JP2005045432A

JP2005045432A - Surface acoustic wave device

Info

Publication number: JP2005045432A
Application number: JP2003201639A
Authority: JP
Inventors: Yasuhide Onozawa; 康秀小野澤; Yuji Ogawa; 祐史小川
Original assignee: Toyo Communication Equipment Co Ltd
Current assignee: Toyo Communication Equipment Co Ltd
Priority date: 2003-07-25
Filing date: 2003-07-25
Publication date: 2005-02-17

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a SAW device which has a large electromechanical coupling coefficient for realizing a wide-band filter and also has small transmission loss. <P>SOLUTION: The surface acoustic wave device is constituted by arranging IDT electrodes on the main surface of rotary Y-cut X-propagation lithium niobate (LiNbO<SB>3</SB>) in the propagation direction of a Love wave, and the metal material of the IDT electrodes is an alloy which is principally comprised of Ag and contains 0.1 to 3.0 wt.% Pd and 0.1 to 3.0 wt.% Cu. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は弾性表面波デバイスに関し、特に大きな電気機械結合係数ｋ^２を有し、伝送損失の小さな弾性表面波デバイスに関する。
【０００２】
【従来の技術】
近年、弾性表面波デバイス（以下、ＳＡＷデバイスと称する）は通信分野で広く利用され、高性能、小型、量産性等の優れた特徴を有することから特に携帯電話、無線ＬＡＮ等に多く用いられている。周知のように、弾性表面波とは媒質の表面付近にエネルギーを集中させて伝搬する波の総称で、圧電基板の表面上に形成したＩＤＴ電極により弾性表面波を励振し、また受信することができる。ＳＡＷデバイスに利用されている主な弾性表面波としてはレイリー波がよく知られているが、この他にＳＨ波（ＳＨ波タイプ）、ラブ波（Ｌｏｖｅｗａｖｅ）、漏洩弾性表面波（Ｌｅａｋｙ）等がある。
【０００３】
ＳＡＷデバイスに最も多く用いられているレイリー波は、図４（ａ）に示すように半無限の個体表面にエネルギーを集中させて伝搬する弾性表面波で、レイリー波の変位は表面波の進行方向Ｘ１の成分ｕ１（Ｐ波）と、深さ方向Ｘ３の成分ｕ３（ＳＶ波）のみを有し、ｕ３はｕ１と位相が９０°ずれている。即ち、レイリー波は（Ｐ＋ＳＶ）波ということができる。レイリー波は表面近くではｕ３がｕ１に対して９０°進むことから、後方楕円回転を示し、深さＸ３＝０．２λ（λはレイリー波の波長）より深いところでは前方楕円回転となり、深さＸ３＝２λより深いところでは変位ｕ１、ｕ３共ほぼ零となる。また、伝搬速度が周波数に無関係に一定であり、速度分散性が無いことも大きな特徴である。図４（ｂ）はレイリー波を用いたＳＡＷ共振子の構成を示す平面図であって、圧電基板２１の主表面上にレイリー波の伝搬方向に沿ってＩＤＴ電極２２と、その両側にグレーティング反射器（以下、反射器と称す）２３ａ、２３ｂをそれぞれ配置する。ＩＤＴ電極２２は互いに間挿し合う複数の電極指を有する一対の電極より構成され、一方の電極はＴ１端子に、他方の端子はＴ２端子に接続してＳＡＷ共振子を完成する。
【０００４】
圧電基板に高結合材料といわれる１２８°回転ＹカットＸ伝搬のニオブ酸リチウム（１２８°Ｙ−ＸＬｉＮｂＯ_３）を用い、レイリー波を利用したＳＡＷデバイスを構成しても電気機械結合係数ｋ^２は５．５％と小さく、最近要求される広帯域のＳＡＷフィルタの要求を満たすことは出来ない。そこで、大きな電気機械結合係数ｋ^２が期待できる弾性表面波としてＳＨ波（ＳＨ波タイプ）を用いたＳＡＷデバイスがある。ＳＨ波は図５に示すように波動の進行方向Ｘ１と変位方向ｕ２とが直交した横波で、圧電媒質に異方性があるとその表面にエネルギーを集中させて伝搬する性質がある。この表面波は圧電表面すべり波、あるいは発見者の名前をとってＢＧＳ波とも呼ばれる。このＳＨ波は六方晶系６ｍｍ圧電結晶、あるいは圧電セラミック板のＣ軸または分極軸が基板表面に平行な場合などに存在する。
【０００５】
特開２００１−７７６６２号公報には、オイラー角が（０°，１２５°〜１４６°，０°±５°）の回転ＹカットＸ伝搬のＬｉＴａＯ_３上に比重の重い金属（Ａｕ、Ａｇ、Ｔａ、Ｍｏ等）のＩＤＴ電極を形成してＳＨ波を励起したＳＡＷデバイスの伝送損失、電気機械結合係数ｋが開示されている。この発明によると伝送損失も良好であり、電気機械結合係数ｋも２２％から３０％（ｋ^２＝５％〜９％）程度のものが得られたと記されている。
【０００６】
大きな電気機械結合係数ｋ^２が期待できる弾性表面波の１つにラブ波を用いたＳＡＷデバイスがあり、ラブ波は図６に示すように圧電媒質Ｂの上に表面層Ａを形成し、表面層Ａの音速Ｖａと圧電媒質Ｂの音速Ｖｂとの間にＶａ＜Ｖｂの関係が成り立つ時に生ずる弾性表面波で、周波数が高いほど変位（エネルギー）は表面に集中することになる。現象的には表面層Ａの遅い波のために圧電媒質Ｂの波が引きずられ、押し上げられる形でエネルギーが表面に集中するものと考えられる。
【０００７】
ラブ波を利用したＳＡＷデバイスは特開昭５９−１５６０１３号公報に開示されており、圧電基板に回転Ｙ−ＸＬｉＮｂＯ_３を用い、該圧電基板上に導波路を形成するように音速の遅い高密度の金属薄膜、または誘電体膜を形成し、さらにＩＤＴ電極を配置して構成している。ここで、高密度の金属としては金、銀、白金を使用している。このようにして構成したＳＡＷデバイスの電気機械結合係数ｋ^２は２８％から１４％に達すると記されている。
さらに、特開平６−１６４３０６号公報には回転Ｙ−ＸＬｉＴａＯ_３の主表面上に比重の大きな金属のＩＤＴ電極を配置してラブ波型ＳＡＷデバイスを構成した例が開示されている。この発明によると構成されたＳＡＷデバイスの電気機械結合係数ｋ^２は１１％以上に達すると記されている。
【特許文献１】特開２００１−７７６６２号公報
【特許文献２】特開昭５９−１５６０１３号公報
【特許文献３】特開平６−１６４３０６号公報
【０００８】
【発明が解決しようとする課題】
しかしながら、上述のようにＬｉＴａＯ_３上にＩＤＴ電極を形成しＳＨ波を励起するＳＡＷデバイスは、伝送損失、電気機械結合係数ｋ^２が良好であるものの、ＩＤＴ電極にＡｕを用いればコストが高価になり、Ａｇ、Ｔａ、Ｍｏ、Ｃｕ、Ｎｉ、Ｃｒ、Ｚｎ、Ｗ等を用いれば対耐候性に難点があるという問題があった。
また、ＬｉＮｂＯ_３、ＬｉＴａＯ_３上にＩＤＴ電極を形成しラブ波を利用するＳＡＷデバイスでは、金、銀あるいは白金等の膜を厚く付着する必要があり、金、白金の場合は高価に、銀の場合は耐候性に難点があるという問題があった。
しかし、特開２００１−１９２７５２号公報にはＡｇを主成分として、Ｐｄを０．１〜３ｗｔ％含有し、Ａｌ、Ａｕ、Ｐｔ、Ｃｕ、Ｔａ、Ｃｒ、Ｔｉ、Ｎｉ、Ｃｏ、Ｓｉから複数の元素を合計で０．１〜３ｗｔ％含有する電子部品用金属材料が開示され、耐候性にも優れ、比抵抗も小さいと記述されている。
また、特開２００２−１４０９２９号公報にはＡｇを主成分とし、Ａｕを０．１ｗｔ％以上１０ｗｔ％以下の範囲で含有し、Ｐｄ、Ａｌ、Ｃｕ、Ｔａ、Ｃｒ、Ｔｉ、Ｎｉ、Ｖ、Ｗ、Ｍｏ、Ｒｕ、Ｍｇから１種類以上の元素を０．１ｗｔ％以上５ｗｔ％以下添加した電子部品用金属材料が開示され、耐候性にも優れ、比抵抗も小さいと記述されている。
さらに、特開２００３−５５７２１号公報にはＡｇに、ＡｕとＣｕ、Ｔｉ及びＳｎから選択された少なくとも１つの金属を添加したＡｇ合金の薄膜で、０．１〜４．０ａｔ％のＡｕ、０〜５．０ａｔ％のＣｕ、０〜１．０ａｔ％のＴｉ、０〜１．０ａｔ％のＳｎを含有するＡｇ合金膜が開示され、密着性、比抵抗とも従来のものより優れていると記述されている。
本発明は上記問題を解決するためになされたものであって、低コストで且つ大きな電気機会結合係数ｋ^２を有するＳＡＷデバイスを提供することを目的とする。
【特許文献４】特開２００１−１９２７５２号公報
【特許文献５】特開２００２−１４０９２９号公報
【特許文献６】特開２００３−５５７２１号公報
【０００９】
【課題を解決するための手段】
上記目的を達成するために本発明に係る弾性表面波デバイスの請求項１記載の発明は、オイラー角が（０°，９０°〜１５０°，０°±５°）であるニオブ酸リチウム（ＬｉＮｂＯ_３）の主表面上にラブ波の伝搬方向に沿ってＩＤＴ電極を配置して構成した弾性表面波デバイスにおいて、前記ＩＤＴ電極の材料としてＡｇを主成分とし、０．１ｗｔ％〜３．０ｗｔ％のＰｄと、０．１ｗｔ％〜３．０ｗｔ％のＣｕとを含有した合金を用いたこと特徴とする弾性表面波デバイスである。
請求項２記載の発明は、オイラー角が（０°，８０°〜１４０°，０°±５°）であるタンタル酸リチウム（ＬｉＴａＯ_３）の主表面上にラブ波の伝搬方向に沿ってＩＤＴ電極を配置して構成した弾性表面波デバイスにおいて、前記ＩＤＴ電極の材料としてＡｇを主成分とし、０．１ｗｔ％〜３．０ｗｔ％のＰｄと、０．１ｗｔ％〜３．０ｗｔ％のＣｕとを含有した合金を用いたこと特徴とする弾性表面波デバイスである。
請求項３記載の発明は、オイラー角が（０°，１２５°〜１４６°，０°±５°）であるＬｉＴａＯ_３基板にＳＨ波を励起するＩＤＴ電極を形成した弾性表面波デバイスにおいて、前記ＩＤＴ電極の材料としてＡｇを主成分とし、０．１ｗｔ％〜３．０ｗｔ％のＰｄと、０．１ｗｔ％〜３．０ｗｔ％のＣｕとを含有した合金を用いると共に規格化膜厚Ｈ／λ（Ｈは電極膜厚、λは励起されるＳＨ波の波長）を０．２％から５％としたこと特徴とする弾性表面波デバイスである。
請求項４記載の発明は、請求項１乃至３に記載のいずれかに記載の弾性表面波デバイスのＩＤＴ電極の材料をＡｇを主成分とし、０．１ｗｔ％〜３．０ｗｔ％のＡｕと、０．１ｗｔ％〜３．０ｗｔ％のＣｕとを含有した合金に代えたこと特徴とする弾性表面波デバイスである。
請求項５記載の発明は、請求項１乃至３に記載のいずれかに記載の弾性表面波デバイスのＩＤＴ電極の材料をＡｇを主成分とし、０．１ｗｔ％〜４．０ａｔ％のＡｕと、０〜５．０ａｔ％のＣｕと、０〜１．０ａｔ％のＴｉと、０〜１．０ａｔ％のＳｎとを含有した合金に代えたこと特徴とする弾性表面波デバイスである。
請求項６記載の発明は、所定の配線が施されたプリント基板と、その上にフリップチップ実装した弾性表面波素子と、前記弾性表面波素子と前記プリント基板との間に気密空間を確保するようにこれらの上面を覆う絶縁性の気密部材とを備えた弾性表面波デバイスにおいて、前記弾性表面波素子が請求項１乃至５のいずれかに該当することを特徴とする弾性表面波デバイスである。
請求項７記載の発明は、所定の配線が施されたプリント基板と、その上にフリップチップ実装した弾性表面波素子と、前記弾性表面波素子と前記プリント基板との間に気密空間を確保するようにこれらの上面を覆う絶縁性の気密部材と、該気密部材の外面に付着した第１の金属膜と、第１の金属膜とは異なる金属からなる第２の金属膜とを順次付着した多層金属膜と、該多層金属膜の上に樹脂層とを備えた弾性表面波デバイスにおいて、前記弾性表面波素子が請求項１乃至５のいずれかに該当することを特徴とする弾性表面波デバイスである。
【００１０】
【発明の実施の形態】
以下本発明を図面に示した実施の形態に基づいて詳細に説明する。
図１（ａ）は本発明に係るＳＡＷデバイスの構成の実施の形態を示す平面図、同図（ｂ）はＱ−Ｑにおける断面図である。圧電基板１の主表面上に弾性表面波の伝搬方向に沿ってＩＤＴ電極２とその両側に反射器３ａ、３ｂを配置する。ＩＤＴ電極２は互いに間挿し合う複数の電極指を有する一対の電極より構成され、一方の電極は端子Ｔ１に、他方の電極は端子Ｔ２に接続されてＳＡＷ共振子を構成する。
【００１１】
圧電基板１に回転ＹカットＸ伝搬のニオブ酸リチウム（ＬｉＮｂＯ_３）を用い、ＩＤＴ電極２、反射器３ａ、３ｂの電極材料にＡｇを主成分とし、０．１ｗｔ％〜３．０ｗｔ％のＰｄと、０．１ｗｔ％〜３．０ｗｔ％のＣｕとを含有した合金からなる薄膜を所定の膜厚で付着することによりラブ波を励起し、ラブ波型ＳＡＷデバイスを構成することができる。該ラブ波型ＳＡＷデバイスは大きな電気機械結合係数ｋ^２有する。上記のＡｇを主成分とした合金を電極に用いることにより、コストを低減し、且つ耐候性に強いＳＡＷデバイスを実現することが可能となる。
【００１２】
圧電基板１に回転角が−１０°から５０°の範囲の所定の角度で切断されたＹカットＸ伝搬のタンタル酸リチウム（ＬｉＴａＯ_３）を用い、ＩＤＴ電極２、反射器３ａ、３ｂの電極材料にＡｇを主成分とし、０．１ｗｔ％〜３．０ｗｔ％のＰｄと、０．１ｗｔ％〜３．０ｗｔ％のＣｕとを含有した合金からなる薄膜を用いることによりラブ波を励起し、ラブ波型ＳＡＷデバイスを構成することができる。該ラブ波型ＳＡＷデバイスは大きな電気機械結合係数ｋ^２有する。上記のＡｇを主成分とした合金を電極に用いることにより、コストを低減し、且つ耐候性に強いＳＡＷデバイスを実現することが可能となる。
【００１３】
圧電基板１にオイラー角が（０°，１２５°〜１４６°，０°±５°）であるＹカットＸ伝搬のＬｉＴａＯ_３基板を用い、ＩＤＴ電極２、反射器３ａ、３ｂの電極材料にＡｇを主成分とし、０．１ｗｔ％〜３．０ｗｔ％のＰｄと、０．１ｗｔ％〜３．０ｗｔ％のＣｕとを含有した合金からなる薄膜を用い、規格化膜厚Ｈ／λ（Ｈは電極膜厚、λは励起されるＳＨ波の波長）を０．２％から５％とすることによりＳＨ波を励起し、ＳＨ波型ＳＡＷデバイスを構成することができる。該ＳＨ波型ＳＡＷデバイスは大きな電気機械結合係数ｋ^２有する。上記のＡｇを主成分とした合金を電極に用いることにより、コストを低減し、且つ耐候性に強いＳＡＷデバイスを実現することが可能となる。
【００１４】
ＩＤＴ電極２、反射器３ａ、３ｂの電極材料にＡｇを主成分とし、０．１ｗｔ％〜３．０ｗｔ％のＡｕと、０．１ｗｔ％〜３．０ｗｔ％のＣｕとを含有した合金を用いてもコストを低減し、且つ耐候性に強いＳＡＷデバイスを実現することができる。また、ＩＤＴ電極２、反射器３ａ、３ｂの電極材料にＡｇを主成分とし、０．１ａｔ％〜４．０ａｔ％のＡｕと、０〜５．０ａｔ％のＣｕと、０〜１．０ａｔ％のＴｉと、０〜１．０ａｔ％のＳｎとを含有した合金を用いてもよい。
【００１５】
以上では１つのＩＤＴ電極１とその両側に反射器を配置して構成したＳＡＷ共振子について説明したが、図２に示すように圧電基板１の主表面上に弾性表面波（ラブ波、ＳＨ波等）の伝搬方向に沿って３つのＩＤＴ電極４、５、６を配置すると共に、それらの両側に反射器７ａ、７ｂを配設して構成した縦結合１次−３次二重モードＳＡＷフィルタにも適用すれば、広帯域のＳＡＷフィルタが実現することができる。さらに、縦結合多重モードＳＡＷフィルタ、横結合多重モードＳＡＷフィルタ、ラダー型ＳＡＷフィルタ、トランスバーサル型ＳＡＷフィルタ等にも適用できることは説明するまでもない。
【００１６】
図３は本発明の係る他の実施例の構成を示す断面図である。絶縁基板１１、例えばセラミック基板の上面と裏面にそれぞれ接続端子１２と外部端子１３を形成すると共に、接続端子１２、外部端子１３間を導通する内部導体１４を形成する。そして、接続端子１２に金属バンプ１５を介してＳＡＷデバイス素子１６をフリップチップ方式でボンディングすると共に、フェイスダウン状態のＳＡＷデバイス素子１６と絶縁基板１１の上面とに絶縁性樹脂１７を付着した上で熱硬化させ、ＳＡＷデバイス素子１６と絶縁基板１１の上面との間に気密空間１８を形成して、所謂ＣＳＰタイプのＳＡＷデバイスを完成する。なお、前記ＳＡＷデバイス素子１６は圧電基板に回転ＹカットＸ伝搬のＬｉＴａＯ_３、ＬｉＮｂＯ_３を用いたラブ波型ＳＡＷデバイス素子を使用する。また、前記ＳＡＷデバイス素子１６は圧電基板にオイラー角が（０°，１２５°〜１４６°，０°±５°）であるＬｉＴａＯ_３基板を用い、その上に規格化膜厚Ｈ／λ（Ｈは電極膜厚、λは励起されるＳＨ波の波長）が０．２％から５％のＩＤＴ電極を形成し、ＳＨ波を励起した弾性表面波デバイス素子を使用してもよい。前記ＳＡＷデバイス素子１６のＩＤＴ電極にＡｇを主成分とし、０．１ｗｔ％から３．０ｗｔ％のＰｄと０．１ｗｔ％から３．０ｗｔ％のＣｕを含有した合金を用いれば電極膜の比抵抗が小さく、耐候性に優れたＳＡＷデバイスを構成することができる。
さらに、熱硬化した絶縁性樹脂１７の外側表面に絶縁性樹脂との密着性の良い第１の金属膜１９ａを付着し、さらに第１の金属膜１９ａの上に第２の金属膜１９ｂを積層して、耐候性が優れ、且つＳＡＷデバイス周辺の電子部品からの電磁気的影響を受けないＳＡＷデバイスを完成することができる。
また、前記積層金属膜１９（１９ａ、１９ｂ）の上に樹脂２０でコーティングすれば耐候性に優れ、外部からの衝撃等にも優れたＳＡＷデバイスを得ることができる。
【００１７】
【発明の効果】
本発明は、以上説明したように構成したので、請求項１に記載の発明はニオブ酸リチウム基板上にラブ波を励起し、大きな電気機械結合係数ｋ^２のＳＡＷデバイスが得られるという優れた効果を表す。請求項２に記載の発明はタンタル酸リチウム基板上にラブ波励起し、大きな電気機械結合係数ｋ^２のＳＡＷデバイスが得られるという優れた効果を表す。請求項３に記載の発明はタンタル酸リチウム基板上にＳＨ波励起し、大きな電気機械結合係数ｋ^２のＳＡＷデバイスが得られるという優れた効果を表す。請求項４あるいは５に記載の発明は大きな電気機械結合係数ｋ^２のＳＡＷデバイスが得られるという優れた効果を奏す。請求項６あるいは７に記載の発明は、大きな電気機械結合係数ｋ^２が得られると共に小型のＳＡＷデバイスが実現できるという優れた効果を奏する。
【図面の簡単な説明】
【図１】本発明に係る弾性表面波共振子の、（ａ）は平面図、（ｂ）は断面図である。
【図２】本発明に係る縦結合二重モードＳＡＷフィルタの平面図である。
【図３】本発明に係る弾性表面波デバイス素子を簡易パッケージに収容した断面図で、（ａ）は樹脂に積層金属膜を付着したもの、（ｂ）はさらにその上に樹脂でコーティングしたものである。
【図４】（ａ）レイリー波を説明する図、（ｂ）はレイリー波を用いたＳＡＷデバイスの平面図である。
【図５】ＳＨ波を説明する図である。
【図６】ラブ波を説明する図である。
【符号の説明】
１・・圧電基板
２、４、５、６・・ＩＤＴ電極
３ａ、３ｂ、７ａ、７ｂ・・グレーティング反射器
１１・・絶縁基板
１２・・接続端子
１３・・外部端子
１４・・内部導体
１５・・金属バンプ
１６・・ＳＡＷデバイス素子
１７・・絶縁性樹脂
１８・・気密空間
１９・・積層金属膜
１９ａ・・第１の金属膜
１９ｂ・・第２の金属膜
２０・・樹脂[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface acoustic wave device, and more particularly to a surface acoustic wave device having a large electromechanical coupling coefficient k ² and a small transmission loss.
[0002]
[Prior art]
In recent years, surface acoustic wave devices (hereinafter referred to as SAW devices) have been widely used in the communication field, and have been widely used particularly in mobile phones, wireless LANs and the like because they have excellent characteristics such as high performance, small size, and mass productivity. Yes. As is well known, a surface acoustic wave is a general term for a wave that propagates by concentrating energy near the surface of a medium. The surface acoustic wave is excited and received by an IDT electrode formed on the surface of a piezoelectric substrate. it can. Rayleigh waves are well known as main surface acoustic waves used in SAW devices, but other than this, SH waves (SH wave type), Love waves, leaky surface acoustic waves (Leaky), etc. There is.
[0003]
As shown in FIG. 4A, the Rayleigh wave most frequently used in the SAW device is a surface acoustic wave that propagates by concentrating energy on a semi-infinite solid surface. The displacement of the Rayleigh wave is the traveling direction of the surface wave. It has only a component u1 (P wave) of X1 and a component u3 (SV wave) in the depth direction X3, and u3 is 90 ° out of phase with u1. That is, the Rayleigh wave can be called a (P + SV) wave. Since the Rayleigh wave moves 90 ° relative to u1 near the surface, it indicates backward elliptical rotation, and forward elliptical rotation occurs at a depth deeper than the depth X3 = 0.2λ (λ is the wavelength of the Rayleigh wave). At locations deeper than X3 = 2λ, both displacements u1 and u3 are substantially zero. Another significant feature is that the propagation velocity is constant regardless of the frequency and there is no velocity dispersion. FIG. 4B is a plan view showing the configuration of the SAW resonator using Rayleigh waves. The IDT electrode 22 is formed on the main surface of the piezoelectric substrate 21 along the propagation direction of the Rayleigh waves, and gratings are reflected on both sides thereof. The devices (hereinafter referred to as reflectors) 23a and 23b are respectively arranged. The IDT electrode 22 is composed of a pair of electrodes having a plurality of electrode fingers interleaved with each other, and one electrode is connected to the T1 terminal and the other terminal is connected to the T2 terminal to complete the SAW resonator.
[0004]
Even if a SAW device using Rayleigh waves is constructed using 128 ° rotated Y-cut X-propagating lithium niobate (128 ° Y-XLiNbO ₃ ), which is said to be a high coupling material, on the piezoelectric substrate, the electromechanical coupling coefficient k ² is 5 .5%, which cannot meet the requirements for a wideband SAW filter that has recently been required. Therefore, there is a SAW device using an SH wave (SH wave type) as a surface acoustic wave from which a large electromechanical coupling coefficient k ² can be expected. As shown in FIG. 5, the SH wave is a transverse wave in which the wave traveling direction X1 and the displacement direction u2 are orthogonal to each other. If the piezoelectric medium has anisotropy, it has the property of concentrating energy on its surface and propagating. This surface wave is also called a piezoelectric surface slip wave or a BGS wave in the name of the discoverer. This SH wave exists when the hexagonal 6 mm piezoelectric crystal or the C-axis or polarization axis of the piezoelectric ceramic plate is parallel to the substrate surface.
[0005]
Japanese Patent Application Laid-Open No. 2001-77662 discloses a heavy metal (Au, Ag, Ta) on a rotating Y-cut X-propagating LiTaO _{3 with} Euler angles (0 °, 125 ° to 146 °, 0 ° ± 5 °). , Mo, etc.), the transmission loss and the electromechanical coupling coefficient k of a SAW device in which an SH wave is excited by forming an IDT electrode are disclosed. According to this invention, the transmission loss is also good, and it is described that an electromechanical coupling coefficient k of about 22% to 30% (k ² = 5% to 9%) was obtained.
[0006]
There is a SAW device using a Love wave as one of surface acoustic waves that can be expected to have a large electromechanical coupling coefficient k ^{2. The} Love wave forms a surface layer A on a piezoelectric medium B as shown in FIG. A surface acoustic wave generated when the relationship Va <Vb is established between the sound velocity Va of the layer A and the sound velocity Vb of the piezoelectric medium B. The higher the frequency, the more the displacement (energy) is concentrated on the surface. Phenomenologically, it is considered that the energy of the piezoelectric medium B is dragged due to the slow wave of the surface layer A, and energy is concentrated on the surface.
[0007]
A SAW device using a Love wave is disclosed in Japanese Patent Application Laid-Open No. 59-156013. A rotating Y-XLiNbO ₃ is used as a piezoelectric substrate, and a high-density sound having a low sound speed is formed so as to form a waveguide on the piezoelectric substrate. A metal thin film or a dielectric film is formed, and an IDT electrode is further arranged. Here, gold, silver, or platinum is used as the high-density metal. Thus electromechanical coupling coefficient k ² of the SAW device which is constructed is marked to reach 14% to 28%.
Further, Japanese Patent Laid-Open No. 6-164306 discloses an example in which a love wave type SAW device is configured by disposing a metal IDT electrode having a large specific gravity on the main surface of rotating Y-XLiTaO ₃ . Electromechanical coupling coefficient k ² of the SAW devices configured According to the present invention are described to reach more than 11%.
[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-77662 [Patent Document 2] Japanese Patent Application Laid-Open No. 59-156013 [Patent Document 3] Japanese Patent Application Laid-Open No. 6-164306
[Problems to be solved by the invention]
However, the SAW device that excites the SH wave by forming the IDT electrode on LiTaO ₃ as described above has good transmission loss and electromechanical coupling coefficient k ^2, but the cost is high if Au is used for the IDT electrode. Thus, there is a problem that there is a problem in weather resistance when Ag, Ta, Mo, Cu, Ni, Cr, Zn, W or the like is used.
In addition, in a SAW device using a Love wave by forming an IDT electrode on LiNbO ₃ or LiTaO ₃ , it is necessary to deposit a thick film of gold, silver, platinum, or the like. In some cases, there was a problem that the weather resistance was difficult.
However, Japanese Patent Application Laid-Open No. 2001-192752 contains Ag as a main component, contains 0.1 to 3 wt% of Pd, and contains a plurality of elements from Al, Au, Pt, Cu, Ta, Cr, Ti, Ni, Co, and Si. A metal material for electronic parts containing 0.1 to 3 wt% of elements in total is disclosed, and is described as having excellent weather resistance and low specific resistance.
Japanese Patent Application Laid-Open No. 2002-140929 contains Ag as a main component and contains Au in a range of 0.1 wt% to 10 wt%, and contains Pd, Al, Cu, Ta, Cr, Ti, Ni, V, W , Mo, Ru, and Mg, a metal material for electronic parts to which one or more elements are added in an amount of 0.1 wt% to 5 wt% is disclosed, and is described as having excellent weather resistance and low specific resistance.
Further, JP-A-2003-55721 discloses a thin film of an Ag alloy in which at least one metal selected from Au, Cu, Ti, and Sn is added to Ag, and 0.1 to 4.0 at% Au, 0 An Ag alloy film containing ˜5.0 at% Cu, 0 to 1.0 at% Ti, and 0 to 1.0 at% Sn is disclosed, and it is described that both adhesion and specific resistance are superior to conventional ones. Has been.
The present invention was made to solve the above problems, and an object thereof is to provide a SAW device having and at low cost large electrical opportunity coupling coefficient k ^2.
[Patent Document 4] JP 2001-192752 [Patent Document 5] JP 2002-140929 [Patent Document 6] JP 2003-55721 A
[Means for Solving the Problems]
In order to achieve the above object, the surface acoustic wave device according to claim 1 of the present invention is characterized in that lithium niobate (LiNbO) having an Euler angle of (0 °, 90 ° to 150 °, 0 ° ± 5 °). ₃ ) In the surface acoustic wave device constructed by arranging IDT electrodes on the main surface along the propagation direction of the Love wave, the material of the IDT electrode is mainly composed of Ag, 0.1 wt% to 3.0 wt% It is a surface acoustic wave device characterized by using an alloy containing Pd of 0.1 wt% and Cu of 0.1 wt% to 3.0 wt%.
The invention according to claim 2 is directed to IDT along the propagation direction of the Love wave on the main surface of lithium tantalate (LiTaO ₃ ) having Euler angles (0 °, 80 ° to 140 °, 0 ° ± 5 °). In the surface acoustic wave device configured by arranging electrodes, the material of the IDT electrode is mainly composed of Ag, 0.1 wt% to 3.0 wt% Pd, 0.1 wt% to 3.0 wt% Cu, It is a surface acoustic wave device characterized by using an alloy containing.
The invention according to claim 3 is a surface acoustic wave device in which an IDT electrode for exciting SH waves is formed on a LiTaO ₃ substrate having an Euler angle (0 °, 125 ° to 146 °, 0 ° ± 5 °). As an IDT electrode material, an alloy containing Ag as a main component, 0.1 wt% to 3.0 wt% of Pd, and 0.1 wt% to 3.0 wt% of Cu is used, and a normalized film thickness H / λ is used. The surface acoustic wave device is characterized in that (H is the electrode film thickness, and λ is the wavelength of the excited SH wave) is 0.2% to 5%.
The invention according to claim 4 is characterized in that the material of the IDT electrode of the surface acoustic wave device according to any one of claims 1 to 3 is mainly composed of Ag, 0.1 wt% to 3.0 wt% Au, The surface acoustic wave device is characterized by being replaced with an alloy containing 0.1 wt% to 3.0 wt% of Cu.
The invention according to claim 5 is characterized in that the material of the IDT electrode of the surface acoustic wave device according to any one of claims 1 to 3 is mainly composed of Ag, 0.1 wt% to 4.0 at% Au, The surface acoustic wave device is characterized in that it is replaced with an alloy containing 0 to 5.0 at% Cu, 0 to 1.0 at% Ti, and 0 to 1.0 at% Sn.
The invention according to claim 6 secures an airtight space between the printed circuit board on which the predetermined wiring is applied, the surface acoustic wave element flip-chip mounted thereon, and the surface acoustic wave element and the printed circuit board. In the surface acoustic wave device provided with an insulating hermetic member covering these upper surfaces, the surface acoustic wave element corresponds to any one of claims 1 to 5, wherein the surface acoustic wave device is a surface acoustic wave device. .
The invention according to claim 7 secures an airtight space between the printed circuit board on which the predetermined wiring is applied, the surface acoustic wave element flip-chip mounted thereon, and the surface acoustic wave element and the printed circuit board. In this manner, an insulating hermetic member covering these upper surfaces, a first metal film adhered to the outer surface of the hermetic member, and a second metal film made of a metal different from the first metal film were sequentially adhered. A surface acoustic wave device comprising a multilayer metal film and a resin layer on the multilayer metal film, wherein the surface acoustic wave element corresponds to any one of claims 1 to 5. It is.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the drawings.
FIG. 1A is a plan view showing an embodiment of the configuration of a SAW device according to the present invention, and FIG. 1B is a cross-sectional view taken along the line Q-Q. An IDT electrode 2 and reflectors 3a and 3b are arranged on both sides of the piezoelectric substrate 1 on the main surface along the propagation direction of the surface acoustic wave. The IDT electrode 2 is composed of a pair of electrodes having a plurality of electrode fingers interleaved with each other, one electrode being connected to the terminal T1, and the other electrode being connected to the terminal T2, thereby constituting a SAW resonator.
[0011]
Rotating Y-cut X-propagating lithium niobate (LiNbO ₃ ) is used for the piezoelectric substrate 1, and the electrode material of the IDT electrode 2 and the reflectors 3 a and 3 b is mainly composed of Ag, and 0.1 to 3.0 wt% Pd Then, a love wave is excited by attaching a thin film made of an alloy containing 0.1 wt% to 3.0 wt% of Cu at a predetermined film thickness, and a Love wave type SAW device can be configured. The Love wave type SAW device having a large electromechanical coupling coefficient k ^2. By using an alloy containing Ag as a main component for the electrode, it is possible to realize a SAW device with reduced cost and strong weather resistance.
[0012]
Using Y-cut X-propagating lithium tantalate (LiTaO ₃ ) cut at a predetermined angle in the range of −10 ° to 50 ° on the piezoelectric substrate 1, electrode materials for the IDT electrode 2 and the reflectors 3 a and 3 b In addition, a Love wave is excited by using a thin film made of an alloy containing Ag as a main component, 0.1 wt% to 3.0 wt% Pd, and 0.1 wt% to 3.0 wt% Cu. A wave SAW device can be constructed. The Love wave type SAW device having a large electromechanical coupling coefficient k ^2. By using an alloy containing Ag as a main component for the electrode, it is possible to realize a SAW device with reduced cost and strong weather resistance.
[0013]
A Y-cut X-propagating LiTaO ₃ substrate having Euler angles (0 °, 125 ° to 146 °, 0 ° ± 5 °) is used for the piezoelectric substrate 1 and Ag is used as the electrode material for the IDT electrode 2 and the reflectors 3a and 3b. Is a thin film made of an alloy containing 0.1 wt% to 3.0 wt% of Pd and 0.1 wt% to 3.0 wt% of Cu, and a normalized film thickness H / λ (H is The SH wave type SAW device can be constructed by exciting the SH wave by changing the electrode film thickness, λ, is the wavelength of the excited SH wave) from 0.2% to 5%. The SH wave type SAW device having a large electromechanical coupling coefficient ^{k 2.} By using an alloy containing Ag as a main component for the electrode, it is possible to realize a SAW device with reduced cost and strong weather resistance.
[0014]
The electrode material of the IDT electrode 2 and the reflectors 3a and 3b is made of an alloy containing Ag as a main component and containing 0.1 wt% to 3.0 wt% Au and 0.1 wt% to 3.0 wt% Cu. However, it is possible to realize a SAW device with reduced cost and strong weather resistance. The electrode material of the IDT electrode 2 and the reflectors 3a and 3b is mainly composed of Ag, 0.1 at% to 4.0 at% Au, 0 to 5.0 at% Cu, and 0 to 1.0 at%. An alloy containing Ti and 0 to 1.0 at% Sn may be used.
[0015]
In the above, the SAW resonator formed by arranging one IDT electrode 1 and reflectors on both sides thereof has been described. However, as shown in FIG. 2, surface acoustic waves (love waves, SH waves) are formed on the main surface of the piezoelectric substrate 1. And the like, and three IDT electrodes 4, 5, 6 are arranged along the propagation direction, and reflectors 7 a, 7 b are arranged on both sides of the IDT electrodes 4, 5, 6. In addition, a broadband SAW filter can be realized. Furthermore, it goes without saying that the present invention can also be applied to a longitudinally coupled multimode SAW filter, a laterally coupled multimode SAW filter, a ladder type SAW filter, a transversal type SAW filter, and the like.
[0016]
FIG. 3 is a sectional view showing the structure of another embodiment of the present invention. A connection terminal 12 and an external terminal 13 are formed on the top surface and the back surface of an insulating substrate 11, for example, a ceramic substrate, and an internal conductor 14 that conducts between the connection terminal 12 and the external terminal 13 is formed. Then, the SAW device element 16 is bonded to the connection terminal 12 via the metal bump 15 by a flip chip method, and the insulating resin 17 is attached to the SAW device element 16 in the face-down state and the upper surface of the insulating substrate 11. Heat-curing is performed to form an airtight space 18 between the SAW device element 16 and the upper surface of the insulating substrate 11 to complete a so-called CSP type SAW device. The SAW device element 16 is a Love wave type SAW device element using a rotating Y-cut X-propagating LiTaO ₃ or LiNbO ₃ for a piezoelectric substrate. The SAW device element 16 uses a LiTaO ₃ substrate having Euler angles (0 °, 125 ° to 146 °, 0 ° ± 5 °) as a piezoelectric substrate, and a normalized film thickness H / λ (H It is also possible to use a surface acoustic wave device element in which an IDT electrode having an electrode film thickness and λ is a wavelength of an excited SH wave (0.2 to 5%) is formed and the SH wave is excited. If an alloy containing Ag as a main component, 0.1 wt% to 3.0 wt% Pd and 0.1 wt% to 3.0 wt% Cu is used for the IDT electrode of the SAW device element 16, the specific resistance of the electrode film Therefore, it is possible to construct a SAW device having a small size and excellent weather resistance.
Further, a first metal film 19a having good adhesion to the insulating resin is attached to the outer surface of the thermally cured insulating resin 17, and a second metal film 19b is laminated on the first metal film 19a. Thus, it is possible to complete a SAW device that has excellent weather resistance and is not affected by electromagnetic influence from electronic components around the SAW device.
Further, if the laminated metal film 19 (19a, 19b) is coated with the resin 20, a SAW device having excellent weather resistance and excellent impact from the outside can be obtained.
[0017]
【The invention's effect】
Since the present invention is configured as described above, the invention according to claim 1 excites a Love wave on a lithium niobate substrate and provides an excellent effect that a SAW device having a large electromechanical coupling coefficient k ² can be obtained. Represents. The invention described in claim 2 exhibits an excellent effect that a SAW device having a large electromechanical coupling coefficient k ² is obtained by exciting a Love wave on a lithium tantalate substrate. The invention described in claim 3 exhibits an excellent effect that a SAW device having a large electromechanical coupling coefficient k ² is obtained by SH wave excitation on a lithium tantalate substrate. The invention according to claim 4 or 5 has an excellent effect that a SAW device having a large electromechanical coupling coefficient k ² can be obtained. The invention according to claim 6 or 7 has an excellent effect that a large electromechanical coupling coefficient k ² can be obtained and a small SAW device can be realized.
[Brief description of the drawings]
1A is a plan view and FIG. 1B is a cross-sectional view of a surface acoustic wave resonator according to the present invention.
FIG. 2 is a plan view of a longitudinally coupled double mode SAW filter according to the present invention.
FIG. 3 is a cross-sectional view of a surface acoustic wave device element according to the present invention housed in a simple package, where (a) shows a laminated metal film attached to a resin, and (b) shows a resin coated thereon. It is.
4A is a diagram for explaining Rayleigh waves, and FIG. 4B is a plan view of a SAW device using Rayleigh waves.
FIG. 5 is a diagram for explaining SH waves;
FIG. 6 is a diagram illustrating a love wave.
[Explanation of symbols]
1. ・ Piezoelectric substrates 2,4,5,6 ・・ IDT electrodes 3a, 3b, 7a, 7b ・・ Grating reflector 11 ・・ Insulating substrate 12 ・・ Connection terminal 13 ・・ External terminal 14 ・・ Internal conductor 15 ・Metal bump 16 SAW device element 17 Insulating resin 18 Airtight space 19 Multilayer metal film 19a First metal film 19b Second metal film 20 Resin

Claims

Elasticity configured by arranging IDT electrodes along the propagation direction of Love waves on the main surface of lithium niobate (LiNbO ₃ ) having Euler angles (0 °, 90 ° to 150 °, 0 ° ± 5 °) In surface wave devices,
An elastic surface characterized by using an alloy containing Ag as a main component, 0.1 wt% to 3.0 wt% Pd, and 0.1 wt% to 3.0 wt% Cu as the material of the IDT electrode. Wave device.

Elasticity constructed by arranging IDT electrodes along the propagation direction of Love waves on the main surface of lithium tantalate (LiTaO ₃ ) with Euler angles (0 °, 80 ° -140 °, 0 ° ± 5 °) In surface wave devices,
An elastic surface characterized by using an alloy containing Ag as a main component, 0.1 wt% to 3.0 wt% Pd, and 0.1 wt% to 3.0 wt% Cu as the material of the IDT electrode. Wave device.

In a surface acoustic wave device in which an IDT electrode for exciting SH waves is formed on a LiTaO ₃ substrate having an Euler angle (0 °, 125 ° to 146 °, 0 ° ± 5 °),
As an IDT electrode material, an alloy containing Ag as a main component, 0.1 wt% to 3.0 wt% of Pd, and 0.1 wt% to 3.0 wt% of Cu is used and a normalized film thickness H / A surface acoustic wave device characterized in that λ (H is the electrode film thickness, λ is the wavelength of the excited SH wave) is 0.2% to 5%.

The material of the IDT electrode of the surface acoustic wave device according to any one of claims 1 to 3 is mainly composed of Ag, 0.1 wt% to 3.0 wt% Au, and 0.1 wt% to 3.0 wt%. A surface acoustic wave device characterized in that the surface acoustic wave device is replaced with an alloy containing 1% Cu.

The material of the IDT electrode of the surface acoustic wave device according to any one of claims 1 to 3, comprising Ag as a main component, 0.1 wt% to 4.0 at% Au, and 0 to 5.0 at% Cu. And a surface acoustic wave device that is replaced with an alloy containing 0 to 1.0 at% Ti and 0 to 1.0 at% Sn.

A printed circuit board on which a predetermined wiring is provided, a surface acoustic wave element flip-chip mounted on the printed circuit board, and an insulating covering the upper surface so as to secure an airtight space between the surface acoustic wave element and the printed circuit board In a surface acoustic wave device comprising a gas-tight airtight member,
6. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave element corresponds to any one of claims 1 to 5.

A printed circuit board on which a predetermined wiring is provided, a surface acoustic wave element flip-chip mounted on the printed circuit board, and an insulating covering the upper surface so as to secure an airtight space between the surface acoustic wave element and the printed circuit board Airtight member, a first metal film adhering to the outer surface of the airtight member, a second metal film made of a metal different from the first metal film, and a multi-layer metal film In a surface acoustic wave device including a resin layer on a film,
6. The surface acoustic wave device according to claim 1, wherein the surface acoustic wave element corresponds to any one of claims 1 to 5.