JP7362525B2 - Crystal oscillator - Google Patents

Crystal oscillator Download PDF

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JP7362525B2
JP7362525B2 JP2020054189A JP2020054189A JP7362525B2 JP 7362525 B2 JP7362525 B2 JP 7362525B2 JP 2020054189 A JP2020054189 A JP 2020054189A JP 2020054189 A JP2020054189 A JP 2020054189A JP 7362525 B2 JP7362525 B2 JP 7362525B2
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重隆 加賀
正積 窪田
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Nihon Dempa Kogyo Co Ltd
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Description

本発明は、励振電極の周囲に傾斜部が形成されたＡＴカットの水晶振動子に関する。 The present invention relates to an AT-cut crystal resonator in which a sloped portion is formed around an excitation electrode.

厚み滑り振動する水晶振動子では、外周付近の厚さを薄くしたいわゆるコンベックス形状の水晶片を用いることによって、振動エネルギーを水晶片に閉じ込めて、不要振動を抑圧することができる。しかし、水晶片をコンベックス形状に形成するためには、加工の手間及びコストがかかるという問題がある。 In a crystal resonator that vibrates through thickness shear, by using a so-called convex-shaped crystal piece that is thinner near the outer periphery, vibration energy can be confined in the crystal piece and unnecessary vibrations can be suppressed. However, there is a problem in that forming a crystal piece into a convex shape requires processing time and cost.

そこで、特許文献１では、水晶片は平板状のままで、両主面に形成される励振電極それぞれの縁に励振電極の厚さが漸減する傾斜部を形成することで、コンベックス形状の効果を生じさせて、水晶片の加工の手間及びコストを削減する旨が示されている。 Therefore, in Patent Document 1, the effect of the convex shape is improved by forming an inclined part where the thickness of the excitation electrode gradually decreases at the edge of each excitation electrode formed on both principal surfaces, while the crystal piece remains flat. It has been shown that the effort and cost of processing the crystal piece can be reduced by causing the crystal blank to occur.

特開２００２－２１７６７５JP2002-217675 特開２０１８－９８５９２JP2018-98592

一方、特許文献２には、特許文献１に開示された水晶振動子の構造、すなわち、水晶片の両両面に設ける励振電極それぞれが、縁に傾斜部を有したものであると、周波数調整のために励振電極をトリミングする際に傾斜部が消失して、振動エネルギーの損失が大きくなる場合があることが、記載されている（特許文献２の例えば図４、段落２６等）。そして、その改善を図るため、水晶片の一方の主面に形成する第１励振電極は全体が一様な厚さのものとし、他方の主面に形成する第２励振電極は一定の厚さで形成される主厚部及び主厚部の周囲に形成され主厚部に接する部分から外に向かい厚さが徐々に薄くなる傾斜部を有するものとし、かつ、主厚部は第１励振電極の厚さよりも厚くする構造が記載されている。 On the other hand, Patent Document 2 discloses that the structure of the crystal resonator disclosed in Patent Document 1, that is, that each of the excitation electrodes provided on both sides of the crystal piece has a sloped portion at the edge allows frequency adjustment. Therefore, it is described that when the excitation electrode is trimmed, the slope portion may disappear and the loss of vibration energy may become large (for example, FIG. 4, paragraph 26, etc. of Patent Document 2). In order to improve this, the first excitation electrode formed on one main surface of the crystal blank has a uniform thickness throughout, and the second excitation electrode formed on the other main surface has a constant thickness. The main thick part has a main thick part formed around the main thick part and a slope part formed around the main thick part and whose thickness gradually becomes thinner toward the outside from the part in contact with the main thick part, and the main thick part is the first excitation electrode. A structure in which the thickness is thicker than that is described.

この特許文献２に開示された水晶振動子は、第１励振電極側を周波数調整することによって、周波数調整をしても振動損失の悪化の程度を軽減できるものであった。
しかしながら、特許文献２は、具体的な周波数及び大きさのＡＴカット水晶振動子に関する適正構造の言及は、必ずしも満足のゆくものではなかった。
この出願は上記の点に鑑みなされたものであり、従って、この出願の目的は、一様な厚みの第１励振電極と、外周付近に傾斜部を持つ第２励振電極と、を有したＡＴカット水晶振動子において、個別の周波数において好ましい具体的な構造を提供することにある。 In the crystal resonator disclosed in Patent Document 2, by adjusting the frequency on the first excitation electrode side, the degree of deterioration of vibration loss can be reduced even if the frequency is adjusted.
However, Patent Document 2 is not necessarily satisfactory in mentioning an appropriate structure for an AT-cut crystal resonator with a specific frequency and size.
This application was filed in view of the above points, and therefore, the purpose of this application is to provide an AT having a first excitation electrode having a uniform thickness and a second excitation electrode having an inclined portion near the outer periphery. The object of the present invention is to provide a preferable concrete structure for each frequency in a cut crystal resonator.

この目的の達成を図るため、この発明のＡＴカットの水晶振動子によれば、パッケージと、該パッケージに内蔵されていて平板かつ平面形状が矩形のＡＴカットの水晶片と、該水晶片の主面の一方の面に設けられ厚さが一様な第１励振電極と、前記主面の他方の面に設けられ外周付近が傾斜部となっていて該傾斜部以外は一様な厚みの主圧部となっている前記第１励振電極の厚みより厚い水晶振動子において、
前記水晶片は、水晶のＸ軸方向を長辺とし、水晶のＺ′方向を短辺とし、発振周波数が基本波で３８ＭＨｚの水晶片であり、
前記第１励振電極及び第２励振電極の質量／水晶の質量の比を４．７％とし、前記第1励振電極及び第2励振電極による、前記水晶片の水晶Ｚ′軸方向の閉じ込め係数を、３．５～３．８としてあるか、
又は、前記第１励振電極及び第２励振電極の質量／水晶の質量の比を５．３％とし、前記第1励振電極及び第2励振電極による、前記水晶片の水晶Ｚ′軸方向の閉じ込め係数を、３．７～３．８としてあり、
前記傾斜部の幅を、前記水晶片で生じる屈曲モードの振動の波長λに対し１～２．５λの寸法としてあり、
前記第１励振電極及び第２励振電極各々は、前記水晶片の長辺方向を長軸、前記水晶片の短辺方向を短軸とする楕円形状としてあり、かつ、長軸長さ／短軸長さ＝１．２６５±１０％としてあること
を特徴とする。 In order to achieve this object, the AT-cut crystal resonator of the present invention includes a package, an AT-cut crystal piece built in the package and having a flat and rectangular planar shape, and a main body of the crystal piece. A first excitation electrode provided on one of the surfaces and having a uniform thickness, and a main excitation electrode provided on the other surface of the main surface and having an inclined portion near the outer periphery and having a uniform thickness except for the inclined portion. In a crystal resonator that is thicker than the thickness of the first excitation electrode serving as a pressure part,
The crystal piece has a long side in the X-axis direction of the crystal, a short side in the Z′ direction of the crystal, and has an oscillation frequency of 38 MHz as a fundamental wave,
The ratio of the mass of the first excitation electrode and the second excitation electrode to the mass of the crystal is 4.7%, and the confinement coefficient of the crystal piece in the crystal Z' axis direction by the first excitation electrode and the second excitation electrode is , 3.5 to 3.8,
Alternatively, the ratio of the mass of the first excitation electrode and the second excitation electrode to the mass of the crystal is 5.3%, and the crystal piece is confined in the crystal Z' axis direction by the first excitation electrode and the second excitation electrode. The coefficient is set to 3.7 to 3.8,
The width of the inclined portion is set to a dimension of 1 to 2.5λ with respect to the wavelength λ of vibration in a bending mode generated in the crystal piece,
Each of the first excitation electrode and the second excitation electrode has an elliptical shape with a long axis in the direction of the long side of the crystal piece and a short axis in the direction of the short side of the crystal piece, and has a long axis length/short axis. It is characterized in that the length is 1.265±10%.

なお、この発明を実施するに当たり、前記水晶片は、水晶のＸ軸方向の寸法をＬ１、水晶のＺ′軸方向の寸法をＷ１、厚みをｔと表したとき、Ｌ１／ｔ≧５０、Ｗ１／ｔ≧３３を満たす水晶片とすることが好ましい。例えば、長辺寸法Ｌ１が２．１±０．１ｍｍ、短辺寸法Ｗ１が１．３８１±０．１ｍｍの水晶片は、Ｌ１／ｔ＝５１、Ｗ１／ｔ＝３３であり、本発明で使用可能な水晶片の一例である。
また、前記水晶片の発振周波数が基本波で３８ＭＨｚとは、例えば、３８ＭＨｚ、３８．８８ＭＨｚなどの良く使用される周波数を含む、例えば、３８ＭＨｚ±３ＭＨｚの周波数帯のことである。
また、上記の閉じ込め係数とは、ｎ（Ｗｅ／βｚ・ｔｑ）√Δで決まる値である。ここで、ｎは水晶振動子の振動次数（例えば基本波であれば１）、Ｗｅは励振電極の水晶結晶軸のＺ′方向の寸法、βｚは水晶結晶軸のＺ′方向の異方性係数１．５３８、ｔｑは水晶片の厚みある。また、Δは、励振電極の質量／水晶の質量で決まる値であり、具体的には、（２ρｅ・ｔｅ／ρｑ・ｔｑ）で求まる値である。ここで、ρｑは水晶の密度、ｔｑは水晶の厚み、ρｅは励振電極の密度、ｔｅは励振電極の厚みである。 In carrying out the present invention, the crystal piece has the following characteristics: L1/t≧50, W1, where L1 is the dimension of the crystal in the X-axis direction, W1 is the dimension of the crystal in the Z'-axis direction, and t is the thickness. It is preferable to use a crystal piece that satisfies /t≧33. For example, a crystal piece with a long side dimension L1 of 2.1±0.1 mm and a short side dimension W1 of 1.381±0.1 mm has L1/t=51 and W1/t=33, and is used in the present invention. This is an example of a possible crystal piece.
Furthermore, when the oscillation frequency of the crystal piece is a fundamental wave of 38 MHz, it refers to a frequency band of, for example, 38 MHz±3 MHz, which includes frequently used frequencies such as 38 MHz and 38.88 MHz.
Further, the above-mentioned confinement coefficient is a value determined by n(We/βz·tq)√Δ. Here, n is the vibration order of the crystal oscillator (for example, 1 for the fundamental wave), We is the dimension in the Z' direction of the crystal axis of the excitation electrode, and βz is the anisotropy coefficient in the Z' direction of the crystal axis of the excitation electrode. 1.538, tq is the thickness of the crystal piece. Further, Δ is a value determined by the mass of the excitation electrode/mass of the crystal, and specifically, is a value determined by (2ρe·te/ρq·tq). Here, ρq is the density of the crystal, tq is the thickness of the crystal, ρe is the density of the excitation electrode, and te is the thickness of the excitation electrode.

なお、上記の発明において、長軸長さ／短軸長さ＝１．２６５±１０％とした理由は、ＡＴカット水晶片の異方性係数比（Ｘ軸方向：１．９４５、Ｚ′軸方向：１．５３８の比＝１．９４５／１．５３８≒１．２６５）と、その許容度±１０％とに基づく。なお、異方性係数については、例えば文献「弾性波デバイス技術（株オーム社２０１４年版）、ｐｐ。１８３－１８５」等に記載されているので、説明は省略する。
また、上記の各発明を実施するに当たり、パッケージとしては、外形寸法でいって長辺が３．２ｍｍ、短辺が２．５ｍｍのセラミック製のパッケージ、いわゆる３２２５サイズのセラミックパッケージが好ましい。ただし、長辺、短辺いずれもパッケージの一般的な公差である±０．２ｍｍは許容される。
また、第１励振電極及び第２励振電極の質量／水晶の質量の比を示した上記値は、それぞれの値に対し±０．１％は、本発明に含まれる。 In the above invention, the reason why the major axis length/minor axis length is set to 1.265±10% is because the anisotropy coefficient ratio of the AT-cut crystal piece (X-axis direction: 1.945, Z'-axis Direction: 1.538 ratio = 1.945/1.538≈1.265) and its tolerance ±10%. Note that the anisotropy coefficient is described in, for example, the document "Acoustic Wave Device Technology (Ohmsha Co., Ltd. 2014 edition), pp. 183-185", so the explanation will be omitted.
In carrying out each of the above inventions, the package is preferably a ceramic package having external dimensions of 3.2 mm on the long side and 2.5 mm on the short side, that is, a so-called 3225 size ceramic package. However, a general tolerance of ±0.2 mm for both the long and short sides of the package is allowed.
Further, the above values showing the ratio of the mass of the first excitation electrode and the second excitation electrode to the mass of the crystal are included in the present invention within ±0.1% of each value.

本発明の水晶振動子によれば、周波数が５０ＭＨｚ付近で、かつ、一様な厚みの第１励振電極と、外周付近に傾斜部を持つ第２励振電極とを有した水晶振動子において、不要振動を抑えることができると共に周波数調整の際の振動エネルギーの損失を防ぐことができる。 According to the crystal resonator of the present invention, in a crystal resonator having a frequency of around 50 MHz and having a first excitation electrode with a uniform thickness and a second excitation electrode having an inclined portion near the outer periphery, unnecessary Vibration can be suppressed and vibration energy loss during frequency adjustment can be prevented.

図１（Ａ）は実施形態の水晶振動子１０を説明する平面図、図１（Ｂ）は実施形態の水晶振動子１０を説明する断面図であって、図１（Ａ）のＩ－Ｉ線に沿う断面図である。FIG. 1(A) is a plan view for explaining the crystal resonator 10 of the embodiment, and FIG. 1(B) is a cross-sectional view for explaining the crystal resonator 10 of the embodiment. It is a sectional view along a line. 図２（Ａ）は実施形態の水晶振動子１０の励振電極における傾斜部を説明する断面図、図２（Ｂ）は楕円電極を説明する平面図である。FIG. 2(A) is a cross-sectional view illustrating the inclined portion of the excitation electrode of the crystal resonator 10 of the embodiment, and FIG. 2(B) is a plan view illustrating the elliptical electrode. 実施例１のシミュレーション結果を説明する図である。3 is a diagram illustrating simulation results of Example 1. FIG. 実施例２のシミュレーション結果を説明する図である。FIG. 7 is a diagram illustrating simulation results of Example 2.

以下、図面を参照してこの発明の実施形態について説明する。なお、説明に用いる各図はこれら発明を理解できる程度に概略的に示してあるにすぎない。また、説明に用いる各図において、同様な構成成分については同一の番号を付して示し、その説明を省略する場合もある。また、以下の実施形態中で述べる形状、寸法、材質等はこの発明の範囲内の好適例に過ぎない。従って、本発明が以下の実施形態のみに限定されるものではない。 Embodiments of the present invention will be described below with reference to the drawings. Note that the drawings used in the explanation are merely shown schematically to the extent that these inventions can be understood. Moreover, in each figure used for explanation, the same number is attached|subjected and shown about the same component, and the explanation may be abbreviate|omitted. Furthermore, the shapes, dimensions, materials, etc. described in the following embodiments are merely preferred examples within the scope of the present invention. Therefore, the present invention is not limited only to the following embodiments.

１．水晶振動子の構造
先ず、図１（Ａ）及び（Ｂ）を参照して実施形態の水晶振動子１０の構造について説明する。
実施形態の水晶振動子１０は、パッケージ１１、ＡＴカット水晶片１３、第１励振電極１５及び第２励振電極１７を備えている。
パッケージ１１は、この例の場合、セラミック製のパッケージであって、ＡＴ水晶片を実装する凹部１１ａを有したものである。凹部１１ａの周囲は土手部１１ｂとなっている。このセラミック製パッケージ１１では、蓋部材（図示を省略）を土手１１ｂ部に、シーム封止、ガラス封止、金錫封止等の任意好適な方法によって接合することによって、水晶片１１を封止できる。なお、後述するシミュレーションで用いた水晶片１３の大きさを考慮すると、パッケージ１１の外形寸法は、長辺Ｌ０が約３．２ｍｍ、短辺Ｗ０が約２．５ｍｍの、いわゆる３２２５サイズが良い。
ＡＴ水晶片１３は、平板かつ平面形状が矩形のもので、周波数に応じた厚みを有したものである。なお、ＡＴカット水晶片自体は公知のものなので、その説明を省略する。
このＡＴカット水晶片１１の一方の主面に、第１励振電極１５を設けてあり。他方の主面に、第２励振電極１７を設けてある。これら電極１５，１７は例えばクロム膜と金膜との積層膜で構成できる。
第１励振電極１５は、厚さが一様となっている。第２励振電極１７は、図１（Ｂ）に示したように、外周付近が、水晶片の中央側から縁に向かって厚さが減じている傾斜部１７ａとなっていて、傾斜部１７ａ以外は一様な厚みの主圧部１７ｂとなっている。第２励振電極１７の主厚部１７ｂの厚みは、第１励振電極１５の厚みより厚くなっている。
そして、この実施形態の水晶振動子１０は、水晶片１３の周波数に応じて、以下のような構造となっている。 1. Structure of Crystal Resonator First, the structure of the crystal resonator 10 of the embodiment will be described with reference to FIGS. 1(A) and (B).
The crystal resonator 10 of the embodiment includes a package 11, an AT-cut crystal piece 13, a first excitation electrode 15, and a second excitation electrode 17.
In this example, the package 11 is a ceramic package, and has a recess 11a in which an AT crystal piece is mounted. The periphery of the recessed portion 11a is a bank portion 11b. In this ceramic package 11, the crystal piece 11 is sealed by joining a lid member (not shown) to the bank 11b by any suitable method such as seam sealing, glass sealing, gold-tin sealing, etc. can. In addition, considering the size of the crystal piece 13 used in the simulation described later, the package 11 preferably has a so-called 3225 size, in which the long side L0 is about 3.2 mm and the short side W0 is about 2.5 mm.
The AT crystal piece 13 is a flat plate with a rectangular planar shape, and has a thickness depending on the frequency. Note that the AT-cut crystal piece itself is well known, so its explanation will be omitted.
A first excitation electrode 15 is provided on one main surface of this AT-cut crystal piece 11. A second excitation electrode 17 is provided on the other main surface. These electrodes 15 and 17 can be composed of, for example, a laminated film of a chromium film and a gold film.
The first excitation electrode 15 has a uniform thickness. As shown in FIG. 1(B), the second excitation electrode 17 has a sloped part 17a near the outer periphery where the thickness decreases from the center side toward the edge of the crystal blank, and other than the sloped part 17a. The main pressure portion 17b has a uniform thickness. The thickness of the main thick portion 17b of the second excitation electrode 17 is thicker than the thickness of the first excitation electrode 15.
The crystal resonator 10 of this embodiment has the following structure depending on the frequency of the crystal piece 13.

当該水晶片１３は、水晶のＸ軸方向を長辺とし、水晶のＺ′方向を短辺とし、発振周波数が基本波で３８ＭＨｚの水晶片となっている。
さらに、第１励振電極１５及び第２励振電極１７の質量／水晶片１３の質量の比を４．７％とし、第1励振電極及び第２励振電極による、水晶片の水晶Ｚ′軸方向の閉じ込め係数を、３．３～３．９としてある。
又は、第１励振電極１５及び第２励振電極１７の質量／水晶の質量の比を５．３％とし、第1励振電極１５及び第２励振電極１７による、水晶片の水晶Ｚ′軸方向の閉じ込め係数を、３．７～３．８としてある。
さらに、傾斜部１７の幅Ｗｋ（図２（Ａ）参照）を、水晶片１３で生じる屈曲モードの振動の波長λに対し１～２．５λの寸法としてある。
さらに、第１励振電極１５及び第２励振電極１７各々は、水晶片１３の長辺方向を長軸、水晶片１３の短辺方向を短軸とする楕円形状としてあり、かつ、長軸長さＬａ／短軸長さＷａ＝１．２６５±１０％としてある。
ここで、長軸長さＬａ、短軸長さＷａは、この例の場合は、傾斜部１７の中間点同士を結んだ長さと定義している（図２（Ｂ）参照）。
なお、閉じ込め係数と、長軸長さＬａ／短軸長さＷａ＝１．２６５±１０％とについては、上記の「課題を解決するための手段の項」にて説明したものである。 The crystal piece 13 has a long side in the X-axis direction of the crystal, a short side in the Z' direction of the crystal, and has an oscillation frequency of 38 MHz as a fundamental wave.
Furthermore, the ratio of the mass of the first excitation electrode 15 and the second excitation electrode 17 to the mass of the crystal blank 13 is set to 4.7%, and the crystal Z' axis direction of the crystal blank is The confinement coefficient is set to 3.3 to 3.9.
Alternatively, the ratio of the mass of the first excitation electrode 15 and the second excitation electrode 17 to the mass of the crystal is set to 5.3%, and the first excitation electrode 15 and the second excitation electrode 17 cause the crystal blank to move in the crystal Z' axis direction. The confinement factor is set to 3.7 to 3.8.
Further, the width Wk (see FIG. 2A) of the inclined portion 17 is set to a dimension of 1 to 2.5λ with respect to the wavelength λ of the vibration in the bending mode generated in the crystal piece 13.
Furthermore, each of the first excitation electrode 15 and the second excitation electrode 17 has an elliptical shape with a long axis in the direction of the long side of the crystal piece 13 and a short axis in the direction of the short side of the crystal piece 13, and has a long axis length. La/minor axis length Wa=1.265±10%.
Here, in this example, the major axis length La and the minor axis length Wa are defined as lengths connecting the midpoints of the inclined portions 17 (see FIG. 2(B)).
Note that the confinement coefficient and major axis length La/minor axis length Wa = 1.265±10% are explained in the above "Means for Solving the Problems" section.

２．シミュレーション及びその結果
上記の実施形態の水晶振動子１０について、以下に実施例１、実施例２として示す各種条件による有限要素法によるシミュレーションを行った。なお、これらのシミュレーションでは、図２（Ａ）に示したように、傾斜部１７ａが、第１部分１７ａａ、第２部分１７ａｂ及び第３部分１７ａｃの階段状の３つの部分からなる傾斜部を持つモデルを用いた。
また、傾斜部１７ａの幅Ｗｋを６９μｍとした。この６９μｍとは、３８ＭＨｚの水晶片で生じる屈曲モードの不要信号の波長λの１倍に相当する寸法である。 2. Simulation and Results The crystal resonator 10 of the above embodiment was subjected to a simulation using the finite element method under various conditions shown as Examples 1 and 2 below. In addition, in these simulations, as shown in FIG. 2(A), the slope portion 17a has a slope portion consisting of three step-shaped portions: a first portion 17aa, a second portion 17ab, and a third portion 17ac. A model was used.
Further, the width Wk of the inclined portion 17a was set to 69 μm. This 69 μm is a dimension corresponding to one time the wavelength λ of an unnecessary signal in a bending mode generated in a 38 MHz crystal piece.

なお、シミュレーションで用いた水晶片の大きさであるが、長辺寸法Ｌ１が２．１ｍｍ、短辺寸法Ｗ１が１．３８１ｍｍである。もちろん、水晶片の大きさはこれらの例に限られない。例えば、水晶片の長辺寸法Ｌ１、短辺寸法Ｗ１が上記より大きければ、厚みｔに対するＬ１／ｔ、Ｗ１／ｔ、すなわち辺比が水晶振動子の特性に有利になるので、水晶片は上記より大きくても良い。 In addition, regarding the size of the crystal piece used in the simulation, the long side dimension L1 is 2.1 mm, and the short side dimension W1 is 1.381 mm. Of course, the size of the crystal piece is not limited to these examples. For example, if the long side dimension L1 and short side dimension W1 of the crystal piece are larger than the above, L1/t and W1/t, that is, the side ratio with respect to the thickness t, will be advantageous for the characteristics of the crystal resonator, so the crystal piece will be It may be larger.

また、実施例１、実施例２各々のモデルの第１部分１７ａａの幅Ｗｋａ、第２部分１７ａｂの幅Ｗｋｂ及び第３部分１７ａｃの幅Ｗｋｃ（それぞれ図２（Ａ）参照）は、それぞれ、傾斜部の幅Ｗｋの３分の１の寸法とした。
第１部分１７ａａの厚さｔ１、第２部分１７ａｂの厚さｔ２及び第３部分１７ａｃの厚さｔ３（それぞれ図２（Ａ）参照）は、それぞれ、主厚部１７ｂの厚さｔの４分の１とした。
また、実施例１のモデルは、第２励振電極１７の主厚部１７ｂの厚さを１３５ｎｍとし、実施例２のモデルは、第２励振電極１７の主厚み部１７ｂの厚さを１５０ｎｍとした。
そして、実施例１、実施例２のいずれのモデルも、第１励振電極１５の厚さは、第２励振電極１７の主厚部１７ｂの厚さより３０ｎｍ薄くした。第１励振電極の膜厚及び第２励振用電極の膜厚を上記の値としたのは、電極の質量／水晶片の質量の比を、本願でいう４．７％や、５．３％等にするためである。なお、第１励振電極の膜厚を第２励振用電極の膜厚より３０ｎｍ薄くしたが、これは一例であり、薄くする程度はこれに限られない。第１励振電極が膜として成立する範囲までさらに薄くしても良い。ただし、周波数調整ができなくなる程度まで薄い場合は、本発明の範囲外である。 In addition, the width Wka of the first portion 17aa, the width Wkb of the second portion 17ab, and the width Wkc of the third portion 17ac (see FIG. 2(A), respectively) of the models of Example 1 and Example 2 are respectively inclined. The dimension is one-third of the width Wk of the section.
The thickness t1 of the first portion 17aa, the thickness t2 of the second portion 17ab, and the thickness t3 of the third portion 17ac (see FIG. 2A) are each a quarter of the thickness t of the main thick portion 17b. It was set as 1.
Further, in the model of Example 1, the thickness of the main thickness part 17b of the second excitation electrode 17 was 135 nm, and in the model of Example 2, the thickness of the main thickness part 17b of the second excitation electrode 17 was 150 nm. .
In both the models of Example 1 and Example 2, the thickness of the first excitation electrode 15 was made 30 nm thinner than the thickness of the main thick portion 17b of the second excitation electrode 17. The reason why the film thickness of the first excitation electrode and the film thickness of the second excitation electrode are set to the above values is that the ratio of the mass of the electrode/mass of the crystal blank is 4.7% or 5.3% in the present application. This is to make it equal. Although the film thickness of the first excitation electrode was made 30 nm thinner than the film thickness of the second excitation electrode, this is just an example, and the degree of thinning is not limited to this. The first excitation electrode may be further thinned to the extent that it can be formed as a film. However, if the thickness is so thin that frequency adjustment is impossible, it is outside the scope of the present invention.

上記の実施例１のシミュレーションモデルについて、表１に示したように励振電極の楕円形状の長軸及び短軸寸法を振ることで、閉じ込め係数が異なる５種類のモデルを構成し、それらモデルの第１励振電極１５の膜厚を減じた場合、すなわち水晶振動子の周波数調整によって第１励振電極１５がアルゴンイオンなどによって削られた場合の、当該水晶振動子での損失（１／Ｑ）を、有限要素法によって算出した。 Regarding the simulation model of Example 1 above, five types of models with different confinement coefficients were constructed by varying the long and short axis dimensions of the elliptical shape of the excitation electrode as shown in Table 1. When the film thickness of the first excitation electrode 15 is reduced, that is, when the first excitation electrode 15 is scraped by argon ions or the like due to frequency adjustment of the crystal resonator, the loss (1/Q) in the crystal resonator is calculated as follows: Calculated using the finite element method.

また、上記の実施例２のシミュレーションモデルについて、表２に示したように励振電極の楕円形状の長軸および短軸寸法を振ることで、閉じ込め係数が異なる５種類のモデルを構成し、それらモデルの第１励振電極１５の膜厚を減じた場合、すなわち水晶振動子の周波数調整によって第１励振電極１５がアルゴンイオンなどによって削られた場合の、当該水晶振動子での損失（１／Ｑ）を、有限要素法によって算出した。 Furthermore, regarding the simulation model of Example 2 above, five types of models with different confinement coefficients were constructed by varying the long and short axis dimensions of the elliptical shape of the excitation electrode as shown in Table 2. Loss (1/Q) in the crystal resonator when the film thickness of the first excitation electrode 15 is reduced, that is, when the first excitation electrode 15 is scraped by argon ions etc. due to frequency adjustment of the crystal resonator. was calculated using the finite element method.

Figure 0007362525000001
Figure 0007362525000001

Figure 0007362525000002
Figure 0007362525000002

図３は、表１に示した５種類の試料について、横軸に第１励振電極１５の周波数調整で減った膜厚（ｎｍ）をとり、縦軸にその際の水晶振動子の損失（１／Ｑ）をとって、両者の関係を示した図である。
図３、表１から、周波数が３８ＭＨｚの場合で、励振電極の質量／水晶片の質量の比を４．７％とした場合、短軸長Ｗ２を１．０１７～１．０９７ｍｍすなわち閉じ込め係数を３．５～３．８とすると、第１励振電極１５の膜厚を周波数調整によって減じても、損失は小さく抑えられることが分かる。 In FIG. 3, for the five types of samples shown in Table 1, the horizontal axis shows the film thickness (nm) reduced by adjusting the frequency of the first excitation electrode 15, and the vertical axis shows the loss (1 nm) of the crystal resonator at that time. /Q) and shows the relationship between the two.
From Fig. 3 and Table 1, when the frequency is 38 MHz and the ratio of excitation electrode mass/crystal blank mass is 4.7%, the short axis length W2 is 1.017 to 1.097 mm, that is, the confinement coefficient is It can be seen that when the value is 3.5 to 3.8, the loss can be kept small even if the film thickness of the first excitation electrode 15 is reduced by frequency adjustment.

図４は、表２に示した５種類の試料について、横軸に第１励振電極１５の周波数調整で減った膜厚（ｎｍ）をとり、縦軸にその際の水晶振動子の損失（１／Ｑ）をとって、両者の関係を示した図である。
図４、表２から、周波数が３８ＭＨｚの場合で、励振電極の質量／水晶片の質量の比を５．３％とした場合、短軸長Ｗ２を１．０１７～１．０５７ｍｍすなわち閉じ込め係数を３．７～３．８とすると、第１励振電極１５の膜厚を周波数調整によって減じても、損失は小さく抑えられることが分かる。 In FIG. 4, for the five types of samples shown in Table 2, the horizontal axis shows the film thickness (nm) reduced by adjusting the frequency of the first excitation electrode 15, and the vertical axis shows the loss (1 nm) of the crystal resonator at that time. /Q) and shows the relationship between the two.
From Fig. 4 and Table 2, when the frequency is 38 MHz and the ratio of excitation electrode mass/crystal blank mass is 5.3%, the short axis length W2 is 1.017 to 1.057 mm, that is, the confinement coefficient is It can be seen that when the value is 3.7 to 3.8, the loss can be kept small even if the film thickness of the first excitation electrode 15 is reduced by frequency adjustment.

以上、本発明の実施形態について説明したが、本発明は上記の例に限られない。例えば、上記実施形態における傾斜部の段差は４段であるが、段差は４段に限らず、これよりも多くても少なくとも良い。また、上記の実施形態は様々に組み合わせて実施されても良い。
また、シミュレーションによる実施例として、周波数が３８ＭＨｚ帯で長辺寸法Ｌ１が２．１ｍｍ、短辺寸法Ｗ１が１．３８１ｍｍの水晶片の例を挙げたが、パッケージ寸法がいわゆる３２２５サイズに収納できる対応として、長辺寸法Ｌ１が２～２．４ｍｍ、短辺寸法Ｗ１が１．２～１．５ｍｍまでの範囲の水晶片においても同様の効果を確認している。 Although the embodiments of the present invention have been described above, the present invention is not limited to the above examples. For example, although the slope portion has four steps in the above embodiment, the number of steps is not limited to four steps, and may be more than four steps. Furthermore, the above embodiments may be implemented in various combinations.
In addition, as an example based on simulation, an example of a crystal piece with a frequency of 38 MHz and a long side dimension L1 of 2.1 mm and a short side dimension W1 of 1.381 mm was given, but the package size can be accommodated in a so-called 3225 size. Similar effects have been confirmed for crystal pieces having a long side dimension L1 of 2 to 2.4 mm and a short side dimension W1 of 1.2 to 1.5 mm.

１０：実施形態の水晶振動子 １１：パッケージ
１３：ＡＴカット水晶片 １５：第１励振電極
１７：第２励振電極 １７ａ：傾斜部
１７ａａ：第１部分 １７ａｂ：第２部分
１７ａｃ：第３部分 １７ｂ：主圧部
10: Crystal resonator of embodiment 11: Package 13: AT-cut crystal piece 15: First excitation electrode 17: Second excitation electrode 17a: Inclined portion 17aa: First portion 17ab: Second portion 17ac: Third portion 17b: Main pressure section

Claims (3)

パッケージと、該パッケージに内蔵されていて平板かつ平面形状が矩形のＡＴカットの水晶片と、該水晶片の主面の一方の面に設けられ厚さが一様な第１励振電極と、前記主面の他方の面に設けられ外周付近が傾斜部となっていて該傾斜部以外は一様な厚みの主厚部となっている第２励振電極と、を備え、前記主厚部の厚みが前記第１励振電極の厚みより厚い水晶振動子において、
前記水晶片は、水晶のＸ軸方向を長辺とし、水晶のＺ′方向を短辺とし、発振周波数が基本波で３８ＭＨｚの水晶片であり、
前記第１励振電極及び第２励振電極の質量／水晶の質量を４．７％とし、前記第1励振電極及び第2励振電極による、前記水晶片の水晶Ｚ′軸方向の閉じ込め係数を、３．５～３．８としてあり、
前記傾斜部の幅を、前記水晶片で生じる屈曲モードの振動の波長λに対し１～２．５λの寸法としてあり、
前記第１励振電極及び第２励振電極各々は、前記水晶片の長辺方向を長軸、前記水晶片の短辺方向を短軸とする楕円形状としてあり、かつ、長軸長さ／短軸長さ＝１．２６５±１０％としてあること
を特徴とする水晶振動子。 a package, an AT-cut crystal piece built in the package and having a flat plate and a rectangular planar shape; a first excitation electrode provided on one main surface of the crystal piece and having a uniform thickness; a second excitation electrode provided on the other surface of the main surface and having an inclined portion near the outer periphery and a main thick portion having a uniform thickness except for the inclined portion; is thicker than the first excitation electrode,
The crystal piece has a long side in the X-axis direction of the crystal, a short side in the Z′ direction of the crystal, and has an oscillation frequency of 38 MHz as a fundamental wave,
The mass of the first excitation electrode and the second excitation electrode/mass of the crystal is 4.7%, and the confinement coefficient of the crystal piece in the crystal Z' axis direction by the first excitation electrode and the second excitation electrode is 3. There are .5 to 3.8,
The width of the inclined portion is set to a dimension of 1 to 2.5λ with respect to the wavelength λ of vibration in a bending mode generated in the crystal piece,
Each of the first excitation electrode and the second excitation electrode has an elliptical shape with a long axis in the direction of the long side of the crystal piece and a short axis in the direction of the short side of the crystal piece, and has a long axis length/short axis. A crystal resonator characterized in that the length is 1.265±10%. パッケージと、該パッケージに内蔵されていて平板かつ平面形状が矩形のＡＴカットの水晶片と、該水晶片の主面の一方の面に設けられ厚さが一様な第１励振電極と、前記主面の他方の面に設けられ外周付近が傾斜部となっていて該傾斜部以外は一様な厚みの主厚部となっている第２励振電極と、を備え、前記主厚部の厚みが前記第１励振電極の厚みより厚い水晶振動子において、
前記水晶片は、水晶のＸ軸方向を長辺とし、水晶のＺ′方向を短辺とし、発振周波数が基本波で３８ＭＨｚの水晶片であり、
前記第１励振電極及び第２励振電極の質量／水晶の質量を５．３％とし、前記第1励振電極及び第2励振電極による、前記水晶片の水晶Ｚ′軸方向の閉じ込め係数を、３．７～３．８としてあり、
前記傾斜部の幅を、前記水晶片で生じる屈曲モードの振動の波長λに対し１～２．５λの寸法としてあり、
前記第１励振電極及び第２励振電極各々は、前記水晶片の長辺方向を長軸、前記水晶片の短辺方向を短軸とする楕円形状としてあり、かつ、長軸長さ／短軸長さ＝１．２６５±１０％としてあること
を特徴とする水晶振動子。 a package, an AT-cut crystal piece built in the package and having a flat plate and a rectangular planar shape; a first excitation electrode provided on one main surface of the crystal piece and having a uniform thickness; a second excitation electrode provided on the other surface of the main surface and having an inclined portion near the outer periphery and a main thick portion having a uniform thickness except for the inclined portion; is thicker than the first excitation electrode,
The crystal piece has a long side in the X-axis direction of the crystal, a short side in the Z′ direction of the crystal, and has an oscillation frequency of 38 MHz as a fundamental wave,
The mass of the first excitation electrode and the second excitation electrode/the mass of the crystal is 5.3%, and the confinement coefficient of the crystal piece in the crystal Z' axis direction by the first excitation electrode and the second excitation electrode is 3. There are .7 to 3.8,
The width of the inclined portion is set to a dimension of 1 to 2.5λ with respect to the wavelength λ of vibration in a bending mode generated in the crystal piece,
Each of the first excitation electrode and the second excitation electrode has an elliptical shape with a long axis in the direction of the long side of the crystal piece and a short axis in the direction of the short side of the crystal piece, and has a long axis length/short axis. A crystal resonator characterized in that the length is 1.265±10%. 前記水晶片は、長辺寸法が２～２．４ｍｍ、短辺寸法Ｗ１が１．２～１．５ｍｍから選ばれる大きさであり、前記パッケージは外形の長辺寸法が３．２±０．２ｍｍ及び短辺寸法が２．５±０．２ｍｍであることを特徴とする請求項１又は２に記載の水晶振動子。

以 上 The crystal piece has a long side dimension W1 of 2 to 2.4 mm and a short side dimension W1 of 1.2 to 1.5 mm, and the package has an external long side dimension of 3.2±0. 3. The crystal resonator according to claim 1, wherein the crystal resonator has a length of 2 mm and a short side dimension of 2.5±0.2 mm.

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007214941A (en) 2006-02-10 2007-08-23 Epson Toyocom Corp Piezoelectric vibration chip and piezoelectric device
JP2018033122A (en) 2016-08-22 2018-03-01 日本電波工業株式会社 Crystal oscillator
JP2018098592A (en) 2016-12-12 2018-06-21 日本電波工業株式会社 Piezoelectric vibration piece and piezoelectric device
JP2018117198A (en) 2017-01-17 2018-07-26 日本電波工業株式会社 Piezoelectric vibration piece and piezoelectric device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2007214941A (en) 2006-02-10 2007-08-23 Epson Toyocom Corp Piezoelectric vibration chip and piezoelectric device
JP2018033122A (en) 2016-08-22 2018-03-01 日本電波工業株式会社 Crystal oscillator
JP2018098592A (en) 2016-12-12 2018-06-21 日本電波工業株式会社 Piezoelectric vibration piece and piezoelectric device
JP2018117198A (en) 2017-01-17 2018-07-26 日本電波工業株式会社 Piezoelectric vibration piece and piezoelectric device

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