JPH10190401A - Piezoelectric resonance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a stabilized operation by a tertiary higher harmonic by arranging rectangular vibration electrodes facing each other so as to make the longitudinal direction be parallel to one diagonal of a piezoelectric substrate and make the width direction be parallel to the other diagonal. SOLUTION: The rectangular vibration electrodes 2a and 2b facing each other are formed on both main surfaces of a rectangular ceramic piezoelectric substrate 1. The vibration electrodes 2a and 2b are arranged so as to make the longitudinal direction be a direction parallel to one diagonal X of the piezoelectric substrate 1 and make the width direction be the direction parallel to the other diagonal Y of the piezoelectric substrate 1. When an alternating voltage is applied to the vibration electrodes 2a and 2b and the operation is performed, vibration leaked from the side of the vibration electrodes 2a and 2b is propagated to an end side for constituting the corner part of the piezoelectric substrate 1, and since intervals with the respective end sides are not uniform, a lot of spuriousness is generated. Thus, the peak valley of the resonance frequency of a fundamental wave component is reduced and an operating frequency is prevented from being moved from a tirtiary higher harmonic frequency to a fundamental wave frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonance element utilizing the piezoelectric effect of piezoelectric ceramics.

[0002]

2. Description of the Related Art A piezoelectric resonance element is used as a piezoelectric resonator.
It is often used as an oscillator for operating an IC chip mounted on an electronic device, or as an oscillator for an oscillator circuit used in a communication device. As a piezoelectric filter, a communication signal, an audio signal, etc. of an electronic device, a communication device, etc. Is often used for the processing circuit.

In particular, as the frequency of an oscillation circuit or a circuit for signal processing or the like increases, the device is operated at a resonance frequency of a harmonic component, for example, three times the fundamental frequency.

In operating at the frequency of the harmonic component, it is important to eliminate the frequency shift between the resonance frequency of the harmonic component and the resonance frequency of the fundamental wave and to perform stable operation.

In a conventional piezoelectric resonance element, as shown in FIG. 5, opposing vibration electrodes 12a and 12b are formed on both main surfaces of a piezoelectric substrate 11. The vibration electrode 12
a and 12b are connected to the predetermined printed wiring board according to the connection structure of the piezoelectric resonance element.
At one end, extraction electrodes 13a and 13b connected to the vibration electrodes 12a and 12b were formed. The piezoelectric substrate 11
The vibrating electrode on the back side does not appear in FIG. 5 of the external perspective view.

The piezoelectric substrate 11 uses a rectangular flat plate because it is necessary to improve mass productivity and spurious characteristics, and the vibrating electrodes 12 a and 12 b have a similar shape to the piezoelectric substrate 1. Opposing vibrating electrode 12a of the piezoelectric substrate 1, when an alternating voltage is applied to 12b, so that resonates at the resonance frequency f _O.

In the above-described piezoelectric resonance element, high-frequency operation can be performed by using a triple frequency f ₃ instead of the basic resonance frequency f _O. In order to operate stably at such a harmonic component frequency, it is important to suppress spurious near the main peak at the resonance frequency f3 of the _third harmonic. Specifically, the operation is performed by appropriately selecting the thickness and dimensions of the piezoelectric substrate 1 and the dimensions of the vibration electrode.

[0008]

However, as described above, when the spurious is suppressed near the main peak at the _third harmonic resonance frequency f ₃ and the peak valley is increased, the spurious near the fundamental resonance frequency f _O is also increased. Is suppressed and the peak valley of the fundamental wave becomes relatively large.
Movement from the next harmonic resonance frequency f ₃ to the fundamental resonant frequency f _O is a problem that occurs.

This is because, when an alternating voltage is applied to the opposing electrodes of the piezoelectric substrate, vibrations leaking from the electrodes in the width direction or the length direction at a certain frequency cause the width edge or the length edge of the piezoelectric substrate to leak. Resonance occurs, and spurious is generated. However, in the conventional structure, the planar shape of the piezoelectric substrate is rectangular, and the vibrating electrodes 12a and 12b are similar in shape to the piezoelectric substrate, so that each side of the vibrating electrodes 12a and 12b and the end of the piezoelectric substrate 1 , The occurrence of spurious is reduced. This is because the main peak of the vibration at the third harmonic frequency has a small spurious characteristic and can be said to be a good impedance characteristic, but at the same time, the characteristic has a small spurious characteristic up to the fundamental frequency and has a large peak valley. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an energy trapping type piezoelectric vibrator using a flat piezoelectric substrate that generates third harmonic vibration. An object of the present invention is to provide a piezoelectric resonance element capable of performing a stable operation at a wave resonance frequency.

[0011]

According to the present invention, there is provided a piezoelectric resonance element in which rectangular vibration electrodes opposed to each other are formed on both main surfaces of a rectangular piezoelectric substrate. The piezoelectric resonance element is arranged so that a longitudinal direction is parallel to one diagonal line of the piezoelectric substrate and a width direction is parallel to the other diagonal line of the piezoelectric substrate.

[0012]

According to the piezoelectric resonance element of the present invention, the shape of the piezoelectric substrate is substantially rhombic with respect to the rectangular vibration electrode. That is, the distance between the rectangular vibration electrode and the edge of the piezoelectric substrate is not uniform. Therefore, the length of the vibration that leaks from the end of the vibrating electrode resonating at the end of the piezoelectric substrate greatly changes, and the occurrence of spurious becomes remarkable. Many of these spurious components are generated at the fundamental wave frequency, and as a result, the waveform of the fundamental wave is deteriorated, and particularly, the peak valley can be reduced. As a result, it is possible to prevent the operating resonance frequency from shifting from the third harmonic frequency to the fundamental frequency, and to stably operate at the third harmonic frequency. Although the increase in the number of spurious components is slightly observed near the third harmonic, the vibration displacement distribution is small and the energy leakage to the outside of the electrode is small in the third harmonic. The waveform does not dull. Furthermore, even if the piezoelectric resonance element of the present invention is roughly diamond-shaped, when separating and cutting from a large substrate, the cutting separation lines in the same direction are parallel to each other, so that it can be cut at a time by a wire saw or the like, A large number of elements can be easily manufactured and excellent in mass productivity.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a piezoelectric resonance device according to the present invention will be described with reference to the drawings.

FIG. 1 is an external perspective view of a piezoelectric resonance element according to the present invention, and FIG. 2 is a sectional view thereof.

In FIG. 1, reference numeral 10 denotes a piezoelectric resonance element, 1 denotes a piezoelectric substrate, and 2a and 2b denote vibration electrodes.

The piezoelectric substrate 1 is, for example lead zirconate titanate _{(Pb (Zr X Ti X-} 1) O 3 ( hereinafter referred to as PZT)) made of a piezoelectric ceramic such, has a substantially rectangular shape. The piezoelectric substrate 1 has been subjected to a polarization process according to the vibration mode.

The vibrating electrodes 2a and 2b are formed on both main surfaces of the piezoelectric substrate 1 by baking a conductive paste mainly composed of Ag (Ag alone or an Ag alloy such as Ag-Pd).

The vibrating electrodes 2a and 2b have a rectangular shape. The long side LD of the vibrating electrodes 2a and 2b is parallel to one diagonal line X of the piezoelectric substrate 1, and the short side WD is Are arranged in parallel with the other diagonal line Y. That is, when viewed from the rectangular vibration electrodes 2a and 2b, the piezoelectric substrate 1 has a substantially rhombic shape.

The vibrating electrodes 2a and 2b are connected to the extraction electrode 3
a and 3b are formed to facilitate connection with an external circuit. Each of the extraction electrodes 3a and 3b is a vibrating electrode 2.
For example, a vibrating electrode 2a formed on one main surface of the piezoelectric substrate 1 has a lead electrode extending to a corner of the piezoelectric substrate 1 in one direction. A vibration electrode 2b formed on the other main surface of the piezoelectric substrate 1 is provided with a lead electrode 3b extending to a corner paired with a corner in one direction of the piezoelectric substrate 1. Have been. In the drawing, the extraction electrodes 3a and 3b are formed at corners forming a pair of the piezoelectric substrates 1, but may be formed at a pair of end sides forming a pair of the piezoelectric substrates 1, respectively.

Such a piezoelectric resonance element 10 is used by applying a predetermined alternating voltage between the opposing vibrating electrodes 2a and 2b via the extraction electrodes 3a and 3b.

In the piezoelectric resonance element 10 having the above-described structure, the two diagonal lines X,
Rectangular vibration electrodes 2a and 2b are formed such that each side is parallel to Y. Therefore, between the edges of the rectangular vibration electrodes 2 a and 2 b and the edges of the piezoelectric substrate 1, substantially triangular piezoelectric ceramic exposed portions are generated near the corners of the piezoelectric substrate 1.

When the piezoelectric resonance element 10 is operated by applying a predetermined alternating voltage, the vibration electrodes 2a,
The vibration leaked from the side 2b propagates to the edges (two oblique sides when viewed from one side of the vibrating electrodes 2a and 2b) constituting the corners of the piezoelectric substrate 1, but each edge is inclined. Since the intervals between them are not uniform, many spurs occur. Many spurs occur near the resonance frequency of the fundamental wave component.

As a result, in the vicinity of the resonance frequency of the fundamental wave component, spurious signals are synthesized, and the waveform becomes dull. As a result, the peak valley of the resonance frequency of the fundamental wave component can be reduced.

Therefore, in the piezoelectric resonance element which resonates with the third harmonic component, the movement to the resonance frequency portion of the fundamental wave component is effectively suppressed, and the piezoelectric resonance element is stably operated at the resonance frequency of the third harmonic component. be able to.

Next, a method for manufacturing the piezoelectric resonance element of the present invention will be described in detail. The piezoelectric resonance element of the present invention is obtained, for example, by wet-mixing a PZT-based ceramic raw material prepared so as to obtain predetermined electric characteristics, dehydrating and drying the mixture, and then calcining at 800 to 1200 ° C. for 1 to 3 hours. Then, the calcined product is pulverized again by a ball mill.

Next, an organic binder is mixed with the pulverized material, and a large-sized sheet body having a predetermined thickness is formed by a doctor blade method, an extrusion molding method or the like.

Next, in the substantially rhombic element regions on both main surfaces of the large sheet body, a conductor film serving as the rectangular vibrating electrodes 2a and 2b and a conductor film serving as the lead electrodes 3a and 3b are Ag-coated.
Print a conductive paste such as Pd.

After that, the binder is removed at a predetermined temperature in the air, and baked in the air at a temperature of 1200 to 1300 ° C. for 2 to 6 hours to produce a large-sized resonant element substrate from which a large number can be obtained. Next, an Ag paste (conductive polymer) containing a polymer that cures at about 150 ° C. is printed on the electrode surfaces formed on both end faces of the large-sized resonance element substrate, and after curing, about 3 KV / mm in silicon oil at a predetermined temperature. The electric field is applied to perform the polarization treatment, and then the conductive polymer is washed off with water.

The large-sized resonant element substrate that has been subjected to the polarization processing is individually cut by a wire saw or a dicing saw into a predetermined shape to obtain a piezoelectric resonant element shown in FIG.

Incidentally, in order to stabilize the polarization, heat aging may be performed at 150 to 250 ° C. for 1 hour after the polarization treatment.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The inventor of the present invention has a product having a length of one side of 2.34 mm and a longer diagonal of 4.50 m.
m, the length of the shorter diagonal is 1.30 mm, and the thickness is 0.3 mm.
Using a 224 mm piezoelectric substrate 1, at the center of both main surfaces,
The rectangular vibration electrodes 2a and 2b each having a side of 0.5 mm were formed. At this time, one side of the vibrating electrodes 2a, 2b is parallel to the longer diagonal line X of the piezoelectric substrate 1, and the other pair is parallel to the shorter diagonal line Y of the piezoelectric substrate 1. Formed. The thickness of the vibrating electrodes 2a and 2b is 0.01
mm. As a conventional product, a rectangular vibration electrode having a side of 0.5 mm was formed on both main surfaces of a rectangular piezoelectric substrate having a length of 4.5 mm, a width of 1.28 mm and a thickness of 0.224 mm.

An alternating current was applied to the vibrating electrodes of each sample, and the impedance characteristics of the piezoelectric resonance element were evaluated for the vicinity of the fundamental wave and the vicinity of the third harmonic using an impedance analyzer. The results are shown in FIGS. FIG. 3A shows the impedance characteristics near the fundamental wave of the product of the present invention, and FIG. 3B shows the impedance characteristics near the third harmonic. FIG. 4A shows the impedance characteristics near the fundamental wave of the conventional product, and FIG.
Is the impedance characteristic near the third harmonic.

By comparing FIG. 3 (a) with FIG. 4 (a), FIG. 3 (a) of the product of the present invention can generate a large number of complicated spurs near the fundamental wave component, In FIG. 4 (a) of the product, it can be seen that the occurrence of spurious is less than in FIG. 3 (a). Moreover, as for the peak valley of the fundamental wave, in FIG. 3A of the product of the present invention, the value of the peak valley is small due to a large number of complicated spurious components.
In addition, it becomes unclear. On the other hand, FIG.
In (a), it can be understood that the value of the peak barre is large and the state is clear.

That is, a piezoelectric resonance element operated by the third harmonic, the frequency shift easily occurs from the third harmonic to the fundamental wave in the conventional product, and the frequency shift occurs from the third harmonic to the fundamental wave in the present invention. It can be understood that it is difficult to do.

Further, comparing FIG. 3B and FIG. 4B showing the impedance characteristics of the third harmonic, FIG. 3B of the present invention shows that a slight spurious is found near the third harmonic component. Although it is generated, its amplitude is relatively small, and it can be understood that the peak valley value of the third harmonic component is comparable to the conventional one (FIG. 4B).

That is, it can be understood that the product of the present invention is a piezoelectric resonance element which can be stably operated at the resonance frequency of the third harmonic component and is hard to move to the resonance frequency of the fundamental wave component.

In the above embodiment, the piezoelectric substrate 1 has been described as having a rhombic shape so that the shape relationship between the piezoelectric substrate 1 and the vibrating electrodes 2a and 2b is clear.
The shape may be a parallelogram (including a square shape and a rectangular shape as a special case). This is because, when each element is cut and separated from the large sheet body (large resonance element substrate), no loss occurs in the large sheet body and the production efficiency is increased.

The vibrating electrodes 2a and 2b are rectangular, and the long side LD is parallel to one diagonal line X of the piezoelectric substrate 1 and the short side WD is the other diagonal line Y of the piezoelectric substrate 1. As described above, the surface of the piezoelectric substrate 1 exposed around the vibrating electrodes 2a and 2b is formed in an irregular shape (a shape that can be regarded as a triangle having the corners of the piezoelectric substrate as vertices) as described above. Here, the vibrating electrodes 2a, 2b,
This is because the positioning of the vibrating electrodes 2a and 2b on both main surfaces is required in order to make the electrodes b and b have a predetermined area. That is,
Clarifying the geometric criteria, as in the present invention, greatly simplifies the positioning of the formation of the vibrating electrodes 2a, 2b.

[0039]

As described above, according to the present invention, a large number of spurious components are generated in the vicinity of the fundamental wave by positively generating vibration that resonates with the edge of the piezoelectric substrate around the rectangular vibration electrode. This causes the waveform of the fundamental wave to become dull, and the value of the peak valley of the fundamental wave to be reduced, so that the oscillation frequency becomes 3
It is possible to suppress the shift from the second harmonic to the fundamental wave, and obtain a normal and stable third harmonic piezoelectric resonance element.

Further, since the piezoelectric substrate is substantially rectangular, the productivity is very stable and the production efficiency does not deteriorate.

[Brief description of the drawings]

FIG. 1 is an external perspective view showing a piezoelectric resonance element of the present invention.

FIG. 2 is a sectional view showing a piezoelectric resonance element of the present invention.

3A and 3B show frequency-impedance characteristics of the piezoelectric resonance element of the present invention, and FIG. 3A is a characteristic diagram near a fundamental wave;
(B) is a characteristic diagram around the third harmonic component.

FIG. 4 shows a frequency-impedance characteristic of a conventional piezoelectric resonance element, where (a) is a characteristic diagram near a fundamental wave;
(B) is a characteristic diagram around the third harmonic component.

FIG. 5 is an external perspective view showing a conventional piezoelectric resonance element.

[Explanation of symbols]

 10 Piezoelectric resonance element 1 Piezoelectric substrate 2a, 2b Vibration electrode 3a, 3b Leader electrode

Claims (1)

[Claims] 1. A piezoelectric resonance element in which rectangular vibration electrodes opposed to each other are formed on both main surfaces of a rectangular piezoelectric substrate, wherein the vibration electrode has a longitudinal direction which corresponds to one diagonal line of the piezoelectric substrate. A piezoelectric resonance element, which is arranged in parallel so that its width direction is parallel to the other diagonal line of the piezoelectric substrate.