RU2099858C1 - Radio-frequency piezoelectric element - Google Patents

Abstract

FIELD: piezoelectronics, applicable in production of piezoelectric elements for RF piezoelectric resonators and monolithic filters. SUBSTANCE: RF piezoelectric element of the back-type mesa- structure is made of a single-crystal wafer in the form of a thinned central part with a thicker shoulder surrounding it; the shoulder is made with a rupture, whose width makes up 20 to 400 thickness of the thinned part of the piezoelectric element. EFFECT: improved design. 4 dwg

Description

 The invention relates to the field of piezoelectronics and can be used in the manufacture of piezoelectric elements for high-frequency piezoresonators and monolithic filters.

 Known high-frequency piezoresonators with piezoelectric elements in the form of an inverse mesastructure, which are a monolithic structure, the central oscillating part of which is much thinner than the surrounding flange. This design (see, for example, Pat. France N 2666705, class H 03 H 9/17, 9/25), 1992, allows you to perform a piezoelectric element with a thickness of up to 1 μm and increase the frequency to 1.5 GHz. The frequency response of the described piezoelectric element has a number of spurious bursts and the resistance of such a piezoelectric element is of the order of several tens of ohms.

 Improve the frequency response of piezoelectric elements such as inverse mesastructure is possible using the design described in US Pat. EPO N 0468051 cl. H 03 H 9/19), 1992. Due to the change in the shape of the piezoelectric element, spurious oscillations can be reduced, but they still affect the frequency response, because and in this case, the piezoelectric element is clamped on all sides around the entire perimeter.

 The task of the invention is to improve the monofrequency characteristics of the oscillations of the piezoelectric element and reduce its dynamic resistance.

 The solution of this problem is achieved by the fact that in a high-frequency piezoelectric element of the inverse mesostructure type made of a single-crystal plate in the form of a refined central part with a thicker collar surrounding it, the collar is made with a gap, the width of which is from 20 to 400 thicknesses of the refined part of the piezoelectric element.

 In the drawings of FIG. 1 4 presents several versions of the proposed piezoelectric element. In FIG. 1 shows a piezoelectric element of a circular shape with a cut off segment, in which the rim gap has a variable width. In FIG. 2 shows a piezoelectric element of a round shape in which the bead has a gap of constant width. In FIG. 3 shows a piezoelectric element of a rectangular shape with a gap of a shoulder of constant width. In FIG. 4 shows a rectangular piezoelectric element, in which the width of the rupture of the shoulder coincides with the width of one of the sides of the piezoelectric element.

 The proposed device contains (see figure 1) a piezoelectric element consisting of a round crystalline plate having a thinned part 1 and a shoulder 2 containing a gap 3, the width of which is from 20 to 400 thicknesses of the thinned part of the piezoelectric element. Similarly, the refined part of the piezoelectric element and the flange with a gap shown in figure 2, 3 and 4.

 The presence of a gap on the flange surrounding the active part of the piezoelectric element contributes to a significant release of the central oscillating part of the piezoelectric element, which leads to a significant reduction in spurious oscillations and an improvement in the amplitude-frequency characteristic of the piezoelectric element. Moreover, the width of the rim gap is from 20 to 400 thicknesses of the refined part of the piezoelectric element. With a gap of less than 20 thicknesses, the effect of the gap on the frequency response is insignificant, and with a gap of more than 400 thicknesses of the thinned part of the piezoelectric element, the structure becomes mechanically unstable, which leads to significant deformations and breakdowns of the piezoelectric element during its installation in the crystal holder.

 The device operates as follows. When applying an alternating voltage to the exciting electrodes of the piezoelectric element / not shown / in the refined part of the crystal plate located between the exciting electrodes, oscillations occur. When the frequency of the exciting alternating voltage coincides with the natural frequency of the thickness-shear vibrations of the thinned part of the plate, a resonance of the structure occurs, while the conductivity of the device increases sharply.

 The presence of a gap in the shoulder reduces the rigidity of the structure and contributes to the appearance of more active oscillations of the operating frequency. In addition, the absence of plate deformations caused by stresses arising during a closed flange significantly reduces the number of possible side vibrations of the plate and contributes to a decrease in the dynamic resistance of the piezoelectric element, as well as significantly reduces the occurrence of twins in the thinned part of the plate, which reduces twinning losses by no less than 80%

Claims (1)

 A high-frequency piezoelectric element of the inverse mesastructure type made of a single-crystal plate in the form of a refined central part with a thicker collar surrounding it, characterized in that the collar is made with a gap whose width is 20,400 thicknesses of the refined part of the piezoelectric element.

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