【０００１】
【発明の属する技術分野】
本発明は、半導体素子や圧電振動子等の電子部品を搭載するための配線基板に関するものである。
【０００２】
【従来の技術】
従来、半導体素子や圧電振動子等の電子部品を搭載するための配線基板は、一般に、略四角板状のセラミックス材料から成り、上面に電子部品搭載部を有する絶縁基体と、該絶縁基体の電子部品搭載部より絶縁基体内部を介して側面に導出されている複数個の配線層と、前記絶縁基体の上面で、前記電子部品搭載部を取り囲むように形成されている枠状の金属層と、前記絶縁基体の下面外周部に形成されている複数個の接続パッドと、前記絶縁基体の側面に形成されるとともに内壁面に導体が被着され、該導体（キャスタレーション導体）により各配線層と各接続パッドとを電気的に接続する複数個の溝状の凹部とにより構成されており、絶縁基体の電子部品搭載部に電子部品を搭載するとともに、電子部品の信号用、接地用等の各電極を各配線層にボンディングワイヤ等の導電性接続部材を介して電気的に接続し、しかる後、絶縁基体上面の枠状金属層に電子部品を覆うようにして鉄−ニッケル−コバルト合金や鉄−ニッケル合金等から成る金属製の蓋体をロウ材等を介して接合し電子部品を封止することによって電子装置となる。
【０００３】
かかる電子装置は、絶縁基体下面の外周部に形成した接続パッドを外部電気回路基板の配線導体に錫−鉛半田等の半田を介して接続することによって外部電気回路基板に実装され、同時に電子部品の各電極は配線層と凹部内壁面の導体（キャスタレーション導体）と接続パッドとを介して外部電気回路に電気的に接続されることとなる。
【０００４】
なお、前記凹部内壁面の導体（キャスタレーション導体）のうち、少なくとも電子部品の接地用の電極が接続されるもの（通常、全接続パッド中約２０〜５０％）は、一部が絶縁基体上面に形成されている枠状の金属層まで導出されており、枠状金属層を接地できるようになっている。
【０００５】
また、前記導体が被着される溝状の凹部は、絶縁基体の側面に、通常は半円形の横断面で、ほぼ同一の内径で垂直方向に形成されており、枠状金属層と接続される導体が被着されるものは絶縁基体の側面で下面部から上面部にかけて形成されている。
【０００６】
【特許文献１】
特開平７−５０３５５号公報
【０００７】
【発明が解決しようとする課題】
しかしながら、近時、各種電子装置は環境、人体に対する悪影響を防止するため従来使用されている錫−鉛半田に代わり、錫−銀−ビスマス系、錫−銀−銅−ビスマス系等の鉛を含有しない、いわゆる鉛フリー半田を用いて外部電気回路基板に接続されるようになってきており、かかる鉛フリー半田は、従来の錫−鉛半田に比べて溶融時に流れやすいため電子装置を外部電気回路基板に実装するとき、半田が導体の被着された凹部内壁面を伝って絶縁基体上面の枠状金属層や枠状金属層に取着されている金属製蓋体にまで這い上がり、その結果、絶縁基体の接続パッドと、外部電気回路の配線導体との間に介在する半田の量が極めて少量となり、電子装置を外部回路基板に強固に実装することができないという欠点を有していた。
【０００８】
本発明は、上記欠点に鑑み案出されたものであり、その目的は、接続パッドを外部電気回路基板の配線導体に鉛フリー半田を介して強固に接合し、それにより外部電気回路基板に強固に実装することが可能な配線基板を提供することにある。
【０００９】
【課題を解決するための手段】
本発明の配線基板は、上面に電子部品搭載部および該搭載部を取り囲む枠状の金属層を有し、下面の外周部に接続パッドを有する絶縁基体と、前記絶縁基体の側面に前記接続パッドと枠状の金属層とを接続するようにして形成され、内壁面に導体が被着された溝状の凹部とを具備する配線基板であって、前記溝状の凹部の一部に、内径が他の部分より小さい小径部が形成されており、かつ前記溝状の凹部は、前記小径部よりも上の上部領域の深さが、前記小径部よりも下の下部領域の深さよりも浅いことを特徴とする配線基板。
【００１０】
また本発明の配線基板は、前記小径部の内径が７５μｍ以下であることを特徴とするものである。
【００１１】
本発明の配線基板によれば、絶縁基体の側面に形成され、枠状金属層と接続パッドとを電気的に接続する導体（キャスタレーション導体）が内壁面に被着された溝状の凹部の一部に小径部が形成されていることから、接続パッドと外部電気回路の配線導体とを鉛フリー半田を用いて接合し、鉛フリー半田が凹部内壁面を伝って這い上がろうとしたとしても、この鉛フリー半田は前記小径部で遮られ、枠状金属層や金属製蓋体にまで多量に這い上がることはなく、その結果、接続パッドと外部電気回路基板の配線導体との間に十分な量の半田を介在させることができ、配線基板（電子装置）を外部電気回路基板に極めて強固に接合することができる。
【００１２】
また本発明によれば、枠状の金属層と接続パッドとを接続するようにして形成されている溝状の凹部のうち、前記小径部よりも上の上部領域の深さを、前記小径部よりも下の下部領域の深さより浅くしたことから枠状金属層の幅を凹部により狭くすることはなく、これによって枠状金属層に金属製の蓋体をロウ材等を介して接合させた場合、枠状金属層と金属製蓋体との間に介在するロウ材の量は多くなって電子部品の気密封止の信頼性が大幅に向上する。
【００１３】
【発明の実施の形態】
次に、本発明を添付図面に基づき詳細に説明する。
図１（ａ）乃至（ｃ）は、本発明の配線基板を半導体素子を収容する半導体素子収納用パッケージに適用した場合の一実施例を示し、１は絶縁基体、２は配線層、３は枠状金属層、４は接続パッド、５は絶縁基体１の側面に形成され、内壁面に導体６が形成された溝状の凹部である。この絶縁基体１、配線層２、枠状金属層３、接続パッド４、溝状の凹部５および導体６により半導体素子７を搭載するための配線基板８が形成される。
【００１４】
前記絶縁基体１は、酸化アルミニウム質焼結体、窒化アルミニウム質焼結体、ムライト質焼結体、ガラスセラミック焼結体等の電気絶縁材料から成り、その上面に半導体素子７を搭載する搭載部を有し、該搭載部に半導体素子７がガラス、樹脂、ロウ材等の接着材を介して接着固定される。
【００１５】
前記絶縁基体１は、例えば、酸化アルミニウム質焼結体から成る場合には、酸化アルミニウム、酸化珪素、酸化カルシウム、酸化マグネシウム等の原料粉末に適当な有機バインダー、溶剤を添加混合して泥漿状のセラミックスラリーとなし、次に前記セラミックスラリーを従来周知のドクターブレード法やカレンダーロール法等のシート成形技術によりシート状となして所定形状のセラミックグリーンシート（セラミック生シート）を得る、最後に前記セラミックグリーンシートを複数枚積層するとともに還元雰囲気中、約１６００℃の温度で焼成することによって製作される。
【００１６】
また前記絶縁基体１はその上面の半導体素子７が搭載される搭載部周囲から絶縁基体１の内部を介し側面にかけて複数個の配線層２が形成されており、該配線層２は半導体素子７の信号用、接地用の各電極を接続パッド４に接続するための導電路として作用し、搭載部側の一端には半導体素子７の信号用、接地用等の電極がボンディングワイヤ９を介して電気的に接続される。
【００１７】
前記配線層２はタングステン、モリブデン、マンガン、銅、銀、金、パラジウム等の金属粉末から成り、タングステン等の金属粉末に適当な有機バインダーや溶剤を添加混合して得た金属ペーストを絶縁基体１となる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所定パターンに印刷塗布しておくことによって絶縁基体１の上面から絶縁基体１の内部を介し側面にかけて被着形成される。
【００１８】
また前記絶縁基体１はその上面で、半導体素子７が搭載される搭載部を取り囲むようにして枠状の金属層３が被着されており、該枠状の金属層３は後述する金属製蓋体１０を絶縁基体１に取着させる際の下地金属層として作用し、タングステン、モリブデン、マンガン、銅、銀、金、パラジウム等の金属粉末により形成されている。
【００１９】
前記枠状金属層３には金属製蓋体１０がロウ材を介してロウ付け取着され、これによって絶縁基体１の半導体素子搭載部に搭載されている半導体素子７は大気から気密に封止されることとなる。
【００２０】
なお、前記枠状金属層３は前述の配線層２と同様の方法によって絶縁基体１の上面で、半導体素子搭載部を取り囲むように形成される。
【００２１】
更に前記絶縁基体１の下面外周部には複数個の接続パッド４が形成されており、該接続パッド４は外部電気回路基板の配線導体に鉛フリー半田を介して接続され、半導体素子７の信号用、接地用の各電極を外部電気回路に電気的に接続する作用をなす。
【００２２】
前記接続パッド４は、タングステン、モリブデン、マンガン、銅、銀、金、パラジウム等の金属粉末より成り、前述の配線層２と同様の方法によって絶縁基体１の下面外周部に所定形状に形成される。
【００２３】
また更に前記絶縁基体１はその側面に複数個の溝状の凹部５（通常は、断面半円状）が形成されているとともに、その内壁面に導体（キャスタレーション導体）６が被着されており、該凹部内壁面の導体（キャスタレーション導体）６は配線層２と接続パッド４とを電気的に接続する作用をなす。
【００２４】
前記凹部内壁面の導体６はタングステン、モリブデン、マンガン、銅、銀、金、パラジウム等の金属粉末より成り、絶縁基体１となるセラミックグリーンシートの側面に打ち抜き加工法により半円形の凹部５を形成するとともに該凹部５内にタングステン等の金属粉末に適当な有機バインダーや溶剤を添加混合して得た金属ペーストを予め従来周知のスクリーン印刷法により所定パターンに印刷塗布しておくことによって絶縁基体１の側面に所定形状に形成される。
【００２５】
前記凹部内壁面の導体（キャスタレーション導体）６はまた半導体素子７の接地用の電極と導通する配線層２に接続されるものについては一部が絶縁基体１上面の枠状金属層３にまで導出されており、枠状金属層３を接地するようになっており、また、このような、半導体素子７の接地用の電極と導通する配線層２に接続される導体６が被着される溝状の凹部５は絶縁基体１の下面から上面にかけて、接続パッド４と枠状の金属層３とを接続するようにして形成されている。
【００２６】
なお、前記配線層２、枠状の金属層３、接続パッド４及び（キャスタレーション）導体６は、その露出する表面に、ニッケル、金等の耐蝕性やボンディングワイヤ９のボンディング性、半田の濡れ性等が良好な金属から成るめっき層を被着させておくと配線層２や枠状の金属層３等の酸化腐食を有効に防止することができるとともに枠状金属層３への金属製蓋体１０の取着、接続パッド４の外部電気回路基板への接続が確実、強固となる。従って、前記配線層２、枠状金属層３、接続パッド４及び凹部５内壁面の導体（キャスタレーション導体）６は、その露出する表面に、ニッケル、金等の耐蝕性やボンディング性、半田の濡れ性等が良好な金属をめっき法により被着させておくことが好ましく、特に、例えば、厚さ１〜１０μｍのニッケルめっき層、０．０５〜３μｍの厚さの金めっき層を順次被着させておくことが好ましい。
【００２７】
この場合、金めっき層の厚みは、被着する部位や金めっき層の結晶配向等に応じて異なる厚みとしてもよく、例えば、金めっき層のＸ線回折における結晶配向を極力（１１１）面に揃えるようにするとともに、ボンディングワイヤ９が接続される領域も含め、全域で約０．３〜１μｍとするようにしてもよく、半田付け用の領域のみ約０．３μｍ以下の薄いものとし、錫−金の脆い金属間化合物の生成を抑えて半田付けの信頼性を高めるようにしてもよい。
【００２８】
かくして本発明の配線基板８によれば、絶縁基体１上面の搭載部に半導体素子７を搭載するとともに半導体素子７の信号用、接地用の各電極を配線層２にボンディングワイヤ９を介して接続し、しかる後、絶縁基体１上面の枠状金属層３に鉄−ニッケル−コバルト合金や鉄−ニッケル合金等からなる金属製蓋体１０をロウ材等を介して接合させ、金属製蓋体１０で半導体素子７を気密に封止することによって製品としての電子装置（半導体装置）が完成する。
【００２９】
なお、この半導体装置は絶縁基体１下面外周部の接続パッド４を外部電気回路基板の配線導体に鉛フリー半田を介して接合することによって外部電気回路基板上に実装され、同時に半導体素７の信号用、接地用の各電極が外部電気回路基板の配線導体に電気的に接続される。
【００３０】
本発明の配線基板８においては、図２および図３に示すように、凹部５のうち枠状金属層３と接続パッド４とを接続している導体６が被着された凹部５ａについて、内径が他の部分より小さい小径部５ｂを設けておくことが重要である。
【００３１】
前記枠状金属層３と接続パッド４とを接続している導体６が内壁面に被着された凹部５ａについて、他の部分よりも内径の小さい小径部５ｂを設けておくと、接続パッド４と外部電気回路の配線導体とを鉛フリー半田を用いて接合し、鉛フリー半田が凹部５ａの内壁面を伝って這い上がろうとしたとしても、この鉛フリー半田は前記小径部５ｂで遮られて、枠状金属層３や金属製蓋体１０にまで多量に這い上がることはなく、その結果、接続パッド４と外部電気回路基板の配線導体との間に十分な量の半田を介在させることができ、配線基板（電子装置）を外部電気回路基板に極めて強固に接合することができる。
【００３２】
この場合、前記小径部５ｂは、その内径が７５μｍを超えると鉛フリー半田の這い上がりを遮ることが難しくなり、接続パッド４と外部電気回路基板の配線導体との間に十分な量の半田を介在させることが困難となる。従って、溝状の凹部５ａの小径部５ｂは、深さおよび幅を７５μｍ以下としておくことが好ましく、生産性を考慮すれば、２５μｍ〜７５μｍの範囲とすることがより一層好ましい。
【００３３】
また前記小径部５ｂは、溝状の凹部５ａの中央部よりも上側に設けた場合、鉛フリー半田の凹部５ａ内への這い上がり量が多くなり、接続パッド４と外部電気回路基板の配線導体との間に介在する半田量が少なくなり、配線基板の接合強度が低下する傾向がある。従って、前記小径部５ｂは、凹部５ａの中央部乃至下部に設けることが好ましい。
【００３４】
また前記小径部５ｂは、その幅を絶縁基体１の厚みに対し１０〜２０％の範囲としておくと鉛フリー半田の這い上がりを効果的に遮断して、かつ接続パッド４と外部電気回路基板の配線導体との間に介在する半田量が適量となって外部電気回路基板の配線導体に対する配線基板の接合強度を強くすることができる。従って、前記小径部５ｂは、その幅を絶縁基体１の厚みに対し１０〜２０％の範囲としておくことが好ましい。
【００３５】
また本発明の配線基板８においては、図２乃至図４に示すように、前記枠状金属層３と接続パッド４とを接続している導体６が被着され、小径部５ｂが形成された凹部５ａについて、小径部５ｂよりも上の上部領域５ｃの深さを、小径部よりも下の下部領域５ｄの深さより浅くしておくことが重要である。
【００３６】
前記凹部５ａのうち、上端部で枠状の金属層と接続する上部領域５ｃの深さを、接続パッド４と接続する下部領域５ｄの深さより浅くしておくと、枠状金属層３の幅を凹部５ａにより狭くすることはなく、これによって枠状金属層３に金属製の蓋体１０をロウ材等を介して接合させた場合、枠状金属層３と金属製の蓋体１０との間に介在するロウ材の量は多くなって電子部品（半導体素子）７の気密封止の信頼性が大幅に向上する。
【００３７】
更に、前記凹部５ａのうち接続パッド４と接続する下部領域５ｄの深さを深くしたことから接続パッド４を外部電気回路の配線導体に半田を介して接合させ内部に収容する電子部品（半導体素子）７を外部電気回路に接続する際、凹部５ａの下部領域５ｄ表面の導体６と外部電気回路基板の配線導体との間に半田の溜まり（メニスカス）が形成され、これによって接続パッド４（含下部領域５ｄ表面の導体６）と外部電気回路基板の配線導体との接合が強固となり、電子部品を外部電気回路に確実、強固に電気的接続することが可能となる。
【００３８】
なお、前記枠状金属層３と接続する導体６が被着された凹部５ａの上部領域５ｃの深さは０．２ｍｍ以下としておくと枠状金属層３の幅が凹部５ａにより狭くなることがほとんどなく、これによって枠状金属層３に金属製の蓋体１０を極めて強固に接合させて内部に収容する電子部品（半導体素子）６の気密封止の信頼性が極めて高いものとなる。従って、前記枠状金属層３と接続する導体が被着された凹部５ａの上部領域５ｃの深さは０．２ｍｍ以下としておくことが好ましい。
【００３９】
また更に前記凹部５、５ａは、図５に示すように、その内側に突出する突出部１１を形成しておくとともに、突出部１１の表面にも導体６を延在させるようにしておけば接続パッド４を外部電気回路基板の配線導体に半田を介して接合するとき、前記突出部１１が半田の中に食い込むようにして接合されて接合強度がより一層強固となる。従って、前記凹部５、５ａは、図５に示すように、その内側に突出する突出部１１を形成しておくことが好ましい。
【００４０】
なお、本発明は上述の実施例に限定されるものではなく、本発明の要旨を逸脱しない範囲であれば種々の変更は可能であり、例えば、上述の実施例では本発明の配線基板を半導体素子を収容する半導体素子収納用パッケージに適用したが、混成集積回路基板等の他の用途に適用してもよい。
【００４１】
【発明の効果】
本発明の配線基板によれば、絶縁基体の側面に形成され、枠状金属層と接続パッドとを電気的に接続する導体（キャスタレーション導体）が内壁面に被着された溝状の凹部の一部に小径部が形成されていることから、接続パッドと外部電気回路の配線導体とを鉛フリー半田を用いて接合し、鉛フリー半田が凹部内壁面を伝って這い上がろうとしたとしても、この鉛フリー半田は前記小径部で遮られ、枠状金属層や金属製蓋体にまで多量に這い上がることはなく、その結果、接続パッドと外部電気回路基板の配線導体との間に十分な量の半田を介在させることができ、配線基板（電子装置）を外部電気回路基板に極めて強固に接合することができる。
【００４２】
また本発明によれば、枠状の金属層と接続パッドとを接続するようにして形成されている溝状の凹部のうち、前記小径部よりも上の上部領域の深さを、前記小径部よりも下の下部領域の深さより浅くしたことから枠状金属層の幅を凹部により狭くすることはなく、これによって枠状金属層に金属製の蓋体をロウ材等を介して接合させた場合、枠状金属層と金属製蓋体との間に介在するロウ材の量は多くなって電子部品の気密封止の信頼性が大幅に向上する。
【図面の簡単な説明】
【図１】（ａ）（ｂ）（ｃ）は本発明の配線基板の一実施例を示す側面図、平面図、底面図である。
【図２】本発明の配線基板の要部拡大底面図である。
【図３】本発明の配線基板の要部拡大側面図である。
【図４】本発明の配線基板の要部拡大斜視図である。
【図５】本発明の配線基板の他の実施例の要部拡大図である。
【符号の説明】
１・・・・・絶縁基体
２・・・・・配線層
３・・・・・枠状の金属層
４・・・・・接続パッド
５・・・・・凹部
５ａ・・・・接続パッドと枠状金属層とを接続している導体が被着された凹部
５ｂ・・・・小径部
５ｃ・・・・上部領域
５ｄ・・・・下部領域
６・・・・・導体
７・・・・・半導体素子
８・・・・・配線基板
９・・・・・ボンディングワイヤ
１０・・・・蓋体
１１・・・・突出部[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wiring board for mounting electronic components such as a semiconductor element and a piezoelectric vibrator.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a wiring board for mounting an electronic component such as a semiconductor element or a piezoelectric vibrator is generally made of a substantially square plate-shaped ceramic material, and has an insulating base having an electronic component mounting portion on an upper surface, and an electronic component of the insulating base. A plurality of wiring layers led to the side surface from the component mounting portion through the inside of the insulating base, and a frame-shaped metal layer formed on the upper surface of the insulating base so as to surround the electronic component mounting portion, A plurality of connection pads formed on an outer peripheral portion of a lower surface of the insulating base, a conductor formed on a side surface of the insulating base and an inner wall surface, and each of the wiring layers is formed by the conductor (castellation conductor); It is composed of a plurality of groove-shaped concave portions that electrically connect to each connection pad. The electronic component is mounted on the electronic component mounting portion of the insulating base, and each of the electronic component for signal, grounding, etc. Each electrode The wire layer is electrically connected to the wire layer through a conductive connection member such as a bonding wire, and then the iron-nickel-cobalt alloy or the iron-nickel alloy is covered with the frame-shaped metal layer on the upper surface of the insulating substrate so as to cover the electronic components. An electronic device is obtained by joining a metal lid made of the same or the like via a brazing material and sealing the electronic component.
[0003]
Such an electronic device is mounted on an external electric circuit board by connecting a connection pad formed on an outer peripheral portion of a lower surface of an insulating base to a wiring conductor of the external electric circuit board via a solder such as tin-lead solder, and is simultaneously mounted on the external electric circuit board. These electrodes are electrically connected to an external electric circuit via the wiring layer, the conductor (castellation conductor) on the inner wall surface of the concave portion, and the connection pad.
[0004]
Among the conductors (castellation conductors) on the inner wall surface of the concave portion, at least one of the conductors to which the ground electrode of the electronic component is connected (generally, about 20 to 50% of all connection pads) is partially covered with the upper surface of the insulating base. Is led out to the frame-shaped metal layer formed on the substrate, so that the frame-shaped metal layer can be grounded.
[0005]
Further, the groove-shaped concave portion to which the conductor is attached is formed in the side surface of the insulating substrate, usually in a semicircular cross section, with substantially the same inner diameter in the vertical direction, and is connected to the frame-shaped metal layer. The conductor on which the conductor is attached is formed from the lower surface to the upper surface on the side surface of the insulating base.
[0006]
[Patent Document 1]
Japanese Patent Application Laid-Open No. 7-50355
[Problems to be solved by the invention]
However, recently, various electronic devices contain lead such as tin-silver-bismuth and tin-silver-copper-bismuth instead of tin-lead solder which has been conventionally used to prevent adverse effects on the environment and the human body. No, so-called lead-free solder has been used to connect to an external electric circuit board. Such lead-free solder is easier to flow at the time of melting than conventional tin-lead solder, so electronic devices must be connected to an external electric circuit. When mounted on the board, the solder travels along the inner wall surface of the concave portion where the conductor is attached and climbs up to the frame-shaped metal layer on the upper surface of the insulating substrate and the metal lid attached to the frame-shaped metal layer, and as a result, In addition, the amount of solder interposed between the connection pad of the insulating base and the wiring conductor of the external electric circuit is extremely small, so that the electronic device cannot be firmly mounted on the external circuit board.
[0008]
The present invention has been devised in view of the above-mentioned drawbacks, and an object of the present invention is to firmly join a connection pad to a wiring conductor of an external electric circuit board via lead-free solder, thereby firmly connecting the external electric circuit board. It is an object of the present invention to provide a wiring board that can be mounted on a wiring board.
[0009]
[Means for Solving the Problems]
A wiring board according to the present invention has an electronic component mounting portion on the upper surface, a frame-shaped metal layer surrounding the mounting portion, an insulating substrate having connection pads on an outer peripheral portion on the lower surface, and the connection pad on a side surface of the insulating substrate. And a groove-shaped recess formed so as to connect the metal layer and the frame-shaped metal layer, and a conductor is attached to the inner wall surface of the wiring board. Is formed with a small-diameter portion smaller than the other portion, and the groove-shaped recess has a depth in an upper region above the small-diameter portion is smaller than a depth in a lower region below the small-diameter portion. A wiring board characterized by the above-mentioned.
[0010]
In the wiring board according to the present invention, the small diameter portion has an inner diameter of 75 μm or less.
[0011]
ADVANTAGE OF THE INVENTION According to the wiring board of this invention, the conductor (castellation conductor) formed in the side surface of an insulating base | substrate and electrically connecting a frame-shaped metal layer and a connection pad is attached to the inner wall surface. Since the small diameter part is formed in part, the connection pad and the wiring conductor of the external electric circuit are joined using lead-free solder, and even if the lead-free solder tries to crawl along the inner wall surface of the recess However, this lead-free solder is blocked by the small-diameter portion and does not crawl in a large amount up to the frame-shaped metal layer or the metal lid. As a result, there is sufficient space between the connection pad and the wiring conductor of the external electric circuit board. An appropriate amount of solder can be interposed, and the wiring board (electronic device) can be extremely firmly joined to the external electric circuit board.
[0012]
According to the present invention, the depth of the upper region above the small-diameter portion of the groove-shaped concave portion formed so as to connect the frame-shaped metal layer and the connection pad is set to the small-diameter portion. The width of the frame-shaped metal layer was not made narrower by the recess because the depth was lower than the depth of the lower region below, and a metal lid was joined to the frame-shaped metal layer via a brazing material or the like. In this case, the amount of brazing material interposed between the frame-shaped metal layer and the metal lid increases, and the reliability of hermetic sealing of the electronic component is greatly improved.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, the present invention will be described in detail with reference to the accompanying drawings.
FIGS. 1A to 1C show an embodiment in which the wiring board of the present invention is applied to a semiconductor element housing package for housing a semiconductor element, 1 is an insulating base, 2 is a wiring layer, and 3 is The frame-shaped metal layer 4, connection pads 5, and groove-shaped recesses 5 are formed on the side surfaces of the insulating base 1, and the conductors 6 are formed on the inner wall surfaces. The insulating substrate 1, the wiring layer 2, the frame-shaped metal layer 3, the connection pad 4, the groove-shaped recess 5, and the conductor 6 form a wiring board 8 on which the semiconductor element 7 is mounted.
[0014]
The insulating base 1 is made of an electrically insulating material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a mullite sintered body, or a glass ceramic sintered body, and has a mounting portion on which a semiconductor element 7 is mounted. The semiconductor element 7 is bonded and fixed to the mounting portion via an adhesive such as glass, resin, brazing material, or the like.
[0015]
When the insulating base 1 is made of, for example, an aluminum oxide sintered body, a suitable organic binder and a solvent are added to and mixed with a raw material powder such as aluminum oxide, silicon oxide, calcium oxide, and magnesium oxide to form a slurry. A ceramic green sheet (ceramic green sheet) having a predetermined shape is obtained by forming the ceramic slurry into a sheet by a sheet forming technique such as a doctor blade method or a calender roll method which is well known in the art. It is manufactured by stacking a plurality of green sheets and firing at a temperature of about 1600 ° C. in a reducing atmosphere.
[0016]
The insulating substrate 1 has a plurality of wiring layers 2 formed from the periphery of the mounting portion on which the semiconductor element 7 is mounted on the upper surface to the side surface via the inside of the insulating substrate 1. Each of the electrodes for signal and ground functions as a conductive path for connecting to the connection pad 4. Electrodes for signal and ground of the semiconductor element 7 are electrically connected via bonding wires 9 to one end of the mounting portion. Connected.
[0017]
The wiring layer 2 is made of a metal powder such as tungsten, molybdenum, manganese, copper, silver, gold, or palladium. A metal paste obtained by adding a suitable organic binder or solvent to a metal powder such as tungsten is mixed with an insulating substrate 1. The ceramic green sheet is printed and applied in a predetermined pattern by a conventionally well-known screen printing method so that the ceramic green sheet is adhered and formed from the upper surface of the insulating substrate 1 to the side surface through the inside of the insulating substrate 1.
[0018]
On the upper surface of the insulating base 1, a frame-shaped metal layer 3 is attached so as to surround a mounting portion on which the semiconductor element 7 is mounted, and the frame-shaped metal layer 3 is formed of a metal cover described later. It functions as a base metal layer when attaching the body 10 to the insulating base 1 and is made of a metal powder such as tungsten, molybdenum, manganese, copper, silver, gold, palladium, or the like.
[0019]
A metal lid 10 is brazed and attached to the frame-shaped metal layer 3 via a brazing material, whereby the semiconductor element 7 mounted on the semiconductor element mounting portion of the insulating base 1 is hermetically sealed from the atmosphere. Will be done.
[0020]
The frame-shaped metal layer 3 is formed on the upper surface of the insulating base 1 so as to surround the semiconductor element mounting portion by the same method as that for the wiring layer 2 described above.
[0021]
Further, a plurality of connection pads 4 are formed on the outer peripheral portion of the lower surface of the insulating base 1, and the connection pads 4 are connected to wiring conductors of an external electric circuit board via lead-free solder. It functions to electrically connect each electrode for grounding and grounding to an external electric circuit.
[0022]
The connection pad 4 is made of a metal powder such as tungsten, molybdenum, manganese, copper, silver, gold, palladium, etc., and is formed in a predetermined shape on the outer peripheral portion of the lower surface of the insulating base 1 by the same method as the wiring layer 2 described above. .
[0023]
Further, the insulating base 1 has a plurality of groove-shaped concave portions 5 (usually semicircular in cross section) formed on the side surface thereof, and a conductor (castellation conductor) 6 is applied to the inner wall surface thereof. The conductor (castellation conductor) 6 on the inner wall surface of the recess functions to electrically connect the wiring layer 2 and the connection pad 4.
[0024]
The conductor 6 on the inner wall surface of the concave portion is made of a metal powder such as tungsten, molybdenum, manganese, copper, silver, gold, palladium, etc., and a semicircular concave portion 5 is formed on a side surface of a ceramic green sheet serving as the insulating substrate 1 by a punching process. In addition, a metal paste obtained by adding a suitable organic binder or a solvent to a metal powder such as tungsten in the concave portion 5 is preliminarily printed and applied in a predetermined pattern by a conventionally well-known screen printing method. Is formed in a predetermined shape on the side surface of the.
[0025]
The conductor (castellation conductor) 6 on the inner wall surface of the concave portion is partially connected to the wiring layer 2 that is electrically connected to the ground electrode of the semiconductor element 7, and a part of the conductor (castellation conductor) extends to the frame-shaped metal layer 3 on the upper surface of the insulating base 1. The conductor 6 connected to the wiring layer 2 which is led out and grounds the frame-shaped metal layer 3 and is electrically connected to the ground electrode of the semiconductor element 7 is attached. The groove-shaped recess 5 is formed so as to connect the connection pad 4 and the frame-shaped metal layer 3 from the lower surface to the upper surface of the insulating base 1.
[0026]
The wiring layer 2, the frame-shaped metal layer 3, the connection pads 4, and the (castellation) conductor 6 are provided on their exposed surfaces with the corrosion resistance of nickel, gold, etc., the bonding property of the bonding wires 9, the wettability of solder. When a plating layer made of a metal having good properties and the like is adhered, oxidative corrosion of the wiring layer 2 and the frame-shaped metal layer 3 can be effectively prevented, and a metal cover for the frame-shaped metal layer 3 is provided. The attachment of the body 10 and the connection of the connection pads 4 to the external electric circuit board are surely and firmly made. Therefore, the conductor (castellation conductor) 6 on the inner wall surface of the wiring layer 2, the frame-shaped metal layer 3, the connection pad 4, and the concave portion 5 has a corrosion resistance and a bonding property of nickel, gold, etc. It is preferable to deposit a metal having good wettability or the like by a plating method. In particular, for example, a nickel plating layer having a thickness of 1 to 10 μm and a gold plating layer having a thickness of 0.05 to 3 μm are sequentially deposited. It is preferable to keep it.
[0027]
In this case, the thickness of the gold plating layer may be different depending on the portion to be adhered, the crystal orientation of the gold plating layer, and the like. For example, the crystal orientation in the X-ray diffraction of the gold plating layer is set to the (111) plane as much as possible. In addition, the entire area including the area to which the bonding wire 9 is connected may be set to about 0.3 to 1 μm, and only the area for soldering may be as thin as about 0.3 μm or less. -The formation of brittle intermetallic compounds of gold may be suppressed to increase the reliability of soldering.
[0028]
Thus, according to the wiring board 8 of the present invention, the semiconductor element 7 is mounted on the mounting portion on the upper surface of the insulating base 1, and the signal and ground electrodes of the semiconductor element 7 are connected to the wiring layer 2 via the bonding wires 9. After that, a metal lid 10 made of an iron-nickel-cobalt alloy or an iron-nickel alloy is joined to the frame-shaped metal layer 3 on the upper surface of the insulating base 1 via a brazing material or the like. The semiconductor device 7 is hermetically sealed to complete an electronic device (semiconductor device) as a product.
[0029]
This semiconductor device is mounted on the external electric circuit board by joining the connection pads 4 on the outer periphery of the lower surface of the insulating base 1 to the wiring conductors of the external electric circuit board via lead-free solder. And grounding electrodes are electrically connected to the wiring conductors of the external electric circuit board.
[0030]
In the wiring board 8 of the present invention, as shown in FIGS. 2 and 3, the inner diameter of the concave portion 5 a in which the conductor 6 connecting the frame-shaped metal layer 3 and the connection pad 4 is attached is formed. It is important to provide a small diameter portion 5b which is smaller than the other portions.
[0031]
When the conductor 5 connecting the frame-shaped metal layer 3 and the connection pad 4 is attached to the inner wall surface of the recess 5a, a small-diameter portion 5b having an inner diameter smaller than other portions is provided. And the wiring conductor of the external electric circuit are joined by using lead-free solder, and even if the lead-free solder tries to crawl along the inner wall surface of the recess 5a, the lead-free solder is blocked by the small-diameter portion 5b. As a result, a large amount of solder does not crawl up to the frame-shaped metal layer 3 or the metal lid 10, and as a result, a sufficient amount of solder is interposed between the connection pad 4 and the wiring conductor of the external electric circuit board. Thus, the wiring board (electronic device) can be very firmly joined to the external electric circuit board.
[0032]
In this case, if the inner diameter of the small diameter portion 5b exceeds 75 μm, it becomes difficult to block the rise of lead-free solder, and a sufficient amount of solder is supplied between the connection pad 4 and the wiring conductor of the external electric circuit board. It becomes difficult to intervene. Therefore, it is preferable that the small-diameter portion 5b of the groove-shaped concave portion 5a has a depth and a width of 75 μm or less, and more preferably in the range of 25 μm to 75 μm in consideration of productivity.
[0033]
When the small-diameter portion 5b is provided above the central portion of the groove-shaped concave portion 5a, the amount of lead-free solder creeping up into the concave portion 5a increases, and the connection pad 4 and the wiring conductor of the external electric circuit board are formed. , The amount of solder interposed therebetween is reduced, and the bonding strength of the wiring board tends to decrease. Therefore, it is preferable that the small diameter portion 5b is provided at the central portion or the lower portion of the concave portion 5a.
[0034]
When the width of the small diameter portion 5b is in the range of 10% to 20% with respect to the thickness of the insulating base 1, the creeping of lead-free solder can be effectively blocked, and the connection pad 4 and the external electric circuit board can be effectively connected. With an appropriate amount of solder interposed between the wiring conductor and the wiring conductor, the bonding strength of the wiring board to the wiring conductor of the external electric circuit board can be increased. Therefore, it is preferable that the width of the small-diameter portion 5 b is set in a range of 10 to 20% with respect to the thickness of the insulating base 1.
[0035]
Further, in the wiring board 8 of the present invention, as shown in FIGS. 2 to 4, the conductor 6 connecting the frame-shaped metal layer 3 and the connection pad 4 is attached, and the small-diameter portion 5b is formed. It is important for the recess 5a that the depth of the upper region 5c above the small diameter portion 5b is smaller than the depth of the lower region 5d below the small diameter portion.
[0036]
If the depth of the upper region 5c connected to the frame-shaped metal layer at the upper end of the concave portion 5a is smaller than the depth of the lower region 5d connected to the connection pad 4, the width of the frame-shaped metal layer 3 is reduced. Is not narrowed by the concave portion 5a, and when the metal lid 10 is joined to the frame-shaped metal layer 3 via a brazing material or the like, the gap between the frame-shaped metal layer 3 and the metal lid 10 is reduced. The amount of the brazing material interposed therebetween increases, and the reliability of hermetic sealing of the electronic component (semiconductor element) 7 is greatly improved.
[0037]
Further, since the depth of the lower region 5d of the recess 5a connected to the connection pad 4 is increased, the connection pad 4 is joined to the wiring conductor of the external electric circuit via solder and accommodated in the electronic component (semiconductor element). 7) is connected to an external electric circuit, a solder pool (meniscus) is formed between the conductor 6 on the surface of the lower region 5d of the concave portion 5a and the wiring conductor of the external electric circuit board. The connection between the conductor 6) on the surface of the lower region 5d and the wiring conductor of the external electric circuit board is strengthened, and the electronic component can be securely and firmly electrically connected to the external electric circuit.
[0038]
If the depth of the upper region 5c of the concave portion 5a on which the conductor 6 connected to the frame-shaped metal layer 3 is attached is set to 0.2 mm or less, the width of the frame-shaped metal layer 3 may be reduced by the concave portion 5a. There is hardly any, and thus, the reliability of hermetic sealing of the electronic component (semiconductor element) 6 housed in the frame-shaped metal layer 3 with the metal lid 10 extremely firmly joined to the inside is extremely high. Therefore, it is preferable that the depth of the upper region 5c of the concave portion 5a to which the conductor connected to the frame-shaped metal layer 3 is attached be 0.2 mm or less.
[0039]
Furthermore, as shown in FIG. 5, the recesses 5 and 5a are formed with a protruding portion 11 protruding inward thereof, and the conductor 6 is also extended on the surface of the protruding portion 11. When the pad 4 is joined to the wiring conductor of the external electric circuit board via solder, the projecting portion 11 is joined so as to bite into the solder, and the joining strength is further enhanced. Therefore, as shown in FIG. 5, it is preferable that the recesses 5 and 5a have a protruding portion 11 that protrudes inward.
[0040]
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 spirit of the present invention. Although the present invention has been applied to a semiconductor device housing package for housing an element, it may be applied to other uses such as a hybrid integrated circuit board.
[0041]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the wiring board of this invention, the conductor (castellation conductor) formed in the side surface of an insulating base | substrate and electrically connecting a frame-shaped metal layer and a connection pad is attached to the inner wall surface. Since the small diameter part is formed in part, the connection pad and the wiring conductor of the external electric circuit are joined using lead-free solder, and even if the lead-free solder tries to crawl along the inner wall surface of the recess However, this lead-free solder is blocked by the small-diameter portion and does not crawl in a large amount up to the frame-shaped metal layer or the metal lid. As a result, there is sufficient space between the connection pad and the wiring conductor of the external electric circuit board. An appropriate amount of solder can be interposed, and the wiring board (electronic device) can be extremely firmly joined to the external electric circuit board.
[0042]
According to the present invention, the depth of the upper region above the small-diameter portion of the groove-shaped concave portion formed so as to connect the frame-shaped metal layer and the connection pad is set to the small-diameter portion. The width of the frame-shaped metal layer was not made narrower by the recess because the depth was lower than the depth of the lower region below, and a metal lid was joined to the frame-shaped metal layer via a brazing material or the like. In this case, the amount of brazing material interposed between the frame-shaped metal layer and the metal lid increases, and the reliability of hermetic sealing of the electronic component is greatly improved.
[Brief description of the drawings]
FIGS. 1A, 1B, and 1C are a side view, a plan view, and a bottom view showing an embodiment of a wiring board of the present invention.
FIG. 2 is an enlarged bottom view of a main part of the wiring board of the present invention.
FIG. 3 is an enlarged side view of a main part of the wiring board of the present invention.
FIG. 4 is an enlarged perspective view of a main part of the wiring board of the present invention.
FIG. 5 is an enlarged view of a main part of another embodiment of the wiring board of the present invention.
[Explanation of symbols]
1 insulating base 2 wiring layer 3 frame-shaped metal layer 4 connection pad 5 recess 5a connection pad A concave portion 5b on which a conductor connecting the frame-shaped metal layer is adhered .... a small-diameter portion 5c ... an upper region 5d ... a lower region 6 ... a conductor 7 ... · Semiconductor element 8 · · · · · Wiring board 9 · · · · Bonding wire 10 · · · Lid 11 · · · Projection
