JP3779599B2 - Epoxy resin composition for semiconductor encapsulation and semiconductor device using the same - Google Patents

Description

【００２５】
（式中、Ｒ₁ 〜Ｒ₄ は水素原子または炭素数１〜５のアルキル基を示し、Ｒ₁ 〜Ｒ₄ は相互に同じであっても異なっていてもよい。）
【００２６】
上記一般式（１）中のＲ₁ 〜Ｒ₄ は、水素原子（−Ｈ）または炭素数１〜５のアルキル基を示し、上記アルキル基としては、メチル基、エチル基、ｎ−プロピル基、イソプロピル基、ｎ−ブチル基、イソブチル基、ｓｅｃ−ブチル基、ｔｅｒｔ−ブチル基等の直鎖状または分岐状の低級アルキル基があげられ、特にメチル基が好ましく、上記Ｒ₁ 〜Ｒ₄ は互いに同一であっても異なっていてもよい。なかでも、低吸湿性および反応性という観点から、上記Ｒ₁ 〜Ｒ₄ が全てメチル基である下記の式（２）で表される構造のビフェニル型エポキシ樹脂を用いることが特に好適である。
【００２７】
【化２】

【００２８】
上記エポキシ樹脂（Ａ成分）とともに用いられるフェノール樹脂（Ｂ成分）は、上記エポキシ樹脂の硬化剤として作用するものであって、特に限定するものではなく従来公知のものが用いられる。例えば、フェノールノボラック、クレゾールノボラック、ビスフェノールＡ型ノボラック、ナフトールノボラックおよびフェノールアラルキル樹脂等があげられる。なかでも、上記エポキシ樹脂（Ａ成分）としてビフェニル型エポキシ樹脂を用いる場合には、フェノール樹脂として下記の一般式（３）で表されるフェノールアラルキル樹脂を用いることが好ましい。
【００２９】
【化３】

（式中、ｎは０〜４０である。）
【００３０】
そして、上記エポキシ樹脂（Ａ成分）と上記フェノール樹脂（Ｂ成分）の配合割合は、上記エポキシ樹脂中のエポキシ基１当量当たり、フェノール樹脂中の水酸基が０．７〜１．３当量となるように設定することが好ましく、なかでも０．９〜１．１当量となるよう設定することが特に好ましい。
【００３１】
上記の充填剤（Ｃ成分）は、特に限定されるものではなく、従来公知の各種充填剤を用いることができる。例えば、石英ガラス粉末、タルク、シリカ粉末、アルミナ粉末、窒化アルミニウム粉末、窒化珪素粉末等の無機質充填剤が挙げられる。これらは単独でももしくは２種以上で併用して用いられる。そして、上記充填剤として、得られる硬化物の線膨張係数を低減できるという点からシリカ粉末を用いることが好ましい。なかでも、シリカ粉末として溶融シリカ粉末、とりわけ球状溶融シリカ粉末を用いることが樹脂組成物の良好な流動性という点から特に好ましい。
【００３２】
また、上記充填剤において、その平均粒径が１０〜７０μｍの範囲であることが好ましく、より好ましくは１０〜５０μｍである。すなわち、充填剤の平均粒径が上記範囲内であると、樹脂組成物の良好な流動性が得られる。また、上記シリカ粉末としては、場合によりシリカ粉末を摩砕処理してなる摩砕シリカ粉末を用いることもできる。
【００３３】
上記充填剤の含有量は、半導体封止用エポキシ樹脂組成物全体の６０〜９５重量％となるよう設定することが好ましい。
【００３４】
上記Ａ〜Ｃ成分とともに用いられる赤燐系難燃剤（Ｄ成分）は、赤燐粒子の表面に第一次被覆が水酸化亜鉛の被覆からなり、第二次被覆が酸化亜鉛を含有するフェノール樹脂被覆からなる二重被覆層が形成された、Ｐ含有量が６５〜９７重量％の赤燐系難燃剤であり、本発明で用いる赤燐系難燃剤は、第一次被覆が水酸化亜鉛からなること、好ましくは可溶性亜鉛化合物とアルカリ剤をｐＨ６．５以上の条件下において反応させて生成する水酸化亜鉛の結晶構造を保った状態の被覆からなること、及び下記の（Ｄ１）〜（Ｄ３）の特性を有するものを用いることが特に重要な要件となる。
（Ｄ１）酸及びアルカリから選ばれる少なくとも１種以上で洗浄処理した赤燐粒子の表面に水酸化亜鉛の第一次被覆が形成され、かつ赤燐粒子に対する水酸化亜鉛の被覆量が０．５〜１０重量％で、
（Ｄ２）２０℃の水に赤燐系難燃剤を１０重量％分散させたスラリー（以降、１０重量％スラリーと記す）の電気伝導度が３０μｓ／ｃｍ以下で、
（Ｄ３）該赤燐系難燃剤８ｇに水８０ｍｌを加えて８０℃で２０時間加熱した際に溶出するＰＯ₄イオン濃度が１０ｐｐｍ以下で、ＰＨＯ₃イオン濃度が２００ｐｐｍ以下で、ＰＨ₂Ｏ₂イオン濃度が１５０ｐｐｍ以下で、且つ８０℃で２０時間放置後の電気伝導度が１００μｓ／ｃｍ以下である。
【００３５】
以下にかかる赤燐系難燃剤について説明する。
本発明にかかる第一層の水酸化亜鉛の被覆は、可溶性亜鉛化合物とアルカリ剤の反応により生成する水酸化亜鉛の被覆からなる。本発明者らは、水酸化亜鉛の被覆は、反応中のｐＨの管理により異なってくることを見出した。例えば、図１および図２に示す水酸化亜鉛の被覆により説明する。図１は後述する本発明の実施例の赤燐系難燃剤試料１の（ａ２−２）工程後の赤燐粒子表面上に形成させた水酸化亜鉛被膜の状態を示す赤燐粒子構造の電子顕微鏡写真（倍率２０００倍）であり、図２は後述する実施例の赤燐系難燃剤試料２の（ａ２−１）工程後の赤燐粒子表面上に形成させた水酸化亜鉛被膜の状態を示す赤燐粒子構造の電子顕微鏡写真（倍率２０００倍）である。
【００３６】
即ち、図２の水酸化亜鉛の被覆は、可溶性亜鉛化合物とアルカリ剤を最初にｐＨ６．５以上に調整しただけで、反応中のｐＨを管理しないで得られたものであり、電子顕微鏡写真に示す様に、水酸化亜鉛の結晶が反応中に副生する酸に溶解した状態を示す表面がつるつるした平滑な水酸化亜鉛の被覆であり、粒子の大きさも小さいものである。これに対して、図１の水酸化亜鉛の被覆は、電子顕微鏡写真に示す様に、可溶性亜鉛化合物とアルカリ剤の反応中ｐＨを６．５以上に維持するので、反応中に酸が副生することが抑制され、生成した水酸化亜鉛の結晶が酸に溶解することはなく、結晶構造を保った状態で角ばった強固な緻密な被覆であり、粒子の大きさも大きいものである。
【００３７】
本発明における赤燐系難燃剤においては、図１及び図２に示す様に、赤燐粒子の表面を被覆したものが用いられるが、本発明において、この水酸化亜鉛を被覆した赤燐系難燃剤は、赤燐粒子に対する水酸化亜鉛の被覆量が、添加した可溶性亜鉛化合物およびアルカリの理論量論比より求めた理論量の４０重量％以上、好ましくは６０重量％以上、さらに好ましくは８０重量％以上で水酸化亜鉛を被覆したものが好ましく、特に上記の図１の結晶構造を保った水酸化亜鉛の被覆を有するものを用いることが好ましく、更に、その表面に酸化亜鉛を含有するフェノール樹脂で被覆することにより、リンのオキソ酸の溶出を低減させることができる。
【００３８】
本発明において、この赤燐粒子に対する水酸化亜鉛の被覆量は０．５〜１０重量％、好ましくは０．６〜３重量％、更に好ましくは０．８〜２重量％である。この被覆量が０．５重量％未満では溶出するリン酸分イオンの固定化能が不足し、一方、被覆量が１０重量％を超えると赤燐系難燃剤の凝集や再凝集が起こりやすくなり、所望の粒度調整を行うことが困難になったり、或いは赤燐系難燃剤の粒度調整をおこなっても、保管時やエポキシ樹脂組成物の混練時に再凝集し、このため粒子径が大きくなって樹脂分散性が悪くなり、後述するように凝集粒子自体の最大粒径が後述する範囲であればよいが、その範囲を超える粒子は、基板とＩＣチップとの隙間（Ｇａｐ）に存在することとなるため不良品の発生の一つの原因となることから好ましくない。
【００３９】
本発明で用いる赤燐系難燃剤は、水酸化亜鉛の被覆表面、特に上記の結晶構造を保った水酸化亜鉛の被覆表面を、更に酸化亜鉛を含有するフェノール樹脂で被覆した赤燐系難燃剤である。
【００４０】
前記赤燐系難燃剤は、赤燐の含有量が６５〜９７重量％、好ましくは７５〜９５重量％であることが好ましい。この理由は、赤燐含有量が６５重量％未満では被覆成分量が多くなるためバインダー効果で赤燐粒子が凝集するため粒子径が大きくなって、封止樹脂中の分散性が低下し、難燃効果も低下する傾向にあり、一方、赤燐含有量が９７重量％を超えると、被覆成分が少ないため、リン酸成分の溶出やホスフィンガスの発生を伴う傾向があることから好ましくない。
【００４１】
本発明において、上記した赤燐系難燃剤は、２０℃の水に１０重量％スラリーとしたときの電気伝導度が３０μｓ／ｃｍ以下、好ましくは２０μｓ／ｃｍ以下のものを用いることが重要な要件となり、この理由は、電気伝導度が３０μｓ／ｃｍを超えると、例えば、封止材等のエポキシ樹脂の難燃剤として用いた場合、電気信頼性が劣る傾向があるため好ましくない。
【００４２】
更に本発明において、用いる赤燐系難燃剤は、通常の封止材の調製の際のエポキシ樹脂との混練温度においても安定性を有するものであることが重要な要件となる。即ち、該赤燐系難燃剤８ｇに水８０ｍｌを加えて８０℃で２０時間加熱した際に溶出するＰＯ₄ イオン濃度が１０ｐｐｍ以下、好ましくは８ｐｐｍ以下で、ＰＨＯ₃ イオン濃度が２００ｐｐｍ以下、好ましくは１５０ｐｐｍ以下で、ＰＨ₂ Ｏ₂ イオン濃度が１５０ｐｐｍ以下、好ましくは１００ｐｐｍ以下で、且つ８０℃で２０時間放置後の電気伝導度が１００μｓ／ｃｍ以下、好ましくは８０μｓ／ｃｍ以下である。
【００４３】
溶出するＰＯ₄ イオン濃度、ＰＨＯ₃ イオン濃度及びＰＨ₂ Ｏ₂ イオン濃度を上記範囲とする理由は、この範囲を超えると溶出するＰＯ₄ イオン、ＰＨＯ₃ イオン及びＰＨ₂ Ｏ₂ イオンにより、例えば、この赤燐系難燃剤を封止材のエポキシ樹脂の難燃剤として用いた場合、半導体素子の表面に形成されたアルミニウム配線の腐食が発生し、半導体封止材の耐湿電気信頼性が損なわれる傾向があるため好ましくない。
【００４４】
また、８０℃における２０時間放置後の電気伝導度を上記範囲とする理由は、この範囲を超えると上記したとおり、例えば、この赤燐系難燃剤を封止材のエポキシ樹脂の難燃剤として用いた場合、半導体封止材の耐湿電気信頼性が損なわれるため好ましくない。なお、本発明においてこの電気伝導度は、塩素イオン、臭素イオン、ＰＯ₄ イオン、ＰＨＯ₃ イオン、ＰＨ₂ Ｏ₂ イオン、ＳＯ₄ イオン、ＮＨ₄ イオン、Ｎａイオン、Ｋイオン等のイオン性化合物に起因する値である。
【００４５】
また、本発明にかかる赤燐系難燃剤は、更に高温下での安定性を有するものであることが好ましく、即ち、該赤燐系難燃剤８ｇに水８０ｍｌを加えて１６０℃で２０時間加熱した際に溶出するＰＯ₄ イオン濃度が１００ｐｐｍ以下、好ましくは８０ｐｐｍ以下で、ＰＨＯ₃ イオン濃度が２５０ｐｐｍ以下、好ましくは２００ｐｐｍ以下で、ＰＨ₂ Ｏ₂ イオン濃度が２０００ｐｐｍ以下、好ましくは１９００ｐｐｍ以下であり、また、この条件下でのスラリーの電気伝導度が２０００μｓ／ｃｍ以下、好ましくは１９００μｓ／ｃｍ以下である。本発明にかかる赤燐系難燃剤は、この高温の１６０℃の加熱条件下においても、溶出する上記のイオン性化合物の低減したものを用いることにより高温の条件下においても電気信頼性に優れている。
【００４６】
また、本発明に係る赤燐系難燃剤は、赤燐系難燃剤中のフェノール樹脂の含有量が固形分換算で０．５〜２０重量％、好ましくは１〜１０重量％である。フェノール樹脂の含有量を上記範囲とする理由は、０．５重量％未満では樹脂被覆効果が得られなくなるためリンのオキソ酸の溶出やホスフィンガスの発生量が多くなる傾向があり、一方、２０重量％を超えると凝集により赤燐の粒径が大きくなって樹脂分散性が悪くなり難燃効果も低下する傾向があるので好ましくない。
【００４７】
また、酸化亜鉛の含有量は、フェノール樹脂（固形分）１００重量部に対して５０〜１０００重量部、好ましくは１００〜５００重量部とすることが好ましい。酸化亜鉛の含有量を上記範囲とする理由は、５０重量部未満では溶出するリン酸成分の固定化能が不足するだけでなく、被膜樹脂の強度が低下して容易に被膜が破れ、半導体封止用エポキシ樹脂組成物とした時に、封止材の信頼性試験において、赤燐から溶出するリンのオキソ酸によりＩＣが腐食され、電気信頼性が低下する傾向があることから好ましくない。一方、１０００重量部を超えると赤燐系難燃剤全体のＰ含有量が小さくなり、難燃効果が低下する傾向があることから好ましくない。
【００４８】
本発明において、用いることができる酸化亜鉛の物性としては、微細なものが被覆樹脂との均一分散性および溶出するリンのオキソ酸との反応性の面で好ましく、通常レーザー法により求められる平均粒径が２μｍ以下、好ましくは０．２〜１μｍのものが好ましい。
【００４９】
また、かかる赤燐系難燃剤は、レーザー法により求められる平均粒径が１〜５０μｍであり、特に３〜３０μｍのものが好ましい。この理由は、平均粒径が１μｍ未満のものは技術的に被覆処理することが困難なことから被覆に欠陥が生じやすいため実用的でなく、一方、５０μｍを超えると樹脂分散性が悪くなり、好ましい難燃効果も得られない傾向があることから好ましくない。
【００５０】
また、かかる赤燐系難燃剤は、半導体封止用エポキシ樹脂の難燃剤として用いる場合には、平均粒径と最大粒径を使用するＩＣパッケージの形態に合わせて好適な範囲の平均粒径を選択することが好ましい。更に詳述すると、赤燐系難燃剤が使用されるＩＣパッケージの形態により、それぞれ好適な範囲の粒径が存在する。例えば、ＣＳＰ（Ｃｈｉｐ ｓｉｚｅ ｐａｃｋａｇｅ、チップサイズパッケージ）やＢＧＡ（Ｂａｌｌ ｇｒｉｄ Ａｒｒａｙ、ボールグリッドアレイ）などの液状封止材やトランスファーＢＧＡと呼ばれる薄型パッケージに使用する場合は、基板とＩＣチップとの隙間（Ｇａｐ）よりも大きい粒子が存在することは好ましくなく、この場合は、レーザー法により求められる平均粒径が１〜１０μｍ、最大粒径が２０μｍ以下であることが好ましい。これに対して、ＤＩＰ（Ｄｕａｌ ｉｎｌｉｎ ｐａｃｋａｇｅ、デュアル インライン パッケージ）やＺＩＰ（Ｚｉｇ−Ｚａｇ ｉｎｌｉｎ ｐａｃｋａｇｅ、ジグザグ インライン パッケージ）と呼ばれる比較的厚型のＩＣパッケージに使用する場合は、レーザー法により求められる平均粒径が１０〜５０μｍ、最大粒径が１５０μｍ以下が好ましい。ＴＳＯＰ（Ｔｈｉｎ ｓｍａｌｅ ｏｕｔｌｉｎｅ ｐａｃｋａｇｅ、薄型スモールアウトラインパッケージ）、ＴＱＦＰ（Ｔｈｉｎ ｑｕａｄｆｌａｔ ｐａｃｋａｇｅ、薄型クリッド フラット パッケージ）とよばれる薄型ＩＣパッケージに使用する場合は、この中間の粒度特性のものを使用することが好ましく、レーザー法により求められる平均粒径が５〜２０μｍ、最大粒径が４５μｍ以下が好ましい。
【００５１】
本発明で用いる、特に上記の図１の結晶構造を保った水酸化亜鉛の被覆を有し、更らに、その表面に酸化亜鉛を含有するフェノール樹脂で被覆した特性の赤燐系難燃剤は、以下の製造方法により製造することができる。
【００５２】
即ち、赤燐系難燃剤の製造方法は、下記の（ａ１）〜（ａ５）工程を含むことを特徴とする。
（ａ１）赤燐粒子を少なくとも酸で洗浄する工程
（ａ２−１）該洗浄処理した赤燐粒子を水に分散させたスラリーに、可溶性亜鉛化合物及びアルカリ剤を添加してスラリーのｐＨを６．５以上に調整した後、反応させ赤燐粒子表面を水酸化亜鉛で被覆処理する工程、または（ａ２−２）該洗浄処理した赤燐粒子を水に分散させたスラリーに、可溶性亜鉛化合物及びアルカリ剤を添加してスラリーのｐＨを６．５以上に維持しながら赤燐粒子表面を水酸化亜鉛で被覆処理する工程。
（ａ３）該水酸化亜鉛を被覆した赤燐粒子を純水で１０％スラリーとした時の電気伝導度が１０００μＳ／ｃｍ以下となるまで洗浄処理する工程。
（ａ４）該洗浄処理した水酸化亜鉛で被覆した赤燐粒子を水に分散させたスラリーに、酸化亜鉛及びフェノール樹脂の初期縮合物を添加し、ｐＨ６．５以上で重合反応をおこなって水酸化亜鉛で被覆した赤燐粒子表面にフェノール樹脂で被覆して二重被覆赤燐を得る工程。
（ａ５）該二重被覆赤燐を２０℃の水に１０重量％分散したスラリーの電気伝導度が３０μｓ／ｃｍ以下となるまで純水で洗浄して赤燐系難燃剤を得る工程。
【００５３】
前記（ａ１）の工程は、酸及びアルカリから選ばれる少なくとも１種以上で洗浄を行う。すなわち少なくとも酸で洗浄処理した後、赤燐粒子を水に分散させ、赤燐粒子スラリーとする。この赤燐粒子の洗浄工程は、硝酸等の酸によりスラリーのｐＨを２以下、好ましくは１．５以下とし、鉄、ニッケル、銅等の赤燐の酸化触媒となる金属分や、化学的に不安定で、発火性があるとともにリン酸分イオンの溶出に一つの要因となる黄燐分を除去する。また、この酸による洗浄処理を行う前、赤燐粒子スラリーに水酸化ナトリウム等のアルカリを添加して、スラリーのｐＨを９以上、好ましくは１０以上とし、予め大部分の黄燐分を除去し、次いで、上記した酸処理を施して、鉄、ニッケル、銅等の金属分や、黄燐分の除去操作を行ってもよい。なお、アルカリ処理は、過酸化水素等の酸化剤の存在下に行って、ホスフィンガスを酸化させながら行うことが好ましい。
【００５４】
このような酸で洗浄処理した赤燐粒子は、更に純水で赤燐粒子スラリーのｐＨが２以上、好ましくは２．５以上となるまで洗浄処理することが好ましく、このように酸で洗浄処理した赤燐粒子は無処理のものと比べ、リン酸成分の溶出を低減することができる。
【００５５】
なお、赤燐粒子は、予め、所望の平均粒径、最大粒径等の粒度を調製したものを用いることが好ましく、更に、粒径１μｍ未満のものを被覆することが技術的に難しいためこの粒子の占める割合が１０重量％以下としたものを用いることが好ましい。
【００５６】
（ａ２−１）または（ａ２−２）工程は、（ａ１）工程後の赤燐粒子を水に分散させたスラリーに、可溶性亜鉛化合物及びアルカリ剤を添加して水酸化亜鉛で赤燐粒子表面を被覆処理する工程である。この（ａ２−１）または（ａ２−２）工程において、ｐＨ６．５以上で水酸化亜鉛を赤燐粒子に沈着させ、熟成することが重要な要件となる。
【００５７】
具体的には、（ａ１）工程後の赤燐粒子５〜３０重量部、好ましくは１０〜２０重量部を水１００重量部に分散させ赤燐スラリーを調製し、次いで、赤燐スラリーに、硫酸亜鉛、硝酸亜鉛、酢酸亜鉛等の可溶性亜鉛化合物０．０５〜３重量部、好ましくは０．２〜２重量部を添加し、アンモニアガス、アンモニア水、苛性ソーダ、苛性カリ、ＮａＨＣＯ₃ 、Ｎａ₂ ＣＯ₃ 、Ｋ₂ ＣＯ₃ 、ＫＨＣＯ₃ 、Ｃａ（ＯＨ）₂ 等の無機アルカリ剤またはエタノールアミン等の有機アルカリ剤から選ばれた少なくとも１種以上のアルカリ剤を添加し、該スラリーのｐＨを６．５以上、好ましくは７．５〜８．５に調製し、温度４０〜９５℃、好ましくは７５〜９０℃で反応および熟成を行って結晶構造を保った微細な水酸化亜鉛を赤燐粒子表面に沈着させる。
【００５８】
この（ａ２−１）または（ａ２−２）工程では赤燐粒子の表面を水酸化亜鉛で被覆するが、結晶構造を保った水酸化亜鉛の被覆を形成させるためには、可溶性亜鉛化合物にアルカリ剤添加後のｐＨ管理が特に重要となる。
【００５９】
（ａ２−１）工程では、かかる反応は可溶性亜鉛化合物を溶解した反応系にアルカリ剤をｐＨが６．５〜９になるように添加するが、反応が進行するに従って、例えば、原料として可溶性亜鉛化合物として硫酸亜鉛、アルカリ剤としてアンモニアを用いた場合には、硫酸等の酸成分が副生する。このため、反応系内のｐＨは反応当初よりｐＨ６以下の酸性側にシフトしたものとなる。この反応系のｐＨが６．５未満では水酸化亜鉛の溶解性が増す傾向があるが水酸化亜鉛の被覆が形成される。
【００６０】
一方、（ａ２−２）工程では、反応原料のアルカリ剤を添加した後でも、反応中、常にｐＨを６．５以上に保持するために、上記したアルカリ剤により適宜ｐＨ調製を行いながら酸成分の副生を防いで水酸化亜鉛を析出させること及びその後の熟成を行うことを特徴とする。
【００６１】
次に、放冷した後、（ａ３）工程により、処理後の赤燐を１０％スラリーとした時の電気伝導度が１０００μｓ／ｃｍ以下、好ましくは５００μｓ／ｃｍ以下となるまで水酸化亜鉛を被覆した赤燐をろ過洗浄する。この（ａ３）工程を施すことにより、後の（ａ５）工程の洗浄操作を赤燐粒子の被覆を傷つけることなく容易に実施することができるようになり、また、次の（ａ４）工程で被覆したフェノール樹脂中に極力不純物が取り込まれないで済むので、その使用の最中にこの被覆成分中に取り込まれた不純物による溶出を抑えることができる。
【００６２】
かかる（ａ３）工程において、水酸化亜鉛を被覆した赤燐を洗浄する方法としては、特に制限はないがリパルプ等の手段により行うことが特に好ましい。
【００６３】
（ａ４）工程は、（ａ３）工程後の水酸化亜鉛を被覆した赤燐を水に分散させたスラリーに、酸化亜鉛とフェノール樹脂の初期縮合物を添加し、フェノール樹脂の単独重合条件で重合反応を行って、水酸化亜鉛で被覆した赤燐粒子表面に酸化亜鉛を含有するフェノール樹脂を被覆して二重被覆赤燐を得る工程である。この（ａ４）工程において、ｐＨ６．５以上で重合反応及びその後の熟成を行うことが重要な要件となる。
【００６４】
具体的には、（ａ３）工程後の水酸化亜鉛を被覆した赤燐５〜３０重量部、好ましくは１０〜２０重量部を水１００重量部に分散させ赤燐スラリーを調製し、次いで、該赤燐スラリーを、アンモニア、水酸化ナトリウム等のアルカリ又は塩酸、硝酸、硫酸等の酸を添加し、ｐＨを７以上に調製し、次いで、前記の酸化亜鉛の粉末を０．２５〜２０重量部、好ましくは０．５〜１０重量部と、フェノール樹脂（初期縮合物：固形分として）０．２５〜３重量部、好ましくは０．５〜２重量部を添加して、６０〜９０℃で１〜３時間攪拌しながら重合反応を行う。
【００６５】
この（ａ４）工程では上記したとおり、反応系のｐＨを常に６．５以上に維持することが重要であり、通常、反応開始前にｐＨを６．５以上に調製しても反応中や熟成中に赤燐から溶出するリン酸成分によりｐＨが次第に酸性側にシフトする。このため上記したようにｐＨが６．５未満になると赤燐粒子を被覆した水酸化亜鉛が溶解するため、この工程が終了するまで反応系内にアルカリ剤を適宜添加し、ｐＨが６．５以上となるようにｐＨ管理を行う。また、フェノール樹脂の重合反応は、ｐＨが８を超えると極端に反応が遅くなることから重合反応中は好ましくは６．５〜７．５の範囲にｐＨを調製することが好ましい。
【００６６】
なお、この（ａ４）工程において、赤燐スラリーに微細な酸化亜鉛を均一に分散させるため、必要に応じてヘキサメタリン酸アルカリや界面活性剤のような所望の分散剤の添加やコロイドミルやホモジナイザー又は超音波などの強力セン断分散処理等の分散処理を行ってもよい。
【００６７】
反応終了後、（ａ５）工程で、該二重被覆赤燐を２０℃の水に１０重量％分散したスラリーの電気伝導度が３０μｓ／ｃｍ以下、好ましくは２０μｓ／ｃｍ以下となるまで純水で洗浄し、乾燥し、所望により粒度調整を行って製品とする。
【００６８】
かかる（ａ５）工程において、二重被覆した赤燐を洗浄する方法としては、特に制限はないがリパルプ等の手段により行うことが特に好ましい。
【００６９】
そして、上記赤燐系難燃剤（Ｄ成分）の含有量は、樹脂組成物全体中の０．１〜２重量％の範囲に設定することが好ましく、特に好ましくは０．１〜１．０重量％である。すなわち、０．１重量％未満では、難燃性が不足し、また、２重量％を超えるとリンのオキソ酸等の不純物の増加等のため耐湿性の低下を引き起こすと同時に多量に添加すると難燃性を示さなくなる傾向がみられるからである。
【００７０】
そして、本発明の半導体封止用エポキシ樹脂組成物には、上記Ａ〜Ｄ成分、および場合により、赤燐系難燃剤以外の他の難燃剤と併用して用いることができる。
【００７１】
併用することができる他の難燃剤としては、水和金属酸化物、含窒素系難燃剤、リン系難燃剤等が挙げられる。
【００７２】
水和金属酸化物としては、吸熱反応による燃焼抑制作用のあるＭ_m Ｏ_n ・ｘＨ₂ Ｏ（Ｍは金属、ｍ、ｎは金属の原子価によって定まる１以上の整数、ｘは含有結晶水を示す。）で表わされる化合物または該化合物を含む複塩であり、具体的には、水酸化アルミニウム、水酸化マグネシウム、塩基性炭酸マグネシウム、水酸化カルシウム、水酸化バリウム、水酸化ジルコニウム、ドーソナイト、スズ酸亜鉛、ホウ酸亜鉛、ホウ酸アルミニウム、塩基性炭酸亜鉛、ホウ砂、モリブデン酸亜鉛、リン酸亜鉛、リン酸マグネシウム、ハイドロタルサイト、ハイドロカルマイト、カオリン、タルク、セリサイト、パイロフィライト、ベントナイト、カオリナイト、硫酸カルシウム、硫酸亜鉛等或いは特開２０００―１９５９９３号公報に記載の多面体形状の複合金属水酸化物が挙げられる。
【００７３】
含窒素系難燃剤としては、メラミン、メラミンシアヌレート、メチロール化メラミン、（イソ）シアヌール酸、メラム、メレム、メロン、サクシノグアミン、硫酸メラミン、硫酸アセトグアナミン、硫酸メラム、硫酸グアニルメラミン、メラミン樹脂、ＢＴレジン、シアヌール酸、イソシアネール酸、イソシアヌール酸誘導体、メラミンイソシアヌレート、ベンゾグアナミン、アセトグアナミン等のメラミン誘導体、グアニジン系化合物等が挙げられる。
【００７４】
リン系難燃剤としては、例えば、リン酸トリエチル、リン酸トリクレジル、リン酸トリフェニル、リン酸クレジルフェニル、リン酸オクチルジフェニル、ジエチレンリン酸エチルエステル、ジヒドロキシプロピレンリン酸ブチルエステル、エチレンリン酸ジナトリウムエステル、メチルホスホン酸、メチルホスホン酸ジメチル、メチルホスホン酸ジエチル、エチルホスホン酸、プロピルホスホン酸、ブチルホスホン酸、２−メチル―プロピルホスホン酸、ｔ−ブチルホスホン酸、２，３−ジメチルブチルホスホン酸、オクチルホスホン酸、フェニルホスホン酸、ジオクチルフェニルホスホネート、ジメチルホスフィン酸、メチルエチルホスフィン酸、メチルプロピルホスフィン酸、ジエチルホスフィン酸、ジオクチルホスフィン酸、フェニルホスフィン酸、ジエチルフェニルホスフィン酸、ジフェニルホスフィン酸、ビス（４−メトキシフェニル）ホスフィン酸、リン酸アンモニウム、ポリリン酸アンモニウム、リン酸メラミン、リン酸グアニル尿素、ポリリン酸メラミン、リン酸グアニジン、エチレンジアミンリン酸塩、ホスファゼン、メチルホスホン酸メラミン塩等が挙げられる。
【００７５】
前記した他の難燃剤は１種又は２種以上で用いられ、これらの中、水和金属酸化物が好ましい。他の難燃剤の添加量は、エポキシ樹脂組成物中０．１〜５重量％、好ましくは０．５〜２重量％である。
【００７６】
なお、本発明に係る半導体封止用エポキシ樹脂組成物には、上記Ａ〜Ｄ成分以外に、所望によりリン酸成分と反応して不溶性又は難溶性のリン酸塩として固定する他の金属酸化物、金属水酸化物、金属炭酸塩又は金属リン酸塩や無機イオン交換体を併用して用いることが出来る。
【００７７】
他の金属酸化物、金属水酸化物、金属炭酸塩又は金属リン酸塩としては、例えば、Ｚｎ、Ｍｇ、Ｔｉ、Ｃａ、Ａｌ、Ｃｏ、Ｚｒ、Ｓｎから選ばれる酸化物、水酸化物、炭酸塩又はリン酸塩の１種又は２種以上が挙げられる。具体的には、酸化亜鉛、水酸化亜鉛、オルト珪酸亜鉛、酸化マグネシウム、水酸化マグネシウム、酸化チタン、酸化カルシウム、水酸化カルシウム、炭酸カルシウム、リン酸カルシウム、第三リン酸カルシウム、ヒドロキシアパタイト、珪酸カルシウム、酸化アルミニウム、水酸化アルミニウム、酸化コバルト、水酸化コバルト、酸化ジルコニウム、水酸化ジルコニウム、酸化スズ、水酸化スズが挙げられ、これらは１種又は２種以上で用いられる。これらは含水物であっても無水物でもあってもよいが含水物の場合は、エポキシ樹脂と混練成型する際に、成型温度により水分が発生し、この水分が赤燐と反応してホスフィンを発生するなど不具合が生じる傾向があることから無水物の方が好ましい。
【００７８】
無機イオン交換体としては、ハイドロカルマイト系無機アニオン交換体、ハイドロタルサイト系無機アニオン交換体、ＢｉＯ_X （ＯＨ）_Y （ＮＯ₃ ）_Z （Ｘ＝０．９〜１．１、Ｙ＝０．６〜０．８、Ｚ＝０．２〜０．４）、Ｍｇ_4.3 Ａｌ₂ （ＯＨ）_12.6ＣＯ₃ ・３．５Ｈ₂ Ｏ、Ｓｂ₂ Ｏ₅ ・２Ｈ₂ Ｏ、ＳｂＳｉ_v Ｂｉ_w Ｏ_x （ＯＨ）_y （ＮＯ３）_z ・ｎＨ₂ Ｏ（ｖ＝０．１〜０．３、ｗ＝１．５〜１．９、ｘ＝４．１〜４．５、ｙ＝１．２〜１．６、ｚ＝０．２〜０．３、ｎ＝１〜２）の無機アニオン交換体等を例示することが出来る。
【００７９】
これらの金属酸化物、金属水酸化物、金属炭酸塩又は金属リン酸塩や無機イオン交換体の配合割合は、赤燐系難燃剤１００重量部に対して、１〜２０重量部、好ましくは５〜２０重量部とすることが好ましい。
【００８０】
本発明の半導体封止用エポキシ樹脂組成物において、上記（Ａ）〜（Ｄ）成分以外に、更に硬化促進剤、顔料、離型剤、表面処理剤、可撓性付与剤等を必要に応じて適宜に添加することができる。
【００８１】
上記硬化促進剤としては、特に限定するものではなくエポキシ基と水酸基の反応を促進するものであればよく、例えば、１，８−ジアザビシクロ（５，４，０）ウンデセン−７等のジアザビシクロアルケン系化合物、トリエチレンジアミン等の三級アミン類、２−メチルイミダゾール等のイミダゾール類、トリフェニルホスフィン等のリン系化合物等があげられる。これら化合物は単独でもしくは２種以上併せて用いられる。
【００８２】
上記顔料としては、カーボンブラック、酸化チタン等があげられる。また、上記離型剤としては、カルナバワックス、ポリエチレンワックス、パラフィンや脂肪酸エステル、脂肪酸塩等があげられる。
【００８３】
さらに、上記表面処理剤としては、シランカップリング剤等のカップリング剤があげられる。また、上記可撓性付与剤としては、各種シリコーン化合物やブタジエン−アクリロニトリルゴム等があげられる。
【００８４】
本発明に係る半導体封止用エポキシ樹脂組成物は、例えばつぎのようにして製造することができる。すなわち、エポキシ樹脂（Ａ成分）、フェノール樹脂（Ｂ成分）、無機充填剤（Ｃ成分）及び赤燐系難燃剤（Ｄ成分）ならびに必要に応じて他の添加剤を所定の割合で配合する。なお、赤燐系難燃剤は、予めエポキシ樹脂やフェノール樹脂等に所望により更に硬化剤、硬化促進剤、着色剤、離型剤、表面処理剤を混合したマスターバッチとして配合することもできる。
【００８５】
つぎに、この混合物をミキシングロール機等の混練機を用いて加熱状態で溶融混練し、これを室温に冷却する。そして、公知の手段によって粉砕し、必要に応じて打錠するという一連の工程によって目的とする半導体封止用エポキシ樹脂組成物を製造することができる。
【００８６】
あるいは、上記半導体封止用エポキシ樹脂組成物の混合物を混練機に導入して溶融状態で混練した後、これを略円柱状の顆粒体に連続的に成形するという一連の工程によって顆粒状の半導体封止用エポキシ樹脂組成物を製造することができる。
【００８７】
さらに、上記半導体封止用エポキシ樹脂組成物の混合物をパレット上に受け入れし、これを冷却後、プレス圧延，ロール圧延，あるいは溶媒を混合したものを塗工してシート化する等の方法によりシート状の半導体封止用エポキシ樹脂組成物を製造することができる。
【００８８】
このようにして得られる半導体封止用エポキシ樹脂組成物（粉末状，タブレット状，顆粒状等）を用いて半導体素子を封止する方法は、特に限定するものではなく、通常のトランスファー成形等の公知の成形方法によって行うことができる。
【００８９】
また、上記シート状の半導体封止用エポキシ樹脂組成物を用いて、例えば、つぎのようにしてフリップチップ実装による半導体装置を製造することができる。すなわち、上記シート状半導体封止用エポキシ樹脂組成物を、接合用バンプを備えた半導体素子の電極面側に、あるいは、回路基板のバンプ接合部側に配置し、上記半導体素子と回路基板とをバンプ接合するとともに両者を樹脂封止による接着封止を行うことによりフリップチップ実装して半導体装置を製造することができる。
【００９０】
【実施例】
以下、本発明を実施例により詳細に説明するが本発明はこれらの実施例に限定されるものではない。
【００９１】
〔赤燐系難燃剤の調製〕
・赤燐系難燃剤試料１
＜（ａ１）工程＞
塊状の赤燐を粉砕、分級して平均粒径が２０μｍで最大粒径が４５μｍ、粒径１μｍ未満の粒子の含有量２重量％の赤燐を得た。この赤燐２１０ｇに水５２５ｇを加えて赤燐スラリーとし、過酸化水素水溶液を０．７ｍｌ加えた。次いで水酸化ナトリウム水溶液でｐＨを１０に調製し、８０℃で６時間保持した。次いで、硝酸を加え、ｐＨを１に調製した後、８０℃で４時間処理した後、ろ過し、スラリーのｐＨが２．５となるまで水で洗浄を行った。
【００９２】
＜（ａ２−２）工程＞
この洗浄した赤燐粉末１００ｇを純水８００ｍｌに懸濁させて赤燐のスラリーを調製した。次いで、硫酸亜鉛を０．０１モル含有する硫酸亜鉛水溶液３０ｍｌを添加した後、温度８０℃において攪拌しながらアンモニア水溶液をｐＨが８になるまで添加した。添加終了後、更にｐＨを７．０〜７．５の範囲となるようにアンモニア水溶液を用いて、ｐＨ管理を行いながら８０℃で１時間攪拌を継続して、水酸化亜鉛の沈着処理を行った。このときの水酸化亜鉛の被覆量はＩＣＰ発光分析の結果０．９重量％であった。なお、化学量論比より求めた理論量は０．９９重量％である。また、得られた水酸化亜鉛を被覆した赤燐の電子顕微鏡写真を図１に、この水酸化亜鉛を被覆した赤燐について８０℃における溶出試験を行った結果を表１に示す。
【００９３】
＜（ａ３）工程＞
次いで、常法によりろ過して反応液からこの被覆赤燐を分離回収し、再び水を加えてスラリーとした後、常法によりリパルプして、この被覆赤燐の１０％スラリーとした時の電気伝導度が３００μｓ／ｃｍ以下になるまでろ過、リパルプを繰り返して行った。
【００９４】
＜（ａ４）工程＞
洗浄終了後赤燐２０ｇを純水１８０ｇに分散させ、攪拌しながらここにアンモニア水を加え、ｐＨを１０．０に調製した。次いで、平均粒径０．３μｍの酸化亜鉛（東邦亜鉛社製；商品名：銀嶺）２ｇおよびフェノール樹脂（大日本インキ社製、初期縮合物、フェノライトＴＤ２３８８；固形分２６％）３．８ｇを添加し、添加終了後、１０分間攪拌した後、塩酸を滴下しｐＨを７〜７．５に調製した。
次に、９０℃で１時間、ｐＨが下がらないようにアンモニア水を滴下して反応系のｐＨを６．５〜７に維持しながら９０℃で１時間反応させた。
【００９５】
＜（ａ５）工程＞
次に、放冷したのち、２０℃の１０％スラリーの電気伝導度が３０μｓ／ｃｍ以下になるまで純水でろ過、洗浄を行った。ろ過ケーキは軽く分散させながら減圧乾燥したのち、１４０℃で２時間硬化処理を行い、放冷後、１００メッシュのフルイを通過させて赤燐系難燃剤試料１を調製した。この赤燐系難燃剤試料１の主物性を表２に示す。
【００９６】
・赤燐系難燃剤試料２
＜（ａ１）工程＞
塊状の赤燐を粉砕、分級して平均粒径が２０μｍで最大粒径が４５μｍ、粒径１μｍ未満の粒子の含有量２重量％の赤燐を得た。この赤燐２１０ｇに水５２５ｇを加えて赤燐スラリーとし、過酸化水素水溶液を０．７ｍｌ加えた。次いで水酸化ナトリウム水溶液でｐＨを１０に調製し、８０℃で６時間保持した。次いで、硝酸を加え、ｐＨを１に調製した後、８０℃で４時間処理した後、ろ過し、スラリーのｐＨが２．５となるまで水で洗浄を行った。
【００９７】
＜（ａ２−１）工程＞
この洗浄した赤燐粉末１００ｇを純水８００ｍｌに懸濁させて赤燐のスラリーを調製した。次いで、硫酸亜鉛を０．０１モル含有する硫酸亜鉛水溶液３０ｍｌを添加した後、温度８０℃において攪拌しながらアンモニア水溶液をｐＨが８になるまで添加した。添加終了後、ｐＨ管理をおこなわず、そのまま８０℃で１時間攪拌を継続して、水酸化亜鉛の沈着処理を行った。このときの水酸化亜鉛の被覆量はＩＣＰ発光分析の結果０．３重量％であった。なお、化学量論比より求めた理論量は０．９９重量％であり、沈着処理終了後の反応系のｐＨは５であった。
【００９８】
また、得られた水酸化亜鉛を被覆した赤燐の電子顕微鏡写真を図２に示し、この水酸化亜鉛を被覆した赤燐について８０℃における溶出試験を行った結果を表１に示す。
【００９９】
＜（ａ３）工程＞
次いで、常法によりろ過して反応液からこの被覆赤燐を分離回収し、再び水を加えてスラリーとした後、常法によりリパルプして、この被覆赤燐の１０％スラリーとした時の電気伝導度が３００μｓ／ｃｍ以下になるまでろ過、リパルプを繰り返して行った。
【０１００】
＜（ａ４）工程＞
洗浄終了後赤燐２０ｇを純水１８０ｇに分散させ、攪拌しながらここにアンモニア水を加え、ｐＨを１０．０に調製した。次いで、平均粒径０．３μｍの酸化亜鉛（東邦亜鉛社製；商品名：銀嶺）２ｇおよびフェノール樹脂（大日本インキ社製、初期縮合物、フェノライトＴＤ２３８８；固形分２６％）３．８ｇを添加し、添加終了後、１０分間攪拌した後、塩酸を滴下しｐＨを７．０〜７．５に調製した。
次に、９０℃で１時間、ｐＨ管理をおこなわずそのまま反応させた。反応終了後の反応系内のｐＨは５であった。
【０１０１】
＜（ａ５）工程＞
次に、放冷したのち、２０℃の１０％スラリーの電気伝導度が３０μｓ／ｃｍ以下になるまで純水でろ過、洗浄を行った。ろ過ケーキは軽く分散させながら減圧乾燥したのち、１４０℃で２時間硬化処理を行い、放冷後、１００メッシュのフルイを通過させて赤燐系難燃剤試料２を調製した。この赤燐系難燃剤試料２の主物性を表２に示す。
【０１０２】
＜水酸化亜鉛を被覆した赤燐の８０℃における溶出試験＞
赤燐系難燃剤試料１と２の（ａ２−１）および（ａ２−２）工程後の水酸化亜鉛を被覆した赤燐について下記の要領で溶出イオンの濃度の測定を行った。
水酸化亜鉛を被覆した赤燐８．０ｇを１００ｍｌのポリプロピレン製ビンに採取し、蒸留水８０ｍｌを加えて密栓する。送風定温乾燥機にて８０℃で、２０時間加熱、抽出後、乾燥機より取り出し、１０分以内に常温まで冷却し、上澄み液をろ過した後、ろ液中の溶出ＰＯ₄ イオン濃度、ＰＨＯ₃ イオン濃度、ＰＨ₂ Ｏ₂ イオン濃度をイオンクロマトグラフで測定した。その結果を表１に示す。なお、表中のＮ．Ｄ．は、溶出ＰＯ₄イオン濃度が０．０９ｐｐｍ以下を示す。
【０１０３】
【表１】

【０１０４】
図１、図２及び表１の結果より赤燐系難燃剤試料１の（ａ２−２）工程後の水酸化亜鉛の被覆と、赤燐系難燃剤試料２の（ａ２−１）工程後の水酸化亜鉛の被覆とでは、水酸化亜鉛の被覆特性が明らかに異なり、赤燐系難燃剤試料１の水酸化亜鉛の被覆は、試料２のものと比べ結晶構造を保った緻密な被覆が形成され、粒子の大きさも大きいことが分かる。
【０１０５】
・赤燐系難燃剤試料３
前記赤燐系難燃剤試料１の（ａ５）工程において、洗浄を１００μｓ／ｃｍでやめた以外は前記赤燐系難燃剤試料１と同様な条件で赤燐系難燃剤試料３を得た。この赤燐系難燃剤試料３の主物性を表２に示す。
【０１０６】
・赤燐系難燃剤試料４
前記赤燐系難燃剤試料１の（ａ４）工程において、酸化亜鉛を添加しない以外は前記赤燐系難燃剤試料１と同様な条件で赤燐系難燃剤試料４を得た。この赤燐系難燃剤試料４の主物性を表２に示す。
【０１０７】
・赤燐系難燃剤試料５
塊状の赤燐を粉砕、分級して平均粒径が２０μｍで最大粒径が４５μｍ、粒径１μｍ未満の粒子の含有量２重量％の赤燐を得た。この赤燐２１０ｇに水５２５ｇを加えて赤燐スラリーとし、過酸化水素水溶液を０．７ｍｌ加えた。次いで水酸化ナトリウム水溶液でｐＨを１０に調製し、８０℃で６時間保持した。次いで、硝酸を加え、ｐＨを１に調製した後、８０℃で４時間処理した後、ろ過し、スラリーのｐＨが２．５となるまで水で洗浄を行った。
【０１０８】
この洗浄した赤燐粉末１００ｇを純水１０００ｍｌに懸濁させて赤燐のスラリーを調製した。次いで、水酸化アルミニウム（Ａｌ（ＯＨ）₃ ）換算で１ｇに相当する量の硫酸アルミニウムを添加した。添加終了後、３０分間攪拌した後、水酸化ナトリウムを添加してスラリーのｐＨを８．０に調製し、その後液温を８５℃まで上げて８５℃で２時間熟成を行った。
【０１０９】
次いで、常法によりろ過して反応液からこの被覆赤燐を分離回収し、再び水を加えてスラリーとした後、常法によりリパルプして、この被覆赤燐の１０％スラリーとした時の電気伝導度が３００μｓ／ｃｍ以下になるまでろ過、リパルプを繰り返して行った。
【０１１０】
ろ過ケーキを水に分散させて、攪拌しながらフェノール樹脂（フェノール樹脂（大日本インキ社製、初期縮合物、フェノライトＴＤ２３８８；固形分２６％）を固形物換算で赤燐に対して５％相当分を添加し、更に塩酸を添加してスラリーのｐＨを２以下とした。スラリーを加熱して９０℃で１時間保持してフェノール樹脂の硬化反応を完結させた。
【０１１１】
放冷した後、１０％スラリーの電気伝導度が３０μｓ／ｃｍ以下になるまで十分にスラリーのろ過、洗浄を行った。ろ過ケーキは軽く分散させながら減圧乾燥したのち、１４０℃で２時間硬化処理を行い、放冷後、１００メッシュのフルイを通過させて赤燐系難燃剤試料５を調製した。この赤燐系難燃剤試料５の主物性を表２に示す。
【０１１２】
＜電気伝導度の測定＞
上記で調製した赤燐系難燃剤を純水に分散させ１０重量％スラリーとした時の電気伝導度を測定した。その結果を表２に示す。なお、電気伝導度の測定は溶出イオンの測定用検液を使用して、電気伝導度計により測定した。
【０１１３】
＜粒径の測定＞
上記で調製した赤燐系難燃剤試料をレーザー法で、マイクロトラック（Ｘ１００型）粒度分布測定装置により、平均粒径を測定した。また、分析用フルイにて最大粒径を測定した。その結果を表２に示す。
【０１１４】
＜赤燐系難燃剤試料の溶出イオン及び電気伝導度の評価＞
赤燐系難燃剤試料１〜５について下記の要領で溶出イオンの濃度の測定を行った。
赤燐系難燃剤試料８．０ｇを１００ｍｌのポリプロピレン製ビンに採取し、蒸留水８０ｍｌを加えて密栓する。送風定温乾燥機にて８０℃で、２０時間加熱、抽出後、乾燥機より取り出し、１０分以内に常温まで冷却し、上澄み液をろ過した後、ろ液中の溶出ＰＯ₄ イオン濃度、ＰＨＯ₃ イオン濃度、ＰＨ₂ Ｏ₂ イオン濃度をイオンクロマトグラフで測定した。その結果を表３に示す。
【０１１５】
また、加熱条件を１６０℃で、２０時間にし、ろ液中の溶出ＰＯ₄ イオン濃度、ＰＨＯ₃ イオン濃度、ＰＨ₂ Ｏ₂ イオン濃度をイオンクロマトグラフで測定した。その結果を表３に示す。
【０１１６】
また、上記の溶出イオンの測定で用いたろ液の電気伝導度を２０℃で測定した。その結果を表３に示す。なお、電気伝導度の測定は溶出イオンの測定用検液を使用して、電気伝導度計により測定した。
【０１１７】
【表２】

【０１１８】
（注）水酸化亜鉛の被覆量の値は、（ａ２−１），（ａ２−２）工程後のものをＩＣＰ発光分析で測定した値である。
【０１１９】
【表３】

【０１２０】
（注）表３中の＊１は８０℃×２０ｈｒｓ、＊２は１６０℃×２０ｈｒｓの測定条件を示す。
【０１２１】
＜半導体封止用エポキシ樹脂の調製＞
以下に、上記にて得られた各種赤燐系難燃剤を含有してなる半導体封止用エポキシ樹脂組成物に関する実施例を記載する。
まず、半導体封止用エポキシ樹脂組成物を得るために、上記にて作製した赤燐系難燃剤以外に以下のものを準備した。
【０１２２】
［エポキシ樹脂Ａ］
クレゾールノボラック型エポキシ樹脂（日本化薬社製、商品名 ＥＯＣＮ−１０２０、エポキシ当量１９８、軟化点７５℃）
［エポキシ樹脂Ｂ］
４，４’−ビス（２，３−エポキシプロポキシ）−３，３’，５，５’−テトラメチルビフェニル（エポキシ当量１９４、軟化点１０８℃）
［フェノール樹脂Ｃ］
フェノールノボラック樹脂（荒川化学社製、商品名 Ｐ−１８０、水酸基当量１０５、軟化点８０℃）
［フェノール樹脂Ｄ］
前記一般式（３）にて表されるフェノールアラルキル樹脂（水酸基当量１７５、軟化点７０℃）
［イオン捕捉剤］
ハイドロタルサイト類化合物：Ｍｇ_4.3 Ａｌ₂ （ＯＨ）_12.6ＣＯ₃ ・３．５Ｈ₂ Ｏ（平均粒径２μｍ）（ＤＨＴ−４Ａ、協和化学社製）
［カーボンブラック］
［離型剤］
酸化ポリエチレン系ワックス（ＰＥＤ−５２１、クラリアント社製）
［硬化促進剤］
トリフェニルホスフィン
［無機質充填剤］
溶融シリカ粉末（球形、平均粒径２５μｍ、比表面積１．４ｍ² ／ｇ）
【０１２３】
実施例１〜４および比較例１〜３
下記の表４に示す各成分を同表に示す割合で配合し、ミキシングロール機（温度１００℃）で３分間溶融混練を行い、冷却固化した後粉砕して目的とする粉末状の半導体封止用エポキシ樹脂組成物を得た。
【０１２４】
【表４】

【０１２５】
上記のようにして得られた各実施例および比較例の半導体封止用エポキシ樹脂組成物について、下記の評価を行い、その結果を表５に記載した。
【０１２６】
＜流動性の評価＞（フローテスター粘度、ゲルタイム）
上記各実施例および比較例にて得た粉末状のエポキシ樹脂組成物を２ｇ秤量し、タブレット状に成形した。これを高化式フローテスターのポット内に入れ、１０ｋｇの荷重をかけた。１７５℃の温度下で溶融したエポキシ樹脂組成物はダイスの孔（直径１．０ｍｍ×１０ｍｍ）を通過して押し出される時のピストンの移動速度から、各サンプルの溶融粘度（フローテスター粘度）を求めた。
【０１２７】
また、１７５℃の熱平板上に各実施例および比較例にて得た粉末状のエポキシ樹脂組成物の試料を２００〜５００ｍｇを載せ、攪拌しながら熱平板上に薄く引き延ばし、試料が熱平板上に溶融した時点から硬化するまでの時間を読み取り、ゲル化時間（ゲルタイム）とした。
【０１２８】
＜不純物特性＞
各実施例および比較例にて得たエポキシ樹脂組成物を、１７５℃で２分間タブレット状に成形したのち、さらに１７５℃で５時間のポストキュア条件下で硬化させたのち、この硬化物を振動ミルにて微粉末状に粉砕し、目開き１５０μｍの網に通過させ、５ｇを採取し、外側が金属（ＳＵＳ）で内側がテフロン（登録商標）製の容器に５０ｍｌのイオン交換水と共に投入し、１６０℃×２０時間にて抽出を行った。
【０１２９】
その抽出水について不純物量（Ｎａ⁺ 、Ｃｌ^- 、ＨＰＯ₃ ^2- 、ＰＯ₄ ^3- ）をイオンクロマトグラフィにて測定すると共に、上記抽出水についてＥＣ（電気伝導度）を電気伝導度計（Ｅｌｅｃｔｒｉｃａｌ Ｃｏｎｄｕｃｔｉｖｉｔｙ）にて測定した。併せて、ｐＨメーターでｐＨ値も測定した。
【０１３０】
＜耐湿信頼性＞
上記各実施例および比較例にて得たエポキシ樹脂組成物を用いて、タブレット化し、成形条件１７５℃×６．８６７ＭＰａ×１２０秒間で難燃性試験用試験片を成形した。一方、ＴＯＷＡ自動成形機でＬＱＦＰ−１１４（大きさ：２０ｍｍ×２０ｍｍ×厚み１．４ｍｍ）のパッケージ（半導体装置）に成形した。このようにして得たパッケージを用いて、プレッシャークッカーバイアステスト（ＰＣＢＴ）を、１３０℃、８５％Ｒ．Ｈ．、３０Ｖバイアスの条件下で行った。そして、評価に用いたパッケージの５０％が不良モードとなった時間を測定した。なお、不良モードとしては、リーク不良およびオープン不良を測定した。
【０１３１】
＜難燃性＞
上記耐湿信頼性試験にて得た難燃性試験用試験片を用いて、ＵＬ−９４Ｖ−０規格の方法に従って難燃性を評価した。なお、合格とは９４Ｖ−０合格を意味する。
【０１３２】
【表５】

【０１３３】
上記表５の結果から明らかなように、実施例品は優れた難燃性を示し、さらに、不純物である各種イオンの含有量も少なく、流動性に関してもフローテスター粘度およびゲルタイムの両値共に良好であることがわかる。特に、耐湿信頼性については、比較例品と比べて格段に向上していることが明確である。
【０１３４】
【発明の効果】
以上のように、本発明の半導体封止用エポキシ樹脂組成物は、赤燐の表面に特定の被覆層を有するノンハロゲン、ノンアンチモンタイプの複合化難燃剤を用いるので、優れた難燃効果を発揮すると共に、耐湿性や耐水性を有するものである。
【０１３５】
従って、上記赤燐系難燃剤をエポキシ樹脂組成物に含有させた半導体封止用エポキシ樹脂組成物を用いて半導体素子を封止してなる半導体装置へ、難燃性や耐湿信頼性を付与することができるという効果を奏するものである。
【図面の簡単な説明】
【図１】赤燐系難燃剤試料１の（ａ２−２）工程後の赤燐粒子表面上に形成させた水酸化亜鉛被膜の状態を示す赤燐粒子構造の電子顕微鏡写真（倍率２０００倍）である。
【図２】赤燐系難燃剤試料２の（ａ２−１）工程後の赤燐粒子表面上に形成させた水酸化亜鉛被膜の状態を示す赤燐粒子構造の電子顕微鏡写真（倍率２０００倍）である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an epoxy resin composition for semiconductor encapsulation excellent in moisture resistance and flame retardancy, and a semiconductor device using the same.
[0002]
[Prior art]
The sealing material protects the semiconductor IC from moisture and dust in the air and facilitates the handling of the semiconductor IC. Currently, the epoxy resin sealing material occupies most.
[0003]
Conventionally, a halogenated epoxy resin or a combination of a halogenated epoxy resin and antimony trioxide has been used as a flame retardant for an epoxy resin sealing material. Recently, however, problems of global environmental pollution and health hazards have emerged, and the demand for non-halogenated flame retardants has increased. Halogen compounds such as chlorine and bromine and antimony trioxide tend not to be used. As a non-halogen flame retardant, red phosphorus is a powerful flame retardant. However, when red phosphorus is used, there is a problem that a small amount of phosphine gas is generated due to the reaction between red phosphorus and moisture in the air. The problem was that the phosphorus oxoacids eluted.
[0004]
Phosphorus oxo acid eluted from the surface of red phosphorus corrodes the aluminum wiring when it comes into contact with the semiconductor IC circuit, causing a decrease in reliability. The reduction of these eluted ions encapsulates red phosphorus flame retardant with epoxy resin. It was a big problem when applied to materials.
[0005]
There have been many studies on the problem of phosphine generation from red phosphorus. The surface of red phosphorus is coated with inorganic metal hydroxides such as aluminum and titanium, and organic materials such as phenol resin and melamine resin are used. A method of reducing the amount of phosphine generated by performing a coating treatment with a compound or a double coating treatment method of an inorganic compound and an organic compound has been proposed.
[0006]
[Problems to be solved by the invention]
However, even in the case of the above-described coated red phosphorus, the phosphorus oxo acid from the surface of the red phosphorus is eluted, so that the present invention is applied to a field requiring electrical reliability such as a semiconductor sealing material. It was difficult. For example, when a red phosphorus flame retardant is used for an epoxy resin for semiconductor encapsulation, in the reliability test of the sealing material, the IC circuit is corroded by the oxo acid of phosphorus eluted from the red phosphorus, and the reliability is improved. There is a problem of lowering.
[0007]
One reason that phosphorus oxoacids are eluted from red phosphorus is that, even when the surface treatment method of red phosphorus is good, red phosphorus may be used in other materials, such as epoxy resin, when producing an epoxy resin sealing material. When mixing and kneading together with a phenol resin curing agent, silica filler, etc., red phosphorus particles are subjected to mechanical frictional force and shearing force, and the red phosphorus coating layer is peeled off. It is considered that phosphorus and oxo acid of phosphorus are eluted by direct contact between phosphorus and water. In this case, the sealing material reliability test often fails.
[0008]
As the red phosphorus flame retardant for epoxy resin for semiconductor encapsulation, for example, melamine polyphosphate and red phosphorus coated with epoxy silane coupling agent and aminosilane coupling agent after coating with phenol resin on the surface (Japanese Patent Laid-Open No. 10-182940), the surface layer is Ti_x O_y (X and y are positive numbers, x: y = 1: 2 to 1: 4) A method using a red phosphorus flame retardant (JP-A-7-173372), the surface of red phosphorus is aluminum hydroxide After coating, a method using a red phosphorus flame retardant having an average particle diameter of 2 to 8 μm and a maximum particle diameter of 20 μm or less (JP 10-152599 A) The surface layer is Si_x O_y A method using a red phosphorus flame retardant in which X and Y are positive numbers and X: Y = 1: 2 to 1: 4 (JP-A-7-157542) has been proposed.
[0009]
Also, the coated red phosphorus flame retardant and BiO_X (OH)_Y (NO_Three )_Z (X = 0.9 to 1.1, Y = 0.6 to 0.8, Z = 0.2 to 0.4) and Mg_4.3 Al₂ (OH)_12.6CO_Three ・ 3.5H₂ A method in which an ion scavenger such as O is used in combination has also been proposed (JP-A-8-151427, JP-A-9-227765).
[0010]
However, the red phosphorus-based flame retardant coated with the above-described red phosphorus particles is subjected to mechanical frictional force or shearing force when the epoxy resin sealing material is produced, and the red phosphorus coating layer peels off, Red phosphorus and water come into direct contact with the peeled portion to elute phosphorus oxoacids. In addition, even in a method using an ion scavenger in combination, since the ability of phosphorus to capture oxoacids is low, a practical problem has not yet been solved.
[0011]
Japanese Patent Application Laid-Open No. 62-21704 discloses moisture resistance and corrosion resistance in which the surface of red phosphorus particles is coated with a hydroxide of Al or Zn and further double coated with a thermosetting resin containing zinc hydroxide. An improved flame retardant coated red phosphorus has been proposed.
[0012]
However, the red phosphorus disclosed in Japanese Patent Application Laid-Open No. 62-21704 is prepared by adding a water-soluble metal salt to a slurry in which red phosphorus particles are dispersed in water, and then adding an alkali agent to form a metal oxide on the surface of the red phosphorus particles. Alternatively, an ion deposited as a hydroxide to obtain red phosphorus coated with an inorganic substance, and the electric conductivity after completion of the reaction is 10,000 μs / cm or more without washing the red phosphorus coated with the inorganic substance. It is manufactured by directly adding zinc hydroxide and a thermosetting resin synthetic raw material or an initial condensate thereof to a slurry containing a curable impurity and performing a polymerization reaction under the homopolymerization conditions of the thermosetting resin. The stabilized red phosphorus obtained in this way has a large amount of ionic impurities taken into the coating resin during the polymerization reaction, and it is difficult to remove the ionic impurities in the resin even after subsequent washing treatment. If washing is repeated to forcibly reduce the electrical conductivity, the coating on the surface of the red phosphorus particles is broken, and the amount of phosphorus oxoacid eluted increases.
[0013]
JP-A-2000-281874 discloses that the total content of phosphate ions and phosphite ions eluted when extracted at 80 ° C. for 20 hours is 2000 ppm or less, and the P content is 20 to 40% by weight. An epoxy resin composition for semiconductor encapsulation using a red phosphorus flame retardant has been proposed.
However, the red phosphorus flame retardant disclosed in Japanese Patent Application Laid-Open No. 2000-281874 has a low P content, so that the flame retardant effect is insufficient.
[0014]
That is, the present invention has been made to solve such problems of the prior art, and comprises an epoxy resin composition for semiconductor encapsulation having excellent flame retardancy and moisture resistance, and the same. An object of the present invention is to provide a semiconductor device.
[0015]
[Means for Solving the Problems]
The inventors of the present invention have excellent flame retardancy and moisture resistance using a red phosphorus flame retardant coated with a thermosetting resin containing an anhydrous zinc compound after first coating the surface of the red phosphorus particles with an inorganic substance. An epoxy resin composition (PCT01 / JP01 / 04363) was proposed.
[0016]
In addition, as a result of extensive research on red phosphorus flame retardants that can be used as flame retardants for epoxy resins for semiconductor encapsulation, the first coating layer has red phosphorus particles coated with zinc hydroxide as red phosphorus flame retardants. Further, in the red phosphorus flame retardant having a second coating layer coated with a phenol resin containing zinc oxide, the primary coating is caused by reacting a soluble zinc compound and an alkaline agent under conditions of pH 6.5 or more. The electrical conductivity of the slurry dispersed in water at 20 ° C., which is densely coated while maintaining the crystal structure of the generated zinc hydroxide and is strictly subjected to a washing step to remove impurities in the production process, The amount of phosphorus oxoacid that elutes after standing at 80 ° C. for 20 hours and the electrical conductivity of the slurry after standing at 80 ° C. for 20 hours are determined by the aggregation during coating treatment and the subsequent The present invention has been found out that the use of this red phosphorus flame retardant as a flame retardant for epoxy resin for semiconductor encapsulation is excellent in flame retardancy and moisture resistance reliability. It came to complete.
[0017]
  That is, according to the first aspect of the present invention, at least the epoxy resin (component A), the phenol resin (component B), the filler (component C) and the surface of the red phosphorus particles are coated with zinc hydroxide as the primary coating. An epoxy resin composition containing a red phosphorus flame retardant (D component) having a P content of 65 to 97% by weight, wherein the secondary coating is formed with a double coating layer comprising a phenolic resin coating containing zinc oxide The red phosphorus flame retardant has the following properties (D1) to (D3), and provides an epoxy resin composition for semiconductor encapsulation.
(D1)A primary coating of zinc hydroxide is formed on the surface of the red phosphorus particles washed with at least one selected from acids and alkalis; andThe zinc hydroxide coating amount on the red phosphorus particles is 0.5 to 10% by weight,
(D2) The electrical conductivity of a slurry in which 10% by weight of a red phosphorus flame retardant is dispersed in 20 ° C. water is 30 μs / cm or less,
(D3) PO that elutes when 80 ml of water is added to 8 g of the red phosphorus flame retardant and heated at 80 ° C. for 20 hours._FourWhen the ion concentration is 10 ppm or less, PHO_ThreeWhen the ion concentration is 200 ppm or less, PH₂O₂The ion concentration is 150 ppm or less, and the electric conductivity after standing at 80 ° C. for 20 hours is 100 μs / cm or less.
[0018]
The red phosphorus particles used in the red phosphorus flame retardant (component D) are water produced by reacting zinc hydroxide, which is the primary coating on the surface thereof, particularly with a soluble zinc compound and an alkaline agent at a pH of 6.5 or higher. Those consisting of a zinc oxide coating are preferred.
[0019]
Further, the red phosphorus flame retardant (component D) is eluted when 80 ml of water is added to 8 g of the red phosphorus flame retardant and heated at 160 ° C. for 20 hours._Four When the ion concentration is 100 ppm or less, PHO_Three When the ion concentration is 250 ppm or less, PH₂ O₂ It is preferable that the ion conductivity is 2000 ppm or less and the electric conductivity after standing at 160 ° C. for 20 hours is 2000 μs / cm or less.
The red phosphorus flame retardant (component D) preferably further has an average particle size in the range of 1 to 50 μm.
[0020]
According to a second aspect of the present invention, there is provided a semiconductor device comprising the semiconductor sealing epoxy resin composition.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The present invention will be described in detail below.
The epoxy resin composition for semiconductor encapsulation of the present invention uses at least an epoxy resin (A component), a phenol resin (B component), a filler (C component), and a red phosphorus flame retardant (D component). In general, it is used as a powder or a tablet obtained by tableting this. Or after melt-kneading the resin composition, it is used as a sealing material in the form of granules formed into granules having a substantially cylindrical shape, and further into sheets.
[0022]
The epoxy resin (component A) is not particularly limited, and various conventionally known epoxy resins are used. For example, bisphenol A type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, biphenyl type epoxy resin and the like can be mentioned.
[0023]
And among the said epoxy resins, it is preferable to use a biphenyl type epoxy resin, for example, the biphenyl type epoxy resin represented by following General formula (1) is used.
[0024]
[Chemical 1]

[0025]
(Wherein R₁ ~ R_Four Represents a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, R₁ ~ R_Four May be the same or different from each other. )
[0026]
R in the general formula (1)₁ ~ R_Four Represents a hydrogen atom (—H) or an alkyl group having 1 to 5 carbon atoms, and examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, sec- Examples thereof include linear or branched lower alkyl groups such as a butyl group and a tert-butyl group, and a methyl group is particularly preferable.₁ ~ R_Four May be the same as or different from each other. Among these, from the viewpoint of low hygroscopicity and reactivity, the above R₁ ~ R_Four It is particularly preferable to use a biphenyl type epoxy resin having a structure represented by the following formula (2) in which all are methyl groups.
[0027]
[Chemical formula 2]

[0028]
The phenol resin (component B) used together with the epoxy resin (component A) acts as a curing agent for the epoxy resin and is not particularly limited, and conventionally known ones are used. Examples thereof include phenol novolak, cresol novolak, bisphenol A type novolak, naphthol novolak, and phenol aralkyl resin. Especially, when using a biphenyl type epoxy resin as said epoxy resin (A component), it is preferable to use the phenol aralkyl resin represented by following General formula (3) as a phenol resin.
[0029]
[Chemical Formula 3]

(In the formula, n is 0 to 40.)
[0030]
And the compounding ratio of the said epoxy resin (A component) and the said phenol resin (B component) is such that the hydroxyl group in a phenol resin will be 0.7-1.3 equivalent per 1 equivalent of epoxy groups in the said epoxy resin. It is preferable to set it to be 0.9 to 1.1 equivalent.
[0031]
The filler (component C) is not particularly limited, and various conventionally known fillers can be used. Examples thereof include inorganic fillers such as quartz glass powder, talc, silica powder, alumina powder, aluminum nitride powder, and silicon nitride powder. These may be used alone or in combination of two or more. And as said filler, it is preferable to use a silica powder from the point that the linear expansion coefficient of the hardened | cured material obtained can be reduced. Especially, it is especially preferable from the point of the favorable fluidity | liquidity of a resin composition to use a fused silica powder as a silica powder, especially a spherical fused silica powder.
[0032]
Moreover, in the said filler, it is preferable that the average particle diameter is the range of 10-70 micrometers, More preferably, it is 10-50 micrometers. That is, when the average particle diameter of the filler is within the above range, good fluidity of the resin composition can be obtained. In addition, as the silica powder, a ground silica powder obtained by grinding a silica powder can be used in some cases.
[0033]
The content of the filler is preferably set to be 60 to 95% by weight of the entire semiconductor sealing epoxy resin composition.
[0034]
  The red phosphorus flame retardant (D component) used together with the components A to C is a phenol resin in which the primary coating is made of zinc hydroxide on the surface of the red phosphorus particles, and the secondary coating contains zinc oxide. A red phosphorus flame retardant having a P content of 65 to 97% by weight formed with a double coating layer made of a coating, and the red phosphorus flame retardant used in the present invention has a primary coating made of zinc hydroxide. Preferably, it consists of a coating in a state in which the crystal structure of zinc hydroxide produced by reacting a soluble zinc compound and an alkali agent under the condition of pH 6.5 or higher is maintained, and the following (D1) to (D3) It is a particularly important requirement to use those having the characteristics of).
(D1)A primary coating of zinc hydroxide is formed on the surface of the red phosphorus particles washed with at least one selected from acids and alkalis; andThe zinc hydroxide coating amount on the red phosphorus particles is 0.5 to 10% by weight,
(D2) The electrical conductivity of a slurry in which 10% by weight of a red phosphorus flame retardant is dispersed in water at 20 ° C. (hereinafter referred to as 10% by weight slurry) is 30 μs / cm or less,
(D3) PO that elutes when 80 ml of water is added to 8 g of the red phosphorus flame retardant and heated at 80 ° C. for 20 hours._FourWhen the ion concentration is 10 ppm or less, PHO_ThreeWhen the ion concentration is 200 ppm or less, PH₂O₂The ion concentration is 150 ppm or less, and the electric conductivity after standing at 80 ° C. for 20 hours is 100 μs / cm or less.
[0035]
The red phosphorus flame retardant according to the following will be described.
The zinc hydroxide coating of the first layer according to the present invention comprises a zinc hydroxide coating produced by the reaction of a soluble zinc compound and an alkali agent. The inventors have found that the coating of zinc hydroxide varies with the control of the pH during the reaction. For example, a description will be given using the zinc hydroxide coating shown in FIGS. FIG. 1 is an electron having a red phosphorus particle structure showing a state of a zinc hydroxide film formed on the surface of red phosphorus particles after the step (a2-2) of a red phosphorus flame retardant sample 1 of an embodiment of the present invention described later. FIG. 2 is a photomicrograph (magnification 2000 times). FIG. 2 shows the state of the zinc hydroxide coating formed on the surface of the red phosphorus particles after the step (a2-1) of the red phosphorus flame retardant sample 2 of the example described later. It is an electron micrograph (magnification 2000 times) of the red phosphorus particle structure shown.
[0036]
That is, the coating of zinc hydroxide in FIG. 2 was obtained by adjusting the soluble zinc compound and the alkaline agent to pH 6.5 or higher without controlling the pH during the reaction. As shown, the surface of the zinc hydroxide crystal dissolved in the acid produced as a by-product during the reaction is a smooth zinc hydroxide coating with a smooth surface, and the particle size is small. On the other hand, as shown in the electron micrograph, the zinc hydroxide coating shown in FIG. 1 maintains the pH at 6.5 or higher during the reaction between the soluble zinc compound and the alkaline agent, so that acid is a by-product during the reaction. Therefore, the generated zinc hydroxide crystal is not dissolved in the acid, and it is a strong and dense coating that is square in a state where the crystal structure is maintained, and has a large particle size.
[0037]
As shown in FIGS. 1 and 2, the red phosphorus flame retardant used in the present invention is coated on the surface of red phosphorus particles. In the present invention, the red phosphorus flame retardant coated with zinc hydroxide is used. In the flame retardant, the coating amount of zinc hydroxide on the red phosphorus particles is 40% by weight or more, preferably 60% by weight or more, more preferably 80% by weight of the theoretical amount determined from the stoichiometric ratio of the added soluble zinc compound and alkali. % Of which is preferably coated with zinc hydroxide, particularly preferably one having a coating of zinc hydroxide which maintains the crystal structure shown in FIG. 1, and further, a phenol resin containing zinc oxide on the surface thereof. By coating with, elution of phosphorus oxoacids can be reduced.
[0038]
In the present invention, the coating amount of zinc hydroxide on the red phosphorus particles is 0.5 to 10% by weight, preferably 0.6 to 3% by weight, and more preferably 0.8 to 2% by weight. If the coating amount is less than 0.5% by weight, the ability to fix the eluted phosphate ions is insufficient. On the other hand, if the coating amount exceeds 10% by weight, the red phosphorus flame retardant tends to aggregate and reaggregate. Even if it becomes difficult to adjust the desired particle size, or even when adjusting the particle size of the red phosphorus flame retardant, it re-aggregates during storage and kneading of the epoxy resin composition, so that the particle size increases. As described later, the resin dispersibility deteriorates, and the maximum particle size of the aggregated particles itself may be in the range described later. However, particles exceeding the range are present in the gap (Gap) between the substrate and the IC chip. Therefore, it is not preferable because it becomes a cause of generation of defective products.
[0039]
The red phosphorus flame retardant used in the present invention is a red phosphorus flame retardant in which a zinc hydroxide coating surface, particularly a zinc hydroxide coating surface having the above crystal structure, is further coated with a phenol resin containing zinc oxide. It is.
[0040]
The red phosphorus flame retardant has a red phosphorus content of 65 to 97% by weight, preferably 75 to 95% by weight. The reason for this is that when the red phosphorus content is less than 65% by weight, the amount of the coating component increases, so that the red phosphorus particles aggregate due to the binder effect, the particle size increases, and the dispersibility in the sealing resin decreases, which is difficult. On the other hand, if the red phosphorus content exceeds 97% by weight, the coating component is small, and this is not preferable because it tends to involve elution of the phosphoric acid component and generation of phosphine gas.
[0041]
In the present invention, it is important to use the above-mentioned red phosphorus flame retardant having an electric conductivity of 30 μs / cm or less, preferably 20 μs / cm or less when 10 wt% slurry is formed in water at 20 ° C. For this reason, when the electrical conductivity exceeds 30 μs / cm, for example, when used as a flame retardant for an epoxy resin such as a sealing material, the electrical reliability tends to be inferior.
[0042]
Furthermore, in the present invention, it is an important requirement that the red phosphorus flame retardant to be used has stability even at a kneading temperature with an epoxy resin in the preparation of a normal sealing material. That is, PO that elutes when 80 ml of water is added to 8 g of the red phosphorus flame retardant and heated at 80 ° C. for 20 hours._Four When the ion concentration is 10 ppm or less, preferably 8 ppm or less, PHO_Three When the ion concentration is 200 ppm or less, preferably 150 ppm or less, PH₂ O₂ The ion concentration is 150 ppm or less, preferably 100 ppm or less, and the electric conductivity after standing at 80 ° C. for 20 hours is 100 μs / cm or less, preferably 80 μs / cm or less.
[0043]
Eluting PO_Four Ion concentration, PHO_Three Ion concentration and PH₂ O₂ The reason for setting the ion concentration within the above range is that the PO that elutes when this range is exceeded._Four Ion, PHO_Three Ion and PH₂ O₂ For example, when this red phosphorus flame retardant is used as a flame retardant for an epoxy resin as a sealing material due to ions, corrosion of aluminum wiring formed on the surface of the semiconductor element occurs, and the moisture resistance electrical reliability of the semiconductor sealing material This is not preferable because the property tends to be impaired.
[0044]
Further, the reason why the electric conductivity after standing at 80 ° C. for 20 hours is in the above range is that, if this range is exceeded, as described above, for example, this red phosphorus flame retardant is used as a flame retardant for epoxy resin as a sealing material. In such a case, the moisture resistance electrical reliability of the semiconductor sealing material is impaired, which is not preferable. In the present invention, the electrical conductivity is represented by chlorine ion, bromine ion, PO_Four Ion, PHO_Three Ion, PH₂ O₂ Ion, SO_Four Ion, NH_Four It is a value resulting from ionic compounds such as ions, Na ions and K ions.
[0045]
Further, the red phosphorus flame retardant according to the present invention is preferably one having stability at a higher temperature. That is, 80 ml of water is added to 8 g of the red phosphorus flame retardant and heated at 160 ° C. for 20 hours. PO that elutes_Four When the ion concentration is 100 ppm or less, preferably 80 ppm or less, PHO_Three When the ion concentration is 250 ppm or less, preferably 200 ppm or less,₂ O₂ The ion concentration is 2000 ppm or less, preferably 1900 ppm or less, and the electrical conductivity of the slurry under this condition is 2000 μs / cm or less, preferably 1900 μs / cm or less. The red phosphorus flame retardant according to the present invention is excellent in electrical reliability even under high temperature conditions by using a reduced amount of the ionic compound that elutes even under high temperature 160 ° C. heating conditions. Yes.
[0046]
In the red phosphorus flame retardant according to the present invention, the content of the phenol resin in the red phosphorus flame retardant is 0.5 to 20% by weight, preferably 1 to 10% by weight in terms of solid content. The reason why the content of the phenol resin is within the above range is that if less than 0.5% by weight, the resin coating effect cannot be obtained, so that the elution of oxo acid of phosphorus and the generation amount of phosphine gas tend to increase. Exceeding% by weight is not preferred because the particle size of red phosphorus increases due to aggregation, resin dispersibility tends to deteriorate, and the flame retardant effect tends to decrease.
[0047]
The content of zinc oxide is 50 to 1000 parts by weight, preferably 100 to 500 parts by weight, based on 100 parts by weight of phenol resin (solid content). The reason why the zinc oxide content is within the above range is that if it is less than 50 parts by weight, not only the ability to immobilize the phosphoric acid component to be eluted is insufficient, but also the strength of the coating resin is lowered and the coating is easily broken, and the semiconductor sealing When the epoxy resin composition for stopping is used, in the reliability test of the sealing material, the IC is corroded by the oxo acid of phosphorus eluted from red phosphorus, which is not preferable because the electrical reliability tends to be lowered. On the other hand, if it exceeds 1000 parts by weight, the P content of the red phosphorus flame retardant as a whole is reduced, and the flame retardant effect tends to decrease, such being undesirable.
[0048]
In the present invention, as the physical properties of zinc oxide that can be used, fine particles are preferable in terms of uniform dispersibility with the coating resin and reactivity of the eluted phosphorus with oxoacid, and the average particle size usually obtained by a laser method is preferred. The diameter is 2 μm or less, preferably 0.2 to 1 μm.
[0049]
Further, such red phosphorus flame retardant has an average particle size of 1 to 50 μm, particularly 3 to 30 μm, which is determined by a laser method. The reason for this is that those having an average particle size of less than 1 μm are not practical because it is difficult to technically coat the coating, and defects are likely to occur in the coating. On the other hand, if it exceeds 50 μm, the resin dispersibility becomes poor. It is not preferable because there is a tendency that a preferable flame retardant effect is not obtained.
[0050]
In addition, when the red phosphorus flame retardant is used as a flame retardant for an epoxy resin for semiconductor encapsulation, the average particle size within a suitable range according to the form of the IC package using the average particle size and the maximum particle size. It is preferable to select. More specifically, a suitable range of particle sizes exists depending on the form of the IC package in which the red phosphorus flame retardant is used. For example, when used in a liquid sealing material such as CSP (Chip size package) or BGA (Ball grid Array, ball grid array) or a thin package called transfer BGA, the gap between the substrate and the IC chip ( It is not preferable that particles larger than (Gap) are present. In this case, it is preferable that the average particle size obtained by the laser method is 1 to 10 μm and the maximum particle size is 20 μm or less. On the other hand, when used in a relatively thick IC package called DIP (Dual inline package) or ZIP (Zig-Zag inline package), the average grain required by the laser method The diameter is preferably 10 to 50 μm and the maximum particle diameter is preferably 150 μm or less. When used in a thin IC package called TSOP (Thin small outline package), TQFP (Thin quadflat package, Thin Clid Flat Package), it is preferable to use a medium grain size characteristic. The average particle size determined by the laser method is preferably 5 to 20 μm, and the maximum particle size is preferably 45 μm or less.
[0051]
In particular, the red phosphorus flame retardant having the characteristic of having a zinc hydroxide coating maintaining the crystal structure shown in FIG. 1 and having a surface coated with a phenol resin containing zinc oxide is used in the present invention. It can be manufactured by the following manufacturing method.
[0052]
That is, the method for producing a red phosphorus flame retardant includes the following steps (a1) to (a5).
(A1) A step of washing the red phosphorus particles with at least an acid
(A2-1) To the slurry in which the washed red phosphorus particles are dispersed in water, a soluble zinc compound and an alkaline agent are added to adjust the pH of the slurry to 6.5 or more, and then reacted to react with the surface of the red phosphorus particles Or (a2-2) adding a soluble zinc compound and an alkali agent to a slurry in which the washed red phosphorus particles are dispersed in water to make the pH of the slurry 6.5 or more. A step of coating the surface of the red phosphorus particles with zinc hydroxide while maintaining at a low temperature.
(A3) A step of washing the red phosphorus particles coated with zinc hydroxide until the electrical conductivity becomes 1000 μS / cm or less when 10% slurry is made with pure water.
(A4) An initial condensate of zinc oxide and a phenol resin is added to a slurry in which the red phosphorus particles coated with the washed zinc hydroxide are dispersed in water, and a polymerization reaction is performed at a pH of 6.5 or more to perform hydroxylation. A process of obtaining double-coated red phosphorus by coating the surface of red phosphorus particles coated with zinc with a phenol resin.
(A5) A step of obtaining a red phosphorus flame retardant by washing with pure water until the slurry obtained by dispersing 10 wt% of the double-coated red phosphorus in water at 20 ° C. has an electric conductivity of 30 μs / cm or less.
[0053]
In the step (a1), washing is performed with at least one selected from acids and alkalis. That is, after washing with at least an acid, the red phosphorus particles are dispersed in water to obtain a red phosphorus particle slurry. The cleaning process of the red phosphorus particles is performed by adjusting the pH of the slurry to 2 or less, preferably 1.5 or less with an acid such as nitric acid. Eliminates yellow phosphorus, which is unstable, ignitable, and one factor in the elution of phosphate ions. Moreover, before performing the washing treatment with this acid, an alkali such as sodium hydroxide is added to the red phosphorus particle slurry, the pH of the slurry is 9 or more, preferably 10 or more, and most of the yellow phosphorus content is removed in advance. Next, the above-described acid treatment may be performed to remove a metal component such as iron, nickel, copper, or yellow phosphorus. The alkali treatment is preferably performed in the presence of an oxidizing agent such as hydrogen peroxide while oxidizing the phosphine gas.
[0054]
Such red phosphorus particles washed with acid are preferably washed with pure water until the pH of the red phosphorus particle slurry is 2 or higher, preferably 2.5 or higher. The red phosphorus particles can reduce the elution of the phosphoric acid component compared to the untreated particles.
[0055]
In addition, it is preferable to use red phosphorus particles prepared in advance with a desired average particle size, maximum particle size, etc., and it is technically difficult to coat particles with a particle size of less than 1 μm. It is preferable to use those in which the proportion of particles is 10% by weight or less.
[0056]
In the step (a2-1) or (a2-2), the surface of the red phosphorus particles is added with zinc hydroxide by adding a soluble zinc compound and an alkali agent to the slurry in which the red phosphorus particles after the step (a1) are dispersed in water. Is a coating process. In the step (a2-1) or (a2-2), it is an important requirement that zinc hydroxide is deposited on the red phosphorus particles at a pH of 6.5 or more and then ripened.
[0057]
Specifically, 5 to 30 parts by weight, preferably 10 to 20 parts by weight of the red phosphorus particles after step (a1) are dispersed in 100 parts by weight of water to prepare a red phosphorus slurry, and then the red phosphorus slurry is mixed with sulfuric acid. Add 0.05 to 3 parts by weight, preferably 0.2 to 2 parts by weight of a soluble zinc compound such as zinc, zinc nitrate and zinc acetate, and add ammonia gas, aqueous ammonia, caustic soda, caustic potash, NaHCO 3_Three , Na₂ CO_Three , K₂ CO_Three , KHCO_Three , Ca (OH)₂ At least one alkali agent selected from an inorganic alkali agent such as ethanolamine or an organic alkali agent such as ethanolamine, and the pH of the slurry is adjusted to 6.5 or more, preferably 7.5 to 8.5. Then, reaction and aging are performed at a temperature of 40 to 95 ° C., preferably 75 to 90 ° C., to deposit fine zinc hydroxide having a crystal structure on the surface of the red phosphorus particles.
[0058]
In this step (a2-1) or (a2-2), the surface of red phosphorus particles is coated with zinc hydroxide. In order to form a coating of zinc hydroxide that maintains the crystal structure, an alkali is added to the soluble zinc compound. PH control after addition of the agent is particularly important.
[0059]
In the step (a2-1), the reaction is performed by adding an alkaline agent to the reaction system in which the soluble zinc compound is dissolved so that the pH becomes 6.5 to 9, but as the reaction proceeds, for example, soluble zinc is used as a raw material. When zinc sulfate is used as the compound and ammonia is used as the alkaline agent, acid components such as sulfuric acid are by-produced. For this reason, the pH in the reaction system is shifted to the acidic side of pH 6 or less from the beginning of the reaction. If the pH of this reaction system is less than 6.5, the solubility of zinc hydroxide tends to increase, but a coating of zinc hydroxide is formed.
[0060]
On the other hand, in the step (a2-2), in order to always maintain the pH at 6.5 or higher during the reaction even after adding the alkali agent of the reaction raw material, the acid component is appropriately adjusted with the above-mentioned alkali agent while adjusting the pH appropriately. It is characterized by precipitating zinc hydroxide while preventing by-product formation and subsequent aging.
[0061]
Next, after allowing to cool, in step (a3), zinc hydroxide is coated until the electrical conductivity is 10 μs / cm or less, preferably 500 μs / cm or less when the treated red phosphorus is made into a 10% slurry. Filter and wash the red phosphorus. By performing the step (a3), the cleaning operation in the subsequent step (a5) can be easily performed without damaging the coating of the red phosphorus particles, and the coating is performed in the next step (a4). As a result, it is possible to suppress impurities from being incorporated into the coating component during use.
[0062]
In the step (a3), the method for washing the red phosphorus coated with zinc hydroxide is not particularly limited, but it is particularly preferably performed by means such as repulping.
[0063]
In the step (a4), an initial condensate of zinc oxide and a phenol resin is added to a slurry in which the red phosphorus coated with zinc hydroxide after the step (a3) is dispersed in water, and polymerized under the homopolymerization conditions of the phenol resin. In this step, the surface of red phosphorus particles coated with zinc hydroxide is coated with a phenol resin containing zinc oxide to obtain double-coated red phosphorus. In this step (a4), it is an important requirement to perform the polymerization reaction and subsequent aging at pH 6.5 or higher.
[0064]
Specifically, 5 to 30 parts by weight, preferably 10 to 20 parts by weight of red phosphorus coated with zinc hydroxide after step (a3) is dispersed in 100 parts by weight of water to prepare a red phosphorus slurry, The red phosphorus slurry is added with an alkali such as ammonia or sodium hydroxide or an acid such as hydrochloric acid, nitric acid or sulfuric acid to adjust the pH to 7 or more, and then 0.25 to 20 parts by weight of the zinc oxide powder. , Preferably 0.5 to 10 parts by weight and phenol resin (initial condensate: as solid content) 0.25 to 3 parts by weight, preferably 0.5 to 2 parts by weight, and at 60 to 90 ° C. The polymerization reaction is carried out with stirring for 1 to 3 hours.
[0065]
In the step (a4), as described above, it is important to always maintain the pH of the reaction system at 6.5 or higher. Usually, even if the pH is adjusted to 6.5 or higher before the start of the reaction, the reaction system is aged or aged. The pH gradually shifts to the acidic side due to the phosphoric acid component eluted from the red phosphorus. Therefore, as described above, when the pH is less than 6.5, zinc hydroxide coated with red phosphorus particles dissolves. Therefore, an alkali agent is appropriately added to the reaction system until this step is completed, and the pH is 6.5. PH control is performed so that it becomes the above. The polymerization reaction of the phenol resin is extremely slow when the pH exceeds 8, so that the pH is preferably adjusted in the range of 6.5 to 7.5 during the polymerization reaction.
[0066]
In this step (a4), in order to uniformly disperse fine zinc oxide in the red phosphorus slurry, addition of a desired dispersant such as alkali hexametaphosphate or a surfactant, a colloid mill, a homogenizer, Dispersion processing such as strong shearing dispersion processing such as ultrasonic waves may be performed.
[0067]
After completion of the reaction, in the step (a5), pure water is used until the electric conductivity of the slurry in which the double-coated red phosphorus is dispersed by 10% by weight in 20 ° C. water is 30 μs / cm or less, preferably 20 μs / cm or less. Wash, dry, and adjust the particle size as desired to obtain a product.
[0068]
In the step (a5), the method for washing the double-coated red phosphorus is not particularly limited, but it is particularly preferably performed by means such as repulping.
[0069]
And it is preferable to set content of the said red phosphorus flame retardant (D component) in the range of 0.1 to 2 weight% in the whole resin composition, Most preferably, it is 0.1 to 1.0 weight %. That is, if it is less than 0.1% by weight, the flame retardancy is insufficient, and if it exceeds 2% by weight, it causes a decrease in moisture resistance due to an increase in impurities such as oxo acid of phosphorus, and it is difficult to add in a large amount. This is because there is a tendency to show no flammability.
[0070]
And in the epoxy resin composition for semiconductor sealing of this invention, it can use together with said flame retardant other than a red phosphorus flame retardant with the said AD component and depending on the case.
[0071]
Examples of other flame retardants that can be used in combination include hydrated metal oxides, nitrogen-containing flame retardants, and phosphorus flame retardants.
[0072]
As a hydrated metal oxide, M has a combustion suppressing action by an endothermic reaction._m O_n XH₂ A compound represented by O (M is a metal, m, n is an integer of 1 or more determined by the valence of the metal, and x is a contained crystal water) or a double salt containing the compound, specifically, water Aluminum oxide, magnesium hydroxide, basic magnesium carbonate, calcium hydroxide, barium hydroxide, zirconium hydroxide, dosonite, zinc stannate, zinc borate, aluminum borate, basic zinc carbonate, borax, zinc molybdate, Zinc phosphate, magnesium phosphate, hydrotalcite, hydrocalumite, kaolin, talc, sericite, pyrophyllite, bentonite, kaolinite, calcium sulfate, zinc sulfate, etc. or polyhedron described in JP 2000-195993 A Examples of the shape are composite metal hydroxides.
[0073]
Nitrogen-containing flame retardants include melamine, melamine cyanurate, methylolated melamine, (iso) cyanuric acid, melam, melem, melon, succinoguanamine, melamine sulfate, acetoguanamine sulfate, melam sulfate, guanylmelamine sulfate, melamine resin, BT Resins, cyanuric acid, isocyanuric acid, isocyanuric acid derivatives, melamine derivatives such as melamine isocyanurate, benzoguanamine, acetoguanamine, and guanidine compounds.
[0074]
Examples of phosphorus flame retardants include triethyl phosphate, tricresyl phosphate, triphenyl phosphate, cresyl phenyl phosphate, octyl diphenyl phosphate, diethylene phosphate ethyl ester, dihydroxypropylene phosphate butyl ester, ethylene phosphate diester. Sodium ester, methylphosphonic acid, dimethyl methylphosphonate, diethyl methylphosphonate, ethylphosphonic acid, propylphosphonic acid, butylphosphonic acid, 2-methyl-propylphosphonic acid, t-butylphosphonic acid, 2,3-dimethylbutylphosphonic acid, octyl Phosphonic acid, phenylphosphonic acid, dioctylphenylphosphonate, dimethylphosphinic acid, methylethylphosphinic acid, methylpropylphosphinic acid, diethylphosphinic acid, dioctylphosphinic acid, phenyl Sphinic acid, diethylphenylphosphinic acid, diphenylphosphinic acid, bis (4-methoxyphenyl) phosphinic acid, ammonium phosphate, ammonium polyphosphate, melamine phosphate, guanylurea phosphate, melamine polyphosphate, guanidine phosphate, ethylenediamine phosphate Examples include salts, phosphazenes, and melamine methylphosphonate.
[0075]
One or more of the other flame retardants described above are used, and among these, a hydrated metal oxide is preferred. The amount of other flame retardant added is 0.1 to 5% by weight, preferably 0.5 to 2% by weight in the epoxy resin composition.
[0076]
The epoxy resin composition for semiconductor encapsulation according to the present invention includes, in addition to the above-described components A to D, other metal oxides that react with a phosphoric acid component and fix as an insoluble or hardly soluble phosphate as desired. Further, a metal hydroxide, a metal carbonate, a metal phosphate or an inorganic ion exchanger can be used in combination.
[0077]
Examples of other metal oxides, metal hydroxides, metal carbonates, or metal phosphates include oxides, hydroxides, and carbonates selected from Zn, Mg, Ti, Ca, Al, Co, Zr, and Sn. 1 type or 2 types or more of a salt or a phosphate are mentioned. Specifically, zinc oxide, zinc hydroxide, ortho orthosilicate, magnesium oxide, magnesium hydroxide, titanium oxide, calcium oxide, calcium hydroxide, calcium carbonate, calcium phosphate, tricalcium phosphate, hydroxyapatite, calcium silicate, aluminum oxide , Aluminum hydroxide, cobalt oxide, cobalt hydroxide, zirconium oxide, zirconium hydroxide, tin oxide, tin hydroxide, and these may be used alone or in combination. These may be hydrated or anhydrous, but in the case of hydrated substances, when kneading and molding with an epoxy resin, moisture is generated depending on the molding temperature, and this moisture reacts with red phosphorus to produce phosphine. Anhydrides are preferred because they tend to cause problems such as occurrence.
[0078]
Inorganic ion exchangers include hydrocalumite inorganic anion exchangers, hydrotalcite inorganic anion exchangers, BiO_X (OH)_Y (NO_Three )_Z (X = 0.9 to 1.1, Y = 0.6 to 0.8, Z = 0.2 to 0.4), Mg_4.3 Al₂(OH)_12.6CO_Three ・ 3.5H₂ O, Sb₂ O_Five ・ 2H₂ O, SbSi_vBi_w O_x(OH)_y (NO3)_z ・ NH₂ O (v = 0.1-0.3, w = 1.5-1.9, x = 4.1-4.5, y = 1.2-1.6, z = 0.2-0. 3, n = 1-2) inorganic anion exchangers and the like.
[0079]
The compounding ratio of these metal oxide, metal hydroxide, metal carbonate, metal phosphate or inorganic ion exchanger is 1 to 20 parts by weight, preferably 5 with respect to 100 parts by weight of the red phosphorus flame retardant. It is preferable to set it as -20 weight part.
[0080]
In the epoxy resin composition for semiconductor encapsulation of the present invention, in addition to the above components (A) to (D), a curing accelerator, a pigment, a release agent, a surface treatment agent, a flexibility imparting agent, and the like may be added as necessary. Can be added as appropriate.
[0081]
The curing accelerator is not particularly limited as long as it accelerates the reaction between an epoxy group and a hydroxyl group, and examples thereof include diazabicyclo such as 1,8-diazabicyclo (5,4,0) undecene-7. Examples include alkene compounds, tertiary amines such as triethylenediamine, imidazoles such as 2-methylimidazole, and phosphorus compounds such as triphenylphosphine. These compounds may be used alone or in combination of two or more.
[0082]
Examples of the pigment include carbon black and titanium oxide. Examples of the mold release agent include carnauba wax, polyethylene wax, paraffin, fatty acid ester, and fatty acid salt.
[0083]
Furthermore, examples of the surface treatment agent include coupling agents such as silane coupling agents. Examples of the flexibility-imparting agent include various silicone compounds and butadiene-acrylonitrile rubber.
[0084]
The epoxy resin composition for semiconductor encapsulation according to the present invention can be produced, for example, as follows. That is, an epoxy resin (component A), a phenol resin (component B), an inorganic filler (component C), a red phosphorus flame retardant (component D), and other additives as required are blended in a predetermined ratio. The red phosphorus flame retardant may be blended in advance as a master batch in which an epoxy resin, a phenol resin, or the like is further mixed with a curing agent, a curing accelerator, a colorant, a release agent, and a surface treatment agent as desired.
[0085]
Next, the mixture is melt-kneaded in a heated state using a kneader such as a mixing roll machine, and cooled to room temperature. And the target epoxy resin composition for semiconductor sealing can be manufactured according to a series of processes of grind | pulverizing by a well-known means, and tableting as needed.
[0086]
Alternatively, the semiconductor-encapsulating epoxy resin composition is introduced into a kneader and kneaded in a molten state, and then continuously molded into a substantially cylindrical granule, thereby forming a granular semiconductor. An epoxy resin composition for sealing can be produced.
[0087]
Further, the mixture of the epoxy resin composition for semiconductor encapsulation is received on a pallet, and after cooling, the sheet is formed by a method such as press rolling, roll rolling, or applying a mixture of solvent to form a sheet. An epoxy resin composition for semiconductor encapsulation can be produced.
[0088]
The method of sealing a semiconductor element using the epoxy resin composition for semiconductor sealing (powder, tablet, granule, etc.) obtained in this way is not particularly limited, such as ordinary transfer molding It can be performed by a known molding method.
[0089]
Further, by using the above sheet-like epoxy resin composition for encapsulating a semiconductor, for example, a semiconductor device by flip chip mounting can be manufactured as follows. That is, the sheet-shaped semiconductor sealing epoxy resin composition is disposed on the electrode surface side of a semiconductor element provided with bonding bumps or on the bump bonding portion side of a circuit board, and the semiconductor element and circuit board are disposed. A semiconductor device can be manufactured by flip-chip mounting by performing bump bonding and performing adhesive sealing by resin sealing.
[0090]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.
[0091]
(Preparation of red phosphorus flame retardant)
・ Red phosphorus flame retardant sample 1
<(A1) Process>
Agglomerated red phosphorus was pulverized and classified to obtain red phosphorus having an average particle size of 20 μm, a maximum particle size of 45 μm, and a content of 2% by weight of particles having a particle size of less than 1 μm. 525 g of water was added to 210 g of this red phosphorus to form a red phosphorus slurry, and 0.7 ml of an aqueous hydrogen peroxide solution was added. Subsequently, the pH was adjusted to 10 with an aqueous sodium hydroxide solution and held at 80 ° C. for 6 hours. Nitric acid was then added to adjust the pH to 1, followed by treatment at 80 ° C. for 4 hours, followed by filtration and washing with water until the pH of the slurry was 2.5.
[0092]
<(A2-2) Step>
100 g of the washed red phosphorus powder was suspended in 800 ml of pure water to prepare a red phosphorus slurry. Next, 30 ml of an aqueous zinc sulfate solution containing 0.01 mol of zinc sulfate was added, and then an aqueous ammonia solution was added until the pH reached 8 while stirring at a temperature of 80 ° C. After completion of the addition, an aqueous ammonia solution was used so that the pH was in the range of 7.0 to 7.5, and the stirring was continued at 80 ° C. for 1 hour while performing pH control to perform the zinc hydroxide deposition treatment. It was. The coating amount of zinc hydroxide at this time was 0.9% by weight as a result of ICP emission analysis. The theoretical amount determined from the stoichiometric ratio is 0.99% by weight. Further, FIG. 1 shows an electron micrograph of the obtained red phosphorus coated with zinc hydroxide, and Table 1 shows the results of an elution test at 80 ° C. for the red phosphorus coated with zinc hydroxide.
[0093]
<(A3) Process>
Next, the coated red phosphorus is separated and recovered from the reaction solution by filtration by a conventional method, and after adding water again to form a slurry, the pulp is repulped by a conventional method to obtain a 10% slurry of the coated red phosphorus. Filtration and repulping were repeated until the conductivity reached 300 μs / cm or less.
[0094]
<(A4) Process>
After washing, 20 g of red phosphorus was dispersed in 180 g of pure water, and ammonia water was added thereto while stirring to adjust the pH to 10.0. Next, 2 g of zinc oxide having an average particle size of 0.3 μm (manufactured by Toho Zinc Co., Ltd .; trade name: silver candy) and 3.8 g of phenol resin (Dainippon Ink Co., Ltd., initial condensate, phenolite TD2388; solid content 26%) After the addition and stirring was completed for 10 minutes, hydrochloric acid was added dropwise to adjust the pH to 7 to 7.5.
Next, ammonia water was added dropwise at 90 ° C. for 1 hour so as not to lower the pH, and the reaction was carried out at 90 ° C. for 1 hour while maintaining the pH of the reaction system at 6.5-7.
[0095]
<(A5) Process>
Next, after cooling, it was filtered and washed with pure water until the electric conductivity of 10% slurry at 20 ° C. became 30 μs / cm or less. The filter cake was dried under reduced pressure while being lightly dispersed, then cured at 140 ° C. for 2 hours, allowed to cool, and then passed through a 100 mesh sieve to prepare a red phosphorus flame retardant sample 1. Table 2 shows the main physical properties of the red phosphorus flame retardant sample 1.
[0096]
・ Red phosphorus flame retardant sample 2
<(A1) Process>
Agglomerated red phosphorus was pulverized and classified to obtain red phosphorus having an average particle size of 20 μm, a maximum particle size of 45 μm, and a content of 2% by weight of particles having a particle size of less than 1 μm. 525 g of water was added to 210 g of this red phosphorus to form a red phosphorus slurry, and 0.7 ml of an aqueous hydrogen peroxide solution was added. Subsequently, the pH was adjusted to 10 with an aqueous sodium hydroxide solution and held at 80 ° C. for 6 hours. Nitric acid was then added to adjust the pH to 1, followed by treatment at 80 ° C. for 4 hours, followed by filtration and washing with water until the pH of the slurry was 2.5.
[0097]
<(A2-1) Process>
100 g of the washed red phosphorus powder was suspended in 800 ml of pure water to prepare a red phosphorus slurry. Next, 30 ml of an aqueous zinc sulfate solution containing 0.01 mol of zinc sulfate was added, and then an aqueous ammonia solution was added until the pH reached 8 while stirring at a temperature of 80 ° C. After completion of the addition, the pH was not controlled, and the stirring was continued at 80 ° C. for 1 hour to deposit zinc hydroxide. The coating amount of zinc hydroxide at this time was 0.3% by weight as a result of ICP emission analysis. The theoretical amount obtained from the stoichiometric ratio was 0.99% by weight, and the pH of the reaction system after the deposition treatment was 5.
[0098]
Further, FIG. 2 shows an electron micrograph of the obtained red phosphorus coated with zinc hydroxide, and Table 1 shows the results of an elution test at 80 ° C. for the red phosphorus coated with zinc hydroxide.
[0099]
<(A3) Process>
Next, the coated red phosphorus is separated and recovered from the reaction solution by filtration by a conventional method, and after adding water again to form a slurry, the pulp is repulped by a conventional method to obtain a 10% slurry of the coated red phosphorus. Filtration and repulping were repeated until the conductivity reached 300 μs / cm or less.
[0100]
<(A4) Process>
After washing, 20 g of red phosphorus was dispersed in 180 g of pure water, and ammonia water was added thereto while stirring to adjust the pH to 10.0. Next, 2 g of zinc oxide having an average particle size of 0.3 μm (manufactured by Toho Zinc Co., Ltd .; trade name: silver candy) and 3.8 g of phenol resin (Dainippon Ink Co., Ltd., initial condensate, phenolite TD2388; solid content 26%) After the addition and stirring was completed for 10 minutes, hydrochloric acid was added dropwise to adjust the pH to 7.0 to 7.5.
Next, the reaction was performed at 90 ° C. for 1 hour without performing pH control. The pH in the reaction system after completion of the reaction was 5.
[0101]
<(A5) Process>
Next, after cooling, it was filtered and washed with pure water until the electric conductivity of 10% slurry at 20 ° C. became 30 μs / cm or less. The filter cake was dried under reduced pressure while being lightly dispersed, then cured at 140 ° C. for 2 hours, allowed to cool, and then passed through a 100 mesh sieve to prepare a red phosphorus flame retardant sample 2. Table 2 shows the main physical properties of the red phosphorus flame retardant sample 2.
[0102]
<Elution test of red phosphorus coated with zinc hydroxide at 80 ° C>
For the red phosphorus coated with zinc hydroxide after the steps (a2-1) and (a2-2) of the red phosphorus flame retardant samples 1 and 2, the concentration of eluted ions was measured in the following manner.
Collect 8.0 g of red phosphorus coated with zinc hydroxide in a 100 ml polypropylene bottle, add 80 ml of distilled water and seal. Extraction from the dryer after heating and extraction at 80 ° C. for 20 hours in a blast constant temperature dryer, cooling to room temperature within 10 minutes, filtering the supernatant, and elution PO in the filtrate_Four Ion concentration, PHO_Three Ion concentration, PH₂ O₂ The ion concentration was measured with an ion chromatograph. The results are shown in Table 1. In the table, N.I. D. Elution PO_FourThe ion concentration is 0.09 ppm or less.
[0103]
[Table 1]

[0104]
1 and 2 and Table 1, the coating of zinc hydroxide after the (a2-2) step of the red phosphorus flame retardant sample 1 and the after the (a2-1) step of the red phosphorus flame retardant sample 2 The coating characteristics of zinc hydroxide are clearly different from the coating of zinc hydroxide, and the coating of zinc hydroxide of red phosphorus flame retardant sample 1 is a dense coating that maintains the crystal structure compared to that of sample 2 It can be seen that the size of the particles is large.
[0105]
・ Red phosphorus flame retardant sample 3
In the step (a5) of the red phosphorus flame retardant sample 1, a red phosphorus flame retardant sample 3 was obtained under the same conditions as the red phosphorus flame retardant sample 1 except that cleaning was stopped at 100 μs / cm. The main physical properties of this red phosphorus flame retardant sample 3 are shown in Table 2.
[0106]
・ Red phosphorus flame retardant sample 4
In the step (a4) of the red phosphorus flame retardant sample 1, a red phosphorus flame retardant sample 4 was obtained under the same conditions as the red phosphorus flame retardant sample 1 except that zinc oxide was not added. Table 2 shows the main physical properties of the red phosphorus flame retardant sample 4.
[0107]
・ Red phosphorus flame retardant sample 5
Agglomerated red phosphorus was pulverized and classified to obtain red phosphorus having an average particle size of 20 μm, a maximum particle size of 45 μm, and a content of 2% by weight of particles having a particle size of less than 1 μm. 525 g of water was added to 210 g of this red phosphorus to form a red phosphorus slurry, and 0.7 ml of an aqueous hydrogen peroxide solution was added. Subsequently, the pH was adjusted to 10 with an aqueous sodium hydroxide solution and held at 80 ° C. for 6 hours. Nitric acid was then added to adjust the pH to 1, followed by treatment at 80 ° C. for 4 hours, followed by filtration and washing with water until the pH of the slurry was 2.5.
[0108]
100 g of the washed red phosphorus powder was suspended in 1000 ml of pure water to prepare a red phosphorus slurry. Then aluminum hydroxide (Al (OH)_Three ) An amount of aluminum sulfate corresponding to 1 g in terms of conversion was added. After completion of the addition, the mixture was stirred for 30 minutes, sodium hydroxide was added to adjust the pH of the slurry to 8.0, and then the solution temperature was raised to 85 ° C. and aging was performed at 85 ° C. for 2 hours.
[0109]
Next, the coated red phosphorus is separated and recovered from the reaction solution by filtration by a conventional method, and after adding water again to form a slurry, the pulp is repulped by a conventional method to obtain a 10% slurry of the coated red phosphorus. Filtration and repulping were repeated until the conductivity reached 300 μs / cm or less.
[0110]
Disperse the filter cake in water and stir with phenol resin (phenol resin (manufactured by Dainippon Ink and Co., Ltd., initial condensate, phenolite TD2388; solid content 26%) equivalent to 5% of red phosphorus in terms of solid matter. Then, hydrochloric acid was added to adjust the pH of the slurry to 2. The slurry was heated and held at 90 ° C. for 1 hour to complete the phenol resin curing reaction.
[0111]
After allowing to cool, the slurry was sufficiently filtered and washed until the electrical conductivity of the 10% slurry was 30 μs / cm or less. The filter cake was dried under reduced pressure while being lightly dispersed, then cured at 140 ° C. for 2 hours, allowed to cool, and then passed through a 100 mesh sieve to prepare a red phosphorus flame retardant sample 5. Table 2 shows the main physical properties of the red phosphorus flame retardant sample 5.
[0112]
<Measurement of electrical conductivity>
The electrical conductivity was measured when the red phosphorus flame retardant prepared above was dispersed in pure water to make a 10 wt% slurry. The results are shown in Table 2. The electrical conductivity was measured with an electrical conductivity meter using a test solution for measuring eluted ions.
[0113]
<Measurement of particle size>
The average particle size of the red phosphorus flame retardant sample prepared above was measured by a laser method using a microtrack (X100 type) particle size distribution analyzer. The maximum particle size was measured with an analytical sieve. The results are shown in Table 2.
[0114]
<Evaluation of eluted ions and electrical conductivity of red phosphorus flame retardant samples>
The concentration of eluted ions was measured for red phosphorus flame retardant samples 1 to 5 in the following manner.
Collect 8.0 g of red phosphorus flame retardant sample in a 100 ml polypropylene bottle, add 80 ml of distilled water, and seal tightly. Extraction from the dryer after heating and extraction at 80 ° C. for 20 hours in a blast constant temperature dryer, cooling to room temperature within 10 minutes, filtering the supernatant, and elution PO in the filtrate_Four Ion concentration, PHO_Three Ion concentration, PH₂ O₂ The ion concentration was measured with an ion chromatograph. The results are shown in Table 3.
[0115]
In addition, the heating conditions were set at 160 ° C. for 20 hours, and the eluted PO in the filtrate was_Four Ion concentration, PHO_Three Ion concentration, PH₂ O₂ The ion concentration was measured with an ion chromatograph. The results are shown in Table 3.
[0116]
In addition, the electrical conductivity of the filtrate used in the measurement of the eluted ions was measured at 20 ° C. The results are shown in Table 3. The electrical conductivity was measured with an electrical conductivity meter using a test solution for measuring eluted ions.
[0117]
[Table 2]

[0118]
(Note) The value of the coating amount of zinc hydroxide is the value measured by ICP emission analysis after the steps (a2-1) and (a2-2).
[0119]
[Table 3]

[0120]
(Note) * 1 in Table 3 indicates the measurement conditions of 80 ° C. × 20 hrs, and * 2 indicates the measurement conditions of 160 ° C. × 20 hrs.
[0121]
<Preparation of epoxy resin for semiconductor encapsulation>
Below, the Example regarding the epoxy resin composition for semiconductor sealing containing the various red phosphorus flame retardants obtained above is described.
First, in order to obtain an epoxy resin composition for semiconductor encapsulation, the following were prepared in addition to the red phosphorus flame retardant prepared above.
[0122]
[Epoxy resin A]
Cresol novolac type epoxy resin (Nippon Kayaku Co., Ltd., trade name EOCN-1020, epoxy equivalent 198, softening point 75 ° C.)
[Epoxy resin B]
4,4'-bis (2,3-epoxypropoxy) -3,3 ', 5,5'-tetramethylbiphenyl (epoxy equivalent 194, softening point 108 ° C)
[Phenolic resin C]
Phenol novolac resin (trade name P-180, hydroxyl group equivalent 105, softening point 80 ° C., manufactured by Arakawa Chemical Co., Ltd.)
[Phenolic resin D]
Phenol aralkyl resin represented by the general formula (3) (hydroxyl equivalent: 175, softening point: 70 ° C.)
[Ion scavenger]
Hydrotalcite compounds: Mg_4.3 Al₂ (OH)_12.6CO_Three ・ 3.5H₂ O (average particle size 2 μm) (DHT-4A, manufactured by Kyowa Chemical Co., Ltd.)
[Carbon black]
[Release agent]
Oxidized polyethylene wax (PED-521, manufactured by Clariant)
[Curing accelerator]
Triphenylphosphine
[Inorganic filler]
Fused silica powder (spherical, average particle size 25 μm, specific surface area 1.4 m² / G)
[0123]
Examples 1-4 and Comparative Examples 1-3
Each component shown in Table 4 below is blended in the proportions shown in the same table, melt kneaded for 3 minutes in a mixing roll machine (temperature 100 ° C.), cooled and solidified, and then pulverized to obtain the desired powdered semiconductor encapsulating An epoxy resin composition was obtained.
[0124]
[Table 4]

[0125]
The following evaluation was performed about the epoxy resin composition for semiconductor sealing of each Example and comparative example obtained as mentioned above, and the result was described in Table 5.
[0126]
<Evaluation of fluidity> (flow tester viscosity, gel time)
2 g of the powdery epoxy resin composition obtained in each of the above Examples and Comparative Examples was weighed and formed into a tablet. This was put into a pot of Koka type flow tester and a 10 kg load was applied. The epoxy resin composition melted at a temperature of 175 ° C. determines the melt viscosity (flow tester viscosity) of each sample from the moving speed of the piston when extruded through a hole (diameter: 1.0 mm × 10 mm) of a die. It was.
[0127]
Also, 200 to 500 mg of a powdered epoxy resin composition sample obtained in each of the examples and comparative examples was placed on a hot plate at 175 ° C., and the sample was thinly stretched on the hot plate while stirring. The time from the time of melting to the time of curing was read and used as the gel time (gel time).
[0128]
<Impurity characteristics>
The epoxy resin composition obtained in each example and comparative example was molded into a tablet shape at 175 ° C. for 2 minutes, and further cured under post-curing conditions at 175 ° C. for 5 hours. Grind into a fine powder with a mill, pass through a mesh with a mesh size of 150 μm, collect 5 g, and put it in a container made of metal (SUS) on the outside and Teflon (registered trademark) on the inside with 50 ml of ion-exchanged water. And extraction at 160 ° C. for 20 hours.
[0129]
The amount of impurities (Na⁺ , Cl^- , HPO_Three ^2- , PO_Four ^3- ) Was measured by ion chromatography, and EC (electrical conductivity) of the extracted water was measured by an electric conductivity meter (Electrical Conductivity). In addition, the pH value was also measured with a pH meter.
[0130]
<Moisture resistance reliability>
Using the epoxy resin compositions obtained in each of the above examples and comparative examples, tablets were formed, and a test piece for flame retardancy test was molded under molding conditions of 175 ° C. × 6.867 MPa × 120 seconds. On the other hand, it was molded into a package (semiconductor device) of LQFP-114 (size: 20 mm × 20 mm × thickness 1.4 mm) with a TOWA automatic molding machine. Using the package thus obtained, a pressure cooker bias test (PCBT) was performed at 130 ° C., 85% R.D. H. , Under the condition of 30V bias. And the time when 50% of the packages used for the evaluation were in the defective mode was measured. As the failure mode, leakage failure and open failure were measured.
[0131]
<Flame retardance>
Flame retardancy was evaluated according to the method of UL-94V-0 standard using the test piece for flame retardancy test obtained in the moisture resistance reliability test. Pass means 94V-0 pass.
[0132]
[Table 5]

[0133]
As is apparent from the results in Table 5 above, the example products showed excellent flame retardancy, and the content of various ions as impurities was small, and both the flow tester viscosity and gel time were good in terms of fluidity. It can be seen that it is. In particular, it is clear that the moisture resistance reliability is remarkably improved as compared with the comparative product.
[0134]
【The invention's effect】
As described above, the epoxy resin composition for semiconductor encapsulation of the present invention uses a non-halogen, non-antimony type composite flame retardant having a specific coating layer on the surface of red phosphorus, and thus exhibits an excellent flame retardant effect. In addition, it has moisture resistance and water resistance.
[0135]
Therefore, flame retardancy and moisture resistance reliability are imparted to a semiconductor device in which a semiconductor element is encapsulated using an epoxy resin composition for encapsulating a semiconductor containing the red phosphorus flame retardant in an epoxy resin composition. There is an effect that it is possible.
[Brief description of the drawings]
FIG. 1 is an electron micrograph of a red phosphorus particle structure showing a state of a zinc hydroxide coating formed on the surface of a red phosphorus particle after step (a2-2) of a red phosphorus flame retardant sample 1 (magnification 2000 times). It is.
FIG. 2 is an electron micrograph of a red phosphorus particle structure showing the state of a zinc hydroxide coating formed on the surface of red phosphorus particles after step (a2-1) of red phosphorus flame retardant sample 2 (magnification 2000 times). It is.

Claims (5)

At least epoxy resin (component A), phenol resin (component B), filler (component C), and the surface of red phosphorus particles, the primary coating consists of zinc hydroxide coating, the secondary coating contains zinc oxide An epoxy resin composition containing a red phosphorus flame retardant (component D) having a P content of 65 to 97% by weight, on which a double coating layer composed of a phenol resin coating is formed, wherein the red phosphorus flame retardant Has the following properties (D1) to (D3): an epoxy resin composition for semiconductor encapsulation.
(D1) A primary coating of zinc hydroxide is formed on the surface of red phosphorus particles washed with at least one selected from acids and alkalis, and the coating amount of zinc hydroxide on the red phosphorus particles is 0.5. -10 wt%,
(D2) The electrical conductivity of a slurry in which 10% by weight of a red phosphorus flame retardant is dispersed in 20 ° C. water is 30 μs / cm or less,
(D3) When 80 ml of water is added to 8 g of the red phosphorus flame retardant and heated at 80 ° C. for 20 hours, the PO ₄ ion concentration eluted is 10 ppm or less, the PHO ₃ ion concentration is 200 ppm or less, and the PH ₂ O ₂ ion The concentration is 150 ppm or less, and the electric conductivity after standing at 80 ° C. for 20 hours is 100 μs / cm or less.   The epoxy resin composition for semiconductor encapsulation according to claim 1, wherein the primary coating on the surface of the red phosphorus particles comprises a coating of zinc hydroxide formed by reacting a soluble zinc compound and an alkaline agent at pH 6.5 or higher. The red phosphorus flame retardant (component D) has a PO ₄ ion concentration of 100 ppm or less and a PHO ₃ ion concentration that is eluted when 80 ml of water is added to 8 g of the red phosphorus flame retardant and heated at 160 ° C. for 20 hours. 3. The epoxy resin composition for encapsulating a semiconductor according to claim 1, wherein the epoxy resin composition has a pH of 250 ppm or less, a PH ₂ O ₂ ion concentration of 2000 ppm or less, and an electric conductivity of 2000 μs / cm or less after standing at 160 ° C. for 20 hours.   The epoxy resin composition for semiconductor encapsulation according to claim 1 or 3, wherein the red phosphorus flame retardant (D component) has an average particle size in the range of 1 to 50 µm.   A semiconductor device obtained by encapsulating a semiconductor element using the epoxy resin composition for encapsulating a semiconductor according to claim 1.

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