JP2004096456A

JP2004096456A - Surface mounted type surface acoustic wave device and manufacturing method therefor

Info

Publication number: JP2004096456A
Application number: JP2002255369A
Authority: JP
Inventors: Yasuhide Onozawa; 小野澤　康秀; Yuji Ogawa; 小川　祐史
Original assignee: Toyo Communication Equipment Co Ltd
Current assignee: Toyo Communication Equipment Co Ltd
Priority date: 2002-08-30
Filing date: 2002-08-30
Publication date: 2004-03-25
Anticipated expiration: 2022-08-30
Also published as: JP4131149B2

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problems that a wiring board increase in area and the productivity of mass-production using a wiring board base material decreases since a space is secured to join a 2nd sealing layer directly with the top surface of the wiring board. <P>SOLUTION: The surface mounted type SAW device, equipped with the wiring board 2 with an external electrode 4 and an upper electrode 5, a connection pad 16 which is mounted on a flip-chip basis on the upper electrode across a conductor bump 10, a SAW chip 15 having an IDT electrode 17 on its reverse surface, and a 1st sealing layer 20 interposed at least between the wiring board and a SAW chip skirt part to form an airtight space S between the reverse surface of the SAW chip and the top surface of the wiring board, is equipped with an exposed part 8 formed on the outer circumferential edge of the wiring board by cutting the outer circumferential edge of the 1st sealing layer together with the surface layer of the wiring board and the 2nd sealing layer 21 which covers the exposed part, the 1st sealing layer, and the external surface of the SAW chip. <P>COPYRIGHT: (C)2004,JPO

Description

【０００１】
【発明の属する技術分野】
本発明は、配線基板上にフリップチップ実装した弾性表面波チップを樹脂にて封止した構造の弾性表面波デバイスや、その製造工程において発生する種々の不具合を解決した表面実装型弾性表面波デバイス、及びその製造方法に関するものである。
【０００２】
【従来の技術】
弾性表面波デバイス（ＳＡＷデバイス）は、水晶等の圧電基板上に櫛歯状の電極指（ＩＤＴ電極）を配置した構成を備え、例えばＩＤＴ電極に高周波電界を印加することによって弾性表面波を励起し、弾性表面波を圧電反作用によって高周波電界に変換することによってフィルタ特性を得るものである。
図４には従来の表面実装型のＳＡＷデバイスの縦断面図が示されている。このＳＡＷデバイス１０１は、絶縁基板１０３、該絶縁基板１０３の底部に設けた表面実装用の外部電極１０４、該絶縁基板の上面に設けた上部電極１０５、及び外部電極１０４と上部電極１０５とを接続する接続導体１０６とから成る配線基板１０２と、上部電極１０５上に導体バンプ１１０を介して電気的機械的に接続される接続パッド１１６、及びＩＤＴ電極１１７を下面に備えた圧電基板１１８を備えたＳＡＷチップ１１５と、ＳＡＷチップ１１５の下端周縁と上部電極１０５との間に充填されてＳＡＷチップ１１５の下面と配線基板１０３の上面との間に弾性表面波伝搬用の気密空間Ｓを形成する硬化処理前粘度の高い第１の封止樹脂１２０と、ＳＡＷチップ１１５の外面全体及び第１の封止樹脂１２０の外面、更には第１の封止樹脂１２０によって被覆されていない配線基板上面にかけて被覆形成された硬化処理前粘度の低い第２の封止樹脂１２１と、を有している。
【０００３】
第１の封止樹脂１２０から成る封止部は、気密空間Ｓを形成し得るように、スクリーン印刷、ディスペンサによる充填等によってＳＡＷチップ１１５の裾部に形成される。第２の封止樹脂１２１は、スクリーン印刷、ディスペンサによる充填等によって形成され、予め第１の封止樹脂により被覆されないように露出形成された配線基板上面の一部に被覆される。
第１の封止樹脂１２０として、粘度の高い樹脂を使用するのは、ＳＡＷの伝搬路である圧電基板１１８の下面に樹脂が浸入することを防止するためであり、第２の封止樹脂１２１として粘度の低い樹脂を使用するのは、配線基板の露出部、第１の封止樹脂外面、及びＳＡＷチップ外面との間の密着性を確保するためである。粘度の高い第１の封止樹脂１２０だけでは、前記被覆対象物との間の密着性を確保することが困難であるため、粘度が低く被覆対象物とのぬれ性の良好な第２の封止樹脂により密着性を高めているものである（特開平６−２０４２９３号公報参照）。
【０００４】
次に、図５は、配線基板（個片）１０２を複数シート状に連結した構成の配線基板母材１２５を用いて図４のＳＡＷデバイス１０１を製造する手順を説明するための図であり、配線基板母材１２５上の各個片領域上にＳＡＷチップ１１５をフリップチップ実装した後で、第１の封止樹脂１２０によるＳＡＷチップ１１５の裾部に位置する間隙の封止を行って気密空間Ｓを形成してから、第２の封止樹脂１２１を一括して被覆形成する。その後、配線基板個片１０２の境界線に沿ってダイシングブレード等によって分割することにより複数個のＳＡＷデバイス個片１０１を得る。
しかし、図４に示したＳＡＷデバイス１０１にあっては、第２の封止樹脂１２１を配線基板上面に被覆させるために、第１の封止樹脂１２０を塗布した後のＳＡＷチップ１１５間の谷間に配線基板上面の一部を露出させる必要がある。図５のようにＳＡＷチップ間隔が狭い場合には、図６のようにＳＡＷチップ間の谷間に位置する配線基板上面が第１の封止樹脂１２０によって被覆されてしまい、第２の封止樹脂１２１が配線基板上面に接触することができず、第２の封止樹脂による封止効果（気密性の確保）が十分に発揮されない状況となる。
図５の如く隣接し合う各ＳＡＷチップ１１５の裾部に夫々配置した第１の封止樹脂１２０同士が未分離状態になることを防止するためには、ＳＡＷチップ間隔を拡張すればよいのであるが、ＳＡＷチップ間隔の拡張は、配線基板個片の大型化によるＳＡＷデバイスの大型化と、配線基板母材１２５の面積の大型化と、配線基板母材一枚当りから製作できるＳＡＷデバイス数が減少するという不具合をもたらす。
また、ディスペンサのノズルは直線状に延びているため、ＳＡＷチップ１１５の裾部に位置する間隙全周に沿って樹脂を充填するためには、ＳＡＷチップ１１５間の谷間状の間隙内に斜めにノズルを差し入れてＳＡＷチップの裾部に充填作業を行う必要がある。このような充填作業を可能ならしめるためには、ＳＡＷチップ間の間隔を予め広く設定しておく必要があり、図示した例では１，０００μｍ程度の広い間隔が必要である。
このような問題に対処するために、ＳＡＷチップを更に小型化することも考えられるが、無理な小型化には限界があり、設計上の自由度の制限、その他の不利不便をもたらす。
【０００５】
次に、特開平２−１８６６６２号公報（日立製作所）には、配線基板上にフェイスダウン状態でフリップチップ実装したＳＡＷチップの裾部を第１封止層にて封止した後で、これらの部品の外面を第２封止層にて被覆する構成が開示され、この第２の封止層としてＳＯＧ（Ｓｐｉｎ　Ｏｎ　Ｇｌａｓｓ）材料を用いる例を示している。この公報には、ＳＯＧ材料を第２封止層として使用することにより、ＳＡＷチップの下面と配線基板表面との間の段差が大きい場合にも確実な気密封止を実現できる旨が示されている。しかし、ＳＯＧ材料についての沖電気（株）による１９９５年２月２１日付けの自社ホームページでは、ＳＯＧ材料は、完全に無機化するための硬化温度が３５０〜４００℃であり、ガラスが無機化する温度としては比較的低温であるものの、この温度はＳＡＷチップの構成材料や封止樹脂にとっては、高温に過ぎることが明らかである。即ち、例えば、図４に示したバンプ１１０が金から成り、バンプ１１０と接続されるＳＡＷチップ１１５側の接続パッド１１６がアルミニウムを主成分とした合金である場合には、上記範囲の高温にさらされることにより、両金属の接合部に、硬くてもろい金とアルミニウムの合金層が形成されてしまい、金バンプの信頼性が低下する。また、第１の封止樹脂１２０を高温にさらすと、第１の封止樹脂から発生するアウトガスによってＳＡＷチップを構成する各電極が腐食する、という不具合が発生する。
【０００６】
【発明が解決しようとする課題】
本発明は上記に鑑みてなされたものであり、表面実装用の配線基板上の上部電極上にバンプを介してＳＡＷチップをフェイスダウン搭載し、ＳＡＷチップの裾部と配線基板との間の間隙内に第１の封止層を充填することにより、ＳＡＷチップ下方に弾性表面波伝搬用の気密空間を形成し、更に第１の封止層、及びＳＡＷチップ外面を第２の封止層にて被覆したＳＡＷデバイスにおいて、第２の封止層を配線基板上面と直接接合させるためのスペースを確保するために、配線基板の面積が増大したり、配線基板母材を用いた量産時の生産性の低下を招くという不具合を解決することができる表面実装型弾性表面波デバイス、及びその製造方法を提供することを課題とする。
【０００７】
【課題を解決するための手段】
上記課題を解決するため、本発明は次の如き手段を備える。
請求項１の発明に係るＳＡＷデバイスは、絶縁基板、該絶縁基板の下部に設けた表面実装用の外部電極、該絶縁基板の上部に設けた上部電極、及び外部電極と上部電極間を導通する接続導体から成る配線基板と、圧電基板、該圧電基板下面に形成され前記上部電極上に導体バンプを介して接続される接続パッド、及びＩＤＴ電極、を備えたＳＡＷチップと、前記ＳＡＷチップ下面と前記配線基板上面との間に気密空間を形成するように、少なくとも配線基板とＳＡＷチップ裾部との間に介在する樹脂から成る第１の封止層と、を備えた表面実装型ＳＡＷデバイスにおいて、前記第１の封止層の外周縁を配線基板の表層とともに切除することにより配線基板の外周縁上部に形成した露出部と、前記露出部、前記第１の封止層、及び前記ＳＡＷチップ外面を被覆する第２の封止層と、を備えたことを特徴とする。
配線基板上にフェイスダウン状態でＳＡＷチップをフリップチップ実装し、ＳＡＷチップ裾部と配線基板上面との間を全周にわたって第１の封止層により封止し、更にその外面に第２の封止層を被覆形成する場合、第２の封止層の裾部を配線基板上面と直接接合することが気密性、接合性を高める上で重要である。しかし、第１の封止層の外側に配線基板上面を張り出すことによって第２の封止層との接合マージンを確保しようとすると、配線基板が大型化する。一方、第１の封止層を塗布、充填する際の塗布面積を、前記接合マージンを確保し得るように所定の狭い範囲にコントロールすることは困難である。
そこで、本発明では、ＳＡＷチップよりも外側に位置する配線基板上面全体を覆うように第１の封止層を形成してから、第１の封止層の外周部と配線基板表層を切除して露出部を形成し、この露出部を第２の封止層との接合部として利用した。このため、配線基板の大型化を招くことなく、第２の封止層を配線基板上面と密着させることが可能となった。
なお、第２の封止層は、ＳＡＷチップの下面を除いた露出面全体を被覆する場合と、ＳＡＷチップの上面以外の側面を被覆する場合がある。
【０００８】
請求項２の発明は、請求項１において、前記第２の封止層は、樹脂材料から成り、前記第２の封止層を構成する樹脂の硬化処理前の粘度が、前記第１の封止層を構成する樹脂の硬化処理前の粘度よりも低いことを特徴とする。
第１の封止層（第１の封止樹脂）の粘度を高くすることにより、これをＳＡＷチップの裾部の空間に充填したとしても気密空間内に入り込む虞がなくなる一方で、露出部、第１の封止樹脂外面、及びＳＡＷチップ外面に密着して被覆する必要がある第２の封止層（第２の封止樹脂）についてはその粘度を低下させるようにしたものである。
請求項３の発明方法は、絶縁基板、該絶縁基板の下部に設けた表面実装用の外部電極、及び該絶縁基板の上部に設けた上部電極から成る配線基板と、該上部電極上に導体バンプを介してフリップチップ実装される接続パッド、及びＩＤＴ電極を夫々圧電基板の下面に備えたＳＡＷチップと、該ＳＡＷチップ下面と前記配線基板上面との間に気密空間を形成するように配置される第１の封止層と、から成る表面実装型ＳＡＷデバイスの製造方法において、前記上部電極と前記ＳＡＷチップの接続パッドとを、バンプを介して接続するフリップチップ実装工程と、前記ＳＡＷチップ下面と前記配線基板上面との間に気密空間を形成するようにＳＡＷチップ外面の少なくとも一部を樹脂から成る第１の封止層にて被覆する第１の封止層形成工程と、前記第１の封止層の外周部を配線基板の表層とともに切除して配線基板の露出部を形成する露出部形成工程と、前記露出部と、前記第１の封止層と、前記ＳＡＷチップ外面を第２の封止層により被覆する第２の封止層形成工程と、を備えたことを特徴とする。
これによれば、配線基板個片毎に、ＳＡＷチップの搭載、樹脂被覆、接地用露出部の形成、導電性金属被膜の被覆形成による接地用露出部との接続を行うことにより、請求項１、２に記載したＳＡＷデバイスを得ることができる。
【０００９】
請求項４の発明は、絶縁基板、該絶縁基板の下部に設けた表面実装用の外部電極、及び該絶縁基板の上部に設けた上部電極から成る配線基板を、複数個シート状に連結した大面積の配線基板母材を用いた、表面実装型ＳＡＷデバイスの製造方法において、圧電基板の下面に接続パッドとＩＤＴ電極を備えたＳＡＷチップの該接続パッドを、前記上部電極上に導体バンプを介して接続するフリップチップ実装工程と、前記各ＳＡＷチップ下面と前記各配線基板上面との間に気密空間を形成するようにＳＡＷチップ間の谷間に樹脂から成る第１の封止層を充填する第１の封止層形成工程と、前記ＳＡＷチップ間の谷間に位置する第１の封止層を分断すると共に前記配線基板の表層を切除して配線基板の露出部を形成する露出部形成工程と、前記露出部と、前記第１の封止層と、前記ＳＡＷチップ外面を第２の封止層により被覆する第２の封止層形成工程と、前記各工程を経た配線基板母材を、配線基板個片毎に切断する切断工程と、から成ることを特徴とする。
この製造方法では、大面積の配線基板母材を用いたバッチ処理により請求項１、２に記載のＳＡＷデバイスを量産する。なお、第２の封止層による被覆範囲は、ＳＡＷチップの下面を除いた露出面全体を被覆する場合と、ＳＡＷチップの上面以外の側面を被覆する場合がある。第１の封止樹脂による封止作業においては、スクリーン印刷が用いられ、ディスペンサによる狙いを定めた充填は行わないので、ＳＡＷチップ間の間隔を広く確保する必要もなくなる。
請求項５の発明は、請求項４において、前記露出部形成工程では、ＳＡＷチップ間に位置する第１の封止層及び配線基板上面の一部をダイシングブレードにてハーフカットすることを特徴とする。
露出部形成工程では、ＳＡＷチップ間の谷間を埋めるように充填された第１の封止層を、肉厚が厚いダイシングブレードを用いて分断する際に、配線基板表層（接地用導体としての上部電極、及び／或いは接続導体の一部を含む）を同時に切除するので、極めて簡単に露出部を確保することが可能となり、ＳＡＷチップ間の間隔を広く確保する必要もなくなる。
【００１０】
請求項６の発明は、請求項５において、前記切断工程において使用するダイシングブレードは、前記ハーフカットの際に用いるダイシングブレードよりも肉厚が薄いことを特徴とする。
ハーフカットに際しては、配線基板の表層の一部を切除して露出させる狙いがあるため、厚肉のカッタを用いたが、最後の切断をダイシングブレードにて行う場合には、配線基板間の境界線を単に切断するだけでよいので、薄肉のダイシングブレードを用いる。
請求項７の発明は、請求項５又は６において、前記ハーフカット後に、配線基板の露出部、第１の封止層、及びＳＡＷデバイスの外面に金属皮膜を形成し、金属皮膜形成後に前記第２の封止層形成工程を実施することを特徴とする。
樹脂は吸水性を有するため、気密空間内のＩＤＴ電極に結露が生じ腐食が発生する虞がある。そこで、第１の封止層を含むＳＡＷチップ外面に金属被膜を形成し、更にその外面に第２の封止層を形成することにより、気密性、水密性を高めることができ、しかも金属被膜を配線基板の露出部に露出した接地導体と導通させることにより、シールド効果を発揮することができる。
請求項８の発明は、請求項３乃至７において、前記第２の封止層は樹脂材料から成り、該第２の封止層を構成する樹脂の硬化処理前の粘度が、該第１の封止層を構成する樹脂の硬化処理前の粘度よりも低いことを特徴とする。
第１の封止層（第１の封止樹脂）の粘度を高くすることにより、これをＳＡＷチップの裾部の空間に充填したとしても気密空間内に入り込む虞がなくなる一方で、露出部、第１の封止樹脂外面、及びＳＡＷチップ外面に密着して被覆する必要がある第２の封止層（第２の封止樹脂）についてはその粘度を低下させるようにしたものである。
【００１１】
請求項９の発明は、請求項１において、前記第２の封止層はガラス膜から成り、該ガラス膜は、シリカ溶液を２００℃以下で加熱して硬化させることにより形成されたことを特徴とする。
ガラス膜を硬化させる温度が高温である場合には、バンプ、接続パッド等の接続導体や、ＳＡＷチップや樹脂に対して悪影響を及ぼす。そこで、本発明では、２００℃以下の低温加熱によって硬化させることができるシリカ溶液を使用した。
請求項１０の発明は、前記シリカ溶液には、Ａｌ_２Ｏ_３、ＴｉＯ_２、又はＺｒＯ_２のうちの何れかが含まれていることを特徴とする。
これによれば、使用する溶液の種類の選択範囲を拡大することができる。
請求項１１の発明は、前記第２の封止層形成工程において被覆される第２の封止層は、ガラス膜であり、該ガラス膜はシリカ溶液を２００℃以下で加熱して硬化されることを特徴とする。
ガラス膜を硬化させる温度が高温である場合には、バンプ、接続パッド等の接続導体や、ＳＡＷチップや樹脂に対して悪影響を及ぼす。そこで、本発明では、２００℃以下の低温加熱によって硬化させることができるシリカ溶液を使用した。
請求項１２の発明は、前記シリカ溶液には、Ａｌ_２Ｏ_３、ＴｉＯ_２、又はＺｒＯ_２のうちの何れかが含まれていることを特徴とする。
これによれば、使用する溶液の種類の選択範囲を拡大することができる。
【００１２】
【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より詳細に説明する。
図１（ａ）及び（ｂ）は本発明の一実施形態に係る表面実装型弾性表面波デバイス（以下、ＳＡＷデバイス、という）の外観斜視図、及び縦断面図である。
このＳＡＷデバイス１は、セラミック、ガラスエポキシ等から成る絶縁基板３、絶縁基板３の底部（下部）に設けた表面実装用の外部電極４、及び、絶縁基板３の上面（上部）に設けられ且つ接続導体６を介して外部電極４と導通した上部電極５、から成る配線基板２と、上部電極５と導体バンプ１０を介して電気的機械的に接続される接続パッド１６、及びＩＤＴ電極１７を夫々圧電基板１８の下面に備えたＳＡＷチップ１５と、上部電極５の上面を含む配線基板２とＳＡＷチップ１５の側面及び上面に対して被覆一体化されると共にＳＡＷチップ１５の裾部と配線基板上面との間の空隙に充填される第１の封止樹脂（第１の封止層）２０と、第１の封止樹脂２０による封止によってＳＡＷチップ１５下面と配線基板上面との間に形成される弾性表面波伝搬用の気密空間Ｓと、を備えている。
第１の封止樹脂２０の外周縁及び配線基板２の上部を切除することによって、第１の封止樹脂２０の外側には配線基板２の露出部８が形成されている。この例では、配線基板２上の複数の上部電極５のうちの少なくとも一つの上部電極（接地導体）５ａの外側部、及び接続導体（接地導体）６ａの表層は、それらの一部が第１の封止樹脂２０と共に切除されて導体部分が露出した露出部８となっている。第１の封止樹脂２０の外面全体には第２の封止樹脂（第２の封止層）２１が被覆形成され、この第２の封止樹脂２１を露出部８に密着させて高い気密性を確保することができる。
このように配線基板３の上面外周に被覆形成された第１の封止樹脂２０の外周縁を切除することにより配線基板の上面を露出させるようにしたので、配線基板の面積を大型化することなく露出部８を確保することができ、この露出部８を利用して第２の封止樹脂２１と配線基板との密着を確保できる。
【００１３】
なお、この実施形態では、第２の封止層２１は樹脂材料から成り、第２の封止層２１を構成する第２の封止樹脂の硬化処理前の粘度を、第１の封止樹脂２０を構成する第１の封止樹脂の硬化処理前の粘度よりも低く設定することにより、第１の封止樹脂の気密空間Ｓ内への浸入を防止でき、第２の封止樹脂による露出部８、第１の封止樹脂２０の外面、ＳＡＷチップ外面への密着性を十分に高めることができる。
なお、上部電極５は、例えばタングステン膜の表面にニッケルメッキ、金メッキを順次施した構成を備え、上部電極５は接続導体６を介して対応する外部電極４と導通している。互いに導通した外部電極４、上部電極５、及び接続導体６から成る導電体組は、入出力用と、接地用が複数組配置されており、接地用の上部電極（接地導体）５ａの外側端部と、接地用の接続導体（接地導体）６ａの上部を夫々第１の封止樹脂２０と共に切除することによって露出部（接地用露出部）８ａを形成している。第２の封止樹脂２１を被覆する前に、この接地用露出部８ａに位置する接地用上部電極５ａ、及び接地用接続導体６ａと導通し、且つ第１の封止樹脂２０及びＳＡＷチップ外面を被覆するように、図示しない導電性金属被膜をメッキ、蒸着、スパッタリング等によって成膜し、この導電性金属被膜の外面に第２の封止樹脂２１を被覆形成するようにしてもよい。
このように本発明のＳＡＷデバイスにおいては、配線基板の外側端部を大きく張り出すことによって第１の封止樹脂２０による非被覆部分を形成する必要がなく、第１の封止樹脂によって被覆された配線基板の外側部分を第１の封止樹脂と共に切除して露出部８を形成したので、従来のＳＡＷデバイスと比較した場合に、配線基板２の面積を小さくすることができる。また、露出部８のうちの導体露出部８ａを導電性金属被膜と接続することが可能となるので、シールド効果のみならず、より高い気密効果を得ることができる。
【００１４】
次に、図２（ａ）乃至（ｄ）に基づいて図１のＳＡＷデバイス１の製造手順を説明する。この例では複数の配線基板個片２をシート状に連結一体化した配線基板母材２５を用いたバッチ処理によるＳＡＷデバイスの生産方法を示す。
まず、図２（ａ）に示した如き、絶縁基板３の下面に外部電極４を有すると共に上面に上部電極５を備え、更に外部電極４と上部電極５との間を導通する接続導体６を有した配線基板個片２を複数個、シート状に連結した大面積の配線基板母材２５を製作し、配線基板母材２５の各個片領域に対して、下面に接続パッド１６とＩＤＴ電極１７を備えた圧電基板１８から成るＳＡＷチップ１５の接続パッド１６を、上部電極５の上面に導体バンプ１０を介して電気的機械的に接続する（フリップチップボンディング）。導体バンプ１０は、予め接続パッド１６側に形成しておいてもよいし、露出領域５ａ上に形成してもよい。導体バンプ１０は、例えば金等の導体から成るバンプであってもよいし、塊状の樹脂の外周に導体膜を被覆したものであってもよい。
次いで、図２（ａ）に示した第１の封止樹脂形成工程では、ＳＡＷチップ１５下面と各配線基板個片２の上面との間に気密空間Ｓを形成するように、各配線基板２と各ＳＡＷチップ１５の裾部（下面周縁部、側面の下端縁部）との間の空隙を封止するように第１の封止樹脂（第１の封止層）２０を充填する。換言すれば、ＳＡＷチップ１５下面と配線基板２上面との間に気密空間Ｓを形成するようにＳＡＷチップ間の谷間（間隙）に第１の封止樹脂２０を充填する。この工程では、例えば、スクリーン印刷等の方法によって、比較的粘度の高い第１の封止樹脂２０を塗布、充填する。粘度の高い樹脂を使用する理由は、ＳＡＷ伝搬のための気密空間Ｓを確実に確保する必要があるためである。
この実施形態では、ＳＡＷチップ１５間の間隙を埋めるように第１の封止樹脂２０をスクリーン印刷により一括して充填、被覆するため、ディスペンサによりノズルをＳＡＷチップ間に斜めに差し入れてＳＡＷチップ裾部を狙い打ちして充填する従来例と比べた場合に、ＳＡＷチップ間の間隔を狭くしても不具合がなく、大幅に狭くすることができる。
【００１５】
次に、図２（ｂ）に示した露出部形成工程では、ＳＡＷチップ１５間の谷間を埋めるように充填された封止樹脂２０を比較的肉厚の厚いダイシングブレードによってハーフカットする。即ち、ダイシングブレードによってＳＡＷチップ間の第１の封止樹脂２０を寸断すると共に各配線基板２間の境界線に沿った位置の表層を部分的に切除する程度にハーフカットすることにより、配線基板の上面と、上部電極（接地用導体）５ａの外側部及び接続導体（接地用導体）６ａの上部を夫々第１の封止樹脂と共に切除して露出部８（接地用露出部８ａ）を形成する。ハーフカットされた部分の幅は２００μｍ程度である。そして、ＳＡＷチップ１５間の間隔Ｌ２は、このハーフカットされる部分の幅にマージンを考慮して４００μｍ程度に予め設定する。
次に、図２（ｃ）の第２の封止樹脂被膜形成工程では、露出部８、第１の封止樹脂２０の外面、ＳＡＷチップの外面全体（下面を除く）を、第２の封止樹脂（第２の封止層）２１により被覆する。
なお、第２の封止樹脂２１を被覆する前に、露出部８、第１の封止樹脂２０の外面、及びＳＡＷチップ１５の外面に金属被膜をメッキ、蒸着、スパッタリング等により成膜して、接地用露出部８ａを介した接地によるシールド効果を得るとともに、第１の封止樹脂２０によっては十分に確保できない気密性を確保するようにしてもよい。
なお、第２の封止層２１を構成する第２の封止樹脂の硬化処理前の粘度を、第１の封止樹脂２０を構成する第１の封止樹脂の硬化処理前の粘度よりも低く設定することにより、第１の封止樹脂の気密空間Ｓ内への浸入を防止でき、第２の封止樹脂による露出部８、第１の封止樹脂２０の外面、ＳＡＷチップ外面への密着性を十分に高めることができる。
最後に、図２（ｃ）中に示した切断ラインＣに沿って、図２（ｂ）の工程で使用したダイシングブレードよりも肉厚の薄いダイシングブレードにより、配線基板母材２５を切断ラインＣに沿って個片ごとに分割する切断工程を実施する。この切断工程により、図２（ｄ）に示した如きＳＡＷデバイス個片１を得ることとなる。
【００１６】
次に、図３（ａ）（ｂ）は本発明の他の実施形態に係る製造方法の部分的な説明図であり、図３（ａ）は第２の封止樹脂被覆工程、図３（ｂ）は完成した個片を示す断面図である。この実施形態に係る製造方法におけるフリップチップ実装工程と、第１の封止樹脂形成工程と、露出部形成工程は、図２に示した実施形態に係る製造方法における図２（ａ）（ｂ）の工程と同様である。この実施形態に係る製造方法が図２の製造方法と異なる点は、第２の封止樹脂形成工程において、第２の封止樹脂２１を、ＳＡＷチップ１５の外面全体に被覆するのではなく、露出部８と、第１の封止樹脂２０の外面と、ＳＡＷ１５の側面のみにかけて被覆した構成にある。更に、図２（ｂ）において厚肉のダイシングブレードによって導体露出部８を形成するようにした点等、他の工程は図２と同様である。
従って、図３の製造方法を実施した場合にも、配線基板母材２５上のＳＡＷチップ１５間の間隔を狭くすることができ、同面積の配線基板母材から採ることができるＳＡＷデバイス数を増やすことができる。このようにして得られたＳＡＷデバイスは、その上面に第２の封止層２１が存在しない分だけ薄型化することができる。
次に、図１に示した実施形態に係るＳＡＷデバイスは、露出部８、第１の封止樹脂２０、及びＳＡＷチップ外面を被覆する第２の封止層２１として樹脂材料を使用したが、樹脂の代わりにガラス膜を使用してもよい。ガラス膜は、樹脂材料よりも吸水性の点、気密性の点で優れており、ＳＡＷデバイスの耐久性をより高めることができる。ここで使用するガラス材料としては、特開平６−１９９５２８号公報に開示されている如き２００℃以下でガラス化する材料を用いる。具体的には、例えばＳｉＯ_２を４０重量％以上含有するシリカ溶液を用い、これを塗布してから硬化させることにより第２の封止層２１を形成する。２００℃以下で無機化する材料を使用するため、ＳＡＷチップや第１の封止樹脂に悪影響を及ぼす程度の高温が加えられることがなく、ＳＡＷデバイスの性能、信頼性を悪化させることが無くなる。
また、これ以外の材料、例えばＡｌ_２Ｏ_３、ＴｉＯ_２、又はＺｒＯ_２の何れかを主成分とした溶液、例えば、ＳｉＯ_２＋Ａｌ_２Ｏ_３、ＳｉＯ_２＋ＴｉＯ_２、ＳｉＯ_２＋ＺｒＯ_２を用いても、前記シリカ溶液を用いた場合と同様の機能を有した第２の封止層２１を形成することができる。
ガラス膜から成る第２の封止層２１は、ＳＡＷチップの上面を含む外面に被覆してもよいし、ＳＡＷチップの側面に被覆してもよい。後者の場合には、ＳＡＷデバイスを薄型化することができる。
また、図２、図３において夫々説明した製造方法の第２の封止層形成工程において、第２の封止層２１として上記の如き材料を用いてガラス膜を形成するようにしてもよい。即ち、上記のいずれかの溶液を露出部８、第１の封止樹脂２０、及びＳＡＷチップ外面（全面、或いは側面）に印刷形成してから、２００℃以下で加熱して硬化させることにより、ガラス膜を形成する。
【００１７】
【発明の効果】
以上のように本発明によれば、表面実装用の配線基板上の上部電極上にバンプを介してＳＡＷチップをフェイスダウン搭載し、ＳＡＷチップの裾部と配線基板との間に第１の封止樹脂を充填することにより、ＳＡＷチップ下方に弾性表面波伝搬用の気密空間を形成し、更に第１の封止層、及びＳＡＷチップ外面を第２の封止層にて被覆したＳＡＷデバイスにおいて、第２の封止層を配線基板上面と直接接合させるためのスペースを確保するために、配線基板の面積が増大したり、配線基板母材を用いた量産時の生産性の低下を招くという不具合を解決することができる。
請求項１の発明では、ＳＡＷチップよりも外側に位置する配線基板上面全体を覆うように第１の封止層を形成してから、第１の封止層の外周部と配線基板表層を切除して露出部を形成し、この露出部を第２の封止層との接合部として利用した。このため、配線基板の大型化を招くことなく、第２の封止層を配線基板上面と密着させることが可能となった。
請求項２の発明は、第１の封止層（第１の封止樹脂）の粘度を高くすることにより、これをＳＡＷチップの裾部の空間に充填したとしても気密空間内に入り込む虞がなくなる一方で、露出部、第１の封止樹脂外面、及びＳＡＷチップ外面に密着して被覆する必要がある第２の封止層（第２の封止樹脂）についてはその粘度を低下させるようにしたものである。
請求項３の発明方法によれば、配線基板個片毎に、ＳＡＷチップの搭載、樹脂被覆、接地用露出部の形成、導電性金属被膜の被覆形成による接地用露出部との接続を行うことにより、請求項１、２に記載したＳＡＷデバイスを得ることができる。
請求項４の発明方法では、大面積の配線基板母材を用いたバッチ処理により請求項１、２に記載のＳＡＷデバイスを量産することができる。
【００１８】
請求項５の発明では、露出部形成工程において、ＳＡＷチップ間の谷間を埋めるように充填された第１の封止層を、肉厚が厚いダイシングブレードを用いて分断する際に、配線基板表層（接地用導体としての上部電極、及び／或いは接続導体の一部を含む）を同時に切除するので、極めて簡単に露出部を確保することが可能となり、ＳＡＷチップ間の間隔を広く確保する必要もなくなる。
請求項６の発明では、最後の切断をダイシングブレードにて行う場合には、配線基板間の境界線を単に切断するだけでよいので、薄肉のダイシングブレードを用いる。
請求項７の発明では、第１の封止層を含むＳＡＷチップ外面に金属被膜を形成し、更にその外面に第２の封止層を形成することにより、気密性、水密性を高めることができ、しかも金属被膜を配線基板の露出部に露出した接地導体と導通させることにより、シールド効果を発揮することができる。
請求項８の発明では、第１の封止層（第１の封止樹脂）の粘度を高くすることにより、これをＳＡＷチップの裾部の空間に充填したとしても気密空間内に入り込む虞がなくなる一方で、露出部、第１の封止樹脂外面、及びＳＡＷチップ外面に密着して被覆する必要がある第２の封止層（第２の封止樹脂）についてはその粘度を低下させるようにしたものである。
請求項９及び１１の発明では、２００℃以下の低温加熱によって硬化させることができるシリカ溶液を使用し、高温加熱する場合の悪影響を回避した。
請求項１０及び１２の発明によれば、使用する溶液の種類の選択範囲を拡大することができる。
【図面の簡単な説明】
【図１】（ａ）（ｂ）は本発明の一実施形態に係る表面実装型弾性表面波デバイスの外観斜視図、及び縦断面図。
【図２】（ａ）乃至（ｄ）は図１のＳＡＷデバイスの製造工程を説明する図。
【図３】（ａ）（ｂ）は本発明の変形例に係るＳＡＷデバイスの製造工程を説明する図。
【図４】従来例に係るＳＡＷデバイスの縦断面図。
【図５】（ａ）（ｂ）は図４に示したＳＡＷデバイスを製造する手順を示す工程図。
【図６】他の従来例の製造工程を説明するための図。
【符号の説明】
１　弾性表面波デバイス（ＳＡＷデバイス）、２　配線基板、３　絶縁基板、４　外部電極、５、５ａ　上部電極、６、６ａ　接続導体、８、８ａ　露出部、１０　導体バンプ、Ｓ　気密空間、１５　弾性表面波チップ（ＳＡＷチップ）、１６　接続パッド、１７　ＩＤＴ電極、１８　圧電基板、２０　第１の封止層（第１の封止樹脂）、２１　第２の封止層（第２の封止樹脂、ガラス膜）、２５　配線基板母材。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a surface acoustic wave device having a structure in which a surface acoustic wave chip flip-chip mounted on a wiring board is sealed with a resin, and a surface-mounted surface acoustic wave device that solves various problems that occur during the manufacturing process. , And a method of manufacturing the same.
[0002]
[Prior art]
A surface acoustic wave device (SAW device) has a configuration in which comb-shaped electrode fingers (IDT electrodes) are arranged on a piezoelectric substrate such as quartz, and for example, a surface acoustic wave is excited by applying a high-frequency electric field to the IDT electrodes. Then, a filter characteristic is obtained by converting a surface acoustic wave into a high-frequency electric field by a piezoelectric reaction.
FIG. 4 is a longitudinal sectional view of a conventional surface mount type SAW device. The SAW device 101 includes an insulating substrate 103, an external electrode 104 for surface mounting provided on the bottom of the insulating substrate 103, an upper electrode 105 provided on the upper surface of the insulating substrate, and a connection between the external electrode 104 and the upper electrode 105. A wiring substrate 102 including a connecting conductor 106 to be connected, a connecting pad 116 electrically and mechanically connected to the upper electrode 105 via a conductive bump 110, and a piezoelectric substrate 118 having an IDT electrode 117 on a lower surface. The SAW chip 115 and a hardening that is filled between the lower edge of the SAW chip 115 and the upper electrode 105 to form an airtight space S for surface acoustic wave propagation between the lower surface of the SAW chip 115 and the upper surface of the wiring board 103. The first sealing resin 120 having high viscosity before processing, the entire outer surface of the SAW chip 115, the outer surface of the first sealing resin 120, and the first sealing resin It has a second sealing resin 121 having low curing viscosity before coated formed over the wiring substrate top surface not covered by the fat 120.
[0003]
The sealing portion made of the first sealing resin 120 is formed on the bottom of the SAW chip 115 by screen printing, filling with a dispenser, or the like so that the airtight space S can be formed. The second sealing resin 121 is formed by screen printing, filling with a dispenser, or the like, and covers a part of the upper surface of the wiring board that is exposed and formed in advance so as not to be covered with the first sealing resin.
The reason why the resin having a high viscosity is used as the first sealing resin 120 is to prevent the resin from entering the lower surface of the piezoelectric substrate 118 which is the SAW propagation path. The reason why the resin having a low viscosity is used is to secure the adhesion between the exposed portion of the wiring board, the outer surface of the first sealing resin, and the outer surface of the SAW chip. It is difficult to secure adhesion to the object to be coated with only the first sealing resin 120 having a high viscosity, and thus the second sealing resin having a low viscosity and a good wettability with the object to be coated is difficult. The adhesion is enhanced by a resin (see JP-A-6-204293).
[0004]
Next, FIG. 5 is a diagram for explaining a procedure for manufacturing the SAW device 101 of FIG. 4 using the wiring board base material 125 having a configuration in which the wiring boards (pieces) 102 are connected in a plurality of sheets. After the SAW chip 115 is flip-chip mounted on each of the individual regions on the wiring board base material 125, the first sealing resin 120 is used to seal the gap located at the bottom of the SAW chip 115, and the airtight space S is formed. Is formed, and the second sealing resin 121 is collectively formed by coating. Then, the plurality of SAW device pieces 101 are obtained by dividing the wiring board pieces 102 along a boundary line with a dicing blade or the like.
However, in the SAW device 101 shown in FIG. 4, in order to cover the upper surface of the wiring board with the second sealing resin 121, the valley between the SAW chips 115 after the first sealing resin 120 is applied. It is necessary to expose a part of the upper surface of the wiring board. When the interval between the SAW chips is narrow as shown in FIG. 5, the upper surface of the wiring substrate located in the valley between the SAW chips is covered with the first sealing resin 120 as shown in FIG. 121 cannot contact the upper surface of the wiring board, and the sealing effect (ensurement of airtightness) by the second sealing resin is not sufficiently exhibited.
In order to prevent the first sealing resins 120 arranged at the bottoms of the adjacent SAW chips 115 from being in an unseparated state as shown in FIG. 5, the SAW chip interval may be increased. However, the expansion of the SAW chip interval requires an increase in the size of the SAW device due to an increase in the size of the wiring substrate piece, an increase in the area of the wiring substrate base material 125, and an increase in the number of SAW devices that can be manufactured per wiring substrate base material. This leads to the problem of reduction.
Further, since the nozzle of the dispenser extends linearly, in order to fill the resin along the entire circumference of the gap located at the foot of the SAW chip 115, the resin is obliquely inserted into the valley-shaped gap between the SAW chips 115. It is necessary to insert a nozzle to perform filling work on the bottom of the SAW chip. In order to make such a filling operation possible, it is necessary to previously set a large interval between SAW chips, and in the illustrated example, a wide interval of about 1,000 μm is required.
To cope with such a problem, it is conceivable to further reduce the size of the SAW chip. However, there is a limit to the unreasonable size reduction, which causes a limitation in design flexibility and other disadvantages.
[0005]
Next, Japanese Patent Application Laid-Open No. 2-186662 (Hitachi, Ltd.) discloses that a skirt portion of a SAW chip mounted flip-chip in a face-down state on a wiring board is sealed with a first sealing layer. A configuration in which the outer surface of a component is covered with a second sealing layer is disclosed, and an example is shown in which an SOG (Spin On Glass) material is used as the second sealing layer. This publication discloses that by using SOG material as the second sealing layer, reliable hermetic sealing can be realized even when a step between the lower surface of the SAW chip and the surface of the wiring board is large. I have. However, according to the company's website on February 21, 1995 by Oki Electric Co., Ltd. regarding the SOG material, the curing temperature for completely mineralizing the SOG material is 350 to 400 ° C., and the glass is mineralized. Although the temperature is relatively low, it is clear that this temperature is too high for the constituent material of the SAW chip and the sealing resin. That is, for example, when the bump 110 shown in FIG. 4 is made of gold, and the connection pad 116 on the SAW chip 115 side connected to the bump 110 is made of an alloy containing aluminum as a main component, the bump 110 is exposed to a high temperature in the above range. As a result, a hard and brittle alloy layer of gold and aluminum is formed at the joint between the two metals, and the reliability of the gold bump is reduced. In addition, when the first sealing resin 120 is exposed to a high temperature, there occurs a problem that each electrode constituting the SAW chip is corroded by outgas generated from the first sealing resin.
[0006]
[Problems to be solved by the invention]
The present invention has been made in view of the above, and a SAW chip is mounted face-down via bumps on an upper electrode on a wiring board for surface mounting, and a gap between a skirt portion of the SAW chip and the wiring board is provided. By filling the inside with the first sealing layer, an airtight space for surface acoustic wave propagation is formed below the SAW chip, and further, the first sealing layer and the outer surface of the SAW chip are used as the second sealing layer. In a SAW device covered with a wiring board, the area of the wiring board is increased to secure a space for directly joining the second sealing layer to the upper surface of the wiring board, or production in mass production using the wiring board base material is performed. It is an object of the present invention to provide a surface-mount type surface acoustic wave device that can solve the problem of causing a decrease in performance, and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
In order to solve the above problems, the present invention includes the following means.
The SAW device according to the first aspect of the present invention provides an insulating substrate, an external electrode for surface mounting provided below the insulating substrate, an upper electrode provided above the insulating substrate, and conduction between the external electrode and the upper electrode. A SAW chip including a wiring substrate formed of a connection conductor, a piezoelectric substrate, a connection pad formed on the lower surface of the piezoelectric substrate and connected to the upper electrode via a conductor bump, and an IDT electrode; and a lower surface of the SAW chip. And a first sealing layer made of a resin interposed between at least the wiring board and the bottom of the SAW chip so as to form an airtight space between the wiring board and the upper surface of the wiring board. An exposed portion formed above the outer peripheral edge of the wiring substrate by cutting off the outer peripheral edge of the first sealing layer together with the surface layer of the wiring substrate; the exposed portion, the first sealing layer, and the SAW chip; A second sealing layer covering up the outer surface, characterized by comprising a.
A SAW chip is flip-chip mounted face-down on the wiring board, and the space between the foot of the SAW chip and the upper surface of the wiring board is sealed over the entire circumference by a first sealing layer, and a second sealing is formed on the outer surface thereof. When the stop layer is formed by coating, it is important to directly join the skirt of the second sealing layer to the upper surface of the wiring board in order to improve the airtightness and the joining property. However, if an attempt is made to secure a bonding margin with the second sealing layer by projecting the upper surface of the wiring board outside the first sealing layer, the wiring board becomes large. On the other hand, it is difficult to control the application area when applying and filling the first sealing layer to a predetermined narrow range so as to secure the bonding margin.
Therefore, in the present invention, the first sealing layer is formed so as to cover the entire upper surface of the wiring board located outside the SAW chip, and then the outer peripheral portion of the first sealing layer and the surface layer of the wiring board are cut off. Thus, an exposed portion was formed, and this exposed portion was used as a joint portion with the second sealing layer. Therefore, the second sealing layer can be brought into close contact with the upper surface of the wiring substrate without increasing the size of the wiring substrate.
Note that the second sealing layer may cover the entire exposed surface excluding the lower surface of the SAW chip, or may cover the side surface other than the upper surface of the SAW chip.
[0008]
According to a second aspect of the present invention, in the first aspect, the second sealing layer is made of a resin material, and the viscosity of the resin constituting the second sealing layer before the curing treatment is changed to the first sealing layer. It is characterized in that the viscosity of the resin constituting the stop layer is lower than the viscosity before the curing treatment.
By increasing the viscosity of the first sealing layer (first sealing resin), even if the first sealing layer is filled in the space at the foot of the SAW chip, there is no danger of entering the airtight space. The viscosity of the second sealing layer (the second sealing resin) which needs to be tightly coated on the outer surface of the first sealing resin and the outer surface of the SAW chip is reduced.
A method according to a third aspect of the present invention provides a wiring board comprising an insulating substrate, an external electrode for surface mounting provided below the insulating substrate, and an upper electrode provided above the insulating substrate, and a conductive bump on the upper electrode. A SAW chip provided with a connection pad and an IDT electrode mounted on the lower surface of the piezoelectric substrate via a flip chip, and an airtight space is formed between the lower surface of the SAW chip and the upper surface of the wiring substrate. A method of manufacturing a surface-mounted SAW device, comprising: a first sealing layer; a flip-chip mounting step of connecting the upper electrode and a connection pad of the SAW chip via a bump; A first sealing layer forming step of covering at least a part of the outer surface of the SAW chip with a first sealing layer made of resin so as to form an airtight space between the wiring board and the upper surface; An exposed portion forming step of forming an exposed portion of the wiring board by cutting off an outer peripheral portion of the first sealing layer together with a surface layer of the wiring board; the exposed portion; the first sealing layer; And a second sealing layer forming step of covering the outer surface with the second sealing layer.
According to this, the mounting of the SAW chip, the formation of the resin coating, the formation of the exposed portion for grounding, and the connection with the exposed portion for grounding by forming the coating of the conductive metal film are performed for each wiring board piece. 2 can be obtained.
[0009]
According to a fourth aspect of the present invention, there is provided a large-sized sheet formed by connecting a plurality of wiring boards each including an insulating substrate, an external electrode for surface mounting provided below the insulating substrate, and an upper electrode provided above the insulating substrate. In a method of manufacturing a surface-mounted SAW device using a wiring board base material having a large area, a connection pad of a SAW chip having a connection pad and an IDT electrode on a lower surface of a piezoelectric substrate is provided via a conductive bump on the upper electrode. And a first sealing layer made of resin filled in a valley between the SAW chips so as to form an airtight space between the lower surface of each SAW chip and the upper surface of each wiring board. (1) forming a sealing layer; and exposing a first sealing layer located in a valley between the SAW chips, and exposing a surface layer of the wiring substrate to form an exposed portion of the wiring substrate. , The dew Part, the first sealing layer, a second sealing layer forming step of covering the outer surface of the SAW chip with a second sealing layer, and a wiring board base material that has gone through each of the above steps. And a cutting step for cutting each piece.
In this manufacturing method, the SAW devices according to the first and second aspects are mass-produced by batch processing using a large-area wiring board base material. The range covered by the second sealing layer may cover the entire exposed surface excluding the lower surface of the SAW chip, or may cover the side surface other than the upper surface of the SAW chip. In the encapsulation operation using the first encapsulation resin, screen printing is used, and the targeted filling by the dispenser is not performed, so that it is not necessary to secure a large space between the SAW chips.
According to a fifth aspect of the present invention, in the fourth aspect, in the exposing portion forming step, the first sealing layer located between the SAW chips and a part of the upper surface of the wiring substrate are half-cut with a dicing blade. I do.
In the exposed portion forming step, when the first sealing layer filled so as to fill the valley between the SAW chips is cut using a thick dicing blade, the surface layer of the wiring board (the upper portion as a grounding conductor) is cut. Since the electrode and / or a part of the connection conductor are cut off at the same time, the exposed portion can be secured very easily, and it is not necessary to secure a large space between the SAW chips.
[0010]
According to a sixth aspect of the present invention, in the fifth aspect, a dicing blade used in the cutting step is thinner than a dicing blade used in the half cutting.
At the time of half-cutting, a thick cutter was used because it was intended to cut off and expose a part of the surface layer of the wiring board, but when the last cutting was performed with a dicing blade, the boundary between the wiring boards was Since it is only necessary to cut the wire, a thin dicing blade is used.
According to a seventh aspect of the present invention, in the fifth or sixth aspect, a metal film is formed on the exposed portion of the wiring board, the first sealing layer, and the outer surface of the SAW device after the half-cut, and the metal film is formed after the metal film is formed. The method is characterized in that the sealing layer forming step 2 is performed.
Since the resin has water absorbability, dew condensation may occur on the IDT electrode in the hermetic space, and corrosion may occur. Therefore, by forming a metal coating on the outer surface of the SAW chip including the first sealing layer and further forming a second sealing layer on the outer surface, airtightness and watertightness can be improved, and the metal coating can be formed. Is electrically connected to the ground conductor exposed at the exposed portion of the wiring board, whereby a shielding effect can be exhibited.
According to an eighth aspect of the present invention, in the third aspect, the second sealing layer is made of a resin material, and the viscosity of the resin constituting the second sealing layer before the curing treatment is the first sealing layer. It is characterized in that the viscosity of the resin constituting the sealing layer is lower than that before the curing treatment.
By increasing the viscosity of the first sealing layer (first sealing resin), even if the first sealing layer is filled in the space at the foot of the SAW chip, there is no danger of entering the airtight space. The viscosity of the second sealing layer (the second sealing resin) which needs to be tightly coated on the outer surface of the first sealing resin and the outer surface of the SAW chip is reduced.
[0011]
In a ninth aspect of the present invention, in the first aspect, the second sealing layer is formed of a glass film, and the glass film is formed by heating and curing a silica solution at a temperature of 200 ° C. or less. And
If the temperature at which the glass film is cured is high, it has an adverse effect on connection conductors such as bumps and connection pads, as well as on SAW chips and resins. Therefore, in the present invention, a silica solution that can be cured by heating at a low temperature of 200 ° C. or less was used.
The invention according to claim 10 is that the silica solution contains Al ₂ O ₃ , TiO ₂ Or ZrO ₂ Is included.
According to this, the selection range of the type of the solution to be used can be expanded.
In the invention according to claim 11, the second sealing layer coated in the second sealing layer forming step is a glass film, and the glass film is cured by heating a silica solution at 200 ° C. or lower. It is characterized by the following.
If the temperature at which the glass film is cured is high, it has an adverse effect on connection conductors such as bumps and connection pads, as well as on SAW chips and resins. Therefore, in the present invention, a silica solution that can be cured by heating at a low temperature of 200 ° C. or less was used.
The invention according to claim 12 is that the silica solution contains Al ₂ O ₃ , TiO ₂ Or ZrO ₂ Is included.
According to this, the selection range of the type of the solution to be used can be expanded.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to embodiments shown in the drawings.
1A and 1B are an external perspective view and a longitudinal sectional view of a surface-mounted surface acoustic wave device (hereinafter, referred to as a SAW device) according to an embodiment of the present invention.
The SAW device 1 is provided on an insulating substrate 3 made of ceramic, glass epoxy, or the like, an external electrode 4 for surface mounting provided on the bottom (lower) of the insulating substrate 3, and an upper surface (upper) of the insulating substrate 3; The wiring board 2 including the upper electrode 5 electrically connected to the external electrode 4 via the connection conductor 6, the connection pad 16 electrically and mechanically connected to the upper electrode 5 via the conductor bump 10, and the IDT electrode 17 The SAW chip 15 provided on the lower surface of the piezoelectric substrate 18, the wiring substrate 2 including the upper surface of the upper electrode 5, and the side and upper surfaces of the SAW chip 15 are covered and integrated, and the bottom of the SAW chip 15 and the wiring substrate A first sealing resin (first sealing layer) 20 filling a gap between the upper surface and the upper surface of the SAW chip 15 and an upper surface of the wiring board by sealing with the first sealing resin 20. Formed And a, and airtight space S for the surface acoustic wave propagation.
The exposed portion 8 of the wiring board 2 is formed outside the first sealing resin 20 by cutting off the outer peripheral edge of the first sealing resin 20 and the upper part of the wiring board 2. In this example, the outer portion of at least one upper electrode (ground conductor) 5a of the plurality of upper electrodes 5 on the wiring board 2 and the surface layer of the connection conductor (ground conductor) 6a have a part of the first layer. The exposed portion 8 is exposed together with the sealing resin 20 to expose the conductor portion. The entire outer surface of the first sealing resin 20 is coated with a second sealing resin (second sealing layer) 21, and the second sealing resin 21 is brought into close contact with the exposed portion 8 to achieve high airtightness. Property can be ensured.
Since the upper surface of the wiring board is exposed by cutting off the outer peripheral edge of the first sealing resin 20 formed on the outer circumference of the upper surface of the wiring board 3, the area of the wiring board can be increased. The exposed portion 8 can be secured without using the exposed portion 8, and the close contact between the second sealing resin 21 and the wiring board can be secured using the exposed portion 8.
[0013]
In this embodiment, the second sealing layer 21 is made of a resin material, and the viscosity of the second sealing resin constituting the second sealing layer 21 before the curing treatment is changed to the first sealing resin. By setting the viscosity of the first sealing resin constituting the second sealing resin to be lower than that before the curing treatment, the first sealing resin can be prevented from entering the hermetic space S, and can be exposed by the second sealing resin. The adhesion to the portion 8, the outer surface of the first sealing resin 20, and the outer surface of the SAW chip can be sufficiently improved.
The upper electrode 5 has, for example, a structure in which nickel plating and gold plating are sequentially applied to the surface of a tungsten film, and the upper electrode 5 is electrically connected to the corresponding external electrode 4 via the connection conductor 6. A plurality of conductor sets each composed of the external electrode 4, the upper electrode 5, and the connection conductor 6 which are electrically connected to each other are arranged for input / output and for grounding, and the outer end of the grounding upper electrode (ground conductor) 5a is provided. The exposed portion (grounded exposed portion) 8a is formed by cutting off the upper portion of the portion and the grounding connection conductor (grounded conductor) 6a together with the first sealing resin 20. Before the second sealing resin 21 is coated, the second sealing resin 21 is electrically connected to the grounding upper electrode 5a and the grounding connection conductor 6a, and the first sealing resin 20 and the outer surface of the SAW chip. , A conductive metal film (not shown) may be formed by plating, vapor deposition, sputtering, or the like, and the outer surface of the conductive metal film may be coated with a second sealing resin 21.
As described above, in the SAW device of the present invention, it is not necessary to form an uncovered portion with the first sealing resin 20 by extending the outer end portion of the wiring board largely, and the portion covered with the first sealing resin is not necessary. Since the exposed portion 8 is formed by cutting off the outer portion of the wiring board together with the first sealing resin, the area of the wiring board 2 can be reduced as compared with a conventional SAW device. In addition, since the conductor exposed portion 8a of the exposed portion 8 can be connected to the conductive metal film, not only a shielding effect but also a higher airtight effect can be obtained.
[0014]
Next, a manufacturing procedure of the SAW device 1 of FIG. 1 will be described with reference to FIGS. In this example, a method of producing a SAW device by batch processing using a wiring board base material 25 in which a plurality of wiring board pieces 2 are connected and integrated in a sheet shape is shown.
First, as shown in FIG. 2A, an external electrode 4 is provided on the lower surface of the insulating substrate 3, an upper electrode 5 is provided on the upper surface, and a connection conductor 6 that conducts between the external electrode 4 and the upper electrode 5 is formed. A large-area wiring board base material 25 is manufactured by connecting a plurality of the wiring board pieces 2 having a plurality of pieces in a sheet shape, and a connection pad 16 and an IDT electrode 17 are formed on the lower surface of each piece area of the wiring board base material 25. Is electrically and mechanically connected to the upper surface of the upper electrode 5 via the conductive bump 10 (flip chip bonding). The conductor bump 10 may be formed on the connection pad 16 side in advance, or may be formed on the exposed region 5a. The conductor bump 10 may be a bump made of a conductor such as gold, for example, or may be a lump-shaped resin whose outer periphery is covered with a conductor film.
Next, in the first sealing resin forming step shown in FIG. 2A, each wiring board 2 is formed so as to form an airtight space S between the lower surface of the SAW chip 15 and the upper surface of each wiring board piece 2. A first sealing resin (first sealing layer) 20 is filled so as to seal a gap between the bottom of the SAW chip 15 (the lower edge and the lower edge of the side surface). In other words, the first sealing resin 20 is filled into the valleys (gaps) between the SAW chips 15 so as to form an airtight space S between the lower surface of the SAW chip 15 and the upper surface of the wiring board 2. In this step, for example, the first sealing resin 20 having a relatively high viscosity is applied and filled by a method such as screen printing. The reason why a resin having a high viscosity is used is that it is necessary to ensure an airtight space S for SAW propagation.
In this embodiment, since the first sealing resin 20 is collectively filled and covered by screen printing so as to fill the gap between the SAW chips 15, a nozzle is obliquely inserted between the SAW chips by a dispenser, and the bottom of the SAW chip is inserted. As compared with the conventional example in which the portion is filled by aiming at the portion, even if the interval between the SAW chips is reduced, there is no problem and the width can be significantly reduced.
[0015]
Next, in the exposed portion forming step shown in FIG. 2B, the sealing resin 20 filled so as to fill the valley between the SAW chips 15 is half-cut by a relatively thick dicing blade. That is, the first sealing resin 20 between the SAW chips is cut by the dicing blade, and the surface layer at a position along the boundary between the respective wiring boards 2 is partially cut to such an extent that the surface layer is partially cut off. , The outer portion of the upper electrode (grounding conductor) 5a and the upper portion of the connection conductor (grounding conductor) 6a are cut off together with the first sealing resin to form an exposed portion 8 (grounded exposed portion 8a). I do. The width of the half-cut portion is about 200 μm. The space L2 between the SAW chips 15 is set to about 400 μm in advance in consideration of the margin of the width of the half-cut portion.
Next, in the second sealing resin film forming step of FIG. 2C, the exposed portion 8, the outer surface of the first sealing resin 20, and the entire outer surface (excluding the lower surface) of the SAW chip are sealed with the second sealing resin. It is covered with a sealing resin (second sealing layer) 21.
Before coating with the second sealing resin 21, a metal film is formed on the exposed portion 8, the outer surface of the first sealing resin 20, and the outer surface of the SAW chip 15 by plating, vapor deposition, sputtering, or the like. Alternatively, a shielding effect may be obtained by grounding via the grounding exposed portion 8a, and airtightness that cannot be sufficiently secured by the first sealing resin 20 may be secured.
Note that the viscosity of the second sealing resin forming the second sealing layer 21 before the curing treatment is set to be lower than the viscosity of the first sealing resin forming the first sealing resin 20 before the curing treatment. By setting it low, it is possible to prevent the first sealing resin from penetrating into the hermetic space S, and to expose the exposed portion 8 by the second sealing resin, the outer surface of the first sealing resin 20, and the outer surface of the SAW chip. Adhesion can be sufficiently increased.
Finally, along the cutting line C shown in FIG. 2C, the wiring board base material 25 is cut by the dicing blade thinner than the dicing blade used in the step of FIG. A cutting step is performed for dividing the wafer into individual pieces along. By this cutting step, a SAW device piece 1 as shown in FIG. 2D is obtained.
[0016]
Next, FIGS. 3A and 3B are partial explanatory views of a manufacturing method according to another embodiment of the present invention. FIG. 3A shows a second sealing resin coating step, and FIG. (b) is a sectional view showing the completed individual piece. The flip-chip mounting step, the first sealing resin forming step, and the exposed portion forming step in the manufacturing method according to this embodiment are the same as those in the manufacturing method according to the embodiment shown in FIG. This is the same as the step. The manufacturing method according to this embodiment is different from the manufacturing method in FIG. 2 in that the second sealing resin 21 is not coated on the entire outer surface of the SAW chip 15 in the second sealing resin forming step. The exposed portion 8, the outer surface of the first sealing resin 20, and only the side surface of the SAW 15 are covered. Further, other steps are the same as those in FIG. 2, such as the point that the conductor exposed portion 8 is formed by a thick dicing blade in FIG. 2B.
Therefore, even when the manufacturing method of FIG. 3 is carried out, the distance between the SAW chips 15 on the wiring board base material 25 can be reduced, and the number of SAW devices that can be obtained from the same area of the wiring board base material is reduced. Can be increased. The SAW device thus obtained can be made thinner by the absence of the second sealing layer 21 on the upper surface.
Next, the SAW device according to the embodiment shown in FIG. 1 uses a resin material as the exposed portion 8, the first sealing resin 20, and the second sealing layer 21 covering the outer surface of the SAW chip. A glass film may be used instead of the resin. The glass film is superior to the resin material in terms of water absorption and airtightness, and can further enhance the durability of the SAW device. As the glass material used here, a material that vitrifies at 200 ° C. or lower as disclosed in JP-A-6-199528 is used. Specifically, for example, SiO 2 ₂ The second sealing layer 21 is formed by applying a silica solution containing 40% by weight or more and then curing it. Since a material that is mineralized at a temperature of 200 ° C. or less is used, a high temperature that adversely affects the SAW chip and the first sealing resin is not applied, and the performance and reliability of the SAW device are not deteriorated.
Further, other materials such as Al ₂ O ₃ , TiO ₂ Or ZrO ₂ A solution containing any one of ₂ + Al ₂ O ₃ , SiO ₂ + TiO ₂ , SiO ₂ + ZrO ₂ Can be used to form the second sealing layer 21 having the same function as the case where the silica solution is used.
The second sealing layer 21 made of a glass film may cover the outer surface including the upper surface of the SAW chip, or may cover the side surface of the SAW chip. In the latter case, the thickness of the SAW device can be reduced.
Further, in the second sealing layer forming step of the manufacturing method described with reference to FIGS. 2 and 3, a glass film may be formed as the second sealing layer 21 using the above-described material. That is, any one of the above solutions is printed and formed on the exposed portion 8, the first sealing resin 20, and the outer surface (entire or side surface) of the SAW chip, and then cured by heating at 200 ° C. or lower. A glass film is formed.
[0017]
【The invention's effect】
As described above, according to the present invention, a SAW chip is mounted face-down on an upper electrode on a surface mounting wiring board via a bump, and a first sealing is provided between the foot of the SAW chip and the wiring board. In a SAW device in which an airtight space for surface acoustic wave propagation is formed below the SAW chip by filling the sealing resin, and the first sealing layer and the outer surface of the SAW chip are further covered with a second sealing layer. In order to secure a space for directly joining the second sealing layer to the upper surface of the wiring board, the area of the wiring board is increased or productivity is reduced in mass production using the wiring board base material. Problems can be solved.
According to the first aspect of the present invention, after forming the first sealing layer so as to cover the entire upper surface of the wiring board located outside the SAW chip, the outer peripheral portion of the first sealing layer and the surface layer of the wiring board are cut off. Thus, an exposed portion was formed, and this exposed portion was used as a joint with the second sealing layer. Therefore, the second sealing layer can be brought into close contact with the upper surface of the wiring substrate without increasing the size of the wiring substrate.
According to the second aspect of the present invention, by increasing the viscosity of the first sealing layer (first sealing resin), there is a possibility that the first sealing layer (first sealing resin) may enter the airtight space even if it is filled in the space at the foot of the SAW chip. On the other hand, the viscosity of the second sealing layer (the second sealing resin) which needs to be closely adhered to the exposed portion, the first sealing resin outer surface, and the outer surface of the SAW chip is reduced. It was made.
According to the third aspect of the present invention, the mounting of the SAW chip, the formation of the resin coating, the formation of the exposed ground portion, and the connection with the exposed ground portion by forming the coating of the conductive metal film are performed for each wiring board piece. Accordingly, the SAW device according to the first and second aspects can be obtained.
In the method according to the fourth aspect, the SAW devices according to the first and second aspects can be mass-produced by batch processing using a large-area wiring board base material.
[0018]
In the invention according to claim 5, when the first sealing layer filled so as to fill the valley between the SAW chips is divided using a thick dicing blade in the exposed portion forming step, the surface layer of the wiring board is formed. Since the upper electrode (including the upper electrode as a grounding conductor and / or a part of the connection conductor) is cut off at the same time, it is possible to extremely easily secure the exposed portion, and it is also necessary to secure a wide space between the SAW chips. Disappears.
According to the sixth aspect of the present invention, when the last cutting is performed with a dicing blade, a thin dicing blade is used because it is sufficient to simply cut the boundary between the wiring boards.
In the invention of claim 7, a metal film is formed on the outer surface of the SAW chip including the first sealing layer, and the second sealing layer is further formed on the outer surface, whereby airtightness and watertightness can be improved. In addition, by conducting the metal coating to the ground conductor exposed at the exposed portion of the wiring board, a shielding effect can be exhibited.
In the invention of claim 8, by increasing the viscosity of the first sealing layer (first sealing resin), there is a possibility that the first sealing layer (the first sealing resin) may enter the airtight space even if it is filled in the space at the foot of the SAW chip. On the other hand, the viscosity of the second sealing layer (the second sealing resin) that needs to be closely adhered to the exposed portion, the outer surface of the first sealing resin, and the outer surface of the SAW chip is reduced. It was made.
In the ninth and eleventh aspects of the present invention, a silica solution that can be cured by heating at a low temperature of 200 ° C. or less is used, and the adverse effect of heating at a high temperature is avoided.
According to the tenth and twelfth aspects, the selection range of the type of the solution to be used can be expanded.
[Brief description of the drawings]
FIGS. 1A and 1B are an external perspective view and a longitudinal sectional view of a surface mount type surface acoustic wave device according to an embodiment of the present invention.
FIGS. 2A to 2D are diagrams illustrating a manufacturing process of the SAW device of FIG. 1;
FIGS. 3A and 3B are diagrams illustrating a manufacturing process of a SAW device according to a modification of the present invention.
FIG. 4 is a longitudinal sectional view of a SAW device according to a conventional example.
FIGS. 5A and 5B are process diagrams showing a procedure for manufacturing the SAW device shown in FIG.
FIG. 6 is a diagram for explaining a manufacturing process of another conventional example.
[Explanation of symbols]
Reference Signs List 1 surface acoustic wave device (SAW device), 2 wiring substrate, 3 insulating substrate, 4 external electrode, 5 5a upper electrode, 6, 6a connecting conductor, 8, 8a exposed portion, 10 conductor bump, S hermetic space, 15 elasticity Surface acoustic wave chip (SAW chip), 16 connection pads, 17 IDT electrodes, 18 piezoelectric substrate, 20 first sealing layer (first sealing resin), 21 second sealing layer (second sealing resin) , Glass film), 25 wiring board base material.

Claims

An insulating substrate, an external electrode for surface mounting provided below the insulating substrate, an upper electrode provided above the insulating substrate, and a connection conductor that conducts between the external electrode and the upper electrode;
A SAW chip including a piezoelectric substrate, a connection pad formed on the lower surface of the piezoelectric substrate and connected to the upper electrode via a conductor bump, and an IDT electrode;
A first sealing layer made of a resin interposed between at least the wiring substrate and the bottom of the SAW chip so as to form an airtight space between the lower surface of the SAW chip and the upper surface of the wiring substrate;
In a surface mount type SAW device provided with
An exposed portion formed above the outer peripheral edge of the wiring board by cutting off the outer peripheral edge of the first sealing layer together with the surface layer of the wiring board;
A surface-mounted SAW device, comprising: the exposed portion, the first sealing layer, and a second sealing layer that covers an outer surface of the SAW chip.

The second sealing layer is made of a resin material, and the viscosity of the resin constituting the second sealing layer before the curing treatment is higher than the viscosity of the resin constituting the first sealing layer before the curing treatment. The surface mount SAW device according to claim 1, wherein the surface mount SAW device is also low.

A wiring board including an insulating substrate, an external electrode for surface mounting provided below the insulating substrate, and an upper electrode provided above the insulating substrate, and flip-chip mounted on the upper electrode via a conductive bump; A SAW chip provided with a connection pad and an IDT electrode on the lower surface of the piezoelectric substrate, respectively, a first sealing layer disposed so as to form an airtight space between the lower surface of the SAW chip and the upper surface of the wiring substrate; In a method of manufacturing a surface-mounted SAW device having
A flip chip mounting step of connecting the upper electrode and the connection pad of the SAW chip via a bump;
A first sealing layer forming step of covering at least a part of the outer surface of the SAW chip with a first sealing layer made of resin so as to form an airtight space between the lower surface of the SAW chip and the upper surface of the wiring board; ,
An exposed portion forming step of forming an exposed portion of the wiring board by cutting off an outer peripheral portion of the first sealing layer together with a surface layer of the wiring board;
A surface-mounted SAW, comprising: the exposed portion, the first sealing layer, and a second sealing layer forming step of covering an outer surface of the SAW chip with a second sealing layer. Device manufacturing method.

A large-area wiring board base material is formed by connecting a plurality of insulating boards, a surface mounting external electrode provided below the insulating substrate, and a wiring board including an upper electrode provided above the insulating substrate in a sheet shape. In the method for manufacturing a surface-mounted SAW device used,
A flip chip mounting step of connecting the connection pad of a SAW chip having a connection pad and an IDT electrode on the lower surface of the piezoelectric substrate to the upper electrode via a conductor bump;
A first sealing layer forming step of filling a first sealing layer made of resin between valleys between the SAW chips so as to form an airtight space between the lower surface of each of the SAW chips and the upper surface of each of the wiring boards;
Exposing a first sealing layer located in a valley between the SAW chips and cutting off a surface layer of the wiring substrate to form an exposed portion of the wiring substrate;
A second sealing layer forming step of covering the exposed portion, the first sealing layer, and an outer surface of the SAW chip with a second sealing layer;
A cutting step of cutting the wiring board base material after each of the steps, for each wiring board piece,
A method for manufacturing a surface-mount SAW device, comprising:

5. The manufacturing of the surface-mounted SAW device according to claim 4, wherein in the exposed portion forming step, the first sealing layer located between the SAW chips and the surface layer of the wiring board are half-cut by a dicing blade. Method.

The method according to claim 5, wherein a dicing blade used in the cutting step has a smaller thickness than a dicing blade used in the half cutting.

After the half-cut, a metal film is formed on the exposed portion of the wiring board, the first sealing layer, and the outer surface of the SAW device, and the second sealing layer forming step is performed after the metal film is formed. The method for manufacturing a surface-mounted SAW device according to claim 5.

The second sealing layer is made of a resin material, and the viscosity of the resin constituting the second sealing layer before the curing treatment is higher than the viscosity of the resin constituting the first sealing layer before the curing treatment. The method for manufacturing a surface-mounted SAW device according to claim 3, wherein the surface-mount SAW device is also low.

The surface-mounted SAW according to claim 1, wherein the second sealing layer is formed of a glass film, and the glass film is formed by heating and curing a silica solution at a temperature of 200 ° C or lower. device.

Wherein the silica _{_{_{solution, Al 2 O 3, TiO 2}}} , or a surface-mount SAW device of claim 9, characterized in that one of ZrO ₂ is contained.

The second sealing layer coated in the second sealing layer forming step is a glass film, and the glass film is cured by heating a silica solution at 200 ° C. or less. The method for manufacturing a surface-mounted SAW device according to any one of claims 3 to 7.

Wherein the silica _{_{_{solution, Al 2 O 3, TiO 2}}} , or a surface-mount SAW device according to any one of claims 3 to 7, characterized in that one of ZrO ₂ is contained Manufacturing method.