JPH0426212A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To prevent the characteristic of a piezoelectric resonator from being degraded by forming more than two piezoelectric resonance parts on the same piezoelectric substrate and capacitor parts respectively between these piezoelectric resonance parts, and mutually inverting the polarizing directions of the adjacent piezoelectric resonance parts. CONSTITUTION:This piezoelectric resonator is composed of oscillating electrodes 14 and 14 formed on one face of a piezoelectric substrate 12, capacitor electrode 16, drawing electrodes 18 and 18 and common electrode 20 formed on the other face. The piezoelectric substrate 12 is polarized by fitting the electrodes on the both sides of a piezoelectric board, which is board-shaped by a piezoelectric body, and impressing a high voltage between the electrodes, and the polarizing direction is inverted with the almost central part of the piezoelectric substrate 12 as the boundary. Thus, the piezoelectric resonator can be obtained with a satisfactory characteristic by respectively canceling each other either an electric field to be generated by the piezoelectric resonance parts formed at spots in various polarizing directions or oscillation to be generated by the electric field applied to the capacitor parts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric resonator, and particularly to an esurgical confinement type piezoelectric resonator.

[Conventional technology and issues to be solved]

2. Description of the Related Art A piezoelectric resonator has been conventionally provided in which two piezoelectric resonators having the same pressure on a substrate and a capacitive part formed between the piezoelectric resonators are formed. An example of this piezoelectric resonator will be briefly explained based on the drawings.

In FIGS. 13 and 14, the piezoelectric resonator 1 is a piezoelectric resonator that utilizes an energy confinement type thickness vibration mode. Piezoelectric resonator 1 is pressure! A resonance electrode 3.3, a capacitor electrode 4, and an extraction electrode 6 are formed on one surface of the substrate 2, and a ground electrode 5 and an extraction electrode 6, which serve as a ground electrode, a common electrode, or a capacitance NFk, are formed on the other surface. A piezoelectric resonant section 7.7 is constructed in the region of the resonant electrode 3.3, and a capacitive region 8 is constructed in the region of the capacitive electrode 4.

In the piezoelectric resonator 1 having such a configuration, the piezoelectric resonator 7.
7 and capacitor 8 are uniformly polarized at the same pressure! Since it is configured on the substrate 2, there is a problem in that when the piezoelectric resonator 1 is operated, not only the piezoelectric resonator parts 7, 7 but also the capacitive part 8 resonate due to the reverse piezoelectric effect.

One way to solve this problem is to heat-treat the capacitor 8 at a temperature higher than the Curie temperature, so that the pressure 'r! A method is used in which the piezoelectricity of one substrate 2 is eliminated. However, since this method may cause the piezoelectricity of parts other than the capacitive part 8 to disappear, it is necessary to use a large piezoelectric substrate 2 and to increase the distance between the piezoelectric resonant parts 7 and the capacitive part 8. It was not possible to downsize. In addition, it is complicated to partially heat-treat, and it is not suitable for mass production.

Further, as another means for solving the above problem, a method is used in which the resonant vibration is damped by mounding solder on the surface of the capacitor section 8. However, with this method, it is impossible to completely suppress the resonance vibration of the capacitor section 8. Furthermore, the work of applying solder to the capacitance of the capacitor portion 8 on the scraper 4 is complicated and is not suitable for mass production.

Moreover, in any of these methods, the piezoelectric resonator 7
, 7 spreads to the capacitive part 8, and an electric field is generated due to the piezoelectric effect. In order to prevent this phenomenon, the capacitive section 8 needs to be formed sufficiently apart from the piezoelectric resonator section 7.7, making it impossible to downsize the piezoelectric resonator 1.

Furthermore, since the piezoelectric resonator I manufactured by this method is subjected to a special operation to damp the resonance vibration in the capacitive portion 8, there is a problem that the characteristics of the piezoelectric resonator 1 are deteriorated.

Therefore, the inventor of the present invention has conducted extensive research to solve the above problems, and as a result, has obtained a piezoelectric resonator according to the present invention.

[Means to solve the problem]

The gist of the present invention is to provide a piezoelectric resonator in which two or more piezoelectric resonators and a capacitive part are formed between each of the piezoelectric resonators on the same piezoelectric substrate, in which polarization of adjacent piezoelectric resonators is The reason is that the directions are opposite to each other.

Further, in such a piezoelectric resonator, the capacitance portion is
The reason is that the polarization distribution of the substrate is provided at a position where the polarization direction is opposite and almost symmetrical.

[For production]

According to the piezoelectric resonator of the present invention, the piezoelectric resonant section and the capacitive section are formed on the same piezoelectric substrate, and the polarization directions of the piezoelectric substrate in adjacent piezoelectric resonant sections sandwiching the capacitive section are opposite directions. ing. That is, the polarization direction of the piezoelectric substrate is alternately reversed along the way, and the piezoelectric effect or inverse piezoelectric effect at the location where the polarization direction is reversed is canceled out by the interaction of parts with different decentralization directions. Therefore, the piezoelectric resonant parts formed on the piezoelectric substrate can be formed close to each other within a range where they are not influenced by adjacent piezoelectric resonant parts having different directions of power distribution.

In addition, by providing a capacitive portion at a position where the polarization direction is reversed and the polarization distribution is symmetrical, the piezoelectricity is canceled out by the interaction of the piezoelectric effect and the inverse piezoelectric effect from locations with different polarization directions. It is possible to form a capacitance section equivalent to one made of only a dielectric.

〔Example〕

Next, one embodiment of the present invention will be described in detail based on the drawings.

In FIGS. 1 to 3, reference numeral 10 indicates a piezoelectric resonator according to the present invention. The piezoelectric resonator 10 is made of barium titanate or PZ made by firing a mixture of lead titanate and lead zirconate.
A pressure ' formed in a plate shape by a piezoelectric material such as T is applied to the substrate 12.
and a vibrating electrode 1 formed on the - side of this piezoelectric substrate 12.
4.14, a capacitor ti16, an extraction electrode 18.18, and a common electrode 20 formed on the other surface of the piezoelectric substrate 12.

The piezo@substrate 12 is a piezoelectric plate formed into a plate shape, with electrodes attached to both sides thereof, and is polarized by applying a high voltage between the electrodes. As shown in FIG. 1, the piezoelectric substrate 12 has a piezoelectric substrate 1.
The polarization direction is reversed across the approximately central portion of 2.

Such a piezoelectric substrate 12, as shown in FIG. 4(a),
First, the electrode 24 is formed only on one half of the piezoelectric plate 22,
After polarization by applying a high voltage, the electrode 24 is removed. Next, as shown in the same figure (b), the piezoelectric body plate 22
This was obtained by forming an electrode 25 on the other half of the electrode and polarizing it by applying a high voltage with the positive and negative polarities reversed. Here, pressure! The polarization levels of the substrates 12 are preferably approximately equal and are polarized by applying equal voltages.

As mentioned above, the obtained piezoelectric substrate 12 has the polarization direction reversed at the center (in FIG. 1, the polarization direction is indicated by an arrow), and near this boundary, the polarization direction on both sides is reversed. It will be affected by the piezoelectricity of the area.

Therefore, the capacitive electrode 16 is arranged at the boundary of the piezoelectric substrate 12 whose polarization direction is reversed, and the vibrating electrode 14 is placed at a symmetrical position about the boundary.
14 is arranged and pressure is applied again! Extracting electrodes 18.18 are arranged at appropriate positions on the substrate 12, and these electrodes 14.16.1
8 are connected by leads and patterned. The patterned electrode 14.16° 18 is connected to the -
A good electrical conductor is formed by vacuum deposition on the surface using, for example, a mask method. On the other hand, a common electrode 20 connected by a lead is disposed on the other surface of the pressure 1 substrate 12 at a position facing the vibrating electrode 14, 14 and the capacitive electrode 16, and the common electrode 20 is similarly formed by vacuum evaporation or the like. be done. Note that the extraction electrode portion 26 is integrally formed on the common t1420. The obtained piezoelectric resonator 10 is represented by an equivalent circuit shown in FIG.

In the piezoelectric resonator 10 having such a configuration, the vibrating electrode 14.
The 14th section functions as the piezoelectric resonance section 28, 28, and the capacitive electrode 16 section functions as the capacitive section 30. In this piezoelectric resonator 28.28, the substrate 12 is caused to vibrate in an energy-trapped vibration mode.

On the other hand, when an electric field is applied between the capacitive electrode 16 and the common electrode 20 in the capacitive part 30 and the capacitive part 30 is caused to vibrate, the polarization direction is reversed at the center of the capacitive part 30, so that the phase becomes 1.
Vibrations that are 80 degrees apart occur simultaneously, and the vibrations are canceled out by the vibrations that are out of phase. Furthermore, when vibration is transmitted from both piezoelectric resonance parts 28 and 28 to the capacitive part 30 and an electric field is generated in the capacitive part 30 by the vibration, the electric fields generated at two points with different polarization directions are positive and negative, respectively. is reversed, so
It will be electrically neutralized.

Therefore, the piezoelectric substrate 12 in the capacitive section 30 is not made to function as a piezoelectric material, but only as a dielectric material, and the characteristics of the capacitive section 30 are improved. Furthermore, as is clear from the above explanation, not only can the piezoelectric resonant parts 28 and 28 be disposed close to each other, but also the piezoelectric resonant part 28 and the capacitive part 30 can be disposed close to each other. This makes it possible to reduce the size of the piezoelectric resonator lO.

Although the embodiments of the present invention have been described in detail above, the present invention can be implemented in other embodiments as well.

For example, as shown in FIG. 6, as a method of polarizing the piezoelectric substrate 12, it is not necessary to polarize the vicinity of the center of the capacitive electrode 32 shown by the two-dot chain line. Electrodes 34 and 35 facing each other are attached at two locations, and a high voltage with reversed plus and minus is applied between the picture electrodes 3435 to polarize them. Similarly, the piezoelectric plate 22 may be polarized only at the location where the piezoelectric resonance section is formed; even in this case, the polarization direction needs to be reversed, and the capacitance section It is necessary to be symmetrical about the point where the

In addition, as a method of polarizing the piezoelectric plate 22, as shown in the seventh section, after applying a decentralizing electrode 36 beyond the center of the piezoelectric plate 22 and polarizing it by applying a high voltage, The electrode 36 may be removed, and then an electrode 37 may be provided so as to partially overlap the electrode 36, and a high voltage with the positive and negative polarity reversed may be applied between 1 and 37 to polarize it.

Even if the piezoelectric plate 22 is polarized by such a method, the polarization is canceled out at the location where the electrodes 36 and 37 overlap, as shown in FIG. 8, and the piezoelectric plate 22 functions as a dielectric.

Furthermore, the configuration of the piezoelectric resonator to which the present invention is applicable is not limited to the above-mentioned example; for example, as shown in FIG. 9, piezoelectric resonators 40.
42, 44, and a piezoelectric resonator 5 in which capacitive parts 46, 48 are formed at two places between the piezoelectric resonant parts 40, 42, 44.
It is possible to configure 0. Such a piezoelectric resonator 50
In this case, as shown in FIG.
The polarization direction is reversed at the center of each. Further, as shown in FIG. 9, the positional relationship between the capacitive portions 46.48 and the piezoelectric resonant portions 4042.44 is symmetrical with respect to the boundary portion thereof.

Therefore, in the capacitive portions 46 and 48, piezoelectricity and inverse piezoelectricity are canceled out in the same way as described above, and the capacitive portions 46 and 48 exhibit characteristics equivalent to those made of a dielectric material. Incidentally, an equivalent circuit of the piezoelectric resonator 50 having such a configuration is shown in FIG.

In addition, as shown in FIG. 12, two capacitor parts 56 are formed by providing capacitors 54 at substantially symmetrical positions with respect to the center where the polarization directions of the piezoelectric substrate 52 are in opposite directions. It is also possible to apply the present invention to a type of piezoelectric resonator 58. It goes without saying that the shape of the electrode pattern is not limited in any way.

Although the embodiments of the present invention have been described above in detail based on the drawings, it is obvious that the present invention is not limited to the form of the piezoelectric resonator shown in the drawings. Further, the present invention can be applied to a thickness longitudinal vibration mode, a thickness shear vibration mode, etc. as long as the vibration mode is of an energy confinement type.

In addition, the present invention can be implemented with various improvements, modifications, and variations based on the knowledge of those skilled in the art without departing from the spirit thereof.

〔Effect of the invention〕

According to the piezoelectric resonator of the present invention, the direction of polarization of the same piezoelectric substrate is reversed at the position where the capacitive part is formed, so that vibrations from the piezoelectric resonant part formed at the position where the polarization direction is different is generated. The electric field generated by the capacitive part and the vibration generated by the electric field applied to the capacitive part cancel each other out, and the capacitive part is not affected by piezoelectricity. Therefore, it has become possible to obtain a piezoelectric resonator with excellent characteristics.

Furthermore, the piezoelectric resonant parts can be disposed close to each other across the boundary where the polarization direction is reversed, and the piezoelectric resonant part and the capacitive part can be disposed close to each other, resulting in an overall compact piezoelectric It became possible to obtain a resonator. Also,
The present invention has excellent effects such as being able to use a small pressure tL substrate and reducing manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram for explaining an embodiment of the piezoelectric resonator according to the present invention, FIG. 2 is a plan view of the piezoelectric resonator shown in FIG. 1, and FIG. FIG. 3 is a rear view of the resonator. 4(a) and 4(b) are explanatory diagrams showing an example of a method for manufacturing the piezoelectric substrate shown in FIG. 1, and FIG. 5 is an equivalent circuit diagram of the piezoelectric resonator shown in FIG. 2. 6 and 7 are both explanatory diagrams showing other embodiments for manufacturing a piezoelectric substrate according to the present invention, and FIG. 8 is an explanatory diagram showing a piezoelectric substrate obtained by the method of FIG. FIG. 3 is an explanatory diagram showing the polarization distribution of a substrate. 9 to 11 are diagrams showing other embodiments of the piezoelectric resonator according to the present invention, with FIG. 9 being a plan view and FIG. 10 being a piezoelectric resonator according to another embodiment of the present invention. An explanatory diagram showing the polarization distribution of the substrate, FIG. 11 is an equivalent circuit diagram of the piezoelectric resonator shown in FIG. 9. FIG. 12 is a plan view showing an example of a piezoelectric resonator according to the present invention in which another type of electrode pattern is created. 13 and 14 are both diagrams for explaining a conventional piezoelectric resonator, FIG. 12 is a front view, and FIG. 13 is an explanatory diagram showing the polarization distribution of the piezoelectric S plate shown in FIG. 12. It is. 10.50.58; piezoelectric resonator 12.3B, 52; piezoelectric substrate 14, vibrating electrode 16.32.54; capacitive electrode 20; common electrode 28.40.42.44; piezoelectric resonator 30.46.4B, 56; Capacity unit patent applicant Murata Manufacturing Co., Ltd. ON Figure Figure Figure Figure

Claims (2)

[Claims] (1) In a piezoelectric resonator in which two or more piezoelectric resonant parts and a capacitive part are formed between each of the piezoelectric resonant parts on the same piezoelectric substrate, the polarization directions of the adjacent piezoelectric resonant parts are opposite to each other. A piezoelectric resonator characterized by: (2) The piezoelectric resonator according to claim 1, wherein the capacitive portion is provided at a position where the polarization distribution of the piezoelectric substrate is opposite in polarization direction and substantially symmetrical.