JPH11289236A - Piezo-resonator and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezo-resonator capable of suppressing the oscillation of a reference wave and oscillating tertiary higher harmonic by forming a suppression load on a position where displacement due to the oscillation of tertiary higher harmonic on a piezoelectric substrate is minimizsed and displacement due to the oscillation of a reference wave exists and to provide a piezo- resonator manufacturing method. SOLUTION: A pair of rectangular oscillation electrodes 2a, 3a are formed across a piezoelectric substrate 1a constituted of lead titanate group piezoelectric ceramic so as to be extended from respective opposed end parts of the surface and rear face of the substrate 1a to the center part of the substrate 1a. Then a suppression load having prescribed weight is formed at least on one of both the sides of the opposed end parts on the surface of the substrate 1a by a sputtering, vacuum deposition or printing method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric resonator capable of suppressing oscillation of a fundamental wave and oscillating a third harmonic, and a method of manufacturing the same.

[0002]

2. Description of the Related Art FIG. 1 is a view showing an example of the configuration of a conventional piezoelectric resonator, and FIG.
FIG. 1B is a cross-sectional view taken along line XX ′ of FIG. As shown in FIGS. 1A and 1B, a pair of vibrating electrodes 20a and 20b are formed on the front and back surfaces of a piezoelectric substrate 10 made of a piezoelectric ceramic or the like with the piezoelectric substrate 10 interposed therebetween. The vibrating electrodes 20a and 20b formed on the front and back surfaces of the piezoelectric substrate 10 extend to the terminal electrode portions 14a and 14b, respectively, and extend to the terminal electrode portions 14a and 14b.
b. Terminal electrode portions 14a, 14
The lead frame terminals 16a and 16b are soldered to b.

The entire piezoelectric resonator is covered and molded with a resin 18, and cavities 30a and 30b are formed in the vibrating portion of the piezoelectric resonator so as not to suppress the vibration of the piezoelectric resonator.

[0004]

By the way, in the above-described piezoelectric resonator, variations in the diameters of the cavities 30a and 30b formed to suppress the oscillation of the fundamental wave,
In some cases, the suppression of the vibration of the fundamental wave was insufficient due to the variation in the load (difference in film thickness) of the resin 18 constituting the a and 30b. In this case, oscillation of the fundamental wave is caused, which may make it impossible to oscillate the third harmonic that should be used.

[0005] In order to prevent such a third harmonic oscillation from being impossible, Japanese Patent No. 2669099 discloses that
A dummy electrode is provided in a region outside the region where the third harmonic is excited on the piezoelectric substrate and in which the fundamental wave is excited, and solder is attached to the dummy electrode or a part of the lead terminal is soldered. An oscillator using a piezoelectric resonator in which the excitation of the fundamental wave is suppressed without affecting the excitation of the third harmonic by attaching the piezoelectric resonator is disclosed.

However, in order to efficiently suppress the oscillation of the fundamental wave without affecting the oscillation of the third harmonic, and to manufacture a piezoelectric resonator that can use the third harmonic, it is necessary to use the 3rd harmonic on the piezoelectric substrate. The point (position) where the displacement due to the vibration of the second harmonic is minimized
It is desired to accurately form a suppression load having a predetermined weight at a point (position) where displacement due to vibration of the fundamental wave exists.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to extend from each of opposite ends of a front surface and a rear surface of a piezoelectric substrate toward the center of the substrate and sandwich the piezoelectric substrate. A vibrating electrode is formed, and a predetermined weight is applied by sputtering, vacuum deposition, or printing at a position where displacement due to third harmonic vibration on the piezoelectric substrate is minimized and at a position where displacement due to fundamental wave vibration exists. By forming a suppression load having
It is an object of the present invention to provide a piezoelectric resonator capable of oscillating a third harmonic while minimizing degradation of piezoelectric characteristics in the second harmonic, and a method of manufacturing the same.

[0008]

In order to solve the above-mentioned problems, a piezoelectric resonator according to the present invention is characterized in that a central portion of the piezoelectric substrate is arranged from each of opposite ends on the front and back surfaces of the piezoelectric substrate. And a pair of vibrating electrodes formed so as to sandwich the piezoelectric substrate, and a position where the displacement due to the vibration of the third harmonic of at least one of the front and back surfaces of the piezoelectric substrate is minimized and the vibration of the fundamental wave And a suppression load formed at a position where the displacement due to is present.

In order to solve the above problem, a piezoelectric resonator according to a second aspect of the present invention extends from each of opposing ends on a front surface and a back surface of a piezoelectric substrate toward a central portion of the piezoelectric substrate. A pair of vibrating electrodes formed with the piezoelectric substrate interposed therebetween, and a suppression load formed on at least one of both sides of the opposed end of at least one of the front surface and the back surface of the piezoelectric substrate. I do.

[0010] In the piezoelectric resonator according to the first or second aspect of the invention, the third aspect of the invention is characterized in that the suppression load is formed of a metal film or a resin.

According to a fourth aspect of the present invention, there is provided a method for manufacturing a piezoelectric resonator, comprising: A pair of vibrating electrodes are formed to extend toward the piezoelectric substrate with the piezoelectric substrate interposed therebetween. A suppression load is formed at a position where the exists.

According to another aspect of the present invention, there is provided a method of manufacturing a piezoelectric resonator, comprising the steps of: A pair of vibrating electrodes formed so as to extend toward the piezoelectric substrate, and a suppression load is formed on at least one of both sides of the facing end of at least one of a front surface and a back surface of the piezoelectric substrate. .

In the method for manufacturing a piezoelectric resonator according to the fourth or fifth aspect, the invention according to the sixth aspect is characterized in that:
The suppression load is formed by any one of sputtering, vacuum deposition, and a printing method.

In the method of manufacturing a piezoelectric resonator according to any one of claims 4 to 6, the invention according to claim 7 is characterized in that the suppression load is formed of a metal film or a resin. I do.

[0015]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a configuration of a piezoelectric resonator according to an embodiment of the present invention before a load is formed. FIG. 2 (a)
Shows a plan view of a piezoelectric resonator having a rectangular vibrating electrode,
FIG. 2B is a plan view of a piezoelectric resonator having a circular vibrating electrode, and FIG. 2C is a cross-sectional view of a piezoelectric resonator according to an embodiment of the present invention.

A piezoelectric resonator according to an embodiment of the present invention shown in FIG. 2A includes a piezoelectric substrate 1a made of a lead titanate (PbTiO3, PT) -based piezoelectric ceramic, and a piezoelectric substrate 1a.
and a pair of rectangular vibrating electrodes 2a and 3a extending toward the center of the piezoelectric substrate 1a from opposite ends of the front and back surfaces of the piezoelectric substrate 1a and sandwiching the piezoelectric substrate 1a.

The piezoelectric resonator according to the embodiment of the present invention shown in FIG. 2B has a piezoelectric substrate 1b made of a lead titanate-based piezoelectric ceramic and a front surface and a rear surface of the piezoelectric substrate 1b opposed to each other. It is constituted by a pair of circular vibrating electrodes 2b and 3b extending from each of the ends toward the center of the piezoelectric substrate 1b and sandwiching the piezoelectric substrate 1b.

FIGS. 3 and 4 show the displacement and the third order of vibration of the fundamental wave on the surface of the piezoelectric substrate of the piezoelectric resonator before the suppression load is formed according to the embodiment of the present invention shown in FIG. It is a figure showing distribution of displacement by vibration of a harmonic. The displacement distribution shown in FIG. 3 corresponds to the piezoelectric substrate 1a of the piezoelectric resonator shown in FIG.
4 is a result obtained by a displacement measurement using an optical fiber interferometer along a line aa 'on the surface of the piezoelectric resonator 1a of the piezoelectric resonator shown in FIG. It is the result obtained by the displacement measurement using the optical fiber interferometer along the line bb ′ on the surface. 3 and 4, the vertical axis represents the displacement (unit: angstrom) of the surface of the piezoelectric substrate 1a, and the horizontal axis represents the surface position of the piezoelectric resonator.

In FIG. 3, the displacement due to the vibration of the third harmonic is minimum at both ends of the piezoelectric resonator, but the displacement due to the vibration of the fundamental wave is uniform on the surface of the piezoelectric resonator.
However, in FIG. 4, there is a large difference between the displacement caused by the vibration of the fundamental wave and the displacement caused by the vibration of the third harmonic.
In the portion where the vibrating electrode 2a and the vibrating electrode 3a overlap, both the displacement due to the vibration of the fundamental wave and the displacement due to the vibration of the third harmonic are large.

From the above, in order to use the third harmonic while suppressing the vibration of the fundamental wave in the piezoelectric resonator, the difference between the displacement due to the vibration of the fundamental wave and the displacement due to the vibration of the third harmonic is required. It is understood that it is necessary to form a load having a predetermined weight at a position where the load is increased. Therefore, here, as shown in FIG. 4, 12 suppression points A as suppression points for suppressing the vibration of the fundamental wave on the piezoelectric substrate of the piezoelectric resonator.
1, B1, C1, A1 ', B1', C1 ', A2, B
2, C2, A2 ', B2', and C2 'are set, and a load is formed at these suppression points to measure the piezoelectric characteristics of the piezoelectric resonator.

The measurement of the piezoelectric characteristics of the piezoelectric resonator according to the embodiment of the present invention is performed by the following (a) to (c) shown in FIG.
The case of (f) is performed.

(A) A case where a load is formed at each of the suppression points A1 and A2 located on one side of the opposite end on the surface of the piezoelectric substrate of the piezoelectric resonator (see FIG. 5A).

(B) Suppression points A1 and A2 shown in FIG.
A case where loads are respectively formed at the suppression points B1 and B2 located closer to the center of the piezoelectric resonator along the longitudinal direction than the piezoelectric resonator (see FIG. 5B).

(C) Suppression points B1 and B2 shown in FIG.
In the case where loads are respectively formed at the suppression points C1 and C2 located closer to the center of the piezoelectric resonator along the longitudinal direction than the piezoelectric resonator (see FIG. 5C).

(D) Suppression points A1, A2, A1 ', A2' located on both sides of the opposite end of the piezoelectric resonator on the surface of the piezoelectric substrate (ie, four corners on the surface of the piezoelectric resonator).
(See FIG. 5D).

(E) Suppression points A1 and A shown in FIG.
2, suppression points B1, B2, B1 located closer to the center of the piezoelectric resonator along the longitudinal direction than A1 ', A2'
′ And B2 ′ (FIG. 5E)
reference).

(F) Suppression points B1 and B shown in FIG.
2, suppression points C1, C2, and C1 located closer to the center of the piezoelectric resonator along the longitudinal direction than B1 'and B2'.
′, C2 ′ (FIG. 5F)
reference).

FIG. 6 shows the measurement results of the piezoelectric characteristics of the piezoelectric resonator according to the embodiment of the present invention when a load is formed at a predetermined suppression point as in the cases (a) to (f) described above. FIG. The vertical axis in FIG. 6 shows Qmax indicating the sharpness of resonance in the fundamental wave and the third harmonic, and this Qmax
The larger the value, the better the piezoelectric characteristics of the piezoelectric resonator.
When the piezoelectric resonator is actually used, for example, when the frequency f is 16 MHz, Qmax needs to be 10 or more.

From FIG. 6, in the above-mentioned cases (a) and (d) (in the case where loads are respectively formed at the suppression points located on both sides of the opposite end on the surface of the piezoelectric substrate of the piezoelectric resonator). Qmax at the second harmonic is a predetermined value (for example, frequency f
At 16 MHz, the value is 10) or more, and the ratio of Qmax between the fundamental wave and the third harmonic has a value of 1/2 or less. On the other hand, (b),
(C), (e), and (f) (ie, the suppression located closer to the center of the piezoelectric resonator than the suppression points located on both sides of the opposing end on the surface of the piezoelectric substrate of the piezoelectric resonator. When a load is formed at each point), the Qmax of the third harmonic is reduced together with the Qmax of the fundamental wave, and a Qmax of a predetermined value (for example, 10 at a frequency f = 16 MHz) cannot be obtained. In addition, there is no difference between Qmax of the third harmonic and Qmax of the fundamental wave, which makes it impossible to oscillate the third harmonic stably.

From the above results, as in the cases (a) and (d), damping is performed by forming a suppression load on one or both sides of the opposite end on the surface of the piezoelectric resonator, respectively. The vibration of the fundamental wave can be suppressed, and the reduction of the piezoelectric characteristic (Qmax) in the third harmonic can be minimized, so that the third harmonic can be used in the piezoelectric resonator.

Therefore, in the piezoelectric resonator according to the embodiment of the present invention, the positions (suppression points A1, A2, A1 ', A2') on both sides of the opposing ends on the surface of the piezoelectric substrate are the third harmonic. A piezoelectric resonator that can oscillate the third harmonic by forming a suppression load at these positions where the displacement due to the vibration of the element becomes the minimum and the displacement due to the vibration of the fundamental wave exists. Can be obtained.

Next, a piezoelectric resonator in which a load is formed at a predetermined suppression point according to the embodiment of the present invention (here, FIG. 2A)
A method for manufacturing a piezoelectric resonator having a rectangular vibrating electrode shown in FIG.

First, a pair of vibrating electrodes 2a extend from the opposing ends 2a ', 3a' on the front and back surfaces of the plate-shaped piezoelectric substrate 1a toward the center of the piezoelectric substrate 1a with the piezoelectric substrate 1a interposed therebetween. , 3a.

Next, from the above measurement results, the piezoelectric substrate 1
A point on the surface of a where the displacement due to the vibration of the harmonics is minimized and the point where the displacement due to the vibration of the fundamental wave exists is suppressed using a load having a predetermined weight as a vibration suppression point. Specifically, it is performed as follows.

That is, after forming a mask pattern in which holes are provided at positions where a load is to be formed on the surface of the piezoelectric substrate 1a on which the vibrating electrode 2a is formed, a metal film is formed by sputtering or vacuum evaporation. The metal material constituting this metal film is silver (Ag), copper (Cu),
Nickel (Ni), aluminum (Al), gold (A
u), platinum (Pt), titanium (Ti), chromium (Cr)
The metal film is formed to have a predetermined weight at the vibration suppression point.

After forming the metal film made of the above-described metal material, the previously formed mask pattern is removed. The weight of the metal film formed at the vibration suppression point depends on the piezoelectric characteristics of the piezoelectric substrate 1a made of piezoelectric ceramic and the state of displacement caused by the vibration of the fundamental wave and the third harmonic on the surface of the piezoelectric substrate 1a. Approximately 0.05 mg here.

Through the steps described above, it is possible to manufacture a piezoelectric resonator capable of suppressing the oscillation of the fundamental wave and minimizing the deterioration of the piezoelectric characteristics at the third harmonic and capable of oscillating the third harmonic. .

When the printing film is formed at the vibration suppression point by a printing method instead of forming the metal film at the vibration suppression point by sputtering or vacuum deposition, the vibration of the fundamental wave is suppressed and the third harmonic is suppressed. Deterioration of piezoelectric characteristics can be minimized. It should be noted that an epoxy-based, acrylic-based, or phenol-based resin is used as a printing material for forming the printing film.

FIG. 7 is a plan view showing the configuration of various piezoelectric resonators in which loads are formed at predetermined vibration suppression points by the above-described manufacturing method. As described above, the positions of both sides of the opposing end of the piezoelectric resonator on the surface of the piezoelectric substrate (4
Corresponding to the two corners, ie, the suppression points A1, A2, A
1 ′, A2 ′) correspond to the position where the displacement due to the vibration of the third harmonic is minimized and the position where the displacement due to the vibration of the fundamental wave exists, and the load is applied to each of the opposite ends on the surface of the piezoelectric substrate. It is desirable to be formed on one side or both sides.
However, in order to prevent the deterioration of the piezoelectric characteristics, it is necessary to form the loads symmetrically with respect to both centers of the piezoelectric substrate. Therefore, in FIG. 7, the loads are respectively formed at the vibration suppression points satisfying these forming conditions. FIG.

That is, FIG. 7A shows the vibration suppression point A1,
A2 shows a piezoelectric resonator in which loads 5 and 6 are formed, respectively. FIG. 7B shows a piezoelectric resonator in which loads 7 and 8 are formed in vibration suppression points A1 'and A2', respectively. c)
7 shows a piezoelectric resonator in which loads 5 and 8 are formed at vibration suppression points A1 and A2 ', respectively.
2 and A1 'show piezoelectric resonators in which loads 6 and 7 are formed, respectively, and FIG. 7E shows vibration suppression points A1, A2 and A1.
3 shows a piezoelectric resonator in which loads 5, 6, 7, and 8 are formed on A2 'and A2', respectively.

FIG. 8 is a diagram showing an example of impedance characteristics and phase characteristics at the third harmonic of the piezoelectric resonator according to the embodiment of the present invention. In FIG. 8, the vertical axis indicates the impedance Imp (Ω) and the phase θ (゜), and the horizontal axis indicates the frequency Freq (Mz). FIG. 8 shows that the piezoelectric resonator according to the embodiment of the present invention has a frequency of 16.20 MHz.
It can be seen that extremely stable operation is possible when the phase θ is about 85 ° or more near z.

In the embodiment of the present invention, the case where a load is formed at a predetermined vibration suppression point on the surface of the piezoelectric substrate of the piezoelectric resonator has been described. Even when the load is formed at a position where the displacement due to the vibration of the third harmonic is minimized on only the back surface or both surfaces and a position where the displacement due to the vibration of the fundamental wave is present is suppressed, the excellent piezoelectric characteristics as described above are obtained. And the third harmonic oscillation is possible.

[0044]

As described above, according to the present invention, there is provided a piezoelectric resonator in which a pair of vibrating electrodes are formed from the opposing ends on the front and back surfaces of the piezoelectric substrate toward the center of the piezoelectric substrate with the piezoelectric substrate interposed therebetween. In the element, a suppression load having a predetermined weight is formed by sputtering, vacuum deposition, or printing at a position where displacement due to harmonic vibration on the piezoelectric substrate is minimized and at a position where displacement due to vibration of fundamental wave exists. This effectively suppresses the vibration of the fundamental wave,
It is possible to manufacture a piezoelectric resonator that can oscillate higher harmonics while minimizing the deterioration of the piezoelectric characteristics at the third harmonic.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a configuration of a conventional piezoelectric resonator.

FIG. 2 is a diagram illustrating a configuration of a piezoelectric resonator according to an embodiment of the present invention before a load is formed.

FIG. 3 is a diagram showing distributions of displacement due to fundamental wave vibration and third harmonic vibration on the surface of a piezoelectric substrate of a piezoelectric resonator before a load is formed according to the embodiment of the present invention. .

FIG. 4 is a diagram showing distributions of displacement due to fundamental wave vibration and displacement due to third harmonic vibration on the surface of a piezoelectric substrate of a piezoelectric resonator before a load is formed according to the embodiment of the present invention. .

FIG. 5 is a diagram for describing a piezoelectric resonator in which a load is formed at a predetermined suppression point according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating measurement results of piezoelectric characteristics of a piezoelectric resonator in which a load is formed at a predetermined suppression point according to the embodiment of the present invention.

FIG. 7 is a plan view showing a configuration of various piezoelectric resonators according to the embodiment of the present invention, in which a load is formed at a predetermined vibration suppression point.

FIG. 8 is a diagram illustrating an example of impedance characteristics and phase characteristics of the piezoelectric resonator according to the embodiment of the present invention.

[Explanation of symbols]

 1a, 1b Piezoelectric substrate 2a, 2b, 3a, 3b Vibration electrode 2a ', 2b', 3a ', 3b' End 5, 6, 7, 8 Load

 ──────────────────────────────────────────────────の Continued from the front page (72) Inventor Junichi Yamazaki 1-13-1 Nihonbashi, Chuo-ku, Tokyo Inside TDK Corporation

Claims (7)

[Claims] A pair of vibrating electrodes extending from respective opposing ends on a front surface and a back surface of the piezoelectric substrate toward a central portion of the piezoelectric substrate and formed to sandwich the piezoelectric substrate; and a front surface of the piezoelectric substrate. Or a suppression load formed at a position where displacement due to vibration of at least one third harmonic of the back surface is minimized and at a position where displacement due to vibration of the fundamental wave exists. 2. A pair of vibrating electrodes extending from respective opposing ends on the front and back surfaces of the piezoelectric substrate toward the center of the piezoelectric substrate and formed with the piezoelectric substrate interposed therebetween, and a front surface of the piezoelectric substrate. Or a suppression load formed on at least one of both sides of the opposite end of at least one of the back surface. 3. The piezoelectric resonator according to claim 1, wherein the suppression load is formed of a metal film or a resin. 4. A pair of vibrating electrodes are formed extending from respective opposing ends on the front surface and the back surface of the piezoelectric substrate toward the center of the piezoelectric substrate so as to sandwich the piezoelectric substrate therebetween. A method for manufacturing a piezoelectric resonator, wherein a suppression load is formed at a position on the rear surface where displacement due to vibration of at least one third harmonic is minimized and at a position where displacement due to vibration of a fundamental wave exists. 5. A pair of vibrating electrodes extending from respective opposing ends on the front and back surfaces of the piezoelectric substrate toward the center of the piezoelectric substrate, sandwiching the piezoelectric substrate, and forming a pair of vibrating electrodes; A method of manufacturing a piezoelectric resonator, comprising: forming a suppression load on at least one of both sides of at least one of the opposite ends of the back surface. 6. The method according to claim 4, wherein the suppression load is formed by any one of sputtering, vacuum deposition, and printing. 7. The method for manufacturing a piezoelectric resonator according to claim 4, wherein the suppression load is formed of a metal film or a resin.