TW201924102A - Piezoelectric vibrating piece and piezoelectric device - Google Patents

Abstract

A piezoelectric vibrating piece and a piezoelectric device are provided for ensuring the reduced occurrence of the unnecessary vibration. The piezoelectric vibrating piece (240) includes: a piezoelectric substrate (241), being formed in a flat plate shape and vibrates in a thickness-shear vibration mode; and excitation electrodes (242), being formed on respective both principal surfaces of the piezoelectric substrate. And, each excitation electrode includes: a main thickness portion (242a), having a first thickness; and a flat portion (242b), being formed in a peripheral area of the main thickness portion and has a second thickness that is thinner than the first thickness between from a portion contacting the main thickness portion to an outermost periphery of the excitation electrode, extends from the portion contacting the main thickness portion to the outermost periphery of the excitation electrode, and has a width (XB) formed to have a length of 0.63 times or more and 1.88 times or less of a flexural wavelength of an unnecessary vibration.

Description

Piezoelectric vibrating piece and piezoelectric element

The present invention relates to a piezoelectric vibrating piece and a piezoelectric element, in which an inclined portion is formed around the excitation electrode.

The piezoelectric vibrating piece in which the excitation electrode is formed on the piezoelectric substrate can close the vibration energy by forming the thickness of the periphery of the piezoelectric substrate into a thin convex shape to suppress the unnecessary vibration. However, there is a problem in that the piezoelectric substrate is formed into a convex shape, which is labor intensive and costly.

On the other hand, Patent Document 1 discloses that the piezoelectric substrate is held in a flat shape, and an inclined surface shape in which the thickness of the excitation electrode is gradually reduced is formed around the excitation electrode, thereby reducing the effort and cost of the piezoelectric substrate processing.

[Prior Art Document] [Patent Document] Patent Document 1: Japanese Patent Laid-Open Publication No. 2002-217675

[Problems to be Solved by the Invention] However, it is understood that even if the shape of the inclined surface as described in Patent Document 1 is formed, the effect of suppressing the unnecessary vibration is greatly different depending on the size of the inclined surface shape. That is, there is a problem in that even when an inclined surface shape is formed around the excitation electrode, excessive vibration cannot be sufficiently suppressed.

Accordingly, an object of the present invention is to provide a piezoelectric vibrating piece in which a size is appropriately adjusted by an excitation electrode formed on a flat piezoelectric substrate. The flat portion suppresses excessive vibration.

[Means for Solving the Problem] The piezoelectric vibrating piece of the first aspect includes: a piezoelectric substrate formed in a flat plate shape and vibrating in the form of a thickness shearing vibration; and an excitation electrode formed on each of the piezoelectric substrate Main face. Further, the excitation electrode includes: a main thick portion formed at a first thickness; and a flat portion thinner than the second thickness of the first thickness, formed around the main thick portion and from a portion in contact with the main thick portion The outermost circumference of the electrode is excited. Further, the width of the flat portion, that is, the width from the portion in contact with the main thick portion to the outermost periphery of the excitation electrode is formed to be 0.63 times or more and 1.88 times or less the wavelength of the bending vibration which is the excess vibration, that is, the bending wavelength. length.

The piezoelectric vibrating piece of the second aspect includes: a piezoelectric substrate formed in a flat plate shape and vibrating in a thickness shearing vibration; and excitation electrodes formed on the two main faces of the piezoelectric substrate, respectively. Further, the excitation electrode includes: a main thick portion formed at a first thickness; and a flat portion having a predetermined width thinner than the second thickness of the first thickness, formed around the main thick portion and coming into contact with the main thick portion Partially between the outermost circumferences of the excitation electrodes. Further, the predetermined width of the flat portion is formed to be a length of the bending vibration of the unnecessary vibration, that is, a length of 0.35 times or more and 1.73 times or less of the bending wavelength.

The piezoelectric vibrating piece of the third aspect further includes: a first inclined portion that is inclined with respect to the main surface from a portion in contact with the main thick portion to the flat portion; and a second inclined portion from the flat portion to the excitation electrode It is inclined with respect to the main surface up to the outermost circumference. Further, at least one of the width of the first inclined portion from the portion in contact with the main thick portion to the flat portion and the width of the second inclined portion from the flat portion to the outermost periphery of the excitation electrode is: The wavelength of the bending vibration of the vibration is 1λ or less of the bending wavelength. Alternatively, the width of the first inclined portion from the portion in contact with the main thick portion to the flat portion and the width of the second inclined portion from the flat portion to the outermost periphery of the excitation electrode are respectively as: The wavelength of the bending vibration is 1λ or less of the bending wavelength.

Further, as another viewpoint, the thickness of the main thick portion may be formed between 100 nm and 200 nm. Moreover, the shape of the excitation electrode can also be formed into a circular shape or an elliptical shape. Furthermore, as a fourth aspect, a piezoelectric element including the piezoelectric vibrating piece of the first aspect and the like, and a package on which the piezoelectric vibrating piece is placed may be provided.

[Effects of the Invention] According to the piezoelectric vibrating piece and the piezoelectric element of the present invention, generation of excessive vibration can be suppressed.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings. Further, the scope of the present invention is not limited to the embodiments as long as it is not specifically described in the following description.

<AT Cutting> FIG. 1A is a perspective view of the piezoelectric element 100. The piezoelectric element 100 is mainly composed of a base 110, a lid 120, and a piezoelectric vibrating piece 140 (see FIG. 1B) that vibrates at a predetermined vibration frequency. The outer shape of the piezoelectric element 100 is formed, for example, in a substantially rectangular parallelepiped shape. The piezoelectric vibrating piece 140 is formed by using an AT-cut crystal material that vibrates in a thickness shear vibration as a substrate. The AT-cut crystal material is formed by rotating the main surface (XZ plane) with respect to the Y-axis of the crystal axis (XYZ) around the X-axis and rotating by 35 degrees and 15 minutes from the Z-axis-Y-axis direction. In the following description, the tilted new axis of the AT-cut crystal material is represented as the Y' axis and the Z' axis. The piezoelectric element 100 shown in FIG. 1A has a longitudinal direction which is an X-axis direction, a height direction of the piezoelectric element 100 is a Y′-axis direction, and a direction perpendicular to the X-axis direction and the Y′-axis direction is a Z′-axis direction. The way to form.

A mounting terminal 111 is formed on a surface on the -Y'-axis side of the chassis 110, that is, a mounting surface 112a that is a surface on which the piezoelectric element 100 is mounted. The mounting terminal 111 is composed of a hot terminal 111a as a terminal connected to the piezoelectric vibrating piece 140 and a terminal (hereinafter referred to as a ground terminal) 111b which can be used for grounding. In the base 110, a hot terminal 111a is formed on an angle on the -Z'-axis side of the +X-axis side of the mounting surface 112a and an angle on the +Z'-axis side on the -X-axis side, respectively, on the +X-axis side of the mounting surface 112a. A ground terminal 111b is formed at an angle on the +Z' axis side and an angle on the -Z' axis side on the -X axis side, respectively. A cavity 113 (see FIG. 1B) as a space on which the piezoelectric vibrating piece 140 is placed is formed on the surface on the +Y'-axis side of the base 110, and the cavity 113 is sealed by the cover 120 via the sealing material 130. .

FIG. 1B is a perspective view of the piezoelectric element 100 with the cover 120 removed. The cavity 113 formed on the surface on the +Y'-axis side of the base 110 is a surface on the opposite side of the mounting surface 112a, that is, a mounting surface 112b on which the piezoelectric vibrating piece 140 is placed, and a periphery of the mounting surface 112b. Surrounded by side walls 114. Further, on the mounting surface 112b, a pair of connection electrodes 115 electrically connected to the thermal terminals 111a are formed.

The piezoelectric vibrating piece 140 is configured to include a piezoelectric substrate 141 which is formed in a flat plate shape and vibrates in a thickness shear vibration; and the excitation electrodes 142 are formed on the +Y'-axis side of the piezoelectric substrate 141, respectively. The main faces on the -Y' axis side and the extraction electrode 143 are drawn from the respective excitation electrodes 142 to both ends of the side of the piezoelectric substrate 141 on the -X axis side. Further, the excitation electrode 142 formed on the surface on the +Y'-axis side of the piezoelectric substrate 141 and the excitation electrode 142 formed on the surface on the -Y'-axis side are formed in the same shape and the same size, and are entirely in Y' Formed in such a manner that the axial directions overlap each other. Although not shown in FIG. 1A and FIG. 1B, the details will be described below with reference to FIGS. 3A and 3B. However, the excitation electrode 142 includes a main thick portion and a flat portion, and may have an inclined portion. The piezoelectric vibrating piece 140 is placed on the mounting surface 112b such that the extraction electrode 143 and the connection electrode 115 are electrically connected via a conductive adhesive (not shown).

<M-SC Cut Structure> FIG. 2 is an explanatory diagram of a modified-stress compensation (M-SC) cut crystal material. In Fig. 2, the crystal axes of the crystal are represented as an X-axis, a Y-axis, and a Z-axis. The M-SC cutting crystal material is one of two rotating and cutting crystal materials, which is equivalent to rotating the XZ plate of the crystal by f degrees with the Z axis of the crystal as the center of rotation, and making the X'Z plate produced by this rotation X' The X'Z'' plate obtained by further rotating the θ degree from the axis. In the case of M-SC cutting, f is about 24 degrees and θ is about 34 degrees. In Fig. 2, the new axis of the crystal piece produced by the two rotations is represented by the expressions of the X' axis, the Y'' axis, and the Z'' axis. The two-rotation-cut piezoelectric substrate 241 thus cut is a crystal material having a so-called C mode or a B mode having a shear displacement propagating in the thickness direction as a main vibration. The two-rotation-cut crystal piece has a crystal piece such as an IT cut such that f is about 19 degrees and θ is about 34 degrees in addition to the SC cut. These C-mode or B-mode vibrations are classified into thickness shear vibrations in the same manner as AT cuts. When the excitation electrode and the extraction electrode are formed in the same manner as in FIG. 1A and FIG. 1B, the present embodiment can be applied as the piezoelectric vibrating piece 240.

<Structure of Excitation Electrode> FIGS. 3A and 3B are views for explaining the configuration of the piezoelectric vibrating piece 140 or the piezoelectric vibrating piece 240, particularly the excitation electrode. In particular, FIG. 3A is a plan view of the piezoelectric vibrating piece 140 or the piezoelectric vibrating piece 240, and FIG. 3B is a partial cross-sectional view taken along line IIIB-IIIB of FIG. 3A. In the two figures, the case of the AT cut and the case of the M-SC cut (indicated by the brackets) indicate the sitting mark number.

Since the piezoelectric vibrating piece 140 and the piezoelectric vibrating piece 240 are all described in the same manner, in the following description, the piezoelectric vibrating piece 240 cut by the M-SC will be described. The piezoelectric substrate 241 is a flat substrate having a rectangular flat surface in which the long sides extend in the X′ axis direction and the short sides extend in the Z′′ axis direction. The excitation electrode 242 formed on the +Y''-axis side and the -Y'-axis side main surface of the piezoelectric substrate 241 is formed in a circular shape. Further, each of the excitation electrodes 242 has a main thick portion 242a formed to have a constant thickness, and a flat portion 242b formed to have a constant width around the main thick portion 242a and thinner than the main thick portion 242a. Further, each of the excitation electrodes 242 has a first inclined portion 242c that is inclined with respect to the main surface from a portion that is in contact with the main thick portion 242a to the flat portion 242b, and the most from the flat portion 242b to the excitation electrode 242. The second inclined portion 242d that is inclined with respect to the main surface up to the outer circumference.

In the present embodiment, the thickness of the main thick portion 242a of the excitation electrode 242 is YA, and specifically, it is 140 nm (1400 Å) in the present embodiment. Further, the height of the flat portion 242b is formed as YB, and specifically, it is formed at 70 nm (700 Å) in the present embodiment. Typically, these main thick portions and flat portions are formed by sputtering or vacuum deposition using a metal mask for electrode formation. When such a forming method is used, metal particles generated by sputtering or vapor deposition are wound into the gap between the mask and the piezoelectric substrate 241, thereby forming the first inclined portion 242c and the second inclined portion 242d. The wide width from the end of the main thick portion 242a to the outermost circumference of the excitation electrode 242 is formed as XL, the wide width of the first inclined portion 242c is formed as XA, and the width of the flat portion 242b is formed as XB, and the second inclined portion is formed. The wide width of 242d is formed as XC. Sometimes it is difficult to have a tilt due to the film forming device. Regarding the apparatus used by the inventors, it was found that the total width (XA+XC) of the XA and XC was about 70 μm. In other words, when the wavelength of the bending vibration which is an unnecessary vibration to be described later is 140 μm, XA+XC=70 μm at this time is XA+XC<1λ.

Further, as shown in FIG. 4A and FIG. 4B, depending on the case, there is a piezoelectric element having almost no configuration such as the first inclined portion 242c and the second inclined portion 242d shown in FIGS. 3A and 3B. When the excitation electrode is formed by, for example, a vapor deposition method, and the adhesion between the mask and the piezoelectric substrate is good, and the metal particles reach the piezoelectric substrate with good linearity, the first inclined portion 242c and the second are hardly formed. The inclined portion 242d.

In the piezoelectric element vibrating in the form of thickness shear vibration, when the width XA of the inclined portion or the width XC of the inclined portion is larger than the excess vibration generated by the piezoelectric element, that is, the wavelength of the bending vibration, that is, In the example, when the excitation electrode is formed by sputtering and the width of the inclined portion is relatively large, the effect of suppressing the bending vibration is easily obtained. Therefore, deterioration of the characteristics of the piezoelectric element can be suppressed, but there is a problem in other cases. On the other hand, according to the study by the inventors of the present application, the vibration including the main thick portion 242a, the first inclined portion 242c, the flat portion 242b, and the second inclined portion 242d described with reference to Figs. 3A and 3B is used. The piezoelectric element of the electrode 242 is also a piezoelectric element having the excitation electrode 242 including the main thick portion 242a and the flat portion 242b described with reference to FIGS. 4A and 4B, and the width of the flat portion is appropriately set as described below. Even if the piezoelectric substrate 241 to be used is a flat substrate which is processed without beveling or convex processing, it is possible to prevent loss of vibration energy.

<First example: loss of width and vibration energy of the flat portion of the piezoelectric vibrating piece 240> <Basic wave simulation> Hereinafter, the vibration energy of the piezoelectric vibrating piece 240 formed by cutting the crystal material by the M-SC The loss-related simulation results are explained. This simulation is a basic wave 20 MHz model.

5A and 5B are graphs showing the relationship between the width XB of the flat portion 242b of the piezoelectric vibrating piece 240 and the loss (1/Q) of the vibration energy of the main vibration. The graph of Fig. 5A is a graph of the excitation electrode having the flat portion 242b, the first inclined portion 242c, and the second inclined portion 242d shown in Fig. 3B, and the graph of Fig. 5B is the flat portion 242b shown in Fig. 4B and has almost no A diagram of the excitation electrode of the inclined portion.

In FIGS. 5A and 5B, as an analysis model, it is shown that all of the excitation electrodes are formed of gold (Au), the film thickness YA of the main thick portion 242a is 140 nm (1400 Å), and the frequency of the main vibration is 20 MHz of the fundamental wave. The calculation result of the simulation of the case of the model. Further, the film thickness YB of the flat portion 242b is an example of 105 nm (1050 Å) and 70 nm (700 Å). In the graphs of FIGS. 5A and 5B, 1050 Å+350 Å is described, which means that the film thickness YB of the flat portion 242b is 1050 Å, and the thickness from the surface of the flat portion 242b to the surface of the main thick portion 242a is 350 Å. Further, 700 Å + 700 Å is described, which means that the film thickness YB of the flat portion 242b is 700 Å, and the thickness from the surface of the flat portion 242b to the surface of the main thick portion 242a is 700 Å. Further, the piezoelectric vibrating piece 240 of the excitation electrode of 1050 Å + 350 Å is indicated by a broken line and a circular mark. Further, the piezoelectric vibrating piece 240 of the 700 Å + 700 Å excitation electrode is indicated by a solid line and a square symbol.

The piezoelectric vibrating piece generates a main vibration (for example, a C mode) while generating a vibration which is different from the main vibration and which is unintended in design, that is, an unnecessary vibration. The piezoelectric vibrating reed which is formed by a piezoelectric substrate which is formed by a crystal material such as SC-cut and which vibrates in a thickness shear vibration has a particularly large influence on bending vibration as an unnecessary vibration. The horizontal axis of the graphs of FIGS. 5A and 5B indicates the width XB of the flat portion normalized by the bending wavelength λ (=about 140 μm) which is the wavelength of the bending vibration. Therefore, in the graphs of FIGS. 5A and 5B, the actual size of the flat portion indicated by "1" is 1 × λ, and when the width of the flat portion is indicated by 1.00 in the piezoelectric vibrating piece 240, it becomes 1 × λ. = about 140 μm. The vertical axis of the graphs of Figs. 5A and 5B indicates the reciprocal of the Q value, and the reciprocal of the Q value indicates the loss of the vibration energy of the main vibration. In addition, in the analysis model of FIG. 5A, XA and XC are respectively set to 35 μm as the width XA of the first inclined portion 242c and the width XC of the second inclined portion 242d (see FIG. 3B), and therefore (XA+XC)=70 μm. .

In the piezoelectric vibrating piece having the inclined portion shown in FIG. 5A, the piezoelectric vibrating piece 240 of the excitation electrode of 1050 Å + 350 Å and the piezoelectric vibrating piece 240 of the excitation electrode of 700 Å + 700 Å are all flattened at the bending wavelength λ. The width XB of 242b is in the range of about "0.3" to "2", and the loss of vibration energy 1/Q is as low as 2.5 × 10-6 or less. In other words, when the width XB of the flat portion 242b is formed to be 0.3 times or more and twice or less the bending wavelength λ, the loss of vibration energy can be suppressed. As described in detail, the piezoelectric vibrating piece 240 of the excitation electrode of 1050 Å + 350 Å has a width XB of the flat portion 242b normalized by the bending wavelength λ in the range of "0.33" to "1.77", and the size of 1/Q. It is low, and its changes are also reduced. In the piezoelectric vibrating piece 240 of the 700 Å+700 Å excitation electrode, the width XB of the flat portion 242b normalized by the bending wavelength λ is in the range of “0.35” to “1.73”, and the magnitude of 1/Q is low, and the variation thereof is also Fewer. In other words, when the width XB of the flat portion 242b is a length of 0.35 to 1.73 times the bending wavelength λ, the loss of vibration energy is stably lowered.

The bending vibration is mainly caused by the vibration energy being converted into a bending vibration at the end of the excitation electrode, and is superimposed on the main vibration, and the bending vibration vibrates throughout the piezoelectric vibrating piece, so that the vibration energy can maintain the conductivity of the piezoelectric vibrating piece. Then absorbed by the agent. The energy loss caused by such bending vibration becomes a loss of vibration energy. In the piezoelectric vibrating piece 240 having the inclined portion, it is considered that the width XB of the flat portion 242b is formed to have a length of 0.35 times or more and 1.73 times or less of the bending wavelength λ, whereby generation of bending vibration can be suppressed, thereby suppressing Loss of vibrational energy.

In the piezoelectric vibrating piece having no inclination portion shown in FIG. 5B, the piezoelectric vibrating piece 240 of the excitation electrode of 1050 Å + 350 Å and the piezoelectric vibrating piece 240 of the excitation electrode of 700 Å + 700 Å are flat portions normalized by the bending wavelength λ. The width XB of 242b is in the range of about "0.3" to "2", and the loss of vibration energy 1/Q is as low as 2.5 × 10-6 or less. In other words, when the width XB of the flat portion 242b is formed to be 0.3 times or more and twice or less the bending wavelength λ, the loss of vibration energy can be suppressed. As described in detail, the piezoelectric vibrating piece 240 of the excitation electrode of 1050 Å + 350 Å has a width XB of the flat portion 242b normalized by the bending wavelength λ in the range of "0.63" to "1.88", and the size of 1/Q. It is low, and its changes are also reduced. In the piezoelectric vibrating piece 240 of the 700 Å+700 Å excitation electrode, the width XB of the flat portion 242b normalized by the bending wavelength λ is in the range of “0.38” to “1.88”, and the magnitude of 1/Q is low, and the variation thereof is also Fewer. In other words, when the width XB of the flat portion 242b is a length of 0.63 to 1.88 times the bending wavelength λ, the loss of vibration energy is stably lowered.

In the piezoelectric vibrating piece 240 having no inclined portion, it is considered that the width XB of the flat portion 242b is formed to have a length of 0.63 times or more and 1.88 times or less of the bending wavelength λ, whereby generation of bending vibration can be suppressed, thereby suppressing Loss of vibrational energy.

In consideration of the wide width of the flat portion normalized by the bending wavelength λ, it is considered that the tendency and magnitude of 1/Q are stable irrespective of the difference in piezoelectric material used for the piezoelectric substrate. Therefore, although the first example shows an example of the AT-cut crystal material and the M-SC-cut crystal material, it is not limited to these crystal materials, and it is considered that even other crystal materials vibrating in the form of thickness shear vibration, for example, Other piezoelectric materials such as LiNbO ₃ , LiTaO ₄ , GaPO ₄ , or piezoelectric ceramic materials vibrating in the form of SC cutting, IT cutting, or in the form of thickness shear vibration, 1/Q is also in contact with the piezoelectric vibrating piece 240 The same range of tilt width is reduced.

<Preparation of Piezoelectric Vibrating Piece 240> FIGS. 5A and 5B show simulations relating to the loss of vibration energy of the piezoelectric vibrating piece 240 of the excitation electrode of 1050 Å+350 Å and the piezoelectric vibrating piece 240 of the excitation electrode of 700 Å+700 Å. result. Based on this simulation, the inventors prototyped the piezoelectric vibrating piece 240 having a main vibration frequency of 20 MHz. Hereinafter, a procedure of forming the excitation electrode 242 by the vapor deposition method for the piezoelectric substrate 241 illustrated in FIGS. 3A and 3B will be described.

Fig. 6A is a partial cross-sectional view of the piezoelectric vibrating piece 240 (240a) manufactured by the first method. Fig. 6A is a partial cross-sectional view including a cross section corresponding to a section IIIB-IIIB of Fig. 3A. The excitation electrode 242 of the piezoelectric vibrating piece 240a is formed by using a first mask (not shown) having a first opening (for example, f 2.1 mm) to adhere the vapor deposition particles to the piezoelectric substrate 241 to form the first layer 245a. . Next, using a second mask (not shown) having a second opening (for example, f 2.4 mm), the vapor deposition particles are attached to the first layer 245a and the piezoelectric substrate 241 so as to cover the first layer 245a. The second layer 245b. In this forming step, the first inclined portion 242c and the second inclined portion 242d can be formed. The width of the first inclined portion 242c and the second inclined portion 242d will be described in detail below using FIG. 6C, but each is about 35 μm, and the sum of the widths of the other inclined portions is about 70 μm. In other words, when the width of each of the inclined portions is normalized by the wavelength λ (at this time, λ = 140 μm) of the bending vibration, it is 1λ or less, more specifically, less than 0.5λ, and the two inclined portions. The sum of the widths is also 1 λ or less. In addition, in FIG. 6A, only two layers are shown, and illustration of the base layer, such as a chromium film, etc. normally provided in order to ensure the adhesiveness of the piezoelectric substrate 241 and the excitation electrode gold (Au) is abbreviate|omitted.

Fig. 6B is a partial cross-sectional view of the piezoelectric vibrating piece 240 (240b) manufactured by the second method. Fig. 6B is also a partial cross-sectional view including a cross section corresponding to the IIIB-IIIB cross section of Fig. 3A. That is, this method differs from the first method in that the second method is a method of increasing the area of the lower layer, and the area of the upper layer is smaller than that of the lower layer to form the layers. Specifically, the excitation electrode 242 of the piezoelectric vibrating piece 240b is formed by using a second mask (not shown) having a second opening (for example, f 2.4 mm) to adhere the target atoms to the piezoelectric substrate 241. One layer 246a. In the case of this example, a vacuum evaporation method was also used. In this case, as long as the widths of the first inclined portion 242c and the second inclined portion 242d are each normalized by the λ, they may be 1λ or less. Specifically, it is preferably about 0.47λ, and the sum of the widths of the two inclined portions is also 1λ or less. In addition, only one of the first inclined portion 242c or the second inclined portion 242d may be formed. Moreover, the illustration of the chromium film etc. used for ensuring adhesiveness is abbreviate|omitted.

6C is a graph for actually measuring the thickness and shape of the excitation electrode formed as described above by an analysis method using Energy Dispersive X-ray Spectroscopy (EDS). This graph is a surface height indicating a section IIIB-IIIB of FIG. 3A, and a line on the upper side of the left side indicates a region of the main thick portion 242a, and this line starts to become a region indicating the first inclined portion 242c. Further, the first inclined portion 242c reaches a region indicating the flat portion 242b, and further to the right is a region indicating the second inclined portion 242d.

<Confirmation of Effect of Present Embodiment by Reassembly Experiment> In order to confirm the effect of the present embodiment, the inventors conducted the following experiment. First, piezoelectric elements of nine comparative examples were produced by a vacuum deposition method using a mask having a diameter of 2.4 mm, and the piezoelectric element of the comparative example had a thickness of a simple layer not having a main thick portion or a flat portion. The excitation electrode of 140 nm was used, and then the temperature characteristics of the crystal impedance (Crystal Impedance, CI) of these nine piezoelectric elements in the range of -40 ° C to 120 ° C were measured. Then, the piezoelectric elements of the nine comparative examples were disassembled at one time to regenerate the piezoelectric substrate, and the main piezoelectric layer, the flat portion, and the inclined portion described with reference to FIGS. 3A and 3B were produced on the regenerated piezoelectric substrate. Piezoelectric element of the embodiment. Then, the temperature characteristics of the crystal impedance (CI) of the piezoelectric elements of the nine examples in the range of -40 ° C to 120 ° C were measured. Further, in the investigation of the reassembly and the CI temperature characteristics from the comparative example to the example, nine piezoelectric substrates were reassembled in one-to-one correspondence, and the change in the CI temperature characteristics was followed.

In Fig. 7, the horizontal axis represents the product number of the nine piezoelectric elements, that is, the number of the piezoelectric substrate numbered, and the vertical axis represents the maximum CI value of each piezoelectric element in the range of -40 ° C to 120 ° C. The difference ΔCI(Ω) from the minimum CI value is plotted against the relationship between the two. In the figure, the square symbol indicates the CI variation amount of the piezoelectric vibrating piece 240 in the embodiment (reassembly), and the circular symbol is the CI variation amount of the piezoelectric element in the comparative example (before reassembly).

The CI fluctuation amounts of the nine piezoelectric vibrating reeds 240 reassembled by the electrode structure of the present embodiment are all stabilized by 2 Ω or less. On the other hand, the CI fluctuation amount of the nine comparative piezoelectric vibrating pieces is varied from 2 Ω to 13 Ω, and the average value of the nine CI fluctuation amounts is also as high as 6 Ω. In other words, the comparative vibration is generated by the piezoelectric vibrating piece, and the CI value is largely changed. However, the CI value of the piezoelectric vibrating piece 240 is stable, and the oscillation can be stably performed at 20 MHz. 8A is a view showing the entire CI temperature characteristics of the nine piezoelectric elements of the comparative example, and FIG. 8B is a view showing the entire CI temperature characteristics of the nine piezoelectric elements of the embodiment which are reassembled by the electrode structure of the present embodiment. Figure. In any of the figures, the vertical axis is a CI/CI (95 ° C) which is a value obtained by normalizing the CI value at each temperature with a CI value at a temperature of 95 ° C. 8A and 8B, the structure of the present embodiment can contribute to the stabilization of the characteristics of the piezoelectric element.

<Second Example: Wide and Vibration Energy Loss of Flat Part of Piezoelectric Vibrating Piece 240> <5 Wave Simulation> The following is a piezoelectric vibrating piece 240 formed by cutting and IT cutting a crystal material by M-SC The simulation results related to the loss of vibration energy are explained. This simulation is a 5x wave 21.64MHz model.

9A and 9B are graphs showing the relationship between the width XB of the flat portion 242b of the piezoelectric vibrating piece 240 and the loss (1/Q) of the vibration energy of the main vibration. 9A and 9B are piezoelectric vibrating reeds each having an excitation electrode having a flat portion 242b, a first inclined portion 242c, and a second inclined portion 242d shown in FIG. 3A. In addition, in the analysis model of FIG. 9A and FIG. 9B, as the wide XA of the first inclined portion 242c and the wide XC of the second inclined portion 242d (see FIG. 3B), XA and XC are respectively set to 35 μm, so (XA+XC) ) = 70 μm.

In addition, in FIG. 9A and FIG. 9B, as an analysis model, all of the excitation electrodes are formed of gold (Au), the film thickness YA of the main thick portion 242a is 140 nm (1400 Å), and the film thickness YB of the flat portion 242b is 70 nm (700 Å). . In addition, the graph of FIG. 9A is a graph of M-SC cut, and the graph of FIG. 9B is a graph of IT cut.

When the piezoelectric vibrating piece generates a main vibration (for example, a C mode), it generates a vibration which is different from the main vibration and which is unexpectedly designed, that is, an unnecessary vibration. The piezoelectric vibrating reed which is formed by a piezoelectric substrate which is formed by a crystal material such as SC cutting or IT cutting and vibrates in a thickness shear vibration has a particularly large influence as a bending vibration. The horizontal axis of the graph of FIGS. 9A and 9B indicates the width XB of the flat portion normalized by the bending wavelength λ (=about 150 μm) which is the wavelength of the bending vibration. Therefore, in the graphs of FIGS. 9A and 9B, the actual size of the flat portion indicated by "1" is 1 × λ, and when the width of the flat portion is indicated by 1.00 in the piezoelectric vibrating piece 240, it becomes 1 × λ. = about 150 μm. The vertical axis of the graphs of Figs. 9A and 9B indicates the reciprocal of the Q value, and the reciprocal of the Q value indicates the loss of the vibration energy of the main vibration.

In the M-SC-cut piezoelectric vibrating piece shown in FIG. 9A, the piezoelectric vibrating piece 240 of the 700 Å+700 Å excitation electrode has a width XB of the flat portion 242b normalized by the bending wavelength λ of about "0.5" to "2.25". In the range of "the vibration energy loss 1/Q is as low as 3.0 × 10-6 or less. In other words, when the width XB of the flat portion 242b is formed to be 0.5 times or more and 2.25 times or less of the bending wavelength λ, the loss of vibration energy can be suppressed.

In the IT-cut piezoelectric vibrating piece shown in FIG. 9B, the piezoelectric vibrating piece 240 of the 700 Å+700 Å excitation electrode has a width XB of the flat portion 242b normalized by the bending wavelength λ of about "0.5" to "2.5". Within the range, the loss of vibration energy 1/Q is as low as 3.0 × 10 -6 or less. In other words, when the width XB of the flat portion 242b is formed to be 0.5 times or more and 2.5 times or less the bending wavelength λ, the loss of vibration energy can be suppressed. Although the range of the M-SC-cut piezoelectric vibrating piece is slightly different from the range of the IT-cut piezoelectric vibrating piece, it is roughly the same range.

In the piezoelectric vibrating piece 240 of the double-rotation of the double-wavelength, it is considered that the formation of the bending vibration can be suppressed by forming the width XB of the flat portion 242b to a length of 0.5 times or more and 2.25 times or less of the bending wavelength λ. Thereby, the loss of vibration energy can be suppressed.

In consideration of the wide width of the flat portion normalized by the bending wavelength λ, it is considered that the tendency and magnitude of 1/Q are stable irrespective of the difference in piezoelectric material used for the piezoelectric substrate. Therefore, in the second example, although an example of a 5-fold wave of the M-SC-cut crystal material and the IT-cut crystal material is shown, it is not limited to these crystal materials, and it is considered that even other crystals vibrating in the form of thickness shear vibration The material is, for example, SC cut, AT cut, or other piezoelectric material such as LiNbO ₃ , LiTaO ₄ , GaPO ₄ , or piezoelectric ceramic material vibrating in the form of thickness shear vibration, 1/Q is also with 5 times wave The piezoelectric vibrating piece 240 is reduced in the same range of inclination width.

The preferred embodiments of the present invention have been described in detail above, and it is obvious to those skilled in the art that the present invention can be variously modified and modified.

For example, the film thickness YA of the main thick portion of the excitation electrode has been described as 140 nm (1400 Å), but it has been confirmed that it can be applied even at 100 nm to 200 nm. Further, in the present embodiment, the outer shape of the excitation electrode is circular, but it is not limited to a circular shape, and may be elliptical.

100‧‧‧Piezoelectric components

110‧‧‧Base

111‧‧‧Installation terminal

111a‧‧‧hot terminal

111b‧‧‧ Grounding terminal

112a‧‧‧Installation surface

112b‧‧‧Loading surface

113‧‧‧ cavity

114‧‧‧ side wall

115‧‧‧Connecting electrode

120‧‧‧ Cover

130‧‧‧ Sealing material

140, 240 (240a, 240b) ‧ ‧ piezoelectric vibrating piece

141, 241‧‧ ‧ piezoelectric substrate

142, 242‧‧‧ excitation electrode

143, 243‧‧‧ lead electrode

242a‧‧‧Main Thick Department

242b‧‧‧flat

242c‧‧‧First inclined part

242d‧‧‧Second inclined part

245a, 246a‧‧‧ first floor

245b, 246b‧‧‧ second floor

XA‧‧‧The width of the first inclined part (width of the inclined part)

XB‧‧‧flat width

XC‧‧‧ Wide width of the second inclined portion (wide width of the inclined portion)

XL‧‧‧ Wide width from the main thick side to the outermost circumference of the excitation electrode

YA‧‧‧ Thickness of the main thick portion of the excitation electrode (film thickness of the main thick portion)

The height of the flat section of YB‧‧

θ, f ‧‧‧ angle

FIG. 1A is a perspective view of the piezoelectric element 100. FIG. 1B is a perspective view of the piezoelectric element 100 with the cover 120 removed. 2 is an explanatory view of an M-SC cut crystal material. 3A is a plan view of the piezoelectric vibrating pieces 140 and 240 in which the flat portion and the inclined portion are formed on the outer circumference of the excitation electrode. Fig. 3B is a cross-sectional view taken along line IIIB-IIIB of Fig. 3A. 4A is a plan view of the piezoelectric vibrating piece 240 in which only a flat portion is formed on the outer circumference of the excitation electrode. Fig. 4B is a cross-sectional view taken along line IVB-IVB of Fig. 4A. 5A is a graph showing the relationship between the width XB of the flat portion 242b and the loss of vibration energy (1/Q) when the piezoelectric vibrating piece 240 depicted in FIGS. 3A and 3B vibrates in a fundamental wave. 5B is a graph showing the relationship between the width XB of the flat portion 242b and the loss of vibration energy (1/Q) when the piezoelectric vibrating piece 240 depicted in FIGS. 4A and 4B vibrates in a fundamental wave. FIG. 6A is a first example of forming an excitation electrode in the piezoelectric vibrating piece 240. FIG. 6B is a second example in which the excitation electrode is formed in the piezoelectric vibrating piece 240. FIG. 6C is a graph for actually measuring the thickness of the excitation electrode of the prototype piezoelectric vibrating piece 240. FIG. 7 is a graph showing the state of the CI fluctuation amount due to the temperature change of the piezoelectric vibrating piece 240 depicted in FIGS. 3A and 3B and the comparative piezoelectric vibrating piece to which the present embodiment is not applied. FIG. 8A is a view showing a general view of CI temperature characteristics of nine piezoelectric elements of a comparative example (the piezoelectric vibrating piece for comparison of the present embodiment is not applied). 8B is a view showing an overall view of CI temperature characteristics of the nine piezoelectric elements of the embodiment in which the electrode structures of the piezoelectric vibrating piece 240 shown in FIGS. 3A and 3B are reassembled. FIG. 9A is a graph showing the relationship between the width XB of the flat portion 242b and the loss of vibration energy (1/Q) when the piezoelectric vibrating piece 240 cut by the M-SC is vibrated at 5 times. FIG. 9B is a graph showing the relationship between the width XB of the flat portion 242b and the loss (1/Q) of the vibration energy when the IT-cut piezoelectric vibrating piece 240 vibrates at 5 times.

Claims (10)

A piezoelectric vibrating piece, comprising: a piezoelectric substrate formed in a flat plate shape and vibrating in a thickness shearing vibration; and excitation electrodes respectively formed on two main faces of the piezoelectric substrate, Wherein the excitation electrode comprises: a main thick portion formed with a first thickness; and a flat portion thinner than the second thickness of the first thickness, formed around the main thick portion and from the main The portion where the thick portion contacts is between the outermost circumferences of the excitation electrodes, and the flat portion of the second thickness is from a portion in contact with the main thick portion to an outermost circumference of the excitation electrode, The width of the flat portion is formed to be a length of the bending vibration of the unnecessary vibration, that is, a length of 0.63 times or more and 1.88 times or less of the bending wavelength. A piezoelectric vibrating piece, comprising: a piezoelectric substrate formed in a flat plate shape and vibrating in a thickness shearing vibration; and excitation electrodes respectively formed on two main faces of the piezoelectric substrate, Wherein the excitation electrode comprises: a main thick portion formed with a first thickness; and a flat portion of a second thickness thinner than a first thickness of the main thick portion, the width of the flat portion of the second thickness The length of the bending vibration which is the excess vibration, that is, the length of the bending wavelength is 0.35 times or more and 1.73 times or less. The piezoelectric vibrating piece according to claim 2, further comprising: a first inclined portion that is inclined with respect to the main surface from a portion in contact with the main thick portion to the flat portion; The second inclined portion is inclined with respect to the main surface from the flat portion to the outermost circumference of the excitation electrode. The piezoelectric vibrating piece according to any one of claims 1 to 3, wherein the thickness of the main thick portion is formed to be between 100 nm and 200 nm. The piezoelectric vibrating piece according to any one of the first to third aspect, wherein the excitation electrode has an outer shape formed in a circular shape or an elliptical shape. The piezoelectric vibrating piece according to any one of the first aspect, wherein the piezoelectric substrate vibrates in a fundamental wave. A piezoelectric vibrating piece, comprising: a piezoelectric substrate formed in a flat plate shape and vibrating at a frequency doubled wave of 5 times in a thickness shearing vibration; and an excitation electrode formed on the piezoelectric element Two main faces of the substrate, wherein the excitation electrode comprises: a main thick portion formed with a first thickness; a first tilt inclined with respect to the main surface from a portion in contact with the main thick portion a flat portion thinner than the second thickness of the first thickness from the first inclined portion; and a flat portion to an outermost circumference of the excitation electrode with respect to the main surface The inclined second inclined portion is formed such that the width of the flat portion is a wavelength which is a wavelength of the bending vibration of the unnecessary vibration, that is, a length of 0.50 times or more and 2.25 times or less of the bending wavelength. The piezoelectric vibrating piece according to claim 3, wherein the first inclined portion has a width and a width from a portion in contact with the main thick portion to the flat portion. At least one of the widths of the second inclined portion from the flat portion to the outermost circumference of the excitation electrode is 1λ or less of the bending wavelength which is the wavelength of the bending vibration as the unnecessary vibration. The piezoelectric vibrating piece according to claim 3, wherein the first inclined portion has a width and a width from a portion in contact with the main thick portion to the flat portion. The width of the second inclined portion from the flat portion to the outermost circumference of the excitation electrode is 1λ or less of the bending wavelength which is the wavelength of the bending vibration as the unnecessary vibration. A piezoelectric element according to any one of claims 1 to 9, wherein the piezoelectric vibrating piece is mounted on the piezoelectric vibrating piece.