JP2003008391A - Thickness longitudinal piezoelectric resonator and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thickness longitudinal piezoelectric resonator of an energy confining type by which a specific band can easily be adjusted without causing the changing of a phase rotation. SOLUTION: In the thickness longitudinal piezoelectric resonator 1, first and second exciting electrodes 3 and 4 are formed so as to oppose the first and second main surfaces 2a and 2b of a piezoelectric substrate 2 polarized in a thickness direction, a piezoelectric resonating part of the energy confining type is formed at a part where the first and second exciting electrodes 3 and 4 oppose each other, and a part of the thickness direction is unpolarized or has lower polarizability compared with the other piezoelectric substrate part at the piezoelectric resonating part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thickness extensional piezoelectric resonator used for a piezoelectric oscillator, a piezoelectric filter and the like, and a method for manufacturing the same, and more particularly, an energy trap type piezoelectric resonance utilizing a thickness extensional vibration mode. The present invention relates to a child and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, energy trap type piezoelectric resonators utilizing a thickness extensional vibration mode have been widely used for piezoelectric oscillators, piezoelectric filters and the like. In this type of thickness extensional piezoelectric resonator, a pair of excitation electrodes are formed so as to partially oppose each other on both main surfaces of the piezoelectric body, and the piezoelectric body is uniformly polarized in the thickness direction.

By the way, in the thickness extensional piezoelectric resonator, the ratio band is controlled by increasing or decreasing the polarization degree obtained by polarization. However, when the ratio band is reduced, the amount of phase rotation in the resonance characteristic also sharply decreases. If the amount of phase rotation sharply decreases, the oscillation in the oscillation circuit becomes unstable.

On the other hand, Japanese Patent Laid-Open No. 1-232816 discloses an energy trap type electrostrictive resonance device shown in FIG. Here, the excitation electrode 102 is formed on the upper surface of the electrostrictive material body 101, the excitation electrode 103 is formed on the lower surface, and the internal excitation electrode 104 is formed at the intermediate height position. The excitation electrodes 102 and 103 and the internal excitation electrode 104 are opposed to each other via the electrostrictive material layers 105 and 106. Here, the polarizability of the electrostrictive material layer 105 and the polarizability of the electrostrictive material layer 106 are different from each other, which suppresses spurious appearing between the resonance frequency and the antiresonance frequency. There is.

[0005]

As described above, in the conventional bandwidth control method, a method of increasing or decreasing the polarization degree of the uniformly polarized piezoelectric material has been used. However, there has been a problem that the amount of phase rotation changes rapidly with the control of the ratio band.

On the other hand, in the electrostrictive material device described in Japanese Patent Laid-Open No. 1-28816, the polarization degree of a plurality of electrostrictive material layers is made different to suppress spurious.
However, in this method, the boundary between the electrostrictive material layer 105 and the electrostrictive material layer 106 coincides with the position where the internal excitation electrode 104 is provided. The stress is most concentrated on the boundary between the electrostrictive material layers 105 and 106 having different polarizability due to polarization strain. Further, the coupling between the internal excitation electrode 104 and the electrostrictive material layers 105 and 106 is a coupling between ceramics and metal, and therefore the coupling force is weak. Therefore, the electrostrictive material device described in this prior art has a problem that cracks are likely to occur in a portion where the internal excitation electrode 4 is provided during long-term use.

An object of the present invention is to provide an energy confinement type thickness extensional piezoelectric resonator utilizing a thickness extensional vibration mode, capable of controlling a specific band while suppressing an abrupt change in the amount of phase rotation, and mechanically. A thickness longitudinal piezoelectric resonator excellent in strength and a method for manufacturing the same.

[0008]

According to a broad aspect of the first invention of the present application, a piezoelectric body having first and second main surfaces facing each other in the thickness direction and polarized in the thickness direction, First and second excitation electrodes that are partially polarized on the first and second main surfaces of the piezoelectric body and that are arranged to face each other with the piezoelectric body interposed therebetween. In the energy confinement type piezoelectric resonance part in which the two excitation electrodes face each other, a part of the piezoelectric body is unpolarized in the thickness direction of the piezoelectric body or its polarization degree is lower than that of other piezoelectric body parts. Will be provided.

In a particular aspect of the thickness extensional piezoelectric resonator according to the first aspect of the invention, there is provided a thickness extensional piezoelectric resonator utilizing harmonics of Nth order (N is an integer of 2 or more) thickness extensional vibration. According to the present invention, it is possible to provide a thickness extensional piezoelectric resonator which can be used in a higher frequency range and whose ratio band can be easily controlled without causing a drastic change in the amount of phase rotation.

In another specific aspect of the first invention, the piezoelectric body is formed of an elongated rectangular plate-shaped piezoelectric substrate, and the first and second excitation electrodes are provided at the center in the longitudinal direction of the piezoelectric substrate. Opposed via the piezoelectric substrate, and the first and second
Drive electrodes are formed so as to reach both ends in the width direction of the piezoelectric substrate, whereby the ratio band can be easily controlled according to the present invention without causing a sudden change in the amount of phase rotation. A mold thickness longitudinal piezoelectric resonator can be provided.

In a more specific aspect of the thickness extensional piezoelectric resonator according to the first invention, the piezoelectric substrate has first and second end faces located at both ends in the length direction of the piezoelectric substrate. The excitation electrode is formed so as to reach a ridgeline formed by the first main surface and the first end surface, and the second excitation electrode is formed by the second main surface and the second end surface.
Is formed so as to reach the ridgeline with the end face of the.

According to the second broad aspect of the present invention, the first and second main surfaces facing each other, the first and second end surfaces located at both ends in the length direction, and the first and second end surfaces. An elongated rectangular plate-shaped piezoelectric substrate having two side surfaces, and first and second piezoelectric substrates
The first and second excitation electrodes respectively formed on the main surface of the piezoelectric substrate so as to reach both ends in the width direction of the piezoelectric substrate, and the piezoelectric substrate layer is disposed inside the piezoelectric substrate. At least one layer of an internal excitation electrode that is at least partially opposed to at least one of the first and second excitation electrodes, and at least one of the first and second excitation electrodes and the internal excitation electrode. In the piezoelectric resonance part that is overlapped via the piezoelectric substrate layer, resonance characteristics using the Nth harmonic of the thickness longitudinal vibration mode are obtained, and in the piezoelectric resonance part, the thickness of the piezoelectric body is Provided is a thickness extensional piezoelectric resonator in which a part of the direction has a lower degree of polarization than that of unpolarized or other regions.

A method of manufacturing a thickness extensional piezoelectric resonator according to the present invention comprises a step of preparing a mother piezoelectric body having first and second main surfaces facing each other in a thickness direction, and a step of preparing the mother piezoelectric body. Forming a first polarization electrode on the entire main surface of 1.
A plurality of second short-circuited to the second main surface by the conductive connection portion.
The step of forming the polarization electrode, and applying an electric field between the first polarization electrode and the second polarization electrode polarizes the mother piezoelectric body to obtain the thickness of the mother piezoelectric body. Forming a region where the degree of polarization is locally small or unpolarized in the direction, and a plurality of first and second excitation electrodes are formed on the first and second main surfaces of the piezoelectric body of the polarized mother. And a step of cutting the mother piezoelectric body into individual piezoelectric resonator units.

In a particular aspect of the method of manufacturing a thickness extensional piezoelectric resonator according to the present invention, the mother piezoelectric body is at least one.
A plurality of layers of internal excitation electrodes are provided, and the second polarization electrode is formed so as to have a portion that partially overlaps with the internal excitation electrode via the piezoelectric layer and a portion that does not overlap.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings. FIG. 1 is a vertical sectional view of a thickness extensional piezoelectric resonator according to a first embodiment of the present invention, and FIG. 2 is a perspective view showing its appearance.

The thickness extensional piezoelectric resonator 1 has an elongated rectangular plate-shaped piezoelectric substrate 2 as a piezoelectric body. The piezoelectric substrate 2 is made of piezoelectric ceramics such as lead zirconate titanate-based ceramics. The piezoelectric substrate 2 has first and second main surfaces 2a and 2b facing each other in the thickness direction, first and second end surfaces 2c and 2d facing each other, and side surfaces 2e and 2 respectively.
f and.

The piezoelectric substrate 2 is polarized in the thickness direction. The thickness direction means the first and second main surfaces 2a, 2
It is the direction of connecting b. The polarization structure of the piezoelectric substrate 2 will be described later in detail.

From the center of the main surface 2a of the piezoelectric substrate 2, the main surface 2
b and the end face 2c so as to reach the ridgeline of the first excitation electrode 3
Are formed. From the center of the second main surface 2b of the piezoelectric substrate 2 to the ridge line formed by the main surface 2b and the end surface 2d,
The excitation electrode 4 of is formed. The first and second excitation electrodes 3 and 4 are opposed to each other via the piezoelectric substrate 2 at the center in the length direction of the piezoelectric substrate 2. The exciting electrodes 3 and 4 have their opposing portions forming an energy trap type piezoelectric resonance portion. Further, the excitation electrodes 3 and 4 are formed so as to reach the entire width of the piezoelectric substrate 2.

In the thickness extensional piezoelectric resonator 1, a part of the energy trap type piezoelectric resonator in the thickness direction of the piezoelectric substrate 2 is separated from the polarization degree P of the other piezoelectric body portion as shown by an arrow P1. It is extremely low. That is, the polarization degree of the energy confinement type piezoelectric resonance portion is lower than the polarization degree P of the other area of the piezoelectric substrate 2 in the region near the excitation electrode 3 formed on the one main surface 2a.

Since the polarization degree of a part of the region of the piezoelectric resonator in the thickness direction is lower than that of the other piezoelectric substrate parts, the ratio band can be narrowed without changing the phase rotation amount so much. . This will be described based on a concrete experimental example.

As the energy trapping type thickness extensional piezoelectric resonator 1 utilizing the fundamental wave of the thickness extensional mode, the following specifications were produced. The piezoelectric substrate 2 is made of lead zirconate titanate ceramics and has a length of 2.5 and a width of 0.4 ×.
A piezoelectric body having a thickness of 0.15 mm was prepared, and the piezoelectric body 2 was polarized according to a method substantially the same as the method described later with reference to FIGS. A region having a relatively low polarization degree P1 was formed in the resonance part.

On the upper surface and the lower surface of the piezoelectric substrate 2, 0.4
The excitation electrodes 3 and 4 were formed so as to face each other in the range of 0.6 mm. With respect to the thickness extensional piezoelectric resonator 1 prepared as described above, the relative band was measured and found to be 3%, and the amount of phase rotation was 87 degrees. The characteristic was measured for the thickness longitudinal piezoelectric resonator of the first comparative example prepared in the same manner as the above-mentioned example except that the piezoelectric substrate 2 was uniformly polarized, and the specific band was 6%. And the phase rotation amount is 88
It was degree.

Therefore, according to this embodiment, it is understood that the ratio band can be significantly narrowed without changing the phase rotation amount. As is clear from the comparison between the above-described embodiment and the first comparative example, the relative bandwidth is adjusted by relatively lowering the polarization degree of a partial region of the piezoelectric substrate 2 in the thickness direction of the piezoelectric substrate 2. be able to. In the above-described embodiment, the polarization degree of the portion near the excitation electrode 3 of the piezoelectric resonance part is relatively low, but the portion near the excitation electrode 4 has a relatively low polarization degree. Good. Further, an unpolarized portion may be formed instead of the portion having a relatively low degree of polarization.

In this embodiment, the internal electrodes are not formed. Further, in the portion where the piezoelectric resonance portion of the piezoelectric substrate 2 is configured, a portion that is unpolarized or has a relatively low degree of polarization is configured in a part in the thickness direction. Breakage due to stress concentration at the boundary with the relatively high intensity is also unlikely to occur.

FIG. 3 is a vertical sectional view of a thickness extensional piezoelectric resonator according to a second embodiment of the present invention. The thickness extensional piezoelectric resonator 11 of the second embodiment uses the third harmonic of the thickness extensional vibration, and the other configurations are the same as those of the first embodiment.

As the thickness extensional piezoelectric resonator of this example, one having the following specifications was produced. A piezoelectric substrate 2 made of lead titanate-based ceramics having a length of 2.5, a width of 0.4, and a thickness of 0.45 mm was prepared. Also in this example, the polarization degree P1 of the piezoelectric layer portion having a thickness of 1/3 on the side of the excitation electrode 3 was made relatively lower than the polarization degrees P of the remaining piezoelectric substrate portions. Such a polarized structure was obtained by performing the polarization treatment in the substantially same manner as in FIGS. 9 to 13 except that the internal electrode was not provided.

As described above, the piezoelectric substrate 2 was obtained in which the degree of polarization of the piezoelectric resonance portion of the thickness 1/3 near the excitation electrode 3 was about 50% of the remaining piezoelectric substrate portion. The excitation electrodes 3 and 4 were formed in the same manner as in the experimental example of the first embodiment, and the characteristics were measured.

For comparison, an energy trap type thickness longitudinal piezoelectric resonator of a second comparative example using a piezoelectric substrate 2 uniformly polarized in the thickness direction with a polarization degree of 100% is prepared. The characteristics were measured in the same manner.

As a result, in the thickness extensional piezoelectric resonator of the second embodiment, the ratio band was 0.6% and the phase rotation amount was 82 degrees. The ratio band of the thickness extensional piezoelectric resonator using the third harmonic wave of the second comparative example is 1%, and the phase rotation amount is 83.
It was degree. Therefore, even in the thickness extensional piezoelectric resonator using the third harmonic of the thickness extensional vibration, a part of the piezoelectric resonance part in the thickness direction is unpolarized or has a lower polarization degree than other parts of the piezoelectric body. By doing so, it can be seen that the ratio band can be adjusted with almost no change in the phase rotation amount as in the first embodiment.

4 and 5 are a schematic perspective view and a front sectional view showing a thickness extensional piezoelectric resonator according to a third embodiment of the present invention. The thickness extensional piezoelectric resonator 21 of the present embodiment is an energy trap type thickness extensional piezoelectric resonator that utilizes a second harmonic of the thickness extensional vibration.

The thickness extensional piezoelectric resonator 21 has a rectangular plate-shaped piezoelectric body 22. The piezoelectric body 22 is polarized in the thickness direction. However, as will be described later, in the energy trap type piezoelectric resonance part, a part in the thickness direction is in a non-polarized state, and the other part is uniformly polarized.

A first excitation electrode 23 is formed in the center on the main surface 22a of the piezoelectric body 22. Piezoelectric substrate 2
A second excitation electrode 24 is formed on the second main surface 22b of No. 2 as shown in FIG. Further, an internal excitation electrode 25 is formed at the intermediate height position of the piezoelectric substrate 22. Excitation electrodes 23, 24
The internal excitation electrode 25 has a circular shape in this embodiment, and is arranged so as to face each other with the piezoelectric layer in between in the thickness direction of the piezoelectric substrate 22. Terminal electrodes 25 and 26 are connected to the first and second excitation electrodes 23 and 24 via connection conductive portions 23a and 24a.

The portion where the excitation electrodes 23 and 24 and the internal excitation electrode 25 face each other constitutes an energy trap type piezoelectric resonance portion A (FIG. 5). The first and second excitation electrodes 23 and 24 do not necessarily have to face each other, and the internal excitation electrode 25 may face only one of the excitation electrodes 23 or 24.

As shown in FIG. 5, of the piezoelectric resonance part A,
The piezoelectric plate portion 22c above the internal excitation electrode 25 is in a non-polarized state, and the piezoelectric plate portion below the internal excitation electrode 24 and the piezoelectric plate portion around the piezoelectric resonance portion A have a polarization degree P. It is polarized in the thickness direction.

In this embodiment, since the piezoelectric plate portion 22c in the piezoelectric resonance portion A is not polarized,
Similar to the second embodiment, the ratio band can be narrowed without changing the phase rotation amount.

6 and 7 are a perspective view and a vertical sectional view for explaining a thickness extensional piezoelectric resonator according to a fourth embodiment of the present invention. The thickness longitudinal piezoelectric resonator 31 of the fourth embodiment is
Similar to the third embodiment, this is an energy trap type thickness extensional piezoelectric resonator utilizing the second harmonic of thickness extensional vibration. However, in the thickness extensional piezoelectric resonator 31, an elongated rectangular plate-shaped piezoelectric substrate 32 is used as the piezoelectric substrate. Piezoelectric substrate 3
A first excitation electrode 33 is formed on the second main surface 32a of the second electrode. A second excitation electrode 34 is formed on the second main surface 32b of the piezoelectric substrate 32. Excitation electrodes 33, 3
4 is the piezoelectric substrate 32 from the center in the length direction of the piezoelectric substrate 32.
It is extended toward the one end face 32c side and is formed so as to reach the ridgeline formed by the main faces 32a and 32b and the end face 32c. In addition, the excitation electrodes 33, 34
Are electrically connected by a connection electrode 36 formed on the end face 32c.

On the other hand, at the intermediate height position of the piezoelectric substrate 32,
The internal excitation electrode 35 is formed. Internal excitation electrode 35
Is the excitation electrode 3 at the center of the piezoelectric substrate 32 in the length direction.
3, 34 are opposed to each other via the piezoelectric substrate layer. The portion where the excitation electrodes 33, 34 and the internal excitation electrode 35 face each other constitutes an energy trap type piezoelectric resonance portion. The excitation electrodes 33 and 34 do not necessarily have to face each other. The internal excitation electrode 35 is the excitation electrode 3
You may oppose only one of 3, 34.

The excitation electrode 35 is formed so as to reach the second end face 32d of the piezoelectric substrate 32, and the second end face 32 is formed.
It is electrically connected to the terminal electrode 37 formed on d. The terminal electrode 37 is formed so as to extend from the end surface 32d of the piezoelectric substrate 32 to the main surfaces 32a and 32b. Therefore, the piezoelectric resonator 31 includes the terminal electrode 37 and the excitation electrode 34.
And the connection electrode 36, and can be surface-mounted on a printed circuit board or the like.

By the way, the excitation electrodes 33 and 34 and the internal excitation electrode 35 are formed on the piezoelectric substrate 32 so as to reach the entire width in the width direction. Therefore, in the thickness extensional piezoelectric resonator 31, the piezoelectric resonance portion extending to the entire width in the width direction of the piezoelectric substrate 32 is formed at the center in the length direction. In addition, the piezoelectric substrate 3
A vibration damping portion is formed on both sides of the piezoelectric resonance portion in the length direction 2.

A part of the piezoelectric resonance portion in the thickness direction is unpolarized. That is, as shown in FIG.
In the piezoelectric resonator, the internal excitation electrode 35 and the excitation electrode 3
The piezoelectric substrate portion between 3 and 3 is in an unpolarized state, and the other regions are polarized so as to have the same degree of polarization as indicated by arrow P.

In this embodiment, the terminal electrode 37 and the connection electrode 3 are
By applying an AC voltage to the piezoelectric resonance part 6, the piezoelectric resonance part is excited, and the resonance characteristic using the second harmonic of the thickness longitudinal vibration can be obtained. In this case, since the polarization structure of the piezoelectric resonance part is configured as described above, similar to the first to third embodiments, there is almost no change in the phase rotation amount,
The bandwidth can be narrowed. This will be described based on a concrete experimental example.

As the piezoelectric substrate 32 constituting the thickness longitudinal piezoelectric resonator 31, a lead titanate-based ceramic having a length of 2.5 × width of 0.4 × thickness of 0.30 mm was used.
The facing area of the excitation electrodes 33, 34 and the internal excitation electrode 35 was 0.4 × 0.6 = 0.24 mm ² .

Polarization treatment was performed according to the conventional manufacturing method described with reference to FIGS. 9 to 13 so that the upper portion of the internal excitation electrode 35 was not polarized. For the purpose of comparison, a fourth substrate constructed in the same manner as the fourth embodiment, except that the entire region of the piezoelectric substrate 32 is uniformly polarized so as to have a 100% polarized state. A thickness longitudinal piezoelectric resonator of a comparative example was prepared.

When the characteristics of the thickness extensional piezoelectric resonators of the fourth embodiment and the fourth comparative example prepared as described above were measured, it was found that the relative bandwidth was 6% in the fourth comparative example. On the other hand, in the fourth example, it was confirmed to be 1% or less. Further, FIG. 8 shows changes in the amount of phase rotation when the polarizability of the piezoelectric substrates prepared in the present example and the comparative example are variously changed, ◯ indicates the example, and × indicates the result of the comparative example. .
DF / Fa (%) on the horizontal axis is a specific band (however,
DF is Fa-Fr, Fa is antiresonance frequency, Fr is resonance frequency), and the degree of polarization is correlated. As is apparent from FIG. 8, in the example in which the unpolarized region is provided, the phase rotation amount does not change so much regardless of the change in the polarization degree of the remaining region, whereas in the comparative example, the polarization degree changes. It can be seen that the amount of phase rotation changes greatly by doing so.

Therefore, according to the present invention, when the degree of polarization is changed and the relative bandwidth is changed, the change in the amount of phase rotation can be suppressed as compared with the conventional example, and therefore the amount of phase rotation is reduced. It can be seen that the relative bandwidth can be adjusted to a large extent by controlling the polarization degree without incurring so much.

Next, the manufacturing method of the present invention will be clarified by explaining the manufacturing method of the thickness extensional piezoelectric resonator of the fourth embodiment with reference to FIGS. First, as shown in FIG. 9, a mother piezoelectric body 32A is prepared. A plurality of internal excitation electrodes 35A are formed inside the mother piezoelectric body 32A. A plurality of second polarization electrodes 41 are formed on the upper surface of the mother piezoelectric body 32A with a predetermined gap therebetween. The plurality of polarization electrodes 41 are short-circuited to each other. On the other hand, the first polarization electrode 40 is formed on the entire lower surface of the mother piezoelectric body 32A.

As is clear from FIG. 9, the mother internal excitation electrode 35A is the second excitation electrode 35A in the direction of the arrow X in FIG.
Of the polarizing electrode 41 and the non-overlapping portion thereof.

Therefore, when a DC electric field is applied between the polarization electrodes 40 and 41 to perform polarization treatment, the polarization electrodes 40 and 41
The portion facing 41 is polarized as indicated by arrow P. On the other hand, due to the presence of the internal excitation electrode 35A, in the portion where the polarization electrodes 40 and 41 do not face each other, the upper portion of the internal excitation electrode 35A is in a non-polarized state as shown by hatching of multiple points. .

Next, as shown in FIG. 10, the polarization electrodes 40 and 41 are removed after the polarization process. Then, the piezoelectric body 32A of the mother after polarization shown in FIG.
Cut along the broken line B of 0. In this way, FIG.
As a result, the second mother piezoelectric body 32B shown in FIG. Then, as shown in FIG. 11, the mother excitation electrodes 33A and 34A and the mother connection electrode 3 are attached to the mother piezoelectric body 32B.
6 and the mother terminal electrode 37A are formed. Thereafter, as shown in FIG. 12, by cutting along the broken line C, the thickness extensional piezoelectric resonator 31 shown in FIG. 13 is obtained.

That is, by using the polarization method shown in FIG. 10, in the piezoelectric resonance portion of the thickness extensional piezoelectric resonator 31, the piezoelectric plate portion above the internal excitation electrode 35 is in a non-polarized state, and the remaining portion has a thickness. It can be polarized uniformly in the direction.

As is apparent from the above manufacturing method, in obtaining the polarization structure, a plurality of polarization electrodes 41 shown in FIG. 9 are used.
It is understood that the thickness extensional piezoelectric resonator 31 of the present embodiment can be obtained by simply arranging the above, without adding a special processing step to the conventional production method of the thickness extensional piezoelectric resonator. That is, it is possible to provide a thickness extensional piezoelectric resonator in which the bandwidth can be easily adjusted without significantly increasing the manufacturing cost.

In the above-mentioned first to fourth embodiments,
Although the fundamental wave, the second harmonic wave, or the third harmonic wave of the thickness longitudinal vibration is used, in the present invention, it is also possible to use a proper harmonic wave of the thickness longitudinal vibration of the fourth harmonic or more.

Further, in the third and fourth embodiments, one layer of internal excitation electrode is provided in the piezoelectric substrate, but two or more layers of internal excitation electrode may be arranged.

[0054]

In the thickness extensional piezoelectric resonator according to the first aspect of the invention, in the energy trap type piezoelectric resonance portion where the first and second excitation electrodes face each other, a part in the thickness direction is unpolarized or other Since the polarization degree is lower than that of the piezoelectric portion, the specific band can be easily adjusted by adjusting the polarization degree without changing the phase rotation amount.
Therefore, it is possible to easily provide a piezoelectric oscillator or a piezoelectric filter having desired characteristics and good characteristics.

Further, when the harmonic of the Nth-order thickness longitudinal vibration is used, the adjustment of the ratio band is easy according to the present invention.
It is possible to provide a thickness extensional piezoelectric resonator that can be used in a higher frequency range.

Further, in the second invention, the first and second excitation electrodes are opposed to each other at the center in the longitudinal direction of the elongated rectangular plate-shaped piezoelectric substrate, and at least one internal excitation electrode is formed in the piezoelectric substrate. The first and second excitation electrodes are partially opposed to each other, and an energy trap type piezoelectric resonance portion is formed in a portion where the first and second excitation electrodes and the internal excitation electrode overlap with each other via the piezoelectric substrate layer. In the piezoelectric resonating portion, a part of the piezoelectric substrate in the thickness direction is unpolarized or has a lower degree of polarization than other regions. Therefore, the phase rotation amount should be almost changed as in the first invention. Therefore, the relative bandwidth can be easily adjusted, and the piezoelectric oscillator or the piezoelectric filter having the desired relative bandwidth can be easily provided.

In the method of manufacturing the thickness extensional piezoelectric resonator according to the present invention, the first polarization electrode is provided on the entire first main surface of the mother piezoelectric body, and the plurality of second polarization electrodes is provided on the second main surface. A piezoelectric body of the mother is polarized by forming an application electrode and applying an electric field between the first and second polarization electrodes. In this case, the portions where the first and second polarization electrodes do not face each other are set to the unpolarized state or the state where the degree of polarization is low. Therefore, the first and second mother piezoelectric bodies polarized as described above are
After forming a plurality of first and second excitation electrodes on the main surface of
By cutting into individual piezoelectric resonator units, the thickness extensional piezoelectric resonator according to the present invention can be easily obtained. Therefore, in the conventional method for manufacturing a thickness extensional piezoelectric resonator, a plurality of second layers are added.
It is possible to obtain an inexpensive thickness extensional piezoelectric resonator in which the ratio band can be easily adjusted by adding the step of forming the polarization electrode, and the other steps are hardly changed.

In the step of preparing the mother piezoelectric body, in the case where a plurality of internal electrodes of at least one layer are formed in the mother piezoelectric body, according to the present invention, the thickness-longitudinal piezoelectric utilizing the Nth harmonic is used. The resonator can be easily provided.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a thickness extensional piezoelectric resonator according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing the external appearance of the thickness extensional piezoelectric resonator of the first embodiment.

FIG. 3 is a longitudinal sectional view of a thickness extensional piezoelectric resonator according to a second embodiment.

FIG. 4 is a schematic perspective view showing the appearance of a thickness extensional piezoelectric resonator according to a third embodiment.

5 is a front sectional view of the thickness extensional piezoelectric resonator shown in FIG.

FIG. 6 is a perspective view showing the appearance of a thickness extensional piezoelectric resonator according to a fourth embodiment.

FIG. 7 is a vertical sectional view of a thickness extensional piezoelectric resonator according to a fourth embodiment.

FIG. 8 is a diagram showing changes in the amount of phase rotation according to changes in the polarization degree in the thickness extensional piezoelectric resonator of the fourth example and the thickness extensional piezoelectric resonator of the comparative example.

FIG. 9 is a perspective view for explaining a method of manufacturing a thickness extensional piezoelectric resonator according to a fourth embodiment, and is a perspective view for explaining a polarization step.

FIG. 10 is a perspective view showing a mother piezoelectric body that has been polarized.

FIG. 11 is a perspective view showing a state in which a mother piezoelectric material is cut and a mother excitation electrode is formed on the obtained second mother piezoelectric material.

12 is a perspective view for explaining a step of cutting the piezoelectric body of the second mother shown in FIG.

13 is a perspective view showing a thickness extensional piezoelectric resonator according to a fourth example obtained by cutting the piezoelectric body of the second mother shown in FIG.

FIG. 14 is a front sectional view showing an example of a conventional thickness extensional piezoelectric resonator.

[Explanation of symbols]

1 ... Thickness longitudinal piezoelectric resonator 2 ... Piezoelectric substrate as piezoelectric body 2a, 2b ... First and second main surfaces 2c, 2d ... First and second end faces 2e, 2f ... Sides 3 ... First excitation electrode 4 ... Second excitation electrode 11 ... Thickness longitudinal piezoelectric resonator 21 ... Thickness longitudinal piezoelectric resonator 22 ... Piezoelectric substrate 22a, 22b ... First and second main surfaces 23, 24 ... First and second excitation electrodes 25 ... Internal excitation electrode 31 ... Thickness longitudinal piezoelectric resonator 32 ... Piezoelectric substrate 32A ... Mother piezoelectric body 32B ... Piezoelectric body of second mother 32a, 32b ... First and second main surfaces 32c, 32d ... First and second end faces 32e, 32f ... Side surface 33, 34 ... First and second excitation electrodes 33A, 34A ... Mother excitation electrodes 35 ... Internal excitation electrode 35A ... Mother internal excitation electrode 36 ... Connection electrode 37 ... Terminal electrode 40, 41 ... First and second polarization electrodes A ... Piezoelectric resonator

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Jiro Inoue             2-10-10 Tenjin, Nagaokakyo, Kyoto Stock             Murata Manufacturing Co., Ltd. F term (reference) 5J108 BB04 CC04 CC13 DD01 DD06                       FF01 FF11 KK02 MM12 MM14

Claims (7)

[Claims] 1. A piezoelectric body having first and second main surfaces facing each other in the thickness direction, polarized in the thickness direction, and partially polarized on the first and second main surfaces of the piezoelectric body. And the first and second excitation electrodes arranged so as to face each other via the piezoelectric body, and the energy trapping type piezoelectric resonance part in which the first and second excitation electrodes face each other, A thickness extensional piezoelectric resonator in which a part of the piezoelectric body is unpolarized in the thickness direction or has a lower degree of polarization than other piezoelectric body portions. 2. The thickness extensional piezoelectric resonator according to claim 1, wherein a harmonic of Nth order (N is an integer of 2 or more) thickness extensional vibration is used. 3. The piezoelectric body is composed of a piezoelectric substrate having an elongated rectangular plate shape, and the first and second excitation electrodes are opposed to each other at the center in the length direction of the piezoelectric substrate via the piezoelectric substrate. The thickness extensional piezoelectric resonator according to claim 1 or 2, wherein the first and second excitation electrodes are formed so as to reach both ends in the width direction of the piezoelectric substrate. 4. The piezoelectric substrate has first and second end faces located at both ends in the length direction of the piezoelectric substrate, and the first excitation electrode is formed by the first main face and the first end face. 4. The thickness longitudinal piezoelectric resonance according to claim 3, wherein the second excitation electrode is formed so as to reach a ridgeline, and the second excitation electrode is formed so as to reach a ridgeline between the second main surface and the second end surface. Child. 5. The first and second main surfaces facing each other, the first and second end surfaces located at both ends in the length direction, and the first and second end surfaces.
An elongated rectangular plate-like piezoelectric substrate having a side surface of the piezoelectric substrate, and a first piezoelectric substrate formed on each of the first and second main surfaces of the piezoelectric substrate and extending to both ends in the width direction of the piezoelectric substrate. First and second excitation electrodes, and at least one layer of internal excitation that is disposed in the piezoelectric substrate and at least partially opposes at least one of the first and second excitation electrodes via the piezoelectric substrate layer. An N-th harmonic of a thickness longitudinal vibration mode is used in a piezoelectric resonance part including an electrode, and at least one of the first and second excitation electrodes and the internal excitation electrode are overlapped with each other via a piezoelectric substrate layer. It is configured so that the resonance characteristics described above can be obtained, and in the piezoelectric resonance part, a part of the piezoelectric body in the thickness direction is
A thickness extensional piezoelectric resonator having a polarization degree lower than that of unpolarized or other regions. 6. A first and a second that face each other in the thickness direction.
And a step of preparing a mother piezoelectric body having a main surface of the first main surface, a first polarization electrode is formed on the entire first main surface of the mother piezoelectric body, and a plurality of second main electrodes are formed on the second main surface. A step of forming a polarization electrode; and, by applying an electric field between the first polarization electrode and the second polarization electrode, polarize the mother piezoelectric body, and the thickness direction of the mother piezoelectric body A step of forming a region where the degree of polarization is locally small or unpolarized, and forming a plurality of first and second excitation electrodes on the first and second main surfaces of the polarized piezoelectric body of the mother And a step of cutting the mother piezoelectric body into individual piezoelectric resonator units. 7. The piezoelectric body of the mother has a plurality of internal excitation electrodes of at least one layer, and the second polarization electrode partially overlaps with the internal excitation electrode via the piezoelectric layer. The method of manufacturing a thickness extensional piezoelectric resonator according to claim 6, wherein the thickness extensional piezoelectric resonator is formed so as to have a non-overlapping portion.