JP3740355B2

JP3740355B2 - Optical semiconductor element storage package

Info

Publication number: JP3740355B2
Application number: JP2000255961A
Authority: JP
Inventors: 美津夫柳沢; 伸松田; 清吾松園
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2000-08-25
Filing date: 2000-08-25
Publication date: 2006-02-01
Anticipated expiration: 2020-08-25
Also published as: JP2002076493A

Description

【０００１】
【発明の属する技術分野】
本発明は、光半導体素子を収納するための光半導体素子収納用パッケージに関するものである。
【０００２】
【従来の技術】
従来の光半導体素子を収納するための光半導体素子収納用パッケージ（以下、光半導体パッケージという）を図３，図４に示す。これらの図に示すように、基体１１は、凹状または平板状のアルミナ（Ａｌ₂Ｏ₃）セラミックス，窒化アルミニウム（ＡｌＮ）セラミック，ガラスセラミックス等のセラミックスから成り、上面に光半導体素子１３と光ファイバ１５とを載置するための載置部１１ａを有し、この載置部１１ａ上に光半導体素子１３と光ファイバ１５とが間に載置用基板１４を挟んで金（Ａｕ）−錫（Ｓｎ）ロウ材等の接着剤により接着固定され、さらに基体１１の下面には、相対する２辺沿いに形成され、外部電気回路基板１７と半導体パッケージとを電気的に接続する電極パッド１６が設けられている。
【０００３】
この基体１１の上面には、光半導体素子１３を封止するために、蓋体１２がシーム溶接，ロウ付け，樹脂付け等により接合され、その蓋体１２は鉄（Ｆｅ）−ニッケル（Ｎｉ）−コバルト（Ｃｏ）合金やＦｅ−Ｎｉ合金等の金属材料や、アルミナセラミックス，窒化アルミニウムセラミックス，ガラスセラミックス等のセラミックスや、エポキシ樹脂等の樹脂から成る。
【０００４】
そして、光半導体パッケージは基本的に基体１１と蓋体１２とから成り、内部に光半導体素子１３を収納する容器を構成する。
【０００５】
なお、電極パッド１６は、光半導体パッケージと外部電気回路基板１７との高周波信号の反射による損失や実装ずれ等を有効に防止し、高周波信号の伝送を円滑なものとするために、外部電気回路基板１７に形成された錫（Ｓｎ）−鉛（Ｐｂ）半田，錫−銀（Ａｇ）半田等から成る半田ペーストや半田ボール等の導体バンプ１７ａを介して外部電気回路基板１７に接合される。
【０００６】
【発明が解決しようとする課題】
しかしながら、上記の従来の光半導体パッケージの内部に、光の結合効率が良好となるように光半導体素子１３と光ファイバ１５とを間に載置用基板１４を介して接着固定した後、外部電気回路基板１７に電極パッド１６を介して実装し温度サイクル試験（Thermal Cycle Test；ＴＣＴ）や熱衝撃試験（Thermal Shock Test；ＴＳＴ）等の環境試験を行うと、光半導体パッケージと外部電気回路基板１７との熱膨張差による歪みが発生する。
【０００７】
この歪みは、導体バンプ１７ａが緩衝機能をも有していることから、下面の相対する２辺であって光ファイバ１５に平行な２辺沿いに形成される電極パッド１６の周辺部では非常に小さいものとなるが、基体１１下面の導体バンプ１７ａが配されない部位では、光半導体パッケージと外部電気回路基板との間の熱膨張差による歪みが大きくなる。即ち、導体バンプ１７ａが配されない基体１１下面の載置用基板１４直下の部位では歪みが大きくなり、そのため、基体１１に強固に接合されている載置用基板１４が基体１１の歪みと同様に変形する。そのため、光半導体素子１３と光ファイバ１５との光軸がずれ、光の結合効率が低下し光半導体素子１３の作動性を損なうという問題点を有していた。
【０００８】
この熱歪みを有効に防止するために、電極パッド１６の面積をより大きくし、半導体パッケージと外部電気回路基板１７との接合を強固なものとすることも考えられるが、この場合、電極パッド１６に濡れる半田から成る導体バンプ１７ａも大きくなるため、高周波信号の反射による損失が大きくなり、１ＧＨｚ以上の高周波信号の伝送には不向きなものとなる。
【０００９】
また、基体１１下面の厚さを厚くし、その剛性を強化することにより外部電気回路基板１７との熱膨張差による歪みを小さくすることも考えられるが、この場合、半導体パッケージを高背化することとなり、近時の光半導体パッケージの低背化，軽量化の目的から外れることとなる。
【００１０】
本発明は、上記問題点に鑑み完成されたものであり、その目的は、高周波信号の伝送特性の劣化を有効に防止し、また光半導体パッケージを高背化するようなことがなく、更には環境試験によって光の結合効率が低下するのを有効に防止することにより、光半導体素子の作動性を長期間にわたり正常かつ安定なものとすることにある。
【００１１】
【課題を解決するための手段】
本発明は、光半導体素子を載置用基板を介して載置し収容するための凹部が上面に形成され、かつ前記載置用基板上に端部が載置固定される光ファイバを挿入するための貫通孔が側部に形成された略直方体の基体と、前記基体の下面の前記光ファイバに略平行な相対する２辺に沿って配列形成され、前記光半導体素子と外部との電気的な接続を行う複数の電極パッドと、前記基体の上面に前記光半導体素子を封止するように取着される蓋体とを具備した光半導体素子収納用パッケージであって、前記下面の前記載置用基板直下の領域とこれを前記光ファイバの光軸方向に延長した領域とに、幅が０．３ｍｍ以上で前記電極パッドよりも小さい接続パッドが配列のピッチを０．５ｍｍ以上として複数設けられていることを特徴とする。
【００１２】
本発明は、上記の構成により、光半導体素子を載置固定し、光の結合効率が良好となるように光ファイバを光半導体パッケージに装着した後、外部電気回路基板に電極パッド，接続パッドをそれぞれ導体バンプ，バンプを介して実装し温度サイクル試験や熱衝撃試験等の環境試験を行っても、接続パッドにより光半導体パッケージと外部電気回路基板との間に発生する熱歪みを非常に小さいものとできる。
【００１３】
即ち、複数の接続パッドが基体下面の載置用基板直下の領域とこれを光ファイバの光軸方向に延長した領域とに分布して形成されているため、接続パッドに接合されるバンプが、環境試験の際に外部電気回路基板と基体下面の載置用基板直下の部位との間に発生する熱歪みを非常に小さいものとする。即ち、接続パッドに接合されるバンプは熱歪みの緩衝機能および剛性強化機能を有する。その結果、載置用基板の変形が有効に防止され、載置用基板上面に載置固定される、光半導体素子と光ファイバとの光軸がずれることがなく、それらの光の結合効率を良好に保持し得る。
【００１４】
従って、高周波信号の伝送特性の劣化を有効に防止し、また半導体パッケージを高背化するようなことがなく、更には環境試験による光の結合効率が低下するのを有効に防止でき、光半導体素子を長期間にわたり正常かつ安定に作動させ得る。
【００１５】
【発明の実施の形態】
本発明の光半導体パッケージについて以下に説明する。図１は本発明の光半導体パッケージの断面図，図２は基体の下面の平面図を示し、これらの図において、１は基体、２は蓋体である。これら基体１と蓋体２とで、内部に光半導体素子３が収納される容器が構成される。
【００１６】
基体１は、アルミナ（Ａｌ₂Ｏ₃）セラミックス，窒化アルミニウム（ＡｌＮ）セラミック，ガラスセラミックス等のセラミックスから成り、その形状は略直方体である。基体１は、その上面に形成された凹部の底面に光半導体素子３を載置するための載置部１ａを有し、この載置部１ａに光半導体素子３と光ファイバ５の端部とが、載置用基板４を介して金−錫ロウ材等の接着剤により接着固定される。また、基体１の側部には光ファイバ５を挿入するための貫通孔１ｂが形成される。
【００１７】
基体１の下面には、その下面の光ファイバ５に略平行な相対する２辺に沿って配列形成され、外部電気回路基板７と半導体パッケージとを接続する複数の電極パッド６を有する。更には、下面の載置用基板４直下の領域とこれを光ファイバ５の光軸方向に延長した領域とを合わせた領域Ｒ、すなわち光ファイバ５の光軸方向における載置用基板４の長さＬを超えた領域Ｒ内に分布するとともに、電極パッド６よりも幅（円形の場合は直径）が小さい接続パッド８が複数設けられる。この接続パッド８は、熱歪みの緩衝効果および剛性強化効果を向上させるために設けられる。
【００１８】
この基体１は、その原料粉末に適当な有機バインダや溶剤等を添加混合しペースト状と成すとともに、このペーストをドクターブレード法やカレンダーロール法によってセラミックグリーンシートと成し、しかる後セラミックグリーンシートに適当な打ち抜き加工を施し、これを複数枚積層し約１６００℃の高温で焼成することによって作製される。
【００１９】
また、光半導体素子３を載置する載置部１ａに耐蝕性に優れかつロウ材との濡れ性に優れる金属、具体的には厚さ０．５〜９μmのニッケル（Ｎｉ）層と厚さ０．５〜９μmの金（Ａｕ）層とを順次メッキ法により被着させておくと、基体１内部の底面に光半導体素子３を強固に接着固定できる。
【００２０】
また、この基体１内部の載置用基板４は、シリコン（Ｓｉ）等の放熱性および加工性の良好な基板から成り、その上面には光半導体素子３や光ファイバ５等を搭載する搭載部を有している。
【００２１】
また、この基体１の下面の相対する２辺沿いには、外部電気回路基板７と半導体パッケージとを接続する複数の電極パッド６が形成されている。この電極パッド６は、光半導体パッケージと外部電気回路基板７との高周波信号の反射による損失や実装ずれ等を有効に防止し、高周波信号の伝送を円滑なものとするために、外部電気回路基板７に形成された錫−鉛半田，錫−銀半田等から成る半田ペーストや半田ボール等の導体バンプ７ａを介して外部電気回路基板７に接合される。
【００２２】
この電極パッド６は、タングステン（Ｗ）やモリブデン（Ｍｏ）、マンガン（Ｍｎ）等のメタライズ層で形成されており、例えば、タングステン等の粉末に有機溶剤、溶媒等を添加混合して得た金属ペーストを、上述のセラミックグリーンシートに、予め従来周知のスクリーン印刷法により、円形状等の所定パターンに印刷塗布しておくことによって成される。
【００２３】
なお、この電極パッド６表面には、耐蝕性に優れかつロウ材との濡れ性に優れる金属、具体的には厚さ０．５〜９μmのニッケル層と、厚さ０．５〜９μmの金層を順次メッキ法により被着させておくと、電極パッド６が酸化腐食するのを有効に防止できるとともに、外部電気回路基板７に形成された錫−鉛半田，錫−銀半田等から成る半田ペーストや半田ボール等の導体バンプ７ａを介して外部電気回路基板７に強固に接合できる。
【００２４】
また、本発明において、基体１下面の載置用基板４直下を含む領域Ｒに複数の接続パッド８が形成されて成る。この接続パッド８は、光半導体素子３を載置固定し、光の結合効率が良好となるように光ファイバ５を光半導体パッケージに装着した後、外部電気回路基板７に電極パッド６，接続パッド８をそれぞれ導体バンプ７ａ，バンプ７ｂを介して実装し、温度サイクル試験や熱衝撃試験等の環境試験を行っても、光半導体パッケージと外部電気回路基板７との間に発生する熱歪みを非常に小さいものとできる。
【００２５】
即ち、接続パッド８が領域Ｒに形成されているため、接続パッド８に接合されるバンプ７ｂが、環境試験により外部電気回路基板７と基体１下面の載置用基板４直下面との間に発生する熱歪みを非常に小さいものとできる所謂緩衝機能、剛性強化機能を有することとなる。そのため、載置用基板４の変形が有効に防止され、載置用基板４上面に載置固定される光半導体素子３と光ファイバ５との光軸がずれることがなく、それらの光の結合効率を損なうことがない。その結果、高周波信号の伝送特性の劣化を有効に防止し、また光半導体パッケージを高背化するようなことがなく、更には環境試験によって光の結合効率が低下するのを有効に防止でき、光半導体素子３を長期間にわたり正常かつ安定に作動させ得る。
【００２６】
具体的には、基体１下面の熱歪みによる光半導体素子３と光ファイバ５との光軸のずれは、光ファイバ５の光軸方向において大きくなる。即ち、光軸方向が上下にずれることにより、それらの光学的な結合効率が低下することとなる。従って、基体１の下面の載置用基板４直下の領域とこれを光ファイバ５の光軸方向に延長した領域に接続パッド８を分布させることで、光ファイバ５の光軸方向における基体１の下面の変形を効果的に抑えることができる。また、電極パッド６よりも幅の小さい接続パッド８とすることで、さらに基体１の下面の変形量が小さくなるようにし得る。
【００２７】
この接続パッド８は、その平面形状は円形状，楕円形状，多角形状であっても良いが、バンプ７ｂが十分な緩衝機能を有するようにするためには、円形状でかつその寸法を調整しておくほうが好ましい。一方、バンプ７ｂが十分な剛性強化機能を有するようにするためには、バンプ７ｂの基体１，外部電気回路基板７に対する接触面積が大きいものとするのが好ましい。例えば、接続パッド８を０．３ｍｍφ（直径），０．５ｍｍピッチで基体１下面の領域Ｒに複数形成し環境試験を行った場合、光ファイバ５からの光出力が、一般的な光出力の要求値である±０．５ｄＢを十分に満足できることが判った。即ち、接続パッド８に接合されているバンプ７ｂが、外部電気回路基板７と基体１下面の載置用基板４直下の部位との間に発生する熱歪みを十分に緩和する緩衝機能を有することが判明した。
【００２８】
一方、接続パッド８を０．３ｍｍφ未満とした場合、光出力の要求値を十分に満足できなかった。この場合のバンプ７ｂを環境試験後に観察すると、バンプ７ｂの外部電気回路基板７側やバンプ７ｂの基体１側にクラックや、剥がれが発生しており、即ち外部電気回路基板７と基体１下面の載置用基板４直下との間に発生する熱歪みを十分に緩和することができないことが分かった。従って、接続パッド８は０．３ｍｍφ以上であることが好ましい。
【００２９】
また、０．３ｍｍφの接続パッド８を０．５ｍｍピッチ未満で領域Ｒに複数形成した場合、半田等から成る隣接したバンプ７ｂ同士がブリッジ状に接続される現象（通称ブリッジ）を起こす危険性がある。即ち、バンプ７ｂが全てブリッジを起こせばよいが、ブリッジを起こしたり起こさなかったりする部位が発生することの方が多く、その場合基体１とバンプ７ｂとの間で発生する熱応力のバランスが崩れて、ブリッジを起こす部位での熱歪みが非常に大きくなる。その結果、外部電気回路基板７と基体１下面の載置用基板４直下の部位との間に発生する熱歪を十分に緩和できなくなる。
【００３０】
好ましくは、接続パッド８のピッチは２ｍｍ以下がよく、２ｍｍを超えると、バンプ７ｂによる剛性強化機能が不十分となり、その結果外部電気回路基板７と基体１下面の載置用基板４直下の部位との間に発生する熱歪を十分に緩和できなくなる。
【００３１】
また、この接続パッド８は、光半導体素子３やその周囲の配線パターンと外部電気回路基板７とを電気的に接続するように、基体１の底面にビアホール等の貫通導体を形成しその貫通導体に接続されていても構わない。
【００３２】
また、バンプ７ｂは、導体バンプ７ａと同様に錫−鉛半田，錫−銀半田等から成る半田ペーストや半田ボールであっても良いが、銅ボール，銀ボール等の軟性に優れる金属ボールを半田ペーストを介して接合したものであっても良い。
【００３３】
なお、バンプ７ｂは、導体バンプ７ａと同じ高さであることがよく、その場合、バンプ７ｂと接続パッド８との接合信頼性および導体バンプ７ａと電極パッド６との接合信頼性を同様のものとできる。即ち、光半導体パッケージを外部電気回路基板７に接続した際に、その接合部位における接合信頼性のばらつきが発生し難くなる。このように、光半導体パッケージと外部電気回路基板７との接合信頼性は、その接合部位の高さによっても影響を受けるため、高さのばらつきはない方がよい。
【００３４】
このように、本発明の接続パッド８は、環境試験を行った場合に、基体１下面の載置用基板４直下面と外部電気回路基板７との熱歪みによる、光半導体素子３と光ファイバ５との光の結合効率の低下を有効に防止するためのもの、即ち緩衝機能、剛性強化機能を有するバンプ７ｂを接合するための媒体として機能する。
【００３５】
また基体１の上面には、光半導体素子３を封止するための蓋体２がシーム溶接，ロウ付け，樹脂付け等により接合される。この蓋体３は、Ｆｅ−Ｎｉ−Ｃｏ合金やＦｅ−Ｃｏ合金等の金属材料や、アルミナセラミックス，窒化アルミニウムセラミック，ガラスセラミックス等のセラミックス、エポキシ樹脂等の樹脂から構成されている。
【００３６】
本発明の光半導体パッケージは、基体１の載置部１ａにＬＤ，ＰＤ等の光半導体素子３と光ファイバ５の端部とを載置用基板４を介して接着固定するとともに、基体１上面の凹部内に光半導体素子３を収容して蓋体２で封止し、この基体１の下面の電極パッド６と接続パッド８とをそれぞれ導体バンプ７ａ，バンプ７ｂを介して外部電気回路基板７に接合することにより製品としての光半導体装置となる。
【００３７】
かくして、本発明は、基体１下面の載置用基板４直下の部位を含む領域に形成された接続パッド８が、基体１下面の載置用基板４直下の部位と外部電気回路基板７との熱歪みを緩和，抑制するバンプ７ｂを接合するための媒体として機能する。その結果、基体１と外部電気回路基板７との熱歪みによって、光半導体素子３と光ファイバ５との光軸がずれて光の結合効率が低下するのを有効に防止でき、光半導体素子の作動性を長期間にわたり正常かつ安定なものとできる。
【００３８】
なお、本発明は上記実施の形態に限定されず、本発明の要旨を逸脱しない範囲内において種々の変更を行うことは何等支障ない。例えば、基体１が平板状のものの場合、別個の枠体を基体１の上面の周縁部に接合させてもよい。また、光半導体素子３を気密に封止する必要の無い場合、基体１は凹部を有するものではなく平板状から成る場合であっても良く、この場合蓋体２はエポキシ樹脂等から成る樹脂から成り、これを光半導体素子３に覆うように樹脂モールドすれば良い。
【００３９】
【発明の効果】
本発明は、基体の下面の光ファイバに略平行な相対する２辺に沿って配列形成され、光半導体素子と外部との電気的な接続を行う複数の電極パッドと、基体の上面に光半導体素子を封止するように取着される蓋体とを具備し、下面の載置用基板直下の領域とこれを光ファイバの光軸方向に延長した領域とに、幅が０．３ｍｍ以上で電極パッドよりも小さい接続パッドが配列のピッチを０．５ｍｍ以上として複数設けられていることにより、光半導体素子を載置固定し、光の結合効率が良好となるように光ファイバを光半導体パッケージに装着した後、外部電気回路基板に電極パッド，接続パッドをそれぞれ導体バンプ，バンプを介して実装し温度サイクル試験や熱衝撃試験等の環境試験を行っても、接続パッドにより光半導体パッケージと外部電気回路基板との間に発生する熱歪みを非常に小さいものとできる。即ち、接続パッドに接合されるバンプは熱歪みの緩衝機能および剛性強化機能を有するものとなり、その結果載置用基板の変形が有効に防止され、載置用基板上面に載置固定される、光半導体素子と光ファイバとの光軸がずれることがなく、それらの光の結合効率を良好に保持し得る。従って、高周波信号の伝送特性の劣化を有効に防止し、また半導体パッケージを高背化するようなことがなく、光半導体素子を長期間にわたり正常かつ安定に作動させ得る。
【図面の簡単な説明】
【図１】本発明の光半導体パッケージを示し、実施の形態の一例を示す断面図である。
【図２】図１の光半導体パッケージの基体下面の平面図である。
【図３】従来の光半導体パッケージの断面図である。
【図４】図３の光半導体パッケージの基体下面の平面図である。
【符号の説明】
１：基体
１ａ：載置部
２：蓋体
３：光半導体素子
５：光ファイバ
６：電極パッド
８：接続パッド[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical semiconductor element storage package for storing an optical semiconductor element.
[0002]
[Prior art]
A conventional optical semiconductor element housing package (hereinafter referred to as an optical semiconductor package) for housing an optical semiconductor element is shown in FIGS. As shown in these drawings, the base 11 is made of ceramics such as concave or flat alumina (Al ₂ O ₃ ) ceramics, aluminum nitride (AlN) ceramics, glass ceramics, etc., and an optical semiconductor element 13 and an optical fiber on the upper surface. 15, and an optical semiconductor element 13 and an optical fiber 15 sandwich the mounting substrate 14 between the gold (Au) -tin ( Sn) Bonded and fixed by an adhesive such as a brazing material, and further provided on the lower surface of the base 11 along two opposite sides, and electrode pads 16 are provided for electrically connecting the external electric circuit board 17 and the semiconductor package. It has been.
[0003]
A lid 12 is joined to the upper surface of the base 11 by seam welding, brazing, resin bonding or the like in order to seal the optical semiconductor element 13. The lid 12 is made of iron (Fe) -nickel (Ni). -It consists of metal materials, such as a cobalt (Co) alloy and a Fe-Ni alloy, ceramics, such as an alumina ceramics, aluminum nitride ceramics, and glass ceramics, and resin, such as an epoxy resin.
[0004]
The optical semiconductor package basically includes a base body 11 and a lid body 12 and constitutes a container for storing the optical semiconductor element 13 therein.
[0005]
The electrode pad 16 effectively prevents loss or mounting displacement due to reflection of the high-frequency signal between the optical semiconductor package and the external electric circuit board 17, and makes it possible to smoothly transmit the high-frequency signal. The substrate 17 is bonded to the external electric circuit substrate 17 through a conductor bump 17a such as a solder paste or a solder ball made of tin (Sn) -lead (Pb) solder, tin-silver (Ag) solder, or the like.
[0006]
[Problems to be solved by the invention]
However, after the optical semiconductor element 13 and the optical fiber 15 are bonded and fixed to each other through the mounting substrate 14 in the above conventional optical semiconductor package so that the light coupling efficiency is good, the external electric When an environmental test such as a temperature cycle test (Thermal Cycle Test; TCT) or a thermal shock test (Thermal Shock Test; TST) is performed on the circuit board 17 via the electrode pads 16, the optical semiconductor package and the external electric circuit board 17 And distortion due to the difference in thermal expansion.
[0007]
This distortion is very large at the periphery of the electrode pad 16 formed along two opposite sides of the lower surface and parallel to the optical fiber 15 because the conductor bump 17a also has a buffering function. Although it is small, the distortion due to the difference in thermal expansion between the optical semiconductor package and the external electric circuit board becomes large at the portion where the conductor bump 17a on the lower surface of the base 11 is not disposed. That is, distortion is increased at a portion directly below the mounting substrate 14 on the lower surface of the base body 11 where the conductor bumps 17 a are not disposed. Therefore, the mounting substrate 14 firmly bonded to the base body 11 is similar to the distortion of the base body 11. Deform. For this reason, the optical axes of the optical semiconductor element 13 and the optical fiber 15 are deviated, so that the light coupling efficiency is lowered and the operability of the optical semiconductor element 13 is impaired.
[0008]
In order to effectively prevent this thermal distortion, it is conceivable to increase the area of the electrode pad 16 and strengthen the bonding between the semiconductor package and the external electric circuit board 17, but in this case, the electrode pad 16 Since the conductor bumps 17a made of solder that gets wet with the solder also become larger, the loss due to the reflection of the high-frequency signal becomes large, making it unsuitable for transmission of a high-frequency signal of 1 GHz or higher.
[0009]
It is also conceivable to reduce the distortion due to the difference in thermal expansion with the external electric circuit board 17 by increasing the thickness of the lower surface of the base 11 and strengthening its rigidity. In this case, however, the semiconductor package is made taller. In other words, it will be out of the recent aim of reducing the height and weight of the optical semiconductor package.
[0010]
The present invention has been completed in view of the above problems, and its purpose is to effectively prevent the deterioration of the transmission characteristics of high-frequency signals, and without increasing the height of the optical semiconductor package. It is to make the operability of the optical semiconductor element normal and stable for a long period of time by effectively preventing the light coupling efficiency from being lowered by the environmental test.
[0011]
[Means for Solving the Problems]
The present invention inserts an optical fiber having a recess formed on the upper surface for mounting and housing an optical semiconductor element via a mounting substrate, and an end mounted and fixed on the mounting substrate. A substantially rectangular parallelepiped base having through-holes formed on the side portions thereof, and an array formed along two opposing sides substantially parallel to the optical fiber on the lower surface of the base. A package for storing an optical semiconductor element, comprising: a plurality of electrode pads for performing simple connection; and a lid attached to the upper surface of the base so as to seal the optical semiconductor element. A plurality of connection pads having a width of 0.3 mm or more and smaller than the electrode pads are provided in a region immediately below the mounting substrate and a region extending in the optical axis direction of the optical fiber with an arrangement pitch of 0.5 mm or more. It is characterized by being.
[0012]
According to the present invention, the optical semiconductor element is mounted and fixed by the above configuration, and after the optical fiber is mounted on the optical semiconductor package so that the light coupling efficiency is good, the electrode pad and the connection pad are attached to the external electric circuit board. Even if they are mounted via conductor bumps and bumps and are subjected to environmental tests such as temperature cycle tests and thermal shock tests, the thermal distortion generated between the optical semiconductor package and the external electric circuit board by the connection pads is very small. And can.
[0013]
That is, since a plurality of connection pads are distributed and formed in a region directly below the mounting substrate on the lower surface of the base and a region extending in the optical axis direction of the optical fiber, the bumps bonded to the connection pads are It is assumed that the thermal strain generated between the external electric circuit board and the portion directly under the mounting board on the lower surface of the base during the environmental test is very small. That is, the bump bonded to the connection pad has a thermal strain buffering function and a rigidity enhancing function. As a result, the deformation of the mounting substrate is effectively prevented, and the optical axis between the optical semiconductor element and the optical fiber mounted and fixed on the upper surface of the mounting substrate is not shifted, and the coupling efficiency of the light is increased. It can hold well.
[0014]
Therefore, it is possible to effectively prevent the deterioration of the transmission characteristics of high-frequency signals, to prevent the height of the semiconductor package from being increased, and to effectively prevent the light coupling efficiency from being lowered by the environmental test. The device can operate normally and stably over a long period of time.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
The optical semiconductor package of the present invention will be described below. FIG. 1 is a cross-sectional view of an optical semiconductor package of the present invention, and FIG. 2 is a plan view of the lower surface of a base. In these figures, 1 is a base and 2 is a lid. The base body 1 and the lid body 2 constitute a container in which the optical semiconductor element 3 is accommodated.
[0016]
The substrate 1 is made of ceramics such as alumina (Al ₂ O ₃ ) ceramics, aluminum nitride (AlN) ceramics, and glass ceramics, and has a substantially rectangular parallelepiped shape. The base 1 has a mounting portion 1a for mounting the optical semiconductor element 3 on the bottom surface of the recess formed on the upper surface thereof, and the optical semiconductor element 3 and the end portions of the optical fiber 5 are placed on the mounting portion 1a. Are bonded and fixed by an adhesive such as a gold-tin brazing material through the mounting substrate 4. Further, a through hole 1 b for inserting the optical fiber 5 is formed in the side portion of the base 1.
[0017]
The lower surface of the substrate 1 has a plurality of electrode pads 6 that are arranged along two opposite sides substantially parallel to the optical fiber 5 on the lower surface and connect the external electric circuit board 7 and the semiconductor package. Furthermore, a region R obtained by combining a region immediately below the mounting substrate 4 on the lower surface with a region obtained by extending the region in the optical axis direction of the optical fiber 5, that is, the length of the mounting substrate 4 in the optical axis direction of the optical fiber 5. A plurality of connection pads 8 that are distributed in the region R exceeding the length L and have a smaller width (or diameter in the case of a circle) than the electrode pads 6 are provided. The connection pad 8 is provided in order to improve the thermal strain buffering effect and the rigidity enhancing effect.
[0018]
The base 1 is made into a paste by adding and mixing an appropriate organic binder or solvent to the raw material powder, and this paste is formed into a ceramic green sheet by a doctor blade method or a calender roll method. Appropriate punching is performed, and a plurality of these are laminated and fired at a high temperature of about 1600 ° C.
[0019]
Further, a metal having excellent corrosion resistance and wettability with a brazing material, specifically a nickel (Ni) layer having a thickness of 0.5 to 9 μm, and a thickness are provided on the mounting portion 1a on which the optical semiconductor element 3 is mounted. When the gold (Au) layer of 0.5 to 9 μm is sequentially deposited by the plating method, the optical semiconductor element 3 can be firmly bonded and fixed to the bottom surface inside the substrate 1.
[0020]
The mounting substrate 4 in the substrate 1 is made of a substrate having good heat dissipation and workability such as silicon (Si), and a mounting portion on which the optical semiconductor element 3 and the optical fiber 5 are mounted. have.
[0021]
A plurality of electrode pads 6 for connecting the external electric circuit board 7 and the semiconductor package are formed along two opposite sides of the lower surface of the base 1. This electrode pad 6 effectively prevents loss, mounting deviation, etc. due to reflection of high-frequency signals between the optical semiconductor package and the external electric circuit board 7, and enables smooth transmission of the high-frequency signals. 7 is bonded to the external electric circuit board 7 through conductor bumps 7a such as solder paste or solder balls made of tin-lead solder, tin-silver solder or the like.
[0022]
The electrode pad 6 is formed of a metallized layer such as tungsten (W), molybdenum (Mo), or manganese (Mn). For example, a metal obtained by adding an organic solvent, a solvent, or the like to a powder of tungsten or the like. The paste is formed by applying the paste in a predetermined pattern such as a circular shape in advance to the above-described ceramic green sheet by a conventionally known screen printing method.
[0023]
The surface of the electrode pad 6 has a metal excellent in corrosion resistance and wettability with the brazing material, specifically a nickel layer having a thickness of 0.5 to 9 μm and a gold having a thickness of 0.5 to 9 μm. If the layers are sequentially deposited by the plating method, the electrode pad 6 can be effectively prevented from being oxidatively corroded, and the solder made of tin-lead solder, tin-silver solder or the like formed on the external electric circuit board 7 can be used. It can be firmly joined to the external electric circuit board 7 through conductor bumps 7a such as paste and solder balls.
[0024]
Further, in the present invention, a plurality of connection pads 8 are formed in a region R including a portion under the mounting substrate 4 on the lower surface of the base 1. This connection pad 8 is formed by mounting and fixing the optical semiconductor element 3 and mounting the optical fiber 5 on the optical semiconductor package so that the light coupling efficiency is good, and then the electrode pad 6 and the connection pad on the external electric circuit board 7. 8 is mounted via the conductor bumps 7a and 7b, respectively, and even if an environmental test such as a temperature cycle test or a thermal shock test is performed, the thermal strain generated between the optical semiconductor package and the external electric circuit board 7 is extremely low. Can be small.
[0025]
That is, since the connection pad 8 is formed in the region R, the bump 7b bonded to the connection pad 8 is between the external electric circuit board 7 and the lower surface of the mounting substrate 4 on the lower surface of the base body 1 by an environmental test. It has a so-called buffering function and rigidity strengthening function that can reduce the generated thermal strain. Therefore, the deformation of the mounting substrate 4 is effectively prevented, the optical axes of the optical semiconductor element 3 and the optical fiber 5 mounted and fixed on the upper surface of the mounting substrate 4 are not shifted, and the light is coupled. There is no loss of efficiency. As a result, it is possible to effectively prevent the transmission characteristics of the high-frequency signal from being deteriorated, to prevent an increase in the height of the optical semiconductor package, and to effectively prevent the light coupling efficiency from being lowered by the environmental test, The optical semiconductor element 3 can be operated normally and stably over a long period of time.
[0026]
Specifically, the deviation of the optical axis between the optical semiconductor element 3 and the optical fiber 5 due to the thermal strain on the lower surface of the substrate 1 increases in the optical axis direction of the optical fiber 5. That is, when the optical axis direction is shifted up and down, their optical coupling efficiency is reduced. Accordingly, the connection pads 8 are distributed in a region immediately below the mounting substrate 4 on the lower surface of the base 1 and a region extending in the optical axis direction of the optical fiber 5, so that the base 1 in the optical axis direction of the optical fiber 5 is distributed. The deformation of the lower surface can be effectively suppressed. Further, by using the connection pad 8 having a width smaller than that of the electrode pad 6, the deformation amount of the lower surface of the substrate 1 can be further reduced.
[0027]
The connection pad 8 may have a circular shape, an elliptical shape, or a polygonal shape in plan view. However, in order to make the bump 7b have a sufficient buffer function, the connection pad 8 is circular and the size thereof is adjusted. It is better to keep it. On the other hand, in order for the bump 7b to have a sufficient rigidity enhancing function, it is preferable that the contact area of the bump 7b with respect to the substrate 1 and the external electric circuit board 7 is large. For example, when an environmental test is performed by forming a plurality of connection pads 8 in the region R on the lower surface of the substrate 1 at a pitch of 0.3 mmφ (diameter) and 0.5 mm, the light output from the optical fiber 5 is a general light output. It was found that the required value ± 0.5 dB can be sufficiently satisfied. That is, the bump 7b bonded to the connection pad 8 has a buffering function that sufficiently relaxes the thermal distortion generated between the external electric circuit board 7 and the portion immediately below the mounting board 4 on the lower surface of the base 1. There was found.
[0028]
On the other hand, when the connection pad 8 was less than 0.3 mmφ, the required value of light output could not be sufficiently satisfied. When the bumps 7b in this case are observed after the environmental test, cracks and peeling occur on the external electric circuit board 7 side of the bumps 7b and the base body 1 side of the bumps 7b. It was found that the thermal strain generated between the substrate 4 and the mounting substrate 4 cannot be sufficiently relaxed. Therefore, the connection pad 8 is preferably 0.3 mmφ or more.
[0029]
Further, when a plurality of 0.3 mmφ connection pads 8 are formed in the region R with a pitch of less than 0.5 mm, there is a risk of causing a phenomenon in which adjacent bumps 7b made of solder or the like are connected in a bridge shape (commonly called bridge). is there. That is, it is sufficient that the bumps 7b all cause bridging, but there are more portions where bridging occurs or does not occur. In this case, the balance of the thermal stress generated between the substrate 1 and the bumps 7b is lost. As a result, the thermal strain at the site where the bridge occurs becomes very large. As a result, the thermal strain generated between the external electric circuit board 7 and the portion directly below the mounting board 4 on the lower surface of the base body 1 cannot be sufficiently relaxed.
[0030]
Preferably, the pitch of the connection pads 8 is 2 mm or less, and if it exceeds 2 mm, the function of strengthening the rigidity by the bumps 7 b becomes insufficient, and as a result, the portion immediately below the mounting board 4 on the lower surface of the external electric circuit board 7 and the base 1. The thermal strain generated between the two cannot be sufficiently relaxed.
[0031]
Further, the connection pad 8 is formed by forming a through conductor such as a via hole on the bottom surface of the base 1 so as to electrically connect the optical semiconductor element 3 or its surrounding wiring pattern and the external electric circuit board 7. It does not matter if it is connected to.
[0032]
The bump 7b may be a solder paste or a solder ball made of tin-lead solder, tin-silver solder or the like, similar to the conductor bump 7a. It may be joined via a paste.
[0033]
The bump 7b is preferably the same height as the conductor bump 7a. In this case, the bonding reliability between the bump 7b and the connection pad 8 and the bonding reliability between the conductor bump 7a and the electrode pad 6 are the same. And can. That is, when the optical semiconductor package is connected to the external electric circuit board 7, it is difficult for variations in bonding reliability to occur at the bonding site. As described above, since the bonding reliability between the optical semiconductor package and the external electric circuit board 7 is also affected by the height of the bonding portion, it is preferable that the height does not vary.
[0034]
As described above, the connection pad 8 of the present invention has the optical semiconductor element 3 and the optical fiber due to the thermal distortion between the lower surface of the mounting substrate 4 on the lower surface of the substrate 1 and the external electric circuit substrate 7 when an environmental test is performed. 5 functions as a medium for effectively preventing a decrease in the coupling efficiency of light with 5, that is, as a medium for bonding the bump 7 b having a buffer function and a rigidity enhancement function.
[0035]
A lid 2 for sealing the optical semiconductor element 3 is joined to the upper surface of the substrate 1 by seam welding, brazing, resin bonding, or the like. The lid 3 is made of a metal material such as Fe—Ni—Co alloy or Fe—Co alloy, ceramics such as alumina ceramics, aluminum nitride ceramics, and glass ceramics, or a resin such as epoxy resin.
[0036]
In the optical semiconductor package of the present invention, the optical semiconductor element 3 such as LD and PD and the end of the optical fiber 5 are bonded and fixed to the mounting portion 1a of the base body 1 via the mounting substrate 4, and the top surface of the base body 1 is fixed. The optical semiconductor element 3 is accommodated in the concave portion and sealed with the lid 2, and the electrode pad 6 and the connection pad 8 on the lower surface of the base 1 are connected to the external electric circuit board 7 via the conductor bump 7 a and the bump 7 b, respectively. By joining to the optical semiconductor device as a product.
[0037]
Thus, according to the present invention, the connection pad 8 formed in the region including the portion immediately below the mounting substrate 4 on the lower surface of the base 1 is connected to the portion of the lower surface of the base 1 immediately below the mounting substrate 4 and the external electric circuit substrate 7. It functions as a medium for bonding the bumps 7b that relieve and suppress thermal distortion. As a result, it is possible to effectively prevent the optical coupling between the optical semiconductor element 3 and the optical fiber 5 from deviating due to thermal strain between the base 1 and the external electric circuit board 7, thereby reducing the light coupling efficiency. The operability can be normal and stable over a long period of time.
[0038]
It should be noted that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention. For example, when the substrate 1 is a flat plate, a separate frame may be bonded to the peripheral edge of the upper surface of the substrate 1. Further, when the optical semiconductor element 3 does not need to be hermetically sealed, the base body 1 may have a flat shape instead of having a concave portion. In this case, the lid 2 is made of a resin made of epoxy resin or the like. It is sufficient to mold the resin so as to cover the optical semiconductor element 3.
[0039]
【The invention's effect】
The present invention includes a plurality of electrode pads that are formed along two opposite sides substantially parallel to the optical fiber on the lower surface of the base, and that electrically connect the optical semiconductor element to the outside, and an optical semiconductor on the upper surface of the base A lid that is attached so as to seal the element, and a width of 0.3 mm or more between a region immediately below the mounting substrate on the lower surface and a region that extends in the optical axis direction of the optical fiber. By providing a plurality of connection pads smaller than the electrode pads with an arrangement pitch of 0.5 mm or more, the optical semiconductor is mounted and fixed, and the optical fiber is packaged so that the light coupling efficiency is good. After mounting to the external electrical circuit board, the electrode pads and connection pads are mounted via conductor bumps and bumps, respectively, and environmental tests such as temperature cycle test and thermal shock test are performed. Thermal distortion generated between the electric circuit board can be extremely small. That is, the bump bonded to the connection pad has a thermal strain buffering function and a rigidity enhancement function, and as a result, deformation of the mounting substrate is effectively prevented, and the mounting substrate is placed and fixed on the upper surface of the mounting substrate. The optical axes of the optical semiconductor element and the optical fiber are not displaced, and the coupling efficiency of these lights can be maintained well. Therefore, it is possible to effectively prevent the deterioration of the transmission characteristics of the high-frequency signal and to operate the optical semiconductor element normally and stably over a long period of time without increasing the height of the semiconductor package.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing an example of an embodiment showing an optical semiconductor package of the present invention.
2 is a plan view of the lower surface of the base of the optical semiconductor package of FIG. 1. FIG.
FIG. 3 is a cross-sectional view of a conventional optical semiconductor package.
4 is a plan view of the lower surface of the base of the optical semiconductor package of FIG. 3. FIG.
[Explanation of symbols]
1: Base 1a: Placement part 2: Cover body 3: Optical semiconductor element 5: Optical fiber 6: Electrode pad 8: Connection pad

Claims

A through hole for inserting an optical fiber having a recess formed on the top surface for mounting and housing the optical semiconductor element via the mounting substrate, and an end portion mounted and fixed on the mounting substrate. Are arranged along two opposing sides substantially parallel to the optical fiber on the lower surface of the base to make electrical connection between the optical semiconductor element and the outside. An optical semiconductor element storage package comprising a plurality of electrode pads and a lid attached to the upper surface of the base so as to seal the optical semiconductor element, wherein the package is directly below the mounting substrate. A plurality of connection pads having a width of 0.3 mm or more and smaller than the electrode pads are provided in a region extending in the optical axis direction of the optical fiber with an arrangement pitch of 0.5 mm or more. An optical semiconductor element storage pad characterized by Cage.