JPH0766655A - Manufacturing method for piezoelectric resonator - Google Patents

Abstract

PURPOSE:To obtain a piezoelectric resonator where dispersion is low by preventing dielectric breakdown generated at the time of the polarization of a main ferroelectric substance ceramic plate. CONSTITUTION:When a main ferroelectric substance plate 1 is prepared by using Pb (Zr, Ti) O3 whose outside dimension is 52X52X0.35mm, for instance, silver electrodes 2 and 3 of 50X50mm angles are formed on these both main surfaces by a screen printing and parts where silver electrodes 1 and 2 of 0.5 to 1.5mm do not exist are provided on the edges of the silver electrodes 2 and 3 and the main surface. Next, when a resonator to be a resonance frequency Fr=438.5kHz and an antiresonant frequency Fa=455kHz is prepared by using the ceramic plate 1 where the silver electrodes 2 and 3 are formed, perform the followings. Namely, the + side and - side of a DC power source 4 are connected with the silver electrodes 2 and 3, respectively, DC high voltage 200+ or -20V is added so that the difference of the resonance frequency and the antiresonant frequency of DELTAFa-Fr may be 16.5kHz, a polarization 6 is provided, generating electric field 5 in the ceramic plate 1, the polarization 6 is made to exist even if impression voltage is eliminated and a main piezoelectric ceramic plate 7 showing a piezoelectricity is made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a piezoelectric resonator used in a ceramic ladder type filter such as a portable radio device.

[0002]

2. Description of the Related Art Piezoelectric resonators are generally used in ceramic ladder type filters for portable radios, taxi radios, pager receivers and the like. A conventional method of manufacturing this type of piezoelectric resonator will be described below with reference to FIGS.

In FIG. 5, reference numeral 10 designates a ceramic [BaTiO ₃ , PbTiO ₃ , Pb (Z
r, Ti) O ₃ , (NaK) NbO _{3 and the} like as a basic composition], and the two main surfaces of the mother ferroelectric ceramic plate 10 facing each other are entirely covered with silver or the like. Electrode 11 made of conductive material by printing or vapor deposition,
Forming twelve.

Next, a method of manufacturing a piezoelectric resonator having a predetermined resonance frequency (Fr) and antiresonance frequency (Fa) using the mother ferroelectric ceramic plate 10 on which the electrodes 11 and 12 are formed will be described. .

First, as shown in FIG. 6, the electrodes 1 formed on the entire main surfaces of the mother ferroelectric ceramic plate 10 on the (+) side and the (-) side of the DC power source 13, respectively.
1 and 12 and by applying a predetermined high DC voltage, an electric field 14 is generated in the mother ferroelectric ceramic plate 10 and polarization 15 is applied. Even if the applied voltage is removed, the polarization 15 exists and the piezoelectric effect is exerted. It becomes the mother piezoelectric ceramic plate 16 shown.

Next, as shown in FIG. 7, the dicing saw 1
One of a large number of chips obtained by cutting the mother piezoelectric ceramic plate 16 polarized by using 7 into a predetermined size serves as the piezoelectric resonator 18.

When an AC electric field is applied between the electrodes 12 and 13 of the piezoelectric resonator 18 to raise the frequency, the absolute value of the admittance of the piezoelectric resonator 18 changes as shown in FIG. 8, and the maximum and minimum admittances are obtained. Is the resonance frequency (F
r) and the anti-resonance frequency (Fa).

[0008]

However, when the piezoelectric resonator 18 is manufactured by using the above-mentioned conventional technique, the electrodes 12, 13 are formed on the entire surfaces of both main surfaces of the ferroelectric ceramic plate 10.
Since a DC high voltage is applied between the electrodes 12 and 13 to perform polarization, the electric field strength at the peripheral portion of the mother ferroelectric ceramic plate 10 is stronger than that at the central portion. ) There is a problem that dielectric breakdown is likely to occur, and when the dielectric breakdown occurs, the characteristics of the piezoelectric resonator 18 after cutting may vary.

The present invention solves the above-mentioned conventional problems, and provides a manufacturing method for obtaining a piezoelectric resonator which is capable of preventing dielectric breakdown even when polarization is performed by applying a high DC voltage, and has less characteristic variation. To aim.

[0010]

In order to achieve this object, the present invention provides an electrode on one main surface or both main surfaces of the mother ferroelectric ceramic plate excluding the peripheral portion by printing or vapor deposition. Forming step, applying a predetermined direct current high voltage between the electrodes of the mother ferroelectric ceramic plate for polarization, and dicing saw so that the polarized mother piezoelectric ceramic plate has a predetermined piezoelectric resonator characteristic. The method for manufacturing a piezoelectric resonator includes a step of cutting into a predetermined size.

[0011]

By this manufacturing method, the strength of the electric field applied to the vicinity of the peripheral portion of the mother-ferroelectric ceramic plate during polarization is weakened, dielectric breakdown of the peripheral portion is prevented, and a piezoelectric resonator with less characteristic variation is manufactured. Will be possible.

[0012]

[Embodiment] As one embodiment of the present invention, an IF 45
A method of manufacturing a piezoelectric resonator used for a 5 kHz ladder type filter will be described with reference to FIGS.

FIG. 1 (a) is a perspective view of the mother ferroelectric ceramic plate, FIG. 1 (b) is a plan view thereof, and FIG. 2 shows a polarization by applying a high DC voltage to the mother ferroelectric ceramic plate. FIG. 3 is an explanatory diagram for explaining the manufacturing process of the piezoelectric resonator by cutting the mother piezoelectric ceramic plate after polarization, and FIG. 4 is a characteristic diagram showing the admittance-frequency relationship of the piezoelectric resonator.

In FIGS. 1A and 1B, 1 is Pb (Zr, Ti) having an outer dimension of 52 × 52 × 0.35 (mm).
It is a mother ferroelectric ceramic plate made of O ₃ (lead zirconate titanate), and both main surfaces of this mother ferroelectric ceramic plate 1 should not cover the sub-surfaces of the mother ferroelectric ceramic plate 1. , The silver electrodes 2 and 3 are formed by screen printing in a size of 50 × 50 (mm) square. Here, the edges of the silver electrodes 2 and 3 and the main surface are 0.5 to 1.5 (m
The part where the silver electrodes 1 and 2 of m) do not exist is provided.

Next, using the mother ferroelectric ceramic plate 1 on which the silver electrodes 2 and 3 are formed, the resonance frequency: Fr = 43.
A method of manufacturing a piezoelectric resonator having 8.5 kHz and an antiresonance frequency of Fa = 455 kHz will be described.

First, as shown in FIG. 2, the (+) side and the (-) side of the DC power source 4 are connected to the silver electrodes 2 and 3 formed on both main surfaces of the mother ferroelectric ceramic plate 1, respectively.
Difference between resonance frequency and anti-resonance frequency (Δ = Fa−Fr) is 1
DC high voltage (200 ± 20) so that it becomes 6.5 kHz.
By applying V), an electric field 5 is generated in the mother ferroelectric ceramic plate 1 and polarization 6 is applied. Even if the applied voltage is removed, the polarization 6 exists and the mother piezoelectric ceramic plate 7 exhibits a piezoelectric effect. It should be noted that the ferroelectric ceramic portion having no electrode formed around the silver electrodes 2 and 3 has a thickness of 0.5 to 1.5.
Since the width is (mm), the strength of the electric field applied to the peripheral portion of the electrode is weaker than in the case of the full-face electrode.

Next, as shown in FIG. 3, one of a large number of chips obtained by cutting the mother piezoelectric ceramic plate 7 polarized by using the dicing saw 8 into a size (4.8 mm) at which the antiresonance frequency becomes 455 kHz. The piezoelectric resonator 9. The electrodes of the completed piezoelectric resonator 9 are formed on the entire surfaces of both main surfaces of the piezoelectric resonator 9.

When an AC electric field is applied between the electrodes of the piezoelectric resonator 9 to raise the frequency, the absolute value of the admittance of the piezoelectric resonator 9 changes as shown in FIG. 4, and the frequency showing the maximum and minimum of the admittance. Indicates a resonance frequency: Fa = 438.
5 kHz, anti-resonance frequency: Fr = 455 kHz.

Next, Table 1 shows the measurement results when the piezoelectric resonators were manufactured in this example and the conventional example.

[0020]

[Table 1]

Further, FIG. 9 shows a histogram of ΔF in this embodiment, FIG. 10 shows a histogram of Fa in this embodiment, FIG. 11 shows a histogram of ΔF in the conventional example, and FIG. 12 shows a histogram of Fa in the conventional example. Show.

As can be seen from Table 1 and the histogram, by the manufacturing method according to this embodiment,
It was possible to prevent dielectric breakdown during polarization and reduce variations in the characteristics of the piezoelectric resonator.

In this embodiment, since electrodes are formed on one main surface or both main surfaces of the mother ferroelectric ceramic plate 1 excluding the peripheral portions and polarization is performed by applying a high DC voltage, dielectric breakdown occurs. It is possible to prevent this from happening and manufacture a piezoelectric resonator with less characteristic variation.

[0024]

As is clear from the description of the above embodiment,
By using the manufacturing method of the present invention, it is possible to prevent dielectric breakdown from occurring during polarization of the mother ferroelectric ceramic plate and manufacture a piezoelectric resonator with less variation.

[Brief description of drawings]

FIG. 1A is a perspective view of a mother-ferroelectric ceramic plate used for manufacturing an embodiment of the present invention, and FIG. 1B is an electrode shape explanatory diagram of the same mother-ferroelectric ceramic plate.

FIG. 2 is an explanatory diagram of a polarization process of a mother ferroelectric ceramic plate according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a piezoelectric resonator manufacturing process after the same polarization process.

FIG. 4 is an admittance-frequency characteristic diagram of the piezoelectric resonator.

FIG. 5 is an explanatory view of an electrode shape of a mother ferroelectric ceramic plate used for conventional manufacturing.

FIG. 6 is an explanatory diagram of a polarization process of the mother ferroelectric ceramic plate.

FIG. 7 is an explanatory diagram of a manufacturing process of the piezoelectric resonator after the same polarization process.

FIG. 8 is a admittance-frequency characteristic diagram of the piezoelectric resonator.

FIG. 9 is a histogram of ΔF in the present invention.

FIG. 10 is a histogram of Fa according to the present invention.

FIG. 11 is a histogram of ΔF in the conventional example.

FIG. 12 is a histogram of Fa in a conventional example.

[Explanation of symbols]

 1 Mother Ferroelectric Ceramic Plate 2 Silver Electrode 3 Silver Electrode 4 DC Power Supply 5 Electric Field 6 Polarization 7 Mother Piezoelectric Ceramic Plate 8 Dicing Saw 9 Piezoelectric Resonator

Claims (1)

[Claims] 1. A step of forming electrodes by printing, vapor deposition or the like on one main surface of a mother ferroelectric ceramic plate or a part of both main surfaces excluding peripheral portions, and between electrodes of the mother ferroelectric ceramic plate. A step of applying a predetermined direct current high voltage to the polarization,
A method of manufacturing a piezoelectric resonator, which comprises a step of cutting a polarized mother piezoelectric ceramic plate into a predetermined size with a dicing saw so as to have predetermined piezoelectric resonator characteristics.