JP3801666B2

JP3801666B2 - Electrode connection method and connection member used therefor

Info

Publication number: JP3801666B2
Application number: JP12202595A
Authority: JP
Inventors: 功塚越; 寛松岡; 遵一小出; 宏治小林; 勝幸上野
Original assignee: Hitachi Chemical Co Ltd; Showa Denko Materials Co Ltd
Current assignee: Showa Denko Materials Co Ltd
Priority date: 1995-05-22
Filing date: 1995-05-22
Publication date: 2006-07-26
Anticipated expiration: 2021-07-26
Also published as: JPH08316625A

Description

【０００１】
【産業上の利用分野】
本発明は、電子部品と回路基板や、回路基板同士を接着固定すると共に、両者の電極同士を電気的に接続する電極の接続方法と、これに用いる接続部材に関する。
【０００２】
【従来の技術】
近年、電子部品の小型薄型化に伴い、これらに用いる回路は高密度、高精細化しており、このような電子部品と微細電極の接続は、従来のハンダやゴムコネクタなどでは対応が困難であることから、最近では分解能に優れた接着剤や膜状物（以下接続部材）が多用されている。この接続部材としては、絶縁性の接着剤を用いて両電極の直接接触により導電性を得ることや、加圧により厚み方向のみに導電性の得られる程度の導電粒子を含有してなる異方導電性の接着剤を用いて、両電極間に導電粒子を介在させる導電粒子などの導電材料を所定量含有した接着剤からなるものが知られている。これら接続部材の使用法は、接続部材を電子部品と電極や回路との間に介在させ、加圧または加熱加圧手段を講じることによって、両者の電極同士が電気的に接続されると共に、電極に隣接して形成されている電極同士には絶縁性を付与して、電子部品と回路とが接着固定されるものである。上記接続部材の中で、導電粒子を含有する接続部材を高分解能化するための基本的な考えは、導電粒子の粒径を隣接電極間の絶縁部分よりも小さくすることで隣接電極間における絶縁性を確保し、併せて導電粒子の含有量をこの粒子同士が接触しない程度とし、かつ電極上に確実に存在させることにより接続部分における導電性を得ることである。このような微細電極の接続レベルは、最近では回路ピッチが５０μｍ以下も検討されており、接続装置の位置合わせ精度も３μｍ以下が実用化の域にある。
【０００３】
【発明が解決しようとする課題】
上記従来の方法は、個別の材料すなわち、電極・接続部材・接続装置の個々には高レベルの微細な製品が開発されつつあるものの、これらを組み合わせて実際の接続体を得る時の接続方法に問題があった。すなわち、これらの接続部材は加熱加圧手段を講じることによって、両者の電極同士の電気的な接続を得る方式であるため、加熱時に電極間の接続部材の接着剤が溶融流動し、せっかく高精度に位置合わせした電極がずれてしまう欠点があることである。さらに接続電極のリペアが行いにくい欠点もあった。これは接続電極の微小化に対応させるために、接着剤の架橋度が向上しており、そのため接続後に剥離しにくく、また接着剤を除去しにくいことによる。また、導電粒子含有の接続部材の場合、電極面積や隣接電極間（スペース）の微細化により電極上の導電粒子が接続時の加圧または加熱加圧により接着剤と共に隣接電極間に流出してしまい、接続部材の高分解能化の妨げとなっていた。この時、接続部材の接着剤の流出を抑制するために、接着剤を高粘度とすると電極と導電粒子の接触が不十分となり、相対峙する電極の接続が不可能となる。一方接着剤を低粘度とすると導電粒子の流出に加えてスペース部に気泡を含みやすく、接続信頼性、特に耐湿性が低下してしまう欠点がある。本発明は上記欠点に鑑みなされたもので、電極のずれがなく高精度の位置合わせが可能で、加えてリペア性に優れ、また導電粒子の電極上からの流出が少なく保持可能で、さらに接続部に気泡を含み難いことから長期接続信頼性に優れた、電極の接続方法およびこれに好適な接続部材に関する。
【０００４】
【課題を解決するための手段】
本発明は、相対峙する電極間に硬化性接着剤を含む接続部材を介在させ加熱加圧により両電極の接続を得る方法であって、前記接続部材は活性化温度の異なる硬化剤を含有するものであり、両電極の位置合わせを行い、次いで活性温度の高い硬化剤の活性温度よりは低いが、活性温度の低い硬化剤の活性温度よりは高い温度で加熱して接続部材の反応を進行せしめ、あるいは活性温度の高い硬化剤の活性温度よりは低いが、活性温度の低い硬化剤の活性温度よりは高い温度で加熱して接続部材の反応を進行せしめ半硬化させるとともに通電検査を行い、その後活性温度の高い硬化剤の活性温度よりも高い温度に昇温して加熱加圧することを特徴とする電極の接続方法に関し、この接続に好適な接着剤として異なる温度条件下で活性化する活性化温度の異なる硬化剤と導電粒子とを含有してなる接続部材に関する。
【０００５】
本発明を図面を参照しながら説明する。図１は、本発明の一実施例を説明する電極の接続方法を示す断面模式図である。本発明は、相対峙する電極４、５間に接続部材８を介在させ、加熱加圧により両電極の接続を得る方法であって、両電極４、５の位置合わせを行い、活性温度の高い硬化剤の活性温度よりは低いが、活性温度の低い硬化剤の活性温度よりは高い温度で加熱して接続部材の反応を進行せしめ半硬化させ（第１次接続）、あるいは活性温度の高い硬化剤の活性温度よりは低いが、活性温度の低い硬化剤の活性温度よりは高い温度で加熱後に必要により通電検査を行い、次いで接続部材８に配合された活性温度の高い硬化剤の活性温度よりも高い温度に昇温して加熱加圧（第２次接続）することを特徴とする。第一次接続の反応の進行は、反応率や粘度の上昇の他、両電極の仮固定が可能な状態に達することを目安にできる。なお第１次接続は活性温度の高い硬化剤の活性化温度以下で行うことが、第２次接続迄の保存性を確保する点から好ましい。
【０００６】
接続装置は、上下動可能な加熱ヘッド１と受け台２を有する。受け台２の少なくとも一部は、光の透過が可能な材質、例えば石英やガラス類とする。受け台２の下にはエネルギー線源を有する。エネルギー線３としては、赤外線などがある。エネルギー線３は必要に応じて受け台２の下面側を走査できる。またエネルギー線と併用して電熱などの他の電熱手段を使用できる。接続すべき電極４、５は、これを保持する基板６、７に形成されてなるものが一般的である。基板６、７としては、ポリイミドやポリエステルなどのプラスチックフィルム、ガラスエポキシなどの複合体、シリコーンなどの半導体、ガラスやセラミックスなどの無機物などを例示できる。受け台２側の基板６、７としてはエネルギー線３が透過し易いほど好ましく、液晶用基板として多用されるガラスやプラスチックフィルム等の透明性材料が特に好適である。電極４、５としては各種回路類や端子類があり、半導体チップのような電子部品のバンプやパッド類を含むことができる。これらはそれぞれ任意に組み合わせて適用できる。
【０００７】
接続部材８は、絶縁性接着剤９のみ（図２ａ）でも、導電材料１０と絶縁性接着剤９とよりなる（図２ｂ）加圧方向に導電性を有する異方導電性接着剤でもよい。また絶縁性接着剤と異方導電性接着剤を積層した機能分離構成でも良い。異方導電性接着剤は含有する導電材料により、電極４、５の凹凸や高さのばらつきに対応し易く好ましい。これらはフィルム状であると一定厚みの連続状で得られることから好ましく、これらの表面には不要な粘着性やゴミなどの付着防止のために、図示していないが剥離可能なセパレータが必要に応じて存在して良い。接続部材８の導電材料１０としては、加圧または加熱加圧手段を講じることで接着剤の厚み減少によって導電性を得る、すなわち接着剤の厚み以下の小粒径のものが接着剤により保持されるので取扱い時に導電材料の脱落防止が可能で好ましい。これはまた、接着剤の厚みに対して一層程度で存在できると、本発明の第１次接続のような甘い接続条件下でも導電性が得やすいので好ましい。接着剤に対する導電材料の割合は、２０体積％以下が導電異方性が得やすく好ましい。また厚み方向の導電性を得易くするため、接続部材の厚さは膜形成の可能な範囲で薄い方が好ましく、３０μｍ以下、より好ましくは２０μｍ以下である。
【０００８】
導電材料である導電粒子としては、Ａｕ、Ａｇ、Ｐｔ、Ｎｉ、Ｃｕ、Ｗ、Ｓｂ、Ｓｎ、はんだ等の金属粒子やカーボン等があり、またこれら導電粒子を核材とするか、あるいは非導電性のガラス、セラミックス、プラスチック等の高分子などからなる核材に前記したような材質からなる導電層を被覆形成したものでも良い。さらに導電材料を絶縁層で被覆してなる絶縁被覆粒子や導電粒子と絶縁粒子の併用なども適用可能である。粒径の上限は微小な電極上に１個以上、好ましくは５個以上と多くの粒子数を確保するには小粒径粒子が好適であり、１５μｍ以下、より好ましくは８μｍ以下である。粒径の上限は粒子の凝集性や、電極面の凹凸に対応可能とするために、０．５μｍ以上、好ましくは１μｍ以上である。これら導電粒子の中では、はんだ等の熱溶融金属やプラスチック等の高分子核材に導電層を形成したものが、加熱加圧もしくは加圧により変形性を有し、積層時に回路との接触面積が増加し信頼性が向上するので好ましい。特に高分子類を核とした場合、はんだのように融点を示さないので軟化の状態を接続温度で広く抑制でき、電極の厚みや平坦性のばらつきに対応し易い接続部材が得られるので特に好ましい。
【０００９】
また例えばＮｉやＷ等の硬質金属粒子や、表面に多数の突起を有する粒子の場合、導電粒子が電極や配線パターンに突刺さるので、酸化膜や汚染層の存在する場合にも低い接続抵抗が得られ、信頼性が向上するので好ましい。これら導電粒子は、粒径の分布の狭い均一粒径の球状粒子が好ましい。粒径の分布が狭いと電極接続時の加圧により電極間で保持されて流出が少ない。粒径の分布幅としては、電極表面の凹凸を考慮して最大粒径の１／２以下とすることが好ましい。例えば高分子核材に導電層を被覆形成した変形性粒子の場合、中心径±０．２μｍ以内といった高精度の粒子もあり、特に好ましく適用できる。また硬質金属粒子の場合、電極に突刺さるので粒径の分布幅は最大粒径の１／２以下と比較的広くても良い。導電粒子１０と併用して絶縁粒子１１を用いる（図２ｃ）ことも可能である。絶縁粒子を併用した場合、隣接電極との絶縁性の向上や接続電極のギャップ調節の作用がある。ギャップ調節の場合、好ましくは絶縁粒子の粒径を変形性の導電粒子より小さくし、導電粒子に比べ硬質とすると良好な結果が期待できる。絶縁粒子１１としては、ガラス、シリカ、セラミックスなどの無機物やポリスチレン、エポキシ、ベンゾグアナミンなどの有機物があり、これらは、球状、繊維状などの形状でも良い。これらは単独または複合して用いることができる。
【００１０】
接続部材８の接着剤は、反応性接着剤であって異なる条件下で活性化する硬化剤を含有してなるものや、Ｂステージ状態で安定なものが好ましい。異なる条件下とは、熱、光、湿気などがあり、これらで活性化する硬化剤としては、熱分解型のアミンイミド、光分解型の芳香族ジアゾニウム塩、湿気硬化型のケチミンなどの組み合わせがある。また、例えばルイス酸系などのカチオン触媒やベンゾフェノン／ミヒラーケトンなどの紫外線硬化剤と各種アミン類などの熱硬化剤との複合系や、熱硬化剤同士の場合での活性温度の異なる硬化剤との複合系などがある。またＢステージ状態で安定なものとしては、芳香族ポリアミン類やマイクロカプセル等の潜在性硬化剤類を例示できる。本発明では、接続部材８の接着剤として、熱硬化剤同士の場合で活性温度の異なる硬化剤を用いる。接着剤の活性化温度は、反応性樹脂と潜在性硬化剤との共存混合試料３ｍｇをＤＳＣ（ＤｉｆｆｅｒｅｎｔｉａｌＳｃａｎｎｉｎｇＣａｌｏｒｉｍｅｔｅｒ指差走査型熱量計）を用い、１０℃／分で常温（３０℃）から２５０℃迄上昇させた時の発熱量の最大を示すピーク温度とする。これらの中でエポキシ系接着剤は、短時間硬化が可能で接続作業性が良く、分子構造上接着性に優れる等の特徴から好ましく適用できる。エポキシ系接着剤は、例えば高分子量のエポキシ、固形エポキシと液状エポキシ、ウレタンやポリエステル、アクリルゴム、ＮＢＲ、ナイロン等で変性したエポキシを主成分とし、硬化剤や触媒、カップリング剤、充填剤などを添加してなるものが一般的である。
【００１１】
【作用】
本発明によれば、両電極の位置合わせを行い、少なくともエネルギーにより接続部材の反応を進行せしめ（第１次接続）、次いで活性温度の高い硬化剤の活性温度よりも高い温度に昇温して加熱加圧（第２次接続）する。すなわち第１次接続は第２次接続に比べて低温度で行うので両電極および基板の熱膨張に基づく変位が少なく、また接続部材の増粘により両電極の仮固定がされているので、電極のずれがなく高精度の位置合わせが可能である。接続部材は第２次接続の高温下でも通常状態に比べ増粘しており、両電極が仮固定され、ずれが少ない。第２次接続では、接着剤の溶融粘度が第２次接続による反応の進行による増粘により高いので、電極上の導電粒子が接続時の加圧または加熱加圧により接着剤と共に隣接電極間に流出し難く、またスペース部に気泡を含まないので接続信頼性、特に耐湿性が向上する。加えて、エネルギー線照射により接続部材が低粘度化して両電極および／または導電材料の加圧接触により第１次接続において両電極の導通が得られるので、この状態で導通などの電気検査を行い、不良が見つかれば剥離して再度接続（リペア）をやり直しても良い。この場合、接着剤の反応が不十分な状態で行えるので、不良部の剥離や洗浄が極めて簡単に行える利点がある。電気検査は接着剤の増粘による凝集力で無加圧でも可能であるが、必要により加圧を併用できる。
【００１２】
【実施例】
以下実施例でさらに詳細に説明するが、本発明はこれに限定されない。
参考例１
（１）異方導電フィルム
高分子量エポキシ樹脂と液状エポキシ樹脂（エポキシ当量１８５）の比率を２０／８０とし、芳香族ジアゾニウム塩系の硬化剤を５部含有した酢酸エチルの３０％溶液を得た。この溶液に、粒径５±０．２μｍのポリスチレン系粒子にＮｉ／Ａｕの厚さ０．２／０．０２μｍの金属被覆を形成した導電性粒子を３体積％添加し、混合分散した。この分散液をセパレータ（シリコーン処理ポリエチレンテレフタレートフィルム、厚み４０μｍ）にロールコータで塗布し、１１０℃２０分乾燥し厚み１５μｍの異方導電フィルム（活性化温度は１３０℃）を得た。
（２）接続回路
ポリイミドフィルム上に高さ１８μｍの銅の回路を有する２層ＦＰＣ回路板（回路ピッチは７０μｍ、電極幅３０μｍの平行回路の電極）と、ガラス１．１ｍｍ上に酸化インジウム厚み０．２μｍ（ＩＴＯ、表面抵抗２０Ω／□）の薄膜回路を有する平面電極との接続を行った。まず平面電極側に導電性接着層がくるようにした。前記接続部材を１．５ｍｍ幅で載置し貼り付けた。この後セパレータを剥離し、他の回路板と上下回路を位置合わせした。
（３）接続
図１の接続装置のエネルギー線として紫外線を照射（１．５Ｊ／ｃｍ²）した。接続部の異方導電フィルムの温度は１００℃以下であった。この状態で接着剤の反応率が１０％に進行し、両電極の保持が可能であった。ここに反応率は、前記活性化温度の測定と同じであるが、反応前後の熱量比から求めた。その後で、１７０℃、２０ｋｇｆ／ｍｍ²、１５秒で第２次接続した。
（４）評価
両電極を顕微鏡下で透視し、電極間の最大ずれ量を測定したところ５μｍ以下であり、ほとんどずれがなかった。相対峙する電極間を接続抵抗、隣接する電極間を絶縁抵抗として評価したところ、接続抵抗は２Ω以下、絶縁抵抗は１０⁸Ω以上であり、これらは８５℃、８５％ＲＨ１０００時間処理後の耐湿信頼性も変化がほとんどなく良好な長期信頼性を示した。芳香族ジアゾニウム塩系の硬化剤は、いわゆるカチオン硬化剤であり、紫外線などの光と熱硬化性とを合わせて持つので、本参考例のような接続が可能である。
【００１３】
比較例１
参考例１と同様であるが、紫外線照射工程を設けずに、いきなり１７０℃、２０ｋｇｆ／ｍｍ²、１５秒で接続（反応率８２％）した。電極間の最大ずれ量を測定したところ２５μｍであり、ずれが大きいために電極間スペースが減少し絶縁性がなくなった。
【００１４】
参考例２
参考例１と同様であるが、ＦＰＣに変えてＩＣチップ（２×１０ｍｍ、高さ０．５ｍｍ、４辺周囲にバンプと呼ばれる５０μｍ角、高さ２０μｍの金電極が２００個形成）を用いた。ガラス側のＩＴＯ電極を前記ＩＣチップのバンプ電極のサイズに対応するように変更した。この場合の最大ずれ量を測定したところ、３μｍ以下であり、ほとんどずれがなく良好であった。
【００１５】
実施例１
参考例１と同様であるが、異方導電フィルムの硬化剤をマイクロカプセル型潜在性硬化剤とし、硬化剤の活性化温度が９０℃と１４０℃の１対２の混合体（フィルムの活性化温度１３４℃）とした。接続部の異方導電フィルムの温度が１００℃となるように熱源をコントロールし、２０ｋｇｆ／ｍｍ²、２０秒熱線をあてた（反応率１２％）。その後で、１５０℃、２０ｋｇｆ／ｍｍ²、１５秒で第２次接続した。この場合の最大ずれ量は５μｍ以下でずれが少なく、耐湿信頼性も良好であった。
【００１６】
参考例３および参考比較例１
参考例１および比較例１と同様であるが、第１次の接続工程の紫外線照射後に通電検査を行った後で、ＦＰＣを剥離したところ極めて簡単に剥離できた。その部分をアセトンで軽く洗浄し再接続したところ良好な接続を得た（参考例３）。一方、比較例１の接続体は剥離が困難であり剥離部に残った接着剤はアセトンで除去しにくく、再接続後の接続抵抗も比較例１に比べ高かった（参考比較例１）。
【００１７】
参考例４および参考比較例２
参考例２の接続で参考例３および参考比較例１と同様な工程を行った。参考例４は紫外線照射後に通電検査を行った後で、ＩＣチップを剥離したところ極めて簡単に剥離できた。その部分をアセトンで軽く洗浄し再接続したところ良好な接続を得た。一方、参考比較例２の接続体は、いきなり１７０℃、２０ｋｇｆ／ｍｍ²、１５秒で接続したため剥離が困難であり、強引に治具で剥がそうとしたらＩＣチップが破壊してしまった。
【００１８】
【発明の効果】
以上詳述したように本発明によれば、電極のずれがなく高精度の位置合わせが可能である。また接着剤架橋度の低い状態で電気検査を行えるので、リペアが容易である。また電極上の導電粒子が接続時の加圧または加熱加圧により接着剤と共に隣接電極間に流出し難く、スペース部に気泡を含まないので接続信頼性、特に耐湿性が向上する。従って高精度な微細電極の接続を提供できる。
【図面の簡単な説明】
【図１】本発明の一実施例を示す電極の接続方法を示す断面模式図である。
【図２】本発明の一実施例を示す接続部材の断面模式図である。
【図３】本発明の一実施例を示す接続部材の平面模式図である。
【符号の説明】
１加熱ヘッド２受け台
２エネルギー線４電極
５電極６基板
７基板８接続部材
９絶縁性接着剤１０導電材料
１１絶縁粒子１２中央部
１３端部[0001]
[Industrial application fields]
The present invention relates to an electronic component and a circuit board, an electrode connecting method for bonding and fixing circuit boards together, and electrically connecting both electrodes, and a connection member used therefor.
[0002]
[Prior art]
In recent years, with the miniaturization and thinning of electronic components, the circuits used for these have become dense and high definition, and it is difficult to connect such electronic components and fine electrodes with conventional solders or rubber connectors. For this reason, recently, adhesives and film-like materials (hereinafter referred to as connection members) having excellent resolution have been frequently used. As this connection member, an anisotropic material containing conductive particles that can obtain conductivity by direct contact between both electrodes using an insulating adhesive, or that can obtain conductivity only in the thickness direction by pressurization. 2. Description of the Related Art An adhesive made of an adhesive containing a predetermined amount of a conductive material such as conductive particles in which conductive particles are interposed between both electrodes using a conductive adhesive is known. These connecting members are used by interposing the connecting member between an electronic component and an electrode or circuit, and by applying pressure or heating / pressing means, both electrodes are electrically connected to each other. The electrodes formed adjacent to each other are provided with insulating properties so that the electronic component and the circuit are bonded and fixed. Among the above connecting members, the basic idea for increasing the resolution of a connecting member containing conductive particles is to make the particle size of the conductive particles smaller than the insulating portion between adjacent electrodes, thereby insulating between adjacent electrodes. It is to obtain the conductivity at the connection portion by ensuring the property, and at the same time, the content of the conductive particles is set to such an extent that the particles do not contact each other and is surely present on the electrode. With regard to the connection level of such fine electrodes, a circuit pitch of 50 μm or less has recently been studied, and the positioning accuracy of the connection device is in the range of practical use of 3 μm or less.
[0003]
[Problems to be solved by the invention]
Although the above conventional methods are being developed for individual materials, that is, electrodes, connection members, and connection devices, a high-level fine product is being developed, these are combined into a connection method for obtaining an actual connection body. There was a problem. That is, these connecting members are a method of obtaining an electrical connection between the two electrodes by taking a heating and pressing means, so that the adhesive of the connecting member between the electrodes melts and flows at the time of heating, so that it is highly accurate. There is a defect that the electrode aligned with the position is shifted. Further, there is a drawback that it is difficult to repair the connection electrode. This is because the degree of cross-linking of the adhesive is improved in order to cope with the miniaturization of the connection electrode, and therefore it is difficult to peel off after connection and it is difficult to remove the adhesive. In the case of a connection member containing conductive particles, the conductive particles on the electrodes flow out between the adjacent electrodes together with the adhesive by pressurization at the time of connection or heating and pressurization due to the miniaturization of the electrode area and between adjacent electrodes (space). This has hindered the high resolution of the connecting member. At this time, if the adhesive has a high viscosity in order to suppress the outflow of the adhesive from the connecting member, the contact between the electrode and the conductive particles becomes insufficient, and the opposing electrodes cannot be connected. On the other hand, if the adhesive has a low viscosity, in addition to the outflow of the conductive particles, air bubbles are likely to be included in the space portion, and there is a drawback that connection reliability, particularly moisture resistance, is lowered. The present invention has been made in view of the above-mentioned drawbacks, and can be aligned with high accuracy without any electrode displacement, and in addition, it has excellent repairability, and can be held with less outflow of conductive particles from the electrode. The present invention relates to an electrode connection method that is excellent in long-term connection reliability because it does not easily contain bubbles, and a connection member suitable for this.
[0004]
[Means for Solving the Problems]
The present invention is a method of interposing a connecting member containing a curable adhesive between electrodes facing each other and obtaining a connection between both electrodes by heating and pressing, wherein the connecting member contains a curing agent having a different activation temperature. Both electrodes are aligned, and then the reaction of the connecting member proceeds by heating at a temperature lower than the activation temperature of the curing agent with a higher activation temperature but higher than the activation temperature of the curing agent with a lower activation temperature. allowed, or is lower than the activation temperature of the activation temperature high curing agent performs than the activation temperature of the activation temperature lower curing agent is heated at a high temperature allowed to proceed the reaction of the connecting member Rutotomoni energization test is semi-cured Then , the present invention relates to a method for connecting electrodes characterized in that the temperature is raised to a temperature higher than the activation temperature of the curing agent having a high activation temperature and heated and pressurized, and the adhesive is activated under different temperature conditions as an adhesive suitable for this connection. Activity On connecting member comprising a different curing agent and conductive particles temperature.
[0005]
The present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view illustrating an electrode connection method for explaining an embodiment of the present invention. The present invention is a method of interposing a connecting member 8 between electrodes 4 and 5 facing each other and obtaining a connection between both electrodes by heating and pressurization. The electrodes 4 and 5 are aligned, and the activation temperature is high. Heating at a temperature lower than the activation temperature of the curing agent but higher than the activation temperature of the curing agent having a lower activation temperature to cause the reaction of the connecting member to proceed and semi-cured (primary connection), or to cure at a higher activation temperature Although it is lower than the activation temperature of the curing agent but higher than the activation temperature of the curing agent having a lower activation temperature, an energization inspection is performed as necessary after heating, and then the activation temperature of the curing agent having a higher activation temperature blended in the connecting member 8 The temperature is raised to a high temperature and heated and pressurized (secondary connection). The progress of the primary connection reaction can be based on reaching a state where both electrodes can be temporarily fixed, as well as an increase in reaction rate and viscosity. The primary connection is preferably performed at a temperature lower than the activation temperature of the curing agent having a high activation temperature, from the viewpoint of ensuring storage stability until the secondary connection.
[0006]
The connecting device has a heating head 1 and a cradle 2 that can move up and down. At least a part of the cradle 2 is made of a material capable of transmitting light, such as quartz or glass. An energy ray source is provided under the cradle 2. Examples of the energy ray 3 include infrared rays. The energy beam 3 can scan the lower surface side of the cradle 2 as necessary. In addition, other electric heating means such as electric heating can be used in combination with energy rays. The electrodes 4 and 5 to be connected are generally formed on the substrates 6 and 7 that hold them. Examples of the substrates 6 and 7 include plastic films such as polyimide and polyester, composites such as glass epoxy, semiconductors such as silicone, and inorganic materials such as glass and ceramics. As the substrates 6 and 7 on the cradle 2 side, it is preferable that the energy rays 3 are easily transmitted, and a transparent material such as glass or plastic film frequently used as a liquid crystal substrate is particularly suitable. The electrodes 4 and 5 include various circuits and terminals, and can include bumps and pads of electronic components such as semiconductor chips. These can be applied in any combination.
[0007]
The connecting member 8 may be only the insulating adhesive 9 (FIG. 2a) or may be an anisotropic conductive adhesive having conductivity in the pressurizing direction composed of the conductive material 10 and the insulating adhesive 9 (FIG. 2b). Moreover, the function separation structure which laminated | stacked the insulating adhesive and the anisotropic conductive adhesive may be sufficient. The anisotropic conductive adhesive is preferable because it can easily cope with unevenness and height variations of the electrodes 4 and 5 depending on the conductive material contained. These are preferably film-like because they can be obtained in a continuous form with a constant thickness, and in order to prevent unnecessary adhesion and adhesion of dust etc. on these surfaces, a separator that is not shown but needs to be peeled off is required. May be present accordingly. As the conductive material 10 of the connecting member 8, conductivity is obtained by reducing the thickness of the adhesive by applying pressure or heating and pressing means, that is, a material having a small particle size equal to or smaller than the thickness of the adhesive is held by the adhesive. Therefore, it is preferable that the conductive material can be prevented from falling off during handling. This is also preferable if it can be present to a certain extent with respect to the thickness of the adhesive because it is easy to obtain conductivity even under sweet connection conditions such as the primary connection of the present invention. The ratio of the conductive material to the adhesive is preferably 20% by volume or less because it is easy to obtain conductive anisotropy. In order to make it easier to obtain conductivity in the thickness direction, the thickness of the connecting member is preferably as thin as possible in the range where film formation is possible, and is 30 μm or less, more preferably 20 μm or less.
[0008]
Examples of conductive particles that are conductive materials include metal particles such as Au, Ag, Pt, Ni, Cu, W, Sb, Sn, and solder, carbon, and the like, and these conductive particles are used as a core material or non-conductive. Alternatively, a core material made of a polymer such as glass, ceramics, or plastic may be coated with a conductive layer made of the above-described material. Further, insulating coating particles formed by coating a conductive material with an insulating layer, or a combination of conductive particles and insulating particles can be applied. The upper limit of the particle diameter is preferably 1 or more, preferably 5 or more on a minute electrode, and a small particle diameter is suitable for securing a large number of particles, and it is 15 μm or less, more preferably 8 μm or less. The upper limit of the particle diameter is 0.5 μm or more, preferably 1 μm or more in order to be able to cope with the cohesiveness of the particles and the unevenness of the electrode surface. Among these conductive particles, those in which a conductive layer is formed on a polymer core material such as a hot-melt metal such as solder or plastic, are deformable when heated or pressurized, and the contact area with the circuit during lamination This increases the reliability and improves the reliability. Particularly when a polymer is used as a core, it does not show a melting point like solder, so that the softening state can be widely suppressed at the connection temperature, and a connection member that can easily cope with variations in electrode thickness and flatness is obtained, which is particularly preferable. .
[0009]
Also, for example, in the case of hard metal particles such as Ni and W, or particles having a large number of protrusions on the surface, the conductive particles pierce the electrodes and the wiring pattern, so that even when an oxide film or a contamination layer is present, a low connection resistance is obtained. It is preferable because it is obtained and reliability is improved. These conductive particles are preferably spherical particles having a uniform particle size with a narrow particle size distribution. If the particle size distribution is narrow, it is held between the electrodes by pressurization when the electrodes are connected, and the outflow is small. The distribution width of the particle diameter is preferably set to 1/2 or less of the maximum particle diameter in consideration of the unevenness of the electrode surface. For example, in the case of deformable particles obtained by coating a polymer core with a conductive layer, there are also highly accurate particles having a center diameter within ± 0.2 μm, which can be particularly preferably applied. Further, in the case of hard metal particles, since they pierce the electrodes, the distribution width of the particle diameters may be relatively wide as 1/2 or less of the maximum particle diameter. It is also possible to use the insulating particles 11 in combination with the conductive particles 10 (FIG. 2c). When the insulating particles are used in combination, there is an effect of improving the insulation with the adjacent electrode and adjusting the gap of the connection electrode. In the case of adjusting the gap, a favorable result can be expected when the particle diameter of the insulating particles is preferably smaller than that of the deformable conductive particles and is harder than the conductive particles. Examples of the insulating particles 11 include inorganic substances such as glass, silica, and ceramics, and organic substances such as polystyrene, epoxy, and benzoguanamine, and these may be spherical or fibrous. These can be used alone or in combination.
[0010]
The adhesive of the connecting member 8 is preferably a reactive adhesive that contains a curing agent that is activated under different conditions, or one that is stable in the B-stage state. Under different conditions, there are heat, light, moisture, etc. As the curing agent activated by these, there are combinations of thermal decomposition type amine imide, photo decomposition type aromatic diazonium salt, moisture hardening type ketimine, etc. . Also, for example, a composite system of a cationic catalyst such as Lewis acid type, a UV curing agent such as benzophenone / Michler ketone and a thermosetting agent such as various amines, or a curing agent having different activation temperatures in the case of thermosetting agents. There are complex systems. Moreover, as a thing stable in a B stage state, latent hardening agents, such as aromatic polyamines and a microcapsule, can be illustrated. In the present invention, as the adhesive for the connection member 8, a curing agent having a different activation temperature is used in the case of thermosetting agents. The activation temperature of the adhesive was 250 ° C. from 10 ° C./min to 250 ° C. using a differential scanning calorimeter (DSC) for 3 mg of a coexisting mixed sample of a reactive resin and a latent curing agent. The peak temperature indicates the maximum calorific value when the temperature is raised to ° C. Among these, the epoxy adhesive can be preferably applied because of its characteristics such that it can be cured for a short time, has good connection workability, and has excellent molecular adhesion. Epoxy adhesives include, for example, high molecular weight epoxy, solid epoxy and liquid epoxy, urethane, polyester, acrylic rubber, NBR, nylon, etc. modified epoxy as the main component, curing agent, catalyst, coupling agent, filler, etc. What is added is generally.
[0011]
[Action]
According to the present invention, the electrodes are aligned, the reaction of the connecting member is advanced by at least energy (primary connection), and then the temperature is raised to a temperature higher than the activation temperature of the curing agent having a high activation temperature. Heat and pressurize (secondary connection). That is, since the primary connection is performed at a lower temperature than the secondary connection, the displacement due to the thermal expansion of both electrodes and the substrate is small, and both electrodes are temporarily fixed by the thickening of the connection member. High-precision alignment is possible without any deviation. The connecting member is thicker than the normal state even at a high temperature of the secondary connection, both electrodes are temporarily fixed, and there is little deviation. In the secondary connection, since the melt viscosity of the adhesive is higher due to the thickening due to the progress of the reaction due to the secondary connection, the conductive particles on the electrode are pressed together with the adhesive between the adjacent electrodes by the pressurization or heating and pressurization. Since it does not easily flow out and does not contain bubbles in the space portion, connection reliability, particularly moisture resistance, is improved. In addition, the connection member has a reduced viscosity due to energy beam irradiation, and both electrodes and / or conductive material are brought into conduction in the primary connection by pressure contact between the electrodes and / or the conductive material. If a defect is found, it may be peeled off and reconnected (repaired). In this case, since the reaction of the adhesive can be performed in an insufficient state, there is an advantage that the defective portion can be peeled off and cleaned very easily. The electrical inspection can be performed without pressure by the cohesive force due to the thickening of the adhesive, but pressure can be used together if necessary.
[0012]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto.
Reference example 1
(1) Anisotropic conductive film The ratio of high molecular weight epoxy resin to liquid epoxy resin (epoxy equivalent 185) was 20/80, and a 30% solution of ethyl acetate containing 5 parts of an aromatic diazonium salt-based curing agent was obtained. . To this solution, 3% by volume of conductive particles in which a Ni / Au 0.2 / 0.02 μm thick metal coating was formed on polystyrene particles having a particle size of 5 ± 0.2 μm was added and mixed and dispersed. This dispersion was applied to a separator (silicone-treated polyethylene terephthalate film, thickness 40 μm) with a roll coater and dried at 110 ° C. for 20 minutes to obtain an anisotropic conductive film (activation temperature 130 ° C.) having a thickness of 15 μm.
(2) Connection circuit Two-layer FPC circuit board (circuit pitch is 70 μm, electrode of parallel circuit with electrode width of 30 μm) having a copper circuit with a height of 18 μm on a polyimide film, and an indium oxide thickness of 0 on glass 1.1 mm Connection with a planar electrode having a thin film circuit of 2 μm (ITO, surface resistance 20Ω / □) was made. First, the conductive adhesive layer was placed on the planar electrode side. The connecting member was placed and pasted with a width of 1.5 mm. Thereafter, the separator was peeled off, and the other circuit board and the upper and lower circuits were aligned.
(3) Connection Ultraviolet rays were irradiated (1.5 J / cm ² ) as the energy rays of the connection device of FIG. The temperature of the anisotropic conductive film in the connection portion was 100 ° C. or lower. In this state, the reaction rate of the adhesive progressed to 10%, and both electrodes could be held. Here, the reaction rate was the same as the measurement of the activation temperature, but was determined from the calorimetric ratio before and after the reaction. Thereafter, secondary connection was made at 170 ° C., 20 kgf / mm ² , and 15 seconds.
(4) Evaluation Both electrodes were seen through under a microscope, and the maximum deviation between the electrodes was measured. As a result, it was 5 μm or less, and there was almost no deviation. When the resistance between the electrodes facing each other was evaluated as the connection resistance, and the insulation resistance between the adjacent electrodes was evaluated, the connection resistance was 2Ω or less and the insulation resistance was 10 ⁸ Ω or more. These were moisture resistance after treatment at 85 ° C. and 85% RH for 1000 hours. There was almost no change in reliability, and good long-term reliability was demonstrated. The aromatic diazonium salt-based curing agent is a so-called cationic curing agent, and has both light such as ultraviolet rays and thermosetting, and thus can be connected as in this reference example.
[0013]
Comparative Example 1
Although it was the same as that of the reference example 1, it connected at 170 degreeC, 20 kgf / mm < ² >, and 15 seconds (reaction rate 82%) without providing the ultraviolet irradiation process. The maximum amount of displacement between the electrodes was measured and found to be 25 μm. Since the displacement was large, the space between the electrodes was reduced and insulation was lost.
[0014]
Reference example 2
Similar to Reference Example 1, but instead of the FPC, an IC chip (2 × 10 mm, height 0.5 mm, 200 gold electrodes of 50 μm square and 20 μm height called bumps formed around 4 sides) was used. . The glass-side ITO electrode was changed to correspond to the size of the bump electrode of the IC chip. When the maximum deviation amount in this case was measured, it was 3 μm or less, and it was good with almost no deviation.
[0015]
Example 1
Same as Reference Example 1, except that the anisotropic conductive film curing agent is a microcapsule type latent curing agent, and the activation temperature of the curing agent is 90 ° C. and 140 ° C. Temperature 134 ° C.). The heat source was controlled so that the temperature of the anisotropic conductive film at the connection was 100 ° C., and 20 kgf / mm ² , 20-second heat ray was applied (reaction rate 12%). Thereafter, secondary connection was made at 150 ° C. and 20 kgf / mm ² for 15 seconds. In this case, the maximum deviation amount was 5 μm or less, and the deviation was small, and the moisture resistance reliability was also good.
[0016]
Reference Example 3 and Reference Comparative Example 1
Although it was the same as that of the reference example 1 and the comparative example 1, after performing the electricity supply inspection after the ultraviolet irradiation of a 1st connection process, when peeling FPC, it was able to peel very easily. When the part was lightly washed with acetone and reconnected, a good connection was obtained (Reference Example 3). On the other hand, the connection body of Comparative Example 1 was difficult to peel off, and the adhesive remaining in the peeled portion was difficult to remove with acetone, and the connection resistance after reconnection was higher than that of Comparative Example 1 (Reference Comparative Example 1).
[0017]
Reference Example 4 and Reference Comparative Example 2
The same steps as in Reference Example 3 and Reference Comparative Example 1 were performed in the connection of Reference Example 2. In Reference Example 4, the IC chip was peeled off after conducting an energization test after UV irradiation, and it was very easy to peel off. When this part was lightly washed with acetone and reconnected, a good connection was obtained. On the other hand, since the connection body of Reference Comparative Example 2 was suddenly connected at 170 ° C., 20 kgf / mm ² for 15 seconds, it was difficult to peel off, and the IC chip was destroyed if it was forcibly peeled off with a jig.
[0018]
【The invention's effect】
As described in detail above, according to the present invention, there is no displacement of the electrodes, and highly accurate alignment is possible. In addition, since the electrical inspection can be performed in a state where the adhesive crosslinking degree is low, the repair is easy. In addition, the conductive particles on the electrodes are unlikely to flow out between the adjacent electrodes together with the adhesive due to the pressurization or heating and pressurization at the time of connection. Accordingly, it is possible to provide a highly accurate connection of fine electrodes.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing an electrode connection method according to an embodiment of the present invention.
FIG. 2 is a schematic cross-sectional view of a connection member showing an embodiment of the present invention.
FIG. 3 is a schematic plan view of a connection member showing an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Heating head 2 Base 2 Energy beam 4 Electrode 5 Electrode 6 Substrate 7 Substrate 8 Connection member 9 Insulating adhesive 10 Conductive material 11 Insulating particle 12 Central part 13 End part

Claims

A method of obtaining a connection between both electrodes by heating and pressing by interposing a connecting member containing a curable adhesive between electrodes facing each other, wherein the connecting member contains a curing agent having a different activation temperature, Align both electrodes, then heat at a temperature lower than the activation temperature of the curing agent with a higher activation temperature but higher than the activation temperature of the curing agent with a lower activation temperature to allow the reaction of the connecting member to proceed and then activate A method for connecting electrodes, characterized in that the temperature is raised to a temperature higher than the activation temperature of the curing agent having a high temperature and heated and pressurized.

A method of obtaining a connection between both electrodes by heating and pressing by interposing a connecting member containing a curable adhesive between electrodes facing each other, wherein the connecting member contains a curing agent having a different activation temperature, Align both electrodes, and then heat at a temperature lower than the activation temperature of the curing agent with a higher activation temperature but higher than the activation temperature of the curing agent with a lower activation temperature to advance the reaction of the connecting member and allow it to be semi-cured A method of connecting electrodes, comprising conducting an energization inspection together with the temperature , and then heating and pressurizing by raising the temperature to a temperature higher than the activation temperature of the curing agent having a high activation temperature .

A connection member used in the electrode connection method according to claim 1 or 2, comprising a curing agent having a different activation temperature and conductive particles, wherein the adhesive is activated under different temperature conditions.