JPS63190413A - Piezoelectric resonator - Google Patents

Abstract

PURPOSE:To improve spurious characteristic by forming a vibrating electrode made of a conductive coating film to both main surfaces of a piezoelectric substrate and applying conductive or insulation paste to at least one surface of the conductive coating film thereby reducing the parasitic vibration of the piezoelectric resonator itself. CONSTITUTION:Vibration electrodes 2a, 2b made of conductive film are formed to both major surfaces of a piezoelectric substrate 1 and the resonator is used at the spread vibration mode. A conductive or insulation paste 3a is applied to at least one surface of the conductive film. Thus, a mass is added to the vibration electrodes 2a, 2b. Thus, the parasitic vibration of high order is suppressed especially by the added mass and the spurious level is drastically reduced, Furthermore, the coating film by the conductive or insulation paste 3a stuck on the vibration electrodes 2a, 2b does not give much effect onto the vibration of the fundamental wave and the characteristic in the fundamental frequency is not almost deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to a piezoelectric resonator in a spread vibration mode used in filters and the like.

(b) Prior Art As a piezoelectric resonator used in a frequency band from IQOKHz to several MHz, piezoelectric resonators utilizing so-called spread vibration modes such as area vibration mode and radial vibration mode have been used.・(C) Problems to be solved by the invention However, in this type of piezoelectric resonator, a large number of parasitic vibrations are excited in addition to the frequency of the fundamental wave, and when a filter or oscillator is configured, the spurious characteristics deteriorate. This was a contributing factor. FIG. 4 is a diagram showing spurious level characteristics of a conventional piezoelectric resonator. The resonant frequency of the fundamental wave is approximately 4
00 Hz, but a large parasitic vibration occurs on the higher side, for example, 4 MHz or higher, and this spurious characteristic becomes a problem when used as a filter or an oscillator. For this reason, conventionally, the areas and shapes of the piezoelectric substrate and the vibrating electrode have been designed to increase the vibration of the fundamental wave and reduce the parasitic vibration as much as possible. In addition, as a countermeasure against spurious noise on the circuit, it is possible to suppress spurious noise by using an intermediate frequency transformer together with an LC low-pass or bypass filter, or by using two piezoelectric resonators to cancel out spurious waves. However, in order to fundamentally eliminate the spurious problem, it is necessary to reduce the parasitic vibration of the piezoelectric resonator itself.The purpose of this invention is to reduce the parasitic vibration of the piezoelectric resonator itself. Therefore, it is an object of the present invention to provide a piezoelectric resonator with good spurious characteristics.

(Means for Solving Problem d1) The piezoelectric resonator of the present invention has vibrating electrodes made of conductive films formed on both main surfaces of a piezoelectric substrate, and is used in a spread vibration mode. It is characterized in that a tetraelectric or insulating paste is applied to at least one surface of the coating.

(ill) Function In the piezoelectric resonator of the present invention, since a conductive or insulating paste is adhered to the surface of the vibrating electrode made of a conductive film, mass is added to the vibrating electrode. Therefore, parasitic vibrations, especially on the higher order side, are suppressed by this additional mass,
Spurious levels are significantly reduced. In addition, the piezoelectric resonator is attached onto the vibrating electrode (r) Embodiment FIG. 1 is a sectional view showing the structure of a piezoelectric resonator according to an embodiment of the present invention. In the figure, 1 is Pb(Ti, Zr)O
It is a substrate made of piezoelectric ceramics such as s., and silver paste is applied to both main surfaces.

Vibrating electrodes 2a and 2b are formed by firing, and these vibrating electrodes are patterned so as to spread and vibrate the piezoelectric substrate 1. Further, a conductive paste (3a) made of, for example, Ag powder dispersed in an epoxy resin is applied to the surface of the vibrating electrode 2a and dried and solidified. This conductive paste 3a acts as an additional mass to the vibrating electrode 2a, suppressing parasitic vibrations. In particular, parasitic vibrations in the thickness vibration mode are efficiently suppressed, and high-order spurious levels are sufficiently reduced.

FIG. 2 is a diagram showing spurious level characteristics of the same piezoelectric resonator. As is clear from the comparison with the spurious characteristics of the conventional piezoelectric resonator shown in FIG. 4, the parasitic vibration due to the thickness vibration mode of % 4 MHz or higher is sufficiently reduced.

Although the example was an example in which conductive paste was applied to only one of the vibrating electrodes formed on both main surfaces of the piezoelectric substrate, it is possible to apply conductive paste to both vibrating electrodes. FIG. 3 is a sectional view showing the structure of the piezoelectric resonator in that case. As shown in the figure, a vibrating electrode 2a,
Electrosensitive pastes 3a and 3b are applied to both of the electrodes 2b. Also in this case, parasitic vibrations are suppressed by the action of the additional mass of the conductive pastes 3a and 3b.

In all of the above embodiments, a conductive paste was applied to the vibrating electrode, but if the configuration is such that signals are directly input/output to the vibrating electrode without going through the conductive paste, an insulating paste can be used. is also possible. Furthermore, the vibrating electrode may be formed by vapor deposition or sputtering instead of thick film firing.

(&1 Effects of the Invention As described above, according to the present invention, the parasitic vibrations of the piezoelectric resonator are efficiently suppressed, and when this piezoelectric resonator is used as a filter or oscillator, the passage of unnecessary frequency bands and spurious oscillations are avoided. can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing the structure of a piezoelectric resonator according to an embodiment of the present invention, FIG. 2 is a diagram showing spurious characteristics of the same piezoelectric resonator, and FIG. 3 is a diagram showing a piezoelectric resonator according to another embodiment. FIG. 4, a cross-sectional view showing the structure, is a diagram showing spurious characteristics of a conventional piezoelectric resonator. 1 - piezoelectric substrate, 2a, 2b - vibrating electrode, 3a, 3b - conductive paste.

Claims (1)

[Claims] (1) In a piezoelectric resonator that is used in a spread vibration mode with vibrating electrodes made of conductive films formed on both main surfaces of a piezoelectric substrate, conductive or insulating paste is applied to at least one surface of the conductive film. A piezoelectric resonator characterized by being coated with.