JPH0748627B2 - Piezoelectric vibrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Outline] Regarding the structure of a piezoelectric vibrator, particularly an electrode formed on the opposing main surface of a piezoelectric body, the rate of change of the oscillation frequency within an allowable operating temperature range is aimed at improving the temperature characteristics of the oscillation frequency. The electrode formed on the opposing main surface of the piezoelectric body having the minimum point in the temperature characteristic is provided with a narrow width portion which forms a plurality of minimum points in the temperature range in the middle portion in the length direction.

[Industrial application field]

The present invention relates to a structure of a piezoelectric vibrator, and more particularly, to a structural improvement for reducing a change rate of an oscillation frequency in a predetermined operating temperature range.

[Conventional technology]

Crystals, ceramics, lithium tantalate, lithium niobate, etc. are used for the piezoelectric body of the oscillator. For example, the rate of change of the oscillation frequency (oscillation frequency) in the operating temperature range determined as -10 ° C to + 60 ° C. Temperature characteristic of Δf / f is
Manufactured to meet a specified value such as ± 200ppm.

Such a temperature characteristic changes depending on the material and crystal orientation of the piezoelectric body used, the capacity of the external capacitor, etc., forming an electrode with a constant width, and the change rate characteristic of the resonance frequency having one minimum point in the operating temperature range. In a piezoelectric element, that is, a piezoelectric vibrator using quartz, ceramics, and lithium tantalate as a piezoelectric body, the local minimum point is located substantially in the center of the temperature range.

FIG. 3 is a perspective view (a) showing a conventional piezoelectric element and a view (b) showing the relationship between the facing length of electrodes formed on the piezoelectric body and the rate of change of the oscillation frequency. Electrodes 3 or 4 formed over the entire width of the piezoelectric body 2 are formed on the opposing main surfaces of the piezoelectric body 2 made of tantalate or the like, and the lead terminals 3a or 4a for external connection are formed from the electrodes 3 and 4 to the piezoelectric body. 2 is led to the end.

In the piezoelectric element 1, the thickness of the piezoelectric body 2 is H,
When the opposing length of the electrodes 3 and 4 is l, the change rate Δf / f (ppm) of the oscillation frequency of the piezoelectric element 1 changes with l / H, and the vertical axis shows the change rate Δf / f (of the oscillation frequency). ppm) and the horizontal axis is temperature T (° C) in FIG. 3 (b), the curve shown by the solid line is the frequency-temperature characteristic of the piezoelectric element 1 where l / H is 3.6, and the curve shown by the dashed line is l / H. Is 3.2 and the frequency-temperature characteristic of the piezoelectric element 1 is the frequency-temperature characteristic of the piezoelectric element 1 in which l / H is 5.2.

Therefore, the conventional piezoelectric element 1 has the center of its operating temperature range,
For example, +25 when the operating temperature range is -10 ℃ to + 60 ℃
Although the minimum point of the frequency temperature characteristic is located at ° C, the frequency temperature characteristic of the piezoelectric element 1 also changes depending on the crystal orientation of the piezoelectric body 2.

FIG. 4 is a diagram showing the crystal orientation of a piezoelectric body made of a lithium tantalate single crystal and the temperature characteristic of the oscillation frequency, where the vertical axis represents the change rate Δf / f (ppm) of the oscillation frequency and the horizontal axis represents the temperature T.
(° C) in FIG. 4, the curve shown by the solid line is the temperature characteristic of the frequency of the piezoelectric body whose rotation angle θ about the X axis is 0 degrees, and the curve shown by the alternate long and short dash line is the rotation angle θ about the X axis is −.
The temperature characteristic of the frequency of the piezoelectric body which is 1 degree, the curve shown by the chain double-dashed line is the temperature characteristic of the frequency of the piezoelectric body whose rotation angle θ around the X axis is +1 degree, and the operating temperature of -10 ℃ to + 60 ℃ The frequency change rate Δf / f of the piezoelectric element with θ = 0 degree in the range is 0 to 80p
In contrast to pm, those of the piezoelectric element with θ = + 1 degree and θ = −1 degree are about −20 to +135 ppm and −10 to +135 ppm.

[Problems to be solved by the invention]

As described above, the conventional piezoelectric vibrator has only one minimum point of the rate of change of the oscillation frequency, and the crystal orientation of the piezoelectric body and the counter electrode of the counter electrode are set so that the minimum point is located substantially in the center of the operating temperature range. Although the facing length and the like were set, the crystal orientation is determined by cutting out from the single crystal, and since the facing length of the facing electrode is related to the oscillation frequency, it is extremely difficult to adjust the temperature characteristics. There was a point.

[Means for solving problems]

The piezoelectric vibrator of the present invention intended to eliminate the above problems,
According to Fig. 1, a piezoelectric body that has a minimum point in the temperature characteristic of the rate of change of the oscillation frequency in the allowable operating temperature range of -10 ° C to + 60 ° C.
The electrodes 13 and 14 formed on the opposing main surfaces of 12 are narrow width portions 13 that form a plurality of minimum points in the temperature range in the middle portion in the length direction.
It is characterized by the provision of d.

[Action]

According to the present invention, in the middle portion in the lengthwise direction of the electrode formed on the opposing main surface of the piezoelectric body 12, a narrow width portion for providing a plurality of minimum points of the rate of change of the oscillation frequency within the allowable operating temperature range is provided. As a result, the range of the rate of change in the temperature range can be narrowed as compared with the conventional case.

〔Example〕

A piezoelectric vibrator according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view showing a piezoelectric element according to an embodiment of the present invention (a) and a frequency temperature characteristic of the piezoelectric element (b).
FIG. 2 is a perspective view showing a piezoelectric element according to another embodiment of the present invention (a) and a frequency temperature characteristic of the piezoelectric element (b).
Is.

In FIG. 1 (a), the piezoelectric vibrator 11 has an opposing main surface of a piezoelectric body (for example, a piezoelectric body cut from a single crystal of lithium tantalate) 12 whose oscillation frequency change rate characteristic forms a local minimum point in the operating temperature range. Electrodes 13 and 14 are formed on each of the electrodes, and a pair of Ls formed by laser trimming are formed in the middle of the electrodes 13 in the longitudinal direction.
The groove 15 and the linear groove 16 are formed, and the groove 1 is formed on the electrode 14.
Grooves (not shown) corresponding to 5 and 16 are formed.

Grooves 15 and 16 formed in the electrode 13 having lead terminals 13a
Is to separate a part of the electrode 13 from the electrode 13 so that the electrode 13 is composed of full width portions 13b and 13c extending over the entire width of the piezoelectric body 12 and a narrow width portion 13d narrower than the piezoelectric body 12. Electrode 1
The lead terminal 1 is formed by the groove formed in FIG. 4 and not shown.
The electrode 14 having 4a is composed of the full width portions 13b and 13c and the narrow width portion corresponding to the narrow width portion 13d and the narrow width portion.

As shown in FIG. 1B, the temperature characteristic of the change rate of the oscillation frequency of the piezoelectric body 11 is as shown in FIG. 1B, the vertical axis shows the change rate Δf / f (ppm) of the oscillation frequency, and the horizontal axis shows the temperature T (° C. ), If the measured values are plotted and the plots are connected by an appropriate curve, the curve will form two minimum points in the operating temperature range of −10 ° C. to + 60 ° C., and the frequency change rate Δf / f comes to fall within the range of 0 to -70 ppm in the operating temperature range.

In FIG. 2 (a) in which the same reference numerals are used for the same parts as in FIG. 1 (a), the piezoelectric vibrator 21 has electrodes 22 and 23 formed on the main surface facing each other of the piezoelectric body 12 by using the photoetching technique. ,
A lead terminal 22a or 23a is led out from the electrodes 22 and 23.

The electrode 22 formed on the entire width of the piezoelectric body 12 has a plurality of (four in the figure) through holes 24 aligned in the width direction of the piezoelectric body 12 at two positions in the middle portion in the length direction thereof. It is composed of three full width portions 22b covering the entire width of the piezoelectric body 12 and two narrow width portions 22c where the actual electrode width is narrowed by the through holes 24.

On the other hand, the electrode 23 (not shown) formed on the lower surface of the piezoelectric body 12 is also provided with a through hole corresponding to the through hole 24, and by the through hole, a full width portion corresponding to the full width portion 22b and a narrow width portion 22c and a narrow width portion are provided. Are formed on the electrodes 23.

As shown in FIG. 1B, the temperature characteristic of the change rate of the oscillation frequency of the piezoelectric body 21 is as shown in FIG. 1B, in which the vertical axis represents the change rate Δf / f (ppm) of the oscillation frequency and the horizontal axis represents the temperature T ( C), three minimum points are formed in the operating temperature range of −10 ° C. to + 60 ° C., and the frequency change rate Δf / f in the operating temperature range falls within the range of about 50 ppm.

In addition, when the narrow width portion is formed in a part of the electrode according to the present invention, the resonance frequency is thereby lowered. Therefore, the electrode according to the present invention predicts such a change in advance, and the resonance frequency before the formation of the narrow portion is formed to be a resonance frequency that is appropriately higher than the desired value.

〔The invention's effect〕

As described above, according to the present invention, in the middle portion in the length direction of the electrode formed on the opposing main surface of the piezoelectric body 12, a plurality of local minimums are exhibited in the temperature characteristic of the change rate of the oscillation frequency in the allowable operating temperature range. The temperature characteristic of the piezoelectric vibrator is improved by providing the narrow width portion for forming the point and narrowing the width of the rate of change in the temperature range as compared with the conventional case.

[Brief description of drawings]

FIG. 1 is a piezoelectric element according to one embodiment of the present invention and its temperature characteristics, FIG. 2 is a piezoelectric element according to another embodiment of the present invention and its temperature characteristics, and FIG. 3 is a conventional piezoelectric element and its temperature characteristics. FIG. 4 shows the crystal orientation and temperature characteristics of the piezoelectric body. In the figure, 11,21 is a piezoelectric vibrator, 12 is a piezoelectric body, 13,14,22,23 are electrodes,
13b, 13c and 22b are full width portions, 13d and 22c are narrow width portions, 15 and 16 are trimming grooves, and 24 is a through hole.

Claims (1)

[Claims] 1. An electrode (13,14,22,23) formed on an opposing main surface of a piezoelectric body (12) having a minimum point in temperature characteristics of a change rate of an oscillation frequency in an allowable operating temperature range has a longitudinal direction. Narrow width part (13d, 22d) that forms a plurality of minimum points in the temperature range in the middle part of
A piezoelectric vibrator characterized by being provided in step c).