JP3876842B2 - Mass measuring chip and mass measuring device - Google Patents

Description

ただし、ｄｆは圧電振動片の共振周波数の変化量、ｆ₀は圧電振動片の共振周波数の初期値、ρは圧電材料の密度、μは圧電材料のせん断応力、ｄｍは励振電極に結合した検出物質の質量、Ａは励振電極の面積である。上式からわかるように、圧電振動片の共振周波数の初期値ｆ₀が高いほど、その変化量ｄｆが大きくなり、質量測定チップが高感度化する。例えば、ｆ₀を従来の２７ＭＨｚから１５０ＭＨｚまで高周波化すれば、感度を３０倍にすることができる。そして圧電振動片を高周波化するには、圧電振動片の振動部における肉厚を薄くすればよい。
【００２３】
図３に、センサ部の説明図を示す。なお、図３（１）は図３（２）のＣ−Ｃ線における側面断面図であり、図３（２）は底面図である。センサ部１０は、主に圧電振動片２０および平板部材１１によって構成する。第１実施形態では、圧電振動片２０としていわゆる逆メサ型圧電振動片を使用する。逆メサ型圧電振動片は、水晶等の圧電材料を平板状に切り出し、その中央に凹部を形成して薄肉化し、その薄肉部の両面に励振電極２２ａ，２２ｂを形成したものである。また、圧電振動片２０の周縁の厚肉部には、励振電極２２ａ，２２ｂと導通する接続電極２４ａ，２４ｂを形成する。さらに、圧電振動片２０の上面側の接続電極２４ａを側面および下面に延長して、圧電振動片２０の下面にセンサ部側接続電極２４ａ，２４ｂを形成する。なお、各電極はＡｕ／ＣｒまたはＡｇ／Ｃｒの２層によって構成する。このような逆メサ型圧電振動片では、周縁の厚肉部により中央の薄肉振動部が保護されるので、外力による振動部の破壊を防止することができる。これにより、高周波の圧電振動片が利用可能となり、質量測定チップを高感度化することができる。
【００２４】
また、圧電振動片２０を接合する平板部材１１を形成する。平板部材１１は、圧電材料と同等の熱膨張係数を有するガラス材料やセラミック材料等で構成するのが好ましい。これにより、平板部材１１および圧電振動片２０の熱膨張率および熱収縮率が同等となるので、両者の接合部における破壊を防止することができる。また、振動片への応力の影響も最小限に押さえることができる。一方、平板部材１１の中央部には貫通孔１２を形成する。貫通孔１２は、図２に示す矩形や円形など任意の形状に形成すればよいが、少なくとも圧電振動片２０の上面側における励振電極２２ａの全体が貫通孔１２を通して平板部材１１の上面側に露出する大きさに形成する。そして、平板部材１１の下面側に圧電振動片２０を配置し、圧電振動片２０の周縁厚肉部を平板部材１１の貫通孔１２の周辺部に対して接着剤１８等により接合する。接着剤１８として、電気絶縁性を有するシリコーン系の接着剤等を使用する。なお、貫通孔１２を密閉封止すべく、貫通孔１２の周辺部の全周を接着剤１８等により接合する。
【００２５】
図４に、センサ部の変形例の説明図を示す。図３に示すセンサ部１０に代えて、図４に示すセンサ部１１０を使用することも可能である。この変形例に係るセンサ部１１０の圧電振動片１２０は、図３のセンサ部１０の圧電振動片２０と同様に形成する。一方、平板部材１１１の下面には、センサ側接続電極１１４ａ，１１４ｂを形成する。なお、平板部材１１１の上面には圧電振動片の接続電極１２４ａ，１２４ｂに対応する電極パッドを形成し、スルーホールを通じてセンサ側接続電極１１４ａ，１１４ｂとの導通を確保する。ここで、変形例に係るセンサ部１１０では、平板部材１１１の上面側に圧電振動片１２０を配置する。そして、圧電振動片の接続電極１２４ａ，１２４ｂと、平板部材１１１の電極パッドとを、Ａｇペースト等の導電性接着剤１１８を介して接合する。さらに、圧電振動片１２０の全周にわたって、圧電振動片１２０の側面と平板部材の上面との角部に、電気絶縁性を有するシリコーン系の封止剤１１９等を塗布する。これにより、圧電振動片１２０における下面側の各電極が密閉封止され、上面側の各電極との短絡が防止される。なお、平板部材１１１の代わりに、リードフレームを樹脂モールドしたものを使用してもよい。
【００２６】
図５に、ベース部の説明図を示す。ベース部３０は、主に発振回路基板４０と台座３２とによって構成する。発振回路基板４０は、主に発振回路素子４１と基板４３とによって構成する。基板４３は、セラミックやエポキシ等の電気絶縁性を有する材料によって構成する。基板４３の上面には、センサ側接続電極２４ａ，２４ｂ（図３参照）に対応して、ベース側接続電極４４ａ，４４ｂを形成する。なお、基板４３の下面には発振回路素子４１を実装する電極パッドを形成し、スルーホールを通じてベース側接続電極４４ａ，４４ｂとの導通を確保する。また基板４３の下面には、発振回路素子４１と周波数カウンタ５（図７参照）との導通を図るため、配線パターン４６を形成する。
【００２７】
一方、発振回路素子４１は、発振回路を構成する集積回路素子（ＩＣ）である。この発振回路素子４１の電極パッド部（不図示）に、金属ワイヤを用いたスタッドバンプ形成装置を使用して、バンプ４２を形成する。そして、基板４３の下面に形成された電極パッドおよび配線パターン４６に対して、フリップチップボンディングを行うことにより、発振回路素子４１を電気的および機械的に接続する。なおフリップチップボンディングには、加熱加圧による圧着および超音波印加による圧着のいずれを採用してもよい。
【００２８】
一方、台座３２はプラスチック材料等により成形する。台座３２の上面には、発振回路基板４０の配線パターン４６に対応する電極パッド３６を設ける。この電極パッド３６から信号入出力部３７にかけて、台座３２の内部に配線を埋設する。なお、信号入出力部３７から周波数カウンタ５（図７参照）への配線は、ビニルチューブ３８等で被覆する。また、台座３２上面の中央部には、発振回路素子４１を挿入可能な大きさの凹部３４を形成する。そして、その凹部３４に発振回路素子４１を挿入しつつ、発振回路基板４０を台座３２の上面に載置する。その際、発振回路基板４０の配線パターン４６を台座３２の電極パッド３６に当接させ、導電性接着剤等により両者を接続する。これにより、発振回路素子４１と周波数カウンタ５（図７参照）との導通が確保される。
【００２９】
ところで、発振回路素子４１として、通常の発振回路に温度補償回路等を付加したものを使用する場合がある。第１実施形態に係る質量測定チップでは、通常の発振回路素子を搭載した発振回路基板と、温度補償回路等を付加した発振回路素子を搭載した発振回路基板とを、必要に応じて交換して使用することも可能である。この場合には、台座３２の電極パッド３６に対して、発振回路基板４０の配線パターン４６を着脱自在に当接させた状態で使用する。
【００３０】
そして、図１に示すように、ベース部３０の上面にセンサ部１０を載置する。その際、ベース部３０における基板４３の上面に形成したベース側接続電極４４ａ，４４ｂに対して、センサ部１０における圧電振動片２０の下面に形成したセンサ側接続電極２４ａ，２４ｂを、着脱自在に当接させる。これにより、発振回路素子４１から圧電振動片２０の励振電極２２ａ，２２ｂに対して通電可能となる。
【００３１】
さらに、センサ部１０における平板部材１１の上面周縁部に、リング状のゴムパッキン５８を装着する。そして、センサ部１０の上方からキャップ部材５０をかぶせて、ベース部３０における台座３２の側面に螺合させる。キャップ部材５０はプラスチック材料等で構成する。その上面中央部には貫通孔５２を形成し、図２に示すように圧電振動片２０の上方の励振電極２２ａを露出させる。また、キャップ部材５０の上面周縁部によりゴムパッキン５８を平板部材１１に押し付けて、貫通孔５２を密閉封止する。これと同時に、センサ部１０をベース部３０に押し付け、また発振回路基板４０を台座３２に押し付けて、それぞれの導通を確保する。さらに、キャップ部材５０を台座３２に螺合させることにより、キャップ部材５０の下部を密閉封止する。以上により、圧電振動片２０の下方の励振電極２２ｂおよびこれに導通する各配線がキャップ部材５０の内部に密閉封止され、検体溶液７（図７参照）の流入による配線間の短絡が防止される。
以上により、本実施形態に係る質量測定チップ３が完成する。
【００３２】
図６に、キャップ部材の変形例の説明図を示す。変形例に係るキャップ部材１５０は、ゴム材料等により中空円筒状に形成する。なお、上下両端面の中央部には貫通孔１５２を形成する。そして、下端面の貫通孔を拡径し、センサ部１１０の上方からベース部１３０の中段にかけて、キャップ部材１５０をかぶせる。キャップ部材１５０の上端面は、センサ部１１０における平板部材１１１の上面に当接させる。またキャップ部材１５０の下端面は、台座１３２の側面全周に形成した溝部１３３に係合させる。これにより、キャップ部材１５０の内部が密閉封止され、検体溶液７（図７参照）の流入による配線間の短絡が防止される。
【００３３】
次に、上述した本実施形態に係る質量測定チップの使用方法について説明する。
図７に、第１実施形態に係る質量測定装置の説明図を示す。第１実施形態に係る質量測定チップ３は、周波数カウンタ５に接続する。周波数カウンタ５は、質量測定チップ３における圧電振動片の共振周波数を測定する。また、周波数カウンタ５はコンピュータ６に接続する。コンピュータ６は、周波数カウンタ５が測定した圧電振動片の共振周波数から、励振電極に付着した検出物質の質量を算出する。加えて、検出物質の付着量の経時変化から、検体溶液７中における検出物質の濃度等を解析し得るようにコンピュータ６を構成するのが好ましい。
【００３４】
質量測定の具体的手順は以下の通りである。まず、図１に示す質量測定チップ３において、圧電振動片２０の上面側の励振電極２２ａに検出物質の感応膜を塗布する。次に、発振回路素子４１から圧電振動片２０に通電して圧電振動片２０を発振させる。なお、図７に示す周波数カウンタ５により、圧電振動片の共振周波数を連続的に計測しておく。そして、図７に示すように、検体溶液７中に質量測定チップ３を浸漬する。検体溶液７中では、圧電振動片の励振電極上の感応膜に対して検出物質が結合する。これにより励振電極の質量が増加して、圧電振動片の共振周波数が低下する。この共振周波数の低下量等をコンピュータ６で解析することにより、検出物質の有無および濃度等を算出する。
【００３５】
なお、質量測定チップを検体溶液に浸漬して使用するだけでなく、質量測定チップに検体溶液を滴下して使用することも可能である。具体的には、図１に示す質量測定チップ３において、圧電振動片２０の上面側の励振電極２２ａに検出物質の感応膜を塗布した後、貫通孔１２を通して検体溶液を滴下すればよい。なお、検体溶液を滴下して使用する場合には、キャップ部材５０により質量測定チップ３の内部を密閉封止する必要がない。したがって、キャップ部材５０を装着することなく質量測定チップを使用することも可能である。一方、質量測定チップを検体ガスに暴露して使用することにより、検体ガス中の検出物質の質量を測定することも可能である。
【００３６】
ところで、質量測定チップは微少質量を測定するものであるから、一度測定に使用した圧電振動片を洗浄したとしても、これを再利用することはできない。そこで、質量測定チップによる再測定を行う前に、センサ部の交換を行う。図１に示す質量測定チップ３において、センサ部１０を交換するには、まずキャップ部材５０を取り外す。次に、ベース部３０からセンサ部１０およびゴムパッキン５８を分離する。なお、使用済みのセンサ部１０は廃棄する。そして、新しいセンサ部１０をベース部３０の上面に載置する。その後、ゴムパッキン５８を装着し、キャップ部材５０を装着すれば、質量測定チップ３におけるセンサ部１０の交換が完了する。
以上に詳述した第１実施形態に係る質量測定チップにより、高感度化および低コスト化を両立することができる。
【００３７】
すなわち、第１実施形態に係る質量測定チップでは、圧電振動片を発振回路素子に接続するためのセンサ側接続電極が形成されたセンサ部と、発振回路素子を圧電振動片に接続するためのベース側接続電極を形成したベース部とを有し、センサ側接続電極をベース側接続電極に着脱自在に当接させる構成とした。質量測定チップに発振回路を搭載することにより、圧電振動片と発振回路との電気長が短くなって伝送回路の損失が低下する。これにより、高周波の圧電振動片を検体溶液中で使用した場合でも、発振の不安定を解消することができる。したがって、質量測定チップの高感度化に対応することができる。
【００３８】
しかも、質量測定センサをセンサ部とベース部に分離し、センサ部をベース部に着脱可能に当接させる構成としたので、使用済みのセンサ部だけを廃棄して、高価な発振回路を再利用することができる。したがって、高感度化および低コスト化を両立することができる。
【００３９】
なお、第１実施形態に係る質量測定チップでは、図１に示すように、センサ部１０における平板部材１１、ならびにベース部３０における発振回路基板４０および台座３２を、平面視円形状に形成した。これは、図１および図２に示すように、円筒状のキャップ部材５０を使用して質量測定チップを密閉封止するためである。したがって、円筒状のキャップ部材５０以外の手段により質量測定チップを密閉封止する場合には、上記各部材を平面視矩形状に形成することも可能である。
【００４０】
また、第１実施形態に係る質量測定チップでは、１個の圧電振動片および１個の発振回路素子のみを搭載した。この場合、１回の測定により１種類の物質のみを検出することができる。近時では、１回の測定により多種類の物質を検出可能とするため、質量測定チップのマルチセンサ化が求められている。この点、第１実施形態と同様の構成により、複数の圧電振動片および複数の発振回路素子を搭載した質量測定チップを形成することも可能である。具体的には、平板部材に複数の貫通孔を形成し、これに複数の圧電振動片を接合してセンサ部を形成する。また、発振回路基板にも複数の発振回路素子を搭載してベース部を形成する。そして、このベース部およびセンサ部を組み合わせればよい。これにより、質量測定チップのマルチセンサ化に対応することができる。
【００４１】
次に、第２実施形態について説明する。
図８に、第２実施形態に係る質量測定チップの説明図を示す。なお図８では、ベース部２３０における台座の記載を省略している。第２実施形態に係る質量測定チップ２０３は、圧電振動片２２０におけるベース部２３０とは反対側の表面のみに励振電極２２２ａを形成し、ベース部２３０における圧電振動片２２０との対面位置に、圧電振動片２２０におけるベース部側の励振電極２２２ｂを形成したものである。なお、第１実施形態と同様の構成となる部分については、その説明を省略する。
【００４２】
第２実施形態に係る質量測定チップ２０３の圧電振動片２２０は、薄肉振動部の上面のみに励振電極２２２ａを形成する。なお、励振電極２２２ａと導通する接続電極２２４ａを周縁の厚肉部に形成し、これを圧電振動片２２０の側面および下面に延長して、センサ側接続電極２２４ａを形成する。そして、圧電振動片２２０の下面側の励振電極２２２ｂを、ベース部２３０における発振回路基板２４０の上面に形成する。なお、圧電振動片２２０の表面から励振電極２２２ｂが離れていても、圧電振動片２２０を駆動することは可能である。
【００４３】
第２実施形態に係る質量測定チップでは、圧電振動片の下面側の励振電極を発振回路基板の上面に形成したので、励振電極と発振回路との電気長が最短となり、伝送回路の損失を最小化することができる。これにより、高周波の圧電振動片を検体溶液中で使用した場合でも、発振の不安定を解消することが可能となる。したがって、質量測定チップの高感度化に対応することができる。
【００４４】
なお、水晶振動子マイクロバランス法は、所定の雰囲気温度で行う必要がある。ここで、逆メサ型圧電振動片は、雰囲気温度のわずかな変化により共振周波数が変化し、測定精度が低下するおそれがある。その原因として、逆メサ型圧電振動片は振動部の厚さに対する励振電極の厚さの比率が大きく、励振電極の影響を強く受けることが考えられる。この点、第２実施形態では、逆メサ型圧電振動片の振動部表面から一定距離をおいて励振電極を配置したので、励振電極の影響を受けることがない。これにより、温度変化に対する共振周波数の変化が小さくなり、逆メサ型圧電振動片の周波数温度特性を改善することができる。したがって、質量測定の精度を向上させることができる。
【００４５】
次に、第３実施形態について説明する。
図９に、第３実施形態に係る質量測定チップの説明図を示す。なお図９では、ベース部３３０における台座の記載を省略している。第３実施形態に係る質量測定チップは、センサ部３１０の位置決め用突起３４８を、ベース部３３０に形成したものである。なお、第１実施形態と同様の構成となる部分については、その説明を省略する。
【００４６】
第３実施形態では、ベース部３３０における発振回路基板３４０の上面に、圧電振動片の位置決め用突起３４８を形成する。例えば、基板３４３のパターンを形成したセラミックシートに、突起３４８のパターンを形成したセラミックシートを積層・焼成して、基板３４３とともに位置決め用突起３４８を形成する。突起３４８は、矩形の圧電振動片３２０における対向する側面を支持できる位置に形成する。なお、圧電振動片３２０を位置決めすることにより、センサ部全体を位置決めすることができる。
【００４７】
第３実施形態では、ベース部の位置決め用突起を設けたので、ベース部の上面にセンサ部を載置する際に、ベース側接続電極とセンサ側接続電極との位置が相互にずれることがなくなり、両者の導通を確保することができる。
【００４８】
なお、図１に示す質量測定チップでは、キャップ部材５０を台座３２に締め込む際に、ベース部３０に対してセンサ部１０が回転するおそれがある。しかし第３実施形態では、圧電振動片の位置決め用突起を設けたので、センサ部の回転を防止することが可能となる。したがって、ベース側接続電極とセンサ側接続電極との位置が相互にずれることがなくなり、両者の導通を確保することができる。
【００４９】
次に、第４実施形態について説明する。
図１０に、第４実施形態に係る質量測定チップの説明図を示す。なお図１０では、ベース部における台座の記載を省略している。第４実施形態に係る質量測定チップは、位置決め用突起４４８における圧電振動片４２０との当接面に、ベース側接続電極４４４ａ，４４４ｂを配置したものである。なお、第１および第３実施形態と同様の構成となる部分については、その説明を省略する。
【００５０】
第４実施形態では、第３実施形態と同様に位置決め用突起４４８を形成する。これに加えて第４実施形態では、位置決め用突起４４８における圧電振動片４２０との当接面に、ベース側接続電極４４４ａ，４４４ｂを配置する。具体的には、突起４４８の上面または基板４４３の上面に形成した電極を、位置決め用突起４４８の内側面に延長して、ベース側接続電極４４４ａ，４４４ｂを形成する。一方、圧電振動片４２０の接続電極４２４ａ，４２４ｂも、それぞれ圧電振動片４２０の側面に延長して、センサ側接続電極４２４ａ，４２４ｂを形成する。そして、圧電振動片４２０を一対の位置決め用突起４４８の間に挿入することにより、センサ側接続電極４２４ａ，４２４ｂをベース側接続電極４４４ａ，４４４ｂに当接させる。これにより、発振回路素子４４１から圧電振動片４２０に対して通電可能となる。
【００５１】
第４実施形態では、位置決め用突起における圧電振動片との当接面にベース側接続電極を配置したので、ベース側接続電極とセンサ側接続電極との導通を確実に取ることができる。また、センサ側接続電極を圧電振動片の側面に形成したので、圧電振動片は上下に対称となる。これにより、平板部材に対する圧電振動片の誤組み付けを防止することができる。
【００５２】
次に、第５実施形態について説明する。
図１１に、第５実施形態に係る質量測定チップの説明図を示す。第５実施形態に係る質量測定チップは、発振回路基板５４０の位置決め用突起５３９を台座５３２に設けたものである。なお、第１および第３実施形態と同様の構成となる部分については、その説明を省略する。
【００５３】
第５実施形態では、台座５３２の上面に、基板５４３の位置決め用突起５３９を設ける。突起５３９は、台座５３２と一体成形してもよいし、別部材を付加して形成してもよい。また突起５３９の形状は、図９における一対の突起３４８と同様に、対向する平行面を形成しうる形状とする。この場合、基板５４３には突起５３９に対応する平行な側面を形成する。なお、突起５３９をピン形状とし、基板５４３に係合穴を設けてもよい。上記に加えて、第３実施形態と同様に、センサ部の位置決め用突起５４８を発振回路基板５４０に形成してもよい。
【００５４】
第５実施形態では、発振回路基板の位置決め用突起を台座に設けたので、台座の上面に発振回路基板を載置する際に、台座の電極パッドと発振回路基板の配線パターンとの位置が相互にずれることがなくなり、両者の導通を確保することができる。なお、第１実施形態で述べたように、台座に載置した通常の発振回路基板を、温度補償回路等を付加した発振回路基板に交換して使用する場合がある。第５実施形態に係る質量測定チップでは、このように発振回路基板を交換して使用する際に、台座の電極パッドと発振回路基板の配線パターンとの位置を簡単に合わせることが可能となる。
【００５５】
なお、上述した各実施形態では、本発明に係る質量測定装置を検体溶液中の特定物質の質量を測定する装置として使用する方法について説明したが、本発明に係る質量測定装置は、例えばメッキ膜厚モニタや粘度計、密度計、イオンセンサ、においセンサなどにも使用することが可能である。まず、メッキ膜厚モニタとして使用する場合には、メッキ対象物とともに質量測定チップをメッキ液中に浸漬する。この場合、励振電極の表面に付着したメッキ膜厚の増加とともに、圧電振動片の共振周波数が低下する。したがって、メッキ対象物のメッキ膜厚を検知することができる。また、イオンセンサとして使用する場合には、感応膜としてイオン吸着物質を塗布すればよい。また、においセンサとして使用する場合には、感応膜としてにおい成分の吸着物質を塗布すればよい。
【００５６】
一方、粘度計として使用する場合には、質量測定チップを被測定流体中に浸漬する。この場合、被測定流体の粘度の増加とともに、圧電振動片の共振周波数が変化する。したがって、被測定流体の粘度を検知することができる。なお、質量測定チップの感度は、液体の粘度による周波数変化として次式が導かれている。
【数２】

ただし、ｄｆは圧電振動片の共振周波数の変化量、ｆ₀は圧電振動片の共振周波数の初期値、ηは液体の粘度、ρ_Lは液体の密度、μは圧電材料の弾性率、ρは圧電材料の密度である。数２によれば液体の粘度または密度のどちらか一方を一定とすれば、液体の密度変化または粘度変化を測定することができる。
【図面の簡単な説明】
【図１】 第１実施形態に係る質量測定チップの側面断面図である。
【図２】 第１実施形態に係る質量測定チップの平面図である。
【図３】 センサ部の説明図である。
【図４】 センサ部の変形例の説明図である。
【図５】 ベース部の説明図である。
【図６】 キャップ部材の変形例の説明図である。
【図７】 第１実施形態に係る質量測定装置の説明図である。
【図８】 第２実施形態に係る質量測定チップの説明図である。
【図９】 第３実施形態に係る質量測定チップの説明図である。
【図１０】 第４実施形態に係る質量測定チップの説明図である。
【図１１】 第５実施形態に係る質量測定チップの説明図である。
【図１２】 従来技術に係る質量測定チップの説明図である。
【図１３】 従来技術に係る質量測定装置の説明図である。
【符号の説明】
３………質量測定チップ、１０………センサ部、１１………平板部材、２０………圧電振動片、２２ａ，２２ｂ………励振電極、２４ａ，２４ｂ………センサ側接続電極、３０………ベース部、３２………台座、４０………発振回路基板、４１………発振回路素子、４３………基板、４４ａ，４４ｂ………ベース側接続電極、５０………キャップ部材、５８………ゴムパッキン。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a mass measuring chip and a mass measuring device, and more particularly to a mass measuring chip that measures a concentration of a specific substance in a sample solution using a piezoelectric vibrating piece.
[0002]
[Prior art]
In the fields of food, biochemistry, environment, and the like, the quartz crystal microbalance method is used to measure the presence and concentration of a specific substance. Specifically, a sensitive film of a specific substance to be detected is first applied to the surface of the excitation electrode on one side of the piezoelectric vibrating piece. Then, the piezoelectric vibrating piece is immersed in the sample solution containing the detection substance. Then, the detection substance in the sample solution is combined with the sensitive film, and the mass of the excitation electrode is increased. As the mass of the excitation electrode increases, the resonance frequency of the piezoelectric vibrating piece decreases. Thereby, the presence or absence of the specific substance in the sample solution can be determined.
[0003]
By the way, when the piezoelectric vibrating piece is immersed in the sample solution, if the excitation electrodes formed on both surfaces thereof are short-circuited with each other, the piezoelectric vibrating piece cannot be oscillated. Therefore, it is necessary to prevent the short circuit between the electrodes by covering the other excitation electrode to which the sensitive film is not applied with a covering member or the like to seal the excitation electrode from the sample solution.
[0004]
FIG. 12 is an explanatory diagram of the mass measurement chip described in Patent Document 1. 12A is a plan view, and FIG. 12B is a side cross-sectional view taken along the line GG in FIG. The mass measuring chip 803 includes a piezoelectric vibrating piece 820 in which circular excitation electrodes 822a and 822b are formed on both sides of a rectangular piezoelectric flat plate. Also, a covering member 850 made of an insulating thin plate is bonded to one surface side of the piezoelectric vibrating piece 520 with an adhesive 858. Thereby, the excitation electrode 822b on the one surface side is sealed from the sample solution, and a short circuit between the electrodes is prevented. Furthermore, a lead wire 824 is attached to each excitation electrode, and a portion of the lead wire 824 that is immersed in the specimen solution is covered with an adhesive 858.
[0005]
FIG. 13 is an explanatory diagram of a conventional mass measuring apparatus. In the mass measuring device 801, the above-described mass measuring chip 803 is connected to an external oscillation circuit 840. The mass is measured by immersing the mass measuring chip 803 in the sample solution 7 after applying the above-described sensitive film (not shown) on the surface of the excitation electrode 822a. First, the oscillation circuit 840 energizes the piezoelectric vibrating piece in the mass measuring chip 803 to oscillate the piezoelectric vibrating piece, and the frequency counter 5 measures the resonance frequency of the piezoelectric vibrating piece. As described above, when the specific substance in the sample solution is combined with the sensitive film and the mass of the excitation electrode is increased, the resonance frequency of the piezoelectric vibrating piece is lowered. By analyzing the amount of decrease in the resonance frequency by the computer 6, the concentration of the specific substance in the sample solution is calculated.
[0006]
[Patent Document 1]
JP-A-6-138125
[0007]
[Problems to be solved by the invention]
Recently, high sensitivity is required for mass measurement chips. In order to increase the sensitivity of the mass measuring chip, it is necessary to increase the frequency of the piezoelectric vibrating piece. However, if the high-frequency piezoelectric vibrating piece is used while immersed in the sample solution, oscillation becomes unstable. In particular, as shown in FIG. 13, when the electrical length between the high-frequency piezoelectric vibrating piece and the oscillation circuit 840 is long, the loss of the transmission path increases, and therefore the oscillation of the piezoelectric vibrating piece becomes unstable. Therefore, there exists a problem that it cannot respond to the high sensitivity of a mass measurement chip | tip.
[0008]
In order to solve this problem, an oscillation circuit element may be mounted on the mass measurement chip to shorten the electrical length with the piezoelectric vibrating piece. However, the mass measurement chip measures a minute mass, and cannot be reused even if the mass measurement chip once used for measurement is washed. Therefore, an expensive oscillation circuit element is discarded together with the used mass measurement chip, and there is a problem that a great deal of cost is required for mass measurement.
The present invention focuses on the above problems and aims to provide a mass measuring chip and a mass measuring device capable of achieving both high sensitivity and low cost.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, a mass measurement chip according to the present invention includes a piezoelectric vibrating piece, a sensor portion on which a sensor-side connection electrode for connecting the piezoelectric vibrating piece to an oscillation circuit is formed, and a first surface Having a base-side connection electrode with which the sensor-side connection electrode is abutted, and having a lower electrode electrically and mechanically connected to the oscillation circuit on the second surface opposite to the first surface An oscillation circuit board that conducts the base-side connection electrode and the lower electrode through the through-hole, a base on which the oscillation circuit board is mounted, a base having the oscillation circuit board and the base, and The sensor-side connection electrode is detachably brought into contact with the base-side connection electrode to electrically connect the piezoelectric vibrating piece and the oscillation circuit.
[0010]
By mounting the oscillation circuit on the mass measurement chip, the electrical length between the piezoelectric vibrating piece and the oscillation circuit is shortened, and the loss of the transmission circuit is reduced. Thereby, even when a high-frequency piezoelectric vibrating piece is used in the sample solution, instability of oscillation can be eliminated. Therefore, it is possible to cope with high sensitivity of the mass measuring chip. Moreover, the mass measurement sensor is separated into the sensor part and the base part, and the sensor part is detachably brought into contact with the base part, so that only the used sensor part is discarded and the expensive oscillation circuit is reused. can do. Therefore, both high sensitivity and low cost can be achieved.
[0011]
The piezoelectric vibrating piece may be an inverted mesa type piezoelectric vibrating piece. In the inverted mesa type piezoelectric vibrating piece, the central thin-walled vibrating portion is protected by the thick-walled portion at the periphery, so that the vibrating portion can be prevented from being broken by an external force. Thereby, a high-frequency piezoelectric vibrating piece can be used, and the mass measurement chip can be highly sensitive.
[0012]
In addition, a cap member may be provided that hermetically seals the other excitation electrode in the piezoelectric vibrating piece and the wiring that leads to the other excitation electrode while exposing one excitation electrode in the piezoelectric vibrating piece. Accordingly, it is possible to prevent a short circuit between the wirings due to the inflow of the sample solution while enabling mass measurement. Therefore, the mass measuring chip can be used by being immersed in the sample solution.
[0013]
The flat plate member having a through hole and the piezoelectric vibrating piece disposed on one surface side of the flat plate member constitute the sensor unit, and the excitation electrode of the piezoelectric vibrating piece is placed on the other surface side of the flat plate member through the through hole. The piezoelectric vibrating piece is bonded to the flat plate member to hermetically seal the through hole, and the sensor-side connection electrode is formed on the surface of the piezoelectric vibrating piece opposite to the flat plate member. Also good. Further, the flat plate member and the piezoelectric vibrating piece disposed on one surface side of the flat plate member constitute the sensor unit, and the piezoelectric vibrating piece is joined to the flat plate member, and the electrode on the flat plate member side in the piezoelectric vibrating piece The sensor-side connection electrode may be formed on the other surface of the flat plate member.
[0014]
Since the sensor part is configured by joining the piezoelectric vibrating piece to the flat plate member, even in the case of a thin piezoelectric vibrating piece, a large stress acts on the piezoelectric vibrating piece due to pressure during mounting or solidification of the adhesive. Therefore, the piezoelectric vibrating piece can be prevented from being damaged. Therefore, a thin high-frequency piezoelectric vibrating piece can be used, and the mass measuring chip can be highly sensitive. In addition, since the sensor unit is configured by joining the piezoelectric vibrating piece to the flat plate member, handling in the manufacturing process is facilitated even when the piezoelectric vibrating piece is downsized. Therefore, the mass measuring chip can be reduced in size.
[0015]
Further, the base portion is configured by a pedestal and an oscillation circuit board disposed on the surface of the pedestal, and an oscillation circuit is mounted on a surface of the oscillation circuit board on the pedestal side, and the opposite side of the oscillation circuit board from the pedestal The base-side connection electrode may be formed on the surface. As a result, the oscillation circuit board on which the oscillation circuits having different functions are mounted can be used as necessary.
[0016]
The piezoelectric vibrating piece has an excitation electrode only on the surface opposite to the base portion, and the excitation electrode on the base portion side of the piezoelectric vibrating piece is located at a position facing the piezoelectric vibrating piece in the base portion. May be formed. Thereby, the electrical length between the excitation electrode on the base portion side and the oscillation circuit is minimized, and the loss of the transmission circuit can be minimized. Thus, even when a high-frequency piezoelectric vibrating piece is used in the sample solution, it is possible to eliminate oscillation instability. Therefore, it is possible to cope with high sensitivity of the mass measuring chip.
[0017]
Moreover, you may form the positioning protrusion of the said sensor part in the said base part. Thereby, when mounting a sensor part on the upper surface of a base part, the position of a base side connection electrode and a sensor side connection electrode does not shift | deviate mutually, and electrical conduction of both can be ensured.
[0018]
Further, the base-side connection electrode may be disposed on a contact surface of the positioning protrusion with the sensor unit. Thereby, electrical connection with a base side connection electrode and a sensor side connection electrode can be taken reliably.
[0019]
Further, a positioning projection of the oscillation circuit board may be formed on the surface of the pedestal. Thereby, when mounting an oscillation circuit board on the surface of a base, both conduction | electrical_connection can be ensured.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
A preferred embodiment of a mass measuring chip and a mass measuring device according to the present invention will be described in detail with reference to the accompanying drawings. In addition, what is described below is only one aspect | mode of embodiment of this invention, and this invention is not limited to these.
[0021]
First, the first embodiment will be described.
FIG. 1 is an explanatory diagram of the mass measurement chip according to the first embodiment, and is a side cross-sectional view taken along line AA of FIG. FIG. 2 is a plan view of the mass measuring chip according to the first embodiment. In the mass measurement chip according to the first embodiment, the sensor unit 10 on which the sensor-side connection electrodes 24a and 24b for connecting the piezoelectric vibrating piece 20 to the oscillation circuit element 41 are formed, and the oscillation circuit element 41 is connected to the piezoelectric vibrating piece 20. The base side connection electrode 44a, 44b for connecting to the base portion 30 is formed, and the sensor side connection electrodes 24a, 24b are detachably brought into contact with the base side connection electrodes 44a, 44b. In addition, a cap member 50 is provided that hermetically seals the other excitation electrode 22b and the wiring that conducts to the other excitation electrode 22a while exposing one excitation electrode 22a of the piezoelectric vibrating piece 20.
[0022]
The mass measurement chip according to the first embodiment is obtained by increasing the sensitivity of a conventional mass measurement chip. The sensitivity of the mass measuring chip can be expressed by the following equation.
[Expression 1]

Where df is the amount of change in the resonance frequency of the piezoelectric vibrating piece, f ₀ Is the initial value of the resonance frequency of the piezoelectric vibrating piece, ρ is the density of the piezoelectric material, μ is the shear stress of the piezoelectric material, dm is the mass of the detection substance coupled to the excitation electrode, and A is the area of the excitation electrode. As can be seen from the above equation, the initial value f of the resonance frequency of the piezoelectric vibrating piece ₀ Is higher, the amount of change df is larger, and the sensitivity of the mass measuring chip is increased. For example, f ₀ If the frequency is increased from the conventional 27 MHz to 150 MHz, the sensitivity can be increased by 30 times. In order to increase the frequency of the piezoelectric vibrating piece, the thickness of the vibrating portion of the piezoelectric vibrating piece may be reduced.
[0023]
FIG. 3 is an explanatory diagram of the sensor unit. 3A is a side cross-sectional view taken along the line CC of FIG. 3B, and FIG. 3B is a bottom view. The sensor unit 10 is mainly composed of the piezoelectric vibrating piece 20 and the flat plate member 11. In the first embodiment, a so-called inverted mesa type piezoelectric vibrating piece is used as the piezoelectric vibrating piece 20. The inverted mesa type piezoelectric vibrating piece is obtained by cutting a piezoelectric material such as quartz into a flat plate shape, forming a recess in the center thereof to reduce the thickness, and forming excitation electrodes 22a and 22b on both surfaces of the thin portion. In addition, connection electrodes 24 a and 24 b that are electrically connected to the excitation electrodes 22 a and 22 b are formed on the thick portion around the periphery of the piezoelectric vibrating piece 20. Further, the connection electrode 24 a on the upper surface side of the piezoelectric vibrating piece 20 is extended to the side surface and the lower surface, and the sensor unit side connection electrodes 24 a and 24 b are formed on the lower surface of the piezoelectric vibrating piece 20. Each electrode is composed of two layers of Au / Cr or Ag / Cr. In such a reverse mesa type piezoelectric vibrating piece, the thin-walled vibration part at the center is protected by the thick-walled part at the periphery, so that the vibration part can be prevented from being broken by an external force. Thereby, a high-frequency piezoelectric vibrating piece can be used, and the mass measurement chip can be highly sensitive.
[0024]
Further, the flat plate member 11 to which the piezoelectric vibrating piece 20 is joined is formed. The flat plate member 11 is preferably made of a glass material or a ceramic material having a thermal expansion coefficient equivalent to that of the piezoelectric material. Thereby, since the thermal expansion coefficient and the thermal contraction rate of the flat plate member 11 and the piezoelectric vibrating piece 20 are equal, it is possible to prevent breakage at the joint portion between them. In addition, the influence of stress on the resonator element can be minimized. On the other hand, a through hole 12 is formed in the central portion of the flat plate member 11. The through hole 12 may be formed in an arbitrary shape such as a rectangle or a circle shown in FIG. 2, but at least the entire excitation electrode 22 a on the upper surface side of the piezoelectric vibrating piece 20 is exposed to the upper surface side of the flat plate member 11 through the through hole 12. Form to the size to be. Then, the piezoelectric vibrating piece 20 is disposed on the lower surface side of the flat plate member 11, and the thick peripheral portion of the piezoelectric vibrating piece 20 is bonded to the peripheral portion of the through hole 12 of the flat plate member 11 with an adhesive 18 or the like. As the adhesive 18, a silicone-based adhesive having electrical insulation is used. In addition, in order to hermetically seal the through hole 12, the entire periphery of the peripheral portion of the through hole 12 is joined with an adhesive 18 or the like.
[0025]
FIG. 4 is an explanatory diagram of a modified example of the sensor unit. It is also possible to use the sensor unit 110 shown in FIG. 4 instead of the sensor unit 10 shown in FIG. The piezoelectric vibrating piece 120 of the sensor unit 110 according to this modification is formed in the same manner as the piezoelectric vibrating piece 20 of the sensor unit 10 of FIG. On the other hand, sensor side connection electrodes 114 a and 114 b are formed on the lower surface of the flat plate member 111. Note that electrode pads corresponding to the connection electrodes 124a and 124b of the piezoelectric vibrating reed are formed on the upper surface of the flat plate member 111 to ensure electrical continuity with the sensor side connection electrodes 114a and 114b through the through holes. Here, in the sensor unit 110 according to the modification, the piezoelectric vibrating piece 120 is disposed on the upper surface side of the flat plate member 111. Then, the connection electrodes 124a and 124b of the piezoelectric vibrating piece and the electrode pad of the flat plate member 111 are joined via a conductive adhesive 118 such as an Ag paste. Furthermore, an electrically insulating silicone sealant 119 or the like is applied to the corners between the side surface of the piezoelectric vibrating piece 120 and the upper surface of the flat plate member over the entire circumference of the piezoelectric vibrating piece 120. Thereby, each electrode on the lower surface side of the piezoelectric vibrating piece 120 is hermetically sealed, and a short circuit with each electrode on the upper surface side is prevented. Instead of the flat plate member 111, a lead frame resin-molded may be used.
[0026]
FIG. 5 is an explanatory diagram of the base portion. The base part 30 is mainly constituted by an oscillation circuit board 40 and a pedestal 32. The oscillation circuit board 40 is mainly composed of an oscillation circuit element 41 and a board 43. The substrate 43 is made of an electrically insulating material such as ceramic or epoxy. Base-side connection electrodes 44a and 44b are formed on the upper surface of the substrate 43 corresponding to the sensor-side connection electrodes 24a and 24b (see FIG. 3). An electrode pad for mounting the oscillation circuit element 41 is formed on the lower surface of the substrate 43 to ensure electrical continuity with the base side connection electrodes 44a and 44b through the through holes. A wiring pattern 46 is formed on the lower surface of the substrate 43 in order to establish conduction between the oscillation circuit element 41 and the frequency counter 5 (see FIG. 7).
[0027]
On the other hand, the oscillation circuit element 41 is an integrated circuit element (IC) constituting the oscillation circuit. Bumps 42 are formed on electrode pad portions (not shown) of the oscillation circuit element 41 using a stud bump forming apparatus using a metal wire. The oscillation circuit element 41 is electrically and mechanically connected to the electrode pads and the wiring pattern 46 formed on the lower surface of the substrate 43 by performing flip chip bonding. For flip chip bonding, either pressure bonding by heating and pressing or pressure bonding by applying ultrasonic waves may be employed.
[0028]
On the other hand, the base 32 is formed of a plastic material or the like. An electrode pad 36 corresponding to the wiring pattern 46 of the oscillation circuit board 40 is provided on the upper surface of the pedestal 32. A wiring is embedded in the base 32 from the electrode pad 36 to the signal input / output unit 37. The wiring from the signal input / output unit 37 to the frequency counter 5 (see FIG. 7) is covered with a vinyl tube 38 or the like. In addition, a recess 34 having a size capable of inserting the oscillation circuit element 41 is formed at the center of the upper surface of the base 32. Then, the oscillation circuit board 40 is placed on the upper surface of the base 32 while the oscillation circuit element 41 is inserted into the recess 34. At that time, the wiring pattern 46 of the oscillation circuit board 40 is brought into contact with the electrode pad 36 of the pedestal 32, and both are connected by a conductive adhesive or the like. Thereby, conduction between the oscillation circuit element 41 and the frequency counter 5 (see FIG. 7) is ensured.
[0029]
By the way, as the oscillation circuit element 41, there may be used an ordinary oscillation circuit obtained by adding a temperature compensation circuit or the like. In the mass measurement chip according to the first embodiment, an oscillation circuit board on which a normal oscillation circuit element is mounted and an oscillation circuit board on which an oscillation circuit element to which a temperature compensation circuit or the like is added are replaced as necessary. It is also possible to use it. In this case, the wiring pattern 46 of the oscillating circuit board 40 is used in a state where it is detachably contacted with the electrode pad 36 of the base 32.
[0030]
Then, as shown in FIG. 1, the sensor unit 10 is placed on the upper surface of the base unit 30. At this time, the sensor side connection electrodes 24a and 24b formed on the lower surface of the piezoelectric vibrating piece 20 in the sensor unit 10 are detachable from the base side connection electrodes 44a and 44b formed on the upper surface of the substrate 43 in the base unit 30. Make contact. Thereby, it is possible to energize the excitation electrodes 22 a and 22 b of the piezoelectric vibrating piece 20 from the oscillation circuit element 41.
[0031]
Further, a ring-shaped rubber packing 58 is attached to the peripheral edge of the upper surface of the flat plate member 11 in the sensor unit 10. Then, the cap member 50 is placed over the sensor unit 10 and screwed to the side surface of the base 32 in the base unit 30. The cap member 50 is made of a plastic material or the like. A through hole 52 is formed at the center of the upper surface to expose the excitation electrode 22a above the piezoelectric vibrating piece 20 as shown in FIG. Further, the rubber packing 58 is pressed against the flat plate member 11 by the peripheral edge of the upper surface of the cap member 50, and the through hole 52 is hermetically sealed. At the same time, the sensor unit 10 is pressed against the base unit 30 and the oscillation circuit board 40 is pressed against the pedestal 32 to ensure the respective conduction. Furthermore, the lower part of the cap member 50 is hermetically sealed by screwing the cap member 50 to the base 32. As described above, the excitation electrode 22b below the piezoelectric vibrating piece 20 and each of the wirings connected thereto are hermetically sealed inside the cap member 50, and a short circuit between the wirings due to the inflow of the sample solution 7 (see FIG. 7) is prevented. The
Thus, the mass measuring chip 3 according to the present embodiment is completed.
[0032]
FIG. 6 is an explanatory diagram of a modified example of the cap member. The cap member 150 according to the modification is formed in a hollow cylindrical shape using a rubber material or the like. A through hole 152 is formed at the center of the upper and lower end faces. Then, the diameter of the through hole in the lower end surface is increased, and the cap member 150 is covered from above the sensor part 110 to the middle stage of the base part 130. The upper end surface of the cap member 150 is brought into contact with the upper surface of the flat plate member 111 in the sensor unit 110. The lower end surface of the cap member 150 is engaged with a groove 133 formed on the entire side surface of the pedestal 132. Thereby, the inside of the cap member 150 is hermetically sealed, and a short circuit between wires due to the inflow of the sample solution 7 (see FIG. 7) is prevented.
[0033]
Next, a method for using the above-described mass measuring chip according to the present embodiment will be described.
FIG. 7 is an explanatory diagram of the mass measuring apparatus according to the first embodiment. The mass measurement chip 3 according to the first embodiment is connected to the frequency counter 5. The frequency counter 5 measures the resonance frequency of the piezoelectric vibrating piece in the mass measurement chip 3. The frequency counter 5 is connected to the computer 6. The computer 6 calculates the mass of the detection substance attached to the excitation electrode from the resonance frequency of the piezoelectric vibrating piece measured by the frequency counter 5. In addition, it is preferable to configure the computer 6 so that the concentration of the detection substance in the sample solution 7 can be analyzed from the temporal change in the amount of detection substance attached.
[0034]
The specific procedure for mass measurement is as follows. First, in the mass measurement chip 3 shown in FIG. 1, a sensitive film of a detection substance is applied to the excitation electrode 22 a on the upper surface side of the piezoelectric vibrating piece 20. Next, the piezoelectric vibrating piece 20 is oscillated by energizing the piezoelectric vibrating piece 20 from the oscillation circuit element 41. Note that the resonance frequency of the piezoelectric vibrating piece is continuously measured by the frequency counter 5 shown in FIG. Then, as shown in FIG. 7, the mass measurement chip 3 is immersed in the sample solution 7. In the sample solution 7, the detection substance is bonded to the sensitive film on the excitation electrode of the piezoelectric vibrating piece. As a result, the mass of the excitation electrode increases, and the resonance frequency of the piezoelectric vibrating piece decreases. By analyzing the decrease amount of the resonance frequency and the like by the computer 6, the presence / absence and concentration of the detection substance are calculated.
[0035]
Note that it is possible not only to use the mass measurement chip by immersing it in the sample solution, but also to use the sample solution by dropping it onto the mass measurement chip. Specifically, in the mass measuring chip 3 shown in FIG. 1, a sample solution may be dropped through the through-hole 12 after applying a sensitive film of a detection substance to the excitation electrode 22 a on the upper surface side of the piezoelectric vibrating piece 20. When the sample solution is dropped and used, it is not necessary to hermetically seal the inside of the mass measuring chip 3 with the cap member 50. Therefore, it is possible to use the mass measurement chip without attaching the cap member 50. On the other hand, it is also possible to measure the mass of the detection substance in the sample gas by using the mass measuring chip exposed to the sample gas.
[0036]
By the way, since the mass measuring chip measures a minute mass, even if the piezoelectric vibrating piece used for the measurement is once washed, it cannot be reused. Therefore, the sensor unit is replaced before re-measurement using the mass measuring chip. In order to replace the sensor unit 10 in the mass measuring chip 3 shown in FIG. 1, first, the cap member 50 is removed. Next, the sensor unit 10 and the rubber packing 58 are separated from the base unit 30. The used sensor unit 10 is discarded. Then, the new sensor unit 10 is placed on the upper surface of the base unit 30. Thereafter, when the rubber packing 58 is attached and the cap member 50 is attached, the replacement of the sensor unit 10 in the mass measuring chip 3 is completed.
The mass measurement chip according to the first embodiment described in detail above can achieve both high sensitivity and low cost.
[0037]
That is, in the mass measuring chip according to the first embodiment, the sensor part on which the sensor-side connection electrode for connecting the piezoelectric vibrating piece to the oscillation circuit element is formed, and the base for connecting the oscillation circuit element to the piezoelectric vibrating piece. And a base portion on which the side connection electrode is formed, and the sensor side connection electrode is detachably brought into contact with the base side connection electrode. By mounting the oscillation circuit on the mass measurement chip, the electrical length between the piezoelectric vibrating piece and the oscillation circuit is shortened, and the loss of the transmission circuit is reduced. Thereby, even when a high-frequency piezoelectric vibrating piece is used in the sample solution, instability of oscillation can be eliminated. Therefore, it is possible to cope with high sensitivity of the mass measuring chip.
[0038]
Moreover, the mass measurement sensor is separated into the sensor part and the base part, and the sensor part is detachably brought into contact with the base part, so that only the used sensor part is discarded and the expensive oscillation circuit is reused. can do. Therefore, both high sensitivity and low cost can be achieved.
[0039]
In the mass measurement chip according to the first embodiment, as shown in FIG. 1, the flat plate member 11 in the sensor unit 10, and the oscillation circuit board 40 and the base 32 in the base unit 30 are formed in a circular shape in plan view. This is because the mass measuring chip is hermetically sealed using a cylindrical cap member 50 as shown in FIGS. Therefore, when the mass measuring chip is hermetically sealed by means other than the cylindrical cap member 50, the above members can be formed in a rectangular shape in plan view.
[0040]
In the mass measurement chip according to the first embodiment, only one piezoelectric vibrating piece and one oscillation circuit element are mounted. In this case, only one kind of substance can be detected by one measurement. Recently, in order to be able to detect many kinds of substances by one measurement, it is required to make a mass measuring chip a multi-sensor. In this regard, a mass measurement chip on which a plurality of piezoelectric vibrating pieces and a plurality of oscillation circuit elements are mounted can be formed by the same configuration as that of the first embodiment. Specifically, a plurality of through holes are formed in the flat plate member, and a plurality of piezoelectric vibrating pieces are joined to the plate member to form a sensor unit. A plurality of oscillation circuit elements are also mounted on the oscillation circuit board to form a base portion. And what is necessary is just to combine this base part and a sensor part. Thereby, it can respond to multi-sensor-izing of a mass measurement chip | tip.
[0041]
Next, a second embodiment will be described.
FIG. 8 is an explanatory diagram of a mass measuring chip according to the second embodiment. In FIG. 8, the description of the pedestal in the base portion 230 is omitted. In the mass measuring chip 203 according to the second embodiment, the excitation electrode 222a is formed only on the surface of the piezoelectric vibrating piece 220 opposite to the base portion 230, and the piezoelectric electrode is formed at the position facing the piezoelectric vibrating piece 220 in the base portion 230. The excitation electrode 222b on the base part side in the vibration piece 220 is formed. Note that the description of the same configuration as in the first embodiment is omitted.
[0042]
The piezoelectric vibrating piece 220 of the mass measuring chip 203 according to the second embodiment forms the excitation electrode 222a only on the upper surface of the thin vibrating portion. In addition, the connection electrode 224a electrically connected to the excitation electrode 222a is formed in the thick part at the periphery, and this is extended to the side surface and the lower surface of the piezoelectric vibrating piece 220 to form the sensor side connection electrode 224a. Then, the excitation electrode 222 b on the lower surface side of the piezoelectric vibrating piece 220 is formed on the upper surface of the oscillation circuit substrate 240 in the base portion 230. Even if the excitation electrode 222b is separated from the surface of the piezoelectric vibrating piece 220, the piezoelectric vibrating piece 220 can be driven.
[0043]
In the mass measurement chip according to the second embodiment, since the excitation electrode on the lower surface side of the piezoelectric vibrating piece is formed on the upper surface of the oscillation circuit substrate, the electrical length between the excitation electrode and the oscillation circuit is minimized, and the loss of the transmission circuit is minimized. Can be Thus, even when a high-frequency piezoelectric vibrating piece is used in the sample solution, it is possible to eliminate oscillation instability. Therefore, it is possible to cope with high sensitivity of the mass measuring chip.
[0044]
The quartz crystal microbalance method needs to be performed at a predetermined atmospheric temperature. Here, in the inverted mesa type piezoelectric vibrating piece, the resonance frequency changes due to a slight change in the ambient temperature, and the measurement accuracy may be lowered. As a cause thereof, the ratio of the thickness of the excitation electrode to the thickness of the vibrating part is large in the inverted mesa type piezoelectric vibrating piece, and it is considered that the influence is greatly influenced by the excitation electrode. In this respect, in the second embodiment, since the excitation electrode is arranged at a certain distance from the surface of the vibration part of the inverted mesa type piezoelectric vibrating piece, it is not affected by the excitation electrode. Thereby, the change of the resonant frequency with respect to a temperature change becomes small, and the frequency temperature characteristic of an inverted mesa type piezoelectric vibrating piece can be improved. Therefore, the accuracy of mass measurement can be improved.
[0045]
Next, a third embodiment will be described.
FIG. 9 is an explanatory diagram of a mass measuring chip according to the third embodiment. In FIG. 9, the pedestal in the base portion 330 is not shown. In the mass measurement chip according to the third embodiment, a positioning projection 348 of the sensor unit 310 is formed on the base unit 330. Note that the description of the same configuration as in the first embodiment is omitted.
[0046]
In the third embodiment, the positioning protrusion 348 of the piezoelectric vibrating piece is formed on the upper surface of the oscillation circuit board 340 in the base portion 330. For example, the ceramic sheet on which the pattern of the protrusion 348 is formed is laminated and fired on the ceramic sheet on which the pattern of the substrate 343 is formed, and the positioning protrusion 348 is formed together with the substrate 343. The protrusion 348 is formed at a position where the opposing side surfaces of the rectangular piezoelectric vibrating piece 320 can be supported. Note that the entire sensor unit can be positioned by positioning the piezoelectric vibrating piece 320.
[0047]
In the third embodiment, since the positioning protrusion of the base portion is provided, the position of the base side connection electrode and the sensor side connection electrode is not shifted from each other when the sensor portion is placed on the upper surface of the base portion. The conduction between the two can be ensured.
[0048]
In the mass measurement chip illustrated in FIG. 1, the sensor unit 10 may rotate with respect to the base unit 30 when the cap member 50 is fastened to the pedestal 32. However, in the third embodiment, since the positioning protrusion of the piezoelectric vibrating piece is provided, the rotation of the sensor unit can be prevented. Therefore, the positions of the base-side connection electrode and the sensor-side connection electrode are not shifted from each other, and conduction between the two can be ensured.
[0049]
Next, a fourth embodiment will be described.
FIG. 10 is an explanatory diagram of a mass measuring chip according to the fourth embodiment. In FIG. 10, the description of the pedestal in the base portion is omitted. In the mass measurement chip according to the fourth embodiment, base-side connection electrodes 444 a and 444 b are arranged on the contact surface of the positioning protrusion 448 with the piezoelectric vibrating piece 420. Note that the description of the same components as those in the first and third embodiments is omitted.
[0050]
In the fourth embodiment, positioning protrusions 448 are formed as in the third embodiment. In addition, in the fourth embodiment, the base side connection electrodes 444a and 444b are arranged on the contact surface of the positioning protrusion 448 with the piezoelectric vibrating piece 420. Specifically, an electrode formed on the upper surface of the protrusion 448 or the upper surface of the substrate 443 is extended to the inner surface of the positioning protrusion 448 to form the base side connection electrodes 444a and 444b. On the other hand, the connection electrodes 424a and 424b of the piezoelectric vibrating piece 420 are also extended to the side surfaces of the piezoelectric vibrating piece 420 to form sensor side connection electrodes 424a and 424b. Then, by inserting the piezoelectric vibrating piece 420 between the pair of positioning protrusions 448, the sensor side connection electrodes 424a and 424b are brought into contact with the base side connection electrodes 444a and 444b. Thereby, it is possible to energize the piezoelectric vibrating piece 420 from the oscillation circuit element 441.
[0051]
In the fourth embodiment, since the base side connection electrode is disposed on the contact surface of the positioning protrusion with the piezoelectric vibrating piece, electrical connection between the base side connection electrode and the sensor side connection electrode can be ensured. In addition, since the sensor-side connection electrode is formed on the side surface of the piezoelectric vibrating piece, the piezoelectric vibrating piece is vertically symmetric. Thereby, the incorrect assembly | attachment of the piezoelectric vibrating piece with respect to a flat plate member can be prevented.
[0052]
Next, a fifth embodiment will be described.
FIG. 11 is an explanatory diagram of a mass measuring chip according to the fifth embodiment. In the mass measurement chip according to the fifth embodiment, a positioning projection 539 of the oscillation circuit board 540 is provided on the base 532. Note that the description of the same components as those in the first and third embodiments is omitted.
[0053]
In the fifth embodiment, the positioning protrusion 539 of the substrate 543 is provided on the upper surface of the base 532. The protrusion 539 may be integrally formed with the base 532 or may be formed by adding another member. The shape of the protrusion 539 is a shape that can form opposing parallel surfaces, like the pair of protrusions 348 in FIG. 9. In this case, parallel side surfaces corresponding to the protrusions 539 are formed on the substrate 543. Note that the protrusion 539 may have a pin shape, and an engagement hole may be provided in the substrate 543. In addition to the above, the positioning projection 548 of the sensor unit may be formed on the oscillation circuit board 540 as in the third embodiment.
[0054]
In the fifth embodiment, since the positioning projection of the oscillation circuit board is provided on the pedestal, when the oscillation circuit board is placed on the upper surface of the pedestal, the positions of the electrode pads of the pedestal and the wiring pattern of the oscillation circuit board are mutually aligned. Therefore, the conduction between the two can be ensured. As described in the first embodiment, the normal oscillation circuit board placed on the pedestal may be used by replacing it with an oscillation circuit board to which a temperature compensation circuit or the like is added. In the mass measurement chip according to the fifth embodiment, when the oscillation circuit board is exchanged and used in this manner, the positions of the electrode pads on the base and the wiring pattern on the oscillation circuit board can be easily matched.
[0055]
In each of the above-described embodiments, the method of using the mass measuring device according to the present invention as a device for measuring the mass of a specific substance in a sample solution has been described. However, the mass measuring device according to the present invention is, for example, a plating film It can also be used for thickness monitors, viscometers, density meters, ion sensors, odor sensors, and the like. First, when using as a plating film thickness monitor, a mass measuring chip is immersed in a plating solution together with a plating object. In this case, the resonance frequency of the piezoelectric vibrating piece decreases as the thickness of the plating film attached to the surface of the excitation electrode increases. Therefore, the plating film thickness of the plating object can be detected. Moreover, what is necessary is just to apply | coat an ion adsorption substance as a sensitive film | membrane when using as an ion sensor. Further, when used as an odor sensor, an adsorbent of an odor component may be applied as a sensitive film.
[0056]
On the other hand, when using as a viscometer, a mass measuring chip is immersed in a fluid to be measured. In this case, the resonance frequency of the piezoelectric vibrating piece changes as the viscosity of the fluid to be measured increases. Therefore, the viscosity of the fluid to be measured can be detected. The sensitivity of the mass measuring chip is derived from the following equation as a frequency change due to the viscosity of the liquid.
[Expression 2]

Where df is the amount of change in the resonance frequency of the piezoelectric vibrating piece, f ₀ Is the initial value of the resonance frequency of the piezoelectric vibrating piece, η is the viscosity of the liquid, ρ _L Is the density of the liquid, μ is the elastic modulus of the piezoelectric material, and ρ is the density of the piezoelectric material. According to Equation 2, if either one of the viscosity or density of the liquid is made constant, the change in density or viscosity of the liquid can be measured.
[Brief description of the drawings]
FIG. 1 is a side cross-sectional view of a mass measuring chip according to a first embodiment.
FIG. 2 is a plan view of the mass measuring chip according to the first embodiment.
FIG. 3 is an explanatory diagram of a sensor unit.
FIG. 4 is an explanatory diagram of a modified example of the sensor unit.
FIG. 5 is an explanatory diagram of a base portion.
FIG. 6 is an explanatory diagram of a modified example of the cap member.
FIG. 7 is an explanatory diagram of a mass measuring apparatus according to the first embodiment.
FIG. 8 is an explanatory diagram of a mass measuring chip according to a second embodiment.
FIG. 9 is an explanatory diagram of a mass measuring chip according to a third embodiment.
FIG. 10 is an explanatory diagram of a mass measuring chip according to a fourth embodiment.
FIG. 11 is an explanatory diagram of a mass measuring chip according to a fifth embodiment.
FIG. 12 is an explanatory diagram of a mass measuring chip according to a conventional technique.
FIG. 13 is an explanatory diagram of a mass measuring apparatus according to a conventional technique.
[Explanation of symbols]
3... Mass measurement chip, 10... Sensor part, 11... Flat plate member, 20. 30... Base portion 32... Pedestal 40... Oscillator circuit board 41. Cap member, 58... Rubber packing.

Claims (9)

A sensor unit including a piezoelectric vibrating piece, and formed with a sensor-side connection electrode for connecting the piezoelectric vibrating piece to an oscillation circuit;
A lower surface having a base-side connection electrode with which the sensor-side connection electrode is brought into contact with the first surface, and being electrically and mechanically connected to the oscillation circuit on a second surface opposite to the first surface An oscillation circuit board having an electrode and conducting the base-side connection electrode and the lower electrode through the through hole;
A base on which the oscillation circuit board is mounted;
The oscillation circuit board and a base having the pedestal,
A mass measuring chip, wherein the sensor-side connection electrode is detachably brought into contact with the base-side connection electrode to electrically connect the piezoelectric vibrating piece and the oscillation circuit. The mass measuring chip according to claim 1,
The mass measuring chip, wherein the piezoelectric vibrating piece is an inverted mesa type piezoelectric vibrating piece. The mass measuring chip according to claim 1 or 2,
A mass measurement device comprising: a cap member that hermetically seals the other excitation electrode of the piezoelectric vibrating piece and a wiring that is electrically connected to the other excitation electrode while exposing one excitation electrode of the piezoelectric vibrating piece. Chip. In the mass measurement chip according to any one of claims 1 to 3,
The sensor unit is configured by a flat plate member having a through hole and the piezoelectric vibrating piece disposed on one surface side of the flat plate member,
The excitation electrode of the piezoelectric vibrating piece is exposed to the other surface side of the flat plate member through the through hole, the piezoelectric vibrating piece is bonded to the flat plate member, and the through hole is hermetically sealed. A mass measuring chip, wherein the sensor-side connection electrode is formed on a surface opposite to the flat plate member. In the mass measurement chip according to any one of claims 1 to 3,
The sensor unit is constituted by a flat plate member and the piezoelectric vibrating piece arranged on one side of the flat plate member,
The piezoelectric vibrating piece is bonded to the flat plate member, and the electrode on the flat plate member side of the piezoelectric vibrating piece is hermetically sealed, and the sensor-side connection electrode is formed on the other surface of the flat plate member. Mass measuring chip to be used. In the mass measurement chip according to any one of claims 1 to 5,
The piezoelectric vibrating piece has an excitation electrode only on the surface opposite to the base portion,
A mass measuring chip, wherein an excitation electrode on the base portion side of the piezoelectric vibrating piece is formed at a position facing the piezoelectric vibrating piece in the base portion. The mass measuring chip according to any one of claims 1 to 6,
A mass measuring chip, wherein a positioning projection of the sensor unit is formed on the base unit. The mass measuring chip according to claim 7,
The mass measuring chip, wherein the base side connection electrode is disposed on a contact surface of the positioning protrusion with the sensor unit. The mass measuring chip according to any one of claims 4 to 8,
A mass measuring chip, wherein a positioning projection of the oscillation circuit board is formed on a surface of the pedestal.

Images