JP2000133855A - Ceramic dielectric device and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify a ceramic dielectric device in a manufacturing process and improved in characteristics by a method, wherein a layer that contains ceramic dielectric is formed on a substrate, and a piezoelectric layer is jointed to the substrate through the intermediary of the dielectric-containing layer. SOLUTION: A Pt film is formed on a substrate 3 of silicon or the like using a sputtering method to serve as a lower electrode, and then a ceramic dielectric-containing layer 1 is formed, where the ceramic dielectric is synthesized through a mixture process in which an ethylenediamine tetracetic acid complex solution is utilized. A piezoelectric material paste is applied onto the substrate 3, where the ceramic dielectric-containing layer 1 is formed and burned into a piezoelectric layer 2. Finally, an upper electrode 5 is formed on the surface of the piezoelectric layer 2 through vapor deposition method. With this setup, unwanted spurious vibrations are restrained from occurring, admittance characteristic is improved, and motor can be improved in efficiency and durability.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic dielectric device represented by a piezoelectric actuator such as an ultrasonic motor and a method for manufacturing the same.

[0002]

2. Description of the Related Art The configuration of a vibrating portion of a conventional ceramic dielectric device will be described based on a piezoelectric actuator which is one of the most promising products of the ceramic dielectric device. 2. Description of the Related Art In recent years, piezoelectric actuators have attracted attention as new motors replacing electromagnetic motors. The piezoelectric actuator does not generate electromagnetic noise when driven, and is not affected by the noise. Further, the piezoelectric actuator has been attracting attention as a technique for producing a sub-millimeter class device as typified by a micromachine, and a minute piezoelectric actuator is required as a driving source thereof.

An example of such a piezoelectric actuator is an ultrasonic motor. FIG. 10 is an enlarged view of a vibrating portion of a conventional ultrasonic motor. This ultrasonic motor includes a stator 13 and a moving body 7 (rotor). further,
The stator 13 includes a vibrating body 6 made of an elastic material generally using stainless steel or brass and a piezoelectric body 1 with electrodes.
The vibrating body 6 and the piezoelectric body 15 are bonded together with an adhesive 14. In the ultrasonic motor having such a configuration, when an AC voltage is applied to the piezoelectric body 15, the force generated by the piezoelectric effect propagates to the vibrating body 6 and the moving body 7 (rotor ) Will be driven.

As typified by the description of the ultrasonic motor, the basic structure of a piezoelectric actuator has a structure in which a piezoelectric body and an elastic material are bonded with an adhesive.

[0005]

However, the conventional structure and manufacturing method have the following problems. That is, when an adhesive is used as in the past, the force generated from the piezoelectric body is irregularly reflected or absorbed by the adhesive layer when the force is propagated, and as a result, the electrical and mechanical performance and There is a problem that not only the reliability is lowered, but also a peeling phenomenon occurs at the bonding interface with the piezoelectric body. The problem is that when the vibrating portion of the ceramic dielectric device is to be realized as a driving source for a microstructure, the size of the vibrating portion is in the sub-millimeter class, so that the influence of the adhesive layer is relatively large.

The essential cause of such a problem is that the adhesive layer and its interface are mechanically unstable. In order to solve this problem, a method of directly forming a piezoelectric body on a vibrating body has been actively studied in recent years. As a manufacturing method for directly forming a piezoelectric body, a sputtering method or a CVD method is a typical manufacturing method. However, there is an advantage that an element having a small size can be manufactured, but there is a problem that it requires a great deal of man-hour. Further, in order to output the driving force of the actuator, it is necessary to form the piezoelectric layer to have a thickness of several to several tens of μm. However, in the above-described conventional method, a film having a thickness of several to several tens of μm is formed. It was difficult to form.

As another manufacturing method, there is a screen printing method widely used for a piezoelectric element of an ink jet printer head. This manufacturing method is a method in which a piezoelectric paste is applied to a substrate, dried, and then fired to manufacture. However, since firing is performed at a high temperature of 1000 ° C. or more, there is a restriction that cracks occur due to a difference in thermal stress between the substrate and the piezoelectric paste, and a heat-resistant substrate must be used.

[0008] Similarly, a hydrothermal method is known as a manufacturing method for directly forming a piezoelectric body. In this method, a ferroelectric ceramic solution containing lead zirconate titanate (PZT) as a main component is reacted in an autoclave to form PZT on a titanium or titanium oxide substrate. . Here, the substrate on which PZT can be formed is limited to titanium or a material containing titanium.

Accordingly, an object of the present invention is to solve the above problems and to provide a method and apparatus for manufacturing a ceramic dielectric device in which the manufacturing process can be simplified, the characteristics are improved, and the ceramic dielectric device is stabilized.

[0010]

Means for Solving the Problems In order to solve the above problems, a manufacturing method of the present invention relates to a ceramic synthesized by a mixing process of a solution containing an ethylenediaminetetraacetic acid (hereinafter referred to as EDTA) complex provided on a substrate. A first step of forming a layer containing a dielectric and a second step of joining the substrate and the piezoelectric layer via the layer containing the dielectric are provided.

[0011]

According to the present invention, a lower electrode 4 is formed at a predetermined position on a vibrating body 6, and a layer 1 containing a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution is formed thereon. Is formed. In addition, P
A ZT-based piezoelectric layer 2 is formed, and an upper electrode 5 is formed on the upper surface of the piezoelectric layer 2. When the substrate 3 (corresponding to the vibrating body 6) functions as a lower electrode, a layer 1 containing a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution is provided directly on the substrate 3.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. A method for manufacturing a vibrating portion of the ceramic dielectric device of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram showing the steps of a method of manufacturing a vibrating portion of a ceramic dielectric device, and FIG. 2 is a flowchart of the manufacturing steps. The substrate shown here corresponds to the vibrating body of the ceramic dielectric device, but is referred to as a substrate here in order to simplify the manufacturing process.

First, a lower electrode 4 is formed on the surface of the substrate 3 cleaned in the substrate cleaning step (step A) by vapor deposition or sputtering (step B). Specifically, a Pt film serving as the lower electrode 4 was sputtered on a substrate of silicon or the like by about 3000 ° using a sputtering method. This sputtering was performed under the conditions of an argon flow rate of 120 SCCM, an RF power of 2 kW, and a pressure of 4 mtorr. Here, the reason why the lower electrode is made of Pt is that Pt is not deteriorated by high-temperature heat treatment.

Next, the step of forming a layer containing a ceramic dielectric synthesized by the mixing process of the EDTA complex-containing solution is shown in Step C. First, an ethanol solution of a titanium complex and an ethanol solution of a zircon complex are synthesized by an existing method. An ethanol solution containing lead (II) was synthesized as follows. EDTA was added to hot water at 80 ° C. in which lead (II) acetate trihydrate was dissolved to cause a reaction, and the cooled solution was concentrated to isolate white salt in a high yield of 90% or more. The salt was reacted with 2 equivalents of dibutylamine in an ethanol solution to obtain a homogeneous solution of the PZT compound. The two kinds of precursor solutions are mixed at a ratio at which PZT-based piezoelectric ceramics are synthesized (for example, the composition is a molar ratio of Pb:
Zr: Ti = 100: 53: 47), and the mixed solution was concentrated under reduced pressure. The resulting oil was heated at 180 ° C. to give a tan powder. 400 ~
The resultant was baked at 700 ° C. for 30 minutes to form a layer 1 containing a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution.

Next, in step D, a bonding step of the substrate 3 and the piezoelectric layer 2 via the layer 1 containing the ceramic dielectric synthesized by the mixing process of the solution containing the EDTA complex will be described. In Step D, a paste of a PZT-based piezoelectric material to be bonded to the substrate 3 on which the layer 1 including the ceramic dielectric synthesized by the mixing process of the EDTA complex-containing solution is formed is applied and baked.

The piezoelectric material is prepared by adding about 1% of polyvinyl alcohol (hereinafter referred to as PVA) as a binder to a ceramic dielectric powder material having a particle size of 1 μm or less, kneading and defoaming to prepare a piezoelectric paste. This piezoelectric paste is applied to and adhered to a substrate 3 on which a layer 1 including a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution has been formed, and is adhered at 500 to 900 ° C. for 30 minutes to 1 minute.
The piezoelectric layer 2 was obtained by performing heat treatment and bonding in an air atmosphere under the conditions of time. X-ray analysis of the piezoelectric layer 2 revealed a crystal peak having a perovskite structure.

Finally, a gold electrode (upper electrode 5) is formed on the surface of the piezoelectric layer 2 by a vapor deposition method in an upper electrode forming step (step E). When the physical properties were measured, it showed excellent characteristics of a relative dielectric constant of 1200 and a voltage distortion constant of 110 pC / N. In the embodiment, the composition of the PZT piezoelectric body is a pure two-component system. However, in order to improve the piezoelectric characteristics,
For example, a three-component system such as lead magnesium niobate-lead zirconate-lead titanate, iron for improving the withstand voltage, chromium for reducing the change with time, and antimony for improving the strength. May be added.
In this case, it can be dealt with by preparing the composition of the EDTA complex-containing solution according to the desired composition.

FIG. 3 shows a longitudinal sectional view of the basic structure of an ultrasonic motor which is one of the ceramic dielectric devices formed in this way. The vibrating body 6 provided with the piezoelectric layer 2 via the layer 1 containing the ceramic dielectric synthesized by the mixing process of the EDTA complex-containing solution is made of an elastic member made of metal or the like. Supported by such. Further, the central shaft 11 is incorporated as a guide, and is arranged so as to be in pressure contact with the vibrating body 6 by the pressure spring 10 located above. Here, by applying signals to the two lead wires 12 that are different in time phase by approximately 90 °, the piezoelectric layer 2 and the vibrating body 6 generate a mechanical traveling wave due to the bending motion and pressurize the vibrating body 6. This is a configuration in which the moving body 7 that is in contact makes a rotational movement. An ultrasonic motor having a diameter of 4 mm was actually manufactured using the vibrator 6 according to the present invention. The material of the vibrating body 6 is aluminum or SU
S304 material was used. The material of the friction material 8 was a composite plastic containing carbon fiber. The shape of the vibrating body 6 is formed by processing the round bar raw material by the NC lathe, and the agitating surface is also finished by cutting.

FIG. 4 shows a schematic cross section of the structure of the vibration part of the ultrasonic motor shown in FIG. A lower electrode 5 is formed at a predetermined position on a vibrator 6 (corresponding to a substrate) made of stainless steel, and a layer 1 containing a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution is formed thereon. ing. Further, a PZT-based piezoelectric layer 2
And an upper electrode 5 is formed on the upper surface of the piezoelectric layer 2. When the vibrating body 6 also functions as the lower electrode 5, the layer 1 containing the ceramic dielectric synthesized by the mixing process of the EDTA complex-containing solution is directly provided on the vibrating body 6, and the mixing process of the EDTA complex-containing solution is performed. The piezoelectric layer 2 is formed on the layer 1 containing the ceramic dielectric synthesized by the above.

The characteristics of the ultrasonic motor constructed as described above will be described below. FIG. 5 shows the admittance characteristics of an ultrasonic motor provided with a vibrator constituted by a conventional bonding method using an adhesive 14, and FIG. 6 shows the vibrator 6 and the piezoelectric layer 2.
7 shows admittance characteristics of an ultrasonic motor according to the present invention including a vibrator provided with a layer 1 containing a ceramic dielectric synthesized by a mixing process of a solution containing an EDTA complex between the two. However, the admittance characteristics shown are measured with the moving body removed, that is, with the vibrating body free in the vertical direction. Table 1 below shows an outline of the target motor specifications.

[0021]

[Table 1]

In FIG. 5, spurious vibrations other than the main resonance point are seen, whereas in FIG. 6, the mechanical Q value is high,
No spurious vibrations other than the main resonance point are observed. In these admittance characteristics, spurious vibration is a phenomenon caused by irregular reflection of force at a boundary surface, and the Q value indicates a degree of attenuation when a force propagates. Therefore, an actuator according to the present invention is a conventional type. It turns out that the performance is greatly improved as compared with the actuator.

FIG. 7 is a table showing frequency-speed characteristics of a progressive ultrasonic motor having a layer containing a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution according to the present invention. Driving voltage is about 6V with sine waveform
pp, the pressure of the moving body 7 to the vibrating body 6 is about 10 gf. According to the configuration of the present invention, since the rotation frequency region is relatively wide and the maximum rotation speed is as high as 6000 rpm or more, it is possible to apply an ultrasonic motor in a medium speed to high speed region. It is shown.

Next, the torque performance and durability when this ultrasonic motor was driven were investigated. FIG. 8 shows the measurement results of the efficiency indicating the torque performance of the ultrasonic motor, and FIG. 9 shows the measurement results of the durability. (A) in the figure shows a measurement result of an ultrasonic motor having a vibrating portion provided with a layer including a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution according to the present invention,
(B) shows a measurement result of an ultrasonic motor having a vibrating portion according to a conventional example. As is apparent from these results, the ultrasonic motor having the structure of the vibrating portion according to the present invention is clearly superior to the conventional method in both efficiency and durability. As described above, it can be said that the performance and the durability are improved in the ultrasonic motor having the vibrating portion in which the vibrating body and the piezoelectric body are joined through the layer including the ceramic dielectric synthesized by the mixing process of the solution containing the EDTA complex.

That is, according to the structure of the vibrating portion provided with the layer containing the ceramic dielectric synthesized by the mixing process of the EDTA complex-containing solution according to the present invention, high efficiency can be achieved even in a small and thin ultrasonic motor. It can be said that it can be realized. It should be noted that a standing wave method and a traveling wave method can be considered for an ultrasonic motor using a piezoelectric vibrator, but the structure of the vibrating portion according to the present invention can be used in any method.

[0026]

According to the present invention, a layer containing a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution can be directly formed on a substrate.
A bulk piezoelectric body and a substrate can be joined via a layer containing a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution without using a conventional adhesive.

According to the present invention, a piezoelectric layer and a substrate are formed by forming a layer containing a ceramic dielectric synthesized by a mixing process of an EDTA complex-containing solution on a substrate on which a lower electrode is formed or a substrate functioning as a lower electrode. During the process, the adhesive layer that degrades the piezoelectric characteristics was eliminated. As a result, the force generated from the piezoelectric layer is irregularly reflected by the adhesive layer,
It propagates without being absorbed, does not generate unnecessary spurious vibrations, and exhibits good admittance characteristics. Further, the efficiency and durability of the motor can be improved.
In particular, as a driving source of a microstructure such as a micromachine, electric and mechanical performance can be improved, and reliability can be improved. In addition, by using the layer containing the ceramic dielectric synthesized by the mixing process of the EDTA complex-containing solution, not only can a dense film be formed, but also the adhesion to the substrate can be improved, and furthermore, the piezoelectric layer can be used. It is possible to increase the adhesion.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a manufacturing process according to an embodiment of the present invention.

FIG. 2 is a flowchart illustrating a manufacturing process according to an embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of an ultrasonic motor which is a ceramic dielectric device of the present invention.

FIG. 4 is a schematic diagram showing a structure of a vibrating portion of the ceramic dielectric device according to the present invention.

FIG. 5 is a table showing characteristics of a conventional ultrasonic motor.

FIG. 6 is a table showing characteristics of the ultrasonic motor according to the present invention.

FIG. 7 is a table showing frequency-rotation characteristics of the ultrasonic motor according to the present invention.

FIG. 8 is a table showing the efficiency of the ultrasonic motor according to the present invention.

FIG. 9 is a table showing the durability of the ultrasonic motor according to the present invention.

FIG. 10 is a schematic view showing a structure of a vibrating portion according to a conventional manufacturing method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Layer containing ceramic dielectric synthesized by mixing process of EDTA complex-containing solution 2 Piezoelectric layer 3 Substrate 4 Lower electrode 5 Upper electrode 6 Vibrating body 7 Moving body (rotor) 8 Friction material 9 Fixed base 10 Pressure spring 11 Central axis 12 Lead wire 13 Stator 14 Adhesive 15 Piezoelectric body

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshihiko Sakuhara 1-8-8 Nakase, Mihama-ku, Chiba-shi, Chiba Seiko Instruments Inc.

Claims (1)

[Claims] A first step of forming a layer containing a ceramic dielectric synthesized on a substrate by a mixing process of a solution containing an ethylenediaminetetraacetic acid complex; and a step of forming a piezoelectric substance on the substrate via the layer containing the ceramic dielectric. And a second step of joining the layers. A method for manufacturing a ceramic dielectric device, comprising: