JP3562565B2 - Epoxy resin composition for semiconductor encapsulation and semiconductor device - Google Patents

Description

（但し、式中Ｒ^１，Ｒ^２はそれぞれ独立に水素原子、メチル基又はｔｅｒｔ−ブチル基であり、Ｒ^３は水素原子、メチル基又はエチル基、好ましくは水素原子である。ｋは１〜５の整数である。）
【００１２】
【化７】

（但し、式中Ｒ^１，Ｒ^２，Ｒ^３は上記と同じ意味を示し、ｎは１〜５の整数である。）
【００１３】
【化８】

【００１４】
【化９】

（式中、Ａは炭素数１〜４のアルキル基又はアルコキシ置換アルキル基、ａは０又は１、Ｒ^６は水素原子、−Ｃ_２Ｈ_４ＮＨ_２又は−Ｃ_６Ｈ_５を示す。）
【００１５】
従って、本発明は、上記一般式（１）で表わされる多官能型エポキシ樹脂と、上記一般式（２）で表わされる多官能型フェノール樹脂硬化剤と、上記一般式（３）で表わされる有機リン系硬化促進剤と、上記一般式（４）で表わされるアミノシランカップリング剤と、無機質充填剤とを必須成分として含有してなることを特徴とする半導体封止用エポキシ樹脂組成物及びこの組成物の硬化物で封止された半導体装置を提供する。
【００１６】
以下、本発明につき更に詳細に説明すると、本発明の半導体封止用エポキシ樹脂組成物は、下記一般式（１）で示される多官能型エポキシ樹脂である。
【００１７】
【化１０】

（但し、式中Ｒ^１，Ｒ^２はそれぞれ独立に水素原子、メチル基（−ＣＨ_３）及びｔｅｒｔ−ブチル基（−Ｃ（ＣＨ_３）_３）から選ばれる基である。また、Ｒ^３は水素原子、メチル基（−ＣＨ_３）又はエチル基（−Ｃ_２Ｈ_５）である。ｋは１〜５、好ましくは１〜３の整数である。）
【００１８】
上記式（１）の多官能型エポキシ樹脂は、分子運動が抑制されるためにガラス転移温度（以下、Ｔｇと記す）が高いという特徴を有している。ＢＧＡパッケージは、ガラス繊維積層板にＢＴレジンなど有機樹脂を含浸させた回路基板に対する片面樹脂封止、いわゆるバイメタル構造のために大変反り易く、樹脂の選択によって反り量を低減する必要がある。反り量を低減する方法としては、その基板と同じ収縮率をもつ樹脂組成物、つまりほぼ同じＴｇと膨張係数の樹脂組成物で封止すればよい。従って、Ｔｇの高いエポキシ樹脂組成物が望ましく、上記式（１）のエポキシ樹脂を使用することにより、高Ｔｇのエポキシ樹脂組成物を得ることができる。
【００１９】
この場合、式（１）の構造に導入される置換基Ｒ^１，Ｒ^２は、それぞれ水素原子、−ＣＨ_３基、−Ｃ（ＣＨ_３）_３基、あるいはこれらの混合されたものである。樹脂組成物の硬化物のＴｇを高くしたい場合、置換基Ｒ^１，Ｒ^２は水素原子又は−ＣＨ_３基で置換した構造が望ましく、また、吸水率を小さくしたい場合は、−Ｃ（ＣＨ_３）_３基で置換した構造が望ましい。また、式（１）の構造に導入される置換基Ｒ^３は水素原子、メチル基又はエチル基であるが、好適には水素原子である。
【００２０】
上記式（１）の多官能型エポキシ樹脂は、その分子量について特に制限はないが、一般的には４００〜１，２００程度、好ましくは５００〜８００程度の範囲のものであればよい。また、エポキシ当量に関しても特に限定はないが、一般的には１５０〜３００程度、好ましくは１６０〜２００程度の範囲のものであればよい。また、シリコーン変性されていても問題はない。
【００２１】
更に、上記式（１）のエポキシ樹脂は、耐湿信頼性向上のためにこれらのエポキシ樹脂中に含有されるアルカリ金属、アルカリ土類金属、ハロゲンその他イオン性不純物が極力少ないことが望ましい。
【００２２】
本発明において、エポキシ樹脂としては、上記式（１）のエポキシ樹脂以外の他のエポキシ樹脂、例えばオルソクレゾールノボラック型エポキシ樹脂、フェノールノボラック型エポキシ樹脂等のノボラック型エポキシ樹脂；ビフェニル型エポキシ樹脂；ビスフェノールＡ型エポキシ樹脂、ビスフェノールＦ型エポキシ樹脂等のビスフェノール型エポキシ樹脂；式（１）以外のトリフェノールメタン型エポキシ樹脂；ナフタレン型エポキシ樹脂；ジシクロペンタジエン変性エポキシ樹脂；フェノールアラルキル型エポキシ樹脂；ビフェニルアラルキル型エポキシ樹脂などを併用して配合することができる。
【００２３】
本発明組成物に使用されるエポキシ樹脂は、全エポキシ樹脂中の７０重量％以上、特に９０〜１００重量％が式（１）の多官能型エポキシ樹脂であることが望ましい。式（１）の多官能型エポキシ樹脂の含有量が７０重量％未満で他のエポキシ樹脂が３０重量％を超えると、Ｔｇが低下し、ＢＧＡの反り量が増加してしまう場合がある。
【００２４】
次に、硬化剤としては、下記一般式（２）で表わされる多官能型フェノール樹脂硬化剤を使用するものであり、本発明では式（１）の多官能型エポキシ樹脂と同様の理由で式（２）の多官能型フェノール樹脂硬化剤が使用される。
【００２５】
【化１１】

（但し、式中Ｒ^１，Ｒ^２はそれぞれ独立に水素原子、メチル基又はｔｅｒｔ−ブチル基であり、好ましくは水素原子である。Ｒ^３は水素原子、メチル基又はエチル基であり、好ましくは水素原子である。ｎは１〜５、好ましくは１〜３の整数である。）
【００２６】
上記式（２）の多官能型フェノール樹脂硬化剤の分子量については特に制限はないが、一般的には２００〜１，０００程度、好ましくは３００〜６００程度の範囲のものであればよい。水酸基当量に関しても特に限定はないが、一般的には１００〜１５０程度、好ましくは１１０〜１２０程度の範囲のものであればよい。また、シリコーン変性されていても問題はない。
【００２７】
更に、式（２）の多官能型フェノール樹脂硬化剤は、耐湿信頼性向上のためにフェノール樹脂中に含有されるアルカリ金属、アルカリ土類金属、ハロゲンその他イオン性不純物が極力少ないことが望ましい。
【００２８】
硬化剤としては、上記式（２）の多官能型フェノール樹脂以外の他のフェノール樹脂、例えばフェノールノボラック樹脂、クレゾールノボラック樹脂等のノボラック樹脂；ビスフェノールＡ型樹脂、ビスフェノールＦ型樹脂等のビスフェノール型フェノール樹脂；パラキシリレン変性フェノール樹脂；メタキシリレン変性フェノール樹脂；オルソキシリレン変性フェノール樹脂；式（２）以外のトリフェノールアルカン型樹脂；ナフタレン型フェノール樹脂；ジシクロペンタジエン変性フェノール樹脂；ビフェニル型フェノール樹脂；フェノールアラルキル樹脂；ビフェニルアラルキル樹脂などを併用して配合してもよい。
【００２９】
本発明組成物に使用されるフェノール樹脂硬化剤は、全フェノール樹脂硬化剤中の７０重量％以上、好ましくは９０〜１００重量％が式（２）の多官能型フェノール樹脂であることが望ましい。式（２）の多官能型フェノール樹脂の含有量が７０重量％未満で他のフェノール樹脂硬化剤が３０重量％を超えると、Ｔｇが低下し、ＢＧＡの反り量が増加してしまう場合がある。
【００３０】
フェノール樹脂硬化剤の配合量は、エポキシ樹脂とフェノール樹脂硬化剤の合計に対して２５〜４０重量％が好ましい。２５重量％未満もしくは４０重量％を超える場合には、エポキシ樹脂中のエポキシ基数とフェノール樹脂硬化剤中の水酸基数との差が大きすぎて、組成物の硬化性が低下し、それが硬化物のＴｇの低下、線膨張係数の上昇につながり、ＢＧＡの反り量が増加してしまう場合がある。従って、フェノール樹脂硬化剤の配合量は、エポキシ樹脂中に含まれるエポキシ基１モルに対し、フェノール樹脂中に含まれるフェノール性水酸基のモル比が０．５〜１．５、特には０．８〜１．２の範囲となるように配合することもできる。
【００３１】
本発明で使用される硬化促進剤は、下記一般式（３）で表わされる有機リン系硬化促進剤である。
【００３２】
【化１２】

【００３３】
上記式（３）において、Ｒ^４は水素原子、同一もしくは異種の炭素数１〜４のアルキル基又はアルコキシ基であり、例えば水素原子、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｔｅｒｔ−ブチル基、メトキシ基、エトキシ基、プロポキシ基、イソプロポキシ基、ブトキシ基、イソブトキシ基、ｔｅｒｔ−ブトキシ基等が挙げられる。ｔは０〜４の整数であり、ｑ，ｒはそれぞれ０〜１２、好ましくは０〜４、特には０又は１の整数である。
【００３４】
上記式（５）のＲ^５の水素原子、同一もしくは異種の炭素数１〜４のアルキル基又はアルコキシ基としては、上記Ｒ^４と同様の基を挙げることができる。
【００３５】
このような有機リン系化合物として具体的には、下記構造の化合物が例示される。
【００３６】
【化１３】

【００３７】
【化１４】

【００３８】
これらの硬化促進剤は、１種を単独で使用しても２種以上を併用してもよく、また、その添加量は特に制限されないが、エポキシ樹脂及び硬化剤の合計量１００重量部に対して０．００１〜１０重量部、より好ましくは０．００５〜５重量部、更に好ましくは０．０１〜１重量部の範囲にすることが好ましい。配合量が少なすぎると硬化反応が十分に起こりにくく、金型離型性が悪くなる場合があり、多すぎると成形時の粘度が高くなるとともに、耐湿性などの信頼性が悪くなる場合がある。
【００３９】
硬化促進剤として、上記式（３）の有機リン系硬化促進剤と共に必要に応じて公知のその他の硬化促進剤を併用して添加することもできる。その他の硬化促進剤としては、例えばトリフェニルホスフィン、トリブチルホスフィン、トリ（ｐ−トルイル）ホスフィン、トリ（ｐ−メトキシフェニル）ホスフィン、トリ（ｐ−エトキシフェニル）ホスフィン、トリフェニルホスフィン・トリフェニルボレートなどの上記式（３）以外の有機ホスフィン化合物；テトラフェニルホスホニウム・テトラフェニルボレートなどの４級ホスホニウム塩類；トリエチルアミン、ベンジルジメチルアミン、α−メチルベンジルジメチルアミン等の第３級アミン化合物や１，８−ジアザビシクロ（５．４．０）ウンデセン等のシクロアミジン化合物などのアミン系化合物；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−エチル−４，５−ジ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、２−フェニル−４−ヒドロキシ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）イミダゾールなどのイミダゾール類が挙げられる。なお、その他の硬化促進剤の配合量は、本発明の効果を妨げない範囲で通常量とすることができ、通常エポキシ樹脂とフェノール樹脂との総量１００重量部に対して０〜５重量部、特に０〜１重量部とすることができる。
【００４０】
上記硬化促進剤は、樹脂組成物中に分散し易くするために予め樹脂成分と混合し、これを粉砕してもよい。
【００４１】
本発明で使用されるシランカップリング剤は、下記一般式（４）で表わされるアミノシランカップリング剤である。
【００４２】
【化１５】

（式中、Ａは炭素数１〜４のアルキル基又はアルコキシ置換アルキル基、ａは０又は１、Ｒ^６は水素原子、−Ｃ_２Ｈ_４ＮＨ_２又は−Ｃ_６Ｈ_５を示す。）
【００４３】
Ａのアルキル基又はアルコキシ置換アルキル基としては、例えば、メチル基、エチル基、プロピル基、イソプロピル基、ブチル基、イソブチル基、ｔｅｒｔ−ブチル基、メトキシメチル基、エトキシメチル基、メトキシエチル基、エトキシエチル基等が挙げられる。
【００４４】
上記式（４）の化合物は、樹脂組成物中のエポキシ樹脂やフェノール樹脂硬化剤、そしてＢＧＡ基板上のソルダマスクなどのような有機成分やシリカ表面のような無機成分に対して親和性が高いため、樹脂組成物中への分散性が良好である。そのため、シリカフィラーに対する有機樹脂のぬれ性を改善し、樹脂組成物の流動性向上、有機樹脂とシリカフィラー界面の接着力向上、樹脂組成物とソルダマスクとの接着力向上効果が高い。このような特性から樹脂組成物の低粘度化が可能となり、ワイヤー流れを防止し、接着力の向上は半田浸漬時の信頼性向上につながる。
【００４５】
このようなシランカップリング剤として具体例には、下記構造の化合物が例示される。
（ＣＨ_３Ｏ）_３ＳｉＣ_３Ｈ_６ＮＨＣ_２Ｈ_４ＮＨ_２
（Ｃ_２Ｈ_５Ｏ）_３ＳｉＣ_３Ｈ_６ＮＨＣ_２Ｈ_４ＮＨ_２
（ＣＨ_３Ｏ）_３ＳｉＣ_３Ｈ_６ＮＨ_２
（Ｃ_２Ｈ_５Ｏ）_３ＳｉＣ_３Ｈ_６ＮＨ_２
（ＣＨ_３Ｏ）_３ＳｉＣ_３Ｈ_６ＮＨＣ_６Ｈ_５
【００４６】
【化１６】

【００４７】
上記式（４）のシランカップリング剤の添加量は特に制限されないが、エポキシ樹脂及び硬化剤の合計量１００重量部に対して０．２〜３重量部、特に０．１５〜１．５重量部の範囲とすることが好ましい。
【００４８】
また、本発明のシランカップリング剤は、他の種類のカップリング剤と併用しても差し支えなく、これにより他の要求性能とのバランスを向上させることができる。他のカップリング剤としては、エポキシ基やメルカプト基を有するもの、例えばγ−グリシドキシプロピルトリメトキシシラン、メルカプトプロピルトリメトキシシランなどが挙げられる。なお、他のカップリング剤を併用する場合は、上記式（４）のアミノシランカップリング剤の使用割合が全カップリング剤中の３０重量％以上、特に５０〜７０重量％となるように他のカップリング剤の添加量を調整することが好ましく、３０重量％未満では、ＢＧＡ基板上のソルダマスクなどのような有機成分やシリカ表面のような無機成分に対しての親和性が低下し、接着性が低下したり、組成物の溶融粘度が上昇して、モールド時にワイヤー流れの原因になることがある。
【００４９】
本発明の半導体封止用エポキシ樹脂組成物は、無機質充填剤を配合することにより封止材の膨張係数を小さくし、半導体素子に加わる応力を低下させることができる。このような無機質充填剤としては、通常のエポキシ樹脂組成物に配合されるものを使用することができる。具体的には、破砕状、球状の形状を有する溶融シリカ、結晶性シリカが主に用いられ、この他にアルミナ、窒化珪素、窒化アルミニウム、ボロンナイトライド、酸化チタン、ガラス繊維等を使用することもできる。
【００５０】
更に、硬化物の低膨張化と成形性を両立させるためには、上記無機質充填剤として球状と破砕品とのブレンド、あるいは球状品のみを用いることが好ましい。更に、上記無機質充填剤の平均粒径は５〜３０μｍの範囲が好適である。この平均粒径は、例えば、レーザー光回折法の分析手段による重量平均値（又はメジアン径）などとして求めることができる。
【００５１】
なお、無機質充填剤は、樹脂と無機質充填剤表面との結合強度を強くするため、予めシランカップリング剤などで表面処理したものを配合することが好ましい。ここで、表面処理に用いるカップリング剤量及び表面処理方法については特に制限されない。
【００５２】
この無機質充填剤の配合量は特に限定されないが、エポキシ樹脂及び硬化剤の合計量１００重量部に対して２００〜１，２００重量部、特に４００〜１，０００重量部とすることが好ましい。配合量が２００重量部未満では膨張係数が大きくなり、半導体素子に加わる応力が増大し、素子特性の劣化を招く場合があり、１，２００重量部を超えると成形時の粘度が高くなり、成形性が悪くなる場合がある。
【００５３】
本発明のエポキシ樹脂組成物は、前述の原料以外に必要に応じてカーボンブラック等の着色剤、ブロム化エポキシ樹脂、三酸化アンチモン等の難燃剤、シリコーンオイル、シリコーンゴム、オルガノポリシロキサンとエポキシ樹脂、フェノール樹脂等の芳香族樹脂との共重合体等の低応力成分などを添加することができる。なお、これら任意成分の添加量は、本発明の効果を妨げない範囲で通常量とすることができる。
【００５４】
本発明の樹脂組成物は、上記エポキシ樹脂、フェノール樹脂硬化剤、アミノシランカップリング剤、無機質充填剤、硬化促進剤、その他の添加剤をミキサーにて常温混合し、ロールや押出し機などの一般混練機にて混練して冷却後、粉砕することで成形材料とすることができる。なお、硬化条件は、１６５〜１８５℃で１〜３分程度、ポストキュアーは１７０〜１８０℃で４〜８時間程度とすることができる。
【００５５】
【発明の効果】
本発明の半導体封止用エポキシ樹脂組成物は、流動性、保存安定性、硬化性、接着性に優れ、ソルダマスクへの接着性も良好であり、パッケージ反り量が少なく、かつワイヤー流れ率が小さく、作業性及び信頼性に優れる硬化物を与えるもので、ＢＧＡ封止用樹脂等として好適に使用することができる。
【００５６】
【実施例】
以下、実施例及び比較例を示して本発明を具体的に説明するが、本発明は下記実施例に制限されるものではない。なお、以下の例において部はいずれも重量部である。
【００５７】
〔実施例１〜６、比較例１〜５〕
表１，２に示す成分を熱２本ロールにて均一に溶融混合し、冷却、粉砕して半導体封止用エポキシ樹脂組成物を得た。なお、使用したエポキシ樹脂、フェノール樹脂硬化剤、硬化促進剤、シランカップリング剤の構造は下記の通りである。
【００５８】
これらの組成物につき、次の（イ）〜（チ）の諸特性を測定した。結果を表１，２に併記する。
（イ）スパイラルフロー値
ＥＭＭＩ規格に準じた金型を使用して、１７５℃、７０ｋｇｆ／ｍｍ^２、成形時間９０秒の条件で測定した。
（ロ）ゲル化時問
組成物のゲル化時間を１７５℃熱板上で測定した。
（ハ）溶融粘度
高下式フローテスター（島津製作所社製）を用いて１７５℃で測定した。
（ニ）熱時硬度
ＪＩＳ−Ｋ ６９４４に準じて１７５℃、７０ｋｇｆ／ｍｍ^２、成形時間６０秒の条件で４×１０×１００ｍｍの硬化物を成形したとき、その熱時硬度をバーコール硬度計で測定した。
（ホ）ガラス転移温度及び線膨張係数
１７５℃、７０ｋｇｆ／ｍｍ^２、成形時間９０秒の条件で５×５×１５ｍｍの試験片を成形し、１８０℃で４時間ポストキュアーしたものを用い、ディラトメーターにより５℃／分で昇温させることにより測定した。
（ヘ）保存安定性
エポキシ樹脂組成物をアルミニウム製の密封袋に入れ、２５℃で７２時間高温器中に放置した。放置後の組成物のスパイラルフロー値を（イ）と同様に測定し、初期値に比べて低下したパーセンテージを算出した。
【００５９】
（ト）パッケージ反り量
図１に示されるようなＢＧＡパッケージについて、チップを実装した回路基板１上に１７５℃、７０ｋｇｆ／ｍｍ^２、成形時間９０秒の条件で５×５×１５ｍｍの試験片を封止樹脂２として成形後、モールド樹脂面の反り量をレーザー式うねり測定装置（安永社製）で測定した。更に、１８０℃で４時間ポストキュアーした後、再び同様に測定した。測定条件は下記の通りである。
【００６０】
測定方法：うねり測定装置（μｍ）
チップ無し：３５×３５ｍｍ
サンプル数：ｎ＝３
反り量：平均値
成形温度：１７５℃
成形時間：９０秒
ポストキュアー：１８０℃で４時間
【００６１】
（チ）基材接着性
１７５℃、７０ｋｇｆ／ｍｍ^２、成形時間９０秒の条件で図２に示されるような接着性評価サンプル３を基板４上に成形し、１８０℃で４時間ポストキュアーをした後、プッシュプルゲージを用いて剪断接着力の測定を行った。測定条件は下記の通りである。
【００６２】
測定方法：剪断接着力（ｋｇｆ） 剪断速度 １ｍｍ／秒
基板：ＰＳＲ４０００ＡＵＳ５コートＢＴ板
接着面積：１０ｍｍ^２
サンプル数：ｎ＝８
接着力データ：平均値
成形温度：１７５℃
成形時間：９０秒
ポストキュアー：１８０℃で４時間
劣化条件：８５℃、８５％ＲＨ、７２時間−ＩＲリフロー２回
【００６３】
【化１７】

【００６４】
【化１８】

【００６５】
【表１】

【００６６】
【表２】

【００６７】
表１，２の結果より、本発明の特定構造のエポキシ樹脂、フェノール樹脂硬化剤、硬化促進剤、シランカップリング剤を配合したエポキシ樹脂組成物は、流動性が良好であり、速硬化性に優れると共に保存安定性に優れ、また、高いガラス転移温度を有し、ＢＧＡパッケージの反り量が小さい上、ソルダマスクへの接着性が良好である。従って、本発明のエポキシ樹脂組成物を使用した半導体装置は、リフロー時の耐クラック性及び信頼性に優れるものであることが確認された。
【図面の簡単な説明】
【図１】パッケージ反り量評価に使用するＢＧＡパッケージの概略図である。
【図２】基材接着性に使用した接着性評価サンプルの概略図である。
【符号の説明】
１ 回路基板
２ 封止樹脂
３ 接着性評価サンプル
４ 基板[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention provides a cured product having good fluidity, storage stability, good curability, excellent adhesiveness, small package warpage, small wire flow, and excellent moisture resistance reliability. The present invention relates to an epoxy resin composition for semiconductor encapsulation suitable for array (hereinafter referred to as BGA) encapsulation, and a semiconductor device encapsulated with a cured product of the composition, particularly a BGA package.
[0002]
Problems to be solved by the prior art and the invention
At present, resin-encapsulated devices are the mainstream in the semiconductor industry, but epoxy resins generally have better moldability, adhesiveness, electrical properties, mechanical properties, moisture resistance, etc. than other thermosetting resins. Therefore, semiconductor devices are often sealed with an epoxy resin composition.
[0003]
In particular, in recent years, a package called BGA has been developed by Motorola, which has a special structure in which a chip is directly mounted on a circuit board and a plastic is sealed thereon. In the BGA, since only one side of the substrate is sealed with resin, a package warping phenomenon caused by a difference in shrinkage between the substrate and the resin is a serious problem.
[0004]
In order to overcome this problem, various attempts have been made to reduce the difference in shrinkage between the substrate and the resin by increasing the Tg (glass transition temperature) and reducing the expansion of the resin, thereby suppressing the amount of package warpage. Specifically, a proposal has been made to increase the Tg by using a polyfunctional epoxy resin as an epoxy resin, a phenol novolak resin as a curing agent, and an imidazole compound as a curing accelerator, and to reduce the expansion by increasing the amount of silica filler. ing. In addition, to maintain a high level of silica filler and maintain high fluidity, use spherical silica that does not contain crushed silica and optimize the particle size distribution, and optimize the silica surface treatment with a coupling agent Techniques for making the same known are also known.
[0005]
In addition, a characteristic that must be emphasized when evaluating the reliability of the device is the adhesiveness between the solder mask covering the substrate surface and the resin. It is well known that the adhesiveness between the resin and the solder mask can be dramatically improved by selecting an epoxy silane coupling agent or a mercapto silane coupling agent as the coupling agent.
[0006]
However, it has been found that the above-mentioned prior art has various disadvantages described below. That is, the epoxy resin composition using the imidazole compound as the curing accelerator has poor storage stability as compared with the case where the phosphorus-based curing accelerator is used. Filling is likely to occur. In addition, since the hydrolyzable chlorine in the epoxy resin is easily extracted, a problem also occurs in the moisture resistance reliability. Further, in order to cope with an ever-increasing package size, it is necessary to further reduce the expansion. However, with the current high filling of silica, the flow of the wire frequently occurs due to the high viscosity.
[0007]
Further, in the epoxy resin composition, depending on the type of the coupling agent to be added, the curability at the time of resin encapsulation is inhibited, and as a result, the amount of package warpage may increase.
[0008]
The conventional resin composition for BGA encapsulation has various problems as described above, and at present, no effective solution has been found yet.
[0009]
The present invention has been made to solve the above problems, and has good fluidity, storage stability and curability, excellent adhesiveness, small package warpage and wire flow rate, workability and reliability. It is an object of the present invention to provide an epoxy resin composition for semiconductor encapsulation that gives a cured product excellent in heat resistance, and a semiconductor device encapsulated with a cured product of this composition.
[0010]
Means for Solving the Problems and Embodiments of the Invention
The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a polyfunctional epoxy resin represented by the following general formula (1) and a polyfunctional phenol resin curing agent represented by the following general formula (2) And an organic phosphorus-based curing accelerator represented by the following general formula (3), an aminosilane coupling agent represented by the following general formula (4), and an inorganic filler are combined and blended as essential components. It solves the problems of conventional epoxy resin compositions, has good fluidity, is stable even when stored at high temperatures for a long time, has fast curing properties, has excellent moisture resistance reliability, and has excellent substrate adhesion. And a hardened product having little wire warpage and a small wire flow rate even at the time of BGA package encapsulation. Therefore, the epoxy resin composition is used as a BGA encapsulating resin or the like. It was found that can be suitably used, the present invention has been accomplished.
[0011]
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(Wherein, R ¹ and R ² are each independently a hydrogen atom, a methyl group or a tert-butyl group, and R ³ is a hydrogen atom, a methyl group or an ethyl group, preferably a hydrogen atom. It is an integer of 5.)
[0012]
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(Wherein, R ¹ , R ² , and R ³ have the same meaning as described above, and n is an integer of 1 to 5.)
[0013]
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[0014]
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(In the formula, A represents an alkyl group having 1 to 4 carbon atoms or an alkoxy-substituted alkyl group, a represents 0 or 1, R ⁶ represents a hydrogen atom, —C ₂ H ₄ NH ₂ or —C ₆ H _5. )
[0015]
Accordingly, the present invention provides a polyfunctional epoxy resin represented by the general formula (1), a polyfunctional phenol resin curing agent represented by the general formula (2), and an organic compound represented by the general formula (3). An epoxy resin composition for semiconductor encapsulation, comprising a phosphorus-based curing accelerator, an aminosilane coupling agent represented by the above general formula (4), and an inorganic filler as essential components, and a composition thereof. Provided is a semiconductor device sealed with a cured product.
[0016]
Hereinafter, the present invention will be described in more detail. The epoxy resin composition for semiconductor encapsulation of the present invention is a polyfunctional epoxy resin represented by the following general formula (1).
[0017]
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(However, a radical selected from each of ^R 1, ^{R 2} has the formula independently represent a hydrogen atom a methyl group (-CH ₃₎ and tert- butyl _{(-C (CH 3) 3)} . In addition, ^{R 3} is hydrogen atom, a methyl group (-CH ₃₎ or ethyl _(-C 2 _{H 5)} .k 1 to 5, preferably an integer of 1 to 3.)
[0018]
The polyfunctional epoxy resin of the above formula (1) has a feature that a glass transition temperature (hereinafter, referred to as Tg) is high because molecular motion is suppressed. The BGA package is very easily warped because of a so-called bimetal structure in which a glass substrate is impregnated with an organic resin such as BT resin on a glass fiber laminate, which is a so-called bimetal structure, and it is necessary to reduce the amount of warpage by selecting a resin. As a method for reducing the amount of warpage, the substrate may be sealed with a resin composition having the same shrinkage as the substrate, that is, a resin composition having substantially the same Tg and expansion coefficient. Therefore, an epoxy resin composition having a high Tg is desirable, and an epoxy resin composition having a high Tg can be obtained by using the epoxy resin of the above formula (1).
[0019]
In this case, the substituents R ¹ and R ² introduced into the structure of the formula (1) are a hydrogen atom, a —CH ₃ group, a —C (CH ₃ ) ₃ group, or a mixture thereof. If you want to increase the Tg of the cured product of the resin composition, the substituents R ^1, R ² is desirably substituted with structures hydrogen atom or -CH ₃ group, and if you want to decrease the water absorption, -C (CH ₃ A structure substituted with _three groups is desirable. The substituent R ³ introduced into the structure of the formula (1) is a hydrogen atom, a methyl group or an ethyl group, but is preferably a hydrogen atom.
[0020]
The molecular weight of the polyfunctional epoxy resin of the above formula (1) is not particularly limited, but may be generally about 400 to 1,200, preferably about 500 to 800. Although there is no particular limitation on the epoxy equivalent, it is generally 150 to 300, preferably 160 to 200. There is no problem even if the silicone is modified.
[0021]
Further, the epoxy resin of the above formula (1) desirably contains as little alkali metal, alkaline earth metal, halogen and other ionic impurities as possible in these epoxy resins in order to improve the moisture resistance reliability.
[0022]
In the present invention, as the epoxy resin, an epoxy resin other than the epoxy resin of the above formula (1), for example, a novolak type epoxy resin such as an orthocresol novolak type epoxy resin and a phenol novolak type epoxy resin; a biphenyl type epoxy resin; bisphenol Bisphenol type epoxy resins such as A type epoxy resin and bisphenol F type epoxy resin; Triphenol methane type epoxy resin other than formula (1); Naphthalene type epoxy resin; Dicyclopentadiene modified epoxy resin; Phenol aralkyl type epoxy resin; Biphenyl aralkyl It can be used in combination with a type epoxy resin.
[0023]
The epoxy resin used in the composition of the present invention is desirably 70% by weight or more, particularly 90 to 100% by weight, of the total epoxy resin is a polyfunctional epoxy resin of the formula (1). If the content of the polyfunctional epoxy resin of the formula (1) is less than 70% by weight and the content of the other epoxy resin exceeds 30% by weight, Tg may decrease and the warpage of the BGA may increase.
[0024]
Next, as the curing agent, a polyfunctional phenol resin curing agent represented by the following general formula (2) is used. In the present invention, the formula (1) is used for the same reason as the polyfunctional epoxy resin of the formula (1). The polyfunctional phenol resin curing agent of (2) is used.
[0025]
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(Wherein, R ¹ and R ² are each independently a hydrogen atom, a methyl group or a tert-butyl group, preferably a hydrogen atom. R ³ is a hydrogen atom, a methyl group or an ethyl group, preferably A hydrogen atom, and n is an integer of 1 to 5, preferably 1 to 3.)
[0026]
The molecular weight of the polyfunctional phenolic resin curing agent of the formula (2) is not particularly limited, but may be generally in the range of about 200 to 1,000, preferably about 300 to 600. Although there is no particular limitation on the hydroxyl group equivalent, it is generally about 100 to 150, preferably about 110 to 120. There is no problem even if the silicone is modified.
[0027]
Further, the polyfunctional phenol resin curing agent of the formula (2) desirably contains as little alkali metal, alkaline earth metal, halogen and other ionic impurities as possible in the phenol resin in order to improve moisture resistance reliability.
[0028]
As the curing agent, other phenolic resins other than the polyfunctional phenolic resin of the above formula (2), for example, novolak resins such as phenol novolak resin and cresol novolak resin; bisphenol type phenols such as bisphenol A type resin and bisphenol F type resin Resin; para-xylylene-modified phenolic resin; meta-xylylene-modified phenolic resin; ortho-xylylene-modified phenolic resin; triphenolalkane-type resin other than formula (2); naphthalene-type phenolic resin; Resin; biphenyl aralkyl resin or the like may be used in combination.
[0029]
The phenolic resin curing agent used in the composition of the present invention is desirably 70% by weight or more, preferably 90 to 100% by weight, of the total phenolic resin curing agent is a polyfunctional phenolic resin of the formula (2). If the content of the polyfunctional phenolic resin of the formula (2) is less than 70% by weight and the amount of the other phenolic resin curing agent exceeds 30% by weight, the Tg may decrease and the warpage of the BGA may increase. .
[0030]
The compounding amount of the phenol resin curing agent is preferably 25 to 40% by weight based on the total of the epoxy resin and the phenol resin curing agent. When the content is less than 25% by weight or more than 40% by weight, the difference between the number of epoxy groups in the epoxy resin and the number of hydroxyl groups in the phenolic resin curing agent is too large, and the curability of the composition is reduced. Of TGA and an increase of the coefficient of linear expansion, and the amount of warpage of the BGA may increase. Therefore, the compounding amount of the phenolic resin curing agent is such that the molar ratio of the phenolic hydroxyl group contained in the phenolic resin to the mol of epoxy group contained in the epoxy resin is 0.5 to 1.5, particularly 0.8. It can be blended so as to be in the range of -1.2.
[0031]
The curing accelerator used in the present invention is an organic phosphorus curing accelerator represented by the following general formula (3).
[0032]
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[0033]
In the above formula (3), R ⁴ is a hydrogen atom, the same or different alkyl group or alkoxy group having 1 to 4 carbon atoms, for example, a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, Examples include an isobutyl group, a tert-butyl group, a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, a butoxy group, an isobutoxy group, and a tert-butoxy group. t is an integer of 0 to 4, and q and r are each an integer of 0 to 12, preferably 0 to 4, particularly 0 or 1.
[0034]
Examples of the hydrogen atom, the same or different alkyl group or alkoxy group having 1 to 4 carbon atoms of R ^{5 in} the above formula (5) include the same groups as those of the above R ⁴ .
[0035]
Specific examples of such an organic phosphorus compound include compounds having the following structures.
[0036]
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[0037]
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[0038]
One of these curing accelerators may be used alone, or two or more of them may be used in combination. The amount of the curing accelerator is not particularly limited, but the total amount of the epoxy resin and the curing agent is 100 parts by weight. It is preferably in the range of 0.001 to 10 parts by weight, more preferably 0.005 to 5 parts by weight, still more preferably 0.01 to 1 part by weight. If the amount is too small, the curing reaction does not easily occur sufficiently, and the mold releasability may deteriorate.If the amount is too large, the viscosity at the time of molding increases, and the reliability such as moisture resistance may deteriorate. .
[0039]
As a curing accelerator, other known curing accelerators can be used in combination with the organic phosphorus-based curing accelerator of the above formula (3), if necessary. Other curing accelerators include, for example, triphenylphosphine, tributylphosphine, tri (p-tolyl) phosphine, tri (p-methoxyphenyl) phosphine, tri (p-ethoxyphenyl) phosphine, triphenylphosphine triphenylborate and the like. Organic phosphine compounds other than the above formula (3); quaternary phosphonium salts such as tetraphenylphosphonium / tetraphenylborate; tertiary amine compounds such as triethylamine, benzyldimethylamine and α-methylbenzyldimethylamine; Amine compounds such as cycloamidine compounds such as diazabicyclo (5.4.0) undecene; 2-methylimidazole, 2-ethylimidazole, 2-ethyl-4-methylimidazole, 2-ethyl-4,5-dimethylimidazole Tetrazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-phenyl-4-hydroxymethylimidazole, 2-phenyl-4,5-di (hydroxymethyl) imidazoles such as imidazole. In addition, the compounding amount of the other curing accelerator can be a normal amount as long as the effect of the present invention is not impaired, and is usually 0 to 5 parts by weight based on 100 parts by weight of the total amount of the epoxy resin and the phenol resin. In particular, it can be 0 to 1 part by weight.
[0040]
The curing accelerator may be preliminarily mixed with a resin component so as to be easily dispersed in the resin composition, and may be pulverized.
[0041]
The silane coupling agent used in the present invention is an aminosilane coupling agent represented by the following general formula (4).
[0042]
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(In the formula, A represents an alkyl group having 1 to 4 carbon atoms or an alkoxy-substituted alkyl group, a represents 0 or 1, R ⁶ represents a hydrogen atom, —C ₂ H ₄ NH ₂ or —C ₆ H _5. )
[0043]
Examples of the alkyl group or the alkoxy-substituted alkyl group of A include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a methoxymethyl group, an ethoxymethyl group, a methoxyethyl group, and an ethoxy group. And an ethyl group.
[0044]
The compound of the above formula (4) has a high affinity for an epoxy resin or a phenol resin curing agent in a resin composition, and an organic component such as a solder mask on a BGA substrate or an inorganic component such as a silica surface. Good dispersibility in the resin composition. Therefore, the wettability of the organic resin with respect to the silica filler is improved, the fluidity of the resin composition is improved, the adhesive strength between the organic resin and the silica filler is improved, and the adhesive strength between the resin composition and the solder mask is enhanced. Due to such characteristics, the viscosity of the resin composition can be reduced, the flow of the wire is prevented, and the improvement of the adhesive strength leads to the improvement of the reliability at the time of solder immersion.
[0045]
Specific examples of such a silane coupling agent include compounds having the following structures.
(CH ₃ O) ₃ SiC ₃ H ₆ NHC ₂ H ₄ NH ₂
(C ₂ H ₅ O) ₃ SiC ₃ H ₆ NHC ₂ H ₄ NH ₂
(CH ₃ O) ₃ SiC ₃ H ₆ NH ₂
(C ₂ H ₅ O) ₃ SiC ₃ H ₆ NH ₂
(CH ₃ O) ₃ SiC ₃ H ₆ NHC ₆ H ₅
[0046]
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[0047]
The addition amount of the silane coupling agent of the above formula (4) is not particularly limited, but is 0.2 to 3 parts by weight, particularly 0.15 to 1.5 parts by weight based on 100 parts by weight of the total amount of the epoxy resin and the curing agent. Is preferably in the range of parts.
[0048]
In addition, the silane coupling agent of the present invention may be used in combination with other types of coupling agents, thereby improving the balance with other required performance. As other coupling agents, those having an epoxy group or a mercapto group, for example, γ-glycidoxypropyltrimethoxysilane, mercaptopropyltrimethoxysilane and the like can be mentioned. When another coupling agent is used in combination, the aminosilane coupling agent of the above formula (4) is used in an amount of 30% by weight or more, particularly 50 to 70% by weight of the total coupling agent. It is preferable to adjust the amount of the coupling agent to be added. If the amount is less than 30% by weight, the affinity for an organic component such as a solder mask on a BGA substrate or an inorganic component such as a silica surface is reduced, and the adhesive property is lowered. Or the melt viscosity of the composition may increase, causing wire flow during molding.
[0049]
The epoxy resin composition for semiconductor encapsulation of the present invention can reduce the expansion coefficient of the encapsulant and reduce the stress applied to the semiconductor element by incorporating an inorganic filler. As such an inorganic filler, those which are blended in a usual epoxy resin composition can be used. Specifically, crushed, spherical fused silica and crystalline silica are mainly used, and in addition, alumina, silicon nitride, aluminum nitride, boron nitride, titanium oxide, glass fiber, etc. You can also.
[0050]
Furthermore, in order to achieve both low expansion of the cured product and moldability, it is preferable to use a blend of spherical and crushed products or only spherical products as the inorganic filler. Further, the average particle size of the inorganic filler is preferably in the range of 5 to 30 μm. The average particle size can be determined, for example, as a weight average value (or a median diameter) by a laser beam diffraction analysis method.
[0051]
It is preferable that the inorganic filler be surface-treated with a silane coupling agent or the like in advance in order to increase the bonding strength between the resin and the surface of the inorganic filler. Here, the amount of the coupling agent used for the surface treatment and the surface treatment method are not particularly limited.
[0052]
The blending amount of the inorganic filler is not particularly limited, but is preferably 200 to 1,200 parts by weight, particularly preferably 400 to 1,000 parts by weight based on 100 parts by weight of the total amount of the epoxy resin and the curing agent. If the compounding amount is less than 200 parts by weight, the expansion coefficient increases, the stress applied to the semiconductor element increases, and the element characteristics may deteriorate. If the compounding amount exceeds 1,200 parts by weight, the viscosity at the time of molding increases, May worsen.
[0053]
The epoxy resin composition of the present invention may further contain a coloring agent such as carbon black, a brominated epoxy resin, a flame retardant such as antimony trioxide, a silicone oil, a silicone rubber, an organopolysiloxane and an epoxy resin, if necessary, in addition to the above-mentioned raw materials. And a low stress component such as a copolymer with an aromatic resin such as a phenol resin. In addition, the addition amount of these optional components can be a usual amount as long as the effect of the present invention is not hindered.
[0054]
The resin composition of the present invention is prepared by mixing the epoxy resin, phenolic resin curing agent, aminosilane coupling agent, inorganic filler, curing accelerator, and other additives at room temperature with a mixer, and kneading with a general kneader such as a roll or an extruder. After kneading and cooling in a machine, the mixture is pulverized to obtain a molding material. The curing condition can be set at 165 to 185 ° C. for about 1 to 3 minutes, and the post cure can be performed at 170 to 180 ° C. for about 4 to 8 hours.
[0055]
【The invention's effect】
The epoxy resin composition for semiconductor encapsulation of the present invention has excellent fluidity, storage stability, curability, adhesiveness, good adhesiveness to a solder mask, a small amount of package warpage, and a low wire flow rate. It provides a cured product excellent in workability and reliability, and can be suitably used as a BGA sealing resin or the like.
[0056]
【Example】
Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following examples, all parts are parts by weight.
[0057]
[Examples 1 to 6, Comparative Examples 1 to 5]
The components shown in Tables 1 and 2 were uniformly melt-mixed with a hot two roll, cooled and pulverized to obtain an epoxy resin composition for semiconductor encapsulation. The structures of the epoxy resin, phenol resin curing agent, curing accelerator, and silane coupling agent used are as follows.
[0058]
With respect to these compositions, the following various properties (a) to (h) were measured. The results are shown in Tables 1 and 2.
(A) Spiral flow value A spiral flow value was measured using a mold conforming to the EMMI standard under the conditions of 175 ° C., 70 kgf / mm ² , and a molding time of 90 seconds.
(B) Gelation time The gelation time of the composition was measured on a hot plate at 175 ° C.
(C) Melt viscosity The melt viscosity was measured at 175 ° C. using a low-profile flow tester (manufactured by Shimadzu Corporation).
(D) Hardness at the time of heating A cured product of 4 × 10 × 100 mm was molded at 175 ° C., 70 kgf / mm ² , and molding time of 60 seconds according to JIS-K 6944, and the hardness at the time of heating was measured with a Barcol hardness meter. It was measured.
(E) A 5 × 5 × 15 mm test piece was molded under the conditions of a glass transition temperature and a coefficient of linear expansion of 175 ° C., 70 kgf / mm ² , and a molding time of 90 seconds. The measurement was performed by raising the temperature at 5 ° C./min with a tomometer.
(F) Storage stability The epoxy resin composition was put in a sealed aluminum bag and left in a high-temperature device at 25 ° C for 72 hours. The spiral flow value of the composition after standing was measured in the same manner as in (a), and the percentage decreased compared to the initial value was calculated.
[0059]
(G) Amount of package warpage For a BGA package as shown in FIG. 1, a 5 × 5 × 15 mm test piece was placed on a circuit board 1 on which a chip was mounted at 175 ° C., 70 kgf / mm ² , and a molding time of 90 seconds. After molding as the sealing resin 2, the amount of warpage of the mold resin surface was measured with a laser type undulation measuring device (manufactured by Yasunaga). Further, after post-curing at 180 ° C. for 4 hours, the same measurement was performed again. The measurement conditions are as follows.
[0060]
Measurement method: undulation measurement device (μm)
Without tip: 35 × 35mm
Number of samples: n = 3
Warpage: average value Molding temperature: 175 ° C
Molding time: 90 seconds Post cure: 4 hours at 180 ° C.
(H) Substrate adhesion 175 ° C., 70 kgf / mm ² , molding time 90 seconds, an adhesive evaluation sample 3 as shown in FIG. 2 was molded on a substrate 4 and post-cured at 180 ° C. for 4 hours. After that, the shear adhesion was measured using a push-pull gauge. The measurement conditions are as follows.
[0062]
Measurement method: Shear adhesive strength (kgf) Shear rate 1 mm / sec Substrate: PSR4000AUS5 coated BT board Adhesive area: 10 mm ²
Number of samples: n = 8
Adhesion data: average molding temperature: 175 ° C
Molding time: 90 seconds Post cure: 4 hours at 180 ° C. Deterioration conditions: 85 ° C., 85% RH, 72 hours—2 times of IR reflow
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[0064]
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[0065]
[Table 1]

[0066]
[Table 2]

[0067]
From the results of Tables 1 and 2, the epoxy resin composition containing the epoxy resin having a specific structure of the present invention, a phenol resin curing agent, a curing accelerator, and a silane coupling agent has a good fluidity and a rapid curing property. It is excellent, has excellent storage stability, has a high glass transition temperature, has a small amount of warpage of the BGA package, and has good adhesion to a solder mask. Therefore, it was confirmed that the semiconductor device using the epoxy resin composition of the present invention was excellent in crack resistance and reliability during reflow.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of a BGA package used for evaluating package warpage.
FIG. 2 is a schematic view of an adhesion evaluation sample used for substrate adhesion.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Circuit board 2 Sealing resin 3 Adhesion evaluation sample 4 Substrate

Claims (2)

A polyfunctional epoxy resin represented by the following general formula (1), a polyfunctional phenol resin curing agent represented by the following general formula (2), and an organic phosphorus curing accelerator represented by the following general formula (3). An epoxy resin composition for semiconductor encapsulation comprising, as essential components, an aminosilane coupling agent represented by the following general formula (4) and an inorganic filler.

(However, in the formula, R ¹ and R ² are each independently a hydrogen atom, a methyl group or a tert-butyl group, and R ³ is a hydrogen atom, a methyl group or an ethyl group. K is an integer of 1 to 5.)

(Wherein, R ¹ and R ² are each independently a hydrogen atom, a methyl group or a tert-butyl group, R ³ is a hydrogen atom, a methyl group or an ethyl group, and n is an integer of 1 to 5.)

[However, in the formula, R ⁴ each independently represent a hydrogen atom, the same or different alkyl group or alkoxy group having 1 to 4 carbon atoms, and m is each independently an integer of 0 to 4. X is - _{(CH 2) p} - (wherein, p is 3 to 12 integer.) Is a group represented by following general formula (5).

(Wherein R ⁵ represents a hydrogen atom, an identical or different alkyl group or alkoxy group having 1 to 4 carbon atoms, t is an integer of 0 to 4, and q and r are each independently an integer of 0 to 12) is there.)〕

(In the formula, A represents an alkyl group having 1 to 4 carbon atoms or an alkoxy-substituted alkyl group, a represents 0 or 1, R ⁶ represents a hydrogen atom, —C ₂ H ₄ NH ₂ or —C ₆ H _5. ) A semiconductor device sealed with a cured product of the epoxy resin composition according to claim 1.

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