Piezoelectric vibration element and piezoelectric vibrator

Abstract

This piezoelectric vibration element comprises: a piezoelectric plate; a pair of mounted electrodes; and a conductor pattern. The piezoelectric plate has a vibration part, and a thick part that is positioned along at least a portion of the vibration part and is thicker than the vibration part. The pair of mounted electrodes are respectively positioned at the thick part on both surfaces of the piezoelectric plate. The conductor pattern spreads across both surfaces of the thick part and is not electrically connected to the mounted electrodes. The pair of mounted electrodes may be positioned at diagonal positions on the piezoelectric plate in planar perspective. The conductor pattern may be positioned at a corner of the thick part where the pair of mounted electrodes are not positioned.

Description

Piezoelectric vibration element and piezoelectric vibrator

[0001] The present disclosure relates to a piezoelectric vibration element and a piezoelectric vibrator.

[0002] Piezoelectric vibration elements deform and vibrate in response to a periodic voltage pattern applied between excitation electrodes located on both sides of the piezoelectric material. They also output an electrical signal between the electrodes in response to the deformation of the piezoelectric material. To output a signal of the appropriate frequency with low loss and stability, the equivalent circuit parameters that represent the characteristics of the piezoelectric vibration element are adjusted.

[0003] Japanese Patent Application Laid-Open No. 2021-29013 describes a quartz crystal element having an adjustment electrode connected to an excitation electrode on one side and not facing the electrode on the other side, which allows the series capacitance to be easily adjusted by the adjustment electrode without changing the series resistance or resonant frequency in the equivalent circuit.

[0004] One aspect of the present disclosure is as follows: (1) A piezoelectric vibration element comprising: a piezoelectric plate having a vibration portion and a thick portion located along at least a portion of the vibration portion and thicker than the vibration portion; a pair of mounting electrodes located in the thick portion on each side of the piezoelectric plate; and a conductor pattern extending across both sides of the thick portion and not electrically connected to the mounting electrodes. (2) The piezoelectric vibration element according to (1), in which the pair of mounting electrodes are located at diagonal corners of the piezoelectric plate in a planar perspective view. (3) The piezoelectric vibration element according to (2), in which the conductor pattern is located at a corner of the thick portion where the pair of mounting electrodes are not located. (4) A piezoelectric vibrator comprising: the piezoelectric vibration element according to any one of (1) to (3); and a package having a recess and an electrode surface located within the recess, wherein the piezoelectric vibration element is located within the recess and the mounting electrodes are bonded to the electrode surface via a conductive bonding member.

[0005] 1 is an overall perspective view of a piezoelectric vibrator; FIG. 2 is a plan view of the piezoelectric vibrator; FIG. 3 is a cross-sectional view of the piezoelectric vibrator; FIG. 4 is a cross-sectional view of the piezoelectric vibrator; FIG. 5 is a perspective view of a piezoelectric vibration element.

[0006] Hereinafter, an embodiment will be described with reference to the drawings. FIG. 1 is an overall perspective view of a piezoelectric vibrator 1 according to this embodiment. This FIG. 1 shows a state in which a lid 30 is removed. Note that in the drawings of this disclosure, the ratios of size in the X direction representing the length, the Y direction representing the width, and the Z direction representing the height are for the purpose of explanation and do not necessarily reflect actual values. The piezoelectric vibrator 1, which is a piezoelectric device according to one embodiment, has a package 10, a piezoelectric vibration element 20, and a lid 30.

[0007] The package 10 is a housing made of, for example, a ceramic material, a semiconductor material, a glass material, or a combination of these. The package 10 also has conductive signal lines inside and on its surface. The signal lines include those related to power supply and grounding. The signal lines may be made of, for example, molybdenum, copper, silver, tungsten, or the like. Some or all of the signal lines may be nickel-plated, gold-plated, or the like. The package 10 has a recess 10a at its top end, which is the positive end in the Z direction, that is open.

[0008] The piezoelectric vibration element 20 of this embodiment is a quartz crystal vibration element. The piezoelectric vibration element 20 is located inside the recess 10a.

[0009] The lid 30 is bonded to the upper end of the package 10, i.e., to the upper surface of the sidewall of the recess 10a, thereby sealing the recess 10a. The lid 30 is a flat plate of a metal conductor, such as a metal containing iron, copper, nickel, cobalt, molybdenum, or tungsten, or an alloy thereof, such as kovar. The bonding material used for sealing with the lid 30 is preferably bonded by heating within a temperature range that does not adversely affect the characteristics of the piezoelectric vibration element 20 sealed therein. For example, the lid 30 is bonded using a brazing material or the like. A frame-shaped metallization layer may be located between the upper end of the package 10 and the lid 30. The metallization layer may be a plated layer or a conductive layer that is applied and baked.

[0010] Fig. 2A is a plan view of the piezoelectric vibrator 1. Figs. 2B and 2C are cross-sectional views of the piezoelectric vibrator 1. In Fig. 2A, for the purpose of explanation, a portion of the configuration that is not visible from above is shown in plan view with dashed lines. Fig. 2B is a cross-sectional view taken along the cross-sectional line AA in Fig. 2A. Fig. 2C is a cross-sectional view taken along the cross-sectional line BB in Fig. 2A.

[0011] 2A, the piezoelectric vibration element 20 is located near the center of the recess 10a. The piezoelectric vibration element 20 has a quartz crystal blank 21, a pair of excitation electrodes 22, a pair of mounting electrodes 23, an inspection electrode 24, a connecting conductor 25, and a metal pattern 26. That is, the piezoelectric vibration element 20 of this embodiment is a quartz crystal vibration element.

[0012] The crystal blank 21 is a piezoelectric plate according to this embodiment, and is generally rectangular in plan view, with its normal direction aligned along the Z-direction. As shown in FIGS. 2B and 2C , the crystal blank 21 has a central vibrating portion 211 and thick portions 212 located on the periphery. The thick portions 212 are thicker than the vibrating portion 211, i.e., are thicker in the Z-direction. The thick portions 212 are located along at least a portion of the crystal blank 21, in this case along two sides. The crystal blank 21 may be an inverted mesa type, in which the thick portions 212 completely surround the vibrating portion 211. Furthermore, the thick portions 212 do not necessarily have to protrude in the ± directions in the Z-direction relative to the vibrating portion 211, i.e., not both above and below. In this case, the protruding widths may be different between the top and bottom. The thick portions may also protrude only above or below the vibrating portion 211. This shape allows the thin vibrating portion 211 to be supported from the periphery, thereby reducing distortion due to stress. Therefore, adverse effects on the vibration of the vibrating portion 211 are reduced. The boundary between the vibrating portion 211 and the thick portion 212 does not have to have a step-like change in thickness. The boundary may have a slope where the thickness changes gradually. The excitation electrodes 22 are located opposite to both the upper and lower surfaces of the vibrating portion 211 of the quartz crystal blank 21.

[0013] The mounting electrode 23, the testing electrode 24, and the metal pattern 26 are located in the thick portion 212. The mounting electrode 23 and the excitation electrode 22 are connected by a connecting conductor 25 across the vibration portion 211 and the thick portion 212. In this embodiment, the connecting conductor 251 on the upper surface extends to the mounting electrode 23 at the upper right in the plan view of FIG. 2A . The connecting conductor 252 on the lower surface extends to the mounting electrode 23 at the lower left in the plan view of FIG. 2A . In other words, the pair of mounting electrodes 23 may be located at diagonal positions on the crystal blank 21 in a planar perspective view. The excitation electrode 22 is a laminate of a base layer containing chromium (Cr), titanium (Ti), or nickel (Ni), or an alloy (NiCr) containing two or more of these, and a conductor layer containing gold (Au), silver (Ag), copper (Cu), or aluminum (Al), or an alloy (AuPdCu) ​​containing two or more of these. Like the excitation electrode 22, the mounting electrode 23, the inspection electrode 24, the connection conductor 25, and the metal pattern 26 may be a laminate of a base layer and a conductor layer.

[0014] As shown in FIG. 2B , the mounting electrode 23 connected to the connecting conductor 251 on the upper surface is connected to the lower surface via the side surface of the crystal blank 21. The mounting electrode 23 is bonded to the electrode pad 11 located on the bottom surface of the recess 10a on the underside of the crystal blank 21 by a conductive bonding member 15. The electrode pad 11 is the electrode surface in this embodiment. Note that the piezoelectric vibration element 20 may be bonded and fixed to the bottom surface of the recess 10a in areas other than where the mounting electrode 23 and electrode pad 11 are bonded. The bonding member at the bonding portion other than the electrode pad 11 does not have to be a conductive bonding member.

[0015] As shown in FIG. 2C , the mounting electrode 23 connected to the lower surface connecting conductor 25 may be connected to the upper surface portion 231 via the side of the crystal blank 21. Also, as shown in FIGS. 2A and 2B , a connecting conductor 253 may extend from the upper surface excitation electrode 22 to a corner of the crystal blank 21 different from the corner where the pair of mounting electrodes 23 are located. This connecting conductor 253 connects the testing electrode 24 to the excitation electrode 22. The upper surface portion 231 extending from the lower surface mounting electrode 23 and the testing electrode 24 are connected to testing wiring or electrodes on the wafer before being separated from the wafer during manufacturing. These are used to test the electrical characteristics of the piezoelectric vibration element 20 using a prober.

[0016] As shown in FIG. 2C , external connection pads 12 are located on the bottom surface of the package 10. The external connection pads 12 are located at at least two of the four corners of the bottom surface of the package 10. One of the external connection pads 12 is connected to one of the two electrode pads 11 via wiring within the package 10 and on the surface. One or more of the other external connection pads 12 may be ground electrodes and are connected to the opposite side of one of the electrode pads 11. If the external connection pad 12 includes two or more ground electrodes, these may be commonly connected to one of the external connection pads 12 via wiring within the package 10. When the external connection pad 12 is connected to a substrate of an electronic device or the like and an electrical signal is supplied, the electrical signal is supplied to the piezoelectric vibration element 20. Furthermore, an electrical signal corresponding to the vibration of the piezoelectric vibration element 20 is output to the substrate.

[0017] As shown in FIG. 2A , the metal pattern 26, which is a conductor pattern of this embodiment, is located at one of the four corners of the crystal blank 21 in a planar view, where no electrodes are located. The "corner" here does not necessarily mean that the metal pattern 26 is in contact with the corner, but refers to a position closer to the corner than the center of a longitudinal side of the crystal blank 21. The metal pattern 26 is not electrically connected to any electrode, and does not face any electrode or connecting conductor 25 across the crystal blank 21. The metal pattern 26 is located across both the top and bottom surfaces via the side surfaces. The width of the metal pattern 26 in the X direction does not need to be uniform. For example, the width of the metal pattern 26 on the side surfaces may be narrower than the width of the metal pattern 26 on the top and bottom surfaces.

[0018] FIG. 3 is a perspective view of the piezoelectric vibration element 20. The metal pattern 26 has a top surface portion 261, a side surface portion 262, and a bottom surface portion 263 that are connected together. Therefore, the entire metal pattern 26 is at the same potential. The metal pattern 26 also has capacitance between itself and each of the mounting electrodes 23. This capacitance is parallel to the capacitance between the excitation electrodes 22. In other words, the metal pattern 26 forms part of the parallel capacitance C0 in the equivalent circuit of the piezoelectric vibration element 20. The top surface portion 261 and the bottom surface portion 263 do not need to be the same size and shape. The planar size of the metal pattern 26 is approximately the same as or smaller than the mounting electrodes 23, but is not limited to this.

[0019] With this structure, the parallel capacitance C0 of the piezoelectric vibration element 20 can be adjusted by adjusting the position, size, or shape of the metal pattern 26, or a combination of these. In particular, because the metal pattern 26 is continuous on the top and bottom surfaces, it generates a single capacitance overall with respect to the mounting electrode 23. This simplifies adjustment of the parallel capacitance C0 using this metal pattern 26. Furthermore, because the metal pattern 26 is located near a different corner of the crystal blank 21 from the mounting electrode 23, the distance between the metal pattern 26 and the mounting electrode 23 is greater. As a result, the size, shape, and other aspects of the metal pattern 26 do not need to be adjusted too precisely, making it easier to adjust the parallel capacitance C0.

[0020] As described above, the piezoelectric vibration element 20 of this embodiment includes a crystal blank 21, a pair of mounting electrodes 23, and a metal pattern 26. The crystal blank 21 has a vibrating portion 211 and a thick portion 212 that is located along at least a portion of the vibrating portion 211 and is thicker than the vibrating portion 211. The pair of mounting electrodes 23 are located in the thick portion 212 on each side of the crystal blank 21. The metal pattern 26 extends across both sides of the thick portion 212 and is not electrically connected to the mounting electrode 23. In this manner, a parallel capacitance C0 is obtained by the metal pattern 26, which is electrically isolated from the mounting electrode 23. Because this continuous metal pattern 26 is located across both sides of the crystal blank 21, the metal pattern 26 has the same potential on both sides. This facilitates adjustment of the parallel capacitance C0. In particular, the upper surface portion 261 and the lower surface portion 263 of the metal pattern 26, which are not directly connected to the wiring to the excitation electrode and are located in the thick portion 211, make it easy to adjust the parallel capacitance C0. Therefore, the piezoelectric vibration element 20 does not require any changes to the conventional circuit design, and the effort and cost for adjustments can be reduced. Therefore, the piezoelectric vibration element 20 that oscillates stably at a desired frequency can be obtained more easily.

[0021] Furthermore, the pair of mounting electrodes 23 may be located diagonally across the crystal blank 21 in a planar perspective view. When the oscillation frequency of the piezoelectric vibration element 20 is high, particularly in the frequency band of 50 to 75 MHz or higher, the vibrating portion 211 becomes thin. The shape of this embodiment efficiently produces a piezoelectric vibration element 20 with a thin vibrating portion 211 properly supported. In particular, even when the vibrating portion 211 is vibrating, the piezoelectric vibration element 20 is securely held and fixed, allowing the piezoelectric vibration element 20 to output appropriate vibrations or voltage signals corresponding to the vibrations. Furthermore, by locating the mounting electrodes 23 at diagonal positions, the piezoelectric vibration element 20 can be easily fixed in an appropriate positional relationship with respect to the bottom surface of the recess 10a when mounted with a conductive adhesive. The appropriate positional relationship may be parallel to the bottom surface of the recess 10a.

[0022] The metal pattern 26 may be located at a corner of the thick portion 212 where the mounting electrode 23 is not located. This makes it easier for the piezoelectric vibration element 20 to adjust the parallel capacitance C0 with the mounting electrode 23. Furthermore, the possibility of short-circuiting with each electrode or the connecting conductor 25 is further reduced.

[0023] Furthermore, the piezoelectric vibrator 1 of this embodiment includes the above-described piezoelectric vibrating element 20, and a package 10 having a recess 10a and an electrode pad 11 located within the recess 10a. The piezoelectric vibrating element 20 is located within the recess 10a, and the mounting electrode 23 is bonded to the electrode pad 11 via a conductive bonding member 15. This piezoelectric vibrator 1 enables operation by the piezoelectric vibrating element 20, which oscillates more stably at an appropriate oscillation frequency.

[0024] The above embodiment is merely an example, and various modifications are possible. For example, the piezoelectric vibrating element 20 does not necessarily have to have the testing electrode 24.

[0025] Furthermore, the metal pattern 26 does not have to be located near a corner of the crystal blank 21 in plan view. That is, the metal pattern 26 may be located near the center of a side along the longitudinal direction. Alternatively, the metal pattern 26 may be located adjacent to a short side of the crystal blank 21 in plan view.

[0026] Furthermore, the pair of mounting electrodes 23 do not have to be located at diagonal corners of the crystal blank 21 in a plan view. For example, the pair of mounting electrodes 23 may be located at both ends of a short side in a plan view. In this case, the side of the crystal blank 21 opposite the mounting electrodes 23 in the X direction does not have to be bonded to the bottom surface of the recess 10a. In other words, the piezoelectric vibration element 20 may be fixed in a state of being held in one hand.

[0027] Furthermore, the thick portion 212 may be located along two or three of the four sides of the crystal blank 21. That is, the vibrating portion 211 may be in contact with one or two of the four sides of the crystal blank 21. When the thick portion 212 is located along two sides, the two sides may be in contact with each other across a corner, or may be two sides that do not contact each other.

[0028] Furthermore, the vibrating section 211 does not necessarily have to be rectangular in plan view. For example, the planar shape of the vibrating section 211 may be circular, elliptical, or rectangular with rounded corners. In this case, the thick-walled section 212 only needs to be located along at least half the circumference of the vibrating section 211.

[0029] Furthermore, the shape of the excitation electrode 22 in plan view does not have to be circular. For example, the excitation electrode 22 may be an ellipse or a rectangle with rounded corners in plan view.

[0030] Furthermore, the piezoelectric vibrating element may have another piezoelectric vibrating piece instead of the crystal piece 21. Any material may be used as long as it converts between electrical force and mechanical deformation.

[0031] Furthermore, the piezoelectric vibrator 1 may have a package 10 with a different shape. For example, the recess 10a of the package 10 may have a step inside. Furthermore, the recess 10a does not have to be rectangular in plan view. For example, the corners of the inner surface of the recess 10a may be rounded. Furthermore, the package 10 may have a recess other than the recess 10a.

[0032] The bottom and side surfaces of the package 10 may be integral, or may be separate components joined together.

[0033] Furthermore, the piezoelectric vibrator 1 may house other electronic components in addition to the piezoelectric vibrating element 20 in the recess 10a or another recess. The specific details of the structure, configuration, material, size, etc. shown in the above embodiment may be modified as appropriate without departing from the spirit of the present disclosure. The scope of the present invention includes the scope of the invention described in the claims and their equivalents.

[0034] The present disclosure can be used for a piezoelectric vibration element and a piezoelectric vibrator.

[0035] REFERENCE SIGNS LIST 1 Piezoelectric vibrator 10 Package 10a Recess 11 Electrode pad 12 External connection pad 15 Bonding member 20 Piezoelectric vibrating element 21 Crystal blank 211 Vibrating portion 212 Thick portion 22 Excitation electrode 23 Mounting electrode 231 Top surface portion 24 Inspection electrode 25, 251 to 253 Connecting conductor 26 Metal pattern 261 Top surface portion 262 Side surface portion 263 Bottom surface portion 30 Lid

Claims

1. A piezoelectric vibration element comprising: a piezoelectric plate having a vibration portion and a thick portion located along at least a portion of the vibration portion and thicker than the vibration portion; a pair of mounting electrodes located in the thick portion on each side of the piezoelectric plate; and a conductor pattern extending across both sides of the thick portion and not electrically connected to the mounting electrodes.

2. The piezoelectric vibration element according to claim 1, wherein the pair of mounting electrodes are located at diagonal positions of the piezoelectric plate in a plan view.

3. The piezoelectric vibration element according to claim 2, wherein the conductive pattern is located at a corner of the thick portion where the pair of mounting electrodes are not located.

4. A piezoelectric vibrator comprising: a piezoelectric vibration element according to any one of claims 1 to 3; and a package having a recess and an electrode surface located within the recess, wherein the piezoelectric vibration element is located within the recess and the mounting electrode is bonded to the electrode surface via a conductive bonding member.

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