JP2004303874A

JP2004303874A - Semiconductor device and manufacturing method therefor

Info

Publication number: JP2004303874A
Application number: JP2003093650A
Authority: JP
Inventors: Yuji Sakamoto; 有史坂本
Original assignee: Sumitomo Bakelite Co Ltd
Current assignee: Sumitomo Bakelite Co Ltd
Priority date: 2003-03-31
Filing date: 2003-03-31
Publication date: 2004-10-28

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method for a semiconductor device in which electrical problems such as a leakage current on a reliability as a severe moisture-absorption bias test, and the problem or the like of the deterioration of the reliability due to the lowering of adhesive properties in the case of moisture absorption, do not occur, in which a resin composition having a flux activity is used, and which has excellent reliability. <P>SOLUTION: In an area mounting method in which a semiconductor element having a solder electrode on a circuit surface is joined with a circuit board; the circuit board or the circuit surface (a solder-electrode forming surface) of the semiconductor element is coated with a liquefied sealing resin composition mainly comprising a hydrazide compound containing a liquefied epoxy resin and an aromatic dicarboxylic-acid hydrazide of ≥50 wt. %, the circuit board and the semiconductor element are aligned so that the electrode is joined electrically, the solder electrode and the circuit board are joined electrically by a heating, and the resin is cured, thus manufacturing the semiconductor device. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、フラックス活性を有する液状封止樹脂組成物を用いて回路基板に、半導体回路面に半田電極が具備された半導体チップを接合し封止することにより得られる半導体装置の製造方法に関する。
【０００２】
【従来の技術】
近年半導体パッケージの軽薄短小化の技術革新は目覚しいものがあり、さまざまなパッケージ構造が提唱され、製品化されている。従来のリードフレーム接合に代わり、半田のような突起電極により、回路基板（マザーボード）に接合するエリア実装方式は特に重要である。
【０００３】
その中で半導体素子の回路面に直接突起電極が具備されたフリップチップはパッケージを最小化できる方法のひとつである。フリップチップ実装は、半田電極の場合、半田電極の表面の酸化膜を除去するためにフラックスで処理した後リフロー等の方法により接合する。この場合、半田電極、回路基板等の周囲にフラックスが残存し、不純物として問題となるためフラックスを除去する洗浄を行った後液状封止を行う。その理由としては、直接回路基板（マザーボード）に半田電極で接合するため、熱衝撃試験のような信頼性試験を行うと、素子と回路板の線膨張係数の差により電極接合部の電気的不良が発生するためである。
【０００４】
液状樹脂による封止は、素子の一辺または複数面に液状封止樹脂を塗布し毛細管現象を利用して樹脂を回路板とチップの間隙に流れ込ませる。しかしこの方法はフラクッス処理、洗浄を行うため工程が長くなりかつ洗浄廃液の処理問題等環境管理を厳しくしなければならない。更に液状封止を毛細管現象で行うため封止時間が長くなり、生産性に問題があった。
【０００５】
そこで直接回路基板に樹脂を塗布し、半田電極を持った素子をその上から搭載し半田接合と樹脂封止を同時に行う方法が考案された（特許文献１）。この場合、半田を回路基板に接合させるために、熱硬化製樹脂、硬化剤からなる樹脂組成物にフラックス作用を有する成分を添加することが特徴である。しかし、フラックス作用を有する物質として、酸性度の強いカルボン酸が例示されており、封止樹脂に添加する場合はイオン性不純物または電気伝導性が増加する恐れがあり、特に吸湿処理したときの封止材料の絶縁性に問題を起こす可能性があった。
【０００６】
これらを改良するための方法として、硬化剤自身にフラックス活性を持たせた樹脂組成物の検討が行なわれている。
例えば、特許文献２では硬化剤として酸無水物が検討されている。また特許文献３では、フェノール性水酸基とカルボン酸を有する化合物を硬化剤とした検討が行なわれている。
【０００７】
しかしながら、これらの改良はいずれもカルボン酸のフラックス作用を応用したものであり、厳しい吸湿バイアステストのような信頼性においてリーク電流等の電気的問題が生じるおそれがあり、且つ吸湿時の密着性の低下による信頼性の劣化の問題があった。さらに、カルボン酸類は吸湿性が高いために、樹脂を塗布する際の吸湿、樹脂を製造する際の吸湿等組成物の厳密な水分管理が必要であることが判明した。その中でアミン系化合物を硬化剤であれば前記問題点は無いことが予想されるため検討を行なった。これらの検討は既に公知であり、例えば特許文献４で示されているようにエポキシ樹脂／アミン系硬化剤による実験では、アミンアダクト、ヒドラジド、イミダゾールの検討がなされている。しかし、具体的な化合物の例示がなされておらず、詳細は不明であるが、結果としてはフラックス活性が無いという評価であった。その中でヒドラジド化合物は、ある程度までの温度では反応が進まず、かなり高温になりエポキシ樹脂との反応活性が発現する化合物として公知であり、本発明の用途に硬化挙動に関し適しているため、該硬化剤に注目し鋭意検討の結果、ある条件下ではフラックス活性が発現することを見出し、信頼性も良好であるため本願発明を完成させるに至ったものである。
【０００８】
【特許文献１】
米国特許ＵＳ５，１２８，７４６
【特許文献２】
特開平２００１−３２９０４８号公報
【特許文献３】
特開平２００１−１０６７７０号公報
【特許文献４】
特開平２００２−２９３８８３号公報
【０００９】
【発明が解決しようとする課題】
本発明の目的は、厳しい吸湿バイアステストのような信頼性においてリーク電流等の電気的問題、吸湿時の密着性の低下による信頼性の劣化の問題等を起こさず、更にフラックス活性がある樹脂組成物を用いた、信頼性に優れた半導体装置の製造方法を提供することにある。
【００１０】
【課題を解決するための手段】
すなわち本発明は、
［１］回路基板に、回路面に半田電極が具備された半導体素子を接合するエリア実装法において、回路基板または半導体素子の回路面（半田電極形成面）に液状エポキシ樹脂および芳香族ジカルボン酸ジヒドラジドを５０重量％以上含むヒドラジド化合物を主成分とし、半田電極に用いられる半田の融点をＴｓ（℃）、ヒドラジド化合物の融点をＴｈ（℃）（但し、複数添加の場合は最も高い融点を持つ化合物の融点）としてＴｓ−２０＜Ｔｈ＜Ｔｓ＋５０である液状封止樹脂組成物を塗布し、電極が電気接合されるように回路基板と半導体素子とを位置合わせした後、加熱することによって上記半田電極と回路基板とを電気的に接合し、樹脂を硬化させて製造することを特徴とする半導体装置の製造方法、
［２］該液状封止樹脂組成物が平均粒径５μｍ以下、最大粒径２０μｍ以下の球状フィラーを含んでなる［１］項記載の半導体装置の製造方法、
［３］［１］又は［２］記載の半導体装置の製造方法を用いて製造されてなる半導体装置
である。
【００１１】
【発明の実施の形態】
本発明に用いる液状エポキシ樹脂は、平均エポキシ基が２以上であれば、特に制限は無いが、その例としては既存のビスフェノール系ジグリシジルエーテル類、またそれらの水素添加反応により芳香環を飽和炭化水素化したもの、フェノールノボラックとエピクロールヒドリンとの反応で得られるグリシジルエーテルのうち常温で液状のもの、アリルフェノールノボラックとエピクロールヒドリンとの反応で得られるもの、アミノフェノールのトリグリシジルエーテル等、またはそれらを混合したものが挙げられる。またこれらの液状エポキシ樹脂にジヒドロキシナフタレンのジグリシジルエーテル、テトラメチルビフェノールのジグリシジルエーテル等の結晶性エポキシ樹脂を混合し、液状にしたものを使用することもできる。より好ましくは液状エポキシ樹脂の粘度は２５℃において２００Ｐａｓ以下であることが好ましい。これより高いと組成物としての粘度が高すぎ作業性に支障をきたす。また加水分解性イオン性不純物として塩素量が１０００ｐｐｍ以下であることが好ましい。これより高いと吸湿時信頼性において電気的不良の恐れがあるからである。
【００１２】
次に本発明に用いるヒドラジド化合物は芳香族ジカルボン酸ジヒドラジドを全ヒドラジド化合物中５０重量％以上含むことが必須である。これを下回るとフラックス活性力の低下が著しくなり好ましくない。
本発明に用いる芳香族ジカルボン酸ジヒドラジドの例としては、イソフタル酸ジヒドラジド、テレフタル酸ジヒドラジド、２，６−ナフタレンジカルボン酸ジヒドラジド、１，４−ナフトエ酸ジヒドラジド、４，４’−カルボキシビスフェノールＡのジヒドラジド等が挙げられる。また他のジヒドラジド化合物としては、カルボヒドラジド、マロン酸ジヒドラジド、コハク酸ジヒドラジドアジピン酸ジヒドラジド、セバチン酸ジヒドラジド、ドデカン二酸ジヒドラジド等が挙げられる。
【００１３】
本発明に用いるヒドラジド化合物は、更に物性を調節するためにモノヒドラジド化合物を添加することも可能であり、その例としては、サリチル酸ヒドラジド、プロピオン酸ヒドラジド、３−ヒドロキシ−２−ナフトエ酸ヒドラジド、等が挙げられる。
本発明での硬化剤としてのヒドラジド化合物は適用する半田電極に使われる半田の融点Ｔｓ（℃）に対し、構成ヒドラジド化合物のなかで最も高いヒドラジド化合物の融点Ｔｈ（℃）がＴｓ−２０＜Ｔｈ＜Ｔｓ＋５０であることが必要である。より好ましくはＴｓ−２０＜Ｔｈ＜Ｔｓ＋４０である。
ＴｈがＴｓ−２０℃を下回ると、半田の融点よりかなり低い段階でヒドラジド化合物が溶解し、半田の融点近傍で起こるフラックス活性化による半田表面の酸化膜除去、半田の基板への接合が起きうる前に樹脂組成物が硬化またはゲル化をはじめるため接続性の妨げになる。また、同様にＴｈがＴｓ＋５０を上回るとヒドラジド化合物を融解させるためにかなりの熱量を加える必要があり、半田の変形やパッケージの熱ダメージが起き問題となるからである。
【００１４】
本発明に用いる液状封止樹脂組成物の粘度は特に制限は無いが作業性の観点から２５℃で１００Ｐａｓ以下であり、より好ましくは６０Ｐａｓ以下である。粘度が１００Ｐａｓを越えると液状封止樹脂組成物の粘度上昇に伴うボイド発生、素子の濡れ不足、更には半田電極と回路基板の間に樹脂による接合不良を起こすという問題があり、エリア実装法の液状封止樹脂組成物としては好ましくない。
【００１５】
本発明に用いる全ヒドラジド化合物添加量はエポキシ樹脂に対し５〜６０重量％が好ましく、さらに好ましくは１０〜４０重量％である。６０重量％以上になると製品粘度の増加による問題を引き起こす。またはヒドラジド化合物が融解した直後の硬化性が著しく早くなり、接続性に支障をきたす。１０重量％以下になるとフラックス活性が低くなりやはり接続不良を起こす。
【００１６】
本発明に用いる液状封止樹脂組成物には、本発明の効果を損なわない範囲でヒドラジド化合物以外の硬化剤を添加することも可能である。その例としては、フェノールノボラック樹脂、オルソクレゾールノボラック樹脂等のフェノール樹脂、各種２官能以上のフェノール化合物、及びイミダゾール、ジアザ化合物、ジシアンジアミド等のアミン系化合物等が挙げられる。その添加量は全硬化剤中１０重量％以下であることが好ましい。これを上回るとフラックスとしての効果が減少する。
【００１７】
本発明で用いる球状フィラーの例としては、炭酸カルシウム、シリカ、アルミナ、窒化アルミ等が挙げられる。用途によりこれらを複数混合してもよいが、信頼性、コストの点でシリカが好ましい。その添加量は特に制限がないが、封止樹脂としての特性（耐湿性、作業性等）を保つため液状封止樹脂組成物の８０重量％以下である。より好ましくは５０％以下である。８０重量％を超えると、接合の際、絶縁性のフィラーが半導体素子の半田電極と回路板電極との接合を妨げるからである。
またフィラーの形状は球状であることが必須である。破砕フィラーの場合はその鋭利な面により半導体素子表面の回路を破壊する恐れがあるからである。
【００１８】
本発明の液状封止樹脂組成物は、前記液状エポキシ樹脂、硬化剤以外に、必要に応じて反応性希釈剤、顔料、染料、レベリング剤、消泡剤、カップリング材等の添加剤を混合し、真空脱泡することにより製造することができる。
【００１９】
次に組み立て方法について説明する。
まず、前記液状封止樹脂組成物を用いて半田電極が具備された半導体素子または対応する回路基板上に塗布する。この場合ディスペンス法が最も好ましい方法である。基板は吸湿によるボイドの発生を防ぐために予め行なっていることが好ましい。次にフリップチップボンダーを用いて半田電極と回路基板側の対応するパッドを位置決めし、素子を回路基板に正確に載置する。樹脂粘度を下げ作業性を改善させるため素子且つ又は基板側を加熱することが好ましい。つきにこのまま試験片を該ボンダー上で急速加熱を行なういわゆる部分加熱法、又はリフロー炉を通すことにより（全体化熱法）、接合と封止を同時に行なう。その後必要あれば樹脂を後硬化してより特性を向上させることも可能である。
【００２０】
本発明の液状封止樹脂組成物はフラックス活性を有した硬化剤として新たにフラックス添加することも無いため、それで封止した半導体素子により信頼性の優れた半導体装置を提供することができる。更に従来技術であるカルボン酸起因のフラックス活性と異なるため特に耐湿性により優れた半導体装置を提供することができる。
【００２１】
【実施例】
以下、本発明を実施例により説明するが、本発明はこれらの実施例に何ら限定されるものではない。
［実施例１］
液状エポキシ樹脂として、エポキシ当量１６５のビスフェノールＦ型エポキシ樹脂１００重量部、ヒドラジド化合物としてイソフタル酸ジヒドラジド（融点２２０℃）を予め２５℃、５０％の環境下に２４時間曝した物を３０重量部を混錬し、真空脱泡して液状封止樹脂組成物を得た。
次に評価として以下の項目を行なった
【００２２】
（１）接続性
１０ｍｍ角のサイズ２５０μｍピッチ、８０μｍギャップのＳｎ／Ｐｂ系共晶半田（融点１８３℃）が具備されたフリップチップ模擬素子（バンプ数約１００、デイジーチェーンによるすべての電極接続性確認可能）と対応する接合パッド（金メッキ）が具備された１５ｍｍ角のＢＴ基板（予め１２０℃、３時間で乾燥させたもの）を用意し、フリップチップボンダー（渋谷工業社製ＤＢ−２００）にて位置決めをした後、素子側を加熱し（温度条件：常温から２２０℃まで７秒、その後５秒間約２２０℃で保持し強制冷却）半田電極の接合を行なった。更にオーブンにて後硬化１５０℃、１時間行い樹脂を硬化させた。その後接続性を調べた。
（接続性＝全電極接続数／全電極数（５００）、サンプル数＝５）
【００２３】
（２）ボイド
（１）で作製した試験片を超音波探傷装置（ＳＡＴ）にてボイドの確認を行なった。半田電極にまたがるボイドの個数をカウントした（５ケのサンプルに対する総計）。
（３）信頼性―１
３０℃、６０％の環境下で作製した試験片を１９６時間吸湿させた後、リフロー（前記半田に適合する条件：最高温度２４５−２５５℃を一分間保持）三回通した後、１）と同様な接続性を調べ、ＳＡＴにてボイドを観察した。更に熱衝撃試験（条件−４０℃（３０分）−１２５℃（３０分））を行い２５０サイクル毎に接続性、界面剥離を観察し１０００サイクルまで行なった。剥離は一箇所でも出たものを一個とカウントした（サンプル数＝５）
【００２４】
（４）信頼性−２
間隔２５μｍ、配線幅２５μｍの銅線くし型電極が具備された基板に作製した樹脂でコートし、接続試験と同様の硬化条件で硬化させ、１２５℃、８５％ＲＨの湿度条件下印加電圧６Ｖの条件でバイアステストを行なった。時間は２０００時間まで行い５００時間毎に電極間の絶縁性を調べた。
（サンプル数＝５）
【００２５】
［実施例２］
模擬素子の半田電極をＳｎ−Ａｇ−Ｃｕ（融点２１７℃）にかえた以外は実施例１と同一の樹脂を用いて試験片を組み立て、各試験を行った。
（この場合のボンダーでの接続温度条件：常温から２４０℃まで８秒、その後５秒間約２４０℃で保持し強制冷却）
［実施例３］
液状エポキシ樹脂として、エポキシ当量１６５のビスフェノールＦ型エポキシ樹脂１００重量部、イソフタル酸ジヒドラジド２０重量部、他のヒドラジド化合物としてアジピン酸ジヒドラジド（融点１８０℃）１０重量部を混錬し、真空脱泡して液状封止樹脂組成物を得た。
この樹脂を用いて実施例１と同様の試験片を作製し、各試験を行った。
【００２６】
［実施例４］
液状エポキシ樹脂として、エポキシ当量１６５のビスフェノールＦ型エポキシ樹脂１００重量部、ヒドラジド化合物としてイソフタル酸ジヒドラジド３０重量部し、平均粒径２μｍ、最大粒径１０μｍの球状シリカ８０重量部を混錬し真空脱泡して液状封止樹脂組成物を得た。この樹脂を用いて実施例１と同様の試験片を作製し、各試験を行った。
【００２７】
［比較例１］
液状エポキシ樹脂として、エポキシ当量１６５のビスフェノールＦ型エポキシ樹脂１００重量部、ヒドラジド化合物としてアジピン酸ジヒドラジド（融点１８０℃）を予め２５℃、５０％の環境下に２４時間曝した物を２６重量部を混錬し、真空脱泡して液状封止樹脂組成物を得た。の樹脂を用いて実施例２と同様の試験片を作製し、各試験を行った。
［比較例２］
液状エポキシ樹脂として、エポキシ当量１６５のビスフェノールＦ型エポキシ樹脂１００重量部、イソフタル酸ジヒドラジド１０重量部、他のヒドラジド化合物としてアジピン酸ジヒドラジド（融点１８０℃）２０重量部を混錬し、真空脱泡して液状封止樹脂組成物を得た。
この樹脂を用いて実施例１と同様の試験片を作製し、各試験を行った。
【００２８】
［比較例３］
液状エポキシ樹脂として、エポキシ当量１６５のビスフェノールＦ型エポキシ樹脂１００重量部、予め２５℃、５０％ＲＨの環境下に曝した２，５−ジヒドロキシ安息香酸３０重量部、硬化促進剤として、２−フェニル−４−メチルイミダゾール０．５重量部を混錬し、真空脱泡して液状封止樹脂組成物を得た。これを用いて実施例１と同様の試験を行った。
［比較例４］
液状エポキシ樹脂として、エポキシ当量１６５のビスフェノールＦ型エポキシ樹脂１００重量部、予め２５℃、５０％ＲＨの環境下に曝した後、１５０℃、３時間、１０ｔｏｒｒの条件で乾燥させた２，５−ジヒドロキシ安息香酸３０重量部、硬化促進剤として、２−フェニル−４−メチルイミダゾール０．５重量部を混錬し、真空脱泡して液状封止樹脂組成物を得た。これを用いて実施例１と同様の試験を行った。
【００２９】
［比較例５］
液状エポキシ樹脂として、エポキシ当量１６５のビスフェノールＦ型エポキシ樹脂１００重量部、予め２５℃、５０％ＲＨの環境下に曝した２，６−ナフトエ酸ジヒドラジド（融点３００℃）３６重量部を混錬し、真空脱泡して液状封止樹脂組成物を得た。
この樹脂を用いて実施例２と同様の試験片を作製し際し、フラックス活性を発現させるために３００℃以上の温度をかけなければならないため回路基板の劣化が起き以後の評価を中止した。
［比較例６］
実施例１で作製した液状封止樹脂組成物を用いて融点２６２℃のＡｇ−Ｂｉ系半田電極が具備された模擬素子を用いた以外は実施例１と同様に試験片を作製したが半田の融点が高すぎるため樹脂が硬化してしまい、接続性は全くなかったので以下の評価を中止した。
【００３０】
【表１】

【００３１】
以上表１に示した通り、実施例では初期の接合性は良好であった。更に、信頼性−１においては熱衝撃試験５００サイクルまでは良好な結果を示し、以後芳香族ジカルボン酸ジヒドラジドの割合が多いと信頼性は向上した。更にフィラーの添加はより優れた信頼性を示した。また信頼性−２において実施例はいずれも良好な絶縁特性を示した。
一方、比較例１，２においては芳香族ジカルボン酸ジヒドラジドが必要量存在しないためフラックス活性力が不十分であり、接続歩留まりが低下し、以後の熱衝撃試験結果にも影響があった。
【００３２】
比較例３は硬化剤としてカルボン酸を含む化合物による評価を行なったが、硬化剤が吸湿したため電極接合時に多量の揮発分起因によるボイドが生じ、同時に接合性も大幅に低下した。比較例４では比較例３の硬化剤を予め十分に乾燥を行なったものを用いたため、接合性、ボイド共良好であった。また信頼性に関しても熱衝撃試験では５００サイクルで不良がなく信頼性は十分であった。しかし、吸湿バイアステストにおいて抵抗率が初期値、及び時間経過による低下が見られた。
比較例５では、使用した半田の融点より硬化剤のヒドラジド化合物の融点が、本発明の範囲を逸脱しているため接続させるために試験片にその耐熱性を超えた熱がかかりパッケージとして使用に耐えないものになった。また比較例６では使用した半田の融点より硬化剤のヒドラジド化合物の融点が本発明を逸脱して低いため半田の接合するよりも前に硬化剤が溶解して反応が進行し、全く接合ができなかった。
【００３３】
【発明の効果】
本発明に従うとフラックス材を添加することなくエリア実装素子を回路基板に実装することができ封止プロセスの短縮化とともに、耐湿性、信頼性に優れた封止樹脂を提供でき、パッケージとしての信頼性も向上する。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a semiconductor device obtained by joining and sealing a semiconductor chip provided with a solder electrode on a semiconductor circuit surface to a circuit board using a liquid sealing resin composition having flux activity.
[0002]
[Prior art]
2. Description of the Related Art In recent years, there has been a remarkable technological innovation to reduce the size and weight of semiconductor packages, and various package structures have been proposed and commercialized. An area mounting method of bonding to a circuit board (mother board) using a projecting electrode such as solder instead of the conventional lead frame bonding is particularly important.
[0003]
Among them, a flip chip in which a protruding electrode is directly provided on a circuit surface of a semiconductor device is one of methods for minimizing a package. In flip-chip mounting, in the case of a solder electrode, the solder electrode is treated with a flux to remove an oxide film on the surface of the solder electrode, and then joined by a method such as reflow. In this case, the flux remains around the solder electrode, the circuit board, and the like, and becomes a problem as an impurity. Therefore, the liquid is sealed after performing cleaning for removing the flux. The reason for this is that when a reliability test, such as a thermal shock test, is performed to directly bond a circuit board (motherboard) to a circuit board (mother board) with a solder electrode, the difference in the coefficient of linear expansion between the element and the circuit board causes an electrical failure at the electrode joint. Is caused.
[0004]
In sealing with a liquid resin, a liquid sealing resin is applied to one side or a plurality of surfaces of the element, and the resin is caused to flow into a gap between the circuit board and the chip by utilizing a capillary phenomenon. However, this method requires a long process due to the flux treatment and cleaning, and requires strict environmental management such as a problem of treating a cleaning waste liquid. Furthermore, since the liquid sealing is performed by the capillary phenomenon, the sealing time becomes longer, and there is a problem in productivity.
[0005]
Therefore, a method has been devised in which a resin is directly applied to a circuit board, an element having solder electrodes is mounted thereon, and solder bonding and resin sealing are performed simultaneously (Patent Document 1). In this case, in order to bond the solder to the circuit board, a characteristic feature is that a component having a flux action is added to a resin composition comprising a thermosetting resin and a curing agent. However, as a substance having a flux action, a carboxylic acid having a strong acidity is exemplified, and when added to a sealing resin, ionic impurities or electric conductivity may increase. There was a possibility of causing a problem in the insulating properties of the stop material.
[0006]
As a method for improving these, a resin composition in which a curing agent itself has flux activity has been studied.
For example, Patent Document 2 studies an acid anhydride as a curing agent. In Patent Document 3, a study using a compound having a phenolic hydroxyl group and a carboxylic acid as a curing agent has been conducted.
[0007]
However, these improvements are all based on the flux action of carboxylic acid, and may cause electrical problems such as leak current in reliability such as severe moisture absorption bias test, and the adhesion during moisture absorption. There was a problem of reliability deterioration due to the decrease. Furthermore, since carboxylic acids have high hygroscopicity, it was found that strict water management of the composition such as moisture absorption when applying a resin and moisture absorption when manufacturing a resin was required. Among them, if the amine-based compound is a curing agent, it is expected that the above-mentioned problems will not occur. These studies are already known. For example, as shown in Patent Document 4, in an experiment using an epoxy resin / amine-based curing agent, studies have been made on amine adducts, hydrazides, and imidazoles. However, no specific compounds have been exemplified and the details are unknown, but as a result, the evaluation was that there was no flux activity. Among them, the hydrazide compound is known as a compound which does not proceed the reaction at a certain temperature up to a relatively high temperature and exhibits a reaction activity with the epoxy resin, and is suitable for the use of the present invention with respect to the curing behavior. As a result of an intensive study focusing on the curing agent, it has been found that a flux activity is exhibited under certain conditions, and the reliability of the present invention is satisfactory, and thus the present invention has been completed.
[0008]
[Patent Document 1]
US Patent US 5,128,746
[Patent Document 2]
JP 2001-329048 A [Patent Document 3]
JP 2001-106770 A [Patent Document 4]
JP-A-2002-293883
[Problems to be solved by the invention]
An object of the present invention is to provide a resin composition having a flux activity without causing an electrical problem such as a leak current in reliability such as a strict moisture absorption bias test, a problem of deterioration in reliability due to a decrease in adhesion during moisture absorption, and the like. An object of the present invention is to provide a method for manufacturing a semiconductor device having excellent reliability by using a product.
[0010]
[Means for Solving the Problems]
That is, the present invention
[1] In an area mounting method for joining a semiconductor element having a solder electrode on a circuit surface to a circuit board, a liquid epoxy resin and an aromatic dicarboxylic acid dihydrazide are formed on a circuit surface of the circuit board or the semiconductor element (solder electrode formation surface). Hydrazide compound containing 50% by weight or more as a main component, the melting point of the solder used for the solder electrode is Ts (° C.), and the melting point of the hydrazide compound is Th (° C.) (however, a compound having the highest melting point in the case of plural additions) The melting point of the solder electrode is determined by applying a liquid sealing resin composition that satisfies Ts−20 <Th <Ts + 50, aligning the circuit board and the semiconductor element so that the electrodes are electrically joined, and then heating the soldering electrode. And a circuit board, and a method for manufacturing a semiconductor device, characterized by manufacturing by curing the resin,
[2] The method of manufacturing a semiconductor device according to [1], wherein the liquid sealing resin composition contains a spherical filler having an average particle diameter of 5 μm or less and a maximum particle diameter of 20 μm or less.
[3] A semiconductor device manufactured using the method for manufacturing a semiconductor device according to [1] or [2].
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
The liquid epoxy resin used in the present invention is not particularly limited as long as it has an average epoxy group of 2 or more. Examples thereof include existing bisphenol-based diglycidyl ethers, and saturated hydrogenation of an aromatic ring by a hydrogenation reaction thereof. Hydrogenated, glycidyl ether obtained by the reaction of phenol novolak and epichlorhydrin, liquid at room temperature, glycidyl ether obtained by the reaction of allylphenol novolak and epichlorhydrin, triglycidyl ether of aminophenol Or a mixture thereof. Further, a liquid epoxy resin such as a diglycidyl ether of dihydroxynaphthalene and a diglycidyl ether of tetramethylbiphenol may be mixed with these liquid epoxy resins to make them liquid. More preferably, the viscosity of the liquid epoxy resin at 25 ° C. is preferably 200 Pas or less. If it is higher than this, the viscosity of the composition is too high, which impairs workability. Further, the amount of chlorine as a hydrolyzable ionic impurity is preferably 1000 ppm or less. If it is higher than this, there is a risk of electrical failure in reliability during moisture absorption.
[0012]
Next, it is essential that the hydrazide compound used in the present invention contains an aromatic dicarboxylic acid dihydrazide in an amount of 50% by weight or more based on the whole hydrazide compound. If it is less than this, the flux activation power is significantly reduced, which is not preferable.
Examples of the aromatic dicarboxylic acid dihydrazide used in the present invention include isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthalenedicarboxylic acid dihydrazide, 1,4-naphthoic acid dihydrazide, 4,4′-carboxybisphenol A dihydrazide and the like. Is mentioned. Examples of other dihydrazide compounds include carbohydrazide, malonic acid dihydrazide, succinic acid dihydrazide adipic acid dihydrazide, sebacic acid dihydrazide, dodecane diacid dihydrazide and the like.
[0013]
The hydrazide compound used in the present invention may further contain a monohydrazide compound for further controlling the physical properties. Examples thereof include salicylic acid hydrazide, propionic acid hydrazide, 3-hydroxy-2-naphthoic acid hydrazide, and the like. Is mentioned.
The hydrazide compound as a curing agent in the present invention is such that the melting point Th (° C.) of the hydrazide compound, which is the highest among constituent hydrazide compounds, is Ts−20 <Th with respect to the melting point Ts (° C.) of the solder used for the applied solder electrode. <Ts + 50 is required. More preferably, Ts−20 <Th <Ts + 40.
When Th is lower than Ts-20 ° C., the hydrazide compound dissolves at a stage considerably lower than the melting point of the solder, and an oxide film on the solder surface may be removed by flux activation occurring near the melting point of the solder, and bonding of the solder to the substrate may occur. Before that, the resin composition starts to harden or gel, which hinders connectivity. Similarly, when Th exceeds Ts + 50, it is necessary to apply a considerable amount of heat to melt the hydrazide compound, which causes a problem such as deformation of solder and thermal damage of the package.
[0014]
The viscosity of the liquid sealing resin composition used in the present invention is not particularly limited, but is preferably 100 Pas or less at 25 ° C, more preferably 60 Pas or less from the viewpoint of workability. If the viscosity exceeds 100 Pas, there is a problem that voids are generated due to an increase in the viscosity of the liquid sealing resin composition, insufficient wetting of the element is caused, and further, bonding failure between the solder electrode and the circuit board is caused by the resin. It is not preferable as a liquid sealing resin composition.
[0015]
The total amount of the hydrazide compound used in the present invention is preferably 5 to 60% by weight, more preferably 10 to 40% by weight, based on the epoxy resin. When the content is more than 60% by weight, a problem due to an increase in product viscosity occurs. Alternatively, the curability immediately after the hydrazide compound is melted becomes remarkably fast, which impairs the connectivity. When the content is less than 10% by weight, the flux activity becomes low, and the connection failure also occurs.
[0016]
A curing agent other than the hydrazide compound can be added to the liquid sealing resin composition used in the present invention as long as the effect of the present invention is not impaired. Examples thereof include phenol resins such as phenol novolak resins and ortho-cresol novolak resins, phenol compounds of various bifunctional or higher, and amine compounds such as imidazole, diaza compounds and dicyandiamide. It is preferable that the addition amount is 10% by weight or less based on the whole curing agent. Above this, the effect as flux decreases.
[0017]
Examples of the spherical filler used in the present invention include calcium carbonate, silica, alumina, aluminum nitride and the like. A plurality of these may be mixed depending on the application, but silica is preferred in terms of reliability and cost. The addition amount is not particularly limited, but is 80% by weight or less of the liquid sealing resin composition in order to maintain the properties (moisture resistance, workability, etc.) as the sealing resin. It is more preferably at most 50%. If the amount exceeds 80% by weight, the insulating filler prevents the bonding between the solder electrode of the semiconductor element and the circuit board electrode at the time of bonding.
It is essential that the filler has a spherical shape. This is because, in the case of the crushed filler, the sharp surface may destroy the circuit on the surface of the semiconductor element.
[0018]
The liquid sealing resin composition of the present invention contains, in addition to the liquid epoxy resin and the curing agent, additives such as a reactive diluent, a pigment, a dye, a leveling agent, an antifoaming agent, and a coupling material as necessary. Then, it can be produced by vacuum degassing.
[0019]
Next, an assembling method will be described.
First, the liquid sealing resin composition is applied to a semiconductor element having a solder electrode or a corresponding circuit board. In this case, the dispensing method is the most preferable method. The substrate is preferably preliminarily formed in order to prevent generation of voids due to moisture absorption. Next, the solder electrodes and the corresponding pads on the circuit board side are positioned using a flip chip bonder, and the element is accurately placed on the circuit board. It is preferable to heat the element and / or the substrate in order to reduce the resin viscosity and improve the workability. At the same time, bonding and sealing are performed simultaneously by a so-called partial heating method in which the test piece is rapidly heated on the bonder, or by passing through a reflow furnace (overall heat method). Thereafter, if necessary, the resin can be post-cured to further improve the characteristics.
[0020]
Since the liquid encapsulating resin composition of the present invention does not newly add a flux as a curing agent having a flux activity, a semiconductor device having excellent reliability can be provided by a semiconductor element sealed with the flux. Further, since the flux activity is different from the flux activity caused by carboxylic acid in the prior art, it is possible to provide a semiconductor device having more excellent moisture resistance.
[0021]
【Example】
Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.
[Example 1]
100 parts by weight of a bisphenol F type epoxy resin having an epoxy equivalent of 165 as a liquid epoxy resin, and 30 parts by weight of a product obtained by previously exposing isophthalic acid dihydrazide (melting point: 220 ° C.) as a hydrazide compound to an environment of 25 ° C. and 50% for 24 hours for 24 hours. The mixture was kneaded and vacuum degassed to obtain a liquid sealing resin composition.
Next, the following items were evaluated.
(1) Connectivity A flip-chip simulated device equipped with a 10 mm square, 250 μm pitch, 80 μm gap Sn / Pb eutectic solder (melting point: 183 ° C.) (approximately 100 bumps, all electrode connectivity confirmed by daisy chain) Possible) and a 15 mm square BT substrate (pre-dried at 120 ° C. for 3 hours) provided with a corresponding bonding pad (gold plating), and prepared with a flip chip bonder (DB-200 manufactured by Shibuya Kogyo Co., Ltd.). After positioning, the element side was heated (temperature condition: from normal temperature to 220 ° C. for 7 seconds, and then maintained at about 220 ° C. for 5 seconds and forcibly cooled) to join the solder electrodes. The resin was further cured in an oven at 150 ° C. for 1 hour. Then the connectivity was examined.
(Connectivity = total number of connected electrodes / number of all electrodes (500), number of samples = 5)
[0023]
(2) Void The voids in the test piece prepared in (1) were confirmed by an ultrasonic flaw detector (SAT). The number of voids straddling the solder electrodes was counted (total for 5 samples).
(3) Reliability-1
After a test piece prepared under an environment of 30 ° C. and 60% was absorbed for 196 hours, reflow (conditions compatible with the above-mentioned solder: holding a maximum temperature of 245 to 255 ° C. for 1 minute) was passed three times. Similar connectivity was examined, and voids were observed by SAT. Further, a thermal shock test (conditions: -40 ° C. (30 minutes) -125 ° C. (30 minutes)) was performed, and the connectivity and interfacial peeling were observed every 250 cycles, and the test was performed up to 1000 cycles. Peeling was counted as one when it came out even at one place (number of samples = 5)
[0024]
(4) Reliability-2
A substrate provided with a copper wire comb-shaped electrode having an interval of 25 μm and a wiring width of 25 μm was coated with the prepared resin, cured under the same curing conditions as in the connection test, and applied at a voltage of 6 V under a humidity condition of 125 ° C. and 85% RH. A bias test was performed under the conditions. The time was up to 2000 hours, and the insulation between the electrodes was examined every 500 hours.
(Number of samples = 5)
[0025]
[Example 2]
A test piece was assembled using the same resin as in Example 1 except that the solder electrode of the simulation element was changed to Sn-Ag-Cu (melting point: 217 ° C), and each test was performed.
(Connection temperature condition in the bonder in this case: from normal temperature to 240 ° C for 8 seconds, then hold at about 240 ° C for 5 seconds and forcibly cool)
[Example 3]
As a liquid epoxy resin, 100 parts by weight of a bisphenol F type epoxy resin having an epoxy equivalent of 165, 20 parts by weight of isophthalic acid dihydrazide, and 10 parts by weight of adipic acid dihydrazide (melting point: 180 ° C.) as another hydrazide compound are kneaded, followed by vacuum degassing. Thus, a liquid sealing resin composition was obtained.
Test pieces similar to those in Example 1 were prepared using this resin, and each test was performed.
[0026]
[Example 4]
100 parts by weight of a bisphenol F type epoxy resin having an epoxy equivalent of 165 as a liquid epoxy resin, 30 parts by weight of isophthalic acid dihydrazide as a hydrazide compound, and 80 parts by weight of spherical silica having an average particle size of 2 μm and a maximum particle size of 10 μm are kneaded and vacuum-evacuated. The foam was bubbled to obtain a liquid sealing resin composition. Test pieces similar to those in Example 1 were prepared using this resin, and each test was performed.
[0027]
[Comparative Example 1]
100 parts by weight of a bisphenol F type epoxy resin having an epoxy equivalent of 165 as a liquid epoxy resin, and 26 parts by weight of a product obtained by previously exposing adipic dihydrazide (melting point: 180 ° C.) as a hydrazide compound to an environment of 25 ° C. and 50% for 24 hours were used. The mixture was kneaded and vacuum degassed to obtain a liquid sealing resin composition. A test piece similar to that of Example 2 was prepared using the above resin, and each test was performed.
[Comparative Example 2]
As a liquid epoxy resin, 100 parts by weight of a bisphenol F type epoxy resin having an epoxy equivalent of 165, 10 parts by weight of isophthalic acid dihydrazide, and 20 parts by weight of adipic acid dihydrazide (melting point: 180 ° C.) as another hydrazide compound are kneaded, and vacuum defoamed. Thus, a liquid sealing resin composition was obtained.
Test pieces similar to those in Example 1 were prepared using this resin, and each test was performed.
[0028]
[Comparative Example 3]
100 parts by weight of a bisphenol F type epoxy resin having an epoxy equivalent of 165 as a liquid epoxy resin, 30 parts by weight of 2,5-dihydroxybenzoic acid previously exposed to an environment of 25 ° C. and 50% RH, and 2-phenyl as a curing accelerator 0.5 parts by weight of -4-methylimidazole was kneaded and deaerated in vacuo to obtain a liquid sealing resin composition. The same test as in Example 1 was performed using this.
[Comparative Example 4]
As a liquid epoxy resin, 100 parts by weight of a bisphenol F-type epoxy resin having an epoxy equivalent of 165 was previously exposed to an environment of 25 ° C. and 50% RH, and then dried at 150 ° C. for 3 hours at 10 torr. 30 parts by weight of dihydroxybenzoic acid and 0.5 part by weight of 2-phenyl-4-methylimidazole as a curing accelerator were kneaded and deaerated in vacuo to obtain a liquid sealing resin composition. The same test as in Example 1 was performed using this.
[0029]
[Comparative Example 5]
As a liquid epoxy resin, 100 parts by weight of a bisphenol F type epoxy resin having an epoxy equivalent of 165 and 36 parts by weight of 2,6-naphthoic acid dihydrazide (melting point: 300 ° C.) previously exposed to an environment of 25 ° C. and 50% RH are kneaded. Then, the mixture was subjected to vacuum degassing to obtain a liquid sealing resin composition.
When a test piece similar to that of Example 2 was prepared using this resin, a temperature of 300 ° C. or higher had to be applied in order to exert flux activity, and the circuit board was deteriorated, and the subsequent evaluation was stopped.
[Comparative Example 6]
A test piece was prepared in the same manner as in Example 1 except that a simulated element provided with an Ag-Bi-based solder electrode having a melting point of 262 ° C. was used using the liquid sealing resin composition prepared in Example 1, Since the melting point was too high, the resin was cured and there was no connectivity, so the following evaluation was stopped.
[0030]
[Table 1]

[0031]
As shown in Table 1, in the examples, the initial bondability was good. Further, in reliability-1, good results were shown up to 500 cycles of the thermal shock test. Thereafter, the reliability was improved when the proportion of the aromatic dicarboxylic acid dihydrazide was large. Furthermore, the addition of filler showed better reliability. Further, in the example of reliability-2, all the examples showed good insulating properties.
On the other hand, in Comparative Examples 1 and 2, the required amount of aromatic dicarboxylic acid dihydrazide was not present, so that the flux activation power was insufficient, the connection yield was reduced, and the results of the subsequent thermal shock test were also affected.
[0032]
Comparative Example 3 was evaluated with a compound containing a carboxylic acid as a curing agent. However, since the curing agent absorbed moisture, a large amount of voids were generated due to a large amount of volatile components at the time of electrode joining, and at the same time, the joining property was significantly reduced. In Comparative Example 4, since the curing agent of Comparative Example 3 was sufficiently dried in advance, both the bonding property and the void were good. Regarding the reliability, in the thermal shock test, there were no defects in 500 cycles, and the reliability was sufficient. However, in the moisture absorption bias test, the resistivity was found to be the initial value and decreased with time.
In Comparative Example 5, since the melting point of the hydrazide compound as the curing agent was out of the range of the present invention from the melting point of the solder used, the test piece was subjected to heat exceeding its heat resistance in order to connect, so that it was used as a package. It became intolerable. In Comparative Example 6, since the melting point of the hydrazide compound of the hardener is lower than the melting point of the solder used, which is outside the scope of the present invention, the hardener dissolves before the solder is joined, and the reaction proceeds. Did not.
[0033]
【The invention's effect】
According to the present invention, an area mounting element can be mounted on a circuit board without adding a flux material, and a sealing process can be shortened, and a sealing resin having excellent moisture resistance and reliability can be provided. The performance is also improved.

Claims

In an area mounting method in which a semiconductor element having a solder electrode on a circuit surface is joined to a circuit board, a liquid epoxy resin and an aromatic dicarboxylic acid dihydrazide are added to the circuit board or the circuit surface of the semiconductor element (solder electrode forming surface) by 50 weight parts. % Of the hydrazide compound as a main component, the melting point of the solder used for the solder electrode is Ts (° C.), and the melting point of the hydrazide compound is Th (° C.) After applying a liquid sealing resin composition satisfying Ts-20 <Th <Ts + 50, aligning the circuit board and the semiconductor element so that the electrodes are electrically connected, and then heating the solder electrode and the circuit board by heating. And a method of manufacturing by curing the resin.

2. The method for manufacturing a semiconductor device according to claim 1, wherein the liquid sealing resin composition contains a spherical filler having an average particle size of 5 μm or less and a maximum particle size of 20 μm or less.

A semiconductor device manufactured using the method for manufacturing a semiconductor device according to claim 1.