JP2002076825A - Small-sized rectangular piezoelectric vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a layout for an electrode structure that enhances a temperature characteristic of a small-sized rectangular AT-cut crystal vibrator. SOLUTION: This invention provides the small-sized rectangular piezoelectric vibrator that configures an electrode on both major sides of a rectangular crystal vibrator chip with its length in the X axis direction and its width in the Z' axis direction for oscillating a fundamental wave. The electrodes of the rectangular crystal vibrator chip are laid out such that the electrodes placed on both the major sides are offset within a range of 50 μm<=d<=500 μm in the Z' axis direction from the center position (d) of the vibration chip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an electrode arrangement of a small rectangular AT-cut quartz resonator that oscillates a fundamental wave for improving temperature characteristics.

[0002]

2. Description of the Related Art Electronic devices such as consumer communication devices are required to have a vibrator having less variation in frequency characteristics with respect to temperature. AT-cut quartz resonators are used in many electronic devices because of their excellent frequency characteristics with respect to temperature. The AT-cut quartz resonator is cut out at an angle of about 35 ° 15 ′ rotated about the Y-axis about the X-axis of the artificial quartz, and a rectangular quartz-crystal resonator piece having the X-axis and the Z′-axis as external dimensions. It is widely used for surface mount type vibrators that are advantageous for miniaturization.

The resonance frequency is determined by the thickness of the crystal unit, and the frequency deviation (characteristic) with respect to the temperature is determined by the cutting angle of the crystal unit. The frequency characteristic of an AT-cut quartz resonator generally used as an electronic component with respect to temperature is a cubic curve having an inflection point near room temperature. However, the frequency characteristic of FIG. Thus, the frequency deviation changes. The relationship between the frequency characteristics with respect to the cutting angle and the temperature is 60 relative to the room temperature.
At present, the frequency change amount (° F / F) in ° C. is about 3 × 10 ⁻⁶ / 1 ′, and the cutting angle accuracy of about ± 15 ″ is required for communication equipment at present.

[0004]

However, the artificial quartz has a crystal structure and is used in the process of manufacturing a quartz oscillator piece.
Using an X-ray apparatus or the like, for example, if the cutting angle is an AT cut, the X axis is the rotation axis and the Y axis is the crystal axis direction of the crystal unit.
Even if cutting is performed at an angle set at about 35 ° 15 'with respect to the axis, it is difficult to secure the above-mentioned accuracy and secure a desired cutting angle (frequency deviation characteristic) due to restrictions on the disassembling accuracy of the processing machine. The yield in the sorting and cutting process after cutting and the cutting process is not necessarily high. For this reason, there is a factor that the management cost for the crystal resonator piece is generated and the unit price of the crystal resonator piece tends to increase.

[0005]

In order to solve these problems, the present invention is directed to a small-sized rectangular crystal vibrating piece having a length in the X-axis direction and a width in the Z'-axis direction, wherein electrodes are formed on both main surfaces of a rectangular crystal resonator element. In the piezoelectric vibrator, the electrode arrangement of the rectangular piezoelectric vibrator piece is such that the electrodes arranged on both main surfaces from the center position of the vibrator piece are Z ′.
A small rectangular piezoelectric vibrator characterized by being formed eccentric in the axial direction.

At this time, the cut angle of the crystal unit is an AT cut, has a small rectangular shape subjected to beveling, and the detailed size of the eccentricity is the distance d in the Z′-axis direction of the main surface of the crystal unit piece. In this case, the problem is solved by forming an electrode in which 50 μm ≦ d ≦ 500 μm electrode is eccentric in the same direction on the main surface of the vibrator piece.

[0007]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In each drawing, the same reference numeral indicates the same object. FIG. 1 shows a perspective view of the arrangement of the crystal resonator element 1 of the present invention and its electrode 3 (FIG. 1).
(A)) and a dimensional diagram showing the electrode displacement from the center (FIG. 1)
(B)). By displacing the excitation electrode 3 arranged on the crystal unit relative to the two main surfaces 2 of the crystal unit piece 1 in the Z′-axis direction by 50 μm ≦ d ≦ 500 μm, the crystal The frequency characteristic with respect to temperature changes in the clockwise direction in the same manner as when the cutting angle in the cutting step of the child piece 1 is shifted.

FIG. 2 is a sectional view focusing on the electrode position of the crystal resonator element 1 of the present invention and a contour diagram showing the state of the main surface 2 surface. FIG. 2A is a cross-sectional view of FIG. 1A-A portion of the quartz-crystal vibrating piece 1, and shows how the electrode 3 is formed so as to be eccentric in the same Z′-axis direction with respect to the main surface 2. Things. FIG. 2B shows that the main surface 2 of the crystal unit 1 is beveled so that the thickness of the crystal unit 1 at the center of the main surface is thicker. The ellipse drawn on the main surface 2 represents a contour line, indicating that it has been thinned. At this time, since the crystal resonator element 1 is beveled, the confinement of the fundamental wave vibration works effectively, and the equivalent series resistance, which is one of the important characteristics of the crystal resonator, can be seen in FIG. No major change occurs.

On the other hand, FIG. 4 is a graph showing the relationship between the displacement of the electrode 3 and the temperature characteristics. As an example of the external dimensions of the crystal unit 1, the size of the crystal unit 1 is 6.0 mm in the X-axis direction and 1.8 mm in the Z′-axis direction. This is an AT-cut crystal resonator having a fundamental wave of 13,000 kHz, in which a counter electrode 3 is disposed on the main surface 2 of the first electrode 1 and the dimension of the electrode 3 in the Z′-axis direction is 1.4 mm (electrode width in the Z′-axis direction). The electrode 3 is arranged on the two main surfaces 2 of the crystal unit 1 in the Z′-axis direction by an etching method in which a quartz plate called a spacer of a vapor deposition frame is inserted. The plate was gradually displaced by 50 μm from the center in the Z′-axis direction at a maximum of 150 μm, and the numerical value was measured during the course.

FIG. 4 is a graph showing the temperature characteristics and the displacement of the electrode 3 on the X long side piece. The case where the inventor arranges the counter electrode 3 on the main surface 2 of the crystal resonator element 1 and shifts the electrode 3 to a position where the electrode 3 is attached to A to D in the Z ′ axis direction of the crystal resonator element 1 on both main surfaces When the temperature characteristics were confirmed, a frequency change characteristic almost equivalent to a general temperature characteristic due to a change in the cutting angle of the conventional crystal resonator was obtained.

In short, usually, the center of the opposed excitation electrode 3 is formed by a method such as vapor deposition or sputtering so as to coincide with the center of the quartz crystal plate. The electrodes 3 arranged on both main surfaces 2 are eccentric from the center position in the Z′-axis direction of FIG. 2B, and the main surface of the crystal resonator element 1 subjected to beveling shown in FIG. Although FIG. 2 is a contour diagram, there is a correlation between the “X dimension / thickness” and the “temperature characteristic” even in the crystal resonator element 1 having the same cut angle.
The temperature characteristics are improved by utilizing the difference in the thickness distribution of the crystal resonator element 1 subjected to beveling.

[0012] As can be seen from FIG.
The same change as changing the cutting angle was confirmed,
When shifted by 150 μm, it was equivalent to 3 ′ at the cutting angle. This indicates that it is possible to increase ± 15 ″ of the cutting angle selection standard when the electrode 3 is not displaced up to six times, and it is considered that defects due to the selection are almost eliminated. In order to do so, it is also considered practical to be able to obtain it by changing only the inexpensive jig used conventionally.

By utilizing such a feature, among the defective cutting angles of the quartz crystal plate after cutting, when the electrode 3 is formed as usual, it is shifted in the counterclockwise direction with respect to the standard. By shifting the excitation electrode 3 in the Z′-axis direction by a required amount, it becomes possible to satisfy the frequency characteristic with respect to the temperature of the product. Note that the method of the present invention does not change the facing area of the excitation electrode 3, so that there is little change in constants such as the parallel capacitance, and can be handled in the same manner as a normal crystal resonator that does not shift the electrode 3. Quality control is easy.

[0014]

According to the present invention, a rectangle A oscillating a fundamental wave
The electrodes arranged on both main surfaces of the piezoelectric vibrator in which the excitation electrodes are formed on the two main surfaces of the T-cut quartz crystal plate are biased in the Z′-axis direction with respect to the center position of the quartz vibrator piece. By allowing the cut angle of the vibrator to be cut, the design time can be reduced, the manufacturing yield can be improved, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an arrangement of a crystal resonator element and electrodes according to the present invention, and an electrode displacement dimension.

FIG. 2 is a sectional view showing electrode positions of the crystal unit of the present invention and a contour diagram showing a beveling state of a main surface.

FIG. 3 is a graph showing a relationship between a displacement dimension of an electrode arrangement and a CI value in a crystal unit piece of the present invention.

FIG. 4 is a graph showing a deviation dimension of an electrode arrangement and a temperature characteristic in the crystal unit piece of the present invention.

FIG. 5 is a graph showing general temperature characteristics that change depending on a difference in a cutting angle of an AT-cut quartz resonator.

[Explanation of symbols]

 1 rectangular crystal oscillator piece 2 main surface 3 electrode

Claims (2)

[Claims] 1. A small rectangular piezoelectric vibrator having electrodes on both main surfaces of an AT-cut rectangular crystal vibrator piece having a length in the X-axis direction and a width in the Z′-axis direction, When the distance from the center position of the vibrator piece is d, the electrodes arranged on both main surfaces are facing electrodes in the Z′-axis direction and are 50 μm ≦ d ≦ 5 in the same direction.
A small rectangular piezoelectric vibrator characterized in that it is eccentric by 00 μm. 2. The small rectangular piezoelectric vibrator according to claim 1, wherein the vibrator piece is an AT-cut crystal vibrator that oscillates a fundamental wave, and the main surface of the vibrator is beveled.