JP4593728B2 - Piezoelectric resonator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a piezoelectric resonator having a vibrating electrode facing the central portion of the both main surfaces of the piezoelectric substrate, in particular, it relates to a piezoelectric resonator for third harmonic using thickness longitudinal vibration mode is there.
[0002]
[Prior art]
Generally, a piezoelectric resonator using a thickness longitudinal vibration mode, as shown in FIG. 6, the central portion of the both main surfaces of the piezoelectric substrate 1, the vibrating electrodes 2 and 3 formed so as to face, these vibrations the electrodes 2 and 3, is constructed by connecting the extraction electrodes 5 and 6 drawn out in opposite directions towards the short sides of both main surfaces of the piezoelectric substrate 1, the thickness by the vibration electrodes 2 and 3 facing vertical vibration was expressed resonance characteristics based on such fundamental frequency or the third harmonic, the vertical thickness is excited.
[0003]
Since the resonance frequency of the piezoelectric resonator using a thickness Tatefu dynamic is inversely proportional to the thickness of the piezoelectric substrate 1, in order to realize a piezoelectric resonator having a number 10MHz resonant frequency in a typical piezoelectric material, the fundamental frequency When used, it is necessary to produce a thin piezoelectric substrate 1 of 100 μm or less. Therefore, since it becomes difficult to manufacture a piezoelectric resonator when the resonance frequency is high, when a piezoelectric resonator having a high resonance frequency is manufactured, a harmonic mode such as a third harmonic is generally used. ing.
[0004]
However, in a normal design, the fundamental vibration is generally excited more strongly than the harmonic vibration. Therefore, in order to excite correctly with the harmonic, the impedance peak of the harmonic is at least relative to the fundamental vibration. A large design is required. For this reason, when using harmonics, a tuning circuit for harmonic frequencies is provided on the output side to oscillate with harmonics instead of oscillating at the fundamental frequency. However, a piezoelectric resonator that does not require the use of a tuning circuit has been desired for miniaturization and cost reduction.
[0005]
Conventionally, there has been proposed a quartz crystal vibrator in which a damping material for damping only the fundamental vibration is applied around the vibration electrode by making use of the fact that the spread of the fundamental vibration is slightly wider than the harmonic. As such a crystal resonator, Japanese Patent Laid-Open No. 9-139651 discloses a crystal resonator that excites in a thickness-shear vibration mode in which a metal is disposed on the main surface of an AT-cut crystal piece to suppress fundamental vibration. Thus, a structure in which the third harmonic is vibrated without a tuning circuit is disclosed.
[0006]
As shown in FIG. 7, the crystal resonator disclosed in this publication includes square-shaped vibrating electrodes 12 and 13 provided at the center of both main surfaces of the AT-cut quartz piece 11, 13 are respectively connected to the lead electrodes 15 and 16 drawn in the length direction of the main surface, and the fundamental wave suppression formed at predetermined intervals in the width direction of the main surface of the crystal piece 1 from the vibration electrodes 12 and 13. And the electrode 17.
[0007]
This is to suppress only the fundamental wave by utilizing the difference in the vibration spread between the fundamental wave having a relatively large vibration spread and the harmonic having a relatively small vibration spread.
[0008]
The fundamental wave suppressing electrode 17 is made to have a larger film thickness than the vibrating electrodes 12 and 13 or to deposit a material having a large mass for the purpose of suppressing the vibration of the fundamental wave so as to obtain a large mass. Yes. Further, in this publication, as another example of a crystal resonator, the fundamental wave suppression electrodes 17 facing each other on both main surfaces of the crystal piece 11 are made to conduct through the end surfaces in the width direction of the main surface to suppress the fundamental wave. Is disclosed.
[0009]
[Problems to be solved by the invention]
However, for the purpose of adding an extra mass to the fundamental wave suppressing electrode 17, the film thickness is made thicker than the vibrating electrodes 12, 13, or the fundamental wave suppressing electrode 17 is formed by vapor deposition with a material having a large mass. In order to form such a fundamental wave suppressing electrode 17, an extra resin coating process or a process such as vapor deposition is required, and the accuracy of the film thickness and the like when the fundamental wave suppressing electrode 17 is formed varies. There was a problem that it was difficult to obtain the originally planned characteristics and the yield was deteriorated.
[0010]
In this way, a structure that suppresses only the fundamental wave by using only the difference in spread between the vibration modes of the fundamental wave and the harmonic wave, and does not suppress the harmonic wave is particularly accurate in a high-frequency resonator. Since it requires formation of a high fundamental wave suppression electrode shape and a resin coating technique, it has been difficult to implement.
[0011]
Further, in the quartz resonator disclosed in Japanese Patent Laid-Open No. 9-139651, the fundamental wave leaking from between the vibrating electrodes can be suppressed, but the fundamental wave remaining between the vibrating electrodes cannot be actively leaked. was there.
[0012]
Invention, it is an object to provide a more simple and effective possible to suppress the fundamental wave, a piezoelectric resonator for harmonic resonating in thickness Tatefu very much over de.
[0013]
[Means for Solving the Problems]
The piezoelectric resonator of the present invention, both main surfaces and a rectangular piezoelectric substrate is rectangular, a pair of which are arranged to face each other with the piezoelectric substrate to a center portion of the both main surfaces of the piezoelectric substrate a vibration electrode, said being arranged on the both main surfaces of the piezoelectric substrate, together with the respective one end is connected to the vibration electrode, toward the end face of the opposite side in the length direction before Symbol piezoelectric substrate One end of the pair of extraction electrodes drawn in opposite directions and the vibration electrode on both main surfaces of the piezoelectric substrate and both end surfaces in the width direction of the piezoelectric substrate are predetermined to the vibration electrode. The vibration electrode is made of the same material and has the same thickness so as to be adjacent to each other with the other end thereof in contact with the end surface in the width direction of the piezoelectric substrate and to face each other through the piezoelectric substrate. 2 pairs of 1st fundamental wave leakage A piezoelectric resonator using third-order harmonic of a thickness extensional vibration and a conductor, when viewed in plan, the center in the length direction of the piezoelectric substrate of the vibrating electrode, the piezoelectric of the vibrating electrode The substrate is recessed toward the center in the width direction of the substrate .
[0014]
By adopting such a configuration, not only the vibration that causes the ripples that are easily leaked and attenuated originally, but also the energy confinement is relatively good, and it is difficult to be attenuated by attaching a resin or the like around the vibrating electrode. The fundamental vibration can also be leaked to the long side (end face) of the piezoelectric substrate through the first fundamental wave leakage conductor without affecting the desired vibration (third harmonic) and is excited by the vibration electrode. The fundamental wave and the leakage wave (fundamental wave) reflected from the end face of the long side are caused to interfere, and the peak of the amplitude of the fundamental wave vibration mode can be output outside the vibrating electrode. Impedance peaks due to vibration can be suppressed. In addition, when viewed in plan, the central portion of the vibrating electrode in the length direction of the piezoelectric substrate is recessed toward the central portion of the vibrating electrode in the width direction of the piezoelectric substrate. When shifting from the center of the vibrating electrode toward the end face in the width direction of the piezoelectric substrate, the area of the vibrating electrode that overlaps the portion where the amplitude of the fundamental wave is large is reduced, so that the impedance peak due to vibration of the fundamental wave is further suppressed. Can do.
[0015]
That is, there is a conventional piezoelectric resonator in which a plurality of conductors are provided around a vibrating electrode. However, these originally leaked easily and caused a vibration causing ripples. In this piezoelectric resonator, energy is relatively placed between the vibrating electrodes. It has been difficult to attenuate a fundamental wave that is easily trapped.
[0016]
Further, in the conventional third-order harmonic piezoelectric resonator using thickness longitudinal vibration, as shown in FIG. 8, the fundamental vibration component 20 and the third-order harmonic vibration component 21 are vibrations at the center of the piezoelectric substrate. The excess fundamental vibration that is present near the electrode and is relatively easy to confine energy in the vibration electrode is difficult to leak from the vibration electrode, but in the present invention, the first basic material having the same material and the same thickness as the vibration electrode. Since the wave leakage conductor is provided between the vibrating electrode and the long side, the desired vibration (third harmonic) in which energy is strongly confined between the vibrating electrodes as shown in FIG. However, the vibration (fundamental vibration) that causes the ripple to be confined weaker than the desired vibration is guided to the long side end face of the piezoelectric substrate through the first fundamental wave leakage conductor having a different potential difference, and the vibration Basics from electrodes When, a reflecting fundamental wave reflected from the end face of the long sides, causing interference in the first fundamental wave leakage conductor, it is possible to reduce the impedance peaks due to the fundamental vibration.
[0017]
In addition, because the first fundamental wave leakage conductor with the same material and thickness is used, the vibration electrode, extraction electrode and fundamental wave leakage conductor must be formed together in the process of forming the vibration electrode and extraction electrode. Therefore, the fundamental wave leakage conductor can be easily manufactured with high accuracy because it is formed by the same process. In order to separate the fundamental wave from the vibration electrode, it is desirable that the length of the first fundamental wave leakage conductor is the same as that of the vibration electrode.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
In the piezoelectric resonator shown in FIG. 1, vibration electrodes 32 and 33 are formed so as to face each other at the center of both main surfaces of the piezoelectric substrate 31, and both main surfaces of the piezoelectric substrate 31 are formed on these vibration electrodes 32 and 33. Are connected to lead electrodes 35 and 36 drawn in opposite directions toward the short side.
[0022]
A first fundamental wave leakage conductor 39 having the same material and the same thickness as the vibrating electrodes 32 and 33 is provided on the long sides of the vibrating electrodes 32 and 33 on the main surface of the piezoelectric substrate 31. The length L of the first fundamental wave leakage conductor 39 is the same as the length of the vibrating electrodes 32 and 33.
[0023]
The vibrating electrodes 32 and 33, the extraction electrodes 35 and 36, and the first fundamental wave leakage conductor 39 are, for example, applied and baked with a conductive paste containing Ag, Ag-Pd, Ag-glass, Pd, or It is formed by sequentially depositing Cu, Ni, and Au thin films.
[0024]
The first fundamental wave leakage conductor 39 extends to the end face (long side) in the width direction of the piezoelectric substrate 31, and the vibration electrodes 32 and 33 and the first fundamental wave are broken so that the energy confinement of only the fundamental wave is broken. A predetermined interval is provided between the wave leakage conductor 39. The distance x between the vibrating electrodes 32 and 33 and the first fundamental wave leakage conductor 39 is set to a thickness t of the piezoelectric substrate 31 so as not to be in a region (between vibrating electrodes) where the third and higher harmonic modes are confined. It is desirable to set it to 1/2 or more.
[0025]
The Rukoto provided a first fundamental wave leakage conductor 39, because it is possible to leak the fundamental wave vibration to the outside of the vibrating electrodes 32 and 33, the fundamental wave which leaks are excited by the vibration electrodes 32 and 33, leakage by Ru to cause interference with the reflected wave reflected from the end face in the width direction of the piezoelectric substrate 31 (long side) and can win suppress the impedance peak of the fundamental wave.
[0027]
That is, for example, in the conventional thickness longitudinal resonator, since the width W of the piezoelectric substrate is wide, as shown in FIG. 2A, the amplitude is increased only in a region slightly larger than the vibration electrode, and energy confinement is established. However, when the width of the main surface of the piezoelectric substrate is narrowed and brought closer to the electrode width, energy confinement becomes worse as shown in FIG. 2B, and the vibration wave reaching the end in the width direction appears on the end surface. It rebounds and changes to a mode that has wave strength in the width direction in addition to the thickness longitudinal vibration. The repetition wavelength of the intensity changes depending on the material and thickness of the piezoelectric substrate. By further reducing the width of the substrate, a vibration amplitude pattern with a small fundamental wave at the center of the vibration electrode as shown in FIG. Can be made.
[0028]
At this time, the resonance peak of impedance due to fundamental wave vibration is suppressed, but if the width of the substrate is wide enough not to reach the harmonic vibration mode, the harmonic vibration mode is as shown in FIG. However, the energy confinement remains well established, and the resonance peak is not suppressed.
[0029]
Can generate a mode as shown in FIG. 2 (c) only by design width w of the piezoelectric substrate 31 as long as the piezoelectric resonator using the third harmonic mode until about 20MHz in the piezoelectric ceramic of normal Oh Ru.
[0030]
However, reducing the thickness t of the piezoelectric substrate 31 to 100μm or less in order to correspond to the high frequency while reducing the width w of the piezoelectric substrate 31 so that the vibration mode of the shown in FIG. 2 (c) occurs, the piezoelectric group The strength of the plate 31 is significantly reduced, and the yield in manufacturing and mounting of the piezoelectric substrate 31 is reduced. According to the piezoelectric resonator of this example, by using the first fundamental wave leakage conductor 39 , the fundamental wave is transmitted to the width of the piezoelectric substrate 31 without bringing the end face in the width direction of the piezoelectric substrate 31 close to the vibration electrodes 32 and 33. it is possible by leaking to the end face direction is reflected by the end surface, that eliminates the need for small fence width w of the piezoelectric substrate 31.
[0031]
Accordingly, the present invention is particularly, Ru suitably used for a piezoelectric resonator used in the above resonance frequency 20MHz. Further , in order to leak the fundamental wave and perform the energy confinement of the third harmonic with high accuracy, the vibrating electrodes 32 and 33 , the extraction electrodes 35 and 36 , and the first fundamental wave leakage conductor are formed by a single thin film formation process. 39 may be formed. The distance x between the first fundamental wave leakage conductor 39 and the vibrating electrodes 32 and 33 is slightly dependent on the electrode thickness, but is preferably about ½ of the thickness of the piezoelectric substrate 31 .
[0032]
In the present invention, as shown in FIG. 4, the rectangular recess 51 (FIG. 4A) or the arc-shaped recess 53 (FIG. 4) is formed on the vibration electrode 32 , 33 on the first fundamental wave leakage conductor 39 side. you form a 4 (b)). This is because, as shown in FIG. 3, the peak of the fundamental wave is more first fundamental wave leakage-guide body 39, but Ru can be separation between the third harmonic to the long side of the piezoelectric substrate 31 , the vibration distribution of the fundamental wave is superposed with the end of the vibrating electrodes 32 and 33, a portion of the vibration electrodes 32 and 33 overlapping with the fundamental wave, by removing as shown in FIG. 4, further, the basic This is because it is possible to attenuate the impedance peak of the wave.
[0033]
In addition, as shown in FIG. 5, the vibration electrode 32, 33 and the vibration electrode 32, 33 between the vibration electrode 32, 33 and the short side opposite to the extraction direction of the extraction electrode 35, 36 connected to the vibration electrode 32, 33. 33 and at a short side with a predetermined interval, the same material as the vibrating electrodes 32 and 33, the same thickness, Rukoto provided with the second fundamental wave leakage conductor 55 having the same width is also conceivable. In such a piezoelectric resonator, it is a Yasukusu Turkey leakage also fundamental vibration in the short side direction of the piezoelectric substrate.
[0034]
The piezoelectric resonator of the present invention, breaking around the vibrating electrodes 32 and 33, rather than as an attenuation electrode having a larger weight than the vibration electrodes 32 and 33, the same material, the confinement energy of the fundamental wave having the same thickness By providing a fundamental wave leakage conductor with a role, the impedance peak of the fundamental wave can be attenuated as described above, the impedance peak of the third harmonic can be kept high, and the vibration of the third harmonic can be made to stand out. Can do.
[0035]
【The invention's effect】
The piezoelectric resonator of the present invention, not only those originally liable to be attenuated easily leak energy, relatively energy trapping good hardly be attenuated by placing a resin or the like around the vibrating electrodes 32 and 33, the ripple causing the fundamental vibration, without affecting the third harmonic, Ru can be guided to the long side of the piezoelectric substrate 31 (the end face) via the first fundamental wave leakage conductor 39. Then , interference between the fundamental wave excited by the vibrating electrodes 32 and 33 and a leaky wave (fundamental wave) reflected from the end face of the long side is caused, thereby sufficiently suppressing an impedance peak due to vibration of the fundamental wave. can Ru. This makes it possible to obtain not necessary to provide a tuning circuit utilizing only the third harmonic, a piezoelectric resonator corresponding to a low-cost high frequency small.
[Brief description of the drawings]
[1] shows the pressure conductive resonators, (a) is a perspective view, (b) is a plan view.
FIG. 2 is an explanatory diagram showing changes in the form of a fundamental vibration mode by changing the width of a piezoelectric substrate.
FIG. 3 is an explanatory diagram showing a state where a fundamental vibration component and a third harmonic vibration component are separated.
FIGS. 4A and 4B show an example in which a concave portion is formed on the fundamental wave leakage conductor side of a vibrating electrode, in which FIG. 4A is a plan view showing a state in which a rectangular concave portion and FIG. It is.
FIG. 5 is a plan view showing a state in which a second fundamental wave leakage conductor is formed between a vibrating electrode and a short side.
6A and 6B show a conventional piezoelectric resonator, in which FIG. 6A is a perspective view and FIG. 6B is a plan view.
FIG. 7 is a plan view showing a conventional crystal resonator.
8 is an explanatory view showing a state where the fundamental vibration forming minute third harmonic component of a conventional piezoelectric resonator is present superimposed.
[Explanation of symbols]
31 ... Piezoelectric substrates 32, 33 ... Vibrating electrodes 35, 36 ... Extraction electrodes 39 ... First fundamental wave leakage conductors 51, 53 ... Recesses 55 ... Second fundamental wave leakage Conductor W ... piezoelectric substrate width t ... piezoelectric substrate thickness

Claims (2)

A rectangular parallelepiped piezoelectric substrate having both principal surfaces rectangular;
A pair of vibration electrodes disposed to face each other with the piezoelectric substrate to a center portion of the both main surfaces of the piezoelectric substrate,
Wherein said piezoelectric substrate is disposed on both main surfaces, together with the respective one end is connected to the vibrating electrodes, in opposite directions toward the end face of the opposite side in the length direction before Symbol piezoelectric substrate A pair of extracted electrodes ,
One end of the piezoelectric substrate is adjacent to the vibration electrode at a predetermined interval between the vibration electrode on both the main surfaces of the piezoelectric substrate and the both end surfaces in the width direction of the piezoelectric substrate, and the other end of the piezoelectric substrate. Two pairs of first fundamental wave leakage conductors having the same material and the same thickness as the vibrating electrode, disposed so as to be in contact with the end face in the width direction and facing each other with the piezoelectric substrate interposed therebetween. A piezoelectric resonator using a third harmonic of thickness longitudinal vibration comprising :
When viewed in plan, the center of the vibration electrode in the length direction of the piezoelectric substrate is recessed toward the center of the vibration electrode in the width direction of the piezoelectric substrate . 2. The piezoelectric resonance according to claim 1, wherein a length of the first fundamental wave leakage conductor in a length direction of the piezoelectric substrate is the same as a length of the vibration electrode in a length direction of the piezoelectric substrate. Child.

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