JP4560928B2 - Epoxy resin composition for interposer, prepreg, and copper-clad laminate using the same - Google Patents

Description

【０００６】
【発明の実施の形態】
本発明に用いる（Ａ）式（１）で示される構造のエポキシ樹脂（ただし、Ｇはグリシジル基を示す）は、低吸水、高いガラス転移温度や熱剛性を発現するための多官能エポキシ樹脂である。一般に高いガラス転移温度を発現する多官能エポキシ樹脂は吸水率が高いことが欠点であるが、本発明に使用するエポキシ樹脂は、ナフタレン環のパッキング性のよさにより自由体積が低減され、低吸水性と耐熱性が両立し、ＩＣパッケージのインターポーザとしての耐半田クラック性に優れた性能を発揮する。本発明においてエポキシ樹脂組成物中に占める（Ａ）成分の割合は１０〜５０重量％が好ましい。１０重量％未満では、（Ｂ）１分子中に３個以上のフェノール性水酸基を有するフェノール樹脂系硬化剤を合わせても結合剤成分が少なくなり、耐熱性特にＩＣパッケージのインターポーザとしての耐半田クラック性が低下するようになる。５０重量％を越えると、充填材の割合が低下し、熱膨張、吸水率が増加しＩＣパッケージのインターポーザとしての耐半田クラック性が低下するので好ましくない。ここで、インターポーザとしての耐半田クラック性とは、リジッドインターポーザを使用したＢＧＡやＣＳＰ等において行われるＪＥＤＥＣ実装ランク条件に準じた耐半田クラック試験において、インターポーザに起因するか、または間接的にインターポーザの特性が影響を与えて発生するクラック、または界面剥離に対する耐性を意味する。
なお、エポキシ樹脂として、（Ａ）成分以外のエポキシ樹脂、例えばビスフェノールＡ型のエポキシ樹脂をエポキシ樹脂全体の３０重量％以下配合してもよい。
【０００７】
次に成分（Ｂ）１分子中に３個以上のフェノール性水酸基を有するフェノール樹脂系硬化剤としては、フェノールノボラック、ビスフェノールＡノボラック、フェノールアラルキル樹脂等が例示されるが、フェノール性水酸基当量が比較的小さく、低官能のモノマーを容易に除去できるフェノールノボラックや高いガラス転移温度が得られるビスフェノールＡノボラックが好ましい。本発明では（Ｂ）成分は、エポキシ樹脂のエポキシ基のモル数と、（Ｂ）成分のフェノール性水酸基のモル数の比（当量比）が０．８以上１．２以下となるよう添加することが好ましい。この範囲外ではガラス転移温度の低下や吸水率の増加で特にＩＣパッケージのインターポーザとしての耐半田クラック性の低下やＩＣの耐湿信頼性の低下が生じることがある。
【０００８】
本発明に用いる成分（Ｃ）難燃剤は、耐燃性に寄与するものであれば何ら限定するものではないが、ハロゲンが問題にならない製品に適用する場合は、臭素化フェノールノボラックエポキシ樹脂、臭素化ビスフェノールＡ型エポキシ樹脂などの臭素化エポキシ樹脂がＩＣパッケージのインターポーザとしての耐半田クラック性やＩＣの耐湿信頼性が優れ好適である。臭素化エポキシ樹脂においては難燃化するために必要な臭素添加量は樹脂の配合割合により変動するが、エポキシ樹脂組成物中に占める臭素量の割合で、通常０．５重量％以上２０重量％以下である。ハロゲンフリーであることが求められるものには、リン酸エステル、赤リン、９，１０−ジヒドロ−９−オキサ−１０−ホスファフェナントレン−１０−オキシド（以下ＨＣＡと略す）、トリアリールホスフィンオキサイドなどのリン系難燃剤、ホスファゼンなどが例示されるが、ＩＣパッケージのインターポーザとしての耐半田クラック性やＩＣの耐湿信頼性を維持するには、ＨＣＡ、またはＨＣＡとトリアリールホスフィンオキサイドの併用が好適である。
【０００９】
ＨＣＡは、リンに結合している水素がエポキシ基と反応する反応性リン化合物であり、加水分解して吸水性を高めたり、密着性を低下させたりすることがなく極めて優れたリン系難燃剤である。しかしこの化合物は一方で樹脂の硬化性を遅らせる作用があるため、プレス成形時間を短縮した場合に硬化性に問題が出ることがある。その場合にはＨＣＡとトリアリールホスフィンオキサイドとの併用が好適である。トリアリールホスフィンオキサイドの例としてはトリフェニルホスフィンオキサイド、トリスヒドロキシフェニルホスフィンオキサイド、ビス（ヒドロキシフェニル）フェニルホスフィンオキサイド、トリスアミノフェニルホスフィンオキサイド、ビス（アミノフェニル）フェニルホスフィンオキサイドが例示できるが、トリアリールホスフィンオキサイドのアリール基が無置換であっても、何らかの置換基を有していてもよい。
【００１０】
トリアリールホスフィンオキサイドは、マトリックス樹脂と反応しないかまたは反応性が小さいと考えられるが、耐加水分解性に優れており、加えてＨＣＡのように硬化性に影響を与えない。したがってＨＣＡとトリアリールホスフィンオキサイドを併用すると難燃性と硬化性を維持しながら吸水性や密着性も悪化させず良好な半田耐熱性を実現できる。ＨＣＡとトリアリールホスフィンオキサイドの添加重量比率は１：４〜４：１が好ましい。この範囲をはずれると併用効果が薄れる場合がある。ＨＣＡ、またはＨＣＡとトリアリールホスフィンオキサイドの合計添加量は、エポキシ樹脂組成物全体に対して、０．５〜１０重量％が好ましい。０．５重量％未満では難燃効果が低下するおそれがあり、１０重量％を越えるとガラス転移温度の低下や吸水性を高めたり、密着性を低下させ耐半田クラック性の低下が起こる場合がある。
【００１１】
本発明に用いる成分（Ｄ）球状溶融シリカは、吸水率を低減し、線膨張係数を低下させ、ＩＣパッケージの構成材料であるインターポーザの耐半田クラック性を向上させる重要な成分である。破砕状溶融シリカでは、銅張積層板を構成するガラス基材と銅箔の比較的狭い間隙に充填材が挟まると、角張った形状であるため、プレス成形の際に基材や銅箔に大きなストレスを与えてしまい、それらを損傷し、その損傷部分を起点に半田クラックが発生したり、外観が悪くなることがあり、加えて多量に充填材を使用する場合に流動性が低下する。
【００１２】
球状溶融シリカの場合、粒径、粒度分布、比表面積にかかわらず、破砕状溶融シリカに比べて基材や銅箔へのストレスは小さいが、中でも、平均粒径５μｍ以下（本発明において、粒径はすべてレーザー回折式粒度分布測定の値である）の球状溶融シリカの場合、基材や銅箔にストレスがより小さく好ましい。 平均粒径が５μｍを越えると基材や銅箔へのストレスが次第に大きくなって耐半田クラック性が悪化する場合がある。平均粒径５μｍ以下の球状溶融シリカ中でも最大粒径２４μｍ以下で、平均粒径２μｍ以上５μｍ以下、かつＢＥＴ法による比表面積が５ｍ² ／ｇ以下の球状溶融シリカ、あるいはカップリング剤で予め表面処理された平均粒径２μｍ以下の球状溶融シリカは、基材や銅箔へのストレスが極めて小さいことに加え、凝集が少なく充填材が均一に分散するのでさらに好ましい。 最大粒径が２４μｍを超える粗粒が含まれると銅箔と基材の間で粗粒に起因する空間ができ、吸湿した場合に水が滞留して耐半田クラック性が悪化したり、銅張積層板の外観が悪化する場合がある。また平均粒径が２μｍより小さい場合や比表面積が５ｍ² ／ｇを超える場合、粒子の２次凝集により前述粗粒が含まれる場合と同様の問題が生じる場合がある。
【００１３】
成分（Ｄ）球状溶融シリカは、予めカップリング剤で表面処理したものを使用すれば、凝集が少なく充填材が均一に分散するので好ましい。用いられるカップリング剤は、シランカップリング剤、シロキサン結合の繰り返し単位を２個以上有し、かつアルコキシ基を有するシリコーンオイル型カップリング剤等のケイ素系カップリング剤やチタネート系カップリング剤等が挙げられるが、エポキシ樹脂と溶融球状シリカの表面の塗れ性向上の点で、ケイ素系カップリング剤が好ましい。具体的にはエポキシシランカップリング剤、アミノシランカップリング剤、ウレイドシランカップリング剤、メルカプトシランカップリング剤、ジシラザン、シロキサン結合の繰り返し単位を２個以上有し、かつアルコキシ基を有するシリコーンオイル型カップリング剤からなる群から少なくとも１種選ばれるものなどが挙げられる。特にエポキシシランカップリング剤、アミノシランカップリング剤と、シロキサン結合の繰り返し単位を２個以上有し、かつアルコキシ基を有するシリコーンオイル型カップリング剤を併用した場合、シリカ表面へカップリング剤が効率よく定着する。この場合のカップリング剤の割合は球状溶融シリカ１００重量部に対し０．１重量部以上１０部重量以下が一般的である。
【００１４】
予めカップリング剤で表面処理された球状溶融シリカは、平均粒径２μｍ以下のものが、凝集が少なく充填材が均一に分散することに加え、基材や銅箔へのストレスが極めて小さいのでさらに好ましい。また、同様の理由で、球状溶融シリカとして、最大粒径２４μｍ以下で、平均粒径２μｍ以上５μｍ以下、かつ比表面積が５ｍ² ／ｇ以下の球状溶融シリカと予めカップリング剤で表面処理された平均粒径２μｍ以下の球状溶融シリカとを併用することも好ましい態様の一つである。カップリング剤を用いる場合、シリカ表面のシラノールとカップリング剤の反応を促進するために、少量の水を添加したり、酸やアルカリを用いることは当業者では公知であり、本発明に含まれる。
【００１５】
成分（Ｄ）球状溶融シリカは、エポキシ樹脂組成物中５０重量％以上を占めると熱膨張、吸水率が小さくなるので好ましい。ただし、９０重量％を越えるとエポキシ樹脂組成物中の充填材の割合が大きすぎて含浸等の操作が困難となる。
【００１６】
本発明において前記のカップリング剤以外に、他の成分と共に原料配合などの際に成分（Ｅ）カップリング剤を使用することは、球状シリカを予め表面処理しているか否かにかかわらず球状溶融シリカの均一な分散、凝集防止に効果があり好ましい。使用するカップリング剤は、成分（Ｄ）球状溶融シリカの表面処理に用いるカップリング剤と同様のものが例示される。エポキシ樹脂組成物中に占めるカップリング剤（Ｅ）の割合は０．０５〜１０重量％が好ましい。０．０５重量％未満では充填材の表面全体にカップリング剤を分散させることができない可能性がある。また１０重量％を越えるとガラス転移温度が低下する場合がある。
【００１７】
本発明のエポキシ樹脂組成物は必要に応じて、上記成分以外の添加剤を特性を損なわない範囲で添加することができる。本発明のエポキシ樹脂組成物は溶剤を用いてワニスとして、または無溶剤にて繊維基材に塗布含浸し乾燥することによりプリプレグを得ることができる。基材としてはガラス織布、ガラス不織布、その他有機基材などを用いることができる。このプリプレグの１枚又は複数枚を銅箔とともに加熱成形して銅張積層板が得られる。これらのプリプレグ及び銅張積層板も本発明に含まれるものである。
【００１８】
【実施例】
実施例１
式（１）で示されるナフタレン型４官能エポキシ樹脂（大日本インキ製ＥＸＡ−４７００、エポキシ当量１６３） １６部（重量部、以下同じ）、臭素化フェノールノボラックエポキシ樹脂（エポキシ当量２８４、軟化点８４℃、臭素含量３５重量％）１０部、フェノールノボラック（軟化点１０５℃）７部、ビスフェノールＡノボラック（軟化点１１５℃、水酸基当量１２９）７部、およびエポキシ樹脂と硬化剤量の合計１００部に対し２−フェニル−４−メチルイミダゾールを０．０３部をメチルエチルケトンとメチルセロソルブの混合溶剤に溶解した後、この溶液にγ−グリシドキシプロピルトリメトキシシラン０．５部を加え撹拌し、続いて平均粒径２．５μｍの球状溶融シリカ（２４μｍ以上をカットした平均粒径２．５μｍ、比表面積４．５ｍ² ／ｇの球状溶融シリカ）６０部をいかり型撹拌羽根で撹拌しながら少しずつ添加した。全成分を混合したところで高速攪拌機を用いて１０分撹拌しワニスを調製した。
作製したワニスを用いてガラスクロス（厚さ１８０μｍ、日東紡績製）に含浸し、１５０℃の加熱炉で６分乾燥してワニス固形分（プリプレグ中、ガラスクロスを除く成分）が約５０重量％のプリプレグを得た。このプリプレグを所定枚数重ね、両面に厚み１２μｍの銅箔を重ねて、圧力４０ｋｇｆ／ｃｍ² 、温度１９０℃で１２０分加熱加圧成形を行い両面銅張積層板を得た。
【００１９】
実施例２
平均粒径０．５μｍの球状溶融シリカ７０部をヘンシェルミキサーに投入、攪拌しながらγ−グリシドキシプロピルトリメトキシシランのメタノール１０重量％溶液１０部を少しずつ添加した。添加終了後５分攪拌し取り出した。次に実施例１と同じエポキシ樹脂（ＥＸＡ−４７００、エポキシ当量１６３）１２部、臭素化フェノールノボラックエポキシ樹脂（エポキシ当量２８４、軟化点８４℃、臭素含量３５重量％）８部、フェノールノボラック（軟化点１０５℃）１０部、およびエポキシ樹脂と硬化剤量の合計１００部に対し２−フェニル−４−メチルイミダゾールを０．０３部をメチルエチルケトンとメチルセロソルブの混合溶剤に溶解した後、γ−(2-アミノエチル)アミノプロピルトリメトキシシラン０．１部を加え、続いて先にカップリング剤で表面処理した平均粒径０．５μｍの球状溶融シリカをいかり型撹拌羽根で撹拌しながら少しずつ添加した。全成分を混合したところで高速攪拌機を用いて１０分撹拌しワニスを調製した。
作製したワニスを用いてガラスクロス（厚さ１８０μｍ、日東紡績製）に含浸し、１５０℃の加熱炉で６分乾燥してワニス固形分（プリプレグ中、ガラスクロスを除く成分）が約５０重量％のプリプレグを得た。このプリプレグを所定枚数重ね、両面に厚み１２μｍの銅箔を重ねて、圧力４０ｋｇｆ／ｃｍ² 、温度１９０℃で１２０分加熱加圧成形を行い両面銅張積層板を得た。
【００２０】
実施例４
平均粒径１．５μｍの球状溶融シリカ７０部をヘンシェルミキサーに投入、攪拌しながらγ−グリシドキシプロピルトリメトキシシランのメタノール１０重量％溶液８部とシリコーンオイル型カップリング剤Ａ（日本ユニカー製ＭＡＣ２１０１）のメタノール１０重量％溶液１部を少しずつ添加した。添加終了後５分攪拌し取り出した。次に実施例１と同じエポキシ樹脂（ＥＸＡ−４７００、エポキシ当量１６３）１３部、臭素化フェノールノボラックエポキシ樹脂（エポキシ当量２８４、軟化点８４℃、臭素含量３５重量％）６部、フェノールノボラック（軟化点１０５℃）６部、ビスフェノールＡノボラック（軟化点１１５℃、水酸基当量１２９）５部およびエポキシ樹脂と硬化剤量の合計１００部に対し２−フェニル−４−メチルイミダゾールを０．０３部をメチルエチルケトンとメチルセロソルブの混合溶剤に溶解した後、先にカップリング剤で表面処理した平均粒径１．５μｍの球状溶融シリカをいかり型撹拌羽根で撹拌しながら少しずつ添加した。全成分を混合したところで高速攪拌機を用いて１０分撹拌しワニスを調製した。
作製したワニスを用いてガラスクロス（厚さ１８０μｍ、日東紡績製）に含浸し、１５０℃の加熱炉で６分乾燥してワニス固形分（プリプレグ中、ガラスクロスを除く成分）が約５０重量％のプリプレグを得た。このプリプレグを所定枚数重ね、両面に厚み１２μｍの銅箔を重ねて、圧力４０ｋｇｆ／ｃｍ² 、温度１９０℃で１２０分加熱加圧成形を行い両面銅張積層板を得た。
【００２１】
実施例３、５〜１４及び比較例１〜４
表１、２及び表４に示す配合にて、表中カップリング剤添加方法において、Ａは実施例１と同様の方法で、Ｂは実施例２と同様の方法で、Ｃは実施例４と同様の方法にてワニスを調製し両面銅張積層板を得た。なお実施例６はカップリング剤を使用しない例である。また比較例１はビスマレイミド−トリアジン樹脂（三菱ガス化学製ＢＴレジン、ＣＣＬ−ＨＬ８３０）を用いた。
【００２２】
実施例１５〜２１
表３に示す配合にて、表中カップリング剤添加方法において、Ａは実施例１と同様の方法で、Ｂは実施例２と同様の方法で、Ｃは実施例４と同様の方法にてワニスを調製し、プレス時間１２０分を６０分に変更して両面銅張積層板を得た。
【００２３】
得られた両面銅張積層板の評価方法を▲１▼〜▲３▼に、ＢＧＡの評価方法を▲４▼、▲５▼に示す。
▲１▼ガラス転移温度
厚さ０．６ｍｍの両面銅張積層板を全面エッチングし、得られた積層板から１０ｍｍ×６０ｍｍのテストピースを切り出し、動的粘弾性測定装置を用いて３℃／分で昇温し、ｔａｎδのピーク位置をガラス転移温度とした。
▲２▼線膨張係数
厚さ１．２ｍｍの両面銅張積層板を全面エッチングし、得られた積層板から２ｍｍ×２ｍｍのテストピースを切り出し、ＴＭＡを用いてZ方向の線膨張係数を５℃／分で測定した。
▲３▼難燃性
厚さ０．６ｍｍの両面銅張積層板を全面エッチングし、得られた積層板からＵＬ−９４規格、垂直法により測定した。
【００２４】
▲４▼パッケージ反り量
実施例で作製した厚さ０．４ｍｍの両面銅張積層板をＢＧＡ用に回路加工した。この回路基板（リジッドインターポーザ）と封止材料に住友ベークライト製ＥＭＥ−７７２０を用いて、金型温度１８０℃、注入圧力７５ｋｇ／ｃｍ² 、硬化時間２分で２２５ｐＢＧＡ（パッケージサイズは２４×２４ｍｍ、厚さ１．１７ｍｍ、シリコンチップはサイズ９×９ｍｍ、厚さ０．３５ｍｍ、チップと回路基板のボンディングパッドとを２５μｍ径の金線でボンディングしている。）を成形し、１７５℃、８時間で後硬化した。室温に冷却後、パッケージのゲート部から対角線方向に、パッケージ上面の高さの変位を表面粗さ計により測定し、ゲート部を基準とした最大の変位値を反り量とした。単位はμｍ。
▲５▼耐半田クラック性
▲４▼と同様の方法で得たパッケージ８個を、８５℃、相対湿度６０％の環境下で１９２時間放置した後、ＪＥＤＥＣの方法に準じてＩＲリフロー処理を行った。
処理後の内部の剥離、及びクラックの有無を超音波探傷機で観察し、不良パッケージの個数を数えた。不良パッケージの個数がｎ個であるとき、ｎ／８と表示する。
【００２５】
評価結果を表１、２、３及び表４の下欄に示す。本発明のエポキシ樹脂組成物を用いてなるインターポーザは優れた耐半田クラック性を有し、加えて成形後の反りも極めて小さい。
【００２６】
【表１】

【００２７】
【表２】

【００２８】
【表３】

【００２９】
【表４】

【００３０】
表の注
１）Ａ：実施例１と同様のカップリング剤使用方法
Ｂ：実施例２と同様のカップリング剤使用方法
Ｃ：実施例４と同様のカップリング剤使用方法
２）２４μｍ以上をカットした平均粒径２．５μｍの球状溶融シリカ、比表面積４．５ｍ²／ｇ
３）２４μｍ以上をカットした平均粒径４μｍの球状溶融シリカ、比表面積４ｍ²／ｇ
４）２４μｍ以上の粗粒がカットされていない平均粒径８μｍの球状溶融シリカ
５）２４μｍ以上の粗粒がカットされていない平均粒径１１μｍの球状溶融シリカ
６） メタノールで希釈したγ−グリシドキシプロピルトリメトキシシラン１０重量％溶液
７）シリコーンオイル型カップリング剤Ａ：日本ユニカー製ＭＡＣ２１０１
８）メタノールで希釈したシリコーンオイル型カップリング剤Ａ１０重量％溶 液
９）シリコーンオイル型カップリング剤Ｂ：日本ユニカー製ＭＡＣ２３０１
１０）大日本インキ製ナフタレン型４官能エポキシ樹脂（エポキシ当量１６３）
１１）ビスフェノールＡ型エポキシ樹脂：エポキシ当量２５０
１２）臭素化フェノールノボラックエポキシ樹脂：エポキシ当量２８４、軟化点８４℃、臭素含量３５重量％
１３）フェノールノボラック：軟化点１０５℃、水酸基当量１０４
１４）ビスフェノールＡノボラック：軟化点１１５℃、水酸基当量１２９
１５）フェノールアラルキル樹脂：三井化学製ＸＬ−２２５
１６）２−フェニル−４−メチルイミダゾール：配合量はエポキシ樹脂と硬化剤の合計量１００部に対する量
１７）９，１０−ジヒドロ−９−オキサ−１０−ホスファフェナントレン−１０−オキシド（三光化学製ＨＣＡ）
１８）臭素化ビスフェノールＡ型エポキシ樹脂：エポキシ当量３６５、臭素含量４６重量％
【００３１】
【発明の効果】
本発明のインターポーザ用エポキシ樹脂組成物は高耐熱、低熱膨張、低吸水性という優れた特性を有し、本発明のエポキシ樹脂組成物から得られた銅張積層板は耐半田性に優れ、反りの小さいＩＣパッケージ用基板を提供でき、関連産業に大きく寄与することができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an epoxy resin composition for interposers having excellent solder resistance due to high heat resistance, low thermal expansion, and low water absorption, and a prepreg and a copper clad laminate using the epoxy resin composition.
[0002]
[Prior art]
In the field of semiconductors, a trend of shifting from conventional surface mounting to area mounting is progressing due to progress in high-density mounting technology, and new packages such as BGA and CSP are appearing and increasing. Therefore, the rigid substrate for interposer has been attracting more attention than before, and the demand for a high heat resistance and low thermal expansion substrate has increased. However, a bismaleimide-triazine resin-based substrate used as a current rigid substrate for an interposer has a high water absorption rate and a large linear expansion coefficient, and the solder resistance of an IC package is not always sufficient. On the other hand, in general, in order to reduce the coefficient of thermal expansion of the substrate, inorganic fillers, particularly fused silica, are widely used. However, crushed fused silica that has been used in the past has a square shape. As a result, a large stress is applied to the base material and copper foil during press forming, the base material and the copper foil are damaged, solder cracks may occur from the damaged part, and the appearance may be deteriorated. . Japanese Patent Laid-Open No. 9-272155 discloses a technique using spherical silica in order to solve such a problem, but there is no description of a resin composition optimal for a rigid substrate for an interposer.
[0003]
[Problems to be solved by the invention]
The present invention has been made to solve such problems, and has an epoxy resin composition for interposers having excellent heat resistance, low thermal expansion, and low water absorption, and a prepreg and a copper clad laminate using the same. A board is provided.
[0004]
[Means for Solving the Problems]
The present invention relates to an epoxy resin for an interposer containing, as essential components, a specific epoxy resin that contributes to heat resistance and low water absorption, a phenol resin curing agent, a flame retardant, and spherical fused silica that exhibits low thermal expansion and low water absorption. The composition is used as a technical outline, and the above object has been achieved by such a composition.
[0005]
Specifically, (A) an epoxy resin having a structure represented by the following formula (1) (where G represents a glycidyl group), (B) a phenol resin system having three or more phenolic hydroxyl groups in one molecule An epoxy resin composition for an interposer characterized by comprising a curing agent, C) a flame retardant, (D) spherical fused silica, and (E) a coupling agent , and a base material impregnated with such an epoxy resin composition A prepreg obtained by drying, and a copper-clad laminate obtained by heat molding using the prepreg.
[Chemical 2]

[0006]
DETAILED DESCRIPTION OF THE INVENTION
The epoxy resin having a structure represented by the formula (1) used in the present invention (G represents a glycidyl group) is a polyfunctional epoxy resin for exhibiting low water absorption, high glass transition temperature and thermal rigidity. is there. In general, polyfunctional epoxy resins that exhibit a high glass transition temperature have the disadvantage of high water absorption, but the epoxy resin used in the present invention has a reduced free volume due to the good packing properties of the naphthalene ring, and low water absorption. And heat resistance, and exhibits excellent solder crack resistance as an IC package interposer. In the present invention, the proportion of the component (A) in the epoxy resin composition is preferably 10 to 50% by weight. If it is less than 10% by weight, the binder component will be small even if (B) a phenol resin curing agent having 3 or more phenolic hydroxyl groups in one molecule is combined, and heat resistance, especially solder crack resistance as an interposer of IC packages. Sexuality begins to decline. If it exceeds 50% by weight, the proportion of the filler decreases, thermal expansion and water absorption increase, and solder crack resistance as an IC package interposer decreases, which is not preferable. Here, the solder crack resistance as an interposer is caused by the interposer or indirectly in the solder crack resistance test according to the JEDEC mounting rank condition performed in the BGA or CSP using a rigid interposer. It means the resistance to cracks that occur due to the influence of properties, or interfacial peeling.
In addition, as an epoxy resin, you may mix | blend 30 weight% or less of epoxy resins other than (A) component, for example, a bisphenol A type epoxy resin.
[0007]
Next, examples of the phenol resin curing agent having 3 or more phenolic hydroxyl groups in one molecule of component (B) include phenol novolak, bisphenol A novolak, phenol aralkyl resin, etc., but the phenolic hydroxyl group equivalents are compared. Phenol novolaks that can easily remove small and low-functional monomers and bisphenol A novolacs that can provide a high glass transition temperature are preferred. In the present invention, the component (B) is added so that the ratio (equivalent ratio) of the number of moles of the epoxy group of the epoxy resin to the number of moles of the phenolic hydroxyl group of the component (B) is 0.8 or more and 1.2 or less. It is preferable. Outside this range, a decrease in glass transition temperature and an increase in water absorption may cause a decrease in solder crack resistance as an IC package interposer and a decrease in moisture resistance reliability of the IC.
[0008]
The component (C) flame retardant used in the present invention is not limited as long as it contributes to flame resistance, but when applied to products in which halogen is not a problem, brominated phenol novolac epoxy resin, brominated A brominated epoxy resin such as a bisphenol A type epoxy resin is suitable because it has excellent solder crack resistance as an interposer of an IC package and moisture resistance reliability of the IC. In brominated epoxy resins, the amount of bromine necessary for flame retardancy varies depending on the blending ratio of the resin, but the proportion of bromine in the epoxy resin composition, usually 0.5 wt% to 20 wt% It is as follows. What is required to be halogen-free includes phosphate ester, red phosphorus, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (hereinafter abbreviated as HCA), triarylphosphine oxide, etc. In order to maintain solder crack resistance as an IC package interposer and IC moisture resistance reliability, HCA or a combination of HCA and triarylphosphine oxide is suitable. is there.
[0009]
HCA is a reactive phosphorus compound in which hydrogen bonded to phosphorus reacts with an epoxy group, and is an excellent phosphorus flame retardant that does not hydrolyze to increase water absorption or decrease adhesion. It is. However, this compound, on the other hand, has the effect of delaying the curability of the resin, so that there may be a problem in curability when the press molding time is shortened. In that case, the combined use of HCA and triarylphosphine oxide is preferred. Examples of triarylphosphine oxide include triphenylphosphine oxide, trishydroxyphenylphosphine oxide, bis (hydroxyphenyl) phenylphosphine oxide, trisaminophenylphosphine oxide, and bis (aminophenyl) phenylphosphine oxide. The aryl group of oxide may be unsubstituted or may have some substituent.
[0010]
Triarylphosphine oxide does not react with the matrix resin or is considered to have low reactivity, but has excellent hydrolysis resistance and does not affect the curability like HCA. Therefore, when HCA and triarylphosphine oxide are used together, good solder heat resistance can be realized without deteriorating water absorption and adhesion while maintaining flame retardancy and curability. The addition weight ratio of HCA and triarylphosphine oxide is preferably 1: 4 to 4: 1. If it is out of this range, the combined effect may be weakened. The total amount of HCA or HCA and triarylphosphine oxide added is preferably 0.5 to 10% by weight based on the entire epoxy resin composition. If the amount is less than 0.5% by weight, the flame retardant effect may be lowered. If the amount exceeds 10% by weight, the glass transition temperature may be lowered, the water absorption may be increased, or the adhesiveness may be lowered to lower the solder crack resistance. is there.
[0011]
The component (D) spherical fused silica used in the present invention is an important component that reduces the water absorption rate, lowers the linear expansion coefficient, and improves the solder crack resistance of the interposer that is a constituent material of the IC package. In crushed fused silica, when the filler is sandwiched in a relatively narrow gap between the glass base material and the copper foil constituting the copper clad laminate, the shape is square, so that the base material and copper foil are large during press molding. Stress may be applied, they may be damaged, solder cracks may be generated starting from the damaged portion, and the appearance may be deteriorated. In addition, when a large amount of filler is used, fluidity is lowered.
[0012]
In the case of spherical fused silica, regardless of the particle size, particle size distribution, and specific surface area, the stress on the base material and copper foil is small compared to crushed fused silica, but in particular, the average particle size is 5 μm or less (in the present invention, In the case of spherical fused silica whose diameters are all measured by a laser diffraction particle size distribution measurement, the base material and the copper foil are preferably less stressed. If the average particle size exceeds 5 μm, the stress on the base material and the copper foil is gradually increased, and the solder crack resistance may be deteriorated. Surface treatment with spherical fused silica having a maximum particle size of 24 μm or less, an average particle size of 2 μm or more and 5 μm or less and a specific surface area of 5 m ² / g or less by the BET method, or a coupling agent in advance. The spherical fused silica having an average particle size of 2 μm or less is more preferable because stress on the base material and copper foil is extremely small, and the filler is uniformly dispersed with little aggregation. If coarse particles with a maximum particle size exceeding 24 μm are included, a space resulting from the coarse particles is formed between the copper foil and the base material, and when moisture is absorbed, water stays and solder crack resistance deteriorates, The appearance of the laminate may be deteriorated. Further, when the average particle size is smaller than 2 μm or when the specific surface area exceeds 5 m ² / g, the same problem as in the case where the coarse particles are contained due to secondary aggregation of the particles may occur.
[0013]
It is preferable to use a component (D) spherical fused silica that has been surface-treated with a coupling agent in advance because the filler is uniformly dispersed with little aggregation. Coupling agents used include silane coupling agents, silicon-based coupling agents such as silicone oil-type coupling agents having two or more repeating units of siloxane bonds, and alkoxy groups, and titanate coupling agents. Although mentioned, a silicon-type coupling agent is preferable at the point of the wettability improvement of the surface of an epoxy resin and fused spherical silica. Specifically, an epoxy silane coupling agent, an amino silane coupling agent, a ureido silane coupling agent, a mercapto silane coupling agent, a disilazane, a silicone oil type cup having two or more repeating units of siloxane bond and having an alkoxy group. Examples include at least one selected from the group consisting of ring agents. In particular, when an epoxy silane coupling agent, an amino silane coupling agent, and a silicone oil coupling agent having two or more repeating units of siloxane bond and having an alkoxy group are used in combination, the coupling agent is efficiently applied to the silica surface. To settle. In this case, the ratio of the coupling agent is generally 0.1 to 10 parts by weight with respect to 100 parts by weight of spherical fused silica.
[0014]
Spherical fused silica that has been surface-treated with a coupling agent in advance has an average particle size of 2 μm or less, and since the filler is uniformly dispersed and the stress on the base material and copper foil is extremely small. preferable. For the same reason, spherical fused silica was surface-treated with a coupling agent in advance with spherical fused silica having a maximum particle size of 24 μm or less, an average particle size of 2 μm to 5 μm, and a specific surface area of 5 m ² / g or less. It is also a preferred embodiment to use a spherical fused silica having an average particle size of 2 μm or less in combination. In the case of using a coupling agent, it is known to those skilled in the art to add a small amount of water or use an acid or an alkali in order to promote the reaction between the silanol on the silica surface and the coupling agent, and is included in the present invention. .
[0015]
Component (D) spherical fused silica is preferable if it occupies 50% by weight or more in the epoxy resin composition because thermal expansion and water absorption are reduced. However, if it exceeds 90% by weight, the proportion of the filler in the epoxy resin composition is too large, and operations such as impregnation become difficult.
[0016]
In the present invention, in addition to the above-described coupling agent, the use of the component (E) coupling agent when blending raw materials together with other components is a spherical melt regardless of whether or not the spherical silica has been surface-treated in advance. This is preferable because it is effective in uniform dispersion and prevention of aggregation of silica. Examples of the coupling agent to be used are the same as those used for the surface treatment of component (D) spherical fused silica. The proportion of the coupling agent (E) in the epoxy resin composition is preferably 0.05 to 10% by weight. If it is less than 0.05% by weight, the coupling agent may not be dispersed over the entire surface of the filler. If it exceeds 10% by weight, the glass transition temperature may be lowered.
[0017]
If necessary, the epoxy resin composition of the present invention may contain additives other than the above components as long as the characteristics are not impaired. The epoxy resin composition of the present invention can obtain a prepreg by applying and impregnating a fiber base material with a solvent as a varnish or without a solvent and drying. As the substrate, glass woven fabric, glass nonwoven fabric, and other organic substrates can be used. One or a plurality of the prepregs are thermoformed together with the copper foil to obtain a copper clad laminate. These prepregs and copper clad laminates are also included in the present invention.
[0018]
【Example】
Example 1
Naphthalene-type tetrafunctional epoxy resin represented by formula (1) (EXA-4700 manufactured by Dainippon Ink, epoxy equivalent 163) 16 parts (parts by weight, the same applies hereinafter), brominated phenol novolac epoxy resin (epoxy equivalent 284, softening point 84) 10 parts at 10 ° C., bromine content 35 wt%), 7 parts phenol novolac (softening point 105 ° C.), 7 parts bisphenol A novolac (softening point 115 ° C., hydroxyl equivalent 129), and 100 parts in total of epoxy resin and curing agent amount On the other hand, 0.03 part of 2-phenyl-4-methylimidazole was dissolved in a mixed solvent of methyl ethyl ketone and methyl cellosolve, and 0.5 part of γ-glycidoxypropyltrimethoxysilane was added to this solution, followed by stirring. Spherical fused silica with an average particle size of 2.5 μm (average particle size of 2.5 μm cut from 24 μm or more, specific surface It was added portionwise with stirring 4.5 m ² / g of spherical fused silica) 60 parts of anchor stirring blade. When all the components were mixed, the mixture was stirred for 10 minutes using a high-speed stirrer to prepare a varnish.
The prepared varnish is used to impregnate a glass cloth (thickness 180 μm, manufactured by Nitto Boseki) and dried in a heating furnace at 150 ° C. for 6 minutes to obtain a varnish solid content (a component excluding the glass cloth in the prepreg) of about 50% by weight. Prepreg was obtained. A predetermined number of the prepregs were stacked, a copper foil having a thickness of 12 μm was stacked on both sides, and heat-pressing was performed at a pressure of 40 kgf / cm ² and a temperature of 190 ° C. for 120 minutes to obtain a double-sided copper-clad laminate.
[0019]
Example 2
70 parts of spherical fused silica having an average particle size of 0.5 μm was put into a Henschel mixer, and 10 parts of a 10 wt% methanol solution of γ-glycidoxypropyltrimethoxysilane was added little by little while stirring. After completion of the addition, the mixture was stirred for 5 minutes and taken out. Next, 12 parts of the same epoxy resin (EXA-4700, epoxy equivalent 163) as in Example 1, 8 parts of brominated phenol novolac epoxy resin (epoxy equivalent 284, softening point 84 ° C., bromine content 35% by weight), phenol novolac (softening) After dissolving 0.03 part of 2-phenyl-4-methylimidazole in a mixed solvent of methyl ethyl ketone and methyl cellosolve with respect to 10 parts of a point 105 ° C) and a total of 100 parts of the epoxy resin and the curing agent, γ- (2 -Aminoethyl) aminopropyltrimethoxysilane (0.1 part) was added, and then spherical fused silica having an average particle diameter of 0.5 μm, which had been surface-treated with a coupling agent previously, was added little by little while stirring with a stirring blade. . When all the components were mixed, the mixture was stirred for 10 minutes using a high-speed stirrer to prepare a varnish.
The prepared varnish is used to impregnate a glass cloth (thickness 180 μm, manufactured by Nitto Boseki) and dried in a heating furnace at 150 ° C. for 6 minutes to obtain a varnish solid content (a component excluding the glass cloth in the prepreg) of about 50% by weight. Prepreg was obtained. A predetermined number of the prepregs were stacked, a copper foil having a thickness of 12 μm was stacked on both sides, and heat-pressing was performed at a pressure of 40 kgf / cm ² and a temperature of 190 ° C. for 120 minutes to obtain a double-sided copper-clad laminate.
[0020]
Example 4
70 parts of spherical fused silica having an average particle size of 1.5 μm was put into a Henschel mixer, and 8 parts of a 10% by weight methanol solution of γ-glycidoxypropyltrimethoxysilane and a silicone oil coupling agent A (manufactured by Nippon Unicar Co., Ltd.) were stirred. 1 part of a 10 wt% methanol solution of MAC2101) was added in small portions. After completion of the addition, the mixture was stirred for 5 minutes and taken out. Next, 13 parts of the same epoxy resin (EXA-4700, epoxy equivalent 163) as in Example 1, 6 parts of brominated phenol novolac epoxy resin (epoxy equivalent 284, softening point 84 ° C., bromine content 35% by weight), phenol novolac (softening) 6 parts of bisphenol A novolak (softening point 115 ° C., hydroxyl group equivalent 129) and 0.03 part of 2-phenyl-4-methylimidazole to methyl ethyl ketone for a total of 100 parts of epoxy resin and curing agent Then, spherical fused silica having an average particle diameter of 1.5 μm, which had been surface-treated with a coupling agent previously, was added little by little while stirring with a stirrer type stirring blade. When all the components were mixed, the mixture was stirred for 10 minutes using a high-speed stirrer to prepare a varnish.
The prepared varnish is used to impregnate a glass cloth (thickness 180 μm, manufactured by Nitto Boseki) and dried in a heating furnace at 150 ° C. for 6 minutes to obtain a varnish solid content (a component excluding the glass cloth in the prepreg) of about 50% by weight. Prepreg was obtained. A predetermined number of the prepregs were stacked, a copper foil having a thickness of 12 μm was stacked on both sides, and heat-pressing was performed at a pressure of 40 kgf / cm ² and a temperature of 190 ° C. for 120 minutes to obtain a double-sided copper-clad laminate.
[0021]
Examples 3, 5-14 and Comparative Examples 1-4
In the formulations shown in Tables 1, 2 and 4, in the coupling agent addition method in the table, A is the same method as in Example 1, B is the same method as in Example 2, and C is the same as in Example 4. A varnish was prepared in the same manner to obtain a double-sided copper-clad laminate. Example 6 is an example in which no coupling agent is used. In Comparative Example 1, a bismaleimide-triazine resin (BT resin manufactured by Mitsubishi Gas Chemical Co., Ltd., CCL-HL830) was used.
[0022]
Examples 15-21
In the formulation shown in Table 3, in the coupling agent addition method in the table, A is the same method as Example 1, B is the same method as Example 2, and C is the same method as Example 4. A varnish was prepared, and the press time of 120 minutes was changed to 60 minutes to obtain a double-sided copper-clad laminate.
[0023]
The evaluation methods of the obtained double-sided copper-clad laminate are shown in (1) to (3), and the evaluation methods of BGA are shown in (4) and (5).
(1) A double-sided copper-clad laminate with a glass transition temperature thickness of 0.6 mm is etched all over, and a 10 mm × 60 mm test piece is cut out from the obtained laminate, and 3 ° C./min using a dynamic viscoelasticity measuring device. The tan δ peak position was taken as the glass transition temperature.
(2) Linear expansion coefficient A double-sided copper-clad laminate with a thickness of 1.2 mm is etched all over, a 2 mm x 2 mm test piece is cut out from the resulting laminate, and the linear expansion coefficient in the Z direction is 5 ° C using TMA. Measured at / min.
(3) Flame retardant property A double-sided copper clad laminate having a thickness of 0.6 mm was entirely etched, and the obtained laminate was measured by UL-94 standard and vertical method.
[0024]
{Circle around (4)} Package Warpage A double-sided copper clad laminate having a thickness of 0.4 mm produced in the example was subjected to circuit processing for BGA. Using EME-7720 manufactured by Sumitomo Bakelite as the circuit board (rigid interposer) and sealing material, the mold temperature is 180 ° C., the injection pressure is 75 kg / cm ² , the curing time is 2 minutes, and 225 pBGA (package size is 24 × 24 mm, thickness The silicon chip is 9 × 9 mm in size, the thickness is 0.35 mm, and the bonding pad of the chip and the circuit board is bonded with a gold wire with a diameter of 25 μm.) And molded at 175 ° C. for 8 hours Post-cured. After cooling to room temperature, the height displacement of the upper surface of the package was measured with a surface roughness meter in the diagonal direction from the gate portion of the package, and the maximum displacement value based on the gate portion was taken as the amount of warpage. The unit is μm.
(5) Solder crack resistance Eight packages obtained by the same method as in (4) are left for 192 hours in an environment of 85 ° C. and a relative humidity of 60%, and then IR reflow treatment is performed according to the method of JEDEC. It was.
The internal peeling after processing and the presence or absence of cracks were observed with an ultrasonic flaw detector, and the number of defective packages was counted. When the number of defective packages is n, n / 8 is displayed.
[0025]
The evaluation results are shown in the lower columns of Tables 1, 2, 3 and Table 4. The interposer using the epoxy resin composition of the present invention has excellent solder crack resistance, and in addition, warpage after molding is extremely small.
[0026]
[Table 1]

[0027]
[Table 2]

[0028]
[Table 3]

[0029]
[Table 4]

[0030]
Note 1) A: Coupling agent use method similar to Example 1 B: Coupling agent use method similar to Example 2 C: Coupling agent use method similar to Example 2 2) Cut 24 μm or more Spherical fused silica with an average particle size of 2.5 μm, specific surface area 4.5 m ² / g
3) Spherical fused silica with an average particle size of 4 μm cut from 24 μm or more, specific surface area of 4 m ² / g
4) Spherical fused silica with an average particle size of 8 μm, in which coarse particles of 24 μm or more are not cut 5) Spherical fused silica with an average particle size of 11 μm, in which coarse particles of 24 μm or more are not cut 6) γ-glycid diluted with methanol 10% by weight solution of xylpropyltrimethoxysilane 7) Silicone oil type coupling agent A: MAC2101 manufactured by Nihon Unicar
8) Silicone oil type coupling agent A diluted by methanol 10% by weight Solution 9) Silicone oil type coupling agent B: Nihon Unicar MAC2301
10) Naphthalene-type tetrafunctional epoxy resin made by Dainippon Ink (epoxy equivalent 163)
11) Bisphenol A type epoxy resin: epoxy equivalent 250
12) Brominated phenol novolac epoxy resin: epoxy equivalent 284, softening point 84 ° C., bromine content 35% by weight
13) Phenol novolak: softening point 105 ° C., hydroxyl group equivalent 104
14) Bisphenol A novolak: softening point 115 ° C., hydroxyl equivalent 129
15) Phenol aralkyl resin: XL-225 manufactured by Mitsui Chemicals
16) 2-Phenyl-4-methylimidazole: The amount is 17 parts of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (Sanko Chemical) HCA)
18) Brominated bisphenol A type epoxy resin: epoxy equivalent 365, bromine content 46% by weight
[0031]
【The invention's effect】
The epoxy resin composition for interposers of the present invention has excellent properties such as high heat resistance, low thermal expansion, and low water absorption, and the copper-clad laminate obtained from the epoxy resin composition of the present invention has excellent solder resistance and warpage. Can be provided, and can greatly contribute to related industries.

Claims (13)

(A) an epoxy resin having a structure represented by the following formula (1) (where G represents a glycidyl group), (B) a phenol resin-based curing agent having three or more phenolic hydroxyl groups in one molecule, (C An epoxy resin composition for an interposer characterized by comprising a flame retardant, (D) spherical fused silica, and (E) a coupling agent as essential components.

The epoxy resin composition for interposers according to claim 1 , wherein component (B) is phenol novolac or bisphenol A novolac. The epoxy resin composition for interposers according to claim 1 or 2 , wherein the component (D) is spherical fused silica having a maximum particle size of 24 µm or less, an average particle size of 2 µm to 5 µm, and a specific surface area of 5 m ² / g or less. The epoxy resin composition for interposers according to any one of claims 1 to 3 , wherein component (D) is spherical fused silica that has been surface-treated in advance with a coupling agent. The epoxy resin composition for interposers according to claim 4, wherein component (D) is spherical fused silica having an average particle size of 2 µm or less. Ingredient (D) having a maximum particle size of 24 μm or less, a spherical particle having an average particle size of 2 μm or less and a specific surface area of 5 m ² / g or less and a spherical particle having an average particle size of 2 μm or less that has been surface-treated with a coupling agent in advance. The epoxy resin composition for interposers according to claim 1 or 2 , comprising fused silica. Coupling agent for pre-treating spherical fused silica used for component (D) is an epoxy silane coupling agent, amino silane coupling agent, ureido silane coupling agent, mercapto silane coupling agent, disilazane, repeating unit of siloxane bond. The epoxy resin composition for interposers according to claim 4, 5 or 6 , wherein the epoxy resin composition is at least one selected from the group consisting of silicone oil type coupling agents having two or more and having an alkoxy group. Component (E) is an epoxy silane coupling agent, amino silane coupling agent, ureido silane coupling agent, mercapto silane coupling agent, disilazane, silicone oil type having two or more repeating units of siloxane bond and having an alkoxy group The epoxy resin composition for interposers according to any one of claims 1 to 7 , which is a coupling agent selected from the group consisting of coupling agents. The epoxy resin composition for interposers according to any one of claims 1 to 8 , wherein the flame retardant is a brominated epoxy resin. The epoxy resin composition for interposers according to any one of claims 1 to 8 , wherein the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide. The epoxy resin composition for interposers according to any one of claims 1 to 8 , wherein the flame retardant is 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and triarylphosphine oxide. A prepreg obtained by impregnating a fiber base material with the epoxy resin composition for interposers according to any one of claims 1 to 11 , and drying the fiber base material. A copper-clad laminate obtained by thermoforming the prepreg according to claim 12 .