JPS6025312A - Piezoelectric vibrator - Google Patents

Abstract

PURPOSE:To suppress generation of spurious wave by forming electrodes in parallel with the direction of displacement in a thickness-shear vibrator using a 165+ or -5 deg. rotation Y plate made of lithium niobate. CONSTITUTION:The electrodes 2, 3 are adhered on a plane in parallel with the direction of vibrating displacement and the lengthwise direction of a piezoelectric raw plate 1 is set to an azimuth of 90+ or -5 deg. to the X axis of the crystal in a strip type piezoelectric vibrator where the electrodes 2, 3 are adhered on both faces of the piezoelectric raw plate 1 using the 165+ or -5 deg. rotation Y plate made of lithium niobate and terminal electrodes 4, 5 are provided at both ends of the lengthwise direction of the piezoelectric raw plate 1. Further, an equivalent series resistance is reduced by setting the relation among plate thickness H, length L and width W of the piezoelectric raw plate 1 as L/H>8, W/H<1.3 or 2.5<W/H<4.3.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a piezoelectric vibrator, in particular a piezoelectric vibrator made of niobium oxide (
LiNb03) Regarding a piezoelectric vibrator using a Y plate rotated by 165±5 degrees.

fb) Background of the Technology Mechanical resonators represented by crystal oscillators are widely used as resonators, oscillators, filters, etc. because of their high Q and high stability as electronic circuit components.

In recent years, as electronic devices have become smaller, thinner, and lighter, one of the parts for which there is an increasing demand for chipping is multi-MH.
There are oscillators with a frequency of 100 MHz to several tens of MHz. Tantalate (LiTaO3), Niobate (LiNb)
Due to its large electro-mechanical coupling coefficient, the piezoelectric single crystal (03) has made it possible to create vibrators in fields that were previously considered impossible with crystals, and much research has been conducted with the aim of putting it into practical use. There is.

Furthermore, it is already well known that it is effective to make a piezoelectric element into a strip in order to downsize the vibrator and improve its spurious characteristics, and a strip-shaped piezoelectric vibrator using LiTaO3 has also been announced. There is.

A strip type piezoelectric vibrator has a piezoelectric element plate, electrodes formed on the front and back surfaces of the piezoelectric element plate, and terminals provided at both longitudinal ends of the piezoelectric element plate for applying an alternating current electric field to the electrodes from the outside. Consists of electrodes. When an alternating current electric field is applied to the terminal electrode, the piezoelectric plate generates stress with a frequency equal to the applied electric field, and when the frequency of the applied electric field matches the natural frequency of the piezoelectric plate, it resonates and strong vibrations are obtained.

However, the characteristics of a piezoelectric plate differ depending on the cutting direction and shape when cutting it from the crystal, and in order to obtain a high quality and high precision piezoelectric vibrator, for example, a thickness-shear vibrator ↓ In this case, a thickness-shear mode is required. It is necessary to select the vibration direction of the piezoelectric element, and also to set the shape of the piezoelectric plate that suppresses the generation of spurious waves and reduces the equal series resistance.

(cl) Prior art and problems Piezoelectric vibrators using LiTaO3 have already been put to practical use, and the optimum cutting direction and shape of the piezoelectric plate have been clarified and published.On the other hand, regarding LiNbO3,
Attempts are being made to put it to practical use, focusing on the fact that it has a higher coupling coefficient than LiTaO3, making it possible to miniaturize piezoelectric vibrators, and also being advantageous in terms of manufacturing costs. The IE'5±5 degree rotated Y plate was selected as a piezoelectric plate with strong thickness shear mode vibration and weakest thickness longitudinal mode vibration, and research is underway for its practical application, but spurious The shape of the piezoelectric plate that suppresses the occurrence and reduces the equal series resistance has not yet been elucidated.

(d) Purpose of the Invention The purpose of the present invention is to suppress the generation of spurious in a piezoelectric vibrator using a LiNbO3165±5 degree rotated Y plate,
Another object of the present invention is to provide a shape of a piezoelectric plate that reduces equal series resistance.

(e) Structure and purpose of the invention is to form electrodes parallel to the displacement direction of the piezoelectric element plate, and to set the longitudinal direction of the piezoelectric element plate at an angle of 90±5 degrees to the X axis of the crystal. Thickness is H1 Length is L1 Width is W
When L/H>8, W/H<1.3 or 2.5
This is achieved by selecting such that <W/H< 4.3.

(fl　Embodiments of the invention The present invention will be explained in detail below with reference to the accompanying drawings.

FIG. 1 shows the structure of a strip-type piezoelectric vibrator according to the present invention.

The strip type piezoelectric vibrator includes a piezoelectric element plate 1 using a LiNbO3165±5 degree rotated Y plate, electrodes 2 and 3 made of metal such as a sieve adhered to the front and back surfaces of the piezoelectric element plate 1, and the piezoelectric element plate 1. It is composed of terminal electrodes 4 and 5 provided at both longitudinal ends of the electrode 2 and the terminal electrode 4,
The electrode 3 and the terminal electrode 5 are electrically connected to each other. In order to improve spurious noise and make the vibrator more compact, the electrodes 2 and 3 are formed on a plane parallel to the direction of vibration displacement, and the longitudinal direction of the piezoelectric plate 1 is
The orientation is set at 90±5 degrees with respect to the axis.

FIG. 2 is a diagram showing the relationship between the length ratio of the thickness H1 of the piezoelectric plate and the equal series resistance Rs.

In the figure, the ratio between the thickness H and the length of the piezoelectric plate, that is, L/
It is clear that when H becomes smaller than 8, the equal series resistance Rs increases rapidly, and spurious noise also occurs in that range. Therefore, in order to suppress the generation of spurious waves and to reduce the equal series resistance, the ratio of the thickness H to the length of the piezoelectric plate must be greater than 8.

FIG. 3 is a diagram showing the relationship between the ratio of the thickness H1 of the piezoelectric plate to the width W and the equal series resistance Rs.

In the figure, the ratio of the thickness H to the width W of the piezoelectric plate, that is, W/H
is less than 1.3 or greater than 2.5 and 4.3
It is clear that the equal series resistance Rs becomes smaller in a range smaller than . Therefore, in order to reduce the equal series resistance, the ratio of the thickness H to the width W of the piezoelectric plate must be smaller than 1.3, or larger than 2.5 and smaller than 4.3.

(gl Invention p Effect As mentioned above, according to the present invention, LiNbO3165±
In a piezoelectric vibrator using a 5-degree rotated Y plate, it is possible to provide a shape of the piezoelectric plate that suppresses the generation of spurious waves and reduces equal series resistance.

[Brief explanation of the drawing]

Figure 1 shows the structure of a strip-type piezoelectric vibrator according to the present invention.
Figure 2 is a diagram showing the relationship between the length ratio of the thickness H1 of the piezoelectric plate and the equal series resistance Rs, and Figure 3 is the relationship between the thickness H1 of the piezoelectric plate
FIG. 3 is a diagram showing the relationship between the ratio of the width W and the equal number of series resistors Rs. In the figure, 1 is a piezoelectric plate, 2 and 3 are electrodes, 4 and 5 are terminal electrodes, H is a plate thickness, L is a length, and W is a width. Scales 2

Claims (1)

[Claims] 1) Tium niobate (LiNb03) 165±5
A piezoelectric vibrator characterized in that a thickness shear vibrator using a degree-rotated Y plate has electrodes formed parallel to the direction of displacement. 2. In the piezoelectric vibrator according to claim 1, 1
．． A piezoelectric vibrator characterized in that its longitudinal direction is approximately 90±5 degrees to the X axis. 3) In the piezoelectric vibrator according to claims 1 and 2, the thickness of the piezoelectric plate is H and the length is 1. A piezoelectric vibrator characterized in that when L/I-1>, B. 4) In the piezoelectric vibrator according to claims 1 to 3, when the thickness of the piezoelectric plate is H and the width is W, W/H<1.3 or 2.5<W/ A piezoelectric vibrator characterized in that H<4.3.