JP2008072156A - Composite material vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a composite material vibrator which has a small structure not requiring any space not to hinder the vibration and excellent in mechanical strength and hardly causes characteristic variation due to the difference in coefficient of thermal expansion between constituent members during its manufacture or when the ambient temperature varies. <P>SOLUTION: The composite material vibrator 1 is constituted as follows. Over a plate-shaped piezoelectric resonance element 2 made of a material having an acoustic impedance value Z1, plate-shaped holding member 5 and 6 made of a material having an acoustic impedance value Z3 are stacked with reflective layer 3 and 4 made of a material having an acoustic impedance value Z2 interposed therebetween. The relations between the impedance values are Z2<Z1 and Z2<Z3. When the coefficient of thermal expansion in the direction parallel to the surfaces of the reflective layers 3 and 4 is represented by X and that in the direction parallel to the surfaces of the holding members is represented by Y, the sign of the X is opposite to that of Y, or the Y and X have the same sign and the Y is 3% or less that of the X. Alternatively, the Y is about zero. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a composite material vibration device in which a plurality of material portions having different acoustic impedances are connected, and more specifically, a lamination in which a plurality of material layers having different acoustic impedances are laminated on a vibration element such as a piezoelectric element. The present invention relates to a type of composite material vibration device.

  In order to reduce the size of piezoelectric resonance devices, piezoelectric filter devices, and the like, there are known composite material vibration devices in which a plurality of material layers having different acoustic impedances are connected to piezoelectric elements used in these devices.

  For example, the following Patent Document 1 discloses a composite material vibration device shown in FIGS. 7 (a) and 7 (b). In the composite material vibration device 101, a plate-like piezoelectric resonance element 102 is used as a vibration element. A holding member 104 is laminated on the upper surface of the piezoelectric resonant element 102 with a reflective layer 103 interposed therebetween. A holding member 106 is laminated on the lower surface of the piezoelectric resonant element 102 with a reflective layer 105 interposed therebetween. An external electrode 107 is formed on one end face of the laminate in which these members are laminated, and an external electrode 108 is formed on the other end face.

  In the piezoelectric resonance element 102, an excitation electrode 112 is formed on the upper surface of a plate-like piezoelectric substrate 111, and an excitation electrode 113 is formed on the lower surface. The piezoelectric substrate 111 is made of a lead zirconate titanate piezoelectric ceramic, and is polarized in the length direction, which is a direction connecting the external electrodes 107 and 108. The excitation electrodes 112 and 113 are opposed to each other via the piezoelectric substrate 111 at the center in the length direction of the piezoelectric substrate 111. The facing portions of the excitation electrodes 112 and 113 constitute a vibrating portion to which an electric field is applied during driving, and the piezoelectric resonant element 102 operates as a piezoelectric resonant element utilizing an energy trapping thickness-slip mode. The excitation electrode 112 is electrically connected to the external electrode 107, and the excitation electrode 113 is electrically connected to the external electrode 108.

In the composite material vibration device 101 described in Patent Document 1, the acoustic impedance value Z ₂ of the reflective layers 103 and 105 is smaller than the acoustic impedance value Z ₁ of the piezoelectric substrate 111 and the acoustic impedance value Z of the holding members 104 and 106 is. _It is smaller than ₃ . More specifically, here, the reflection layers 103 and 105 are made of epoxy resin, and the holding members 104 and 106 are made of ceramics. Since Z ₃ > Z ₂ , the vibration propagated from the piezoelectric resonant element 102 to the reflective layers 103 and 105 is reflected at the interface between the reflective layers 103 and 105 and the holding members 104 and 106. Therefore, since vibration is confined between the upper and lower interfaces, even if the piezoelectric resonant element 102 is mechanically held by the holding members 104 and 106, it is difficult to affect the vibration of the piezoelectric resonant element 102.

  In the composite material vibration device 101, the holding member 106 is made of dielectric ceramics. The capacitive electrodes 114 and 115 are opposed to the upper surface of the holding member 106 with a gap in the center. In addition, a capacitive electrode 116 is formed on the lower surface of the holding member 106. The capacitive electrodes 114 and 115 and the capacitive electrode 116 are opposed to each other via the holding member 106, and constitute a three-terminal capacitor.

Patent Document 2 below discloses a method for manufacturing this type of composite material vibration device. Here, an epoxy resin as a flowable material for forming the reflective layer is applied on a holding substrate constituting the holding member. Next, the vibration element is bonded, and the fluid material is cured by heat to form a reflective layer.
JP 2003-332875 A JP 2003-338720 A

In Patent Document 1, the material constituting the reflective layer and the protective layer is not particularly limited, that the suitable material capable of achieving an acoustic impedance value Z _2, Z ₃ of interest is used are described in paragraph Nos. 0046 ing. As a specific example, a reflective layer made of epoxy resin and a protective layer made of ceramics are shown.

  Patent Document 2 discloses a structure in which the reflective layer is formed of a cured epoxy resin.

  By the way, generally, a thermosetting epoxy resin-based curable composition is cured by heating at around 100 ° C. to give a cured product. On the other hand, this cured product has a much larger coefficient of thermal expansion than ceramics. Therefore, when the cured product contracts greatly due to cooling after curing, stress along the surface direction is applied by the contracting reflective layer at the interface between the reflective layer and the piezoelectric substrate constituting the vibration element. That is, as schematically shown by arrows A and -A in FIG. 7, when the reflective layers 103 and 105 contract so that the areas of the main surfaces of the reflective layers 103 and 105 are reduced, the stress in the directions of the arrows A and -A Is added to the surface of the piezoelectric substrate 111. Therefore, there is a problem that the characteristics of the piezoelectric resonant element 102 fluctuate due to the stress.

As in the composite material vibration device 101, in the laminated composite material vibration device 101 in which the holding members 104 and 106 are stacked through the reflection layers 103 and 105 having relatively low acoustic impedance, the acoustic impedance value Z _{2 of the} reflection layer. Therefore, even if the holding member is mechanically supported, the vibration of the piezoelectric resonance element 102 is hardly affected.

  However, in reality, when the reflective layers 103 and 105 are made of a cured product of a thermosetting epoxy resin curable composition, the stress is generated due to shrinkage upon cooling after curing, and piezoelectric resonance occurs. There was a problem that the characteristics of the element 102 deteriorated.

  In addition, even when the reflective layers 103 and 105 are configured without using a thermosetting curable composition, the finally obtained reflective layers 103 and 105 have piezoelectric elements whose vibration expansion coefficients are vibration members. If the thermal expansion coefficient of the material constituting the resonant element 102 is much larger, when the ambient temperature is lowered, the stress in the A and -A directions is also applied in the same manner as described above, and the characteristics are deteriorated. It was apt. Or, conversely, when the ambient temperature rapidly increases, stress in the direction opposite to the A and -A directions is applied, and the characteristics tend to deteriorate.

  An object of the present invention is to have a structure in which a plate-like holding member is laminated on a plate-like vibration element through a reflection layer having a relatively low acoustic impedance in view of the above-described state of the prior art. It is an object of the present invention to provide a composite material vibration device in which the vibration characteristics of the composite material vibration device are hardly deteriorated based on the difference between the thermal expansion coefficient of the material and the thermal expansion coefficient of the material constituting the vibration element.

  The present invention is a composite material vibration device having a structure in which a plurality of members having different acoustic impedances are coupled, and is configured using a plate-like body made of a material having a first acoustic impedance value Z1, And a plate-like vibration element provided with excitation electrodes on at least one of the upper surface and the lower surface of the plate-like body, and a material having a second acoustic impedance value Z2 smaller than the first acoustic impedance value Z1, and A reflective layer laminated on at least one of an upper surface and a lower surface of the vibration element, and a material having a third acoustic impedance value Z3 larger than the second acoustic impedance value Z2, and the vibration element of the reflection layer A plate-shaped holding member laminated on a surface opposite to the laminated side, and a surface of a laminate including the vibration element, the reflective layer, and the holding member. And an external electrode electrically connected to the excitation electrode, so that vibration propagating from the vibration element to the reflection layer is reflected at an interface between the reflection layer and the holding member. In the composite material vibration device, the thermal expansion coefficient of the reflection layer along the surface direction of the interface between the reflection layer and the vibration element is X, and the surface direction of the interface between the reflection layer and the holding member is When the thermal expansion coefficient of the holding member along Y is Y, X and Y have opposite polarities, or X and Y have the same polarity, and Y is 3% or less of X.

  In a specific aspect of the composite material vibration device according to the present invention, the composite material vibration device further includes a plate-like capacitor bonded to a surface opposite to the surface laminated on the reflective layer of the holding member, The capacitor is bonded to a plate-like capacitor including a dielectric substrate and a plurality of capacitance electrodes provided on the dielectric substrate.

  In the composite material vibration device according to the present invention, preferably, the vibration element includes an electromechanical coupling conversion element.

  Examples of the electromechanical coupling conversion element include a piezoelectric element and an electrostrictive element.

  In the composite material vibration device according to the present invention, a reflection layer made of a material having an acoustic impedance value Z2 is laminated on a plate-like vibration element formed using a plate-like body made of a material having an acoustic impedance value Z1. A plate-like holding member made of a material having an acoustic impedance value Z3 larger than the acoustic impedance value Z2 is laminated on the surface of the reflective layer opposite to the side on which the vibration elements are laminated.

  Therefore, as in the case of the composite material vibration device described in Patent Document 1, vibration propagated from the vibration element to the reflection layer is reflected at the interface between the reflection layer and the holding member. Therefore, even if the holding member is used for mechanical support, the influence of the support structure on the vibration characteristics of the vibration element can be suppressed. Therefore, since a space for not preventing vibration is not required, a composite material vibration device that is small in size and excellent in mechanical strength can be provided.

  In addition, in the present invention, when the thermal expansion coefficient along the surface direction of the interface between the reflective layer and the vibration element is X, and the thermal expansion coefficient of the holding member along the interface between the holding member and the reflective layer is Y, Since X and Y have opposite polarities, or X and Y have the same polarity, and Y is 3% or less of X, the deterioration of characteristics due to the difference in thermal expansion coefficient between the reflective layer and the vibration element. Can be suppressed.

  That is, for example, when the reflective layer is greatly contracted due to cooling when the reflective layer is formed, or when the ambient temperature is rapidly changed and the reflective layer contracts or expands, the thermal expansion occurs at the interface between the reflective layer and the vibration element. Stress due to the coefficient difference is applied. However, since X and Y have opposite characteristics, or have the same polarity and Y is 3% or less of X, the surface on the side opposite to the side where the vibration element of the reflective layer is laminated In this case, shrinkage or expansion of the reflective layer is suppressed by the holding member. Therefore, since the contraction or expansion behavior of the reflection layer is suppressed by the holding member, the contraction or expansion of the reflection layer at the interface between the reflection layer and the vibration element is also suppressed, and the stress at the interface can be reduced. Therefore, since the stress due to the difference in thermal expansion coefficient between the reflective layer and the vibration element is reduced, it is possible to reliably suppress the characteristic deterioration due to the difference in thermal expansion coefficient.

  The holding member further includes a plate-like capacitor bonded to the surface opposite to the surface laminated on the reflective layer, and the plate-like capacitor includes a dielectric substrate and a plurality of capacitors provided on the dielectric substrate. In the case of having an electrode, the dielectric substrate constituting the plate-like capacitor is not directly bonded to the vibration element. In the case of a structure in which a plate-like capacitor is directly bonded to the vibration element, the difference between the thermal expansion coefficient of the material constituting the vibration element and the thermal expansion coefficient of the dielectric substrate constituting the plate-like capacitor Must be reduced. This is because peeling occurs at the bonded portion.

  On the other hand, in the present invention, since the plate-like capacitor is not directly bonded to the vibration element as described above, the thermal expansion coefficient of the dielectric substrate constituting the plate-like capacitor is set as the vibration element. The material can be selected without being limited by the thermal expansion coefficient of the material. Therefore, it is possible to select a dielectric substrate from a wide range of materials, with emphasis on the characteristics as a capacitor, such as the magnitude of the dielectric constant ε and the dielectric constant temperature characteristic.

  Therefore, for example, when a built-in capacitor type oscillator is configured, a necessary capacitance can be easily configured by the plate capacitor.

  When the vibration element is an electromechanical coupling conversion element, according to the present invention, it is possible to simplify the indicating structure and easily provide a composite material vibration device that is less likely to change in characteristics due to a change in ambient temperature. can do.

  Hereinafter, the present invention will be clarified by describing specific embodiments of the present invention with reference to the drawings.

  FIG. 1A and FIG. 1B are a front sectional view and a perspective view showing an appearance of a multilayer piezoelectric resonator as a composite material vibration device according to an embodiment of the present invention.

  The piezoelectric resonance device 1 has a plate-like piezoelectric resonance element 2. A first reflective layer 3 is laminated on the upper surface of the plate-like piezoelectric resonance element 2, and a second reflective layer 5 is laminated on the lower surface. A first holding member 4 and a second holding member 6 are laminated on the surface of the reflective layers 3 and 5 opposite to the side laminated with the piezoelectric resonance element 2. In the piezoelectric resonance element 2, a first external electrode 7 is formed on one end surface of a laminate including the reflective layers 3 and 5 and the holding members 4 and 6, and a second external electrode 8 is formed on the other end surface. .

  The plate-like piezoelectric resonance element 2 has a rectangular plate-like piezoelectric plate 11. As shown in FIG. 2A, the first excitation electrode 12 is formed on the upper surface of the piezoelectric plate 11. Further, as shown in a plan view in FIG. 2B, a second excitation electrode 13 is formed on the lower surface of the piezoelectric plate 11. Although the excitation electrodes 12 and 13 are not particularly limited, in this embodiment, the excitation electrodes 12 and 13 are made of a laminated metal film in which three layers of a nichrome thin film, a monel thin film, and a silver thin film are laminated in order.

The piezoelectric plate 11 has an elongated rectangular plate shape, that is, a strip shape. In this embodiment, the piezoelectric plate 11 is made of a lead zirconate titanate-based piezoelectric ceramic, and is polarized in the length direction. The acoustic impedance value Z1 of the piezoelectric plate 11 is 2.87 × 10 ⁷ kg / (m ² s). The piezoelectric plate 11 may be composed of other piezoelectric ceramics or a piezoelectric single crystal.

  The excitation electrodes 12 and 13 are formed to reach the entire width of the piezoelectric plate 11. However, the excitation electrodes 12 and 13 are not necessarily required to reach the entire width of the piezoelectric plate 11.

  The excitation electrodes 12 and 13 are opposed to each other via the piezoelectric plate 11 in the center in the length direction of the piezoelectric plate 11. This opposed portion is a vibrating portion to which a voltage is applied during driving. Vibration attenuating portions are formed on both sides of the vibration portion in the length direction of the piezoelectric plate 11. That is, the piezoelectric resonance element 2 is an energy confinement type piezoelectric resonance element using a thickness shear mode.

In this embodiment, the reflective layers 3 and 5 are made of a cured product of an epoxy resin composition, and the acoustic impedance value Z2 thereof is 2.80 × 10 ⁶ kg / (m ² s). The thermal expansion coefficient X of the reflective layers 3 and 5 in the direction along the interface between the reflective layers 3 and 5 and the piezoelectric resonance element 2 is 50 ppm / ° C.

On the other hand, in this embodiment, the first and second holding members 4 and 6 are made of lead titanate insulating ceramics, and the acoustic impedance value Z3 thereof is 3.43 × 10 ⁷ kg / (m ² s). The thermal expansion coefficient Y in the direction along the interface between the holding members 4 and 6 and the reflective layers 3 and 5 is −0.4 ppm / ° C.

  The excitation electrode 12 is drawn out to one end face of the laminate and is electrically connected to the first external electrode 7. On the other hand, the excitation electrode 13 is drawn out to the other end face of the laminate, and is electrically connected to the second external electrode 8.

  In the present embodiment, the external electrodes 7 and 8 are formed of a laminated metal film in which three layers of a nichrome thin film, a nickel plating film, and a tin plating film are sequentially laminated. Further, the external electrodes 7 and 8 are extended so as to reach the lower surface of the laminated body, that is, the lower surface of the holding member 6 below, for mounting on a circuit board or the like.

  In addition, the material which comprises the external electrodes 7 and 8 is not specifically limited. Further, the extension portions 7a and 8a are not necessarily provided.

  The characteristics of the piezoelectric resonator 1 of the present embodiment are that the acoustic impedance value Z2 is smaller than the acoustic impedance value Z1 and smaller than Z3, and that the polarity of the thermal expansion coefficient Y and the polarity of the thermal expansion coefficient X are reversed. It is in what is said.

  Since the acoustic impedance value Z2 is smaller than the acoustic impedance values Z1 and Z3, even if the vibration generated in the piezoelectric resonant element 2 propagates to the reflective layers 3 and 5, the interface between the reflective layer 3 and the holding member 4 and the reflective layer 5 and the holding member 6 are reflected. Therefore, even if the holding members 4 and 6 are mechanically supported, the vibration characteristics of the piezoelectric resonance element 2 are hardly affected by the support structure.

  In addition, since the polarity of the thermal expansion coefficient Y and the polarity of the thermal expansion coefficient X are opposite, the difference between the thermal expansion coefficient of the piezoelectric plate 11 of the piezoelectric resonant element 2 and the reflective layers 3 and 5 It is difficult to cause deterioration of the resonance characteristics. That is, for example, when the ambient temperature changes abruptly, or when the material constituting the reflective layers 3 and 5 is a thermosetting adhesive and shrinkage occurs upon cooling after the adhesive is cured, as described above. In addition, the thermal expansion coefficient X of the cured product of the epoxy adhesive is much larger than the value of −1.8 ppm / ° C. which is the thermal expansion coefficient of the lead zirconate titanate ceramics constituting the piezoelectric plate 11. . Accordingly, stress in the A, -A direction or the opposite direction in FIG. 1 is generated at the interface between the piezoelectric resonant element 2 and the reflective layers 3 and 5.

  However, in this embodiment, since the polarity of Y and the polarity of X are different, when the reflective layers 3 and 5 contract or expand due to temperature changes, the holding members 4 and 6 are disposed outside the reflective layers 3 and 5. The holding members 4 and 6 tend to expand or contract in contrast to the reflective layers 3 and 5. That is, the contraction or expansion on the outer surfaces of the reflective layers 3 and 5 is offset by the expansion or contraction of the holding members 4 and 6. Therefore, the shrinkage or expansion of the reflection layers 3 and 5 is suppressed, and the stress at the interface between the reflection layers 3 and 5 and the piezoelectric plate 11 is reduced. Therefore, when the reflective layers 3 and 5 are made of, for example, a cured product of the curable composition of epoxy resin as described above, it is possible to suppress the influence of shrinkage upon cooling after curing.

  In addition, even when the ambient temperature changes suddenly after the piezoelectric resonance device 1 is manufactured, the fluctuation of characteristics due to stress based on the difference between the thermal expansion coefficient of the piezoelectric plate 11 and the thermal expansion coefficient of the reflective layers 3 and 5 is caused. It can be effectively suppressed. This will be described based on a specific experimental example.

The piezoelectric plate 11 is made of a lead zirconate titanate ceramic, has a length of 1.8 mm, a width of 0.5 mm, and a thickness of 0.09 mm, and an acoustic impedance value Z1 of 2.87 × 10 ⁷ kg / (m ² s), excitation electrodes 12 and 13 were formed on both surfaces of the piezoelectric plate 11 having a thermal expansion coefficient in the plane direction of −1.8 ppm / ° C. The excitation electrodes 12 and 13 were formed by sequentially sputtering three layers of nichrome, monel, and silver, and the size of the opposing region of the excitation electrodes 12 and 13 was 0.4 mm × 0.5 mm. In this way, a piezoelectric resonant element 2 having a designed resonant frequency of 13 MHz was manufactured.

  An epoxy resin-based curable composition is applied to the upper and lower surfaces of the piezoelectric resonator element 2, and the holding members 4 and 6 are laminated via the curable composition in a semi-cured state, and a temperature of 100 ° C. And the curable composition was cured to form the reflective layers 3 and 5. That is, the curable composition was cured, and the piezoelectric resonance element 2 and the holding members 4 and 6 were bonded to each other by the reflective layers 3 and 5 by the adhesive force of the cured product. Thereafter, it was cooled to room temperature.

The dimensions of the reflective layers 3 and 5 formed as described above are 1.8 mm × 0.5 mm × thickness 0.02 mm, and the acoustic impedance value Z2 is 2.80 × 10 ⁶ kg / (m ² s) and the thermal expansion coefficient X along the surface direction is 50 ppm / ° C.

The dimensions of the holding members 4 and 6 used are 1.8 mm × 0.5 mm × thickness 0.06 mm, the acoustic impedance value Z3 is 3.43 × 10 ⁷ kg / (m ² s), and the thermal expansion coefficient. Y is -0.4 ppm / ° C.

The laminated piezoelectric resonator 1 of the present embodiment thus obtained and the materials constituting the holding members 4 and 6 are changed in various ways to change the thermal expansion coefficient Y along the surface direction of the holding members 4 and 6. Except for the above, a plurality of types of piezoelectric resonance devices constructed in the same manner as described above were produced. For these piezoelectric resonators, the phase and frequency characteristics were measured, and the maximum value θ _max of the phase angle was measured. The phase angle maximum value θ _max is a phase maximum value in the vicinity of the design resonance frequency of 13 MHz in the piezoelectric resonator device 1 of the present embodiment. It can be seen that better resonance characteristics can be obtained as the phase maximum value θ _max in the phase frequency characteristics increases.

FIG. 3A shows the relationship between the thermal expansion coefficient Y of the holding members 4 and 6 and the phase angle maximum value θ _max . As is apparent from FIG. 3A, the maximum phase angle value θ _max is very large when the thermal expansion coefficient Y of the holding members 4 and 6 is a negative value or less than 2 ppm.

FIG. 3B is a result of rewriting the result of FIG. 3A with the horizontal axis of FIG. 3A as Y / X. As is apparent from FIG. 3B, it can be seen that if Y / X is 3% or less, the phase angle maximum value θ _max is very large.

  On the other hand, among the above-described plural types of piezoelectric resonators, the holding members 4 and 6 are calculated by the finite element method of the piezoelectric resonator when the coefficient of thermal expansion Y is 9.3 ppm / ° C and -0.4 ppm / ° C. The stress distribution data is schematically shown in plan views in FIGS.

  In addition, the following symbols a) and b) in FIGS. 4A and 4B indicate compression stress and tensile stress, respectively, and the longer the length, the greater the stress.

  As apparent from FIG. 4B, when the thermal expansion coefficient Y of the holding members 4 and 6 is −0.4 ppm / ° C., the stress value applied to the piezoelectric resonant element 2 is 24 MPa or less, It was found that when the thermal expansion coefficient of the holding members 4 and 6 is 9.3 ppm / ° C., the stress is as large as about 150 MPa, and thus the vibration of the piezoelectric resonant element 2 is strongly inhibited.

As described above, when the thermal expansion coefficient Y of the holding members 4 and 6 is a negative value or 2 ppm / ° C. or less, the phase angle maximum value θ _max becomes very large as shown in FIG. As is clear from the comparison of (b), it can be seen that the stress due to the difference in thermal expansion coefficient applied to the piezoelectric resonant element 2 is very small.

  This is because, as described above, the thermal expansion coefficient of the piezoelectric plate 11 constituting the piezoelectric resonance element 2 is −1.8 ppm / ° C. Therefore, the epoxy resin-based curable composition constituting the reflective layers 3 and 5 It is considered that a large stress is applied to the interface between the piezoelectric resonator element 2 and the reflective layers 3 and 5 due to a large contraction upon cooling after the object is cured. However, when the thermal expansion coefficient Y of the holding members 4 and 6 is a negative value or smaller than 2 ppm / ° C., the holding members 4 and 6 act to suppress the shrinkage of the reflection layers 3 and 5. It is considered that the stress is reduced and good resonance characteristics are obtained.

  That is, in the piezoelectric resonance apparatus 1 of the present embodiment, as described above, the thermal expansion coefficient Y of the holding members 4 and 6 is opposite in polarity to the thermal expansion coefficient of the piezoelectric plate 11 constituting the piezoelectric resonance element 2. If there is or the same polarity, the thermal expansion coefficient Y of the holding members 4 and 6 should be made sufficiently smaller than the thermal expansion coefficient X of the reflective layers 3 and 5, and more specifically, Y should be near zero. By doing so, it can be seen that good resonance characteristics can be realized as described above.

  According to the experiment by the present inventor, when X is sufficiently larger than Y, it is confirmed that if Y is 3% or less of X, good resonance characteristics can be realized as in the above embodiment. It has been. Therefore, to make X sufficiently larger than Y means that Y is 3% or less of X.

  In the present embodiment, the reflective layers 3 and 5 are made of a cured product of an epoxy resin-based curable composition, and the cured product is cured by heating the curable composition. Therefore, the stress was generated by shrinkage after curing.

  However, the piezoelectric resonator device 1 of the present embodiment is not limited to the one using a reflective layer formed by being cured by heating. That is, even when the reflective layer made of a material other than the thermosetting material is configured, for example, when the ambient temperature of the obtained piezoelectric resonator 1 changes rapidly, the thermal expansion coefficient of the reflective layer and the piezoelectric element are configured. The same problem occurs when the thermal expansion coefficient of the piezoelectric plate is greatly different. Therefore, even in such a case, when the thermal expansion coefficient Y of the holding member has a polarity opposite to the thermal expansion coefficient X of the material constituting the reflective layer, or in the case of the same polarity, X is compared with Y. By adopting a configuration that is sufficiently large, that is, Y is 3% or less of X, and further Y = about 0, the stress applied to the interface between the reflective layer and the vibration element is effectively reduced as in the case of the above embodiment. Can be small.

  Therefore, the reflective layer may be formed of a cured product cured by light irradiation, for example, a photocured epoxy resin-based cured product. Further, the reflective layer may be composed of a material other than a cured product of the curable material, or may be composed of a resin material other than epoxy, or another organic or inorganic material.

  The holding members 4 and 6 may also be formed of a material other than ceramics such as other ceramics or resin as long as the thermal expansion coefficient relationship and the acoustic impedance relationship are satisfied.

  FIG. 5 is a perspective view showing a stacked piezoelectric resonance device as a composite material vibration device according to a second embodiment of the present invention. In the piezoelectric resonance device 21 of the second embodiment, in the piezoelectric resonance element 2A, the excitation electrode 12A is electrically connected to the external electrode 8, the excitation electrode 13A is electrically connected to the external electrode 7, and the reflection layers 3A and 5A Except that the thickness is thinner than that of the reflective layers 3 and 5 and that the plate-like capacitor element 23 is laminated on the lower surface of the lower holding member via the adhesive layer 22, the first The configuration is the same as that of the piezoelectric resonance device 1 of the embodiment. Accordingly, the same parts are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the piezoelectric resonance device 21, a plate-like capacitor element 23 is laminated via an adhesive layer 22 made of an appropriate adhesive such as an epoxy adhesive. The plate-shaped capacitor element 23 has a rectangular plate-shaped dielectric substrate 24. On the upper surface of the dielectric substrate 24, a pair of capacitive electrodes 25 and 26 are arranged so as to face each other with a gap in the center. The outer end of the capacitive electrode 25 is connected to the external electrode 7, and the outer end of the capacitive electrode 26 is connected to the external electrode 8. A capacitor electrode 27 is formed at the center of the lower surface of the dielectric substrate 24 so as to face the capacitor electrodes 25 and 26 with the dielectric substrate 24 therebetween. The capacitor electrode 27 not only functions as a terminal electrode when the piezoelectric resonator 21 is mounted on the circuit board, but also functions to take out capacitance between the capacitor electrodes 25 and 26.

  Accordingly, the plate-like capacitor element 23 is a three-terminal capacitor element having the capacitive electrodes 25 and 26 and the terminal electrode 27.

  Since the piezoelectric resonance device 21 has a built-in capacitor composed of the plate-like capacitor element 23, it can be used as a built-in capacitor type piezoelectric oscillator.

  Also in the piezoelectric resonator 21, the acoustic impedance value Z2 of the reflective layers 3A and 5A is made smaller than the acoustic impedance values Z1 and Z3, and the thermal expansion coefficient X of the reflective layers 3A and 5A is the same as that of the holding members 4 and 6. The thermal expansion coefficient Y is opposite in polarity or larger than the thermal expansion coefficient Y. Alternatively, Y = about 0. Therefore, as in the case of the piezoelectric resonator device 1 of the first embodiment, in the present embodiment, the influence of stress caused by contraction or expansion due to temperature change after the formation of the reflective layers 3A and 5A or after the formation is formed. Can be suppressed.

  In this embodiment, the capacitor element 23 is bonded to the lower surface of the holding member 6. In this case, the material constituting the dielectric substrate can be selected from a wide range. That is, in the structure in which the dielectric substrate 24 is directly bonded to the piezoelectric resonant element 2A, if the difference in thermal expansion coefficient between the two is too large, there is a possibility that peeling occurs due to a change in ambient temperature. Therefore, the selection range of the dielectric substrate material constituting the capacitor is narrow.

  On the other hand, in the present embodiment, the dielectric substrate 24 is bonded to the lower surface of the holding member 6 via the adhesive layer 22, so that the dielectric material constituting the dielectric substrate 24 is changed to the piezoelectric resonance element 2A. Can be selected without being restricted by the value of the coefficient of thermal expansion of the piezoelectric plate 11 constituting the. Therefore, the plate-like capacitor element 23 can be formed using a dielectric material necessary and optimal when forming a built-in capacitor type piezoelectric resonance element.

  FIG. 6 is a perspective view showing a piezoelectric resonator device according to a modification of the piezoelectric resonator device 21 of the second embodiment. The piezoelectric resonance device 31 is except that the reflective layer 3A and the holding member 4 provided above the piezoelectric resonance element 2A are not provided, and that the coating film 32 is provided on the upper surface of the piezoelectric resonance element 2A. Is configured in the same manner as the piezoelectric plate 21 of the second embodiment. As apparent from the piezoelectric resonance device 31, in the present invention, the holding member 6 may be laminated only on one surface side of the vibrating member via the reflective layer 5A.

  The coating film 32 is provided to protect the upper surface of the piezoelectric resonant element 2A, and can be made of an appropriate material that performs such a protective action. Examples of such a material include an appropriate insulating material.

  The present invention can be widely applied to the present invention not only in the above-described multilayered piezoelectric resonator but also in a multilayered composite vibration device using a plate-like resonant element other than the piezoelectric resonant element. Therefore, instead of the plate-like piezoelectric resonance elements 2 and 2A, an electromechanical coupling conversion element such as an electrostrictive element may be used, or a plate-like vibration element other than the electromechanical coupling conversion element may be used.

(A) And (b) is a perspective view which shows front sectional drawing and the external appearance of the composite material vibration apparatus which concern on the 1st Embodiment of this invention. (A) And (b) is the top view and bottom view of a piezoelectric resonant element which are used with the composite material vibration apparatus of 1st Embodiment. (A) is the figure which shows the change of phase angle maximum value (theta) _max in the phase-frequency characteristic at the time of changing the thermal expansion coefficient of a holding member in the piezoelectric resonance apparatus of 1st Embodiment, and (b), The result of rewriting the result of (a) with the horizontal axis as Y / X (%) is shown. (A) And (b) shows typically the result of having analyzed the stress added to a piezoelectric resonance element in case the thermal expansion coefficients of a holding member are 9.3 ppm / degrees C and -0.4 ppm / degrees C by the finite element method. It is each figure. The typical front perspective view which shows the lamination type piezoelectric resonance apparatus as a composite material vibration apparatus which concerns on the 2nd Embodiment of this invention. The perspective view which shows the modification of the lamination type piezoelectric resonance apparatus of 2nd Embodiment. (A) And (b) is front sectional drawing and external appearance perspective view of the conventional composite material vibration apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric resonance apparatus 2, 2A ... Piezoelectric resonance element 3, 5 ... Reflection layer 3A, 5A ... Reflection layer 4, 6 ... Holding member 7, 8 ... External electrode 7a, 8a ... Extension part 11 ... Piezoelectric plate 12, 13 ... Excitation electrodes 12A, 13A ... excitation electrodes 21 ... piezoelectric resonance device 22 ... adhesive layer 23 ... capacitor element 24 ... dielectric substrate 25, 26, 27 ... capacitance electrode 31 ... piezoelectric resonance device 32 ... coating layer

Claims (4)

A plate-like vibration element configured using a plate-like body made of a material having a first acoustic impedance value Z1, and having an excitation electrode on at least one of the upper and lower surfaces of the plate-like body;
A reflective layer made of a material having a second acoustic impedance value Z2 smaller than the first acoustic impedance value Z1, and laminated on at least one of the upper surface and the lower surface of the vibration element;
It is made of a material having a third acoustic impedance value Z3 larger than the second acoustic impedance value Z2, and is a plate-like layer laminated on the surface of the reflective layer opposite to the side on which the vibration element is laminated. A holding member;
An external electrode provided on the surface of the laminate composed of the vibration element, the reflective layer and the holding member, and electrically connected to the excitation electrode;
In the composite material vibration device configured to reflect vibration propagating from the vibration element to the reflection layer at the interface between the reflection layer and the holding member,
The thermal expansion coefficient of the reflective layer along the surface direction of the interface between the reflective layer and the vibration element is X, and the thermal expansion coefficient of the holding member along the surface direction of the interface between the reflective layer and the holding member is Y. And X and Y have opposite polarities, or X and Y have the same polarity, and Y is 3% or less of X.   The holding member further includes a plate-like capacitor adhered to a surface opposite to the surface laminated on the reflective layer, and the plate-like capacitor is provided on the dielectric substrate and the dielectric substrate. The composite material vibration device according to claim 1, further comprising a plurality of capacitive electrodes.   The composite material vibration device according to claim 1, wherein the vibration element is an electromechanical coupling conversion element. The composite material vibration device according to claim 3, wherein the electromechanical coupling conversion element is a piezoelectric element or an electrostrictive element.

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