JP3543854B2 - Resin composition for sealing and semiconductor device - Google Patents

Description

（ただし、ｎは２〜１０の整数を表す。また、環のメチレン基の炭素原子または水素原子が部分的に他の原子または他の置換基で置換されていてもよい。）
【化５】

（ただし、Ａｒ^２はフェノ−ル性ヒドロキシル基を有する２価の芳香族基を表す。また、Ａｒ^２およびフェニレン基は有機基またはハロゲン原子によって置換されていても良い。）」
および「前記封止用樹脂組成物の硬化物により、半導体が封止されていることを特徴とする半導体装置。」からなるものである。
【００１２】
以下、本発明の構成を詳述する。
【００１３】
本発明で用いるアザビシクロ化合物（Ａ）とアラルキル樹脂（Ｂ）からなる付加塩（Ｃ）において、アザビシクロ化合物（Ａ）の例としては、原料の入手のしやすさや合成の容易さおよび価格などのバランスの点から前記一般式（Ｉ） においてｎが３〜５が一般的である。具体例としては、１，８−ジアザビシクロ（５，４，０）ウンデセン−７（前述、ＤＢＵ、式ＩＶ） や１，５−ジアザビシクロ（４，３，０）ノネン−５（以下ＤＢＮと略記、式Ｖ ）、７−メチル−１，５，７−トリアザビシクロ（４，４，０）デセン−５（式ＶＩ）およびＤＢＵのジメチルアミノ誘導体（式ＶＩＩ ）などが挙げられる。
【化６】

【００１４】
次に、付加塩（Ｃ）のもう一方の成分であるアラルキル樹脂（Ｂ）は前述の（ＩＩ）の構造単位を有する樹脂である。ここで示されるフェニレン基としては、５０％以上、さらに８０％以上がパラ位で結合しているものが好ましく用いられる。にさらに一般式（ＩＩＩ） の構造を有するアラルキル樹脂が好ましく用いられる。
【化７】

（ただし、Ａｒ^１はフェノ−ル性ヒドロキシル基を有する１価の芳香族基を表し、Ａｒ^２は式（ＩＩ） の説明と同じ。Ａｒ^１およびフェニレン基は有機基またはハロゲン原子によって置換されていても良い。ｍは０以上の整数を表す。）
一般式（ＩＩＩ） の構造を有するアラルキル樹脂の重合度としては、一般式（ＩＩＩ） におけるｍが０〜２０の範囲を有するものが好ましく用いられる。一方重合度の指標として、１５０℃における溶融粘度が０．３〜５０ポイズであるものが好ましく用いられる。
【００１５】
一般式（ＩＩＩ） の構造を有するアラルキル樹脂として好ましい具体例としては、フェノールアラルキル樹脂、オルソクレゾ−ルアラルキル樹脂、α−ナフト−ルアラルキル樹脂、β−ナフト−ルアラルキル樹脂などが挙げられる。これらのうち、フェノールアラルキル樹脂（式ＶＩＩＩ） およびα−ナフト−ルアラルキル樹脂（式ＩＸ） の構造式を以下に示す。
【化８】

（ただし、ｍは０以上の整数）
【００１６】
アラルキル樹脂（Ｂ）の製造法としては、アラルキルエ−テルとフェノ−ル類とをフリ−デルクラフツ触媒で反応させるのが一般的であり、α，α´−ジメトキシパラキシレンとフェノ−ルからの縮合重合によって得られるる（プラスティクス，Ｖｏｌ．３４，Ｎｏ．２（１９８３））。具体的には、“ミレックス”ＸＬ−２２５（三井東圧化学（株）製）や“ＸＹＬＯＫ”２２５（アルブライトアンドウイルソン（株）製）などが挙げられる。
【００１７】
一般式（ＩＩＩ） の構造を有するアラルキル樹脂としては、水酸基当量が１３０〜２５０の範囲のものが好ましく用いられ、さらにフェノールアラルキル樹脂を用いる場合、水酸基当量が１３０〜２２０のものが好ましく、さらに１５０〜２００のものが好ましく用いられる。一方α−ナフトールアラルキル樹脂を用いる場合には、水酸基当量が１９０〜２５０のものが好ましく、さらに１９０〜２３０のものが好ましく用いられる。
【００１８】
また一般式（ＩＩＩ） の構造を有するアラルキル樹脂の軟化点としては、軟化温度が５０〜１１０℃の範囲のもの、さらに６０〜９０℃のものが好ましく用いられる。 本発明の付加塩（Ｃ）の製造方法は、例えば、アラルキル樹脂（Ｂ）を、融点以上、例えば１００〜２００℃の温度の溶融状態で攪拌しながらアザビシクロ化合物を少量ずつ添加し均一に混合させ、付加塩を形成した後、冷却して得ることができる。さらに必要に応じて粉砕して用いられる。反応温度は２００℃を越えると分解による副反応が始まるため好ましくなく、１００℃以下ではアラルキル樹脂（Ｂ）の粘度が高いため攪拌不能となる。より好ましい反応温度は１２０〜１８０℃である。
【００１９】
本発明で用いる付加塩（Ｃ）はアラルキル樹脂（Ｂ）とアザビシクロ化合物 （Ａ）からなるが、付加塩（Ｃ）中のアザビシクロ化合物（Ａ）の割合が５０重量％以下では、付加塩（Ｃ）中のアザビシクロ化合物（Ａ）の含量を増していくと付加塩（Ｃ）の軟化点が高くなる。エポキシ樹脂の硬化促進剤として好ましい軟化点すなわち５０〜１５０℃の範囲の付加塩（Ｃ）を得るためにはアザビシクロ化合物（Ａ）の含量は０．１〜３０重量％が好ましい。さらに、作業性や経済性の面からは３〜１５重量％がより好ましい。
【００２０】
本発明において重要なことは、塩基性のアザビシクロ化合物（Ａ）と酸性基であるヒドロキシル基を有するアラルキル樹脂（Ｂ）からなる付加塩（Ｃ）をエポキシ樹脂硬化促進剤として用いた封止用樹脂組成物を加熱硬化させる際に、付加塩（Ｃ）が樹脂中に良く分散してエポキシ樹脂と硬化剤の硬化促進剤としての能力を十分発揮することである。分散性の良否は硬化反応の際に、一定量の付加塩（Ｃ）を用いて一定時間に所定の熱時硬度に達するかどうかで判断できる。付加塩（Ｃ）の調製時に構成単位であるアザビシクロ化合物（Ａ）の濃度が異常に高い部分ができると全体の軟化点が低くても（例えば１５０℃以下であっても）、局部的に付加塩（Ｃ）の軟化点が１５０℃以上となり、このものを用いて加熱硬化する際に付加塩（Ｃ）が十分溶融されないため樹脂組成物中への分散が悪くなり、十分な硬化反応をさせることができず、結果として短時間に所定の熱時硬度が得られない。そのような理由から、従来のＤＢＵとフェノ−ルノボラック付加塩の調製時には高融点物を生じさせないために混合法など製造プロセスの適正化によって対策とされてきたが、十分とはいえなかった。一方アザビシクロ化合物（Ａ）とアラルキル樹脂（Ｂ）とからなる付加塩（Ｃ）では、予測外に分散性が良好となり、短時間で、成形に必要な熱時硬度に到達することができる。その理由として、従来からのフェノ−ルノボラック樹脂と比べて本発明で用いるヒドロキシル基を有するアラルキル樹脂（Ｂ）は、単位分子鎖当たりの水酸基の数が少ないため酸性度が低く、アザビシクロ化合物（Ａ）との酸性／塩基性のバランスが極めて良いためと思われる。
【００２１】
本発明で用いる付加塩（Ｃ）はエポキシ樹脂と硬化剤が配合された樹脂組成物中に添加して硬化促進剤として用いる。付加塩（Ｃ）の添加量は通常エポキシ樹脂１００重量部に対して０．１〜１５重量部でエポキシ樹脂や硬化剤の反応性に応じて適宜調整されるが、耐湿性の面から０．１〜５重量部が好ましい。
【００２２】
また、本発明の付加塩（Ｃ）の特性を損なわない範囲で他のエポキシ樹脂硬化促進剤２種類以上を併用してもよい。他の硬化促進剤として例えば、２−メチルイミダゾール、２−フェニルイミダゾール、２−フェニル−４−メチルイミダゾール、２−ヘプタデシルイミダゾールなどのイミダゾール化合物およびそれらの付加塩、トリエチルアミン、ベンジルジメチルアミン、α−メチルベンジルジメチルアミン、などの３級アミン化合物およびそれらの付加塩、トリフェニルホスフィン、トリブチルホスフィン、トリ（ｐ−メチルフェニル）ホスフィン、トリ（ノニルフェニル）ホスフィン、トリフェニルホスフィン・トリフェニルボレート、テトラフェニルホスフィン・テトラフェニルボレートなどの有機ホスフィン化合物があげられる。
【００２３】
本発明の封止用樹脂組成物において、エポキシ樹脂としてはエポキシ基を有する化合物であれば任意であるが、フェノ−ル性ヒドロキシル基をグリシジルエ−テルに転化したものが好ましく用いられる。具体例としては、４，４´−ビス （２，３−エポキシプロポキシ）ビフェニル、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、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−２−クロロビフェニル、４、４´−ビス（２，３−エポキシプロポキシ）−３、３´，５，５´−テトラエチルビフェニルなどのビフェニル型エポキシ樹脂、１，５−ジ（２，３−エポキシプロポキシ）ナフタレン、１，５−ジ（２，３−エポキシプロポキシ）−７−メチルナフタレン、１，６−ジ（２，３−エポキシプロポキシ）ナフタレン、１，６−ジ（２，３−エポキシプロポキシ）−２−メチルナフタレン、１，６−ジ（２，３−エポキシプロポキシ）−８−メチルナフタレン、１，６−ジ（２，３−エポキシプロポキシ）−４，８−ジメチルナフタレン、２，７−ジ（２，３−エポキシプロポキシ）ナフタレンなどのナフタレン型エポキシ樹脂、クレゾ−ルノボラック型エポキシ樹脂、フェノ−ルノボラック型エポキシ樹脂、ビスフェノ−ルＡやレゾルシンから合成される各種ノボラック型エポキシ樹脂、フェノ−ルアラルキル型エポキシ樹脂、ナフト−ルアラルキル型エポキシ樹脂などが挙げられる。
【００２４】
また、フェノ−ル系硬化剤としてはフェノールノボラック樹脂、クレゾールノボラック樹脂、トリス（ヒドロキシフェニル）メタン、１，１，２−トリス（ヒドロキシフェニル）エタン、１，１，３−トリス（ヒドロキシフェニル）プロパン、ビスフェノ−ルＡ、ビスフェノールＦ、ジヒドロキシビフェニル、フェノ−ルアラルキル樹脂、ナフト−ルアラルキル樹脂、ポリヒドロキシスチレンなどが挙げられる。
【００２５】
本発明では、エポキシ樹脂とフェノ−ル系硬化剤の配合当量比（例えば、エポキシ基に対するヒドロキシル基のモル比）は、通常、０．７〜１．３であるが好ましくは０．８〜１．１である。
【００２６】
本発明の封止用樹脂組成物において、無機充填材が配合される。その量としては封止用樹脂組成物全体の７５〜９５重量％が好ましい。無機充填材の全体に対する割合が上記の範囲に無い場合は成形性や半田耐熱性が悪くなる。無機充填材として例えば、溶融シリカ、結晶シリカ、アルミナ、タルク、硫酸カルシウム、窒化アルミニウムなどが挙げられる。無機充填材の形状は特に限定されず、例えば、球状や破砕状などのものが任意に用いられる。これらの無機充填剤はエポキシシラン、アミノシラン、メルカプトシランなどのシランカップリング剤で表面処理して用いると耐湿信頼性向上の点で好ましい。
【００２７】
また、封止用樹脂組成物に対する他の添加剤として例えば、シリコ−ンゴム、ブタジエンゴム、変性ニトリルゴム、変性ポリブタジエンゴム、変性シリコ−ンゴムなどのゴム成分、パラフィンワックス、長鎖脂肪酸、長鎖脂肪酸エステル、長鎖脂肪酸の金属塩、変性シリコ−ンオイルなどの離型剤、ハロゲン化エポキシ樹脂、ハロゲン化合物、リン化合物などの難燃剤、三酸化アンチモンなどの難燃助剤、カ−ボンブラックなどの着色剤、ポリエチレンなどの熱可塑樹脂を任意に添加することができる。
【００２８】
本発明の封止用樹脂組成物は溶融混練することが好ましく、たとえばニーダー、ロール、単軸もしくは二軸の押出機およびコニーダーなどの公知の混練方法を用いて溶融混練することにより、製造される。
【００２９】
本発明の封止用樹脂組成物は、通常粉末またはタブレット状態で半導体封止に供される。半導体を基板に固定した部材に対して、例えば低圧トランスファー成形機を用いて、封止用樹脂組成物を、例えば１２０〜２５０℃、好ましくは１５０〜２００℃の温度で成形し、封止用樹脂組成物の硬化物とすることによって、封止用樹脂組成物の硬化物に封止された半導体装置が製造される。また必要に応じて追加熱処理（例えば１５０〜２００℃、２〜１５時間）も行なうことができる。
【００３０】
【実施例】
付加塩の調製例
本発明で用いる付加塩（Ｃ）の調製例を以下に説明する。
【００３１】
２リットルのステンレス容器に前述の（ＶＩＩＩ）の構造を有し、１５０℃の溶融粘度が２．３ポイズのフェノ−ルアラルキル樹脂５５２ｇを入れ、１５０℃で溶融させた。次に、溶融したフェノ−ルアラルキル樹脂を良く攪拌しながら、ＤＢＵ４８ｇを１５分かけて滴下して、滴下後さらに１５分攪拌を続けた。冷却後、粉砕して４２メッシュの篩で分級した（付加塩Ｎｏ．１）。同様の操作で各種付加塩を、表１に記載の内容でその他の付加塩（Ｃ）も調製した。得られた付加塩の物性を表１に示す。
【００３２】
【表１】

【００３３】
実施例１〜５、比較例１〜３
表１および表２に示した配合物を、表３（実施例１〜５、比較例１〜３）に示した組成比でミキサ−を用いてブレンドした。これを、バレル設定温度９０℃の二軸出機を用いて溶融混練後、冷却・粉砕して封止用樹脂組成物を製造した。
【００３４】
なお比較例１、２はフェノールノボラック樹脂とＤＢＵとの付加塩を用いたもの、比較例３はＤＢＵを付加塩とせずに封止用樹脂組成物に配合したものである。
【００３５】
【表２】

【００３６】
【表３】

【００３７】
この封止用樹脂組成物を用いて、半導体を封止し、半導体装置を得た。また以下に示した半田耐熱性試験と成形性試験を行った。
半田耐熱性試験：１６０ｐｉｎＱＦＰデバイス（パッケージサイズ：２８×２８×３．３ｍｍ、チップサイズ：１０．４×１０．４×０．５ｍｍ）に、封止用樹脂組成物を低圧トランスファー成形機を用いて１７５℃×１８０秒の条件で成形し、１７５℃で１２時間硬化した。このテストデバイス１６個を８５℃／８５％ＲＨ雰囲気下で１２０時間加湿した後、２４５℃に加熱したＩＲ（赤外線）リフロ−炉に約１０秒の条件で通した。ここで外部クラックの発生したデバイスを不良とした。
成形性試験：低圧トランスファー成形機を用いて１７５℃×６０秒の条件で円盤（６０φ×３ｍｍ）を成形して、円盤の１７５℃での熱時硬度をバ−コ−ル硬度計を用いて測定した（測定法はＡＳＴＭ、Ｄ２５８３−９２によった）。得られた結果を表４に示す。
【００３８】
【表４】

【００３９】
表４に示したように、本発明の封止用樹脂組成物（実施例１〜５）は比較例の組成物（比較例１〜４）より半田耐熱性に優れている。さらに、本発明の封止用樹脂組成物（実施例１〜５）は１７５℃、６０秒という非常に短い成形時間でも熱時硬度が高いため成形の高速化が可能である。比較例１〜４は成形性も悪い。
【００４０】
【発明の効果】
本発明は、アザビシクロ化合物と特定のヒドロキシル基を有するアラルキル樹脂からなる付加塩を硬化促進剤として用いたことを特徴とする封止用樹脂組成物であり、高速成形性と高い半田耐熱性の両方を兼ね備えるため、表面実装用の半導体封止用樹脂組成物として有用である。また、本発明の封止用樹脂組成物を用いて封止した半導体装置は表面実装後の外部クラック不良が少なく、そのため高い半導体動作の信頼性を有する。[0001]
[Industrial applications]
The present invention relates to a sealing resin composition for surface mounting that is excellent in high-speed moldability and solder heat resistance, and a semiconductor device in which a semiconductor is sealed with a cured product of the sealing resin composition.
[0002]
[Prior art]
In semiconductor encapsulation, the density of components mounted on printed circuit boards has recently been increasing, and instead of the conventional "insertion mounting method" in which lead pins are inserted into holes in the board, components are soldered to the board surface. "Surface mount method" has been adopted. Along with this, the package is also shifting from the conventional DIP (dual inline package) to a thin TSOP (thin small outline package) or QFP (quad flat package) suitable for high-density mounting and surface mounting. .
[0003]
With the shift to the surface mounting method, the soldering process, which has not been a problem so far, has become a major problem. In the conventional pin insertion mounting method, the lead portion is only partially heated in the soldering process, but in the surface mounting method, the entire package is immersed in a heating medium and heated. As a soldering method in the surface mounting method, a solder bath immersion, a solder reflow method of heating with a saturated vapor of an inert liquid or infrared rays is used. In any case, the entire package is heated to a high temperature of 210 to 270 ° C. Will be. For this reason, there has been a problem that a package sealed with a conventional sealing resin has a problem in that cracks occur in a resin portion during soldering, so that the reliability is reduced and the package cannot be used as a product.
[0004]
Cracking in the soldering process is said to be caused by the moisture absorbed between the post-curing and the mounting process explosively turning into steam and expanding during soldering heating. For example, studies have been made to reduce the water absorption of resins for use.
[0005]
Further, from the viewpoint of cost of the semiconductor package, there is a strong demand for automation of molding and speeding up of molding at the time of semiconductor resin sealing, which is a precedent step of the above package mounting.
[0006]
An epoxy resin is generally used as a sealing resin. The main reason is that the cured product of the epoxy resin composition is excellent in heat resistance, moisture resistance, electrical properties, adhesiveness, and the like, and that various properties can be imparted by a compounding formulation. An epoxy resin composition for semiconductor encapsulation generally comprises an epoxy resin, a phenolic curing agent, a curing accelerator and an inorganic filler.
[0007]
For epoxy resin-based semiconductor encapsulants, it is necessary to automate and speed up the molding of semiconductors during resin encapsulation (package manufacturing) and improve the solder heat resistance of semiconductor packages during surface mounting. It is important to develop a high-performance curing accelerator in order to obtain the following physical properties. As a curing accelerator, 1,8-diazabicyclo (5,4,0) undecene-7 (hereinafter abbreviated as DBU) or an addition salt thereof has been proposed (JP-A-62-81416). DBU and phenol-novolak addition salts have also been proposed (JP-A-63-12627).
[0008]
[Problems to be solved by the invention]
However, in a system in which a predetermined amount of a curing accelerator is added using a conventional DBU or a phenol-novolak addition salt of DBU, a high-speed molding cannot be performed because a hardness at a certain level or higher cannot be obtained in a short time. Further, when the addition amount of the curing accelerator is increased to forcibly obtain the hardness at the time of heating, there is a disadvantage that the water absorption of the sealing resin is increased and the solder heat resistance of the package is reduced.
[0009]
An object of the present invention is to provide a high-performance epoxy resin composition for semiconductor encapsulation that satisfies both high-speed moldability and excellent solder heat resistance so as to obtain a certain level of heat hardness in a short time. is there. Another object of the present invention is to provide a highly reliable semiconductor device which has few defects such as external cracks due to heating by solder during surface mounting.
[0010]
[Means for Solving the Problems]
The present inventors have conducted intensive studies to achieve the above object, and as a result, by using an addition salt (C) composed of an azabicyclo compound (A) and an aralkyl resin (B) as an epoxy resin curing accelerator, the above problem was solved. Solved and arrived at the present invention.
[0011]
That is, the present invention relates to an azabicyclo compound (A) represented by the following general formula (I) as a curing accelerator in a sealing resin composition containing an epoxy resin, a phenolic curing agent, and an inorganic filler. And an aralkyl resin (B) having a structural unit represented by the following general formula (II).
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(However, n represents an integer of 2 to 10. The carbon atom or hydrogen atom of the methylene group in the ring may be partially substituted with another atom or another substituent.)
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(However, Ar ² represents a divalent aromatic group having a phenolic hydroxyl group. Ar ² and the phenylene group may be substituted with an organic group or a halogen atom.) "
And a semiconductor device characterized in that a semiconductor is sealed with a cured product of the sealing resin composition.
[0012]
Hereinafter, the configuration of the present invention will be described in detail.
[0013]
In the addition salt (C) composed of the azabicyclo compound (A) and the aralkyl resin (B) used in the present invention, examples of the azabicyclo compound (A) include, for example, balance between availability of raw materials, ease of synthesis, and price. In view of the above, n is generally 3 to 5 in the general formula (I). Specific examples include 1,8-diazabicyclo (5,4,0) undecene-7 (DBU, formula IV described above) and 1,5-diazabicyclo (4,3,0) nonene-5 (hereinafter abbreviated as DBN; Formula V), 7-methyl-1,5,7-triazabicyclo (4,4,0) decene-5 (Formula VI) and the dimethylamino derivative of DBU (Formula VII).
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[0014]
Next, the aralkyl resin (B) which is the other component of the addition salt (C) is a resin having the structural unit of the above (II). As the phenylene group shown here, those having 50% or more, more preferably 80% or more, bonded in the para position are preferably used. Further, an aralkyl resin having a structure of the general formula (III) is preferably used.
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(However, Ar ¹ represents a monovalent aromatic group having a phenolic hydroxyl group, and Ar ² is the same as described in the formula (II). Ar ¹ and the phenylene group are substituted by an organic group or a halogen atom.) M represents an integer of 0 or more.)
As the polymerization degree of the aralkyl resin having the structure of the general formula (III), those having m in the general formula (III) having a range of 0 to 20 are preferably used. On the other hand, those having a melt viscosity at 150 ° C. of 0.3 to 50 poise are preferably used as an index of the degree of polymerization.
[0015]
Specific preferred examples of the aralkyl resin having the structure of the general formula (III) include a phenol aralkyl resin, an orthocresol aralkyl resin, an α-naphtho-ar aralkyl resin, and a β-naphtho-ar aralkyl resin. Among these, the structural formulas of the phenol aralkyl resin (Formula VIII) and the α-naphthyl aralkyl resin (Formula IX) are shown below.
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(However, m is an integer of 0 or more)
[0016]
As a method for producing the aralkyl resin (B), it is common to react an aralkyl ether and a phenol with a Freedel Crafts catalyst, and to condense α, α′-dimethoxyparaxylene with phenol. Obtained by polymerization (Plastics, Vol. 34, No. 2 (1983)). Specific examples include "Mirex" XL-225 (manufactured by Mitsui Toatsu Chemicals, Inc.) and "XYLOK" 225 (manufactured by Albright & Wilson, Inc.).
[0017]
As the aralkyl resin having the structure of the general formula (III), those having a hydroxyl equivalent of 130 to 250 are preferably used, and when a phenol aralkyl resin is used, those having a hydroxyl equivalent of 130 to 220 are preferable, and 150 ~ 200 are preferably used. On the other hand, when an α-naphthol aralkyl resin is used, those having a hydroxyl equivalent of 190 to 250 are preferable, and those having a hydroxyl equivalent of 190 to 230 are more preferably used.
[0018]
As the softening point of the aralkyl resin having the structure of the general formula (III), those having a softening temperature in a range of 50 to 110 ° C, and more preferably those having a softening temperature of 60 to 90 ° C are preferably used. In the production method of the addition salt (C) of the present invention, for example, the azabicyclo compound is added little by little while the aralkyl resin (B) is stirred in a molten state at a temperature not lower than the melting point, for example, at a temperature of 100 to 200 ° C., and uniformly mixed. After forming an addition salt, it can be obtained by cooling. Further, it is pulverized and used as needed. When the reaction temperature exceeds 200 ° C., side reactions due to decomposition start, which is not preferable. When the reaction temperature is 100 ° C. or less, stirring becomes impossible because the viscosity of the aralkyl resin (B) is high. A more preferred reaction temperature is 120 to 180 ° C.
[0019]
The addition salt (C) used in the present invention comprises an aralkyl resin (B) and an azabicyclo compound (A). When the ratio of the azabicyclo compound (A) in the addition salt (C) is 50% by weight or less, the addition salt (C) As the content of the azabicyclo compound (A) in ()) increases, the softening point of the addition salt (C) increases. The content of the azabicyclo compound (A) is preferably 0.1 to 30% by weight in order to obtain an addition salt (C) having a softening point which is preferable as a curing accelerator for an epoxy resin, that is, in the range of 50 to 150 ° C. Further, from the viewpoint of workability and economy, 3 to 15% by weight is more preferable.
[0020]
What is important in the present invention is a sealing resin using an addition salt (C) comprising a basic azabicyclo compound (A) and an aralkyl resin (B) having an acidic hydroxyl group as an epoxy resin curing accelerator. When the composition is cured by heating, the addition salt (C) is well dispersed in the resin to sufficiently exhibit the ability of the epoxy resin and the curing agent as a curing accelerator. Whether the dispersibility is good or not can be determined by using a certain amount of the addition salt (C) at the time of the hardening reaction or not to reach a predetermined hot hardness in a certain time. When a portion having an abnormally high concentration of the azabicyclo compound (A) as a constitutional unit is formed during the preparation of the addition salt (C), even if the overall softening point is low (for example, 150 ° C. or lower), the addition is locally performed. The salt (C) has a softening point of 150 ° C. or higher, and when heated and cured using this, the addition salt (C) is not sufficiently melted, so that the dispersion in the resin composition becomes poor and a sufficient curing reaction is caused. As a result, a predetermined hot hardness cannot be obtained in a short time. For this reason, in the preparation of conventional DBU and phenol-novolak addition salts, measures have been taken by optimizing the production process such as a mixing method in order to prevent the formation of a high melting point substance, but it has not been sufficient. On the other hand, with the addition salt (C) comprising the azabicyclo compound (A) and the aralkyl resin (B), the dispersibility is unexpectedly good, and the hot hardness required for molding can be reached in a short time. The reason is that the aralkyl resin (B) having a hydroxyl group used in the present invention has a lower acidity because the number of hydroxyl groups per unit molecular chain is smaller than that of the conventional phenol-novolak resin, and the azabicyclo compound (A) This is probably because the balance between acidity and basicity is extremely good.
[0021]
The addition salt (C) used in the present invention is used as a curing accelerator by adding it to a resin composition containing an epoxy resin and a curing agent. The addition amount of the addition salt (C) is usually 0.1 to 15 parts by weight based on 100 parts by weight of the epoxy resin, and is appropriately adjusted depending on the reactivity of the epoxy resin and the curing agent. 1 to 5 parts by weight is preferred.
[0022]
Two or more other epoxy resin curing accelerators may be used in combination as long as the properties of the addition salt (C) of the present invention are not impaired. As other curing accelerators, for example, imidazole compounds such as 2-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 2-heptadecylimidazole and their addition salts, triethylamine, benzyldimethylamine, α- Tertiary amine compounds such as methylbenzyldimethylamine, and their addition salts, triphenylphosphine, tributylphosphine, tri (p-methylphenyl) phosphine, tri (nonylphenyl) phosphine, triphenylphosphine triphenylborate, tetraphenyl Organic phosphine compounds such as phosphine / tetraphenylborate are exemplified.
[0023]
In the encapsulating resin composition of the present invention, any epoxy resin may be used as long as it has an epoxy group, but a resin obtained by converting a phenolic hydroxyl group to glycidyl ether is preferably used. Specific examples include 4,4'-bis (2,3-epoxypropoxy) biphenyl, 4,4'-bis (2,3-epoxypropoxy) -3,3 ', 5,5'-tetramethylbiphenyl, 4,4'-bis (2,3-epoxypropoxy) -3,3 ', 5,5'-tetramethyl-2-chlorobiphenyl, 4,4'-bis (2,3-epoxypropoxy) -3, Biphenyl type epoxy resin such as 3 ', 5,5'-tetraethylbiphenyl, 1,5-di (2,3-epoxypropoxy) naphthalene, 1,5-di (2,3-epoxypropoxy) -7-methylnaphthalene 1,6-di (2,3-epoxypropoxy) naphthalene, 1,6-di (2,3-epoxypropoxy) -2-methylnaphthalene, 1,6-di (2,3-epoxypropoxy) -8 -Methyl naph Naphthalene-type epoxy resins such as len, 1,6-di (2,3-epoxypropoxy) -4,8-dimethylnaphthalene and 2,7-di (2,3-epoxypropoxy) naphthalene, and cresol-novolak-type epoxy resins And phenol novolak type epoxy resins, various novolak type epoxy resins synthesized from bisphenol A and resorcinol, phenol aralkyl type epoxy resins, and naphtho aralkyl type epoxy resins.
[0024]
Phenol-based curing agents include phenol novolak resin, cresol novolak resin, tris (hydroxyphenyl) methane, 1,1,2-tris (hydroxyphenyl) ethane, and 1,1,3-tris (hydroxyphenyl) propane. , Bisphenol A, bisphenol F, dihydroxybiphenyl, phenol aralkyl resin, naphtho aralkyl resin, polyhydroxystyrene and the like.
[0025]
In the present invention, the mixing equivalent ratio of the epoxy resin and the phenolic curing agent (for example, the molar ratio of hydroxyl group to epoxy group) is usually 0.7 to 1.3, but preferably 0.8 to 1.3. .1.
[0026]
In the sealing resin composition of the present invention, an inorganic filler is blended. The amount is preferably from 75 to 95% by weight of the entire sealing resin composition. When the ratio of the inorganic filler to the whole is not in the above range, the moldability and the solder heat resistance deteriorate. Examples of the inorganic filler include fused silica, crystalline silica, alumina, talc, calcium sulfate, and aluminum nitride. The shape of the inorganic filler is not particularly limited, and for example, a spherical or crushed inorganic filler is arbitrarily used. These inorganic fillers are preferably surface-treated with a silane coupling agent such as epoxy silane, amino silane, mercapto silane and the like, from the viewpoint of improving the moisture resistance reliability.
[0027]
Further, as other additives to the sealing resin composition, for example, rubber components such as silicone rubber, butadiene rubber, modified nitrile rubber, modified polybutadiene rubber, modified silicone rubber, paraffin wax, long-chain fatty acids, and long-chain fatty acids Release agents such as esters, metal salts of long chain fatty acids, modified silicone oils, flame retardants such as halogenated epoxy resins, halogen compounds and phosphorus compounds, flame retardant aids such as antimony trioxide, and carbon black. A coloring agent and a thermoplastic resin such as polyethylene can be optionally added.
[0028]
The sealing resin composition of the present invention is preferably melt-kneaded, and is manufactured by melt-kneading using a known kneading method such as a kneader, a roll, a single-screw or twin-screw extruder and a co-kneader. .
[0029]
The encapsulating resin composition of the present invention is usually used for encapsulating a semiconductor in a powder or tablet state. For a member in which the semiconductor is fixed to the substrate, for example, using a low-pressure transfer molding machine, the sealing resin composition is molded at a temperature of, for example, 120 to 250 ° C., preferably 150 to 200 ° C. By using the cured product of the composition, a semiconductor device sealed with the cured product of the sealing resin composition is manufactured. If necessary, additional heat treatment (for example, 150 to 200 ° C., 2 to 15 hours) can be performed.
[0030]
【Example】
Example of Preparation of Addition Salt An example of preparation of the addition salt (C) used in the present invention is described below.
[0031]
A 2-liter stainless steel container was charged with 552 g of a phenol aralkyl resin having the above-mentioned structure (VIII) and having a melt viscosity of 2.3 poise at 150 ° C. and melted at 150 ° C. Next, while the molten phenol aralkyl resin was being stirred well, 48 g of DBU was added dropwise over 15 minutes, and after the addition, stirring was continued for another 15 minutes. After cooling, it was pulverized and classified with a 42-mesh sieve (addition salt No. 1). Various addition salts were prepared in the same manner, and other addition salts (C) were prepared as shown in Table 1. Table 1 shows the physical properties of the obtained addition salt.
[0032]
[Table 1]

[0033]
Examples 1 to 5, Comparative Examples 1 to 3
The blends shown in Tables 1 and 2 were blended using a mixer at the composition ratios shown in Table 3 (Examples 1 to 5, Comparative Examples 1 to 3). This was melt-kneaded using a twin-screw extruder with a barrel setting temperature of 90 ° C., and then cooled and pulverized to produce a sealing resin composition.
[0034]
Comparative Examples 1 and 2 used an addition salt of a phenol novolak resin and DBU, and Comparative Example 3 added DBU to an encapsulating resin composition without using an addition salt.
[0035]
[Table 2]

[0036]
[Table 3]

[0037]
A semiconductor was sealed using this sealing resin composition to obtain a semiconductor device. In addition, the following solder heat resistance test and formability test were performed.
Solder heat resistance test: A 160-pin QFP device (package size: 28 × 28 × 3.3 mm, chip size: 10.4 × 10.4 × 0.5 mm) using a low-pressure transfer molding machine to apply the sealing resin composition. It was molded under the conditions of 175 ° C. × 180 seconds and cured at 175 ° C. for 12 hours. The 16 test devices were humidified in an 85 ° C./85% RH atmosphere for 120 hours, and then passed through an IR (infrared) reflow furnace heated to 245 ° C. for about 10 seconds. Here, the device in which the external crack occurred was regarded as defective.
Formability test: A disk (60φ × 3 mm) was molded at 175 ° C. × 60 seconds using a low-pressure transfer molding machine, and the disk's hot hardness at 175 ° C. was measured using a bar call hardness tester. The measurement was performed (the measurement method was based on ASTM, D2583-92). Table 4 shows the obtained results.
[0038]
[Table 4]

[0039]
As shown in Table 4, the resin composition for sealing of the present invention (Examples 1 to 5) is more excellent in solder heat resistance than the compositions of Comparative Examples (Comparative Examples 1 to 4). Furthermore, the sealing resin composition (Examples 1 to 5) of the present invention has a high heat hardness even at a very short molding time of 175 ° C. and 60 seconds, so that molding can be performed at high speed. Comparative Examples 1-4 also have poor moldability.
[0040]
【The invention's effect】
The present invention is a sealing resin composition characterized by using an addition salt composed of an azabicyclo compound and an aralkyl resin having a specific hydroxyl group as a curing accelerator, and has both high-speed moldability and high solder heat resistance. Therefore, it is useful as a resin composition for semiconductor encapsulation for surface mounting. In addition, a semiconductor device encapsulated with the encapsulating resin composition of the present invention has few external crack defects after surface mounting, and thus has high semiconductor operation reliability.

Claims (7)

In an encapsulating resin composition containing an epoxy resin, a phenolic curing agent, and an inorganic filler, an azabicyclo compound (A) represented by the following general formula (I) as a curing accelerator and a general formula (II) A resin composition for sealing characterized by adding an addition salt (C) with an aralkyl resin (B) having a structural unit represented by the formula (1):

(However, n represents an integer of 2 to 10. The carbon atom or hydrogen atom of the methylene group in the ring may be partially substituted with another atom or another substituent.)

(However, Ar ² represents a divalent aromatic group having a phenolic hydroxyl group. Ar ² and the phenylene group may be substituted with an organic group or a halogen atom.) The sealing resin composition according to claim 1, wherein the softening temperature of the addition salt (C) is 50 to 150C. The sealing resin composition according to claim 1, wherein the aralkyl resin (B) is represented by the general formula (III).

(However, Ar ¹ represents a monovalent aromatic group having a phenolic hydroxyl group, and Ar ² is the same as described in the formula (II). Ar ¹ and the phenylene group are substituted by an organic group or a halogen atom.) M represents an integer of 0 or more.) The resin composition for sealing according to claim 3, wherein m in the general formula (III) representing the aralkyl resin (B) is 0 to 20. The sealing resin composition according to claim 3, wherein the aralkyl resin (B) has a melt viscosity at 150C of 0.3 to 50 poise. The content of the azabicyclo compound (A) in the addition salt (C) is 0.1 to 30% by weight, and the content of the aralkyl resin (B) is 99.9 to 70% by weight. 5. The encapsulating resin composition according to any one of 5. A semiconductor device, wherein a semiconductor is sealed with a cured product of the sealing resin composition according to claim 1.