JP3939992B2 - Method for manufacturing piezoelectric resonator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a piezoelectric resonator.
[0002]
[Prior art]
As a conventional piezoelectric resonator using a piezoelectric resonator, for example, an oscillator using a piezoelectric resonator 53 made of quartz as shown in FIG. 6 is known. The piezoelectric resonator 53 includes a piezoelectric substrate 530, drive electrodes 531 and 533, and extraction electrodes 532 and 534. The piezoelectric substrate 530 is composed of a rectangular plate-like base portion 530a and wedge portions 530b formed on both sides of the base portion 530a and gradually decreasing in thickness toward the distal end portion in the length direction. The drive electrodes 531 and 533 are formed as follows. The base portion 530a having a uniform thickness is formed so as to face both main surfaces.
[0003]
The drive electrodes 531 and 533 are connected to lead electrodes 532 and 534, respectively, and are drawn out to one wedge portion 530b.
[0004]
Although not shown, the piezoelectric resonator 53 is formed on the bottom surface of the cavity of the ceramic package by using a conductive resin paste on a ceramic package or the like that is a storage container, on the bottom surface of the cavity of the ceramic package. It was connected and fixed to the electrode pad to constitute an oscillator.
[0005]
Such a piezoelectric resonator 53 is connected and fixed to a storage container such as a ceramic package as described above, and then, as shown in FIG. 7, Ag or the like is vapor-deposited on the drive electrode 531 on one main surface, The oscillation frequency has been adjusted by irradiating Ar ions and thinning the Au layer on the surface.
[0006]
[Problems to be solved by the invention]
However, in such a rolling resonator, thickness shear vibration is mainly used as a vibration mode, and the oscillation frequency is determined by the thickness of the base portion 530a of the piezoelectric substrate 530 on which the drive electrodes 531 and 533 are formed. The thickness of the base portion 530a of the piezoelectric substrate 530 can be reduced only to about 20 μm (that is, a thickness capable of oscillation at 80 MHz with a fundamental wave) because the piezoelectric resonator 53 is difficult to handle when it is thin. could not. That is, it can only oscillate at 80 MHz or less, and it has been difficult to oscillate at a high frequency of 100 MHz or more using the fundamental wave.
[0007]
On the other hand, there has conventionally been a method of oscillating a vibrator using a third harmonic. That is, when an oscillation circuit such as a Colpitts circuit is manufactured by combining the piezoelectric resonator 53 made of quartz with an inverter, a transistor, or the like, if a feedback resistor Rf having a value of several KΩ to several tens KΩ is used, the third harmonic is obtained. Although it was possible to fabricate an oscillator capable of oscillating, it was necessary to determine the numerical value of the feedback resistor Rf used in the oscillation circuit, such as the feedback resistor Rf.
[0008]
However, even when the numerical value of the feedback resistor Rf is determined in this way, if conditions such as voltage and temperature change, oscillation occurs in an undesired order such as oscillation at a higher order than the fundamental wave or even a third harmonic wave. It may be difficult to operate reliably.
[0009]
In addition, since the oscillation frequency is determined by the thickness of the base portion 530a, it is necessary to strictly control the thickness by etching or the like, making it difficult to manufacture and increasing the manufacturing cost.
[0010]
Furthermore, fine adjustment of the oscillation frequency was performed by a method such as vapor-depositing Ag or the like on the drive electrode 531 on one main surface, or thinning the Au layer on the surface of the drive electrode 531 by irradiating Ar ions. In such a method, since the frequency adjustment is performed by changing the weight of the drive electrode 531, the frequency change due to the weight change of the drive electrode 531 is small, and it is difficult to adjust the oscillation frequency.
[0011]
An object of the present invention is to provide a piezoelectric resonator and a piezoelectric resonance device that can resonate at a high frequency using a fundamental wave, can easily adjust the resonance frequency, and are inexpensive.
[0016]
[Means for Solving the Problems]
The method for manufacturing a piezoelectric resonator according to the present invention is such that a drive electrode is formed on both opposing main surfaces of the front end portion of the wedge portion of the piezoelectric substrate having a wedge portion whose thickness gradually decreases toward the front end via the front end of the wedge portion. A continuous body is formed, and a wedge electrode tip portion of the drive electrode continuum is simultaneously polished together with the wedge tip end, and drive electrodes are formed on both main surfaces of the wedge tip end portion, respectively.
[0017]
According to such a manufacturing method, first, a continuous drive electrode continuous body is formed at the front end of the wedge portion via the front end of the wedge portion, and then, along with the front end of the wedge portion, the front end portion of the drive electrode continuous body (drive electrode) The driving electrode can be formed on both main surfaces of the front end portion of the wedge portion by polishing and removing the bridge portion) with a rotating grindstone or the like. In particular, by setting the thickness of the wedge tip to a frequency that is slightly higher than the oscillation frequency, the amount of polishing removal at the wedge tip can be minimized, and damage during polishing and polishing time are minimized. Limit. In order to drive the frequency, when polishing the tip of the wedge while monitoring the oscillation frequency, the drive electrode is polished so that the thickness of the wedge increases, so the resonance frequency is moved to the low frequency side to obtain the desired frequency. Can do.
[0018]
In this way, the drive electrode continuum is formed at the wedge tip, and then the wedge electrode tip side of the drive electrode continuum is simultaneously polished together with the wedge tip, and the drive electrode is made small to fit the optimum size. As a result, it becomes possible to obtain a piezoelectric resonator having stable and good electrical characteristics, and it is possible not only to adjust the frequency but also to adjust the resonance frequency in a lower direction, As a result, the yield is improved and the production efficiency is improved. As a result, it becomes possible to stably supply a vibrator capable of oscillating at a high frequency of 100 MHz or more, particularly 100 shells 00 MHz, and the design efficiency and production efficiency. Can be improved dramatically.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a piezoelectric resonator manufactured by the manufacturing method of the present invention will be described in detail with reference to the drawings. FIG. 1 is a perspective view of a piezoelectric resonator using a piezoelectric substrate made of quartz, and FIG. 2 is a side sectional view of the piezoelectric resonator. The piezoelectric resonator 3 includes a piezoelectric substrate 30 made of quartz, and a drive electrode 31. , 32 and lead electrodes 33, 34. The piezoelectric substrate 30 is a concept including a substrate made of quartz, ceramics, or single crystal having piezoelectricity.
[0022]
The piezoelectric substrate 30 is cut according to a predetermined crystal orientation angle (AT cut), and is configured by providing a wedge portion 30b having a trapezoidal side surface on both sides in the length direction of a rectangular plate-shaped base portion 30a. The inclined surfaces of both main surfaces of the wedge portion 30b are formed by bevel processing or convex processing. Since the piezoelectric substrate 30 has the base portion 30a having a large thickness, even a resonator used at a high frequency can increase the strength.
[0023]
The piezoelectric substrate 30 may be a case where an inclined surface is formed on one surface of the wedge portion 30b. In this case, the lower surface of the base portion 30a and the lower surface of the wedge portion 30b are the same plane, and the upper surface of the wedge portion 30b is an inclined surface. The inclined surface is formed by bevel processing or convex processing, but it is needless to say that processing such as etching may be used. In terms of ease of manufacture, bevel processing or convex processing is desirable.
[0024]
As shown in FIG. 2, the piezoelectric substrate 30 has the thinnest wall portion 300a (the tip of the wedge portion 30b) having the thinnest thickness at both ends in the direction along the long side, and is most at the center in the long side direction. A thick base 30a is formed. The thickness of the thinnest wall portion 300a is 0.2 times or more the thickness of the base portion 30a. The taper of the inclined surface formed between the thinnest wall portion 300a and the base portion 30a is 2/100 or less.
[0025]
That is, when the length of the wedge portion 30b of the piezoelectric substrate 30 is L, the thickness of the thinnest portion 300a is t1, and the thickness of the base portion 30a is t2, t2> t1 ≧ 0.2t2, and the taper of each inclined surface is The total taper is represented by (t2-t1) / 2L, and the total taper is (t2-t1) / L ≦ 2/100.
[0026]
When the thickness of the thinnest portion 300a is t1 and the thickness of the base portion 30a is t2, t1 ≧ 0.2t2 is the reason that the thinnest portion 300a is beveled even when the piezoelectric substrate 30 having a thickness of several microns is manufactured. Since the processing variation of the piezoelectric substrate 30 due to the above can be suppressed to 20% or less, the desired resonance frequency can be obtained by forming the drive electrodes 31 and 32 at a desired position between the thinnest portion 300a and the base portion 30a. This is because it can be obtained with good reproducibility. In particular, from the viewpoint of placing the drive electrodes 31 and 32 on the front end portion of the wedge portion 30b of the piezoelectric substrate 30, it is desirable to suppress the thickness processing variation of the front end portion to 5% or less.
[0027]
The total taper (t2−t1) / L is set to 2/100 or less because the energy confinement by the drive electrodes 31 and 32 is not greatly broken, and the thickness distribution of the drive electrodes 31 and 32 is devised. This is because, by gradually increasing the thickness of the drive electrodes 31 and 32 toward the thinnest portion 300a, a vibration mode close to the fundamental vibration that can be originally realized by a flat plate can be realized. In particular, since the thickness of the drive electrodes 31 and 32 formed by vapor deposition or the like is 1 μm or less, in order to realize a vibration condition near a flat plate by simulating the thickness distribution of the drive electrodes 31 and 32, This is because the difference between the substrate thickness at the thinnest portion 300a side end of the drive electrodes 31 and 32 and the substrate thickness at the base 30a side end is preferably equal to or less than the thickness of the drive electrodes 31 and 32.
[0028]
The length of the piezoelectric substrate 30 is 0.5 to 5.0 mm because it can be processed by bevel processing and convex processing, and the total taper (t2-t1) / L of the inclined surface is 2/100 or less. Is desirable. The average thickness of the thinnest thickness portion 300a and the thickness t2 of the base portion 30b, that is, the average thickness of the piezoelectric substrate is set to match a desired oscillation frequency.
[0029]
In the above example, inclined surfaces are formed on both sides of the wedge portion 30b, and the total taper (t2-t1) / L of the inclined surface in this case is set to 2/100 or less, but the inclined surface is formed only on one main surface. In the case where the other main surface is a flat surface, the taper may be viewed as a thin portion and a thick portion, and similarly, (t2-t1) / L may be 2/100 or less. desirable.
[0030]
Further, drive electrodes 31 and 32 are formed on both main surfaces of the wedge portion 30b formed on the right side in FIGS. 1 and 2, and the drive electrodes 31 and 32 are provided on the left wedge portion in FIGS. The lead electrodes 33 and 34 formed on 30 b are connected via lead lines 312 and 322. The extraction electrodes 33 and 34 are continuously formed so as to face both main surfaces of the tip of the wedge portion 30b.
[0031]
By forming the extraction electrodes 33 and 34 on the left wedge 30b, the piezoelectric resonator can be supported and fixed as a cantilever in the storage container, so that the vibration of the drive electrodes 31 and 32 is not hindered. When the conductive adhesive is fixed to the storage container, the conductive adhesive is not damaged due to stress during curing, and the frequency temperature characteristics are not deteriorated due to the stress. In other words, when the piezoelectric resonator is fixed by supporting both ends, the thinner the piezoelectric substrate is, the more likely it is to inhibit vibration and the influence of stress during curing of the conductive adhesive. The above-mentioned problem can be prevented because it can be fixed with
[0032]
Note that the wedge portion 30b may be provided only on one side of the base portion 30a. In this case, the piezoelectric resonator can be reduced in size, and an extraction electrode is provided on the base 30a, and the thick base 30a is fixed to the storage container. Therefore, the piezoelectric resonator can be securely fixed to the storage container.
[0033]
In the piezoelectric resonator of the present invention, as shown in FIG. 3, the tip of the wedge portion 30 b and the tip of the drive electrodes 31, 32 are simultaneously polished by the rotating grindstone 7 or the like, and the tip of the wedge portion 30 b is formed on the tip surface of the piezoelectric substrate 30. The tips of the drive electrodes 31 and 32 are exposed on the same plane. In other words, the tip of the wedge 30b and the tips of the drive electrodes 31 and 32 exist on the polished surface.
[0034]
For such a piezoelectric resonator 3, first, a substrate made of a rectangular crystal is prepared, inclined surfaces are formed on both ends of the rectangular shape by bevel processing or convex processing, and wedge portions 30 b are formed on both sides of the base portion 30 a. The piezoelectric substrate 30 on which is formed is manufactured.
[0035]
Thereafter, a mask having a predetermined shape is disposed on the upper and lower surfaces of the piezoelectric substrate 30, and Au, Ag, Cr, etc. are vapor-deposited using means such as vapor deposition and sputtering, and the drive electrode continuum 37 (described later). By this polishing, the drive electrodes 31 and 32 are formed), lead electrodes 33 and 34, and lead lines 312 and 322 are formed. The drive electrode continuum 37 is formed by connecting the drive electrodes 31 and 32 with a bridge portion 310 formed on the distal end surface of the wedge portion 30b. The drive electrodes 31 and 32 may be formed without forming the drive electrode continuum 37, but as shown in FIG. 2 before polishing, the tips of the drive electrodes 31 and 32 are the tips of the wedge portions 30b. Being present on the surface is desirable because the resonance frequency control width is increased.
[0036]
Then, as shown in FIG. 3, the resonance frequency is controlled by polishing the bridge portion 310 of the drive electrode continuous body 37 with the rotating grindstone 7 or the like from the tip of the piezoelectric substrate 30, that is, the tip of the wedge portion 30b. The continuum 37 is separated into drive electrodes 31 and 32. As a result, the frequency can be adjusted in the direction of decreasing the resonance frequency. As a result, the room for making good products by frequency adjustment increases, so that the yield can be increased and high production efficiency can be realized.
[0037]
After the frequency adjustment by polishing, as shown in FIG. 4, the base electrode 30a side portion of the drive electrodes 31, 33 may be removed by irradiating the laser beam from above to adjust the frequency to the high frequency side. good.
[0038]
Further, the frequency adjustment by the polishing of the present invention described above may be performed as a frequency coarse adjustment step, and then a method using an ion gun such as Ar ion irradiation may be used in combination as the frequency fine adjustment step.
[0039]
In the piezoelectric resonator 3 of the present invention, frequency adjustment for compensating for thickness variation can be performed. That is, since the thickness of the piezoelectric substrate 30 is gradually reduced from the base portion 30a toward the thinnest portion 300a, even if the wedge portion 30b on which the drive electrodes 31 and 32 are formed varies in thickness, an appropriate drive electrode 31 is provided. , 32 can be selected to obtain a substantially desired resonance frequency, and further, the tip of the drive electrode 31, 32 is simultaneously polished from the tip of the piezoelectric substrate 30 together with the tip of the wedge portion 30b. Can be fine-tuned.
[0040]
Such a piezoelectric resonator is accommodated in a storage container to produce a piezoelectric resonance device. FIG. 5 shows a piezoelectric resonator. A piezoelectric resonator 3 as shown in FIGS. 1 and 2 is accommodated in a storage container 41 made of a ceramic package, and lead terminals 33 and 34 of the piezoelectric resonator 3 are electrically conductive. The adhesive lid 43 is bonded and fixed to the inner bottom surface of the storage container 41, and a metal lid 45 is bonded to the opening of the storage container 41 via an annular seal ring 44.
[0041]
That is, the lead terminals 33 and 34 of the piezoelectric resonator 3 are connected to the electrode pad 47 on the inner bottom surface of the storage container 41 via the conductive adhesive 43, and this electrode pad 47 is formed on the lower surface of the storage container 41. The external electrode 49 is electrically connected.
[0042]
Note that the above-described frequency adjustment by polishing and laser beam irradiation is preferably performed after the piezoelectric resonator 3 is bonded and fixed in the storage container 41 from the viewpoint of reliable frequency adjustment.
[0043]
【The invention's effect】
In the piezoelectric resonator of the present invention, by providing the drive electrode on the wedge portion whose thickness gradually decreases toward the tip, the resonance frequency can be set to 100 MHz or more, and the piezoelectric substrate has a thick portion, so that the strength is high. Expensive. Further, the drive electrode is formed on a wedge portion having an inclined surface, and a desired resonance frequency can be obtained to some extent by controlling the formation position of the drive electrode. Furthermore, the resonance frequency can be finely adjusted by polishing the tip of the wedge portion and the tip of the drive electrode.
[0044]
Further, even when a piezoelectric substrate made of quartz manufactured by bevel processing or convex processing is used, a piezoelectric resonator made of quartz that can resonate at a high frequency of 100 MHz or more using a fundamental wave can be provided at low cost.
[Brief description of the drawings]
FIG. 1 is a perspective view of a piezoelectric resonator according to the present invention.
FIG. 2 is a side sectional view of FIG.
FIG. 3 is an enlarged view of a main part for explaining frequency adjustment of the piezoelectric resonator.
FIG. 4 is a cross-sectional view of an essential part for explaining frequency adjustment by laser light irradiation.
FIG. 5 is a cross-sectional view showing a piezoelectric resonance device of the present invention.
FIG. 6 is a perspective view of a conventional piezoelectric resonator.
7 is a perspective view for explaining frequency adjustment of the piezoelectric resonator of FIG. 6; FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 3 ... Piezoelectric resonator 30 ... Piezoelectric substrate 30b ... Wedge part 31, 32 ... Drive electrode 37 ... Drive electrode continuous body 41 ... Storage container

Claims (1)

A drive electrode continuum continuous through the wedge portion tip is formed on both opposing main surfaces of the wedge portion tip portion of the piezoelectric substrate having a wedge portion whose thickness gradually decreases toward the tip, and the wedge tip In addition, a method for manufacturing a piezoelectric resonator is characterized in that a front end portion of a wedge portion of the drive electrode continuous body is simultaneously polished to form drive electrodes on both main surfaces of the front end portion of the wedge portion.

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