表面にタルクが０．６重量％、オスモスが０．２重量％固着した破断時の伸度が１３．３％で破断時の強度が３．７０ｃＮ／ｄｔｅｘ（４．２ｇ／ｄｅ）、比重が１．３４９であり、且つ、単繊維繊度：２．２２ｄｔｅｘ（２．０ｄｅ）、繊維長：５ｍｍ、長さ方向の平均熱膨張係数が−４．６×１０^-6／℃、平衡水分率：３．９％の短繊維（帝人（株）製）：７重量％と、実質的に硬化しているノボラック型フェノール樹脂繊維からなり、破破断時の伸度が５．６％で破断時の強度が１．２４ｃＮ／ｄｔｅｘ（１．４ｇ／ｄｅ）、比重が１．２８７である単繊維繊度：２．２２ｄｔｅｘ（２．０で）、繊維長：5ｍｍ、長さ方向の平均熱膨張係数が＋２４．５×１０^-6／℃、平衡水分率：４．６％の短繊維（日本カイノール(株)製「カイノール」）：５重量％、バインダー成分として平衡水分率が４．４％のコポリパラフェニレン・３，４’―オキシジフェニレン・テレフタルアミドからなるフィブリッド（帝人（株）製）：５重量％とを加えて、パルパーにより水中に離解分散させ、これに０．０２％濃度になるように分散剤（松本油脂（株）製「ＹＭ−８０」）を添加して、繊維濃度が０．１５重量％である抄紙用スラリー液を作成した。
【００６４】
次に、タッピー式角型手抄機を用い、該抄紙用スラリー液を使用して抄紙し、軽く加圧脱水後に、さらにバインダー成分として、固形分濃度：１０重量％のビスフェノールＡエピクロルヒドリン型水分散性エポキシ樹脂バインダー（大日本インキ化学工業（株）製）を、該樹脂分が１０重量％となるようにスプレー方式で付与して混抄紙を得た。該混抄紙を温度：１３０℃のロール状乾燥機で約１分間乾燥後、さらに温度：１５０℃の熱風乾燥機中で約１０分間乾燥して、乾燥混抄紙を得た。この乾燥混抄紙を直径約４００ｍｍの一対の硬質表面金属ロールからなるカレンダー機を用いて、温度：２００℃、線圧：１９６０Ｎ／ｃｍ（２００ｋｇ／ｃｍ）の条件で加熱、加圧した後、直径約５００ｍｍの一対の硬質表面金属ロールからなる高温ハイカレンダー機を用いて、温度：３１０℃、線圧：１９６０Ｎ／ｃｍ（２００ｋｇ／ｃｍ）の条件で加熱、加圧加工して、前記の高伸度で低強度、低比重のコポリパラフェニレン・３，４’―オキシジフェニレン・テレフタルアミドからなる短繊維（帝人（株）製「テクノーラ」）及び／又はコポリパラフェニレン・３，４’―オキシジフェニレン・テレフタルアミドからなるフィブリッドを軟化、部分溶融させてバインダーとしての性能を発揮させて混抄紙を構成する単繊維同士を固着し、同時に付着している前記ビスフェノールＡエピクロルヒドリン型樹脂バインダー（大日本インキ化学工業（株）製）も半硬化及び／又は完全硬化させて、坪量：７２ｇ／ｍ^２の目的とする混抄紙を得た。なお、該混抄紙の主な製造条件は表１に示した。また、この混抄紙について前記の測定方法により測定した特性値は表２に示す通りであった。
【００６５】
次に、このようにして得られた混抄紙を用いて、前記の電気回路用積層板の作成方法により積層板を作成し、該積層板の面方向と厚さ方法の平均熱膨張係数を前記の測定方法により測定した。その結果は表２に示す通りであった。
【００６６】
［比較例１］
実施例１において、芳香族ポリアミドからなる低伸度、高強度、高比重である短繊維の混合比率を７３重量％から７６重量％に変更し、さらに、ノボラック型フェノール樹脂繊維からなる短繊維の混合比率を５重量％から２重量％に変更した以外は、実施例１と同様に行って混抄紙を得た。この混抄紙の他の主な製造条件を表１に、また、実施例１と同様にして得られた電気回路用積層板の特性を表２に併せて示す。
【００６７】
［実施例２〜５、比較例２］
実施例１において、芳香族ポリアミドからなる低伸度、高強度、高比重である短繊維の混合比率を７３重量％から実施例２では６９重量％に、実施例３では６２重量％に、実施例４では５７重量％に、実施例５では４８重量％に、比較例２では４０重量％になるように、それぞれ変更し、さらに、ノボラック型フェノール樹脂繊維からなる短繊維の混合比率を５重量％から実施例２では９重量％に、実施例３では１６重量％に、実施例４では２１重量％に、実施例５では３０重量％に、比較例２では３８重量％になるように、それぞれ変更した以外は、実施例１と同様に行って混抄紙を得た。この混抄紙の他の主な製造条件を表１に、また、実施例１と同様にして得られた電気回路用積層板の特性を表２に併せて示す。
【００６８】
［実施例６〜９、比較例３〜５］
実施例３において、芳香族ポリアミドからなる高伸度、低強度、低比重の短繊維の混合量を７重量％に固定し、芳香族ポリアミドからなる低伸度、高強度、高比重である短繊維の混合比率、ノボラック型フェノール樹脂繊維からなる短繊維の混合比率、及び、バインダー成分として用いるコポリパラフェニレン・３，４’―オキシジフェニレン・テレフタルアミドからなるフィブリッドの混合比率を表１に示した値になるように、それぞれ変更して加え、パルパーにより水中に離解分散させて実施例３と同様にして抄紙用スラリー液を作成し、このスラリー液を用いてタッピー式角型手抄機で抄造し、軽く加圧脱水後、さらに他のバインダー成分として用いるビスフェノールＡエピクロルヒドリン型水分散性エポキシ樹脂バインダーの樹脂分の比率も表１に示した値になるように、それぞれ変更してスプレー方式で付与した以外は、実施例３と同様に行って混抄紙を得た。この混抄紙の他の主な製造条件を表１に、また、実施例３と同様にして得られた電気回路用積層板の特性を表２に併せて示す。
【００６９】
［実施例１０〜１２、比較例６〜７］
実施例３において、最終カレンダーの温度を３１０℃から実施例１０では２２０℃に、実施例１１では２８０℃に、実施例１２では３４０℃に、比較例６では１６０℃に、比較例７では４００℃になるように、それぞれ変更した以外は実施例３と同様に行って混抄紙を得た。この混抄紙の他の主な製造条件を表１に、また、実施例３と同様にして得られた電気回路用積層板の特性を表２に併せて示す。
【００７０】
［実施例１３〜１４、比較例８〜９］
実施例３において、最終カレンダーの線圧力を１９６０Ｎ／ｃｍ（２００ｋｇ／ｃｍ）から実施例１３では１４７０Ｎ／ｃｍ（１５０ｋｇ／ｃｍ）に、実施例１４では３４３０Ｎ／ｃｍ（３５０ｋｇ／ｃｍ）に、比較例８では７８４Ｎ／ｃｍ（８０ｋｇ／ｃｍ）に、比較例９では４４１０Ｎ／ｃｍ（４５０ｋｇ／ｃｍ）になるように、それぞれ変更した以外は実施例３と同様に行って混抄紙を得た。この混抄紙の他の主な製造条件を表１に、また、実施例３と同様にして得られた電気回路用積層板の特性を表２に併せて示す。
【００７１】
【表１】

【００７２】
【表２】

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a substrate for a laminate, and more particularly, to a substrate for a laminate which has excellent thermal dimensional stability and can be suitably used for a laminate for an electric circuit.
[0002]
[Prior art]
The base material used for laminates for electric circuit boards is heat-resistant, heat-resistant dimensional stability, moisture-resistant dimensional stability, electrical insulation, deformation resistance (it is unlikely to cause twisting, warping, waving, etc.), light weight, etc. Characteristics are required. Since heat-resistant fiber paper is superior to paper made of other materials in heat resistance, electrical insulation, heat-resistant dimensional stability, lightness, etc., it has recently been used as a base material for laminates for electric circuit boards. It is being used for
[0003]
For example, paper (for example, JP-A-2-236907, JP-A-2-106840, etc.) comprising short fibers of polymetaphenylene isophthalamide ("CONEX" manufactured by Teijin Limited) and pulp of polymetaphenylene isophthalamide. And heat-resistant fiber paper comprising copolyparaphenylene / 3,4'-oxydiphenylene / terephthalamide fiber ("Technola" manufactured by Teijin Limited) and an organic resin binder (Japanese Patent Laid-Open No. 1-92233, 2-47392) and the like have been proposed.
[0004]
However, in the former, when heat-treated at a high temperature of 250 ° C. or more, not only shrinks to cause dimensional change, the equilibrium moisture content (water content) of the fiber is as large as 5 to 6%, and the content of impurity ions is high. Therefore, it cannot be used as a base material for electric insulation, which is inferior in electric insulation particularly under high humidity and requires high reliability.
[0005]
On the other hand, the latter has a small equilibrium moisture content and a low content of impurity ions, but when an organic resin is used as a binder component in a large amount, the binder component is not included in the heat-resistant fiber paper during the manufacturing process. As a result of migration to the back side and uneven distribution, the amount of the binder component present in the middle layer of the paper becomes very small, causing a problem that the non-uniformity in the thickness direction of the paper and the reliability are deteriorated.
[0006]
When such a heat-resistant fiber paper is used as a base material for a laminate for an electric circuit board, a manufacturing process thereof, in particular, a prepreg preparation process of impregnating and drying a compounded varnish such as an epoxy resin, and a process of laminating and forming the prepreg product, etc. As a result, the dispersion of the impregnation amount (particularly in the thickness direction) and the adhesion amount of the compounded varnish increases, and a part of the binder resin is melted to lower the adhesive force between the fibers, so that the paper base material is cut. Or the short fibers forming the paper move with each other, deteriorating the uniformity of the fiber density distribution, especially after the solder reflow step where high temperature treatment is performed, etc. This may cause a problem that deformation (twisting, warping, waving, etc.) occurs in the object, which is not preferable.
[0007]
Further, instead of using an organic resin as a binder component, a fibrid of a meta-type aromatic polyamide is used, and a para-type aromatic polyamide short fiber ("Kevlar" manufactured by DuPont) and a fibrillated para-type aromatic polyamide are used. Paper (Japanese Patent Laid-Open No. 61-160500, Japanese Patent Publication No. 5-65640) in which fine fibers ("Kevlar" manufactured by DuPont) are mechanically bound by the entanglement action of the fibrid is also proposed. ing.
[0008]
This paper has excellent properties such as heat resistance, heat-resistant dimensional stability, moisture-resistant dimensional stability, and deformation resistance (it is unlikely to cause twisting, warping, and waving), but only fibrid is used as the binder component. In addition, in each step of manufacturing a laminate for an electric circuit board, in order to maintain the required tensile strength, the amount of added fibrids had to be increased during actual production. However, fibrids composed of a meta-type aromatic polyamide, which is a binder component used in this paper, have a high equilibrium moisture content and a high content of impurity ions. Naked paper had the problem of frequent rejects.
[0009]
That is, a laminate for an electric circuit board, which is prepared by using a large amount of a base material having a high water absorption (equilibrium moisture content) as a main material, contains impurity ions that migrate when subjected to long-term energization under high humidity. This is because electrical insulation failure occurs and long-term reliability cannot be maintained.
[0010]
Also, an aromatic polyamide fiber paper (Japanese Patent Application No. 8-30426) composed of short fibers composed of para-type aromatic polyamide and short fibers composed of meta-type aromatic polyamide has been proposed. Since the meta-type aromatic polyamide fiber is used, the water absorption rate is high and the impurity ion content is high, so that as described above, defects easily occur in the electrical insulation test of the substrate performed under high humidity. Similarly, there is a problem that the amount of change in the interlayer conduction resistance value in the thickness direction of the printed wiring board when the moisture absorption / desorption is repeated increases.
[0011]
In recent years, electronic devices have become smaller and higher in density, and components mounted on printed wiring boards have changed from insertion types to imposition types. The surface mounting method has become mainstream. In this system, the reliability of connection between the printed wiring board and components such as chips mounted on the surface of the printed wiring board becomes a serious problem. That is, in order to obtain the reliability of the connection, it is expected that the thermal expansion coefficients of the printed wiring board and components such as chips mounted on the printed wiring board are set as close as possible to each other.
[0012]
In response to this, Japanese Patent Application Laid-Open No. H11-131385 proposes a laminate substrate using a mixed nonwoven fabric composed of para-aramid fibers and phenol resin fibers. However, in the laminate substrate disclosed herein, uncured or semi-cured fibers are used as the phenol resin fibers, that is, fibers that have not been completely cured are used as binder components. Is insufficient, and it is necessary to lower the temperature at the time of heating and compressing the mixed nonwoven fabric (paper) to 250 ° C. or less, and it is not possible to provide a sufficient heat history. Is reduced.
[0013]
Further, in the drying step of the mixed nonwoven fabric (paper) after the formation of the mixed nonwoven fabric (paper), the uncured or semi-cured phenol resin fibers are softened and melted to form a lump, If the treatment temperature is increased when the phenol resin fiber is cured, the phenol resin fiber is deformed to form a lump, and the uniformity of the fiber density distribution of the mixed nonwoven fabric (paper) may be reduced. Furthermore, since the uncured or semi-cured phenolic resin fiber undergoes a time-dependent change (cures when stored at room temperature), there is a problem that the characteristics of mixed paper made under the same papermaking conditions are likely to be different. There was also.
[0014]
As described above, various substrates for laminates have been proposed, but have a low water absorption and a low content of impurity ions, are excellent in electrical insulation, have heat resistance, and are uniform in the thickness direction of the substrate. Laminate base materials that have excellent thermal properties and thermal dimensional stability and enable laminates with a coefficient of thermal expansion as close as possible to the thermal expansion coefficient of components such as chips mounted on a laminate have been realized. Did not.
[0015]
[Problems to be solved by the invention]
The present invention is to provide a laminate substrate excellent in heat resistance and thermal dimensional stability and suitably used for an electrical circuit laminate, and has a small thermal dimensional change in the thickness direction of the laminate. And a base material for a laminate that enables a laminate for an electric circuit to have a thermal expansion coefficient in a plane direction as close as possible to the thermal expansion coefficient thereof, corresponding to a component such as a chip surface-mounted on the laminate. To provide.
[0016]
[Means for Solving the Problems]
The present invention It is composed of undrawn or low-ratio drawn para-type aromatic polyamide fiber having a specific gravity of 1.380 or less, an elongation at break of 5.3% or more, and a strength at break of 15.44 cN / Contains short fibers with high elongation characteristics of dtex or less Short fibers made of aromatic polyamide , And fibrid consisting of organic resin binder and / or heat-resistant organic high molecular polymer 3-40% by weight And a short fiber composed of aromatic polyamide: 95 to 60% by weight and a phenol resin fiber. : In the range of 5 to 40% by weight, and the short fibers made of the phenolic resin fibers are heat-cured in advance, and these short fibers are By heating and pressing at a temperature of 220 to 350 ° C. and a linear pressure of 1470 to 3920 N / cm (150 to 400 kg / cm), A prepreg using the laminate base material, wherein the prepreg is bound by a fibrid made of the organic resin binder and / or a heat-resistant organic polymer. And a laminate for an electric circuit.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The laminate substrate of the present invention, Including undrawn or low draw para-type aromatic polyamide fiber Short fibers made of aromatic polyamide and short fibers made of phenol resin fibers, and fibrids made of organic resin binder and / or heat-resistant organic high-molecular polymer 3-40% by weight And a heat-resistant fiber paper formed by using as a main component. Further, in the present invention, the laminate refers to a laminate obtained by heating and pressing a plurality of prepregs or a laminate having a metal foil. It also includes a so-called multilayer board having printed wiring on the inner layer and the surface layer. The prepreg is a single sheet obtained by impregnating a base material such as a nonwoven fabric (paper) with a thermosetting resin and drying the sheet, and is a sheet used for the above-mentioned laminated board and the like.
[0018]
The aromatic polyamide fiber used in the base material for a laminate of the present invention is, for example, an aromatic polyamide fiber in which 80% by mole or more (preferably 90% by mole or more) of the repeating unit constituting the polyamide is represented by the following formula (1). A fiber made of an aromatic homopolyamide or an aromatic copolyamide is passed through a high-temperature atmosphere in a manufacturing process thereof, or is brought into contact with a high-temperature heater or the like to impart a heat history, or is manufactured by a known method. An aromatic polyamide fiber obtained by storing the obtained fiber in a high-temperature atmosphere or passing through the high-temperature atmosphere, or by contacting with a high-temperature heater or the like and imparting a heat history by a post-processing method is preferably exemplified. . Further, an aromatic polyamide fiber that is partially substituted with a halogen atom or the like and modified so that the aromatic polyamide fiber has lower water absorption is optimal.
[0019]
Where Ar ₁ , Ar _Two Represents an aromatic group, and among them, the same or different aromatic groups selected from the following formula (2) are preferable. However, the hydrogen atom of the aromatic group may be substituted with a halogen atom, a lower alkyl group, a phenyl group, or the like.
[0020]
Embedded image

[0021]
Embedded image

[0022]
Regarding the basic production method and fiber properties of the aromatic polyamide fiber, for example, British Patent No. 1501948, US Pat. No. 3,733,964, US Pat. No. 3,767,756, JP-A-3869429, and Japanese Patent Application Publication No. JP-A-49-100322, JP-A-47-10863, JP-A-58-144152, JP-A-4-65513, and the like. Polyamide fibers are mentioned, which are ₁ , Ar _Two Of which are para-coordinated aromatic groups, specifically, polyparaphenylene terephthalamide short fibers ("Kevlar" manufactured by DuPont) or copolyparaphenylene-3,4 '-Oxydiphenylene terephthalamide short fiber ("Technola" manufactured by Teijin Limited) and the like.
[0023]
In particular, the latter is more preferable because it has a low content of impurity ions and thus has excellent electrical insulation. Further, copolyparaphenylene / 3,4′-oxydiphenylene / terephthalamide fiber in which a solid cation-converting and non-ion-adsorbing inorganic compound is fixed on the fiber surface, the impregnation property of the compounded varnish is also high. Also, since the adhesion to the compounding varnish is also improved through the inorganic compound, the effect of reducing the amount of deformation in the manufacturing process of an electric insulating material or a laminate for an electric circuit, and the electric insulating property under high humidity It is more preferable because it also has the effect of improving thermal dimensional stability and the like.
[0024]
Here, the cation-converting and non-ion-adsorbing inorganic compound is a compound having a cation-converting ability and also having a non-ionic adsorbing ability, and specific examples thereof include silica-alumina and silica-magnesia. , Kaolin, acid clay, activated clay, talc, bentonite, osmos and the like.
[0025]
These inorganic compounds are preferably fixed as solid particles to the fiber surface, since the bonding effect is further improved. Particles having a size of about 0.01 to 5.00 μm are used. In order to fix the inorganic compound on the fiber surface, for example, the inorganic compound particles may be pressed against the fiber surface in a state where the fiber surface is softened so as to bite into the extremely surface layer portion of the fiber.
[0026]
When the base material for a laminate of the present invention is applied to an electrical insulating material, a laminate for an electric circuit, or the like, impurities such as extracted sodium ions, extracted potassium ions, and extracted chlorine ions contained in the fiber interior. Since the ions induce insulation failure and become a problem, the content of the impurity ions in the manufacturing process or in a subsequent process is as described in (1) to (3) below, preferably in (4) to (4) below. It is necessary to perform sufficient cleaning treatment to satisfy 6).
(1) Amount of extracted sodium ion ≦ 40 mg / liter
(2) Amount of extracted potassium ion ≦ 3.0 mg / liter
(3) Amount of extracted chloride ion ≦ 7.5 mg / liter
(4) Amount of extracted sodium ion ≦ 35 mg / liter
(5) The amount of extracted potassium ion ≦ 2.5 mg / liter
(6) Amount of extracted chloride ion ≦ 6.5 mg / liter
When the content of the impurity ions exceeds the above (1) to (3), poor insulation is likely to be caused, and it cannot be used in the field of electric insulating materials.
[0027]
In addition, one part of the aromatic polyamide short fibers used in the present invention has an elongation at break of 5.3% or more (high elongation) and a strength at break of 15.44 cN / dtex (17. 5 g / de) or less (low strength) and a short fiber (not commercially available) composed of para-type aromatic polyamide fiber having a specific gravity of 1.380 or less (low specific gravity). Need to . Such a high elongation, low strength, short fiber composed of a para-type aromatic polyamide fiber having a low specific gravity refers to, for example, the above-mentioned copolyparaphenylene / 3,4′-oxydiphenylene / terephthalamide fiber production process. It can be obtained under manufacturing conditions such as using unstretched so that crystallization is not promoted, using a low stretch ratio, and reducing heat history.
[0028]
Such undrawn or low draw aromatic polyamide fibers have characteristics such as softening, deformation, melting (including semi-molten), and easy cutting at low temperatures. The other short fiber (which is obtained by softening, deforming, partially melting, and partially cutting the undrawn or low-magnification drawn aromatic polyamide fiber during heating and press working by calendering or the like to form paper) The entanglement and adhesion with other aromatic polyamide staple fibers and phenol resin staple fibers, etc.), the degree of fixation between short fibers and the degree of adhesion between the short fibers are improved by increasing the adhesion area and the like. Since the effect of increasing the tensile strength, delamination strength, and thermal dimensional stability is exhibited, the laminate for electrical circuits made using this mixed paper also reduces the amount of deformation and thermal dimensional change in the manufacturing process. Laminate obtained It becomes also excellent thermal dimensional stability.
[0029]
The short fiber composed of the meta-type aromatic polyamide used in the present invention is an aromatic polyamide in which 50 mol% or more of the extended chain bonds are non-coaxial and non-parallel, such as dicarboxylic acid, among the aromatic polyamides described above. , Terephthalic acid, one or more of isophthalic acid, etc., and one or more of diamines such as metaphenylenediamine, 4,4-diaminophenyl ether, 4,4′-diaminodiphenylmethane, xylylenediamine, etc. Short fibers made of a homopolymer or a copolymer can be cited, and typical examples thereof include polymetaphenylene isophthalamide, polymetaxylene terephthalamide, or isophthalic acid chloride, terephthalic acid chloride, and metaphenylenediamine. Fibers made of copolymerized copolymer You.
[0030]
In general, the meta-type aromatic polyamide fiber has a higher equilibrium moisture content (water content) and a higher impurity ion content than the para-type aromatic polyamide fiber, and thus has an electrical insulating property, particularly under high humidity. When used as a base material for electrical materials or laminates for electrical circuits that require high reliability over a long period of time due to a decrease in electrical insulation, perform a sufficient cleaning treatment to remove impurities It is necessary to take measures such as lowering the thermal history or giving a severer heat history than the para-type aromatic polyamide fiber described above.
[0031]
In this case, as described above, the solid cation-converting and non-ion-adsorbing inorganic compound is fixed to the surface of the aromatic polyamide fiber to improve the impregnation property of the compounded varnish. In order to improve the adhesiveness with the compounding varnish via the compound, from the viewpoint of reducing the amount of deformation in the manufacturing process of electrical insulating materials and laminates for electrical circuits, etc., and improving the electrical insulation under high humidity and improving the thermal dimensional stability, etc. More preferred.
The aromatic polyamide fiber used in the present invention preferably has a single fiber fineness of 0.33 to 11.11 dtex (0.3 to 10.0 de) and a fiber length of 0.5 to 60 mm. .
[0032]
Next, as the short fiber made of the phenol resin fiber used for the laminate substrate of the present invention, a novolak type phenol resin fiber having relatively low hygroscopicity is suitable, but is not limited thereto. However, those using an uncured or semi-cured phenolic resin fiber have no heat resistance and cannot not only measure the average thermal expansion coefficient in the temperature range of 110 to 250 ° C., but also perform a heat-pressing treatment performed after blending. As a result, the phenolic resin fiber is cut, deformed to an uneven thickness, or formed into a lump, which is not preferable because the uniformity of the coefficient of thermal expansion in the entire paper and the expression of the adjusting function are insufficient.
[0033]
Therefore, particularly in the present invention, it is important to use a phenol resin fiber which has been subjected to a thermosetting treatment in advance. That is, it is necessary to use at least 90% by weight of all phenolic resin fibers that have been subjected to a heat-curing treatment in advance, and use a curing agent (hexamethylenetetramine, resole-type phenolic resin, etc.) prior to mixing papermaking. The hardened material or the one already heat-cured in the production process of the phenol resin fiber is cut into short fibers for use. Therefore, after the aromatic polyamide short fiber and the phenol resin short fiber are mixed and formed, a curing agent for the phenol resin fiber is unnecessary. By using the phenolic resin fiber that has been heat-cured in this way, the phenolic resin fiber To Although it can no longer function as a binder, it becomes possible to adjust the thermal dimensional stability and the coefficient of thermal expansion of the resulting heat-resistant fiber paper. As the phenol resin short fibers, those having a single fiber fineness of 0.56 to 11.11 dtex (0.5 to 10.0 de) and a fiber length of 0.5 to 10 mm are preferably used.
[0034]
When such an aromatic polyamide short fiber and a phenol resin short fiber are used, the use ratio of the aromatic polyamide short fiber to the total short fiber is 95 to 60% by weight, and the phenol resin short fiber is 5 to 40% by weight. Those used in the range of weight% are preferred. When the use ratio of the aromatic polyamide short fiber exceeds 95% by weight, the effect of using the phenol resin short fiber is not sufficiently exhibited, and the properties of the obtained laminate base material, particularly, the thermal expansion coefficient, are reduced. It is not preferable because adjustment becomes difficult. When the use ratio of the phenol resin short fibers exceeds 40% by weight, the excellent properties obtained by using the aromatic polyamide short fibers are impaired, and in particular, the heat resistance decreases. In addition, the equilibrium moisture content increases, and the electrical insulation and the reliability of the electrical insulation under high humidity are impaired.
[0035]
In the present invention, the average thermal expansion coefficient of the aromatic polyamide short fibers in the temperature range of 110 to 250 ° C. is −1.0 × 10 ^-6 / ° C or less, and the average thermal expansion coefficient in the length direction of the short fiber made of a phenol resin fiber in the same temperature range as above is + 1.0 × 10 ^-6 / ° C. or more makes it possible to control the coefficient of thermal expansion of the heat-resistant fiber paper obtained according to the application. That is, by using such an aromatic polyamide short fiber and a phenol resin short fiber in combination, the average heat expansion coefficient in the same temperature range in the plane direction of the obtained heat-resistant fiber paper is + 10 × 10 ^-6 / ° C to -10 x 10 ^-6 / ° C. It is possible to obtain a laminated board base material that has an optimum thermal dimensional change according to the application and its use temperature by using such heat-resistant fiber paper. .
[0036]
Generally, the coefficient of thermal expansion in the length direction of a short fiber made of an aromatic polyamide is usually minus (contraction direction), and the value varies depending on manufacturing conditions, composition (homotype, copolymer type, etc.), but is commercially available. The average coefficient of thermal expansion in the temperature range of 110 to 250 ° C. is −1.5 to −15 × 10 ^-6 / ° C.
[0037]
On the other hand, the thermal expansion coefficient in the longitudinal direction of the phenol resin fiber subjected to the thermosetting treatment is, on the contrary, plus (extending direction), and the value varies depending on the manufacturing conditions, the degree of curing, and the composition. The average coefficient of thermal expansion in the temperature range of ° C. is +4.5 to + 30 × 10 ^-6 / ° C, it is possible to adjust the average thermal expansion coefficient in the surface direction of the base material for a laminate to the above-mentioned range by controlling the mixing ratio of both fibers well. The average thermal expansion coefficient in the plane direction of the material can be made as close as possible to zero.
[0038]
As described above, the staple fiber made of a phenol resin has a thermal expansion coefficient (length direction) of about 2 to 20 times in the opposite direction to that of the aromatic polyamide fiber. Therefore, it is preferable to adjust the mixing ratio of the phenol resin fiber to the aromatic polyamide fiber within the range of 1/2 to 1/20. When the mixing ratio of the phenol resin fiber is increased, the heat resistance of the mixed paper is reduced, and the equilibrium water content is also increased. Therefore, as described above, the mixing ratio of the phenol resin fiber is in the range of 5 to 40% by weight. Are preferably used.
[0039]
Further, the heat-resistant fiber paper (base material) obtained by mixing the phenol resin short fibers which have been subjected to the thermosetting treatment in advance is subjected to a heat and pressure treatment in a calendering step or the like, and then again under a high temperature atmosphere. Surprisingly, even when the heat treatment is performed, the dimensional change (thickness change) of the base material in the thickness direction is smaller than that of the conventional aromatic polyamide paper. That is, the dimensional change in the thickness direction of the heat-resistant fiber paper after heat treatment at 335 ° C. for 5 minutes is 7% or less, substantially in the range of 0.5 to 5%, It shows a remarkably low value as compared with polyamide paper (8 to 35%).
[0040]
The reason is that the phenolic resin fibers form a uniform distribution without forming an uneven portion such as a lump, and the short fibers constituting the heat-resistant fiber paper are compression-deformed and heat-set under heat and pressure. Therefore, it is presumed that the state of the uniform distribution is fixed as it is and is continuously maintained. Such a small dimensional change in the thickness direction is suitable when used for a substrate for an electric circuit laminate. In general, a laminate for an electric circuit is subjected to not only a high temperature of 250 ° C. or more in a manufacturing process and 300 ° C. or more in a solder heat resistance model test, but also a product after component mounting, from room temperature to 100 ° C. depending on use conditions. It is used in situations where the temperature rise and fall to the above high temperature is repeated. Therefore, the smaller the amount of dimensional change in the thickness direction of the electric circuit laminate during the temperature rise / fall process, the higher the reliability of electric circuit connection via through holes and vias between the laminate layers.
Can be
[0041]
Next, among the organic resin binder used in the present invention and / or the fibrid comprising a heat-resistant organic polymer, the organic resin binder may be a thermosetting organic resin such as an epoxy resin or a phenol resin. , A polyurethane resin, a melamine resin, etc., and among them, a water-dispersible epoxy resin having an epoxy functional group in the molecule is preferable because of good compatibility with the compounded varnish impregnated in the prepreg preparation step.
[0042]
The equilibrium moisture content of the organic high molecular weight fibrid used in the present invention is preferably 7.5% or less. In the wet papermaking process, the thin fibril or scale having fine fibrils exhibiting binder performance is provided. Is a generic term for small fibrils or randomly short fibrils which are fibrillated at random.For example, as described in JP-B-35-11851, JP-B-37-5732, etc., an organic polymer solution is used. Fibrid produced by mixing a polymer solution in a system in which a precipitant and a shear force are present, and a polymer solution exhibiting optical anisotropy as described in JP-B-59-603. Fibrids which are randomly fibrillated by applying a mechanical shearing force such as beating to a molded product having molecular orientation molded from According to what is optimal.
[0043]
Further, as the organic high molecular polymer forming such a fibrid, a fiber, or a heat-resistant high molecular polymer having a film forming ability and having a thermal decomposition initiation temperature of 260 ° C. or higher, preferably 310 ° C. Any of the above can be used.
[0044]
For example, an aromatic polyamide, a molten liquid crystalline wholly aromatic polyester, a heterocyclic-containing aromatic polymer and the like can be used. Among them, particularly, copolyparaphenylene-3,4′-oxy having a low impurity ion content is preferable. Diphenylene terephthalamide (“Technola” manufactured by Teijin Limited) or a molten liquid crystalline wholly aromatic polyester made of a copolymer of p-hydroxybenzoic acid and 2,6-hydroxynaphthoic acid having a small equilibrium moisture content (( "Vectran" manufactured by Kuraray Co., Ltd.) is preferably used, and when heat resistance is required, those using the above-mentioned polyparaphenylene benzobisoxazole ("PBO" manufactured by Toyobo Co., Ltd.) are preferable. .
[0045]
The ratio of the fibrid comprising the organic resin binder and / or the heat-resistant organic high molecular polymer in the heat-resistant fiber paper is in the range of 3 to 40% by weight, preferably 4 to 30% by weight. More preferably, it is in the range of 5 to 25% by weight. When the ratio of the fibrid comprising the organic resin binder and / or the heat-resistant organic high molecular polymer in the heat-resistant fiber paper is less than 3% by weight, the short fibers are sufficiently bound to each other. But the bulk density of the resulting heat-resistant fiber paper is 0.46 g / cm ^Three If the ratio exceeds 40% by weight, the bulk density is 0.90 g / cm ^Three Is not preferable because of the reasons described later.
[0046]
Further, the heat-resistant fiber paper used in the present invention can be manufactured by a conventionally known method, for example, Including undrawn or low draw para-type aromatic polyamide fiber Para-aromatic polyamide short fibers, meta-aromatic polyamide short fibers, and phenol resin short fibers are weighed so as to have a predetermined mixing ratio, and the fiber concentration is in the range of 0.15 to 0.40% by weight. If necessary, fibrid and / or an organic resin binder as a binder component are added to an aqueous slurry prepared by uniformly dispersing the mixture in water, and if necessary, a dispersant or a viscosity modifier is further added. After adding, a wet web is formed by a wet papermaking method using a paper machine such as a long net or inclined short net or a round net, and the organic resin binder is sprayed again on the wet paper if necessary, After being applied to a predetermined solid content ratio by an impregnation method or the like, it is dried to obtain a dry paper. Also, The dried paper is It can be heated and pressurized again to obtain a heat-resistant fiber paper having a predetermined basis weight, bulk density, tensile strength, etc. is necessary .
[0047]
As the heating and pressurizing process, for example, a process of heating and pressurizing using a calender is exemplified. When heating and pressing using a calender, between one hard surface roll having a diameter of about 15 to 80 cm and one surface deformable elastic roll having a diameter of about 30 to 100 cm, or It may be performed between two hard surface rolls having a diameter of about 20 to 80 cm. Is 2 20-350 ° C, linear pressure Is 1 Perform in the range of 470-3920 N / cm (150-400 kg / cm) It is necessary .
[0048]
The heat-resistant fiber paper obtained by such a heating and pressurizing process has a bulk density of 0.46 to 0.90 g / cm. ^Three , Preferably 0.50 to 0.80 g / cm ^Three Therefore, the conditions for the heating and pressurizing may be performed within the above range so as to obtain such a paper density.
[0049]
The bulk density is 0.46 g / cm ^Three If less than, the adhesive strength between short fibers in the middle layer of the paper is reduced, the impregnation amount of the compound varnish into the paper becomes too large, the prepreg manufacturing process and the manufacturing process of the electric circuit laminate, particularly, In the laminating press process, the single fibers partially move due to the flow of the impregnating varnish, and the density unevenness of the fibers occurs inside the obtained laminate for electric circuit boards, and the heat resistance dimensional stability and deformation resistance decrease. May be invited. On the other hand, the bulk density is 0.90 g / cm ^Three In the case where the ratio exceeds 3, the impregnation of the compounded varnish into the paper is reduced, and the electrical insulation, heat-resistant dimensional stability, and deformation resistance of the obtained laminate for an electric circuit board may be deteriorated.
[0050]
Effect of the Invention
A laminate substrate made of such heat-resistant fiber paper has an aromatic polyamide short fiber having a negative (contraction in the length direction) thermal expansion coefficient at a high temperature and a positive (expansion in the length direction) thermal expansion coefficient. It is composed of phenolic resin short fibers having a high thermal expansion coefficient. It has the property.
[0051]
Furthermore, since the phenol resin short fibers used are those that have been heat-cured before being mixed and formed, a higher temperature treatment is possible when producing heat-resistant fiber paper. Excellent heat resistance can be imparted to the heat-resistant fiber paper obtained, and no wrinkles are generated due to shrinkage during heating and pressing, and uniform heat-resistant fiber paper is obtained without uneven distribution of short fibers. Therefore, it is possible to provide an excellent base material for a laminate.
[0052]
In particular, the laminate base material of the present invention, after being subjected to the heat and pressure processing in the manufacturing process, the amount of dimensional change of the base material in the thickness direction even if the heat treatment is performed again in a high-temperature atmosphere. (Amount of change in thickness) is smaller than that of a conventional aromatic polyamide paper, and is excellent as a base material of a laminate for electric circuits. The average thermal expansion coefficient (temperature range: 50 to 250 ° C.) in the thickness direction of a laminate obtained by forming a prepreg by using such a laminate substrate, further laminating the prepreg, and heating and press-molding the laminate is obtained. , 260 × 10 ^-6 / ° C or less, and an excellent laminate for electric circuits with extremely small dimensional change in the thickness direction due to heat change can be obtained.
[0053]
In addition, phenolic resin fibers generally have a higher equilibrium moisture content than fibers made of para-type aromatic polyamide, and there are restrictions on their use in electrical insulating materials and laminates for electric circuits. By doing so, an excellent laminate base material can be obtained because the equilibrium moisture content is also within the allowable range.
[0054]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples. The measured values of the physical properties used in the examples are as follows, and the manufacturing method of the laminate (laminate for electric circuit) is as follows.
[0055]
(1) Bulk density
It measured by the method based on 6.1 of JISC-2111.
[0056]
(2) Tensile strength and elongation
A: Tensile strength and elongation of fiber
Using a constant-speed elongation type tensile tester, it was measured according to JIS L-1013-7.
B: Tensile strength and elongation of paper
The measurement was performed using a constant-speed elongation type tensile tester according to JIS C-2111-7.
[0057]
(3) Specific gravity
It was determined by a density gradient tube method (N-heptane / carbon tetrachloride, 25 ° C.).
[0058]
(4) Equilibrium moisture content
It was measured by the following method in accordance with JIS L-1013.
A: Equilibrium moisture content of fiber
After the fiber to be used is dried (absolutely dried) for 24 hours in an atmosphere at a temperature of 105 ° C., the temperature is adjusted to 20 ° C. and the relative humidity is 65% RH for 72 hours, and the moisture content in the fiber is determined. Then, the ratio to the weight in the absolutely dry state in the fiber was calculated, and this was expressed as a percentage (%). However, when two or more kinds of fibers are mixed and used, the equilibrium moisture content of each fiber is independently measured, and expressed as a weight average according to the mixing ratio.
B: Equilibrium moisture content of fiber paper (mixed paper)
The heat-resistant mixed paper after papermaking and heat-press processing is absolutely dried for 24 hours in an atmosphere at a temperature of 105 ° C., and is then adjusted at a temperature of 20 ° C. and a relative humidity of 65% RH for 72 hours. The moisture content of the heat-resistant mixed paper was determined, and the ratio to the weight of the heat-resistant mixed paper in an absolutely dry state was calculated. The ratio was expressed as a percentage (%).
[0059]
(5) Average thermal expansion coefficient of fiber and mixed paper
(Average coefficient of thermal expansion in the fiber length direction and the mixed paper surface direction)
A: Average thermal expansion coefficient of fiber (average thermal expansion coefficient in fiber length direction)
Using a thermal analyzer (TMA; Thermoflex type manufactured by Rigaku Denki Co., Ltd.), the initial sample length between the chucks was 200 mm, and the temperature was raised and lowered at a rate of 20 ° C./min. Put the sample together with the mounting jig in phosphorus pentoxide (P _Two 0 _Five ), After cooling in a desiccator, the temperature was again raised from room temperature to 280 ° C. (second time), and the coefficient of thermal expansion was calculated from the dimensional change in the range of 110 to 250 ° C., n = 5 The average coefficient of thermal expansion was determined and represented by the above measured values. The sample used for the measurement was dried at 105 ° C. for about 24 hours in advance, and then phosphorus pentoxide (P _Two O _Five ) Was used after cooling for 48 hours.
B: Average thermal expansion coefficient of mixed paper (average thermal expansion coefficient in the plane direction of mixed paper)
The average coefficient of thermal expansion was determined in the same manner as in the case of the above fiber except that a sample having a width of 5 mm was used as a measurement sample.
[0060]
(6) Fiber paper (mixed paper) thickness change rate
After adjusting the heat-resistant mixed paper after the heat and pressure processing at a temperature of 20 ° C. and a relative humidity of 65% RH for 48 hours, the thickness was measured at five places (marked) of the heat-resistant mixed paper. The average thickness (A) of the heat-resistant mixed paper was then heat-treated in a high-temperature atmosphere at a temperature of 335 ° C. for 5 minutes, and the heat-resistant mixed paper after the heat treatment was heated at a temperature of 20 ° C. Further, after adjusting the relative humidity for 48 hours at 65% RH, the thickness was measured at the same place as above (five places marked) to determine the average thickness (B), and the average thickness before and after the heat treatment was obtained. The amount of change (C = BA) of the heat-resistant mixed paper before heat treatment was calculated, and the ratio (C ÷ A) to the average thickness (A) of the heat-resistant mixed paper was calculated, and this was calculated as a percentage (%). expressed.
[0061]
(7) Method of making laminate for electric circuit
An epoxy resin composition comprising a high-purity brominated bisphenol A type epoxy resin and an orthocresol novolak type epoxy resin mixed with dicyandiamide as a curing agent and 2-ethyl-4-methylimidazole as a curing accelerator is prepared by mixing methyl ethyl ketone and methyl cellosolve. A blend varnish obtained by dissolving in a mixed solution is impregnated into an aromatic polyamide fiber paper, and then dried at a temperature of 110 to 120 ° C. for 5 to 10 minutes, and a B stage having a resin content of 55% by volume. Made prepreg paper. After fifteen of the prepreg papers are laminated, the resin is cured by heating and pressing by hot pressing under reduced pressure at a temperature of 170 ° C. and a pressure of 392 N / cm (40 kg / cm) for 50 minutes. After obtaining a circuit laminate, a post-curing treatment is performed for about 20 minutes in a hot air dryer at a temperature of 200 ° C. to produce a target electric circuit laminate.
[0062]
(8) Average thermal expansion coefficient in the plane direction and thickness direction of the laminate for electric circuits
A: Average thermal expansion coefficient in the plane direction of the laminate
Using a thermal analyzer ("TMA (120) SSC / 5200" manufactured by Seiko Instruments Inc.), an electric circuit laminate having a thickness of about 1.5 mm is cut into a 5 mm x 7 mm square, and its plane direction ( = Direction of length 7 mm). The measuring method is as follows: after the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./minute, the temperature is subsequently cooled to room temperature, and subsequently, the temperature is raised to 250 ° C. under the same conditions, and the second heating process , The coefficient of thermal expansion was calculated from the change in the length in the plane direction within the range of 50 ° C. to 250 ° C., and the average coefficient of thermal expansion (plane direction) was determined and expressed from the measured values of n = 5 or more.
B: Average thermal expansion coefficient in the thickness direction of the laminate
Using a thermal analyzer (“TMA (120) SSC / 5200” manufactured by Seiko Instruments Inc.), an electric circuit laminate having a thickness of about 1.5 mm is cut into a 5 mm × 5 mm square, and its thickness direction is measured. (In the direction of thickness of about 1.5 mm), the coefficient of thermal expansion was measured. The measuring method is as follows: after the temperature is raised from room temperature to 200 ° C. at a heating rate of 10 ° C./minute, the temperature is subsequently cooled to room temperature, and subsequently, the temperature is raised to 250 ° C. under the same conditions, and the second heating process The coefficient of thermal expansion (thickness direction) was calculated from the change in thickness within the range of 50 ° C. to 250 ° C. in Example 2, and the average coefficient of thermal expansion was determined and expressed from measured values of n = 5 or more.
[0063]
[Example 1]
As a short fiber of aromatic polyamide, low elongation, high strength and high specific gravity, copolyparaphenylene / 3,4'-oxydiphenylene terephthalamide, 0.5% by weight of talc on the fiber surface, Osmos Is 0.1% by weight and the elongation at break is 4.6%, the strength at break is 25.93 cN / dtex (29.4 g / de), and the specific gravity is 1.398. 67 dtex (1.5 de), fiber length: 3 mm, average thermal expansion coefficient in the length direction is -9.2 × 10 ^-6 / ° C, equilibrium moisture content: 1.8% staple fiber ("Technola" manufactured by Teijin Limited): 73% by weight and a high elongation, low strength, low specific gravity staple fiber composed of aromatic polyamide. It consists of phenylene-3,4'-oxydiphenylene terephthalamide, and 0.6% by weight of talc and 0.2% by weight of osmos adhere to the fiber surface. Has a strength of 3.70 cN / dtex (4.2 g / de), a specific gravity of 1.349, a single fiber fineness of 2.22 dtex (2.0 de), a fiber length of 5 mm, and an average heat in the length direction. Expansion coefficient is -4.6 × 10 ^-6 / ° C, equilibrium moisture content: 3.9% short fiber (manufactured by Teijin Limited): 7% by weight, consisting of substantially hardened novolak-type phenolic resin fiber, having an elongation at break of 5 Single fiber fineness with a strength at break of 1.24 cN / dtex (1.4 g / de) and a specific gravity of 1.287 at 2.2%: 2.22 dtex (at 2.0), fiber length: 5 mm, length The average thermal expansion coefficient in the direction is + 24.5 × 10 ^-6 / ° C, equilibrium moisture content: short fiber of 4.6% ("Kynol" manufactured by Nippon Kainol Co., Ltd.): 5% by weight, and copolyparaphenylene-3,4 'having an equilibrium moisture content of 4.4% as a binder component. -Fibrid made of oxydiphenylene terephthalamide (manufactured by Teijin Limited): 5% by weight, disintegrated and dispersed in water with a pulper, and a dispersant (Matsumoto Yushi "YM-80" manufactured by K.K.) was added to prepare a papermaking slurry liquid having a fiber concentration of 0.15% by weight.
[0064]
Next, using a tappy type square hand machine, papermaking is performed using the papermaking slurry liquid, and after light pressure dehydration, a bisphenol A epichlorohydrin type aqueous dispersion having a solid content of 10% by weight is further used as a binder component. An epoxy resin binder (manufactured by Dainippon Ink and Chemicals, Inc.) was applied by a spray method so that the resin content was 10% by weight to obtain a mixed paper. The mixed paper was dried in a roll dryer at a temperature of 130 ° C. for about 1 minute, and further dried in a hot air dryer at a temperature of 150 ° C. for about 10 minutes to obtain a dry mixed paper. The dried mixed paper was heated and pressurized at a temperature of 200 ° C. and a linear pressure of 1960 N / cm (200 kg / cm) using a calender comprising a pair of hard surface metal rolls having a diameter of about 400 mm. Using a high-temperature high calender machine consisting of a pair of hard surface metal rolls of about 500 mm, heating and pressing at a temperature of 310 ° C. and a linear pressure of 1960 N / cm (200 kg / cm), the high elongation is performed. Fiber consisting of copolyparaphenylene-3,4'-oxydiphenylene terephthalamide with low strength and low specific gravity ("Technola" manufactured by Teijin Limited) and / or copolyparaphenylene-3,4'-oxy Softens and partially melts the diphenylene / terephthalamide fibrid to exhibit the performance as a binder, and fixes the single fibers that make up the mixed paper. Said bisphenol A epichlorohydrin type resin binder (Dainippon Ink and Chemicals, Incorporated) also is semi-cured and / or fully hardened adhering simultaneously, basis weight: 72 g / m ² The desired mixed paper was obtained. The main production conditions for the mixed paper are shown in Table 1. The characteristic values of the mixed paper measured by the above-described measurement method are as shown in Table 2.
[0065]
Next, using the mixed paper thus obtained, a laminate was prepared by the above-described method for producing a laminate for an electric circuit, and the average thermal expansion coefficient of the laminate in the surface direction and the thickness method was determined as the above. Was measured according to the measurement method described above. The results were as shown in Table 2.
[0066]
[Comparative Example 1]
In Example 1, the mixing ratio of short fibers made of aromatic polyamide having low elongation, high strength, and high specific gravity was changed from 73% by weight to 76% by weight. A mixed paper was obtained in the same manner as in Example 1 except that the mixing ratio was changed from 5% by weight to 2% by weight. Table 1 shows other main production conditions of the mixed paper, and Table 2 shows characteristics of the laminate for electric circuits obtained in the same manner as in Example 1.
[0067]
[Examples 2 to 5, Comparative Example 2]
In Example 1, the mixing ratio of short fibers made of aromatic polyamide having low elongation, high strength, and high specific gravity was changed from 73% by weight to 69% by weight in Example 2, and 62% by weight in Example 3. In Example 4, the weight ratio was changed to 57% by weight, in Example 5, to 48% by weight, and in Comparative Example 2, to 40% by weight. Further, the mixing ratio of the short fibers composed of novolak type phenol resin fibers was changed to 5% by weight. % To 9% by weight in Example 2, 16% by weight in Example 3, 21% by weight in Example 4, 30% by weight in Example 5, and 38% by weight in Comparative Example 2. Except having changed each, it carried out similarly to Example 1 and obtained the mixed paper. Table 1 shows other main production conditions of the mixed paper, and Table 2 shows characteristics of the laminate for electric circuits obtained in the same manner as in Example 1.
[0068]
[Examples 6 to 9, Comparative Examples 3 to 5]
In Example 3, the mixing amount of the high-strength, low-strength, low-specific-gravity short fibers made of an aromatic polyamide was fixed at 7% by weight, and the low-extension, high-strength, high-specific-gravity short of aromatic polyamide was used. Table 1 shows the mixing ratio of the fibers, the mixing ratio of the short fibers composed of novolak type phenol resin fibers, and the mixing ratio of the fibrid composed of copolyparaphenylene / 3,4′-oxydiphenylene / terephthalamide used as a binder component. The slurry was then disintegrated and dispersed in water with a pulper to prepare a papermaking slurry liquid in the same manner as in Example 3, and this slurry liquid was used with a tappy-type square hand machine. After papermaking and lightly dehydrating under pressure, the resin content of the bisphenol A epichlorohydrin type water-dispersible epoxy resin binder used as another binder component is further reduced. A mixed paper was obtained in the same manner as in Example 3, except that the ratio was changed to each of the values shown in Table 1 and applied by a spray method. Other main production conditions of the mixed paper are shown in Table 1, and characteristics of the electric circuit laminate obtained in the same manner as in Example 3 are also shown in Table 2.
[0069]
[Examples 10 to 12, Comparative Examples 6 to 7]
In Example 3, the temperature of the final calender was changed from 310 ° C. to 220 ° C. in Example 10, 280 ° C. in Example 11, 340 ° C. in Example 12, 160 ° C. in Comparative Example 6, and 400 ° C. in Comparative Example 7. C. to obtain a mixed paper by carrying out in the same manner as in Example 3 except that each temperature was changed. Other main production conditions of the mixed paper are shown in Table 1, and characteristics of the electric circuit laminate obtained in the same manner as in Example 3 are also shown in Table 2.
[0070]
[Examples 13 and 14, Comparative Examples 8 and 9]
In Example 3, the linear pressure of the final calender was changed from 1960 N / cm (200 kg / cm) to 1470 N / cm (150 kg / cm) in Example 13 and 3430 N / cm (350 kg / cm) in Example 14. A mixed paper was obtained in the same manner as in Example 3, except that the sample No. 8 was changed to 784 N / cm (80 kg / cm) and the sample No. 9 was changed to 4410 N / cm (450 kg / cm). Other main production conditions of the mixed paper are shown in Table 1, and characteristics of the electric circuit laminate obtained in the same manner as in Example 3 are also shown in Table 2.
[0071]
[Table 1]

[0072]
[Table 2]

Claims (5)

It is composed of undrawn or low-ratio drawn para-type aromatic polyamide fiber having a specific gravity of 1.380 or less, an elongation at break of 5.3% or more, and a strength at break of 15.44 cN / short fibers composed of an aromatic polyamide containing short fibers having the following strength and elongation properties dtex, and a short fiber made of phenol resin fibers, fibrids 3 made of an organic resin binder and / or heat-resistant organic high molecular polymer -40 % by weight of a heat-resistant fiber paper formed as a main component, and the use ratio of the short fibers is 95-60% by weight of a short fiber made of an aromatic polyamide with respect to all the short fibers, and a phenol resin fiber. consists short fibers: in the range of 5 to 40 wt%, and a fiber staple fibers consisting of the phenolic resin fibers are pre thermosetting treatment, these short fibers is 220 to 35 ℃ temperature, 1470~3920N / cm (150~400kg / cm ) by a line pressure heated and pressurized, the organic resin binder and / or binder by fibrids comprising a heat-resistant organic high molecular polymer A base material for a laminate, characterized in that the base material is made. The substrate for a laminate according to claim 1, wherein the aromatic polyamide is a para-type aromatic polyamide fiber. The base material for a laminate according to claim 1 or 2 , wherein the para-type aromatic polyamide fiber is a polyparaphenylene terephthalamide fiber or a copolyparaphenylene / 3,4'-oxydiphenylene terephthalamide fiber. A prepreg formed by impregnating a thermosetting resin into a laminate base material, wherein the laminate base material comprises the laminate base material according to any one of claims 1 to 3. A prepreg characterized by the following. An electric circuit laminate obtained by laminating prepregs and subjecting the prepreg to heat and pressure molding, wherein the prepreg comprises the one described in claim 4 .