JP2007271284A - Qcm sensor element and method of manufacturing same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the symmetricalness of the outside and inside shapes, to prevent the occurrence of unnecessary parasitic oscillation, to reduce the adhesion of a contaminant and to enhance reliability with respect to damage. <P>SOLUTION: A slope 21 is formed to the outer peripheral part of a quartz plate 2 so as to become thin toward the outside by applying dry bevelling processing to the quartz plate 2 subjected to lapping processing so as to become uniform in predetermined thickness and mirror surface processing is applied to the surface and back of the quartz plate 2 containing a part (slope 21) subjected to dry processing after the dry bevelling processing by wet bevelling processing and an exciting electrode 3 is provided to the central part of the quartz plate 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a QCM sensor element that detects a minute amount of mass change by a decrease amount of a resonance frequency.

Conventionally, a QCM (Quartz Crystal Microbalance) sensor element in a lapped quartz crystal plate (see FIG. 2A), the outer circumference portion of the quartz crystal plate having a circular shape in plan view is inclined by dry beveling. The shape is That is, the conventional QCM sensor element includes a flat portion having a constant thickness and an inclined portion that decreases in thickness toward the outside (see FIG. 2B). Excitation electrodes (not shown) are formed. As a result, the QCM sensor element can detect a minute amount of mass change adhering to the surface of the excitation electrode by the amount of decrease in the resonance frequency of the element.
In such a QCM sensor element, for example, a conventionally used liquid phase QCM sensor element has a large CI (Crystal Impedance) due to frictional resistance with the sample liquid. A surface in which the surface of a flat portion serving as a portion is mirror-finished has been proposed (for example, see Patent Document 1).
JP 2004-128979 A (paragraphs 0011 to 0017, FIG. 1)

However, a taper (inclined part) can be attached to the outer peripheral portion of the quartz plate by the dry beveling process so that the thickness decreases toward the outside. A processing flaw may be caused locally by the collision of each other. For this reason, in order to make the flat portion into a mirror surface, a polishing process with a large processing amount is required, such as increasing the processing amount when performing the polishing process, or performing the polishing process after lapping. . At this time, the polishing process of the upper and lower surfaces by the double-side processing machine results in an unbalanced processing amount between the upper surface and the lower surface, and the symmetry of the entire QCM sensor element is deteriorated (see FIG. 2C). Further, if the symmetry of the entire QCM sensor element is deteriorated, unnecessary parasitic vibration is generated.
In addition, the beveled inclined portion is rough because no subsequent polishing process is performed by the double-sided processing machine, and when used in the sample liquid, the dirt is likely to adhere.
In addition, since the edge portion where the side surface of the QCM sensor element intersects with the inclined portion stands, chipping is likely to occur in the manufacturing stage, and there is a risk of breakage in an environment where a temperature cycle is applied for a long time.

  Therefore, in the present invention, a QCM sensor element that solves the above-described problems, improves the symmetry of the shape of the front and back, prevents the occurrence of unnecessary parasitic vibration, reduces the adhesion of dirt, and improves the reliability against breakage, and It is an object to provide a method for manufacturing a QCM sensor element.

  In order to solve the above-mentioned problems, the present invention is a QCM sensor element, characterized in that a dry beveled quartz plate surface is wet beveled and an excitation electrode is formed at a central portion of the quartz plate. To do.

  The present invention is also a method for manufacturing a QCM sensor element, wherein the quartz plate includes a step of dry-beveling a quartz plate lapped to a predetermined thickness, and a portion that is dry-beveled after the dry beveling. It is characterized by comprising a step of performing a mirror surface treatment on the surface of the plate by wet beveling and a step of providing an excitation electrode at the center of the quartz plate.

According to such a QCM sensor element, the symmetry of the shape of the back and front of the entire QCM sensor element can be improved, so that unnecessary parasitic vibration can be prevented and the adhesion of dirt can be reduced. Reliability against breakage can be improved.
Further, according to the manufacturing method of the QCM sensor element, the symmetry of the front and back shapes of the entire QCM sensor element can be improved, so that unnecessary parasitic vibration is prevented and the adhesion of dirt is reduced, and the reliability against damage is reduced. A QCM sensor element capable of improving the performance can be manufactured.

Next, the best mode for carrying out the present invention (hereinafter referred to as “embodiment”) will be described in detail with reference to the drawings as appropriate.
1A is a cross-sectional view showing an example of the shape of a quartz plate after lapping, FIG. 1B is a cross-sectional view showing an example of the shape of a quartz plate after dry beveling, and FIG. It is sectional drawing which shows an example of the shape of the quartz plate after a beveling process, (d) is sectional drawing which shows an example of the QCM sensor element which concerns on embodiment of this invention.

  As shown in FIG. 1 (d), the QCM sensor element 10 according to the embodiment of the present invention includes a crystal plate 2 and a pair of excitation electrodes 3 sandwiching the crystal plate 2.

The quartz plate 2 includes an inclined portion 21 (see FIG. 1B) whose thickness decreases toward the outside and a flat portion 22 whose thickness becomes constant.
The quartz plate 2 is first formed into a disk shape (see FIG. 1A) from a wafer that has been cut at a predetermined cut angle and then lapped so as to have a predetermined thickness.
The quartz plate 2 is subjected to a dry beveling process on the outer peripheral portion to form an inclined portion 21 whose thickness decreases toward the outside (see FIG. 1B).
Since the inclined portion 21 is formed so that the shape of the inclined surface is symmetrical, the symmetry of the shape of the reverse surface of the QCM sensor element 10 is improved.

  The dry beveling process is performed by putting an abrasive (for example, GC (Green Silicon Carbide) # 800) and a piezoelectric element plate (crystal plate 2) in a metal beveling container and rotating the metal beveling container. This refers to a process in which the end (outer peripheral portion) of the piezoelectric element plate is cut with an abrasive to form the inclined portion 21. In this dry-type beveling process, the surface of the inclined portion 21 to be formed becomes a rough surface (a degree that the transparent member becomes cloudy) with a predetermined abrasive or the like.

  Further, wet beveling is performed on the front and back surfaces of the inclined portion 21 and the back and front surfaces of the flat portion 22, and the back and front surfaces of the inclined portion 21 and the back and front surfaces of the flat portion 22 become mirror surfaces. Thus, the edge portion between the inclined portion 21 and the side surface of the QCM sensor element 10 is cut into a round shape (see FIG. 1C).

  The wet beveling process is a piezoelectric element plate (crystal plate 2) to be processed in a solution such as water, an abrasive (for example, cerium oxide having a particle size of 0.9 μm), a medium (for example, smaller than the crystal plate 2). This refers to processing performed by placing an irregular shape) in a processing container.

  For example, when wet beveling is performed on the crystal plate 2 under the above-described conditions (abrasive material (for example, cerium oxide having a particle size of 0.9 μm) and media (for example, an irregular shape smaller than the crystal plate 2), Since the medium and the abrasive contained in the water move in the water while being in contact with the quartz plate 2, the back and front surfaces of the inclined portion 21 of the quartz plate 2 and the back and front surfaces of the flat portion 22 are uniformly distributed. In contact, the front and back surfaces of the inclined portion 21 of the quartz plate 2 and the back and front surfaces of the flat portion 22 can be mirror surfaces.

  Thus, the crystal plate 2 has a circular shape in plan view, and includes the inclined portion 21 that becomes thinner toward the outside and the flat portion 22 that has a constant thickness, and the front and back surfaces of the inclined portion 21 and the flat portion 22. The front and back surfaces of the mirror are mirror surfaces.

  The excitation electrode 3 is provided on the inner side of the surface of the flat portion 22 whose surface is a mirror surface by a conventionally known vapor deposition method (see FIG. 1D). That is, the excitation electrode 3 is formed with a diameter smaller than the diameter of the flat portion 22. The excitation electrode 3 is provided on the flat portion 22 without being shifted so as to be symmetric with respect to the front and back.

  Note that the front and back surfaces of the flat portion 22 may be polished before providing the excitation electrode 3 on the flat portion 22. Thereby, the flatness accuracy of the flat part 22 which is a vibrating part is improved, and variation in frequency can be improved.

  Since the QCM sensor element of the present invention is configured as described above, the wet beveling process is performed after the dry beveling process. Therefore, the processing amount of the front and back surfaces of the flat portion 22 becomes uniform, so that the entire QCM sensor element 10 is obtained. Symmetry can be improved. In addition, since the symmetry of the entire QCM sensor element 10 is improved, unnecessary parasitic vibration can be prevented, and stable vibration characteristics can be obtained. In addition, the inclined portion 21 subjected to the dry beveling process becomes a mirror surface, so that adhesion of dirt can be reduced.

  Further, in the wet beveling process, since water functions as a cushioning material, the momentum when the quartz plates 2 come into contact with each other is reduced. Can be improved.

Next, a method for manufacturing the QCM sensor element according to the embodiment of the present invention will be described.
As an initial step, dry beveling is performed on the outer peripheral portion of the quartz plate 2 (see FIG. 1A) lapped to a predetermined thickness. In the state of the quartz plate 2 after the dry beveling process, the front and back surfaces of the inclined portion 21 (see FIG. 1B) formed by the dry beveling process are rough. Then, as the next step, wet beveling is performed on the front and back surfaces of the inclined portion 21 and the front and back surfaces of the flat portion 22 as the rough surface. That is, wet beveling is performed on the front and back surfaces of the quartz plate 2 including the dry beveled portion (inclined portion 21). As a result, the front and back surfaces of the quartz plate 2 are mirror-finished, and the edge portion of the quartz plate 2 is formed round (see FIG. 1C). In this state, as the next step, the excitation electrode 3 is provided in the central portion (flat portion 22) of the crystal plate 2 (see FIG. 1D).

Since the QCM sensor element 10 is manufactured in this manner, the flat portion 22 and the inclined portion 21 of the quartz plate 2 are uniformly contacted by the abrasive and media contained in water during the wet beveling process. The front and back surfaces of the flat portion 22 and the back and front surfaces of the inclined portion 21 are simultaneously polished, and both can be made to have a good mirror surface, and the crystal plate 2 has a good symmetry in the shape of the back and front. be able to.
In addition, during the wet beveling process, water becomes a buffer material and the momentum of contact between the crystal plates 2 can be reduced, so that scratches and chipping are less likely to occur during contact.

(A) is sectional drawing which shows an example of the shape of the quartz plate after a lapping process, (b) is sectional drawing which shows an example of the shape of the quartz plate after a dry-type beveling process, (c) is a wet beveling process It is sectional drawing which shows an example of the shape of a subsequent quartz plate, (d) is sectional drawing which shows an example of the QCM sensor element which concerns on embodiment of this invention. It is a figure which shows the conventional process, Comprising: (a) is sectional drawing which shows an example of the shape of the quartz plate after lapping, (b) is a cross section which shows an example of the shape of the quartz plate after dry-type beveling processing It is a figure and (c) is sectional drawing which shows an example of the shape of the quartz plate after a grinding | polishing process.

Explanation of symbols

10 QCM sensor element 2 Crystal plate 21 Inclined part 22 Flat part 3 Excitation electrode

Claims (2)

  A QCM sensor element, wherein a surface of a quartz plate subjected to a dry beveling process is subjected to a wet beveling process, and an excitation electrode is formed at a central portion of the quartz plate. A process of dry beveling a quartz plate lapped to a predetermined thickness;
Performing a mirror surface treatment by wet beveling on the surface of the quartz plate including the dry beveled portion after the dry beveling; and
Providing an excitation electrode in the center of the quartz plate;
A method of manufacturing a QCM sensor element, comprising:

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