JP3255456B2 - Manufacturing method of ultra-thin piezoelectric resonator element plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an ultra-thin piezoelectric resonator element, and more particularly to a method of fine-tuning the resonance frequency of the element.

[0002]

2. Description of the Related Art As the demands for ultra-miniaturization, ultra-thinness and high frequency of various communication devices and electronic devices become strict, piezoelectric devices such as piezoelectric vibrators and filters used in these devices are also becoming ultra-miniaturized. Required and improved temperature characteristics,
It has become an essential condition to remove an accessory circuit including an element which is difficult to be integrated into a circuit such as a part oscillation circuit.
In view of such a trend, the present inventors, for example, use an AT-cut quartz crystal and provide a thick annular surrounding portion integrally with a vibrating portion having a thickness of about 15 μm around the vibrating portion, thereby reducing the mechanical shape of the vibrating portion. We have established a basic manufacturing technique for ultra-thin-plate piezoelectric resonators that can maintain and obtain resonance exceeding 100 MHz by fundamental wave vibration.

[0003] However, the thickness of the ultra-thin vibrating portion formed by the concave bottom portion in the annular surrounding portion does not fall within a desired value and variation only by the process of forming the concave portion by, for example, machining. After forming a number of depressions on the piezoelectric wafer, each fine adjustment amount is determined by measuring the thickness of the vibrating portion of each depression bottom, and it is necessary to process these by etching. The spacing between the recesses is very small and the depth of the recesses is between 60 and 7
Due to the thickness of about 0 μm, the etching solution flows into another adjacent recess, the vapor of the etching solution invades the bottom of the recess which does not require fine adjustment, and further reduces the thickness of the vibrating portion, or reduces the etching solution. There is a problem that the etching liquid is not sufficiently dropped due to slight modulation of the dispenser to be dropped, and the etching liquid evaporates before a required etching time elapses, and there is a defect that the product yield is not improved.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate defects in the conventional fine adjustment process of the vibrating portion plate thickness at the base plate stage of the ultra-thin piezoelectric resonator as described above, and to reduce the product yield due to failure of the process. It is an object of the present invention to provide a method of manufacturing an ultra-thin piezoelectric resonator element that can be prevented.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the manufacturing method according to the present invention takes the following procedures. That is, after forming a large number of recesses on a piezoelectric wafer by machining or etching, the thickness of the bottom of the recess, which is the vibrating portion of the resonator, is converted into the resonance frequency of each portion, and the vibration portion is formed based on the measurement result. When the thickness adjustment is determined and these adjustments are performed by etching, a thick plate provided with holes corresponding to the positions of the recesses is adhered to the surface of the piezoelectric wafer on the side of the recess, and the piezoelectric plate is inserted through the holes. A predetermined amount of an etching solution is dropped into each of the recesses of the wafer.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the drawings. Prior to the description of the embodiments, an outline of a method of finely adjusting the thickness of the vibrating portion of the ultra-thin piezoelectric resonator element plate, which has been conventionally performed by the inventor of the present application, will be described to assist understanding of the present invention. FIG. 2 (a) shows a semi-finished product of an ultra-thin piezoelectric resonator element plate having a large number of recesses 2, 2,... However, it is almost impossible to finish the thickness of the vibrating portion, which substantially determines the resonance frequency of the resonator, to a required value and in a range of variation only by such processing. Therefore, the recesses 2, 2,.
The bottom plate thickness is determined by a known method, that is, the electrodes are brought into contact with the front and back surfaces of the vibrating portion to measure the respective resonance frequencies, and the results are converted into the plate thickness to determine the plate thickness adjustment amount. As shown in ()), each of the vibrating portions is dropped by using a method in which the etching solution 4 is dropped by the dispenser 3 in order from the one that requires a long time for etching, and the wafer 1 is washed after a predetermined time has elapsed after the dropping of the etching solution 4. The thickness of the recess is set to a desired value, but the depth of the recess is about 60 to 70 μm, and the planar dimension of the resonator element including the recess is about 3 mm × 3 mm when cut out from the piezoelectric wafer. Due to the close proximity to each other, inflow of the etchant into adjacent recesses, overetching of the recesses without fine adjustment by the vapor of the etchant or slight modulation of the dispenser There is etching liquid issues so insufficient adjustment of the vibration part thickness due to insufficient as previously described to yield at processing steps result resonator element plate has a defect referred low.

In order to solve this problem, the following method is used for manufacturing the ultra-thin piezoelectric resonator element plate according to the present invention. That is, as shown in FIG. 1 (a), the concave portions 2, 2,... Of the piezoelectric wafer 1 are formed on the concave side surface of the piezoelectric wafer 1 after the primary processing is completed and the vibration part plate thickness measurement of each concave bottom is completed. A plate 6 of bakelite provided with holes 5, 5,... Corresponding to the positions is bonded with an adhesive 7, and recesses 2, 2,.
..., the etching solution 4 is dropped therein (see FIG. 3B). In this manner, even if a sufficient amount of the etching solution is dripped into each of the depressions, there is no possibility that the etching solution flows into the other adjacent depressions. Equipment could be inexpensive. Further, since a sufficient etching solution is supplied to each of the recesses, the solution does not evaporate during the etching process and a failure such as incomplete adjustment of the thickness of the vibrating portion does not occur. Further, since the vapor of the etching solution in the adjacent recess is hard to flow into the recess which does not require the adjustment of the vibration portion plate thickness, there is no danger of excessive adjustment of the vibration portion plate thickness due to this.

Although the embodiment of the present invention has been described above, the present invention is not limited to this, and the porous thick plate may be any one which is not affected by an etching solution such as a Teflon resin. A thickness of about 5 to 10 mm is sufficient. Further, any adhesive may be used as long as the adhesive between the perforated plate and the piezoelectric wafer is not affected by the etchant and a solvent exists that can easily separate the two. As a step after the above-mentioned fine adjustment of the vibrating portion plate thickness, first, the porous plate 6 is separated from the piezoelectric wafer 1 by using a solvent, and for example, aluminum is entirely deposited on the concave side of the piezoelectric wafer and the entire electrode 8 is formed. A required partial electrode 9 is formed at a position substantially corresponding to the center of the recesses 2, 2,... On the flat side by mask evaporation or photo-etching. (C) to obtain an ultra-thin piezoelectric resonator element as shown in FIG.
After the necessary wiring is performed, the final resonance frequency is adjusted by additional deposition on the electrodes.

[0009]

According to the present invention, since the resonance frequency is finely adjusted at the raw plate stage of the ultra-thin piezoelectric resonator element by the method described above, only a simple jig and a slight increase in the number of steps are required. Thus, excessive or insufficient etching which has occurred in the fine adjustment step is prevented, and a remarkable effect is exhibited in improving the product yield.

[0010]

[Brief description of the drawings]

FIG. 1A is a perspective view showing one embodiment of a porous thick plate used in the manufacturing method according to the present invention. (B) is sectional drawing which shows the state which is performing the resonance frequency fine adjustment by the manufacturing method which concerns on this invention. (C) is a sectional view of an ultra-thin plate piezoelectric resonator element as a product.

FIG. 2 (a) is a perspective view of a piezoelectric wafer having a large number of recesses to which the present invention is applied. FIG. 4B is a cross-sectional view illustrating a conventional method of adjusting the resonance frequency by finely adjusting the thickness of the piezoelectric wafer concave bottom plate.

[Description of sign]

 DESCRIPTION OF SYMBOLS 1 ... Piezoelectric wafer which formed many recesses 2 ... Depression 4 ... Etching liquid 5 ... Hole 6 ... Perforated plate 7 ... Adhesive

Claims (1)

(57) [Claims] 1. A plurality of ultra-thin piezo-resonator blanks having a thick annular surrounding portion integrated therewith around an ultra-thin oscillating portion are formed on a single piezoelectric wafer at the same time. When finely adjusting the thickness of the piezoelectric wafer by etching, a thick plate provided with holes respectively corresponding to the recesses is adhered to the surface of the piezoelectric wafer surrounded by the annular surrounding portion on the side where the recesses are formed. The required amount of the etching solution is dropped into the recesses through the recesses, so that the etching solution or the vapor thereof in one recess does not affect the fine adjustment of the thickness of the vibrating portion constituting another adjacent recess bottom portion. A method for manufacturing an ultra-thin piezoelectric resonator element plate, comprising the steps of: