JPH0211008A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To miniaturize a resonator while maintaining a satisfactory single resonance by chamfering the partial electrode constitution surface of a piezoelectric flat plate to face two surfaces vertical to a polarization axis and constitute a partial electrode and the ridge to intersect the surface vertically. CONSTITUTION:Opposing partial electrodes 3 and 4 are provided on two surfaces perpendicular to a polarization axis 2 which lies in the thickness direction of a rectangular piezoelectric flat plate 1 axis, and these and electrode pads 5 and 6 are connected by leadout electrodes 7 and 8. The chamfering is executed at a ridge part 9 to intersect with two surfaces to constitute the partial electrodes 3 and 4 and two surfaces in the lengthwise direction parallel to the polarization shaft 2. When the width of the partial electrodes 3 and 4 is a=4t, by executing the chamfering, even when the width (w) of the piezoelectric flat plate 1 is made smaller up to w=5t, an unnecessary resonance is not superimposed on the resonance part of the longitudinal mode in the thickness direction and a satisfactory single resonance is obtained. Thus, the resonator can be miniaturized while the satisfactory single resonance is maintained.

Description

[Detailed description of the invention] (Industrial application field) The present invention uses piezoelectric ceramics and piezoelectric single crystals.

This invention relates to a piezoelectric resonator driven in a thickness longitudinal vibration mode.

(Prior Art) FIG. 3 is a perspective view of a piezoelectric resonator using a general thickness longitudinal vibration mode. In the figure, 31 is a piezoelectric plate made of piezoelectric ceramic, piezoelectric single crystal, or the like.

The polarization axis is parallel to the thickness and is indicated by arrow 32 in Figure 1. In the case of piezoelectric ceramics, polarization treatment is performed in the direction of arrow 32, and in the case of piezoelectric single crystals, the spontaneous polarization axis is indicated by arrow 32.
It is cut in two directions.

Reference numerals 33 and 34 denote partial electrodes that are formed approximately at the center of the piezoelectric plate by a method such as vapor deposition and are opposed to each other. 35.36 are extraction electrodes, 37.311 electrode pads and partial electrode 3
3 and 34 are connected. Lead wires or terminals 39,40 are connected to the electrode pads 37,38 by solder or the like.

When an alternating current voltage is applied to the lead wires or terminals 39, 40, an electric field is generated between the partial electrodes 33, 34, and longitudinal vibration is excited by the piezoelectricity of the piezoelectric plate 31. At this time, if the mass of the composition 1 partial electrodes 33.34 of the piezoelectric plate 31 is appropriately selected, a so-called energy-trapped resonator can be constructed in which vibrational energy is concentrated in and around the partial electrode portions 33.34. In this type of resonator, vibration energy is concentrated approximately at the center of the piezoelectric plate 31, so that a single resonance response is obtained without unnecessary resonance caused by reflection of vibrations at the contour portion of the piezoelectric plate.

Figure 4 shows a resonator created to study the miniaturization of the above-mentioned thickness longitudinal energy confinement resonator.
7.38 is configured with a width W in the depth direction. Piezoelectric plate 3
The width Q of 1 is cut from Q=Q, taking into account the symmetry with respect to the partial electrodes 33 and 34. The width a of the partial electrodes 33 and 34 is set to four times the thickness of the piezoelectric plate 31.

Figures 5 (a) to (f) show the frequency response (attenuation vs. frequency characteristics) of this resonator as Q changes, when Q is sufficiently large compared to the thickness (roughly 12=20 or more) ) has (a
), a good single resonance with no unnecessary resonance can be obtained. When Q becomes small and approximately Q = 45t, an unnecessary resonance response S appears on the lower side of the resonance frequency f as shown in (b), but the resonance 1 anti-resonance frequency of this unnecessary resonance response S appears. The difference in attenuation (dynamic range) is small,
In (C), when approximately Q=10t, Sl approaches f, the dynamic range becomes large, and an unnecessary resonance response S2 appears on the low frequency side. (d) shows that when Q=9t, the S is superimposed on the part f of the fundamental resonance response, the minimum value of the attenuation becomes large, and a new unnecessary resonance S appears. (e) is a resonance response when approximately c=7t, and (f) is a resonance response when approximately Q=5t, and many unnecessary resonances are superimposed, making it impossible to use as a resonator. (g) shows the spectral dispersion with respect to Q/l of the resonance frequency of unnecessary resonance responses of 81 to S5.

(Problems to be Solved by the Invention) As explained above, when the shape of the piezoelectric plate is made smaller in an attempt to downsize the thickness longitudinal energy trapping resonator, a large number of unnecessary resonance responses become the basic resonance response. There were some flaws that appeared in some parts.

SUMMARY OF THE INVENTION An object of the present invention is to provide a piezoelectric resonator that eliminates the drawbacks of the conventional piezoelectric resonator and suppresses unnecessary resonance that occurs when the piezoelectric resonator is made smaller.

(Means for Solving the Problems) The piezoelectric resonator of the present invention includes a partial electrode forming surface of a piezoelectric flat plate in which partial electrodes are formed facing two surfaces perpendicular to the polarization axis;
The ridge that intersects with the surface perpendicular to this is chamfered.

(Function) By using the thickness longitudinal vibration piezoelectric resonator of the present invention, it is possible to downsize the resonator while maintaining good single resonance.

(Example) An example of the present invention will be described based on FIG. 1, FIG. 2, and FIG. 6.

FIG. 1 shows a first embodiment of the piezoelectric resonator of the present invention. In the figure, a rectangular piezoelectric plate 1 with a polarization axis in the thickness direction.
Partial electrodes 3 and 4 are provided facing each other on two surfaces perpendicular to the polarization axis 2 of the polarization axis 2, and these are connected to electrode pads 5.6 by lead electrodes 7 and 8. Reference numeral 9 denotes a chamfered portion formed on a ridge that intersects with two planes forming the partial electrodes 3 and 4 and two planes in the longitudinal direction parallel to the polarization axis 2. When the width of the partial electrodes 3 and 4 is a = 4t, by performing this chamfering, even if the width W of the piezoelectric plate 1 is reduced to w = 5t, unnecessary resonance will not be superimposed on the resonance part of the thickness longitudinal mode. , good single resonance can be obtained. As W becomes smaller than 5t, single resonance can be obtained, but resonance resistance increases.

The chamfer can be easily formed by polishing.

10 and 11 are lead wires.

FIG. 2 shows a second embodiment of the piezoelectric resonator of the present invention. In this embodiment, it is composed of two surfaces forming the electrode and a surface perpendicular to the two surfaces. Chamfering 9 has been applied to all of the mausoleum. Although the width of the extraction electrode is shown to be smaller than the width a of the partial electrode, they may have the same size.

Further, the shape of the partial electrode is not limited to a rectangle, but may be circular, elliptical, or the like.

FIG. 6 is a displacement distribution diagram of a resonator to show the effects of the present invention. FIG. 6 is a view of FIG. 4 from a direction perpendicular to the thickness. However, the drawing electrode and electrode pad portion are omitted from the illustration. In the figure, 12 to 16 are displacement amplitude distributions seen on the A-E axis, and although the direction of displacement is the thickness direction, the displacement distributions are shown in the same way as transverse waves for ease of viewing. The point of maximum displacement is at the piezoelectric plate surface portion, and the displacement decreases as vibration propagates from the electrode portion toward the end face 17. When Q is sufficiently large, the vibration displacement at the end face 17 of the piezoelectric plate is approximately zero, but when Q becomes small, the vibration displacement at the end face 17
The ridge where the surface 18 intersects with the surface 18 on which the electrode structure is formed vibrates. The vibration propagated to the end face 17 is reflected here,
It propagates to the partial electrode section and is further reflected repeatedly, generating unnecessary resonance. In order to suppress this unnecessary resonance, the intersecting line (ridge) between the electrode forming surface 18 and the end surface 17 is polished to scatter the vibrations reflected at this portion, thereby preventing a resonance response from occurring.

(Effects of the Invention) According to the present invention, by using a thickness longitudinal oscillating piezoelectric resonator, it is possible to downsize the resonator while maintaining good single resonance, and the practical effects thereof are significant. .

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a piezoelectric resonator according to a first embodiment of the present invention, FIG. 2 is a perspective view of a piezoelectric resonator of the second embodiment, and FIG. 3 is a perspective view of a conventional piezoelectric resonator. , Fig. 4 is a perspective view of the resonator for considering miniaturization, Fig. 5 is a frequency characteristic diagram near the resonator part of the resonator, and Fig. 6 is a displacement distribution diagram of the resonator showing the effects of the present invention. It is. 1...Piezoelectric flat plate, 2...Polarization axis, 3°4...
・Partial electrode, 5, 6...electrode pad. 7.8... Extraction electrode, 9... Chamfered portion, 10
, 11... Lead wire, 12-16... Displacement amplitude distribution, 17... End surface, 18... Electrode configuration surface. Patent applicant: Matsushita Electric Industrial Co., Ltd.

Claims (1)

[Claims] A thickness-longitudinal mode piezoelectric device characterized by chamfering the ridges at the intersection of the partial electrode-forming surfaces and a surface perpendicular to these, of a piezoelectric flat plate that forms partial electrodes facing two surfaces perpendicular to the polarization axis. resonator.