Piezoelectric vibrator

Abstract

The present invention comprises: a vibrator layer having a vibration unit, a holding part surrounding the vibration unit in a plan view, and a holding arm connecting the holding part and the vibration unit, with the vibration unit having a piezoelectric layer, an upper electrode layer provided on a first main surface of the piezoelectric layer, and a lower electrode layer provided on a second main surface of the piezoelectric layer, the second main surface opposing the first main surface; an upper lid layer provided on the upper electrode layer side of the vibrator layer; a lower lid layer provided on the lower electrode layer side of the vibrator layer; a first joining member that is provided so as to surround the vibration unit in a plan view and that joins the upper lid layer and the holding part of the vibrator layer; a second joining member that is provided so as to surround the vibration unit in a plan view and that joins the lower lid layer and the holding part of the vibrator layer; and a covering member provided so as to cover the entire circumference of an inner surface and / or an outer surface of the first joining member and / or the second joining member. At least one of the joining members is configured by a first insulating material, and the covering member is configured from a second insulating material having lower gas permeability than that of the first insulating material.

Description

[Technical Field]

[0001] The present invention relates to a piezoelectric vibrator. [Background technology]

[0002] In recent years, the miniaturization of resonators has progressed. Also, crystal resonators with a wafer-level package structure, in which three wafers, a lid layer, a resonator layer, and a substrate layer, are bonded together, are generally known. For example, Patent Document 1 discloses a crystal resonator in which three crystal wafers are bonded together using low-melting-point glass or polyimide resin as an insulating material. Furthermore, Patent Document 2 discloses a crystal resonator in which three crystal wafers are bonded together using Au as a conductor. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-38524 [Patent Document 2] Japanese Patent Publication No. 2022-99603 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in a configuration like that of Patent Document 1, when three quartz crystal wafers are bonded together using resin, resin generally has high gas permeability, so there is a possibility that moisture and oxygen may penetrate through the resin sealing portion made of resin into the inside of the quartz crystal resonator. This can cause the moisture and oxygen that penetrates the inside of the quartz crystal resonator to react with the metal of the electrode film of the quartz crystal resonator element, causing the mass of the quartz crystal resonator element to fluctuate, which may result in a loss of the long-term frequency stability of the quartz crystal resonator element. Furthermore, if all of the bonding members of the three wafers are made of gold metal, as in Patent Document 2, the surface roughness of each wafer must be extremely small, making it difficult to reduce costs.

[0005] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a low-cost, highly reliable piezoelectric vibrator. [Means for solving the problem]

[0006] A piezoelectric vibrator according to one embodiment of the present invention comprises: a vibrating section having a piezoelectric layer, an upper electrode layer provided on a first main surface of the piezoelectric layer, and a lower electrode layer provided on a second main surface opposite the first main surface of the piezoelectric layer; a vibrator layer having a holding section that surrounds the vibrating section in a planar view and a holding arm that connects the holding section to the vibrating section; an upper cover layer provided on the upper electrode layer side of the vibrator layer; a lower cover layer provided on the lower electrode layer side of the vibrator layer; a first bonding member that is provided to surround the vibrating section in a planar view and bonds the holding section of the vibrator layer to the upper cover layer; a second bonding member that is provided to surround the vibrating section in a planar view and bonds the holding section of the vibrator layer to the lower cover layer; and a covering member that is provided to cover the entire periphery of at least one of the inner surface and the outer surface of at least one of the first bonding member and the second bonding member, wherein at least one bonding member is made of a first insulating material, and the covering member is made of a second insulating material that has lower gas permeability than the first insulating material.

[0007] In the present invention, the first insulating material gas A covering member made of a second insulating material with low permeability is used. This covering member covers the entire periphery of at least one of the inner and outer surfaces of at least one of the first and second bonding members, thereby improving the internal airtight sealing and suppressing frequency fluctuations of the piezoelectric vibrator. Furthermore, because at least one of the first and second bonding members is made of the first insulating material, costs can be reduced compared to a configuration in which all bonding members are metal-bonded. Therefore, a highly reliable piezoelectric vibrator can be provided at low cost. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a low-cost, highly reliable piezoelectric vibrator. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view schematically showing a piezoelectric vibrator according to a first embodiment. [Figure 2] 2 is a cross-sectional view of the piezoelectric vibrator according to the first embodiment taken along line II-II in FIG. 1. [Figure 3] FIG. 4 is a cross-sectional view showing the configuration of a piezoelectric vibrator according to a second embodiment. [Figure 4] FIG. 10 is a cross-sectional view showing the configuration of a piezoelectric vibrator according to a third embodiment. [Figure 5] FIG. 10 is a plan view illustrating the configuration of a quartz crystal vibrating element according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings of the present embodiment are merely examples, and the dimensions and shapes of each part are schematic, so the technical scope of the present invention should not be interpreted as being limited to the embodiment.

[0011] To clarify the relationship between the drawings and to aid in understanding the positional relationships of each component, each drawing may conveniently include a Cartesian coordinate system consisting of the X-axis, Y'-axis, and Z'-axis. The X-axis, Y'-axis, and Z'-axis correspond to each other in each drawing. The X-axis, Y'-axis, and Z'-axis correspond to the crystallographic axes of the quartz blank, which will be described later. The X-axis corresponds to the electrical axis (polarity axis) of the quartz, the Y-axis corresponds to the mechanical axis of the quartz, and the Z-axis corresponds to the optical axis of the quartz. The Y'-axis and Z'-axis are axes obtained by rotating the Y-axis and Z-axis around the X-axis by 35 degrees 15 minutes ± 1 minute 30 seconds in the direction from the Y-axis to the Z-axis.

[0012] First Embodiment The configuration of a piezoelectric vibrator 1 according to a first embodiment of the present invention will be described with reference to Figures 1 and 2. Figure 1 is an exploded perspective view schematically showing the piezoelectric vibrator 1 according to this embodiment. Figure 2 is a cross-sectional view of the piezoelectric vibrator 1 according to this embodiment taken along line II-II in Figure 1.

[0013] The piezoelectric vibrator 1 according to this embodiment includes a quartz vibrating element 10, a first bonding member 20, an upper lid layer 30, a second bonding member 40, and a lower lid layer 50. In the following description, a quartz vibrating element 10 including a quartz crystal blank 12 (quartz crystal blank) will be used as an example of the piezoelectric vibrating element of the piezoelectric vibrator 1. The quartz crystal blank 12 is a type of piezoelectric material (piezoelectric piece) that vibrates in response to an applied voltage. Note that the piezoelectric vibrating element is not limited to the quartz vibrating element 10, and other piezoelectric materials such as ceramic may also be used. The piezoelectric vibrating element may also be a MEMS vibrating element manufactured using MEMS technology.

[0014] The quartz crystal vibrating element 10 (an example of an "oscillator layer") is an element that vibrates quartz crystal using the piezoelectric effect and converts electrical energy into mechanical energy. The quartz crystal vibrating element 10 includes an AT-cut quartz crystal blank 12. The AT-cut quartz crystal blank 12 is cut with the XZ' plane, defined by the X-axis and Z'-axis, as the principal surface, when the Y-axis and Z-axis are rotated 35 degrees 15 minutes ± 1 minute 30 seconds from the Y-axis to the Z-axis around the X-axis. The quartz crystal blank 12 may also be a tuning-fork shaped quartz crystal blank.

[0015] The rotation angles of the Y'-axis and Z'-axis of the AT-cut crystal blank 12 may be inclined within a range of -5 degrees to +15 degrees from 35 degrees 15 minutes. 12 The cut angle may be a different cut other than the AT cut, such as a BT cut, a GT cut, or an SC cut.

[0016] Quartz crystal vibration elements using AT-cut quartz crystal blanks have high frequency stability over a wide temperature range. They also have excellent aging characteristics and can be manufactured at low cost. Furthermore, AT-cut quartz crystal vibration elements use the thickness shear vibration mode as their primary vibration mode.

[0017] The quartz crystal vibrating element 10 includes a pair of excitation electrodes. An alternating electric field is applied between the pair of excitation electrodes. This causes the vibrating portion of the quartz crystal blank 12 to vibrate at a predetermined oscillation frequency in a thickness-shear vibration mode, resulting in resonance characteristics associated with this vibration.

[0018] In this way, since the main vibration of the quartz crystal vibration element 10 is thickness-shear vibration mode, by using, for example, an AT-cut quartz crystal piece 12, it is possible to easily realize a quartz crystal vibration element that performs thickness-shear vibration at vibration frequencies in the MHz range.

[0019] The crystal blank 12 (which corresponds to an example of a "piezoelectric layer") has a first principal surface 12a and a second principal surface 12b that are opposed to each other and are in the XZ' plane. The crystal blank 12 has a flat plate shape. Therefore, the first principal surface 12a and the second principal surface 12b of the crystal blank 12 are each flat surfaces. Note that the crystal blank 12 is not limited to a flat plate shape, and may have, for example, a convex or concave central portion.

[0020] The AT-cut crystal blank 12 has a long side direction in which the long sides extend parallel to the X-axis direction, a short side direction in which the short sides extend parallel to the Z'-axis direction, and a thickness direction in which the thickness extends parallel to the Y'-axis direction. When the first main surface 12a of the crystal blank 12 is viewed in a plan view (hereinafter simply referred to as "plan view"), the crystal blank 12 has a rectangular shape. For example, the crystal blank 12 may be bonded to the second bonding member 40 while still having a larger thickness, and then polished to reduce the thickness to a predetermined value.

[0021] The planar shape of the crystal blank 12 is not limited to a rectangular shape, but may be a polygonal shape, a circular shape, an elliptical shape, or a combination thereof.

[0022] The quartz crystal vibrating element 10 includes a vibrating portion 16, a holding arm 17, and a holding portion 18. The vibrating portion 16 includes a quartz crystal blank 12 and a set of excitation electrodes. The set of excitation electrodes includes a first excitation electrode 14a (corresponding to an example of an "upper electrode layer") and a second excitation electrode 14b (corresponding to an example of a "lower electrode layer"). The first excitation electrode 14a is provided on a first main surface 12a of the vibrating portion 16, and the second excitation electrode 14b is provided on a second main surface 12b of the vibrating portion 16. The first excitation electrode 14a and the second excitation electrode 14b are provided opposite each other with the quartz crystal blank 12 sandwiched therebetween. When the first main surface 12a is viewed in plan, the first excitation electrode 14a and the second excitation electrode 14b each have a rectangular shape and are arranged so that they substantially entirely overlap in the XZ' plane.

[0023] The first excitation electrode 14a and the second excitation electrode 14b are not limited to a rectangular shape, and may be a polygon, a circle, an ellipse, or a combination thereof.

[0024] The quartz crystal vibrating element 10 has extraction electrodes and connection electrodes (not shown), and by these electrodes, for example, the first excitation electrode 14a is electrically connected to the external electrode 51a, and the second excitation electrode 14b is electrically connected to the external electrode 51d. By applying an alternating electric field to the first excitation electrode 14a and the second excitation electrode 14b via these external electrodes 51a, 51d, the vibrating portion 16 (specifically, the portion of the quartz crystal blank 12 where the first excitation electrode 14a and the second excitation electrode 14b are provided) vibrates in a predetermined vibration mode.

[0025] The first excitation electrode 14a, the second excitation electrode 14b, the extraction electrode, and the connection electrode are made of, for example, aluminum (Al), molybdenum (Mo), or gold (Au). Each of the electrodes may be a laminate consisting of, for example, a titanium (Ti) layer provided on the crystal blank 12 side and a gold (Au) layer provided on the front surface side.

[0026] The quartz crystal vibrating element 10 is housed in an internal space 60 formed between the first bonding member 20, the upper lid layer 30, the second bonding member 40, and the lower lid layer 50. The internal space 60 is, for example, hermetically sealed. Note that the internal space 60 may be hermetically sealed in a vacuum state, or may be hermetically sealed in a state filled with a gas such as an inert gas.

[0027] The vibrating portion 16 is a part of the quartz crystal vibrating element 10 and is located in the center of the internal space 60. As shown in FIG. 2, the vibrating portion 16 has a first main surface 12a and a second main surface 12b facing the first main surface 12a. The vibrating portion 16 also has a first excitation electrode 14a provided on the first main surface 12a and a second excitation electrode 14b provided on the second main surface 12b. The first excitation electrode 14a is provided on the surface of the quartz crystal blank 12 facing the upper lid layer 30, and the second excitation electrode 14b is provided on the surface facing the lower lid layer 50.

[0028] The holding arm 17 is located in the internal space 60, similar to the vibrating part 16, and connects the vibrating part 16 and the holding part 18. An extraction electrode (not shown) is formed on the holding arm 17, and the first excitation electrode 14a and the second excitation electrode 14b can be routed to a connection electrode provided on the holding part 18.

[0029] The holding portion 18 is configured in a frame shape that surrounds the periphery of the vibrating portion 16 in a plan view. The holding portion 18 is joined to the first joining member 20 and the second joining member 40 from above and below. The holding portion 18 is connected to the holding arm 17.

[0030] The covering member 19 is made of an insulating material that has lower gas permeability than the insulating material of the second bonding member 40, which will be described later. For example, aluminum oxide (Al2O3) is used as the insulating material of the covering member 19. In the example shown in FIG. 2, the covering member 19 is provided so as to cover the inner surface 40a of the second bonding member 40. Specifically, the covering member 19 covers the surface of the quartz vibrating element 10, the inner surface 40a of the second bonding member 40, and the portion of the lower cover layer 50 facing the vibrating portion. Top partFor example, when a first wafer including a plurality of lower cover layers 50, a second wafer including a plurality of crystal vibrating elements 10, and a wafer including a plurality of upper cover layers 30 are bonded together, and then each wafer is diced to obtain a plurality of piezoelectric vibrators 1, the covering member 19 can be formed after the first wafer and the second wafer are bonded together. The thickness of the covering member 19 is 1 nm or more and 100 nm or less, and more preferably 5 nm or more and 50 nm or less. The covering member 19 can be formed by ALD (Atomic Layer Deposition), CVD (Chemical Vapor Deposition), PVD (Physical Vapor Deposition), or the like. A film with low gas permeability can be easily formed by forming the film using the above-mentioned ALD, CVD, or PVD. In particular, when ALD is used, the covering member 19 with low gas permeability can be formed even on a thick structure with unevenness or undulations. The areas covered by the covering member 19 are not limited to those described above, and may be provided, for example, only on the inner surface 40a of the second joining member 40 as in the second embodiment described later, or may be provided to cover the outer surface 20b of the first joining member 20 and the outer surface 40b of the second joining member 40 as in the third embodiment described later.

[0031] In this embodiment, the first bonding member 20 is made of a metal material. The first bonding member 20 is provided between the upper surface of the holding portion 18 and the upper cover layer 30, and metallurgically bonds them together. The first bonding member is also provided to surround the vibrating portion 16 in a plan view, and bonds the holding portion 18 of the quartz vibrating element 10 to the upper cover layer 30 in a frame shape. The first bonding member 20 has an inner surface 20a that contacts the internal space 60, and an outer surface 20b on the opposite side of the first bonding member 20 from the inner surface 20a. Any metal bonding may be used as long as it provides airtightness to the internal space 60, and an Au-Au bonding, an AuSn bonding, an AlGe bonding, or the like may be used.

[0032] The upper lid layer 30 is configured, for example, in a flat plate shape. The dimensions of the upper lid layer 30 in a plan view are the same as or approximately the same as the dimensions of the quartz crystal vibrating element 10. The upper lid layer 30 is provided on the first excitation electrode 14a side of the quartz crystal vibrating element 10. The upper lid layer 30 forms part of the internal space 60 by being bonded to the first bonding member 20. The upper lid layer 30 may be made of quartz crystal, silicon, ceramic, or glass.

[0033] In this embodiment, the second bonding member 40 is made of an insulating material. For example, resin or glass is used as the insulating material of the second bonding member 40. For example, polyimide resin may be used as the resin. Furthermore, low-melting-point glass may be used as the glass. The second bonding member 40 is provided between the lower surface of the holding portion 18 and the lower cover layer 50 to bond them together. The second bonding member is also provided to surround the vibrating portion 16 in a plan view and bonds the holding portion 18 of the quartz vibrating element 10 to the lower cover layer 50 in a frame-like shape. The second bonding member 40 has an inner surface 40a facing the internal space 60 and an outer surface 40b on the opposite side of the inner surface 40a and the second bonding member 40. In this embodiment, a covering member 19 is provided on the inner surface 40a. This allows the covering member 19 to block gas that has permeated the second bonding member 40, thereby improving the airtight sealing of the internal space 60. Furthermore, by forming the second bonding member 40 on the lower lid layer 50 side, on which the external electrodes 51 (described later) are provided, from an insulating material, it is possible to achieve a smaller size and better electrical characteristics compared to, for example, the configuration using metal bonding disclosed in Patent Document 2. That is, in the configuration using metal bonding disclosed in Patent Document 2, wiring cannot be routed across the metal bonding member, so vias must be formed in the vibration element, making it difficult to ensure a sufficient area for the vibration portion. In contrast, in the configuration of this embodiment, the quartz vibrating element 10 and the lower lid layer 50 are bonded with the second bonding member 40 made of an insulating material. This allows wiring to be routed across the second bonding member 40, eliminating the need to form vias in the quartz vibrating element 10. Therefore, the first excitation electrode 14a and the second excitation electrode 14b of the vibration portion 16 can be maximized, resulting in good electrical characteristics equivalent to those of a large product, while also enabling the piezoelectric vibrator 1 to be miniaturized.

[0034] The lower lid layer 50 is formed, for example, in a flat plate shape. The dimensions of the lower lid layer 50 in a plan view are the same or approximately the same as the dimensions of the quartz crystal vibrating element 10. The lower lid layer 50 is provided on the second excitation electrode 14b side of the quartz crystal vibrating element 10. The lower lid layer 50 forms part of the internal space 60 by being bonded to the second bonding member 40. The lower lid layer 50 may be made of quartz crystal, or may be made of silicon, ceramic, or glass. By making at least one of the upper lid layer 30 and the lower lid layer 50 of silicon, glass, or ceramic, which has low transparency to visible light, image recognition and mounting positioning can be easily performed when mounting the piezoelectric vibrator 1. The lower lid layer 50 has an external electrode 51 on the side opposite to the side facing the quartz crystal vibrating element 10.

[0035] External electrodes 51a, 51b, 51c, and 51d are provided at the four corners of the lower cover layer 50. The external electrode 51a is electrically connected to the first excitation electrode 14a, and the external electrode 51d is electrically connected to the second excitation electrode 14b. The external electrodes 51b and 51c may be used as dummy electrodes that are not electrically connected to the quartz crystal vibrating element 10. With this electrode arrangement, the piezoelectric vibrator 1 can be mounted on a substrate even if it is inverted upside down, because the positions of the external electrodes are symmetrical. Furthermore, by ensuring the maximum distance between the external electrodes 51a and 51d, short circuits between the two electrodes can be suppressed.

[0036] An internal space 60 is formed inside the piezoelectric vibrator 1 by the first bonding member 20, the upper lid layer 30, the second bonding member 40, and the lower lid layer 50. The internal space 60 is provided with the vibrating part 16 and the holding arms 17, and forms a vibration space for the quartz crystal vibrating element 10.

[0037] As described above, in the piezoelectric vibrator 1 according to this embodiment, the inner surface 40a of the second bonding member 40 is covered with the covering member 19. This allows the covering member 19, which is made of an insulating material with lower gas permeability than the insulating material of the second bonding member 40, to block gas that penetrates the second bonding member 40 from the outside of the piezoelectric vibrator 1, thereby improving the airtight sealing of the internal space 60. Furthermore, by making the second bonding member 40 out of an insulating material, costs can be reduced compared to a configuration in which all bonding members are metallic.

[0038] In the present embodiment, the covering member 19 is provided on the inner surface 40a of the second bonding member 40. However, this is not limiting. The covering member 19 may be provided to cover the entire periphery of at least one of the inner surfaces 20a and 40a and the outer surfaces 20b and 40b of at least one of the first bonding member 20 and the second bonding member 40. For example, the covering member 19 may be provided on the outer surface 40b of the second bonding member 40, or on both the inner surface 40a and the outer surface 40b. Furthermore, in the present embodiment, the crystal vibrating element 10 and the upper cover layer 30 are metal-bonded by the first bonding member 20. However, if the first bonding member is made of an insulating material, at least one of the inner surface 20a and the outer surface 20b of the first bonding member 20 may be covered with the covering member 19, as with the second bonding member 40.

[0039] In addition, in this embodiment, the first bonding members 20 are made of a metal material, the second bonding members 40 are made of an insulating material, and the second bonding members 40 are covered with the covering member 19. However, this is not limited to this, and it is sufficient that at least one of the bonding members is made of an insulating material. For example, when the first bonding members 20 are made of an insulating material, the first bonding members 20 may be covered with the covering member 19.

[0040] Furthermore, in this embodiment, a covering member 19 is provided on each surface of the first excitation electrode 14a and the second excitation electrode 14b of the quartz-crystal vibrating element 10. By covering the surfaces of the first excitation electrode 14a and the second excitation electrode 14b with the covering member 19, oxidation of the first excitation electrode 14a and the second excitation electrode 14b can be suppressed.

[0041] The following describes the configuration of a resin sealing apparatus and a resin sealing method according to another embodiment of the present invention. fruit In this embodiment, the description of the matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar effects resulting from similar configurations will not be mentioned one by one.

[0042] Second Embodiment Next, the structure of a piezoelectric vibrator 2 according to a second embodiment will be described with reference to FIG. 3. FIG. 3 is a cross-sectional view that schematically shows the structure of a piezoelectric vibrator according to the second embodiment.

[0043] This embodiment differs from the first embodiment in the position where the covering member 19 is provided. Specifically, in the first embodiment, the surface of the crystal vibrating element 10, the inner surface 40a of the second bonding member 40, and the portion of the lower cover layer 50 facing the vibrating portion are covered with the covering member 19. Top part In the previous embodiment, the covering member 19 was provided on the inner surface 40a of the second bonding member 40, whereas in this embodiment, the covering member 19a is provided partially on the inner surface 40a of the second bonding member 40. In this case, the covering member 19a is provided so as to avoid the bonding surface of the quartz-crystal vibrating element 10 with the first bonding member 20. This improves the bonding between the quartz-crystal vibrating element 10 and the upper cover layer 30. Furthermore, the covering member 19a is provided so as to avoid the surfaces of the first excitation electrode 14a and the second excitation electrode 14b of the vibrating part 16. This makes it possible to suppress fluctuations in the vibration characteristics of the vibrating part 16 due to fluctuations in the weight of the covering member, if the covering member 19a has gas adsorption properties.

[0044] <Third embodiment> Next, the structure of a piezoelectric vibrator 3 according to a third embodiment will be described with reference to FIG. 4. FIG. 4 is a cross-sectional view that schematically shows the structure of a piezoelectric vibrator according to the third embodiment.

[0045] This embodiment differs from the first embodiment in the position where the covering member 19 is provided. Specifically, in the first embodiment, the surface of the crystal vibrating element 10, the inner surface 40a of the second bonding member 40, and the portion of the lower cover layer 50 facing the vibrating portion are covered with the covering member 19. Top part In contrast to the conventional method in which a covering member 19 is provided on the piezoelectric vibrator 3, in this embodiment, a covering member 19b is provided on the entire side surface of the piezoelectric vibrator 3 so as to cover the outer surface 20b of the first bonding member 20 and the outer surface 40b of the second bonding member 40. This allows not only the second bonding member 40 but also the first bonding member 20 to be covered, and therefore, by making the first bonding member from an insulating material, further cost reduction can be achieved.

[0046] <Fourth embodiment> Next, the structure of a quartz crystal vibrating element 110 according to a fourth embodiment will be described with reference to FIG. 5. FIG. 5 is a plan view schematically showing the structure of the quartz crystal vibrating element according to the fourth embodiment.

[0047] In this embodiment, unlike the first embodiment, the quartz crystal vibrating element 110 further includes a functional element that assists the function of the piezoelectric vibrator. For example, as shown in FIG. 5, a temperature sensor mounting portion 121 and a temperature sensor 122 are provided in the internal space 60. The quartz crystal vibrating element 110 has a holding arm 117a that connects the vibrating portion 116 and the holding portion 118, and a holding arm 117b that connects the holding portion 118 and the temperature sensor mounting portion 121. The temperature sensor 122 is provided on the temperature sensor mounting portion 121. For example, a thermistor that detects temperature changes as changes in resistance value is used as the temperature sensor 122. By providing a thermistor, frequency temperature correction can be improved compared to conventional quartz crystal vibrators. When a thermistor is used, by providing it near the quartz crystal blank 112 and the first excitation electrode 114a of the vibrating portion 116 as shown in FIG. 5, Temperature changes Furthermore, by adjusting the heat flow from the substrate on which the crystal unit is mounted so that it is equal between the vibrating portion 116 and the temperature sensor mounting portion 121, and by adjusting the heat capacity of the crystal blank 112 and the temperature sensor 122 so that it is equal, the temperature of the crystal blank 112 can be detected with higher accuracy.

[0048] An inductor may be used as an example of a functional element. When formed as part of an LC circuit, the inductor functions as a high-pass filter that cuts off frequencies below a predetermined frequency. By providing this inductor on the quartz crystal resonator element 110, a quartz crystal resonator element with an inductor can be produced at lower cost than a configuration in which a filter using an inductor is formed in an external circuit. Furthermore, by providing these functional elements in the internal space 60 with a high degree of airtight sealing, deterioration of the functional elements over time can be suppressed. Furthermore, by providing them in the internal space 60, the number of protective components for the functional elements can be reduced.

[0049] Some or all of the embodiments of the present invention will be described below, but the present invention is not limited to the following descriptions.

[0050] <1> As described above, according to one aspect of the present invention, a piezoelectric element includes a vibrating section having a piezoelectric layer, an upper electrode layer provided on a first main surface of the piezoelectric layer, and a lower electrode layer provided on a second main surface opposite the first main surface of the piezoelectric layer; a vibrator layer having a holding section that surrounds the vibrating section in a planar view and a holding arm that connects the holding section to the vibrating section; an upper cover layer provided on the upper electrode layer side of the vibrator layer; a lower cover layer provided on the lower electrode layer side of the vibrator layer; a first bonding member that is provided to surround the vibrating section in a planar view and bonds the holding section of the vibrator layer to the upper cover layer; a second bonding member that is provided to surround the vibrating section in a planar view and bonds the holding section of the vibrator layer to the lower cover layer; and a covering member that is provided to cover the entire periphery of at least one of the inner surface and the outer surface of at least one of the first bonding member and the second bonding member, wherein at least one bonding member is made of a first insulating material, and the covering member is made of a second insulating material that has lower gas permeability than the first insulating material.

[0051] According to the above aspect, by covering the inner and outer surfaces of at least one of the first and second bonding members with a covering member having low gas permeability, it is possible to suppress gas intrusion from the first or second bonding member and improve long-term frequency stability. Furthermore, by forming at least one of the first and second bonding members from the first insulating material, it is possible to achieve lower costs compared to a configuration in which all bonding members are metal bonding.

[0052] <2> In one embodiment, the lower cover layer has an external electrode on the side opposite to the side facing the vibrator layer, the first bonding member is made of a metal material, and the second bonding member is made of a first insulating material. <1> The piezoelectric vibrator according to claim 1 is provided.

[0053] According to the above aspect, compared to a configuration in which the second bonding member and the lower lid layer are metallurgically bonded, there is no need to provide vias in the lower lid layer, so the upper electrode layer and the lower electrode layer can be maximized, allowing for miniaturization.

[0054] <3> In one embodiment, the oscillator layer further includes a functional element. <2> The piezoelectric vibrator according to claim 1 is provided.

[0055] <4> In one aspect, the covering member is provided so as to avoid the surfaces of the upper electrode layer and the lower electrode layer of the vibration section. <1> The piezoelectric vibrator according to claim 1 is provided.

[0056] According to the above aspect, it is possible to prevent the frequency characteristics of the vibrating portion from fluctuating due to the gas adsorption properties of the covering member.

[0057] <5> In one embodiment, the covering member is further provided on each surface of the upper electrode layer and the lower electrode layer of the vibration section. <1> from <3> The piezoelectric vibrator according to any one of the above items is provided.

[0058] According to the above aspect, the covering member covers the upper electrode and the lower electrode, thereby making it possible to suppress frequency fluctuations due to oxidation of the electrodes.

[0059] <6> In one aspect, the covering member is provided to avoid a bonding surface of the vibrator layer with the first bonding member. <1> from <3> The piezoelectric vibrator according to any one of the above items is provided.

[0060] According to the above aspect, it is possible to improve the bonding strength between the vibrator layer and the first bonding member.

[0061] <7> In one embodiment, the piezoelectric layer of the vibrator layer is made of quartz crystal. <1> from <6> The piezoelectric vibrator according to any one of the above items is provided.

[0062] <8> In one embodiment, the upper and lower cover layers are made of quartz. <1> from <7> The piezoelectric vibrator according to any one of the above items is provided.

[0063] <9> In one embodiment, at least one of the upper and lower lid layers is made of silicon, ceramic, or glass. <1> from <7> The piezoelectric vibrator according to any one of the above items is provided.

[0064] According to the above aspect, image recognition can be easily performed when mounting the piezoelectric vibrator on a substrate.

[0065] <10> In one embodiment, the coating member has a thickness of 1 nm or more and 100 nm or less. <1> from <9> The piezoelectric vibrator according to any one of the above items is provided.

[0066] <11> In one embodiment, the first insulating material is made of resin or glass, and the second insulating material is made of aluminum oxide. <1> from <10> The piezoelectric vibrator according to any one of the above items can be provided.

[0067] The above-described embodiments are intended to facilitate understanding of the present invention and are not intended to limit the scope of the present invention. The present invention may be modified or improved without departing from its spirit, and equivalents are also included within the scope of the present invention. In other words, designs modified by those skilled in the art as appropriate are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention. For example, the elements of the embodiments, as well as their arrangement, materials, conditions, shape, size, etc., are not limited to those exemplified and can be modified as appropriate. Furthermore, the elements of the embodiments can be combined to the extent technically possible, and such combinations are also encompassed within the scope of the present invention as long as they incorporate the characteristics of the present invention. [Explanation of symbols]

[0068] 1, 2, 3... Piezoelectric vibrator 10, 110...quartz crystal element 12, 112...Crystal piece 12a, 112a...first main surface 12b...Second principal surface 14a, 114a...first excitation electrode 14b,...second excitation electrode 16, 116...Vibration part 17, 117a, 117b...holding arms 18, 118...holding part 19, 19a, 19b...Covering members 20...First joining member 20a…Inner surface 20b…outer surface 30…upper lid layer 40...Second joining member 40a…Inner surface 40b…Outer surface 50…Lower lid layer 51, 51a, 51b, 51c, 51d...external electrode 60...Interior space 121...Temperature sensor mounting portion 122...Temperature sensor

Claims

1. a vibrator layer including a vibrating section having a piezoelectric layer, an upper electrode layer provided on a first main surface of the piezoelectric layer, and a lower electrode layer provided on a second main surface opposite to the first main surface of the piezoelectric layer, a holding section surrounding the periphery of the vibrating section in a plan view, and holding arms connecting the holding section and the vibrating section; an upper cover layer provided on the upper electrode layer side of the vibrator layer; a lower lid layer provided on the lower electrode layer side of the vibrator layer; a first bonding member that is provided to surround the vibrating portion in a plan view and bonds the holding portion of the vibrator layer and the upper lid layer; a second bonding member that is provided to surround the vibration portion in a plan view and bonds the holding portion of the vibrator layer and the lower lid layer; a covering member provided so as to cover the entire periphery of an inner surface of at least one of the first joining member and the second joining member; Equipped with the at least one joining member is made of a first insulating material; The covering member is made of a second insulating material having a lower gas permeability than the first insulating material. Piezoelectric vibrator.

2. the lower lid layer has an external electrode on the side opposite to the side facing the vibrator layer, the first joining member is made of a metal material, the second bonding member is made of the first insulating material; The piezoelectric vibrator according to claim 1 .

3. The oscillator layer further includes a functional element. The piezoelectric vibrator according to claim 2 .

4. the covering member is provided to avoid the surfaces of the upper electrode layer and the lower electrode layer of the vibration section; The piezoelectric vibrator according to claim 1 .

5. The covering member is further provided on each surface of the upper electrode layer and the lower electrode layer of the vibration section. The piezoelectric vibrator according to claim 1 .

6. the covering member is provided to avoid a bonding surface of the vibrator layer with the first bonding member; The piezoelectric vibrator according to claim 1 .

7. the piezoelectric layer of the vibrator layer is made of quartz crystal. The piezoelectric vibrator according to claim 1 .

8. The upper lid layer and the lower lid layer are made of quartz crystal. The piezoelectric vibrator according to claim 1 .

9. At least one of the upper lid layer and the lower lid layer is made of silicon, ceramic, or glass. The piezoelectric vibrator according to claim 1 .

10. The coating member has a thickness of 1 nm or more and 100 nm or less. The piezoelectric vibrator according to claim 1 .

11. the first insulating material is made of resin or glass, The second insulating material is made of aluminum oxide. The piezoelectric vibrator according to claim 1 .

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