JPH0695622B2 - Piezoelectric resonance device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an energy confinement type piezoelectric resonance device using harmonics of a thickness longitudinal vibration mode, and in particular, an electrode structure for energy confinement is improved. Regarding things

[Conventional technology]

BACKGROUND ART Conventionally, energy confinement type piezoelectric vibrators utilizing a thickness longitudinal vibration mode using PZT-based piezoelectric ceramics have been known. This type of energy confinement type piezoelectric vibrator
It is configured by forming electrodes having an area smaller than that of the piezoelectric ceramic plate on both surfaces of the piezoelectric ceramic plate.

As the piezoelectric ceramics, a material having an effective Poisson's ratio of 1/3 or more, such as PZT, was used. This is because, when a material having an effective Poisson's ratio of less than 1/3 was used, it was not possible to confine the frequency-decreasing energy of thickness longitudinal vibration.

On the other hand, there is a demand for a piezoelectric resonance device that can be used in a higher frequency range. Therefore, a structure that can be used in a high frequency range by utilizing the secondary high frequency of the thickness longitudinal vibration has been proposed by the present inventor (Japanese Patent Application No. 62-235948).
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This not yet known prior art structure will be described with reference to FIGS. 2 and 3. As shown in FIG.
Prepare ceramic green sheets 1 and 2 made of PZT-based piezoelectric material. On the upper surface of the ceramic green sheet 1, an electrode paste is applied to a portion 3 which becomes an energy confinement type electrode and a portion 4 which becomes a connection conductive portion (hereinafter, in the present specification, an electrode paste which becomes an electrode is applied. The same reference numerals as those given to the portion to be the connecting portion and the connecting conductive portion are also given to the completed electrode and connecting conductive portion).

On the upper surface of the ceramic green sheet 2, the electrode paste is applied to the electrode portion 5 and the portion 6 to be the connection conductive portion.
Further, an electrode paste is applied to the lower surface of the ceramic green sheet 2 to form a portion 7 that will be an electrode and a portion 8 that will be a connection conductive portion.

Next, the ceramic green sheets 1 and 2 are laminated and integrally fired to obtain the piezoelectric resonance device shown in FIG.

Referring to FIG. 3, in the sintered body 10, the piezoelectric ceramic layer
Electrodes 3,5 and 5,7 for energy confinement via 1,2 (same reference number as ceramic green sheet)
Are overlapping. The second harmonic of the thickness longitudinal vibration is confined in the overlapping area A.

That is, since the resonance frequency is determined according to the thickness of the piezoelectric material layer 1 or 2, the first response of the thickness longitudinal vibration appears at a higher frequency than the conventional single-plate type piezoelectric resonance device. Therefore, according to this structure, a piezoelectric resonance device that can be used in a higher frequency range can be realized.

[Technical problem to be solved by the invention]

When manufacturing the piezoelectric resonance device of FIG. 3, the electrodes 3, 5,
The seven must be formed so that they exactly overlap. That is, when the electrodes 3, 5, 7 are misaligned, the resonance characteristics greatly vary. However, it is difficult to prevent such positional displacement between the electrodes, and therefore, the complicated work of measuring the characteristics of mass-produced piezoelectric resonance devices and selecting them according to the characteristics is required.

On the other hand, in order to eliminate the above variations in characteristics, it is possible to adopt a structure as shown in FIG. Here, by forming the entire surface electrode 5a on the upper surface of the ceramic green sheet 2, the influence of the positional deviation between the upper and lower electrodes 3 and 7 can be prevented.

However, due to the stray capacitance generated between the entire surface electrode 5a and the upper and lower connecting conductive portions 4 and 8, the spurious mode is excited in the frequency region between the resonance frequency and the anti-resonance frequency, and the resonator or the like is excited. When applied, it causes defects such as oscillation stop. Furthermore, since the stray capacitance increases the capacitance, the anti-resonance frequency decreases, narrowing the frequency range between the resonance frequency and the anti-resonance frequency, and when applied to a filter, the pass band as designed is obtained. There was a problem that I could not.

Therefore, an object of the present invention is to effectively suppress spurious vibrations that are superimposed on higher harmonics of thickness longitudinal vibration, and to effectively reduce characteristic variations due to electrode position shifts for energy confinement. Another object is to provide a piezoelectric resonance device having a structure.

[Means for solving technical problems]

The present invention is an energy confinement type piezoelectric resonance device that utilizes harmonics of a thickness extensional vibration mode, wherein a main body made of a polarized piezoelectric material and a main body made of polarized piezoelectric material are overlapped in the thickness direction of the main body with a piezoelectric material layer interposed therebetween. And three or more electrodes arranged in the above, at least one electrode is formed in a region including the electrodes for energy confinement arranged above and below the electrode and is electrically connected to each other. It is characterized in that it is constituted by a plurality of linear electrode portions which are not provided.

[Action]

Since at least one electrode is composed of a plurality of linear electrode portions formed above and below the region including the electrodes for energy confinement, even if the upper and lower electrode formation positions are slightly displaced. As long as it is included in the region where the plurality of linear electrode portions are configured, it is difficult for the characteristics to vary.

Moreover, since the plurality of linear electrode portions are not electrically connected to each other, the capacitance formed between the upper and lower connecting conductive portions and the respective linear electrode portions is inserted in series between the electrodes. It will be. Therefore, the overall capacitance of the piezoelectric resonance device is effectively reduced. Therefore, it is possible to effectively suppress the generation of spurious due to the stray capacitance between the connection conductive portion and the electrode.

[Explanation of Examples]

First, with reference to FIG. 1, a manufacturing process of a piezoelectric resonance device according to an embodiment of the present invention will be described.

Two ceramic green sheets 11 and 12 made of a piezoelectric material such as PZT are prepared. On the upper surface of one of the ceramic green sheets 11, an electrode paste is applied to a portion 13 serving as an electrode for confining energy and a portion 14 constituting a connecting conductive portion.

On the other hand, when the ceramic green sheets 11 and 12 are stacked on the upper surface of the ceramic green sheet 12, the electrode 13
A plurality of linear electrodes 15 in a region including in the thickness direction.
The electrode paste is linearly applied to form a to 15j. Furthermore, on the lower surface of the ceramic green sheet 12,
An electrode paste is applied to a portion 17 which will be an electrode for energy confinement and a portion 18 which forms a connection conductive portion.

By stacking the ceramic green sheets 11 and 12 in the illustrated state, press-bonding them in the thickness direction, baking them, and subjecting them to a predetermined polarization treatment (described later), the piezoelectric resonance device shown in FIGS. 5 and 6 is obtained. be able to.

The polarization treatment is performed by strip electrodes 15a exposed on the end surface of the sintered body.
This is performed by applying a + potential to the ˜15j side and a − potential to the upper and lower electrodes 13 and 17. As a result, the two piezoelectric ceramic layers are polarized in the opposite directions in the thickness direction, that is, in the directions of the arrows shown in the figure.

After the polarization treatment, the plurality of linear electrodes 15a to 15j are not electrically connected to each other, that is, when the end faces are connected in polarization treatment, by polishing the end faces,
Release the mutual electrical connection.

At the time of driving, by applying either one of + or − potential to the electrode 13 from the connection conductive portion 14 and periodically applying the other potential to the connection conductive portion 18 connected to the electrode 17,
Can be resonated. Also in this structure, as in the example of FIG. 3, since the second harmonic of the thickness longitudinal vibration mode is greatly excited, the second harmonic can be used,
Therefore, a piezoelectric resonance device that can be used in a higher frequency range can be obtained.

The impedance-frequency characteristics of the embodiment shown in FIGS. 5 and 6 are shown by the solid line in FIG. For comparison, the impedance-frequency characteristics in the structural example of FIG. 4 formed using the same material and having the same size are shown by the broken line in FIG.

As is apparent from FIG. 7, in the structure example of FIG. 4, waveform division based on the spurious mode occurs in the antiresonance frequency-frequency region, whereas in the present embodiment, such waveform division occurs. Therefore, it can be seen that the generation of spurious modes is effectively suppressed.

It is understood that not only the frequency bandwidth between the resonance and anti-resonance frequencies can be expanded in this embodiment.
This is because in the structure example of FIG. 4, stray capacitance is generated between the internal electrode 5a and the upper and lower connecting conductive parts, the spurious mode is excited by the stray capacitance, and the electrode where the stray capacitances overlap each other. This is because the capacitance between the electrodes is added in parallel and the total capacitance between the electrodes is increased.

On the other hand, in this embodiment, the internal electrodes are linear electrode parts.
Since it is composed of 15a to 15j, the upper and lower connecting conductive parts 14,1
A stray capacitance is generated between the stray capacitances 8 and 8, and the stray capacitances are individually formed in each of the linear electrode portions 15a to 15j, and are inserted in series between the electrodes. Therefore,
It is considered that this is because the contribution of the capacitance between the connecting conductive portions 14 and 18 becomes small, so that the spurious level is reduced and the frequency bandwidth between the resonance and antiresonance frequencies is expanded.

Further, as is clear from the above description of the manufacturing process, in the present embodiment, the plurality of linear electrode portions 15a to 15j are formed in the region including the vertically overlapping electrodes 13 and 17. Therefore, even if the positions where the electrodes 13 and 17 are formed are slightly deviated with respect to the linear electrode portions 15a to 15j, as long as they are included in the region where the linear electrode portions 15a to 15j are formed, the characteristic Variation is unlikely to occur. Therefore, since there is no variation in the characteristics as in the structural example shown in FIG. 2, it is not necessary to perform a complicated selection work according to the characteristics.

A more preferred embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 8, a plurality of linear electrodes 25 are formed inside the sintered body 20. Up to this point, the structure is the same as that shown in FIG. The difference is that prior to polarization, the full-surface electrodes 23a and 27a are formed on the upper and lower surfaces of the sintered body 20, and the polarization treatment is performed in that state. That is,
By applying a-potential to the entire-surface electrodes 23a and 27a and applying a + potential to each linear electrode portion 25, it is possible to perform a polarization treatment over a wide range within the sintered body 20 as shown by the arrow in the figure. .

Then, the entire surface electrodes 23a and 25a are etched to form electrodes for energy confinement and connection conductive portions. That is, as shown in FIG. 9A, the circular electrode 23 and the connecting conductive portion 24 are formed on the upper surface of the sintered body 20. Also on the lower surface side, the electrode portion and the connection conductive portion are similarly formed.

The embodiment thus obtained is shown in FIG. 9 (b).
As is clear from FIG. 9 (b), in this embodiment, energy is confined in the sintered body between the electrodes 23 and 27 formed on the upper surface and the lower surface, that is, in the area indicated by the arrow B. ,
The sintered body is also polarized in the region around it. Therefore, more complete energy confinement is possible.

In the sintered body of FIG. 8, when forming the entire surface electrodes 23a and 27a, the electrode paste may be applied to the entire surface in the state of the ceramic green sheet, or the entire surface may be obtained after the sintered body 20 is obtained. Alternatively, the electrode paste may be printed / baked on. Also in this embodiment, it goes without saying that it is necessary to disconnect the electrical connection between the linear electrode portions 25 prior to driving.

In the embodiment described above, the electrode located at the center among the three layers of electrodes is composed of the linear electrode portions 15a to 15j, 25, but the present invention is arranged so that four or more electrodes overlap each other. The piezoelectric resonance device described above can also be applied. Even in that case, as long as at least one electrode is composed of a plurality of linear electrode portions, the same effect as the present invention can be obtained. That is, it is possible to increase the allowable amount of electrode forming positions for energy confinement located above and below the electrode formed by the linear electrode portion, and to effectively suppress spurious vibration in that portion. Of.

〔The invention's effect〕

As described above, according to the present invention, the
Since the electrode of is composed of a plurality of linear electrode portions that are not electrically connected to each other, the tolerance of the formation position of the electrodes that overlap the linear electrode portions through the piezoelectric ceramic layer is increased. There is. Therefore, since it is possible to obtain a piezoelectric resonance device with less variation in characteristics, it is possible to eliminate complicated selection work according to characteristics.

Not only that, stray capacitance between the connecting conductive parts arranged so as to overlap vertically is inserted in series between the electrodes for each linear electrode part, so spurious vibrations are effectively suppressed. Since the stray capacitance as a whole can be reduced, it is possible to prevent a decrease in anti-resonance resistance and prevent a narrowing of the frequency bandwidth between the resonance and anti-resonance frequencies. It is possible to realize a piezoelectric resonance device having stable resonance characteristics, and when applied to an oscillator, for example, it is possible to configure an oscillation circuit with excellent reliability that is unlikely to cause an accident such as oscillation stop. .

[Brief description of drawings]

FIG. 1 is a perspective view for explaining a process for manufacturing an embodiment of the present invention, and FIG. 2 is an exploded perspective view for explaining a process for obtaining a piezoelectric resonance device which triggered the present invention. FIG. 3 is a sectional view of a piezoelectric resonance device obtained through the process of FIG.
FIG. 4 is a cross-sectional view for explaining another example of the conventional piezoelectric resonance device, and FIG. 5 is a cross-sectional view of the piezoelectric resonance device of the embodiment obtained in the step of FIG. 1. FIG. 6 is a sectional view corresponding to a portion along the line VV, FIG. 6 is a sectional view of an example corresponding to a portion along the line VI-VI in FIG. 1, and FIG. 7 is an example and a comparative example. Showing impedance-frequency characteristics of the device, FIG. 8 is a sectional view for explaining the polarization treatment in another embodiment of the present invention, and FIGS. 9 (a) and 9 (b) are other embodiments of the present invention. FIG. 3 is a plan view and a sectional view of FIG. In the figure, 10 is a main body, 13 and 17 are electrodes, 15a to 15h are linear electrode parts, 23 and 27 are electrodes, and 25a to 25h are linear electrode parts.

Claims (1)

[Claims] 1. A piezoelectric resonance device of energy confinement type using harmonics of a thickness longitudinal vibration mode, comprising a plate-shaped main body made of a polarized piezoelectric material, and a piezoelectric material layer in a thickness direction of the main body. At least three electrodes arranged so as to overlap each other with at least one of the electrodes being formed in a region including the electrodes arranged above and below, and being electrically connected to each other. A piezoelectric resonance device comprising a plurality of linear electrode parts which are not provided.