JP2004352785A

JP2004352785A - Anisotropic electroconductive adhesive

Info

Publication number: JP2004352785A
Application number: JP2003149840A
Authority: JP
Inventors: Masakazu Kawada; 政和川田; Tetsuya Miyamoto; 哲也宮本
Original assignee: Sumitomo Bakelite Co Ltd
Current assignee: Sumitomo Bakelite Co Ltd
Priority date: 2003-05-27
Filing date: 2003-05-27
Publication date: 2004-12-16
Anticipated expiration: 2023-05-27
Also published as: JP3981341B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anisotropic electroconductive adhesive which particularly enables connection at low temperatures in a short time in electrical connections of fine circuits with each other such as connections between LCD and TCP and between TCP and PCB, and excels in storage stability, connectability, and connection reliability. <P>SOLUTION: The anisotropic electroconductive adhesive comprises electroconductive particles dispersed in an insulating electroconductive adhesive having a microencapsulated imidazole derivative epoxy compound as an essential component, and by making the average particle diameter of the microencapsulated imidazole derivative compound 0.1-3 μm, the anisotropic electroconductive adhesive enables connection at a low temperature in a short time and excels in storage stability. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、微細な回路同志の電気的接続、更に詳しくはＬＣＤ（液晶ディスプレイ）とフレキシブル回路基板（以下ＦＰＣ）の接続，ＣＯＦ（ＣｈｉｐＯｎＦｐｃ）やＴＣＰ（ＴａｐｅＣａｒｒｉｅｒＰａｃｋａｇｅ）との接続や半導体ＩＣとＩＣ搭載用基板のマイクロ接合等に用いることのできる異方導電性接着剤に関するものである。
【０００２】
【従来の技術】
近年、ＬＣＤとＴＣＰ、あるいはＴＣＰとＰＣＢの接続など、各種微細回路接続の必要性が飛躍的に増大してきており、その接続方法として接着剤樹脂中に導電性粒子を分散させた異方導電性接着剤が使用されてきている。この方法は、接続したい部材間に異方導電性接着剤を挟み加熱加圧することにより、面方向の隣接端子間では電気的絶縁性を保ちつつ、上下端子間では電気的に導通させるものである。
【０００３】
この異方導電性接着剤は、高い接続信頼性を得るため熱硬化タイプの接着剤樹脂が用いられ、その中でも被着体との密着性や耐湿信頼性を実現できるエポキシ樹脂系が用いられる。更に硬化性と保存安定性を両立させるために、エポキシ樹脂の硬化剤として潜在性を持つものを配合したタイプのものが広く用いられている。ここで用いられる潜在性硬化剤としては、ＢＦ３アミン錯体、ジシアンジアミド、有機酸ヒラジド、イミダゾール化合物等が挙げられる。これらの潜在性硬化剤を配合した熱硬化タイプのものは、保存安定性には優れるものの、１７０℃〜２００℃の温度で１０〜３０秒前後加熱硬化することが必要とされているものが通常である（例えば、特許文献１、２）。
【０００４】
最近では、ＬＣＤモジュールの大画面化、高精度化、狭額縁化となり、これに伴って接続ピッチの微細化や接続の細幅化も急速に進んできている。そのため、例えば、ＬＣＤとＴＣＰの接続においては、接続時の加熱によるＴＣＰの伸びのために接続部分にずれが生じたり、接続部分が細幅のため接続時の温度でＬＣＤ内部の部材が熱的影響を受けたり、また、ＴＣＰとＰＣＢの接続においては、ＰＣＢが長尺化していたため接続時の加熱によりＰＣＢとＬＣＤが反り、ＴＣＰの配線が断線するという問題等が生じてきた。これらの問題を解決するため、十分な接続信頼性を保ちながら、低温で且つ短時間での接続が可能な異方導電性接着剤が求められてきている。
【０００５】
このような市場の要求に対し、エポキシ樹脂系の熱硬化タイプの異方導電性接着剤は、潜在性硬化剤を適用しても、市場の要求に対応可能なレベルの低温短時間で硬化できるものは保存安定性に劣り、逆に保存安定性に優れるものは硬化に長時間または高温を必要とするといった問題があり、いずれも一長一短で十分に満足できるものはなかった。
一方、低温で且つ短時間での硬化が可能な異方導電性接着剤としては、ラジカル重合性樹脂、有機過酸化物、熱可塑性エラストマーを配合した樹脂組成物中に導電性粒子を分散させたものも提案されている（例えば、特許文献３）。しかし、この樹脂系では、低温短時間での接続は可能であるが、硬化収縮が大きく、各種の被着体に対する接続後の密着性が悪いものがあり、接続信頼性の面でも十分なものではなかった。
【０００６】
【特許文献１】
特開平５−２１０９４号公報
【特許文献２】
特開２００２−３２７１６２号公報
【特許文献３】
特開２０００−４４９０５号公報
【０００７】
【発明が解決しようとする課題】
本発明は、このような従来の問題点を鑑みて種々の検討の結果たどり着いたものであり、ＬＣＤとＴＣＰとの接続や、ＴＣＰとＰＣＢとの接続などの微細回路同士の電気的接続において、潜在性硬化剤を用いた異方導電性接着剤で低温且つ短時間での接続が可能で、保存安定性、密着性、接続信頼性に優れる異方導電性接着剤を提供するものである。
【０００８】
【課題を解決するための手段】
本発明は、
（１）マイクロカプセル化イミダゾール誘導体エポキシ化合物を必須成分とする絶縁性接着剤に導電性粒子を分散させた異方導電性接着剤において、マイクロカプセル化イミダゾール誘導体エキシ化合物の平均粒径が０．１〜３μｍであることを特徴とする異方導電性接着剤、
（２）マイクロカプセル化イミダゾール誘導体エポキシ化合物のマイクロカプセル壁材膜の厚さが０．００１〜０．３μｍで（１）項記載の異方導電性接着剤、
（３）異方導電性接着剤が、さらにエラストマーを含んでなる（１）又は（２）項記載の異方導電性接着剤、
（４）異方導電性接着剤が、さらにエポキシ樹脂を含んでなる（１）（２）又は（３）項記載の異方導電性接着剤、
（５）（１）〜（４）いずれか１項に記載の異方導電性接着剤を用いて、電子・電機部品の電気的な接合が行われたことを特徴とする電子機器、
（６）該電子・電機部品が半導体素子、半導体装置、プリント回路基板、液晶ディスプレイ（ＬＣＤ）パネル、プラズマディスプレイ（ＰＤＰ）パネル、エレクトロルミネッセンス（ＥＬ）パネル又はフィールドエミッションディスプレイ（ＦＥＤ）パネル、である（５）記載の電子機器、
である。
【０００９】
【発明の実施の形態】
以下、本発明に関して詳細に説明する。
本発明の異方導電性接着材に潜在性硬化剤として使用するマイクロカプセル化イミダゾール誘導体エキシ化合物の平均粒径は、０．１〜３μｍであり、好ましくは０．５〜２．５μｍ、さらに好ましくは１〜２μｍである。平均粒径を小さくすることで、潜在性硬化剤と樹脂との反応点の増加により硬化反応性を高め、低温で且つ短時間での接続を可能とした。潜在性硬化剤の平均粒径が下限値未満の場合は、粘度が上昇してマイクロカプセル化イミダゾール誘導体エポキシ化合物の作製が困難となり、保存安定性が得られない。一方、平均粒径が上限値を超える場合は、反応点の減少、硬化時間の増加となり、低温短時間での硬化が難しい。なお、本発明で用いる潜在性硬化剤の平均粒径とは、レーザー回折型測定装置ＲＯＤＯＳＳＲ型（ＳＹＭＰＡＴＥＣＨＥＲＯＳ＆ＲＯＤＯＳ）での体積換算平均粒径とした。
【００１０】
また、マイクロカプセル化イミダゾール誘導体エポキシ化合物のカプセル壁材膜の厚さは０．００１〜０．３μｍであり、好ましくは０．００５〜０．２μｍ、より好ましくは０．０１〜０．１μｍである。カプセル壁材膜の厚さが下限値未満であると壁材膜の強度が不足するとともに、欠陥の無い壁材膜を作製することが難しくなる。このため、他の原料との調合中に機械的なシェアや溶剤により壁材膜が破損し、保存安定性が悪くなる。一方、上限値を超える場合は、壁材膜は安定し保存安定性は高くなるが、壁材膜が破壊までの時間が長くなり低温短時間での接着が難しい。
【００１１】
本発明に潜在性硬化剤として用いるマイクロカプセル化イミダゾール誘導体エポキシ化合物は、イミダゾール誘導体とエポキシ化合物との反応生成物をマイクロカプセル化し微粉末化したものであれば特に限定するものではない。マイクロカプセル化イミダゾール誘導体エポキシ化合物とイソシアネート化合物とを反応させ、耐薬品性及び貯蔵安定性を高めたものも更に好適である。
また、ここで用いるエポキシ化合物としては、例えば、ビスフェノールＡ、ビスフェノールＦ及びブロム化ビスフェノールＡ等のグリシジルエーテル型エポキシ樹脂、ダイマー酸ジグリシジルエステル、フタル酸ジグリシジルエステル等が挙げられる。
【００１２】
また、ここで用いられるイミダゾール誘導体としては、イミダゾール、２−メチルイミダゾール、２−エチルイミダゾール、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、２−フェニル−４−メチルイミダゾール、１−ベンジル−２−メチルイミダゾール、１−ベンジル−２−エチルイミダゾール、１−ベンジル−２−エチル−５−メチルイミダゾール、２−フェニル−４−メチル−５−ヒドロキシジメチルイミダゾール、２−フェニル−４，５−ジヒドロキシメチルイミダゾール等が挙げられる。
【００１３】
本発明では、さらにエラストマーを用いることが好ましい。また本発明に用いるエラストマーは反応性エラストマーであることがさらに好ましい。本発明に用いられるエラストマーは、特に限定するものではないが、フィルム形成性があるようなもの、例えば、フェノキシ樹脂、ポリエステル樹脂、ポリウレタン樹脂、ポリイミド樹脂、ポリブタジエン、ポリプロピレン、スチレン−ブタジエン−スチレン共重合体、ポリアセタール樹脂、ポリビニルブチラール樹脂、ブチルゴム、クロロプレンゴム、ポリアミド樹脂、アクリロニトリル−ブタジエン共重合体、アクリロニトリル−ブタジエン−メタクリル酸共重合体、アクリロニトリル−ブタジエン−スチレン共重合体、ポリ酢酸ビニル樹脂、ナイロン、スチレン−イソプレン共重合体、スチレン−ブチレン−スチレンブロック共重合体などを用いることができ、単独、あるいは２種以上混合しても良い。
エラストマーの配合量は特に限定されないが、エポキシ樹脂とマイクロカプセル化イミダゾール誘導体エポキシ化合物の合計１００部に対して１０〜３００部であることが好ましい。配合量が３００部を越えると異方導電性接着剤とした時の流動性が不足し、十分な接続信頼性が得られないことや各種被着体との濡れ性が低下し十分な密着性が得られない。また１０部未満であると、異方導電性接着剤とした時の製膜性が悪いことや、硬化物の弾性率が高くなるため各種被着体に対する密着性が悪いと言った問題や熱衝撃試験後の接続信頼性に劣るといった問題が発生する。
【００１４】
本発明ではさらにエポキシ樹脂を用いることが好ましい。本発明に用いられるエポキシ樹脂は、１分子中に少なくとも２個以上のエポキシ基を有するものであれば、特に限定されるものではない。例えば、ビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂、ビスフェノールＳ型エポキシ樹脂、フェノールノボラック型エポキシ樹脂、クレゾールノボラック型エポキシ樹脂等が挙げられるが、これらに限定されるものではなく、単独でも混合して用いても差し支えない。
エポキシ樹脂の配合量は、マイクロカプセル化イミダゾール誘導体エポキシ化合物１００部に対して１０〜２００部であることが好ましい。配合量が２００部を越えると異方導電性接着剤とした時の硬化性が悪くなり、また、１０部未満であると耐熱・耐湿性に劣るため、異方導電性接着剤とした時の十分な接続信頼性がえられない。
【００１５】
マイクロカプセル化イミダゾール誘導体エポキシ化合物の添加量は特に限定するものではないが、エラストマーとエポキシ樹脂の合計１００部に対して２０〜４００部であることが好ましい。配合量が４００部を越えると異方導電性接着剤とした時の耐熱性・耐湿性が不足し、十分な接続信頼性が得られない。また、２０部未満であると、硬化性の低下が懸念されるという問題がある。
【００１６】
本発明に用いられる導電性粒子は、特にその組成は限定されるものではない。例えば、金属粒子としては、金、銀、亜鉛、錫、半田、インジウム、パラジウム等の単体もしくは２種以上を組み合わせても良い。また、高分子核材に金属被覆をした粒子としては、高分子核材に、エポキシ樹脂、ウレタン樹脂、メラミン樹脂、フェノール樹脂、アクリル樹脂、ポリエステル樹脂、ポリスチレン樹脂、スチレン−ブタジエン共重合体などのポリマーの中から１種あるいは２種以上組み合わせたもの、金属薄膜皮膜に、金、ニッケル、銀、銅、亜鉛、錫、インジウム、パラジウム、アルミニウムなどの中から１種あるいは２種以上組み合わせて良い。また、金属薄膜皮膜の厚さにも特に制限はないが、薄すぎると異方導電性接着剤とした場合接続が不安定になり、厚すぎると凝集が生じるため、異方導電性接着剤とした場合絶縁不良を起こす可能性があるため、０．０１〜１μｍが好ましい。さらに、金属薄膜皮膜にむらや欠けがあると接続が不安定になるため、均一に被覆されていることが好ましい。これらの、導電粒子の粒径や材質、配合量は接続したい回路のピッチやパターン、回路端子の厚みや材質等によって適切に選ぶことができる。
【００１７】
導電性粒子の配合量は、エラストマー、エポキシ樹脂、マイクロカプセル化イミダゾール誘導体エポキシ化合物の合計に対して０．１〜１０体積％であることが好ましい。配合量が１０体積％を越えると、異方導電性接着剤中の導電性粒子絶対量が多くなるため、被着体接続端子間の絶縁性が極端に低下する。また、０．１体積％未満であると、異方導電性接着剤中の導電性粒子絶対量が少なくなるため、被着体接続端子上の導電性粒子が不足し、接続抵抗値が極端に高くなる。
【００１８】
本発明の異方導電性接着剤には、必要に応じてカップリング剤を適量添加しても良い。カップリング剤を添加する目的は、異方導電性接着剤の接着界面の接着性改質や、耐熱性、耐湿性を向上するものである。カップリング剤としては特に限定するものではないが、シランカップリング剤を好適に使用することができ、例えば、γ−グリシドキシプロピルトリエトキシシラン、β−（３，４エポキシシクロヘキシル）エチルトリメトキシシラン、γ―メタクリロキシプロピルトリメトキシシラン、γ−アミノプロピルトリエトキシシラン、γ−メルカプトプロピルトリメトキシシラン、ビニルトリメトキシシラン、γ−ウレイドプロピルトリエトキシシラン等が挙げられるが、１種あるいは２種以上混合しても良い。
【００１９】
さらに、本発明の異方導電接着剤には、樹脂の相溶性、安定性、作業性等の各種特性向上のため、各種添加剤、例えば、非反応性希釈剤、反応性希釈剤、揺変性付与剤、増粘剤、無機充填剤等を適宜添加しても良い。
【００２０】
【実施例】
以下、本発明を実施例により説明する。
実施例、比較例で作成した接着剤の配合量／評価結果を表１にまとめた。
【００２１】
【表１】

【００２２】
【表２】

【００２３】
（１）密着性、接続信頼性、保存性測定用サンプルの作製
被着体は銅箔／ポリイミド＝８μｍ／３８μｍに、Ｎｉ／Ａｕメッキを施した２層ＦＰＣ（ピッチ５０μｍ、端子数４００本）とＩＴＯ（インジウム／錫酸化物）ベタガラス（３０Ω□）を用いた。
（２）密着性評価方法
１６０℃、３ＭＰａ、１０ｓｅｃの条件で圧着し、９０度剥離試験によって評価を行った。
（３）接続信頼性測定方法
サンプル作製直後および温度８５℃湿度８５％、１０００時間放置後の接続抵抗を２端子法により測定した。測定できないものをＯＰＥＮ（導通不良）とした。
（４）保存性測定方法
異方導電性接着剤を２５℃雰囲気中に２週間放置後、１６０℃、３ＭＰａ、１０ｓｅｃの条件で圧着し、接続抵抗を測定した。５．０Ω未満を◎（保存性非常に良好）、５．０Ω以上〜１０．０Ω未満を○（保存性良好）、１０．０Ω以上を×（保存性不良）とした。
【００２４】
＜実施例１＞
ビスフェノールＡ型フェノキシ樹脂（Ｍｗ：５０，０００）の酢酸エチル２０％溶液１００重量部、ポリビニルブチラール樹脂（重合度１７００、ブチラール化度７０ｍｏｌ％）の２０％酢酸エチル溶液５０重量部、ビスフェノールＡ型エポキシ樹脂（エポキシ当量：１８０ｇ／ｅｑ）を２０重量部、マイクロカプセル化２−メチルイミダゾール誘導体エポキシ化合物を５０重量部、平均粒径５μｍのＮｉ／Ａｕメッキアクリル粒子を前記接着剤樹脂混合物の固形分に対して３重量部を混合・均一分させた後、離型処理を施したポリエチレンテレフタレート上に乾燥後の厚さが１５μｍになるように流延・乾燥した後、幅１．５ｍｍに切断して異方導電性接着剤を得た。
【００２５】
＜実施例２〜１２＞
表１及び表２に示す配合割合、条件で実施例１と同様にして異方導電性接着剤を得た。
【００２６】
＜比較例１＞
マイクロカプセル化イミダゾール誘導体エポキシ化合物の硬化剤の平均粒子径を６μｍのものに変えた以外は実施例１と同様にして異方導電性接着剤を得た。
【００２７】
＜比較例２、３＞
表２に示す配合割合、条件で比較例１と同様にして異方導電性接着剤を得た。
【００２８】
【発明の効果】
本発明により、保存安定性、低温短時間の接続性に優れた異方導電性接着剤を得ることが出来る。この異方導電性接着剤を用いることによりＬＣＤとＣＯＦ等の微細な回路電極の接続が可能である。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to electrical connection between fine circuits, more specifically, connection between an LCD (liquid crystal display) and a flexible circuit board (hereinafter, FPC), connection between a COF (Chip On Fpc), TCP (Tape Carrier Package), and a semiconductor IC. The present invention relates to an anisotropic conductive adhesive which can be used for micro-joining between a substrate and an IC mounting substrate.
[0002]
[Prior art]
In recent years, the necessity of various fine circuit connections, such as connection between LCD and TCP, or connection between TCP and PCB, has been dramatically increased, and an anisotropic conductive material in which conductive particles are dispersed in an adhesive resin is used as a connection method. Adhesives have been used. In this method, an anisotropic conductive adhesive is sandwiched between members to be connected and heated and pressurized to maintain electrical insulation between adjacent terminals in the surface direction and electrically conduct between upper and lower terminals. .
[0003]
As the anisotropic conductive adhesive, a thermosetting adhesive resin is used in order to obtain high connection reliability, and among them, an epoxy resin system which can realize adhesion to an adherend and moisture resistance reliability is used. Furthermore, in order to achieve both curability and storage stability, a type containing a latent curing agent as an epoxy resin curing agent is widely used. Examples of the latent curing agent used here include BF3 amine complex, dicyandiamide, organic acid hydrazide, imidazole compound and the like. The thermosetting type compounded with these latent curing agents has excellent storage stability, but usually requires heating and curing at a temperature of 170 ° C to 200 ° C for about 10 to 30 seconds. (For example, Patent Documents 1 and 2).
[0004]
In recent years, LCD modules have become larger in size, higher in accuracy, and narrower in frame, and accordingly, finer connection pitches and narrower connection widths have been rapidly advanced. Therefore, for example, in the connection between the LCD and the TCP, the connection portion is displaced due to the elongation of the TCP due to the heating at the time of connection, and the members inside the LCD are thermally affected by the temperature at the time of connection because the connection portion is narrow. In connection with the connection between the TCP and the PCB, there has been a problem that the PCB and the LCD are warped due to heating at the time of connection because the PCB is elongated, and the wiring of the TCP is disconnected. In order to solve these problems, anisotropic conductive adhesives that can be connected at low temperature and in a short time while maintaining sufficient connection reliability have been demanded.
[0005]
In response to such market demands, epoxy resin-based thermosetting anisotropic conductive adhesives can be cured at a low temperature and short time at a level that can respond to market demands even when a latent curing agent is applied. Those having inferior storage stability, on the other hand, those having excellent storage stability have the problem of requiring a long time or a high temperature for curing, and none of them have advantages and disadvantages and are not sufficiently satisfactory.
On the other hand, as the anisotropic conductive adhesive that can be cured at a low temperature and in a short time, the conductive particles are dispersed in a resin composition containing a radical polymerizable resin, an organic peroxide, and a thermoplastic elastomer. Some have been proposed (for example, Patent Document 3). However, this resin system can be connected in a short time at a low temperature, but has a large curing shrinkage, has poor adhesion to various adherends after connection, and has a sufficient connection reliability. Was not.
[0006]
[Patent Document 1]
JP-A-5-21094 [Patent Document 2]
Japanese Patent Application Laid-Open No. 2002-327162 [Patent Document 3]
JP 2000-44905 A
[Problems to be solved by the invention]
The present invention has been made as a result of various studies in view of such conventional problems, and has been found in connection between LCDs and TCP, and electrical connection between microcircuits such as connection between TCP and PCB. It is an object of the present invention to provide an anisotropic conductive adhesive which can be connected at a low temperature and in a short time with an anisotropic conductive adhesive using a latent curing agent and has excellent storage stability, adhesion and connection reliability.
[0008]
[Means for Solving the Problems]
The present invention
(1) In an anisotropic conductive adhesive in which conductive particles are dispersed in an insulating adhesive containing a microencapsulated imidazole derivative epoxy compound as an essential component, the microencapsulated imidazole derivative exci compound has an average particle size of 0.1. Anisotropic conductive adhesive, characterized in that
(2) The anisotropic conductive adhesive according to (1), wherein the thickness of the microcapsule wall material film of the microencapsulated imidazole derivative epoxy compound is 0.001 to 0.3 μm,
(3) The anisotropic conductive adhesive according to (1) or (2), wherein the anisotropic conductive adhesive further comprises an elastomer;
(4) The anisotropic conductive adhesive according to (1), (2) or (3), wherein the anisotropic conductive adhesive further contains an epoxy resin.
(5) An electronic device characterized in that electronic and electric parts are electrically joined using the anisotropic conductive adhesive according to any one of (1) to (4).
(6) The electronic / electrical component is a semiconductor element, a semiconductor device, a printed circuit board, a liquid crystal display (LCD) panel, a plasma display (PDP) panel, an electroluminescence (EL) panel or a field emission display (FED) panel. (5) the electronic device according to the above,
It is.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
The average particle size of the microencapsulated imidazole derivative exci compound used as a latent curing agent in the anisotropic conductive adhesive of the present invention is 0.1 to 3 μm, preferably 0.5 to 2.5 μm, and more preferably. Is 1 to 2 μm. By reducing the average particle size, the curing reactivity was increased by increasing the number of reaction points between the latent curing agent and the resin, and connection at a low temperature and in a short time was enabled. If the average particle size of the latent curing agent is less than the lower limit, the viscosity increases and it becomes difficult to prepare the microencapsulated imidazole derivative epoxy compound, and storage stability cannot be obtained. On the other hand, when the average particle size exceeds the upper limit, the number of reaction points decreases and the curing time increases, and it is difficult to cure at a low temperature for a short time. In addition, the average particle diameter of the latent curing agent used in the present invention was an average particle diameter in terms of volume using a laser diffraction type measuring apparatus RODOS SR type (SYMPATEC HEROS & RODOS).
[0010]
Further, the thickness of the capsule wall material film of the microencapsulated imidazole derivative epoxy compound is 0.001 to 0.3 μm, preferably 0.005 to 0.2 μm, and more preferably 0.01 to 0.1 μm. . If the thickness of the capsule wall material film is less than the lower limit, the strength of the wall material film becomes insufficient, and it becomes difficult to produce a wall material film having no defect. For this reason, the wall material film is damaged by the mechanical shear and the solvent during the mixing with other raw materials, and the storage stability is deteriorated. On the other hand, when it exceeds the upper limit, the wall material film is stable and the storage stability is high, but the time until the wall material film is broken is long, and it is difficult to bond at a low temperature in a short time.
[0011]
The microencapsulated imidazole derivative epoxy compound used as a latent curing agent in the present invention is not particularly limited as long as the reaction product of the imidazole derivative and the epoxy compound is microencapsulated and pulverized. Those in which a microencapsulated imidazole derivative epoxy compound is reacted with an isocyanate compound to enhance chemical resistance and storage stability are also more suitable.
Examples of the epoxy compound used herein include glycidyl ether type epoxy resins such as bisphenol A, bisphenol F and brominated bisphenol A, diglycidyl dimer acid, and diglycidyl phthalate.
[0012]
Examples of the imidazole derivative used herein include imidazole, 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, and 1-benzyl-imidazole. 2-methylimidazole, 1-benzyl-2-ethylimidazole, 1-benzyl-2-ethyl-5-methylimidazole, 2-phenyl-4-methyl-5-hydroxydimethylimidazole, 2-phenyl-4,5-dihydroxy Methyl imidazole and the like can be mentioned.
[0013]
In the present invention, it is preferable to use an elastomer. Further, the elastomer used in the present invention is more preferably a reactive elastomer. The elastomer used in the present invention is not particularly limited, but one having a film forming property, for example, phenoxy resin, polyester resin, polyurethane resin, polyimide resin, polybutadiene, polypropylene, styrene-butadiene-styrene copolymer. Coalesce, polyacetal resin, polyvinyl butyral resin, butyl rubber, chloroprene rubber, polyamide resin, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-methacrylic acid copolymer, acrylonitrile-butadiene-styrene copolymer, polyvinyl acetate resin, nylon, Styrene-isoprene copolymer, styrene-butylene-styrene block copolymer and the like can be used, and they may be used alone or in combination of two or more.
The amount of the elastomer is not particularly limited, but is preferably from 10 to 300 parts based on 100 parts of the epoxy resin and the microencapsulated imidazole derivative epoxy compound in total. If the compounding amount exceeds 300 parts, the fluidity of the anisotropic conductive adhesive becomes insufficient, so that sufficient connection reliability cannot be obtained, and the wettability with various adherends is reduced, resulting in sufficient adhesion. Can not be obtained. If the amount is less than 10 parts, the film-forming property when anisotropic conductive adhesive is used is poor, and the elasticity of the cured product is high, so that the adhesion to various adherends is poor, A problem such as poor connection reliability after the impact test occurs.
[0014]
In the present invention, it is preferable to use an epoxy resin. The epoxy resin used in the present invention is not particularly limited as long as it has at least two or more epoxy groups in one molecule. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin, bisphenol S type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, and the like, but are not limited thereto. Can be used.
The mixing amount of the epoxy resin is preferably 10 to 200 parts based on 100 parts of the microencapsulated imidazole derivative epoxy compound. If the compounding amount exceeds 200 parts, the curability of the anisotropic conductive adhesive becomes poor, and if it is less than 10 parts, the heat and moisture resistance is poor. Sufficient connection reliability cannot be obtained.
[0015]
The addition amount of the microencapsulated imidazole derivative epoxy compound is not particularly limited, but is preferably 20 to 400 parts with respect to 100 parts in total of the elastomer and the epoxy resin. If the amount exceeds 400 parts, the heat resistance and moisture resistance of the anisotropic conductive adhesive will be insufficient, and sufficient connection reliability cannot be obtained. Further, when the amount is less than 20 parts, there is a problem that curability may be reduced.
[0016]
The composition of the conductive particles used in the present invention is not particularly limited. For example, metal particles may be used alone or in combination of two or more of gold, silver, zinc, tin, solder, indium, palladium and the like. In addition, as the particles obtained by coating the polymer core material with metal, the polymer core material includes epoxy resin, urethane resin, melamine resin, phenol resin, acrylic resin, polyester resin, polystyrene resin, and styrene-butadiene copolymer. One or a combination of two or more polymers may be used, and a metal thin film may be used alone or in combination of two or more of gold, nickel, silver, copper, zinc, tin, indium, palladium, aluminum and the like. There is no particular limitation on the thickness of the metal thin film, but if the thickness is too small, the connection becomes unstable when the anisotropic conductive adhesive is used, and if the thickness is too large, aggregation occurs. In this case, there is a possibility of causing insulation failure. Furthermore, if the metal thin film film has unevenness or chipping, the connection becomes unstable, so that it is preferable that the metal thin film film is uniformly coated. The particle size, material, and amount of these conductive particles can be appropriately selected depending on the pitch and pattern of the circuit to be connected, the thickness and material of the circuit terminal, and the like.
[0017]
The amount of the conductive particles is preferably 0.1 to 10% by volume based on the total amount of the elastomer, the epoxy resin, and the microencapsulated imidazole derivative epoxy compound. If the amount exceeds 10% by volume, the absolute amount of the conductive particles in the anisotropic conductive adhesive increases, so that the insulating property between the adherend connecting terminals is extremely reduced. On the other hand, when the content is less than 0.1% by volume, the absolute amount of the conductive particles in the anisotropic conductive adhesive becomes small, so that the conductive particles on the adherend connection terminal become insufficient, and the connection resistance becomes extremely low. Get higher.
[0018]
An appropriate amount of a coupling agent may be added to the anisotropic conductive adhesive of the present invention, if necessary. The purpose of adding the coupling agent is to improve the adhesiveness of the adhesive interface of the anisotropic conductive adhesive and to improve heat resistance and moisture resistance. The coupling agent is not particularly limited, but a silane coupling agent can be suitably used. For example, γ-glycidoxypropyltriethoxysilane, β- (3,4 epoxycyclohexyl) ethyltrimethoxy Silane, γ-methacryloxypropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, vinyltrimethoxysilane, γ-ureidopropyltriethoxysilane and the like, but one or two kinds The above may be mixed.
[0019]
Further, the anisotropic conductive adhesive of the present invention includes various additives such as a non-reactive diluent, a reactive diluent, and thixotropic to improve various properties such as resin compatibility, stability, and workability. An imparting agent, a thickener, an inorganic filler, and the like may be appropriately added.
[0020]
【Example】
Hereinafter, the present invention will be described with reference to examples.
Table 1 summarizes the amounts of the adhesives prepared in Examples and Comparative Examples / evaluation results.
[0021]
[Table 1]

[0022]
[Table 2]

[0023]
(1) Preparation of Samples for Measuring Adhesion, Connection Reliability, and Preservation The adherend is a copper / polyimide = 8 μm / 38 μm, Ni / Au plated two-layer FPC (pitch: 50 μm, number of terminals: 400) And ITO (indium / tin oxide) solid glass (30Ω □).
(2) Adhesion evaluation method A pressure was applied under the conditions of 160 ° C., 3 MPa, and 10 seconds, and evaluation was performed by a 90 ° peel test.
(3) Method of Measuring Connection Reliability The connection resistance was measured by a two-terminal method immediately after the preparation of the sample and after leaving at a temperature of 85 ° C. and a humidity of 85% for 1000 hours. Those that could not be measured were defined as OPEN (conduction failure).
(4) Method of Measuring Storage The anisotropic conductive adhesive was left in an atmosphere at 25 ° C. for 2 weeks, and then pressure-bonded under the conditions of 160 ° C., 3 MPa, and 10 seconds, and the connection resistance was measured. Less than 5.0 Ω was evaluated as ◎ (very good preservability), from 5.0 Ω to less than 10.0 Ω was evaluated as ○ (good preservation), and 10.0 Ω or more was evaluated as × (poor preservation).
[0024]
<Example 1>
100 parts by weight of a 20% solution of bisphenol A phenoxy resin (Mw: 50,000) in ethyl acetate, 50 parts by weight of a 20% solution of polyvinyl butyral resin (polymerization degree: 1700, butyralization degree: 70 mol%), bisphenol A type epoxy 20 parts by weight of a resin (epoxy equivalent: 180 g / eq), 50 parts by weight of a microencapsulated 2-methylimidazole derivative epoxy compound, and Ni / Au-plated acrylic particles having an average particle diameter of 5 μm are added to the solid content of the adhesive resin mixture. After 3 parts by weight were mixed and evenly distributed, the mixture was cast and dried on polyethylene terephthalate subjected to a mold release treatment so that the thickness after drying was 15 μm, and then cut to a width of 1.5 mm. An anisotropic conductive adhesive was obtained.
[0025]
<Examples 2 to 12>
An anisotropic conductive adhesive was obtained in the same manner as in Example 1 under the mixing ratios and conditions shown in Tables 1 and 2.
[0026]
<Comparative Example 1>
An anisotropic conductive adhesive was obtained in the same manner as in Example 1 except that the average particle size of the curing agent for the microencapsulated imidazole derivative epoxy compound was changed to 6 μm.
[0027]
<Comparative Examples 2 and 3>
An anisotropic conductive adhesive was obtained in the same manner as in Comparative Example 1 under the mixing ratios and conditions shown in Table 2.
[0028]
【The invention's effect】
According to the present invention, an anisotropic conductive adhesive having excellent storage stability and low-temperature short-time connectivity can be obtained. By using this anisotropic conductive adhesive, it is possible to connect the LCD to fine circuit electrodes such as COF.

Claims

In an anisotropic conductive adhesive obtained by dispersing conductive particles in an insulating adhesive containing a microencapsulated imidazole derivative epoxy compound as an essential component, the microencapsulated imidazole derivative epoxy compound has an average particle size of 0.1 to 3 μm. An anisotropic conductive adhesive, characterized in that:

The anisotropic conductive adhesive according to claim 1, wherein the thickness of the microcapsule wall material film of the microencapsulated imidazole derivative epoxy compound is 0.001 to 0.3 m.

3. The anisotropic conductive adhesive according to claim 1, wherein the anisotropic conductive adhesive further comprises an elastomer.

4. The anisotropically conductive adhesive according to claim 1, wherein the anisotropically conductive adhesive further comprises an epoxy resin.

An electronic device, wherein electronic and electrical components are electrically connected using the anisotropic conductive adhesive according to claim 1.

The electronic / electrical component is a semiconductor element, a semiconductor device, a printed circuit board, a liquid crystal display (LCD) panel, a plasma display (PDP) panel, an electroluminescence (EL) panel, or a field emission display (FED) panel. Electronic equipment.