JP2004274005A

JP2004274005A - Wiring board

Info

Publication number: JP2004274005A
Application number: JP2003089267A
Authority: JP
Inventors: Masanao Kabumoto; 正尚株元
Original assignee: Kyocera Corp
Current assignee: Kyocera Corp
Priority date: 2003-01-15
Filing date: 2003-03-27
Publication date: 2004-09-30
Anticipated expiration: 2023-03-27
Also published as: JP4349827B2

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that reflection loss occurs due to the mismatching between differential impedances in a part on a wiring board where a line distance between differential transmission lines is increased, and the operationality of a semiconductor element is deteriorated. <P>SOLUTION: On the wiring substrate 1, differential transmission lines 8 surrounded by an earth wiring conductor 4a at a predetermined distance 11 are formed on an insulating substrate 2 and the distance 11 between the differential transmission lines 8 and the earth wiring conductor 4a becomes small at a part 8d where the line distance between the differential transmission lines 8 is increased. Preferably, the distance 11 between the differential transmission line 8 and the earth wiring conductor 4a is decreased so that the differential impedance at a part 8c where the line distance between the differential transmission lines 8 is constant becomes substantially equal to the differential impedance at a part 8d where the line distance is increased. The reflection loss of an HF signal due to the mismatching of differential impedances, which occurs due to a change in the distance between the differential transmission lines 8 at the part 8d where the line distance is increased, can be suppressed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、高速で作動する半導体素子や光半導体素子等の電子部品を搭載するのに好適な、差動伝送線路を有する配線基板に関するものである。
【０００２】
【従来の技術】
高速で作動する半導体素子や光半導体素子等の電子部品を搭載するための配線基板においては、高速信号を正確かつ効率よく伝播させるために、図６に従来の配線基板の例を断面図で、また図７にその差動伝送線路の周辺部を要部拡大平面図で示すように、高速信号が伝播する信号線路に差動伝送線路４８を用いている。
【０００３】
差動伝送線路４８は、図７に示すように、一対の伝送線路４８ａ・４８ｂを用いてそれぞれの伝送線路の入力側に正相および逆相の信号を印加し、出力側でその差をとることによりコモンモードノイズ成分をキャンセルすることができ、高品質の信号を伝送することができる伝送方式に用いられるものである。また、この例においては、差動伝送線路４８における伝送特性の向上を図るために、伝送線路４８ａ・４８ｂが接地配線導体４４ａにより一定の間隔４１１を隔てて囲繞されている。この差動伝送線路４８の構造は、一対の伝送線路４８ａ・４８ｂによって決定される差動インピーダンスが所望の特性に一致するように、絶縁基板４２の絶縁層４２ａ〜４２ｄの材料や、絶縁層４２ａ〜４２ｄの断面構造（配線導体４３・４４の幅，厚みおよび間隔，グランド層やグランド導体との距離等）を制御し決定されている。
【０００４】
また、差動伝送線路４８のレイアウト設計においては、半導体素子４５の電極と導体バンプ４６および半導体素子接続用電極４７を介して電気的に接続された差動伝送線路４８を用いて配線基板４０の上面で信号を伝送し、配線基板４０の二次実装側である外部接続用電極４１０等の配列間隔に応じてその差動伝送線路４８を形成する一対の伝送線路４８ａ・４８ｂ間の線路間隔を広げて、二次実装部である外部接続用電極４１０に接続されている。
【０００５】
【特許文献１】
特開２００２−９５１１号公報
【０００６】
【発明が解決しようとする課題】
しかしながら、従来の配線基板４０上に形成された差動伝送線路４８においては、差動インピーダンスが例えば約１００Ωになるように設計された線路間隔が一定の部分４８ｃに対し、２次実装部である外部接続用電極４１０の配列間隔に合わせて差動伝送線路４８を展開して配線する必要がある。このとき、線路間隔が広がる部分４８ｄにおいて一対の伝送線路４８ａ・４８ｂをそれぞれ接地配線層４４ａで一定の間隔４１１を持って囲繞して展開することから、伝送モードが一対の伝送線路４８ａ・４８ｂで信号を伝送する差動モードから１本の伝送線路４８ａまたは４８ｂで信号を伝送するシングルモードに変化することとなる。
【０００７】
通常、差動インピーダンスは、一対の伝送線路４８ａ・４８ｂのうちの一つの伝送線路４８ａまたは４８ｂの自己インピーダンスからもう一つの伝送線路４８ａまたは４８ｂからの相互インピーダンスの差を２倍した値が１００Ωになるように設定される。つまり、自己インピーダンスと相互インピーダンスとの差が５０Ωになるように設定される。このため、一対の伝送線路４８ａ・４８ｂのうちのそれぞれ一本の伝送線路４８ａまたは４８ｂの自己インピーダンスは５０Ωより高いものとされている。
【０００８】
また、線路間隔が広がる部分４８ｄにおいては、伝送モードが一対の伝送線路４８ａ・４８ｂで信号を伝送する差動モードから１本の伝送線路４８ａまたは４８ｂで信号を伝送するシングルモードに変化するため、それぞれもう一本の伝送線路４８ａまたは４８ｂからの相互インピーダンスの影響が小さくなり、結果として差動伝送線路４８として見た場合に差動伝送線路４８の差動インピーダンスは上昇してしまうこととなる。
【０００９】
このため、伝送モードが差動モードからシングルモードへ切り替わる線路間隔が広がる部分４８ｄにおいては、差動インピーダンスが１００Ωからずれて高くなってしまい、線路間隔が一定の部分４８ｃと線路間隔が広がる部分４８ｄとにおいてインピーダンスの不整合が起こり、反射損失が大きくなって信号の伝送が阻害され、半導体素子４５の作動性が損なわれる場合があるという問題点を有していた。
【００１０】
本発明は上記問題点に鑑み案出されたものであり、その目的は、差動伝送線路において線路間隔が一定の部分から線路間隔が広がる部分において生じる反射損失を非常に小さなものに抑制することができ、それにより半導体素子の作動性を良好なものとできる配線基板を提供することにある。
【００１１】
【課題を解決するための手段】
本発明の配線基板は、絶縁基板上に差動伝送線路が形成されており、この差動伝送線路は、接地配線導体に囲繞されているとともに、その間隔が前記差動伝送線路の線路間隔が一定の部分に対して前記線路間隔が広がる部分において小さくなっていることを特徴とするものである。
【００１２】
また、本発明の配線基板は、上記構成において、前記差動伝送線路と前記接地配線導体との間の前記間隔は、前記差動伝送線路の前記線路間隔が一定の部分における差動インピーダンスと、前記線路間隔が広がる部分における差動インピーダンスとが略同じとなるように小さくされていることを特徴とするものである。
【００１３】
また、本発明の配線基板は、上記各構成において、前記差動伝送線路の線路間隔が広がった後の端部にそれぞれ信号用貫通導体が接続されるとともに、この信号用貫通導体を取り囲むようにそれぞれ複数の接地用貫通導体が形成されていることを特徴とするものである。
【００１４】
また、本発明の配線基板は、上記構成において、前記接地用貫通導体は、前記差動伝送線路の前記線路間隔が広がる部分における差動インピーダンスと前記信号用貫通導体の差動インピーダンスとが略同じとなるように形成されていることを特徴とするものである。
【００１５】
本発明の配線基板によれば、配線基板上に形成された差動伝送線路について、差動伝送線路の線路間隔が広がる部分においてそれぞれの差動伝送線路とそれを囲繞する接地配線導体との間の間隔が小さくなっていることから、それぞれの伝送線路の接地配線導体との間の容量成分の増加による自己インピーダンスの減少によって、一対の差動伝送線路として見た場合に差動インピーダンスが減少することとなるため、線路間隔が広がる部分において差動伝送線路の線路間隔の変化により発生していた差動インピーダンスの不整合による反射損失を効果的に抑えることが可能となる。
【００１６】
また、本発明の配線基板によれば、差動伝送線路と接地配線導体との間の間隔が、差動伝送線路の線路間隔が一定の部分における差動インピーダンスと、線路間隔が広がる部分における差動インピーダンスとが略同じとなるように小さくされているときには、差動伝送線路の線路間隔が広がる部分における差動インピーダンスの不整合をなくすことができ、高周波信号の反射損失を無視できる程度に小さく抑えることが可能となる。
【００１７】
また、差動伝送線路の線路間隔が広がった後の端部にそれぞれ信号用貫通導体が接続されるとともに、この信号用貫通導体を取り囲むようにそれぞれ複数の接地用貫通導体が形成されていることにより、これら信号用貫通導体および接地用貫通導体によって擬似同軸線路が形成され、信号用貫通導体からの放射による高周波信号の透過損失を抑えることが可能となる。
【００１８】
また、差動伝送線路の線路間隔が広がる部分における差動インピーダンスと信号用貫通導体の差動インピーダンスとが略同じとなるように接地用貫通導体が形成されていることにより、差動伝送線路と信号用貫通導体との接続部における差動インピーダンスの不整合をなくすことができ、高周波信号の反射損失を抑えることが可能となる。
【００１９】
これらのことにより、本発明の配線基板によれば、差動伝送線路の線路間隔が広がる部分における高周波信号の反射損失を極めて小さなものとすることができるので、これに搭載される半導体素子の高周波領域における作動性を良好なものとすることができる。
【００２０】
【発明の実施の形態】
本発明の配線基板について以下に図面を参照しつつ詳細に説明する。
【００２１】
図１は本発明の配線基板の実施の形態の一例を示す断面図であり、図２は図１に示す配線基板における差動伝送線路の周辺部の要部拡大平面図である。
【００２２】
この例の配線基板１においては、絶縁基板２を構成する絶縁層２ａ〜２ｄは基本的には同じ比誘電率を有する絶縁材料で形成されている。絶縁層２ｃ上には信号配線群３が形成され、絶縁層２ｂおよび２ｄ上には信号配線群３に対向させて広面積の接地配線層４ｂもしくは電源配線層４ｃが形成されており、信号配線群３の各信号配線はストリップ線路構造を有している。絶縁層２ａ上には接地配線導体４ａが差動伝送線路８を一定の間隔１１で囲繞するように形成されている。なお、電源配線層４ｂおよび接地配線層４ｃは、配線基板１の仕様に応じて入れ換えて配置されることもある。
【００２３】
また、信号配線群３の各信号配線の配線幅および信号配線群３と電源配線層４ｃもしくは接地配線導体４ａおよび接地配線層４ｂとの間に介在する絶縁層２ａ，２ｂおよび２ｃの厚みを適宜設定することで、信号配線群３の特性インピーダンスを任意の値に設定することができるため、良好な伝送特性を有する信号配線群３を形成することが可能となる。信号配線群３の特性インピーダンスは、一般的には５０Ωに設定される場合が多い。
【００２４】
なお、信号配線群３に含まれる複数の信号配線は、それぞれ異なる電気信号を伝送するものとしてもよい。
【００２５】
この例では、配線基板１の上面には高速で動作する半導体素子や光半導体素子等の半導体素子５が搭載され、錫−鉛合金（Ｓｎ−Ｐｂ）等の半田や金（Ａｕ）等から成る導体バンプ６および半導体素子５を接続するための半導体素子接続用電極７を介して差動伝送線路８と電気的に接続されている。また、配線基板１の半導体素子５を搭載する上面と反対側の下面には、半導体素子５に信号の入出力および電源供給を行なうための外部接続用電極１０を有している。
【００２６】
また、差動伝送線路８は、絶縁層２ａの上面に一定の間隔１１をもって囲繞された接地配線導体４ａおよび接地配線層４ｂとの間で形成されたいわゆるグランド付きコプレーナ構造の一対の信号線路８ａ・８ｂで形成され、半導体素子接続用電極７および錫−鉛合金（Ｓｎ−Ｐｂ）等の半田や金（Ａｕ）等から成る導体バンプ６を介して半導体素子５の電極と電気的に接続されており、外部と信号の入出力を行なうために貫通導体９を介して外部接続用電極１０と電気的に接続されている。
【００２７】
これを図２を用いて詳細に説明する。図２は本発明の配線基板の実施の形態の一例における差動伝送線路の周辺部を示す要部拡大平面図である。図２において、絶縁層２は図１に示す絶縁層２ａに相当するものである。
【００２８】
また、差動伝送線路８ａおよび８ｂは、図１に示す差動伝送線路８に相当するものであり、接地配線導体４ａによって一定の間隔１１をもって囲繞されており、半導体素子５と図１に示す導体バンプ６および半導体素子接続用電極７を介して電気的に接続され、また貫通導体９を介して外部接続用電極１０と電気的に接続されている。差動伝送線路８は、一対の信号線路８ａ・８ｂ間の間隔が一定である部分８ｃと一対の信号線路８ａ・８ｂ間の間隔が広がる部分８ｄとによって形成され、信号線路８ａ・８ｂ間の間隔が広がる部分８ｄの信号線路８ａ・８ｂと接地配線導体４ａとの間の間隔１１は、信号線路８ａ・８ｂ間の間隔が一定である部分８ｃにおける差動伝送線路８と接地配線導体４ａとの間の間隔１１より小さく形成されている。そして、その信号線路８ａ・８ｂ間の間隔が広がる部分８ｄの端部において、差動伝送線路８ａおよび８ｂはそれぞれ貫通導体９ａおよび９ｂを介して外部接続用電極１０と電気的に接続されている。
【００２９】
次に、図３は本発明の配線基板の実施の形態の一例における差動伝送線路の周辺部を示す要部拡大断面図である。図３において、差動伝送線路８の信号線路８ａおよび８ｂは、差動伝送線路８の配線幅，配線間隔，配線厚み，電源配線層もしくは接地配線層４ｂとの間に介在する絶縁層２ａの厚みおよび差動伝送線路８と接地配線導体４ａとの間の間隔１１を適宜設定することにより、差動伝送線路８の差動インピーダンスを任意の値に設定することができるため、良好な伝送特性を有する差動伝送線路８を形成することが可能となる。差動伝送線路８の差動インピーダンスは、一般的には１００Ωに設定される場合が多い。
【００３０】
次に、図４は本発明の配線基板の実施の形態の他の例を示す断面図であり、図５は図４に示す配線基板における差動伝送線路の周辺部の要部拡大平面図である。これら図４および図５において、図１〜図３と同様の箇所には同じ符号を付してある。
【００３１】
この例の配線基板１’においては、差動伝送線路８は、その線路間隔が広がる部分８ｄにおいて、線路間隔が広がった後の信号線路８ａ・８ｂの端部に、それぞれ信号用貫通導体９が接続され、これを介して信号用の外部接続用電極１０と電気的に接続されているとともに、信号用貫通導体９を取り囲むようにそれぞれ複数の接地用貫通導体１２が形成され、これら接地用貫通導体１２は電源配線層４ｂもしくは接地配線層４ｃを介して電源もしくは接地用の外部接続用電極１０に電気的に接続されている。
【００３２】
これを図５を用いて詳細に説明する。図５は本発明の配線基板の実施の形態の他の例における差動伝送線路の周辺部を示す図２と同様の要部拡大平面図である。
【００３３】
図５において、差動伝送線路８ａおよび８ｂは、図４に示す差動伝送線路８に相当するものであり、半導体素子５と図４に示す導体バンプ６および半導体素子接続用電極７を介して電気的に接続され、また信号用貫通導体９ａ・９ｂを介して信号用の外部接続用電極１０と電気的に接続されている。信号用貫通導体９ａ・９ｂはそれぞれ複数の接地用貫通導体１２によって疑似同軸線路を構成するように取り囲まれ、接地用貫通導体１２は電源配線層４ｂもしくは接地配線層４ｃを介して電源用もしくは接地用の外部接続用電極１０に接続されている。
【００３４】
このような本発明の配線基板１’によれば、差動伝送線路８の線路間隔が広がった後の信号線路８ａ・８ｂの端部にそれぞれ信号用貫通導体９ａ・９ｂが接続されるとともに、この信号用貫通導体９ａ・９ｂを取り囲むようにそれぞれ複数の接地用貫通導体１２が形成されていることにより、これら信号用貫通導体９ａ・９ｂおよび接地用貫通導体１２によって擬似同軸線路が形成され、信号用貫通導体９ａ・９ｂからの放射による高周波信号の透過損失を抑えることが可能となる。
【００３５】
また、差動伝送線路８の線路間隔が広がる部分８ｄにおける差動インピーダンスと信号用貫通導体９ａ・９ｂの差動インピーダンスとが略同じとなるように接地用貫通導体１２が形成されていることにより、差動伝送線路８と信号用貫通導体９ａ・９ｂとの接続部における差動インピーダンスの不整合をなくすことができ、高周波信号の反射損失を抑えることが可能となる。
【００３６】
本発明の配線基板１・１’は、同様の配線構造をさらに多層に積層して多層配線基板を構成したものであってもよい。
【００３７】
また、信号配線群３および差動伝送線路８の構造は、信号配線群および差動伝送線路の各信号配線に隣接して電源配線層もしくは接地配線層を形成したコプレーナ線路構造の他にも、信号配線群および差動伝送線路に対向して形成された電源配線層もしくは接地配線層を有するマイクロストリップ線路構造や、信号配線群および差動伝送線路の上下に電源配線層もしくは接地配線層を有するストリップ線路構造であってもよく、配線基板１に要求される仕様等に応じて適宜選択して用いることができる。
【００３８】
また、この配線基板１・１’にチップ抵抗・薄膜抵抗・コイルインダクタ・クロスインダクタ・チップコンデンサまたは電解コンデンサ等といったものを取着して、電子回路モジュール等を構成してもよい。
【００３９】
また、各絶縁層２ａ〜２ｄの平面視における形状は、正方形状や長方形状の他に、菱形状・六角形状または八角形状等の形状であってもよい。
【００４０】
そして、このような本発明の配線基板１・１’は、半導体素子収納用パッケージ等の電子部品収納用パッケージや電子部品搭載用基板、多数の半導体素子が搭載されるいわゆるマルチチップモジュールやマルチチップパッケージ、あるいはマザーボード等として使用される。
【００４１】
本発明の配線基板１・１’において、各絶縁層２ａ〜２ｄは、例えばセラミックグリーンシート積層法によって、酸化アルミニウム質焼結体・窒化アルミニウム質焼結体・炭化珪素質焼結体・窒化珪素質焼結体・ムライト質焼結体またはガラスセラミックス等の無機絶縁材料を使用して、あるいはポリイミド・エポキシ樹脂・フッ素樹脂・ポリノルボルネンまたはベンゾシクロブテン等の有機絶縁材料を使用して、あるいはセラミックス粉末等の無機絶縁物粉末をエポキシ樹脂等の熱硬化性樹脂で結合して成る複合絶縁材料等の電気絶縁材料を使用して形成される。
【００４２】
これらの絶縁層２ａ〜２ｄは以下のようにして作製される。例えば酸化アルミニウム質焼結体から成る場合であれば、まず、酸化アルミニウム・酸化珪素・酸化カルシウムまたは酸化マグネシウム等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て泥漿状となすとともに、これをドクターブレード法等を採用してシート状となすことによってセラミックグリーンシートを得る。そして、各信号配線群３および各導体層４と成る金属ペーストを所定のパターンに印刷塗布して上下に積層し、最後にこの積層体を還元雰囲気中にて約１６００℃の温度で焼成することによって製作される。
【００４３】
また、例えばエポキシ樹脂から成る場合であれば、一般に酸化アルミニウム質焼結体から成るセラミックスやガラス繊維を織り込んだ布にエポキシ樹脂を含浸させて形成されるガラスエポキシ樹脂等から成る絶縁層の上面に、有機樹脂前駆体をスピンコート法もしくはカーテンコート法等により被着させ、これを熱硬化処理することによって形成されるエポキシ樹脂等の有機樹脂から成る絶縁層と、銅を無電解めっき法や蒸着法等の薄膜形成技術およびフォトリソグラフィ技術を採用することによって形成される薄膜配線導体層とを交互に積層し、約１７０℃程度の温度で加熱硬化することによって製作される。
【００４４】
これらの絶縁層２ａ〜２ｄの厚みとしては、使用する材料の特性に応じて、要求される仕様に対応する機械的強度や電気的特性等の条件を満たすように適宣設定される。
【００４５】
また、異なる比誘電率を有する絶縁層２ａ〜２ｄを得るための方法としては、例えば酸化アルミニウム・窒化アルミニウム・炭化珪素・窒化珪素・ムライトまたはガラスセラミックス等の無機絶縁材料や、あるいはポリイミド・エポキシ樹脂・フッ素樹脂・ポリノルボルネンまたはベンゾシクロブテン等の有機絶縁材料にチタン酸バリウム・チタン酸ストロンチウム・チタン酸カルシウムまたはチタン酸マグネシウム等の高誘電体材料の粉末を添加混合し、しかるべき温度で加熱硬化することによって、所望の比誘電率のものを得るようにすればよい。
【００４６】
このとき、無機絶縁材料や有機絶縁材料に添加混合する高誘電体材料の粒径は、無機絶縁材料あるいは有機絶縁材料に高誘電体材料を添加混合したことによって起こる絶縁層内の比誘電率のバラツキの発生の低下や、絶縁層の粘度変化による加工性の低下を低減するため、０．５〜５０μｍの範囲とすることが望ましい。
【００４７】
また、無機絶縁材料や有機絶縁材料に添加混合する高誘電体材料の含有量は、絶縁層の比誘電率を大きな値とするためと、無機絶縁材料や有機絶縁材料と高誘電体材料の接着強度の低下を防止するために、５〜７５重量％とすることが望ましい。
【００４８】
また、信号配線群３および各差動伝送線路８や接地配線導体４ａ・接地配線層４ｂもしくは電源配線層４ｃは、例えばタングステン（Ｗ）・モリブデン（Ｍｏ）・モリブデンマンガン（Ｍｏ−Ｍｎ）・銅（Ｃｕ）・銀（Ａｇ）または銀パラジウム（Ａｇ−Ｐｄ）等の金属粉末メタライズ、あるいは銅（Ｃｕ）・銀（Ａｇ）・ニッケル（Ｎｉ）・クロム（Ｃｒ）・チタン（Ｔｉ）・金（Ａｕ）またはニオブ（Ｎｂ）やそれらの合金等の金属材料の薄膜等により形成すればよい。
【００４９】
具体的には、信号配線群３や接地配線導体４ａ・接地配線層４ｂもしくは電源配線層４ｃをＷの金属粉末メタライズで形成する場合は、Ｗ粉末に適当な有機バインダや溶剤等を添加混合して得た金属ペーストを絶縁層２ａ〜２ｄと成るセラミックグリーンシートに所定のパターンに印刷塗布し、これをセラミックグリーンシートの積層体とともに焼成することによって形成することができる。
【００５０】
また、金属材料の薄膜で形成する場合は、例えばスパッタリング法・真空蒸着法またはメッキ法により金属膜を形成した後、フォトリソグラフィ法により所定の配線パターンに形成することができる。
【００５１】
このような配線基板１・１’は、信号配線群３が配設されている絶縁層２ａ〜２ｄの比誘電率に応じて、信号配線群３および差動伝送線路８の各信号配線の配線幅，配線厚み，配線間隔を適宣設定することで、信号配線群３の各信号配線の特性インピーダンス値および差動伝送線路８の差動インピーダンス値を所望の値とすることができる。
【００５２】
本発明の配線基板１・１’において、差動伝送線路８の線路間隔が広がる部分８ｄにおいてそれぞれ小さくなっている差動伝送線路８と接地配線導体４ａとの間の間隔１１は、差動伝送線路８の線路間隔が一定である部分８ｃにおける差動伝送線路８と接地配線導体４ａとの間の間隔１１に対して、差動伝送線路８の線路間隔が広がる部分８ｄにおける線路間隔が、線路間隔が一定である部分８ｃにおける間隔の１．５倍以上大きくなって離れる部分において、差動伝送線路８と接地配線導体４ａとの間の間隔１１を７０％以下の大きさとなるように小さくすればよい。
【００５３】
例えば、誘電率が５．３で絶縁層の厚みが１２０μｍの絶縁基板２上に、導体幅が１００μｍで導体厚みが１２μｍの一対の線路導体８ａ・８ｂが形成され、差動インピーダンスが１００Ωになるよう線路間隔が一定の部分８ｃの線路間隔が１００μｍ、差動伝送線路８と接地配線導体４ａとの間の間隔１１が１００μｍに設定されている差動伝送線路８において、線路間隔が広がる部分８ｄの差動伝送線路８と接地配線導体４ａとの間の間隔１１を約４８μｍに設定することによって、その部分における差動インピーダンスを約１００Ωとすることが可能である。
【００５４】
また、差動伝送線路８の線路間隔が一定の部分８ｃにおける差動インピーダンスと、線路間隔が広がる部分８ｄにおける差動インピーダンスとを略同じとするように差動伝送線路８と接地配線導体４ａとの間の間隔１１を小さくするには、線路間隔が広がる部分８ｄにおける差動インピーダンスが１００Ω±５％となるように線路幅を設定すればよい。例えば、誘電率が５．３で絶縁層厚みが１２０μｍの絶縁基板２上に導体幅が１００μｍで導体厚みが１２μｍの一対の線路導体８ａ・８ｂが形成され、差動インピーダンスが１００Ωになるよう線路間隔が１００μｍ、差動伝送線路８と接地配線導体４ａとの間の間隔１１が１００μｍに設定されている差動伝送線路８において、差動伝送線路８と接地配線導体４ａとの間の間隔１１を４０μｍ〜５８μｍの間に設定することによって、差動伝送線路８の線路間隔が一定の部分８ｃにおける差動インピーダンスと、線路間隔が広がる部分８ｄにおける差動インピーダンスとを略同じとすることが可能である。
【００５５】
また、本発明の配線基板１’において、信号用貫通導体９ａ・９ｂを取り囲むように形成された接地用貫通導体１２は、例えば、誘電率が５．３の絶縁基板２上に線路間隔が広がる部分８ｄにおける差動インピーダンスが１００Ωになるように差動伝送線路８が形成され、線路間隔が広がる部分８ｄの一対の信号線路８ａ・８ｂの端部に接続される直径７５μｍの信号用貫通導体９ａ・９ｂに対して、信号用貫通導体９ａ・９ｂを中心としてそれぞれ２３０μｍの位置に同心円状に接地用貫通導体１２を等間隔で４本設置することにより、その部分における差動インピーダンスを約１００Ωとすることが可能である。
【００５６】
また、信号用貫通導体９ａ・９ｂを取り囲むようにそれぞれ形成された複数の接地用貫通導体１２を、差動伝送線路８の線路間隔が広がる部分８ｄにおける差動インピーダンスと信号用貫通導体９ａ・９ｂの差動インピーダンスとを略同じとなるように形成するには、信号用貫通導体９ａ・９ｂの差動インピーダンスが１００Ω±５％となるように信号用貫通導体９ａ・９ｂと接地用貫通導体１２との距離を設定すればよい。例えば、誘電率が５．３の絶縁基板２上に線路間隔が広がる部分８ｄにおける差動インピーダンスが１００Ωになるよう差動伝送線路８が形成され、線路間隔が広がる部分８ｄの一対の信号線路８ａ・８ｂの端部に接続される直径７５μｍの信号用貫通導体９ａ・９ｂにおいて、信号用貫通導体９ａ・９ｂを中心としてそれぞれ２２５μｍ〜２５０μｍの間の位置に同心円状に接地用貫通導体１２を等間隔で４本設置することにより、その部分における信号用貫通導体９ａ・９ｂの差動インピーダンスを約１００Ω±５％とすることが可能である。
【００５７】
なお、本発明は上記の実施の形態の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種々の変更を行なうことは何ら差し支えない。
【００５８】
例えば、差動伝送線路は、配線基板の内層に形成されてもよく、さらに差動伝送線路が電気的に接続される二次実装部は、コネクタやワイヤボンディングパッド等でもよい。また、線路間隔が一定の部分から線路間隔が広がる部分において、線路幅は変化部を設けて序々に大きくしてもよい。
【００５９】
【発明の効果】
本発明の配線基板によれば、絶縁基板上に形成された差動伝送線路について、差動伝送線路の線路間隔が広がる部分においてそれぞれの差動伝送線路とそれを囲繞する接地配線導体との間の間隔が小さくなっていることから、それぞれの伝送線路の接地配線導体との間の容量成分の増加による自己インピーダンスの減少によって、一対の差動伝送線路として見た場合に差動インピーダンスが減少するため、線路間隔が広がる部分において差動伝送線路の線路間隔の変化により発生していた差動インピーダンスの不整合による反射損失を効果的に抑えることが可能となる。
【００６０】
また、本発明の配線基板によれば、差動伝送線路と接地配線導体との間の間隔が、差動伝送線路の線路間隔が一定の部分における差動インピーダンスと、線路間隔が広がる部分における差動インピーダンスとが略同じとなるように小さくされているときには、差動伝送線路の線路間隔が広がる部分における差動インピーダンスの不整合をなくすことができ、高周波信号の反射損失を無視できる程度に小さく抑えることが可能となる。
【００６１】
また、差動伝送線路の線路間隔が広がった後の端部にそれぞれ信号用貫通導体が接続されるとともに、この信号用貫通導体を取り囲むようにそれぞれ複数の接地用貫通導体が形成されていることにより、これら信号用貫通導体および接地用貫通導体によって擬似同軸線路が形成され、信号用貫通導体からの放射による高周波信号の透過損失を抑えることが可能となる。
【００６２】
また、差動伝送線路の線路間隔が広がる部分における差動インピーダンスと信号用貫通導体の差動インピーダンスとが略同じとなるように接地用貫通導体が形成されていることにより、差動伝送線路と信号用貫通導体との接続部における差動インピーダンスの不整合をなくすことができ、高周波信号の反射損失を抑えることが可能となる。
【００６３】
これらのことにより、本発明の配線基板によれば、差動伝送線路の線路間隔が広がる部分における高周波信号の反射損失を極めて小さなものとすることができるので、これに搭載される半導体素子の高周波領域における作動性を良好なものとすることができる。
【図面の簡単な説明】
【図１】本発明の配線基板の実施の形態の一例を示す断面図である。
【図２】図１に示す配線基板における差動伝送線路の周辺部の要部拡大平面図である。
【図３】図１に示す配線基板における差動伝送線路の周辺部の要部拡大断面図である。
【図４】本発明の配線基板の実施の形態の他の例を示す断面図である。
【図５】図４に示す配線基板における差動伝送線路の周辺部の要部拡大平面図である。
【図６】従来の配線基板の例を示す断面図である。
【図７】図６に示す配線基板における差動伝送線路の周辺部の要部拡大平面図である。
【符号の説明】
１・１’・・・配線基板
２・・・絶縁基板
２ａ〜２ｄ・・・絶縁層
３・・・信号配線群
４・・・電源配線層および接地配線層
４ａ・・・接地配線導体
４ｂ・・・接地配線層
４ｂ・・・電源配線層
５・・・半導体素子
６・・・導体バンプ
７・・・半導体素子接続用電極
８・・・差動伝送線路
８ｃ・・・線路間隔が一定の部分
８ｄ・・・線路間隔が広がる部分
９，９ａ，９ｂ・・・貫通導体
１０・・・外部接続用電極
１１・・・差動伝送線路と接地配線導体との間の間隔
１２・・・接地用貫通導体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wiring board having a differential transmission line suitable for mounting electronic components such as semiconductor elements and optical semiconductor elements that operate at high speed.
[0002]
[Prior art]
In wiring boards for mounting electronic components such as semiconductor elements and optical semiconductor elements operating at high speed, in order to accurately and efficiently propagate high-speed signals, FIG. 6 is a cross-sectional view of an example of a conventional wiring board. As shown in an enlarged plan view of a main part of the differential transmission line in FIG. 7, a differential transmission line 48 is used as a signal line through which a high-speed signal propagates.
[0003]
As shown in FIG. 7, the differential transmission line 48 uses a pair of transmission lines 48a and 48b to apply positive-phase and negative-phase signals to the input side of each transmission line and take the difference at the output side. Thus, the common mode noise component can be canceled, and this is used for a transmission system capable of transmitting a high-quality signal. In this example, in order to improve the transmission characteristics of the differential transmission line 48, the transmission lines 48a and 48b are surrounded by the ground wiring conductor 44a at a constant interval 411. The structure of the differential transmission line 48 is such that the material of the insulating layers 42a to 42d of the insulating substrate 42 and the insulating layer 42a are selected so that the differential impedance determined by the pair of transmission lines 48a and 48b matches desired characteristics. To 42d are determined by controlling the cross-sectional structure (width, thickness and spacing of the wiring conductors 43 and 44, distance from the ground layer and the ground conductor, etc.).
[0004]
In the layout design of the differential transmission line 48, the wiring board 40 is formed using the differential transmission line 48 electrically connected to the electrode of the semiconductor element 45 via the conductor bump 46 and the semiconductor element connection electrode 47. A signal is transmitted on the upper surface, and the line interval between the pair of transmission lines 48a and 48b forming the differential transmission line 48 is determined according to the arrangement interval of the external connection electrodes 410 on the secondary mounting side of the wiring board 40. It is spread and connected to the external connection electrode 410 as a secondary mounting portion.
[0005]
[Patent Document 1]
JP-A-2002-9511
[Problems to be solved by the invention]
However, in the conventional differential transmission line 48 formed on the wiring board 40, the portion 48c having a constant line spacing designed to have a differential impedance of, for example, about 100Ω is a secondary mounting portion. It is necessary to extend and wire the differential transmission line 48 in accordance with the arrangement interval of the external connection electrodes 410. At this time, since the pair of transmission lines 48a and 48b are respectively surrounded and developed at a fixed interval 411 by the ground wiring layer 44a in the portion 48d where the line interval is widened, the transmission mode is set by the pair of transmission lines 48a and 48b. This changes from the differential mode for transmitting signals to the single mode for transmitting signals on one transmission line 48a or 48b.
[0007]
Normally, the differential impedance is 100Ω which is a value obtained by doubling the difference of the mutual impedance from one transmission line 48a or 48b from the self impedance of one transmission line 48a or 48b of the pair of transmission lines 48a and 48b. Is set to That is, the difference between the self impedance and the mutual impedance is set to be 50Ω. Therefore, the self-impedance of one transmission line 48a or 48b of the pair of transmission lines 48a and 48b is higher than 50Ω.
[0008]
In the portion 48d where the line interval is widened, the transmission mode changes from the differential mode in which the signal is transmitted through the pair of transmission lines 48a and 48b to the single mode in which the signal is transmitted through one transmission line 48a or 48b. The influence of the mutual impedance from the other transmission line 48a or 48b is reduced, and as a result, when viewed as the differential transmission line 48, the differential impedance of the differential transmission line 48 increases.
[0009]
For this reason, in the portion 48d where the line interval is widened when the transmission mode is switched from the differential mode to the single mode, the differential impedance is shifted from 100Ω and becomes high, and the portion 48c where the line interval is constant and the portion 48d where the line interval is widened. However, there is a problem in that impedance mismatch occurs between the two, and the reflection loss increases, signal transmission is hindered, and the operability of the semiconductor element 45 may be impaired.
[0010]
The present invention has been devised in view of the above problems, and an object of the present invention is to suppress a reflection loss occurring in a portion of a differential transmission line from a portion where a line interval is constant to a portion where a line interval is widened to a very small one. It is an object of the present invention to provide a wiring board which can improve the operability of a semiconductor element.
[0011]
[Means for Solving the Problems]
In the wiring board of the present invention, a differential transmission line is formed on an insulating substrate, and the differential transmission line is surrounded by a ground wiring conductor, and the interval between the differential transmission lines is equal to the line interval of the differential transmission line. It is characterized in that the line spacing is smaller at a portion where the line interval is wider than a certain portion.
[0012]
Further, in the wiring board of the present invention, in the above configuration, the interval between the differential transmission line and the ground wiring conductor is a differential impedance in a portion where the line interval of the differential transmission line is constant, The differential impedance is reduced so that the differential impedance at a portion where the line interval is widened is substantially the same.
[0013]
Further, in the wiring board of the present invention, in each of the above-described configurations, a signal through conductor is connected to each of the ends of the differential transmission lines after the line spacing is widened and surrounds the signal through conductor. A plurality of grounding through conductors are formed, respectively.
[0014]
Further, in the wiring board according to the present invention, in the above-described configuration, the grounding through conductor has substantially the same differential impedance as that of the signal transmission through conductor at a portion where the line interval of the differential transmission line is widened. It is characterized by being formed so that it becomes.
[0015]
ADVANTAGE OF THE INVENTION According to the wiring board of this invention, about the differential transmission line formed on the wiring board, between each differential transmission line and the ground wiring conductor surrounding it in the part where the line space | interval of a differential transmission line expands. Is reduced, the self-impedance decreases due to an increase in the capacitance component between each transmission line and the ground wiring conductor, and the differential impedance decreases when viewed as a pair of differential transmission lines. Therefore, it is possible to effectively suppress the reflection loss due to the mismatch of the differential impedance caused by the change in the line interval of the differential transmission line in the portion where the line interval is widened.
[0016]
Further, according to the wiring board of the present invention, the distance between the differential transmission line and the ground wiring conductor is different from the differential impedance at the portion where the line interval of the differential transmission line is constant, and the differential impedance at the portion where the line interval is widened. When the dynamic impedance is reduced to be substantially the same, it is possible to eliminate the mismatch of the differential impedance in the portion where the line interval of the differential transmission line is widened, and to reduce the reflection loss of the high-frequency signal to a negligible level. It can be suppressed.
[0017]
In addition, a through conductor for signal is connected to each end of the differential transmission line after the line interval is widened, and a plurality of through conductors for ground are formed so as to surround the through conductor for signal. Accordingly, a pseudo coaxial line is formed by the through conductor for signal and the through conductor for ground, and transmission loss of a high-frequency signal due to radiation from the through conductor for signal can be suppressed.
[0018]
In addition, the through conductor for grounding is formed so that the differential impedance of the portion where the line spacing of the differential transmission line is widened and the differential impedance of the through conductor for signal are substantially the same, so that the differential transmission line It is possible to eliminate the mismatch of the differential impedance at the connection portion with the signal through conductor, and it is possible to suppress the reflection loss of the high-frequency signal.
[0019]
As a result, according to the wiring board of the present invention, the reflection loss of the high-frequency signal in the portion where the line interval of the differential transmission line is widened can be made extremely small. The operability in the region can be improved.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
The wiring board of the present invention will be described below in detail with reference to the drawings.
[0021]
FIG. 1 is a sectional view showing an example of an embodiment of a wiring board according to the present invention, and FIG. 2 is an enlarged plan view of a main part around a differential transmission line in the wiring board shown in FIG.
[0022]
In the wiring board 1 of this example, the insulating layers 2a to 2d constituting the insulating substrate 2 are basically formed of an insulating material having the same relative dielectric constant. A signal wiring group 3 is formed on the insulating layer 2c, and a large-area ground wiring layer 4b or power supply wiring layer 4c is formed on the insulating layers 2b and 2d so as to face the signal wiring group 3. Each signal wiring of group 3 has a strip line structure. On the insulating layer 2a, a ground wiring conductor 4a is formed so as to surround the differential transmission line 8 at a constant interval 11. Note that the power supply wiring layer 4b and the ground wiring layer 4c may be arranged interchangeably according to the specifications of the wiring board 1.
[0023]
The width of each signal wiring of the signal wiring group 3 and the thickness of the insulating layers 2a, 2b and 2c interposed between the signal wiring group 3 and the power supply wiring layer 4c or the ground wiring conductor 4a and the ground wiring layer 4b are appropriately determined. By setting, the characteristic impedance of the signal wiring group 3 can be set to an arbitrary value, so that the signal wiring group 3 having good transmission characteristics can be formed. Generally, the characteristic impedance of the signal wiring group 3 is often set to 50Ω.
[0024]
The plurality of signal lines included in the signal line group 3 may transmit different electric signals.
[0025]
In this example, a semiconductor element 5 such as a semiconductor element or an optical semiconductor element that operates at a high speed is mounted on the upper surface of the wiring board 1 and is made of a solder such as a tin-lead alloy (Sn-Pb) or gold (Au). It is electrically connected to a differential transmission line 8 via a semiconductor element connection electrode 7 for connecting the conductor bump 6 and the semiconductor element 5. On the lower surface of the wiring substrate 1 opposite to the upper surface on which the semiconductor element 5 is mounted, an external connection electrode 10 for inputting / outputting signals and supplying power to the semiconductor element 5 is provided.
[0026]
Further, the differential transmission line 8 is a pair of signal lines 8a having a so-called grounded coplanar structure formed between the ground wiring conductor 4a and the ground wiring layer 4b which are surrounded on the upper surface of the insulating layer 2a at a fixed interval 11. 8b, which is electrically connected to the electrode of the semiconductor element 5 through the semiconductor element connection electrode 7 and the conductor bump 6 made of solder such as tin-lead alloy (Sn-Pb) or gold (Au). It is electrically connected to an external connection electrode 10 via a through conductor 9 for inputting / outputting a signal to / from the outside.
[0027]
This will be described in detail with reference to FIG. FIG. 2 is an enlarged plan view of a main part showing a peripheral portion of a differential transmission line in an example of a wiring board according to an embodiment of the present invention. 2, the insulating layer 2 corresponds to the insulating layer 2a shown in FIG.
[0028]
The differential transmission lines 8a and 8b correspond to the differential transmission line 8 shown in FIG. 1, and are surrounded by the ground wiring conductor 4a at a fixed interval 11, and are shown in FIG. It is electrically connected via the conductor bump 6 and the semiconductor element connection electrode 7, and is also electrically connected with the external connection electrode 10 via the through conductor 9. The differential transmission line 8 is formed by a portion 8c in which the interval between the pair of signal lines 8a and 8b is constant and a portion 8d in which the interval between the pair of signal lines 8a and 8b is wide, and between the signal lines 8a and 8b. The distance 11 between the signal lines 8a and 8b and the ground wiring conductor 4a in the portion 8d where the distance is widened is different from the difference transmission line 8 and the ground wiring conductor 4a in the portion 8c where the distance between the signal lines 8a and 8b is constant. Is formed smaller than the interval 11 between them. At the end of the portion 8d where the interval between the signal lines 8a and 8b is widened, the differential transmission lines 8a and 8b are electrically connected to the external connection electrode 10 via the through conductors 9a and 9b, respectively. .
[0029]
Next, FIG. 3 is an enlarged sectional view of a main part showing a peripheral portion of a differential transmission line in an example of an embodiment of a wiring board of the present invention. In FIG. 3, the signal lines 8a and 8b of the differential transmission line 8 are formed of the wiring width, the wiring interval, the wiring thickness of the differential transmission line 8, and the insulating layer 2a interposed between the power transmission wiring layer and the ground wiring layer 4b. By appropriately setting the thickness and the interval 11 between the differential transmission line 8 and the ground wiring conductor 4a, the differential impedance of the differential transmission line 8 can be set to an arbitrary value. Can be formed. In general, the differential impedance of the differential transmission line 8 is often set to 100Ω.
[0030]
Next, FIG. 4 is a cross-sectional view showing another example of the embodiment of the wiring board of the present invention, and FIG. 5 is an enlarged plan view of a main part around a differential transmission line in the wiring board shown in FIG. is there. 4 and 5, the same parts as those in FIGS. 1 to 3 are denoted by the same reference numerals.
[0031]
In the wiring board 1 'of this example, the differential transmission line 8 has a signal through conductor 9 at the end of the signal line 8a or 8b after the line interval is widened at the portion 8d where the line interval is wide. And a plurality of grounding through-conductors 12 are formed so as to surround the signal through-conductor 9 while being electrically connected to the signal external connection electrode 10 through the connection. The conductor 12 is electrically connected to the power supply or ground external connection electrode 10 via the power supply wiring layer 4b or the ground wiring layer 4c.
[0032]
This will be described in detail with reference to FIG. FIG. 5 is an enlarged plan view of a main part similar to FIG. 2 showing a peripheral portion of a differential transmission line in another example of the embodiment of the wiring board of the present invention.
[0033]
In FIG. 5, the differential transmission lines 8a and 8b correspond to the differential transmission line 8 shown in FIG. 4, via the semiconductor element 5 and the conductor bump 6 and the semiconductor element connection electrode 7 shown in FIG. It is electrically connected and is electrically connected to the external signal connection electrode 10 via the signal through conductors 9a and 9b. The signal through conductors 9a and 9b are each surrounded by a plurality of ground through conductors 12 so as to form a pseudo coaxial line, and the ground through conductors 12 are used for power supply or ground via the power supply wiring layer 4b or the ground wiring layer 4c. Connected to the external connection electrode 10.
[0034]
According to such a wiring board 1 ′ of the present invention, the signal through conductors 9a and 9b are connected to the ends of the signal lines 8a and 8b after the line interval of the differential transmission line 8 is widened, respectively. Since a plurality of ground through conductors 12 are formed so as to surround the signal through conductors 9a and 9b, a pseudo coaxial line is formed by the signal through conductors 9a and 9b and the ground through conductor 12. It is possible to suppress transmission loss of high-frequency signals due to radiation from the signal through conductors 9a and 9b.
[0035]
Further, the grounding through conductor 12 is formed so that the differential impedance of the portion 8d of the differential transmission line 8 where the line interval is widened and the differential impedance of the signal through conductors 9a and 9b are substantially the same. In addition, it is possible to eliminate the mismatch of the differential impedance at the connection between the differential transmission line 8 and the signal through conductors 9a and 9b, and to suppress the reflection loss of the high-frequency signal.
[0036]
The wiring boards 1 and 1 ′ of the present invention may have a multilayer wiring board in which the same wiring structure is further laminated in multiple layers.
[0037]
The structure of the signal wiring group 3 and the differential transmission line 8 is not limited to a coplanar line structure in which a power supply wiring layer or a ground wiring layer is formed adjacent to each signal wiring of the signal wiring group and the differential transmission line. A microstrip line structure having a power supply wiring layer or a ground wiring layer formed facing the signal wiring group and the differential transmission line, or a power supply wiring layer or a ground wiring layer above and below the signal wiring group and the differential transmission line A strip line structure may be used, and may be appropriately selected and used according to specifications required for the wiring board 1 and the like.
[0038]
Further, an electronic circuit module or the like may be configured by attaching a chip resistor, a thin film resistor, a coil inductor, a cross inductor, a chip capacitor, an electrolytic capacitor, or the like to the wiring board 1.1 ′.
[0039]
Further, the shape of each of the insulating layers 2a to 2d in plan view may be a shape such as a diamond shape, a hexagonal shape, or an octagonal shape in addition to a square shape or a rectangular shape.
[0040]
Such a wiring board 1 1 ′ of the present invention includes a package for storing electronic components such as a package for storing semiconductor elements, a board for mounting electronic components, a so-called multi-chip module or multi-chip on which a large number of semiconductor elements are mounted. Used as a package or motherboard.
[0041]
In the wiring board 1 ・ 1 ′ of the present invention, each of the insulating layers 2a to 2d is formed by, for example, a ceramic green sheet lamination method using an aluminum oxide-based sintered body, an aluminum nitride-based sintered body, a silicon carbide-based sintered body, or silicon nitride. Using an inorganic insulating material such as porous sintered body, mullite sintered body or glass ceramics, or using an organic insulating material such as polyimide, epoxy resin, fluororesin, polynorbornene or benzocyclobutene, or ceramics It is formed using an electric insulating material such as a composite insulating material formed by bonding inorganic insulating powder such as powder with a thermosetting resin such as epoxy resin.
[0042]
These insulating layers 2a to 2d are manufactured as follows. For example, if it is made of an aluminum oxide sintered body, first, an appropriate organic binder and a solvent are added to a raw material powder such as aluminum oxide, silicon oxide, calcium oxide, or magnesium oxide to form a slurry. This is formed into a sheet by using a doctor blade method or the like to obtain a ceramic green sheet. Then, a metal paste to be each of the signal wiring groups 3 and each of the conductor layers 4 is printed and applied in a predetermined pattern and laminated vertically, and finally, the laminate is fired in a reducing atmosphere at a temperature of about 1600 ° C. Produced by
[0043]
Further, for example, in the case of an epoxy resin, an insulating layer made of a glass epoxy resin or the like formed by impregnating a ceramic or glass fiber woven cloth of an aluminum oxide sintered body with an epoxy resin is generally used. An organic resin precursor is applied by a spin coating method or a curtain coating method or the like, and an insulating layer made of an organic resin such as an epoxy resin formed by subjecting the organic resin precursor to a thermosetting treatment, and copper is formed by electroless plating or vapor deposition. It is manufactured by alternately laminating thin film wiring conductor layers formed by adopting a thin film forming technique such as a method and a photolithography technique and heating and curing at a temperature of about 170 ° C.
[0044]
The thicknesses of the insulating layers 2a to 2d are appropriately set according to the characteristics of the material to be used so as to satisfy conditions such as mechanical strength and electric characteristics corresponding to required specifications.
[0045]
As a method for obtaining the insulating layers 2a to 2d having different relative dielectric constants, for example, an inorganic insulating material such as aluminum oxide, aluminum nitride, silicon carbide, silicon nitride, mullite or glass ceramics, or a polyimide / epoxy resin・ Add powder of high dielectric material such as barium titanate, strontium titanate, calcium titanate or magnesium titanate to organic insulating material such as fluororesin, polynorbornene or benzocyclobutene, and heat and cure at appropriate temperature By doing so, a material having a desired relative permittivity may be obtained.
[0046]
At this time, the particle diameter of the high dielectric material added and mixed with the inorganic insulating material or the organic insulating material is determined by the relative dielectric constant in the insulating layer caused by adding the high dielectric material to the inorganic insulating material or the organic insulating material. In order to reduce the occurrence of variation and the reduction in workability due to a change in the viscosity of the insulating layer, the thickness is desirably 0.5 to 50 μm.
[0047]
In addition, the content of the high dielectric material to be added to and mixed with the inorganic insulating material and the organic insulating material is to increase the relative dielectric constant of the insulating layer and to adhere the inorganic insulating material or the organic insulating material to the high dielectric material. In order to prevent a decrease in strength, the content is desirably 5 to 75% by weight.
[0048]
The signal wiring group 3 and each differential transmission line 8, the ground wiring conductor 4a, the ground wiring layer 4b, or the power wiring layer 4c are made of, for example, tungsten (W), molybdenum (Mo), molybdenum manganese (Mo-Mn), copper (Cu) / silver (Ag) or metal powder such as silver palladium (Ag-Pd), or copper (Cu) / silver (Ag) / nickel (Ni) / chromium (Cr) / titanium (Ti) / gold ( It may be formed of a thin film of a metal material such as Au) or niobium (Nb) or an alloy thereof.
[0049]
Specifically, when the signal wiring group 3, the ground wiring conductor 4a, the ground wiring layer 4b, or the power wiring layer 4c is formed by metallizing metal powder of W, an appropriate organic binder or solvent is added to the W powder and mixed. The metal paste thus obtained can be formed by printing and applying a predetermined pattern on a ceramic green sheet to be the insulating layers 2a to 2d, and firing this together with a laminate of ceramic green sheets.
[0050]
When a thin film of a metal material is used, a metal film can be formed by, for example, a sputtering method, a vacuum evaporation method, or a plating method, and then can be formed into a predetermined wiring pattern by a photolithography method.
[0051]
Such wiring boards 1 and 1 ′ are provided with the signal wiring group 3 and the wiring of each signal wiring of the differential transmission line 8 according to the relative permittivity of the insulating layers 2 a to 2 d on which the signal wiring group 3 is provided. By appropriately setting the width, the wiring thickness, and the wiring interval, the characteristic impedance value of each signal wiring of the signal wiring group 3 and the differential impedance value of the differential transmission line 8 can be set to desired values.
[0052]
In the wiring boards 1 and 1 'of the present invention, the distance 11 between the differential transmission line 8 and the ground wiring conductor 4a, which is reduced at the portion 8d where the line interval of the differential transmission line 8 is widened, is different from that of the differential transmission line. Compared with the distance 11 between the differential transmission line 8 and the ground wiring conductor 4a in the portion 8c where the line interval of the line 8 is constant, the line interval in the portion 8d where the line interval of the differential transmission line 8 is widened At a part which is 1.5 times or more as large as the distance in the part 8c having a constant distance, the distance 11 between the differential transmission line 8 and the ground wiring conductor 4a is reduced to 70% or less. Just fine.
[0053]
For example, a pair of line conductors 8a and 8b each having a conductor width of 100 μm and a conductor thickness of 12 μm are formed on an insulating substrate 2 having a dielectric constant of 5.3 and an insulation layer thickness of 120 μm, and have a differential impedance of 100Ω. In the differential transmission line 8 in which the line interval of the portion 8c having a constant line interval is set to 100 μm and the interval 11 between the differential transmission line 8 and the ground wiring conductor 4a is set to 100 μm, the portion 8d in which the line interval is widened By setting the distance 11 between the differential transmission line 8 and the ground wiring conductor 4a to about 48 μm, the differential impedance at that portion can be about 100Ω.
[0054]
Further, the differential transmission line 8 and the ground wiring conductor 4a are connected to each other so that the differential impedance of the differential transmission line 8 at the portion 8c where the line interval is constant is substantially equal to the differential impedance at the portion 8d where the line interval is widened. In this case, the line width may be set such that the differential impedance at the portion 8d where the line interval is widened is 100Ω ± 5%. For example, a pair of line conductors 8a and 8b each having a conductor width of 100 μm and a conductor thickness of 12 μm are formed on an insulating substrate 2 having a dielectric constant of 5.3 and an insulation layer thickness of 120 μm, and the line impedance is set so that the differential impedance becomes 100Ω. In the differential transmission line 8 in which the interval is set to 100 μm and the interval 11 between the differential transmission line 8 and the ground wiring conductor 4a is set to 100 μm, the interval 11 between the differential transmission line 8 and the ground wiring conductor 4a is set. Is set between 40 μm and 58 μm, it is possible to make the differential impedance in the portion 8c where the line interval of the differential transmission line 8 is constant equal to the differential impedance in the portion 8d where the line interval is widened. It is.
[0055]
In the wiring board 1 'of the present invention, the grounding through-conductors 12 formed so as to surround the signal through-conductors 9a and 9b have, for example, a wider line spacing on the insulating substrate 2 having a dielectric constant of 5.3. The differential transmission line 8 is formed such that the differential impedance in the portion 8d becomes 100Ω, and the signal through conductor 9a having a diameter of 75 μm is connected to the ends of the pair of signal lines 8a and 8b in the portion 8d where the line interval is widened. By setting four concentrically-spaced through-conductors 12 at 230 μm around the signal through-conductors 9 a and 9 b at equal intervals with respect to the signal through-conductors 9 a and 9 b, the differential impedance at that portion is reduced to about 100Ω. It is possible to do.
[0056]
Further, the plurality of grounding through-conductors 12 formed so as to surround the signal through-conductors 9a and 9b are connected to the differential impedance and the signal through-conductors 9a and 9b at the portion 8d where the line interval of the differential transmission line 8 is increased. Of the signal through conductors 9a and 9b and the ground through conductor 12 so that the differential impedance of the signal through conductors 9a and 9b becomes 100Ω ± 5%. What is necessary is just to set the distance with. For example, the differential transmission line 8 is formed on the insulating substrate 2 having a permittivity of 5.3 so that the differential impedance at the portion 8d where the line interval is widened becomes 100Ω, and a pair of signal lines 8a of the portion 8d where the line interval is widened. In the signal through conductors 9a and 9b with a diameter of 75 μm connected to the end of 8b, the ground through conductors 12 are arranged concentrically at positions between 225 μm and 250 μm around the signal through conductors 9a and 9b. By providing four at intervals, the differential impedance of the signal through conductors 9a and 9b at that portion can be set to about 100Ω ± 5%.
[0057]
Note that the present invention is not limited to the above-described embodiment, and various changes may be made without departing from the spirit of the present invention.
[0058]
For example, the differential transmission line may be formed on an inner layer of the wiring board, and the secondary mounting portion to which the differential transmission line is electrically connected may be a connector, a wire bonding pad, or the like. In a portion where the line interval is widened from a portion where the line interval is constant, the line width may be gradually increased by providing a change portion.
[0059]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the wiring board of this invention, about the differential transmission line formed on the insulating substrate, between each differential transmission line and the ground wiring conductor surrounding it in the part where the line space | interval of a differential transmission line expands. Is reduced, the self-impedance decreases due to an increase in the capacitance component between each transmission line and the ground wiring conductor, and the differential impedance decreases when viewed as a pair of differential transmission lines. Therefore, it is possible to effectively suppress the reflection loss due to the mismatch of the differential impedance caused by the change in the line interval of the differential transmission line in the portion where the line interval is widened.
[0060]
Further, according to the wiring board of the present invention, the distance between the differential transmission line and the ground wiring conductor is different from the differential impedance at the portion where the line interval of the differential transmission line is constant, and the differential impedance at the portion where the line interval is widened. When the dynamic impedance is reduced to be substantially the same, it is possible to eliminate the mismatch of the differential impedance in the portion where the line interval of the differential transmission line is widened, and to reduce the reflection loss of the high-frequency signal to a negligible level. It can be suppressed.
[0061]
In addition, a through conductor for signal is connected to each end of the differential transmission line after the line interval is widened, and a plurality of through conductors for ground are formed so as to surround the through conductor for signal. Accordingly, a pseudo coaxial line is formed by the through conductor for signal and the through conductor for ground, and transmission loss of a high-frequency signal due to radiation from the through conductor for signal can be suppressed.
[0062]
In addition, the through conductor for grounding is formed so that the differential impedance of the portion where the line spacing of the differential transmission line is widened and the differential impedance of the through conductor for signal are substantially the same, so that the differential transmission line It is possible to eliminate the mismatch of the differential impedance at the connection portion with the signal through conductor, and it is possible to suppress the reflection loss of the high-frequency signal.
[0063]
As a result, according to the wiring board of the present invention, the reflection loss of the high-frequency signal in the portion where the line interval of the differential transmission line is widened can be made extremely small. The operability in the region can be improved.
[Brief description of the drawings]
FIG. 1 is a sectional view showing an example of an embodiment of a wiring board of the present invention.
FIG. 2 is an enlarged plan view of a main part around a differential transmission line in the wiring board shown in FIG. 1;
FIG. 3 is an enlarged cross-sectional view of a main part around a differential transmission line in the wiring board shown in FIG. 1;
FIG. 4 is a sectional view showing another example of the embodiment of the wiring board of the present invention.
FIG. 5 is an enlarged plan view of a main part around a differential transmission line in the wiring board shown in FIG. 4;
FIG. 6 is a cross-sectional view illustrating an example of a conventional wiring board.
7 is an enlarged plan view of a main part around a differential transmission line in the wiring board shown in FIG. 6;
[Explanation of symbols]
1 1 ′ Wiring board 2 Insulating substrates 2a to 2d Insulating layer 3 Signal wiring group 4 Power wiring layer and ground wiring layer 4a Ground wiring conductor 4b ..Grounding wiring layer 4b power supply wiring layer 5 semiconductor element 6 conductor bump 7 semiconductor element connecting electrode 8 differential transmission line 8c line spacing is constant Part 8d: part where line spacing is widened 9, 9a, 9b ... through conductor 10 ... external connection electrode 11 ... distance between differential transmission line and ground wiring conductor 12 ... ground For through conductor

Claims

A differential transmission line is formed on the insulating substrate, and the differential transmission line is surrounded by a ground wiring conductor, and the interval between the differential transmission line and the line interval of the differential transmission line is constant. A wiring board characterized in that it is reduced in a portion where a line interval is widened.

The distance between the differential transmission line and the ground wiring conductor is substantially equal to the differential impedance at a portion where the line interval of the differential transmission line is constant and the differential impedance at a portion where the line interval is widened. 2. The wiring board according to claim 1, wherein the wiring board is made smaller to be the same.

A signal through conductor is connected to each of the ends of the differential transmission line after the line spacing is widened, and a plurality of ground through conductors are formed so as to surround the signal through conductor. The wiring board according to claim 1 or 2, wherein

The ground through conductor is formed such that the differential impedance of the differential transmission line at a portion where the line interval is widened and the differential impedance of the signal through conductor are substantially the same. The wiring board according to claim 3.