JP2006187000A - Shear-mode vibrating element utilizing mass load effect and piezoelectric resonator utilizing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-size multilayer vibrating element which has a large electromechanical coupling coefficient and vibrates in a thickness shear mode. <P>SOLUTION: The vibrating element comprises an vibrator, a base substrate including a capacitor, and a protection cover. In the vibrator, a plurality of piezoelectric sheets 10 on which an internal electrode pattern 20 is printed are stacked, input electrodes 30 extended from a middle end to one end portion are mutually linked by an auxiliary electrode 40 in the internal electrode, end portions of output electrodes formed between the input electrodes are mutually linked by an external electrode, and the vibrator polarized in a longitudinal direction so that the vibrator vibrates in the longitudinal direction. Also, a mass load layer 50 is formed on the whole or a part of at least one of outer surfaces in the longitudinal direction, and a vibration frequency of the vibrator is adjusted by utilizing the mass load effect. Such a vibrator can be used as a part of a small-size Colpitts oscillator circuit. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an oscillating element and a piezoelectric resonator using the oscillating element, and more specifically, a piezoelectric sheet is laminated so as to be suitable for a high-frequency oscillating element, but is horizontal to the laminated electrode surface. As described above, the present invention relates to an oscillation element that is vibrated in a thickness shear mode by being polarized in the length direction of the element, and a piezoelectric resonator using the oscillation element.

In addition, the present invention not only uses the mass load effect to adjust the vibration frequency of the vibrator, but also has a thickness with a large electromechanical coupling coefficient so as to minimize the vibration area and minimize the vibration element. The present invention relates to a laminated vibration element that vibrates in a shear mode and a piezoelectric resonator using the same.

Conventional technology

In general, a piezoelectric resonator is an essential component in most electronic devices that employ a microcomputer as a timing device that provides a reference signal for the microcomputer. It is a component corresponding to the inductance portion of the circuit, and the oscillation frequency is mainly determined by physical dimensions such as the thickness of the vibration element.

Recently, the demand for resonators used in communication environments such as USB and smart cards is rapidly increasing, and the characteristics require particularly precise oscillation frequency. There is a demand for a precise oscillating element with a frequency adjusted and a piezoelectric resonator using the same. In addition, as the function of the microcomputer improves, the operating frequency tends to increase, and the electronic equipment tends to be downsized. Accordingly, the piezoelectric resonator also supports high frequency oscillation and downsizing. It is essential.

In such a vibration element, the oscillation frequency is inversely proportional to the thickness of the vibration element. Therefore, if the thickness is reduced, the oscillation frequency is improved, but the mechanical strength of the vibration element is weakened and is easily destroyed. Therefore, application as a part becomes impossible.

For example, since the oscillation frequency of a 0.3 mm thick thickness mode vibration element is in the vicinity of 8 MHz, a very good frequency can be obtained, but when considering mechanical strength, the limit of the thickness that can be actually manufactured is At this time, the oscillation frequency is around 24MHz.

Therefore, in the conventional case, in order to increase the oscillation frequency, the vibration mode of the single plate type vibration element is not a fundamental vibration mode whose thickness is a half wavelength, but a higher order vibration mode that is an odd multiple of the fundamental vibration is used to increase the frequency. ing.

However, in the case of high-order vibration, the intensity of oscillation is weaker than that of the fundamental vibration, so in reality, most of the vibrations are 3 times the fundamental vibration. The element can oscillate at 24 MHz, which is 3 times 8 MHz, and when considering mechanical strength, it can oscillate at 48 MHz, which is twice the 24 MHz, at the approximate thickness limit of 0.15 mm. This is the limit of high-frequency oscillation by the conventional technology.

In addition, in the case of a single-plate type oscillation element that uses a higher-order vibration mode, a vibration attenuation part that does not vibrate in a part of the single-plate type vibration element is indispensable to eliminate unnecessary vibrations. There are limits.

As shown in FIG. 1, the conventional laminated vibration element includes a laminated piezoelectric sheet 1, an internal electrode 2 printed between the piezoelectric sheets 1, an external electrode 3 and auxiliary electrodes formed on both ends of the sheet. 4 and is polarized in the direction perpendicular to the length of the piezoelectric sheet and vibrates in the thickness direction (hereinafter referred to as “thickness vibration”). The direction of the electric field and the direction of polarization are formed opposite to each other between the stacked sheets.

Therefore, when one layer expands, the other layer contracts, and vice versa, a vibration mode is formed, resulting in the oscillation frequency corresponding to the thickness of the stacked sheets, When it is a single plate type, a vibration corresponding to twice the oscillation frequency corresponding to the thickness of the entire element is formed. However, in the case of thickness vibration, since the electromechanical coupling coefficient is small compared to the shear mode, there is a disadvantage in reducing the effective vibration area, so there is a limit to downsizing the vibration element and the piezoelectric resonator using this. is there.

Moreover, although a high frequency can be obtained by making the laminated sheet thin, there is a problem that the oscillation frequency cannot be precisely controlled.

The object of the present invention created to solve the above-mentioned problems is a laminated type that vibrates in a thickness shear mode with a large electromechanical coupling coefficient in order to minimize the effective vibration area and reduce the size of the vibration element. The object is to provide a vibration element.

Another object of the present invention is to provide a resonator element capable of precisely controlling the oscillation frequency and a piezoelectric resonator using the resonator element.

Furthermore, the present invention controls the resonance frequency of the vibration element so as to have a desired oscillation frequency by forming a mass load layer capable of imparting a mass load effect to the outer surface of the multilayer vibration element. It is an object of the present invention to provide a piezoelectric resonator having a precise oscillation frequency with a low component height by installing a resonator element on a laminated base substrate in which a capacitor is built to constitute a piezoelectric resonator.

To achieve the above object, the present invention provides a vibrating element in which at least two or more piezoelectric sheets on which an internal electrode pattern is printed are laminated, and the internal electrodes are arranged from the middle end. The input electrodes formed to extend to the side ends are interconnected by auxiliary electrodes, and the ends of the output electrodes formed between the input electrodes are connected to each other by external electrodes and vibrate in the length direction. In this way, the vibration element is characterized by being polarized in the length direction.

In the piezoelectric resonator, at least two or more piezoelectric sheets printed with an internal electrode pattern are laminated and formed so as to extend from the middle end to one side end portion of the internal electrodes. The input electrodes are interconnected by auxiliary electrodes and formed between the input electrodes, but the ends of the output electrodes formed so as to partially overlap the input electrodes are connected to each other by external electrodes, It comprises a piezoelectric resonator comprising: a vibrating element polarized in the length direction of the body sheet; a base substrate with a capacitor installed therein; and a protective cover for protecting the vibrating element.

Furthermore, a mass load layer is formed on a part or all of at least one of the external surfaces in the length direction of the vibration element polarized in the length direction as described above. It holds.

The above objects, other features and advantages of the present invention will become apparent from the following description of the preferred embodiments of the present invention referred to below.

Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings.
First, a vibration element that vibrates in a shear mode and a piezoelectric resonator manufactured thereby will be described.

As shown in FIG. 4, the basic configuration of the shear mode vibration element according to the present invention includes a piezoelectric sheet 10 laminated in two or more layers, an internal electrode 20 printed between the piezoelectric sheet 10 and the like, and a piezoelectric element. The auxiliary electrode 40 printed on the surface of the sheet 10 and the external electrode 30 are included.

The technology for constructing an oscillation element by laminating such piezoelectric sheets 10 in multiple layers is normal in the field to which the present invention belongs, but the conventional oscillation element oscillates as shown in FIG. In contrast to the fact that the vibration is perpendicular to the length of the vibration element in the direction perpendicular to the length of the element, the present invention has polarization in the length direction of the vibration element as shown in FIG. Vibration is established in the length direction of the vibration element.

As shown in FIGS. 5 and 9, a large number of the internal electrodes 20 can be formed along the number of laminated layers of the piezoelectric sheets 10, and the input electrode 21 and the output electrode 22 are provided. The internal electrodes are alternately arranged, and each internal electrode is formed to extend from the middle end portion of the piezoelectric sheet 10 to both end portions.

The end of the input electrode 21 is connected to the auxiliary electrode 40 formed on one end of the outer surface of the laminated piezoelectric sheet 10, and the end of the output electrode 22 is opposite to the auxiliary electrode 40. The external electrodes 30 formed at the ends are connected to each other.

The portions of the input electrode 21 and the output electrode 22 that are the internal electrodes 20 facing each other, that is, the portion facing the middle end of the piezoelectric sheet 10 are overlapped with each other as shown in FIGS. An overlapping portion OL is formed, and a separation portion S is formed between the end portions of the auxiliary electrode 40 and the external electrode 30 facing each other with a predetermined distance.

Each of the electrodes is formed by a thick film printing method or a vacuum deposition method, and such an electrode forming method is a commonly used method, and a detailed description thereof will be omitted.

The piezoelectric resonator using the vibration element configured as described above is installed on a base substrate 160 in which a capacitor is built, and a cover 120 for protecting the vibration element 140 is installed on the upper part. The

The base substrate 160 may be a laminated substrate or a single plate in which thin plates are laminated.

The protective cover 120 may be formed by pressing a metal or may be formed by compressing and plasticizing ceramics, and a capacitance of a capacitor built in the base substrate 160 may be 3 pF to 50 pF.

The internal electrode 20 and the external electrode 30 of the oscillation element are installed on the base substrate 160 of the piezoelectric resonator and connected to the input and output terminals of the piezoelectric resonator, and an AC signal is approved to the input and output terminals of the piezoelectric resonator. The vibration element 140 causes an inherent vibration corresponding to the polarization direction due to the electric field formed on the internal electrode 20 and the external electrode 30, and a resonance-antiresonance phenomenon occurs along the shape and dimensions of the vibration element 140. become.

Since the piezoelectric resonator is electrically equivalent to an inductive reactive element in the frequency range between the resonance and antiresonance frequencies, it is coupled with the inverting amplifier of the IC as shown in the circuit diagram shown in FIG. By interacting with a part of the Colpit oscillation circuit, the oscillation is performed at the natural resonance frequency determined by the above-described shape and dimensions and the frequency related to the load doses CL1 and CL2 of the oscillation circuit.

The vibration principle of the vibration element 140 according to the present invention will be described with reference to the drawing shown in FIG.

In FIG. 3, the dotted line and the alternate long and short dash line indicate a state where the vibration element is deformed in response to an electrical signal approved between the internal electrode and the external electrode, and a thick solid line indicates a state where the electrical signal is not approved.

As shown in FIG. 3, since the upper and lower vibration forms are symmetric with respect to the solid line dividing the center on the side, the resonance frequency of the vibration element having a thickness of 2T is a laminate having the thickness T. A single-plate vibration element having the same thickness as the resonance frequency of the sheet, and the vibration element having the above structure having a resonance frequency having a frequency twice that of the entire thickness. Two times higher frequency vibration is realized.

When the sheet having the thickness T is manufactured by laminating three layers as the same principle, the resonance frequency of the whole element has a resonance frequency three times that of a single plate type vibration element of the same thickness, Therefore, the resonance frequency of the vibration element manufactured by stacking the sheet of thickness T n times according to the above principle is a frequency corresponding to n times the resonance frequency of the single-plate element having the same thickness. Therefore, in the above configuration, the resonance frequency of the entire element is determined by the thickness T of the laminated sheet. Therefore, the thickness of the laminated sheet can guarantee high mechanical strength while making the sheet very thin, thereby achieving high-frequency oscillation. A corresponding piezoelectric resonator resonator element is provided.

An example of the manufacturing process of the vibration element according to the present invention will be described with reference to FIG.
As the material of the vibration element, a piezoelectric composition of lead zirconate titanate (PZT) is used. The chemical formula of the composition is Pb (Zr0.5Ti0.5) O ₃ , MnO ₂ is added at 0.2% by weight ratio to the PZT to improve the quality factor, and PZT to the molding to improve the sinterability. After adding 10% (mol) ratio and combining raw materials, we put water having the same weight as the powder and alumina balls with a diameter of 10 mm, wet-mixed for 24 hours, and then dried at 100 ° C After drying in an oven, it was broken, placed in an alumina container, heated at 850 ° C for 2 hours, and synthesized with raw materials having PZT magnetic properties.

After adding 40% binder and organic solvent such as alcohol for viscosity adjustment to the synthesized raw material, and performing ball mill for 24 hours to produce slurry, A sheet of 50 μm thickness was prepared by the well-known doctor blade tape casting method.

The manufactured sheet is formed by forming an electrode pattern designed to have an electrode overlap portion OL and a separation portion S of a desired size with a thickness of 2 to 3 μm by screen printing, and then laminating. At the time of printing, the internal electrode material uses Ag / Pd paste.

The laminate is manufactured into a laminated sintered body by cutting and plasticizing the vibration element to a predetermined size, and forming a polarization electrode on the side surface of the laminated sintered body, in a straight line along the length of the electrode surface of the vibration element. After polarization and imparting piezoelectricity, the polarization electrode is sharpened and removed so that the internal electrode 20 is exposed on the side surface of the vibration element.

The auxiliary electrode 40 and the external electrode 30 are formed by evaporating a Cu / Ag electrode to a thickness of 1 μm by a sputtering vacuum deposition method.

At this time, when polishing the polarization electrode, the internal electrode 20 appearing on the side surface is connected to the auxiliary electrode 40 or the external electrode 30 through the side surface, and an electrical input / output terminal is provided to the vibration element.

First practical example As an example of a vibrating element manufactured by the above-described process, the length L of the element is 2.0 mm, the electrode overlap portion OL is 0.8 mm, and the separation part S is 0.4 mm. The overlapping part was arranged symmetrically from the center of the element.

Therefore, the length of the auxiliary electrode 40 was 0.2 mm, and the thickness of the sheet was contracted by plasticity to be 35 μm. A total of four layers were laminated so that the thickness of the entire vibration element was 0.14 mm.

The piezoelectric positive number of the composition constituting the vibration element is d15 = 450 × 10 ⁻¹² m / V, d33 = 280 × 10 ⁻¹² m / V, and d15 related to the thickness shear vibration relates to the thickness vibration. Approximately twice d33. Since the piezoelectric positive number d is proportional to the electromechanical coupling coefficient, the application of the thickness shear mode is a part of the technical problem to be solved by the present invention. The electromechanical coupling coefficient is large and the effective vibration area is large. It can be seen that this is consistent with manufacturing a vibrating element that can be reduced in size and size.

FIG. 7 shows the measurement of the electrical impedance characteristics of the vibration element configured as described above.

Although it is not shown in the figure, it is manufactured using a material such as the present invention, but in the case of a thickness shear vibration element formed in a single plate type without being laminated in multiple layers, it is resonant when the thickness is 0.3 mm. The frequency was 3.5MHz. At this time, the frequency constant (resonance frequency × value value corresponding to the dimension becomes a value value specific to the piezoelectric material) is 1050 KHz / mm. Since the frequency constant is a value specific to the material, it does not change in size.

Therefore, in the case of having a thickness of 35 μm in the actual test example, the calculated value of the resonance frequency can be calculated by dividing the frequency constant of 1050 KHz / mm by the thickness of 35 μm, and the value is 30 MHz.

It can also be seen from the chart shown in FIG. 7 that the resonance frequency is 30 MHz. Since these values are in good agreement with the value calculated above, the resonance frequency of the entire element is determined by the thickness of the laminated sheets, and simultaneously laminated sheets cause symmetric deformation with each other, and unnecessary vibrations occur. It can be seen that it is possible to manufacture a laminated vibration element that does not have any.

Second practical example Further , in order to manufacture a vibration element having a small effective vibration area and capable of being miniaturized, which is one of the technical problems to be solved by the present invention, the same material as described above is used. In this experiment, the vibration element was manufactured with a length L of 1.3 mm, an electrode overlap OL of 0.5 mm, and a separation part S of 0.2 mm. The length of the auxiliary electrode is 0.2mm.

As can be seen from the chart of FIG. 8, the element length was reduced by 35% from 2.0 mm to 1.3 mm, and the electrode overlap OL was reduced by 37.5% from 0.8 mm to 0.5 mm, as compared to the above-mentioned Example 1. However, as described above in Example 1, the resonance frequency of the vibration element was the same as the resonance frequency based on the thickness of the sheet, and there was no unnecessary vibration. Therefore, it can be seen that the vibration element according to the present invention can be miniaturized.

Third experimental example The length L of the element was 0.7mm, the electrode overlap OL was 0.3mm, the separation part S was 0.1mm, and the electrode overlap OL was placed symmetrically at the center of the element. did. The length of the auxiliary electrode was 0.1 mm, the thickness of the laminated sheet was 10 μm after plasticity, and 10 layers were laminated so that the total element thickness was 0.1 mm.

FIG. 9 is a cross-sectional view of the vibration element of the third experimental example, and FIG. 10 shows the electrical impedance characteristics of the vibration element of the third experimental example.

When the element sheet thickness is 10 μm, the calculated value of the resonance frequency can be calculated by dividing the frequency constant from 1050 KHz / mm by the thickness of 10 μm, as described above in Example 1, and the value is 105 MHz. Therefore, the resonance frequency of 95 MHz and an error of about 10% can be seen in the chart of FIG. 10, but generally agree with the idea that the resonance frequency of the vibration element can be determined from the thickness of the laminated sheet. It is possible to manufacture a laminated vibration element in which the laminated sheets cause symmetrical deformation with respect to each other and no unnecessary vibration is generated. Therefore, the present invention can provide a high-frequency vibration element.

As described above, the vibration element according to the present invention has a large electromechanical coupling coefficient, a small effective vibration area, and can be miniaturized by applying a thickness shear mode. The configuration and operation of a piezoelectric resonator using such a vibration element will be described in detail below with reference to the drawing illustrated in FIG.

An example of the piezoelectric resonator uses the vibration element of the first experimental example, and the oscillation circuit is configured as shown in FIG.

Utilizes a cover to protect the vibration element and the laminated base substrate, which is composed of the capacitance that acts between the input electrode and common electrode, and between the output electrode and common electrode, respectively, as capacitors CL1 and CL2, which are elements constituting the circuit Thus, a piezoelectric resonator was manufactured.

The multilayer base substrate acts as a circuit component having an internal capacitor, and at the same time protects the vibration element, and acts as a package element that allows the piezoelectric resonator to be installed on the PC board. Therefore, it is necessary to maintain an appropriate dielectric constant and sheet thickness for forming a predetermined capacitance and a plastic mechanical strength which is a requirement as a package element. A process for manufacturing a piezoelectric resonator, such as manufacturing a laminated base substrate based on such a concept, installing a vibration element, and bonding a cover, will be described in detail.

First, in the manufacturing method of the base substrate, MgTiO ₃ dielectric ceramic material with a dielectric constant of 20 inside and outside was used as the material, and the sheet was formed with a sheet of 50 μm thickness by the doctor blade tape casting method described in the above Example 1. .

The electrodes are Ag / Pd electrodes printed by screen printing so that a capacitance is formed between each layer. In the case of the vibrating element of the third example, printing is performed three times. CL1 and CL2 were each 15 pF.

The capacitance of CL1 and CL2 can be adjusted in the range of 3-50pF by adjusting the number of printings and the pattern size.

In the vibration element, the auxiliary electrode and the external electrode are connected to the input / output electrodes of the base substrate using a conductive adhesive or solder, and the cover is bonded to the base substrate with the adhesive.

Next, a vibration element that has a mass load layer and uses the effect of mass load to easily adjust the vacuum frequency and a piezoelectric resonator that uses the vibration element will be described in detail.

The vibration element having the mass load effect further includes a mass load layer in the shear mode vibration element described above.

As shown in FIG. 14, the mass load layer is coated with a polymer material 50 on the electrode forming portion on the outer surface of the vibration element, or on one or more surfaces of the outer surface of the inner electrode as shown in FIG. The dummy layers 60 and 60 ′ are formed, or the polymer material 50 layer and the dummy layers 60 and 60 ′ are all formed.

Prior to describing the above-described weight load layer, the overall structure of the vibration element according to the present invention will be described.

The vibration element according to the present invention is a well-known method such as cutting and plasticity, in which a piezoelectric material is laminated by forming an internal electrode on a sheet manufactured to a predetermined thickness so as to match a desired oscillation frequency by a tape casting method. The polarization that gives piezoelectricity is made in the length direction of the vibration element, and the internal electrodes 20 are formed so as to cross each other in the length direction of the vibration element. These internal electrodes 20 are connected to auxiliary electrodes or external electrodes and serve as input / output terminals.

In addition, a mass load layer is formed as a layer that provides a mass load effect that serves to adjust the resonance frequency of the vibration element. This mass load layer is a polymer substance 50 such as epoxy or piezoelectric dummy layers 60, 60. 'Is formed on the outer surface of the vibration element.

The resonance frequency of the vibration element is changed by the mass load effect, and the rate of change is proportional to the added mass. Therefore, the resonance frequency of the vibration element is adjusted by adjusting the thicknesses of the epoxy layer and the dummy layer.

Hereinafter, a practical example by the configuration of the mass load layer will be described in detail with reference to the drawings.

Example 4
FIG. 14 is a perspective view illustrating an example of a vibration element according to the present invention, and FIG. 15 is a graph illustrating the electrical characteristics of the vibration element illustrated in FIG.

As described above, the resonator element according to the present invention includes the mass load layer to which the polymer material 50 is applied.

The polymer material 50 is applied in a shape covering a part of the external electrode 30, and can be applied to any one or all of the upper and lower surfaces of the vibration element.

As shown in FIG. 20, the manufacturing process of such a vibration element is the same as the manufacturing process of the shear mode vibration element, but the external electrode 30 and the auxiliary electrode 30 are made of Cu / Ag by sputtering vacuum deposition on both ends of the exposed internal electrode 20 by sputtering. After the electrode 40 is formed by vapor deposition to a thickness of 1 μm, in order to give a mass load effect for frequency adjustment, a polymer epoxy is applied with the polymer material 50 and cured, and the thickness of the epoxy layer is 5 μm. Compared to the case without an epoxy layer.

Epoxy can be applied by printing or dispensing, and the curing method can be thermal curing or UV curing.In Example 1, a thermosetting epoxy with a specific gravity of 1.2 g / cm ³ was screen printed. After the application, it was cured at 150 ° C. for 10 minutes. Fig. 15 shows the electrical impedance characteristics of the manufactured vibration element.

When there is no epoxy layer, the resonance frequency is 17.18 MHz, but when the epoxy layer is 5 μm, the resonance frequency is 17.08 MHz, and when the epoxy layer is 10 μm, the resonance frequency is 16.98 MHz. The resonance frequency has been lowered.

Compared with the case where no epoxy layer was applied in Example 4, the rate of change in resonance frequency after application of epoxy was 0.6% when the epoxy layer was 5 μm and 1.2% when the epoxy layer was 10 μm.

When the thickness of the epoxy layer, which is the application range of Example 4, is within 10 μm, the resonant frequency of the vibration element is linearly proportional to the thickness of the epoxy layer, so the vibration element corresponding to the thickness of the epoxy layer is 1 μm. The rate of change of the resonance frequency is about 0.1%.

Therefore, when adjusting the resonance frequency by adjusting the thickness of the vibration element in the example of the conventional technique, the resonant frequency change rate corresponding to the vibration element thickness of 1 μm is approximately 0.7%. It turns out that the method for adjusting the resonance frequency of the vibration element by the formation of the epoxy layer, which was clarified in the example, is excellent. Since the resonance frequency change of the vibration element due to the formation of the epoxy layer is due to the mass load effect, not only the thickness of the epoxy layer but also the application area of the epoxy layer can be adjusted precisely. The resonance frequency can be controlled.

Although not shown in Example 4, there is also an effect that the unnecessary vibration of the vibration element is suppressed by the mass load effect in the epoxy coating, and the safety of oscillation is improved.

Example 5
FIG. 16 is a perspective view illustrating another example of the vibration element according to the present invention, and FIG. 17 is a graph illustrating the electrical characteristics of the vibration element illustrated in FIG.

In Example 5, as another method for adjusting the resonance frequency of the vibration element, the vibration element is manufactured using the same material and manufacturing method as in Example 1, but the resonance frequency of the vibration element is adjusted. However, unlike Example 4, it is possible to adjust the resonance frequency in a large range where the rate of change reaches several percent. As shown in FIG. 16, the resonator element of Example 5 includes dummy layers 60 and 60 ′.

Since the manufacturing process of the resonator element of Example 5 is the same and similar to that of Example 4, the description of the overall manufacturing process is omitted, and only the step of forming the dummy layers 60 and 60 ′ is performed. This will be described in detail.

First, at the stage of stacking the piezoelectric sheets, in addition to the piezoelectric sheet 20 between the internal electrodes 20 of the vibration element, dummy layers 60 and 60 ′ having no internal electrode 20 are stacked on the top and bottom of the laminate constituting the vibration element. To do.

After measuring the resonance frequency of the laminate in which the dummy layers 60 and 60 ′ are formed and adjusting the thickness of the dummy layers 60 and 60 ′ to have the desired resonance frequency, the external electrode 30 and the auxiliary electrode 40 are formed. .

In Example 5, the element length was 2.0 mm, the electrode overlap OL was 0.8 mm, and the external electrode 30 and auxiliary electrode 40 were 0.4 mm long. The electrode overlap OL was symmetrical from the center of the element. The thickness of the sheet was 75 μm due to plastic contraction, and a total of 4 layers were laminated.

The uppermost and lowermost dummy layers 60 and 60 ′ were processed so that 2.5 μm and 5 μm remained, respectively. Fig. 17 shows the electrical impedance characteristics of the manufactured vibration element.

When there is no dummy layer 60, 60 ', the resonance frequency is 17.18MHz, but when the dummy layer 60, 60' is 2.5μm, the resonance frequency is 16.58MHz, and the dummy layer 60, 60 'is 5μm Since the resonance frequency of 16.03 MHz is 16.03 MHz, the thicker the dummy layers 60, 60 ′, the lower the resonance frequency.

Compared to the case without the dummy layers 60 and 60 ′, the change rate of the resonance frequency was 3.5% when the dummy layers 60 and 60 ′ were 2.5 μm, and 6.7% when the epoxy layer was 10 μm.

When the thickness of the dummy layers 60 and 60 ′ is within 10 μm, the resonance frequency of the vibration element is linearly proportional to the thickness of the dummy layers 60 and 60 ′, so that the thickness of the dummy layers 60 and 60 ′ corresponds to 1 μm. The resonance frequency change rate of the vibrating element is about 0.7%.

The industrial applicability of the resonant frequency adjustment method of the resonator element according to Example 5 is as follows. Piezoelectric resonators are made of variously tailored products based on the oscillation frequency. For example, in the case of 12.0 MHz and 12.5 MHz among the oscillation frequency specifications of currently used resonators, conventionally, when manufacturing a vibration element according to each specification, the thickness of the laminated sheet is made differently. However, according to this Example 5, after manufacturing piezoelectric resonators of two specifications of 12.0 MHz and 12.5 MHz using sheets of equal thickness, the dummy layers 60 and 60 ′ are processed to each Since it can be manufactured with products with two specifications of 12.0MHz and 12.5MHz, it is suitable for mass production compared to conventional technology.

Example 6
18 is a perspective view illustrating still another example of the vibration element according to the present invention, and FIG. 19 is a graph illustrating the electrical characteristics of the vibration element illustrated in FIG.

The vibration element of Example 6 is another method for adjusting the resonance frequency, and in the overall configuration, a dummy layer is formed with a thickness of 2.5 μm, which is equal to Example 5, and Example 4 is used at the final stage. The polymer material layer 50 was formed with epoxy equal to.

The electrical impedance characteristics of the manufactured vibration element are as shown in FIG.

When there is no epoxy layer, the resonance frequency is 16.58MHz, but when the epoxy layer is 5μm, the resonance frequency is 16.48MHz, when the epoxy layer is 10μm, the resonance frequency is 16.38MHz, and the change rate of the resonance frequency is each 0.6% and 1.2% when the epoxy layer was 10 μm.

Therefore, when the thickness of the epoxy layer is within 10 μm, the resonance frequency of the vibration element is linearly proportional to the thickness of the epoxy layer, and the resonance frequency change rate of the vibration element corresponding to the thickness of the epoxy layer is about 0.1 %.

The piezoelectric resonator according to the present invention will be described by taking as an example a piezoelectric resonator using the vibration element of the fourth experimental example among the vibration elements configured as described above.

FIG. 21 is an assembled perspective view illustrating an example of a piezoelectric resonator using the vibration element according to the present invention.

As shown in the drawing, the shear mode piezoelectric resonator having a mass load layer according to the present invention includes a laminated base substrate 160 in which a vibration element 140 having a mass load layer and a capacitor are integrally formed.

In the piezoelectric resonator according to the present invention, as shown in FIG. 12, the capacitors CL1 and CL2 constituting the oscillation circuit are configured with capacitances acting between the input electrode and the common electrode and between the output electrode and the common electrode, respectively. A piezoelectric resonator was manufactured using a multilayer base substrate and a cover for protecting the vibration element.

The multilayer base substrate 160 serves as a circuit component having an internal capacitor, and at the same time protects the vibration element 140 so that the piezoelectric resonator can be installed on a board of an electronic device such as a PC. Therefore, it is necessary to maintain an appropriate dielectric constant and sheet thickness for forming a predetermined capacitance and a plastic mechanical strength which is a requirement for the package element.

The manufacturing process of the piezoelectric resonator, such as the production of such a laminated base substrate, the installation of the vibration element, and the adhesion of the cover, will be described in detail.

First, the base substrate 160 is made of MgTiO ₃ dielectric ceramic material having a dielectric constant of 20 inside and outside, and is a sheet having a thickness of 50 μm by the doctor blade tape casting method described in the first example. Molded. After that, Ag / Pd electrodes were printed in an accompaniment by screen printing method so that capacitance was formed between each layer. In this example, CL1 and CL2 were each set to 15pF by printing three times. .

The capacitances of CL1 and CL2 can be adjusted in the range of 3 to 50 pF by adjusting the number of printings and the pattern size.

In the vibration element 140, the auxiliary electrode 40 and the external electrode 30 are respectively installed on the input / output electrodes of the base substrate by a conductive adhesive 164 or solder, and the cover 120 is adhered to the base substrate 160 by an adhesive on the upper part thereof. It comes to serve to protect.

The cover 120 can be made of a metal material or a ceramic material. The oscillation frequency of the piezoelectric resonator can be achieved by adjusting the resonance frequency of the vibration element, and the stacked base substrate 160 can be used to reduce the height of the component, thereby making it small and precise.

Further, a method of performing application of a mass load effect imparting substance such as a polymer epoxy imposed on the vibration element after the vibration element is installed on the base substrate is obvious to those skilled in the art to which the present invention belongs. It should be clarified that the actual example does not limit the scope of the claims of the present invention.

The electrodes of the vibration element are installed on the base substrate and connected to the input / output terminals of the piezoelectric resonator, and if an AC signal is approved, the vibration element causes a specific vibration corresponding to the polarization direction and has a resonance-antiresonance frequency. Since it is electrically equivalent to a judo reactive element in the frequency range between them, it works with a part of the Colpitts oscillation circuit coupled with the inverting amplifier of the IC, and the above-described inherent resonance frequency and oscillation circuit Oscillates at a frequency related to the load doses CL1 and CL2. Therefore, since the oscillation frequency of the piezoelectric resonator is proportional to the resonance frequency of the vibration element, the oscillation frequency of the piezoelectric resonator can be adjusted.

In the shear mode vibration element according to the present invention configured as described above, the resonance frequency of the entire element is determined by the thickness of the laminated sheet, and each sheet vibrates symmetrically with each other. Not only is it easy to fabricate high-frequency piezoelectric resonators, but it also vibrates in thickness shear vibration mode, so that it uses a vibration mode with a large electromechanical coupling coefficient and a large piezoelectric constant. Even if the effective vibration area of the vibration element is relatively small compared to the conventional method that uses the vibration element, the same vibration performance is maintained, which is effective for manufacturing a vibration element that is smaller than the conventional vibration element. It is.

In addition, when a piezoelectric resonator component is manufactured using a multilayer base substrate, a structure that does not require a separate capacitor element is provided, and a resonator component that is small in size but high in frequency can be provided.

Furthermore, when a vibration element having a mass load layer is laminated, a method of adjusting the thickness of a dummy layer formed in advance and a mass substance layer are formed by applying a polymer substance such as a polymer epoxy on the surface of the vibration element. Therefore, the resonance frequency of the vibration element is adjusted by the mass load effect, and more precise frequency adjustment is possible. A piezoelectric resonator is manufactured using a multilayer base substrate with such a vibration element and a capacitor. By doing so, it is possible to mass-produce piezoelectric resonators, and at the same time, it has the effect of facilitating the manufacture of piezoelectric resonators having a precise oscillation frequency through fine adjustment of the oscillation frequency and a low component height.

It is the perspective view which illustrated an example of the conventional vibration element. It is sectional drawing which illustrated the state before a deformation | transformation of a vibration element. FIG. 6 is a cross-sectional view illustrating a deformed state of a piezoelectric body during oscillation of a vibration element. It is the perspective view which illustrated an example of the vibration element by the present invention. It is sectional drawing which illustrated an example of the vibration element by this invention. 5 is a flowchart for explaining a manufacturing process of the resonator element according to the invention. 5 is a graph illustrating an example of electrical characteristics of the vibration element according to the present invention. 5 is a graph illustrating another example of electrical characteristics of the resonator element according to the invention. It is sectional drawing which illustrated another example of the vibration element by this invention. 10 is a graph illustrating an example of electrical characteristics of the resonator element according to the invention illustrated in FIG. 9; 1 is an assembled perspective view illustrating the structure of a piezoelectric resonator according to the present invention. 1 is a circuit diagram illustrating an example of an oscillation circuit having a piezoelectric resonator according to the present invention. 12 is a graph illustrating an example of electrical characteristics of the piezoelectric resonator according to the present invention illustrated in FIG. It is the perspective view which illustrated another example of the vibration element by this invention. 15 is a graph illustrating electrical characteristics of the vibration element illustrated in FIG. It is the perspective view which illustrated another example of the vibration element by this invention. 17 is a graph illustrating electrical characteristics of the vibration element illustrated in FIG. It is the perspective view which illustrated another example of the vibration element by this invention. 19 is a graph illustrating electrical characteristics of the vibration element illustrated in FIG. It is a flowchart for demonstrating another example of the vibrating element by this invention. 1 is an assembled perspective view illustrating an example of a piezoelectric resonator using a vibration element according to the present invention.

Explanation of symbols

10 Piezoelectric sheet
20 Internal electrode 30 External electrode 40 Auxiliary electrode 50 Polymer material 60, 60 ′ Dummy layer 120 Cover 140 Vibration element 160 Base substrate
162 Electrode 164 Conductive adhesive 200 Piezoelectric resonator

Claims (19)

In the vibration element,
It is composed by laminating at least two or more piezoelectric sheets on which internal electrode patterns are printed,
Among the internal electrodes, the input electrodes formed to extend from the middle end to the one side end are interconnected by auxiliary electrodes, and the ends of the output electrodes formed between the input electrodes are mutually connected by the external electrodes. Connected to
A vibration element characterized by being polarized in the length direction so as to vibrate in the length direction. The input electrode and the output electrode of the internal electrode, and the input electrode and the external electrode overlap each other, and the overlapped electrode overlapping portion is symmetric with respect to the center of the vibration element. The vibration element according to claim 1.  2. The vibration element according to claim 1, wherein a separation portion is formed between the auxiliary electrode and the external electrode. 2. The vibration element according to claim 1, wherein the internal electrode, the auxiliary electrode, and the external electrode are formed by any one of a thick film printing method and a vacuum deposition method. In the piezoelectric resonator,
The input electrode formed by laminating at least two or more piezoelectric sheets printed with the internal electrode pattern and extending from the middle end to one side end of the internal electrode is an auxiliary electrode. Are formed between the input electrodes, but the ends of the output electrodes formed so as to partially overlap the input electrodes are connected to each other by external electrodes, and the length direction of the piezoelectric sheet With a polarized vibration element;
A base substrate with an internal capacitor;
A piezoelectric resonator comprising a protective cover for protecting the vibration element. The piezoelectric resonator according to claim 5, wherein the base substrate is one of a laminated type and a single plate type. The piezoelectric resonator according to claim 5, wherein the protective cover is one of pressed metal and compression molded ceramics. The piezoelectric resonator according to claim 5, wherein a capacitance of a capacitor built in the base substrate is 3 to 50 pF. In the vibration element,
Constructed by laminating at least two or more piezoelectric sheets printed with internal electrode patterns corresponding to input / output electrodes, and extended from the middle end to one side end of the internal electrodes The input electrodes are interconnected by auxiliary electrodes, and the end portions of the output electrodes formed between the input electrodes are connected to each other by external electrodes and polarized in the longitudinal direction so as to vibrate in the longitudinal direction. A vibration element, wherein a mass load layer is formed on one or more of the lateral outer surfaces. 10. The mass load layer formed on one or more surfaces among the outer surfaces in the length direction is formed by applying a polymer material to one or more surfaces including the electrode surface. The vibration element described in 1. The mass load layer formed on one or more of the outer surfaces in the length direction has a thickness different from the interval between the inner electrodes on the outer side of the inner electrodes, and is formed on a material such as a piezoelectric sheet. The vibration element according to claim 9, wherein the vibration element is formed by forming one or more dummy layers. The vibration element according to claim 10, wherein the polymer substance is epoxy. The input electrode and the output electrode of the internal electrode, and the input electrode and the external electrode overlap each other, and the overlapped electrode overlapping portion is symmetric with respect to the center of the vibration element. The vibration element according to claim 9. The vibration element according to claim 9, wherein the internal electrode, the auxiliary electrode, and the external electrode are formed by any one of a thick film printing method and a vacuum deposition method. The vibration element according to claim 11, wherein a thickness of the dummy layer is smaller than ½ of an internal electrode interval. In the piezoelectric resonator,
It is constructed by laminating at least two or more piezoelectric sheets on which internal electrode patterns corresponding to input / output electrodes are printed, and is formed so as to extend from the middle end to one side end in the internal electrodes. The input electrodes are interconnected by auxiliary electrodes, and the ends of the output electrodes formed between the input electrodes are interconnected by external electrodes and polarized in the longitudinal direction so as to vibrate in the longitudinal direction, A dummy layer having a thickness different from the interval between the internal electrodes on the outside of the internal electrodes, or by applying a polymer substance to at least a part or all of one or more of the external surfaces in the longitudinal direction And at least one vibration element formed and configured;
A base substrate with an internal capacitor;
A piezoelectric resonator comprising a protective cover for protecting the vibration element. The piezoelectric resonator according to claim 16, wherein the base substrate is a laminated type or a single plate type.  The piezoelectric resonator according to claim 16, wherein the protective cover is one of press metal and compression molded ceramics. The piezoelectric resonator according to claim 16, wherein a capacitance of a capacitor having the base substrate is 3 to 50 pF.

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