JPH09162684A - Piezoelectric resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To select any of several kinds of widths even at the same frequency without occurrence of spurious radiation and deterioration in the characteristic relating to a shape of a piezoelectric substrate for the piezoelectric resonator used for an oscillator or a filter. SOLUTION: A 165±5 deg. rotation Y-substrate is adopted for an opposed major side of a lithium niobate single crystal, a short-side direction of the Y- piezoelectric substrate is selected to have an angle in excess of 5 deg. till 25 deg. and in excess of -5 deg. till -25 deg. with respect to the X-axis. Then the thickness of the piezoelectric substrate satisfies a relation of W/H=(3.3±0.5)+1.4n, where H is the thickness of the photoelectric conversion element substrate, W is the width and n is a natural number.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator used for an oscillator or a filter.

[0002]

2. Description of the Related Art In recent years, there has been a demand for oscillators to be miniaturized in accordance with higher operating frequencies of microcomputers and higher frequencies of oscillators and higher density of mounting boards.

A conventional example will be described below. Piezoelectric ceramics, filters using piezoelectric single crystals, thickness-slip piezoelectric resonators made of strips such as oscillators, and the resonance frequency of approximately 1 to 2 MHz or more.
Is uniquely determined with respect to frequency. With respect to the determined thickness, the element width dimension W is determined by the behavior of spurious associated with the shape of the piezoelectric resonator.

[0004]

However, in the conventional structure as described above, the substrate shape of the piezoelectric resonator, in particular, the value of W / H related to the behavior of spurious (especially 9 to 1).
It is not clear (in the high frequency band of 0 MHz or more), and even if it is specified, the element thickness is determined if the frequency is determined. Therefore, the element width dimension W is inevitably determined corresponding to the element thickness H. Therefore, it is difficult to share the case size for mounting the resonator, the mounting capability in the process, the processing size from the piezoelectric single crystal, and the like.

The present invention solves the above-mentioned conventional problems, and an object thereof is to provide a piezoelectric resonator of lithium niobate single crystal having sufficient characteristics and quality in a high frequency band.

[0006]

In order to achieve this object, the present invention uses 165 as opposed major surfaces of a lithium niobate single crystal.
± 5 ° rotated Y plate, and the angle formed between the lateral direction of the piezoelectric substrate and the X axis of the rotated Y plate is more than 5 ° to 25 ° and more than −5 ° to −25 °, and both the opposing main surfaces are In a strip type piezoelectric resonator in which an electrode is provided on the substrate, W / H = (3.3 ± 3
It is set to 0.5) + 1.4n (n is a natural number).

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to claim 1 of the present invention, by setting an arbitrary natural number, the generation of spurious and the characteristics related to the shape of a piezoelectric element with respect to an arbitrary frequency (that is, the thickness of the piezoelectric element) is confirmed. It is possible to realize several types of piezoelectric resonators having respective element width W dimensions corresponding to respective natural numbers set even at the same frequency without causing deterioration.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view of a thickness sliding oscillator. A substrate 1 made of a lithium niobate single crystal has a facing main surface of a Y plate rotated by 165 ± 5 degrees, and the Y direction is the Y direction.
The angle formed with the X axis of the plate is + 10 °.

In FIG. 1, the element thickness H is defined by the required frequency, and the element width W can be obtained from the relationship of W / H. The vibrating electrode 2 formed on the opposite main surface has a crossing width l
It is opposite in size.

The resonator shown in FIG. 1 has a W / H = (3.3 ±
0.5) + 1.4n (n is a natural number 1, 2, 3, ...) Is satisfied. When n = 0, a value of W / H = 3.3 ± 0.5 can be obtained. Similarly, when n = 1 and 2, W / H = 4.7 ± 0.5 and 6.1 ± 0.5 are obtained. FIG. 2 shows the characteristics of the resonator based on this relationship. As an example, an example in which the thickness H = 0.138 mm (resonance frequency is approximately 14 MHz) is shown. The element width W can be obtained from the above relation, and for n = 0, 1, 2 respectively, W
= 0.46, 0.65, 0.84. As other element dimensions, the resonator longitudinal dimension L = 5.1 mm,
1 = 0.7 mm is common.

These three characteristics are shown in FIGS. 2 (a) to 2 (c).
In each case, despite having different element width dimensions W, all have good characteristics with little spurious. When n = 1, near resonance and antiresonance, n = 2
In the case of 1, a small spurious is generated near the anti-resonance, but there is no problem in characteristics. Since the thickness H is defined by the frequency in the relationship of W / H, the width dimension W can have a tolerance, and has good characteristics as in FIG. Therefore, it is possible to select more element width dimensions W. Further, there is no problem even if the longitudinal dimension L of the above embodiment is shortened to about 3 mm, and particularly good characteristics can be obtained when the electrode intersection width l is 0.5 ≦ l ≦ 0.7 mm.

By the way, as described above, the present resonator has n
When = 0, the relationship of W / H = 3.3 ± 0.5 is obtained,
In this case, the maximum value of W / H is 3.8 and the minimum value is 2.
It becomes 8. In the above embodiment, H = 0.13
When W is 8mm, W value can be 0.36mm.
≦ W ≦ 0.52 mm. As a matter of course, the W dimension W = 0.46 mm shown in the above embodiment satisfies this relationship. Here, when the range of the W dimension is not satisfied, large spurious is generated between the resonance anti-resonance and in the vicinity of each of the resonance anti-resonance as compared with the good characteristics shown in FIG. I will end up. FIG. 3 shows an example. In this case, similarly to the above, when n = 0, H = 0.138 mm
At that time, W = 0.6 mm. Compared with W = 0.46 mm, a large spurious is generated between the resonance and anti-resonance, and good characteristics cannot be obtained. This relationship is the same even when the value of n is another natural number. That is, after the element thickness H corresponding to the required frequency is determined,
W within the range of W dimension that can be obtained from the relational expression
If the dimensions are selected, good characteristics can be obtained, and conversely, if the dimensions are out of the range, characteristic deterioration such as spurious generation occurs. Further, as the value of n increases, the W dimension also increases correspondingly. That is, it is possible to select a plurality of W dimensions corresponding to the same element thickness (same frequency). An example is shown below.

Since various element widths W can be selected with respect to the element thickness H determined by the frequency, it is possible to unify an arbitrary element width dimension width with respect to different element thickness (frequency). . 4A to 4C, the element thickness H = 0.123 mm (resonance frequency is approximately 16
MHz) Element width W = 0.57 mm (n = 1), element thickness H = 0.165 mm (approx. 12M as resonance frequency)
Hz) Element width W = 0.55 mm (n = 0), element thickness H
= 0.206mm (Approximately 9.6M as resonance frequency
(Hz) W = 0.68 mm (n = 0) is shown as a prototype. It goes without saying that any W dimension satisfies the condition of claim 1. Also, the element longitudinal dimension L
= 5.1 mm and the electrode crossing width is 0.5 ≦ l ≦ 0.7 mm
And Here, the range of the element width dimension can be arbitrarily set from the relationship between the element thickness range and W / H corresponding to the required frequency range. The selection range can be selected from a range of approximately 0.1 ≦ H ≦ 0.25 and 0.4 ≦ W ≦ 1 mm, and it is preferable to select the range depending on the element processing capability and the assembling capability to an oscillator or the like. That is, if the lower limit value of the assembly capacity satisfies W = 0.4 mm, the W dimension in the case of H = 0.123 mm has a large number of elements taken from the same member (that is, the material cost is high). W = 0.41 instead of W = 0.57 (when n = 1)
mm (when n = 0) may be selected. On the other hand, when the assembling ability is not sufficient (that is, when the narrow element cannot be mounted), W = 0.57 mm (in the case of n = 1) may be selected. Further, the angle formed with the X axis of the rotating Y plate can be applied within the range shown in claim 1.

[0014]

As described above, according to the present invention, the opposing main surface of the lithium niobate single crystal is a 165 ± 5 ° rotated Y plate, and the angle formed between the lateral direction of the piezoelectric substrate and the X axis of the rotated Y plate is 5. When the thickness of the piezoelectric substrate is H and the width is W in the directions of more than 25 ° and more than −25 ° and −5 ° to −25 °, W / H =
By designing the piezoelectric resonator so as to satisfy the relationship of (3.3 ± 0.5) + 1.4n (n is a natural number), there is no generation of spurious or deterioration of characteristics related to the shape of the piezoelectric element. It is possible to realize several types of piezoelectric resonators having respective width W dimensions corresponding to respective natural numbers set even at the same frequency.

Thus, it is possible to select the best resonator size in consideration of various conditions such as the case size for mounting the resonator, the mounting capability in the process, and the processing size from the piezoelectric single crystal.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a piezoelectric resonator according to an embodiment of the present invention.

2A is a graph showing frequency impedance characteristics when n = 0, FIG. 2B is a graph showing frequency impedance characteristics when n = 1, and FIG. 2C is a graph showing frequency impedance characteristics when n = 2.

FIG. 3 is a graph showing frequency impedance characteristics when n = 0 and W = 0.6 mm in the example of FIG.

4A is a graph showing frequency impedance characteristics when W = 0.57 mm, and FIG. 4B is a graph showing frequency impedance characteristics when W = 0.55 mm, and FIG. 4C is frequency when W = 0.68 mm. Graph showing impedance characteristics

[Explanation of symbols]

 1 substrate 2 vibrating electrode W element width H element thickness L element length l vibrating electrode crossing length

Claims (1)

[Claims] 1. An opposing main surface of a lithium niobate single crystal is
The Y plate is a 65 ± 5 ° rotating Y plate, and the angle formed by the short-side direction of the piezoelectric substrate and the X axis of the rotating Y plate exceeds 5 ° to 25 °.
When the thickness of the piezoelectric substrate in the direction of more than 5 ° to −25 ° is H and the width is W, W / H = (3.3 ± 0.5) +
A piezoelectric resonator having a relationship of 1.4n (n is a natural number).