Tuning fork-type piezoelectric vibrator and tuning fork-type piezoelectric vibrator using the tuning fork-type piezoelectric vibrator

Abstract

To provide a tuning-fork type piezoelectric vibrating piece that sufficiently damps vibrations caused by a vibrating arm at a holding part even if the tuning-fork type piezoelectric vibrating piece becomes ultra-small, thereby suppressing characteristic fluctuations in a frequency, etc.SOLUTION: A tuning-fork type piezoelectric vibrating piece 2 includes: a base 21 having one edge and the other edge, a width of the other edge being formed to be smaller than a width of the one edge; a pair of vibrating arms 22, 23 extending from the one edge in parallel in an upper direction, excitation electrodes being formed to the respective vibration arms; a holding part 26 which includes an extending part 261 extending in a lower direction from the other edge of the base and a bending / extending part 262 extending from an extending part end in a lateral direction, and in which an extraction electrode connected to each excitation electrode is formed; a first connection provided in the extending part; a second connection provided in the bending / extending part; and a vibration damping part 263 formed between the first connection and the second connection.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a tuning fork type piezoelectric vibrating piece and a tuning fork type piezoelectric vibrating device using the tuning fork type piezoelectric vibrating piece.

Background Art

[0002] Piezoelectric vibrating devices such as tuning fork type crystal resonators and tuning fork type crystal oscillators are used as reference clock sources in various electronic devices. For example, a surface mount type tuning fork type piezoelectric resonator has a configuration in which a tuning fork type piezoelectric vibrating piece is housed in an insulating container on which conductive wiring is formed and is hermetically sealed with a lid.

[0003] As a configuration example of a tuning fork type piezoelectric vibrating piece, there is a configuration including a base portion and a pair of vibrating arms protruding in the same direction from one end side of the base portion, and a narrow portion is formed on the other end side of the base portion and a holding portion bent in an L shape is provided. A pair of exciting electrodes for driving the vibrating arms and the like are formed on the vibrating arms, and the exciting electrodes are led out to the holding portion. The holding portion and the mounting electrode of the insulating container are conductively joined to perform electrical joining. (Patent Document 1)

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The tuning fork type piezoelectric vibrating piece having the above configuration has a configuration in which a narrow portion is formed on the other end side of the base portion and a holding portion bent in an L shape is provided, and has an advantage that the vibration of the tuning fork type piezoelectric vibrating piece, that is, strain energy can be efficiently attenuated.

[0006] However, when further miniaturizing the tuning fork-type piezoelectric vibrator, there was a problem in that vibration damping could not be sufficiently achieved, and vibrations could leak into the container through the holding part, causing characteristic changes such as frequency fluctuations and crystal impedance (CI) fluctuations of the tuning fork-type piezoelectric vibrator.

[0007] The present invention has been made in view of the above, and aims to provide a tuning fork-type piezoelectric vibrator and a tuning fork-type piezoelectric vibrator using the tuning fork-type piezoelectric vibrator, in which vibrations generated by the vibrating arm are sufficiently damped in the holding part even when the tuning fork-type piezoelectric vibrator is made ultra-miniature, thereby suppressing characteristic fluctuations such as frequency. [Means for solving the problem]

[0008] The tuning fork type piezoelectric vibrator according to the present invention comprises: a base having one end and the other end, with the width of the other end being smaller than the width of the one end; a pair of vibrating arms extending parallel upward from the one end and having excitation electrodes formed thereon; an extension portion extending downward from the other end of the base; a holding portion having a bent extension portion extending laterally from the end of the extension portion and having a lead electrode connected to the excitation electrodes formed thereon; a first connecting portion provided on the extension portion and a second connecting portion provided on the bent extension portion; and a vibration damping portion formed between the first connecting portion and the second connecting portion. Furthermore, the base portion has a tapered section in which the width dimension gradually decreases from one end to the other, and a constricted portion is formed at the end of the tapered section; the extension portion extends from the constricted portion and has an expanding tapered section in which its width gradually increases; and the vibration damping portion is formed following the expanding tapered section. It is characterized by the following.

[0009] In this configuration, the base has one end and the other end, and the width of the other end is smaller than the width of the first end. The holding part has an extended part that extends downward from the other end of the base and a bent extended part that extends laterally from the end of the extended part. The vibration damping part is formed between the first connecting part and the second connecting part.

[0010] With this configuration, the tuning fork vibration, i.e., strain energy, caused by the vibrating arm is efficiently attenuated at the base, and the formation of a vibration damping section in the holding part further attenuates the strain energy at the first and second connection parts.

[0011] Also, The tuning fork vibration caused by the vibrating arm, i.e., the strain energy, is further efficiently attenuated at the base, and by having an enlarged tapered section, with the vibration damping section formed following the enlarged tapered section, the strain energy at the first and second connection sections can be minimized.

[0012] Furthermore, the vibration damping section may be configured with notches, bent sections, or thin-walled sections. These notches, bent sections, and thin-walled sections are preferable because they have curvature when viewed in plan, which allows for efficient vibration damping.

[0013] Furthermore, by forming a corner at the boundary region between the vibration damping section and the tapered section, vibration damping can be made even more efficient. The corner may have a curved protrusion at its tip, or it may have a sharp protrusion. The sharper the angle of the corner, the greater the vibration damping effect tends to be, so this is preferable.

[0014] The above configurations can also be applied to tuning fork type piezoelectric vibration devices in which the tuning fork type piezoelectric vibrators are housed in an airtight container. That is, the tuning fork type piezoelectric vibrators are housed in an airtight container having conductive wiring and multiple mounting parts, and the mounting parts The first connection part and the second connection part A tuning fork type piezoelectric vibration device may be formed by electrically bonding each of these components and hermetically sealing the container with a lid. It can also be applied to a tuning fork type piezoelectric vibrator configuration in which only the tuning fork type piezoelectric vibrator is housed in the container, or to a tuning fork type piezoelectric vibration oscillator configuration in which IC components for the oscillation circuit and other discrete components are housed in addition to the tuning fork type piezoelectric vibrator.

[0015] According to the above configuration, it is possible to obtain a tuning fork type piezoelectric vibration device that suppresses vibration during driving of the tuning fork type piezoelectric vibrating piece, that is, strain energy, from leaking into the container. Such vibration leakage causes characteristic variations such as the frequency of the piezoelectric vibration device itself, but according to the present invention, vibration leakage can be suppressed to the maximum extent, so that a tuning fork type piezoelectric vibration device with suppressed characteristic variations can be obtained.

Advantages of the Invention

[0016] As described above, according to the present invention, even when the tuning fork type piezoelectric vibrating piece is ultra-small, the vibration generated by the vibrating arm can be sufficiently vibration-damped in the holding portion, and a tuning fork type piezoelectric vibrating piece with suppressed characteristic variations such as frequency and a tuning fork type piezoelectric vibrator using the tuning fork type piezoelectric vibrating piece can be provided.

Brief Description of the Drawings

[0017] [Figure 1] It is a plan view before lid sealing of a tuning fork type piezoelectric device according to an embodiment of the present invention showing a first embodiment. [Figure 2] It is a cross-sectional view taken along the line A - A after lid sealing in FIG. 1. [Figure 3] It is a plan view of one main surface of a tuning fork type piezoelectric vibrating piece shown in the first embodiment. [Figure 4] It is a plan view of the other main surface of a tuning fork type piezoelectric vibrating piece shown in the first embodiment. [Figure 5] It is a diagram showing the basic shape and dimensions of one main surface in an analysis model by the finite element method. [Figure 6] It is a partially enlarged view of the other main surface of FIG. 5. [Figure 7] It is a diagram (conventional configuration) showing an analysis model by the finite element method. [Figure 8] It is a diagram (configuration of the present invention) showing an analysis model by the finite element method. [Figure 9] It is a graph showing the analysis results of the models of FIGS. 7 and 8 by the finite element method. [Figure 10] It is a diagram (conventional configuration) showing another analysis model by the finite element method. [Figure 11] It is a diagram (configuration of the present invention) showing another analysis model by the finite element method. [Figure 12] It is a graph showing the analysis results of the models in FIGS. 10 and 11 by the finite element method. [Figure 13] It is a partially enlarged view showing the second embodiment. [Figure 14] It is a partially enlarged view showing the third embodiment. BEST MODE FOR CARRYING OUT THE INVENTION

[0018] First Embodiment Explanation of the Tuning Fork Crystal Oscillator Hereinafter, as an embodiment of the present invention, a tuning fork crystal oscillator (tuning fork piezoelectric oscillator) using a tuning fork crystal vibrating piece (tuning fork piezoelectric vibrating piece) will be taken as an example and described with reference to the drawings. The tuning fork crystal oscillator in this embodiment is a surface mount type crystal oscillator having a substantially rectangular parallelepiped package structure. In this embodiment, the outer dimensions in plan view are, for example, 1.6 mm in length and 1.0 mm in width. Note that the outer dimensions in plan view of the tuning fork crystal oscillator are not limited to these dimensions, but the present invention is suitable for ultra-small crystal oscillators having dimensions less than the above dimensions.

[0019] The tuning fork crystal oscillator X according to the embodiment of the present invention comprises a container 1, a tuning fork crystal vibrating piece 2 electrically joined to the container 1, and a lid 3 for hermetically sealing the container, as shown in FIGS. 1 and 2.

[0020] The container 1 is an insulating container having airtightness in a rectangular shape in plan view with electrode wiring, which is formed by a ceramic multilayer technology. The container 1 has a configuration in which an upper frame body 12 is laminated above a flat lower layer body 11, and a sealing portion 13 made of a metal layer is formed in a circumferential shape on the upper surface of the upper frame body 12. In addition, mounting portions 14 and 15 are formed in a state of being close to each other in a part of the lower layer body. These mounting portions 14 and 15 have lower electrodes 14a and 15a made of a metal film and upper electrodes 14b and 15b formed thereon.

[0021] These metal films are formed using multilayer thick film formation technology. In this embodiment, the area of ​​the upper electrode 14b is smaller than the area of ​​the lower electrode 14a, and the area of ​​the upper electrode 15b is smaller than the area of ​​the lower electrode 15a. The mounting portions 14 and 15 are electrically connected to terminal electrodes 1A and 1B, respectively, by electrode wiring formed in the container, although these are not shown in the figures.

[0022] The sealing portion 13, mounting portions 14 and 15, and terminal electrodes 1A and 1B are formed by laminating a nickel (Ni) layer and a gold (Au) layer onto the surface of a tungsten (W) metallized layer using methods such as plating. Molybdenum may be used instead of tungsten as the metallized layer. In the mounting portions 14 and 15, a lower and upper metallized layer are formed, and the Ni and Au layers are plated onto the upper part thereof.

[0023] With this configuration, the container 1 has a concave storage section 10 when viewed in cross-section, and the tuning fork-shaped quartz vibrator 2 is electrically bonded to the mounting section within the storage section 10.

[0024] The tuning fork-shaped quartz vibrator 2 will be described with reference to Figures 3 and 4. The tuning fork-shaped quartz vibrator 2 is formed from a flat plate with the XY axes of a quartz plate, and consists of a base portion 21, a pair of vibrating arms 22 and 23 extending parallel to the Y axis from one end of the base portion 21 in the Y axis direction, wider portions 24 and 25 formed wider than the vibrating arms following the tips of the vibrating arms 22 and 23, and a holding portion 26 extending in the Y axis direction from the other end of the base portion 21 in the Y axis direction.

[0025] The base portion 21 has through holes 21a and 21b formed at positions symmetrical with respect to the central line CL. Inside the through holes 21a and 21b, a metal film is formed to connect the front and back surfaces (not shown in the figure). This avoids the problem of electrode breakage of the wiring electrodes due to minute wire widths (such as cutting of the metal film), and plays a role in ensuring the reliability of the electrode connection between one main surface and the other main surface.

[0026] Furthermore, the base portion 21 is configured such that its width gradually decreases from one end to the other, and has tapered portions 21c and 21d on its outer circumference. In this embodiment, the tapered portions 21c and 21d have a curved configuration in which the curvature changes. A retaining portion is formed at the lower end of the base portion 21, and constricted portions 21e and 21f with a smaller width are formed at the connection point between the base portion 21 and the retaining portion 26.

[0027] The front and back main surfaces of the vibrating arms 22 and 23 are each provided with a single groove 221, 222, 231, and 232, respectively, and each of these grooves extends from near the base to near the wide section. Note that grooves 221, 222 and grooves 231, 232 are formed opposite each other on the front and back surfaces.

[0028] Furthermore, in the region near the base, the width of the vibrating arms is formed to gradually increase, improving the structural strength between the base 21 and the vibrating arms 22 and 23.

[0029] A pair of excitation electrodes E1 and E2 are formed on the vibrating arms 22 and 23, and the electrodes are arranged so that the vibrating arms perform tuning fork vibration. Excitation electrodes are also formed in grooves provided on each of the vibrating arms 22 and 23. For example, one excitation electrode E1 is formed on both main surfaces (front and back including the grooves) of the vibrating arm 22, and the other excitation electrode E2 is formed on both sides of the vibrating arm 22. Similarly, the other excitation electrode E2 is formed on both main surfaces (front and back including the grooves) of the vibrating arm 23, and one excitation electrode E1 is formed on both sides of the vibrating arm 22. When an alternating electric field is applied to each excitation electrode in this electrode configuration, tuning fork vibration based on the piezoelectric effect is excited.

[0030] These excitation electrodes E1 and E2 are electrically connected to the first connection part B1 and the second connection part B2, which will be described later, via electrode wiring formed on the base part 21 and electrode wiring formed on the holding part 26.

[0031] The wide portions 24 and 25 are formed with metal films having the same electrode configuration as the excitation electrodes E1 and E2. Excitation electrodes (metal films) formed on both sides of the vibrating arm 22 are formed on both main surfaces and both sides of the wide portion 24 of the vibrating arm 22, and excitation electrodes formed on both sides of the vibrating arm 23 are formed on both main surfaces and both sides of the wide portion 25 of the vibrating arm 23. As shown in Figure 3, adjustment metal films 24a and 25a are formed on the upper part of the metal film on the wide portion of one of the main surfaces.

[0032] The holding portion 26 consists of an extension portion X extending downward from the lower end of the base, i.e., the constricted portions 21e and 21f, and a bent extension portion 262 that extends laterally by bending from the extension portion 261. A vibration damping portion 263 is also formed in the bent extension portion 262.

[0033] The extended portion 261 forms expanded tapered portions 261a and 261b, which gradually widen from the constricted portions 21e and 21f. The expanded tapered portions 261a and 261b are symmetrically configured. A vibration damping portion 263 is formed from the end of the expanded tapered portion 261b.

[0034] In this embodiment, the vibration damping portion 263 has a notched portion with an arc shape. More specifically, a corner portion 2621 is formed at the boundary between the end of the enlarged tapered portion 261b and the vibration damping portion 263, i.e., the notched portion. The presence of this corner portion 2621 is important for damping the strain energy, along with the presence of the constricted portions 21e, 21f and the enlarged tapered portions 261a, 261b, and the presence of the corner portion 2621 allows for more efficient damping of vibrations. As mentioned above, the corner portion may have a convex portion at its tip with curvature, or it may have a sharp convex portion. The sharper the angle of the corner portion, the greater the vibration damping effect tends to be, so this is preferable.

[0035] A first connection part B1 is formed on the extended portion 261 of the holding part, and a second connection part B2 is formed on the bent extended portion 262. As described above, a pair of electrode wirings are formed on the holding part 26, with one electrode connected to the first connection part B1 and the other electrode formed on the second connection part B2. These first connection part B1 and second connection part B2 consist of a thick metal layer formed by plating on the electrode wiring, forming so-called metal bumps.

[0036] As an example of the metal material used in the excitation electrode and the electrode wiring formed in the base and holding parts, Cr or Ti is used as an underlayer metal film in contact with the quartz piece, and Au is used as an upper layer metal film on top of the underlayer metal film, but other metal materials may also be used. These metal films are formed by PVD (Physical Vapor Deposition) methods such as vacuum deposition or sputtering. In addition, the material for the first and second connection parts can be Au, which is formed by the plating method as described above.

[0037] Lid 3 is a rectangular metallic plate with Kovar as its base material. The sealing surface of the lid, that is, the surface that joins with the sealing portion 13 of the container, is clad with silver solder (a three-element alloy of silver, copper, and zinc) formed by rolling or other methods. Nickel layers are formed on both the front and back surfaces of this clad plate material. The structure of Lid 3 is intended for sealing and joining with the container by seam welding, but if brazing is to be performed, for example, gold-tin solder may be formed on a base material such as Kovar, and brazing may be performed by heating.

[0038] A tuning fork-shaped quartz crystal vibrator 2 with electrodes formed on it is housed in a container 1, and the mounting sections 14 and 15 of the container 1 are joined to the first connection section B1 and the second connection section B2 by flip-chip bonding. This type of bonding allows for conductive bonding over a smaller area compared to bonding with a conductive resin bonding material, and since it does not use a resin material that generates gas, it has the advantage of suppressing fluctuations in the characteristics of the piezoelectric vibrator. Conductive bonding may also be performed using a conductive resin bonding material.

[0039] Simulation of a tuning fork-type quartz oscillator Next, the strain energy density ratio based on the shape of the tuning fork-type quartz crystal vibrator was analyzed using the finite element method. This strain energy density ratio is the ratio of the strain energy density of the entire tuning fork-type quartz crystal vibrator to the strain energy density of the connection points (first connection point and second connection point), and serves as an indicator of how much the connection points move relative to the entire tuning fork-type quartz crystal vibrator. A smaller strain energy density ratio is considered to indicate less vibration leakage, which affects the characteristic variation of the tuning fork-type piezoelectric vibration device.

[0040] Figures 5 and 6 show the basic shape and dimensions of the analysis model. Note that these models have two through holes in the base. The analyses in Figures 7 to 9 show configurations without through holes, but the shape and dimensions other than the through holes are based on this model.

[0041] Figures 7 to 9 show analyses of a configuration without a through hole in the base. Figure 9 is a graph of the results of simulations of the strain energy density ratio for the conventional configuration (the configuration shown in Figure 7) and the configuration of the present invention (the configuration with a vibration damping section shown in Figure 8). In the configuration of the present invention shown in Figure 8, a corner is formed in the boundary region between the enlarged tapered section and the vibration damping section.

[0042] From the graph in Figure 9, it can be seen that the strain energy density ratio is lower in the tuning fork-type quartz vibrator with a vibration damping section (arc-shaped notch) formed in the bent and extended portion compared to the conventional tuning fork-type quartz vibrator without a vibration damping section, indicating that the vibration leakage reduction effect due to the formation of the vibration damping section is achieved.

[0043] Figures 10 to 12 show the analysis of a configuration in which a through hole is formed in the base. Figure 12 is a graph showing the results of simulations of the strain energy density ratio for the conventional configuration (configuration shown in Figure 10) and the present invention configuration (configuration with vibration damping section shown in Figure 11). In the present invention configuration shown in Figure 11, a corner is formed in the boundary region between the enlarged tapered section and the vibration damping section. See Figures 3 and 4 for details of the configuration.

[0044] From the graph in Figure 12, it can be seen that the strain energy density ratio is lower in the tuning fork-type quartz vibrator with a vibration damping section (arc-shaped notch) formed in the bent and extended portion compared to the conventional tuning fork-type quartz vibrator without a vibration damping section, indicating that the vibration leakage reduction effect due to the formation of the vibration damping section is achieved.

[0045] Second Embodiment Next, the second embodiment will be described with reference to Figure 13. In the second embodiment, the configuration of the vibration damping section and the positional relationship between the first connection section B1 and the second connection section B2 are different. The bent extension section 262 extends from the end of the enlarged tapered section 261b, but the vibration damping section 264 is formed on the opposite side from the first embodiment, that is, on the side of the lowest end of the tuning fork-shaped quartz vibrator. The vibration damping section 264 is an arc-shaped notch, and the starting point of this notch begins in the intersection region of the imaginary line L1 and the lowest end side. Note that the imaginary line L1 is a line that extends downward from the end of the enlarged tapered section 261b parallel to the center line CL.

[0046] Furthermore, the first connection point is formed on the center line CL, while the second connection point is formed above the first connection point by the dimension of the gap G (for example, 0.01 mm to 0.02 mm).

[0047] This configuration minimizes the reduction in vibration damping effect due to the formation of a vibration damping section in the holding part, as well as the reduction in the mechanical strength of the holding part itself, resulting in a highly practical tuning fork-type piezoelectric vibrator that balances vibration damping and holding strength. Furthermore, in this embodiment, the first connecting part B1 is positioned on the center line CL of the base part 21. This configuration further enhances the vibration damping effect after joining with the container 1.

[0048] Third Embodiment Next, a third embodiment will be described with reference to Figure 14. In the third embodiment, the configuration of the vibration damping section is different. The bent extension section 262 extends from the end of the enlarged tapered section 261b, but the vibration damping section 265 in this embodiment has a configuration in which a part of it is bent upward. Note that although this bending configuration is bent upward, it may also be bent downward, or it may have a configuration with multiple bends.

[0049] This configuration allows for vibration damping through the formation of a vibration damping section in the holding part, and since it does not involve reducing the width of the holding part itself, it minimizes the reduction in mechanical strength in the holding part, resulting in a highly practical tuning fork-type piezoelectric vibrator that balances vibration damping and holding strength.

[0050] In the embodiments described above, a semicircular notch was used as an example for the vibration damping section, but other configurations may be used. For example, a circular arc longer than a semicircle, such as a 3 / 4 circular arc, may be used. With such a configuration, the angle formed at the boundary between the end of the enlarged tapered section and the vibration damping section becomes sharper (narrower angle), and the vibration damping effect increases. In addition to a circular arc, an elliptical arc configuration or a polygonal configuration with four or more sides may also be used.

[0051] In this embodiment, the vibration damping section has a notched (through) configuration, but it may also have a thin-walled configuration. For example, the vibration damping section may be formed by creating an arc-shaped thin-walled region.

[0052] The present invention can be implemented in various other forms without departing from its spirit or main features. Therefore, the embodiments described above are merely illustrative in all respects and should not be constrained. The scope of the invention is defined by the claims and is not restricted by the text of the specification. Furthermore, any modifications or changes falling within the equivalent scope of the claims are all within the scope of the invention. [Industrial applicability]

[0053] This technology can be applied to the mass production of tuning fork-type piezoelectric vibrators and tuning fork-type piezoelectric transducers. [Explanation of Symbols]

[0054] X Tuning fork type crystal oscillator 1 container 2 Tuning fork-shaped crystal vibrating pieces 21 Base 22,23 Vibrating Arm 24,25 Wide section 26 Holding part 263,264,265 Vibration damping section E1,E2 Excitation electrode 3 Lid

Claims

1. A base having one end and the other end, where the width of the other end is smaller than the width of the first end, A pair of vibrating arms extend parallel upward from one end and have excitation electrodes formed thereon, The base has an extended portion extending downward from the other end, and a bent extended portion extending laterally from the end of the extended portion, and a holding portion on which a wiring electrode connected to the excitation electrode is formed. A first connecting portion provided in the extension portion, and a second connecting portion provided in the bending extension portion It has a vibration damping section formed between the first connection section and the second connection section, The base portion has a tapered section in which the width gradually decreases from one end to the other, and a constricted section is formed at the end of the tapered section. The extension portion extends from the constricted section and has an expanding tapered section in which its width gradually increases, and the vibration damping portion is formed following the expanding tapered section. Tuning fork-shaped piezoelectric vibrator.

2. A tuning fork type piezoelectric vibrator device comprising a tuning fork type piezoelectric vibrator according to Claim 1, housed in a container having conductive wiring and a plurality of mounting parts, the first connection part and the second connection part being electrically joined to the mounting parts, and the container being hermetically sealed with a lid.

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