JP4228652B2 - Circuit connection material and circuit connection method using the connection material - Google Patents

Description

化２中、Ｒ^１がＲ^２及びＲ^３よりも電子吸引性の高い基であり、Ｒ^１、Ｒ^２及びＲ^３は、置換又は非置換の基であり、互いに同じでも異なっていてもよく、Ｙ⁻は、非求核性陰イオンである。
【００１３】
【発明の実施の形態】
Ｒ¹としては、カチオン重合の開始剤として推定されるベンジルカチオンを発生させるために、電子吸引性の基、例えば、ニトロソ基、カルボニル基、カルボキシル基、シアノ基、トリアルキルアンモニウム基、フルオロメチル基などが好ましく、Ｒ²及びＲ³としては、電子供与性の基、例えば、アミノ基、水酸基、メチル基などが好ましい。Ｙ⁻は、非求核性陰イオンであればよく、例えば、ヘキサフルオロアルセネート（ＡｓＦ₆ ）、ヘキサクロロアンチモネート（ＳｂＣｌ₆ ）、ヘキサフルオロホスフェート（ＰＦ₆ ）、テトラフルオロボレート（ＢＦ₄ ）が挙げられる。
【００１４】
これらのスルホニウム塩は１４０℃以下の温度で活性化し、カチオン重合を引き起こすことができ、かつ室温（２５℃）においてカチオン重合性物質の存在下で、１０時間以上経過後の反応性接着剤の粘度が、初期粘度の２倍以下である。また、これらのスルホニウム塩は必要に応じて溶解可能な各種溶媒（例えば酢酸エチル）に溶解して使用できる。スルホニウム塩の配合量は、接着成分１００重量部に対して０．０５〜１０重量部とする。接着成分１００重量部に対して、１．５〜５重量部とするのが特に好ましい。配合量が多いと、電食の原因となりやすく、また、硬化反応が爆発的に進行するので望ましくない。
【００１５】
接着成分中に分散させる導電性粒子としては、加熱加圧又は単なる加圧により変形するものが好ましい。導電性粒子が変形することにより、接続時に回路との接触面積が増加し、接続信頼性が向上し、回路の厚みや平坦性のばらつき、回路が突起したものとそうでないものが混在しているときでも、良好な接続が行える。この変形は、導電性粒子自体が変形するもの、導電性粒子が凝集体を形成していて、接続時に凝集状態を変えるものいずれでもよい。
【００１６】
導電性粒子としては、Ａｕ、Ａｇ、Ｎｉ、Ｃｕ、Ｓｂ、Ｓｎ、はんだなどの金属粒子や、カーボンなど導電性を有する物質の粒子、これらの粒子又は非導電性のガラス、セラミックス、プラスチック粒子を核として表面に他の導電性材料を被覆したものがある。更に、導電性粒子を核とし、この核の表面を絶縁層で被覆し、加圧したときに内部の核が絶縁層を破って接触するようにしたものも有効である。このような導電性粒子を用いると、加圧方向に直角方向の絶縁性が確保され、回路間の狭い細線回路の接続に極めて有効である。導電性粒子の粒径は、回路中で隣接する線間距離よりも小さくないと、隣接回路間を短絡させる。また、接続時の加圧により変形して、横に拡がることも考慮して、導電性粒子の粒径は１〜１８μｍであるのが好ましい。必要により、絶縁粒子を、導電性粒子間の接触を妨げない程度に併用してもよい。
【００１７】
導電性粒子の配合量は、接着時に、加圧方向にのみ導電性を生ずる程度とするのが好ましい。回路中で、隣接する線間距離や導電性粒子の径によって異なるが、接着成分に対して、０．０５〜２０体積％の範囲、好ましくは、０．１〜１５体積％、より好ましくは、０．２〜１０体積％とする。２０体積％をこえると、透明性が悪化し、接続する回路の位置合わせが困難となる。０．０５体積％より少ないと導電性を得られない。
【００１８】
接着成分の１００℃における溶融粘度が、１〜１，０００Ｐａ・ｓ、特に、１０〜１，０００Ｐａ・ｓである場合に、接着成分がよく流動して接続厚みが導電性粒子の径よりも小さくなる。１，０００Ｐａ・ｓ以上であると、流動性が悪く接続厚みが導電性粒子の径よりも厚くなり接続性が悪い。１〜１０Ｐａ・ｓの範囲であるときには、初期に圧力を小さくし、接着成分がある程度硬化してから圧力を高めるなどの注意が必要となる。１Ｐａ・ｓ以下では、流動しすぎて成着成分が接続部外に流れ出し、接続部分に保持されにくく、信頼性が悪くなる。溶融粘度の調整については、後述する。
【００１９】
接着成分中のスルホニウム塩をマイクロカプセル化すると接着成分の貯蔵安定性がよくなる。カチオン重合性物質とスルホニウム塩とが貯蔵中に互いに接触しないためである。マイクロカプセル化する方法は、溶剤蒸発法、スプレードライ法、コアセルベーション法、界面重合法、などとくに制限はない。マイクロカプセルの粒径は小さいほうがよく、スルホニウム塩は疎水性であるので、界面重合法によるのが好ましい。
【００２０】
接着成分中、カチオン重合性物質としては、エポキシ樹脂、ポリビニルエーテル、ポリスチレンなどがあり、これらは、単独で用いてもよく、併用してもよい。また、他のポリマーや重量平均分子量３０００以下の固形樹脂と混合して用いることもできる。
【００２１】
前記カチオン重合性物質のうち、エポキシ樹脂がもっとも好適である。エポキシ樹脂は、１分子中に２個以上のエポキシ基を有する化合物であり、例えば、エピクロルヒドリンとビスフェノールＡ又はビスフェノールＦなどから誘導されるビスフェノール型エポキシ樹脂や、ポリグリシジルエーテル、ポリグリシジルエステル、脂還式エポキシ樹脂などが挙げられる。
【００２２】
カチオン重合性物質と混合可能なポリマーとしては、ポリビニルアセタール、フェノキシ樹脂、ポリエチレンテレフタレート、ポリウレタンなどや、塩化ビニル、オレフィン、エチレン系アイオノマー、ポリアミド系などのポリマー類がある。フィルム形成性や溶融時の流動性、樹脂相互の溶解性を考慮して、これらのポリマーの分子量は１０，０００以上８０，０００以下が好ましい。また、水酸基（ＯＨ基）やカルボキシル基（ＣＯＯＨ基）などの極性基を有すると、エポキシ樹脂との相溶性が向上し均一な外観や特性を有するフィルムが得られ、かつ、エポキシ基との反応性を有するので好ましい。
【００２３】
重量平均分子量３０００以下の固形樹脂としては、ロジンやテルペンなどの天然物系樹脂、脂肪族、脂環族、芳香族、クマロン・インデン・スチレン系などの重合系樹脂、フェノール樹脂やキシレン樹脂などの縮合系樹脂など、及び、これらの変性体や誘導体がある。重量平均分子量３０００以下の固形樹脂は、粘着性や接着性などの調整する必要がある場合に、単独で、又は、混合して用いる。
【００２４】
前記化２で表されるスルホニウム塩は常温で安定であり、かつカチオン重合性物質を１１０℃〜１４０℃では１０〜６０秒、１３０℃〜２００℃では１〜３０秒の加熱で活性化して硬化する。さらに接着成分の溶融粘度を１００℃で１〜１，０００Ｐａ・ｓにすることで、０．５〜５ＭＰａの加圧により接着成分の好適な流動が得られ、導電性粒子を介した回路導体間の接続が得られる。したがって、粘着成分の常温での保存安定性がよく、かつ基板材料に熱的なダメージを与えることなく粘着硬化でき、回路の接続が得られる。
【００２５】
【実施例】
以下、実施例で、より詳細に説明するが、本発明はこれに限定されるものではない。
実施例１
ビスフェノールＡ型液状エポキシ樹脂（油化シェル株式会社、商品名エピコート８２８を使用）５０ｇ、平均分子量２５，０００、水酸基含有量６％のフェノキシ樹脂（ユニオンカーバイト株式会社、商品名ＰＫＨＡを使用）５０ｇを、重量比でトルエン対酢酸エチル１対１の混合溶剤に溶解して、固形分４０％の溶液とした。
【００２６】
ポリスチレンを核とする粒子の表面に、厚み０．２μｍのニッケル層を設け、このニッケル層の外側に、厚み０．０２μｍの金層を設け、平均粒径１０μｍ、比重２．０の導電性粒子を製造した。
【００２７】
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩を酢酸エチルに溶解して、５０重量％溶液とした。
【００２８】
固形重量比で樹脂成分１００、ｐ−アセトキシフェニルジルベンジルメチルスルホニウム塩２となるように配合し、更に、導電性粒子を２体積％配合分散させ、厚み８０μｍのフッ素樹脂フィルムに塗布し、室温で送風乾燥して、厚み２５μｍのフィルム状回路接続材料を得た。
【００２９】
実施例２
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩に代えて、ｐ−メトキシカルボニルオキシフェニルベンジルエチルスルホニウム塩を使用したほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００３０】
実施例３
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩に代えて、ｐ−ヒドロキシフェニルベンジルメチルスルホニウム塩を使用したほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００３１】
実施例４
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩に代えて、ｐ−ヒドロキシフェニル−ｐ−ニトロベンジルメチルスルホニウム塩を使用したほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００３２】
実施例５
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩の配合量を０．２重量部としたほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００３３】
実施例６
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩の配合量を１０重量部としたほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００３４】
実施例７
ビスフェノールＡ型液状エポキシ樹脂に代えて、脂環式エポキシ樹脂（ダイセル化学工業株式会社、商品名セロキサイド２０２１を使用）を使用したほかは、実施例１と同様にしてフィルム状回路用接続材料を得た。
【００３５】
実施例８
ビスフェノールＡ型液状エポキシ樹脂に代えて、ビスフェノールＡ型固形エポキシ樹脂（油化シェルエポキシ株式会社、商品名エピコート１００１を使用）を使用したほかは、実施例１と同様にしてフィルム状回路用接続材料を得た。
【００３６】
実施例９
ビスフェノールＡ型液状エポキシ樹脂に代えて、アクリル樹脂（昭和高分子株式会社、商品名リポキシＳＤ−１５０９を使用、グリシジルアクリレート）を使用したほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００３７】
実施例１０
導電性粒子の量を０．５体積％としたほかは実施例１と同様にしてフィルム状回路接続材料を得た。
【００３８】
実施例１１
導電性粒子の量を５体積％としたほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００３９】
実施例１２
導電性粒子の径を３μｍとしたほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００４０】
実施例１３
導電性粒子を、平均単粒径２μｍ、凝集粒径１０μｍのニッケル粒子に代えたほかは実施例１と同様にしてフィルム状回路接続材料を得た。
【００４１】
実施例１４
導電性粒子を、平均単粒径２μｍ、凝集粒径１０μｍのニッケル粒子を０．５体積％とし、粒径２μｍのシリカ粒子を０．５体積％加えたほかは実施例１同様にしてフィルム状回路接続材料を得た。
【００４２】
実施例１５
ビスフェノールＡ型液状エポキシ樹脂（エピコート８２８）を７０ｇとし、フェノキシ樹脂（ユニオンカーバイト株式会社、商品名ＰＫＨＡを使用）の配合量を３０ｇとしたほかは実施例１と同様にしてフィルム状回路接続材料を得た。
【００４３】
実施例１６
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩１０重量部、メタクリル酸メチル１６重量部、スチレン１６重量部、エチレングリコールジメタクリレート８重量部、アゾ化合物０．０５重量部（和光純薬株式会社製Ｖ−６０、Ｖ−４０各０．０２５重量部）をＡ成分とし、水２００重量部、ドデシルベンゼンスルフォン酸ナトリウム０．２重量部、ポリビニルアルコール０．１２５重量部をＢ成分とし、チッ素雰囲気の密封容器中６０℃で、４時間撹拌し、乾燥してスルホニウム塩をマイクロカプセル化した。以下実施例１と同様にしてフィルム状回路接続材料を得た。
【００４４】
比較例１
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩に代えて、ｐ−ヒドロキシフェニルジメチルスルホニウム塩（ベンジル基のないスルホニウム塩）を使用したほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００４５】
比較例２
ｐ−アセトキシフェニルベンジルメチルスルホニウム塩に代えて、１−シアノエチル−２−メチルイミダゾールを使用したほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００４６】
比較例３
導電性粒子を配合しないほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００４７】
比較例４
導電性粒子の径が２０μｍを用いたほかは、実施例１と同様にしてフィルム状回路接続材料を得た。
【００４８】
比較例５
ビスフェノールＡ型液状エポキシ樹脂（エピコート８２８）を２０ｇとし、フェノキシ樹脂（ＰＫＨＡ）を８０ｇとしたほかは実施例１と同様にしてフィルム状回路接続材料を得た。
【００４９】
ＤＳＣの測定
以上得られたフィルム状回路接続材料を３ｍｇ（±０．１ｍｇ）秤りとり、密閉式アルミパン中で昇温速度１０℃／分でＤＳＣを測定した。用いた分析計は、デュポン社製ＴＡ２０００である。
【００５０】
溶融粘度の測定
実施例１、１５、比較例で、ビスフェノールＡ型液状エポキシ樹脂（エピコート８２８）とフェノキシ樹脂（ＰＫＨＡ）を溶剤に溶解せず２５０℃近辺で溶融し、均一に混合した後、１０ｇ程度を分取し、徐々に冷却し、１００℃での粘度を測定した。このとき硬化剤、導電性粒子は配合しなかった。測定に用いた装置は（株）レスカ製デジタル粘度計ＨＵ−８である。
【００５１】
回路の接続
実施例１〜１６、比較例１〜５のフィルム状回路接続材料を用いてライン幅１００μｍ、ピッチ２００μｍ、厚み３５μｍの銅回路を２５０本有するフレキシブル回路板（ＦＰＣ）と、全面に酸化インジウム（ＩＴＯ）の薄層を形成（表面抵抗４０Ω／□）した、厚み０．５ｍｍのポリカーボネート板（ＡＳＴＭ Ｄ６４８、１．８６ＭＰａでの熱変形温度１４０℃）とを、１３０℃、１．５ＭＰａで２０秒間加熱加圧して幅３ｍｍにわたり接続した。このとき、あらかじめポリカーボネート板上に、フィルム状回路用接続材料の接着剤面を貼り付け後、７０℃、０．５ＭＰａ、５秒間加熱加圧して仮接続し、その後フッ素樹脂フィルムを剥離してＦＰＣと接着した。また、ライン幅１００μｍ、ピッチ２００μｍ厚み３５μｍの銅回路を２５０本有するＦＰＣとＩＴＯの薄層形成したガラス（表面抵抗２０Ω／□）とを、１６０℃、１．５ＭＰａで１０秒間加熱加圧して幅３ｍｍにわたり接続した。このとき上記と同様にＩＴＯガラス上に仮接続を行った。
【００５２】
接続抵抗の測定
回路の接続後、接続部を含むＦＰＣの隣接回路間の抵抗値を、初期と、８５℃、８５％ＲＨの高温高湿下に５００時間保持した後にマルチメータで測定した。
【００５３】
保存安定性
フィルム状回路接続材料を配合溶液のままで、溶剤が揮発しないように密封して、２５℃に放置し、溶液粘度が２倍になった時間を調べた。
【００５４】
接続厚みの測定
ＩＴＯの薄層を形成した基板とＦＰＣの厚みをマイクロメータによりあらかじめ測定しておき、フィルム状回路接続材料により接続後厚みを測定し、接続厚みを算出した。
【００５５】
これらの測定結果を表１及び表２に示す。この結果から、以下のことがわかる。
【００５６】
各実施例について、ＤＳＣのピーク温度は、１００〜１２０℃であり、比較例１及び２のそれよりも１０〜２０℃低い。特に、実施例７の接着剤は、ＤＳＣのピーク温度が、実施例１のそれよりも１０℃低く、接続抵抗の上昇も見られず、良好な接続が得られている。また、各実施例について、初期の抵抗値は、比較例１及び２のそれよりも著しく低く、高温高湿下に保持した後の接続抵抗の上昇も見られないか、小さい値である。比較例１，２は反応不足であったためと考える。実施例８の接続材料は、ＤＳＣのピーク温度が１２０℃と高く、接続抵抗の上昇も若干大きくなっている。この理由は、固形エポキシ樹脂を用いたので、反応性が若干低下したためと考えられる。比較例３は導電性粒子がないので、初期の抵抗も高く、接続抵抗の上昇も著しい。比較例４は導電性粒子が２０μｍと大きいため、２体積％では接続部の導電性粒子数が少なくなったため、若干高い抵抗値となった。導電性粒子として、平均単粒径２μｍで凝集径１０μｍのニッケル粒子を用いた実施例１０のフィルム状接続材料も、実施例１のフィルム状接続材料と同様に、良好な接続がえられている。ニッケル粒子と粒径２μｍのシリカ粒子を体積比で１対１で混合したものを配合した実施例１１の接着剤も、実施例１と同様に良好な接続が得られ、特に、ニッケル粒子の間にシリカ粒子が存在して、隣接回路との絶縁性を良好にしていることがわかった。実施例１及び実施例１５のフィルム状接続材料は、１００℃の溶融粘度が１〜１，０００Ｐａ・ｓの範囲内にあり、接続厚みも導電性粒子の粒径以下になっているが、比較例５のフィルム状接続材料は、溶融粘度が高く、接着成分が十分に流動する前に硬化してしまい、接続厚みが導電性粒子の粒径よりも大きくなった。そのため、接続抵抗は大きくなり、上昇も著しかった。実施例１、５、６及び１６の接着剤溶液について、２５℃で長期間放置したところ、実施例１の溶液は３ヵ月後に、実施例５の溶液は６ヵ月後に、実施例６の溶液は１か月後に、それぞれ、粘度が２倍になった。実施例１６はマイクロカプセル化することにより保存性がのびて３ヵ月から６ヵ月となっている。
【００５７】
【表１】

【００５８】
【表２】

【００５９】
【発明の効果】
本発明のフィルム状接続部材は、熱的にダメージをうけやすい基板に、熱的ダメージを与えない比較的低温域でも互いに向き合う回路導体間の接続可能であり、また、中温域では短時間で確実な接続ができる。[0001]
BACKGROUND OF THE INVENTION
The present invention provides a film-like circuit connection that allows two circuit boards to be bonded to each other, and allows electrical conduction between mutually facing conductors of two circuit boards without short-circuiting adjacent circuits on the same circuit board. The present invention relates to a material and a connection method using the connection material.
[0002]
[Prior art]
Circuit connection materials that can bond two circuit boards to each other and electrically connect the two circuit boards facing each other without short-circuiting the circuit are urethane, polyester, and acrylic. A material in which conductive particles are dispersed in an adhesive component containing a thermoplastic material such as epoxy or a thermosetting material such as an epoxy type or silicone type is known (for example, Japanese Patent Laid-Open No. 52-59889; No. 55-164007).
[0003]
When the adhesive component is a thermosetting substance, as the curing agent or catalyst for curing the thermosetting substance, tertiary amines and imidazoles which are anionic polymerization type curing agents are mainly used for epoxy resins. . Epoxy resins containing tertiary amines and imidazoles are cured at a medium temperature of about 160 ° C. to 200 ° C. by heating for about several tens of seconds to several hours, so that the pot life is relatively long. Furthermore, it is known that the pot life is extended by microencapsulating tertiary amines and imidazoles (see, for example, JP-A-4-314724).
[0004]
In addition to the above anionic polymerization type curing agent, there is a cationic polymerization type curing agent. As the cationic polymerization type curing agent, a photosensitive onium salt that cures a resin by energy ray irradiation, for example, an aromatic diazonium salt, an aromatic sulfonium salt, or the like is known. In addition to energy ray irradiation, aliphatic sulfonium salts are known as those that are activated by heating to cure the epoxy resin (see, for example, JP-A-57-102922 and JP-A-58-198532). .
[0005]
[Patent Document 1]
Japanese Patent Laid-Open No. 52-59889 [Patent Document 2]
JP 55-164007 A [Patent Document 3]
JP-A-4-314724 [Patent Document 4]
JP-A-57-102922 [Patent Document 5]
JP 58-198532 A [0006]
[Problems to be solved by the invention]
When electrically connecting between conductors on a circuit board with a circuit connecting material using an adhesive component such as imidazole as a curing agent, the connection time is limited to, for example, 15 seconds. The reliability of the part was insufficient. When the temperature is 140 ° C. or higher, there is a problem of causing thermal damage to a substrate using a thermoplastic material having a low softening point such as polycarbonate.
[0007]
Furthermore, if the connection time is limited to 5 seconds, the reliability of the connection portion is insufficient at a connection temperature of 200 ° C. or less, and if the connection temperature is 200 ° C. or more, the connection portion may be displaced due to thermal expansion of the circuit board. There was a problem that occurred.
[0008]
In addition, in order to electrically connect between conductors on the circuit board with the circuit connecting material, the thickness of the connecting portion needs to be equal to or smaller than the diameter of the conductive particles in the connecting material. It is important to adjust the reactivity with the composition containing the active substance and the fluidity of the composition. Poor fluidity results in poor connection.
[0009]
An adhesive component having an aromatic diazonium salt as a curing agent cannot be used because the circuit board does not transmit energy rays. Also, those using aliphatic sulfonium salts as curing agents have the same problems as those using imidazoles as curing agents.
[0010]
In the present invention, when connecting between conductors of circuit boards facing each other, even if the connection time is limited to 10 seconds to 20 seconds, thermal damage is not caused even to a substrate having poor heat resistance. It can be cured under relatively low temperature heating conditions of 140 ° C. or lower, and the connection time is limited to a short time. It is an object of the present invention to provide a film-like circuit connecting material having a pot life of 10 hours or more and having an adhesive component sufficiently flowing at the time of connection and having good connectivity.
[0011]
[Means for Solving the Problems]
The present inventors can connect the circuit conductors facing each other on two circuit boards within 60 seconds when heated at 140 ° C. or less, within 30 seconds when heated at 140 to 200 ° C., and inactive at room temperature. As a result of intensive studies on the materials, the inventors have found that the above object can be achieved by using a heat-sensitive sulfonium salt selected from an aromatic sulfonium salt having a benzyl group, and have completed the present invention.
[0012]
The present invention provides a film-like circuit connection that allows two circuit boards to be bonded to each other, and allows electrical conduction between mutually facing conductors of two circuit boards without short-circuiting adjacent circuits on the same circuit board. A sulfonium salt containing a benzyl group represented by Chemical Formula 2 with respect to 100 parts by weight of a composition comprising a cationic polymerizable substance and a polymer having a molecular weight of 10,000 to 80,000, Conductive particles having a particle diameter of 1 to 18 μm are dispersed in an adhesive component containing 10 parts by weight of 0.05 to 20% by volume, and the melt viscosity at 100 ° C. of the adhesive component is 1 to 1,000 Pa · s. Is a film-like circuit connecting material.
[Chemical formula 2]

In Chemical Formula 2, R ¹ is a group having a higher electron-withdrawing property than R ² and R ³ , and R ¹ , R ^2, and R ³ are substituted or unsubstituted groups, and may be the same or different from each other , Y ⁻ is a non-nucleophilic anion.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
R ¹ represents an electron-withdrawing group such as a nitroso group, a carbonyl group, a carboxyl group, a cyano group, a trialkylammonium group, a fluoromethyl group in order to generate a benzyl cation presumed as an initiator for cationic polymerization. R ² and R ³ are preferably electron donating groups such as an amino group, a hydroxyl group, and a methyl group. Y ⁻ may be a non-nucleophilic anion, for example, hexafluoroarsenate (AsF ₆ ), hexachloroantimonate (SbCl ₆ ), hexafluorophosphate (PF ₆ ), tetrafluoroborate (BF ₄ ). Can be mentioned.
[0014]
These sulfonium salts are activated at a temperature of 140 ° C. or lower, can cause cationic polymerization, and the viscosity of the reactive adhesive after 10 hours or more in the presence of a cationic polymerizable substance at room temperature (25 ° C.). Is not more than twice the initial viscosity. Further, these sulfonium salts can be used by dissolving them in various solvents (for example, ethyl acetate) which can be dissolved if necessary. The compounding quantity of a sulfonium salt shall be 0.05-10 weight part with respect to 100 weight part of adhesive components. The amount is particularly preferably 1.5 to 5 parts by weight with respect to 100 parts by weight of the adhesive component. A large amount is undesirable because it tends to cause electrolytic corrosion, and the curing reaction proceeds explosively.
[0015]
The conductive particles dispersed in the adhesive component are preferably those that are deformed by heating or pressing or simply pressing. The deformation of the conductive particles increases the contact area with the circuit at the time of connection, improving the connection reliability, variation in the thickness and flatness of the circuit, and a mixture of protrusions and those that are not. Sometimes a good connection can be made. This deformation may be either one in which the conductive particles themselves are deformed or one in which the conductive particles form an aggregate and change the aggregated state at the time of connection.
[0016]
Examples of the conductive particles include metal particles such as Au, Ag, Ni, Cu, Sb, Sn, and solder, particles of a conductive material such as carbon, these particles, or non-conductive glass, ceramics, and plastic particles. Some cores have a surface coated with another conductive material. Furthermore, it is also effective to use conductive particles as nuclei and coat the surface of these nuclei with an insulating layer so that when pressed, the inner nuclei break the insulating layer and come into contact. When such conductive particles are used, insulation in a direction perpendicular to the pressurizing direction is secured, and it is extremely effective for connecting narrow thin circuit between circuits. If the particle size of the conductive particles is not smaller than the distance between adjacent lines in the circuit, the adjacent circuits are short-circuited. Moreover, it is preferable that the particle diameter of electroconductive particle is 1-18 micrometers considering that it deform | transforms by the pressurization at the time of a connection and spreads sideways. If necessary, insulating particles may be used in combination so as not to prevent contact between the conductive particles.
[0017]
The blending amount of the conductive particles is preferably set so as to produce conductivity only in the pressing direction at the time of bonding. In the circuit, although it varies depending on the distance between adjacent lines and the diameter of the conductive particles, it is in the range of 0.05 to 20% by volume, preferably 0.1 to 15% by volume, more preferably, with respect to the adhesive component. 0.2 to 10% by volume. If it exceeds 20% by volume, the transparency deteriorates and it becomes difficult to align the circuits to be connected. If it is less than 0.05% by volume, conductivity cannot be obtained.
[0018]
When the melt viscosity of the adhesive component at 100 ° C. is 1 to 1,000 Pa · s, particularly 10 to 1,000 Pa · s, the adhesive component flows well and the connection thickness is smaller than the diameter of the conductive particles. Become. If it is 1,000 Pa · s or more, the fluidity is poor and the connection thickness is thicker than the diameter of the conductive particles, resulting in poor connectivity. When the pressure is in the range of 1 to 10 Pa · s, it is necessary to take care such that the pressure is initially reduced and the pressure is increased after the adhesive component is cured to some extent. If it is 1 Pa · s or less, it flows too much and the deposition component flows out of the connecting portion and is difficult to be held in the connecting portion, resulting in poor reliability. The adjustment of the melt viscosity will be described later.
[0019]
When the sulfonium salt in the adhesive component is microencapsulated, the storage stability of the adhesive component is improved. This is because the cationically polymerizable substance and the sulfonium salt do not come into contact with each other during storage. The method for microencapsulation is not particularly limited, such as solvent evaporation, spray drying, coacervation, and interfacial polymerization. The microcapsules should have a small particle size, and the sulfonium salt is hydrophobic, so that the interfacial polymerization method is preferred.
[0020]
Among the adhesive components, examples of the cationically polymerizable substance include an epoxy resin, polyvinyl ether, and polystyrene. These may be used alone or in combination. Moreover, it can also be used by mixing with other polymers or solid resins having a weight average molecular weight of 3000 or less.
[0021]
Of the cationically polymerizable substances, an epoxy resin is most preferable. The epoxy resin is a compound having two or more epoxy groups in one molecule. For example, a bisphenol type epoxy resin derived from epichlorohydrin and bisphenol A or bisphenol F, polyglycidyl ether, polyglycidyl ester, fat reductant. An epoxy resin etc. are mentioned.
[0022]
Examples of the polymer that can be mixed with the cationic polymerizable substance include polyvinyl acetal, phenoxy resin, polyethylene terephthalate, polyurethane, and polymers such as vinyl chloride, olefin, ethylene ionomer, and polyamide. In consideration of film formability, fluidity at the time of melting, and solubility between resins, the molecular weight of these polymers is preferably 10,000 or more and 80,000 or less. In addition, when having a polar group such as a hydroxyl group (OH group) or a carboxyl group (COOH group), compatibility with the epoxy resin is improved, and a film having a uniform appearance and characteristics can be obtained, and reaction with the epoxy group. It is preferable because of its properties.
[0023]
Examples of solid resins having a weight average molecular weight of 3000 or less include natural resins such as rosin and terpene, aliphatic, alicyclic, aromatic, polymer resins such as coumarone, indene and styrene, phenol resins and xylene resins. There are condensed resins, etc., and modified products and derivatives thereof. The solid resin having a weight average molecular weight of 3000 or less is used alone or in combination when it is necessary to adjust the tackiness or adhesiveness.
[0024]
The sulfonium salt represented by Chemical Formula 2 is stable at room temperature, and the cationic polymerizable substance is activated and cured by heating at 110 ° C. to 140 ° C. for 10 to 60 seconds and 130 ° C. to 200 ° C. for 1 to 30 seconds. To do. Furthermore, by setting the melt viscosity of the adhesive component to 1 to 1,000 Pa · s at 100 ° C., a suitable flow of the adhesive component is obtained by pressurization of 0.5 to 5 MPa, and between the circuit conductors via the conductive particles Connection is obtained. Therefore, the adhesive component has good storage stability at room temperature, can be cured by adhesion without thermally damaging the substrate material, and circuit connection can be obtained.
[0025]
【Example】
Hereinafter, although an Example demonstrates in detail, this invention is not limited to this.
Example 1
50 g of bisphenol A type liquid epoxy resin (Oka Shell Co., Ltd., using trade name Epicoat 828), 50 g of phenoxy resin (Union Carbide Co., Ltd., using trade name PKHA) having an average molecular weight of 25,000 and a hydroxyl group content of 6% Was dissolved in a mixed solvent of toluene and ethyl acetate in a weight ratio of 1: 1 to obtain a solution having a solid content of 40%.
[0026]
A nickel layer having a thickness of 0.2 μm is provided on the surface of particles having polystyrene as a core, and a gold layer having a thickness of 0.02 μm is provided outside the nickel layer, and conductive particles having an average particle diameter of 10 μm and a specific gravity of 2.0. Manufactured.
[0027]
p-Acetoxyphenylbenzylmethylsulfonium salt was dissolved in ethyl acetate to give a 50% by weight solution.
[0028]
Blended so that the resin component 100 and p-acetoxyphenyldibenzylmethylsulfonium salt 2 are in a solid weight ratio, and further 2% by volume of conductive particles are dispersed and applied to a fluororesin film having a thickness of 80 μm at room temperature. Blow drying was performed to obtain a film-like circuit connecting material having a thickness of 25 μm.
[0029]
Example 2
A film-like circuit connecting material was obtained in the same manner as in Example 1, except that p-methoxycarbonyloxyphenylbenzylethylsulfonium salt was used instead of p-acetoxyphenylbenzylmethylsulfonium salt.
[0030]
Example 3
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that p-hydroxyphenylbenzylmethylsulfonium salt was used instead of p-acetoxyphenylbenzylmethylsulfonium salt.
[0031]
Example 4
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that p-hydroxyphenyl-p-nitrobenzylmethylsulfonium salt was used in place of the p-acetoxyphenylbenzylmethylsulfonium salt.
[0032]
Example 5
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that the amount of p-acetoxyphenylbenzylmethylsulfonium salt was 0.2 parts by weight.
[0033]
Example 6
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that the amount of p-acetoxyphenylbenzylmethylsulfonium salt was 10 parts by weight.
[0034]
Example 7
A connection material for a film-like circuit was obtained in the same manner as in Example 1 except that an alicyclic epoxy resin (using Daicel Chemical Industries, Ltd., trade name Celoxide 2021) was used instead of the bisphenol A liquid epoxy resin. It was.
[0035]
Example 8
A connection material for a film-like circuit in the same manner as in Example 1 except that a bisphenol A type solid epoxy resin (Oilized Shell Epoxy Co., Ltd., trade name Epicoat 1001 is used) is used instead of the bisphenol A type liquid epoxy resin. Got.
[0036]
Example 9
In place of the bisphenol A type liquid epoxy resin, an acrylic resin (Showa Polymer Co., Ltd., trade name Lipoxy SD-1509 is used, glycidyl acrylate) is used in the same manner as in Example 1 to obtain a film-like circuit connecting material. Obtained.
[0037]
Example 10
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that the amount of conductive particles was changed to 0.5% by volume.
[0038]
Example 11
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that the amount of the conductive particles was 5% by volume.
[0039]
Example 12
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that the diameter of the conductive particles was 3 μm.
[0040]
Example 13
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that the conductive particles were replaced with nickel particles having an average single particle size of 2 μm and an aggregate particle size of 10 μm.
[0041]
Example 14
The conductive particles were formed in the same film form as in Example 1 except that nickel particles having an average single particle size of 2 μm and agglomerated particle size of 10 μm were 0.5% by volume, and silica particles having a particle size of 2 μm were added by 0.5% by volume. A circuit connection material was obtained.
[0042]
Example 15
A film-like circuit connecting material as in Example 1, except that 70 g of bisphenol A liquid epoxy resin (Epicoat 828) and 30 g of phenoxy resin (Union Carbide Co., Ltd., trade name PKHA is used) were used. Got.
[0043]
Example 16
10 parts by weight of p-acetoxyphenylbenzylmethylsulfonium salt, 16 parts by weight of methyl methacrylate, 16 parts by weight of styrene, 8 parts by weight of ethylene glycol dimethacrylate, 0.05 parts by weight of azo compound (V-60 manufactured by Wako Pure Chemical Industries, Ltd. V-40 each 0.025 part by weight) as component A, water 200 parts by weight, sodium dodecylbenzenesulfonate 0.2 part by weight, polyvinyl alcohol 0.125 part by weight as component B, in a nitrogen atmosphere sealed container The mixture was stirred at 60 ° C. for 4 hours and dried to microencapsulate the sulfonium salt. Thereafter, a film-like circuit connecting material was obtained in the same manner as in Example 1.
[0044]
Comparative Example 1
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that p-hydroxyphenyldimethylsulfonium salt (sulfonium salt having no benzyl group) was used instead of p-acetoxyphenylbenzylmethylsulfonium salt.
[0045]
Comparative Example 2
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that 1-cyanoethyl-2-methylimidazole was used in place of the p-acetoxyphenylbenzylmethylsulfonium salt.
[0046]
Comparative Example 3
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that the conductive particles were not blended.
[0047]
Comparative Example 4
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that the diameter of the conductive particles was 20 μm.
[0048]
Comparative Example 5
A film-like circuit connecting material was obtained in the same manner as in Example 1 except that 20 g of bisphenol A type liquid epoxy resin (Epicoat 828) and 80 g of phenoxy resin (PKHA) were used.
[0049]
Measurement of DSC 3 mg (± 0.1 mg) of the film-like circuit connecting material obtained above was weighed, and DSC was measured at a heating rate of 10 ° C./min in a sealed aluminum pan. The analyzer used is TA2000 manufactured by DuPont.
[0050]
Measurement of Melt Viscosity In Examples 1 and 15 and Comparative Example, bisphenol A type liquid epoxy resin (Epicoat 828) and phenoxy resin (PKHA) were melted in the vicinity of 250 ° C. without being dissolved in a solvent, and after mixing uniformly, 10 g The degree was fractionated, gradually cooled, and the viscosity at 100 ° C. was measured. At this time, a curing agent and conductive particles were not blended. The apparatus used for the measurement is a digital viscometer HU-8 manufactured by Resuka Co., Ltd.
[0051]
Circuit connection Examples 1 to 16 and Comparative Examples 1 to 5 are flexible film boards (FPC) having 250 copper circuits having a line width of 100 μm, a pitch of 200 μm, and a thickness of 35 μm using the film-like circuit connection materials, and oxidized on the entire surface. A polycarbonate plate (ASTM D648, heat distortion temperature 140 ° C. at 1.86 MPa) having a thin layer of indium (ITO) formed (surface resistance 40Ω / □) at 130 ° C. and 1.5 MPa. It was heated and pressurized for 20 seconds and connected over a width of 3 mm. At this time, the adhesive surface of the connection material for film-like circuit is pasted on the polycarbonate plate in advance, and then temporarily connected by heating and pressurizing at 70 ° C., 0.5 MPa for 5 seconds, and then the fluororesin film is peeled off to remove the FPC. And glued. Further, FPC having 250 copper circuits with a line width of 100 μm, a pitch of 200 μm and a thickness of 35 μm and glass with a thin layer of ITO (surface resistance 20 Ω / □) were heated and pressed at 160 ° C. and 1.5 MPa for 10 seconds. Connected over 3 mm. At this time, temporary connection was made on the ITO glass in the same manner as described above.
[0052]
After the connection resistance measurement circuit was connected, the resistance value between the adjacent circuits of the FPC including the connection portion was measured with a multimeter after maintaining it at a high temperature and high humidity of 85 ° C. and 85% RH for 500 hours.
[0053]
The storage-stable film-like circuit connecting material was kept as a blended solution, sealed so that the solvent would not evaporate, and allowed to stand at 25 ° C., and the time when the solution viscosity doubled was examined.
[0054]
Measurement of connection thickness The thickness of the substrate on which the ITO thin layer was formed and the thickness of the FPC were measured with a micrometer in advance, the thickness after connection was measured with a film-like circuit connection material, and the connection thickness was calculated.
[0055]
These measurement results are shown in Tables 1 and 2. From this result, the following can be understood.
[0056]
For each example, the DSC peak temperature is 100-120 ° C., which is 10-20 ° C. lower than that of Comparative Examples 1 and 2. In particular, the adhesive of Example 7 has a DSC peak temperature that is 10 ° C. lower than that of Example 1 and does not show an increase in connection resistance, thus providing good connection. In each example, the initial resistance value is significantly lower than that of Comparative Examples 1 and 2, and an increase in connection resistance after holding under high temperature and high humidity is not observed or is a small value. It is considered that Comparative Examples 1 and 2 were insufficient in reaction. In the connection material of Example 8, the peak temperature of DSC is as high as 120 ° C., and the increase in connection resistance is slightly large. The reason for this is considered to be that the reactivity was slightly lowered because a solid epoxy resin was used. Since Comparative Example 3 has no conductive particles, the initial resistance is high and the connection resistance is remarkably increased. In Comparative Example 4, since the conductive particles were as large as 20 μm, the number of conductive particles at the connection portion decreased at 2% by volume, and thus the resistance value was slightly high. As in the case of the film-like connecting material of Example 1, the film-like connecting material of Example 10 using nickel particles having an average single particle diameter of 2 μm and an agglomerated diameter of 10 μm as the conductive particles is also capable of obtaining a good connection. . The adhesive of Example 11 in which nickel particles and silica particles having a particle diameter of 2 μm are mixed at a volume ratio of 1: 1 can also provide good connection as in Example 1, and in particular, between the nickel particles. It was found that silica particles were present in the surface to improve the insulation from the adjacent circuit. The film-like connection material of Example 1 and Example 15 has a melt viscosity at 100 ° C. in the range of 1 to 1,000 Pa · s, and the connection thickness is also equal to or smaller than the particle diameter of the conductive particles. The film-like connecting material of Example 5 had a high melt viscosity and was cured before the adhesive component sufficiently flowed, so that the connection thickness was larger than the particle size of the conductive particles. As a result, the connection resistance increased and the rise was significant. The adhesive solutions of Examples 1, 5, 6 and 16 were allowed to stand at 25 ° C. for a long time. The solution of Example 1 was after 3 months, the solution of Example 5 was after 6 months, and the solution of Example 6 was After one month, the viscosity doubled respectively. In Example 16, the preservability is extended by microencapsulation, which is 3 to 6 months.
[0057]
[Table 1]

[0058]
[Table 2]

[0059]
【The invention's effect】
The film-like connecting member of the present invention can connect between circuit conductors facing each other even in a relatively low temperature range that does not cause thermal damage to a substrate that is thermally damaged. Connection is possible.

Claims (6)

A film-like circuit connecting material capable of electrically connecting two mutually facing conductors of two circuit boards without bonding two circuit boards to each other and short-circuiting adjacent circuits on the same circuit board. , 0.05 to 10 parts by weight of a sulfonium salt containing a benzyl group represented by Chemical Formula 1 with respect to 100 parts by weight of a composition containing a cationic polymerizable substance and a polymer having a molecular weight of 10,000 to 80,000 Conductive particles having a particle size of 1 to 18 μm are dispersed in the adhesive component, and the melt viscosity at 100 ° C. of the adhesive component is 1 to 1,000 Pa · s. Film-like circuit connection material.

In Chemical Formula 1, R ¹ is a group having a higher electron-withdrawing property than R ² and R ³ , and R ¹ , R ^2, and R ³ are substituted or unsubstituted groups, and may be the same or different from each other , Y ⁻ is a non-nucleophilic anion.   The film-like circuit connecting material according to claim 1, wherein the polymers are polyvinyl acetal, phenoxy resin, polyethylene terephthalate, polyurethane, or polyamide.   The conductive particles are selected from particles of a conductive material, particles of a non-conductive material coated with a conductive material, or particles of a conductive particle coated with an insulating material. The film-like circuit connecting material according to claim 1 or 2, characterized in that:   4. The film-like circuit connecting material according to claim 1, wherein a sulfonium salt containing a benzyl group is microencapsulated. 0.05 to 10 parts by weight of a sulfonium salt containing a benzyl group represented by Chemical Formula 1 was added to 100 parts by weight of a composition containing a cationic polymerizable substance and a polymer having a molecular weight of 10,000 to 80,000. A film-like circuit connecting material in which 0.05 to 20% by volume of conductive particles having a particle diameter of 1 to 18 μm is dispersed in the adhesive component, and the melt viscosity at 100 ° C. of the adhesive component is 1 to 1,000 Pa · s. A circuit connection method characterized in that it is sandwiched between two circuit conductors facing each other and laminated and integrated by heating and pressing from the back of the wiring board having the respective circuit conductors.

In Chemical Formula 1, R ¹ is a group having a higher electron-withdrawing property than R ² and R ³ , and R ¹ , R ^2, and R ³ are substituted or unsubstituted groups, and may be the same or different from each other , Y ⁻ is a non-nucleophilic anion.   The circuit connection method according to claim 5, wherein the heating and pressurizing conditions are a temperature of 110 to 140 ° C, a pressure of 0.5 MPa to 5 MPa, and a time of 10 to 60 seconds.