Piezoelectric vibration piece

Abstract

To provide a quartz vibrating piece having a novel structure capable of suppressing unwanted vibrations more effectively than conventional structures.SOLUTION: A crystal vibrating piece 10 is a rectangular AT-cut crystal vibrating piece in plan view. At least two of the four sides of the crystal vibrating piece, intersecting with the displacement direction of the thickness-shear vibration, each have a portion or the entire side formed as a continuous convex-concave surface 10a along the side containing the side surface. Moreover, the protrusions and depressions are randomly arranged, and a height difference h of at least some of the protrusions and depressions is λ / 3 or greater relative to the wavelength λ of bending vibrations that may occur in the piezoelectric vibrating piece.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric vibrating piece that vibrates in a thickness-shear manner, a piezoelectric device using the same, and an intermediate wafer for manufacturing the piezoelectric vibrating piece. [Background technology]

[0002] Suppressing unwanted vibrations is important for improving the characteristics of piezoelectric vibrating reeds that vibrate in thickness-shear mode. For example, Patent Document 1 describes a piezoelectric vibrating reed with multiple continuous notches along its edge to suppress unwanted vibrations (see, for example, paragraphs 27 and 29 of Patent Document 1). Specifically, the document describes an AT-cut quartz crystal vibrating reed that is rectangular in plan view and whose side surfaces have a continuous uneven surface with a predetermined radius of curvature along the edge of the reed (see, for example, Figure 4 of Patent Document 1).

[0003] In the case of this piezoelectric vibrating reed, since the side surfaces have the above-mentioned specified uneven surfaces, it is possible to reduce the increase in unwanted vibrations, such as bending vibrations and contour vibrations, at a certain frequency, thereby reducing the risk of unwanted vibrations coupling with thickness-shear vibrations and therefore reducing the risk of deterioration in the electrical characteristics of the piezoelectric vibrating reed (see, for example, paragraphs 28 and 30 of Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-145948 Summary of the Invention [Problem to be solved by the invention]

[0005] However, according to research by the inventors of this application, it has been found that further structural innovation is required in order to suppress unwanted vibrations by providing uneven surfaces on the side surfaces of the piezoelectric vibrating reed. This application has been made in consideration of the above points, and therefore the purpose of this application is to provide a piezoelectric vibrating piece having an uneven surface on the side surface of the piezoelectric vibrating piece, a piezoelectric vibrating piece having a new structure that can suppress unwanted vibrations better than conventional methods, a piezoelectric device using the same, and an intermediate wafer for manufacturing the piezoelectric vibrating piece.

[0006] In order to achieve this object, according to a first aspect of the present invention, there is provided a piezoelectric vibrating piece that is rectangular in plan view and vibrates in a thickness-shear manner, Of the four side surfaces of the piezoelectric vibrating piece, at least two side surfaces that intersect with the displacement direction of the thickness shear vibration have a continuous uneven surface along the edge that includes the side surface, or all of the side surfaces. The unevenness is random, and the height difference of at least some of the unevenness is λ / 3 or more, where λ is the wavelength of bending vibration that may occur in the piezoelectric vibrating piece. In carrying out this first invention, the piezoelectric vibrating reed may be made of any suitable piezoelectric material that vibrates in thickness shear mode. Specific examples include AT-cut quartz crystal vibrating reeds, double-rotation cut quartz crystal vibrating reeds such as SC cut, reeds made of piezoelectric ceramic, reeds made of lithium tantalate, and reeds made of lithium niobate. However, it is preferable that the piezoelectric vibrating reed is an AT-cut quartz crystal vibrating reed. This is because applying the present invention to AT-cut quartz crystal vibrating reeds, which are widely used in industry, can improve the characteristics of the AT-cut quartz crystal vibrating reed, further increasing the industrial applicability of AT-cut quartz crystal vibrating reeds.

[0007] Here, providing unevenness on a portion of the side surface means that, for example, unevenness may be provided only on the side surface portion corresponding to the area where vibration mainly occurs, such as the area where the excitation electrode of the piezoelectric vibrating reed is provided, or in other words, unevenness may not be provided on the side surface around the end of the piezoelectric vibrating reed, for example. Note that the side surfaces on which unevenness is provided are not limited to the two side surfaces that intersect with the displacement direction of thickness shear vibration, but may be on part or all of the side surfaces of three sides, or even on part or all of the side surfaces of four sides.

[0008] Furthermore, the phrase "at least some of the irregularities have a height difference of λ / 3 or more" means that all of the irregularities may have a height difference of λ / 3 or more. The upper limit (maximum height difference) of the height of unevenness with a height difference of λ / 3 or more and the ratio to the total unevenness may be determined, for example, as follows. If the height of the unevenness (maximum height difference) with a height difference of λ / 3 or more is too high, problems such as increased crystal impedance, which is loss in the piezoelectric vibrating reed, occur. Furthermore, this tendency also varies depending on the side ratio X / t of the piezoelectric vibrating reed, as will be described later with reference to FIG. 8. Here, t is the thickness of the piezoelectric vibrating reed, typically the thickness of a quartz crystal vibrating reed, and X is the dimension of the quartz crystal vibrating reed in the direction parallel to the X-axis. Specifically, in light of the simulation results shown in the embodiment section described later and the characteristic diagram of FIG. 8, the smaller the side ratio of a piezoelectric vibrating reed, the worse the loss becomes as the height of the unevenness (maximum height difference) with a height difference of λ / 3 or more increases (see side ratios 21 and 30 in FIG. 8). On the other hand, when the side ratio is large, the loss remains constant even when the height of the unevenness (maximum height difference) with a height difference of λ / 3 or more increases (side ratios 41, 53, and 68 in FIG. 8). Therefore, in the simulation results for a piezoelectric vibrating piece with a side ratio of 30, for example, in Figure 8, losses begin to increase when the height difference (maximum height difference) of the unevenness normalized by the wavelength of the bending vibration exceeds around 0.4.Therefore, when considering applying the present invention to piezoelectric vibrating pieces with a side ratio of 30 or 30 to 40, it is believed that the upper limit (maximum height difference) of unevenness with a height difference of λ / 3 or more should be 0.4 (i.e., λ / 2.5) in terms of the height difference of the unevenness normalized by the wavelength of the bending vibration.

[0009] Furthermore, the ratio of unevenness with a height difference of λ / 3 or more to the total unevenness is the ratio. If this ratio is too high, the loss of the piezoelectric vibrating reed increases, and if this ratio is too low, the effect of suppressing unwanted vibrations cannot be obtained. In the simulation of the embodiment described below, the ratio of unevenness with a height difference of λ / 3 or more is set to 25%, and in this simulation, the reduction of unwanted vibrations and the increase in loss are within a range that does not cause problems, so it is preferable to set the ratio of unevenness with a height difference of λ / 3 or more to the total unevenness within an appropriate range that includes 25%. This appropriate range will be explained in detail in the section on practical embodiments described below, but for example, 20 to 30% is preferable. Furthermore, it is preferable that the unevenness with a height difference of λ / 3 or more is dispersed among all the unevenness, that is, is present randomly.

[0010] When implementing this first invention, if an AT-cut quartz crystal vibrating piece is used as the piezoelectric vibrating piece, it is preferable to use a quartz crystal vibrating piece with a side ratio X / t of X / t≧30, where t is the thickness of the quartz crystal vibrating piece and X is the dimension of the quartz crystal vibrating piece in the direction parallel to the X-axis of the quartz crystal. The reason why it is preferable to use a quartz crystal vibrating piece with X / t≧30 is as follows. By providing random unevenness on the side of a quartz crystal vibrating piece with an unevenness height of λ / 3 or more, the density of unwanted vibrations occurring near the main vibration can be reduced (see Figures 3 to 6 below). On the other hand, increasing the unevenness can increase the loss (crystal impedance) of the quartz crystal vibrating piece, depending on the side ratio of the quartz crystal vibrating piece (see Figure 8 below). However, it has been found that for quartz crystal vibrating pieces with a side ratio X / t of X / t≧30, the increase in loss of the quartz crystal vibrating piece when the unevenness is increased is small (see Figure 8 below). Therefore, when using an AT-cut quartz crystal vibrating piece as a piezoelectric vibrating piece, it is preferable to use a quartz crystal vibrating piece with X / t≧30. Here, an AT-cut quartz crystal resonator element with X / t≧30 is typically a high-frequency quartz crystal resonator element that has been or will be increasingly used recently, such as a quartz crystal resonator element with a frequency of 38 MHz or higher. Therefore, by applying the present invention to an AT-cut quartz crystal resonator element with X / t≧30, it is possible to provide a high-frequency quartz crystal resonator element that has the advantage of having a concave / convex height of λ / 3 and meets modern demands. Although the height difference of the concave and convex portions is set to λ / 3 or more with respect to the wavelength λ of the bending vibration, the upper limit should be set to any suitable value depending on the side ratio of the piezoelectric vibrating reed. That is, as will be explained later with reference to FIG. 8, it should be determined taking into consideration the loss of the piezoelectric vibrating reed and the side ratio of the piezoelectric vibrating reed. This point will also be explained in the embodiment.

[0011] Furthermore, according to the second invention of this application, a piezoelectric device is provided which includes the piezoelectric vibrating piece of the first invention and a container for accommodating the piezoelectric vibrating piece. Therefore, according to the second invention, it is possible to provide a piezoelectric device such as a piezoelectric vibrator or a piezoelectric oscillator which has the effects of the first invention. Furthermore, the third invention of this application is an intermediate wafer for manufacturing a piezoelectric vibrating piece, which is characterized by comprising a piezoelectric wafer having a large number of the piezoelectric vibrating pieces of the first invention arranged in a matrix. Therefore, according to the third invention, the piezoelectric vibrating piece of the first invention and the piezoelectric device of the second invention can be easily manufactured using a wafer process. [Effects of the Invention]

[0012] According to the piezoelectric vibrating piece of the first invention, the unevenness provided on the side surface is random, and the height difference of at least some of the unevenness is λ / 3 or more, where λ is the wavelength of the bending vibration that may occur in the piezoelectric vibrating piece. When the side surface is a randomly uneven surface, unwanted vibration waves that propagate to the end of the piezoelectric vibrating reed are diffusely reflected by the unevenness, making it more difficult for specific unwanted vibrations to grow than when the side surface is a regularly uneven surface (see Figure 2, described below). Furthermore, because the height of at least some of the unevenness is λ / 3 or more, the density at which unwanted vibrations occur near the main vibration can be reduced to a practically negligible level compared to when this is not the case (see Figures 3 to 6). Therefore, according to the piezoelectric vibrating reed of the first invention, it is possible to provide a piezoelectric vibrating reed having a novel structure that can suppress unwanted vibrations better than conventional methods, a piezoelectric device using the same, and an intermediate wafer for manufacturing the piezoelectric vibrating reed. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram illustrating a quartz crystal vibrating piece 10 according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a diagram for explaining that the effect of reducing unwanted vibrations differs depending on whether the irregularities on the side surface of the quartz crystal vibrating piece are regular or random. [Figure 3] 1 is a diagram for explaining, using a mode chart, the preferred height of the irregularities provided on an AT-cut quartz crystal vibrating piece having a frequency of 76.8 MHz and a side ratio (X / t) of approximately 41. [Figure 4] 1 is a diagram for explaining, using a mode chart, the preferred height of the irregularities provided on an AT-cut quartz crystal vibrating piece having a frequency of 38.4 MHz and a side ratio (X / t) of approximately 21. [Figure 5] 1 is a diagram for explaining, using a mode chart, the preferred height of the irregularities provided on an AT-cut quartz crystal vibrating piece having a frequency of 97.1 MHz and a side ratio (X / t) of approximately 53. [Figure 6] 1 is a diagram for explaining, using a mode chart, the preferred height of the irregularities provided on an AT-cut quartz crystal vibrating piece having a frequency of 122.6 MHz and a side ratio (X / t) of approximately 68. [Figure 7] 10A and 10B are diagrams for explaining the relationship between the height difference of the unevenness and the electrical characteristics. [Figure 8] 10A and 10B are diagrams for explaining a side effect (increased loss) when unevenness is provided on the side surface of a piezoelectric vibrating reed, and a side ratio of the piezoelectric vibrating reed that can easily reduce the influence of the side effect. [Figure 9] 5A to 5C are diagrams illustrating an embodiment of a piezoelectric device according to a second invention. [Figure 10] 10A and 10B are diagrams for explaining an embodiment of an intermediate wafer according to a third invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the inventions of this application will be described with reference to the drawings. Note that the drawings used for the description are merely schematic illustrations to enable understanding of these inventions. Furthermore, in the drawings used for the description, similar components are designated by the same numbers, and their description may be omitted. Furthermore, the shapes, materials, etc. described in the following description are merely preferred examples within the scope of this invention. Therefore, the inventions are not limited to the following embodiments.

[0015] 1. Piezoelectric vibrating piece according to an embodiment of the present invention 1 is a plan view and a partially enlarged perspective view of a piezoelectric vibrating piece 10 according to an embodiment of the first invention. In this embodiment, an AT-cut quartz crystal vibrating piece is used as the piezoelectric vibrating piece, and therefore the X, Y', and Z' crystal axes of the AT-cut quartz crystal are aligned in FIG. The piezoelectric vibrating piece 10 of the embodiment is rectangular in plan view (in this example, rectangular), is a piezoelectric vibrating piece that vibrates in thickness shear, and all four side surfaces of the piezoelectric vibrating piece have a continuous uneven surface 10a along the edge including the side. Moreover, the unevenness of the uneven surface 10a is random, and the height difference h of at least some of the unevenness is λ / 3 or more, where λ is the wavelength of bending vibration that may occur in the piezoelectric vibrating piece. Here, the random unevenness can be designed by, for example, creating it using random numbers. Furthermore, when manufacturing the piezoelectric vibrating piece 10, processing of the uneven surface 10a in particular can be carried out by, for example, methods using photolithography and wet etching techniques, or by processing transparent bodies using ultrashort pulse lasers, which have been advancing in recent years, or by a combination of the two methods.

[0016] The piezoelectric vibrating reed 10 has excitation electrodes 10b on both its front and back principal surfaces. The piezoelectric vibrating reed 10 has extraction electrodes 10c that are extracted from the excitation electrodes 10b toward one side of the piezoelectric vibrating reed 10 in this case. The piezoelectric vibrating piece 10 can be made of, for example, an AT-cut quartz crystal vibrating piece. In this example, a so-called X-long quartz crystal vibrating piece with its long side along the X-axis is shown. The oscillation frequency, outer dimensions, and size of the excitation electrode 10b of the piezoelectric vibrating piece 10 can be set to any suitable dimensions according to the requirements for the piezoelectric vibrating piece 10. Several specific examples with different oscillation frequencies and outer dimensions are shown below (see the table below). The necessity for the irregularities to be random and the necessity for the irregularities to have a height of λ / 3 or more will be explained below in order.

[0017] 2. The bumps and grooves need to be random One of the features of the present invention is that the irregularities provided on the side surface of the piezoelectric vibrating piece 10 are random. The reason for this will be explained below with reference to Figures 2(A) and 2(B). Fig. 2(A) shows the analysis results of unwanted vibrations in a finite element method model (comparative example) with regular unevenness on the side surface, and Fig. 2(B) shows the analysis results of unwanted vibrations in a finite element method model (example) with the same size and frequency as the comparative example but with random unevenness on the side surface. Note that the regular unevenness in the comparative example model is triangular waveform unevenness with a constant amplitude and period. The random unevenness in the example model is unevenness created using random numbers, as described above. In the case of the comparative example model shown in FIG. 2(A), it can be seen that a displacement Y occurs in the thickness direction of the piezoelectric vibrating reed (a direction perpendicular to the plane of the drawing). This displacement Y is a displacement caused by bending vibration, which is an unwanted vibration. In contrast, in the case of the example model shown in FIG. 2(B), no unwanted displacement Y occurs. Therefore, it can be said that random unevenness on the side surface of the piezoelectric vibrating reed is more effective in suppressing unwanted vibration.

[0018] 3. The height difference of at least some of the unevenness must be λ / 3 or more. Next, we will explain why it is necessary for at least some of the irregularities to have a height difference of λ / 3 or more. The inventor of this application created a mode chart using various analytical models for the finite element method of AT-cut quartz crystal vibrating blanks of groups A to D shown in the table below, each of which has a different height difference (maximum height difference) for some of the irregularities on the side surface, and in which the dimension X along the X-axis of the quartz crystal of the quartz crystal vibrating blank is constant and the dimension Z in the direction parallel to the Z'-axis is changed within a certain range. However, for each analytical model, the ratio of the maximum height difference to the total irregularities is set to 25%. TIFF2025152997000002.tif67166

[0019] 3A, 3B, and 3C are mode charts of the models in group A, each of which has a different maximum unevenness height difference. 4(A), (B), and (C) are mode charts for the models in group B, with the maximum unevenness height difference being different for each model. 5(A), (B), and (C) are mode charts of the models in group A, which are mode charts of each model with different maximum unevenness height differences. 6(A), (B), and (C) are mode charts of the models in group A, which are mode charts of each model with different maximum unevenness height differences. In each of Figures 3 to 6, the horizontal axis represents the dimension of the quartz crystal resonator blank in the direction parallel to the Z' axis, and the vertical axis represents frequency, with the center frequency (e.g., 38.4 MHz) set to 0 and a range of approximately ±2000 ppm from the center frequency. Also, in each of Figures 3 to 6, the mode charts show a model in which the maximum height difference h of the unevenness of the side surface increases from Figure (A) to Figure (C). The arrows in each mode chart indicate the region where a resonance spectrum due to unwanted vibration occurs.

[0020] 3 to 6, (A) to (C) show that the density of the resonance spectrum caused by unwanted vibrations decreases as the maximum height difference between the concave and convex portions increases. In other words, increasing the maximum height difference between the concave and convex portions expands the area that is not affected by unwanted vibrations that tend to couple with the main vibration, making it easier to prevent deterioration of characteristics caused by unwanted vibrations of the quartz crystal resonator element. Furthermore, for all models in groups A to D, it can be seen that when the (height difference between the concave and convex portions h) / (wavelength of the bending vibration λ) is greater than λ / 3 = 0.33λ, the density of unwanted vibrations can be reduced to a level that does not practically affect the main vibration. Therefore, it can be said that the robustness of the piezoelectric vibrating reed is increased when the height difference between the concave and convex portions is λ / 3 or more.

[0021] 4.Specific examples of electrical characteristics Next, to deepen understanding of the present invention, specific examples of electrical characteristics will be described using the models in Group B of the above-mentioned analytical models. Figures 7(A) and 7(B) are explanatory diagrams for this purpose. Here, Figure 7(A) shows the temperature characteristics of loss for each analytical model with different maximum height differences between the convex and concave portions, and Figure 7(B) shows the temperature characteristics of frequency for each analytical model with different maximum height differences between the convex and concave portions. Note that Figure 7(A) also shows the loss of the quartz crystal itself with a dashed line. The values ​​on the vertical axis of Figure 7(B) are the residual values, normalized by the main vibration frequency, of the difference between the frequency at each temperature determined by simulation of the analytical model and the frequency at each temperature in the approximate equation (fifth-order approximate equation) obtained from those frequencies.

[0022] From Figure 7(A), we can see that the temperature characteristics of loss tend to become flatter as the maximum height difference of the asperities increases. Specifically, the models with an asperity height difference of 17 μm and 8.5 μm have flatter temperature characteristics of loss than the model with an asperity height difference of 3 μm. Note that the absolute value of loss is larger for the asperity height difference of 17 μm (0.49λ), which raises concerns, but this point will be explained later in section "5. Loss and Side Ratio of Piezoelectric Vibrating Reed." 7(B) also shows that the residual becomes smaller and flatter as the maximum height difference of the unevenness increases. In particular, the model with a height difference of 17 μm has the smallest and flattest residual.

[0023] 5. Loss and aspect ratio of piezoelectric resonator In the explanation above using Figure 7(A), it was explained that as the height difference between the concave and convex portions increases, the temperature characteristic of loss becomes flatter, but on the other hand, the absolute value of loss increases. Since increased loss is not desirable, the results of an investigation into this point, taking into account the side ratio X / t of the AT-cut quartz crystal blank, are explained below. Figure 8 is an explanatory diagram for this purpose, showing the relationship between the maximum height difference of the concaves and convexes and the loss for various analytical models with side ratios of 21, 41, 53, and 68 shown in the table above, and a separate analytical model with a side ratio of 30. The vertical axis of Figure 8, however, shows the ratio of the loss of each model to the loss of one model among the models, i.e., the loss magnification.

[0024] From Figure 8, it can be seen that for a side ratio of 21, loss increases suddenly when the maximum height difference between the concaves and convexities normalized by the wavelength of the bending vibration exceeds 0.2. It can be seen that for a side ratio of 30, the tendency for loss to increase is gradual even when the maximum height difference between the concaves and convexities increases, compared to a side ratio of 21. It can be seen that for side ratios of 41, 53, and 68, there is no increase in loss even when the maximum height difference between the concaves and convexities increases. In light of the fact that it has been stated that in order to suppress unwanted vibrations, the maximum height difference between the concave and convex portions should be λ / 3 or more, where λ is the wavelength of the bending vibration (0.33 when normalized by the wavelength of the bending vibration), when applying a design method that sets the maximum height difference between the concave and convex portions to λ / 3 or more to an AT-cut quartz crystal vibrating piece, it can be said that it is preferable to apply it to one with a side ratio of 30 or more.

[0025] 6. Ratio of maximum height difference to total unevenness Next, we will discuss the ratio of the maximum height difference to the total unevenness. As mentioned above, the simulation was performed with the ratio of the maximum height difference to the total unevenness set to 25%. It has been found that a ratio of 25% can reduce unwanted vibrations without increasing losses. Therefore, it can be said that the ratio of the maximum height difference to the total unevenness should be set to an appropriate range that includes 25%, so we will consider this range. According to the inventor's experience, it can be said that the characteristics of a piezoelectric vibrating reed are practically acceptable if the loss factor is 3 or less. When this idea is applied to the characteristic diagram shown in Figure 8, which is a characteristic diagram of a piezoelectric vibrating reed with a side ratio of 30, the maximum unevenness height difference (value normalized by the bending wavelength) when the loss factor is 3 is 0.4. Using this value of 0.4, when considering the evaluation value when 25% of all unevenness on the side of the piezoelectric vibrating reed has an unevenness height difference of 0.4 normalized by the bending wavelength, the evaluation value obtained is 0.4 x 25% = 0.1.

[0026] If the maximum height difference between the convex and concave portions normalized by the bending wavelength is 0.33, the evaluation value is 0.33×α%=0.1. This α can be said to be the percentage of all the unevenness on the edge of the piezoelectric vibrating piece that can have a maximum height difference of 0.33 without causing loss in the piezoelectric vibrating piece to exceed 3, so when α is calculated from this evaluation value, it is α = 0.1 / 0.33 = 30%. Therefore, it can be said that the upper limit of the unevenness with a maximum height difference of λ / 3 that can be included in the uneven structure provided on the edge of the piezoelectric vibrating piece is preferably 30%. Therefore, the range in which unevenness with a maximum height difference of λ / 3 can be included in the uneven structure on the edge of the piezoelectric vibrating piece should be 30% or less, taking into account loss, and preferably 25% or less as shown in the example. On the other hand, the lower limit of the above ratio is determined depending on the degree of effect of suppressing unwanted vibrations, but according to the inventor's investigation, 15% is good, and 20% is more preferable.

[0027] 7. Piezoelectric Device Embodiments Next, an embodiment of a piezoelectric device, which is the second invention of this application, will be described. Figure 9 is a diagram for explaining a quartz crystal unit 30, which is a piezoelectric device of the embodiment. In particular, Figure 9(A) is a plan view, and Figure 9(B) is a cross-sectional view taken along line P-P in Figure 9(A). Note that Figure 9(A) omits the illustration of the cover member 33 shown in Figure 9(B). The quartz crystal resonator 30 of the embodiment includes the quartz crystal resonator piece 10 of the first invention, a container 31 that houses the quartz crystal resonator piece 10, and a lid member 33 that seals the container 31. In this embodiment, the container 31 includes a recess 31a for accommodating the quartz crystal vibrating piece 10, a wall 31b surrounding the recess 31a, an adhesive pad 31c provided on the bottom of the recess 31a in a position corresponding to the edge of the quartz crystal vibrating piece 10 on the lead electrode side, and an external connection terminal 31d provided on the exterior bottom surface of the container 31. The adhesive pad 31c and the external connection terminal 31d are connected by via wiring or the like (not shown). The container 31 can be formed, for example, from a ceramic package.

[0028] The quartz crystal vibrating piece 10 is connected and fixed at one side to an adhesive pad 31c of the container 31 with a conductive adhesive 40. The opening of the recess 31a is then sealed with a lid member 33, thereby forming the quartz crystal vibrator 30 of this embodiment. The container 31 is not limited to the above example, and may be, for example, a container configured with a flat base and a cap-shaped lid member. Furthermore, although the above description cites quartz crystal resonator 30 as an example of a piezoelectric device, crystal oscillators (including temperature-compensated types) in which a quartz crystal resonator piece and an oscillation circuit for the quartz crystal resonator piece are both mounted in a container, and crystal resonators with temperature sensors in which a quartz crystal resonator piece and a temperature sensor are both mounted in a container are also included in the piezoelectric devices referred to in the present invention.

[0029] 8. Intermediate wafers for manufacturing piezoelectric vibrating pieces Next, an embodiment of an intermediate wafer for manufacturing a piezoelectric vibrating piece, which is the third invention of this application, will be described. 10 is a top view and a partial enlarged view illustrating an intermediate wafer 50 (hereinafter referred to as intermediate wafer 50) for manufacturing a piezoelectric vibrating piece according to an embodiment. In FIG. 10, a quartz crystal wafer as intermediate wafer 50 is illustrated along with the relationship between the X-axis, Y'-axis, and Z'-axis of the quartz crystal. The intermediate wafer 50 of this embodiment is composed of a quartz crystal wafer 50 having a large number of quartz crystal vibrating pieces 10 of the first invention arranged in a matrix. In the illustrated example, the planar shape of the intermediate wafer 50 is circular, but it may also be rectangular. In the intermediate wafer 50, each quartz crystal vibrating piece 10 is connected to a frame portion 51 via a break-off portion 53. Each quartz crystal vibrating piece 10 is broken off from the intermediate wafer 50 at the break-off portion 53, and then separated into individual quartz crystal vibrating pieces 10, which can then be mounted in various containers for quartz crystal resonators or quartz crystal oscillators for use. [Explanation of symbols]

[0030] 10: Piezoelectric vibrating piece according to an embodiment (AT-cut crystal vibrating piece) 10a: Uneven surface 10b: Excitation electrode 10c: Extraction electrode h: Height difference of unevenness t: Thickness of the piezoelectric resonator element (AT-cut quartz crystal resonator element) X: The dimension of the AT-cut quartz crystal piece parallel to the X-axis direction λ: wavelength of bending vibration 30: Crystal unit according to an embodiment 31: Container 33: Lid member 40: Conductive adhesive 50: Intermediate wafer for manufacturing piezoelectric vibrating piece 51: Frame 53: Folding part

Claims

1. A piezoelectric vibrating piece that is rectangular in plan view and vibrates in a thickness-shear manner, Of the four side surfaces of the piezoelectric vibrating piece, at least two side surfaces that intersect with the displacement direction of the thickness shear vibration are partially or entirely formed as uneven surfaces that are continuous along the sides that include the side surfaces, The unevenness is random, and the height difference of at least some of the unevenness is λ / 3 or more, where λ is the wavelength of bending vibration that may occur in the piezoelectric vibrating piece.

2. 2. The piezoelectric vibrating piece according to claim 1, wherein the piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece.

3. The piezoelectric vibrating piece according to claim 1, wherein the piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece having a side ratio X / t of 30 or more (where X is the dimension of the quartz crystal vibrating piece parallel to the X-axis of the quartz crystal, and t is the thickness of the quartz crystal vibrating piece).

4. The piezoelectric vibrating piece according to claim 1, characterized in that the piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece having a side ratio X / t of 41 or more (where X is the dimension of the quartz crystal vibrating piece parallel to the X-axis of the quartz crystal, and t is the thickness of the quartz crystal vibrating piece).

5. The piezoelectric vibrating piece according to claim 1, characterized in that the piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece with a side ratio X / t of 30 to 40, and the height difference of at least some of the irregularities is λ / 3 to λ / 2.5 (where X is the dimension parallel to the X-axis of the quartz crystal of the quartz crystal vibrating piece, and t is the thickness of the quartz crystal vibrating piece).

6. The piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece having a side ratio X / t of 30 or more, The piezoelectric vibrating piece according to claim 1, characterized in that it contains irregularities with a height difference of λ / 3 or more at a ratio of 20 to 30% (where X is the dimension of the quartz crystal vibrating piece parallel to the X-axis of the quartz crystal, and t is the thickness of the quartz crystal vibrating piece).

7. 7. A piezoelectric device comprising: the piezoelectric vibrating piece according to claim 1; and a container for accommodating the piezoelectric vibrating piece.

8. 8. The piezoelectric device according to claim 7, wherein the piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece, and the piezoelectric device is a quartz crystal resonator or a quartz crystal oscillator.

9. 7. An intermediate wafer for manufacturing a piezoelectric vibrating piece, comprising a piezoelectric wafer having a large number of the piezoelectric vibrating pieces according to claim 1 arranged in a matrix.

10. 10. The intermediate wafer for manufacturing a piezoelectric vibrating piece according to claim 9, wherein the piezoelectric vibrating piece is an AT-cut quartz crystal vibrating piece, and the piezoelectric wafer is a quartz crystal wafer.

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