JP2023021842A - Piezoelectric Vibration Piece, Piezoelectric Vibrator and Oscillator - Google Patents

Abstract

To provide a piezoelectric vibration piece having a stable frequency characteristic, a piezoelectric vibrator and an oscillator.SOLUTION: In a piezoelectric vibration piece 3, a piezoelectric plate 30 has vibration arm parts 31 and a base 35. The vibration arm parts 31 extend in a longitudinal direction L and are arranged in line in a width direction W. The base 35 is connected to a base end 31b in the longitudinal direction L of the vibration arm parts 31. The vibration arm part 31 has a groove 34 which is recessed in a thickness direction T. The vibration arm part 31 has: a root part 50 having an R face 51 extending from the base 35 to a tip 31t of the vibration arm part 31 at a constant curvature on both sides of the width direction W; a tapered part 60 extending from an end of the root part 50 closer to a tip 31t toward the tip 31t gradually narrowing the width in the width direction W; and a straight part 70 extending with a constant width from an end closer to the tip 31t of the tapered part 60 toward the tip 31t.SELECTED DRAWING: Figure 5

Description

The present invention relates to a piezoelectric vibrating piece, a piezoelectric vibrator and an oscillator.

For example, in electronic devices such as mobile phones and personal digital assistants, piezoelectric vibrators using crystal or the like are used as devices used as time sources, timing sources such as control signals, and reference signal sources. As a piezoelectric vibrator of this type, there is known one in which a piezoelectric vibrating piece is hermetically sealed in a package having a cavity formed therein.

A so-called tuning fork type piezoelectric vibrating reed is provided with a piezoelectric plate having a base and a pair of vibrating arms extending parallel to each other from the base, and excitation electrodes arranged on the outer surfaces of the vibrating arms. be. In a tuning-fork type piezoelectric vibrating piece, when a voltage is applied to an excitation electrode, each vibrating arm vibrates at a predetermined frequency in a direction toward or away from each other, starting from the base end (connection with the base). (See, for example, Patent Literature 1 and Patent Literature 2).

Furthermore, some tuning-fork type piezoelectric vibrating reeds have grooves formed in the vibrating arms in order to reduce the equivalent series resistance value (crystal impedance) while suppressing a decrease in the strength of the vibrating arms. The vibration modes of the vibrating arms include a secondary vibration mode (secondary bending mode) in addition to the basic vibration mode. In order to obtain stable frequency characteristics, it is preferable to vibrate the vibrating arms in the fundamental vibration mode. As means for vibrating the vibrating arms in the fundamental vibration mode, there is a method of reducing the equivalent series resistance value in the fundamental vibration mode by increasing the ratio of the width of the grooves to the width of the vibrating arms.

Japanese Patent Application Laid-Open No. 2019-41301 Japanese Patent Application Laid-Open No. 2019-41302

However, increasing the ratio of the width of the groove to the width of the vibrating arm also reduces the equivalent series resistance value in the secondary vibration mode. As a result, the vibrating arms are more likely to oscillate in the secondary vibration mode, and relatively less likely to oscillate in the fundamental vibration mode, making it impossible to obtain stable frequency characteristics. In particular, tuning-fork-type piezoelectric vibrating reeds that do not have widened weights at the tips of their vibrating arms tend to oscillate in the secondary vibration mode. Development of technology to effectively suppress oscillation in the secondary vibration mode is desired.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a piezoelectric vibrating piece having stable frequency characteristics, and a piezoelectric vibrator and an oscillator provided with the piezoelectric vibrating piece.

A piezoelectric vibrating piece of the present invention includes a pair of vibrating arms extending in a first direction and arranged side by side in a second direction perpendicular to the first direction, and a base to which a base end is connected, the vibrating arm having a groove recessed in a third direction orthogonal to the first direction and the second direction; On both sides in two directions, a root portion having an R surface extending from the base portion toward the tip end side of the vibrating arm portion with a constant curvature, and the second arm portion extending from the end portion near the tip end of the root portion toward the tip end side. It has a tapered portion that extends while narrowing the width in the direction, and a straight portion that extends from the end of the tapered portion near the tip to the tip with a constant width.

Here, in the secondary vibration mode, the antinode of vibration occurs at a position closer to the proximal end of the vibrating arms than in the fundamental vibration mode. Therefore, if grooves are formed in the vibrating arms in order to reduce the equivalent series resistance value in the fundamental vibration mode, the portions near the base ends of the vibrating arms are more likely to flex, and the piezoelectric vibrating reed oscillates in the secondary vibration mode. easier.
According to the present invention, compared to a configuration in which the vibrating arms are not provided with tapered portions, the vibrating arms are formed thicker, so that portions of the vibrating arms closer to the base ends are less likely to bend in the second direction. be able to. As a result, the equivalent series resistance value in the secondary vibration mode can be reduced by enlarging the grooves formed in the vibrating arms in the second direction. As a result, a decrease in the equivalent series resistance value in the secondary vibration mode can be suppressed. Therefore, even if the grooves formed in the vibrating arms are enlarged in the second direction, the ratio of the equivalent series resistance value in the secondary vibration mode to the equivalent series resistance value in the fundamental vibration mode can be increased. Therefore, the piezoelectric vibrating reed can have stable frequency characteristics.

In the piezoelectric vibrating piece described above, the total length of the vibrating arms in the first direction is defined as L, and from the base ends of the vibrating arms in the first direction to the ends of the tapered portions near the distal ends. is defined as D, D/L may be 0.1 or more and 0.3 or less.

According to the present invention, by setting D/L to 0.3 or less, compared with the case where D/L is 0, the increase in the equivalent series resistance value in the fundamental vibration mode is suppressed to about 10%, and when the circuit is mounted, can reduce the impact on the increase in power consumption. Further, by setting D/L to 0.1 or more, the ratio of the equivalent series resistance value in the secondary vibration mode to the equivalent series resistance value in the fundamental vibration mode can be made larger than in the conventional configuration without the tapered portion. That is, the fundamental vibration mode can be effectively used as the main vibration mode compared to the conventional configuration.

In the above piezoelectric vibrating piece, the groove extends in the first direction with a constant width, the width of the straight portion in the second direction is defined as W1, and the width of the groove in the second direction is defined as W2. If defined, W2/W1 may be between 0.6 and 0.85.

According to the present invention, the ratio of the equivalent series resistance value in the secondary vibration mode to the equivalent series resistance value in the fundamental vibration mode is equal to or higher than that of the conventional configuration in which there is no tapered portion and W2/W1 is 0.65. can be Therefore, compared with the conventional configuration, oscillation in the secondary vibration mode can be suppressed and the fundamental vibration mode can be effectively used as the main vibration mode.

In the piezoelectric vibrating piece described above, the end portion of the tapered portion closer to the tip may be within the formation range of the groove in the first direction.

According to the present invention, since the grooves are also formed on the distal end side of the vibrating arms rather than the tapered portions, it is possible to obtain the effect of the grooves on oscillation in the fundamental vibration mode.

In the piezoelectric vibrating piece described above, the side surfaces of the vibrating arm portions in the second direction may be continuous from the root portion to the straight portion.

According to the present invention, since sharp corners are not formed on the side surfaces, it is possible to prevent the vibrating arms from being easily damaged and the vibration characteristics from deteriorating due to stress concentration at the corners.

A piezoelectric vibrator of the present invention includes the piezoelectric vibrating piece described above and a package for hermetically sealing the piezoelectric vibrating piece.

According to the present invention, since the above-described piezoelectric vibrating piece is included, a high-quality piezoelectric vibrator with excellent operational reliability can be obtained.

An oscillator according to the present invention includes the piezoelectric vibrator described above, and the piezoelectric vibrator is electrically connected to an integrated circuit as an oscillator.

According to the present invention, since the above-described piezoelectric vibrating reed is included, a high-quality oscillator with excellent operational reliability can be obtained.

According to the present invention, it is possible to provide a piezoelectric vibrating piece having stable frequency characteristics, and a piezoelectric vibrator and oscillator provided with the piezoelectric vibrating piece.

1 is a diagram showing an oscillator according to an embodiment; FIG. 1 is an external perspective view of a piezoelectric vibrator according to an embodiment; FIG. FIG. 4 is a plan view of the piezoelectric vibrator showing a state in which the sealing plate is removed; 1 is a plan view of a piezoelectric vibrating piece according to an embodiment; FIG. 1 is a plan view of a piezoelectric plate according to an embodiment; FIG. FIG. 6 is a plan view showing an enlarged part of the piezoelectric plate shown in FIG. 5; 4 is a graph showing the relationship between taper ratio and equivalent series resistance value. 4 is a graph showing the relationship between groove width ratio and equivalent series resistance value. 4 is a graph showing the relationship between groove width ratio and equivalent series resistance value. 4 is a graph showing the relationship between groove width ratio and equivalent series resistance value.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. In the following description, the same reference numerals are given to components having the same or similar functions. Duplicate descriptions of these configurations may be omitted.

(oscillator)
FIG. 1 is a diagram showing an oscillator according to an embodiment.
As shown in FIG. 1, oscillator 100 includes substrate 101 , electronic component 102 , integrated circuit 103 , and piezoelectric vibrator 1 . Electronic component 102 is, for example, a capacitor, and is mounted on substrate 101 . An integrated circuit 103 is for an oscillator and is mounted on the substrate 101 . The integrated circuit 103 is electrically connected to each of the piezoelectric vibrator 1 and the electronic component 102 via wiring (not shown). The piezoelectric vibrator 1 is mounted, for example, on the substrate 101 near the integrated circuit 103 . The piezoelectric vibrator 1 functions as an oscillator. The piezoelectric vibrator 1 will be described later. At least part of the oscillator 100 may be appropriately molded with resin (not shown).

In the oscillator 100, when power is supplied to the piezoelectric vibrator 1, the piezoelectric vibrating piece 3 (see FIG. 5) of the piezoelectric vibrator 1 vibrates. The vibration of the piezoelectric vibrating piece 3 is converted into an electric signal by the piezoelectric characteristics of the piezoelectric vibrating piece 3 . This electrical signal is output from the piezoelectric vibrator 1 to the integrated circuit 103 . The integrated circuit 103 generates a frequency signal by executing various processes on the electrical signal output from the piezoelectric vibrator 1 .

The oscillator 100 can be applied to, for example, a single-function oscillator for clocks, a timing control device for controlling the operation timing of various devices such as computers, and a device for providing time or a calendar. The integrated circuit 103 is configured according to the functions required of the oscillator 100 and may include a so-called RTC (real time clock) module.

(piezoelectric vibrator)
FIG. 2 is an external perspective view of the piezoelectric vibrator according to the embodiment. FIG. 3 is a plan view of the piezoelectric vibrator with the sealing plate removed.
As shown in FIGS. 2 and 3, the piezoelectric vibrator 1 is a so-called ceramic package type surface mount vibrator. A piezoelectric vibrator 1 includes a package 2 having a cavity C hermetically sealed inside, and a piezoelectric vibrating piece 3 housed in the cavity C. As shown in FIG. Note that the piezoelectric vibrator 1 has a rectangular parallelepiped shape. In the present embodiment, the longitudinal direction of the piezoelectric vibrator 1 is referred to as a longitudinal direction L (first direction), and the lateral direction thereof is referred to as a width direction W (second direction). is called a thickness direction T (third direction).

The package 2 includes a package body 5 and a sealing plate 6 joined to the package body 5 and forming a cavity C between the package body 5 and the sealing plate 6 .
The package body 5 includes a first base substrate 10 and a second base substrate 11 that are superimposed and joined together, and a seal ring 12 that is joined onto the second base substrate 11 .

The first base substrate 10 is a ceramic substrate having a rectangular shape in plan view in the thickness direction T. As shown in FIG. A pair of external electrodes 21A and 21B are formed on the lower surface of the first base substrate 10 with a gap therebetween in the longitudinal direction L. As shown in FIG. The external electrodes 21A and 21B are composed of a single-layer film of a single metal formed by vapor deposition, sputtering, or the like, or a laminated film in which different metals are laminated.

The second base substrate 11 is a ceramic substrate having the same shape as the first base substrate 10 when viewed from above, and is integrally bonded to the first base substrate 10 by sintering or the like while being superimposed on the first base substrate 10 . ing. The upper surface of the second base substrate 11 serves as a mounting surface 11a on which the piezoelectric vibrating reed 3 is mounted. As the ceramic material used for the base substrates 10 and 11, for example, HTCC (High Temperature Co-Fired Ceramic) made of alumina, LTCC (Low Temperature Co-Fired Ceramic) made of glass ceramics, etc. can be used. is.

A pair of electrode pads 20A and 20B, which are connection electrodes with the piezoelectric vibrating piece 3, are formed on the mounting surface 11a of the second base substrate 11. As shown in FIG. Like the external electrodes 21A and 21B described above, the electrode pads 20A and 20B are composed of a single-layer film of a single metal formed by vapor deposition, sputtering, or the like, or a laminated film in which different metals are laminated. The electrode pads 20A and 20B are arranged side by side in the width direction W in a portion of the mounting surface 11a that is closer to one side in the longitudinal direction L. As shown in FIG. The electrode pads 20A, 20B and the external electrodes 21A, 21B are electrically connected to each other via through wires (not shown) that penetrate the base substrates 10, 11 in the thickness direction T, respectively.

Further, the second base substrate 11 is formed with a penetrating portion 11b penetrating through the second base substrate 11 in the thickness direction T. As shown in FIG. The penetrating portion 11b is formed in a portion near the other side in the longitudinal direction L with respect to the electrode pads 20A and 20B. The penetrating portion 11b has a rectangular shape with rounded corners in plan view. The penetrating portion 11b avoids contact between each vibrating arm portion 31A, 31B and the second base substrate 11, which will be described later.

At the four corners of each of the base substrates 10 and 11, notch portions 15 having a 1/4 circular arc shape in plan view are formed over the entire thickness direction T of both base substrates 10 and 11. As shown in FIG. Each of the base substrates 10 and 11 is formed by, for example, stacking two wafer-shaped ceramic substrates and bonding them together, and then forming a plurality of through holes penetrating both ceramic substrates in a matrix. is cut into a grid. At that time, the notch portion 15 described above is formed by dividing the through hole into four parts.

The seal ring 12 is a conductive frame-shaped member that is one size smaller than the outer shape of each of the base substrates 10 and 11 and is joined to the mounting surface 11 a of the second base substrate 11 . Specifically, the seal ring 12 is bonded to the second base substrate 11 by baking with a brazing material such as silver brazing or a solder material, or by welding or the like to a metal bonding layer formed on the second base substrate 11. It is The seal ring 12 constitutes the sidewall of the cavity C. As shown in FIG.

Examples of materials for the seal ring 12 include nickel-based alloys, and specifically, they may be selected from Kovar, Elinvar, Invar, 42-alloy, and the like. In particular, as the material for the seal ring 12, it is preferable to select a material having a coefficient of thermal expansion close to that of the base substrates 10 and 11 made of ceramics. For example, when alumina having a coefficient of thermal expansion of 6.8×10 ⁻⁶ /° C. is used for the base substrates 10 and 11, Kovar having a coefficient of thermal expansion of 5.2×10 ⁻⁶ /° C. or A 42-alloy with a modulus of 4.5 to 6.5×10 ⁻⁶ /° C. is preferably used.

The sealing plate 6 is made of a conductive substrate and bonded onto the seal ring 12 to hermetically seal the inside of the package body 5 . A space defined by the seal ring 12, the sealing plate 6, and the base substrates 10 and 11 forms a hermetically sealed cavity C. As shown in FIG.

The piezoelectric vibrating piece 3 is accommodated in a cavity C of the package 2 that is hermetically sealed. The piezoelectric vibrating piece 3 includes a piezoelectric plate 30 made of a piezoelectric material such as crystal, lithium tantalate, or lithium niobate. The piezoelectric plate 30 has a base portion 35 and a pair of vibrating arm portions 31A and 31B extending from the base portion 35 . The piezoelectric vibrating piece 3 is mounted on the package 2 in the cavity C by supporting the base portion 35 on the mounting surface 11a of the package 2 with a conductive adhesive. The piezoelectric vibrating piece 3 is supported in the cavity C with the vibrating arm portions 31A and 31B floating from the base substrates 10 and 11 . Two systems of excitation electrodes 41 and 42 (see FIG. 4) are arranged on the outer surfaces of the vibrating arms 31A and 31B to vibrate the pair of vibrating arms 31A and 31B when a predetermined voltage is applied. .

To operate the piezoelectric vibrator 1, a predetermined voltage is applied to the external electrodes 21A and 21B (see FIG. 2). Then, current flows through the excitation electrodes 41 and 42 and an electric field is generated between the excitation electrodes 41 and 42 . Each of the vibrating arms 31A and 31B vibrates at a predetermined resonance frequency, for example, in a direction toward or away from each other (width direction W) due to a reverse piezoelectric effect caused by an electric field generated between the excitation electrodes 41 and 42 . The vibrations of the respective vibrating arms 31A and 31B are used as a time source, a timing source for control signals, a reference signal source, and the like.

(piezoelectric vibrating piece)
The piezoelectric vibrating piece 3 of the embodiment will be described in detail.
FIG. 4 is a plan view of the piezoelectric vibrating piece according to the embodiment.
As shown in FIG. 4 , the piezoelectric vibrating piece 3 includes a piezoelectric plate 30 and electrode films 40 arranged on the outer surface including the front and back surfaces of the piezoelectric plate 30 . In this embodiment, the longitudinal direction L, the width direction W and the thickness direction T of the piezoelectric vibrator 1 coincide with the longitudinal direction, the width direction and the thickness direction of the piezoelectric vibrating reed 3, respectively. Therefore, in the following description of the piezoelectric vibrating piece 3, the longitudinal direction L, width direction W, and thickness direction T of the piezoelectric vibrator 1 are used.

FIG. 5 is a plan view of the piezoelectric plate according to the embodiment.
As shown in FIG. 5, the piezoelectric plate 30 includes a pair of vibrating arms 31A and 31B that extend in the longitudinal direction L and are arranged side by side in the width direction W. and a base portion 35 to which the proximal end of L is connected. In this embodiment, the piezoelectric material forming the piezoelectric plate 30 will be described using crystal as an example. Here, the electric axis of the quartz crystal is the X axis, the mechanical axis is the Y axis, and the optical axis is the Z axis. With respect to the coordinate system in which these X, Y and Z axes are orthogonal, a new axis obtained by rotating the Z axis around the X axis within the range of -5° to +10° is defined as the Z' axis, and the X axis is the X axis. A new axis when the Y axis is rotated at the same angle as the Z axis in a plane containing the Z axis and the Y axis as rotation axes is defined as the Y′ axis, and these X, Y′, and Z′ axes are Let the orthogonal coordinate system be a new orthogonal coordinate system. At this time, the X-axis coincides with the width direction W, the Y'-axis coincides with the longitudinal direction L, and the Z'-axis coincides with the thickness direction T in this embodiment. At this time, the piezoelectric plate 30 has a thickness in the Z'-axis direction, and the vibrating arms 31A and 31B extend from the base 35 in the Y'-axis direction.

The base portion 35 is formed in a rectangular shape in plan view. The base portion 35 has an end portion 36 on one side in the longitudinal direction L to which the pair of vibrating arm portions 31A and 31B are connected. The end portion 36 extends along the width direction W. As shown in FIG. In this embodiment, the end portion 36 is formed to protrude to both sides in the width direction W from the pair of vibrating arm portions 31A and 31B.

The pair of vibrating arms 31A and 31B are arranged side by side in the width direction W in parallel. Each of the vibrating arm portions 31A and 31B has a base end 31b on the side of the base portion 35 as a fixed end and a tip end 31t as a free end, and vibrates in a direction (width direction W) in which it approaches and separates from each other. A base end 31b of each of the vibrating arm portions 31A and 31B is a portion connected to the end portion 36 of the base portion 35. As shown in FIG. In the present embodiment, the pair of vibrating arms 31A and 31B are formed in the same manner. write.

The vibrating arm portion 31 has a pair of main surfaces 32 facing in the thickness direction T and a pair of side surfaces 33 connecting the pair of main surfaces 32 on both sides in the width direction W. The pair of main surfaces 32 are part of the front and back surfaces of the piezoelectric plate 30 . A groove 34 recessed in the thickness direction T is formed in each main surface 32 . The groove 34 extends in the longitudinal direction L with constant width and depth. The grooves 34 of each main surface 32 are formed so as to match each other in plan view in the thickness direction T. As shown in FIG. Each groove 34 is formed symmetrically with respect to the width center of the vibrating arm portion 31 in plan view. One end of the groove 34 is located at the same position as the base end 31b of the vibrating arm portion 31 in the longitudinal direction L. As shown in FIG. The other end of the groove 34 in the longitudinal direction L is located in the middle of the vibrating arm portion 31 . In the present embodiment, the other end of the groove 34 is equidistant from the distal end 31t and the proximal end 31b of the vibrating arm portion 31, respectively. The vibrating arms 31 extend with a constant thickness except for the range where the grooves 34 are formed.

The vibrating arm portion 31 has a root portion 50, a tapered portion 60, and a straight portion 70 in order from the base end 31b toward the tip end 31t. The root portion 50 includes the base end 31b of the vibrating arm portion 31 . The tapered portion 60 is spaced apart in the longitudinal direction L from the proximal end 31 b and the distal end 31 t of the vibrating arm portion 31 . Straight portion 70 includes tip 31 t of vibrating arm portion 31 .

6 is a plan view showing an enlarged part of the piezoelectric plate shown in FIG. 5. FIG. In FIG. 6, the boundary line between the base portion 35 and the vibrating arm portion 31, the boundary line between the root portion 50 and the tapered portion 60, and the boundary line between the tapered portion 60 and the straight portion 70 are indicated by two-dot chain lines. ing.
As shown in FIG. 6, the root portion 50 has rounded surfaces 51 on both sides in the width direction W. As shown in FIG. The R surface 51 is part of the side surface 33 of the vibrating arm portion 31 . The R surface 51 extends from the end portion 36 of the base portion 35 toward the tip end 31t of the vibrating arm portion 31 with a constant curvature. The R surface 51 is a concave surface. The R surface 51 is smoothly connected to the end portion 36 of the base portion 35 so as to be continuous.

The tapered portion 60 extends from the end of the vibrating arm portion 31 in the base portion 50 near the tip 31t toward the tip 31t while narrowing the width in the width direction W. As shown in FIG. The tapered portion 60 has tapered surfaces 61 on both sides in the width direction W. As shown in FIG. The tapered surface 61 is part of the side surface 33 of the vibrating arm portion 31 . The tapered surface 61 is smoothly connected to the R surface 51 of the root portion 50 so as to be continuous. The tapered surface 61 extends toward the center of the width of the vibrating arm portion 31 from the connecting portion with the R surface 51 toward the tip 31t of the vibrating arm portion 31 . The tapered surface 61 extends toward the distal end 31t of the vibrating arm 31 at a constant inclination with respect to the longitudinal direction L from the connecting portion with the R surface 51 . The tapered surface 61 extends linearly in plan view, except for connecting portions with the R surface 51 at both ends in the longitudinal direction L or a straight surface 71 to be described later.

The straight portion 70 extends with a constant width from the end of the vibrating arm portion 31 near the tip 31t of the tapered portion 60 to the tip 31t. The tip of the straight portion 70 has a shape cut off perpendicular to the longitudinal direction L. As shown in FIG. The straight portion 70 has straight surfaces 71 on both sides in the width direction W. As shown in FIG. The straight surface 71 is part of the side surface 33 of the vibrating arm portion 31 . The straight surface 71 is smoothly connected to the tapered surface 61 of the tapered portion 60 so as to be continuous. Thereby, the side surface 33 of the vibrating arm portion 31 is continuous from the root portion 50 to the straight portion 70 . The straight surface 71 extends in the longitudinal direction L from the connecting portion with the tapered surface 61 to the tip 31 t of the vibrating arm portion 31 .

As shown in FIG. 4, the electrode film 40 includes excitation electrodes 41 and 42 and mount electrodes 43 and 44 .
Two systems of the excitation electrodes 41 and 42 are provided on the outer surface of the vibrating arm portion 31 . Each excitation electrode 41, 42 is patterned so as to be electrically insulated from each other. The excitation electrodes 41 and 42 have a first excitation electrode 41 and a second excitation electrode 42 . The first excitation electrodes 41 are formed on both side surfaces 33 of the vibrating arm portion 31A and on the grooves 34 of the vibrating arm portion 31B. In the longitudinal direction L, an end portion of the vibrating arm portion 31B near the tip 31t of the tapered portion 60 (see FIG. 5) is positioned within the formation range of the first excitation electrode 41 on the groove 34 of the vibrating arm portion 31B. Each part of the first excitation electrode 41 is electrically connected to each other. The second excitation electrodes 42 are formed on the grooves 34 of the vibrating arm portion 31A and on both side surfaces 33 of the vibrating arm portion 31B. In the longitudinal direction L, the ends of the vibrating arms 31A in the tapered portion 60 near the tips 31t are positioned within the formation range of the second excitation electrodes 42 on the grooves 34 of the vibrating arms 31A. Each part of the second excitation electrode 42 is electrically connected to each other. The excitation electrodes 41 and 42 vibrate each vibrating arm portion 31 in the width direction W when a predetermined drive voltage is applied between the excitation electrodes 41 and 42 .

The mount electrodes 43 and 44 are provided as mount portions when the piezoelectric vibrating piece 3 is mounted on the package 2 . Mount electrodes 43 and 44 are provided on the main surface of base 35 . Specifically, the mount electrodes 43 and 44 include a first mount electrode 43 and a second mount electrode 44 spaced apart in the width direction W. As shown in FIG. The first mount electrode 43 is electrically connected to the first excitation electrode 41 . The second mount electrode 44 is electrically connected to the second excitation electrode 42 . Mount electrodes 43 and 44 are electrically connected to electrode pads 20A and 20B of package 2 via a conductive adhesive.

The dimensions and functions of each part of the piezoelectric vibrating piece 3 of the embodiment will be described in detail.
Here, as shown in FIG. 5, the total length of the vibrating arm portion 31 in the longitudinal direction L is defined as L, and from the base end 31b of the vibrating arm portion 31 in the longitudinal direction L to the end portion of the tapered portion 60 near the tip 31t. is defined as D, and D/L is called taper ratio. Further, as shown in FIG. 6, the width of the straight portion 70 in the width direction W is defined as W1, the width of the groove 34 in the width direction W is defined as W2, and W2/W1 is called a groove width ratio. 7 to 10, R1 represents the equivalent series resistance value (crystal impedance) in the fundamental vibration mode, and R2 represents the equivalent series resistance value in the secondary vibration mode. Numerical data in the following description are results obtained by simulation using finite element method analysis software manufactured by Ansys.

FIG. 7 is a graph showing the relationship between taper ratio and equivalent series resistance value. The horizontal axis of the graph shown in FIG. 7 represents the taper ratio. The first vertical axis on the left side of the graph shown in FIG. 7 represents the ratio R2/R1 of the equivalent series resistance value in the secondary vibration mode to the equivalent series resistance value in the fundamental vibration mode. The second vertical axis on the right side of the graph shown in FIG. 7 represents the equivalent series resistance value R1 in the fundamental vibration mode. FIG. 7 shows simulation results of an embodiment in which the groove width ratio is set to 0.76 and the inclination angle of the tapered surface 61 with respect to the longitudinal direction L is set to 1°.

As shown in FIG. 7, R2/R1 is 1 or more if at least the taper ratio is 0 or more and 0.4 or less. Furthermore, as the taper ratio increases in the range of 0 to 0.4, R2/R1 also increases. That is, by increasing the taper ratio in the range of 0 to 0.4, oscillation in the secondary vibration mode can be suppressed and the fundamental vibration mode can be used as the main vibration mode. Here, when compared with a conventional structure without a taper portion (a structure in which the taper ratio is 0), in the conventional structure in which the groove width ratio is set to 0.65, R2/R1 is 3.6. By setting the taper ratio to 0.1 or more in the embodiment, R2/R1 can be made larger than in the conventional configuration. Therefore, the fundamental vibration mode can be effectively used as the main vibration mode compared to the conventional configuration.

On the other hand, when the taper ratio is increased in the range of 0.05 to 0.4, R1 also increases. Here, by setting the taper ratio to 0.3 or less, the increase in R1 can be suppressed to about 10% compared to the case where the taper ratio is 0, and the influence on the increase in power consumption during circuit mounting can be reduced. can. It should be noted that if the taper ratio is 0.25 or less, the increase in R1 can be suppressed to less than 10% compared to the case where the taper ratio is 0, which is more desirable.

8 to 10 are graphs showing the relationship between the groove width ratio and the equivalent series resistance value. The horizontal axis of the graphs shown in FIGS. 8 to 10 represents the groove width ratio. The vertical axis of the graph shown in FIG. 8 represents the equivalent series resistance value R1 in the fundamental vibration mode. The vertical axis of the graph shown in FIG. 9 represents the equivalent series resistance value R2 in the secondary vibration mode. The vertical axis of the graph shown in FIG. 10 represents the ratio R2/R1 of the equivalent series resistance value in the secondary vibration mode to the equivalent series resistance value in the fundamental vibration mode. 8 to 10 show the simulation results of the comparative example and the working example. In the example, the taper ratio was set to 0.1, and in the comparative example, a configuration without a taper portion was used.

As shown in FIG. 8, at least when the groove width ratio is 0.6 or more and 0.85 or less, R1 in the example is equal to or less than that in the comparative example. On the other hand, as shown in FIG. 9, at least when the groove width ratio is 0.6 or more and 0.85 or less, R2 is larger in the example than in the comparative example. As a result, as shown in FIG. 10, at least when the groove width ratio is 0.6 or more and 0.85 or less, R2/R1 is 1 or more and larger in the example than in the comparative example.

In order to use the fundamental vibration mode as the main vibration mode, it is desirable that R1 be smaller. As shown in FIG. 8, since R1 decreases as the groove width ratio increases, a large groove width ratio is desirable from the viewpoint of using the fundamental vibration mode as the main vibration mode. On the other hand, as shown in FIG. 10, R2/R1 also decreases as the groove width ratio increases. For this reason, the groove width ratio is set to 0.85 in the example so that R2/R1 is equal to or greater than the structure (R2/R1=3.6) in which the groove width ratio is 0.65 in the comparative example which is the conventional structure. It is desirable that: In addition, in the embodiment, it is more desirable that the groove width ratio is 0.8 or less so that R2/R1 becomes larger than that of the conventional structure.

As described above, the piezoelectric vibrating piece 3 of this embodiment includes the vibrating arms 31 in which the grooves 34 recessed in the thickness direction T are formed. The vibrating arm portion 31 includes a root portion 50 having R surfaces 51 extending from the base portion 35 toward the tip end 31t side of the vibrating arm portion 31 with a constant curvature on both sides in the width direction W, and a tip end 31t of the vibrating arm portion 31 at the root portion 50. A tapered portion 60 extending from the near end toward the tip 31t while narrowing the width in the width direction W, and a straight extending from the end of the vibrating arm portion 31 near the tip 31t to the tip 31t in the tapered portion 60 with a constant width. a portion 70;

Here, in the secondary vibration mode, the antinode of vibration occurs at a position closer to the base end 31b of the vibrating arm portion 31 than in the fundamental vibration mode. Therefore, if the grooves 34 are formed in the vibrating arm portions 31 in order to reduce the equivalent series resistance value in the fundamental vibration mode, the portions of the vibrating arm portions 31 near the base ends 31b are likely to flex, and the piezoelectric vibrating reeds undergo secondary vibration. It becomes easy to oscillate in the mode. According to the present embodiment, compared to a configuration in which the vibrating arms are not provided with tapered portions, the vibrating arms 31 are formed thicker, and the portions of the vibrating arms 31 closer to the base end 31b are wider in the width direction W. can be made difficult to bend. As a result, the equivalent series resistance value in the secondary vibration mode can be reduced by enlarging the grooves 34 formed in the vibrating arms 31 in the width direction W. Oscillation can be suppressed, and a decrease in the equivalent series resistance value in the secondary vibration mode can be suppressed. Therefore, even if the grooves 34 formed in the vibrating arms 31 are enlarged in the width direction W, the ratio of the equivalent series resistance value in the secondary vibration mode to the equivalent series resistance value in the fundamental vibration mode can be increased. Therefore, the piezoelectric vibrating reed 3 can have stable frequency characteristics.

Further, the total length of the vibrating arm portion 31 in the longitudinal direction L is defined as L, and the distance from the base end 31b of the vibrating arm portion 31 in the longitudinal direction L to the end portion of the vibrating arm portion 31 near the tip 31t in the tapered portion 60 is When defined as D, the taper ratio D/L is preferably 0.1 or more and 0.3 or less. According to this configuration, compared to the case where the taper ratio is 0, the influence on the increase in power consumption during circuit mounting is reduced, and the fundamental vibration mode is more effectively used as the main vibration mode than the conventional configuration without the taper portion. can be used for

Further, when the width of the straight portion 70 in the width direction W is defined as W1 and the width of the groove 34 in the width direction W is defined as W2, the groove width ratio W2/W1 is 0.6 or more and 0.85 or less. According to this configuration, R2/R1 can be made equal to or greater than the conventional configuration having no tapered portion and having a groove width ratio of 0.65. Therefore, compared with the conventional configuration, oscillation in the secondary vibration mode can be suppressed and the fundamental vibration mode can be effectively used as the main vibration mode.

The end portion of the tapered portion 60 near the tip 31t of the vibrating arm portion 31 is within the formation range of the groove 34 in the longitudinal direction L. As shown in FIG. Here, in the fundamental vibration mode, the antinode of vibration occurs at a position closer to the tip 31t of the vibrating arm portion 31 than in the secondary vibration mode. According to this embodiment, since the groove 34 is also formed on the tip 31t side of the tapered portion 60, the effect of the groove 34 on oscillation in the fundamental vibration mode can be obtained.

A side surface 33 in the width direction W of the vibrating arm portion 31 is continuous from the root portion 50 to the straight portion 70 . According to this configuration, since sharp corners are not formed on the side surfaces 33, it is possible to prevent the vibrating arms 31 from being easily damaged or the vibration characteristics from deteriorating due to stress concentration at the corners. A sharp corner is a corner formed by two surfaces that are connected so that the tangent line is discontinuous.

Since the piezoelectric vibrator 1 and the oscillator 100 of this embodiment have the above-described piezoelectric vibrating piece 3, the piezoelectric vibrator 1 and the oscillator 100 can be of high quality with excellent operational reliability.

It should be noted that the present invention is not limited to the above-described embodiments described with reference to the drawings, and various modifications are conceivable within its technical scope.
For example, in the above embodiment, the piezoelectric vibrating piece 3 is of a type supported by the package 2 at the base portion 35, but is not limited to this configuration. For example, the piezoelectric vibrating piece may be of a type in which at least one support arm supported by the package extends from the base. In this case, the piezoelectric vibrating piece may be a so-called side-arm type vibrating piece in which a pair of supporting arms are arranged outside the pair of vibrating arms, or one supporting arm may be a pair of vibrating arms. It may be a so-called center arm type vibrating piece arranged between the parts.

Further, in the above-described embodiment, the tapered portion 60 of each vibrating arm portion 31 has the tapered surfaces 61 on both sides in the width direction W, but the configuration is not limited to this. That is, the tapered portion may have a tapered surface on only one side in the width direction W. Also, in each vibrating arm portion 31, the pair of tapered surfaces 61 may be formed asymmetrically.

In the above-described embodiment, in each vibrating arm 31, the end of the groove 34 near the base end 31b of the vibrating arm 31 is located at the same position as the base end 31b in the longitudinal direction L, but the position of the end of the groove is It is not particularly limited. However, it is desirable that at least a portion of the formation range of the groove in the longitudinal direction L be provided with a tapered portion.

In addition, it is possible to appropriately replace the components in the above-described embodiments with well-known components without departing from the scope of the present invention.

DESCRIPTION OF SYMBOLS 1... Piezoelectric vibrator 2... Package 3... Piezoelectric vibrating piece 31, 31A, 31B... Vibrating arm part 31b... Base end 31t... Tip 33... Side surface 34... Groove 35... Base part 50... Base part 51... R surface 60... Taper part 70... Straight section 100... Oscillator 103... Integrated circuit

Claims (7)

a pair of vibrating arms extending in a first direction and arranged side by side in a second direction orthogonal to the first direction;
a base to which base ends of the vibrating arms in the first direction are connected;
with
grooves recessed in a third direction orthogonal to the first direction and the second direction are formed in the vibrating arms;
The vibrating arms are
a root portion having R surfaces extending from the base portion toward the distal end side of the vibrating arm portion with a constant curvature on both sides in the second direction;
a taper portion extending from an end portion of the root portion near the tip toward the tip side while narrowing the width in the second direction;
a straight portion extending with a constant width from the tip-side end of the tapered portion to the tip;
having
Piezoelectric vibrating piece. The total length of the vibrating arms in the first direction is defined as L,
When the distance from the proximal end of the vibrating arm in the first direction to the end of the tapered portion near the distal end is defined as D,
D / L is 0.1 or more and 0.3 or less,
The piezoelectric vibrating piece according to claim 1. the groove extends in the first direction with a constant width;
The width of the straight portion in the second direction is defined as W1,
When the width of the groove in the second direction is defined as W2,
W2/W1 is 0.6 or more and 0.85 or less,
The piezoelectric vibrating piece according to claim 1 or 2. The end of the tapered portion near the tip is within the formation range of the groove in the first direction,
The piezoelectric vibrating piece according to any one of claims 1 to 3. The side surface of the vibrating arm in the second direction is continuous from the base portion to the straight portion,
The piezoelectric vibrating piece according to any one of claims 1 to 4. a piezoelectric vibrating reed according to any one of claims 1 to 5;
a package for hermetically sealing the piezoelectric vibrating piece;
A piezoelectric vibrator with a A piezoelectric vibrator according to claim 6,
The piezoelectric vibrator is electrically connected to an integrated circuit as an oscillator,
oscillator.

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