JP2513166B2 - Piezoelectric trap using thickness-shear vibration mode and manufacturing method thereof - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a piezoelectric trap using a thickness shear vibration mode and a method for manufacturing the same, and more particularly to a piezoelectric trap having two or more elements provided on one piezoelectric ceramic substrate. Is.

[Conventional technology]

The audio signal of the television receiver depends on the system of each country.
Either frequency of 4.5 / 5.5 / 6.0 / 6.5MHz is used. The video signal circuit is provided with an audio signal trap circuit corresponding to the same frequency in order to prevent such an image failure due to the audio signal.

As this trap circuit, an inductor 30 is connected in series to the video signal system as shown in FIG. 7, and the inductor 30 is connected between the input side and the ground and the inductor 30.
It is known that a piezoelectric trap 31 is provided between the output side of 30 and the ground.

[Problems to be Solved by the Invention]

Most of the piezoelectric traps 31 used in the trap circuit have a two-element resonator formed in the same piezoelectric ceramic substrate. In this case, since the piezoelectric material constant of the piezoelectric ceramic substrate and the thickness of the element part are set to the same,
The resonance characteristics are also the same. Therefore, when it is used as a trap, it has a transmission characteristic as shown by the broken line in FIG. 6, and although the maximum attenuation amount characteristic is good, it has a problem that the trap bandwidth is narrow.

Therefore, an object of the present invention is to provide a piezoelectric trap using a thickness-shear vibration mode that can easily expand the trap bandwidth with a single piezoelectric substrate without changing the thickness and composition of the piezoelectric ceramic substrate, and a method for manufacturing the same. To provide.

[Means for solving the problem]

In order to achieve the above object, the invention described in claim 1 is
In a piezoelectric trap having a plurality of elements formed by forming a plurality of pairs of opposing electrodes on both main surfaces of one piezoelectric ceramic substrate, the piezoelectric ceramic substrate is polarized in a direction parallel to the main surface. And the frequency of each element is made different by inclining the polarization axes of the elements other than one of the above elements in the thickness direction.

A second aspect of the present invention is a method of manufacturing a piezoelectric trap utilizing a thickness shear vibration mode, which comprises a step of performing pre-polarization treatment on a piezoelectric ceramic substrate in a direction parallel to its main surface, and a piezoelectric ceramic. By forming a plurality of pairs of counter electrodes on both main surfaces of the substrate to form a plurality of elements, and by applying a DC voltage between the counter electrodes constituting the other elements except one element, And a step of performing polarization treatment after tilting the polarization axis in the thickness direction.

[Action]

For example, in the case of a thickness-shear vibration mode piezoelectric trap including two elements, if the polarization axis of one element is slightly tilted in the thickness direction, the frequencies of both elements will be different.
Generally, in a piezoelectric ceramic substrate having the same thickness, the frequency of thickness longitudinal vibration is higher than the frequency of thickness shear vibration. Therefore, when the polarization axis is tilted in the thickness direction, the frequency of the element with the tilted polarization axis does not tilt the polarization axis. It is higher than the frequency of the device. Therefore, the resonance characteristics of both elements have two resonance frequencies f _r1 and f _r2 and two anti-resonance frequencies f _a1 and f _a2 in the main thickness-shear vibration mode as shown by the broken line in FIG. And the synthesized resonance characteristic becomes as shown by the solid line. Therefore, if both elements are used in the trap circuit,
The transmission characteristic is that the trap bandwidth is expanded to a high frequency range as shown by the solid line in FIG.

The post-polarization voltage in the thickness direction may have a lower voltage per unit thickness than the voltage pre-polarized in the mother plate state. The reason is that even if the inclination of the polarization axis is slight, the effect of expanding the trap bandwidth as shown by the solid line in FIG. 6 can be exhibited. , Because the desired transmission characteristics cannot be obtained.

In addition, it is not necessary to form a special electrode on the piezoelectric ceramic substrate during the post-polarization process, and the polarization axis can be easily tilted simply by applying a DC voltage to the pre-formed electrode, so the polarization process is easy. Is.

〔Example〕

FIG. 1 shows an example of a piezoelectric trap including two elements according to the present invention.

In this piezoelectric trap 1, input / output electrodes 3 and 4 are provided on one main surface of a piezoelectric ceramic substrate 2, and the electrodes 3 and 4 are circular vibrating electrodes 3a and 4a, and piezoelectric electrodes are formed from the vibrating electrodes 3a and 4a. The ceramic substrate 2 is composed of terminal electrodes 3b and 4b drawn out at both ends of the lower edge. Further, one common electrode 5 is provided on the other main surface of the piezoelectric ceramic substrate 2, and this electrode 5 includes two vibrating electrodes 5a and 5b facing the vibrating electrodes 3a and 4a, and these vibrating electrodes 5a and 5a. 5b and a terminal electrode 5c led out to the center of the lower edge of the piezoelectric ceramic substrate 2. The entire surface of the piezoelectric ceramic substrate 2 has a plane direction (direction of arrow P).
Since the pre-polarization process has been performed on the vibrating electrodes 3a, 4a
The thickness shear vibration is excited in the portion of the piezoelectric ceramic substrate 2 sandwiched between and 5a and 5b.

Of the vibrating electrodes 3a, 4a and 5a, 5b, the portion of the piezoelectric ceramic substrate 2 sandwiched by one vibrating electrode (for example, 4a, 5b) is subjected to post-polarization treatment in the thickness direction, and as shown in FIG. As shown, the polarization axis P'is slightly inclined in the thickness direction. The DC voltage of this post-polarization treatment is about 1/2 to 1/5 of the voltage per unit thickness as compared with the voltage of the pre-polarization treatment in the direction of arrow P. Thus, the polarization axis P'of one of the vibrating electrodes 4a, 5b is
By tilting, the resonance frequency of the two elements composed of the vibrating electrodes 3a, 5a and 4a, 5b will be different as shown by the broken line in FIG. When used in a simple trap circuit, it is possible to obtain transmission characteristics with a wide trap bandwidth as shown by the solid line in FIG.

Here, a method of manufacturing the piezoelectric trap will be described with reference to FIG.

First, after firing the mother plate 10 as shown in FIG. 4A, the electrodes 11 are formed on the front and back surfaces of the mother plate 10 as shown in FIG. 4B.
And a pre-polarization treatment is performed in the thickness direction (arrow P direction). Thereafter, as shown in FIG. 4C, the mother plate 10 is slice-cut in its thickness direction to form a thin strip-shaped mother substrate 12 as shown in FIG. 4D. Subsequently, a large number of electrodes 3 and 4 are formed on the mother substrate 12 as shown in FIG. 4E, and the mother substrate 12 is cut into an appropriate number as shown in FIG. Get Trap 1. In this state, when a DC voltage is applied between the vibrating electrodes 4a and 5b to perform a post-polarization process, the polarization axis of the portion of the piezoelectric ceramic substrate 2 sandwiched between the vibrating electrodes 4a and 5b is slightly shifted from the P direction. It is inclined in the thickness direction P '(see FIG. 2). As shown in Fig. 4H, the terminal electrode is applied to the piezoelectric trap 1 for which post-polarization processing has been completed.
The product is completed by connecting the leads 13, 14 and 15 to 3b, 4b and 5c, respectively, and covering them with an exterior (not shown).

The post-polarization process is performed after the electrode pattern is formed (Fig. 4E).
Or at the lead connection (4H
Alternatively, a DC voltage may be applied between the leads 14 and 15 corresponding to the vibrating electrodes 4a and 5b in the completed state.

The piezoelectric trap of the present invention is not limited to the two-element type as in the above embodiment, but can be similarly applied to a piezoelectric trap having three or more elements. For example, in the case of a three-element type piezoelectric trap as shown in FIG. 5, the polarization axes of one or two elements can be tilted. As a method of inclining the polarization axes of the two elements, for example, the left-side vibrating electrodes 20 and 21 are not subjected to post-polarization processing, and the central vibrating electrodes 22 and 23 and the right-side vibrating electrodes 24 and 25 are post-polarized at different voltages. Once processed, the trap bandwidth can be further increased.

〔The invention's effect〕

As is clear from the above description, according to the invention described in claim 1, since the polarization axis direction of at least one of the two or more elements is tilted in the thickness direction, the resonance frequency of each element is increased. However, when this piezoelectric trap is used in a trap circuit, the trap bandwidth can be expanded to a high frequency range with one piezoelectric substrate.

According to the second aspect of the invention, at least one set of electrodes provided on the piezoelectric ceramic substrate is subjected to post-polarization treatment in the thickness direction, so that the polarization axis direction of the element constituted by the electrodes is set in the thickness direction. It is possible to easily manufacture a piezoelectric trap having a wide trap bandwidth because the piezoelectric trap can be tilted. Moreover, since it is not necessary to provide a special electrode for the post-polarization process, the post-polarization process is simple, and only necessary portions can be polarized, so that there is no adverse effect on the element that does not perform the post-polarization.

[Brief description of drawings]

FIG. 1 is a front view of an example of a piezoelectric trap according to the present invention,
2 is an enlarged sectional view taken along the line II-II in FIG. 1, FIG. 3 is a resonance characteristic diagram of the piezoelectric trap, FIGS. 4A to 4H are manufacturing process diagrams of the piezoelectric trap, and FIG. 5 is a three-element type piezoelectric. FIG. 6 is a front view of the trap, FIG. 6 is a comparison diagram of transmission characteristics between the conventional and the present invention when a piezoelectric trap is used in the trap circuit, and FIG. 7 is a circuit diagram of a general trap circuit. 1 ... Piezoelectric trap, 2 ... Piezoelectric ceramic substrate, 3,4
...... Input / output electrodes, 5 ...... Common electrodes, 3a, 4a, 5a, 5b …… Vibration electrodes.

Claims (2)

(57) [Claims] 1. A piezoelectric trap in which a plurality of pairs of counter electrodes are formed on both main surfaces of one piezoelectric ceramic substrate to form a plurality of elements, wherein the piezoelectric ceramic substrate is parallel to the main surface. The thickness is characterized in that the frequency of each element is made different by tilting the polarization axis of the other element except one of the above-mentioned elements in the thickness direction. Piezoelectric trap using sliding vibration mode. 2. A method of manufacturing a piezoelectric trap using a thickness-shear vibration mode, comprising a step of performing pre-polarization treatment on a piezoelectric ceramic substrate in a direction parallel to the main surface of the piezoelectric ceramic substrate, and both main surfaces of the piezoelectric ceramic substrate. By forming a plurality of pairs of counter electrodes to form a plurality of elements, and by applying a direct-current voltage between the counter electrodes constituting the other elements except one element, the polarization axis is set in the thickness direction. A method of manufacturing a piezoelectric trap, comprising the step of performing a polarization process after tilting.