JP2004193250A

JP2004193250A - Conductive paste and semiconductor device using it

Info

Publication number: JP2004193250A
Application number: JP2002357859A
Authority: JP
Inventors: Masaaki Takekoshi; 正明竹越; Toshiaki Tanaka; 俊明田中
Original assignee: Hitachi Chemical Co Ltd
Current assignee: Resonac Corp
Priority date: 2002-12-10
Filing date: 2002-12-10
Publication date: 2004-07-08
Anticipated expiration: 2022-12-10
Also published as: JP3991269B2

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive paste excellent in a conductivity in a direction orthogonal to a conductive paste applying surface and excellent in stress mitigating property. <P>SOLUTION: The conductive paste 1 has a conductive filler 2, a resin filler 3, and a binder resin as principal constituents the aspect ratio of the conductive filler 2 obtained by dividing the average length in the direction of major axis of the conductive filler 2 by the average length in the direction of minor axis of the same is specified so as to be not less than 5. The aspect ratio of the resin filler 3 obtained by dividing the average length in the direction of major axis of the resin filler 3 by the average length in the direction of minor axis of the same is specified so as to be not more than 3. Further, a value obtained by dividing the average length in the direction of major axis of the conductive filler 2 by the average length in the direction of major axis of the resin filler 3 is specified so as to be not less than 0.05 and not more than 1. A value obtained by dividing the total volume of the conductive filler 2 contained in the conductive paste 1 by the total volume of the resin filler 3 is specified so as to be not less than 2 and not more than 5, while the coefficient of elasticity of the resin filler 3 is specified so as to be 10-2,400MPa. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は半導体素子または半導体装置と支持基板を電気的に接続する、導電性ペースト及びこれを用いた半導体装置に関する。
【０００２】
【従来の技術】
半導体素子や電子部品を支持部材へ接合する際には、接続部材としてはんだが一般的に用いられてきたが、近年、脱ハロゲン化、脱鉛化など環境への配慮を求める声が世界的に盛んになりつつあり、該接続部材に鉛フリーはんだ、異方導電性接着剤及び導電性ペースト等を用いた接続方式が各社より提案されている。なかでも導電性ペーストを用いた実装方法は、接続温度の低温化ならびに接続圧力の低減化が可能であり、基板や電子部品の低コスト化の面からも注目を浴びている。
【０００３】
こうしたはんだ代替材料として導電性ペーストを用いる際に、一般的には、導電のために配合している金属フィラの形状をフレーク状に扁平化処理したものが用いられる。これは、フレーク状とすることでフィラ同士が接触した際の接触面積を増加させ、導電性ペースト硬化後の導電性能を向上するためである。
【０００４】
しかし、フレーク状の導電性フィラを用いると、導電性ペーストを半導体素子や基板の電極にスクリーン印刷法を用いて塗布すると、フレーク状の導電性フィラが、塗布面に対し水平方向に配向する。このようにフレーク状の導電性フィラが一方向に配向して積層構造となると、積層面に対し水平方向の導電性は向上するが、逆に垂直方向の導電性が低下するため、半導体素子や電子部品を実装した際に、接続方向の抵抗が大きくなるという問題があった。
【０００５】
上記のような問題を解決するため、金属粒子に強磁性を付与させたフィラを用い、垂直方向に磁場をかけることで金属粒子を垂直方向に整列させる方法（例えば、特許文献１参照）や、金属のマイグレーションを利用したデンドライトを、特殊な方法で垂直方向に成長させる方法（例えば、特許文献２参照）などが提案されているが、前者の場合、鉄やコバルトといった強磁性粒子に高導電性のめっきを施す必要があり、さらに硬化の際に強磁場を印加しつづけなければならず、後者の場合には電極表面にデンドライトを成長させるために半導体素子や基板全体を電解液に浸したり、電極間に電圧を印加させ続けてデンドライトの成長を促す必要があり、前者後者ともに特別な工程や特殊な装置が必要となり、実装プロセスが煩雑となる問題があった。
【０００６】
【特許文献１】
特開平６−１２２８５７号公報
【特許文献２】
特開平５−２５９１１６号公報
【０００７】
【発明が解決しようとする課題】
本発明は、これらの問題を解決させるためになされたものである。請求項１記載の発明は、導電性ペースト塗布面に対し垂直方向の導電性を向上することができ、かつ接続部の応力緩和性を向上させることのできる導電性ペーストを提供するものである。請求項２記載の発明は、請求項１記載の発明に加えて、導電性ペースト作成時や塗布時の作業性を向上した導電性ペーストを提供するものである。請求項３記載の発明は、請求項１記載の発明に加えて、更に垂直方向の導電性に優れ、かつ水平方向の導電性にも優れた導電性ペーストを提供するものである。請求項４記載の発明は、半導体素子を支持部材に接合する際に、優れた接続抵抗と応力緩和性を示す半導体装置を提供するものである。請求項５記載の発明は、電子部品を支持部材に接合する際に、優れた接続抵抗と応力緩和性を示す半導体装置を提供するものである。
【０００８】
【課題を解決するための手段】
本発明は次のものに関する。
（１）導電性フィラ、樹脂フィラ及びバインダー樹脂を主成分とする導電性ペーストであって、前記導電性フィラの長軸方向の平均長さ（Ａ）を前記導電性フィラの短軸方向の平均長さで除した前記導電性フィラのアスペクト比（Ｂ）及び前記樹脂フィラの長軸方向の平均長さ（Ｃ）を前記樹脂フィラの短軸方向の平均長さで除した前記樹脂フィラのアスペクト比（Ｄ）の間に、０．０５≦（Ａ）／（Ｃ）≦１、かつ（Ｂ）≧５、かつ（Ｄ）≦３の関係が成り立ち、さらに導電性ペースト中に含有する前記導電性フィラの総体積（Ｅ）と前記樹脂フィラの総体積（Ｆ）の間に、２≦（Ｅ）／（Ｆ）≦５の関係が成り立ち、さらに前記樹脂フィラの弾性率（Ｇ）が１０ＭＰａ≦（Ｇ）≦２４００ＭＰａであることを特徴とする導電性ペースト。
（２）前記導電性フィラの平均粒径が０．５μｍ以上、かつ前記樹脂フィラの平均粒径が１００μｍ以下であることを特徴とする上記（１）記載の導電性ペースト。
（３）前記樹脂フィラの表面が、Ａｇ、Ｃｕ、Ａｕ、Ｐｔ、Ｎｉ、Ａｌ、Ｓｎ、Ｚｎ、ＡｇめっきＣｕ、Ａｇ−Ｃｕ合金、ＰｄめっきＡｇ、Ｐｄ−ＡｇめっきＡｇ、Ａｕ、Ａｕ−Ａｇ合金、Ａｕ−Ｃｕ合金、Ｐｔ−Ａｇ合金及びＡｇめっきＮｉ等の導電性金属やその合金等で被覆されていること特徴とする、上記（１）または（２）に記載の導電性ペースト。
（４）上記（１）、（２）または（３）のいずれかに記載の導電性ペーストを用いて、半導体素子の電極パッドと支持基板の電極パッドを電気的に接合することを特徴とする半導体装置。
（５）上記（１）、（２）または（３）のいずれかに記載の導電性ペーストを用いて、電子部品または半導体装置の電極パッドと支持基板の電極パッドを電気的に接合することを特徴とする半導体装置。
【０００９】
【発明の実施の形態】
本発明者は上記導電性ペーストを提供するため鋭意研究を重ねた結果、図１に示すように従来塗布面と水平方向へ配向していたフレーク状の導電性フィラ２が、図２に示すように導電性ペースト１に塊状の樹脂フィラ３を配合することで、塊状の樹脂フィラ３によってその配向を乱され、塗布面と水平方向へ配向していない導電性フィラ２の割合が増加することに着目し、特別な工程や特殊な装置を使用せず、また導電性フィラ２の充填量を増加させることなく塗布面に対し垂直方向の導電性に優れ、さらに、塊状の樹脂フィラ３に低弾性率の樹脂フィラを使用することにより、接続部の低弾性化を果たせる導電性ペーストが得られることを見出した。
【００１０】
本発明に用いる導電性フィラとしては、Ａｇ、Ｃｕ、Ａｕ、Ｐｔ、Ｎｉ、Ａｌ、Ｓｎ、Ｚｎ、ＡｇめっきＣｕ、Ａｇ−Ｃｕ合金、ＰｄめっきＡｇ、Ｐｄ−ＡｇめっきＡｇ、Ａｕ、Ａｕ−Ａｇ合金、Ａｕ−Ｃｕ合金、Ｐｔ−Ａｇ合金及びＡｇめっきＮｉ等が使用でき、そのなかでもＡｇ、ＡｇめっきＣｕが好ましい。また２種以上の導電性フィラを用いてもよく、単独で使用してもよい。
【００１１】
本発明に用いる樹脂フィラとしては、シリコーンゴム、アクリルゴム、ポリエチレン、ポリスチレン、ポリプロピレン、アクリロニトリル−スチレン共重合体、アクリロニトリル−ブタジエン−スチレン共重合体、ポリカーボネート、ポリメチルメタアクリレート等の各種アクリレート、ポリイミド、ポリアミド、ポリエステル、ポリ塩化ビニル、ポリ塩化ビニリデン、ポリジビニルベンゼン、ポリフェニレンオキサイド、ポリフェニレンサルファイド、ポリメチルペンテン、シリコーン樹脂、アクリル樹脂、フッ素樹脂、尿素樹脂、メラミン樹脂、フェノール樹脂、エポキシ樹脂、ベンゾグアナミン樹脂ポリアセタール樹脂、キシレン樹脂、フラン樹脂、ポリイソシアネート樹脂、フェノキシ樹脂、導電性高分子等が使用でき、そのなかでもシリコーンゴム、アクリルゴム、ポリエチレン、ポリスチレン、アクリロニトリル−ブタジエン−スチレン共重合体などが好ましい。また２種以上の樹脂フィラを用いてもよく、単独で使用してもよい。
【００１２】
さらに、前記樹脂フィラの表面が、Ａｇ、Ｃｕ、Ａｕ、Ｐｔ、Ｎｉ、Ａｌ、Ｓｎ、Ｚｎ、ＡｇめっきＣｕ、Ａｇ−Ｃｕ合金、ＰｄめっきＡｇ、Ｐｄ−ＡｇめっきＡｇ、Ａｕ、Ａｕ−Ａｇ合金、Ａｕ−Ｃｕ合金、Ｐｔ−Ａｇ合金及びＡｇめっきＮｉ等の導電性金属やその合金等で被覆されていればより好ましい。また、被覆する金属としてはＡｇ、ＡｇめっきＣｕがより好ましい。なお、表面を被覆された樹脂フィラの長軸方向の平均長さ（Ｃ）は、導電性フィラの長軸方向の平均長さ（Ａ）と０．０５≦（Ａ）／（Ｃ）≦１の関係を満たし、表面を被覆された樹脂フィラのアスペクト比（Ｄ）は（Ｄ）≦３である。
【００１３】
なお、本発明において、（Ａ）／（Ｃ）＞１であると、配向を乱された導電性フィラが塗布面に対しとる角度が小さい傾向にあり、垂直方向の導電性を効率よく向上できず、（Ａ）／（Ｃ）＜０．０５であると、導電性フィラに比べて樹脂フィラの同士の隙間が大きくなり、その隙間に導電性フィラが大量に入り込んでしまうため、効率よく配向を乱すことができず、やはり垂直方向の導電性を効率よく向上できない傾向にあるため、避けるべきである。また、（Ｂ）＜５となると、導電性フィラの形状が球状に近づくため、導電性フィラ同士の接触面積が低下し、大塊状の樹脂フィラによって配向を乱されたとしても、垂直方向の導電性を効率よく向上できず、また、（Ｄ）＞３となると、樹脂フィラの形状がフレーク状に近づくため、塗布時に樹脂フィラそのものが配向してしまうため、導電性フィラの配向を乱す効果が小さくなってしまい、垂直方向の導電性を効率よく向上できない傾向にあるため、避けるべきである。また、（Ｅ）／（Ｆ）＜２であると、樹脂フィラの占める空間が大きくなりすぎて、導電性フィラ同士の接触が妨げられるため、導電性を効率よく向上できず、（Ｅ）／（Ｆ）＞５であると、樹脂フィラの占める空間が小さくなりすぎて、導電性フィラの配向にわずかな影響しか与えられなくなるため、垂直方向の導電性を効率よく向上できない傾向にあるため、避けるべきである。また、（Ｇ）＜１０ＭＰａであると、導電性ペースト作成の際に、混練操作中の圧力でフィラが大きく変形したり潰れたりすることがあり、（Ｇ）＞２４００ＭＰａであると、導電性ペーストを硬化した際に弾性率を低下させる作用が弱く、接続部の低弾性化にはあまり効果的でないため、避けるべきである。
【００１４】
さらに前記導電性フィラの平均粒径が０．５μｍより小さいと、導電性ペーストの粘度が上昇し、導電性ペースト作製時及び塗布時の作業性が低下し、前記樹脂フィラの平均粒径が１００μｍより大きいと、導電性ペースト作成時及び塗布時の作業性が低下し、その塗布表面も平滑にならないため、好ましくはこれも避けるべきである。
【００１５】
本発明における導電性ペーストは、上記導電性フィラと樹脂フィラを適当なバインダー樹脂中に、らいかい機等を使用してフィラ成分をバインダー中に均一に分散させることにより製造できる。該バインダー樹脂としては、エポキシ樹脂、フェノール樹脂、アクリル樹脂、ウレタン樹脂、ポリエステル樹脂、アルキド樹脂、レゾール樹脂、ポリイミド樹脂、ポリアミド樹脂、シリコン樹脂、セルロース樹脂、ロジン樹脂、メラミン樹脂及び尿素樹脂等が使用できる。
【００１６】
本発明における導電性ペーストには、上記必須成分以外に各種溶剤、顔料、染料、分散剤、酸化防止剤、静電気防止剤、消泡剤等を必要に応じて使用し、印刷性、作業性等を適宜調整することができる。
【００１７】
以上、説明した本発明の導電性ペーストは、半導体素子や電子部品等の支持基板への電気的な接合材料等として使用することができる。
【００１８】
本発明の導電性ペーストを用いた半導体装置は、スクリーン印刷、転写、ディスペンス等で、半導体素子もしくは半導体装置及び電子部品の電極、または支持基板の電極の少なくともどちらか一方の電極に塗布したのち、半導体素子もしくは半導体装置及び電子部品と支持基板を導電性ペーストで接合し、加熱硬化して製造することができる。本発明を用いた半導体装置としては、フリップチップ型やチップ積層（スタック）型のＢＧＡ、ＣＳＰ等の半導体パッケージ、ＩＣ接続ガラス基板、コンデンサや抵抗体といった各種表面実装用電子部品を搭載した実装基板、ＱＦＰ、ＢＧＡ及びＣＳＰ等半導体パッケージを搭載した実装基板等が挙げられる。
【００１９】
【実施例】
以下に、本発明の具体的実施例について説明するが、本発明はこれらにより制限されるものではない。
実施例１〜４
バインダー樹脂として、主剤をビスフェノールＦ型、ＡＤ型混合エポキシ樹脂、硬化剤をノボラック型フェノール樹脂及びｐ−ｔ−トリブチルフェニルグリシジルエーテルとした一液性熱硬化型エポキシ樹脂（以下樹脂成分という）を用い、導電性フィラ及び樹脂フィラとして、表１に示すような割合で配合したものをそれぞれ用い、導電性ペースト全体の体積に対する導電性フィラの総体積（フィラの体積分率）が３２ｖｏｌ％になるように樹脂成分とフィラ成分を混合し、（株）石川工場製のらいかい機で真空混練して導電性ペーストを得た。この得られた導電性ペーストの導電性と弾性率を以下の方法で評価したところ、どの導電性ペーストも垂直方向の体積抵抗率ρｚ≦２．５×１０^−４Ω・ｃｍの良好な導電性と、引っ張り弾性率Ｅ≦５ＧＰａの低弾性な接続部を得ることができた。評価結果を表１に示す。
【００２０】
【表１】

【００２１】
評価方法
導電性：接続抵抗を測定できるようにＣｕ配線とＡｕ電極を備えたガラスエポキシ基板のＡｕ電極上に上記導電性ペーストをスクリーン印刷し、同じく接続抵抗を測定できるようにＡｌ配線とＡｕ電極を備えた半導体素子を、互いの電極同士が対向しあうように実装して得られた測定試料を、１５０℃オーブン中で６０分加熱し導電性ペーストを硬化させ、接続部の導電性を４端子法で測定し、接続距離及び接続面積より垂直方向の体積抵抗率ρｚを算出した。
弾性率：導電性ペーストを１５０℃オーブン中で６０分硬化して、短冊状の導電性ペースト硬化物としたものを、エーアンドディ社製テンシロンＲＴＣ−１２１０Ａを用いて、試験速度０．５ｍｍ／秒、試験温度２５℃にて引っ張り試験を行い、得られた応力―ひずみ曲線から算出した。
【００２２】
比較例１〜８
実施例と同様のバインダー樹脂を用い、導電性フィラ及び樹脂フィラとして、表２に示すような割合で配合したものをそれぞれ用い、導電性ペースト全体の体積に対する導電性フィラの総体積（フィラの体積分率）が３２ｖｏｌ％になるように樹脂成分とフィラ成分を混合し、実施例と同様にして導電性ペーストを得た。評価方法も実施例と同様である。評価結果を表２に示す。
【００２３】
【表２】

【００２４】
なお、本発明において、導電性フィラ及び高分子フィラの長さ及びアスペクト比は、導電性ペーストの硬化物のサンプルを作成し、その硬化物断面をＳＥＭ観察し、３０個以上無作為に選択したフィラの、長軸方向の長さと短軸方向の長さの測定結果より得た。サンプルはガラス板の上に適量の導電性ペーストを塗布し、硬化反応が終了するのに必要な熱量を加え、導電性ペーストを硬化させて得た。断面は従来公知の装置でサンプルを切断して露出させた。
また、各フィラの総体積の関係は、導電性ペーストの硬化断面に現れた各フィラの面積比より算出した
【００２５】
【発明の効果】
本発明の導電性ペーストは、低弾性な樹脂フィラを配合することで、導電性に優れるフレーク状の導電性フィラの塗布面と水平方向への配向が効率よく乱され、塗布面と垂直方向へ配向するフィラの割合が増加することによって、塗布面に対し垂直方向の導電性に優れ、さらに接続部の低弾性化による応力緩和性が優れており、支持基板への半導体素子、半導体装置及び電子部品の電気的な接合材料として好適であり、これを用いた半導体装置は接続抵抗と接続部の応力緩和性ともに優れている。
【図面の簡単な説明】
【図１】従来の導電性ペースト層の微細構造を示す断面図。
【図２】本発明の導電性ペースト層の微細構造を示す断面図。
【符号の説明】
１導電性ペースト
２導電性フィラ
３樹脂フィラ[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a conductive paste for electrically connecting a semiconductor element or a semiconductor device and a support substrate, and a semiconductor device using the same.
[0002]
[Prior art]
When joining semiconductor elements and electronic components to supporting members, solder has been commonly used as a connecting member. In recent years, however, voices calling for environmental considerations such as dehalogenation and deleading have been heard worldwide. Various companies have proposed a connection method using lead-free solder, an anisotropic conductive adhesive, a conductive paste, or the like for the connection member. Above all, the mounting method using a conductive paste is capable of lowering the connection temperature and the connection pressure, and is receiving attention from the viewpoint of reducing the cost of the substrate and the electronic components.
[0003]
When a conductive paste is used as such a solder substitute material, generally, a material obtained by flattening the shape of a metal filler compounded for conductivity into a flake shape is used. This is because the flake shape increases the contact area when the fillers come into contact with each other and improves the conductive performance after the conductive paste is cured.
[0004]
However, when a flake-shaped conductive filler is used, when a conductive paste is applied to a semiconductor element or an electrode of a substrate using a screen printing method, the flake-shaped conductive filler is oriented in a horizontal direction with respect to an application surface. When the flake-shaped conductive fillers are oriented in one direction to form a laminated structure, the conductivity in the horizontal direction with respect to the lamination surface is improved, but the conductivity in the vertical direction is reduced. When electronic components are mounted, there is a problem that resistance in the connection direction increases.
[0005]
In order to solve the above problems, a method of aligning metal particles in a vertical direction by applying a magnetic field in a vertical direction by using a filler having ferromagnetism imparted to metal particles (for example, see Patent Document 1), A method has been proposed in which dendrite utilizing metal migration is grown in a vertical direction by a special method (for example, see Patent Document 2). In the former case, ferromagnetic particles such as iron and cobalt have high conductivity. It is necessary to apply a strong magnetic field at the time of curing, and in the latter case, immerse the semiconductor element or the entire substrate in an electrolytic solution in order to grow dendrite on the electrode surface, It is necessary to keep applying voltage between the electrodes to promote the growth of dendrite. Both the former and the latter require special processes and special equipment, which complicates the mounting process. There was.
[0006]
[Patent Document 1]
JP-A-6-122857 [Patent Document 2]
JP-A-5-259116
[Problems to be solved by the invention]
The present invention has been made to solve these problems. The first aspect of the present invention provides a conductive paste capable of improving conductivity in a direction perpendicular to a conductive paste application surface and improving stress relaxation of a connection portion. According to a second aspect of the present invention, there is provided, in addition to the first aspect, a conductive paste having improved workability at the time of preparing and applying the conductive paste. The third aspect of the present invention provides, in addition to the first aspect of the present invention, a conductive paste having excellent vertical conductivity and excellent horizontal conductivity. According to a fourth aspect of the present invention, there is provided a semiconductor device exhibiting excellent connection resistance and stress relaxation when a semiconductor element is joined to a support member. A fifth aspect of the present invention provides a semiconductor device that exhibits excellent connection resistance and stress relaxation when an electronic component is joined to a support member.
[0008]
[Means for Solving the Problems]
The present invention relates to the following.
(1) A conductive paste containing a conductive filler, a resin filler and a binder resin as main components, wherein the average length (A) of the conductive filler in the major axis direction is an average of the average length of the conductive filler in the minor axis direction. The aspect ratio of the resin filler obtained by dividing the aspect ratio (B) of the conductive filler divided by the length and the average length of the resin filler in the major axis direction (C) by the average length of the resin filler in the minor axis direction. The relationship of 0.05 ≦ (A) / (C) ≦ 1, and (B) ≧ 5, and (D) ≦ 3 is satisfied between the ratio (D), and the conductivity contained in the conductive paste. The relationship 2 ≦ (E) / (F) ≦ 5 is established between the total volume (E) of the conductive filler and the total volume (F) of the resin filler, and the elastic modulus (G) of the resin filler is 10 MPa. ≦ (G) ≦ 2400 MPa.
(2) The conductive paste according to the above (1), wherein the average particle size of the conductive filler is 0.5 μm or more, and the average particle size of the resin filler is 100 μm or less.
(3) The surface of the resin filler is made of Ag, Cu, Au, Pt, Ni, Al, Sn, Zn, Ag-plated Cu, Ag-Cu alloy, Pd-plated Ag, Pd-Ag-plated Ag, Au, Au-Ag. The conductive paste according to the above (1) or (2), wherein the conductive paste is coated with a conductive metal such as an alloy, an Au-Cu alloy, a Pt-Ag alloy, and an Ag-plated Ni, or an alloy thereof.
(4) The electrode pad of the semiconductor element and the electrode pad of the support substrate are electrically joined using the conductive paste according to any one of (1), (2) and (3). Semiconductor device.
(5) Using the conductive paste according to any one of (1), (2) and (3), electrically connecting an electrode pad of an electronic component or a semiconductor device to an electrode pad of a support substrate. Characteristic semiconductor device.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
The inventor of the present invention has conducted intensive studies to provide the above-mentioned conductive paste. As a result, as shown in FIG. 1, the flake-shaped conductive filler 2 which has been conventionally oriented in the horizontal direction with respect to the application surface, as shown in FIG. By blending the bulky resin filler 3 with the conductive paste 1, the orientation of the bulky resin filler 3 is disturbed by the bulky resin filler 3 and the proportion of the conductive filler 2 not horizontally oriented with the application surface increases. Paying attention, it has excellent conductivity in the direction perpendicular to the application surface without using any special process or special equipment, and without increasing the filling amount of the conductive filler 2, and has low elasticity to the bulky resin filler 3 It has been found that by using a resin filler having a low ratio, a conductive paste capable of achieving a low elasticity of a connection portion can be obtained.
[0010]
Examples of the conductive filler used in the present invention include Ag, Cu, Au, Pt, Ni, Al, Sn, Zn, Ag-plated Cu, Ag-Cu alloy, Pd-plated Ag, Pd-Ag-plated Ag, Au, Au-Ag. Alloys, Au-Cu alloys, Pt-Ag alloys, Ag-plated Ni, and the like can be used, and among them, Ag and Ag-plated Cu are preferable. Further, two or more conductive fillers may be used, or they may be used alone.
[0011]
As the resin filler used in the present invention, silicone rubber, acrylic rubber, polyethylene, polystyrene, polypropylene, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polycarbonate, various acrylates such as polymethyl methacrylate, polyimide, Polyamide, polyester, polyvinyl chloride, polyvinylidene chloride, polydivinylbenzene, polyphenylene oxide, polyphenylene sulfide, polymethylpentene, silicone resin, acrylic resin, fluorine resin, urea resin, melamine resin, phenol resin, epoxy resin, benzoguanamine resin polyacetal Resin, xylene resin, furan resin, polyisocyanate resin, phenoxy resin, conductive polymer, etc. can be used. Silicone rubber, acrylic rubber, polyethylene, polystyrene, acrylonitrile - butadiene - styrene copolymer. Further, two or more resin fillers may be used, or they may be used alone.
[0012]
Furthermore, the surface of the resin filler is made of Ag, Cu, Au, Pt, Ni, Al, Sn, Zn, Ag-plated Cu, Ag-Cu alloy, Pd-plated Ag, Pd-Ag-plated Ag, Au, Au-Ag alloy. , Au-Cu alloy, Pt-Ag alloy, and Ag-plated Ni are more preferably covered with a conductive metal or an alloy thereof. Further, Ag and Ag plated Cu are more preferable as the metal to be coated. The average length (C) in the major axis direction of the resin filler coated on the surface is the average length (A) in the major axis direction of the conductive filler and 0.05 ≦ (A) / (C) ≦ 1. And the aspect ratio (D) of the resin filler coated on the surface is (D) ≦ 3.
[0013]
In the present invention, when (A) / (C)> 1, the angle of the conductive filler having disordered orientation tends to be small with respect to the coating surface, and the vertical conductivity can be efficiently improved. When (A) / (C) <0.05, the gap between the resin fillers is larger than that of the conductive filler, and a large amount of the conductive filler enters the gap. Should not be used because it tends to be unable to efficiently improve vertical conductivity. When (B) <5, the shape of the conductive filler approaches a sphere, so that the contact area between the conductive fillers is reduced, and even if the orientation is disturbed by the massive resin filler, the conductive property in the vertical direction is reduced. When (D)> 3, the shape of the resin filler approaches a flake shape, and the resin filler itself is oriented at the time of coating, so that the effect of disturbing the orientation of the conductive filler is not achieved. It should be avoided because it tends to be small and the vertical conductivity cannot be improved efficiently. Further, if (E) / (F) <2, the space occupied by the resin filler becomes too large and the contact between the conductive fillers is hindered, so that the conductivity cannot be improved efficiently, and (E) / When (F)> 5, the space occupied by the resin filler becomes too small, and the orientation of the conductive filler is only slightly affected. Therefore, the conductivity in the vertical direction tends to be unable to be efficiently improved. Should be avoided. When (G) <10 MPa, the filler may be greatly deformed or crushed by the pressure during the kneading operation during the preparation of the conductive paste. When (G)> 2400 MPa, the conductive paste may be formed. Since the effect of lowering the elastic modulus when hardening is weak and is not very effective in lowering the elasticity of the connection portion, it should be avoided.
[0014]
Further, when the average particle size of the conductive filler is smaller than 0.5 μm, the viscosity of the conductive paste increases, the workability during preparation and application of the conductive paste decreases, and the average particle size of the resin filler is 100 μm. If it is larger, the workability at the time of preparing and applying the conductive paste is reduced, and the applied surface is not smooth, so that this should preferably be avoided.
[0015]
The conductive paste in the present invention can be produced by uniformly dispersing the above-mentioned conductive filler and resin filler in an appropriate binder resin and using a trimmer or the like to disperse the filler component in the binder. As the binder resin, epoxy resin, phenol resin, acrylic resin, urethane resin, polyester resin, alkyd resin, resole resin, polyimide resin, polyamide resin, silicone resin, cellulose resin, rosin resin, melamine resin, urea resin and the like are used. it can.
[0016]
In the conductive paste of the present invention, various solvents, pigments, dyes, dispersants, antioxidants, antistatic agents, antifoaming agents and the like are used as necessary, in addition to the above essential components, and printability, workability, etc. Can be appropriately adjusted.
[0017]
The conductive paste of the present invention described above can be used as a material for electrically bonding to a support substrate of a semiconductor element, an electronic component, or the like.
[0018]
Semiconductor device using the conductive paste of the present invention, screen printing, transfer, dispensing, etc., after applying to at least one electrode of the semiconductor element or the electrode of the semiconductor device and electronic components, or the electrode of the support substrate, It can be manufactured by bonding a semiconductor element or a semiconductor device and an electronic component to a supporting substrate with a conductive paste, and curing by heating. Examples of the semiconductor device using the present invention include flip-chip type and chip stacked (stacked) type semiconductor packages such as BGA and CSP, IC connection glass substrates, and mounting substrates on which various surface mounting electronic components such as capacitors and resistors are mounted. , QFP, BGA, and CSP.
[0019]
【Example】
Hereinafter, specific examples of the present invention will be described, but the present invention is not limited thereto.
Examples 1-4
As a binder resin, a one-component thermosetting epoxy resin (hereinafter referred to as a resin component) using bisphenol F-type and AD-type mixed epoxy resins as main components, a novolak-type phenol resin as a curing agent and pt-tributylphenylglycidyl ether as curing agents is used. As the conductive filler and the resin filler, those blended at the ratios shown in Table 1 are used, and the total volume of the conductive filler (the volume fraction of the filler) with respect to the total volume of the conductive paste is 32 vol%. Was mixed with a resin component and a filler component, and the mixture was vacuum kneaded with a grinder manufactured by Ishikawa Plant to obtain a conductive paste. When the conductivity and the elastic modulus of the obtained conductive paste were evaluated by the following methods, all the conductive pastes had good volume resistivity ρz ≦ 2.5 × 10 ⁻⁴ Ω · cm in the vertical direction. And a low-elasticity connection part having a tensile modulus of elasticity E ≦ 5 GPa could be obtained. Table 1 shows the evaluation results.
[0020]
[Table 1]

[0021]
Evaluation method Conductivity: The conductive paste is screen-printed on an Au electrode of a glass epoxy substrate provided with a Cu wiring and an Au electrode so that connection resistance can be measured, and an Al wiring and an Au electrode can be similarly measured so that connection resistance can be measured. The measurement sample obtained by mounting the semiconductor device provided with the electrodes so that the electrodes face each other is heated in an oven at 150 ° C. for 60 minutes to cure the conductive paste, and the conductivity of the connection portion is increased by 4%. The measurement was performed by the terminal method, and the volume resistivity ρz in the vertical direction was calculated from the connection distance and the connection area.
Elastic modulus: The conductive paste was cured in an oven at 150 ° C. for 60 minutes to obtain a cured conductive paste in the form of a strip, and the test speed was 0.5 mm / using Tensilon RTC-1210A manufactured by A & D. A tensile test was performed at a test temperature of 25 ° C. for a second, and calculated from the obtained stress-strain curve.
[0022]
Comparative Examples 1 to 8
The same binder resin as in the example was used, and as the conductive filler and the resin filler, those blended at the ratios shown in Table 2 were used, and the total volume of the conductive filler relative to the entire conductive paste (volume of filler) The resin component and the filler component were mixed so that the ratio (fraction) was 32 vol%, and a conductive paste was obtained in the same manner as in the example. The evaluation method is the same as in the embodiment. Table 2 shows the evaluation results.
[0023]
[Table 2]

[0024]
In the present invention, the length and aspect ratio of the conductive filler and the polymer filler were determined by preparing a sample of a cured product of the conductive paste, observing the cross section of the cured product by SEM, and randomly selecting 30 or more pieces. It was obtained from the measurement results of the length of the filler in the major axis direction and the minor axis direction. The sample was obtained by applying an appropriate amount of a conductive paste on a glass plate, applying heat required to complete the curing reaction, and curing the conductive paste. The cross section was exposed by cutting the sample with a conventionally known device.
The relationship between the total volume of each filler was calculated from the area ratio of each filler that appeared on the cured cross section of the conductive paste.
【The invention's effect】
The conductive paste of the present invention, by blending a low-elastic resin filler, effectively disturbs the orientation of the flake-shaped conductive filler having excellent conductivity in the horizontal direction with the application surface, and in the vertical direction with the application surface. By increasing the proportion of the filler to be oriented, the conductivity in the direction perpendicular to the coating surface is excellent, and the stress relaxation property due to the low elasticity of the connection portion is excellent. It is suitable as an electrical joining material for components, and a semiconductor device using the same is excellent in both connection resistance and stress relaxation of the connection portion.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a fine structure of a conventional conductive paste layer.
FIG. 2 is a sectional view showing a fine structure of a conductive paste layer of the present invention.
[Explanation of symbols]
1 conductive paste 2 conductive filler 3 resin filler

Claims

A conductive paste containing a conductive filler, a resin filler, and a binder resin as main components, wherein the average length (A) in the major axis direction of the conductive filler is defined as the average length in the minor axis direction of the conductive filler. The aspect ratio (D) of the resin filler obtained by dividing the aspect ratio (B) of the conductive filler and the average length (C) of the resin filler in the major axis direction by the average length of the resin filler in the minor axis direction. ), The relationship of 0.05 ≦ (A) / (C) ≦ 1, and (B) ≧ 5, and (D) ≦ 3 holds, and the conductive filler contained in the conductive paste is The relationship 2 ≦ (E) / (F) ≦ 5 holds between the total volume (E) and the total volume (F) of the resin filler, and the elastic modulus (G) of the resin filler is 10 MPa ≦ (G A) a conductive paste, wherein ≦ 2400 MPa;

2. The conductive paste according to claim 1, wherein the conductive filler has an average particle size of 0.5 μm or more, and the resin filler has an average particle size of 100 μm or less. 3.

The surface of the resin filler is made of Ag, Cu, Au, Pt, Ni, Al, Sn, Zn, Ag-plated Cu, Ag-Cu alloy, Pd-plated Ag, Pd-Ag-plated Ag, Au, Au-Ag alloy, Au 3. The conductive paste according to claim 1, wherein the conductive paste is coated with a conductive metal such as a Cu alloy, a Pt—Ag alloy, and an Ag-plated Ni, or an alloy thereof. 4.

4. A semiconductor device, wherein an electrode pad of a semiconductor element and an electrode pad of a support substrate are electrically joined by using the conductive paste according to claim 1.

4. A semiconductor device, wherein an electrode pad of an electronic component or a semiconductor device and an electrode pad of a support substrate are electrically joined using the conductive paste according to claim 1.