JP2003087077A - Piezoelectric resonator and piezoelectric component using the piezoelectric resonator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric resonator which can uniquely decide a range, in which excitation of ternary harmonic waves will not be disturbed and can be miniaturized in its dimensions. SOLUTION: In the piezoelectric resonator, vibration electrodes 3, 6 facing a piezoelectric substrate 2 and sandwiching it are formed on both front and rear surfaces of the substrate 2 and damping members 10, 11 for suppressing vibration are provided on at least one surface of the substrate 2 in outer sides of the electrodes 3, 6 so that ternary harmonic waves of thickness longitudinal vibration is excited. In this resonator, shortest distance L from a peripheral edges of the electrode 3, 6 to the members 10, 11 are set to be not less than a thickness t of the substrate 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an energy trapping type piezoelectric resonator such as an oscillator, a discriminator and a trap, and more particularly to a piezoelectric resonator utilizing the third harmonic of thickness longitudinal vibration.

[0002]

2. Description of the Related Art Heretofore, various piezoelectric resonators utilizing the third harmonic of thickness longitudinal vibration have been proposed. For example, Patent No. 2
Japanese Patent No. 669099 discloses a dummy electrode for forming vibration electrodes on both main surfaces of a piezoelectric substrate that face each other with the piezoelectric substrate sandwiched therebetween, and for suppressing vibration outside the vibration electrode on at least one main surface of the piezoelectric substrate. It has been proposed to provide a fundamental wave suppressing mass-added region by attaching a solder to the dummy electrode. In this case, in order to effectively excite the third harmonic and suppress the fundamental wave, the third harmonic is excited in an area outside the area in which the third harmonic is excited and in which the fundamental is excited. A dummy electrode is formed.

Further, in Japanese Patent Laid-Open No. 2000-138554, a sealing substrate is laminated on both main surfaces of a piezoelectric resonator so that the vibration of a vibrating electrode is not hindered between the piezoelectric resonator and the sealing substrate. A piezoelectric component having a sealed space has been proposed. In this case, in order to effectively excite the third harmonic and suppress the fundamental wave, the vibration space has a thickness t of the piezoelectric substrate and a shortest distance from the vibration electrode to the edge of the sealing space. The dimensions are set so that 0 <d / t <5 when d.

[0004]

By the way, in order to excite the third harmonic, it is important to secure the excitation region of the third harmonic. This excitation region changes depending on the frequency and the size of the vibrating electrode. In the former case, a variable correlated with the frequency is not defined, and it is not always easy to uniquely determine the position where the dummy electrode is provided. In the latter case, the shortest distance d from the vibrating electrode to the edge of the sealed space is defined by the relationship with the thickness t of the piezoelectric substrate.
Since the range of d / t is wide and the range around d = 0 is also within the range, the third harmonic may be suppressed.

Therefore, an object of the present invention is to provide a piezoelectric resonator which can unambiguously determine the range in which the excitation of the third harmonic is not disturbed and can be downsized, and a piezoelectric component using this piezoelectric resonator. It is in.

[0006]

The above object is achieved by the invention according to claim 1 or 2. That is, the invention according to claim 1 forms vibrating electrodes on both front and back principal surfaces of the piezoelectric substrate so as to oppose each other with the piezoelectric substrate sandwiched therebetween, and vibrates to the outside of the vibrating electrode on at least one principal surface of the piezoelectric substrate. In a piezoelectric resonator configured to excite a third harmonic of thickness longitudinal vibration by providing a damping member for suppressing the vibration, a shortest distance L from the outer peripheral edge of the vibrating electrode to the damping member.
Is a thickness t or more of the piezoelectric substrate.

According to a second aspect of the invention, vibrating electrodes are formed on both main surfaces of the piezoelectric substrate so as to face each other with the piezoelectric substrate sandwiched therebetween, and the vibrating electrodes extend from the outer peripheral edge of the vibrating electrode to the edge of the closest piezoelectric substrate. In the piezoelectric resonator configured to excite the third harmonic of the thickness longitudinal vibration without providing a damping member for suppressing the vibration in the region, from the outer peripheral edge of the vibrating electrode to the edge of the piezoelectric substrate. The piezoelectric resonator is characterized in that the shortest distance S is not less than the thickness t of the piezoelectric substrate.

The inventor of the present invention relates to a piezoelectric resonator that excites the third harmonic of thickness longitudinal vibration, the ratio of the shortest distance L from the outer peripheral edge of the vibrating electrode to the damping member and the thickness t of the piezoelectric substrate, and the third order. When the relationship between the harmonic resonance resistance (impedance at the resonance frequency) R1 was examined, the results shown in FIG. 1 were obtained. Here, 16.00 MHz and 33.8 MHz
Using 3 types of piezoelectric resonators of 6 MHz and 60.00 MHz, measurement was performed in the state where a resin (adhesive) was applied as a damping material around the vibrating electrode on the surface of the piezoelectric substrate. As is clear from FIG. 1, L / t <in any resonator.
In the range of 1.0, the resonance resistance monotonously decreases as L / t increases, whereas when L / t ≧ 1.0, the resonance resistance is stable at a substantially constant value. Since the resonance resistance R1 is stable means that the third harmonic is excited without being suppressed, it can be understood that L ≧ t may be satisfied. Therefore, in claim 1, the shortest distance L from the outer peripheral edge of the vibrating electrode to the damping member is equal to or larger than the thickness t of the piezoelectric substrate, thereby obtaining a piezoelectric resonator that efficiently excites without suppressing the third harmonic. In addition, it is possible to provide a small piezoelectric resonator by uniquely determining the distance between the vibrating electrode and the damping member.

The reason why the third harmonic is disturbed is not limited to the case where the damping member is provided in the vibration region of the third harmonic,
It is also disturbed at the edge of the piezoelectric substrate. This is because the third harmonic wave is reflected at the edge of the piezoelectric substrate. Therefore, in claim 2, when the external dimensions of the piezoelectric resonator are small and the shortest distance S from the vibrating electrode to the edge portion of the piezoelectric substrate is shorter than the shortest distance L from the vibrating electrode to the damping member, the piezoelectric element from the vibrating electrode is piezoelectric. By setting the shortest distance S to the edge of the substrate to be equal to or greater than the thickness t of the piezoelectric substrate, the vibration region of the third harmonic is secured.

As described in claim 3, it is preferable that the damping member is provided at a position separated from the outer peripheral edge of the vibrating electrode by at least the thickness t of the piezoelectric substrate and within the excitation region of the fundamental wave. That is, if the distance L from the outer peripheral edge of the vibrating electrode to the damping member is equal to or greater than the thickness t of the piezoelectric substrate, there is no problem in terms of exciting the third harmonic, but if the distance L is too long, the fundamental wave is excited. This may result in unnecessary vibration. Therefore,
By providing the damping member in the excitation area of the fundamental wave,
The fundamental wave is effectively suppressed while exciting the third harmonic. As a range in which the fundamental wave can be effectively suppressed, for example, the distance L from the outer peripheral edge of the vibrating electrode to the damping member is preferably within 1.5 times the thickness t of the piezoelectric substrate.

According to a fourth aspect of the present invention, the inner edge of the damping member according to the first aspect is located at a position substantially the same distance as the thickness t of the piezoelectric substrate from the outer peripheral edge of the vibrating electrode. That is, in order to excite the third harmonic, the distance L from the outer peripheral edge of the vibrating electrode to the damping member may be equal to or more than the thickness t of the piezoelectric substrate. However, if the distance L is too large, the piezoelectric resonator The size increases. Therefore, by setting the distance L to be substantially the same as the thickness t of the piezoelectric substrate, it is possible to reduce the size of the piezoelectric resonator to a necessary minimum and reduce the variation in characteristics.

According to a fifth aspect of the present invention, an outer substrate is adhered to both front and back main surfaces of the piezoelectric resonator according to the first aspect with a vibrating space around the vibrating electrode, and the damping member includes the piezoelectric resonator and the outer substrate. And an adhesive layer interposed between and. That is, by applying the piezoelectric resonator of the present invention to a piezoelectric component having a laminated sealing structure, it is possible to obtain a small-sized piezoelectric component capable of efficiently exciting a third harmonic.

The damping member is not limited to the adhesive layer for laminating and bonding the piezoelectric resonator and the exterior substrate as in the fifth aspect. For example, when the periphery of the piezoelectric resonator is molded with an exterior resin, the exterior resin can serve as a damping member. Further, as in Japanese Patent No. 2669099, it is possible to use a dummy electrode with soldering or a terminal electrode with soldering as a dubbing member.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 2 to 5 show a laminated piezoelectric component using a piezoelectric resonator according to the present invention. This example shows an example of a surface mount oscillator. Reference numeral 1 is an energy trapping type piezoelectric resonator using a thickness-extension third-order harmonic, and is a PZT
A vibrating electrode 3 is formed at the center of one main surface of a piezoelectric substrate 2 made of piezoelectric ceramics, such as a terminal electrode 5 formed at one end of the piezoelectric substrate 2 via an extraction electrode 4. It is connected. The terminal electrode 5 may be formed so as to extend around the end surface of the piezoelectric substrate 2. On the other main surface of the piezoelectric substrate 2, a vibrating electrode 6 that faces the vibrating electrode 3 via the substrate 2 is formed. This vibrating electrode 6 has a lead electrode 7 extending in a direction opposite to that of the lead electrode 4. hand,
It is connected to a terminal electrode 8 formed on the other end of the piezoelectric substrate 2. That is, the vibrating electrode 3, the extraction electrode 4 on one main surface
The terminal electrode 5, the vibrating electrode 6, the extraction electrode 7, and the terminal electrode 8 on the other main surface are formed in a symmetrical shape. Although the vibrating electrodes 3 and 6 are circular in this embodiment, they may be rectangular. Further, the vibrating electrodes 3, 6, the extraction electrodes 4,
7 and the terminal electrodes 5 and 8 do not necessarily need to be symmetrical, and may be asymmetrical.

The piezoelectric resonator 1 is provided on the front and back main surfaces of the piezoelectric resonator 1 via adhesive layers (damping members) 10 and 11.
The exterior substrates 20 and 21 having the same shape as the above are bonded and fixed. The exterior substrates 20 and 21 are rectangular insulating thin plates made of alumina ceramics, glass ceramics, glass epoxy resin, heat resistant resin, or the like. Exterior substrate 20, 2
On the inner surface of the piezoelectric resonator 1, concave portions 20a and 21a having a diameter larger than that of the vibrating electrodes 3 and 6 of the piezoelectric resonator 1 are formed. Adhesive layer 1
0 and 11 are made of, for example, an epoxy adhesive,
It is applied to the inner surfaces of the exterior substrates 20 and 21 excluding a and 21a. Therefore, the adhesive layers 10 and 11 are provided with openings 10a and 11a having a diameter larger than that of the vibrating electrodes 3 and 6 of the piezoelectric resonator 1. Therefore, by bonding the exterior substrates 20 and 21 to the front and back main surfaces of the piezoelectric resonator 1, the vibrating space S is formed around the vibrating electrodes 3 and 6 (see FIG. 3). Although the shapes of the openings 10a and 11a and the recesses 20a and 21a are circular, they may be square. Exterior substrate 20, 21
Electrodes 22 and 23 for external connection are formed on the outer peripheral surfaces of both ends of the. These electrodes 22 and 23 are connected to the terminal electrodes 5 and 8 of the piezoelectric resonator 1 exposed on the end faces, respectively.

As the adhesive layers 10 and 11, a liquid adhesive applied to the inner surfaces of the exterior substrates 20 and 21 may be used, or a semi-cured adhesive sheet may be used.
When the adhesive sheet is used, since it can be formed in advance to a thickness corresponding to the vibration space S, it is possible to omit the recesses 20a and 21a formed on the inner surfaces of the exterior substrates 20 and 21.

In the piezoelectric component of the above embodiment, the openings 10 of the adhesive layers 10 and 11 are formed from the outer peripheral edges of the vibrating electrodes 3 and 6.
Letting L be the shortest distance to the inner edges of a and 11a and t be the thickness of the piezoelectric substrate 2, the following relationships are set. L ≧ t Preferably, L≈t is set. For example, in the case of an oscillator having an oscillation frequency of 16.00 MHz, since the thickness of the piezoelectric substrate 2 is 470 μm, if the distance L ≧ 470 μm is set, the third harmonic can be excited without being suppressed. In addition, since the generation region of the fundamental wave is generally set to L <5t, it is preferable that when these are combined, 5t> L ≧ t.

FIG. 6 shows the results of measuring the impedance characteristic and the phase characteristic of the piezoelectric resonator using the third harmonic of the thickness extensional vibration of the above structure. The center frequency is 16.06 MHz. In FIG. 6A, L =
0.470 mm, (b) is L = 0.221 mm, and since the thickness t of the piezoelectric substrate is t = 0.47 mm, L / t = 1.00 in (a) and in (b). L
/T=0.47. In the case of (a), the resistance value at the resonance frequency is low (about 20Ω), whereas in the case of (b), the resistance value at the resonance frequency is high (about 50Ω).
Ω). Further, in the case of (b), the phase changes at the resonance frequency and the anti-resonance frequency are unbalanced, whereas
In the case of (a), a well-balanced and undisturbed phase characteristic is obtained. Therefore, it can be seen that in (a), the third harmonic is excited without being suppressed.

7 and 8 show a second embodiment of the piezoelectric component according to the present invention, showing an example of a lead type oscillator. Since this piezoelectric resonator 1 also has substantially the same shape as that of the piezoelectric resonator 1 in the first embodiment, the same parts are designated by the same reference numerals and duplicate description will be omitted. In this embodiment, the cavity 30 is formed around the vibrating electrodes 3 and 6 of the piezoelectric resonator 1, and the periphery thereof is sealed with the exterior resin 31. Lead terminals 32 and 33 are connected to the terminal electrodes 5 and 8 of the piezoelectric resonator 1, respectively, and these lead terminals 32 and 33 are projected from the exterior resin 31 to the outside.

The diameter of the cavity portion 30 is larger than the width of the piezoelectric resonator 1, and therefore, compared with the distance S from the outer peripheral edge of the vibrating electrodes 3, 4 to the edge portion of the closest piezoelectric substrate 2, the vibrating electrodes 3, 4.
The distance L from the outer peripheral edge of 4 to the exterior resin 31, which is a damping member, is longer. In this case, the distance S from the outer peripheral edges of the vibrating electrodes 3 and 4 to the nearest edge of the piezoelectric substrate 2 is
The thickness t of the piezoelectric substrate 2 is greater than or equal to t. When S <t, the resonance resistance decreases as S / t increases like L / t in FIG. 1, whereas when S ≧ t, the resonance resistance becomes substantially constant. That is, by setting S ≧ t, it can be understood that the influence of the reflection of the third harmonic of the thickness longitudinal vibration by the edge of the piezoelectric substrate 2 is almost eliminated and the third harmonic is effectively excited.

In the above embodiments, the piezoelectric component of the piezoelectric resonator alone has been described, but the piezoelectric resonator and another element (eg, capacitor element) may be laminated or configured as a composite piezoelectric component.

[0022]

As is apparent from the above description, claim 1
According to the invention, the shortest distance L from the outer peripheral edge of the vibrating electrode to the damping member is equal to or larger than the thickness t of the piezoelectric substrate, thereby obtaining a piezoelectric resonator that efficiently excites without suppressing the third harmonic. In addition, it is possible to provide a small piezoelectric resonator by uniquely determining the position where the damping member is provided. According to the invention of claim 2,
When the shortest distance S from the vibrating electrode to the edge of the piezoelectric substrate is shorter than the shortest distance L from the vibrating electrode to the damping member, the shortest distance S from the vibrating electrode to the edge of the piezoelectric substrate is equal to or larger than the thickness t of the piezoelectric substrate. By so doing, it is possible to secure a vibration region of the third harmonic and obtain a small-sized piezoelectric resonator having good characteristics.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a resonance resistance and L / t in a piezoelectric resonator using a third harmonic of thickness longitudinal vibration.

FIG. 2 is a perspective view of a first embodiment of a piezoelectric component using a piezoelectric resonator according to the present invention.

3 is a cross-sectional view taken along the line AA of FIG.

FIG. 4 is a plan view of a piezoelectric resonator used in the piezoelectric component of FIG.

5 is an exploded perspective view of the piezoelectric component shown in FIG.

FIG. 6 is an impedance characteristic and phase characteristic diagram when the L dimension of the piezoelectric resonator is changed.

FIG. 7 is a front view of a second embodiment of a piezoelectric component using the piezoelectric resonator according to the present invention.

FIG. 8 is a sectional view taken along line BB in FIG.

[Explanation of symbols]

1 Piezoelectric resonator 2 Piezoelectric substrate 3,6 Vibrating electrode 10, 11 Adhesive layer (damping member) 10a, 10b opening 31 Exterior resin (damping member)

Continued front page    F term (reference) 5J108 BB04 CC04 DD01 DD06 DD08                       EE03 EE07 EE17 FF11 FF13                       GG03 HH02

Claims (5)

[Claims] 1. A damping member for forming vibration electrodes on both front and back main surfaces of a piezoelectric substrate so as to face each other with the piezoelectric substrate sandwiched therebetween, and suppressing vibration outside at least one main surface of the piezoelectric substrate and outside the vibration electrode. In the piezoelectric resonator configured to excite the third harmonic of thickness longitudinal vibration, the shortest distance L from the outer peripheral edge of the vibrating electrode to the damping member is equal to or greater than the thickness t of the piezoelectric substrate. Piezoelectric resonator. 2. Damping for suppressing vibration in a region from the outer peripheral edge of the vibrating electrode to the edge portion of the piezoelectric substrate closest to the vibrating electrode is formed on both main surfaces of the piezoelectric substrate so as to sandwich the piezoelectric substrate. In a piezoelectric resonator which is not provided with a member and is configured to excite the third harmonic of thickness longitudinal vibration, the shortest distance S from the outer peripheral edge of the vibrating electrode to the edge of the piezoelectric substrate is defined as the thickness of the piezoelectric substrate. A piezoelectric resonator characterized by having t or more. 3. The piezoelectric element according to claim 1, wherein the damping member is provided at a position separated from the outer peripheral edge of the vibrating electrode by at least the thickness of the piezoelectric substrate and within the excitation region of the fundamental wave. Resonator. 4. The piezoelectric resonator according to claim 1, wherein an inner edge of the damping member is located at a position separated from an outer peripheral edge of the vibrating electrode by substantially the same distance as a thickness t of the piezoelectric substrate. 5. An exterior substrate is adhered to both front and back main surfaces of the piezoelectric resonator according to claim 1 with a vibrating space around the vibrating electrode, and the damping member includes the piezoelectric resonator and the exterior. A piezoelectric component, which is an adhesive layer interposed between the substrate and the substrate.