WO2024111495A1 - Thin-plate thermistor and thin-plate thermistor-mounted piezoelectric vibration device - Google Patents

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

Thin plate thermistor and piezoelectric vibration device equipped with thin plate thermistor

The present invention relates to a thin plate thermistor used as a temperature sensor and a piezoelectric vibration device equipped with a thin plate thermistor.

In recent years, with the increasing precision of various electronic devices, there is a demand for temperature-compensated piezoelectric vibration devices that compensate for frequency fluctuations caused by changes in environmental temperature, and thermistor-equipped piezoelectric vibration devices, which are piezoelectric vibration devices equipped with a thermistor as a temperature sensor, are widely used.

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

Such a thermistor-equipped piezoelectric vibration device is configured such that a quartz crystal plate with an excitation electrode formed thereon is housed in a ceramic package, and a thermistor is attached to the outside of the plate to detect the environmental temperature surrounding the quartz crystal unit (see, for example, Patent Document 1).

Thermistors have a laminated structure in which multiple layers of thermistor material and operating electrodes are stacked together, and those with a thickness of about 0.3 mm to 0.1 mm are commercially available and in use.

JP 2016-100737 A

Thermistors are required to detect the temperature environment surrounding the quartz crystal unit with a small time lag. However, the thermistors used to date have a laminated structure, which means that they require a certain thickness (height). In addition, the electrodes of laminated thermistors are made of thick film electrodes produced by screen printing, etc., making the structure unsuitable for making thin thermistors.

For this reason, instead of forming the thermistor in a laminated configuration in which multiple thermistor material layers and operating electrodes are stacked in multiple layers, it is conceivable to form the thermistor in a configuration in which electrodes are formed on the surface of a single thermistor plate, but so far no thermistors in a configuration in which electrodes are formed on the surface of a single thermistor plate have been put to practical use. In such a thermistor in a configuration in which electrodes are formed on the surface of a single thermistor plate, a first split electrode and a second split electrode that are split into two on one surface and each serve as an operating electrode may be formed, and a common electrode that serves as a relay electrode may be formed on the other surface of the thermistor plate (the surface opposite to the first surface). In such cases, it is desirable to improve the resistance characteristics of the thermistor by arranging the first split electrode, the second split electrode, and the common electrode in consideration of the surface roughness of the one surface and the other surface of the thermistor plate.

In view of the above problems, the present invention aims to provide a thin plate thermistor that improves the resistance characteristics of the thin plate thermistor by taking into account the surface roughness between one side and the other side of the thermistor plate, and a piezoelectric vibration device equipped with such a thin plate thermistor.

In order to achieve the above object, the thin plate thermistor of the present invention is characterized by having a single thermistor plate including one surface and another surface opposite to the first surface and having a surface roughness greater than that of the first surface, a first split electrode and a second split electrode formed on the first surface and split on the first surface, and a common electrode formed on the other surface.

　With this configuration, the first and second split electrodes, which serve as the working electrodes, are formed on one side of the thermistor plate with the smaller surface roughness, so there is less variation in the area in which the first and second split electrodes are formed compared to when the first and second split electrodes, which serve as the working electrodes, are formed on the other side with the larger surface roughness, and this makes it possible to suppress variation in the resistance characteristics of the thin plate thermistor. In particular, since the resistance characteristics of a thin plate thermistor are determined by the area of the first and second split electrodes facing the thermistor plate, forming the first and second split electrodes, which require precise areas, on the one side with the smaller surface roughness is an advantageous configuration for stabilizing the resistance characteristics of the thin plate thermistor.

In addition, by forming the first and second split electrodes on the surface with the smaller surface roughness, the adhesion of the first and second split electrodes to that surface of the thermistor plate is improved and electrical conductivity is stabilized, allowing for a stable connection when a measurement probe or the like is brought into contact with the first and second split electrodes, making it possible to accurately measure the resistance characteristics of the thin plate thermistor.

Furthermore, by forming a common electrode that serves as a relay electrode on the other side of the thermistor plate with the greater surface roughness, the surface area of the portion where the common electrode is formed increases relative to the apparent area, and the total amount of conductors involved in the common electrode increases accordingly, improving conductivity. The common electrode plays a role in preventing unnecessary resistance values from occurring in the thin plate thermistor, and since conductivity does not decrease as the surface area of the common electrode increases, the resistance value of the thin plate thermistor is not deteriorated. In particular, with miniaturized thin plate thermistors, as the resistance value of the common electrode increases, it becomes difficult to satisfy characteristics below a specified resistance value, but by forming a common electrode on the other side of the thermistor plate with the greater surface roughness, characteristics below a specified resistance value can be satisfied.

The first and second divided electrodes, as well as the common electrode, may be PVD (Physical Vapor Deposition) films.

With this configuration, the electrodes (first split electrode, second split electrode, common electrode) have a dense film configuration, making them excellent in terms of conductivity and adhesion to the thermistor plate. Also, the electrodes can be formed so that their area is the desired area, which results in stabilizing the resistance characteristics of the thin plate thermistor. This is particularly effective in stabilizing the resistance characteristics of miniaturized thin plate thermistors.

A piezoelectric vibration device equipped with a thin plate thermistor according to the present invention comprises a piezoelectric vibration device including a piezoelectric vibration plate having an excitation electrode formed on its surface and made of a plurality of metal film layers, a first sealing member bonded to one main surface of the piezoelectric vibration plate, and a second sealing member bonded to the other main surface of the piezoelectric vibration plate; and the thin plate thermistor, and is characterized in that the thin plate thermistor is bonded to the surface of the piezoelectric vibration device.

With this configuration, the use of a thin-plate thermistor with excellent resistance characteristics can improve the accuracy of detecting the temperature of the piezoelectric diaphragm.

Another thin plate thermistor-mounted piezoelectric vibration device according to the present invention is characterized in that it has a piezoelectric vibration plate having an excitation electrode made of multiple metal film layers formed on its surface, the thin plate thermistor, and a package that houses the piezoelectric vibration plate and the thin plate thermistor.

With this configuration, the use of a thin-plate thermistor with excellent resistance characteristics can improve the accuracy of detecting the temperature of the piezoelectric diaphragm.

In accordance with the present invention, the first and second split electrodes serving as the working electrodes are formed on one side of the thermistor plate with the smaller surface roughness, so that the areas in which the first and second split electrodes are formed are less likely to vary compared to when the first and second split electrodes serving as the working electrodes are formed on the other side with the larger surface roughness, and the variation in the resistance characteristics of the thin plate thermistor can be suppressed. In particular, since the resistance characteristics of a thin plate thermistor are determined by the areas of the first and second split electrodes facing the thermistor plate, forming the first and second split electrodes, which require precise areas, on one side with the smaller surface roughness is advantageous for stabilizing the resistance characteristics of the thin plate thermistor.

1A is a perspective view of a thin plate thermistor according to a first embodiment of the present invention, and FIG. 1B is a cross-sectional view of the thin plate thermistor of FIG. 1A taken along the line BB. 2A is a plan view showing a first main surface of the thin plate thermistor of FIG. 1, and FIG. 2B is a plan view showing a second main surface of the thin plate thermistor of FIG. 2 is a diagram for explaining a part (laser irradiation onto a thermistor flat plate wafer) in the manufacturing process of the thin plate thermistor of FIG. 1 . FIG. 10 is a plan view of a thin plate thermistor-equipped piezoelectric vibration device according to a second embodiment of the present invention. FIG. 5 is a cross-sectional view of the thin plate thermistor mounted piezoelectric vibration device shown in FIG. 4 along line AA. 5A is a plan view showing a first main surface of a piezoelectric diaphragm in the sandwich structure device of FIG. 4, and FIG. 5B is a plan view showing a second main surface of the piezoelectric diaphragm in the sandwich structure device of FIG. 4. 5A is a plan view showing a first main surface of a first sealing member in the sandwich structure device of FIG. 4, and FIG. 5B is a plan view showing a second main surface of the first sealing member in the sandwich structure device of FIG. 4. 5A is a plan view showing a first main surface of a second sealing member in the sandwich structure device of FIG. 4, and FIG. 5B is a plan view showing a second main surface of the second sealing member in the sandwich structure device of FIG. 4. FIG. 11 is an exploded perspective view of a thin plate thermistor-equipped piezoelectric vibration device according to a third embodiment of the present invention. 10 is a bottom view of the thin plate thermistor mounted piezoelectric vibration device of FIG. 9 during assembly. 11 is a cross-sectional view of the thin plate thermistor-equipped piezoelectric vibration device shown in FIG. 10 along the line CC. A cross-sectional view of a thin plate thermistor-equipped piezoelectric vibration device according to a fourth embodiment of the present invention.

First Embodiment
A thin plate thermistor according to a first embodiment of the present invention will be described in detail below with reference to Figures 1 to 3. Note that Figures 1 to 3 and Figures 4 to 8 used in the following description are illustrated using the same X-axis, Y-axis, and Z-axis.

First, the structure of the thin plate thermistor 5 will be described with reference to Figs. 1 and 2. Fig. 1(a) is a perspective view of the thin plate thermistor 5, and Fig. 1(b) is a cross-sectional view taken along line B-B of the thin plate thermistor 5 shown in Fig. 1(a). Fig. 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 Fig. 1, and Fig. 2(b) is a plan view showing the second main surface 51b, which is the main surface (other main surface) on the opposite side (back side) to the first main surface 51a, of the thin plate thermistor 5 shown in Fig. 1. Note that in Figs. 1 and 2, the electrodes (common electrode 52, split electrodes 53) are hatched, and the thermistor plate 51 is not hatched.

The thin plate thermistor 5 is a thin NTC (Negative Temperature Coefficient) thermistor. An NTC thermistor is a type of thermistor whose resistance value decreases as the temperature increases.

As shown in Figures 1(a) and (b), the thin plate thermistor 5 is configured to have a thermistor plate 51 which is a single plate, a common electrode 52 which is formed on the first main surface 51a of the thermistor plate 51 and serves as a relay electrode, and a polarized electrode 53 which is formed on the second main surface 51b of the thermistor plate 51 by dividing it on the second main surface 51b and serves as an operating electrode.

The thermistor plate 51 is thin and rectangular in plan view. For example, a semiconductor ceramic plate whose main component is manganese or a semiconductor ceramic plate whose main components are manganese and nickel is used as the thermistor plate 51.

In the thermistor plate 51, the first main surface 51a (the center of the first main surface 51a) has a larger surface roughness than 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 center of the main surface (first main surface 51a, second main surface 51b) on which most of the electrodes (common electrode 52, split electrode 53) are formed is compared. In addition, in the first main surface 51a of the thermistor plate 51, the surface roughness is smaller at the ends than at the center. The surface roughness is greatest in the order of the center of the first main surface 51a, the second main surface 51b, and the ends 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 ends of the first main surface 51a). In other words, the ends of the first main surface 51a, the second main surface 51b, and the center of the first main surface 51a are smooth surfaces in that order.

Also, the first main surface 51a of the thermistor plate 51 has a protuberance at least on a part of the edge. This protuberance is formed by a solidified portion 51D that solidifies after the thermistor plate 51 (the thermistor plate wafer 51A that is the basis of the thermistor plate 51) melts, and the solidified portion 51D is a laser mark (see FIG. 3).

As shown in FIG. 2(a), the common electrode 52 is formed on the entire surface (or almost 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 film formation method such as sputtering or vacuum deposition.

As shown in FIG. 2(b), the split electrodes 53 are arranged along one direction of the second main surface 51b of the thermistor plate 51, split into two at both ends with a certain distance between them. In the following, one of the split electrodes 53 may be referred to as the "first split electrode 53a" and the other as the "second split electrode 53b". The split electrodes 53 (first split electrode 53a, second split electrode 53b) are thin metal films, and are PVD films formed by a PVD film formation method such as sputtering or vacuum deposition. By forming the common electrode 52 and split electrodes 53 (first split electrode 53a, second split electrode 53b) as PVD films, an extremely thin plate thermistor 5 can be made.

The thin plate thermistor 5 has terminals as resistors formed by the first split electrode 53a and the second polarized 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 first split electrode 53a and the second polarized electrode 53b to the other of the first split electrode 53a and the second polarized electrode 53b via the common electrode 52. This configuration allows the cross-sectional area of the conductive path to be increased, and also allows the conductive path to be a path in which the first polarized electrode 53a and the second split electrode 53b and the common electrode 52 face each other. For this reason, the resistance value can be reduced with electrodes of small area (the common electrode 52, the first split electrode 53a, the second split electrode 53b), the resistance characteristics of the thin plate thermistor 5 are easily stabilized, and the voltage resistance performance of the thin plate thermistor 5 is improved.

When the thin plate thermistor 5 is configured such that the distance between the first divided electrode 53a and the second divided electrode 53b is small, depending on the applied voltage, the conductive path from one of the first and second polarized electrodes 53a and 53b to the other of the first and second polarized electrodes 53a and 53b (this path does not include the common electrode 52) becomes dominant, and the desired resistance value may not be obtained. Therefore, as shown in FIG. 1(b), if 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 them so that G2a+G2b<G1 is satisfied. When set in this way, the desired resistance value can be obtained, and the accuracy of the temperature detected by the thin plate thermistor 5 can be stabilized.

Furthermore, the larger the contact area of the first split electrode 53a and the second split electrode 53b with the temperature detection target device, the more accurately the thin plate thermistor 5 can detect the temperature of the temperature detection target device. For this reason, it is better for the first split electrode 53a and the second split electrode 53b to have a large area, but if the area is made too large, a short circuit between the first split electrode 53a and the second split electrode 53b is likely to occur. On the other hand, if the contact area of the first split electrode 53a and the second split electrode 53b with the temperature detection target device becomes small, the accuracy of the temperature of the temperature detection target device detected by the thin plate thermistor 5 decreases. Therefore, depending on the desired resistance value, it is preferable that the total area of the first split electrode 53a and the second split electrode 53b is 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 manner, the thin plate thermistor 5 can perform stable temperature detection. If the total area of the first split electrode 53a and the second split electrode 53b is less than 40% of the area of the second main surface 51b of the thermistor plate 51, the first split electrode 53a and the second split electrode 53b of the thin plate thermistor 5 will be too small, and the resistance value of the thin plate thermistor 5 will be too high, which may make it impossible to accurately detect the temperature of the device to be detected. Also, if the total area of the first split electrode 53a and the second split 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 split electrode 53a and the second split electrode 53b, causing the thermistor to no longer function as a thermistor.

Next, the manufacturing process of the thin plate thermistor 5 will be described. In the manufacturing process of 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 or Mn-Fe material) is made into a slurry with a binder or the like, and a wafer-like green sheet of the thermistor plate 51 is created using a pressure film forming technique such as screen printing or doctor blade technology, and this is then sintered and molded into the wafer 51A that will become the thermistor plate 51 using a firing technique (sintering and molding process). Note that, hereinafter, the wafer 51A that will become the thermistor plate 51 is sometimes referred to as the "thermistor plate wafer 51A".

In this sintering process, the green sheet is placed on a firing setter made of alumina (Al ₂ O ₃ ) and fired, but 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 flat plate 51), which is the surface of the thermistor flat plate wafer 51A that was in contact with the firing setter, and the second surface 51bA (the surface that becomes the second main surface 51b of the thermistor flat plate 51), which is the surface opposite (back side) to the surface that was in contact with the firing setter, the first surface 51aA of the thermistor flat plate wafer 51A has a larger surface roughness than the second surface 51bA because manganese has melted out of the first surface 51aA.

Following the sintering process, a break line forming process is carried out to form break lines (small grooves) 51B in the thermistor plate wafer 51A.

In the break line forming process, first, the thermistor flat plate wafer 51A is irradiated from the first surface 51aA with a laser LA1 having a small irradiation area and a large power density (W/ ^cm2 ) as shown in Fig. 3(b) at the portion indicated by the dotted line in Fig. 3(a), and a break line 51B shown in Fig. 3(c) that does not penetrate the thermistor flat plate wafer 51A is formed on the first surface 51aA (first stage laser irradiation). After the break line 51B is formed by this first stage laser irradiation, as shown in Fig. 3(c), steep and tall burrs 51C are formed at both ends of the break line 51b of the thermistor flat plate wafer 51A, and chipping is likely to occur at the burr 51C portion.

Following the first-stage laser irradiation, in order to remove the burrs 51C created by the first-stage laser irradiation, the thermistor flat plate wafer 51A is irradiated with a laser LA2 having a large irradiation area and a small power density (W/cm ² ) as shown in FIG. 3(d) from the first surface 51aA side on which the break lines 51B are formed, at the portion indicated by the dotted line in FIG. 3(a) (second-stage laser irradiation). Comparing the first-stage laser irradiation with the second-stage laser irradiation, the irradiation area in the second-stage laser irradiation is larger than that in the first-stage laser irradiation, and the power density (W/cm ² ) in the second-stage laser irradiation is smaller than ^that in the first-stage laser irradiation. The second-stage laser irradiation melts the burrs 51C, and the melted portion subsequently solidifies, forming a solidified portion 51D as a laser mark. In each of the areas surrounded by the break lines 51B (areas that will become one thermistor flat plate 51) on the first surface 51aA of the thermistor flat plate wafer 51A after the formation of the solidified portion 51D, the surface roughness is smaller at the ends than at the center, and a slight protrusion (a protrusion lower than the height of the burrs 51C) is formed in at least a portion of the ends, thereby ensuring a curved surface at the ends.

Here, in the thermistor plate wafer 51A after the break line formation process, the surface roughness of the end of the area surrounded by the break lines 51B on the first surface 51aA is the smallest, the surface roughness of the second surface 51bA is the second smallest, and the surface roughness of the center of the area surrounded by the break lines 51B on the first surface 51aA is the largest.

In the break line forming process, between the first and second laser irradiations, the thermistor flat plate wafer 51A may be irradiated with a laser from the first surface 51aA side on which the break line 51B is formed to the dotted line in the dashed line in FIG. 3(a) to make the depth of the break line 51B deeper or penetrate the laser irradiated portion (intermediate stage laser irradiation). In this way, when the thermistor flat plate wafer 51 is broken along the break line 51B, damage to the thin plate thermistor 5 can be suppressed. When the intermediate stage laser irradiation is compared with the first stage laser irradiation and the second stage laser irradiation, for example, the irradiation area in the intermediate stage laser irradiation = the irradiation area in the first stage laser irradiation < the irradiation area in the second stage laser irradiation, and the value of the light intensity per unit area in the intermediate stage laser irradiation ≥ the power density in the first stage laser irradiation (W/cm ² ) > the power density in the second stage laser irradiation (W/cm ² ).

Following the break line forming process, an electrode forming process is performed in which electrodes (common electrode 52, first divided electrode 53a, second divided electrode 53b) are formed on the thermistor flat plate wafer 51A. In the electrode forming process, an electrode film (metal film) is formed by sputtering on a predetermined area (area surrounded by break lines 51B on the first surface 51aA) of the thermistor flat plate wafer 51A after the break line forming process, and patterned using photolithography technology to form the common electrode 52, and an electrode film (metal film) is formed by sputtering on a predetermined area (area behind the area surrounded by break lines 51B on the first surface 51aA) of the thermistor flat plate wafer 51A after the break line forming process, and patterned using photolithography technology to form the first divided electrode 53a and the second divided electrode 53b.

As a specific metal material for the common electrode 52, the first polarized electrode 53a, and the second polarized electrode 53b, for example, a laminated film structure is adopted in which a Ti film is formed as a base layer, a NiTi film made of an alloy of Ni and Ti is formed as an upper layer (middle layer), and an Au film is formed as a main layer (top layer) on the surface. When a laminated film structure of a Ti film, a NiTi film, and a Au film is adopted, when the thin plate thermistor 5 is finally soldered to a mounting board, solder erosion is unlikely to occur and a stable conductive bond can be achieved. Note that in the above laminated film structure, a _TiO2 film may be formed between the base layer (Ti film) and the middle layer (NiTi film). In addition, the metal film configurations of the first polarization electrode 53 a and the second split electrode 53 b may be different from those of the common electrode 52. For example, the metal film configurations of the first polarization electrode 53 a and the second split electrode 53 b may be a laminated film configuration of a Ti film, a NiTi film, and an Au film, and the film configuration of the common electrode 52 may be a laminated film configuration of a Ti film and an Au film.

Furthermore, in the above electrode film configuration, a Cr film or Ti film may be formed as an underlayer, and a laminated film configuration of an Au film, an Ag film, a Pt film, etc. may be formed on top of it, or a film configuration using only a Cu film may be formed. Note that when a laminated film configuration of an underlayer of a Cr film or Ti film and an Au film, an Ag film, a Pt film, or a single layer film configuration of a Cu film is adopted, they can be joined with a conductive resin adhesive.

Following the electrode formation process, the thermistor plate wafer 51A on which the common electrode 52, the first divided electrode 53a, and the second divided electrode 53b are formed is broken along the break lines 51B (breaking process). This results in individual thin plate thermistors 5 on which the common electrode 52, the first divided electrode 53a, and the second divided electrode 53b are formed, thereby completing the thin plate thermistors 5.

In the thin plate thermistor 5 described above, the surface roughness of the first main surface 51a of the thermistor plate 51 is smaller at the ends than at the center, so cracks and chips are less likely to occur on the first main surface 51a side of the ends of the thermistor plate 51, and as a result, the mechanical strength of the thin plate thermistor 5 can be improved. In addition, at least a portion of the end of the first main surface 51a of the thermistor plate 51 is raised, so cracks and chips are less likely to occur on the first main surface 51a side of the ends of the thermistor plate 51, and as a result, the mechanical strength of the thin plate thermistor 5 can be improved.

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, which 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, thereby improving the mechanical strength of the thin plate thermistor 5. Furthermore, by forming the solidified portion 51D as a laser mark, a curved surface can be easily formed at the solidified portion 51D.

In addition, since the first and second split electrodes 53a and 53b, which serve as the working electrodes, are formed on the second main surface 51b of the thermistor plate 51, which has the smaller surface roughness, the areas on which the first and second split electrodes 53a and 53b are formed are less likely to vary compared to when the first and second split electrodes 53a and 53b, which serve as the working electrodes, are formed on the first main surface 51a, which has the larger surface roughness, and this makes it possible to suppress 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 areas of the first and second split electrodes 53a and 53b facing the thermistor plate 51, forming the first and second split electrodes 53a and 53b, which require precise areas, on the second main surface 51b, which has the smaller surface roughness, is advantageous for stabilizing the resistance characteristics of the thin plate thermistor 5.

In addition, by forming the first split electrode 53a and the second split electrode 53b on the second main surface 51b of the thermistor plate 51, which has the smaller surface roughness, the adhesion of the first split electrode 53a and the second split electrode 53b to the second main surface 51b of the thermistor plate 5 is improved and the conductivity is stabilized, allowing a stable connection when a measurement probe or the like is brought into contact with the first split electrode 53a and the second split electrode 53b, making it possible to accurately measure the resistance characteristics of the thin plate thermistor 5.

In addition, by forming the common electrode 52, which serves as a relay electrode, on the first main surface 51a of the thermistor plate 51, which has the greater surface roughness, the surface area of the portion where the common electrode 52 is formed increases relative to the apparent area, and the total amount of conductors related to the common electrode 52 increases accordingly, improving the electrical conductivity. The common electrode 52 plays a role in preventing unnecessary resistance values from occurring in the thin plate thermistor 5, and the electrical conductivity does not decrease as the surface area of the common electrode 52 increases, so the resistance value of the thin plate thermistor 5 is not deteriorated. In particular, in a miniaturized thin plate thermistor 5, if the resistance value of the common electrode 52 increases, it becomes difficult to satisfy the characteristics below a predetermined resistance value. However, by forming the common electrode 52 on the first main surface 51a of the thermistor plate 5, which has the greater surface roughness, the characteristics below a predetermined resistance value can be satisfied.

Furthermore, by forming the first split electrode 53a, the second split electrode 53b, and the common electrode 52 as PVD films formed by a PVD film formation method such as sputtering or vacuum deposition, the first split electrode 53a, the second split electrode 53b, and the common electrode 52 have a dense film configuration, making them electrodes with excellent conductivity and adhesion to the thermistor plate 5.Furthermore, the electrodes can be formed so that they 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 a miniaturized thin plate thermistor 5.

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 FIGS.

FIG. 4 is a plan view of a piezoelectric vibration device 1 equipped with a thin plate thermistor. FIG. 5 is a cross-sectional view of the device 1 shown in the plan view in FIG. 4, taken along the line A-A. As shown in FIGS. 4 and 5, the piezoelectric vibration device 1 equipped with a thin plate thermistor is a device having a sandwich-structured piezoelectric vibration device (hereinafter also referred to as a "sandwich-structured device") 2 and the above-mentioned thin plate thermistor 5 mounted on the sandwich-structured device 2. Note that hereinafter, the "thin plate thermistor-equipped piezoelectric vibration device 1" may simply be referred to as "device 1." In device 1, for example, the thickness of the sandwich-structured device 2 is about 120 μm, while the thin plate thermistor 5 can be less than half the thickness of the sandwich-structured device 2 (about 50 μm).

As shown in FIG. 5, the sandwich structure device 2 is configured with 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 bonded together, and the piezoelectric diaphragm 10 and the second sealing member 30 are bonded together, thereby forming a substantially rectangular sandwich structure package.

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

With regard to each of Figures 4 to 8, in the piezoelectric diaphragm 10, both main surfaces of the piezoelectric diaphragm 10 are in the XZ plane, the direction parallel to the short side direction is the X-axis direction, the direction parallel to the long side direction is the Z-axis direction, and the direction perpendicular to the XZ plane is the Y-axis direction.

The piezoelectric diaphragm 10 has a vibration part 13 formed in a substantially rectangular shape, an outer frame part 14 that surrounds the outer periphery of the vibration part 13, and a holding part 15 that holds the vibration part 13 by connecting the vibration part 13 and the outer frame part 14. The area between the vibration part 13 and the outer frame part 14 is a cutout part (an opening that penetrates the piezoelectric diaphragm 10 in the thickness direction) except for the part where the holding part 15 is formed. As a result, the piezoelectric diaphragm 10 is configured such that the vibration part 13, the outer frame part 14, and the holding part 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.

In this embodiment, the holding portion 15 is provided at only one location between the vibration portion 13 and the outer frame portion 14. Furthermore, the vibration 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 the piezoelectric vibrations are not propagated to the outer frame portion 14. Note that the location where the holding portion 15 is formed is not limited to one location, and the holding portion 15 may be provided at two locations between the vibration portion 13 and the outer frame portion 14.

The first excitation electrode 111 is provided on the first main surface 11 side of the vibration part 13, and the second excitation electrode 121 is provided on the second main surface 12 side of the vibration part 13. The first excitation electrode 111 and the second excitation electrode 121 are each connected to an extraction electrode (extraction wiring electrode film) (the first extraction electrode 112 on the first main surface 11 side, and the second extraction electrode 122 on the second main surface 12 side) for connecting these excitation electrodes to external electrode terminals. The first extraction electrode 112 is extracted from the first excitation electrode 111 and connected to the connection bonding pattern 114 formed on the outer frame part 14 via the holding part 15. The second extraction electrode 122 is extracted from the second excitation electrode 121 and connected to the connection bonding pattern 124 formed on the outer frame part 14 via the holding part 15.

The first main surface 11 and the second main surface 12 of the piezoelectric diaphragm 10 are each formed with a bonding pattern for bonding the piezoelectric diaphragm 10 to the first sealing member 20 and the second sealing member 30. The bonding pattern includes a sealing pattern for hermetically sealing the internal space of the package, and a conductive pattern for conducting wiring and electrodes. Note that in Figures 6(a), (b), 7(b), and 8(a), the bonding regions where the bonding patterns are formed are indicated by diagonal hatching.

As sealing patterns in 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 a ring shape in a planar view. The area inside the vibration-side first bonding pattern 113 and the vibration-side second bonding pattern 123 becomes the sealing area of the vibration 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.

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

In addition, 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 a through electrode is formed on the inner wall surface of each through hole 16 to provide electrical continuity between the first main surface 11 and the second main surface 12. Specifically, four through holes 16 and through electrodes are formed to provide electrical continuity between the connection bonding pattern 115 and the connection bonding pattern 125, and one through hole 16 and through electrode is formed to provide electrical continuity between the connection bonding pattern 116 and the connection bonding pattern 124.

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 connection bonding patterns 114 to 116, 124, and 125 can be formed in the same process. Specifically, they can be formed from an underlayer (Ti film) formed by physical vapor deposition on both main surfaces (first main surface 11, second main surface 12) of the piezoelectric diaphragm 10, and a bonding film (Au film) formed by physical vapor deposition on the underlayer. In addition, the configuration of the laminated film forming the bonding pattern is not limited to a two-layer structure of a Ti film and an 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).

Figure 7(a) is a plan view showing the first main surface 21, which is one of the main surfaces (outer surface) of the single 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 (the bonding surface with the piezoelectric diaphragm 10) of the single first sealing member 20 before bonding. The first sealing member 20 is a rectangular 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 and smooth surface (mirror finish).

As shown in FIG. 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. The electrode pattern 211 is a mounting pad for mounting the thin plate thermistor 5 (see FIG. 4). The wiring pattern 212 is a wiring pattern that is part of the wiring path that connects the second excitation electrode 121 to the external electrode terminal 321 (see FIG. 8(b)). The wiring pattern 213 is a wiring pattern that is part of the wiring path that connects the first excitation electrode 111 to the external electrode terminal 321.

As shown in FIG. 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 conducting wiring and electrodes.

The sealing pattern in the first sealing member 20 is a sealing-side first bonding pattern 221. The sealing-side first bonding pattern 221 is formed in a ring shape in a plan view, and its inner region becomes the sealing region. As the conductive pattern in the first sealing member 20, four connection bonding patterns 222 are formed near the four corners (corners) outside the sealing region (outside the sealing-side first bonding pattern 221), and connection bonding patterns 223 to 225 are formed within the sealing region (inside the sealing-side first bonding pattern 221). The connection bonding pattern 224 and the connection bonding pattern 225 are connected by a wiring pattern 226.

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 a through electrode is formed on the inner wall surface of each through hole 23 to provide electrical continuity between the first main surface 21 and the second main surface 22. Specifically, four through holes 23 and through electrodes are formed to provide electrical continuity between the electrode pattern 211 or the wiring patterns 212, 213 and the connection bonding pattern 222, one through hole 23 and through electrode are formed to provide electrical continuity between the wiring pattern 212 and the connection bonding pattern 223, and one through hole 23 and through electrode are formed to provide electrical continuity between the wiring pattern 213 and the connection bonding pattern 225.

In the first sealing member 20, the sealing-side first bonding pattern 221, the connection bonding patterns 222 to 225, and the wiring pattern 226 can be formed in the same process. Specifically, they can be formed from an underlayer (Ti film) formed by physical vapor deposition on the second main surface 22 of the first sealing member 20, and a bonding film (Au film) formed by physical vapor deposition on the underlayer.

Figure 8(a) is a plan view showing the first main surface 31, which is one of the main surfaces (the surface to be bonded to the piezoelectric diaphragm 10), of the second sealing member 30 alone before bonding. Figure 8(b) is a plan view showing the second main surface 32, which is the other main surface (outer surface) of the second sealing member 30 alone before bonding. The second sealing member 30 is a rectangular 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 and smooth surface (mirror-finished).

As shown in FIG. 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 conducting wiring and electrodes.

The sealing pattern in the second sealing member 30 is a sealing-side second bonding pattern 311. The sealing-side second bonding pattern 311 is formed in a ring shape in a plan view, and its inner region becomes the sealing region. As the conductive pattern in the second sealing member 30, four connection bonding patterns 312 are formed near the four corners (corners) outside the sealing region (outside the sealing-side second bonding pattern 311).

As shown in FIG. 8(b), the second main surface 32 of the second sealing member 30 is provided with four external electrode terminals 321 that electrically connect the device 1 to the outside. The external electrode terminals 321 are located at the four corners (corner portions) of the second sealing member 30.

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 a through electrode is formed on the inner wall surface of each through hole 33 to provide electrical continuity between the first main surface 31 and the second main surface 32. Specifically, four through holes 33 and through electrodes are formed to provide electrical continuity between the connection bonding pattern 312 and the external electrode terminal 321.

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

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 each other, 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 each other, to manufacture a sandwich structure package. That is, 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. This hermetically seals the internal space of the package, that is, the space in which the diaphragm 13 is housed.

At this time, the connection 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 conduction is achieved between the first excitation electrode 111 and the second excitation electrode 121 and the external electrode terminals 321 at the lower right and upper left of Figure 8 (b).

The thin plate thermistor 5 is mounted on the sandwich structure device 2 with the second main surface 51b, on which the split electrode 53 is formed, as the underside (the joining surface with the sandwich structure device 2), and the split electrode 53 is electrically joined to the electrode pattern 211 of the first sealing member 20. The thin plate thermistor 5 mounted on the sandwich structure device 2 is also arranged to be electrically conductive with the external electrode terminals 321 at the upper right and lower left of Figure 8 (b).

As described above, the thin plate thermistor 5 has wide-area metal electrodes (common electrode 52, split electrodes 53), and thus can act advantageously as a shielding member for the sandwich structure device 2. In order to utilize the thin plate thermistor 5 also as a shielding member, the thin plate thermistor 5 is arranged in the sandwich structure device 2 so that, in a plan view of the device 1, at least a portion of the thin plate thermistor 5 overlaps with the vibrating portion 13 of the sandwich structure device 2 (see FIG. 4). Furthermore, if the thin plate thermistor 5 is arranged so that it overlaps with the entire first excitation electrode 111 and the second excitation electrode 121 in a plan view, the shielding effect of the thin plate thermistor 5 can be maximized, which is more preferable.

The thin plate thermistor 5 is arranged in the sandwich structure device 2 so that both ends overlap the outer frame portion 14 at least on 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 brittle materials such as glass and quartz are used. For this reason, the strength of the sandwich structure device 2 is particularly low in the center (the area where the outer frame portion 14 of the piezoelectric diaphragm 10 does not exist). In such a sandwich structure device 2, if the thin plate thermistor 5 is arranged in the center 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 response to this, by joining the thin plate thermistor 5 to the outer periphery of the sandwich structure device 2 (the area where the outer frame portion 14 of the piezoelectric diaphragm 10 exists), that is, by arranging the ends of the thin plate thermistor 5 so as to overlap the outer frame portion 14, it is possible to suppress cracking of the first sealing member 20 and ensure the strength of the device 1. In particular, by overlapping the thin plate thermistor 5 with the sealing portion (sealing pattern such as the vibration-side first bonding pattern 113) of the sandwich structure device 2, the strength of the device 1 is stabilized. Note that, although Figs. 4 and 5 show an example in which both ends of the thin plate thermistor 5 are arranged so as to overlap the outer frame portion 14 on two sides facing 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 sides facing in the long direction of the sandwich structure device 2. Furthermore, the thin plate thermistor 5 may be arranged so as to overlap not only two opposing sides of the sandwich structure device 2, but also three or four sides.

The split electrodes 53 and the electrode patterns 211 are electrically connected by a conductive resin adhesive 61 (see FIG. 5). However, this is not limited to this, and the split electrodes 53 and the electrode patterns 211 may be connected by Au (gold) bumps. Furthermore, 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) is filled with a non-conductive resin adhesive 62 (see FIG. 5). The non-conductive resin adhesive 62 may not only be filled on the underside of the thin plate thermistor 5, but may also be used as a sealing resin that seals the entire thin plate thermistor 5. Note that 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.

In this way, when the thin plate thermistor 5 is surface-bonded to the sandwich structure device 2 using the conductive resin adhesive 61 and the 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 maintained at a temperature close to that of the vibrating part 13 of the sandwich structure device 2. 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.

When the conductive resin adhesive 61 and the non-conductive resin adhesive 62 are used to bond the thin plate thermistor 5, it is preferable that the conductive resin adhesive 61 has a higher thermal conductivity than the non-conductive resin adhesive 62. This can further improve the thermal conductivity between the thin plate thermistor 5 and the sandwich structure device 2. In addition, 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 can ensure sufficient thermal conduction between the thin plate thermistor 5 and the sandwich structure device 2, and the accuracy of the temperature of the sandwich structure device 2 detected by the thin plate thermistor 5 can be sufficient. In addition, it is preferable that the non-conductive resin adhesive 62 has a higher hardness than the conductive resin adhesive 61. This can relieve stress between the thin plate thermistor 5 and the sandwich structure device 2 and improve the package strength of the device 1.

The above-mentioned piezoelectric vibration device 1 equipped with a thin plate thermistor is less likely to crack or chip at the end of the thermistor plate 51, and by providing the thin plate thermistor 5 of the first embodiment, which has excellent resistance characteristics, it is possible to improve the temperature detection accuracy. 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 arranged so as to be the surface opposite to the surface facing the sandwich structure device 2 (piezoelectric vibration plate 10), and by arranging at least a solidified portion 51D (curved surface) on the outer surface of the thin plate thermistor 5, the end of the thin plate thermistor 5 is less likely to crack or chip, which is desirable in terms of increasing mechanical strength.

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 Fig. 9 to Fig. 11. Fig. 9 is an exploded perspective view of a thin plate thermistor-mounted piezoelectric vibration device XcX. Fig. 10 is a bottom view of the thin plate thermistor-mounted piezoelectric vibration device XcX shown in the exploded perspective view of Fig. 9. Fig. 11 is a CC cross-sectional view of the thin plate thermistor-mounted piezoelectric vibration device XcX of Fig. 10.

As shown in Figures 9 to 11, the thin plate thermistor-mounted piezoelectric vibration device XcX is a device having a package 1X with an upper storage section 11AX and a lower storage section 11BX, a piezoelectric vibration plate 2X stored in the upper storage section 11AX, the above-mentioned thin plate thermistor 5 stored in the lower storage section 11BX, and a lid 3X that hermetically seals the upper storage section 11A.

The package 1X is made of ceramic and has a rectangular parallelepiped shape overall, with 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.

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

Mount electrodes 16X, 17X are made of multiple metal films, and are laminated in the order of a W (tungsten) layer, a Ni (nickel) layer, and a Au (gold) layer. The W layer is integrally formed by firing with the ceramic material that constitutes the package, and the Ni layer and Au layer are formed on the W layer by plating. Sealing section 10X also has a metal layer configuration similar to that of mounting electrodes 16X, 17X, with a laminated configuration of a W layer, a Ni layer, and a Au layer laminated in that order. Note that mounting electrodes 18X, 19X and mounting electrodes 12X, 13X, 14X, and 15X, which will be described later, are also manufactured using the same manufacturing method, and each has a laminated configuration of a W layer, a Ni layer, and a Au layer laminated in that order.

Lower storage section 11BX has a concave rectangular storage configuration that opens downward, and mounting electrodes 18X, 19X made of metal film are formed on the bottom of lower storage section 11BX. Mounting electrodes 18X, 19X are rectangular with long and short sides, and are formed so that the long side of mounting electrode 18X faces the long side of mounting electrode 19X in the direction along the long side of package 1X. Mounting electrodes 18X, 19X may also be formed so that they are aligned in the direction along the short side of package 1X.

The four corners of the lower storage section 11BX are provided with mounting electrodes 12X, 13X, 14X, and 15X that are located higher than the bottom. Each of the mounting electrodes 12X, 13X, 14X, and 15X has a rectangular shape, and the mounting electrodes 12X and 14X are electrically connected to the mounting electrodes 16X and 17X, and the mounting electrodes 13X and 15X are electrically connected to the mounting electrodes 18X and 19X by internal wiring within the package 1X.

An AT-cut quartz plate is used for the piezoelectric diaphragm 2X, and the piezoelectric diaphragm 2X is generally rectangular. Excitation electrodes 21X and 22X are formed in the center of the front and back of the piezoelectric diaphragm 2X, and the excitation electrodes 21X and 22X are drawn to the outer periphery of the piezoelectric diaphragm 2X by strip-shaped lead electrodes 21aX and 22aX having a width. The excitation electrodes 21X and 22X are rectangular, and on one main surface of the piezoelectric diaphragm 2X, the excitation electrode 21X is drawn from one short corner to an end of one main surface of the piezoelectric diaphragm 2X by the lead electrode 21aX, and on the other main surface of the piezoelectric diaphragm 2X, the excitation electrode 22X is drawn from one short corner to an end of the other main surface of the piezoelectric diaphragm 2X by the lead electrode 22aX. As a result, the excitation electrodes 21X and 22X are drawn to one short side of the piezoelectric diaphragm 2X.

The excitation electrodes 21X, 22X and the extraction electrodes 21aX, 22aX are configured 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 that. Note that the metal film configuration may be other than that described above, and well-known metal film configurations may be used, such as a Cr (chromium) layer as the base metal and an Ag (silver) layer as the upper layer. The excitation electrodes 21X, 22X and the extraction electrodes 21aX, 22aX may be PVD films formed by a PVD film formation method such as sputtering or vacuum deposition.

The thin plate thermistor 5 has the second main surface 51b on which the split electrodes 53 are formed as the upper surface (the surface to be joined to the package 1X), and the split electrodes 53 (the first and second split electrodes 53
The semiconductor device is mounted on the package 1X by electrically connecting the mounting electrodes 18X and 19X at the bottom of the lower storage portion 11BX to the mounting electrodes 18X and 19X at the bottom of the lower storage portion 11BX.

The lid 3X is made of a thin metal or ceramic plate and has a rectangular shape corresponding to the outer size of the sealing portion 10X of the package 1X. The configurations of the lid 3X and the sealing portion 10X differ depending on the airtight 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 is configured by soldering a ring-shaped metal frame, 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 (inside the upper storage portion 11AX) to be in a steady state of a vacuum atmosphere or an inert gas atmosphere.

When hermetically sealing by soldering with a metal brazing material, for example an AuSu brazing material, the AuSu brazing material is preformed around the lid 3X, and the upper layer of the sealing portion 10X is plated with Au. By heating both of them in a specified atmosphere and temperature environment, a hermetic seal can be achieved by metal brazing.

A paste-like conductive resin adhesive S1 is applied to the mounting electrodes 16X and 17X of the upper storage section 11AX of the package 1X using a dispenser or the like. The conductive resin adhesive S1 is made of, for example, a silicone resin adhesive containing metal filler, but other resin materials such as polyimide-based resin materials may also be used. The piezoelectric diaphragm 2X with electrodes formed thereon is mounted on the applied conductive resin adhesive S1. Specifically, the piezoelectric diaphragm 2X is mounted on the upper storage section 11AX so that the extraction electrodes 21aX and 22aX are bonded to the conductive resin adhesive S1. The conductive resin adhesive S1 is then hardened by heating to conductively bond (electrically and mechanically bond) the piezoelectric diaphragm 2X and the mounting electrodes 16X and 17X. Note that the conductive resin adhesive S1 may be applied again from above the piezoelectric diaphragm 2X as necessary. In this embodiment, a configuration in which the adhesive is applied again is illustrated.

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, the metal brazing material sealing is achieved by using the metal brazing material S2, which is, for example, an AuSu brazing material.

The thin plate thermistor 5 is conductively joined to the lower storage section 11BX of the package 1X. A 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 stored in the lower storage section 11BX so that the split electrodes 53 (first split electrode 53a, second split electrode 53b) correspond to the applied conductive resin adhesive S1. The conductive resin adhesive S1 is then hardened by heating to conductively join (electrically and mechanically join) the first split electrode 53a and second split electrode 53b of the thin plate thermistor 5 to the mounting electrodes 18X and 19X. The conductive joining of the thin plate thermistor 5 may be performed by soldering.

Resin material M is injected into the lower storage section 11BX containing the thin plate thermistor 5 using a dispenser or the like to cover the thin plate thermistor 5 with the resin material M, and then the resin material M is hardened by heating. In this embodiment, a polyimide resin is used as the resin material M, but other resin materials may also be used. This protects the thin plate thermistor 5 from the outside air, allowing for stable temperature detection.

The above-mentioned piezoelectric vibration device XcX equipped with a thin plate thermistor is less likely to crack or chip at the end of the thermistor plate 51, and by being equipped with the thin plate thermistor 5 of the first embodiment, which has excellent resistance characteristics, it is possible to improve the accuracy of temperature detection.

Fourth Embodiment
A thin plate thermistor mounted piezoelectric vibrating device according to a fourth embodiment of the present invention will now be described in detail with reference to Fig. 12. Fig. 12 is a cross-sectional view of a thin plate thermistor mounted piezoelectric vibrating device XcY.

In the thin plate thermistor mounted piezoelectric vibration device XcY, a piezoelectric vibration plate 2X and a thin plate thermistor 5 are stored inside a storage section 51Y of a 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 storage section 51Y with an opening at the top. Mounting electrodes 54Y, 55Y (mounting electrode 55Y not shown) for the piezoelectric vibration plate 2X and mounting electrodes 56Y, 57Y for the thin plate thermistor 5 are formed on the bottom of the storage section 51Y. Mounting electrodes 52Y, 53Y are also formed on the bottom surface.

The extraction electrodes 21aX, 22aX (see FIG. 9) formed on both main surfaces of the piezoelectric diaphragm 2X are conductively bonded (electrically and mechanically bonded) to the mounting electrodes 54Y, 55Y by the conductive resin adhesive S1, and the piezoelectric diaphragm 2X is stored inside the storage section 51Y of the package 1Y. In addition, the first and second split electrodes 53a, 53b formed on the second main surface 51b of the thin plate thermistor 5 are conductively bonded (electrically and mechanically bonded) to the mounting electrodes 56Y, 57Y by the conductive resin adhesive S1, and the thin plate thermistor 5 is stored inside the storage section 51Y of the package 1Y.

The piezoelectric diaphragm 2X and thin plate thermistor 5 are stored in parallel inside the storage section 51Y of the package 1Y and are hermetically sealed by the lid 3X.

The above-mentioned piezoelectric vibration device XcY equipped with a thin plate thermistor is less likely to crack or chip at the end of the thermistor plate 51, and by being equipped with the thin plate thermistor 5 of the first embodiment, which has excellent resistance characteristics, it is possible to improve the temperature detection accuracy.

The thin plate thermistor is not limited to the thin plate thermistor 5 of the above embodiment, but can be modified in various ways.

For example, in the above embodiment, instead of performing the first stage laser irradiation and the second stage laser irradiation on the thermistor plate wafer 51 from the first surface 51aA side, which has the greater surface roughness, the first stage laser irradiation and the second stage laser irradiation can be performed from the second surface 51bA side, which has the lesser surface roughness, so that the end portion of the second main surface 51b of the thermistor plate 51 has a smaller surface roughness than the central portion, and at least a portion of the end portion is raised, and the thermistor plate 51 may have a solidified portion (another solidified portion) at the end portion of the second main surface 52b. In addition, by performing the first stage laser irradiation and the second stage laser irradiation on the thermistor flat plate wafer 51 from the first surface 51aA side and the second surface 51bA side, respectively, the surface roughness is smaller at the end portion than at the center portion of the first main surface 51a and the second main surface 51b of the thermistor flat plate 51, and at least a part of the end portion is raised, and the thermistor flat plate 51 may have a solidified portion and another solidified portion at each end portion of the first main surface 51a and the second main surface 51b. In the latter case, by having a solidified portion at each end portion of the first main surface 51a and the second main surface 51b, the thermistor flat plate 51 is less likely to crack or chip on both the first main surface 51a side and the second main surface 51b side of the end portion of the thermistor flat plate 51, and as a result, the mechanical strength of the thin plate thermistor 5 can be further improved.

Furthermore, in the above embodiment, for example, the thin plate thermistor 5 may not include the common electrode 52. For example, the thin plate thermistor 5 may not include the common electrode 52, and the first split electrode 53a and the second split electrode 53b may be replaced with a first split electrode and a second split electrode including a second main surface portion disposed on a part of the second main surface 51b of the thermistor plate 51, a side surface portion connected to the second main surface portion and disposed on a side surface of the thermistor plate 51, and a first main surface portion connected to the side surface portion and disposed on the first main surface 51a of the thermistor plate 51.

The advantage of using the thin plate thermistor 5 is that it can be made smaller and thinner, and by combining it with the sandwich structure device 2, it is advantageous to make the device smaller and thinner, and from this perspective, 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 packages, such as sandwich structure devices. For example, it can also be applied to a molded resin sealed package. In a molded resin sealed package, a piezoelectric vibration device and a thin plate thermistor are mounted flat on top of a glass epoxy substrate, which serves as a base substrate, in a state where they are arranged in parallel with a bonding material, and are electrically connected to the terminal portion of the substrate by wire bonding or the like. Then, the top including each of these components is covered with molded resin. With such a configuration, it is possible to expect improved thermal conductivity.

In addition, in the above embodiment, a laser is used to form the solidified portion 51D at the end of the thermistor plate 51, but this is not limited to the above, and for example, a means other than a laser, such as an electron beam, may be used to form the solidified portion 51D at the end of the thermistor plate 51. Furthermore, the surface roughness of one side and the other side of the thermistor plate can be made different by flat surface polishing with different surface roughness.

In addition, a reinforcing member that is thin and has a certain degree of structural strength, such as a quartz wafer or aluminum foil, may be attached to the common electrode 52 of the thin plate thermistor 5 of 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 is greatly increased, making it easier to attach the thin plate thermistor 5 to the sandwich structure device 2. When a quartz wafer is used as the reinforcing member, it is desirable to form a film on the common electrode 52 to improve adhesion. In addition, if an insulating material is used as the reinforcing member, it is not necessary to perform an insulating process on the top surface of the device 1 (the surface opposite (back side) of the reinforcing member to the surface facing the common electrode 52) after mounting the thin plate thermistor 5 on the sandwich structure device 2.

In the above embodiment, a sintered product obtained by sintering a pure metal such as molybdenum or tungsten as a sintering material may be disposed 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 product used as the common electrode 52. Tungsten has thermal conductivity comparable to that of aluminum, which speeds up heat transfer throughout the thin plate thermistor 5 and improves the thermal response of the thin plate thermistor 5.

In addition, in the above embodiment, for example, Ag paste may be applied to the entire or almost entire first main surface 51a of the thermistor plate 51 and baked to form a common electrode 52 on the first main surface 51a of the thermistor plate 51. In this case, the common electrode 52 functions as an original relay electrode and also functions as a reinforcing member that improves the strength of the thin plate thermistor 5. Instead of Ag paste, the common electrode 52 may be formed of Cr-Au on the first main surface 51a of the thermistor plate 51, and then an epoxy resin may be provided as a reinforcing member on the surface of the common electrode 52 opposite to the surface facing the thermistor plate 51 (back side). In these cases, the strength of the thin plate thermistor 5 can be improved while preventing deterioration of the resistance characteristics of the thin plate thermistor 5.

The above embodiments and variations may be combined as appropriate.

The present invention can be widely applied to thin plate thermistors used as temperature sensors and piezoelectric vibration devices equipped with thin plate thermistors.

1: Piezoelectric vibration device with thin plate thermistor 2: Sandwich structure device 5: Thin plate thermistor 51: Thermistor plate 51a: First main surface 51b: Second main surface 52: Common electrode 53, 53a, 53b: Split electrodes

Claims (4)

1. A single thermistor plate including a first surface and another surface opposite to the first surface and having a surface roughness greater than that of the first surface;
   a first divided electrode and a second divided electrode formed on the one surface and divided on the one surface;
   a common electrode formed on the other surface;
   A thin plate thermistor comprising:
2. The thin plate thermistor according to claim 1, characterized in that the first and second split electrodes, and the common electrode are PVD (Physical Vapor Deposition) films.
3. A piezoelectric vibration device including a piezoelectric diaphragm having an excitation electrode formed on a surface thereof and made of a plurality of metal film layers, a first sealing member bonded to one main surface of the piezoelectric diaphragm, and a second sealing member bonded to the other main surface of the piezoelectric diaphragm;
   The thin plate thermistor according to claim 1 or 2;
   having
   A thin plate thermistor-mounted piezoelectric vibration device, characterized in that the thin plate thermistor is bonded to a surface of the piezoelectric vibration device.
4. A piezoelectric diaphragm having an excitation electrode formed of a plurality of metal film layers on its surface;
   The thin plate thermistor according to claim 1 or 2;
   a package that houses the piezoelectric diaphragm and the thin plate thermistor;
   A piezoelectric vibration device equipped with a thin plate thermistor, comprising:
   

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