Piezoelectric vibration element and piezoelectric vibrator

Abstract

A piezoelectric vibration element includes a piezoelectric plate, a pair of mounting electrodes, and a conductor pattern. The piezoelectric plate includes: a vibrating portion; and a thick portion provided along at least a portion of the vibrating portion and thicker than the vibrating portion. The pair of mounting electrodes is located on the thick portions on both surfaces of the piezoelectric plate. The conductor pattern extends across both surfaces of the thick portion and is not electrically connected to the mounting electrode. The pair of carrying electrodes can be located at diagonal positions of the piezoelectric plate under planar perspective. The conductor pattern may be located at a corner portion of the thick portion where the pair of mounting electrodes is not provided.

Description

TECHNICAL FIELD

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

[0002] A piezoelectric vibration element deforms and vibrates in accordance with a periodic voltage pattern applied between excitation electrodes located on both faces of a piezoelectric member. Furthermore, an electric signal corresponding to the deformation of the piezoelectric member is output between the electrodes. In order to output a signal of an appropriate frequency with low loss and stability, an equivalent circuit parameter representing a characteristic of the piezoelectric vibration element is adjusted.

[0003] JP Patent No. 2021-29013 B describes a crystal element having an adjustment electrode connected to an excitation electrode of one face and not opposed to an electrode of the other face. Thereby, without changing a series resistance and a resonance frequency in an equivalent circuit, a series capacitance can be easily adjusted by the adjustment electrode. SUMMARY

[0004] One embodiment (1) of the present disclosure is a piezoelectric vibration element including: a piezoelectric plate having a vibration portion and a thick wall portion provided along at least a part of the vibration portion and thicker than the vibration portion; a pair of mounting electrodes located at the thick wall portion on both faces of the piezoelectric plate; and a conductor pattern extending over both faces of the thick wall portion and not electrically connected to the mounting electrodes.

[0005] (2) In the piezoelectric vibration element described in (1), the pair of mounting electrodes are located at diagonal positions of the piezoelectric plate in planar perspective.

[0006] (3) In the piezoelectric vibration element described in (2), the conductor pattern is located at a corner portion of the thick wall portion where the pair of mounting electrodes are not provided.

[0007] (4) A piezoelectric vibrator includes: the piezoelectric vibration element described in any one of (1) to (3); and a package having a recess and an electrode face located in the recess, the piezoelectric vibration element being located in the recess, and the mounting electrodes being joined to the electrode face via a conductive joining member. BRIEF DESCRIPTION OF DRAWINGS

[0008] Figure 1 is a perspective view of a piezoelectric vibrator as a whole.

[0009] Figure 2A is a plan view of a piezoelectric vibrator.

[0010] Figure 2B is a cross-sectional view of a piezoelectric vibrator.

[0011] Figure 2C is a cross-sectional view of a piezoelectric vibrator.

[0012] Figure 3 is a perspective view of a piezoelectric vibration element. DETAILED DESCRIPTION

[0013] Hereinafter, an embodiment will be described based on the drawings.

[0014] Figure 1 is an overall perspective view of the piezoelectric vibrator 1 of the present embodiment. In this Figure 1 is shown in a state where the cover 30 is removed. In addition, in the drawings of the present disclosure, the size ratio of the X direction indicating the vertical, the Y direction indicating the horizontal, and the Z direction indicating the height is for the purpose of explanation and does not necessarily reflect the actual value.

[0015] The piezoelectric device of one embodiment, that is, the piezoelectric vibrator 1, has a package 10, a piezoelectric vibration element 20, and a cover 30.

[0016] The package 10 is, for example, a housing of a ceramic material, a semiconductor material, or a glass material, or a combination of these. Furthermore, a signal line of a conductor is provided inside and on the surface of the above-described material of the package 10. The signal line includes a signal line related to power supply and grounding. The signal line is, for example, molybdenum, copper, silver, tungsten, or the like. Part or all of the signal line can be surface-laminated with nickel plating, gold plating, or the like. The package 10 has a recess 10a whose upper end, that is, the end on the positive side with respect to the Z direction, is open.

[0017] The piezoelectric vibration element 20 of the present embodiment is a crystal vibration element. The piezoelectric vibration element 20 is positioned inside the recess 10a.

[0018] The cover 30 is joined to the upper end of the package 10, that is, the side wall upper surface of the recess 10a, to seal the recess 10a. The cover 30 is a flat plate of a metal conductor, for example, a metal including iron, copper, nickel, cobalt, molybdenum, or tungsten, or an alloy of these, such as Kovar. The joining material used in the sealing of the cover 30 is preferably joined by heating within a temperature range that does not adversely affect the characteristics of the piezoelectric vibration element 20 sealed inside, and the like. For example, the cover 30 is joined by a solder or the like. A frame-shaped metallized layer can be provided between the upper end of the package 10 and the cover 30. The metallized layer can be a plating layer, and can also be a conductor layer formed by coating and firing.

[0019] Figure 2A is a plan view of the piezoelectric vibrator 1. Figure 2B and Figure 2C is a cross-sectional view of the piezoelectric vibrator 1. In Figure 2A In the drawing, for the purpose of explanation, a portion of the structure that is not visible from above is shown by a broken line in planar perspective. Figure 2B is a cross-sectional view at the cross-sectional line AA in Figure 2A . Figure 2C is a cross-sectional view at the cross-sectional line BB in Figure 2Aa cross-sectional view at a section line BB in FIG. 1.

[0020] As shown in FIG. 1, a piezoelectric vibration element 20 is provided near the center of the recess 10a. The piezoelectric vibration element 20 has a crystal piece 21, a pair of excitation electrodes 22, a pair of mounting electrodes 23, an inspection electrode 24, a connection conductor 25, and a metal pattern 26. That is, the piezoelectric vibration element 20 of the present embodiment is a crystal vibration element. Figure 2A As shown in FIG. 1, a piezoelectric vibration element 20 is provided near the center of the recess 10a. The piezoelectric vibration element 20 has a crystal piece 21, a pair of excitation electrodes 22, a pair of mounting electrodes 23, an inspection electrode 24, a connection conductor 25, and a metal pattern 26. That is, the piezoelectric vibration element 20 of the present embodiment is a crystal vibration element.

[0021] The crystal piece 21 is a piezoelectric plate of the present embodiment, and the normal direction thereof is along the Z direction, and is rectangular in plan view. As shown in FIG. 1, the crystal piece 21 has a vibration portion 211 at the center, and a thick wall portion 212 at the periphery. The thick wall portion 212 is thicker than the vibration portion 211, that is, has a larger thickness in the Z direction. The thick wall portion 212 is provided along at least a portion of the crystal piece 21, here along both sides. The crystal piece 21 can also be a reverse mesa type in which the thick wall portion 212 entirely surrounds the periphery of the vibration portion 211. Further, the thick wall portion 212 can not be thickened in the Z direction in the ± direction, that is, upward and downward, with respect to the vibration portion 211. In this case, the width of the thickening can be different upward and downward. The thickening can be in only one of upward or downward with respect to the vibration portion 211. According to such a shape, since the thin vibration portion 211 can be supported from the periphery, a strain corresponding to stress can be reduced. Thus, adverse effects on vibration of the vibration portion 211 are reduced. The boundary between the vibration portion 211 and the thick wall portion 212 can not be a step change in thickness. A slope in which the thickness gradually changes can be provided at the boundary. The excitation electrodes 22 can also be provided in opposition to both the upper and lower surfaces of the vibration portion 211 of the crystal piece 21. Figure 2B Figure 2C As shown in FIG. 1, a piezoelectric vibration element 20 is provided near the center of the recess 10a. The piezoelectric vibration element 20 has a crystal piece 21, a pair of excitation electrodes 22, a pair of mounting electrodes 23, an inspection electrode 24, a connection conductor 25, and a metal pattern 26. That is, the piezoelectric vibration element 20 of the present embodiment is a crystal vibration element.

[0022] The mounting electrodes 23, the inspection electrode 24, and the metal pattern 26 are located in the thick wall portion 212. The mounting electrodes 23 and the excitation electrodes 22 are connected across the vibration portion 211 and the thick wall portion 212 by the connection conductor 25. In the present embodiment, the upper surface connection conductor 251 is elongated toward the right upper mounting electrode 23 in plan view of FIG. 1. The lower surface connection conductor 252 is elongated toward the left lower mounting electrode 23 in plan view of FIG. 1. That is, the pair of mounting electrodes 23 can be located at diagonal positions of the crystal piece 21 in plan perspective. Figure 2A Figure 2A The mounting electrodes 23, the inspection electrode 24, and the metal pattern 26 are located in the thick wall portion 212. The mounting electrodes 23 and the excitation electrodes 22 are connected across the vibration portion 211 and the thick wall portion 212 by the connection conductor 25. In the present embodiment, the upper surface connection conductor 251 is elongated toward the right upper mounting electrode 23 in plan view of FIG. 1. The lower surface connection conductor 252 is elongated toward the left lower mounting electrode 23 in plan view of FIG. 1. That is, the pair of mounting electrodes 23 can be located at diagonal positions of the crystal piece 21 in plan perspective.

[0023] ​​The excitation electrode 22 is a laminate of a substrate layer and a conductor layer. The substrate layer contains chromium (Cr), titanium (Ti), or nickel (Ni), or an alloy containing two or more of these (NiCr). The conductor layer contains gold (Au), silver (Ag), copper (Cu), or aluminum (Al), or an alloy containing two or more of these (AuPdCu). The mounting electrode 23, the inspection electrode 24, the connecting conductor 25, and the metal pattern 26 can also be, similarly, a laminate of a substrate layer and a conductor layer as the excitation electrode 22.

[0024] like Figure 2B As shown, the mounting electrode 23, connected to the connecting conductor 251 on the upper surface, is connected to the lower surface via the side of the wafer 21. The mounting electrode 23 is bonded to the electrode pad 11 located on the bottom surface of the bottom of the wafer 21 via a conductive bonding member 15. The electrode pad 11 is the electrode surface of this embodiment.

[0025] Furthermore, the piezoelectric vibration element 20 can be joined and fixed to the bottom surface of the recess 10a, in addition to the portion where the mounting electrode 23 and the electrode pad 11 are joined. The joining member to the portion other than the electrode pad 11 may also be a non-conductive joining member.

[0026] like Figure 2C As shown, the mounting electrode 23, which is connected to the connecting conductor 25 on the lower surface, can also be connected to the upper surface portion 231 via the side of the wafer 21. Furthermore, as... Figure 2A as well as Figure 2B As shown, the connecting conductor 253 can also extend from the excitation electrode 22 on the upper surface to a corner different from the corner of the wafer 21 where the pair of mounting electrodes 23 are located. This connecting conductor 253 connects the inspection electrode 24 to the excitation electrode 22. The upper surface portion 231 extending from the mounting electrode 23 on the lower surface, and the inspection electrode 24, are connected to inspection wiring, electrodes, etc., on the wafer before being diced during manufacturing. These are used in the inspection of the electrical characteristics of the piezoelectric vibrating element 20 using detection.

[0027] like Figure 2CAs shown, external connection pads 12 are provided on the bottom surface of the package 10. At least two of the external connection pads 12 are located at the four corners of the bottom surface of the package 10. One of the external connection pads 12 is connected to either of the two electrode pads 11 via wiring inside and on the surface of the package 10. One or more of the other external connection pads 12 may also be ground electrodes, connected to the opposite side of either of the aforementioned electrode pads 11. When the external connection pads 12 include two or more ground electrodes, they may also be connected to any one of the external connection pads 12 via wiring inside the package 10. Electrical signals are supplied to the piezoelectric vibrating element 20 by connecting the external connection pads 12 to the substrate of an electronic device. Furthermore, an electrical signal corresponding to the vibration of the piezoelectric vibrating element 20 is output to the substrate.

[0028] like Figure 2A As shown, in this embodiment, the conductor pattern, i.e., the metal pattern 26, is located at a corner of the wafer 21 where none of the electrodes are located when viewed from above. The term "corner" here does not necessarily mean that the metal pattern 26 is in contact with a corner; it refers to a position along the long side of the wafer 21 that is closer to the corner than the center. The metal pattern 26 is not electrically connected to any electrode, and it is positioned opposite to any electrode or connecting conductor 25 without clamping onto the wafer 21. The metal pattern 26 is provided across both the upper and lower surfaces via a side surface. Furthermore, the width of the metal pattern 26 in the X direction may not be uniform. For example, the width of the metal pattern 26 on the side surface may be narrower than the width of the metal pattern 26 on the upper and lower surfaces.

[0029] Figure 3 This is a three-dimensional view of the piezoelectric vibration element 20.

[0030] The upper surface portion 261, side portion 262, and lower surface portion 263 of the metal pattern 26 are integrated. Therefore, the entire metal pattern 26 is at the same potential. Furthermore, the metal pattern 26 has electrostatic capacitance between itself and each mounting electrode 23, etc. This electrostatic capacitance is connected in parallel with the capacitance between the excitation electrode 22. That is, the metal pattern 26 forms part of the parallel capacitance C0 in the equivalent circuit of the piezoelectric resonant element 20. The dimensions and shapes of the upper surface portion 261 and the lower surface portion 263 may not be the same. The top-view size of the metal pattern 26 may be the same as or smaller than the mounting electrode 23, but is not limited thereto.

[0031] According to such a configuration, the piezoelectric vibration element 20 can adjust the parallel capacitance Co by the position, size, or shape of the metal pattern 26 or a combination of these. In particular, since the metal pattern 26 is integrated on the upper and lower surfaces, an electrostatic capacity is generated as a whole with respect to the mounting electrode 23. Therefore, adjustment of the parallel capacitance Co based on the metal pattern 26 becomes easy. Further, since the metal pattern 26 is located in the vicinity of a different angle from the mounting electrode 23 in the crystal piece 21, the distance from the mounting electrode 23 becomes large. Accordingly, adjustment of the size, shape, or the like of the metal pattern 26 does not become too fragmented, and adjustment of the parallel capacitance Co is easily performed.

[0032] As above, the piezoelectric vibration element 20 of the present embodiment includes the crystal piece 21, the pair of mounting electrodes 23, and the metal pattern 26. The crystal piece 21 has the vibration portion 211 and the thick wall portion 212 provided along at least a part of the vibration portion 211 and thicker than the vibration portion 211. The pair of mounting electrodes 23 is located at the thick wall portion 212 on both surfaces of the crystal piece 21. The metal pattern 26 extends over both surfaces of the thick wall portion 212 and is not electrically connected to the mounting electrode 23.

[0033] Thus, the parallel capacitance Co is obtained by the metal pattern 26 electrically separated from the mounting electrode 23. Since such an integrated metal pattern 26 is provided across both surfaces of the crystal piece 21, the metal pattern 26 becomes the same potential on both surfaces. Thus, adjustment of the parallel capacitance Co becomes easy. In particular, adjustment of the parallel capacitance Co is easily performed by the upper surface portion 261 and the lower surface portion 263 of the metal pattern 26 located at the thick wall portion 211 without being directly wired to the excitation electrode. Therefore, the piezoelectric vibration element 20 does not involve changes in the existing circuit design or the like, and the effort and cost of adjustment are easily reduced. Thus, it is easier to obtain a piezoelectric vibration element 20 that stably oscillates at a desired frequency.

[0034] Further, the pair of mounting electrodes 23 can be located at diagonal positions of the crystal piece 21 in planar perspective. If the oscillation frequency of the piezoelectric vibration element 20 becomes high, in particular, a frequency band of 50 to 75 MHz or more, the vibration portion 211 becomes thin. According to the shape of the present embodiment, a piezoelectric vibration element 20 that appropriately supports the thin vibration portion 211 can be efficiently obtained. In particular, since the piezoelectric vibration element 20 is fixed in a state that is surely maintained even if the vibration portion 211 vibrates, the piezoelectric vibration element 20 can output an appropriate vibration or a voltage signal corresponding to the vibration. Further, by locating the mounting electrodes 23 at diagonal positions, in the case of mounting the piezoelectric vibration element 20 with a conductive adhesive, the piezoelectric vibration element 20 can be easily fixed in an appropriate positional relationship with respect to the bottom surface of the recess 10a. The appropriate positional relationship can be parallel to the bottom surface of the recess 10a.

[0035] Further, the metal pattern 26 can be located at a corner portion of the thick wall portion 212 where the mounting electrode 23 is not provided. Thus, the piezoelectric vibration element 20 is easily adjusted in parallel capacitance Co with the mounting electrode 23. Further, the possibility of short-circuiting with each electrode and the connection conductor 25 is further reduced.

[0036] Further, the piezoelectric vibrator 1 of the present embodiment includes the piezoelectric vibration element 20 described above, and the package 10 having the recess 10a and the electrode pad 11 located in the recess 10a. The piezoelectric vibration element 20 is located in the recess 10a, and the mounting electrode 23 is joined to the electrode pad 11 via the conductive joining member 15.

[0037] According to this piezoelectric vibrator 1, the operation based on the piezoelectric vibration element 20 oscillating at an appropriate oscillation frequency is more stably performed.

[0038] Further, the above-described embodiment is an example, and various modifications can be made.

[0039] For example, the piezoelectric vibration element 20 can not necessarily have the inspection electrode 24.

[0040] Further, the metal pattern 26 can not be located near a corner of the crystal piece 21 in plan view. That is, the metal pattern 26 can be located near the center of the edge in the long direction. Alternatively, the metal pattern 26 can be located at a position in plan view that is in contact with the short side of the crystal piece 21.

[0041] Further, the pair of mounting electrodes 23 can not be located at opposite corners of the crystal piece 21 in plan view. For example, the pair of mounting electrodes 23 can be located at both ends of the short side in plan view. In this case, the piezoelectric vibration element 20 can be fixed in a single support state without being joined to the bottom surface of the recess 10a on the side opposite the mounting electrodes 23 with respect to the X direction.

[0042] Further, the thick wall portion 212 can be provided along two or three of the four edges of the crystal piece 21. That is, the vibration portion 211 can be in contact with one or two of the four edges of the crystal piece 21. In the case where the thick wall portion 212 is provided along two edges, the two edges can be in contact with each other with a corner therebetween, or the two edges can be non-contacting.

[0043] Further, the vibration portion 211 can not necessarily be rectangular in plan view. For example, the planar shape of the vibration portion 211 can be circular, elliptical, or rectangular with rounded corners. In this case, the thick wall portion 212 can be provided along at least half of the vibration portion 211.

[0044] Further, the planar shape of the excitation electrode 22 can not necessarily be circular. For example, the excitation electrode 22 can be elliptical or rectangular with rounded corners in plan view.

[0045] Further, a piezoelectric vibration element having another piezoelectric vibration piece instead of the crystal piece 21 can be used. As long as the material is transformed between electric power and mechanical deformation, it can be used.

[0046] Further, the piezoelectric vibrator 1 can have another shape of the package 10. For example, a step can be provided in the recess 10a of the package 10. Further, the recess 10a can not be rectangular when viewed from above. For example, the corners of the inner side surface of the recess 10a can be rounded. Further, the package 10 can have another recess other than the recess 10a.

[0047] Further, the bottom surface and the side surface of the package 10 can be integrated, or separate structures can be joined.

[0048] Further, the piezoelectric vibrator 1 can accommodate another electronic component or the like in the recess 10a or in another recess in addition to the piezoelectric vibration element 20.

[0049] The above-described configuration, structure, material, size, and the like of the embodiment can be appropriately changed without departing from the gist of the present disclosure. The scope of the present disclosure includes the scope of the invention recited in the claims and the equivalent scope thereof.

[0050] Industrial Applicability

[0051] The present disclosure can be used in a piezoelectric vibration element and a piezoelectric vibrator.

[0052] Explanation of Symbols

[0053] 1 piezoelectric vibrator

[0054] 10 package

[0055] 10a recess

[0056] 11 electrode pad

[0057] 12 external connection pad

[0058] 15 joining member

[0059] 20 piezoelectric vibration element

[0060] 21 crystal piece

[0061] 211 vibration portion

[0062] 212 thick wall portion

[0063] 22 excitation electrode

[0064] 23 mounting electrode

[0065] 231 upper surface portion

[0066] 24 inspection electrode

[0067] 25, 251-253 connection conductor

[0068] 26 metal pattern

[0069] 261 upper surface portion

[0070] 262 side surface portion

[0071] 263 lower surface portion

[0072] 30 cover

Claims

1. A piezoelectric vibration element, comprising: A piezoelectric plate having a vibrating portion and a thick-walled portion that is thicker than the vibrating portion and is disposed along at least a portion of the vibrating portion; A pair of mounted electrodes are located on opposite sides of the piezoelectric plate in the thick-walled portion; and The conductor pattern extends across both sides of the thick-walled portion and is not electrically connected to the mounted electrode.

2. The piezoelectric vibration element according to claim 1, wherein, The pair of mounted electrodes are located diagonally opposite each other on the piezoelectric plate in planar perspective.

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

4. A piezoelectric oscillator, comprising: The piezoelectric vibration element according to any one of claims 1 to 3; and The package has a recess and an electrode surface located within the recess. 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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