JPH02171011A - Manufacture of piezoelectric resonator - Google Patents

Abstract

PURPOSE:To educe the dispersion in the characteristic at mass-production effectively by decreasing the thickness of a sintered body prior to the formation of an energy confinement electrode placed on an outer surface of the sintered body and adjusting the frequency. CONSTITUTION:An electrode paste 22 made of Pt as a major component is coated onto a ceramic green sheet 21a to form an internal electrode. Then the paste 22 is applied to cover an electrode paste part 22a for an energy confinement electrode and an electrode paste part 22b for a connection conductor part. A sheet 21 is laminated so as to be overlapped onto the sheet 21a, pressed in the broadwise direction to form a laminating body, which is baked to form a sintered body 24. As a result, an internal electrode 32a based on the paste part 22a is formed in the sintered body 24 and piezoelectric ceramic layers 31,31a are formed above and under the electrode 32. Either of the upper and lower parts of the sintered body 24 is ground to make the thickness equal to that of the standard product thereby adjusting the frequency characteristic.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an energy-trapping type piezoelectric resonator using harmonics of thickness longitudinal vibration mode, and in particular, to a method for manufacturing an energy-trapping type piezoelectric resonator that uses harmonics of a thickness longitudinal vibration mode. The present invention relates to a method for obtaining a piezoelectric resonant device that has high characteristics and has less variation in characteristics.

[Conventional technology]

BACKGROUND ART Conventionally, an energy confinement type piezoelectric resonator device using a thickness longitudinal vibration mode using PZT-based piezoelectric ceramics has been known. This type of energy confinement type piezoelectric resonator is constructed by forming electrodes having a smaller area than the piezoelectric ceramic plate on both sides of the piezoelectric ceramic plate. However, it is difficult to use it in a higher frequency range, and when a material with an effective Poisson's ratio of less than 1/3 is used, it is not possible to trap the energy of the frequency-lowering type of thickness longitudinal vibration.

Therefore, in order to solve the above problem, Japanese Patent Application No. 62-235948 proposes that the effective Poisson's ratio can be increased by dividing the piezoelectric ceramic layer into several layers using three or more energy confinement electrodes. A structure has been disclosed that is capable of confining the energy of thickness longitudinal vibration in a frequency-reduced manner even when less than 1/3 of the piezoelectric material is used, and that can be used in a higher frequency range. A method of manufacturing this piezoelectric resonator device will be explained with reference to FIGS. 2 and 3.

As shown in FIG. 2, two ceramic green sheets 1 and 2 made of piezoelectric material are prepared. An electrode paste 3 is applied to the upper surface of the ceramic green sheet 1.2. The electrode paste 3 has an electrode paste part 3a for forming an electrode for energy confinement, and an electrode paste part 3b for forming a connecting conductive part for connection with the outside. Similarly, on the top surface of the ceramic green sheet 2,
The electrode paste 4 includes an electrode paste part 4a for forming an internal electrode and an electrode paste part 4 constituting a connecting conductive part.
b.

Further, an electrode paste 5 is applied to the lower surface of the ceramic green sheet 2 so as to have an electrode paste part 5a for forming an energy confinement electrode and an electrode paste part 5b for forming a connecting conductive part. has been done.

Among the electrode pastes 3 to 5, electrode paste parts 3a, 4a, 5a are used to form energy confinement electrodes.
are arranged so as to overlap in the thickness direction.

The ceramic green sheets 1.2 are stacked as shown in the figure, pressed together in the thickness direction, and then fired, thereby firing the ceramic green sheets and also firing the electrode pastes 3 to 5.

As shown in FIG. 3, in the obtained sintered body 6, an energy confinement electrode 13a formed on the outer surface of the sintered body 6
, 15a and the internal electrode 14a, the sintered body 6 is polarized in the direction indicated by the illustrated arrow.

In the piezoelectric resonator device obtained as described above, the plurality of electrodes 13a, 14a, and 15a are arranged so as to overlap in the thickness direction with the piezoelectric ceramic layer interposed therebetween, so harmonics of thickness longitudinal vibration are confined. Therefore, compared to previous piezoelectric resonator devices, it is possible to use them in a higher frequency range.

By the way, when a piezoelectric resonant device is obtained by the above manufacturing method, the initial frequency varies considerably due to various factors such as variations in the thickness of the ceramic green sheet 1.2 and variations in the piezoelectric ceramic layer after firing. was. Therefore, a mass load is applied by applying an electrode material or the like to the surface of the electrode 138.15a, thereby adjusting the frequency.

[Technical problem to be solved by the invention] However,
Frequency adjustment by applying a mass load as described above not only causes deterioration of characteristics because it damps vibrations, but also can only be adjusted in the direction of lowering the resonant frequency. Since the initial resonance frequency variation before adjustment reaches several percent, it is extremely difficult to make the characteristics of a large number of mass-produced piezoelectric resonator devices uniform by adjusting the frequency only by adjusting the fT amount negative load.

An object of the present invention is to provide a method for manufacturing a stacked piezoelectric resonator device that can effectively reduce variations in characteristics during mass production.

[Means for solving technical problems]

The present invention provides a method for manufacturing an energy confinement type laminated piezoelectric resonator device that has at least 61 internal electrodes and utilizes harmonics of the thickness longitudinal vibration mode, and includes the following steps. It is characterized by being prepared.

First, a ceramic green sheet made of a plurality of piezoelectric materials is prepared. An electrode paste for forming an internal electrode is printed on at least one of the ceramic green sheets on which an internal electrode is planned to be formed.Next, a plurality of ceramic green sheets are printed. A sintered body is obtained by laminating ceramic green sheets, compressing them in the thickness direction, and then firing them. Furthermore, in order to adjust the thickness of the ceramic layer, the sintered body is processed to reduce its thickness. After that, an energy trapping electrode is formed on the outer surface of the sintered body.

[Effect]

In the conventional method, since the electrodes formed on the outer surface of the sintered body were formed at the same time as the inner electrodes, the frequency could only be adjusted by mass loading. The energy confinement electrode is intentionally formed in a separate process, and the frequency is adjusted by processing the sintered body to adjust the thickness. Since the frequency is adjusted by adjusting, the resonant frequency can be adjusted to a large extent, and furthermore, it is possible to adjust the resonant frequency in the direction of increasing it.

[Explanation of Examples]

Hereinafter, a manufacturing method according to an embodiment of the present invention applied to manufacturing a piezoelectric resonator having a structure similar to that shown in FIG. 2 will be described with reference to the process diagram shown in FIG. 1.

First, by various molding methods such as the doctor blade method,
Forming a Ceramic Green Sheet Made of Piezoelectric Material Next, the ceramic green sheet is punched to prepare two ceramic green sheets 21 of a predetermined size as shown in FIG. 4(a).

Next, as shown in FIG. 4(b), one of the two ceramic green sheets 21 is a ceramic green sheet 21a (a different reference number is given to distinguish it from a ceramic green sheet on which internal electrode paste is not printed). ) Apply an electrode paste 22 mainly composed of PT to form internal electrodes.*The i-pole paste 22 is
Electrode paste part 22a forming an electrode for energy confinement
and an electrode paste portion 22b constituting a connecting conductive portion.

Next, the ceramic green sheets 21 are stacked on top of the ceramic green sheets 21a and pressed in the thickness direction to obtain a laminate, and the laminate is fired as shown in FIG. A solid body 24 is obtained.

In the sintered body 24, an internal electrode 32a is formed based on the electrode paste portion 22a. Note that, by firing the ceramic green sheets 21.21a, piezoelectric ceramic layers 31, 31a are formed above and below the internal electrode 32a.

Next, the upper and lower surfaces of the sintered body 24 are polished using a lapping machine to reduce the thickness of the ceramic layer 31, 31a so that it has the same thickness as the standard product. is adjusted.

Next, as shown in FIG. 6, full-surface electrodes 33 and 34 are deposited on the upper and lower surfaces of the sintered body 24 by vapor deposition, sputtering, plating, CV
D or electrode paste baking is formed by any method such as.

After that, the sintered body 24 is polarized using the entire surface electrodes 33, 34 and the internal electrodes 32a. The entire sintered body 24 is polarized in the direction shown by arrow A, and then a potential of 10 is applied to the internal electrode 32a, and the entire surface is polarized at T4.
．． By applying a negative potential to the electrodes 33 and 34, the piezoelectric ceramic layers 31 and 31a on both sides of the internal electrode 32a are polarized in the directions indicated by arrows pointing in opposite directions.

Next, a resist is printed on the entire surface of the electrodes 33 and 34, and then etched to form the energy confinement electrode 33a and the connecting conductive portion 33 on the upper and lower surfaces of the sintered body 24.
(see FIG. 7(a)). In FIG. 7(a), only the energy confinement electrode 33a and the connecting conductive part 33b on the upper surface side are shown, but the same applies to the lower surface side. An energy confinement electrode 34a (see FIG. 7(b)) and a connecting conductive portion are formed.

As described above, a laminated energy confinement type piezoelectric resonator can be obtained. In this embodiment, when the sintered body 24 is obtained, the ceramic layer 31 is The sintered body 24 is polished so that the thickness of .31a is equal to the thickness of the corresponding part of the standard product, thereby performing frequency adjustment. Therefore, variations in the initial resonance frequency caused by variations in the thickness of the ceramic green sheets 21, 21a, variations during firing, etc. can be greatly reduced. Furthermore, since the frequency is adjusted to reduce the thickness, the frequency can be adjusted in a direction that increases the resonance frequency.

Note that after obtaining the piezoelectric resonator shown in FIG. 7(b), the frequency may be further adjusted by applying a mass load as necessary. In this case, the resonance frequency is lowered by the mass load. The resonant frequency can be fine-tuned again in the direction. However, when applying a mass load,
Since vibrations are damped, characteristics deteriorate. Therefore, it is preferable to adjust the resonance frequency only by polishing the sintered body.

In addition, the method for processing the surface of the sintered body 24 is not limited to the method using a lapping machine as described above, but any other arbitrary method can be used. Alternatively, the thickness may be reduced by chemical treatment such as chemical etching.

Furthermore, in the above embodiment, a ceramic mother sheet made of piezoelectric material is molded and then punched to prepare ceramic green sheets 21° 21a of a predetermined size to manufacture individual piezoelectric resonator devices. Multiple piezoelectric resonance devices are integrally formed using the sheet as it is,
At a desired process step, for example, the energy confinement electrode 33a
, 34a may be cut to form a unit resonant device.

In addition, regarding the electrode paste for forming internal electrodes, in addition to those mainly composed of PT, Ag, Ag-Pd5P
A material mainly composed of an arbitrary electrode material such as d can be used as appropriate.

Further, although an embodiment of a method for manufacturing a piezoelectric resonator device having 1 internal electrodes 32a has been described, it is understood that the present invention can be generally applied to a method for manufacturing a laminated piezoelectric resonator device having two or more internal electrodes. Let me point this out.

〔Effect of the invention〕

As described above, in the present invention, prior to forming the energy trapping electrode on the outer surface of the sintered body, frequency adjustment is performed so as to reduce the thickness of the sintered body.

Accordingly, the variation in the initial resonance frequency can be greatly reduced.According to the experiments of the present inventor, it was possible to reduce the variation in the resonance frequency to about 0.5% or less. Therefore, it is possible to dramatically increase the yield during mass production.

In addition, with the method of applying a mass load, deterioration of characteristics due to damping was observed, but in the present invention, such vibration damping does not occur, so it is possible to stably obtain a piezoelectric resonant device with good resonance characteristics. Become. In addition, since the thickness is reduced by processing the surface of the sintered body, variations in the electromechanical coupling coefficient kt, mechanical quality coefficient Qmt, etc. of each element are also reduced as the surface is smoothed.

[Brief explanation of the drawing]

Fig. 1 is a process diagram of an embodiment of the present invention, Fig. 2 is an exploded perspective view for explaining the conventional method of a laminated piezoelectric resonator, and Fig. 3 is a piezoelectric resonance obtained by the process shown in Fig. 2. 4(a) is a perspective view of the prepared ceramic green sheet, and FIG. 4(b) is a cross-sectional view of the device along the line ■-■ in FIG. 2. FIG. 5 is a perspective view showing the printed state of the electrode paste, and FIG.
A cross-sectional view of the part corresponding to the part along the V-■ line in Figure (b), Figure 6 is a cross-sectional view showing the polarized sintered body, and Figures 7 (a) and (b) are the obtained They are a perspective view of the piezoelectric resonator and a cross-sectional view taken along line BB in FIG. 7(a). In the figure, 21 and 21a are ceramic and microgreen sheets, 22a is an electrode base part for forming internal electrodes, 24 is a sintered body, 31.31a is a ceramic layer, and 32a is a sintered body.
denotes an internal electrode, and 33a and 34a denote energy confinement electrodes formed on the outer surface. Figure 1 Figure 2 15α Figure 4 (α) 3! α

Claims (1)

[Claims] A method for manufacturing an energy confinement type piezoelectric resonator having at least one internal electrode and using harmonics of a thickness longitudinal vibration mode, the method comprising a ceramic green made of a plurality of piezoelectric materials. a step of preparing a sheet; a step of printing an electrode paste to constitute an internal electrode on at least one ceramic green sheet; and laminating the plurality of ceramic green sheets, pressing them in the thickness direction, and then firing them. a step of processing the sintered body to reduce its thickness in order to adjust the thickness of the ceramic layer; and forming an energy trapping electrode on the outer surface of the sintered body. A method of manufacturing a piezoelectric resonator device, comprising the steps of: