【０００１】
【発明の属する技術分野】
本発明は圧電振動素子の構造に関し、特に圧電基板に設けたパッド電極（支持部）からの振動エネルギーの漏洩が低減するよう圧電基板の形状を改善した圧電振動素子の構造に関する。
【０００２】
【従来の技術】
上面に凹部を有するパッケージの内底面に水晶振動素子等の圧電振動素子を収容し、パッケージの開口部を蓋にて気密封止した構造の圧電振動子は、各種通信機器の基準周波数発生源等として広く使用されている。
一般に水晶振動子は、ＡＴカットされた水晶基板を用い、エネルギー閉じ込め型の水晶振動子として機能するよう構成され、水晶基板のほぼ中央部の表裏面に所定の面積を有する励振用の電極を対向して形成する。そこで、前記励振用の電極間に外部から電圧を印加すると、励振電極の質量付加効果により所定の振動エネルギーの閉じ込めがおこり、該振動エネルギーは、水晶基板に対して励振電極の中心部を頂点に所定の変位分布を構成する。
【０００３】
図７は、従来の水晶振動素子の外観例を示す図である。水晶振動素子１は、所定のサイズにＡＴカットされた水晶基板２のほぼ中央部の表裏面に、所定の面積を有する励振電極３ａ、及び３ｂを形成し、該励振電極３ａからは、リード電極４ａ及びパッド電極５ａとを導出し、一方、励振電極３ｂからは、リード電極４ｂと側面電極６を介してパッド電極５ｂとを導出している。本水晶振動素子１は、図７に示す如く、励振電極対を水晶基板のほぼ中央部に形成しており、リード電極や水晶基板の支持部であるパッド電極より、振動エネルギーが漏洩しにくい構造となっている。
【０００４】
【発明が解決しようとする課題】
近年、携帯電話機等の移動体通信機器の普及に伴い、水晶振動子の更なる高性能化の要求が高まっている。
しかしながら、従来の水晶振動子は、前述したようにリード電極や水晶基板の支持部であるパッド電極より、振動エネルギーが漏洩しにくい構造となっているものの、水晶振動子の高周波化や高Ｑ値化を進める上には、励振電極に生じた主振動の振動エネルギーが、支持部等から漏洩する量を更に低減する必要がある。例えば、特開平１１−３５５０８８号公報には励振電極の周囲の圧電基板に貫通孔を形成したものが開示されているが、その貫通孔の位置等については詳細に検討されていない。
そこで、本発明は上述したような問題を解決するために為されたものであって、リード電極や圧電基板の支持部であるパッド電極より、振動エネルギーの漏洩を、従来の圧電振動子と比べて更に低減した圧電振動素子の構造を提供する。
【０００５】
【課題を解決するための手段】
上記目的を達成するために本発明に係わる圧電振動素子の構造は、以下の構成をとる。
請求項１記載の圧電振動素子の構造は、平面形状が略長方形を呈する圧電基板の両主表面のほぼ中央に略長方形の励振電極を形成し、各励振電極から圧電基板の一方の短辺に向かって延出するリード電極と圧電基板の前記短辺近傍に配置したパッド電極とを有する圧電振動素子であって、前記圧電基板には各長辺を起点とし短辺と平行に延びる２本ずつの切り込みが形成されており、該切り込みはいずれもその一方の側縁が前記励振電極のいずれかの一辺と接するように配置されるよう構成する。
【０００６】
請求項２記載の圧電振動素子の構造は、平面形状が略長方形を呈する圧電基板の両主表面のほぼ中央に略長方形の励振電極を形成し、各励振電極から圧電基板の一方の短辺に向かって延出するリード電極と圧電基板の前記短辺近傍に配置したパッド電極とを有する圧電振動素子であって、前記圧電基板には短辺と平行に延びる２つの貫通孔が形成されており、該貫通孔はそれぞれ前記励振電極の対向する二辺と接するように配置されるよう構成する。
【０００７】
請求項３記載の圧電振動素子の構造は、平面形状が略長方形を呈する圧電基板の両主表面のほぼ中央に略長方形の励振電極を形成し、各励振電極から圧電基板の一方の短辺に向かって延出するリード電極と圧電基板の前記短辺近傍に配置したパッド電極とを有する圧電振動素子であって、前記圧電基板の少なくとも一方の主表面には各長辺のほぼ中央を起点とし短辺と平行に延びる２条の突起部が圧電基板と一体的に形成されており、該突起部は前記励振電極の領域にまで達するよう構成する。
【０００８】
請求項４記載の圧電振動子の基板構造は、前記圧電基板が、ＡＴカット水晶基板であるよう構成する。
【０００９】
【発明の実施の形態】
以下、図示した実施例に基づいて本発明を詳細に説明する。
本発明においては、リード電極や水晶基板の支持部であるパッド電極より、振動エネルギーが漏洩することを低減させるため、水晶基板に所定の加工を加えた。第一の実施例においては、水晶基板に、各長辺を起点として短辺方向に励振電極の一辺と接するように切り込みを設け、振動エネルギーの漏洩を低減した。第二の実施例においては、水晶基板に、短辺と平行に励振電極の対向する二辺と接するよう貫通孔を設け、振動エネルギーの漏洩を低減した。一方、第三の実施例においては、水晶基板の長辺のほぼ中心を起点とし、短辺と平行に延びる突起部を圧電基板と一体的に形成し、振動エネルギーの漏洩を低減した。
【００１０】
図１は、本発明に係る水晶振動素子の構造の第一の実施例を示す外観図である。水晶振動素子７は、所定のサイズにＡＴカットされた水晶基板８のほぼ中央部の表裏面に、所定の面積を有する励振電極９ａ、及び９ｂを形成し、該励振電極９ａからは、リード電極１０ａ及びパッド電極１１ａとを導出し、一方、励振電極９ｂからは、リード電極１０ｂと側面電極１２を介してパッド電極１１ｂとを導出している。本実施例においては、水晶基板８の長辺方向から水晶基板の中央に向かい、励振電極９ａ、９ｂの側面に接して４箇所の切り込み１３ａ、１３ｂ、１３ｃ及び１３ｄを設けた。
【００１１】
そこで、本実施例に示したような水晶基板に設けた４箇所の切り込みが、振動エネルギーの漏洩の低減にどのように影響を与えるかを認識するため、有限要素法による振動解析を行い、４箇所のｘ方向の切り込みの幅ｄを変化させて、その時の振動変位をシミュレーションにより求めた。
図２は、本発明に係わる水晶振動素子の構造において、第一の実施例における振動解析の結果をグラフに示す。本振動解析に用いたモデルは、水晶基板の厚み寸法が１２８μｍ、ｘ方向寸法が２０４８μｍ、ｚ方向寸法が１２８０μｍのＡＴカット水晶基板に、ｘ方向寸法が１４００μｍ、ｚ方向の寸法が９６０μｍの領域を有した励振電極を形成し、励振電極の厚みは水晶換算で１μｍとした。そこで、水晶基板に切り込みを設けた結果、ｚ方向に残留する水晶基板の寸法ｌを１２８μｍとし、４箇所のｘ方向の切り込みの幅ｄを変化させて振動変位分布を計算した。図２の縦軸は、水晶基板の中心部の振動変位で他の位置での振動変位を割り算した結果である規格化振動変位を示し、横軸は、励振電極の中心部から水晶基板のｘ方向への距離を示す。
【００１２】
図２に示す如く、水晶基板に４箇所の切込みを設けることで、従来の形状の水晶基板と比べて端部での振動変位が減少している。又、シミュレーションの結果、ｘ方向の切り込みの幅ｄを３２μｍとした時に、水晶基板端部での振動変位が最も減少するという結果が得られた。
従って、水晶振動子を設計する際に、等価インピーダンスが決められており励振電極の面積に対して制限が与えられている場合等においても、水晶基板に４箇所の切込みを設けることにより、リード電極やパッド電極から振動エネルギーが漏洩することを低減することが可能となる。又、ｘ方向の切り込みの幅ｄを３２μｍに近い寸法とすることで、リード電極やパッド電極から振動エネルギーが漏洩することをさらに低減することが可能となる。
【００１３】
図３は、本発明に係る水晶振動素子の構造の第二の実施例を示す外観図である。水晶振動素子１４は、所定のサイズにＡＴカットされた水晶基板１５のほぼ中央部の表裏面に、所定の面積を有する励振電極１６ａ、及び１６ｂを形成し、該励振電極１６ａからは、リード電極１７ａ及びパッド電極１８ａとを導出し、一方、励振電極１６ｂからは、リード電極１７ｂと側面電極１９を介してパッド電極１８ｂとを導出している。本実施例においては、水晶基板１５に形成した前記励振電極１６ａ、１６ｂの両短辺側に接して、励振電極１６ａ、１６ｂの短辺と同一長さで所定の幅を有した２箇所の貫通孔２０ａ、２０ｂを設けた。
【００１４】
そこで、本実施例に示したような水晶基板に設けた２箇所の貫通孔が、振動エネルギーの漏洩の低減にどのように影響を与えるかを認識するため、有限要素法による振動解析を行い、２箇所のｘ方向の貫通孔の幅ｄを変化させて、その時の振動変位をシミュレーションにより求めた。
図４は、本発明に係わる水晶振動素子の構造において、第二の実施例における振動解析の結果をグラフに示す。本振動解析に用いたモデルは、第一の実施例における振動解析と同様に、水晶基板の厚み寸法が１２８μｍ、ｘ方向寸法が２０４８μｍ、ｚ方向寸法が１２８０μｍのＡＴカット水晶基板に、ｘ方向寸法が１４００μｍ、ｚ方向の寸法が９６０μｍの領域を有した励振電極を形成し、励振電極の厚みは水晶換算で１μｍとした。そこで、貫通孔のｚ方向の寸法を９６０μｍとし、２箇所のｘ方向の貫通孔の幅ｄを変化させて振動変位分布を計算した。図４の縦軸は、水晶基板の中心部の振動変位で他の位置での振動変位を割り算した結果である規格化振動変位を示し、横軸は、励振電極の中心部から水晶基板のｘ方向への距離を示す。
【００１５】
図４に示す如く、水晶基板に２箇所の貫通孔を設けることで、従来の形状の水晶基板と比べて端部での振動変位が減少している。又、シミュレーションの結果、ｘ方向の切り込みの幅ｄは、何れの寸法にしても水晶基板端部での振動変位の差が認められなかった。
従って、水晶振動子を設計する際に、等価インピーダンスが決められており励振電極の面積に対して制限が与えられている場合等においても、水晶基板に２箇所の貫通孔を設けることにより、リード電極やパッド電極から振動エネルギーが漏洩することを低減することが可能となる。
【００１６】
図５は、本発明に係る水晶振動素子の構造の第三の実施例を示す外観図である。水晶振動素子２１は、所定のサイズにＡＴカットされた水晶基板２２のほぼ中央部の表裏面に、所定の面積を有する励振電極２３ａ、及び２３ｂを形成し、該励振電極２３ａからは、リード電極２４ａ及びパッド電極２５ａとを導出し、一方、励振電極２３ｂからは、リード電極２４ｂと側面電極２６を介してパッド電極２５ｂとを導出している。本実施例においては、水晶基板２２の表裏面の両長辺方向中央部を起点とし夫々水晶基板の短辺と平行に中心部に向かい、水晶基板２２の表裏面の夫々に計４箇所の所定の長さの突起部２７ａ、２７ｂ、２７ｃ、２７ｄを設けた。
【００１７】
そこで、本実施例に示したような水晶基板に設けた４箇所の突起部が、振動エネルギーの漏洩の低減にどのように影響を与えるかを認識するため、有限要素法による振動解析を行い、４箇所の突起部の厚みｄを変化させて、その時の振動変位をシミュレーションにより求めた。
図６は、本発明に係わる水晶振動素子の構造において、第三の実施例における振動解析の結果をグラフに示す。本振動解析に用いたモデルは、第一の実施例における振動解析と同様に、水晶基板の厚み寸法が１２８μｍ、ｘ方向寸法が２０４８μｍ、ｚ方向寸法が１２８０μｍのＡＴカット水晶基板に、ｘ方向寸法が１４００μｍ、ｚ方向の寸法が９６０μｍの領域を有した励振電極を形成し、励振電極の厚みは水晶換算で１μｍとした。そこで、４箇所の突起部を夫々、ｚ方向の寸法を５４４μｍ、ｘ方向の寸法を６４μｍとし、突起物の厚みｄを変化させて振動変位分布を計算した。図６の縦軸は、水晶基板の中心部の振動変位で他の位置での振動変位を割り算した結果である規格化振動変位を示し、横軸は、励振電極の中心部から水晶基板のｘ方向への距離を示す。
【００１８】
図６に示す如く、水晶基板に４箇所の突起物を設けることで、従来の形状の水晶基板と比べて端部での振動変位が減少している。又、シミュレーションの結果、突起物の厚みｄは、ｄ＝２８μｍより大きくしても振動エネルギーの閉じ込めの状態はほとんど変化していない。
従って、水晶振動子を設計する際に、等価インピーダンスが決められており励振電極の面積に対して制限が与えられている場合等においても、水晶基板に４箇所の突起物を設けることにより、リード電極やパッド電極から振動エネルギーが漏洩することを低減することが可能となる。
【００１９】
【発明の効果】
以上説明したように、本発明によれば以下のような優れた効果が得られる。
請求項１記載の発明は、圧電基板に切込みを設けることで、従来の形状の圧電基板と比べて端部での振動変位が減少し、圧電振動子の電気的特性の向上を図る上で大きな効果を発揮する。
【００２０】
請求項２記載の発明は、圧電基板に貫通孔を設けることで、従来の形状の圧電基板と比べて端部での振動変位が減少し、圧電振動子の電気的特性の向上を図る上で大きな効果を発揮する。
【００２１】
請求項３記載の発明は、圧電基板に突起物を設けることで、従来の形状の圧電基板と比べて端部での振動変位が減少し、圧電振動子の電気的特性の向上を図る上で大きな効果を発揮する。
【００２２】
請求項４記載の発明は、圧電基板としてＡＴカットされた水晶基板を用いることにより、周波数温度特性の優れた圧電振動子を構成することが出来、圧電振動子の電気的特性の向上を図る上で大きな効果を発揮する。
【図面の簡単な説明】
【図１】本発明に係る水晶振動素子の構造の第一の実施例を示す外観図である。
【図２】本発明に係わる水晶振動素子の構造において、第一の実施例における振動解析の結果をグラフに示す。
【図３】本発明に係る水晶振動素子の構造の第二の実施例を示す外観図である。
【図４】本発明に係わる水晶振動素子の構造において、第二の実施例における振動解析の結果をグラフに示す。
【図５】本発明に係る水晶振動素子の構造の第三の実施例を示す外観図である。
【図６】本発明に係わる水晶振動素子の構造において、第三の実施例における振動解析の結果をグラフに示す。
【図７】従来の水晶振動素子の外観例を示す図である。
【符号の説明】
１・・水晶振動素子、 ２・・水晶基板、
３ａ、３ｂ・・励振電極、 ４ａ、４ｂ・・リード電極、
５ａ、５ｂ・・パッド電極、 ６・・側面電極、
７・・水晶振動素子、 ８・・水晶基板、
９ａ、９ｂ・・励振電極、 １０ａ、１０ｂ・・リード電極、
１１ａ、１１ｂ・・パッド電極、 １２・・側面電極、
１３ａ、１３ｂ、１３ｃ、１３ｄ・・切込み、
１４・・水晶振動素子、 １５・・水晶基板、
１６ａ、 １６ｂ・・励振電極、 １７ａ、１７ｂ・・リード電極、
１８ａ、１８ｂ・・パッド電極、 １９・・側面電極、
２０ａ、２０ｂ・・貫通孔、 ２１・・水晶振動素子、
２２・・水晶基板、 ２３ａ、２３ｂ・・励振電極、
２４ａ、２４ｂ・・リード電極、 ２５ａ、２５ｂ・・パッド電極、
２６・・側面電極、
２７ａ、２７ｂ、２７ｃ、２７ｄ・・突起物[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a structure of a piezoelectric vibrating element, and more particularly, to a structure of a piezoelectric vibrating element in which the shape of a piezoelectric substrate is improved so that leakage of vibration energy from a pad electrode (support) provided on the piezoelectric substrate is reduced.
[0002]
[Prior art]
A piezoelectric vibrator with a structure in which a piezoelectric vibrating element such as a quartz vibrating element is housed on the inner bottom surface of a package having a concave part on the top surface, and the opening of the package is hermetically sealed with a lid is a reference frequency source for various communication devices Widely used as.
In general, a crystal unit uses an AT-cut crystal substrate, and is configured to function as an energy-trap type crystal unit. An excitation electrode having a predetermined area is opposed to the front and back surfaces of the crystal substrate at a substantially central portion. Formed. Therefore, when a voltage is externally applied between the electrodes for excitation, a predetermined vibration energy is confined due to a mass addition effect of the excitation electrodes, and the vibration energy reaches the vertex at the center of the excitation electrode with respect to the quartz substrate. Construct a predetermined displacement distribution.
[0003]
FIG. 7 is a diagram showing an example of the appearance of a conventional quartz-crystal vibrating element. In the quartz vibrating element 1, excitation electrodes 3a and 3b having a predetermined area are formed on the front and back surfaces of a substantially central portion of a quartz substrate 2 which is AT-cut to a predetermined size, and a lead electrode is formed from the excitation electrode 3a. 4a and the pad electrode 5a are led out, while the pad electrode 5b is led out from the excitation electrode 3b via the lead electrode 4b and the side electrode 6. As shown in FIG. 7, the quartz crystal vibrating element 1 has a structure in which an excitation electrode pair is formed substantially in the center of a quartz substrate, and vibration energy is hardly leaked from a lead electrode or a pad electrode which is a supporting portion of the quartz substrate. It has become.
[0004]
[Problems to be solved by the invention]
2. Description of the Related Art In recent years, with the spread of mobile communication devices such as mobile phones, demands for higher performance quartz oscillators have been increasing.
However, as described above, the conventional crystal resonator has a structure in which vibration energy is less likely to leak than the lead electrode and the pad electrode which is a supporting portion of the crystal substrate, but the higher frequency and higher Q value of the crystal resonator are used. In order to achieve this, it is necessary to further reduce the amount of vibration energy of the main vibration generated in the excitation electrode leaking from the support and the like. For example, Japanese Patent Application Laid-Open No. 11-355088 discloses a piezoelectric substrate in which a through hole is formed in a piezoelectric substrate around an excitation electrode, but the position of the through hole is not studied in detail.
Therefore, the present invention has been made to solve the above-mentioned problem, and compared the leakage of vibration energy from a conventional piezoelectric vibrator through a lead electrode or a pad electrode which is a supporting portion of a piezoelectric substrate. To provide a further reduced piezoelectric vibration element structure.
[0005]
[Means for Solving the Problems]
To achieve the above object, the structure of the piezoelectric vibration element according to the present invention has the following configuration.
In the structure of the piezoelectric vibration element according to the first aspect, a substantially rectangular excitation electrode is formed substantially at the center of both main surfaces of the piezoelectric substrate having a substantially rectangular planar shape, and each excitation electrode is formed on one short side of the piezoelectric substrate. A piezoelectric vibrating element having a lead electrode extending toward the front side and a pad electrode disposed near the short side of the piezoelectric substrate, wherein the piezoelectric substrate has two starting points from each long side and extending in parallel with the short side. Are formed, and each of the cuts is arranged such that one side edge thereof is in contact with any one side of the excitation electrode.
[0006]
In the structure of the piezoelectric vibrating element according to the second aspect, a substantially rectangular excitation electrode is formed substantially at the center of both main surfaces of the piezoelectric substrate having a substantially rectangular planar shape, and from each excitation electrode to one short side of the piezoelectric substrate. A piezoelectric vibrating element having a lead electrode extending toward the substrate and a pad electrode disposed near the short side of the piezoelectric substrate, wherein the piezoelectric substrate is formed with two through holes extending parallel to the short side. The through holes are arranged so as to be in contact with two opposing sides of the excitation electrode.
[0007]
In the structure of the piezoelectric vibration element according to the third aspect, a substantially rectangular excitation electrode is formed substantially at the center of both main surfaces of the piezoelectric substrate having a substantially rectangular planar shape, and each excitation electrode is formed on one short side of the piezoelectric substrate. A piezoelectric vibrating element having a lead electrode extending toward the substrate and a pad electrode disposed near the short side of the piezoelectric substrate, wherein at least one main surface of the piezoelectric substrate has a starting point substantially at the center of each long side. Two protrusions extending parallel to the short side are formed integrally with the piezoelectric substrate, and the protrusions are configured to reach the region of the excitation electrode.
[0008]
The substrate structure of the piezoelectric vibrator according to claim 4 is configured such that the piezoelectric substrate is an AT cut quartz substrate.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the illustrated embodiments.
In the present invention, a predetermined process is applied to the quartz substrate in order to reduce the leakage of vibration energy from the lead electrode and the pad electrode which is a supporting portion of the quartz substrate. In the first embodiment, a cut is provided in the quartz substrate in such a manner that each long side is a starting point and is in contact with one side of the excitation electrode in a short side direction to reduce leakage of vibration energy. In the second embodiment, a through hole is provided in the quartz substrate so as to be in contact with the two opposite sides of the excitation electrode in parallel with the short side, thereby reducing leakage of vibration energy. On the other hand, in the third embodiment, a projection part which starts from substantially the center of the long side of the quartz substrate and extends parallel to the short side is formed integrally with the piezoelectric substrate to reduce leakage of vibration energy.
[0010]
FIG. 1 is an external view showing a first embodiment of the structure of the crystal resonator element according to the present invention. The crystal vibrating element 7 has excitation electrodes 9a and 9b having a predetermined area formed on the front and back surfaces of a substantially central portion of a crystal substrate 8 which has been AT-cut to a predetermined size, and a lead electrode is formed from the excitation electrode 9a. 10a and the pad electrode 11a are led out, while the pad electrode 11b is led out from the excitation electrode 9b via the lead electrode 10b and the side electrode 12. In the present embodiment, four cuts 13a, 13b, 13c and 13d are provided in contact with the side surfaces of the excitation electrodes 9a and 9b from the long side direction of the quartz substrate 8 toward the center of the quartz substrate.
[0011]
Therefore, in order to recognize how the four cuts provided on the quartz substrate as shown in this embodiment affect the reduction of the leakage of the vibration energy, the vibration analysis by the finite element method was performed. The width d of the cut in the x direction at the location was changed, and the vibration displacement at that time was determined by simulation.
FIG. 2 is a graph showing the result of vibration analysis in the first embodiment in the structure of the crystal resonator element according to the present invention. The model used for this vibration analysis is an AT-cut quartz substrate with a thickness of 128 μm, a dimension of 2048 μm in the x direction, and a size of 1280 μm in the z direction on an AT-cut quartz substrate with a region of 1400 μm in the x direction and 960 μm in the z direction. The excitation electrode was formed, and the thickness of the excitation electrode was 1 μm in terms of quartz. Therefore, as a result of providing cuts in the quartz substrate, the size 1 of the quartz substrate remaining in the z direction was set to 128 μm, and the vibration displacement distribution was calculated by changing the width d of the cuts in four places in the x direction. The vertical axis in FIG. 2 shows the normalized vibration displacement obtained by dividing the vibration displacement at other positions by the vibration displacement at the center of the quartz substrate, and the horizontal axis represents x of the quartz substrate from the center of the excitation electrode. Indicates the distance to the direction.
[0012]
As shown in FIG. 2, by providing four cuts in the quartz substrate, the vibration displacement at the end portion is reduced as compared with the conventional quartz substrate. Also, as a result of the simulation, when the width d of the cut in the x direction was set to 32 μm, the result that the vibration displacement at the edge of the quartz substrate was reduced most was obtained.
Therefore, even when the equivalent impedance is determined and the area of the excitation electrode is limited when designing the crystal resonator, the lead electrode can be formed by providing four cuts in the crystal substrate. And leakage of vibration energy from the pad electrode. Further, by setting the width d of the cut in the x direction to a size close to 32 μm, leakage of vibration energy from the lead electrode or the pad electrode can be further reduced.
[0013]
FIG. 3 is an external view showing a second embodiment of the structure of the crystal resonator element according to the present invention. The quartz vibrating element 14 has excitation electrodes 16a and 16b having a predetermined area formed on the front and back surfaces of a substantially central portion of a quartz substrate 15 which has been AT-cut to a predetermined size, and a lead electrode is formed from the excitation electrode 16a. 17a and the pad electrode 18a are led out, while the pad electrode 18b is led out from the excitation electrode 16b via the lead electrode 17b and the side surface electrode 19. In this embodiment, two through-holes having the same length as the short sides of the excitation electrodes 16a and 16b and having a predetermined width are in contact with both short sides of the excitation electrodes 16a and 16b formed on the quartz substrate 15. Holes 20a and 20b were provided.
[0014]
Therefore, in order to recognize how the two through holes provided in the quartz substrate as shown in the present embodiment affect the reduction of the leakage of the vibration energy, a vibration analysis by the finite element method was performed. The width d of the two through holes in the x direction was changed, and the vibration displacement at that time was determined by simulation.
FIG. 4 is a graph showing a result of vibration analysis in the second embodiment in the structure of the crystal resonator element according to the present invention. The model used in the vibration analysis is the same as the vibration analysis in the first embodiment, except that the thickness of the quartz substrate is 128 μm, the dimension in the x direction is 2048 μm, and the dimension in the x direction is 1280 μm. Formed an excitation electrode having an area of 1400 μm and a dimension in the z direction of 960 μm, and the thickness of the excitation electrode was 1 μm in terms of quartz. Thus, the vibration displacement distribution was calculated by setting the size of the through hole in the z direction to 960 μm and changing the width d of the two through holes in the x direction. The vertical axis in FIG. 4 shows the normalized vibration displacement obtained by dividing the vibration displacement at another position by the vibration displacement at the center of the quartz substrate, and the horizontal axis represents x of the quartz substrate from the center of the excitation electrode. Indicates the distance to the direction.
[0015]
As shown in FIG. 4, by providing two through-holes in the quartz substrate, the vibration displacement at the end is reduced as compared with the conventional quartz substrate. As a result of the simulation, no difference in the vibration displacement at the edge of the quartz substrate was recognized regardless of the size of the cut width d in the x direction.
Therefore, even when the equivalent impedance is determined and the area of the excitation electrode is limited when designing the crystal resonator, the lead is provided by providing two through holes in the crystal substrate. Leakage of vibration energy from the electrodes and pad electrodes can be reduced.
[0016]
FIG. 5 is an external view showing a third embodiment of the structure of the crystal resonator element according to the present invention. The crystal vibrating element 21 has excitation electrodes 23a and 23b having a predetermined area formed on the front and back surfaces of a substantially central portion of a crystal substrate 22 which is AT-cut to a predetermined size, and a lead electrode is formed from the excitation electrode 23a. 24a and the pad electrode 25a are led out, while the pad electrode 25b is led out from the excitation electrode 23b via the lead electrode 24b and the side electrode 26. In the present embodiment, starting from the center of each of the long sides of the front and back surfaces of the quartz substrate 22 as starting points, each goes toward the center in parallel with the short side of the quartz substrate, and a total of four predetermined positions are respectively provided on the front and back surfaces of the quartz substrate 22. The projections 27a, 27b, 27c, and 27d having the lengths are provided.
[0017]
Therefore, in order to recognize how the four projections provided on the quartz substrate as shown in the present embodiment affect the reduction of the leakage of the vibration energy, a vibration analysis by the finite element method was performed. By changing the thickness d of the four protrusions, the vibration displacement at that time was obtained by simulation.
FIG. 6 is a graph showing the result of vibration analysis in the third embodiment in the structure of the crystal resonator element according to the present invention. The model used in the vibration analysis is the same as the vibration analysis in the first embodiment, except that the thickness of the quartz substrate is 128 μm, the dimension in the x direction is 2048 μm, and the dimension in the x direction is 1280 μm. Formed an excitation electrode having an area of 1400 μm and a dimension in the z direction of 960 μm, and the thickness of the excitation electrode was 1 μm in terms of quartz. Accordingly, the vibration displacement distribution was calculated by changing the thickness d of the protrusions at 544 μm in the z direction and 64 μm in the x direction for the four protrusions. The vertical axis in FIG. 6 shows the normalized vibration displacement obtained by dividing the vibration displacement at another position by the vibration displacement at the center of the quartz substrate, and the horizontal axis represents x of the quartz substrate from the center of the excitation electrode. Indicates the distance to the direction.
[0018]
As shown in FIG. 6, by providing four projections on the quartz substrate, the vibration displacement at the end portion is reduced as compared with the conventional quartz substrate. Further, as a result of the simulation, even if the thickness d of the protrusion is larger than d = 28 μm, the state of confining the vibration energy hardly changes.
Therefore, even when the equivalent impedance is determined when the crystal resonator is designed and the area of the excitation electrode is restricted, the lead is provided by providing four projections on the crystal substrate. Leakage of vibration energy from the electrodes and pad electrodes can be reduced.
[0019]
【The invention's effect】
As described above, according to the present invention, the following excellent effects can be obtained.
According to the first aspect of the present invention, by providing the cuts in the piezoelectric substrate, the vibration displacement at the end portion is reduced as compared with the conventional shape of the piezoelectric substrate, which is great in improving the electrical characteristics of the piezoelectric vibrator. It is effective.
[0020]
According to the second aspect of the present invention, by providing a through hole in the piezoelectric substrate, vibration displacement at an end portion is reduced as compared with a piezoelectric substrate having a conventional shape, and the electric characteristics of the piezoelectric vibrator are improved. It has a great effect.
[0021]
According to the third aspect of the present invention, by providing protrusions on the piezoelectric substrate, vibration displacement at an end portion is reduced as compared with the conventional shape of the piezoelectric substrate, and the electric characteristics of the piezoelectric vibrator are improved. It has a great effect.
[0022]
According to the fourth aspect of the invention, by using an AT-cut quartz substrate as the piezoelectric substrate, a piezoelectric vibrator having excellent frequency temperature characteristics can be formed, and the electrical characteristics of the piezoelectric vibrator can be improved. It has a great effect.
[Brief description of the drawings]
FIG. 1 is an external view showing a first embodiment of the structure of a crystal resonator element according to the present invention.
FIG. 2 is a graph showing a result of vibration analysis in the first embodiment in the structure of the crystal resonator element according to the present invention.
FIG. 3 is an external view showing a second embodiment of the structure of the crystal resonator element according to the present invention.
FIG. 4 is a graph showing the results of vibration analysis in the second embodiment in the structure of the crystal resonator element according to the present invention.
FIG. 5 is an external view showing a third embodiment of the structure of the crystal resonator element according to the present invention.
FIG. 6 is a graph showing a result of vibration analysis in the third embodiment in the structure of the crystal resonator element according to the present invention.
FIG. 7 is a view showing an example of the appearance of a conventional quartz vibrating element.
[Explanation of symbols]
1. Crystal oscillator element 2. Crystal substrate,
3a, 3b ... excitation electrode, 4a, 4b ... lead electrode,
5a, 5b pad electrode, 6 side electrode,
7. Crystal oscillator, 8. Crystal substrate,
9a, 9b ... excitation electrode, 10a, 10b ... lead electrode,
11a, 11b pad electrode, 12 side electrode,
13a, 13b, 13c, 13d ... cut,
14. Crystal oscillator element, 15 Crystal substrate,
16a, 16b ... excitation electrode, 17a, 17b ... lead electrode,
18a, 18b pad electrode, 19 side electrode,
20a, 20b ... through-hole, 21 ... crystal resonator element,
22 ··· quartz substrate, 23a, 23b ··· excitation electrode,
24a, 24b ··· lead electrode, 25a, 25b · · pad electrode,
26 ・ ・ Side electrode,
27a, 27b, 27c, 27d...
