JP2006067256A - Piezoelectric resonator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric resonator capable of effectively suppressing vibrations other than third harmonics. <P>SOLUTION: This piezoelectric resonator is formed by securing a pair of sealing bodies via a frame surrounding a facing area at both sides of a piezoelectric resonance element, adhered with a pair of vibrating electrodes arranged in both the principal planes of a rectangular piezoelectric substrate so as to partially face each other through the piezoelectric substrate and derived from the facing area in a facing directions parallel to one side of the piezoelectric substrate and generates fundamental waves of a prescribed frequency and its third harmonics within the facing area of the piezoelectric resonance element, accompanying the voltage applied to the vibrating electrodes. In the piezoelectric resonator, a vibration inhibitor, brought into partial contact with the vibrating electrodes only at the outer circumferential part of the facing area, is located in the central part of the facing area related to a direction parallel to the one side and/or the central part of the facing area related to a direction perpendicular to the one side between the piezoelectric resonance element and the sealing bodies, and a spatial layer, brought into contact with the vibrating electrodes, is located in the outer circumferential part of the facing area where the vibration inhibitor not exist. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piezoelectric resonator widely used in an oscillation circuit, a filter circuit, and the like.

  Conventionally, piezoelectric resonators are used in oscillation circuits, filter circuits, and the like.

  Such a conventional piezoelectric resonator, for example, as shown in FIG. 6, is formed on both sides of a piezoelectric resonant element in which vibration electrodes 53a and 53b are arranged so as to partially face both main surfaces of a rectangular piezoelectric substrate 52. A structure in which a pair of sealing bodies 55a and 55b are attached via frame bodies 54a and 54b surrounding an opposing region is known (see, for example, Patent Document 1).

  The conventional piezoelectric resonator described above generates a vibration of a predetermined frequency in a region facing the vibrating electrodes 53a and 53b by applying a predetermined voltage between the vibrating electrodes 53a and 53b. When the piezoelectric resonator is used for an oscillator, for example, it functions as a piezoelectric resonator by generating and outputting a predetermined oscillation signal via an external oscillation circuit, an amplification circuit, and the like based on the resonance frequency of the piezoelectric resonator.

  By the way, in the above-described conventional piezoelectric resonator, when a voltage is applied between the vibrating electrodes 53a and 53b, two types of vibrations mainly applied to the fundamental wave and the third harmonic wave are generated in the opposing region of both the electrodes 53a and 53b. It is supposed to be.

When such a piezoelectric resonator is used for a high-frequency device or the like, it is desirable to use a third-harmonic vibration having a high frequency among the above-described two kinds of vibrations. For this purpose, it is necessary to suppress the vibration of the fundamental wave as much as possible. was there. As a method for suppressing the fundamental wave, for example, the outer dimension of one vibrating electrode 53a is made smaller than that of the other vibrating electrode 53b to leak the fundamental wave around the opposing area, and the leaked wave is transmitted to the frame body 54a, A method of damping with 54b has been proposed (see, for example, Patent Document 2).
JP-A-11-112266 JP 2000-134060 A

  However, in the conventional piezoelectric resonator described above, when the outer dimension of one vibrating electrode 53a is made smaller than that of the other vibrating electrode 53b in order to suppress the vibration of the fundamental wave, the facing area of the vibrating electrodes 53a and 53b is also small. Therefore, it becomes difficult to secure a sufficient capacitance in the area where the vibrating electrodes 53a and 53b are opposed, and when the capacitance is reduced in this way, other harmonics such as a fifth harmonic are also generated. It appeared strongly, and had a drawback that it was impossible to function well as a piezoelectric resonator using a third harmonic.

  The present invention has been devised in view of the above-described drawbacks, and its purpose is to achieve piezoelectric resonance that can satisfactorily suppress vibration applied to the fundamental wave while ensuring sufficient capacitance in the opposed region of the vibrating electrode. Is to provide a vessel.

  The piezoelectric resonator according to the present invention is derived in the opposite direction parallel to one side of the piezoelectric substrate from the opposing region, with the piezoelectric substrate having a rectangular shape partly opposed to both main surfaces through the piezoelectric substrate. A pair of sealing bodies are attached to both sides of the piezoelectric resonant element to which the pair of vibrating electrodes is attached via a frame body surrounding the opposing region, and a voltage is applied to the vibrating electrodes. In the piezoelectric resonator configured to generate a fundamental wave having a predetermined frequency and a third harmonic wave in the opposed region of the piezoelectric resonator element, the piezoelectric resonator element and the sealing body are arranged in a direction parallel to the one side. A vibration suppressor that is in partial contact with the vibration electrode only at the outer peripheral portion of the opposing region at the central portion of the opposing region and / or the central portion of the opposing region in a direction orthogonal to the one side. Before the vibration suppressor does not exist It is characterized in that the space layer in contact with the vibrating electrode on the outer periphery of the opposite region is interposed.

  The piezoelectric resonator according to the present invention is characterized in that the space layer is made of either an inert gas or a vacuum.

  Furthermore, the piezoelectric resonator according to the present invention is characterized in that the vibration suppressing body is made of the same material as the frame.

  Furthermore, the piezoelectric resonator of the present invention is characterized in that the vibration suppressing body and the frame body are integrally formed.

  Furthermore, the piezoelectric resonator of the present invention is characterized in that the vibration suppressing body and the frame body are made of the same material as the sealing body and are formed integrally with the sealing body. is there.

  Furthermore, in the piezoelectric resonator according to the aspect of the invention, the pair of vibrating electrodes may have an extending portion that extends outward from the centroid of the facing region in a direction orthogonal to the one side. It is characterized by.

  Furthermore, the piezoelectric resonator of the present invention is characterized in that the vibration suppressing body is in contact with the vibration electrode at the extending portion.

  According to the piezoelectric resonator of the present invention, between the piezoelectric resonant element and the sealing body, the central portion of the opposing region in the direction parallel to one side of the piezoelectric substrate and / or the opposing region in the direction orthogonal to the one side. A vibration suppression body that partially contacts the vibration electrode only at the outer peripheral portion of the opposing region is interposed in the central portion, and a space layer that is in contact with the vibration electrode is interposed at the outer peripheral portion of the opposing region where the vibration suppression member does not exist. Therefore, a spatial layer is formed in a region where the third harmonic is concentrated in the opposed region, and a vibration suppressing body is formed in a region where the fundamental wave is concentrated. As a result, vibrations other than the third harmonic can be effectively suppressed, and good resonance characteristics can be obtained.

  When such a piezoelectric resonator is used in an oscillation circuit, the piezoelectric resonator can be stably operated at an oscillation frequency corresponding to the third harmonic of the fundamental wave of the piezoelectric resonator. When used in a filter circuit, a sufficient amount of attenuation outside the passband can be secured.

  Further, according to the piezoelectric resonator of the present invention, the vibration suppressing body and the frame body can be formed at the same time by conventionally known screen printing or the like by forming the vibration suppressing body from the same material as the frame body. Productivity of the piezoelectric resonator can be improved.

  Furthermore, according to the piezoelectric resonator of the present invention, the vibration suppression body and the frame body are integrally and continuously formed, so that the vibration electrode is different from the case where the vibration suppression body and the frame body are formed separately. The mass of the object (vibration suppressor and frame) in contact with the substrate increases, and the vibration of the fundamental wave can be more reliably suppressed by bringing a large mass in contact with a predetermined location of the vibration electrode. It becomes possible.

  Furthermore, according to the piezoelectric resonator of the present invention, the pair of vibrating electrodes is provided with an extending portion extending outward from the centroid of the opposing region in a direction orthogonal to one side of the piezoelectric substrate. As a result, the fundamental wave is intensively generated at the extension part, and the third harmonic wave is generated in a wide area centering on the centroid of the opposed area of the vibrating electrode. Characteristics can be obtained. In particular, if the vibration suppressing body is brought into contact with the vibrating electrode at the extending portion, the vibration of the fundamental wave can be suppressed extremely well.

  Hereinafter, a piezoelectric resonator of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an external perspective view of a piezoelectric resonator according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the piezoelectric resonator of FIG. 1. The piezoelectric resonator shown in FIG. A pair of sealing bodies 5a and 5b are attached to both sides of the body via frame bodies 4a and 4b.

  As shown in FIG. 3, the piezoelectric resonant element 1 has a structure in which vibrating electrodes 3 a and 3 b are arranged on both main surfaces of a piezoelectric substrate 2 having a rectangular shape so as to partially face each other through the piezoelectric substrate 2. Have. In addition, the vibrating electrodes 3 a and 3 b in the present embodiment are led out from the facing region A in opposite directions parallel to one side of the piezoelectric substrate 2.

  The piezoelectric substrate 2 is made of, for example, a piezoelectric ceramic material such as lead zirconate titanate or lead titanate, or a piezoelectric single crystal material such as quartz or lithium niobate, and the piezoelectric substrate 2 is polarized in the thickness direction.

  For example, when the piezoelectric substrate 2 is formed of a piezoelectric ceramic material, first, a binder is added to the raw material powder and pressed, or the raw material powder is mixed and dried using a ball mill together with water and a dispersant, and the binder, solvent, plastic After forming a substrate by adding an agent or the like and molding it by a doctor blade method, etc., and then baking at a peak temperature of 1100 ° C. to 1400 ° C. for several tens of minutes to several hours to form a substrate, for example, thickness It is manufactured by applying a voltage of 3 kV / mm to 15 kV / mm at a temperature of 60 ° C. to 150 ° C. in the direction and applying a polarization treatment.

  When the piezoelectric substrate 2 is formed of a piezoelectric single crystal material, the piezoelectric substrate 2 is manufactured by slicing an ingot (base material) of the piezoelectric single crystal material with a predetermined thickness so as to be in a predetermined crystal direction.

  The vibrating electrodes 3a and 3b applied to both main surfaces of the piezoelectric substrate 2 are made of a highly conductive metal such as gold, silver, copper, chromium, nickel, tin, lead, and aluminum. A material is deposited and formed on both main surfaces of the piezoelectric substrate 2 by a conventionally known vacuum deposition or sputtering method, or a predetermined conductor paste containing the above-described metal material is formed into a predetermined pattern by a conventionally known printing method or the like. It is applied and formed by applying and baking at high temperature.

  When a predetermined voltage is applied between the pair of vibrating electrodes 3a and 3b, various vibrations including a fundamental wave and a third harmonic wave are mainly excited by the piezoelectric effect, and resonance peaks caused by the respective vibrations. Appears in the frequency characteristics.

  Further, the pair of sealing bodies 5a and 5b arranged on both the upper and lower sides of the above-described piezoelectric resonance element 1 are attached to both main surfaces of the piezoelectric resonance element 1 via the frame bodies 4a and 4b, and the piezoelectric resonance. A predetermined space layer 7 is formed in a region surrounded by the element 1, the sealing bodies 5a and 5b, and the inside of the frame bodies 4a and 4b.

  The sealing bodies 5a and 5b are formed so that the vertical and horizontal outer dimensions are substantially equal to those of the piezoelectric substrate 2, and the thickness thereof is set to several tens of μm to several mm, for example. Such sealing bodies 5a and 5b are made of a heat-resistant resin, for example, engineering plastic such as polybutylene terephthalate (PBT), a liquid crystal polymer, a glass cloth base epoxy resin, and the like. % Glass cloth base epoxy resin is preferably used. In that case, it joins favorably by hold | maintaining for 40 minutes-90 minutes at the temperature of 180 to 200 degreeC, applying the pressure of 0.2 Mpa-5 Mpa in the vacuum of 100 Pa or less, and heat-resining resin.

  The external terminal electrodes 6 formed on both main surfaces of the sealing bodies 5a and 5b are formed by the same material and method as the vibrating electrodes 3a and 3b, and the surfaces thereof are plated with nickel or tin. Applied.

  The frame bodies 5 a and 5 b interposed between the piezoelectric resonance element 1 and the sealing bodies 5 a and 5 b are formed so as to surround the opposing region A of the piezoelectric resonance element 1. While functioning as a spacer for forming a predetermined vibration space (space layer 7) between the sealing bodies 5a and 5b, it acts as a sealing material for hermetically sealing the vibration space.

  Such frames 5a and 5b are made of, for example, a thermosetting resin such as an epoxy resin, and adopt a conventionally well-known thick film printing method or the like, and a liquid precursor of the thermosetting resin is predetermined on both surfaces of the piezoelectric substrate 2. It is formed by applying to a pattern and thermosetting. Further, in order to adjust the viscosity and thermal expansion coefficient of the frames 4a and 4b, a predetermined amount of filler made of an inorganic material such as silicon oxide may be contained in the frames 4a and 4b.

The space layer 7 is filled with an inert gas such as air, N ₂ , or Ar, or is in a vacuum state. In particular, the space layer 7 is filled with an inert gas or employs a space layer 7 in a vacuum state. In this case, the reliability of the piezoelectric resonance element 1 can be maintained high.

  And between the piezoelectric resonant element 1 and the sealing bodies 5a and 5b described above, the central portion of the facing area A in the direction parallel to one side of the piezoelectric substrate 2 and the facing area A in the direction orthogonal to the one side. A vibration suppressing body 8 that is in partial contact with the vibrating electrodes 3a and 3b only at the outer peripheral portion of the facing region A is interposed in the central portion.

  The vibration suppressing body 8 is formed integrally and continuously with the frame bodies 4a and 4b by, for example, the same thermosetting resin as the frame bodies 4a and 4b described above, specifically, epoxy resin or the like. The space layer 7 is formed in a portion where the vibration suppressing body 8 does not exist.

  Here, a simulation using the finite element method is performed, and the result of analyzing the vibration distribution of the third harmonic and the fundamental wave will be described with reference to FIG.

  According to the figure, the third harmonic wave is concentrated in the central area C of the facing area A and the fundamental wave is concentrated in the outer peripheral area B of the facing area A. It turns out that it concentrates in the central part vicinity of the opposing area | region A which concerns on a parallel direction, and the central part vicinity of the opposing area | region A which concerns on the direction orthogonal to the said one side.

  Therefore, by arranging the spatial layer 7 in the region C where the third harmonic wave is concentrated in the facing region A and arranging the vibration suppressing body 8 in the region B where the fundamental wave is concentrated, the vibration applied to the fundamental wave is effectively made. Therefore, it is possible to obtain good resonance characteristics. Therefore, when such a piezoelectric resonator is used for an oscillation circuit, the piezoelectric resonator can be stably operated at an oscillation frequency corresponding to the third harmonic of the fundamental wave of the piezoelectric resonator. When used in a filter circuit, a sufficient amount of attenuation outside the passband can be secured.

  When the vibration suppressing body 8 is formed of the same material as the frame bodies 4a and 4b, the vibration suppressing body 8 and the frame bodies 4a and 4b can be formed simultaneously by a conventionally known screen printing method or the like, and the piezoelectric resonance. The productivity of the vessel can be improved. Therefore, it is preferable to form the vibration suppressing body 8 and the frame bodies 4a and 4b with the same material.

  Furthermore, in this embodiment, since the vibration suppression body 8 and the frame bodies 4a and 4b are integrally formed continuously, when the vibration suppression body 8 and the frame bodies 4a and 4b are formed separately. In comparison, the mass of the objects (vibration suppressing body 8 and frame bodies 4a and 4b) in contact with the vibration electrodes 3a and 3b is large, and thus a large mass object is kept in contact with a predetermined portion of the vibration electrodes 3a and 3b. Thus, it is possible to more reliably suppress the vibration of the fundamental wave. Therefore, the vibration suppressing body 8 and the frame bodies 4a and 4b are preferably formed integrally.

  The present invention is not limited to the above-described embodiments, and various modifications and improvements can be made without departing from the gist of the present invention.

  For example, in the above-described embodiment, the vibration suppressing body 8 is placed on both the central portion of the opposing region A in the direction parallel to one side of the piezoelectric substrate 2 and the central portion of the opposing region A in the direction orthogonal to the one side. Although provided, even if it is provided on either side, the same vibration suppressing effect as that of the above-described embodiment is exhibited at the portion where the vibration suppressing body 8 is provided.

  In the above-described embodiment, the vibration suppressing body 8 is formed integrally with the frame bodies 4a and 4b. Instead, the vibration suppressing body 8 and the frame bodies 4a and 4b are separated. You may make it form.

  Further, in the above-described embodiment, the pair of vibrating electrodes 3a and 3b is arranged so that the opposing region has a rectangular shape. However, the opposing region is not limited to the rectangular shape, for example, as shown in FIG. As described above, a part of the vibrating electrode may be extended outward from the centroid of the facing region A. In this case, the fundamental wave is intensively generated at the extending portion 23a, and the third harmonic is generated in a wide region centering on the centroid of the facing region A. As a result, better resonance characteristics are obtained. It will be obtained. In this case, the vibration suppressing body 28 is brought into contact with the vibration electrode at the extending portion 23a.

  Furthermore, in the above-described embodiment, a dielectric substrate may be used as a part of the sealing body. In this case, the dielectric substrate has a large capacitance formed by the electrodes formed on the upper and lower surfaces thereof. By using such a dielectric substrate, for example, a Colpitts oscillation circuit is formed in the piezoelectric resonator. Capacitor function can be added.

  Furthermore, the dielectric substrate described above is not used as a part of the sealing body, but may be separately attached to the piezoelectric resonator shown in FIG. Even with the addition of, the thermal expansion coefficients of the sealing bodies formed on both surfaces of the piezoelectric substrate are matched to reduce the occurrence of warping and the like, and a stable resonance characteristic can be obtained.

1 is an external perspective view of a piezoelectric resonator according to an embodiment of the present invention. It is sectional drawing of the piezoelectric resonator of FIG. It is the top view which looked at the piezoelectric resonance element used for the piezoelectric resonator of FIG. 1 from upper direction. It is a figure showing the vibration area | region of each vibration mode in a piezoelectric resonance element. It is the top view which looked at the piezoelectric resonance element used for the piezoelectric resonator which concerns on other embodiment of this invention from upper direction. It is sectional drawing of the conventional piezoelectric resonator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric resonance element 2 ... Piezoelectric substrate 3a, 3b ... Vibration electrode 4a, 4b ... Frame body 5a, 5b ... Sealing body 6 ... External terminal electrode 7 ... Space Layer 8 ... Vibration suppressor A ... Opposite area B ... Area where fundamental wave concentrates C ... Area where third harmonic wave concentrates

Claims (7)

A pair of oscillating electrodes that are partly opposed to both main surfaces of the piezoelectric substrate having a rectangular shape through the piezoelectric substrate and led out in opposite directions parallel to one side of the piezoelectric substrate from the facing region are covered. A pair of sealing bodies are attached to both sides of the attached piezoelectric resonant element via a frame surrounding the opposing area, and the opposing area of the piezoelectric resonant element is applied in accordance with voltage application to the vibration electrode. In a piezoelectric resonator that generates a fundamental wave of a predetermined frequency and a third harmonic thereof,
Between the piezoelectric resonant element and the sealing body, the vibration electrode has a central portion of the opposing region in a direction parallel to the one side and / or a central portion of the opposing region in a direction orthogonal to the one side. On the other hand, a vibration suppressing body that partially contacts only at the outer peripheral portion of the opposing region is interposed, and a space layer that is in contact with the vibrating electrode is interposed at the outer peripheral portion of the opposing region where the vibration suppressing body does not exist. A piezoelectric resonator characterized by the above. The piezoelectric oscillator according to claim 1, wherein the space layer is made of any one of air, an inert gas, and a vacuum. The piezoelectric resonator according to claim 1, wherein the vibration suppressing body is made of the same material as the frame body. The piezoelectric resonator according to claim 3, wherein the vibration suppressing body and the frame are integrally formed. The piezoelectric resonator according to claim 4, wherein the vibration suppressing body and the frame body are made of the same material as the sealing body and are formed integrally with the sealing body. The pair of vibrating electrodes includes an extending portion that extends outward from the centroid of the opposing region in a direction orthogonal to the one side. The piezoelectric resonator according to claim 5. The piezoelectric resonator according to claim 6, wherein the vibration suppressing body is in contact with the vibration electrode at the extension portion.

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