JP2021048651A - Crystal oscillator - Google Patents

Abstract

To provide a new excitation electrode structure that can improve the characteristics of a crystal oscillator that vibrates in a thickness slip mode.SOLUTION: A crystal oscillator includes excitation electrodes 13a and 13b on the front and back of a crystal piece 11. In the crystal piece in a Y' axis direction of the crystal is a thickness, and the X'-Z' plane of the crystal is a main surface. The excitation electrode provided on a plus Y' plane is defined as a first excitation electrode 13a, and the excitation electrode provided on a minus Y' plane is defined as a second excitation electrode 13b. The second excitation electrode moves the first excitation electrode along the X' axis of the crystal in the plus X' direction by a distance dx given by T*tan α with respect to the first excitation electrode (1), and moves the first excitation electrode along the Z' axis of the crystal in the minus Z' direction by a distance dy given by T*tan β (2), and is provided at a location where the state moved in the (1) and (2) cases is projected onto the minus Y' plane. Here, α and β are angles in a predetermined range according to the cut type of the crystal piece in consideration of a difference between a direction of the phase velocity direction and the power flow direction of the elastic wave in the crystal piece.SELECTED DRAWING: Figure 1

Description

The present invention relates to a crystal oscillator that vibrates in a thickness slip mode.

As a crystal oscillator that vibrates in the thickness slip mode, an AT-cut crystal oscillator and a so-called double-rotation crystal oscillator represented by an SC-cut crystal oscillator are known. Since these crystal units are electronic components indispensable for the advanced information and communication society, efforts are being made to improve their characteristics from various aspects.

As a method for improving the characteristics, there is a method focusing on the excitation electrodes provided on both sides of the crystal piece. For example, Patent Document 1 describes a structure in which excitation electrodes provided on both main surfaces of an AT-cut quartz piece are relatively displaced by a predetermined amount in the X-axis direction of the quartz for the purpose of controlling frequency temperature characteristics. Further, in Patent Document 2, in a crystal oscillator having an SMD structure in which one end of an AT-cut crystal piece is supported by a conductive adhesive, the excitation electrode on the lower surface side of the excitation electrodes provided on the front and back surfaces of the crystal piece is described. For the purpose of reducing the influence of the conductive adhesive, a structure is described in which the excitation electrode on the upper surface side is shifted to a position farther from the conductive adhesive than the excitation electrode.

WO98 / 47226 Japanese Unexamined Patent Publication No. 2014-42084

However, a method for improving the characteristics of a crystal unit focusing on an excitation electrode still has potential.
This application was made in view of these points, and therefore, the purpose of this application is a crystal having a novel excitation electrode structure capable of improving the characteristics of a crystal oscillator vibrating in a thickness slip mode. The purpose is to provide an oscillator.

In order to achieve this object, the crystal oscillator of the present invention is a crystal oscillator having excitation electrodes on the front and back surfaces of the crystal piece and vibrating in the thickness sliding mode, and the crystal piece is in the Y'axis direction of the crystal. Is a crystal piece whose main surface is the X'-Z'plane of the crystal, and the excitation electrodes provided on the front and back surfaces have the same planar shape and the same size, and are on the plus Y'plane. When the excitation electrode to be provided is defined as the first excitation electrode and the excitation electrode provided on the minus Y'plane is defined as the second excitation electrode, the second excitation electrode satisfies the following relationship with the first excitation electrode. It is a crystal oscillator characterized by being provided at a position.
(1) The first excitation electrode is moved along the X'axis of the crystal in the plus X'direction by the distance dx given by T · tan α (see FIG. 1).
(2) The first excitation electrode is moved along the Z'axis of the crystal in the minus Z'direction by the distance dy given by T · tan β (see FIG. 1).
(3) The position where the state moved in (1) and (2) above is projected onto the minus Y'plane.

However, T is the thickness of the quartz piece, and α and β are the direction of the phase velocity of the elastic wave in the quartz piece, that is, the thickness direction of the quartz piece due to the fact that the quartz is an anisotropic material. Considering that the direction of energy velocity is different from the direction of power flow, the angle is in a predetermined range according to the cut type (M-SC cut, SC cut, IT cut, etc.) of the crystal piece. Moreover, α is an angle with the Z'axis of the crystal piece as the rotation axis (see FIG. 1 (B)), and β is an angle with the X'axis of the crystal piece as the rotation axis (FIG. 1 (Fig. 1)). See C)).

In the following explanation, the positive and negative angles α and β are considered for each of the plus Z'plane and the plus X'plane of the crystal piece (FIGS. 1 (B) and 1 (C)), and counterclockwise is plus and clockwise. It is negative. These pluses and minuses determine the displacement direction of the front and back excitation electrodes. Further, the angles α and β are angles in a predetermined range for each of the C mode and the B mode when the crystal piece is a double-rotating crystal oscillator such as SC cut.

Further, the above-mentioned X'axis and Z'axis are axes generated by rotating the crystal piece at a cutting angle φ or θ with respect to the X axis and the Y axis, which are the crystal axes of the crystal. That is, in the case of a crystal piece that rotates only once, for example, an AT-cut crystal piece, it is the axis after the one rotation, and twice, for example, an SC cut. In the case of a quartz piece in which the rotations φ and θ of are performed, it is the shaft after the two rotations. However, the dash "'" does not mean the number of rotations. That is, even when the AT-cut crystal piece rotates only around the X-axis and does not rotate around the Z-axis, it is indicated by X', Y', and Z'with a dash symbol "'". There is. In the case of the double-rotated crystal piece, it is also shown with one dash symbol "'".

Further, the present invention is preferably applied to a flat quartz piece, that is, a quartz piece having a substantially uniform thickness over the entire quartz piece. However, it can also be applied to plano-convex-shaped quartz pieces. When the present invention is applied to a plano-convex type crystal piece, the thickness T of the crystal piece is the thickness of the portion where the thickness of the crystal piece is the thickest, and the above (1), (2), (3). Apply the conditions of. When the present invention is applied to a plano-convex type quartz piece, the curved surface of one side of the quartz piece is affected as compared with the case where the present invention is applied to a flat plate, but the curvature of this curved surface is sufficient as compared with the thickness T of the quartz piece. Since it is large, the effect of the present invention can be obtained even if the above conditions (1) to (3) are applied as they are.
In carrying out the present invention, the planar shape of the excitation electrode can be arbitrary. However, preferably, the planar shape of the excitation electrode is elliptical. Moreover, it is preferable that the elliptical ratio of the elliptical electrode is set within a predetermined range and the elliptical electrode is rotated in-plane with respect to the crystal piece within a predetermined range according to the cut type of the crystal piece. However, the ellipse referred to in this preferred example is not only a true ellipse in which the sum of the distances from two fixed points on one plane is constant, but also a shape slightly deformed from the true ellipse of the present invention. Also includes a substantially ellipse showing the same effect as. For example, an ellipse in the present invention includes an ellipse in which a major axis and a minor axis can be defined even if the ellipse is slightly deformed from the true ellipse.
Further, in carrying out the present invention, the thickness of the excitation electrode is reduced toward the end of the excitation electrode at at least one edge of the excitation electrode provided on the front and back surfaces of the quartz piece, and the thickness of the excitation electrode is reduced to a predetermined size ( An inclined portion (inclination width) can be provided.

According to the crystal oscillator of the present invention, the direction of the phase velocity of the elastic wave in the quartz piece, that is, the thickness direction of the quartz piece and the power flow direction, which is the direction of the energy velocity, due to the fact that the quartz is an anisotropic material. The excitation electrodes on the front and back of the crystal piece are shifted in consideration of the difference. Therefore, it is possible to realize a crystal oscillator that vibrates with the same displacement distribution at the edges of the excitation electrodes on the front and back surfaces. Therefore, as compared with the case where the displacement distributions at the edges of the excitation electrodes on the front and back are different, it is easier to suppress the occurrence of unnecessary modes (spurious) at the edges, so that loss during vibration is less likely to occur. In other words, according to the crystal oscillator of the present invention, the excitation electrodes are arranged in a region having vibration displacement distribution (vibration energy) on each of the front and back surfaces of the crystal piece without waste, so that the characteristics of the crystal oscillator are improved. Can be planned. Therefore, according to the present invention, it is possible to provide a novel excitation electrode structure capable of improving the characteristics of a crystal oscillator vibrating in a thickness slip mode.

(A), (B), and (C) are diagrams for explaining the configuration of the crystal unit of the first embodiment. It is a figure explaining the simulation condition with the crystal oscillator of 1st Embodiment. (A) and (B) are diagrams for explaining the simulation result of the crystal oscillator of the first embodiment. (A) and (B) are views following FIG. 3 for explaining the simulation results of the crystal oscillator of the first embodiment. (A) and (B) are views following FIG. 4 for explaining the simulation results of the crystal oscillator of the first embodiment. It is a figure which showed the main point of the simulation result of the crystal oscillator of 1st Embodiment. (A) and (B) are diagrams for explaining the configuration of the crystal oscillator of the second embodiment. (A), (B), and (C) are diagrams for explaining the simulation results of the elliptic ratio of the elliptical electrodes. (A), (B), and (C) are views following FIG. 8 for explaining the simulation results of the elliptical ratio of the elliptical electrodes. (A), (B), and (C) are views following FIG. 9 for explaining the simulation results of the elliptical ratio of the elliptical electrodes. It is a figure which showed the main point of the simulation result of an ellipse ratio. (A), (B), and (C) are diagrams for explaining the simulation result of the in-plane rotation angle δ of the excitation electrode. (A), (B), and (C) are views following FIG. 12, which explains the simulation result of the in-plane rotation angle δ of the excitation electrode. (A), (B), and (C) are views following FIG. 13 for explaining the simulation result of the in-plane rotation angle δ of the excitation electrode. It is a figure which showed the main point of the simulation result of the in-plane rotation angle δ. (A) and (B) are diagrams showing a structural example of an actual crystal unit of the present invention. It is a figure explaining the structure of the crystal oscillator of the 3rd Embodiment. It is a figure explaining the effect of the crystal oscillator of the 3rd Embodiment. It is a figure explaining the structure of the crystal oscillator of 4th Embodiment. It is a figure explaining the effect of the crystal oscillator of 4th Embodiment. It is a figure explaining the effect of the crystal oscillator of the 5th embodiment.

Hereinafter, embodiments of the crystal unit of the present invention will be described with reference to the drawings. It should be noted that the figures used in the description are merely schematically shown to the extent that the present invention can be understood. Further, in each of the figures used for explanation, similar constituent components may be indicated with the same number, and the description thereof may be omitted. Further, the shapes, dimensions, materials and the like described in the following description are merely preferable examples within the scope of the present invention. Therefore, the present invention is not limited to the following embodiments.

1. 1. First Embodiment 1-1. Structure of the Crystal Oscillator of the First Embodiment FIGS. 1 (A) to 1 (C) are explanatory views of the crystal oscillator of the first embodiment, paying particular attention to the crystal piece 11. Specifically, FIG. 1 (A) is a plan view of the crystal piece 11, FIG. 1 (B) is a sectional view of the crystal piece 11 along the line PP in FIG. 1 (A), and FIG. 1 (C) is a sectional view of the crystal piece 11. It is sectional drawing of the crystal piece 11 along the QQ line in FIG. 1 (A).

The crystal oscillator of the first embodiment includes a crystal piece 11 and excitation electrodes 13a and 13b provided on the front and back surfaces thereof. The excitation electrodes 13a are arranged so that the displacement distribution at the edge of the excitation electrode 13a on one surface of the main surface of the crystal piece 11 is the same as the displacement distribution at the edge of the excitation electrode 13b on the other surface. , 13b are provided on the front and back sides of the crystal piece 11.
The crystal piece 11 is various crystal pieces that vibrate in the thickness slip mode. Specific examples thereof include an AT-cut crystal piece, an SC-cut crystal piece called a so-called double-rotating oscillator, an M-SC-cut crystal piece, and an IT-cut crystal piece. The detailed simulations and the like in the following explanation are performed by the M-SC cut crystal piece. The M-SC cut means that the rough crystal is rotated with the Z axis of the crystal as the rotation axis at a predetermined angle φ within the range of 24 ° ± 1 °, and the X'axis generated here is the rotation axis of 34 ° ± 1. It is a crystal piece that is cut out by rotating at a predetermined angle θ in the range of °. Therefore, the crystal piece 11 is a kind of crystal piece having a thickness in the Y'axis direction of the crystal and having the X'-Z'plane of the crystal as the main surface.

Next, a specific configuration of the excitation electrodes 13a and 13b will be described. The excitation electrodes 13a and 13b have the same planar shape and the same size. Of course, the same planar shape and the same size may be substantially the same, and there may be some differences due to manufacturing accuracy and the like. When the excitation electrode provided on the plus Y'plane of the crystal piece 11 is defined as the first excitation electrode 13a and the excitation electrode provided on the minus Y'plane of the crystal piece 11 is defined as the second excitation electrode 13b, the second excitation electrode is defined. The excitation electrode 13b is provided at a position that satisfies the following relationships (1), (2), and (3) with respect to the first excitation electrode 13a. In addition, T in the following formula is the thickness of the crystal piece. Further, the angles α and β are predetermined angles described later.
(1) The first excitation electrode 13a is moved along the X'axis of the crystal in the plus X'direction by the distance dx given by T · tan α (see FIG. 1 (B)).
(2) The first excitation electrode 13a is moved along the Z'axis of the crystal in the minus Z'direction by the distance dy given by T · tan β (see FIG. 1 (C)).
(3) The position where the moved state in (1) and (2) above is projected onto the minus Y'plane (see FIG. 1 (A)).
Therefore, as shown in FIG. 1A, the second excitation electrode 13b seen from the first excitation electrode 13a is in the plus X'direction of the back surface of the crystal piece 11 with respect to the first excitation electrode 13a. Moreover, it is provided at a position deviated by a predetermined distance in the minus Z'direction.

By setting the angles α and β shown in the above equations (1) and (2) to predetermined angles, the displacement distribution at the edge of the first excitation electrode 13a becomes the displacement distribution at the edge of the second excitation electrode 13b. It was found by the simulation based on the finite element method by the inventor of this application that the first and second excitation electrodes can be arranged in the same positional relationship as above. However, it was found that the angles α and β have appropriate values for each cut type of the crystal piece and for each vibration mode to be used. The results are shown in Table 1 below.

1-2. Examples of Examination of Angles α and β of the First Embodiment Table 1 shows predetermined angles α and β and their allowable ranges. Therefore, next, a simulation example regarding the point that the angles α and β should be in a predetermined range will be described. Since the crystal is an anisotropic material, it is known that the direction of the phase velocity of the elastic wave in the medium and the direction of the energy velocity (power flow direction) are different in the crystal oscillator vibrating in the thickness slip mode. ing. Therefore, it is considered that the vibration displacement of the front and back of the crystal piece when the crystal oscillator vibrates does not become the same position on the front and back. The inventor of this application considered that it is not preferable to have excitation electrodes of the same shape and size facing each other on the front and back surfaces of the crystal piece in such a state.

Therefore, as shown in FIG. 2, as a simulation model by the finite element method, a model in which the first and second excitation electrodes 13a and 13b having the same planar shape and the same size are provided on the front and back surfaces of the crystal piece 11 is set. Further, the positions of the edges of the first excitation electrode 13a and the second excitation electrode 13b, that is, the vibration displacements at various points along the edges of the excitation electrodes were calculated by the finite element method. Further, the vibration displacements when the positions of the second excitation electrodes 13b were shifted with respect to the first excitation electrodes 13a were calculated. As shown in FIG. 2, each position of the edge of the excitation electrode is a position on the edge specified by the angle γ, that is, a position of 0 °, a position of 180 °, and so on.

FIGS. 3, 4 and 5 show the displacement distribution obtained by the above simulation. However, these figures are the simulation results when the M-SC cut crystal piece is used as the crystal piece and the vibration is performed in the C mode. In FIGS. 3 to 5, the horizontal axis is the position of the edge of the excitation electrode specified by the above angle γ, and the vertical axis is the displacement when the crystal piece of the model vibrates. The displacement is shown as a value normalized by the maximum displacement. Further, in FIGS. 3 to 5, the characteristic diagram plotted with ◯ is the displacement distribution of the edge of the first excitation electrode 13a, and the characteristic diagram plotted with + is the displacement distribution of the edge of the second excitation electrode 13b. .. However, from the results of various simulations by the inventor, it has been found that the angle β in the case of M-SC cut is preferably around 0.2 °, so the results shown in FIGS. 3 to 5 show. , When the angle β is different from 35 °, 30 °, 25 °, 20 °, 15 ° 0 ° under the condition that the angle β is fixed at 0.2 °, the first and second excitation electrodes The displacement distribution of the edge is shown.
Further, FIG. 6 is a diagram summarizing the main points of the results of FIGS. 3, 4, and 5. Specifically, for each of the above six types of simulations with different angles α, the difference between the displacement distribution at the edge of the first excitation electrode and the displacement distribution at the edge of the second excitation electrode is determined at the same position on the edge. The difference in displacement at is shown as an integrated value integrated over the entire edge. Therefore, the smaller the integrated value, the higher the degree of agreement of the displacement distributions at the edges of the front and back excitation electrodes.

Comparing FIGS. 3 to 5, and as is clear from FIG. 6, the displacement distribution at the edge of the first excitation electrode 13a and the displacement distribution at the edge of the second excitation electrode are at an angle α. It can be seen that it changes when is changed. When the angle α = 25 ° (see FIG. 4A), the displacement distribution at the edge of the first excitation electrode 13a and the displacement distribution at the edge of the second excitation electrode are most consistent. I understand. From the results of many simulations carried out by the inventor, including this simulation, in the case of M-SC cut and in C mode, the first and second angles are around α = 25 ° and around β = 0.2 °. It was found that the displacement distributions at the edges of the second excitation electrode were the most consistent. However, as is particularly clear from FIG. 6, the angle α is preferably -20 to -30 °, that is, α = 25 ± 5 °, and more preferably α = 25, considering the effect of improving the characteristics of the vibrator. It can be seen that ± 3 ° is good. It was also found that β is preferably β = 0 ± 5 °, more preferably β = 0 ± 3 °. Further, from the same simulation result, in the case of M-SC cut and in the case of B mode, the angles α and β are preferably α = -6 ± 5 ° and β = -17 ± 5 °, more preferably. , Α = -6 ± 3 ° and β = -6 ± 3 ° were found to be good.

As other crystal pieces, SC cut, IT cut, and AT cut were also simulated in the same manner as described above, and preferable values of the angles α and β of these crystal pieces were calculated. The results are shown in Table 2 below together with the results of the above M-SC cut.

また、ＳＣカット、ＩＴカット、ＡＴカット各々の角度α、角度βの許容範囲は、シミュレーション結果から、上記の表１に示した通り、各々所定値±５°が良く、より好ましくは所定値±３°が良いことが判明した。

Further, as shown in Table 1 above, the permissible range of the angles α and β of each of the SC cut, IT cut, and AT cut is preferably a predetermined value ± 5 °, more preferably a predetermined value ±, as shown in Table 1 above. It turned out that 3 ° is good.

2. Second Embodiment In the first embodiment, the displacement distribution at the edge of the front and back excitation electrodes is obtained by shifting the front and back excitation electrodes in the predetermined positional relationship shown in (1) to (3) above. Could be the same or similar. However, according to a further study by the inventor, the excitation electrodes on the front and back sides are shifted by a predetermined positional relationship, the planar shape of the excitation electrode is elliptical, and the ellipse of the elliptical electrode is determined according to the cut type of the crystal piece. It has been found that it is preferable to set the ratio within a predetermined range and to provide the elliptical electrode by in-plane rotation within a predetermined range with respect to the crystal piece. By doing so, although the details will be described later, it has been found that the displacement at the edge of the excitation electrode tends to be the same or close to each other at each part of the edge. That is, it was found that the displacement distribution at the edge of the excitation electrode tends to be flat. This second embodiment is an example.

7 (A) and 7 (B) are explanatory views thereof. In the crystal oscillator of the second embodiment, each of the first excitation electrode 13a and the second excitation electrode 13b provided on the crystal piece 11 has an elliptical planar shape and a predetermined elliptical ratio, and is a crystal. It is rotated in-plane within a predetermined angle range with respect to one piece, and is shifted by a predetermined relationship (1) to (3) as in the first embodiment.
Here, the ellipse ratio and the in-plane rotation angle are defined as follows. The dimension of the crystal piece of the elliptical excitation electrode along the X'axis is defined as a, the dimension along the Z'axis is defined as b (FIG. 7 (A)), and the elliptical ratio is defined as a / b. The in-plane rotation angle of the elliptical excitation electrode with respect to the crystal piece is defined as the angle δ of the crystal piece with respect to the X'axis (FIG. 7 (B)). However, as shown in FIG. 7B, this angle δ is defined as a plus Y'axis, a counterclockwise rotation as a plus, and a clockwise rotation as a minus, with the Y'axis as the rotation axis. To do.
Displacement distribution at the edges of the first and second excitation electrodes 13a and 13b using the finite element method by setting a model in which the elliptic ratio a / b and the in-plane rotation angle δ defined in this way are variously changed. Was examined as follows.

2-1. Examination of elliptic ratio First, the preferable range of the elliptic ratio of the excitation electrode was examined as follows. In the simulation, the crystal piece is M-SC cut, the vibration mode is the fundamental wave mode of C mode, and the angles α and β that determine the positional relationship between the first excitation electrode 13a and the second excitation electrode 13b. Α = 25.5 ° and β = 0.2 °, the in-plane rotation angle δ of the excitation electrode with respect to the crystal piece was set to δ = −9 °, and the elliptic ratio was variously changed. The simulated elliptical ratios are 1.584, 1.518, 1.452, 1.386, 1.32, 1.254, 1.188, 1.122, 1.056, and the elliptical ratios are 1. When considered on the basis of 32, each ellipse ratio corresponds to a 20% increase, a 15% increase, a 10% increase, a 5% increase, a 5% decrease, a 10% decrease, a 15% decrease, and a 20% decrease.

FIGS. 8, 9 and 10 show the displacement distribution at the edge of the excitation electrode obtained by the above simulation of the elliptic ratio. In FIGS. 8 to 10, the horizontal axis is the position of the edge of the excitation electrode specified by the angle γ as in the first embodiment, and the vertical axis is the displacement when the crystal piece of the model vibrates. The displacement is shown as a value normalized by the maximum displacement as in the first embodiment. Further, in FIGS. 8 to 10, the characteristic diagram plotted with ◯ is the displacement distribution of the edge of the first excitation electrode 13a, and the characteristic diagram plotted with + is the displacement distribution of the edge of the second excitation electrode 13b. ..
Further, FIG. 11 is a diagram summarizing the main points of the results of FIGS. 8, 9, and 10. Specifically, for each of the above nine types of simulations with different elliptic ratios, the difference between the displacement distribution at the edge of the first excitation electrode and the displacement distribution at the edge of the second excitation electrode is shown on the front and back. Regardless, it is shown by the difference between the maximum value and the minimum value in all displacements. The smaller this difference is, the flatter the displacement distribution at the edges of the front and back excitation electrodes is.

The first thing that is clear from FIGS. 8 to 10 is the edge of each of the first excitation electrode 13a and the second excitation electrode 13b due to the effect of the first embodiment in which the front and back excitation electrodes are displaced by a predetermined positional relationship. The displacement distribution in is similar even if the elliptic ratio is changed, that is, both show a substantially sinusoidal displacement distribution. However, comparing FIGS. 8 to 10 and, as is particularly clear from FIG. 11, the flatness of the displacement distributions at the edges of the first and second excitation electrodes 13a and 13b changes the elliptic ratio. It can be seen that it changes with. That is, it can be seen that the displacement distribution becomes the flattest when the ellipse ratio is 1.32 (see FIG. 9B), and gradually becomes sinusoidal and begins to be uneven when the ellipse ratio increases or decreases from 1.32. It can be said that an excitation electrode having a predetermined elliptical ratio is useful because it is considered that a flat displacement distribution at the edge of the excitation electrode is preferable for suppressing unnecessary vibration as compared with the case where it is not.

According to the simulation results when the ellipse ratio is 1.32, the ellipse ratio is 1.32 ± in the case of a crystal oscillator that vibrates in C mode and vibrates in the fundamental wave with M-SC cut. The range of 10% is good, more preferably the range of 1.32 ± 5%. According to this simulation procedure, preferable elliptic ratios for M-SC cut 3rd harmonic, 5th harmonic, fundamental wave in B mode, 3rd harmonic, and 5th harmonic were also examined. The preferable ellipse ratio at each level determined by these studies is shown in the column of ellipse ratio in Table 3 below. Further, in the same manner, a preferable ellipse ratio for each of the SC cut, the IT cut, and the AT cut was determined. These results are shown in the columns of elliptical ratios in Tables 4, 5, and 6 below. Further, according to the examination of the simulation results of the inventor, it was determined that the preferable allowable range of the elliptical ratio of the excitation electrodes for each cut type was ± 10%, more preferably ± 5%.

2-2. Examination of the in-plane rotation angle of the excitation electrode with respect to the crystal piece Next, the appropriate range of the in-plane rotation angle δ of the elliptical excitation electrode with respect to the crystal piece will be described.
First, the crystal piece is set to M-SC cut, the vibration mode is set to the fundamental wave mode of C mode, and the angles α and β that determine the positional relationship between the first excitation electrode 13a and the second excitation electrode 13b are α =. The results of the simulation were as follows under the conditions that 25.5 °, β = 0.2 °, and the ellipse ratio was 1.32. The angles δ during the simulation are 1 °, -1.5 °, -4 °, -6.5 °, -9 °, -11.5 °, -14 °, -16.5 °, and-. It is 19 °. Here, as shown in FIG. 7B, the direction of the angle δ is defined as the Y'axis as the rotation axis, the counterclockwise direction as plus on the plus Y'plane of the crystal piece 11, and the clockwise direction as minus. There is.

12, 13 and 14 show the displacement distribution obtained by the above simulation. In FIGS. 12 to 14, the horizontal axis is the position of the edge of the excitation electrode specified by the angle γ as in the first embodiment, and the vertical axis is the displacement when the crystal piece of the model vibrates. The displacement is shown as a value normalized by the maximum displacement as in the first embodiment. Further, in FIGS. 10 to 12, the characteristic diagram plotted with ◯ is the displacement distribution of the edge of the first excitation electrode 13a, and the characteristic diagram plotted with + is the displacement distribution of the edge of the second excitation electrode 13b. ..
Further, FIG. 15 is a diagram summarizing the main points of the results of FIGS. 12, 13, and 14. Specifically, for each of the above nine types of simulations with different in-plane rotation angles δ, the difference between the displacement distribution at the edge of the first excitation electrode and the displacement distribution at the edge of the second excitation electrode , It is shown by the difference between the maximum value and the minimum value in all displacements regardless of the front and back. The smaller this difference is, the flatter the displacement distribution at the edges of the front and back excitation electrodes is.

As is clear from the comparison of FIGS. 12 to 14, and as is clear from FIG. 15, the displacement distribution at the edges of the first and second excitation electrodes 13a and 13b is an angle in the direction of the ellipse. It can be seen that it changes by changing δ. That is, in the case of the M-SC cut, the displacement distribution at the edge of each of the first and second excitation electrodes is the flattest as compared with the others when δ = -9 °, and both are the same. It can be seen that when the angle δ increases or decreases from -9 °, the unevenness increases and the difference between the two also increases. Therefore, it can be determined that the angle δ is preferably −9 °, and the permissible range is ± 5 °, more preferably ± 3 °, according to the simulation results of the inventor. According to this simulation procedure, M-SC cut C mode 3rd harmonic, 5th harmonic, M-SC cut B mode fundamental wave, 3rd harmonic, 5th harmonic, SC cut, IT cut, For each AT cut, the preferred angle δ for each mode and each of the fundamental, third and fifth harmonics was determined. These results are shown in the columns of the ellipses in Tables 3, 4, 5, and 6 above. In any case, it was determined that the preferable allowable range of the in-plane rotation angle δ of the ellipse was ± 5 °, more preferably ± 3 °.

3. 3. Actual Structural Example An actual structural example of the crystal unit of the above-described embodiment will be described. 16 (A) and 16 (B) are explanatory views thereof.
The structural example shown in FIG. 16A is an example in which the present invention is applied to the lead-type crystal oscillator 20, and is a schematic view of the crystal oscillator 20 as viewed from the side. The crystal oscillator 20 includes a base 21, a lead 23 provided on the base, and a clip terminal 25 provided at the tip of the lead. The crystal piece 11 is fixed to the clip terminal 25. Specifically, the front and back surfaces of the crystal piece 11 are provided with extraction electrodes 15 drawn from the excitation electrodes 13a and 13b, and the crystal piece 11 has a conductive adhesive 27 attached to the clip terminal 25 near the end of the extraction electrode 15. It is fixed with. And, in reality, a cap (not shown) is joined to the base in order to seal the crystal piece 11.
The structural example shown in FIG. 16B is an example in which the present invention is applied to the surface mount type crystal oscillator 30, and is a schematic view of the crystal oscillator 30 viewed from above. The crystal oscillator 30 includes a ceramic base 31 and a support pad 33 provided on the base. The crystal piece 11 is fixed to the support pad 33. Specifically, the front and back surfaces of the crystal piece 11 are provided with extraction electrodes 15 drawn from the excitation electrodes 13a and 13b, and the crystal piece 11 is attached to the support pad 33 near the end of the extraction electrode 15 with a conductive adhesive 35. It is fixed with. Then, in reality, a lid member (not shown) is joined to the base in order to seal the crystal piece 11. Further, a mounting terminal (not shown) is provided on the outer bottom surface of the ceramic base, and this mounting terminal is electrically connected to the support pad.
Of course, these structural examples are preferable examples of the present invention, and other structures may be used.

4. Third embodiment (a form in which an inclined portion is provided at the edge of the excitation electrode)
In the first and second embodiments described above, the excitation electrodes have substantially the same thickness over the entire area. However, it is more preferable to provide an inclined portion at the edge of the excitation electrode for suppressing unnecessary modes. This third embodiment is an example.
FIG. 17 is an explanatory diagram of the crystal unit of the third embodiment. In particular, it is a figure focusing on the crystal piece 41 included in the crystal oscillator of the third embodiment, (A) is a plan view of the crystal piece 41, and (B) is the RR line of the crystal piece 40. It is a partial sectional view along. In addition, in FIG. 17B, the thickness of the excitation electrode is enlarged and shown in order to deepen the understanding of the inclined portions 13ab and 13bb of the excitation electrodes 13a and 13b.

The crystal piece 41 has main thickness portions 13aa and 13ba formed on the front and back surfaces of the excitation electrodes 13a and 13b having a constant thickness, and portions formed around the main thickness portions and in contact with the main thickness portions. It is characterized by having inclined portions 13ab and 13bb formed so that the thickness gradually decreases from the to the outermost periphery of the excitation electrode. The constant thickness of the main thickness portions 13aa and 13ba includes variations due to unavoidable fluctuations in manufacturing.
In the case of this example, the inclined portion 13ab is composed of four steps. The width from the main thick portion 13aa side to the outermost circumference of the excitation electrode 13a, that is, the inclination width is formed in XA, and the width between the steps is formed in XB. That is, in the case of this example, the width XA is formed to be three times as long as the width XB. The thickness of the main thick portion 13aa is formed in YA. Further, the height of each step of the inclined portion 13ab is formed in YB. Therefore, the thickness YA is four times as thick as the height YB.

The effects of these inclined portions 13ab and 13bb were confirmed by performing the following simulations. That is, as a simulation model of the crystal piece 41, two types of models, a model using an AT-cut crystal piece and a model using an M-SC-cut crystal piece, were prepared. The film thickness YA of each of the main thickness portions 13aa and 13ba of the excitation electrodes of these models is 140 nm, the frequency of the main vibration is 26 MHz, and the width XA of the inclined portions 13ab and 13bb is finite. A simulation was performed by the element method.
In the crystal unit, the main vibration (for example, C mode) and the unnecessary vibration, which is an unintended vibration by design, are generated unlike the main vibration. In a crystal oscillator formed of a crystal material such as AT cut or M-SC cut and vibrating by thickness sliding vibration, the influence of bending vibration is particularly large as unnecessary vibration. The horizontal axis of the graph of FIG. 18 shows the inclination width standardized by the bending wavelength λ, which is the wavelength of the bending vibration. Therefore, the inclination width shown in the graph of FIG. 18 has different inclination width dimensions of the inclined portions 13ab and 13bb depending on whether the crystal piece is AT cut or M-SC cut even if the scale is the same. For example, when vibration with a vibration frequency of 26 MHz is used as the main vibration, the bending wavelength λ of the AT-cut quartz piece is about 100? M, and the bending wavelength λ of the M-SC-cut quartz piece is about 110? M. .. At this time, the actual dimension of the inclination width indicated by "1" in the graph of FIG. 18 is 1 × λ, and in the case of the AT-cut crystal piece, the inclination width is 1 × λ = about 100? M, and the M-SC cut. In the case of a crystal piece, the inclination width is 1 × λ = about 110? M.

The vertical axis of the graph of FIG. 18 shows the reciprocal of the Q value indicating the loss of vibration energy of the main vibration. The characteristics of the AT-cut crystal piece model are indicated by black circles, and the characteristics of the M-SC-cut crystal piece model are indicated by black triangles.
As can be seen from FIG. 18, in both models, 1 / Q indicating the loss of vibration energy in the range where the inclination width standardized by the bending wavelength λ is about “0.5” to “3” is 3.0 ×. It is as low as 10-6 (denoted as "3.0E-6" in FIG. 18) or less. That is, it can be seen that the loss of vibration energy is suppressed when the inclination width is formed to have a length of 0.5 times or more and 3 times or less of the bending wavelength λ. In particular, in both models, the magnitude of 1 / Q is low in the range of the inclination width standardized by the bending wavelength λ from “1” to “2.5”, and the fluctuation is also small. That is, it can be seen that when the inclination width is 1 to 2.5 times the bending wavelength, the loss of vibration energy is more stable and lower.

The configuration in which the inclined portion is provided at the edge of the excitation electrode is particularly suitable for applications where the crystal piece is on a flat plate. In order to improve the characteristics of the crystal unit, a so-called convex-shaped crystal piece having a thin edge region of the crystal piece itself has been conventionally used. By doing so, it is possible to confine the vibration energy and suppress unnecessary vibration. However, there is a problem that it takes time and cost to process the crystal piece into a convex shape. In the case of this third embodiment, the inclined portion of the edge portion of the excitation electrode shows the role of the convex shape of the crystal piece. Therefore, when the structure of the inclined portion is further added to the configuration of the present invention illustrated in the first and second embodiments in which the excitation electrodes on the front and back sides are shifted in a predetermined relationship, the characteristics of the crystal oscillator are improved. Cost can be further reduced.

5. Fourth embodiment (a form in which an inclined portion is provided at the edge of the excitation electrode on one side)
In the third embodiment described above, a structure in which an inclined portion is provided on the edge portion of each of the front and back excitation electrodes has been described. However, in the case of manufacturing a crystal oscillator, the excitation electrode is trimmed with an argon ion beam or the like in order to adjust the vibration frequency. In this trimming step, the inclined portion disappears, which may increase the loss of vibration energy. In order to avoid this, the excitation electrode on the frequency adjusting surface of the crystal piece may not be provided with an inclined portion, and the inclined portion may be provided only on the excitation electrode on the surface opposite to the frequency adjusting surface. This fourth embodiment is an example.

FIG. 19 is an explanatory diagram of the crystal unit of the fourth embodiment. In particular, it is a figure focusing on the crystal piece 51 included in the crystal oscillator of the 4th embodiment, (A) is a plan view of the crystal piece 51, and (B) is the SS line of the crystal piece 51. It is a partial sectional view along. In the case of the fourth embodiment, only the excitation electrode on the side where the frequency of the crystal piece is not adjusted has an inclined portion at the edge thereof. In the example of FIG. 19, only the excitation electrode 13b out of the excitation electrodes 13a and 13b has a structure having a main thickness portion 13ba and an inclined portion 13bb. The configuration of the excitation electrode 13b may be the configuration described in the third embodiment. That is, as described in the third embodiment, the excitation electrode 13b has a main thickness portion 13ba formed of a constant thickness YA2 (YA in the third embodiment) and a main thickness portion 13b of the main thickness portion 13b. It is provided with an inclined portion 13bb formed in the periphery so that the thickness gradually decreases from the portion in contact with the main thick portion to the outermost periphery of the excitation electrode, and the inclined width XA is 0.5 times the bending wavelength λ. The length is 3 times or more, preferably 1 to 2.5 times. On the other hand, the film thickness of the excitation electrode 13a on the side where the inclined portion is not provided is YA1. The details of the configurations of the film thicknesses YA1 and YA2 will be described later. The crystal piece 51 is mounted in a container for a crystal oscillator (see, for example, FIG. 16) so that the excitation electrode 13b side is on the side where the frequency is not adjusted.

Next, matters to be noted in carrying out this fourth embodiment will be described below with reference to FIG.
FIG. 20 shows the results of preparing the following three types of simulation models as simulation models and analyzing the loss (1 / Q) of the main vibration energy in each model by the finite element method. The first of the three types is a model corresponding to the crystal piece 51 of the fourth embodiment, that is, a model in which an inclined portion is provided only on the excitation electrode on one side of the crystal piece. The second is a model corresponding to the crystal piece 41 of the third embodiment, that is, a model in which inclined portions are provided on the excitation electrodes on both sides of the crystal piece. The third is a model corresponding to the crystal piece 11 of the first embodiment, that is, a model in which the excitation electrode of the crystal piece is not provided with an inclined portion.

In each model, the crystal material is M-SC cut, all the excitation electrodes are gold (Au), the frequency of the main vibration is 30 MHz (bending wavelength λ is about 95? M), and the inclined part is provided. The inclination width XA of is 133? M (1.4 times the bending wavelength λ). Regarding the film thickness of the excitation electrode, in the graph of FIG. 20, the thickness YA1 of the excitation electrode 13a and the thickness YA2 of the main thickness portion 13ba of the excitation electrode 13b are shown on the horizontal axis. In the case of this simulation, the total of the thickness YA1 and the thickness YA2 is always set to 280 nm, and in FIG. 20, the thickness YA2 increases toward the right side of the graph. Further, the vertical axis of FIG. 20 shows the loss (1 / Q) of the vibration energy of the main vibration (for example, C mode). Then, in FIG. 20, the calculation result of the model in which the inclined portion is provided only on one side of the excitation electrode is indicated by a black circle ●, and the calculation result of the model in which the inclined portion is provided on both sides of the excitation electrode is indicated by a black rhombus ◆. The calculation results of the model in which the excitation electrode is not provided with an inclined portion are shown by white squares.
The reason for simulating under the condition that the total of the thickness YA1 and the thickness YA2 is always 280 nm is to secure so-called energy confinement in the crystal oscillator. That is, it is because the effect of the present invention is to be confirmed on the premise that energy confinement is secured. However, the value of 280 nm is an example according to the size, shape, and frequency of the crystal piece of the embodiment.

As can be seen from FIG. 20, in the model in which the inclined portion is provided only on the excitation electrode on one side, 1 / Q indicating the loss of vibration energy is about 5.5 when the thickness YA1 and the thickness YA2 are 140 nm. It is × 10-6 (in the graph of FIG. 20, “× 10-6” is expressed as “E-6”). However, in this model, 1 / Q is reduced by reducing the thickness YA1 of the excitation electrode on which the inclined portion is not formed and increasing the thickness YA2 of the exciting electrode provided with the inclined portion instead. When the thickness YA1 is 60 nm and the thickness YA2 is 220 nm, 1 / Q is about 3.1 × 10-6. That is, in the model in which the inclined portion is provided only on the excitation electrode on one side, the crystal oscillator is provided by providing the inclined portion only on the excitation electrode on one side and reducing the thickness of the excitation electrode without the inclined portion. It can be seen that the loss of On the other hand, in the model having inclined portions on the excitation electrodes on both sides, 1 / Q is about 2.4 × 10-6 to about 2.6 × 10- even when the thickness YA1 and the thickness YA2 are changed. 6 is in a flat state, and at first glance, it is preferable as a characteristic. However, in a model having an inclined portion on both sides of the excitation electrode, the inclined portion of the excitation electrode on the frequency adjusting surface side may disappear at the time of frequency adjustment, so that this characteristic cannot be maintained in the actual product. Further, in the model in which the excitation electrodes on both sides do not have an inclined portion, when the thickness YA1 and the thickness YA2 are changed, 1 / Q increases as the thickness YA2 increases, and when the thickness YA2 is 220 nm. 1 / Q is about 9.9 × 10-6. That is, in the model in which the excitation electrodes on both sides do not have an inclined portion, as the thickness of the YA2 increases, an unnecessary mode due to a step at the edge portion of the excitation electrode occurs, and the loss increases.

The effect of the crystal unit of the fourth embodiment occurs for the following reasons. In the crystal unit, the main vibration (for example, C mode) and the unnecessary vibration, which is unintended in design, are generated unlike the main vibration. In a crystal oscillator formed of a crystal piece formed of a crystal material such as AT cut and M-SC cut and vibrating by thickness sliding vibration, modes other than the main vibration are unnecessary modes that hinder the oscillation of the main vibration. .. In the unnecessary vibration, which is the vibration due to the unnecessary mode, it is known that the bending vibration particularly affects the main vibration. In bending vibration, vibration energy is converted into bending vibration mainly at the end of the excitation electrode, which is superimposed on the main vibration, and the bending vibration vibrates in the entire piezoelectric vibration piece, so that the crystal piece is held. Vibration energy is absorbed by the sex adhesive. The energy loss due to such bending vibration leads to the loss of vibration energy.
In the crystal oscillator of the fourth embodiment, when the thicknesses YA1 and YA2 of the excitation electrodes are both 140 nm, the excitation electrode 13b has an inclined portion 13bb, but the excitation electrode 13a has an inclined portion 13bb. Since the inclined portion is not formed, the influence of the bending vibration on the main vibration is not sufficiently suppressed, so that the loss is equivalent to that of the model without the inclined portion and is large. However, in the crystal oscillator according to the fourth embodiment, 1 / Q decreases as the thickness YA1 of the excitation electrode 13a having no inclined portion becomes thinner, and when the thickness YA1 is 60 nm, the loss is lost. , It is close to the model in which the excitation electrodes on both sides are provided with inclined portions. It is considered that this is because the thickness YA1 of the excitation electrode having no inclined portion is reduced, so that the influence of the step at the electrode end portion is reduced, and the occurrence of bending vibration is suppressed. Therefore, in the case of the fourth embodiment, the thickness YA1 of the excitation electrode 13b without the inclined portion can suppress the induction of the unnecessary mode at the end of the excitation electrode 13b, and can be used as the original conductive film of the electrode. It is preferable that it is as thin as possible on the premise that the function can be obtained. It is known that the lower limit range that can be established as a film in thin film technology is a thickness of 60 nm to 100 nm. Considering this, in order to exert the function of an exciting electrode without an inclined portion, the thickness is thick. The YA1 is preferably in the range of 60 nm to 100 nm, preferably 60 nm to 80 nm.

Further, in the crystal piece 51 of the fourth embodiment, the crystal piece 51 is not processed such as bevel processing or convex processing, but the vibration energy is confined by forming the excitation electrode to a predetermined thickness. It is preferable to select the thickness YA2 of the excitation electrode without the inclined portion so that the total thickness of the excitation electrodes YA1 and YA2 is a film thickness capable of confining the vibration energy. Specifically, the total thickness of both excitation electrodes can be determined from a value of about several% of the plate thickness of the crystal piece in consideration of the size and frequency of the piezoelectric vibrating piece, for example, 2 It is good to choose from 5%.
In the case of this fourth practical embodiment, the effect of the present invention illustrated in the first and second embodiments of shifting the front and back excitation electrodes in a predetermined relationship can be obtained, and the effect of providing an inclined portion on the excitation electrode is obtained. Then, the effect that this inclined portion can be prevented from being damaged at the time of frequency adjustment can be obtained.

6. Fifth embodiment (form of inclined portion in consideration of harmonics)
In the third embodiment and the fourth embodiment described above, the appropriate value regarding the fundamental wave has been described for the inclination width XA which is the length of the inclined portion. On the other hand, one of the uses of the crystal oscillator is to simultaneously output signals of two frequencies from one crystal oscillator. For example, International Publication No. 2015/133472 describes the extraction of fundamentals and harmonics from a single crystal piece. In such a case, one frequency can be used as an output signal and the other frequency can be used as a sensor signal for temperature compensation, and since two frequencies can be obtained by one crystal oscillator, a crystal piece It is preferable that the influence of individual differences can be reduced. The fifth embodiment relates to the design in consideration of the fundamental wave and the harmonics in the first to fourth embodiments described above.
In the various embodiments of the first to fourth embodiments, the crystal piece of the fifth embodiment has an inclination width when an inclined portion is provided on the excitation electrode, and the inclination width is set to the fundamental wave of the thickness sliding vibration. It is 0.84 times or more and 1.37 times or less of the first bending wavelength which is the wavelength of bending vibration, and 2.29 times or more and 2.29 times or more of the second bending wavelength which is the wavelength of bending vibration in the third harmonic of thickness slip vibration. It is characterized by having a length of .71 times or less.

FIG. 21 is a diagram showing simulation results for explaining the effect of the fifth embodiment. Specifically, FIG. 21 shows the value obtained by normalizing the inclination width of the excitation electrode with the wavelength of bending vibration and the vibration of the simulation model in which the excitation electrodes on both sides provided with the inclination portions described with reference to FIG. It is a graph which showed the relationship with the energy loss (1 / Q). In the simulation model, the main thickness portion 13aa (frequency: 90 MHz) for the fundamental wave (frequency: 30 MHz) and the triple wave (frequency: 90 MHz) when all the excitation electrodes are made of gold (Au) and the C mode is the main vibration. The calculation results by simulation when the film thickness YA1 of 13ba) is 100 nm, 140 nm, and 180 nm are shown.

The horizontal axis of the graph of FIG. 21 shows the inclination width XA (? M). The vertical axis of the graph of FIG. 21 shows the reciprocal of the Q value indicating the loss of vibration energy of the main vibration. Further, in FIG. 21, the loss of the crystal piece when the fundamental wave is oscillated at a thickness YA of the main thickness portion of 100 nm is shown by a white square □, and the crystal piece when the fundamental wave is oscillated at a thickness YA of 140 nm. The loss of the crystal piece is indicated by a white triangle Δ, and the loss of the crystal piece when the fundamental wave is oscillated at a thickness YA of 180 nm is indicated by a white circle ○. The loss of the crystal piece when oscillating is indicated by a black square ■, the loss of the crystal piece when oscillating a triple wave with a thickness YA of 140 nm is indicated by a black triangle ▲, and the loss of the crystal piece when the thickness YA is 180 nm is a triple wave. The loss of the crystal piece when oscillating is indicated by a black circle.

As can be seen from FIG. 21, the relationship between the inclination width and the loss of vibration energy (1 / Q) in the triple wave shows a similar tendency regardless of the size of the thickness YA of the main thick part. , 1 / Q indicating the loss of vibration energy in the range of inclination width XA from about 30? M to about 130? M is 8.0 × 10-6 (in the graph of FIG. 21, “× 10-6” is changed to “E-”. 6 ”) It is as low as below. Regarding the relationship between the gradient width and the loss of vibration energy (1 / Q) in the fundamental wave, 1 / Q, which indicates the loss of vibration energy in the range where the tilt width XA is about 80? M or more, is 4.0 × 10−. It is as low as 6 or less. From these results, in the range where the inclination width XA at which the loss (1 / Q) of the vibration energy of the fundamental wave and the third harmonic wave is low is about 80? M to about 130? M (range A in FIG. 21), Since the loss of the vibration energy of both the fundamental wave and the third harmonic is suppressed, the loss of the vibration energy of the crystal oscillator when the fundamental wave and the third harmonic are simultaneously oscillated is suppressed.

Further, as can be seen from FIG. 21, in the triple wave, the inclination width XA is stable in the range of about 40? M to about 120? M in a state where 1 / Q indicating the loss of vibration energy is low, which is particularly preferable. .. The fundamental wave is particularly preferable because the 1 / Q indicating the loss of vibration energy is as low as 3.0 × 10-6 or less in the range where the inclination width XA is about 100? M or more. From these results, it is basic in the range of the inclination width XA from about 100? M to about 120? M (range B in FIG. 21) where both the loss (1 / Q) of the vibration energy of the fundamental wave and the third harmonic wave is low. Since the loss of vibration energy in the piezoelectric vibration piece of the wave and the third harmonic wave can be particularly suppressed, the loss of the vibration energy of the crystal oscillator when the fundamental wave and the third harmonic wave are simultaneously oscillated can be particularly suppressed.

7. Other Embodiments In the above, the embodiment of the crystal unit of the present invention has been described, but the present invention is not limited to the above-described embodiment. For example, in the above example, a rectangular crystal piece is shown as the crystal piece, but the planar shape of the crystal piece may be a rectangular shape, a round shape, or an elliptical shape. Further, in each embodiment, a rectangular crystal piece having a long side in the X'direction and a short side in the Z'direction is shown, but the long side and the short side may be reversed. Further, in the case of the first embodiment, the electrode shape may be a quadrangular shape or a round shape in a plan view. Further, as described above, the crystal piece may be a plano-convex type. Further, although an example of a four-stage configuration is shown as the inclined portion provided on the exciting electrode, the configuration of the inclined portion is not limited to this. The inclined portion may have any other configuration, for example, when the number of steps is different from that exemplified, or a configuration having a slope instead of a step structure.

11: Crystal piece, 13a: Excitation electrode (first excitation electrode),
13b: Excitation electrode (second excitation electrode), 13aa, 13ba: Main thickness part,
13ab, 13bb: inclined portion, XA: inclined width (width of inclined portion),
15: Drawer electrode 20: Reed type crystal unit, 21: Base, 23: Reed,
25: Clip terminal, 27: Conductive adhesive 30: Surface mount type crystal oscillator, 31: Ceramic base,
33: Support pad, 35: Conductive adhesive 41: Crystal piece of the third embodiment, 51: Crystal piece of the fourth embodiment

Claims (19)

In a crystal oscillator that has excitation electrodes on the front and back of the crystal piece and vibrates in the thickness slip mode.
The crystal piece is a crystal piece having a thickness in the Y'axis direction of the crystal and having the X'-Z'plane of the crystal as the main surface. If the same is true and the excitation electrode provided on the plus Y'plane is defined as the first excitation electrode and the excitation electrode provided on the minus Y'plane is defined as the second excitation electrode, the second excitation electrode is the first. A crystal oscillator characterized in that it is provided at a position that satisfies the following relationship with respect to the excitation electrode.
(1) The first excitation electrode is moved along the X'axis of the crystal in the plus X'direction by the distance dx given by T. tan α.
(2) The first excitation electrode is moved along the Z'axis of the crystal in the minus Z'direction by the distance dy given by T. tan β.
(3) The position where the state moved in (1) and (2) above is projected onto the minus Y'plane.
However, T is the thickness of the quartz piece, and α and β are directions of the phase velocity of the elastic wave in the quartz piece due to the quartz being an anisotropic material. Considering that the thickness direction and the power flow direction, which is the direction of energy velocity, are different, the angle is in a predetermined range according to the cut type of the crystal piece. Moreover, α is an angle with the Z'axis of the crystal piece as the rotation axis, and β is an angle with the X'axis of the crystal piece as the rotation axis. The crystal piece is an M-SC cut crystal piece, α is α = 25 ± 5 °, β is β = 0 ± 5 °, and the crystal oscillator vibrates in C mode. The crystal oscillator according to claim 1. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 1.32 ± 10%, and an in-plane rotation angle δ = -9 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 2, wherein the crystal oscillator is arranged. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 0.91 ± 10%, and an in-plane rotation angle δ = -15 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 2, wherein the crystal oscillator is arranged. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 0.93 ± 10%, and an in-plane rotation angle δ = -10 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 2, wherein the crystal oscillator is arranged. The crystal piece is an SC-cut crystal piece, α is α = 25 ± 5 °, β is β = 1 ± 5 °, and the crystal oscillator vibrates in C mode. The crystal oscillator according to claim 1. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 1.32 ± 10%, and an in-plane rotation angle δ = -7 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 6, wherein the crystal oscillator is arranged. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 0.93 ± 10%, and an in-plane rotation angle δ = -17 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 6, wherein the crystal oscillator is arranged. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 0.95 ± 10%, and an in-plane rotation angle δ = -12 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 6, wherein the crystal oscillator is arranged. The crystal piece is an IT-cut crystal piece, α is α = 24 ± 5 °, β is β = 2 ± 5 °, and the crystal oscillator vibrates in C mode. The crystal oscillator according to claim 1. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 1.32 ± 10%, and an in-plane rotation angle δ = -3 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 10, wherein the crystal oscillator is arranged. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 0.95 ± 10%, and an in-plane rotation angle δ = −38 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 10, wherein the crystal oscillator is arranged. The first excitation electrode and the second excitation electrode have an elliptical planar shape, an elliptical ratio of 0.98 ± 10%, and an in-plane rotation angle δ = −40 ± 5 ° with respect to the crystal piece. The crystal oscillator according to claim 10, wherein the crystal oscillator is arranged. The crystal unit according to claim 1, wherein the crystal piece is an AT-cut crystal piece, α is α = 0 °, and β is β = 4 ± 3 °. The first excitation electrode and the second excitation electrode are the most of the excitation electrode from the main thick portion formed with a constant thickness and the portion formed around the main thick portion and in contact with the main thick portion. It has an inclined portion formed so that the thickness gradually decreases toward the outer circumference.
The crystal oscillator according to claim 1, wherein the inclination width, which is the width of the inclined portion, is 0.5 times or more and 3 times or less the bending wavelength which is the wavelength of bending vibration which is unnecessary vibration. The first excitation electrode and the second excitation electrode are the most of the excitation electrode from the main thick portion formed with a constant thickness and the portion formed around the main thick portion and in contact with the main thick portion. It has an inclined portion formed so that the thickness gradually decreases toward the outer circumference.
The inclination width, which is the width of the inclined portion, is 0.84 times or more and 1.37 times or less of the first bending wavelength, which is the wavelength of the bending vibration in the fundamental wave of the thickness sliding vibration, and is a triple wave of the thickness sliding vibration. The crystal oscillator according to claim 1, which has a length of 2.29 times or more and 3.71 times or less of the second bending wavelength, which is the wavelength of the bending vibration in the above. The slanted portion according to claim 15 or 16, wherein the inclined portion is provided only on the excitation electrode of the first excitation electrode and the second excitation electrode on the surface opposite to the frequency adjustment surface of the crystal oscillator. Crystal oscillator. The crystal vibration according to claim 17, wherein the thickness of the excitation electrode on the frequency adjustment surface of the crystal oscillator is thinner than the thickness of the main thickness portion of the excitation electrode on the surface opposite to the frequency adjustment surface. Child. The crystal oscillator according to any one of claims 15 to 18, wherein the crystal piece is a flat crystal piece.

Images