JPH07105686B2 - Method for manufacturing piezoelectric resonance device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an energy confinement type piezoelectric resonance device using harmonics of a thickness extensional vibration mode, and particularly, it is easy to adjust the resonance frequency. The present invention relates to a method for obtaining a piezoelectric resonance device having a certain characteristic variation with little variation.

[Conventional technology]

BACKGROUND ART Conventionally, an energy confinement type piezoelectric resonance device using a thickness extensional vibration mode using PZT-based piezoelectric ceramics has been known. This type of energy confinement type piezoelectric resonance device is configured by forming electrodes having an area smaller than that of the piezoelectric ceramic plate on both surfaces of the piezoelectric ceramic plate. However, it is difficult to use it in a higher frequency range, and when a material having an effective Poisson's ratio of less than 1/3 is used, frequency reduction type energy confinement of thickness longitudinal vibration cannot be achieved.

Therefore, in Japanese Patent Application No. 62-235948, in order to solve the above problem, the effective Poisson's ratio is improved by dividing the piezoelectric ceramic layer into a plurality of layers by using three or more energy confining electrodes. Even when a piezoelectric material of less than 1/3 is used, a structure capable of confining the energy of thickness longitudinal vibration in a frequency decreasing type and being usable in a higher frequency range is disclosed. A second method for manufacturing this piezoelectric resonance device is described.
A description will be given with reference to the drawings and FIG.

As shown in FIG. 2, two ceramic green sheets 1 and 2 made of a piezoelectric material are prepared. The electrode paste 3 is applied to the upper surfaces of the ceramic green sheets 1 and 2. The electrode paste 3 has an electrode paste portion 3a for forming an energy confining electrode and an electrode paste portion 3b forming a connection conductive portion for connection with the outside. Similarly, the electrode paste 4 is also formed on the upper surface of the ceramic green sheet 2 to form the internal electrodes.
And an electrode paste portion 4b that constitutes a connection conductive portion. Further, the electrode paste 5 is applied on the lower surface of the ceramic green sheet 2 so as to have an electrode paste portion 5a for forming an energy confining electrode and an electrode paste portion 5b for forming a connection conductive portion. Has been done.

Of the above electrode pastes 3 to 5, in order to form the energy confining electrodes, the electrode paste portions 3a, 4a, 5a are arranged so as to overlap in the thickness direction.

The ceramic green sheets 1 and 2 are overlapped as shown in the drawing, pressure-bonded in the thickness direction, and then the ceramic green sheets are fired by firing and the electrode paste 3
Bake ~ 5.

As shown in FIG. 3, in the obtained sintered body 6, the energy confining electrodes 13a, 15 formed on the outer surface of the sintered body 6
By applying a voltage between a and the internal electrode 14a, the sintered body 6 is polarized in the direction shown by the arrow in the figure.

In the piezoelectric resonance device obtained as described above, since the plurality of electrodes 13a, 14a, 15a are arranged so as to overlap in the thickness direction via the piezoelectric ceramic layer, the harmonics of the thickness longitudinal vibration can be confined. Therefore, it can be used in a higher frequency range than the conventional piezoelectric resonance devices.

By the way, when a piezoelectric resonance device is obtained by the above manufacturing method, the initial frequency fluctuates at a considerable rate due to various factors such as variations in the thickness of the ceramic green sheets 1 and 2, variations in the piezoelectric ceramic layer after firing, and the like. Was there. Therefore, a mass load is applied by applying an electrode material or the like to the surfaces of the electrodes 13a and 15a, and thereby frequency adjustment is performed.

[Technical problem to be solved by the invention]

However, since the frequency adjustment by applying the mass load as described above damps the vibration, the characteristics are deteriorated. In addition, the resonance frequency can be adjusted only in the direction of lowering it. Moreover, since the variation of the initial resonant frequency before the frequency adjustment reaches several%, it is very difficult to make the characteristics of a large number of mass-produced piezoelectric resonators uniform only by the frequency adjustment by the mass load.

It is an object of the present invention to provide a method for manufacturing a laminated piezoelectric resonance 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 resonance device having at least one internal electrode and utilizing harmonics of the thickness extensional vibration mode, and includes the following steps. It is characterized by

First, a ceramic green sheet made of a plurality of piezoelectric materials is prepared. An electrode paste for forming the internal electrodes is printed on at least one ceramic green sheet in which the internal electrodes are to be formed among the plurality of ceramic green sheets. Next, a plurality of ceramic green sheets are laminated, pressure-bonded in the thickness direction, and then fired to obtain a sintered body. Further, in order to adjust the thickness of the ceramic layer, processing is performed so as to reduce the thickness of the sintered body. After that, an energy confining electrode is formed on the outer surface of the sintered body.

[Action]

In the conventional method, since the electrode formed on the outer surface of the sintered body was formed at the same time as the inner electrode, in consideration of the fact that the frequency could be adjusted only by the mass load, the present invention forms it on the outer surface. The energy confining electrode is intentionally formed in a separate step, and the sintered body is processed prior to that to adjust the thickness and frequency. Since the frequency is adjusted by adjusting the thickness of the piezoelectric ceramic layer by processing the sintered body, it is possible to greatly adjust the resonance frequency and further to increase the resonance frequency.

[Explanation of Examples]

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

First, by various molding methods such as doctor blade method,
A ceramic green sheet made of a piezoelectric material is molded. Next, punch the ceramic green sheet,
Two ceramic green sheets 21 of a predetermined size shown in FIG. 4 (a) are prepared.

Next, as shown in FIG. 4 (b), one of the two ceramic green sheets 21 is a ceramic green sheet 21.
On (a different reference number is provided to distinguish it from the ceramic green sheet on which the internal electrode paste is not printed.), the Pt-based electrode paste and 22 for forming the internal electrode are applied. The electrode paste 22 is applied so as to have an electrode paste portion 22a forming an energy confining electrode and an electrode paste portion 22b forming a connection conductive portion.

Next, the ceramic green sheet 21 is laminated on the ceramic green sheet 21a so as to be laminated and pressure-bonded in the thickness direction to obtain a laminated body, and the laminated body is fired to sinter as shown in FIG. Get the body 24.

An internal electrode 32a based on the electrode base portion 22a is formed in the sintered body 24. By firing the ceramic green sheets 21, 21a, the piezoelectric ceramic layers 31, 31a are formed above and below the internal electrodes 32a.

Next, at least one of the upper surface and the lower surface of the sintered body 24 is polished by using a lapping machine to reduce the thickness of the ceramic layers 31, 31a so as to have the same thickness as the standard product. The frequency characteristic is adjusted by this polishing.

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

After that, the sintered body 24 is polarized by utilizing the entire surface electrodes 33, 34 and the internal electrode 32a. For the polarization, first, a positive potential is applied to the entire surface electrode 34, and a negative potential is applied to the entire surface electrode 33 to polarize the entire sintered body 24 in the direction indicated by the arrow A, and then to the inner electrode 32a. By applying a negative potential to the entire-surface electrodes 33, 34, the piezoelectric ceramic layers 31, 31a on both sides of the internal electrode 32a are polarized in directions indicated by arrows opposite to each other.

Next, a resist is printed on the entire surface electrodes 33, 34, and thereafter, etching is performed to form the energy confining electrode 33a and the connecting conductive portion 33b on the upper surface and the lower surface of the sintered body 24 (see FIG. 7 ( See a)). In FIG. 7 (a), only the energy confining electrode 33a and the connecting conductive portion 33b on the upper surface side are shown, but the energy confining electrode 34 on the lower surface side is similarly shown.
a (see FIG. 7B) and the connecting conductive portion are formed.

As described above, a laminated type energy confinement type piezoelectric resonance device can be obtained. In this embodiment, when the sintered body 24 is obtained, prior to the formation of the full-surface electrodes 33, 34, the thickness of the ceramic layers 31, 31a is made equal to the thickness of the corresponding portion of the standard product. The 24 is ground, thereby adjusting the frequency. Therefore, the ceramic green sheets 21,2
It is possible to greatly reduce variations in the initial resonance frequency due to variations in the thickness of 1a, variations during firing, and the like. Moreover, since the frequency is adjusted so as to reduce the thickness, the frequency can be adjusted in the direction of increasing the resonance frequency.

After the piezoelectric resonance device shown in FIG. 7 (b) is obtained, the frequency may be further adjusted by applying a mass load, if necessary. In this case, the resonance frequency can be finely adjusted again in the direction of lowering the resonance frequency by the mass load. However, when applying a mass load,
Since the vibration is damped, the characteristic is deteriorated. Therefore, it is preferable to adjust the resonance frequency only by polishing the above-mentioned sintered body.

Further, the method of processing the surface of the sintered body 24 is not limited to the method using the lapping machine as described above, and any other method can be used. For example, it may be polished by using a flat polishing plate, or the thickness may be reduced by a chemical treatment such as chemical etching.

Further, in the above embodiment, the ceramic green sheets 21 and 21a of a predetermined size were prepared by punching after forming the ceramic mother sheet made of the piezoelectric material, and the individual piezoelectric resonance devices were manufactured. A sheet is used as it is to integrally form a plurality of piezoelectric resonators, and cut at a desired process step, for example, after the etching for forming the energy confining electrodes 33a, 34a is completed to form a unit resonator. May be.

Further, as the electrode paste for forming the internal electrodes, not only Pt as the main component but also any electrode material as the main component such as Ag, Ag-Pd, or Pd can be appropriately used.

Further, although the embodiment of the method for manufacturing the piezoelectric resonance device having one internal electrode 32a has been described, the present invention can be generally applied to the method for manufacturing a laminated piezoelectric resonance device having two or more internal electrodes. I will point out.

〔The invention's effect〕

As described above, in the present invention, frequency adjustment is performed so as to reduce the thickness of the sintered body before forming the energy confining electrode on the outer surface of the sintered body. Therefore, the variation in the initial resonance frequency can be greatly reduced. According to an experiment by the inventor of the present application, it was possible to reduce the variation of the resonance frequency to about 0.5% or less. Therefore, it is possible to dramatically increase the yield during mass production.

Further, although the deterioration of the characteristics due to the damping was observed in the method of applying the mass load, since the damping of such vibration does not occur in the present invention, it is possible to stably obtain the piezoelectric resonance device having the excellent 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, the mechanical quality coefficient Qmt, etc. between elements are also reduced due to the smoothing of the surface.

[Brief description of drawings]

FIG. 1 is a process drawing of an embodiment of the present invention, FIG. 2 is an exploded perspective view for explaining a conventional method of a laminated piezoelectric resonance device, and FIG. 3 is a piezoelectric resonance obtained by the process of FIG. Figure 2 of the device
Sectional view corresponding to the portion along the line III-III, FIG. 4 (a)
Is a perspective view of the prepared ceramic green sheet, No. 4
FIG. 5B is a perspective view showing a state in which an electrode paste for forming internal electrodes is printed, and FIG. 5 is a portion of the obtained sintered body along the line VV in FIG. 4B. 6 is a cross-sectional view of a portion subjected to polarization, FIG. 6 is a cross-sectional view showing a sintered body that is polarized,
7A and 7B are a perspective view of the obtained piezoelectric resonance device and a cross-sectional view taken along the line BB of FIG. 7A. In the figure, 21, 21a are ceramic green sheets, 22a
Is an electrode paste portion for forming an internal electrode, 24 is a sintered body, 31 and 31a are ceramic layers, 32a is an internal electrode, and 33a and 34a are energy confining electrodes formed on the outer surface.

 ─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A-60-74709 (JP, A) JP-A-60-123116 (JP, A) JP-B-63-40491 (JP, B2)

Claims (1)

[Claims] 1. A method of manufacturing an energy confinement type piezoelectric resonance device having at least one internal electrode and utilizing harmonics of a thickness extensional vibration mode, the ceramic green sheet comprising a plurality of piezoelectric materials. And a step of printing an electrode paste for forming an internal electrode on at least one ceramic green sheet, stacking the plurality of ceramic green sheets, press-bonding them in the thickness direction, and then firing. To obtain a sintered body, to adjust the thickness of the ceramic layer, to reduce the thickness of the sintered body, and to form an energy confining electrode on the outer surface of the sintered body. A method of manufacturing a piezoelectric resonance device, comprising: