Thin-plate thermistors and piezoelectric vibration devices equipped with thin-plate thermistors

Abstract

Provided is a thin-plate thermistor in which the resistance characteristics of the thin-plate thermistor are improved in consideration of the surface roughness of one surface and the other surface of a thermistor flat plate.　A thin-plate thermistor 5 comprises: a single-plate thermistor flat plate 51 including a second main surface 51b and a first main surface 51a that is on the opposite to the second main surface 51b and has a greater surface roughness than that of the second main surface 51b; a first split electrode 53a and a second split electrode 53b that are formed on the second main surface 51b and are split on the second main surface 51b; and a common electrode 52 formed on the first main surface 51a.

Description

Technical Field

[0001] The present invention relates to a thin-film thermistor used as a temperature sensor and a piezoelectric vibration device with a thin-film thermistor mounted thereon.

Background Art

[0002] In recent years, with the increasing precision of various electronic devices, a temperature-compensated piezoelectric vibration device that compensates for frequency fluctuations caused by changes in environmental temperature has been demanded, and a thermistor-mounted piezoelectric vibration device with a thermistor as a temperature sensor mounted on the piezoelectric vibration device has been widely used.

[0003] By measuring the environmental temperature of the piezoelectric vibration device with a thermistor and transmitting the frequency information and temperature information to an externally mounted temperature compensation circuit, temperature-compensated frequency information can be obtained, and the operation of the electronic device can be maintained with high precision.

[0004] Such a thermistor-mounted piezoelectric vibration device has a configuration in which a crystal vibration plate with excitation electrodes formed on a ceramic package is housed, and a thermistor is attached outside thereof to detect the environmental temperature surrounding the crystal resonator (see, for example, Patent Document 1).

[0005] The thermistor has a laminated structure in which a plurality of thermistor material layers and operating electrodes are laminated, and those with a thickness of about 0.3 millimeters to 0.1 millimeters are commercially available and used.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] Incidentally, thermistors are required to detect the temperature environment surrounding a quartz oscillator with a small time lag. However, thermistors used so far have a multilayer structure, which requires a certain thickness (height). In addition, the electrodes of multilayer thermistors are made of thick film electrodes produced by screen printing or other methods, making them unsuitable for miniaturizing thermistors.

[0008] Therefore, instead of using a laminated structure in which multiple thermistor material layers and working electrodes are stacked, it is conceivable to use a structure in which electrodes are formed on the surface of a single thermistor plate. However, so far, thermistors with electrodes formed on the surface of a single thermistor plate have not been put into practical use. In such a thermistor with electrodes formed on the surface of a single thermistor plate, a first divided electrode and a second divided electrode are formed on one side of the thermistor plate, each being divided into two parts that serve as the working electrode, and a common electrode is formed on the other side of the thermistor plate (the side opposite to the first side) that serves as the intermediate electrode. In such cases, it is desirable to improve the resistance characteristics of the thermistor by arranging the first divided electrode, the second divided electrode, and the common electrode while considering the surface roughness of the first side and the other side of the thermistor plate.

[0009] In view of the above problems, the present invention aims to provide a thin-plate thermistor that improves the resistance characteristics of a thin-plate thermistor by considering the surface roughness of one surface and the other surface of the thermistor plate, and a thin-plate thermistor-mounted piezoelectric vibration device equipped with the thin-plate thermistor. [Means for solving the problem]

[0010] To achieve the above objective, the thin-plate thermistor according to the present invention is characterized by having a single thermistor plate including one surface and another surface opposite to the one surface and having a surface roughness greater than that of the one surface, a first divided electrode and a second divided electrode formed on the one surface and divided on that surface, and a common electrode formed on the other surface.

[0011] With this configuration, the first and second divided electrodes, which serve as the operating electrodes, are formed on one side of the thermistor plate with less surface roughness. Compared to the case where the first and second divided electrodes, which serve as the operating electrodes, are formed on the other side with greater surface roughness, variations in the area on which the first and second divided electrodes are formed are less likely to occur, thus suppressing variations in the resistance characteristics of the thin-plate thermistor. In particular, in thin-plate thermistors, the resistance characteristics are determined by the area of ​​the first and second divided electrodes facing the thermistor plate. Therefore, forming the first and second divided electrodes, which require precise area measurements, on one side with less surface roughness is an advantageous configuration for stabilizing the resistance characteristics of the thin-plate thermistor.

[0012] Furthermore, by forming the first and second divided electrodes on the side with the lower surface roughness, the adhesion of the first and second divided electrodes to that side of the thermistor plate is improved, resulting in stable conductivity. This allows for stable connection when contacting a measuring probe or the like with the first and second divided electrodes, making it possible to accurately measure the resistance characteristics of the thin-plate thermistor.

[0013] Furthermore, by forming a common electrode, which acts as an intermediate electrode, on the other side of the thermistor plate with greater surface roughness, the surface area of ​​the portion where the common electrode is formed increases relative to the apparent area. This increases the total amount of conductor involved with the common electrode, thus improving conductivity. The common electrode plays a role in preventing unwanted resistance from being generated in the thin-plate thermistor, and since the conductivity does not decrease as the surface area of ​​the common electrode increases, the resistance value of the thin-plate thermistor is not worsened. In particular, with miniaturized thin-plate thermistors, it becomes difficult to satisfy the characteristics below a predetermined resistance value if the resistance value of the common electrode becomes large. However, by forming a common electrode on the other side of the thermistor plate with greater surface roughness, it is possible to satisfy the characteristics below a predetermined resistance value.

[0014] Furthermore, the first divided electrode, the second divided electrode, and the common electrode may be PVD (Physical Vapor Desposition) films.

[0015] This configuration results in electrodes (first segmented electrode, second segmented electrode, and common electrode) with a dense film structure, providing excellent conductivity and adhesion to the thermistor plate. Furthermore, the electrodes can be formed to achieve a desired surface area, thereby stabilizing the resistance characteristics of the thin-plate thermistor. This is particularly effective for stabilizing the resistance characteristics of miniaturized thin-plate thermistors.

[0016] Furthermore, the piezoelectric vibration device equipped with a thin plate thermistor according to the present invention comprises a piezoelectric diaphragm having excitation electrodes made of a plurality of metal film layers formed on its surface, a first sealing member joined to one main surface of the piezoelectric diaphragm, and a second sealing member joined to the other main surface of the piezoelectric diaphragm, and the thin plate thermistor, wherein the thin plate thermistor is joined to the surface of the piezoelectric vibration device.

[0017] This configuration allows for improved temperature detection accuracy of the piezoelectric diaphragm by utilizing a thin-plate thermistor with excellent resistance characteristics.

[0018] Furthermore, another thin-plate thermistor-mounted piezoelectric vibration device according to the present invention is characterized by comprising a piezoelectric diaphragm on which excitation electrodes made of a plurality of metal film layers are formed on its surface, the thin-plate thermistor, and a package that houses the piezoelectric diaphragm and the thin-plate thermistor.

[0019] This configuration allows for improved temperature detection accuracy of the piezoelectric diaphragm by utilizing a thin-plate thermistor with excellent resistance characteristics. [Effects of the Invention]

[0020] According to the present invention, since the first divided electrode and the second divided electrode serving as operating electrodes are formed on one surface of the thermistor flat plate having a smaller surface roughness, compared with the case where the first divided electrode and the second divided electrode serving as operating electrodes are formed on the other surface having a larger surface roughness, variations in the area where the first divided electrode and the second divided electrode are formed are less likely to occur, and variations in the resistance characteristics of the thin-film thermistor can be suppressed. In particular, in the thin-film thermistor, since the resistance characteristics are determined by the area where the first divided electrode and the second divided electrode face the thermistor flat plate, forming the first divided electrode and the second divided electrode that require strictness in area on one surface having a smaller surface roughness is a configuration advantageous for stabilizing the resistance characteristics of the thin-film thermistor.

Brief Description of the Drawings

[0021] [Figure 1] (a) is a perspective view of a thin-film thermistor according to a first embodiment of the present invention, and (b) is a cross-sectional view taken along line B-B of the thin-film thermistor in (a). [Figure 2] (a) is a plan view showing the first main surface of the thin-film thermistor in FIG. 1, and (b) is a plan view showing the second main surface of the thin-film thermistor in FIG. 1. [Figure 3] It is a diagram for explaining a part (laser irradiation on a wafer for a thermistor flat plate) in the manufacturing process of the thin-film thermistor in FIG. 1. [Figure 4] It is a plan view of a piezoelectric vibration device with a thin-film thermistor according to a second embodiment of the present invention. [Figure 5] It is a cross-sectional view taken along line A-A of the piezoelectric vibration device with a thin-film thermistor in FIG. 4. [Figure 6] (a) is a plan view showing the first main surface of the piezoelectric vibration plate in the sandwich structure device in FIG. 4, and (b) is a plan view showing the second main surface of the piezoelectric vibration plate in the sandwich structure device in FIG. 4. [Figure 7] (a) is a plan view showing the first main surface of the first sealing member in the sandwich structure device in FIG. 4, and (b) is a plan view showing the second main surface of the first sealing member in the sandwich structure device in FIG. 4. [Figure 8](a) is a plan view showing the first main surface of the second sealing member in the sandwich structure device of Figure 4, and (b) is a plan view showing the second main surface of the second sealing member in the sandwich structure device of Figure 4. [Figure 9] This is an exploded perspective view of a thin-plate thermistor-mounted piezoelectric vibration device according to a third embodiment of the present invention. [Figure 10] Figure 9 is a bottom view of the assembled piezoelectric vibration device with a thin-plate thermistor. [Figure 11] Figure 10 is a cross-sectional view of a thin-plate thermistor-mounted piezoelectric vibration device. [Figure 12] This is a cross-sectional view of a thin-plate thermistor-mounted piezoelectric vibration device according to a fourth embodiment of the present invention. [Modes for carrying out the invention]

[0022] ≪First Embodiment≫ Hereinafter, a thin-plate thermistor according to the first embodiment of the present invention will be described in detail with reference to Figures 1 to 3. Note that Figures 1 to 3 and Figures 4 to 8 used in the following description utilize the same X, Y, and Z axes.

[0023] First, the configuration of the thin-plate thermistor 5 will be explained with reference to Figures 1 and 2. Figure 1(a) is a perspective view of the thin-plate thermistor 5, and Figure 1(b) is a cross-sectional view of the BB of the thin-plate thermistor 5 shown in the perspective view in Figure 1(a). Figure 2(a) is a plan view showing the first main surface 51a, which is one of the main surfaces of the thin-plate thermistor 5 shown in Figure 1, and Figure 2(b) is a plan view showing the second main surface 51b, which is the main surface on the opposite side (back side) from the first main surface 51a of the thin-plate thermistor 5 shown in Figure 1. Note that in Figures 1 and 2, the electrodes (common electrode 52, divided electrode 53) are hatched, but the thermistor plate 51 is not hatched.

[0024] Thin-plate thermistor 5 is a thinned-down NTC (Negative Temperature Coefficient) thermistor. An NTC thermistor is a type of thermistor in which the resistance decreases as the temperature rises.

[0025] As shown in Figures 1(a) and (b), the thin-plate thermistor 5 is configured to include a single thermistor plate 51, a common electrode 52 formed on the first main surface 51a of the thermistor plate 51 which serves as a relay electrode, and a polarization electrode 53 formed on the second main surface 51b of the thermistor plate 51 in a divided manner on the second main surface 51b which serves as an operating electrode.

[0026] The thermistor plate 51 is thin and rectangular in shape when viewed from above. For example, the thermistor plate 51 can be made of a semiconductor ceramic plate mainly composed of manganese or a semiconductor ceramic plate mainly composed of manganese and nickel.

[0027] In the thermistor plate 51, the surface roughness of the first main surface 51a (the central part of the first main surface 51a) is greater than that of the second main surface 51b. When comparing the surface roughness of the first main surface 51a and the second main surface 51b, unless otherwise specified, the surface roughness of the central part of the main surfaces (first main surface 51a, second main surface 51b) on which the majority of the electrodes (common electrode 52, divided electrode 53) are formed will be compared. Furthermore, in the thermistor plate 51, the surface roughness is less at the edges than at the center. The surface roughness is greater in the order of the center of the first main surface 51a, the second main surface 51b, and the edges of the first main surface 51a (surface roughness of the center of the first main surface 51a > surface roughness of the second main surface 51b > surface roughness of the edges of the first main surface 51a). In other words, the surfaces are smooth in the following order: the edges of the first main surface 51a, the second main surface 51b, and the central part of the first main surface 51a.

[0028] Furthermore, the first main surface 51a of the thermistor plate 51 has a raised area at least on a portion of its edge. This raised area is formed by a solidified portion 51D that solidifies after the thermistor plate 51 (the thermistor plate wafer 51A from which the thermistor plate 51 is derived) melts, and the solidified portion 51D is a laser trace (see Figure 3).

[0029] As shown in Figure 2(a), the common electrode 52 is formed over the entire surface (or nearly the entire surface) of the first main surface 51a of the thermistor plate 51. The common electrode 52 is a thin metal film, and is a PVD (Physical Vapor Deposition) film formed by a PVD deposition method such as sputtering or vacuum deposition.

[0030] As shown in Figure 2(b), the divided electrode 53 is positioned at two points on both ends of the thermistor plate 51, separated by a fixed distance along one direction of the second main surface 51b. In the following, one of the divided electrodes 53 may be referred to as the "first divided electrode 53a" and the other as the "second divided electrode 53b". The divided electrodes 53 (first divided electrode 53a, second divided electrode 53b) are thin metal films, which are PVD films formed by PVD deposition methods such as sputtering or vacuum deposition. By making the common electrode 52 and the divided electrodes 53 (first divided electrode 53a, second divided electrode 53b) PVD films, an extremely thin-walled thin-plate thermistor 5 can be made.

[0031] The thin-plate thermistor 5 has terminals as a resistor formed by a first divided electrode 53a and a second polarization electrode 53b formed on the second main surface 51b of the thermistor plate 51. The conductive path of the thin-plate thermistor 5 is a path from one of the divided electrodes, the first divided electrode 53a and the second polarization electrode 53b, through a common electrode 52 to the other divided electrode. With this configuration, the cross-sectional area of ​​the conductive path can be increased, and the conductive path can be a path where the surfaces of the first polarization electrode 53a and the second divided electrode 53b and the common electrode 52 face each other. As a result, the resistance value can be reduced with electrodes of a small area (common electrode 52, first divided electrode 53a, second divided electrode 53b), the resistance characteristics of the thin-plate thermistor 5 are more stable, and the dielectric strength of the thin-plate thermistor 5 is improved.

[0032] Incidentally, when the thin-film thermistor 5 is configured such that the distance between the first divided electrode 53a and the second divided electrode 53b is small, although it also depends on the applied voltage, the path from one of the first polarized electrode 53a and the second polarized electrode 53b to the other of the first divided electrode 53a and the second polarized electrode as a conductive path (this path is a path without the common electrode 52 intervening) becomes dominant, and a desired resistance value may not be obtained. Therefore, as shown in FIG. 1(b), when the distance between the first polarized electrode 53a and the common electrode 52 is G2a, the distance between the second polarized electrode 53b and the common electrode 52 is G2b, and the distance between the first polarized electrode 53a and the second polarized electrode 53b is G1, it is preferable to set so as to satisfy G2a + G2b < G1. When set in this way, a desired resistance value can be obtained, and the accuracy of the temperature detected by the thin-film thermistor 5 can be stabilized.

[0033] Furthermore, the thinner thermistor 5 can more accurately detect the temperature of a device for temperature detection the larger the contact area between the first divided electrode 53a and the second divided electrode 53b and the device for temperature detection. For this reason, it is better for the first divided electrode 53a and the second divided electrode 53b to have a large area, but if the area is too large, short circuits between the first divided electrode 53a and the second divided electrode 53b are more likely to occur. On the other hand, if the contact area between the first divided electrode 53a and the second divided electrode 53b and the device for temperature detection is small, the accuracy of the temperature of the device detected by the thinner thermistor 5 decreases. Therefore, depending on the desired resistance value, it is preferable to set the total area of ​​the first divided electrode 53a and the second divided electrode 53b to be within the range of 40% to 85% of the area of ​​the second main surface 51b of the thermistor plate 51. When set in this way, the thinner thermistor 5 can perform stable temperature detection. If the combined area of ​​the first divided electrode 53a and the second divided electrode 53b is less than 40% of the area of ​​the second main surface 51b of the thermistor plate 51, the first divided electrode 53a and the second divided electrode 53b of the thin plate thermistor 5 become too small, which may cause the resistance of the thin plate thermistor 5 to become too high, making it impossible to accurately detect the temperature of the device to be temperature detected. Also, if the combined area of ​​the first divided electrode 53a and the second divided electrode 53b exceeds 85% of the area of ​​the second main surface 51b of the thermistor plate 51, a short circuit may occur between the first divided electrode 53a and the second divided electrode 53b, causing the thermistor to cease functioning.

[0034] Next, the manufacturing process for the thin-plate thermistor 5 will be explained. In the manufacturing process for the thin-plate thermistor 5, a material mainly composed of manganese, or mainly composed of manganese and nickel (such as Mn-Fe-Ni-Ti material, Mn-Fe material, etc.) is made into a slurry with a binder, and a wafer of the thermistor plate 51 is created as a green sheet using a film formation technology such as screen printing technology or doctor blade technology. This is then sintered and molded into a wafer 51A, which will be the basis for the thermistor plate 51, using a firing technology (sintering molding process). In the following, the wafer 51A that will be the basis for the thermistor plate 51 may also be referred to as "thermistor plate wafer 51A".

[0035] In this sintering process, a green sheet is placed on a firing setter made of alumina (Al2O3) and fired. However, if the firing temperature is higher than the melting point of manganese, the manganese contained in the green sheet melts into the firing setter. Therefore, when comparing the surface roughness of the first surface 51aA (the surface that becomes the first main surface 51a of the thermistor plate 51), which was in contact with the firing setter of the thermistor plate wafer 51A, and the second surface 51bA (the surface that becomes the second main surface 51b of the thermistor plate 51), which is the opposite side (back side) of the thermistor plate wafer 51A that was in contact with the firing setter, the surface roughness of the first surface 51aA is greater than that of the second surface 51bA because manganese melted out of the first surface 51aA of the thermistor plate wafer 51A.

[0036] Following the sintering process, a breakline formation process is performed to form breaklines (small grooves) 51B on the thermistor wafer 51A.

[0037] In the breakline formation process, first, the thermistor wafer 51A is irradiated from the first surface 51aA side, in the area shown by the dotted line in Figure 3(a), as shown in Figure 3(b), where the irradiation area is small and the power density (W / cm²) is low. 2 A laser LA1 with a large ray diameter is irradiated to form a break line 51B on the first surface 51aA, which does not penetrate the thermistor wafer 51A, as shown in Figure 3(c) (first stage laser irradiation). After the formation of the break line 51B by this first stage laser irradiation, as shown in Figure 3(c), steep and tall burrs 51C are formed at both ends of the break line 51b on the thermistor wafer 51A, and chipping and other damage are likely to occur in the burr 51C area.

[0038] Following the first stage of laser irradiation, in order to remove the burrs 51C created by the first stage of laser irradiation, the thermistor wafer 51A is irradiated from the first surface 51aA side where the break line 51B is formed, to the area indicated by the dotted line in Figure 3(a), as shown in Figure 3(d), with a large irradiation area and power density (W / cm²). 2A laser LA2 with a small power density (W / cm²) is irradiated (second stage laser irradiation). Comparing the first stage laser irradiation and the second stage laser irradiation, the irradiation area in the second stage laser irradiation is larger than the irradiation area in the first stage laser irradiation, and the power density (W / cm²) in the second stage laser irradiation is larger. 2 ) is the power density (W / cm²) during the first stage of laser irradiation. 2 It is smaller than ). In the second stage of laser irradiation, the burr 51C melts, and the melted part solidifies afterward, forming a solidified part 51D as a laser trace. In each region of the first surface 51aA of the thermistor plate wafer 51A after the formation of the solidified part 51D, surrounded by the break line 51B (the region that will become a single thermistor plate 51), the surface roughness is smaller at the edges than in the center, and a slight bulge (a bulge lower than the height of the burr 51C) is formed at least in part of the edges, thereby ensuring a curved surface at the edges.

[0039] In the thermistor wafer 51A after the breakline formation process, the surface roughness at the edges of the region enclosed by the breakline 51B on the first surface 51aA is smallest, the surface roughness of the second surface 51bA is the second smallest, and the surface roughness in the central part of the region enclosed by the breakline 51B on the first surface 51aA is the largest.

[0040] Furthermore, in the breakline formation process, between the first and second laser irradiation stages, the thermistor wafer 51A may be irradiated with a laser from the first surface 51aA side where the breakline 51B is formed, in the area indicated by the dotted line within the dashed line in Figure 3(a), thereby increasing the depth of the breakline 51B in the laser-irradiated area or causing it to penetrate (intermediate laser irradiation). By doing so, damage to the thin-plate thermistor 5 can be suppressed when the thermistor wafer 51 is broken along the breakline 51B. Comparing the intermediate laser irradiation with the first and second laser irradiation stages, for example, the irradiation area in the intermediate stage = irradiation area in the first stage < irradiation area in the second stage, and the value of the light intensity per unit area in the intermediate stage ≥ the power density (W / cm²) in the first stage. 2 )>Power density (W / cm²) in the second stage of laser irradiation 2 )

[0041] Following the breakline formation process, an electrode formation process is performed to form electrodes (common electrode 52, first divided electrode 53a, and second divided electrode 53b) on the thermistor wafer 51A. In the electrode formation process, an electrode film (metal film) is formed by sputtering on a predetermined area of ​​the first surface 51aA of the thermistor wafer 51A after the breakline formation process (the area surrounded by the breakline 51B of the first surface 51aA), and the common electrode 52 is formed by patterning using photolithography technology. Similarly, an electrode film (metal film) is formed by sputtering on a predetermined area of ​​the second surface 51bA of the thermistor wafer 51A after the breakline formation process (the area on the back side of the area surrounded by the breakline 51B of the first surface 51aA), and the first divided electrode 53a and second divided electrode 53b are formed by patterning using photolithography technology.

[0042] As for the specific metallic materials of the common electrode 52, the first polarization electrode 53a, and the second polarization electrode 53b, for example, a multilayer film configuration is adopted in which a Ti film is formed as the base layer, a NiTi film made of an alloy of Ni and Ti is formed on top of it (intermediate layer), and an Au film is formed on the surface as the main layer (uppermost layer). When a multilayer film configuration of Ti film, NiTi film, and Au film is adopted, when the thin plate thermistor 5 is finally soldered to the mounting substrate, solder erosion is less likely to occur and a stable conductive bond can be achieved. In addition, a configuration in which a TiO2 film is formed between the base layer (Ti film) and the intermediate layer (NiTi film) in the above multilayer film configuration is also possible. Furthermore, the metal film configurations of the first polarization electrode 53a and the second divided electrode 53b and the common electrode 52 may be different. For example, the metal film configurations of the first polarization electrode 53a and the second divided electrode 53b may be a laminated film configuration of Ti film, NiTi film and Au film, and the film configuration of the common electrode 52 may be a laminated film configuration of Ti film and Au film.

[0043] Furthermore, in the above electrode film configuration, a Cr film or Ti film may be formed as the underlayer, and a laminated film configuration of an Au film, Ag film, Pt film, etc. may be formed on top thereof, or a film configuration using only a Cu film may be formed. When a laminated film configuration of a Cr film or Ti film underlayer and an Au film, Ag film, or Pt film, or a single-layer Cu film configuration is adopted, the films can be joined using a conductive resin adhesive.

[0044] Following the electrode formation process, the thermistor wafer 51A, on which the common electrode 52, the first divided electrode 53a, and the second divided electrode 53b have been formed, is broken along the break line 51B (breaking process). This separates the thin-plate thermistor 5, on which the common electrode 52, the first divided electrode 53a, and the second divided electrode 53b have been formed, thus completing the thin-plate thermistor 5.

[0045] According to the thin-plate thermistor 5 described above, the surface roughness of the first main surface 51a of the thermistor plate 51 is lower at the edges than in the center, making it less likely for cracks or chips to occur on the first main surface 51a side of the edges of the thermistor plate 51, and as a result, the mechanical strength of the thin-plate thermistor 5 can be improved. In addition, since there is a raised area at least in part of the edges of the first main surface 51a of the thermistor plate 51, cracks or chips to occur on the first main surface 51a side of the edges of the thermistor plate 51, and as a result, the mechanical strength of the thin-plate thermistor 5 can be improved.

[0046] Furthermore, by providing a solidified portion 51D at the end of the first main surface 51a of the thermistor plate 51, the surface condition of the end of the first main surface 51a of the thermistor plate 51 can be smoothed to ensure a curved surface. This makes it less likely for cracks or chips to occur on the first main surface 51a side of the end of the thermistor plate 51, and as a result, the mechanical strength of the thin plate thermistor 5 can be improved. In addition, by making the solidified portion 51D a laser mark, a curved surface can be easily formed in the solidified portion 51D.

[0047] Furthermore, since the first and second divided electrodes 53a and 53b, which serve as operating electrodes, are formed on the second main surface 51b of the thermistor plate 51 with the lower surface roughness, variations in the area on which the first and second divided electrodes 53a and 53b are formed are less likely to occur compared to the case where the first and second divided electrodes 53a and 53b, which serve as operating electrodes, are formed on the first main surface 51a with the higher surface roughness, thus suppressing variations in the resistance characteristics of the thin-plate thermistor 5. In particular, since the resistance characteristics of the thin-plate thermistor 5 are determined by the area of ​​the first and second divided electrodes 53a and 53b facing the thermistor plate 51, forming the first and second divided electrodes 53a and 53b, which require precise area measurements, on the second main surface 51b with the lower surface roughness is an advantageous configuration for stabilizing the resistance characteristics of the thin-plate thermistor 5.

[0048] Furthermore, by forming the first divided electrode 53a and the second divided electrode 53b on the second main surface 51b of the thermistor plate 51, which has a lower surface roughness, the adhesion of the first divided electrode 53a and the second divided electrode 53b to the second main surface 51b of the thermistor plate 5 is improved, and the conductivity is stabilized. This allows for a stable connection when a measuring probe or the like is brought into contact with the first divided electrode 53a and the second divided electrode 53b, making it possible to accurately measure the resistance characteristics of the thin plate thermistor 5.

[0049] Furthermore, by forming a common electrode 52, which acts as an intermediate electrode, on the first main surface 51a of the thermistor plate 51 with the greater surface roughness, the total amount of conductors involved with the common electrode 52 increases as the surface area of ​​the portion where the common electrode 52 is formed increases relative to the apparent area, thereby improving conductivity. The common electrode 52 plays a role in preventing the thin plate thermistor 5 from generating unwanted resistance values, and since the conductivity does not decrease as the surface area of ​​the common electrode 52 increases, the resistance value of the thin plate thermistor 5 is not worsened. In particular, with miniaturized thin plate thermistors 5, it becomes difficult to satisfy the characteristics below a predetermined resistance value if the resistance value of the common electrode 52 becomes large, but by forming the common electrode 52 on the first main surface 51a of the thermistor plate 5 with the greater surface roughness, it is possible to satisfy the characteristics below a predetermined resistance value.

[0050] Furthermore, by forming the first divided electrode 53a, the second divided electrode 53b, and the common electrode 52 as PVD films using PVD deposition methods such as sputtering or vacuum deposition, the first divided electrode 53a, the second divided electrode 53b, and the common electrode 52 will have a dense film structure, resulting in electrodes with excellent conductivity and adhesion to the thermistor plate 5. In addition, the electrodes can be formed to have a desired area, and as a result, the resistance characteristics of the thin-plate thermistor 5 can be stabilized. This is particularly effective in stabilizing the resistance characteristics of miniaturized thin-plate thermistors 5.

[0051] ≪Second Embodiment≫ Hereinafter, a thin-plate thermistor-mounted piezoelectric vibration device according to a second embodiment of the present invention will be described in detail with reference to Figures 4 to 8.

[0052] Figure 4 is a plan view of the thin-plate thermistor-mounted piezoelectric vibration device 1. Figure 5 is a cross-sectional view AA of device 1 shown in the plan view in Figure 4. As shown in Figures 4 and 5, the thin-plate thermistor-mounted piezoelectric vibration device 1 is a device having a sandwich-structure piezoelectric vibration device (hereinafter sometimes referred to as the "sandwich structure device") 2 and the thin-plate thermistor 5 described above mounted on the sandwich structure device 2. Hereafter, the "thin-plate thermistor-mounted piezoelectric vibration device 1" may simply be referred to as "device 1". In device 1, for example, while the thickness of the sandwich structure device 2 is about 120 μm, the thin-plate thermistor 5 can be less than half the thickness of the sandwich structure device 2 (about 50 μm).

[0053] As shown in Figure 5, the sandwich structure device 2 comprises a piezoelectric diaphragm 10, a first sealing member 20, and a second sealing member 30. In the sandwich structure device 2, the piezoelectric diaphragm 10 and the first sealing member 20 are joined together, and the piezoelectric diaphragm 10 and the second sealing member 30 are joined together to form a substantially rectangular parallelepiped sandwich structure package.

[0054] Figure 6(a) is a plan view of the first main surface 11, which is one of the main surfaces (the surface to be joined with the first sealing member 20) of the piezoelectric diaphragm 10 before joining. Figure 6(b) is a plan view of the second main surface 12, which is the other main surface (the surface to be joined with the second sealing member 30) of the piezoelectric diaphragm 10 before joining. The piezoelectric diaphragm 10 is a piezoelectric substrate made of a piezoelectric material such as quartz, and both of its main surfaces (first main surface 11 and second main surface 12) are formed as flat, smooth surfaces (mirror-finished). In this embodiment, an AT-cut quartz plate that performs thickness-sliding vibration is used as the piezoelectric diaphragm 10.

[0055] In Figures 4 to 8, the piezoelectric diaphragm 10 has two main surfaces that form the XZ plane, with the direction parallel to the short side being the X-axis direction, the direction parallel to the long side being the Z-axis direction, and the direction perpendicular to the XZ plane being the Y-axis direction.

[0056] The piezoelectric diaphragm 10 has a vibrating portion 13 formed in a substantially rectangular shape, an outer frame portion 14 surrounding the outer circumference of the vibrating portion 13, and a holding portion 15 that holds the vibrating portion 13 by connecting the vibrating portion 13 and the outer frame portion 14. The space between the vibrating portion 13 and the outer frame portion 14 is a cutout portion (an opening that penetrates the piezoelectric diaphragm 10 in the thickness direction), except for the area where the holding portion 15 is formed. As a result, the piezoelectric diaphragm 10 has a configuration in which the vibrating portion 13, the outer frame portion 14, and the holding portion 15 are integrally provided. A pair of excitation electrodes (a first excitation electrode 111 on the first main surface 11 side and a second excitation electrode 121 on the second main surface 12 side) are formed on the first main surface 11 and the second main surface 12 of the piezoelectric diaphragm 10.

[0057] In this embodiment, the holding portion 15 is provided at only one location between the vibrating portion 13 and the outer frame portion 14. Furthermore, the vibrating portion 13 and the holding portion 15 are formed thinner than the outer frame portion 14. Due to this difference in thickness between the outer frame portion 14 and the holding portion 15, the natural frequencies of the piezoelectric vibrations of the outer frame portion 14 and the holding portion 15 are different, and piezoelectric vibrations are not propagated to the outer frame portion 14. Note that the location of the holding portion 15 is not limited to one location; the holding portion 15 may be provided at two locations between the vibrating portion 13 and the outer frame portion 14.

[0058] The first excitation electrode 111 is provided on the first main surface 11 side of the vibrating section 13, and the second excitation electrode 121 is provided on the second main surface 12 side of the vibrating section 13. Each of the first excitation electrode 111 and the second excitation electrode 121 is connected to a lead electrode (lead-out wiring electrode film) (first lead electrode 112 on the first main surface 11 side, and second lead electrode 122 on the second main surface 12 side) for connecting these excitation electrodes to external electrode terminals. The first lead electrode 112 is led out from the first excitation electrode 111 and connected via the holding section 15 to a connecting joint pattern 114 formed on the outer frame section 14. The second lead electrode 122 is led out from the second excitation electrode 121 and connected via the holding section 15 to a connecting joint pattern 124 formed on the outer frame section 14.

[0059] A bonding pattern is formed on the first main surface 11 and the second main surface 12 of the piezoelectric diaphragm 10 for joining the piezoelectric diaphragm 10 to the first sealing member 20 and the second sealing member 30. This bonding pattern includes a sealing pattern for hermetically sealing the internal space of the package and a conductive pattern for allowing wiring and electrodes to conduct electricity. In Figures 6(a), (b), 7(b), and 8(a), the bonding region where the bonding pattern is formed is indicated by diagonal hatching.

[0060] As sealing patterns for the piezoelectric diaphragm 10, a vibration-side first bonding pattern 113 is formed on the first main surface 11, and a vibration-side second bonding pattern 123 is formed on the second main surface 12. The vibration-side first bonding pattern 113 and the vibration-side second bonding pattern 123 are provided on the outer frame portion 14 and are formed in an annular shape in plan view. The areas inside the vibration-side first bonding pattern 113 and the vibration-side second bonding pattern 123 become the sealing area of ​​the vibrating portion 13 (the area that becomes the internal space of the package after bonding). The first excitation electrode 111 and the second excitation electrode 121 are not electrically connected to the vibration-side first bonding pattern 113 and the vibration-side second bonding pattern 123.

[0061] As conductive patterns in the piezoelectric diaphragm 10, four connecting patterns 115 are formed on the first main surface 11 outside the sealing area (outside the vibration-side first connecting pattern 113), and connecting patterns 114 and 116 are formed inside the sealing area (inside the vibration-side first connecting pattern 113). Similarly, four connecting patterns 125 are formed on the second main surface 12 outside the sealing area (outside the vibration-side second connecting pattern 123), and connecting pattern 124 is formed inside the sealing area (inside the vibration-side second connecting pattern 123). The connecting patterns 115 on the first main surface 11 and the connecting patterns 125 on the second main surface 12 are provided in areas near the four corners (corners) of the outer frame portion 14, respectively.

[0062] Furthermore, the piezoelectric diaphragm 10 has a plurality of through holes 16 formed between the first main surface 11 and the second main surface 12, and through electrodes are formed on the inner wall surface of each through hole 16 to ensure electrical conductivity between the first main surface 11 and the second main surface 12. Specifically, four through holes 16 and through electrodes are formed to ensure electrical conductivity between the connecting bonding pattern 115 and the connecting bonding pattern 125, and one through hole 16 and through electrode is formed to ensure electrical conductivity between the connecting bonding pattern 116 and the connecting bonding pattern 124.

[0063] In the piezoelectric diaphragm 10, the first excitation electrode 111, the second excitation electrode 121, the first extraction electrode 112, the second extraction electrode 122, the vibration-side first bonding pattern 113, the vibration-side second bonding pattern 123, and the connecting bonding patterns 114-116, 124, and 125 can be formed by the same process. Specifically, they can be formed from a base layer (Ti film) formed by physical vapor phase growth on both main surfaces (first main surface 11, second main surface 12) of the piezoelectric diaphragm 10, and a bonding film (Au film) laminated on the base layer by physical vapor phase growth. Furthermore, the configuration of the laminated film forming the bonding pattern is not limited to a two-layer structure of Ti film and Au film, but may be a three-layer or more structure including other films (for example, a barrier film formed between the Ti film and the Au film).

[0064] Figure 7(a) is a plan view showing the first main surface 21, which is one of the main surfaces (outer surfaces) of the first sealing member 20 before bonding. Figure 7(b) is a plan view showing the second main surface 22, which is the other main surface (bonding surface with the piezoelectric diaphragm 10) of the first sealing member 20 before bonding. The first sealing member 20 is a rectangular parallelepiped substrate formed from a single glass wafer or quartz wafer, and the second main surface 22 of this first sealing member 20 is formed as a flat, smooth surface (mirror finish).

[0065] As shown in Figure 7(a), two electrode patterns 211 and wiring patterns 212 and 213 are formed on the first main surface 21 of the first sealing member 20. Electrode pattern 211 is a mounting pad for mounting the thin plate thermistor 5 (see Figure 4). Wiring pattern 212 is a wiring pattern that is part of the wiring path connecting the second excitation electrode 121 to the external electrode terminal 321 (see Figure 8(b)). Wiring pattern 213 is a wiring pattern that is part of the wiring path connecting the first excitation electrode 111 to the external electrode terminal 321.

[0066] As shown in Figure 7(b), a bonding pattern is formed on the second main surface 22 of the first sealing member 20 for bonding the first sealing member 20 to the piezoelectric diaphragm 10. This bonding pattern includes a sealing pattern for hermetically sealing the internal space of the package and a conductive pattern for allowing wiring and electrodes to conduct electricity.

[0067] In the first sealing member 20, a sealing-side first bonding pattern 221 is formed as the sealing pattern. The sealing-side first bonding pattern 221 is formed in an annular shape in plan view, and the area inside it becomes the sealing region. In the first sealing member 20, four connecting bonding patterns 222 are formed near the four corners (corners) outside the sealing region (outside the sealing-side first bonding pattern 221), and connecting bonding patterns 223 to 225 are formed inside the sealing region (inside the sealing-side first bonding pattern 221). Connecting bonding patterns 224 and 225 are connected by a wiring pattern 226.

[0068] Furthermore, the first sealing member 20 has a plurality of through holes 23 formed between the first main surface 21 and the second main surface 22, and through electrodes are formed on the inner wall surface of each through hole 23 to ensure electrical conductivity between the first main surface 21 and the second main surface 22. Specifically, four through holes 23 and through electrodes are formed to ensure electrical conductivity between the electrode pattern 211 or wiring patterns 212, 213 and the connecting joint pattern 222, one through hole 23 and through electrode is formed to ensure electrical conductivity between the wiring pattern 212 and the connecting joint pattern 223, and one through hole 23 and through electrode is formed to ensure electrical conductivity between the wiring pattern 213 and the connecting joint pattern 225.

[0069] In the first sealing member 20, the sealing-side first bonding pattern 221, the connecting bonding patterns 222 to 225, and the wiring pattern 226 can be formed by the same process. Specifically, these can be formed from a base layer (Ti film) formed by physical vapor phase growth on the second main surface 22 of the first sealing member 20, and a bonding film (Au film) laminated on the base layer by physical vapor phase growth.

[0070] Figure 8(a) is a plan view of the first main surface 31, which is one of the main surfaces (the surface to be joined with the piezoelectric diaphragm 10), of the second sealing member 30 before bonding. Figure 8(b) is a plan view of the second main surface 32, which is the other main surface (outer surface), of the second sealing member 30 before bonding. The second sealing member 30 is a rectangular parallelepiped substrate formed from a single glass wafer or quartz wafer, and the first main surface 31 of this second sealing member 30 is formed as a flat, smooth surface (mirror finish).

[0071] As shown in Figure 8(a), a bonding pattern is formed on the first main surface 31 of the second sealing member 30 for bonding the second sealing member 30 to the piezoelectric diaphragm 10. This bonding pattern includes a sealing pattern for hermetically sealing the internal space of the package and a conductive pattern for allowing wiring and electrodes to conduct electricity.

[0072] As a sealing pattern in the second sealing member 30, a sealing-side second bonding pattern 311 is formed. The sealing-side second bonding pattern 311 is formed in an annular shape in plan view, and the area inside it becomes the sealing region. As a conductive pattern in the second sealing member 30, four connecting bonding patterns 312 are formed near the four corners (angles) outside the sealing region (outside the sealing-side second bonding pattern 311).

[0073] As shown in Figure 8(b), the second main surface 32 of the second sealing member 30 is provided with four external electrode terminals 321 for electrically connecting the device 1 to the outside. The external electrode terminals 321 are located at the four corners (corners) of the second sealing member 30.

[0074] Furthermore, the second sealing member 30 has a plurality of through holes 33 formed between the first main surface 31 and the second main surface 32, and through electrodes are formed on the inner wall surface of each through hole 33 to ensure electrical conductivity between the first main surface 31 and the second main surface 32. Specifically, four through holes 33 and through electrodes are formed to ensure electrical conductivity between the connecting bonding pattern 312 and the external electrode terminal 321.

[0075] In the second sealing member 30, the sealing-side second bonding pattern 311 and the bonding pattern 312 can be formed by the same process. Specifically, these can be formed from a base layer (Ti film) formed by physical vapor phase growth on the first main surface 31 of the second sealing member 30, and a bonding film (Au film) laminated on the base layer by physical vapor phase growth.

[0076] In the sandwich structure device 2, the piezoelectric diaphragm 10 and the first sealing member 20 are diffusion-bonded with the vibration-side first bonding pattern 113 and the sealing-side first bonding pattern 221 overlapping, and the piezoelectric diaphragm 10 and the second sealing member 30 are diffusion-bonded with the vibration-side second bonding pattern 123 and the sealing-side second bonding pattern 311 overlapping, thereby manufacturing a sandwich structure package. Specifically, the vibration-side first bonding pattern 113 and the sealing-side first bonding pattern 221 are bonded to form a sealing pattern layer between the piezoelectric diaphragm 10 and the first sealing member 20, and the vibration-side second bonding pattern 123 and the sealing-side second bonding pattern 311 are bonded to form a sealing pattern layer between the piezoelectric diaphragm 10 and the second sealing member 30. As a result, the internal space of the package, that is, the space housing the diaphragm 13, is hermetically sealed.

[0077] In this process, the connecting bonding patterns, which are conductive patterns, are also bonded together, and the bonded conductive patterns form a conductive pattern layer between the piezoelectric diaphragm 10 and the first sealing member 20 or between the piezoelectric diaphragm 10 and the second sealing member 30. In the sandwich structure device 2, electrical conductivity is obtained between the first excitation electrode 111 and the second excitation electrode 121 and the external electrode terminals 321 in the lower right and upper left of Figure 8(b).

[0078] The thin-plate thermistor 5 is mounted on the sandwich structure device 2 with its second main surface 51b, on which the divided electrodes 53 are formed, facing downwards (the bonding surface with the sandwich structure device 2), and electrically joining the divided electrodes 53 with the electrode pattern 211 of the first sealing member 20. Furthermore, the thin-plate thermistor 5 mounted on the sandwich structure device 2 is configured to achieve electrical conductivity with the external electrode terminals 321 in the upper right and lower left of Figure 8(b).

[0079] As described above, the thin-plate thermistor 5 has a large-area metal electrode (common electrode 52, divided electrode 53), which allows it to act advantageously as a shielding member for the sandwich structure device 2. In order to utilize the thin-plate thermistor 5 as a shielding member, in a plan view of the device 1, the thin-plate thermistor 5 is positioned on the sandwich structure device 2 such that at least a portion of it overlaps with the vibrating portion 13 of the sandwich structure device 2 (see Figure 4). Furthermore, it is more preferable, as the shielding effect of the thin-plate thermistor 5 can be maximized if it is positioned so as to overlap the entirety of the first excitation electrode 111 and the second excitation electrode 121 in a plan view.

[0080] Furthermore, the thin-plate thermistor 5 is positioned in the sandwich structure device 2 such that both ends of the thin-plate thermistor 5 overlap the outer frame portion 14 on at least two opposing sides of the sandwich structure device 2. The first sealing member 20 and the second sealing member 30 in the sandwich structure device 2 are extremely thin substrates and are made of brittle materials such as glass or quartz. As a result, the strength of the sandwich structure device 2 is particularly low in the central part (the area in the piezoelectric diaphragm 10 where the outer frame portion 14 does not exist). In such a sandwich structure device 2, if the thin-plate thermistor 5 is positioned in the central area of ​​the sandwich structure device 2, there is a risk that the first sealing member 20 will crack due to the pressing force when mounting the thin-plate thermistor 5. In contrast, by joining the thin-plate thermistor 5 to the outer periphery of the sandwich structure device 2 (the area in the piezoelectric diaphragm 10 where the outer frame portion 14 exists), that is, by positioning the ends of the thin-plate thermistor 5 to overlap the outer frame portion 14, cracking of the first sealing member 20 can be suppressed and the strength of the device 1 can be ensured. In particular, the device 1 is made structurally stable by ensuring that the thin plate thermistor 5 overlaps with the sealing portion of the sandwich structure device 2 (sealing patterns such as the vibration-side first bonding pattern 113). While Figures 4 and 5 show an example where both ends of the thin plate thermistor 5 overlap the outer frame portion 14 on two opposing sides in the short direction of the sandwich structure device 2, the thin plate thermistor 5 may also overlap the outer frame portion 14 on two opposing sides in the longitudinal direction of the sandwich structure device 2. Furthermore, the thin plate thermistor 5 may overlap not only two opposing sides of the sandwich structure device 2, but also three or four sides.

[0081] The divided electrode 53 and the electrode pattern 211 are electrically joined by a conductive resin adhesive 61 (see Figure 5). However, the configuration is not limited to this, and the divided electrode 53 and the electrode pattern 211 may be joined by Au (gold) bumps. Furthermore, a non-conductive resin adhesive 62 (see Figure 5) is filled in the gap between the thin plate thermistor 5 and the sandwich structure device 2 (the gap where the conductive resin adhesive 61 is not present). The non-conductive resin adhesive 62 may not only be filled on the lower surface of the thin plate thermistor 5, but may also be used as a sealing resin to seal the entire thin plate thermistor 5. A silicone-based resin can be used as the conductive resin adhesive 61, and an epoxy-based resin can be used as the non-conductive resin adhesive 62.

[0082] Thus, when a thin-plate thermistor 5 is surface-bonded to the sandwich structure device 2 using conductive resin adhesive 61 and non-conductive resin adhesive 62, the thermal conductivity between the thin-plate thermistor 5 and the sandwich structure device 2 can be improved. This allows the thin-plate thermistor 5 to be kept at a temperature close to that of the vibrating part 13 of the sandwich structure device 2. Furthermore, surface bonding between the sandwich structure device 2 and the thin-plate thermistor 5 also has the advantage of improving the strength of the device 1.

[0083] When a conductive resin adhesive 61 and a non-conductive resin adhesive 62 are used to bond the thin plate thermistor 5, it is preferable that the conductive resin adhesive 61 has higher thermal conductivity than the non-conductive resin adhesive 62. This further improves the thermal conductivity between the thin plate thermistor 5 and the sandwich structure device 2. Furthermore, it is preferable that the thin plate thermistor 5 is surface-bonded to the first main surface 21 of the first sealing member 20 by the conductive resin adhesive 61 and the non-conductive resin adhesive 62 over more than half (50% to 100%) of the area of ​​the thin plate thermistor 5 in a plan view. This ensures sufficient thermal conduction between the thin plate thermistor 5 and the sandwich structure device 2, and allows for sufficient accuracy in the temperature of the sandwich structure device 2 detected by the thin plate thermistor 5. Furthermore, it is preferable that the non-conductive resin adhesive 62 has higher hardness than the conductive resin adhesive 61. This relieves stress between the thin plate thermistor 5 and the sandwich structure device 2 and improves the package strength of the device 1.

[0084] According to the thin-plate thermistor-equipped piezoelectric vibration device 1 described above, cracks and chips are less likely to occur at the ends of the thermistor plate 51, and by providing the thin-plate thermistor 5 of the first embodiment, which has excellent resistance characteristics, the accuracy of temperature detection can be improved. In particular, by electrically and mechanically joining the sandwich structure device 2 with the second main surface 51b of the thin-plate thermistor 5, which has a small surface roughness, the first main surface 51a of the thin-plate thermistor 5 is positioned on the side opposite to the side facing the sandwich structure device 2 (piezoelectric diaphragm 10), and at least a solidified portion 51D (curved surface) is arranged on the outer surface of the thin-plate thermistor 5, so that the side of the thin-plate thermistor 5 is less likely to crack or chip at its ends, which is desirable as it can increase mechanical strength.

[0085] ≪Third Embodiment≫ Hereinafter, a thin-plate thermistor-mounted piezoelectric vibration device according to a third embodiment of the present invention will be described in detail with reference to Figures 9 to 11. Figure 9 is an exploded perspective view of the thin-plate thermistor-mounted piezoelectric vibration device XcX. Figure 10 is a bottom view of the thin-plate thermistor-mounted piezoelectric vibration device XcX, which is shown in the exploded perspective view of Figure 9. Figure 11 is a cross-sectional view (CC) of the thin-plate thermistor-mounted piezoelectric vibration device XcX of Figure 10.

[0086] As shown in Figures 9 to 11, the thin-plate thermistor-mounted piezoelectric vibration device XcX is a device comprising a package 1X having an upper housing section 11AX and a lower housing section 11BX, a piezoelectric diaphragm 2X housed in the upper housing section 11AX, the aforementioned thin-plate thermistor 5 housed in the lower housing section 11BX, and a lid 3X that hermetically seals the upper housing section 11A.

[0087] Package 1X is made of ceramic, has a rectangular parallelepiped shape overall, and has an upper storage section 11AX that opens upward and a lower storage section 11BX that opens downward. The upper storage section 11AX and the lower storage section 11BX are configured so that their closed portions (bottoms) are back to back with respect to the substrate 11CX.

[0088] The upper storage section 11AX has a concave rectangular parallelepiped storage configuration that opens upward, and mounting electrodes 16X and 17X made of metal film are formed at the bottom of the upper storage section 11AX. The mounting electrodes 16X and 17X are formed in a direction along the short side of the package 1X. A rectangular sealing section 10X is provided on the outer periphery of the upper storage section 11AX at a position higher than the bottom, and a metal film layer is formed on the sealing section 10X.

[0089] The mounted electrodes 16X and 17X consist of multiple metal films, stacked in the order of a W (tungsten) layer, a Ni (nickel) layer, and an Au (gold) layer. The W layer is integrally formed by firing together with the ceramic material that constitutes the package, while the Ni and Au layers are formed on the W layer by plating. The sealing portion 10X also has a layered structure with the same metal layer configuration as the mounted electrodes 16X and 17X, with the layers stacked in the order of a W layer, a Ni layer, and an Au layer. The mounted electrodes 18X and 19X and the mounted electrodes 12X, 13X, 14X, and 15X, which will be described later, are manufactured using the same method and each has a layered structure with the layers stacked in the order of a W layer, a Ni layer, and an Au layer.

[0090] The lower storage section 11BX is a concave rectangular parallelepiped storage structure that opens downwards, and mounting electrodes 18X and 19X made of metal film are formed at the bottom of the lower storage section 11BX. The mounting electrodes 18X and 19X are rectangular in shape with a long side and a short side, and are formed so that the long side of mounting electrode 18X and the long side of mounting electrode 19X face each other in the direction along the long side of the package 1X. Alternatively, the mounting electrodes 18X and 19X may be formed to be aligned in the direction along the short side of the package 1X.

[0091] Mounted electrodes 12X, 13X, 14X, and 15X are provided at the four corners of the lower storage section 11BX, positioned higher than the bottom. Each of the mounted electrodes 12X, 13X, 14X, and 15X is rectangular in shape, and mounted electrodes 12X and 14X are electrically connected to mounted electrodes 16X and 17X, while mounted electrodes 13X and 15X are electrically connected to mounted electrodes 18X and 19X, via internal wiring within the package 1X.

[0092] The piezoelectric diaphragm 2X is made of an AT-cut quartz plate and is a rectangular plate in shape overall. Excitation electrodes 21X and 22X are formed in the central part of the front and back surfaces of the piezoelectric diaphragm 2X, and the excitation electrodes 21X and 22X are drawn out to the outer periphery of the piezoelectric diaphragm 2X by strip-shaped lead electrodes 21aX and 22aX with width. The excitation electrodes 21X and 22X are rectangular in shape, and on one main surface of the piezoelectric diaphragm 2X, the excitation electrode 21X is drawn out from one short corner by the lead electrode 21aX to the end of one main surface of the piezoelectric diaphragm 2X, and on the other main surface of the piezoelectric diaphragm 2X, the excitation electrode 22X is drawn out from one short corner by the lead electrode 22aX to the end of the other main surface of the piezoelectric diaphragm 2X. As a result, the excitation electrodes 21X and 22X are drawn out to one short side of the piezoelectric diaphragm 2X.

[0093] The excitation electrodes 21X, 22X and the extraction electrodes 21aX, 22aX are constructed by laminating thin metal films, with a Ti (titanium) layer formed in contact with the piezoelectric diaphragm 2X and an Au (gold) layer formed on top of it. The metal film configuration may be other than the above configuration, and known metal film configurations can be used, such as a Cr (chromium) layer as the base metal or an Ag (silver) layer as the top layer. The excitation electrodes 21X, 22X and the extraction electrodes 21aX, 22aX can be PVD films formed by PVD deposition methods such as sputtering or vacuum deposition.

[0094] The thin plate thermistor 5 has its second main surface 51b, on which the divided electrodes 53 are formed, as the upper surface (the bonding surface with the package 1X), and the divided electrodes 53 (first and second divided electrodes 53 a, 53b) and the mounted electrodes 18X, 19X at the bottom of the lower storage section 11BX are electrically joined and mounted on package 1X.

[0095] The lid 3X is made of a thin metal or ceramic plate and has a rectangular shape that corresponds to the outer dimensions of the sealing portion 10X of the package 1X. The configuration of the lid 3X and the sealing portion 10X differs depending on the hermetically sealing method of the package 1X. For example, when the lid 3X and the sealing portion 10X are joined by seam welding, the lid 3X uses Kovar as the core material and has a Ni plating film formed on its surface. The sealing portion 10X uses a configuration in which a ring-shaped metal frame is brazed, and the lid 3X and the metal frame (sealing portion 10X) are joined by seam welding in a vacuum atmosphere or an inert gas atmosphere, for example. This allows the inside of the package 1X (the inside of the upper storage portion 11AX) to be in a steady state of a vacuum atmosphere or an inert gas atmosphere.

[0096] When hermetically sealing by brazing with a metal brazing material, such as AuSu brazing material, for example, a preform of AuSu brazing material is formed around the lid 3X, and the upper layer of the sealing part 10X is plated with Au, and both are heated in a predetermined atmosphere and temperature environment to achieve hermetically sealing by metal brazing.

[0097] A paste-like conductive resin adhesive S1 is applied to the mounted electrodes 16X and 17X in the upper storage section 11AX of package 1X using a dispenser or the like. The conductive resin adhesive S1 is, for example, a silicone resin adhesive containing a metal filler, but other resin materials such as polyimide-based resin materials may also be used. A piezoelectric diaphragm 2X with electrodes formed on it is mounted on the applied conductive resin adhesive S1. Specifically, the piezoelectric diaphragm 2X is mounted in the upper storage section 11AX so that the lead-out electrodes 21aX and 22aX are joined to the conductive resin adhesive S1. Then, the conductive resin adhesive S1 is cured by heating to conductively join (electrically and mechanically join) the piezoelectric diaphragm 2X and the mounted electrodes 16X and 17X. Note that the conductive resin adhesive S1 may be applied again on top of the piezoelectric diaphragm 2X as needed. In this embodiment, a configuration with re-application is shown as an example.

[0098] The upper storage section 11AX is hermetically sealed by the lid 3X, which is achieved by joining the lid 3X to the sealing section 10X. In this embodiment, metal brazing is performed using metal brazing material S2, which is, for example, AuSu brazing material.

[0099] The thin plate thermistor 5 is electrically bonded to the lower storage compartment 11BX of package 1X. Conductive resin adhesive S1 is applied to the mounting electrodes 18X and 19X using a dispenser or the like. The thin plate thermistor 5 is placed in the lower storage compartment 11BX so that the divided electrodes 53 (first divided electrode 53a, second divided electrode 53b) correspond to the applied conductive resin adhesive S1. Then, the conductive resin adhesive S1 is cured by heating to electrically bond (electrically and mechanically bond) the first divided electrode 53a and the second divided electrode 53b of the thin plate thermistor 5 to the mounting electrodes 18X and 19X. Note that soldering may also be used for the conductive bonding of the thin plate thermistor 5.

[0100] A resin material M is injected into the lower housing 11BX containing the thin plate thermistor 5 using a dispenser or the like to coat the thin plate thermistor 5 with the resin material M, and then the resin material M is cured by heating. In this embodiment, a polyimide resin is used as the resin material M, but other resin materials may also be used. As a result, the thin plate thermistor 5 is protected from the outside air, so that stable temperature detection can be performed.

[0101] According to the thin-plate thermistor-equipped piezoelectric vibration device XcX described above, cracks and chips are less likely to occur at the edges of the thermistor plate 51, and by incorporating the thin-plate thermistor 5 of the first embodiment, which has excellent resistance characteristics, the accuracy of temperature detection can be improved.

[0102] ≪Fourth Embodiment≫ Hereinafter, a thin-plate thermistor-mounted piezoelectric vibration device according to a fourth embodiment of the present invention will be described in detail with reference to Figure 12. Figure 12 is a cross-sectional view of the thin-plate thermistor-mounted piezoelectric vibration device XcY.

[0103] In the thin-plate thermistor-mounted piezoelectric vibration device XcY, the piezoelectric diaphragm 2X and the thin-plate thermistor 5 are housed inside a housing section 51Y of the package 1Y of the thin-plate thermistor-mounted piezoelectric vibration device XcY. The package 1Y is made of ceramic with internal wiring formed therein and has a housing section 51Y with an opening at the top. Mounting electrodes 54Y and 55Y (mounting electrode 55Y is not shown) for the piezoelectric diaphragm 2X and mounting electrodes 56Y and 57Y for the thin-plate thermistor 5 are formed at the bottom of the housing section 51Y. Mounting electrodes 52Y and 53Y are also formed on the bottom surface.

[0104] The lead electrodes 21aX and 22aX (see Figure 9) formed on both main surfaces of the piezoelectric diaphragm 2X are electrically bonded (electrically and mechanically bonded) to the mounted electrodes 54Y and 55Y using a conductive resin adhesive S1, and the piezoelectric diaphragm 2X is housed inside the housing section 51Y of the package 1Y. In addition, the first and second divided electrodes 53a and 53b formed on the second main surface 51b of the thin plate thermistor 5 are electrically bonded (electrically and mechanically bonded) to the mounted electrodes 56Y and 57Y using a conductive resin adhesive S1, and the thin plate thermistor 5 is housed inside the housing section 51Y of the package 1Y.

[0105] The piezoelectric diaphragm 2X and the thin plate thermistor 5 are housed in parallel inside the storage compartment 51Y of package 1Y, and are hermetically sealed by the lid 3X.

[0106] According to the thin-plate thermistor-equipped piezoelectric vibration device XcY described above, cracks and chips are less likely to occur at the edges of the thermistor plate 51, and by incorporating the thin-plate thermistor 5 of the first embodiment, which has excellent resistance characteristics, the accuracy of temperature detection can be improved.

[0107] Furthermore, the thin-plate thermistor is not limited to the thin-plate thermistor 5 of the embodiment described above, and various modifications can be made to it.

[0108] For example, in the above embodiment, instead of performing the first and second stages of laser irradiation on the thermistor wafer 51 from the first surface 51aA side with a larger surface roughness, the first and second stages of laser irradiation may be performed from the second surface 51bA side with a smaller surface roughness. This would result in the second main surface 51b of the thermistor wafer 51 having less surface roughness at the edges than in the center, and at least a portion of the edges being raised, so that the thermistor wafer 51 has a solidified portion (another solidified portion) at the edge of the second main surface 52b. Furthermore, by performing a first-stage laser irradiation and a second-stage laser irradiation on the thermistor plate wafer 51 from the first surface 51aA side and the second surface 51bA side, respectively, the surface roughness of the first main surface 51a and the second main surface 51b of the thermistor plate 51 is smaller at the edges than in the center, and at least a part of the edges is raised, so that the thermistor plate 51 has solidified parts and other solidified parts at the respective edges of the first main surface 51a and the second main surface 51b. In the latter case, because the thermistor plate 51 has solidified parts at the respective edges of the first main surface 51a and the second main surface 51b, cracks and chips are less likely to occur on both the first main surface 51a side and the second main surface 51b side of the thermistor plate 51, and as a result, the mechanical strength of the thin plate thermistor 5 can be further improved.

[0109] Furthermore, in the above embodiment, for example, the thin plate thermistor 5 may be configured without a common electrode 52. Alternatively, for example, the thin plate thermistor 5 may be configured without a common electrode 52, and the first divided electrode 53a and the second divided electrode 53b may be replaced with a first divided electrode and a second divided electrode, which include a second main surface portion located on a part of the second main surface 51b of the thermistor plate 51, a side portion connected to the second main surface portion and located on the side surface of the thermistor plate 51, and a first main surface portion connected to the side portion and located on the first main surface 51a of the thermistor plate 51.

[0110] The advantages of using the thin-plate thermistor 5 described above are miniaturization and thinning. Combining it with the sandwich structure device 2 is advantageous for miniaturizing and thinning the device, and from this viewpoint, it is preferable to combine the thin-plate thermistor 5 with the sandwich structure device 2. The thin-plate thermistor 5 of the above embodiment can be applied to existing packages other than the above-mentioned package, such as the sandwich structure device. For example, it can be applied to molded resin-encapsulated packages. In a molded resin-encapsulated package, the piezoelectric vibration device and the thin-plate thermistor are mounted flat on top of a glass epoxy substrate which serves as the base substrate, in parallel with a bonding material, and are electrically connected to the terminals of the substrate by wire bonding or the like. The upper part, including these components, is then covered with molded resin. With such a configuration, improved thermal conductivity can be expected.

[0111] Furthermore, although a laser is used to form a solidified portion 51D at the end of the thermistor plate 51 in the above embodiment, the invention is not limited to this, and a method other than a laser, such as using an electron beam, may be used to form a solidified portion 51D at the end of the thermistor plate 51. In addition, the surface roughness of one side of the thermistor plate can be made different from that of other sides by planar polishing with different surface roughnesses.

[0112] Furthermore, a reinforcing member, such as a quartz wafer or aluminum foil, that is thin and has a certain degree of structural strength, may be bonded to the common electrode 52 of the thin plate thermistor 5 in the above embodiment. If a hard material such as a quartz wafer is used as the reinforcing member, the strength of the thin plate thermistor 5 will be greatly increased, and the mounting of the thin plate thermistor 5 to the sandwich structure device 2 will be easier. When using a quartz wafer as the reinforcing member, it is desirable to deposit a film on it to improve adhesion to the common electrode 52. In addition, if an insulator is used as the reinforcing member, it will not be necessary to perform an insulating treatment on the top surface of the device 1 (the surface opposite to the surface facing the common electrode 52 of the reinforcing member (the back side)) after mounting the thin plate thermistor 5 to the sandwich structure device 2.

[0113] Furthermore, in the above embodiment, a sintered material obtained by sintering a pure metal such as molybdenum or tungsten as the sintering material may be placed on the first main surface 51a of the thermistor plate 51 to serve as a common electrode. This improves the strength of the thin-plate thermistor 5 and allows the thickness of the thermistor plate 51 to be reduced by the thickness of the sintered material serving as the common electrode 52. In addition, since tungsten has a thermal conductivity similar to that of aluminum, heat transfer throughout the thin-plate thermistor 5 becomes faster, improving the thermal responsiveness of the thin-plate thermistor 5.

[0114] Furthermore, in the above embodiment, for example, a common electrode 52 may be formed on the first main surface 51a of the thermistor plate 51 by applying Ag paste to the entire or substantially entire surface of the first main surface 51a of the thermistor plate 51 and baking it. In this case, the common electrode 52 functions as the original intermediate electrode and also functions as a reinforcing member that improves the strength of the thin plate thermistor 5. Instead of Ag paste, a common electrode 52 may be formed on the first main surface 51a of the thermistor plate 51 using Cr-Au, and then epoxy resin as a reinforcing member may be provided on the surface of the common electrode 52 opposite to the surface facing the thermistor plate 51 (the back side). In these cases, it is possible to improve the strength of the thin plate thermistor 5 while preventing deterioration of the resistance characteristics of the thin plate thermistor 5.

[0115] Furthermore, the contents of the above embodiments and the contents of the modified examples may be combined as appropriate. [Industrial applicability]

[0116] The present invention can be widely applied to thin-plate thermistors used as temperature sensors and thin-plate thermistor-mounted piezoelectric vibration devices that incorporate thin-plate thermistors. [Explanation of symbols]

[0117] 1: Thin-plate thermistor-equipped piezoelectric vibration device 2: Sandwich structure device 5: Thin-plate thermistor 51: Thermistor plate 51a: First Main Face 51b: 2nd main side 52: Common electrode 53, 53a, 53b: Segmented electrodes

Claims

1. A single-plate thermistor plate, including one surface and another surface opposite to the first surface with a rougher surface than the first surface, A first divided electrode and a second divided electrode are formed on the aforementioned surface and divided on the said surface, A common electrode formed on the other surface, A thin-plate thermistor characterized by having the following features.

2. The thin-plate thermistor according to claim 1, characterized in that the first divided electrode, the second divided electrode, and the common electrode are PVD (Physical Vapor Deposition) films.

3. A piezoelectric vibration device comprising a piezoelectric diaphragm having excitation electrodes made of multiple metal film layers formed on its surface, a first sealing member joined to one main surface of the piezoelectric diaphragm, and a second sealing member joined to the other main surface of the piezoelectric diaphragm, The thin plate thermistor according to claim 1 or claim 2, It has, The thin plate thermistor is bonded to the surface of the piezoelectric vibration device. A piezoelectric vibration device equipped with a thin-plate thermistor, characterized by the above features.

4. A piezoelectric diaphragm having excitation electrodes made of multiple metal film layers formed on its surface, The thin plate thermistor according to claim 1 or claim 2, A package housing the piezoelectric diaphragm and the thin-plate thermistor, A piezoelectric vibration device equipped with a thin plate thermistor, characterized by having the following features.

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