JP2864316B2 - Method for manufacturing piezoelectric ceramic element - 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 for manufacturing a piezoelectric ceramic element, and more particularly to a method for forming a sharp edge of an electrode film to be formed on a surface of a ceramic plate.

[0002]

2. Description of the Related Art For example, a piezoelectric ceramic element 1 for constituting a piezoelectric oscillator represented by the circuit of FIG. 5 generally has the following configuration.

[0003] That is, as shown in FIG. 4, electrode coatings 3 are formed on the front and back surfaces of a rectangular strip-shaped piezoelectric ceramic plate 2 having a predetermined thickness, using, for example, silver. The electrode coatings 3, 3 are formed so as to have a predetermined area overlap in a plan view, and the accuracy of the overlapping of the two electrode coatings 3, 3 has a great influence on the impedance characteristics of the piezoelectric oscillator.

[0004] As described above, the formation of the electrode coatings 3 and 3 requires the accuracy of the shape of the electrode coating and the necessity of forming the electrode at a temperature below the so-called Curie point. Usually, it is performed not by a so-called thick film forming method but by a thin film forming method such as evaporation or sputtering.

Meanwhile, a metal etching mask plate is generally used as a mask plate attached to the piezoelectric ceramic plate 2 when performing the above-described vapor deposition or sputtering. However, when such a metal etching mask plate is used, even when the accuracy of the mask plate itself at room temperature is highly achieved, during the process of forming the electrode coating,
Actually, the following problem occurs.

That is, the metal etching mask plate is
Because of the metal, it expands due to the heat generated during film formation,
As a result, the surface of the piezoelectric ceramic plate easily floats. Then, even if the edges of the openings of the mask plate itself are formed sharply and accurately, the edges of the electrode coatings 3, 3 deposited on the surface of the piezoelectric ceramic plate through the openings of the mask plate are blurred. There is. Then, the edges of the electrode coatings 3 on both sides in FIG. 4 change depending on various conditions at the time of film formation, and it becomes difficult to provide uniformity in impedance characteristics as a piezoelectric oscillator. In other words,
In a piezoelectric ceramic element on which an electrode coating is formed by a conventional film forming method, the frequency characteristics when a piezoelectric oscillator is formed vary, and the yield is significantly reduced depending on the required oscillator frequency error range. Results.

The present invention has been devised in view of the above circumstances, and provides a new method capable of forming an electrode film on a surface of a piezoelectric ceramic plate with high accuracy by a simple structure. The method is to provide.

[0008]

Means for Solving the Problems To solve the above problems, the present invention takes the following technical means.

That is, the present invention relates to a method for manufacturing a piezoelectric ceramic element in which electrodes of a predetermined shape are formed on the surface of a ceramic plate by vapor deposition or sputtering, and a ceramic mask plate is attached to the surface of the ceramic plate. The electrode forming process is performed while pressing the mask plate against the surface of the ceramic plate by using a pressing plate which has a tendency to deform so that the outer surface becomes concave when the temperature is raised.

[0010] As the pressing plate, a plurality of plate materials having a larger coefficient of thermal expansion are bonded on a surface closer to the ceramic plate than on a surface separated from the ceramic plate. A so-called bimetal structure can be employed.

[0011]

First, in the present invention,
The mask plate to be attached to the surface of the ceramic plate when the electrode coating is formed on the surface of the ceramic plate by vapor deposition or sputtering is made of ceramic. As is well known, ceramic has a very low coefficient of thermal expansion, and does not easily expand thermally when heated.
Therefore, when performing an electrode coating formation process on the piezoelectric ceramic plate by vapor deposition or sputtering in a state where the ceramic mask plate is attached, a situation may occur in which the mask plate is lifted off from the ceramic plate due to thermal expansion. Absent.

In addition, in the method of the present invention, since the material of the mask plate is the same as the material of the mating member to which the mask plate is to be attached, the mask plate can be easily adhered to the surface of the piezoelectric ceramic plate. Therefore, the adhesion of the mask plate to the surface of the piezoelectric ceramic plate is further enhanced.

Further, in the method of the present invention, as the pressing plate for pressing the above-mentioned mask plate against the piezoelectric ceramic plate, a pressing plate which has a tendency to deform so that its outer surface becomes concave due to a rise in temperature is employed. Therefore, as the temperature increases due to the progress of the vapor deposition process or the sputtering process, the force of pressing the mask plate against the surface of the piezoelectric ceramic plate is increased.

As a result of the above-mentioned operations, according to the method of the present invention, the state in which the mask plate is closely attached to the surface of the ceramic plate on which the electrode coating is to be formed is the progress of the deposition or sputtering process. This is reliably achieved in the entire process, and as a result, an electrode coating having a sharp edge according to the opening shape of the mask plate is reliably formed on the surface of the ceramic plate.

As described above, according to the method of the present invention, it is possible to uniformly form an electrode coating having a uniform shape with sharp edges on the surface of a piezoelectric ceramic plate. Variations in the impedance characteristics of the ceramic element can be significantly reduced, and a high product yield can be achieved.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be specifically described below with reference to the drawings.

As described above, the piezoelectric ceramic element 1 to which the present invention is applied, as shown in FIG. 4, has a rectangular strip-shaped piezoelectric ceramic plate 2 having a predetermined thickness and a predetermined shape formed on both front and back surfaces thereof. The electrode coatings 3 are formed into thin films by vapor deposition or sputtering.

In forming the metal thin film by the above-mentioned vapor deposition or sputtering, a thin mask plate 9 having a predetermined opening is positioned and attached to the surface of the target material plate while being attached thereto, and the mask plate 9 is pressed down. It is necessary to press against the material plate 2 by the plate 10, and a holding device 6 for holding the mask plate pressed against the material ceramic plate by the pressing plate is used.

FIGS. 3 (a), 3 (b), 3 (c) and 3 (d) show members constituting the holding device, respectively. FIG.
Shows a plan view of the holding device 6 in which the above members are stacked, and FIG. 2 shows a cross-sectional view of the holding device. 7 (FIG. 3
(a)) is a base plate made of, for example, stainless steel, and a plurality of holding holes 8a for positioning and holding the piezoelectric ceramic plate 2 are formed on the base plate 7 (see FIG. 3 (b)) are superimposed. The holding plate 8 is also formed of, for example, a stainless steel plate, and the holding holes 8a are adapted to fit the material piezoelectric ceramic plate 2 exactly. The thickness of the holding plate 8 corresponds to the thickness of the material piezoelectric ceramic plate 2, and may be, for example, about 300 μm.

The mask plate 9 (FIG. 3 (c)) is arranged on the holding plate 8 so as to be further overlapped. In the present invention, the mask plate 9 is formed of a ceramic plate such as alumina ceramic. This mask plate 9 has
An opening 9a having a predetermined shape is formed.
The electrode coatings 3, 3 are formed on the surface of the piezoelectric ceramic plate held in the holding plate 8 along the shape of.

It is convenient to make the thickness of the mask plate 9 as thin as, for example, about 50 μm in order to deposit a sharper electrode coating or to form a sputter link.

A pressing plate 10 (FIG. 3 (d)) for pressing the mask plate 9 against the surface of the piezoelectric ceramic plate 2 of each material held by the holding plate 8 is further above the mask plate 9. )) Are superimposed.

The pressing plate 10 is superimposed on the mask plate 9 in correspondence with the spacing between the holding holes 8a formed in the holding plate 8 and the openings 9a formed in the mask plate 9. Window holes 10a are formed so that the openings 9a of the mask plate 9 can be exposed to the outside.

Pressing plate 10 used in the method of the present invention
When the temperature rises, the outer surface, that is, the material piezoelectric ceramic plate 2
It is formed so as to have a tendency to deform so that the surface on the side away from the surface is concave. For this purpose, two metal thin plates having a larger coefficient of thermal expansion on the back side, that is, on the side closer to the material piezoelectric ceramic plate 2, than the metal on the front side, that is, the surface side away from the material piezoelectric ceramic plate 2. Having a so-called bimetal structure formed by superimposing. As a metal constituting such a bimetal, for example, amber can be adopted on the low thermal expansion side and brass can be adopted on the high thermal expansion side.

The base plate 7, the holding plate 8 holding the material piezoelectric ceramic plate 2, the mask plate 9, and the pressing plate 10 are superimposed on each other with accurate positioning in the plane direction. Such positioning is performed by, for example, each member 7,
Knock pin positioning holes 11 are provided in at least two places on 8, 9, and 10, and the knock pins 12 are inserted into the positioning through holes 11 in a state where the members are overlapped as described above, and the four corners are formed. It is performed by connecting with a screw 13.

In the state where the holding device 6 is assembled in this manner, each of the window holes 10a...
The openings 9a of the mask plate 9 are exposed, and the surface of the material ceramic plate 2 is partially exposed through the openings 9a of the mask plate 9.

Therefore, when the holding device 6 is loaded into a vapor deposition tank and a metal is deposited on the surface of the holding device 6 by vapor deposition, only the portion of the mask plate 9 which is exposed by the openings 9a. Then, the metal films 3 and 3 are formed as a thin film.

After the formation of the electrode coating on the surface of the piezoelectric ceramic plate of each material is completed, the electrode coating is formed on the back surface of the piezoelectric ceramic plate of each material by the same procedure as described above.

In the method of the present invention, first of all,
Since the mask plate 9 is formed using the same ceramic material as the piezoelectric ceramic plate to be subjected to the vapor deposition process, the material of the mask plate 9 is well adapted to the surface of the piezoelectric ceramic, and these are conveniently adhered to each other. Contacted. Secondly, as the pressing plate 10 for pressing the mask plate 9 against the piezoelectric ceramic plate, the mask plate 9 has a tendency to be concavely deformed by increasing the temperature. The force for pressing the mask plate 9 against the piezoelectric ceramic plate increases,
This also keeps the adhesion of the mask plate 9 to the piezoelectric ceramic plate of the material to a high degree. Further, since the mask plate 9 is formed of a ceramic having a very low coefficient of thermal expansion, the mask plate thermally expands as the temperature rises during the above-mentioned vapor deposition process, and as a result, the mask plate 9 The material hardly rises with respect to the piezoelectric ceramic plate.

As a comprehensive result, according to the method of the present invention, a mask plate for defining the precision of the edge of the electrode coating formed on the surface of the piezoelectric ceramic plate is made to be a material in the whole process of the vapor deposition process. It can be kept in close contact with the ceramic plate, and as a result, the shape of the electrode coating becomes extremely accurate.

Of course, the scope of the present invention is not limited to the embodiment described above. Various other methods are conceivable for a method of positioning the members for constituting the holding device 6 with each other and a method of connecting the peripheral portions of the members in a state where they are overlapped.

Further, in order to form the holding plate 10 which has a tendency to be deformed so as to become concave when heated, as described above, in addition to employing the bimetal structure, for example, a shape memory alloy is used. It is also conceivable to take a form of a flat plate at normal temperature, and to add a shape memory so as to be deformed so as to be concave upward when a predetermined temperature is reached.

[Brief description of the drawings]

FIG. 1 is a plan view of a mask holding device used in the method of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

3A and 3B are plan views of members constituting the mask holding device, wherein FIG. 3A is a base member, FIG. 3B is a holding plate for holding a ceramic material plate, FIG. 3C is a mask plate, and FIG. Each of the holding plates is shown.

FIG. 4 is a sectional view of a piezoelectric ceramic element manufactured by the method of the present invention.

FIG. 5 is a circuit example of a piezoelectric oscillator using a piezoelectric ceramic element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric ceramic element 2 Piezoelectric ceramic plate 3 Electrode coating 9 Mask plate 10 Holding plate

Claims (2)

(57) [Claims] 1. A method of manufacturing a piezoelectric ceramic element comprising forming an electrode of a predetermined shape on a surface of a ceramic plate by vapor deposition or sputtering, comprising: adhering a ceramic mask plate to the surface of the ceramic plate; Manufacturing the piezoelectric ceramic element, wherein the electrode forming process is performed while pressing the mask plate against the surface of the ceramic plate using a pressing plate that has a tendency to deform so that the outer surface becomes concave due to an increase in temperature. Method. 2. The pressing plate is formed from the ceramic plate.
To the above ceramic plate rather than the one located on the side that separates
The manufacturing method according to claim 1, wherein a plurality of plate members having a larger coefficient of thermal expansion are attached to a plate located closer to the surface to be approached .