【０００１】
【発明の属する技術分野】
本発明は、小型化及び高周波化に対応し、且つ、熱応力による周波数特性の劣化がない水晶振動素子に関する。
【０００２】
【従来の技術】
従来から水晶振動子、特にＡＴカット水晶振動素子は小型、高精度の周波数、高安定性等の優れた特性を有することから、通信機器から民生機器まで多岐に渡って用いられている。近年、各種電子機器や伝送通信機器における情報量の増大と処理速度の高速化及び小型化に伴って、それらの機器に用いる基準周波数信号源として機能する水晶振動子に対して、高周波化及び小型化の要望がますます高まっている。
【０００３】
以下、従来の圧電デバイスについて水晶振動子を例にして説明する。
従来の水晶振動子に用いられる水晶振動素子には、例えば特開平１１−３５５０８８号公報で開示されたようなものがあり、図５は従来の水晶振動素子の平面図である。同図から明らかなように従来の水晶振動素子１０１は、一方主面（手前）に凹陥部１０１ａを有する水晶振動素子本体（ＡＴカット水晶基板）と、凹陥部１０１ａの底面を挟んで両主面に配設する励振電極１０２と、該励振電極１０２夫々から互いに相反する方向に延出する引き出し電極１０３と、凹陥部１０１ａの底面に備える励振電極１０２及び引き出し電極１０３の非形成部位、即ち水晶面が露出する部位で且つ励振電極１０２近傍（振動領域）を囲繞するように穿設する貫通孔１０４と、を備えたものである。水晶振動素子１０１の一般的なパッケージ方法、即ち水晶振動子の構造は、前記引き出し電極１０３と対応する接続電極を備えるセラミックパッケージに搭載し、該引き出し電極１０３と該接続電極とを導電性接着剤を介して機械的及び電気的に接続した上で水晶振動素子１０１を金属製の蓋部材によって気密封止する。前記貫通孔１０４の作用効果は、前記導電性接着剤の弾性力で緩衝されなかった温度変化に起因する水晶振動素子１０１の膨張、収縮（熱応力）の一部が前記振動領域に伝達しようとしても該貫通孔１０４が熱応力の伝達経路を遮断し伝達する熱応力を緩和させ、周波数特性の劣化を抑止するものである。
【０００４】
その他の熱応力を緩和する手段としては、例えば特開平１１−８８１０４号公報で開示されたようなものがあり、図６に示すように、平板状のＡＴカット水晶振動素子１１１におけるＸＺ′面（同図中示す矢印による）上でＸ軸からの回転角度が＋６０度をなす第１の直線又は−６０度をなす第２の直線のいずれかの直線上（第１の直線図示）に前記引き出し電極１１３を配設することで熱応力の緩和、即ち周波数特性の劣化を抑止している。
【０００５】
【特許文献１】特開平１１−３５５０８８号公報。
【特許文献２】特開平１１−８８１０４号公報。
【０００６】
【発明が解決しようとする課題】
しかしながら、近年の水晶振動子の小型化、即ち前記水晶振動素子１０１の小型化に伴い、前記凹陥部１０１ａの底面の大きさと前記振動領域の大きさとが略一致し前記貫通孔１０４を形成することができない。
また、近年の水晶振動子の高周波化、即ち前記凹陥部１０１ａの底面の更なる薄肉化に伴い、僅かな前記熱応力でも反応してしまい、換言すれば熱応力に対する感度が鋭敏になり前述するその他の手段では熱応力の緩和、即ち周波数特性の劣化を抑止することができない。
【０００７】
本発明は、上記の課題を解決するためになされたものであり、小型化及び高周波化に対応し、且つ、熱応力による周波数特性の劣化がない水晶振動素子を提供することを目的とする。
【０００８】
【課題を解決するための手段】
上記課題を解決するために本発明に係わる請求項１記載の発明は、ＡＴカット水晶基板の一方の主面に凹陥部を形成し該凹陥部の底面の周囲を支持する環状囲繞部を一体的に形成し、該環状囲繞部の外周に枠状囲繞部を載置し、該枠状囲繞部と前記環状囲繞部とを機械的に接続すると共に前記水晶基板における結晶のＸＺ′面上でＺ′軸からの回転角度が＋３０度をなす第１の直線または−３０度をなす第２の直線の少なくとも一方の直線上に連結部を架設し、前記凹陥部の底面を挟んで対向配置した励振電極のそれぞれから前記連結部の表面を経由し前記枠状囲繞部１ｃまで延出すると共に互いに相反する方向に延出するリード電極を配設したことを特徴とする。
【０００９】
また請求項２記載の発明は、請求項１において、前記連結部の平面形状が鉤型状であることを特徴とする。
【００１０】
【発明の実施の形態】
以下、図示した本発明の実施の形態に基づいて、本発明を詳細に説明する。
【００１１】
図１は本発明の第１の実施形態の水晶振動素子の平面図である。同図中に図示する矢印は水晶の結晶軸を示すものである。
同図に示すように、水晶振動素子１はＡＴカット水晶基板の基本波厚みすべり振動波を利用した振動子であってその共振周波数が板厚と反比例することから機械的強度を保ちつつ高周波化を図る為に、該水晶振動素子１を構成するＡＴカット水晶基板の一方の主面をエッチングによって凹陥せしめて該凹陥部の底面を超薄肉の振動部１ａとすると共に該振動部１ａの周囲を支持する厚肉の環状囲繞部１ｂを一体的に形成し、該環状囲繞部１ｂに一定間隔の間隙２を隔てて環状囲繞部１ｂと同じ厚みを有する枠状囲繞部１ｃを載置し、該間隙２に枠状囲繞部１ｃと環状囲繞部１ｂとを機械的に接続すると共に水晶振動素子１におけるＸＺ′面上でＺ′軸からの回転角度が＋３０度をなす第１の直線または−３０度をなす第２の直線の少なくとも一方の直線上、例えば第１の直線上に位置する連結部１ｄを架設する。更に、マスクを用いて金を蒸着するか又はフォトリソグラフィにより、前記振動部１ａを挟んで対向する位置に励振電極３を配設し、該励振電極３のそれぞれから前記第１の直線上に備える前記連結部１ｄの表面を経由し前記枠状囲繞部１ｃまで延出すると共に互いに相反する方向に延出するリード電極４を配設し、該リード電極４のそれぞれと電気的導通すると共に前記枠状囲繞部１ｃ上の前記Ｚ軸で線対称となる位置、例えば対向する一方の外端辺部の略中央にパッド電極５を配設する。
【００１２】
図２は本発明の第２の実施形態の水晶振動素子の平面図である。
第２の実施形態の水晶振動素子が第１の実施形態と異なる点は、前記連結部の平面形状を鉤型状に形成した点にある。図２に示すように、連結部２１ｄを鉤型状に形成することで前記枠状囲繞部と前記環状囲繞部との機械的な接続強度、即ち連結部２１ｄの機械的強度を向上させている。
【００１３】
なお、第１及び第２の実施形態での前記連結部は前記第１の直線上のみに配置しているが、前記枠状囲繞部と前記環状囲繞部との機械的な接続強度を向上させるために第２の直線上にも連結部を配置するのが望ましい。その際、前記リード電極のそれぞれの延出（引き出し）方向は互いに相対する方向である必要は無い。
【００１４】
図３（ａ）〜（ｃ）及び図４（ａ）〜（ｂ）は本発明のその他の実施形態の水晶振動素子の平面図であって、以下に説明する実施形態は前述する熱応力の伝達経路の遮断に主眼を置いたものである。
図３（ａ）〜（ｃ）に示す実施形態は連結部を前記枠状囲繞部の外角部と該外角部に対応する前記環状囲繞部の内角部と結ぶ直線上に有する間隙に配設したものである。図３（ａ）に示すように、四隅に連結部３１を配設し対角に位置する一方の連結部３１に前記リード電極４を配設する。また図３（ｂ）に示すように、連結部３２を対角に位置する一方の隅部に配設し該連結部３２にリード電極４を配設する。また図３（ｃ）に示すように、連結部３３を対角に位置しない、即ち任意の一辺部の両隅に配設し該連結部３３にリード電極４を配設する。
図４（ａ）〜（ｂ）に示す実施形態は連結部を前記枠状囲繞部の辺部の略中央と該辺部に対応する前記環状囲繞部の内辺部の略中央と結ぶ直線上に有する間隙に配設したものである。図４（ａ）に示すように、四辺部のそれぞれに連結部４１を配設し対向する一方の辺部に備える連結部４１に前記リード電極４を配設する。また図４（ｂ）に示すように、対向する一方の辺部に連結部４２を配設し該連結部４２にリード電極４を配設する。
【００１５】
なお、本発明の水晶振動素子のパッケージ方法（水晶振動子の構造）は前述した従来と同様である。
【００１６】
前記励振電極が部分電極を配設する多重モード水晶フィルタや弾性表面波フィルタにも本発明を適用することも可能である。
【００１７】
ＡＴカットの水晶振動素子を用いて本発明を説明したが、本発明はＡＴカットに限定するものではなくＢＴカット、ＣＴカット、ＤＴカット、ＳＣカット、ＧＴカット等のカットアングルの水晶基板に適用できることは云うまでもない。
【００１８】
また本発明は、水晶振動素子のみに限定するものではなくランガサイト、四方酸リチウム、タンタル酸リチウム、ニオブ酸リチウム等の圧電振動素子に適用できることは云うまでもない。
なお、前記連結部の引き出し方向は、水晶基板のカットアングルや材料に応じて、応力感度の低い方向を適宜選択すればよい。
【００１９】
【発明の効果】
本発明によれば、小型化及び高周波化に対応し、且つ、熱応力による周波数特性の劣化がない水晶振動素子が得られるという効果を有する。
【図面の簡単な説明】
【図１】本発明の第１の実施形態としての水晶振動素子の平面図。
【図２】本発明の第２の実施形態としての水晶振動素子の平面図。
【図３】本発明のその他の実施形態としての水晶振動素子の平面図。
【図４】本発明のその他の実施形態としての水晶振動素子の平面図。
【図５】従来の水晶振動素子の平面図。
【図６】従来の水晶振動素子の平面図。
【符号の説明】
１…水晶振動素子 １ａ…振動部 １ｂ…環状囲繞部 １ｃ…枠状囲繞部
１ｄ…連結部 ２…間隙 ３…励振電極 ４…リード電極
５…パッド電極 ２１ｄ…連結部 ３１、３２、３３、４１、４２…連結部
１０１、１１１…水晶振動素子 １０２…励振電極
１０３、１１３…引き出し電極 １０４…貫通孔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a quartz crystal resonator element that can be reduced in size and increased in frequency and that does not deteriorate in frequency characteristics due to thermal stress.
[0002]
[Prior art]
Conventionally, quartz resonators, particularly AT-cut quartz resonators, have excellent characteristics such as small size, high-accuracy frequency, and high stability, and thus have been widely used from communication devices to consumer devices. In recent years, as the amount of information in various electronic devices and transmission communication devices has increased, the processing speed has been increased, and the size has been reduced, the frequency and the size have been reduced with respect to the crystal resonator functioning as the reference frequency signal source used in these devices. There is an ever increasing demand for conversion.
[0003]
Hereinafter, a conventional piezoelectric device will be described using a crystal resonator as an example.
Examples of a quartz crystal resonator element used in a conventional quartz resonator include those disclosed in Japanese Patent Laid-Open No. 11-355088, and FIG. 5 is a plan view of the conventional quartz resonator element. As can be seen from the figure, the conventional crystal resonator element 101 has a crystal resonator element body (AT-cut crystal substrate) having a concave portion 101a on one main surface (front side) and both main surfaces sandwiching the bottom surface of the concave portion 101a. The excitation electrode 102 disposed on each of the excitation electrodes 102, the extraction electrodes 103 extending in opposite directions from the excitation electrodes 102, and the excitation electrode 102 and the extraction electrode 103 on the bottom surface of the recess 101 a, i.e., the crystal plane. And a through hole 104 that is drilled so as to surround the vicinity of the excitation electrode 102 (vibration region). A general packaging method of the crystal resonator element 101, that is, the structure of the crystal resonator, is mounted on a ceramic package having a connection electrode corresponding to the extraction electrode 103, and the extraction electrode 103 and the connection electrode are connected with a conductive adhesive. The quartz crystal resonator element 101 is hermetically sealed with a metal lid member after being mechanically and electrically connected via the wire. The effect of the through-hole 104 is that a part of expansion and contraction (thermal stress) of the crystal resonator element 101 due to a temperature change that is not buffered by the elastic force of the conductive adhesive is transmitted to the vibration region. Also, the through-hole 104 blocks the thermal stress transmission path and relaxes the thermal stress transmitted, thereby suppressing the deterioration of the frequency characteristics.
[0004]
As another means for relieving thermal stress, for example, there is one disclosed in Japanese Patent Laid-Open No. 11-88104. As shown in FIG. 6, as shown in FIG. On the straight line (shown by the first straight line) of the first straight line whose rotation angle from the X axis is +60 degrees or the second straight line which is -60 degrees (according to the arrow shown in the figure). By disposing the electrode 113, thermal stress relaxation, that is, deterioration of frequency characteristics is suppressed.
[0005]
Japanese Patent Laid-Open No. 11-355088.
[Patent Document 2] JP-A-11-88104.
[0006]
[Problems to be solved by the invention]
However, with the recent miniaturization of the crystal unit, that is, the miniaturization of the crystal resonator element 101, the size of the bottom surface of the recessed portion 101a and the size of the vibration region substantially coincide to form the through hole 104. I can't.
In addition, with the recent increase in the frequency of quartz resonators, that is, the further thinning of the bottom surface of the recessed portion 101a, the reaction occurs even with a small amount of the thermal stress, in other words, the sensitivity to the thermal stress becomes sharp, as described above. Other means cannot suppress thermal stress relaxation, that is, deterioration of frequency characteristics.
[0007]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a crystal resonator element that can be reduced in size and increased in frequency and that does not deteriorate in frequency characteristics due to thermal stress.
[0008]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the invention according to claim 1 according to the present invention is characterized in that a concave portion is formed on one main surface of an AT-cut quartz substrate and an annular surrounding portion that supports the periphery of the bottom surface of the concave portion is integrated. The frame-shaped surrounding portion is placed on the outer periphery of the annular surrounding portion, the frame-shaped surrounding portion and the annular surrounding portion are mechanically connected to each other, and Z is formed on the XZ ′ plane of the crystal in the crystal substrate. Excitation in which a connecting portion is constructed on at least one of the first straight line having a rotation angle from the axis of +30 degrees or the second straight line having −30 degrees and sandwiching the bottom surface of the recessed portion. A lead electrode extending from each of the electrodes to the frame-shaped surrounding portion 1c through the surface of the connecting portion and extending in a direction opposite to each other is provided.
[0009]
According to a second aspect of the present invention, in the first aspect, the planar shape of the connecting portion is a bowl shape.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on illustrated embodiments of the present invention.
[0011]
FIG. 1 is a plan view of a crystal resonator element according to a first embodiment of the present invention. The arrow shown in the figure indicates the crystal axis of quartz.
As shown in the figure, the quartz crystal resonator element 1 is a vibrator using a fundamental thickness shear vibration wave of an AT-cut quartz substrate, and the resonance frequency is inversely proportional to the plate thickness, so that the mechanical strength is maintained and the frequency is increased. In order to achieve this, one main surface of the AT-cut quartz crystal substrate constituting the crystal resonator element 1 is recessed by etching so that the bottom surface of the recess becomes an ultrathin vibrating portion 1a and the periphery of the vibrating portion 1a. A thick-walled annular surrounding portion 1b that supports the frame-shaped surrounding portion 1b is integrally formed, and a frame-shaped surrounding portion 1c having the same thickness as the annular surrounding portion 1b is placed on the annular surrounding portion 1b with a gap 2 therebetween. The frame-shaped surrounding portion 1c and the annular surrounding portion 1b are mechanically connected to the gap 2, and the first straight line in which the rotation angle from the Z ′ axis forms +30 degrees on the XZ ′ plane of the crystal resonator element 1 or − At least a second straight line of 30 degrees Square on a straight line, to erection for example the connecting portion 1d located in the first straight line. Further, the excitation electrodes 3 are disposed at positions facing each other with the vibration part 1a interposed therebetween by vapor deposition of gold using a mask or by photolithography, and the excitation electrodes 3 are provided on the first straight line from each of the excitation electrodes 3. Lead electrodes 4 extending to the frame-shaped surrounding portion 1c through the surface of the connecting portion 1d and extending in opposite directions are disposed, and are electrically connected to the lead electrodes 4 and the frame. The pad electrode 5 is disposed at a position that is line-symmetric with respect to the Z axis on the surrounding portion 1c, for example, approximately at the center of one opposing outer end side portion.
[0012]
FIG. 2 is a plan view of a crystal resonator element according to a second embodiment of the invention.
The difference between the crystal resonator element of the second embodiment and the first embodiment is that the planar shape of the connecting portion is formed in a bowl shape. As shown in FIG. 2, the connecting portion 21d is formed in a bowl shape to improve the mechanical connection strength between the frame-shaped surrounding portion and the annular surrounding portion, that is, the mechanical strength of the connecting portion 21d. .
[0013]
In addition, although the said connection part in 1st and 2nd embodiment is arrange | positioned only on the said 1st straight line, it improves the mechanical connection strength of the said frame-shaped surrounding part and the said annular surrounding part. For this reason, it is desirable to arrange the connecting portion also on the second straight line. At this time, the extending (drawing) directions of the lead electrodes do not have to be opposite to each other.
[0014]
3 (a) to 3 (c) and FIGS. 4 (a) to 4 (b) are plan views of a crystal resonator element according to another embodiment of the present invention. In the embodiment described below, the thermal stress described above is described. The focus is on blocking the transmission path.
In the embodiment shown in FIGS. 3A to 3C, the connecting portion is disposed in a gap having a straight line connecting the outer corner portion of the frame-shaped surrounding portion and the inner corner portion of the annular surrounding portion corresponding to the outer corner portion. Is. As shown in FIG. 3A, the connecting portions 31 are arranged at the four corners, and the lead electrodes 4 are arranged at one of the connecting portions 31 located diagonally. Further, as shown in FIG. 3B, the connecting portion 32 is disposed at one corner located diagonally, and the lead electrode 4 is disposed at the connecting portion 32. Further, as shown in FIG. 3C, the connecting portion 33 is not positioned diagonally, that is, disposed at both corners of an arbitrary side portion, and the lead electrode 4 is disposed at the connecting portion 33.
4 (a) to 4 (b) is a straight line connecting the connecting portion to the approximate center of the side portion of the frame-shaped surrounding portion and the approximate center of the inner side portion of the annular surrounding portion corresponding to the side portion. It arrange | positions in the space | gap which has. As shown in FIG. 4A, the lead electrode 4 is disposed on the connecting portion 41 provided on one of the opposing side portions provided with the connecting portion 41 on each of the four sides. Further, as shown in FIG. 4B, a connecting portion 42 is provided on one of the opposing side portions, and the lead electrode 4 is provided on the connecting portion 42.
[0015]
The method for packaging a crystal resonator element according to the present invention (the structure of the crystal resonator) is the same as the conventional one described above.
[0016]
The present invention can also be applied to a multimode crystal filter or a surface acoustic wave filter in which the excitation electrode is provided with a partial electrode.
[0017]
Although the present invention has been described using an AT-cut crystal resonator element, the present invention is not limited to an AT-cut, and is applicable to crystal substrates having cut angles such as BT cut, CT cut, DT cut, SC cut, and GT cut. Needless to say, it can be done.
[0018]
Needless to say, the present invention is not limited to the crystal resonator element, but can be applied to piezoelectric resonator elements such as langasite, lithium tetragonal acid, lithium tantalate, lithium niobate and the like.
In addition, what is necessary is just to select suitably the direction with low stress sensitivity according to the cut angle and material of a quartz substrate as the pulling-out direction of the said connection part.
[0019]
【The invention's effect】
According to the present invention, there is an effect that it is possible to obtain a crystal resonator element that can cope with downsizing and high frequency and that does not deteriorate frequency characteristics due to thermal stress.
[Brief description of the drawings]
FIG. 1 is a plan view of a crystal resonator element according to a first embodiment of the invention.
FIG. 2 is a plan view of a crystal resonator element according to a second embodiment of the invention.
FIG. 3 is a plan view of a crystal resonator element according to another embodiment of the invention.
FIG. 4 is a plan view of a crystal resonator element according to another embodiment of the invention.
FIG. 5 is a plan view of a conventional crystal resonator element.
FIG. 6 is a plan view of a conventional crystal resonator element.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Quartz crystal vibration element 1a ... Vibrating part 1b ... Ring-shaped surrounding part 1c ... Frame-shaped surrounding part 1d ... Connection part 2 ... Gap 3 ... Excitation electrode 4 ... Lead electrode 5 ... Pad electrode 21d ... Connection part 31,32,33,41 , 42 ... connecting portions 101, 111 ... crystal resonator element 102 ... excitation electrodes 103, 113 ... extraction electrode 104 ... through-hole