JP3570158B2 - Epoxy resin composition, prepreg and laminate - Google Patents

Description

【００１４】
本発明の請求項２に係るエポキシ樹脂組成物は、請求項１記載のエポキシ樹脂組成物において、変成フェノール生成物の数平均分子量が、１０００〜３０００であることを特徴とする。
【００１７】
本発明の請求項３に係るプリプレグは、請求項１又は請求項２記載のエポキシ樹脂組成物を、基材に含浸乾燥してなる。
【００１８】
本発明の請求項４に係る金属箔張り積層板は、請求項３記載のプリプレグに金属箔を重ね、加熱・加圧してなる。
【００１９】
本発明によると、エポキシ樹脂組成物に、上記式（ａ）で表されるエポキシ樹脂を含有するため、樹脂の硬化物の高温特性が向上すると考えられ、その表面に有する金属箔とボンディングワイヤーとの、加熱時の接着強度が優れた積層板が得られる。また、上記式（ａ）で表されるエポキシ樹脂は、上記変成フェノール生成物と架橋して両者が架橋構造に取り込まれるため、エポキシ樹脂とＰＰＥとの特性が損なわれず、誘電率、誘電正接及びはんだ耐熱性等も優れた積層板が得られる。
【００２０】
【発明の実施の形態】
本発明の請求項１又は請求項２に係るエポキシ樹脂組成物は、数平均分子量が１００００〜３００００のＰＰＥとフェノール性化合物を反応開始剤の存在下で再分配反応させて、その数平均分子量が用いたＰＰＥの数平均分子量の５〜７０％の数平均分子量になるように反応させてなる変成フェノール生成物、エポキシ樹脂及びエポキシ樹脂の硬化剤を、少なくとも含有する。
【００２１】
変成フェノール生成物の製造に用いられるＰＰＥは、別名ポリフェニレンオキサイド樹脂とも呼ばれる樹脂であり、その一例としては、ポリ（２，６−ジメチル−１，４−フェニレンオキサイド）が挙げられる。このようなＰＰＥは、例えば、ＵＳＰ４０５９５６８号明細書に開示されている方法で合成することができる。
【００２２】
変成フェノール生成物の製造に用いられるフェノール性化合物としては、例えば、ビスフェノールＡ、ビスフェノールＦ、フェノ−ルノボラック、クレゾールノボラック等が挙げられる。なお、フェノール性水酸基を分子内に２個以上有するフェノール類を用いると好ましい。このフェノール類のフェノール性水酸基数の上限は特に限定するものではないが、分子内に３０個以下のものが一般に用いられる。なお、フェノール性化合物の量は、ＰＰＥ１００重量部に対して１〜２０重量部が適量であり、反応開始剤と同程度の量が一般的である。
【００２３】
変成フェノール生成物の製造に用いられる反応開始剤としては、過酸化ベンゾイル、ジクミルパーオキサイド、ｔ−ブチルクミルパーオキサイド、ジ−ｔ−ブチルパーオキサイド、２，５−ジメチル−２，５−ジ−ｔ−ブチルパーオキシへキシン−３、２，５−ジメチル−２，５−ジ−ｔ−ブチルパーオキシヘキサン、α，α’−ビス（ｔ−ブチルパーオキシ−ｍ−イソプロピル）ベンゼンなどの過酸化物があげられる。また過酸化物ではないが、市販の反応開始剤である日本油脂株式会社製の商品名「ビスクミル」（１分半減温度３３０℃）を使用することもできる。なお、過酸化ベンゾイルを用いると、反応性が優れ好ましい。なお、反応開始剤の量は、ＰＰＥ１００重量部に対して１〜２０重量部が適量である。
【００２４】
そして変成フェノール生成物を製造する場合には、有機溶媒中で、上記のＰＰＥとフェノール性化合物を反応開始剤の存在下で再分配反応させて、用いたＰＰＥの数平均分子量より低分子量の変成フェノール生成物を製造する。再分配反応の条件としては、例えば、上記のＰＰＥとフェノール性化合物と反応開始剤を撹拌しながら、８０〜１２０℃で１０〜１００分程度加熱して行う。なお、用いる有機溶媒としては、トルエン、ベンゼン、キシレン等の芳香族炭化水素系溶媒が挙げられる。
【００２５】
反応開始剤の存在下で数平均分子量が１００００〜３００００のＰＰＥとフェノール性化合物を反応させると、先ずＰＰＥがラジカル化されると考えられ、直鎖が切断される再分配反応が進行してＰＰＥが低分子量化し、この低分子量化したＰＰＥでフェノール性化合物が変成される。
【００２６】
そして得られる変成フェノール生成物の構造は、低分子化したＰＰＥの一方又は両方の末端部にフェノール性化合物が結合して、ＰＰＥの一方又は両末端にフェノール性水酸基を有する構造となると考えられる。そのため、この末端のフェノール性水酸基がエポキシ樹脂のエポキシ基と反応し、ＰＰＥとエポキシ樹脂が強固に架橋すると考えられる。
【００２７】
なお、再分配反応して得られる変成フェノール生成物の数平均分子量は、用いたＰＰＥの数平均分子量の５〜７０％の数平均分子量であることが重要である。７０％を越える場合、エポキシ樹脂組成物の粘度が高くなって、基材に含浸するときの含浸性が低下し、得られるプリプレグの樹脂付着量がばらついたり、プリプレグの取り扱い時に樹脂が剥がれて樹脂付着量がばらつき、電気特性のばらつきが発生する場合があるという問題や、エポキシ樹脂組成物の保存性が低下して粘度が短期間で高くなりやすく、エポキシ樹脂組成物の使用可能な時間が短くなって、生産に支障を来しやすいという問題が発生しやすくなる。また、５％未満の場合、得られる積層板の機械的強度や耐熱性が低下する場合がある。
【００２８】
なお、変成フェノール生成物の数平均分子量が、用いたＰＰＥの数平均分子量の５〜７０％の数平均分子量であり、かつ、１０００〜３０００の範囲内であると、得られるエポキシ樹脂組成物を基材に含浸するときの含浸性が特に優れ好ましい。
【００２９】
なお、用いたＰＰＥが複数の数平均分子量のＰＰＥの混合物の場合には、その混合物の平均値に対して、５〜７０％の数平均分子量となるように反応させる。また、得ようとする変成フェノール生成物の数平均分子量の調整は、反応開始剤の量を増やすと数平均分子量が低下する傾向があるため、反応開始剤の量で調整すると調整しやすく好ましい。
【００３０】
エポキシ樹脂組成物に含有するエポキシ樹脂には、上記式（ａ）で表されるエポキシ樹脂（以下、式（ａ）樹脂と記す）を含有することが重要である。式（ａ）樹脂を含有しない場合は、このエポキシ樹脂組成物を用いて表面に金属箔の層を有する積層板を製造し、ボンディングワイヤーを積層板表面の金属箔と接合した後、ボンディングワイヤーと金属箔との接着強度の評価を行うと、ボンディングワイヤーと金属箔の接合部で剥がれる場合がある。なお、この式（ａ）樹脂は、２−［４−（２，３−エポキシプロポキシ）フェニル］−２−［４−［１，１−ビス［４−（２，３−エポキシプロポキシ）フェニル］エチル］フェニル］プロパンと一般に命名される。
【００３１】
なお、エポキシ樹脂組成物に含有するエポキシ樹脂は、式（ａ）樹脂のみに限定するものではなく、分子内にエポキシ基を２個有するエポキシ樹脂等をも含有することにより、式（ａ）樹脂を、全エポキシ樹脂１００重量部中に１〜４０重量部含有するようにすると、金属箔とボンディングワイヤーとの接着強度が優れると共に、耐熱性が優れた積層板が得られ好ましい。１重量部未満の場合は、金属箔とボンディングワイヤーとの接着強度を向上させる効果が小さく、４０重量部を越えると吸湿率が高くなってはんだ耐熱性が低下する場合がある。
【００３２】
含有することができるエポキシ樹脂としては、例えば、ビスフェノ−ルＡ型エポキシ樹脂、ビスフェノ−ルＦ型エポキシ樹脂、ビスフェノ−ルＳ型エポキシ樹脂、ヒダントイン型エポキシ樹脂、脂環式エポキシ樹脂、ビフェニル型エポキシ樹脂、及びこれらの樹脂をハロゲン化したエポキシ樹脂等の分子内にエポキシ基を２個有するエポキシ樹脂が挙げられ、２種類以上を併用してもよい。なお、分子内にエポキシ基を１個有するエポキシ樹脂や、ノボラック型エポキシ樹脂等の式（ａ）樹脂以外の分子内にエポキシ基を３個以上有するエポキシ樹脂をも併用することもできる。
【００３３】
エポキシ樹脂組成物に含有するエポキシ樹脂の硬化剤としては、例えばジシアンジアミド、脂肪族ポリアミド等のアミド系硬化剤や、ジアミノジフェニルメタン、メタフェニレンジアミン、アンモニア、トリエチルアミン、ジエチルアミン等のアミン系硬化剤や、ビスフェノールＡ、ビスフェノールＦ、フェノールノボラック樹脂、クレゾールノボラック樹脂、ｐ−キシレン−ノボラック樹脂等のフェノール系硬化剤や、酸無水物類等が挙げられ、２種類以上を併用してもよい。
【００３４】
なお、エポキシ樹脂組成物には硬化反応を促進するために、硬化促進剤の添加が現実的である。含有することができる硬化促進剤としては、例えば、２−メチルイミダゾール、２−エチル−４−メチルイミダゾール、２−フェニルイミダゾール等のイミダゾール類、１，８−ジアザ−ビシクロ［５．４．０］ウンデセン−７、トリエチレンジアミン、ベンジルジメチルアミン等の三級アミン類、トリブチルホスフィン、トリフェニルホスフィン等の有機ホスフィン類、テトラフェニルホスホニウムテトラフェニルボレート、トリフェニルホスフィンテトラフェニルボレート等のテトラフェニルボロン塩等が挙げられ、２種類以上を併用してもよい。
【００３５】
なお、エポキシ樹脂組成物には、必要に応じて無機充填材や、溶剤等を含有することができる。含有することができる無機充填材としては、二酸化チタン系セラミック、チタン酸バリウム系セラミック、チタン酸鉛系セラミック、チタン酸ストロンチウム系セラミック、チタン酸カルシウム系セラミック、チタン酸ビスマス系セラミック、チタン酸マグネシウム系セラミック、ジルコン酸鉛系セラミック等の、誘電率が１００以上の無機充填材や、シリカ粉体、ガラス繊維、タルク等が挙げられ、２種類以上を併用してもよい。誘電率が１００以上の無機充填材を含有すると、高周波特性が特に優れ好ましい。また、含有することができる溶剤としては、トルエン、キシレン、ベンゼン、ケトン、アルコール類等の有機系溶媒が挙げられる。
【００３６】
得られたエポキシ樹脂組成物を、基材に含浸・乾燥してプリプレグを製造する。エポキシ樹脂組成物を、基材に含浸・乾燥する方法としては特に限定するものではなく、例えばエポキシ樹脂組成物中に基材を浸漬して含浸させた後、加熱して溶剤の除去や、エポキシ樹脂組成物を半硬化させてプリプレグを製造する。基材に含浸する樹脂量は特に限定しないが、乾燥後の樹脂含有量が、プリプレグの重量に対して３０〜７０重量％となるように含浸すると、特に電気特性が優れた積層板が得られ好ましい。
【００３７】
なお、含浸時にエポキシ樹脂組成物を２５〜３５℃に保つと、基材への含浸性を安定させることができ、積層板の特性を良好にすることができる。また、エポキシ樹脂組成物を含浸後、乾燥するに当たっては、８０〜１８０℃の温度が好ましい。この乾燥が不十分であると、プリプレグ表面部分のみの乾燥に止まり、溶媒が内部に残留する為にプリプレグの表面と内部との間で樹脂の濃度差に起因する歪が生じ、プリプレグ表面に微細なクラックが発生する場合がある。また、過度の乾燥を行うと、プリプレグ表面では乾燥過程で急激な粘度変化が起こるためにプリプレグ表面に筋むらや樹脂垂れが発生し、金属箔とプリプレグとの密着性にばらつきが生じ、その結果金属箔の引き剥がし強さや誘電特性等にばらつきが発生する場合がある。
【００３８】
なお、エポキシ樹脂組成物を含浸する基材としては、ガラスクロス、アラミドクロス、ポリエステルクロス、ガラス不織布、アラミド不織布、ポリエステル不織布、パルプ紙、リンター紙等が挙げられる。なお、ガラスクロスを用いると、機械強度が優れた積層板が得られ好ましい。なお、基材の厚みとしては０．０４〜０．３ｍｍのものが一般的に使用される。
【００３９】
得られたプリプレグの所定枚数と金属箔を重ねて被圧体とし、この被圧体を加熱・加圧して積層板を製造する。金属箔としては、銅箔、アルミニウム箔等が使用され、厚みとしては、０．０１２〜０．０７０ｍｍのものが一般的に使用される。なお、銅箔を用いると、電気特性が優れた積層板が得られ好ましい。
【００４０】
被圧体を加熱・加圧する条件としては、ＰＰＥで変成した変成フェノール生成物とエポキシ樹脂とエポキシ樹脂の硬化剤の架橋反応は、主としてエポキシ樹脂の硬化剤の反応温度に依存するため、エポキシ樹脂の硬化剤の種類に応じて加熱温度、加熱時間を選ぶとよい。また加圧は、得られる積層板中に気泡が残留しない程度の圧力に適宜調整して加圧する。なお一般には、温度１５０〜３００℃、圧力１〜６ＭＰａ、時間１０〜１２０分程度の条件で加熱・加圧する。
【００４１】
このようにして得られた積層板は、エポキシ樹脂とＰＰＥの特性が損なわれないため、誘電特性等の高周波特性や、はんだ耐熱性、接着強度等が優れると共に、その表面に有する金属箔にボンディングワイヤーを接合した場合に、金属箔とボンディングワイヤーとの接着強度が優れた積層板となる。
【００４２】
なお、本発明のエポキシ樹脂組成物の使用形態は、基材に含浸・乾燥してプリプレグを製造する形態に限るものではなく、たとえばキャスティング法により基材を含まないシートを作成し、このシートをプリプレグに代用することもできる。このキャステング法による方法は、例えばポリエステルフィルム、ポリイミドフィルムなどの、エポキシ樹脂組成物が含有する溶媒に不溶のシートに、エポキシ樹脂組成物を５〜７００μｍの厚みに塗布し、乾燥した後、シートを剥離して製造したり、エポキシ樹脂組成物を熱溶融して押出成形により製造する。シートに塗布して製造する方法の場合、押出成形の方法と比較すると比較的低温でより容易にシー卜を作ることができ好ましい。なお、エポキシ樹脂組成物を塗布するシートは、離型剤で表面処理したシートを用いると剥離が容易になるため生産性が優れ好ましい。
【００４３】
【実施例】
（変成フェノール生成物の調整）
数平均分子量２００００のＰＰＥ［日本Ｇ．Ｅ．プラスチック株式会社製、品番６４０−１１１］、フェノール性化合物としてビスフェノ−ルＡ、反応開始剤として過酸化ベンゾイル及び溶剤としてトルエンを表１に示す割合（単位：重量部）で配合し、９０℃で６０分間攪拌しながら再分配反応させて、液状の変成フェノール生成物（Ａ）〜（Ｇ）を得た。この変成フェノール生成物（Ａ）〜（Ｇ）をゲル浸透クロマトグラフ［カラム構成：東ソー株式会社製、ＳｕｐｅｒＨＭ−Ｍ（１本）＋ＳｕｐｅｒＨＭ−Ｈ（１本）］にて分子量分布を測定し、数平均分子量を求めた。その結果を表１に示す。なお、表１中、分子量比率は、用いたＰＰＥの数平均分子量に対する、得られた変成フェノール生成物の数平均分子量の比率を表す。
【００４４】
【表１】

【００４５】
（実施例１〜１０、比較例１〜５）
上記変成フェノール生成物（Ａ）〜（Ｇ）と、下記３種類のエポキシ樹脂と、エポキシ樹脂の硬化剤としてジアミノジフェニルメタンと、硬化促進剤として２−エチル−４−メチルイミダゾールと、溶剤としてトルエンとを表２に示す割合（単位：重量部）でセパラブルフラスコに配合し、室温で３０分間攪拌して空冷を行い２５℃のエポキシ樹脂組成物を得た。
【００４６】
なお表２中、変成フェノール生成物の配合重量は固形分としての重量を表す。また式（ａ）樹脂比率は、全エポキシ樹脂１００重量部中の式（ａ）樹脂の重量部を表す。
【００４７】
用いたエポキシ樹脂としては、
・エポキシ樹脂１：臭素化ビスフェノールＡ型エポキシ樹脂［東都化成株式会社製、商品名ＹＤＢ５００］（エポキシ当量５００）と、
・エポキシ樹脂２：臭素化ビスフェノールＡ型エポキシ樹脂［東都化成株式会社製、商品名ＹＤＢ４００］（エポキシ当量４００）と、
・エポキシ樹脂３：式（ａ）樹脂［三井石油化学工業株式会社製、商品名ＶＧ３１０１］（エポキシ当量２０９）と、を用いた。
【００４８】
【表２】

【００４９】
次いで、得られたエポキシ樹脂組成物を室温で２４時間保管した後、厚み０．１ｍｍのガラスクロス［旭シュエーベル株式会社製、商品名２１６Ｌ］に含浸し、１４０℃で４分間乾燥して樹脂含有率６５重量％のプリプレグを得た。
【００５０】
得られたプリプレグの両面に１８μｍの銅箔［日鉱グールドフォイル株式会社製、商品名ＪＴＣ］を配置して被圧体とし、温度１９０℃、圧力２ＭＰａの条件で１００分加熱・加圧して両面に銅箔が接着された積層板を得た。
【００５１】
（評価、結果）
得られたエポキシ樹脂組成物の、初期粘度及び保存性を評価した。初期粘度の測定は、Ｂ型粘度計を用いて２５℃で測定し、５００ｃｐｓ以下の場合を良好（○）とし、５００ｃｐｓを越える場合を不良（×）とした。また、保存性の測定は、２５℃で２４時間保存した後、初期粘度と同様にして測定及び判定を行った。
【００５２】
その結果は表２に示したように、各実施例及び比較例１，３，５で得られたエポキシ樹脂組成物は、初期粘度も小さく、析出現象もなく保存性に優れていたが、数平均分子量１７０００の変成フェノール生成物（Ｆ）を用いた比較例２及び４は、初期粘度、保存性とも劣ることが確認された。
【００５３】
また、得られたプリプレグの、外観、取り扱い性及び含浸性を評価した。外観は、スジ状や垂れた形状の外観不具合部の有無を目視で観察し、無しの場合を良好（○）、有りの場合を不良（×）とした。また、取り扱い性は、プリプレグを１８０度折り曲げ、樹脂の脱離の有無を目視で観察し、無しの場合を良好（○）、有りの場合を不良（×）とした。また、含浸性は、切断面を１０００倍でＳＥＭ観察し、内部に気泡が無い場合を良好（○）、わずかに有る場合を△、多数有る場合を不良（×）とした。
【００５４】
その結果は表２に示したように、各実施例及び比較例１，３，５で得られたプリプレグは、数平均分子量１７０００の変成フェノール生成物（Ｆ）を用いた比較例２及び４と比較して、外観、取り扱い性及び含浸性が優れることが確認された。また、変成フェノール生成物の数平均分子量が、１０００〜３０００の範囲内である実施例１〜８は、実施例９，１０と比較して、含浸性が特に優れることが確認された。
【００５５】
また、得られた積層板の、誘電率、誘電正接、はんだ耐熱性、銅箔の引きはがし強さ、及び、銅箔とボンディングワイヤーとの接着強度の評価としてワイヤープル強度を測定した。誘電率及び誘電正接の測定は、ＭＩＬ規格に基づき測定した。はんだ耐熱性及び引きはがし強さは、ＪＩＳ規格Ｃ６４８１に基づき測定した。
【００５６】
ワイヤープル強度は、カイジョー社製のワイヤーボンダー［商品名ＦＢ−１１８Ａ］を用いて、φ３０μｍの金線［田中貴金属工業株式会社製］を積層板表面の銅箔に接合した後、デイジ（Ｄａｇｅ）社製のボンドテスター［商品名ＢＴ２２］を用いて、温度１８０℃、ヘッドスピード０．３ｍｍ／秒の条件で、金線が剥がれる強度を測定した。
【００５７】
その結果は表２に示したように、各実施例で得られた積層板は、式（ａ）樹脂を含有しない比較例１〜３と比較して、ワイヤープル強度が優れることが確認された。
【００５８】
また、各実施例で得られた積層板は、変成フェノール生成物の数平均分子量が用いたＰＰＥの数平均分子量の１０〜７０％の範囲外である比較例２〜５と比較して、はんだ耐熱性が優れることが確認された。また、各実施例で得られた積層板は、誘電率及び誘電正接も優れていることが確認された。
【００５９】
以上の評価結果より、各実施例は、エポキシ樹脂組成物特性、プリプレグ特性、積層板特性の全てが良好であるが、各比較例は、これらの特性のうち少なくとも１つの特性が劣ることが確認された。
【００６０】
【発明の効果】
本発明の請求項１又は請求項２に係るエポキシ樹脂組成物を用いると、誘電率、誘電正接及びはんだ耐熱性を低下することなしに、その表面に有する金属箔にボンディングワイヤーを接合した場合に、金属箔とボンディングワイヤーとの接着強度が優れた金属箔張り積層板が得られる。
【００６１】
本発明の請求項２に係るエポキシ樹脂組成物を用いると、上記の効果に加え、含浸性の優れたプリプレグが得られる。
【００６２】
本発明の請求項３に係るプリプレグを用いると、誘電率、誘電正接及びはんだ耐熱性を低下することなしに、その表面に有する金属箔とボンディングワイヤーを接合した場合に、金属箔とボンディングワイヤーとの接着強度が優れた金属箔張り積層板が得られる。
【００６３】
本発明の請求項４に係る金属箔張り積層板は、誘電率、誘電正接及びはんだ耐熱性が優れると共に、その表面に有する金属箔とボンディングワイヤーを接合した場合に、金属箔とボンディングワイヤーとの接着強度が優れた金属箔張り積層板となる。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to, for example, a laminate used for a printed wiring board used in a high frequency region, a prepreg used for producing the laminate, and an epoxy resin composition used for producing the prepreg.
[0002]
[Prior art]
Laminates used in the manufacture of printed wiring boards used in the X band (8 to 12 GHz) region used for satellite communication and the like, so-called ultra-high frequency regions, have a dielectric constant and a dielectric loss tangent in a wide high frequency range, temperature range and humidity range. Are desired to be constant and preferably have a small dielectric loss tangent. For such applications, lamination using an epoxy resin composition containing an epoxy resin and a polyphenylene ether resin (hereinafter referred to as PPE) is preferred. Boards are used.
[0003]
Conventionally, as a laminated board using an epoxy resin composition containing this epoxy resin and PPE, a cured product of an epoxy resin and a PPE that uses an epoxy resin composition obtained by simply blending an epoxy resin and a PPE is chemically independent. And a laminate made of a cured product of PPE and epoxy resin crosslinked by reacting an epoxy group of an epoxy resin with a terminal hydroxyl group of PPE.
[0004]
Of these, the former laminate is immersed in alkali or chloroform and subjected to an alkali resistance test or a solvent resistance test, which may cause delamination due to insufficient bonding between the epoxy resin and PPE. When the PPE used has a high molecular weight, the reactivity between the terminal phenolic hydroxyl group of the PPE and the epoxy group of the epoxy resin is low, and the unreacted product which does not participate in the crosslinked structure in the cured product. Due to the presence of a large amount of PPE, the problem of low interlayer adhesion strength, and when a solvent resistance test is performed in the same manner as the former laminate, it is superior to the former laminate, but delamination may still occur. There was a problem.
[0005]
Therefore, by reacting a high molecular weight PPE with a phenolic compound in the presence of a reaction initiator such as a peroxide, a modified phenol product modified by PPE having a lower molecular weight than the number average molecular weight of the used PPE is produced. The use of an epoxy resin composition containing the modified phenol product and an epoxy resin to produce a laminate having excellent solvent resistance has been studied. In the case of this laminate, it is considered that PPE is taken into the crosslinked structure in the cured product by the reaction between the phenolic hydroxyl group of the modified phenol product and the epoxy group of the epoxy resin, so that the solvent resistance is excellent.
[0006]
However, after manufacturing a laminate having a layer such as a copper foil on the surface using the epoxy resin composition containing the modified phenol product and the epoxy resin, a bonding wire such as a gold wire is used to connect to a semiconductor chip. When was bonded to the metal foil on the surface of the laminate, the bonding portion between the bonding wire and the metal foil could be peeled off in the evaluation of the bonding strength between the bonding wire and the metal foil during heating, and there was room for improvement.
[0007]
Therefore, when the bonding wire is bonded to the metal foil on its surface without lowering the dielectric constant, dielectric loss tangent, and solder heat resistance, which are the characteristics required for a laminate used in a high frequency region, the bonding is performed. There is a demand for a laminate having excellent adhesive strength at the part.
[0008]
[Problems to be solved by the invention]
The present invention has been made to solve the above problems, and an object thereof is to provide a modified phenol product and an epoxy resin obtained by reacting PPE with a phenolic compound in the presence of a reaction initiator. An epoxy resin composition containing, without lowering the dielectric constant, dielectric loss tangent, and soldering heat resistance, the bonding strength between the metal foil and the bonding wire when the bonding wire is bonded to the metal foil having the surface. The object of the present invention is to provide an epoxy resin composition from which an excellent metal foil-clad laminate can be obtained.
[0009]
Also, when a bonding wire is bonded to a metal foil on its surface without lowering the dielectric constant, dielectric loss tangent, and solder heat resistance, a metal foil-clad laminate having excellent adhesion strength between the metal foil and the bonding wire is provided. It is to provide a prepreg from which a board can be obtained.
[0010]
Another object of the present invention is to provide a laminate having excellent dielectric constant, dielectric loss tangent, and soldering heat resistance, and having excellent bonding strength between a metal foil and a bonding wire when a bonding wire is bonded to a metal foil on the surface thereof. .
[0011]
[Means for Solving the Problems]
The epoxy resin composition according to claim 1 of the present invention is obtained by redistributing a polyphenylene ether resin having a number average molecular weight of 10,000 to 30,000 and a phenolic compound in the presence of a reaction initiator, and using a polyphenylene having a number average molecular weight used. In an epoxy resin composition containing a modified phenol product reacted so as to have a number average molecular weight of 5 to 70% of the ether resin, an epoxy resin and a curing agent for the epoxy resin, the following formula (a) is used as the epoxy resin. The epoxy resin represented by the formula (1) is characterized by containing 1 to 40 parts by weight per 100 parts by weight of the total epoxy resin .
[0012]
Embedded image

[0014]
The epoxy resin composition according to claim 2 of the present invention, the epoxy resin composition according to claim 1, wherein, modified phenol product has a number average molecular weight, characterized in that it is a 1000-3000.
[0017]
A prepreg according to a third aspect of the present invention is obtained by impregnating and drying a substrate with the epoxy resin composition according to the first or second aspect .
[0018]
A metal foil-clad laminate according to a fourth aspect of the present invention is obtained by laminating a metal foil on the prepreg according to the third aspect and applying heat and pressure.
[0019]
According to the present invention, since the epoxy resin composition contains the epoxy resin represented by the above formula (a), it is considered that the high-temperature properties of the cured product of the resin are improved. Thus, a laminate having excellent adhesive strength when heated can be obtained. The epoxy resin represented by the formula (a) crosslinks with the modified phenol product and is incorporated into the crosslinked structure. Therefore, the properties of the epoxy resin and PPE are not impaired, and the dielectric constant, dielectric loss tangent and A laminate having excellent solder heat resistance and the like can be obtained.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
The epoxy resin composition according to claim 1 or 2 of the present invention has a number average molecular weight of 10,000 to 30,000, and a phenolic compound is redistributed in the presence of a reaction initiator, and the number average molecular weight is It contains at least a modified phenol product, an epoxy resin and a curing agent for the epoxy resin, which are reacted so as to have a number average molecular weight of 5 to 70% of the number average molecular weight of the used PPE.
[0021]
The PPE used for the production of the modified phenol product is a resin also called a polyphenylene oxide resin, and an example of which is poly (2,6-dimethyl-1,4-phenylene oxide). Such PPE can be synthesized, for example, by the method disclosed in US Pat. No. 4,059,568.
[0022]
Examples of the phenolic compound used for producing the modified phenol product include bisphenol A, bisphenol F, phenol novolak, and cresol novolak. Note that it is preferable to use a phenol having two or more phenolic hydroxyl groups in the molecule. The upper limit of the number of phenolic hydroxyl groups in the phenols is not particularly limited, but those having 30 or less in the molecule are generally used. The appropriate amount of the phenolic compound is 1 to 20 parts by weight based on 100 parts by weight of PPE, and is generally the same as the amount of the reaction initiator.
[0023]
Benzoyl peroxide, dicumyl peroxide, t-butylcumyl peroxide, di-t-butylperoxide, 2,5-dimethyl-2,5-dioxane may be used as a reaction initiator for producing the modified phenol product. -T-butylperoxyhexine-3, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, α, α'-bis (t-butylperoxy-m-isopropyl) benzene, etc. Peroxides. Although it is not a peroxide, a commercially available reaction initiator, trade name "Biscumil" (1 minute half-life temperature 330 ° C.) manufactured by NOF Corporation can also be used. The use of benzoyl peroxide is preferred because of its excellent reactivity. The appropriate amount of the reaction initiator is 1 to 20 parts by weight based on 100 parts by weight of PPE.
[0024]
In the case of producing a modified phenol product, the above-mentioned PPE and the phenolic compound are redistributed in an organic solvent in the presence of a reaction initiator, so that the PPE used has a lower molecular weight than the number average molecular weight of the used PPE. Produce a phenol product. The redistribution reaction is performed, for example, by heating the PPE, the phenolic compound, and the reaction initiator at 80 to 120 ° C. for about 10 to 100 minutes with stirring. In addition, as the organic solvent to be used, aromatic hydrocarbon solvents such as toluene, benzene, and xylene are given.
[0025]
When a phenolic compound is reacted with a PPE having a number average molecular weight of 10,000 to 30,000 in the presence of a reaction initiator, it is considered that the PPE is radicalized first, and a redistribution reaction in which a straight chain is cut proceeds to form the PPE. Has a low molecular weight, and the phenolic compound is modified by the low molecular weight PPE.
[0026]
Then, the structure of the resulting modified phenol product is considered to be a structure having a phenolic hydroxyl group at one or both terminals of the PPE by binding a phenolic compound to one or both terminals of the low molecular weight PPE. Therefore, it is considered that this terminal phenolic hydroxyl group reacts with the epoxy group of the epoxy resin, and the PPE and the epoxy resin are strongly crosslinked.
[0027]
It is important that the number average molecular weight of the modified phenol product obtained by the redistribution reaction is 5 to 70% of the number average molecular weight of the PPE used. If it exceeds 70%, the viscosity of the epoxy resin composition increases, the impregnation property when impregnating the base material decreases, the amount of adhered resin of the obtained prepreg varies, or the resin is peeled off when the prepreg is handled and the resin is removed. Variations in the amount of adhesion and variations in electrical properties may occur, and the shelf life of the epoxy resin composition may decrease and the viscosity tends to increase in a short period of time. As a result, the problem that production is likely to be hindered is likely to occur. If it is less than 5%, the mechanical strength and heat resistance of the obtained laminate may decrease.
[0028]
When the number average molecular weight of the modified phenol product is 5 to 70% of the number average molecular weight of the used PPE and is in the range of 1000 to 3000, the obtained epoxy resin composition is used as a base material. In particular, the impregnating property when impregnating is preferred.
[0029]
When the PPE used is a mixture of a plurality of PPEs having a number average molecular weight, the reaction is performed so that the number average molecular weight is 5 to 70% with respect to the average value of the mixture. In addition, the number average molecular weight of the modified phenol product to be obtained is preferably adjusted with the amount of the reaction initiator since the number average molecular weight tends to decrease when the amount of the reaction initiator is increased.
[0030]
It is important that the epoxy resin contained in the epoxy resin composition contains an epoxy resin represented by the above formula (a) (hereinafter, referred to as a formula (a) resin). When not containing the resin of the formula (a), a laminate having a metal foil layer on the surface is manufactured using this epoxy resin composition, and a bonding wire is bonded to the metal foil on the surface of the laminate. When the evaluation of the adhesive strength with the metal foil is performed, there is a case that the bonding wire and the metal foil are separated from each other. The resin of the formula (a) is 2- [4- (2,3-epoxypropoxy) phenyl] -2- [4- [1,1-bis [4- (2,3-epoxypropoxy) phenyl]]. Ethyl] phenyl] propane is commonly named.
[0031]
The epoxy resin contained in the epoxy resin composition is not limited to the resin of the formula (a), but may also contain an epoxy resin having two epoxy groups in the molecule. Is preferably contained in an amount of 1 to 40 parts by weight per 100 parts by weight of the total epoxy resin, because a laminate having excellent heat resistance as well as excellent adhesive strength between the metal foil and the bonding wire can be obtained. If the amount is less than 1 part by weight, the effect of improving the bonding strength between the metal foil and the bonding wire is small, and if it exceeds 40 parts by weight, the moisture absorption rate is increased and the solder heat resistance may be reduced.
[0032]
Examples of the epoxy resin that can be contained include bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, hydantoin type epoxy resin, alicyclic epoxy resin, and biphenyl type epoxy resin. Examples thereof include resins and epoxy resins having two epoxy groups in a molecule such as epoxy resins obtained by halogenating these resins. Two or more epoxy resins may be used in combination. An epoxy resin having one epoxy group in the molecule or an epoxy resin having three or more epoxy groups in the molecule other than the resin of formula (a) such as a novolak type epoxy resin can also be used in combination.
[0033]
As the curing agent for the epoxy resin contained in the epoxy resin composition, for example, amide-based curing agents such as dicyandiamide and aliphatic polyamide, amine-based curing agents such as diaminodiphenylmethane, metaphenylenediamine, ammonia, triethylamine, diethylamine, and bisphenol A, bisphenol F, phenol novolak resin, cresol novolak resin, phenolic curing agents such as p-xylene-novolak resin, and acid anhydrides, and the like, and two or more kinds may be used in combination.
[0034]
In addition, it is realistic to add a curing accelerator to the epoxy resin composition in order to accelerate the curing reaction. Examples of the curing accelerator that can be contained include imidazoles such as 2-methylimidazole, 2-ethyl-4-methylimidazole, and 2-phenylimidazole, and 1,8-diaza-bicyclo [5.4.0]. Tertiary amines such as undecene-7, triethylenediamine and benzyldimethylamine; organic phosphines such as tributylphosphine and triphenylphosphine; and tetraphenylboron salts such as tetraphenylphosphonium tetraphenylborate and triphenylphosphinetetraphenylborate. And two or more of them may be used in combination.
[0035]
The epoxy resin composition may contain an inorganic filler, a solvent, and the like, if necessary. As inorganic fillers that can be contained, titanium dioxide-based ceramics, barium titanate-based ceramics, lead titanate-based ceramics, strontium titanate-based ceramics, calcium titanate-based ceramics, bismuth titanate-based ceramics, magnesium titanate-based ceramics Examples include inorganic fillers having a dielectric constant of 100 or more, such as ceramics and lead zirconate-based ceramics, silica powder, glass fiber, and talc. Two or more kinds may be used in combination. When an inorganic filler having a dielectric constant of 100 or more is contained, high-frequency characteristics are particularly excellent and are preferable. Examples of the solvent that can be contained include organic solvents such as toluene, xylene, benzene, ketone, and alcohols.
[0036]
The obtained epoxy resin composition is impregnated into a substrate and dried to produce a prepreg. The method of impregnating and drying the epoxy resin composition on the substrate is not particularly limited.For example, after the substrate is immersed and impregnated in the epoxy resin composition, the solvent is removed by heating, The prepreg is manufactured by semi-curing the resin composition. The amount of resin impregnated in the base material is not particularly limited, but if the resin content after drying is impregnated so as to be 30 to 70% by weight with respect to the weight of the prepreg, a laminate having particularly excellent electrical properties can be obtained. preferable.
[0037]
In addition, when the epoxy resin composition is kept at 25 to 35 ° C. during the impregnation, the impregnation property to the base material can be stabilized, and the characteristics of the laminate can be improved. In addition, when the epoxy resin composition is impregnated and dried, the temperature is preferably from 80 to 180 ° C. If the drying is insufficient, only the surface of the prepreg will be dried, and the solvent will remain inside, causing distortion due to the difference in resin concentration between the surface and the inside of the prepreg. Cracks may occur. Also, if excessive drying is performed, the viscosity of the prepreg surface changes rapidly during the drying process, causing uneven streaks and resin dripping on the prepreg surface, resulting in uneven adhesion between the metal foil and the prepreg, and as a result, Variations may occur in the peel strength, dielectric properties, and the like of the metal foil.
[0038]
The substrate impregnated with the epoxy resin composition includes glass cloth, aramid cloth, polyester cloth, glass nonwoven fabric, aramid nonwoven fabric, polyester nonwoven fabric, pulp paper, linter paper, and the like. In addition, it is preferable to use a glass cloth because a laminated plate having excellent mechanical strength can be obtained. In addition, as a thickness of the base material, a thickness of 0.04 to 0.3 mm is generally used.
[0039]
A predetermined number of the obtained prepregs and a metal foil are overlapped to form a pressure body, and the pressure body is heated and pressed to produce a laminate. As the metal foil, a copper foil, an aluminum foil, or the like is used, and a thickness of 0.012 to 0.070 mm is generally used. In addition, it is preferable to use a copper foil because a laminate having excellent electric characteristics can be obtained.
[0040]
As the conditions for heating and pressurizing the pressurized body, the cross-linking reaction between the modified phenol product denatured by PPE, the epoxy resin, and the curing agent for the epoxy resin mainly depends on the reaction temperature of the curing agent for the epoxy resin. The heating temperature and the heating time may be selected according to the type of the curing agent. The pressure is appropriately adjusted to a pressure at which no air bubbles remain in the obtained laminate, and the pressure is applied. In general, heating and pressurization are performed at a temperature of 150 to 300 ° C., a pressure of 1 to 6 MPa, and a time of about 10 to 120 minutes.
[0041]
The laminate thus obtained does not impair the properties of the epoxy resin and PPE, so it has excellent high-frequency properties such as dielectric properties, solder heat resistance, adhesive strength, etc., and is bonded to the metal foil on its surface. When the wires are joined, a laminate having excellent adhesion strength between the metal foil and the bonding wires is obtained.
[0042]
The use form of the epoxy resin composition of the present invention is not limited to a form in which a prepreg is manufactured by impregnating and drying a base material.For example, a sheet containing no base material is prepared by a casting method, and this sheet is formed. Prepreg can be substituted. The method according to this casting method is, for example, a polyester film, a polyimide film, etc., to a sheet insoluble in the solvent contained in the epoxy resin composition, apply the epoxy resin composition to a thickness of 5 to 700 μm, after drying, the sheet It is manufactured by exfoliation, or manufactured by extrusion molding by hot-melting an epoxy resin composition. In the case of the method of manufacturing by applying to a sheet, the sheet can be easily formed at a relatively low temperature as compared with the extrusion molding method, which is preferable. Note that the sheet to which the epoxy resin composition is applied is preferably excellent in productivity because the use of a sheet surface-treated with a release agent facilitates peeling.
[0043]
【Example】
(Preparation of modified phenol product)
PPE having a number average molecular weight of 20,000 [G. E. FIG. Plastics Co., Ltd., product number 640-111], bisphenol A as a phenolic compound, benzoyl peroxide as a reaction initiator, and toluene as a solvent at a ratio shown in Table 1 (unit: parts by weight), and mixed at 90 ° C. A redistribution reaction was performed with stirring for 60 minutes to obtain liquid modified phenol products (A) to (G). The denatured phenol products (A) to (G) were subjected to gel permeation chromatography [column configuration: Super HM-M (1) + Super HM-H (1), manufactured by Tosoh Corporation] to measure the molecular weight distribution. The average molecular weight was determined. Table 1 shows the results. In Table 1, the molecular weight ratio indicates the ratio of the number average molecular weight of the obtained modified phenol product to the number average molecular weight of the used PPE.
[0044]
[Table 1]

[0045]
(Examples 1 to 10, Comparative Examples 1 to 5)
The modified phenol products (A) to (G), the following three types of epoxy resins, diaminodiphenylmethane as a curing agent for the epoxy resin, 2-ethyl-4-methylimidazole as a curing accelerator, and toluene as a solvent. Was mixed in a separable flask in the ratio (unit: parts by weight) shown in Table 2, and the mixture was stirred at room temperature for 30 minutes and air-cooled to obtain an epoxy resin composition at 25 ° C.
[0046]
In Table 2, the blended weight of the modified phenol product represents the weight as a solid content. The formula (a) resin ratio represents the weight part of the formula (a) resin in 100 parts by weight of the total epoxy resin.
[0047]
As the epoxy resin used,
Epoxy resin 1: brominated bisphenol A type epoxy resin [YDB500 (trade name, manufactured by Toto Kasei Co., Ltd.) (epoxy equivalent 500);
Epoxy resin 2: brominated bisphenol A-type epoxy resin [YDB400 (trade name, manufactured by Toto Kasei Co., Ltd.) (epoxy equivalent: 400);
Epoxy resin 3: A resin of the formula (a) [trade name VG3101 manufactured by Mitsui Petrochemical Industry Co., Ltd. (epoxy equivalent: 209)] was used.
[0048]
[Table 2]

[0049]
Next, after storing the obtained epoxy resin composition at room temperature for 24 hours, it is impregnated with a 0.1 mm-thick glass cloth [trade name: 216L, manufactured by Asahi Schwebel Co., Ltd.] and dried at 140 ° C. for 4 minutes to contain the resin. A prepreg having a ratio of 65% by weight was obtained.
[0050]
An 18 μm copper foil [manufactured by Nippon Gould Foil Co., Ltd., trade name: JTC] is placed on both sides of the obtained prepreg to form a pressure body, and heated and pressed at a temperature of 190 ° C. and a pressure of 2 MPa for 100 minutes to apply pressure to both sides. A laminate having a copper foil bonded thereto was obtained.
[0051]
(Evaluation results)
The initial viscosity and storage stability of the obtained epoxy resin composition were evaluated. The initial viscosity was measured at 25 ° C. using a B-type viscometer. When the viscosity was 500 cps or less, it was evaluated as good (○), and when it exceeded 500 cps, it was evaluated as poor (x). The storage stability was measured and determined in the same manner as the initial viscosity after storing at 25 ° C. for 24 hours.
[0052]
As shown in Table 2, the epoxy resin compositions obtained in Examples and Comparative Examples 1, 3, and 5 had a small initial viscosity, had no precipitation phenomenon, and had excellent storage stability. It was confirmed that Comparative Examples 2 and 4 using the modified phenol product (F) having an average molecular weight of 17000 were inferior in both initial viscosity and storage stability.
[0053]
The appearance, handleability and impregnation of the obtained prepreg were evaluated. The appearance was visually observed for the presence or absence of a streak-like or sagging appearance defect, and the absence was evaluated as good (（), and the existence was evaluated as poor (x). The handling property was determined by bending the prepreg by 180 degrees, visually observing the presence or absence of resin detachment, and determining good (無 し) when no resin was present and poor (x) when present. The impregnating property was observed by a SEM observation of the cut surface at a magnification of 1000 times. The case where there was no air bubble inside was good (に), the case where there was a small amount was Δ, and the case where there were many bubbles was bad (×).
[0054]
As shown in Table 2, the prepregs obtained in each Example and Comparative Examples 1, 3, and 5 were compared with Comparative Examples 2 and 4 using the modified phenol product (F) having a number average molecular weight of 17000. In comparison, it was confirmed that the appearance, handleability and impregnation were excellent. Further, it was confirmed that Examples 1 to 8 in which the number average molecular weight of the modified phenol product was in the range of 1000 to 3000 had particularly excellent impregnation properties as compared with Examples 9 and 10.
[0055]
The obtained laminate was measured for dielectric constant, dielectric loss tangent, solder heat resistance, peel strength of copper foil, and wire pull strength as an evaluation of the adhesive strength between the copper foil and the bonding wire. The dielectric constant and the dielectric loss tangent were measured based on the MIL standard. Solder heat resistance and peel strength were measured based on JIS standard C6481.
[0056]
The wire pull strength was measured using a wire bonder [trade name: FB-118A] manufactured by Kaijo Co., Ltd., after joining a 30-μm-diameter gold wire [manufactured by Tanaka Kikinzoku Kogyo Co., Ltd.] to the copper foil on the surface of the laminate, and then using a daiage (Dage). Using a bond tester (trade name: BT22) manufactured by Co., Ltd., the strength at which the gold wire was peeled was measured at a temperature of 180 ° C. and a head speed of 0.3 mm / sec.
[0057]
As a result, as shown in Table 2, it was confirmed that the laminates obtained in each example had excellent wire pull strength as compared with Comparative Examples 1 to 3 not containing the resin of the formula (a). .
[0058]
In addition, the laminate obtained in each of the examples has a solder heat resistance in comparison with Comparative Examples 2 to 5, in which the number average molecular weight of the modified phenol product is out of the range of 10 to 70% of the number average molecular weight of the PPE used. Was confirmed to be excellent. Further, it was confirmed that the laminates obtained in each of the examples were also excellent in dielectric constant and dielectric loss tangent.
[0059]
From the above evaluation results, it was confirmed that each of the examples had good epoxy resin composition properties, prepreg properties, and laminated board properties, but each comparative example was inferior in at least one of these properties. Was done.
[0060]
【The invention's effect】
When the epoxy resin composition according to claim 1 or 2 of the present invention is used, a bonding wire is bonded to a metal foil having a surface without reducing the dielectric constant, dielectric loss tangent and solder heat resistance. Thus, a metal foil-clad laminate having excellent adhesion strength between the metal foil and the bonding wire can be obtained.
[0061]
When the epoxy resin composition according to claim 2 of the present invention is used, a prepreg excellent in impregnation property in addition to the above effects can be obtained.
[0062]
When the prepreg according to claim 3 of the present invention is used, without lowering the dielectric constant, the dielectric loss tangent and the soldering heat resistance, when the metal foil and the bonding wire having the surface are joined, the metal foil and the bonding wire A metal foil-clad laminate having excellent adhesive strength can be obtained.
[0063]
The metal foil-clad laminate according to claim 4 of the present invention has excellent dielectric constant, dielectric loss tangent and soldering heat resistance, and when the metal foil and the bonding wire on the surface are joined, the metal foil and the bonding wire It becomes a metal foil-clad laminate with excellent adhesive strength.

Claims (4)

The polyphenylene ether resin having a number average molecular weight of 10,000 to 30,000 and a phenolic compound are redistributed in the presence of a reaction initiator so that the number average molecular weight becomes 5 to 70% of the number average molecular weight of the used polyphenylene ether resin. In the epoxy resin composition containing the modified phenol product reacted with the above, an epoxy resin and a curing agent for the epoxy resin, the epoxy resin represented by the following formula (a) is used as the epoxy resin in 100 parts by weight of the total epoxy resin. 1 to 40 parts by weight of an epoxy resin composition.

The epoxy resin composition according to claim 1 , wherein the modified phenol product has a number average molecular weight of 1,000 to 3,000. A prepreg obtained by impregnating and drying a substrate with the epoxy resin composition according to claim 1 . A laminate obtained by laminating a metal foil on the prepreg according to claim 3 and heating and pressing the laminate.