JP3909249B2 - Piezoelectric resonator and method for manufacturing piezoelectric resonator device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a piezoelectric resonator and 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. 5 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 by using conductive resin paste on a ceramic package or the like that is a storage container, and lead electrodes 532 and 534 formed on the bottom surface of the piezoelectric substrate 530 are formed on the bottom surface of the cavity of the ceramic package. It was configured to be connected and fixed to the electrode pad.
[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. 6, 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 piezoelectric 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 the piezoelectric resonator 53 that can oscillate, 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]
The present invention can be resonant at a high frequency with a fundamental wave, and an object thereof is adjustment of the resonance frequency to provide a method for producing easily piezoelectric resonator and a piezoelectric resonator.
[0012]
[Means for Solving the Problems]
Method for manufacturing a piezoelectric resonator of the present invention includes the steps of: preparing a piezoelectric substrate having a wedge portion which becomes gradually thinner toward the tip thickness, the driving electrode disposed to face both major surfaces opposing the wedge portion formed a step of, characterized in that it and a step of trimming by a laser beam the thinnest portion in thickness of the thickest portion the thickness of the driving electrodes is wedge portion formed, and / or the wedge portion.
[0013]
In the piezoelectric resonator according to the present invention, by providing the drive electrode on the wedge portion whose thickness gradually decreases toward the tip, the resonance frequency of 100 MHz or more can be obtained using the fundamental wave, and the piezoelectric substrate is thick. High strength due to having part. Further, since the drive electrode is formed on a wedge portion having an inclined surface, and the thickness of the wedge portion sandwiched between the drive electrodes varies depending on the formation position of the drive electrode, the drive electrode formation position is controlled to some extent. A desired resonance frequency can be obtained.
[0014]
Furthermore, in the present invention, since the drive electrode is provided on the wedge portion whose thickness gradually decreases toward the tip, a piezoelectric substrate made of quartz manufactured by bevel processing or convex processing, which is excellent in mass production but has relatively low processing accuracy. As described above, since the resonance frequency can be easily adjusted, a piezoelectric resonator made of a crystal that can resonate at a high frequency of 100 MHz or higher using a fundamental wave can be provided.
[0015]
In the present invention, the portion of the drive electrode formed in the portion where the wedge portion is thickest and / or the portion of the drive electrode formed in the portion where the wedge portion is thinnest is trimmed by laser light. As a result, the drive electrode can be formed in the wedge portion having the optimum thickness along with the dimensional control of the drive electrode, and the resonance frequency can be finely adjusted.
[0016]
For example, first, drive electrodes are formed on both main surfaces of a piezoelectric substrate made of quartz that are substantially rectangular and slightly longer in the direction along the long side of the piezoelectric substrate (inclination direction) than the optimum design value. The direction along the long side of the electrode, that is, the portion with the thickest wedge portion where the drive electrode is formed and / or the portion with the thinnest wedge portion is irradiated with laser light, and the irradiated drive electrode Remove the part.
[0017]
This makes it possible to stably obtain a piezoelectric resonator having good electrical characteristics and to adjust the frequency by processing the drive electrode small and adjusting it to an optimum size. In addition, it is possible to adjust the resonance frequency in either the increasing direction or decreasing direction. As a result, the yield is improved and the production efficiency is improved. A resonator capable of oscillating at a high frequency of 100 to 300 MHz can be stably supplied, and design efficiency and production efficiency can be dramatically improved.
[0018]
Further, in the present invention, the piezoelectric substrate is made of quartz, a pair of drive electrodes formed to face the both main surfaces of the wedge portion are desirable to be trimmed at the same time and in the same shape by a laser beam from above. When the piezoelectric substrate is made of quartz, the laser beam is transmitted through the piezoelectric substrate, so the pair of drive electrodes formed on both main surfaces of the piezoelectric substrate can be trimmed to the same shape at the same time, thereby producing a piezoelectric vibrator. In this case, since the pair of drive electrodes can be trimmed at once after the piezoelectric resonator is attached to the storage container, trimming can be easily performed. In addition, since the trimming can be performed in the same shape, unnecessary vibration (spurious) generated due to the displacement of the drive electrode positions on the upper and lower surfaces and the imbalance of the electrode area can be suppressed.
[0019]
The method for manufacturing a piezoelectric resonator according to the present invention includes a step of preparing a piezoelectric substrate having a wedge portion whose thickness is gradually reduced toward the tip, a drive electrode disposed opposite to both opposing main surfaces of the wedge portion, and the A step of forming a lead electrode electrically connected to the drive electrode, and a portion where the wedge portion where the drive electrode is formed is thickest and / or a portion where the wedge portion is thinnest is trimmed by laser light. And a step of housing the piezoelectric substrate in a storage container and connecting the lead electrode to an electrode pad provided on the inner bottom surface of the storage container via a conductive adhesive. To do. Since the fine adjustment of the resonance frequency of the piezoelectric resonator is easy, fine adjustment of the oscillation frequency is facilitated even in the piezoelectric resonance device, and the yield can be improved.
[0020]
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.
[0021]
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.
[0022]
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.
[0023]
As shown in FIG. 2, the piezoelectric substrate 30 is formed with the thinnest thin-walled portion 300a (the tip of the wedge portion 30b) at both ends in the direction along the long side, and most around 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.
[0024]
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 It is represented by (t2-t1) / 2L, and the total taper is (t2-t1) / L, and this total taper (t2-t1) / L ≦ 2/100.
[0025]
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 μm 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 that the drive electrodes 31 and 32 are placed near the tip of the wedge portion 30b of the piezoelectric substrate 30, it is desirable to suppress the thickness variation in the vicinity of the tip to 5% or less.
[0026]
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 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.
[0027]
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 t1 of the thinnest portion 300a and the thickness t2 of the base portion 30a, that is, the average thickness of the piezoelectric substrate is set to match a desired oscillation frequency.
[0028]
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.
[0029]
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.
[0030]
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
[0031]
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.
[0032]
The lead lines 312 and 322 are connected to the side surfaces of the drive electrodes 31 and 32 so as not to interfere with trimming.
[0033]
In the piezoelectric resonator of the present invention, as shown in FIG. 3, the drive electrodes 31 and 32 include the portion A and / or the wedge portion where the wedge portion 30 b where the drive electrodes 31 and 32 are formed is the thickest. The thinnest portion B of 30b is trimmed with laser light, and the resonance frequency is finely adjusted. The pair of drive electrodes 31 and 32 are trimmed simultaneously and in the same shape by a laser beam from above. In FIG. 3, the outer shape at the time of forming the drive electrode is indicated by a one-dot chain line.
[0034]
In this example, since the piezoelectric substrate 30 made of quartz is used, the laser light can be transmitted through the piezoelectric substrate 30 and the drive electrodes 31 and 32 on both sides can be trimmed at the same time, but when a piezoelectric substrate made of ceramics is used, etc. You can also trim one side at a time.
[0035]
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.
[0036]
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 by means of vapor deposition, sputtering, etc. Electrodes 33 and 34 and lead lines 312 and 322 are formed. The drive electrodes 31 and 32 are formed slightly longer in the direction along the long side of the piezoelectric substrate 30 than the optimum design value.
[0037]
Then, as shown in FIG. 3, the resonance frequency is controlled by a portion A of the drive electrodes 31 and 32 having the thickest wedge portion 30b and / or a portion of the drive electrodes 31 and 32 having the thinest wedge portion 30b. B is irradiated with laser light from above, the irradiated drive electrodes 31 and 32 are removed, and the drive electrodes 31 and 32 are trimmed to the same shape at the same time.
[0038]
When the portion A near the thickest portion of the piezoelectric substrate 30 is removed from the drive electrodes 31 and 32, the frequency can be adjusted in the direction of increasing the resonance frequency, and the portion B of the piezoelectric substrate 30 near the thinnest portion 300a is adjusted. If removed, 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.
[0039]
The laser light to be used is preferably generated by a YAG laser, a YVO ₄ laser, or a YLF laser because a laser beam focused at a short focal point can be obtained.
[0040]
As a detailed process, the above-described frequency adjustment by the laser beam irradiation trimming may be performed as a coarse frequency adjustment process, and then a technique using an ion gun such as Ar ion irradiation may be used in combination as the fine frequency adjustment process.
[0041]
After the drive electrodes 31 and 32 are formed in this way, one drive electrode 31 is irradiated with laser light to remove the drive electrode 31, and at the same time, the drive electrode formed through the piezoelectric substrate 30 and facing the lower surface The laser beam is also irradiated to the opposing position on the drive electrode 32, and a part of the drive electrode 32 is removed. Thereby, the opposing positions of the drive electrodes 31 and 32 on the upper surface and the lower surface can be simultaneously removed. At this time, the drive electrodes 31 and 32 are previously formed slightly longer in the direction along the long side, and partially removed by laser light irradiation. As a result, the drive electrodes 31 and 32 are adjusted to substantially optimum dimensions. It becomes possible.
[0042]
Such a piezoelectric resonator is accommodated in a storage container to produce a piezoelectric resonance device. FIG. 4 shows a piezoelectric resonance device. 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 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.
[0043]
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.
[0044]
Note that trimming by laser light irradiation is preferably performed after the piezoelectric resonator 3 is bonded and fixed in the storage container 41 in terms of reliable frequency adjustment.
[0045]
【The invention's effect】
In the piezoelectric resonator of the present invention, a resonance frequency of 100 MHz or more can be obtained by providing a drive electrode on the wedge portion where the thickness gradually decreases toward the tip, and the piezoelectric substrate has a thick portion so that the strength is high. Expensive. Moreover, a desired resonance frequency can be obtained to some extent by controlling the formation position of the drive electrode.
[0046]
Furthermore, in the present invention, since the drive electrode is provided on the wedge portion whose thickness gradually decreases toward the tip, even when a piezoelectric substrate made of quartz manufactured by bevel processing or convex processing is used, which has relatively low processing accuracy. Since the resonance frequency can be easily adjusted, it is possible to easily and efficiently provide a piezoelectric resonator made of crystal that can resonate at a high frequency of 100 MHz or more using a fundamental wave.
[0047]
Further, the drive electrode part formed by trimming the drive electrode part formed in the thickest part of the wedge part and / or the drive electrode part formed in the thinnest part of the wedge part with a laser beam is provided. In addition to the dimensional control, the drive electrode can be formed on the wedge portion having the optimum thickness, and the resonance frequency can be finely adjusted.
[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 showing a state in which the drive electrode of the piezoelectric resonator of the present invention is trimmed with laser light.
FIG. 4 is an explanatory view showing a piezoelectric resonance device of the present invention.
FIG. 5 is a perspective view of a conventional piezoelectric resonator.
FIG. 6 is an explanatory diagram showing frequency adjustment of a conventional piezoelectric resonator.
[Explanation of symbols]
3... Piezoelectric resonator 30... Piezoelectric substrate 30 b... Wedge portions 31 and 32.

Claims (5)

Preparing a piezoelectric substrate having a wedge portion whose thickness gradually decreases toward the tip;
Forming a drive electrode disposed opposite to both opposing main surfaces of the wedge portion ;
A method of manufacturing a piezoelectric resonator , comprising: trimming a portion having the thickest wedge portion on which the drive electrode is formed and / or a portion having the thinnest wedge portion with a laser beam. Claim 1, wherein the piezoelectric substrate is made of quartz, a pair of drive electrodes formed to face the both main surfaces of the wedge portion, characterized in that it is trimmed simultaneously and in the same shape by a laser beam from above The manufacturing method of the piezoelectric resonator of description. The method for manufacturing a piezoelectric resonator according to claim 1, wherein the wedge portion of the piezoelectric substrate is formed by bevel processing or convex processing. The method for manufacturing a piezoelectric resonator according to claim 1, further comprising a step of irradiating the drive electrode with Ar ions after the trimming. Preparing a piezoelectric substrate having a wedge portion whose thickness gradually decreases toward the tip;
Forming a drive electrode opposed to both opposing main surfaces of the wedge portion and a lead electrode electrically connected to the drive electrode;
Trimming the portion with the thickest wedge portion formed with the drive electrode and / or the portion with the thinnest wedge portion with a laser beam;
And a step of housing the piezoelectric substrate in a storage container and connecting the lead-out electrode to an electrode pad provided on the inner bottom surface of the storage container via a conductive adhesive.

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