JPH0352313A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To suppress spurious radiation generated slightly toward high frequency side from an anti-resonance point in the impedance characteristic by decreasing the size of an external electrode provided respectively to both outer sides of a piezoelectric substrate in the direction of the length of an internal electrode more than the size of that in the direction of the width of the internal electrode. CONSTITUTION:A stripe shape internal electrode 2 is provided in the inside of a piezoelectric substrate 1 and external electrodes 3, 4 are formed opposite to the internal electrode 2 to both outer sides of the piezoelectric substrate 1. The size (c) of the internal electrode 2 in the lengthwise direction is made shorter than the size (d) of the direction of the width of the internal electrode 2. The area of the external electrodes 3, 4 is selected to be 50-90% of the original circular area. Thus, spurious radiation caused at higher frequency of an anti-resonance point in the impedance characteristic of a double wave resonator is suppressed, and a thickness-shear longitudinal vibration double wave piezoelectric resonator having an excellent characteristic is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a piezoelectric resonator using the second harmonic of thickness longitudinal vibration.

[Background Art Figure 5 shows a double-wave piezoelectric resonator (for example, a double-wave piezoelectric oscillator) that utilizes thickness longitudinal vibration. The conventional double wave piezoelectric resonator C has a piezoelectric substrate 53 formed by laminating a pair of green sheets 51 and 52, and a striped internal electrode 54 extending in one direction is provided inside the piezoelectric substrate 53. Circular or polygonal external electrodes 55 and 56 (the external electrodes 56 are shown within the dashed line frame projected from the lower surface of the green sheet 52) are provided on both outer surfaces of the green sheet 52, facing the internal electrodes 54. Ta. That is, in the conventional double wave piezoelectric resonator C, the external electrodes 55 and 56 provided on both sides of the piezoelectric substrate 53 have the same dimensions corresponding to the length direction and the width direction of the internal electrodes. It was. [Problems to be Solved by the Invention] Figure 6 shows the frequency-impedance characteristics of the double-wave piezoelectric resonator with the conventional structure as described above. In FIG. 6, the vertical axis is impedance Z, and the horizontal axis is frequency f. As is clear from this impedance characteristic, the conventional 2
In a harmonic resonator, there is a problem in that spurious S occurs on the slightly higher frequency side than the anti-resonance point A, which impairs the characteristics of the resonator. However, the present invention was made in view of the drawbacks of the conventional example described above, and its purpose is to suppress the spurious that occurs at a slightly higher frequency side than the anti-resonance point in the impedance characteristic. Our objective is to provide a double-wave piezoelectric resonator that is capable of [Means for Solving the Problems] Therefore, the piezoelectric resonator of the present invention is provided with an internal electrode parallel to the outer surface of the piezoelectric substrate extending in one direction at approximately the center in the thickness direction inside the piezoelectric substrate, and facing the internal electrode. In an energy-trapped piezoelectric resonator using the second harmonic of thickness longitudinal vibration, in which external electrodes are provided on both outer surfaces of a piezoelectric substrate, the internal electrode length direction is The feature is that the dimensions of the internal electrodes are shorter than the dimensions of the internal electrodes in the width direction. [Operations] In the present invention, an internal electrode is provided inside the piezoelectric substrate,
In a double-wave piezoelectric resonator in which external electrodes are provided on both external surfaces facing the internal electrodes, the lengthwise dimension of both external electrodes is made shorter than the widthwise dimension of the internal electrodes. We were able to eliminate the spurious near the anti-resonance point that appeared in the frequency-impedance characteristic of the piezoelectric resonator. [Embodiments] Hereinafter, embodiments of the present invention will be described in detail based on the attached drawings. As shown in FIG. 1, a piezoelectric substrate 1 is formed by laminating a pair of piezoelectric ceramic green sheets 5 and 6. Outer electrodes 3 and extraction electrodes 8 are formed by printing conductive paste 7 on the top surface of one of the pair of green sheets 5 and 6.

Furthermore, a strip-shaped internal electrode 2 extending from one end to the other is formed by printing a conductive paste 7 on the top surface of the other green sheet 6, and a conductive paste 7 is printed on the bottom surface of the strip-shaped internal electrode 2 extending from end to end. As a result, an external electrode 4 and an extraction electrode 9 (in FIG. 1, they are shown within the frame of a broken line projected from the bottom surface of the green sheet 6) are formed. After aligning the positions of each electrode, the green sheet 5,
The piezoelectric resonator B is manufactured by stacking the piezoelectric substrates 6 and crimping them to form the piezoelectric substrate 1, then firing the entire piezoelectric substrate 1, and subjecting the piezoelectric substrate 1 to polarization treatment in the thickness direction. The double wave piezoelectric resonator B manufactured in this way is shown in Fig. 2 (a
) As shown in (b), there are striped internal electrodes 2 inside the piezoelectric substrate 1, and internal electrodes 2 are provided on both outer surfaces of the piezoelectric substrate 1.
External electrodes 3 and 4 are formed so as to face each other. As shown in FIGS. 2(a) and 2(b), both external electrodes 3.4 have a circular shape with a diameter slightly larger than the width of the internal electrode 2, with the portion 10 surrounded by imaginary lines removed. Therefore, the dimension C in the length direction of the internal electrode is shorter than the dimension d in the width direction of the internal electrode. Here, the area of the external electrodes 3 and 4 is approximately 50% to 90% of the original circular area (including the area of the removed portion 10). What is shown in FIG. 3 is the electrode area (expressed as a percentage of the original circular area) of the external electrodes 3 and 4 from which the portions 10 on both sides have been removed, the main vibration response α, and the spurious response β. As is clear from this graph, when the area where the external electrodes 3 and 4 are removed is about 10% or less (electrode surface M is about 90% or more), the spurious response β is sufficiently small. Not,
Spurious suppression effect is small. In addition, the external electrode 4 is
If the electrode area is reduced by more than 0% (if the electrode area is less than 50%), the main vibration will be split. Therefore, external tm3.
The area of 4 is 50% to 9 of the original circular area.
Approximately 0% is suitable. In this way, both external t-poles 3 and 4 are sized 10 times from the original circular area.
% to 50%, the spurious S that appeared on the slightly higher frequency side of the anti-resonance point A in the impedance characteristics of the conventional piezoelectric resonator was suppressed, as shown in Figure 4. Good impedance characteristics with no spurious generated near the resonance point R and anti-resonance point A were obtained. Furthermore, if the shapes of the front and back external electrodes 3 and 4 are made the same, one type of mask is sufficient for applying the conductive paste to the portions that will become the external electrodes 3 and 4.

It should be noted that the present invention can be modified in various ways other than the above-mentioned embodiments. For example, the shape of the external electrode may be polygonal instead of circular. In this case as well, for both external electrodes, the lengthwise dimension of the internal electrode is shorter than the widthwise dimension of the internal electrode. In addition, when making a shape of the outer electrode that has become shorter in the length direction of the inner electrode, after providing a circular electrode on the outer surface of the piezoelectric substrate as explained above, the edge of this circular electrode can be partially cut. may be formed by deleting the
Alternatively, the internal electrode may be formed to have a shortened shape in the length direction from the beginning. Further, each electrode may be provided by a method such as vacuum evaporation or sputtering. [Effects of the Invention] According to the present invention, it is possible to suppress the spurious that occurs on the high frequency side of the anti-resonance point in the impedance characteristics of a conventional double-wave resonator, and it is possible to suppress the spurious that occurs on the high frequency side of the anti-resonance point in the impedance characteristics of a conventional double-wave resonator. We were able to obtain a wave piezoelectric resonator.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the manufacturing process of a piezoelectric resonator according to an embodiment of the present invention, FIGS. 2(a) and (b) are top and bottom views of the same piezoelectric resonator, and FIG. A graph showing the relationship between the electrode area of the external electrode and the main vibration and spurious responses. Fig. 4 is a graph showing the frequency-impedance characteristics of the same as above. Fig. 5 is a perspective view of the manufacturing process of the conventional example. Fig. 6 is a graph showing the relationship between the electrode area of the external electrode and the main vibration and spurious response. This is a graph showing the frequency-impedance characteristics of the same as above. 1... Piezoelectric substrate 2... Internal electrodes 3, 4.
...External electrode Figure 3 Figure 4 Layer sawsaw

Claims (1)

[Claims] (1) Thickness longitudinal vibration in which an internal electrode is provided parallel to the outer surface of the piezoelectric substrate extending in one direction at approximately the center in the thickness direction inside the piezoelectric substrate, and external electrodes are provided on both outer surfaces of the piezoelectric substrate to face the internal electrode. In an energy-trapped piezoelectric resonator using the second harmonic of piezoelectric resonator.