Piezoelectric device

Abstract

A piezoelectric device is provided with: a package having a recess; a piezoelectric vibration element bonded to the first electrode pad in the recess via a first bonding member; and a temperature sensing element that is joined to the second electrode pad via a second joining member below the piezoelectric vibration element in the recess. The surface area of the temperature sensing element in plan view is 0.2-0.9 times the surface area of the piezoelectric vibration element in plan view. The value obtained by dividing the bonding area of the second bonding member by the distance between the bottom surface of the package and the surface including the second electrode pad is 0.7-1.3 times the value obtained by dividing the bonding area of the first bonding member by the first distance between the bottom surface of the package and the surface including the first electrode pad.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a piezoelectric device. BACKGROUND

[0002] The resonant frequency of a piezoelectric vibration element, or the like, has a temperature dependency. For this reason, in Japanese Patent Application Publication No. 2008-205938, a piezoelectric device having a piezoelectric vibration element is disclosed as having a temperature sensing element as a temperature sensor. SUMMARY

[0003] One embodiment of the present disclosure is a piezoelectric device including: a package having a recess, a first electrode pad, and a second electrode pad positioned in the recess; a piezoelectric vibration element joined to the first electrode pad in the recess; and a temperature sensing element joined to the second electrode pad below the piezoelectric vibration element in the recess, the piezoelectric vibration element being joined to the first electrode pad via a first joining member, the temperature sensing element being joined to the second electrode pad via a second joining member, a planar observation area of the temperature sensing element, as viewed from above the recess, being 0.2 times or more and 0.9 times or less of a planar observation area of the piezoelectric vibration element, a value obtained by dividing a first planar observation bonding area of the first joining member in the first electrode pad by a first distance from a bottom surface of the package to a surface of the package including the first electrode pad being 0.7 times or more and 1.3 times or less of a value obtained by dividing a second planar observation bonding area of the second joining member in the second electrode pad by a second distance from the bottom surface of the package to a surface of the package including the second electrode pad.

[0004] [2] In the piezoelectric device described in [1], a thickness of the temperature sensing element is 0.1 mm or less.

[0005] [3] In the piezoelectric device described in [1], the first joining member and the second joining member are the same component.

[0006] [4] In the piezoelectric device described in [1], the first planar observation bonding area is below a planar observation area of the first electrode pad, and the second planar observation bonding area is below a planar observation area of the second electrode pad. BRIEF DESCRIPTION OF DRAWINGS

[0007] Figure 1A is a plan view showing the configuration of the piezoelectric device of the present embodiment.

[0008] Figure 1B is a bottom view showing the configuration of the piezoelectric device of the present embodiment.

[0009] Figure 1Cis a cross-sectional view showing the configuration of the piezoelectric device of the present embodiment.

[0010] Figure 2A is a view showing the position of the temperature sensing element in the piezoelectric device.

[0011] Figure 2B is a perspective view of the temperature sensing element.

[0012] Figure 3A is a cross-sectional view showing the dimensional setting for establishing correspondence between the measured temperature of the temperature sensing element and the temperature of the piezoelectric vibration element.

[0013] Figure 3B is a plan view showing the dimensional setting for establishing correspondence between the measured temperature of the temperature sensing element and the temperature of the piezoelectric vibration element.

[0014] Figure 4A is a graph showing the parameters at the time of calculating the temperature followability in the piezoelectric device of the present embodiment by numerical simulation.

[0015] Figure 4B is a graph showing the result of calculating the temperature followability in the piezoelectric device of the present embodiment by numerical simulation. DETAILED DESCRIPTION

[0016] Hereinafter, the embodiments will be described based on the drawings.

[0017] Figures 1A-1C is a view showing the configuration of the piezoelectric device 1 of the present embodiment. Figure 1A is a plan view of the inside of the piezoelectric device 1 with the cover 10 removed. Figure 1B is a bottom view of the bottom surface of the piezoelectric device 1. Figure 1C is Figure 1A is a cross-sectional view at the cross-sectional line AA of

[0018] The piezoelectric device 1 is provided with a package 20, a piezoelectric vibration element 30, and a temperature sensing element 40. The package 20 has a recess 20a in the center of the upper surface. The piezoelectric vibration element 30 is located inside the recess 20a.

[0019] The package 20 can be a housing of a ceramic material, a semiconductor material, or a glass material, or a combination thereof, for example. Furthermore, signal lines having a conductor inside and on the surface of the above-described material of the package 20. The signal lines can include lines involved in power supply and grounding. The signal line flow can be molybdenum, copper, silver, tungsten, or the like. Part or all of the signal lines can be surface-laminated with nickel plating, gold plating, or the like. At one end in the X direction along the long direction of the recess 20a, the first electrode pads 211, 212 are arranged side by side in the Y direction perpendicular to the X direction. The first electrode pads 211, 212 can be printed on the surface of the recess 20a using gold or the like.

[0020] The piezoelectric vibration element 30 can be a crystal vibrator. The piezoelectric vibration element 30 has, at one end in a long side direction of a crystal piece, side-by-side mounting electrodes 311, 312 in a direction perpendicular to the long side direction. The mounting electrode 311 is connected to an excitation electrode 321 located on an upper surface of the piezoelectric vibration element 30. The mounting electrode 312 is connected to an excitation electrode, the illustration of which is omitted, located on a lower surface of the piezoelectric vibration element 30 at a position overlapping the excitation electrode 321 in a plan view.

[0021] The piezoelectric vibration element 30 can be arranged so that the long side direction is parallel to the X direction of the package 20. The mounting electrodes 311, 312 are connected to the first electrode pads 211, 212 located in the recess 20a via the first bonding members 220. The piezoelectric vibration element 30 is not in contact with the package 20 except for the mounting electrodes 311, 312. Thus, the piezoelectric vibration element 30 is in a cantilevered state. The crystal piece is vibrated by applying a voltage between the excitation electrodes, or a voltage generated between the excitation electrodes in correspondence with the vibration of the crystal piece is output to the outside via the mounting electrodes 311, 312 and the first electrode pads 211, 212.

[0022] The crystal piece is shown here as having planar upper and lower surfaces, but is not limited to this. For example, the crystal piece can have a thicker end where the mounting electrodes 311, 312 are located than other portions. Alternatively, the crystal piece can have a thicker central portion where the excitation electrode 321 is located than a peripheral portion, conversely.

[0023] The first bonding members 220 can be produced by heating and hardening a first electrically conductive adhesive. The first electrically conductive adhesive can be, for example, a silver paste containing silver particles. The first bonding members 220 are attached to a range that is substantially elliptical, for example, circular, with respect to the first electrode pads 211, 212. The first bonding members 220 expand in a range that does not exceed the plan view range of the first electrode pads 211, 212 and the mounting electrodes 311, 312, in correspondence with the wettability and the like of the first electrode pads 211, 212 and the mounting electrodes 311, 312.

[0024] Below the piezoelectric vibrating element 30, a recess 20b is provided on a portion of the bottom surface of the recess 20a. A temperature-sensing element 40 is located within the recess 20b. The temperature-sensing element 40 is a thermistor whose resistance changes with temperature, and can be a particularly thin film such as germanium telluride (GeTe). The temperature-sensing element 40 is connected to the second electrode pads 231 and 232 within the recess 20b via a second bonding member 240. The second bonding member 240 can be produced by heating and curing a second conductive adhesive, and, similar to the first bonding member 220, is attached to the second electrode pads 231 and 232 in a generally elliptical shape. Subsequently, the wettability of the second electrode pads 231 and 232 is extended within a range not exceeding the top-view observation range of the second electrode pads 231 and 232. The thermal conductivity M2 of the second joining member 240, and particularly its material, can be the same as that of the first joining member 220, and particularly its material. The first joining member 220 and the second joining member 240 can be of the same composition. However, the first joining member 220 and the second joining member 240 can also be different from each other.

[0025] like Figure 1B As shown, external connection pads 251 can be provided at the four corners of the bottom surface of the piezoelectric device 1. One of the external connection pads 251 is connected to either of the first electrode pads 211 and 212 via wiring, such as wiring 252, inside and on the surface of the package 20. The other external connection pad 251 is connected to either of the second electrode pads 231 and 232 via wiring inside the package 20. The other of the first electrode pads 211 and 212 and the other of the second electrode pads 231 and 232 can be ground electrodes. In this case, the two ground electrodes can be connected to one of the common external connection pads 251 via wiring inside the package 20. Alternatively, the first electrode pads 211 and 212 and the second electrode pads 231 and 232 can be connected one-to-one to each of the four external connection pads 251.

[0026] like Figure 1C As shown, the second electrode pads 231 and 232 and the temperature sensing element 40 are located within the recess 20b on the bottom surface of the recess 20a. The recess 20b and the temperature sensing element 40 are positioned in the X direction of the package 20, opposite to the first electrode pads 211 and 212. The long side direction of the package 20 and the long side direction of the recess 20b and the temperature sensing element 40 can be the same X direction. (The last sentence appears to be incomplete and possibly refers to a different topic.) Figure 1A As is known, when viewed from above, at least a portion of the temperature sensing element 40 is located at a position overlapping with the piezoelectric vibrating element 30.

[0027] The recessed portion 20b is sealed by joining the cap 10 to the upper end of the package 20, i.e., the side wall upper surface of the recessed portion 20a. The cap 10 is a flat plate of a metal conductor, and can be, for example, a metal containing iron, copper, nickel, cobalt, molybdenum, or tungsten, or an alloy thereof, such as Kovar. The joining material used in the sealing by the cap 10 can be heated within a temperature range that does not adversely affect the characteristics of the temperature sensing element 40 sealed inside. For example, the cap 10 can be joined by a solder or the like. A frame-shaped metallized layer can be provided between the upper end of the package 20 and the cap 10. The metallized layer can be a plated layer, or a conductor layer formed by coating and firing.

[0028] Figure 2A and Figure 2B is a view illustrating the temperature sensing element 40. Figure 2A is a view illustrating the temperature sensing element 40 from the bottom side. Figure 1A is a view illustrating the inside when the piezoelectric vibration element 30 is further removed. Figure 2B is a perspective view illustrating the temperature sensing element 40 from the bottom side.

[0029] As shown in Figure 2A , the ratio of the plan view area of the recessed portion 20b when viewed from above in the Z direction with respect to the size of the recessed portion 20a, i.e., the plan view area, corresponds to the ratio of the plan view area of the temperature sensing element 40 with respect to the plan view area of the piezoelectric vibration element 30. The ratio of the plan view areas can be, for example, 0.2 to 0.9 times. The size of the package 20 is not necessarily made larger than the size of the piezoelectric vibration element 30. Therefore, the plan view area of the temperature sensing element 40 can also be smaller than the plan view area of the piezoelectric vibration element 30.

[0030] As shown in Figure 2B , the temperature sensing element 40 has at least a thin film thermistor 42 that measures resistance, and a thin film thermistor substrate 41. The thickness of the temperature sensing element 40 is not particularly limited, and is typically 100 μm or less, and can be, for example, about 50 μm. The material of the thin film thermistor 42 is not particularly limited as long as it measures resistance, and can be, for example, MAlNO, MnCoNi, MnCoZn, CrO x N 1-x , GeSbTe, and GeTe, or the like, when M is set to at least one kind of Fe, Co, Mn, Cu, and Ni. The film thickness of the thin film thermistor 42 can typically be 50 nm or more and 500 nm or less. The thin film thermistor 42 can be formed on the thin film thermistor substrate 41. The thin film thermistor substrate 41 can be, for example, an insulating film of quartz glass, i.e., silicon dioxide, or the like. The thickness of the thin film thermistor substrate 41 is not particularly limited, and is typically 100 μm or less, and can be, for example, about 50 μm.

[0031] Although not particularly limited, two electrodes 43 can be provided on the side of the thin film thermistor 42 opposite the thin film thermistor substrate 41. The conductive member 44 on the electrode 43 can be obtained, for example, by heat-hardening silver paste. The electrode 43 can be joined to the second electrode pads 231, 232 in the recessed portion 20b via the conductive member 44.

[0032] Such a piezoelectric device 1 can be mounted on a substrate of various electronic devices. The piezoelectric device 1 transmits heat from the substrate via the package 20. Heat transmitted from the external electrodes omitted from the illustration on the bottom surface of the package 20 to the package is transmitted to the temperature sensing element 40 and the piezoelectric vibration element 30, respectively, to cause a change in their temperatures. The temperature sensing element 40 is required to measure a temperature equal to that of the piezoelectric vibration element 30. However, since heat is not uniformly transmitted due to the increase in the area of the temperature sensing element 40, the change in the temperature of the temperature sensing element 40 can not correspond to that of the piezoelectric vibration element 30 at times.

[0033] Figure 3A and Figure 3B is a description of the size setting for establishing correspondence between the measured temperature of the temperature sensing element 40 and the temperature of the piezoelectric vibration element 30. Figure 3A is Figure 1C is a cross-sectional view as shown in Figure 3B is a plan view as shown in Figure 1B is a plan view as shown in

[0034] In the piezoelectric device 1, the distance between the bottom surface and the temperature sensing element 40 is a second distance t2. The distance between the bottom surface and the piezoelectric vibration element 30 is a first distance t1. The joining area of the temperature sensing element 40 to the second electrode pads 231, 232, and more directly to the second joining member 240 is a joining area S2 = s21 + s22. The joining area of the piezoelectric vibration element 30 to the first electrode pads 211, 212, and more directly to the first joining member 220 is a joining area S1 = s11 + s12. These first distance t1, second distance t2, joining area S1, and joining area S2 of the piezoelectric device 1 are within a range of suitable relationship. The joining area S1 is referred to as a first plan view bonding area. The joining area S2 is referred to as a second plan view bonding area.

[0035] As described above, under the condition that the thermal conductivity M1 of the first joining member 220 and the thermal conductivity M2 of the second joining member 240 are equal, the first distance t1, the second distance t2, and the joining areas S1, S2 satisfy the following condition of Equation 1.

[0036] 0.7 ≦ (S2 / t2) / (S1 / t1) ≦ 1.3 … (Equation 1)

[0037] In addition, t1 > t2 in correspondence with the positional relationship of the recess 20a and the recessed portion 20b.

[0038] The greater the first distance t1 and the second distance t2, the more difficult it is to transfer heat. As described above, since the second distance t2 from the bottom surface to the temperature sensing element 40 is smaller than the first distance t1 to the piezoelectric vibration element 30, heat is more easily transferred to the temperature sensing element 40 than to the piezoelectric vibration element 30. On the other hand, the greater the bonding areas S1, S2, the more heat is easily transferred.

[0039] Therefore, by limiting the bonding area S2 of the path for transferring heat to the temperature sensing element 40, which is small in distance from the bottom surface, to be smaller than the bonding area S1 of the piezoelectric vibration element 30, the piezoelectric device 1 controls the amount of heat per unit time transferred to the temperature sensing element 40 and the piezoelectric vibration element 30, respectively.

[0040] Further, as described above, the temperature sensing element 40 is small in thickness and accordingly large in size in plan view, and therefore, if the bonding area S2 is small, the bonding portion of the temperature sensing element 40 becomes a bottleneck, and temperature distribution in the temperature sensing element 40 is easily generated. In the present embodiment, the plurality of bonding portions s21, s22 can be the same degree, and the bonding portions s21, s22 can also be significantly smaller than the plan view area of the temperature sensing element 40.

[0041] According to the above, the size of the distance t with respect to the bonding area S, i.e., S / t, is set to be substantially the same degree. S2 / t2 in the temperature sensing element 40 is in a range of 0.7 times or more and 1.3 times or less of S1 / t1 in the piezoelectric vibration element 30.

[0042] Figure 4A is a graph showing parameters for calculating temperature followability in the piezoelectric device 1 of the present embodiment by numerical simulation. Figure 4B is a graph showing the results of temperature followability obtained in numerical simulation by the above parameters. Numerical simulation is performed by thermal fluid analysis based on software of Ansys Inc. (registered trademark).

[0043] In the numerical simulation, the size of the package was 0.8 mm in the longitudinal direction along the Y direction, 1.0 mm in the lateral direction along the X direction, and 0.2 mm in the thickness along the Z direction. The piezoelectric vibration element was a crystal piece, 0.5 mm in the longitudinal direction, 0.7 mm in the lateral direction, and 0.021 mm in the thickness. The thin film thermistor 42 of the temperature sensing element 40 was a GeTe film, 0.3 mm in the longitudinal direction, 0.4 mm in the lateral direction, and 0.1 μm in the height. The thin film thermistor 42 was on the thin film thermistor substrate 41, 0.05 mm in the thickness. The cap 10 was 0.8 mm in the longitudinal direction, 1.0 mm in the lateral direction, and 0.04 mm in the thickness. The four external connection pads 251 were given heat so as to be warmed at 3.5°C / min. The temperature of the center position of the temperature sensing element 40 and the temperature of the center position of the piezoelectric vibration element 30 were calculated and compared.

[0044] As described above, the cap 10 was Kovar. The package 20 was ceramic, and the material was alumina (AI2O3). The wiring on the inside and the surface of the package 20 had a nickel plating layer and a gold plating layer on molybdenum. The first electrode pads 211, 212 and the second electrode pads 231, 232 were also the same structure as the wiring described above. The first bonding member 220 and the second bonding member 240 were obtained by heat-hardening a silver paste as a conductive adhesive. The piezoelectric vibration element 30 had a gold excitation electrode 321 and the like and the mounting electrodes 311, 312 with respect to the crystal piece. The temperature sensing element 40 had a thin film thermistor 42 of GeTe on the thin film thermistor substrate 41, that is, on a quartz glass substrate.

[0045] In the piezoelectric device 1, the ratio t2 / t1 of the second distance t2 of the bottom surface from the temperature sensing element 40 to the first distance tl of the bottom surface from the piezoelectric vibration element 30 was t2 / t1 = 75 / 105. In the comparative example, the bonding area S2 of the temperature sensing element 40 and the bonding area SI of the piezoelectric vibration element 30 were set to be equal (S2 / S1 = 100 / 100, (S2 / t2) / (S1 / t1) = 1.4). In the embodiment, the bonding area S2 was made smaller than the bonding area SI (S2 / S1 = 80 / 100, (S2 / t2) / (S1 / t1) = 1.12). As a result, in the embodiment, the difference between the temperature of the piezoelectric vibration element 30 and the temperature of the temperature sensing element 40 was reduced to 44.8% of the comparative example.

[0046] Here, the bonding area SI depends on the size of the crystal piece, that is, the resonant frequency and the like, and cannot be made larger than necessary. On the other hand, in order to make the bonding area S2 further smaller than in the above embodiment, it is necessary to reduce the spread of the conductive adhesive. In addition, the size required for maintaining the adhesive strength is also considered, and thus the present situation in the manufacturing is S2 / S1 > 0.5.

[0047] As above, the piezoelectric device 1 of the present embodiment has: the package 20 having the recess 20a, the first electrode pads 211, 212, and the second electrode pads 231, 232 being located within the recess 20a; the piezoelectric vibration element 30 being joined with the first electrode pads 211, 212 within the recess 20a; and the temperature sensing element 40 being joined with the second electrode pads 231, 232 below the piezoelectric vibration element 30 within the recess 20a. The piezoelectric vibration element 30 is joined with the first electrode pads 211, 212 via the first joining members 220. The temperature sensing element 40 is joined with the second electrode pads 231, 232 via the second joining members 240. The planar observation area of the temperature sensing element 40, as viewed from above the recess 20a, is 0.2 times or more and 0.9 times or less of the planar observation area of the piezoelectric vibration element 30. With respect to a value (S1 / t1) obtained by dividing an area of joining S1 of the first joining members 220 in the first electrode pads 211, 212 by a first distance t1 of a bottom surface of the package 20 to a surface of the package 20 including the first electrode pads 211, 212, a value (S2 / t2) obtained by dividing an area of joining S2 of the second joining members 240 in the second electrode pads 231, 232 by a second distance t2 of the bottom surface of the package 20 to a surface of the package 20 including the second electrode pads 231, 232 is 0.7 times or more and 1.3 times or less.

[0048] Corresponding to the low profile of the temperature sensing element 40, the temperature sensing element 40 having an area of a slightly smaller degree compared to the piezoelectric vibration element 30 can be housed in the package 20. In this case, corresponding to a ratio of distances from the bottom surface to the piezoelectric vibration element 30 and the temperature sensing element 40 of heat transfer to the package 20, the area of joining S2 of the temperature sensing element 40 closer to the bottom surface of the package 20 is made smaller than the area of joining S1 of the piezoelectric vibration element 30 to the package 20. Thereby, the temperature sensing element 40 can measure a temperature corresponding to a temperature of the piezoelectric vibration element 30. In particular, by setting the ratio of (S2 / t2) to (S1 / t1) to be 0.7 or more and 1.3 or less, or 0.9 or more and 1.2 or less, the area of joining S2 of the temperature sensing element 40 can be set to be the minimum or more required for maintaining the adhesion strength and the like while not being excessively difficult to manufacture, and a case where the temperature sensing element 40 measures before a temperature change of the piezoelectric vibration element 30 is avoided.

[0049] Further, the thickness of the temperature sensing element 40 can be 0.1 mm or less. By using such a sufficiently thin temperature sensing element 40, appropriate temperature detection by the temperature sensing element 40 can be performed while low profile of the piezoelectric device 1 is sought.

[0050] Further, the first bonding member 220 and the second bonding member 240 can be the same composition. Since the piezoelectric vibration element 30 and the temperature sensing element 40 are the same thermal conductivity and the same characteristics, and are bonded to the package 20, as described above, the detection temperature of the temperature sensing element 40 can be stably made close to the actual temperature of the piezoelectric vibration element 30 by the ratio of the bonding area to the distance from the bottom surface.

[0051] Further, the bonding area S1 of the first bonding member 220 can be below the planar observation area of the first electrode pads 211, 212, and the bonding area S2 of the second bonding member 240 can be below the planar observation area of the second electrode pads 231, 232. In this way, by the conductive adhesive not exceeding the range of the first electrode pads 211, 212 and the second electrode pads 231, 232, the piezoelectric device 1 can obtain a stable bonding area. Further, the piezoelectric device 1 also reduces the generation of unnecessary short circuits and the like.

[0052] In addition, the above-described embodiments are examples, and various modifications can be made.

[0053] For example, the shape of the recessed portion 20a and the recessed portion 20b is not limited to that shown in the above-described embodiments. As long as the temperature sensing element 40 is disposed and fixed below the piezoelectric vibration element 30 in the recessed portion 20a, it can also be other shapes. Further, the recessed portion 20b can also be larger than the planar observation area of the temperature sensing element 40 within a range that can maintain the strength of the package 20.

[0054] Further, the position of the recessed portion 20b in the recessed portion 20a, that is, the planar observation position of the temperature sensing element 40 with respect to the piezoelectric vibration element 30 is not limited to the position shown in the above-described embodiments. Further, these long direction can also not be the same orientation.

[0055] Further, the first bonding member 220 and the second bonding member 240 can be heated and hardened to generate a conductive adhesive containing a conductor particle other than silver. Further, the electrical conductivity of the second bonding member 240 can be resistant to the electrical conductivity of the first bonding member 220.

[0056] Further, the vibration piece of the piezoelectric vibration element 30 is not limited to a crystal piece. As long as conversion between electrical power and mechanical deformation is performed, it can also be other materials.

[0057] In addition to this, the specific contents of the configuration, structure, material, size, and the like shown in the above-described embodiments can be appropriately changed within a range that does not depart from the gist of the present disclosure. The scope of the present invention includes the scope of the invention recited in the claims and the equivalent scope thereof.

[0058] Industrial Applicability

[0059] The present disclosure can be utilized in a piezoelectric device.

[0060] Symbol explanation

[0061] 1 piezoelectric device

[0062] 10 cover

[0063] 20 package

[0064] 20a recess

[0065] 20b recessed portion

[0066] 211, 212 first electrode pad

[0067] 220 first joining member

[0068] 231, 232 second electrode pad

[0069] 240 second joining member

[0070] 251 external connection pad

[0071] 252 wiring

[0072] 30 piezoelectric vibration element

[0073] 311, 312 load electrode

[0074] 321 excitation electrode

[0075] 40 temperature sensing element

[0076] 41 substrate for thin film thermistor

[0077] 42 thin film thermistor

[0078] 43 electrode

[0079] 44 electrically conductive member

Claims

1. A piezoelectric device comprising: A package having a recess, in which a first electrode pad and a second electrode pad are located; A piezoelectric vibrating element, which is coupled to the first electrode pad within the recess; and The temperature-sensing element, located below the piezoelectric vibration element within the recess, is bonded to the second electrode pad. The piezoelectric vibration element is bonded to the first electrode pad via the first bonding member. The temperature sensing element is bonded to the second electrode pad via the second bonding member. The top-view area of ​​the temperature-sensing element, when viewed from above the recess, is more than 0.2 times and less than 0.9 times the top-view area of ​​the piezoelectric vibration element. The value obtained by dividing the first top-view adhesive area of ​​the first bonding member in the first electrode pad by the first distance between the bottom surface of the package and the surface of the package containing the first electrode pad, is more than 0.7 times and less than 1.3 times.

2. The piezoelectric device according to claim 1, wherein, The thickness of the temperature sensing element is less than 0.1 mm.

3. The piezoelectric device according to claim 1 or 2, wherein, The first and second joining members are made of the same material.

4. The piezoelectric device according to any one of claims 1 to 3, wherein, The first top-view adhesive area is below the top-view area of ​​the first electrode pad. The second top-view adhesive area is below the top-view area of ​​the second electrode pad.

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