JPH1051260A - Piezoelectric resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the spurious due to a thickness tilt of a piezoelectric element in the shape of a vibration electrode for a thickness vertical containment type piezoelectric resonator by adding a rectangular vibration electrode to a piezoelectric element that has a tilt in its thickness direction. SOLUTION: A piezoelectric resonator 8 consists of the rectangular vibration electrodes 2 and 3, the extraction electrodes 4 and 6 and the connection electrodes 5 and 7 which are formed on both opposite main surfaces of a piezoelectric element 1. The electrode 2 is connected to the electrode 4 positioned at a point near one of both ends of the element 1 in its longer side direction via the electrode 5, and the electrode 3 is connected to the electrode 6, positioned at a point near the other end of the element 1 in its longer side direction via the electrode 7 respectively. For example, if the element 1 has the thickness vertical containment type resonance frequency of about 25MHz and has a ratio of 0.03 to 0.1% set for a thin part with respect to a thick part of the element 1, the spurious can be reduced most effectively with a ratio of 50 to 70%, set for the shorter side with respect to the longer side of a vibration electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy trapping type piezoelectric resonator and a piezoelectric resonance component which excite thickness confinement vibration by providing vibrating electrodes on both opposing main surfaces of a piezoelectric element.

[0002]

2. Description of the Related Art A conventionally known energy trap type piezoelectric resonator which excites thickness confinement vibrations is disclosed in Japanese Patent Application Laid-Open No. 59-148420. It is configured by providing a circular partial electrode on the surface. FIG. 5 shows a structural example of such a piezoelectric resonator.

FIG. 5 (a) is a schematic plan view of a piezoelectric resonator, FIG. 5 (b) is a schematic side view of the piezoelectric resonator, and FIG. 6 is a diagram showing the piezoelectric resonator in FIG. It is a frequency characteristic diagram of impedance.

In FIG. 5, circular vibrating electrodes 12 and 13 are respectively formed at the center of both opposing main surfaces of a piezoelectric element 11, and the vibrating electrode 12 and one end of the piezoelectric element 11 in the long side direction are provided. The extraction electrode 14 installed in the vicinity is the connection electrode 15, and the vibration electrode 13 and the piezoelectric element 11
The connection electrode 17 is connected to the extraction electrode 16 installed near the other end in the long side direction.

Further, fr and fa in FIG. 6 respectively indicate the resonance frequency and the antiresonance frequency of the thickness longitudinal confinement vibration of the piezoelectric resonator shown in FIG.

[0006]

The anti-resonance frequency of a piezoelectric resonator using thickness longitudinal vibration can be set by parameters such as elastic modulus, density, and thickness of the piezoelectric element, which are material constants of the resonator. The resonance frequency can be set by the density, thickness area, and the like of the vibrating electrode in addition to the parameter for setting the anti-resonance frequency.

In general, a piezoelectric resonator using thickness longitudinal vibration is
It is used in the frequency band of several MHz to several tens of MHz, and the thickness of the piezoelectric element constituting the piezoelectric resonator is about several tens μm to several hundred μm according to the frequency, and the thickness of the piezoelectric element increases as the frequency increases. It becomes thin.

Once the material of the piezoelectric resonator is determined, the thickness of the piezoelectric element must be adjusted in order to set a certain resonance frequency.

If the thickness of the piezoelectric element 11 is constant as shown in FIG. 5B, the frequency characteristic of impedance as shown in FIG. 6 can be obtained. However, depending on the processing accuracy of the piezoelectric element, FIG. As shown in FIG. 9, the piezoelectric element is not uniform in thickness but is processed into a shape such that the element thickness has a gradient from one end to the other end in the long side or short side direction of the piezoelectric element 11. In some cases.

At this time, when the thickness of the piezoelectric element 11 as shown in FIG. 7 is sufficiently large with respect to the inclination of the thickness, that is, when the frequency at which the piezoelectric resonator is used is low, as shown in FIG. In addition, since the impedance of the spurious generated by the inclination of the thickness of the piezoelectric element is sufficiently larger than the impedance at the resonance frequency of the thickness longitudinal vibration, there is not much problem.

However, as shown in FIG.
In the case of a piezoelectric resonator having a small thickness of the piezoelectric element used at a frequency of z or more, as shown in FIG. The spurious impedance exists between the resonance frequency and the anti-resonance frequency of the vibration, and the impedance of the spurious approaches the impedance at the resonance frequency of the thickness longitudinal vibration of the piezoelectric element.

When such a piezoelectric resonator is used as an oscillator or a filter, the oscillation frequency jumps from the resonance frequency of vertical confinement vibration to a spurious frequency, resulting in an oscillator lacking in stability of the oscillation frequency. However, there is a disadvantage that the filter has a disordered group delay time characteristic.

The present invention provides an oscillator having a stable oscillation frequency,
It is an object of the present invention to provide a piezoelectric resonator and a piezoelectric resonance component that can realize a filter having stable group delay characteristics.

[0014]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention provides an energy trap type piezoelectric resonator that excites thickness confinement vibration by providing vibrating electrodes on both opposing main surfaces of a piezoelectric element. The piezoelectric resonator according to any one of claims 1 to 3, wherein a rectangular vibrating electrode is provided on the piezoelectric element inclined in the thickness direction.

The piezoelectric resonator according to the present invention has a rectangular, elliptical or polygonal vibration electrode having a ratio of the long side to the short side, or a long axis and a short axis, depending on the inclination of the thickness of the piezoelectric element. It is characterized in that the ratio with the axis is set.

Further, in the piezoelectric resonance component of the present invention, the thickness of the piezoelectric element is increased by providing a vibration electrode on each of the two main surfaces of the piezoelectric element facing each other. In accordance with the inclination of the rectangular, elliptical or polygonal vibrating electrode, a vibrating electrode having a ratio of the long side to the short side, or a ratio of the long axis to the short axis, is installed, and the piezoelectric resonator First and second laminated on both main surfaces
And a vibration space forming means for forming a space in the vicinity of the resonating portion so as not to hinder the vibration of the resonating portion of the piezoelectric resonator.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to FIGS.

Embodiment 1 FIG. 1A is a schematic plan view of a piezoelectric resonator according to Embodiment 1 of the present invention.
2B is a schematic side view of the piezoelectric element, and FIG. 2 is an impedance characteristic diagram with respect to the frequency of the piezoelectric element. In FIG.
Reference numeral 1 denotes a piezoelectric element, and rectangular vibration electrodes 2 and 3, lead electrodes 4 and 6, and connection electrodes 5 and 7 are formed on both main surfaces of the piezoelectric element 1 facing each other, and constitute a piezoelectric resonator 8. I have. The vibration electrode 2 and the extraction electrode 4 installed near one end of the piezoelectric element 1 in the long side direction are connection electrodes 5,
Further, the vibration electrode 3 and the extraction electrode 6 installed near the other end in the long side direction of the piezoelectric element 1 are connected to the connection electrode 7.
And are connected respectively.

The long and short sides of the vibrating electrodes 2 and 3 are shown in FIG.
As shown in FIG. 1B, when the thickness of the piezoelectric element 1 is smaller on the extraction electrode 4 than on the extraction electrode 6 side, FIG.
As shown in (a), the long sides of the vibrating electrodes 2 and 3 are
In the width direction and the short side in the length direction.

The vibration electrode set under such conditions is made of the same material as the piezoelectric element constituting the piezoelectric resonator shown in FIG.
When mounted on piezoelectric elements having the same thickness gradient, impedance frequency characteristics as shown in FIG. 2 are obtained.
The spurious SP between the resonance frequency of the thickness longitudinal vibration and the anti-resonance frequency as shown in FIG.

Although the ratio of the short side to the long side of the rectangular electrode in the present invention varies depending on the material of the piezoelectric element and the resonance frequency of the set thickness longitudinal vibration, the effect of suppressing the spurious is observed. Within the frequency range where the piezoelectric resonator is used, the ratio of the short side to the long side of the vibrating electrode is 10%.
It is the case of more than 95%.

For example, if the resonance frequency of the vertical confinement is 25
MHz, the ratio of the thinnest portion to the thickest portion of the piezoelectric element is 0.03% to 0.1%.
%, The ratio of the short side to the long side of the vibrating electrode is 5
Between 0% and 70%, the most remarkable effect of suppressing spurious was observed.

Although FIG. 1 shows a case where the vibrating electrodes 2 and 3 have the same shape and the same area, even if one vibrating electrode has a larger area than the other vibrating electrode, the rectangular shape is obtained. When the ratio of the short side to the long side of the electrode is within the above range, the same effect can be obtained.

Also, if the shape of the vibrating electrode is not a rectangle but an ellipse or a polygon and the relationship between the long axis and the short axis is set in the same manner as in the case of the rectangle, the same effect as in the case of the rectangle can be obtained. Can be.

Further, although the material constituting the piezoelectric element is not described in detail, the same effect can be obtained with a ceramic material having a piezoelectric effect, a single crystal, a thin film material or the like.

In addition, the present embodiment describes a case where the inclination of the thickness of the piezoelectric element has a constant inclination from one end of the long side or short side of the piezoelectric element to the other end. However, there is a local inclination within the piezoelectric element, for example, when only the vibrating electrode has a tilt in the thickness direction and the other part has no tilt, or the piezoelectric element thickness is near the vibrating electrode. There is an effect that the above-mentioned spurious is suppressed by the electrode shape shown in the present embodiment even in a case where there is a maximum point and the thickness becomes thinner toward the end of the piezoelectric element.

(Embodiment 2) FIG. 3 is a cutaway perspective view of a piezoelectric resonance component according to Embodiment 2, and FIG. 4 is a perspective view of the piezoelectric resonance component shown in FIG.

In FIGS. 3 and 4, reference numeral 8 denotes the piezoelectric resonator shown in the first embodiment. On both main surfaces of the piezoelectric resonator 8, the vibrating electrodes 2, 3, the lead electrodes 4, 6, and the connection Electrodes 5 and 7 are formed respectively. When a voltage is applied to the vibrating electrodes 2 and 3 from the outside, thickness vertical confinement vibration is excited, and only the vibrating electrodes 2 and 3 vibrate. A resin layer 22 is provided in a layered manner between the piezoelectric resonator 8 and the sealing plate 21 to form a vibration space so as not to hinder the vibration of the piezoelectric resonator 8. The extraction electrodes 4 and 6 are electrically connected to the external electrodes 23 at the end faces.

By forming a vibration space by the resin layer 22 in the vicinity of the vibration electrodes 2 and 3 provided on the piezoelectric resonator 8, vibrations other than the thickness vertical confinement vibration of the frequency of interest are suppressed. Therefore, the spurious suppression effect of the rectangular electrode can be further increased.

In this embodiment, the vibration space is formed by the resin layer. However, the same effect can be obtained when the vibration space is formed by providing a concave portion in the sealing plate.

[0031]

As described above, according to the present invention, the spurious due to the inclination of the thickness of the piezoelectric element can be suppressed by the shape of the vibrating electrode.

Further, by using a piezoelectric resonance component having a laminated structure in which a vibration space of the piezoelectric resonator is formed, the spurious suppression effect by the rectangular electrode can be further increased.

[Brief description of the drawings]

1A is a schematic plan view of a piezoelectric resonator according to Embodiment 1 of the present invention, and FIG. 1B is a schematic side view of the piezoelectric resonator in FIG.

FIG. 2 is a frequency characteristic diagram of impedance of the piezoelectric resonator according to the first embodiment.

FIG. 3 is a cutaway perspective view of a piezoelectric resonance component according to a second embodiment of the present invention.

FIG. 4 is a perspective view of a piezoelectric resonance component according to the second embodiment.

5A is a schematic plan view of a conventional piezoelectric resonator. FIG. 5B is a schematic side view of the piezoelectric resonator when the thickness of the piezoelectric element is uniform.

FIG. 6 is a frequency characteristic diagram of the impedance of the piezoelectric resonator when the thickness of the piezoelectric element is uniform.

FIG. 7 is a schematic side view of the piezoelectric resonator when the thickness of the piezoelectric element is large and the thickness gradient with respect to the thickness of the piezoelectric element is sufficiently small.

FIG. 8 is a frequency characteristic diagram of impedance of the piezoelectric resonator of FIG. 7;

FIG. 9 is a schematic side view of the piezoelectric resonator when the thickness of the piezoelectric element is small and the inclination of the thickness with respect to the thickness of the piezoelectric element is large.

FIG. 10 is a frequency characteristic diagram of impedance of the piezoelectric resonator of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric element 2, 3 Vibration electrode 4, 6 Extraction electrode 5, 7 Connection electrode 8 Piezoelectric resonator 11 Piezoelectric element 12, 13 Vibration electrode 14, 16 Extraction electrode 15, 17 Connection electrode 18 Piezoelectric resonator 21 Sealing plate 22 Resin Layer 23 external electrode

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroyasu Ikeda 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. An energy trapping type piezoelectric resonator which excites thickness confinement vibration by providing vibrating electrodes on both opposing main surfaces of a piezoelectric element. A piezoelectric resonator comprising a vibrating electrode. 2. The piezoelectric resonator according to claim 1, wherein the ratio between the long side and the short side of the rectangular vibrating electrode is set according to the inclination of the thickness of the piezoelectric element. 3. The vibration electrode according to claim 1, wherein the vibration electrode has an elliptical shape or a polygonal shape, and the ratio between the major axis and the minor axis of the vibration electrode is set according to the inclination of the element thickness. Piezoelectric resonator. 4. An energy trap type piezoelectric resonator which excites thickness confinement vibration by providing vibrating electrodes on both opposing main surfaces of a piezoelectric element, respectively. And a first and a second protection substrate laminated on both main surfaces of the piezoelectric resonator, and a space for not hindering vibration of a resonance part of the piezoelectric resonator, for forming a space near the resonance part. A piezoelectric resonance component comprising: a vibration space forming unit.