JPH0834401B2 - Piezoelectric resonator - Google Patents

Description

TECHNICAL FIELD The present invention relates to a piezoelectric resonator using a second harmonic of thickness longitudinal vibration.

BACKGROUND ART FIG. 5 shows a second-harmonic piezoelectric resonator (for example, second-harmonic piezoelectric oscillator) that utilizes thickness longitudinal vibration. In the conventional second harmonic piezoelectric resonator C, a striped internal electrode 54 extending in one direction is provided inside a piezoelectric substrate 53 formed by laminating a pair of green sheets 51, 52, and both piezoelectric substrates 53 are provided. Internal electrodes on the outer surface
Circular external electrodes 55, 56 facing the 54 (external electrode 56 is
The lower surface of the green sheet 52 is shown in a frame surrounded by a broken line. ) Was provided. That is, in the conventional second harmonic piezoelectric resonator C, the external electrodes provided on both surfaces of the piezoelectric substrate 53.
In both 55 and 56, the dimensions corresponding to the lengthwise and widthwise directions of the internal electrodes were the same.

[Problems to be Solved by the Invention] The frequency of the second harmonic piezoelectric resonator having the conventional structure as described above-
The impedance characteristic is shown in FIG. In FIG.
The vertical axis represents impedance Z and the horizontal axis represents frequency f.

As is apparent from this impedance characteristic, in the conventional second-harmonic resonator, spurious S occurs slightly on the higher frequency side than the anti-resonance point A, and there is a problem that the characteristics of the resonator are impaired.

Therefore, the present invention has been made in view of the drawbacks of the above conventional examples, and an object thereof is to suppress spurious that has occurred in the impedance characteristic at a slightly higher frequency side than the anti-resonance point. Another object of the present invention is to provide a double wave piezoelectric resonator that can be manufactured.

[Means for Solving the Problem] For this reason, the piezoelectric resonator of the present invention is provided with an internal electrode that is parallel to the outer surface of the piezoelectric substrate and extends in one direction approximately at the center in the thickness direction inside the piezoelectric substrate. 2 of thickness longitudinal vibration in which external electrodes are provided on both outer surfaces of the piezoelectric substrate so as to face each other.
An energy trap type piezoelectric resonator using a harmonic wave is characterized in that the dimensions of the both outer electrodes in the lengthwise direction of the inner electrode are shorter than the dimensions of the both outer electrodes in the widthwise direction of the inner electrode.

[Operation] In the present invention, the internal electrodes of both external electrodes are provided in the second harmonic piezoelectric resonator in which the internal electrodes are provided inside the piezoelectric substrate, and the external electrodes are provided on both outer surfaces of the piezoelectric substrate so as to face the internal electrodes. By making the dimension in the length direction shorter than the dimension in the width direction of the internal electrodes, it was possible to eliminate the spurious near the anti-resonance point, which appeared in the frequency-impedance characteristic of the conventional piezoelectric resonator.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the accompanying drawings.

As shown in FIG. 1, the piezoelectric substrate 1 is formed by laminating a pair of green sheets 5 and 6 of piezoelectric ceramics. The external electrode 3 and the extraction electrode 8 are formed by printing the conductive paste 7 on the upper surface of one of the pair of green sheets 5 and 6. Further, by printing the conductive paste 7 on the upper surface of the other green sheet 6, the stripe-shaped internal electrodes 2 extending from one end to the other are formed, and by printing the conductive paste 7 on the lower surface thereof. The external electrode 4 and the extraction electrode 9 (in FIG. 1, shown in the frame of the broken line which projected the lower surface of the green sheet 6) are formed. Then, the green sheets 5 and 6 are laminated by aligning the positions of the respective electrodes and pressure-bonded to each other to form the piezoelectric substrate 1, after which the whole is fired and further subjected to polarization treatment in the thickness direction of the piezoelectric substrate 1. The piezoelectric resonator B is manufactured.

The second-harmonic piezoelectric resonator B manufactured in this way has stripe-shaped internal electrodes 2 inside the piezoelectric substrate 1 as shown in FIGS. External electrodes 3 and 4 are formed so as to face the electrode 2. As shown in FIGS. 2 (a) and 2 (b), both external electrodes 3 and 4 have a shape in which a portion 10 surrounded by an imaginary line is removed from a circle having a diameter slightly larger than the width of the internal electrode 2. Therefore, the dimension c in the lengthwise direction of the internal electrode is shorter than the dimension d in the widthwise direction of the internal electrode. Here, the area of the external electrodes 3 and 4 is the original circular area (including the area of the removed portion 10).
It is about 50% to 90%.

FIG. 3 shows the electrode area (expressed as a percentage of the original circular area) of the external electrodes 3 and 4 in which the portions 10 on both sides are deleted, the response α of the main vibration and the response β of the spurious. It is a graph which shows the relationship of. As is clear from this graph, the area where the external electrodes 3 and 4 are removed is 1
When it is about 0% or less (electrode area is about 90% or more), the spurious response β is not sufficiently small, and the spurious suppressing effect is small. When the external electrode 4 is scraped by 50% or more (the electrode area is 50% or less), the main vibration is divided. Therefore, the area of the external electrodes 3 and 4 is preferably about 50% to 90% of the original circular area.

In this way, both external electrodes 3 and 4 are 10% from the original circular area.
After deleting about 50 to 50%, as shown in Fig. 4,
In the impedance characteristic of the conventional piezoelectric resonator, the spurious S that appears on the high frequency side of the anti-resonance point A is suppressed, and as shown in FIG. 4, spurious noise does not occur near the resonance point R and the anti-resonance point A. Impedance characteristics were obtained. If the outer electrodes 3 and 4 on the front and back have the same shape,
One kind of mask is sufficient for applying the conductive paste to the portions to be the external electrodes 3 and 4.

The present invention can be modified in various ways other than the above embodiments, and the original shape of the external electrode may be a regular polygon instead of a circle. In this case as well, the dimension of the external electrodes in the lengthwise direction of the internal electrodes is shorter than the dimension in the widthwise direction of the internal electrodes.

Further, in the case of forming an external electrode that is shortened in the length direction of the internal electrode, after providing a circular electrode or the like on the outer surface of the piezoelectric substrate as described above, the edge portion of the circular electrode is partially removed. The electrode may be formed by removing the first electrode or the electrode may be formed so as to have a shape shortened in the lengthwise direction of the internal electrode from the beginning. Further, each electrode may be provided by a method such as vacuum deposition or sputtering.

[Advantages of the Invention] According to the present invention, in the impedance characteristic of the conventional second harmonic resonator, spurious which is generated on the high frequency side of the anti-resonance point can be suppressed, and the thickness longitudinal vibration doubled with good characteristics. The wave piezoelectric resonator could be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a process of manufacturing a piezoelectric resonator according to an embodiment of the present invention, FIGS. 2 (a) and 2 (b) are a top view and a bottom view of the same piezoelectric resonator, and FIG. A graph showing the relationship between the electrode area of the external electrode and the response of the main vibration and spurious, FIG. 4 is a graph showing the frequency-impedance characteristic of the same, FIG. 5 is a perspective view in the manufacturing process of the conventional example, and FIG. It is a graph which shows the frequency-impedance characteristic same as the above. 1 ... Piezoelectric substrate, 2 ... Internal electrode 3,4 ... External electrode

Claims (1)

[Claims] 1. An internal electrode extending in one direction in parallel with the outer surface of the piezoelectric substrate is provided substantially in the center in the thickness direction inside the piezoelectric substrate, and the external electrode is provided on both outer surfaces of the piezoelectric substrate so as to face the internal electrode. In the provided energy trap type piezoelectric resonator using the second harmonic of the thickness longitudinal vibration, the dimension of the both external electrodes in the lengthwise direction of the internal electrode is made shorter than the dimension of the both external electrodes in the widthwise direction of the internal electrode. Piezoelectric resonator characterized by.