JPH10163543A - Method for polarizing piezoelectric ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To evenly polarize a piezoelectric ceramic by polarizing the ceramic to a polarized state, which does not reach a desired polarized state in the air in an initial polarization treating process and polarizing the ceramic to the desired polarized state in the air in an additional polarization treating process. SOLUTION: In the initial polarization treating process by means of an initial polarization treating device 1, a piezoelectric ceramic substrate 3 is polarized to a polarized state which does not reach a desired polarized state. After the initial polarization treating process, the substrate 3 is brought to an additional polarization treating process 2, in which the substrate 3 is polarized to the desired polarized state. Since the substrate 3 brought to the process 2 is treated through the initial polarization treating process, only an additional polarization is performed on the substrate 3 so as to polarize the substrate 3 to the desired state from the initially polarized state. Since the substrate 3 is polarized in two stages in this way, the ceramic can be polarized evenly and sufficiently.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for polarizing a piezoelectric ceramic used for forming a piezoelectric component.

[0002]

2. Description of the Related Art In general, a piezoelectric ceramic substrate does not exhibit piezoelectric characteristics because the spontaneous polarization in each crystal grain takes a domain structure when the firing treatment is performed, and the piezoelectric deformation is canceled out in the entire piezoelectric ceramic substrate. . In order to impart piezoelectric characteristics, a DC electric field must be applied to the piezoelectric ceramic substrate at a high temperature to perform a polarization process for orienting spontaneous polarization in the electrode direction.

Conventionally, the polarization processing of a piezoelectric ceramic substrate is performed by
In the case of a PZT-based material, after sintering a piezoelectric ceramic substrate, provisional double-sided electrodes made of a conductive paste such as silver are provided on the opposite surface of the piezoelectric ceramic substrate. Simultaneously immersed in insulating silicon oil at ~ 100 ° C and apply 2-3Kv / mm voltage for 30
Polarization was performed by applying for about a minute. Prior art documents on polarization include JP-A-64-12587,
There are JP-B-57-41109 and JP-B-49-32865.

[0004] However, even if the piezoelectric ceramic substrates use the same composition of piezoelectric ceramic substrate materials, the easiness of polarization is not always the same. While some piezoceramic substrates may be polarized to a desired state, other piezoceramic substrates may be under- or over-polarized, making uniform polarization difficult.

Conventionally, as a means for alleviating this problem, it is necessary to keep in mind that insufficient polarization is not caused.
A relatively high voltage of kV / mm was applied for a relatively long time of 30 minutes. For this reason, a discharge may occur in the insulating silicon oil tank, which may adversely affect the piezoelectric ceramic substrate.

In addition, it is inevitable that silver printed on the piezoelectric ceramic substrate as a temporary double-sided electrode will precipitate in silicon oil with the lapse of the polarization treatment time. The deposited silver must be separated and removed from the silicon oil. This is a very cumbersome task.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and an apparatus for polarizing a piezoelectric ceramic uniformly.

Another object of the present invention is to provide a polarization method and apparatus which can accurately perform polarization processing in the atmosphere without immersing the ceramic substrate in silicon oil.

[0009]

In order to solve the above-mentioned problems, a polarization method according to the present invention provides an initial polarization processing step (hereinafter referred to as an initial polarization processing step) for polarizing a piezoelectric ceramic. And a polarization treatment step (hereinafter referred to as a drive-in polarization treatment step). In the initial polarization processing step, polarization is performed in the atmosphere to a polarization state that does not reach a desired polarization state. In the drive polarization process, after the initial polarization process, a polarization process is performed in the atmosphere until a desired polarization state is reached.

As described above, in the initial polarization processing step, polarization is performed to a polarization state that does not reach a desired polarization state. Therefore, in the initial polarization treatment step, the applied voltage required for polarization can be significantly reduced as compared with the conventional case.

The piezoelectric ceramic that has undergone the initial polarization process is subjected to a drive polarization process. In the drive-in polarization process, the polarization process is performed until a desired polarization state is reached. Since the piezoelectric ceramic to be subjected to the drive polarization process has already undergone the initial polarization process, only the necessary polarization from the initial polarization state to the desired polarization state needs to be performed in the drive polarization process. Therefore, even in the drive-in polarization process, the applied voltage required for polarization can be significantly reduced as compared with the conventional case.

In each of the above-mentioned initial polarization processing step and drive-in polarization processing step, not in the insulating silicon oil tank,
Polarize the piezoelectric ceramic in air. As described above, since the applied voltage at the time of polarization may be low, such polarization in the atmosphere becomes possible. For this reason, the conventional problems associated with the polarization in the insulating silicon oil tank, for example, the adverse effects on the ceramic substrate due to the discharge, the deposition of silver from the temporary electrode, the separation and removal work, etc. could not be avoided conventionally. There is no room for problems.

Further, according to the two-step polarization process, even if the ceramic substrates are easily polarized, the polarization process is performed without excess or shortage, and the polarization is uniformly performed without causing insufficient or excessive polarization. Can be polarized.

[0014] Preferably, the drive-in polarization processing step is executed by being divided into a plurality of polarization processing steps. Also, the method includes a step of measuring the polarization state of the polarized piezoelectric ceramic after the initial polarization processing step and before performing the drive polarization processing step. Similarly, the method may include a step of measuring the polarization state of the polarized piezoelectric ceramic after the drive-in polarization processing step is completed. In both the initial polarization processing step and the drive polarization processing step, the polarization processing itself is performed by a method similar to the conventional method.

Other objects, configurations and advantages of the present invention will be described in more detail with reference to the accompanying drawings. The drawings merely show examples.

[0016]

FIG. 1 is a diagram showing the configuration of a polarization processing apparatus for performing a polarization method according to the present invention. The polarization process according to the present invention is performed after the electrode forming step of applying a conductive paste such as silver to the fired piezoelectric ceramic substrate 3 to form a double-sided electrode. It is preferable that the polarization process is performed by providing necessary facilities in a factory, and that the single-wafer process is performed by transporting the piezoelectric ceramic substrate 3 to each device one by one. It is desirable that the piezoelectric ceramic substrate 3 subjected to the polarization treatment is an aggregate having a large number of piezoelectric components.

The polarization processing apparatus according to the present invention comprises a first polarization processing apparatus (hereinafter referred to as an initial polarization processing apparatus) 1 and a second polarization processing apparatus.
(Hereinafter referred to as a drive-in polarizer) 2. The initial polarization processing device 1 polarizes the piezoelectric ceramic substrate 3 in the atmosphere to a polarization state that does not reach a desired polarization state. The polarization processing by the initial polarization processing apparatus 1 is an initial polarization processing step.

The drive polarization processing device 2 performs a polarization process on the piezoelectric ceramic substrate 3 processed by the initial polarization processing device 1 in the atmosphere until a desired polarization state is reached. The polarization processing by the drive polarization processing device 2 is a drive polarization processing step.

In the initial polarization processing step by the initial polarization processing apparatus 1, the piezoelectric ceramic substrate 3 is polarized to a polarization state that does not reach a desired polarization state. Therefore, in the initial polarization treatment step, the applied voltage required for polarization can be significantly reduced as compared with the conventional case. For example, a relatively high voltage of 2-3 kV / mm in the related art can be reduced to about 1 to 3 kV / mm, which is about 1/2 to 1/3.

The piezoelectric ceramic substrate 3 that has undergone the initial polarization processing step is carried into the drive polarization processing apparatus 2 and subjected to the drive polarization processing step. In the drive-in polarization process, a polarization process is performed on the piezoelectric ceramic substrate 3 until a desired polarization state is reached. Since the piezoelectric ceramic substrate 3 that has been subjected to the drive polarization process has already undergone the initial polarization process, only the insufficient polarization from the initial polarization state to the desired polarization state needs to be performed in the drive polarization process. Therefore, even in the drive-in polarization process, the applied voltage required for polarization can be significantly reduced as compared with the conventional case. For example, a relatively high voltage of 2-3 kV / mm in the related art can be reduced to about 1 to 3 kV / mm, which is about 1/2 to 1/3.

In both the initial polarization process and the drive-in polarization process, the piezoelectric ceramic substrate 3 is polarized not in the insulating silicon oil bath but in the atmosphere. For this reason, the conventional problems associated with the polarization in the insulating silicon oil tank, such as the adverse effects on the piezoelectric ceramic substrate 3 due to the discharge, the deposition of silver from the temporary electrode, and the separation and removal thereof, can be avoided conventionally. There is no room for problems that did not exist.

According to the two-stage polarization process, even if the piezoelectric ceramic substrate 3 has a different polarization easiness, the polarization process is performed in accordance with the degree of polarization, and insufficient polarization or excessive polarization occurs. Polarization can be performed uniformly without causing the polarization.

The polarization process itself is performed by a method similar to the conventional one. The initial polarization process and the drive-in polarization process are performed by applying a DC voltage to both electrodes while heating the piezoelectric ceramic substrate 3. As the means, the initial polarization processing apparatus 1 includes a work table 11, a substrate mounting surface of the work table 11 is formed by a heating means 12 such as a hot plate, and a voltage application such as an electrode rod is applied above the heating means 12. Means 13 are provided.

In the embodiment, the driving polarization processing device 2
Includes a plurality of polarization processing stages 21, 22, and 23. Therefore, the drive-in polarization process is divided into a plurality of polarization processes by the polarization process stages 21 to 23 and executed. The drive-in polarization processing apparatus 2 includes one work table 24, and the substrate mounting surface of the work table 24 is formed by one heating unit 25, and the voltage application units 261-2 are provided.
63 is provided above the heating means 25.

The piezoelectric ceramic substrate 3 moves intermittently on the plate surface of the heating means 25. As a result, the polarization process is performed a plurality of times. As described above, the advantage of performing the polarization process in a plurality of times is that the DC applied voltage can be reduced,
The application time can be shortened.

For example, in the initial polarization processing device 1,
The piezoelectric ceramic substrate 3 provided with both electrodes is heated
By applying a voltage of about 1 kV for about 10 minutes while applying a voltage of about 150 ° C. for about 1 minute, a desired polarization state of about 3
The polarization process is performed from about 5% to several tens%.

Next, in each of the polarization processing stages 21 to 23 of the driving polarization device 2, the piezoelectric ceramic substrate 3 is heated by the heating means 12 under the same temperature conditions as those of the initial polarization processing device 1 and at the same time. DC voltage 60 ~
Apply for about 30 seconds. Thereby, polarization is performed until a desired polarization state is reached. In each of the polarization processing stages 21 to 23, the drive-in polarization processing is performed in steps of 10 to several percent. However, this is only an example, and the polarization condition is set according to the material of the piezoelectric ceramic substrate 3.

FIG. 2 is a view showing another embodiment of the polarization processing apparatus according to the present invention. In this embodiment, polarization change measuring devices 31 to 33 for measuring the polarization change of the piezoelectric ceramic substrate 3 after each polarization process are provided in one stage. The polarization change measuring device 31 includes a pair of probes 311, 312, and is arranged at a stage subsequent to the initial polarization processing device 1. The polarization change measuring device 32 includes a pair of probes 321 and 322 and is arranged at a stage subsequent to the first drive-in polarization processing device 21. The polarization change measuring device 33 includes a pair of probes 33.
1 and 332, and is disposed downstream of the second drive-in polarization processing device 22. The initial polarization processing apparatus 1 includes a work table 11, a heating unit 12, and a voltage applying unit 13, as in the embodiment shown in FIG.

The first drive polarization processing device 21 includes a work table 211, a heating unit 212, and a voltage application unit 213.
Is provided. The second drive polarization processing device 22 includes a work table 221, a heating unit 222, and a voltage application unit 223. Therefore, also in this embodiment, since the polarization process can be performed a plurality of times in the drive polarization process, the DC voltage may be a relatively low voltage and the application time may be short. This has already been described with reference to FIG.

As the polarization change measuring devices 31 to 33, a configuration in which a DC voltage is generated from the piezoelectric ceramic substrate 3 subjected to the polarization treatment and the voltage value is measured by a galvanometer can be adopted. In addition, data obtained by the polarization change measuring devices 31 to 33 can be processed by a computer and used as data for setting conditions for the next drive-in polarization process.

According to the above configuration, after the polarization processing of the piezoelectric ceramic substrate 3, the polarization change of the piezoelectric ceramic substrate 3 is measured by the polarization change measuring devices 31 to 33, and based on the measurement data, each of the drive-in polarization processing is performed. The time setting can be adjusted and controlled as needed. Therefore, the polarization processing of the piezoelectric ceramic substrate 3 can be performed more accurately.

However, in the present invention, the polarization process of the piezoelectric ceramic substrate 3 is performed by dividing the polarization process into an initial polarization process and a drive-in polarization process. Can be obtained as The polarization data shows substantially similar numerical values not only in the case of the same piezoelectric ceramic substrate 3 but also in the case of piezoelectric ceramic substrates 3 manufactured in the same lot. Therefore,
By setting the polarization conditions in each step based on the polarization data, it is possible to uniformly perform the polarization processing to a desired polarization state without particularly providing the polarization change measuring devices 31 to 33.

FIG. 3 shows a cleaning step of removing the double-sided electrodes from the piezoelectric ceramic substrate 3 subjected to the polarization treatment. The piezoelectric ceramic substrate 3 that has been subjected to the polarization processing is sent to a cleaning processing step as shown in FIG. 3 and subjected to a cleaning processing for removing temporary double-sided electrodes from the piezoelectric ceramic substrate 3. The cleaning process includes immersion cleaning tank 41, foam cleaning tank 42, shower cleaning tank 4
3 and the ultrasonic cleaning tank 44 are sequentially arranged, and these tanks 4
The piezoelectric ceramic substrates 3 are sequentially processed by 1 to 44. Thereby, the temporary double-sided electrode attached to the piezoelectric ceramic substrate 3 can be reliably removed. The piezo-ceramic substrate 3 after the cleaning process is stored in the stocker 45 and can be transported to the next step.

[0034]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a polarization method and apparatus capable of uniformly polarizing a piezoelectric ceramic. (B) without immersing the ceramic substrate in silicon oil,
It is possible to provide a polarization method and apparatus capable of performing polarization processing accurately in the atmosphere.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a polarization processing apparatus that performs a polarization method according to the present invention.

FIG. 2 is a diagram illustrating another configuration of a polarization processing apparatus that performs the polarization method according to the present invention.

FIG. 3 is a view showing a cleaning step.

[Explanation of symbols]

1 First polarization processing device (initial polarization processing device) 2 Second polarization processing device (run-in polarization processing device)

Claims (14)

[Claims] 1. A method for polarizing a piezoelectric ceramic, comprising: in a first polarization step, a polarization state in air is reduced to a polarization state that does not reach a desired polarization state; A polarization method in which, after the first polarization processing step, a polarization processing is performed in the atmosphere until a desired polarization state is reached. 2. The polarization method according to claim 1, wherein the second polarization processing step is performed in a plurality of polarization processing steps. 3. The polarization method according to claim 1, wherein after the first polarization processing step is completed, and before the second polarization processing step is performed, the polarization-processed piezoelectric ceramic is removed. A polarization method including a step of measuring a polarization state. 4. The polarization method according to claim 1, 2 or 3, further comprising a step of measuring a polarization change of the polarized piezoelectric ceramic after completing the second polarization processing step. Method. 5. The polarization method according to claim 1, wherein the piezoelectric ceramic subjected to the first polarization processing step is subjected to a sintering process, and a temporary double-sided electrode is provided on both opposing surfaces. The substrate is a polarized method. 6. The polarization method according to claim 5, wherein in the first polarization processing step and the second polarization processing step, a DC voltage is applied to the double-sided electrode while heating the piezoelectric ceramic. Polarization method performed by applying. 7. An apparatus for polarizing a piezoelectric ceramic, comprising: a first polarization processing apparatus and a second polarization processing apparatus, wherein the first polarization processing apparatus has a desired polarization in air. The second polarization processing device polarizes the piezoelectric ceramic processed by the first polarization processing device in the air to a polarization state that does not reach the state.
A polarization processing apparatus that performs polarization processing until a desired polarization state is reached. 8. The polarization processing apparatus according to claim 7, wherein the second polarization processing apparatus includes a plurality of polarization processing stages. 9. The apparatus according to claim 7, further comprising a polarization change measuring device, wherein the polarization change measuring device measures a polarization change of the piezoelectric ceramic polarized by the first polarization processing device. Polarization processing equipment. 10. The apparatus according to claim 7, 8 or 9, further comprising a second polarization change measuring device, wherein the second polarization change measuring device is polarized by the second polarization processing device. A polarization processing device that measures the polarization change of the processed piezoelectric ceramic. 11. The apparatus according to claim 7, wherein the first polarization processing device and the second polarization processing device include a heating unit and a voltage application unit, and the heating unit includes: A polarization processing apparatus for heating the piezoelectric ceramic mounted on the upper surface thereof, and wherein the voltage applying means applies a DC voltage to the piezoelectric ceramic mounted on the heating means. 12. The polarization processing apparatus according to claim 11, wherein the second polarization processing apparatus includes a plurality of combinations of the heating unit and the electrode plate. 13. The polarization processing apparatus according to claim 12, wherein a polarization change measuring device is provided for each combination of the heating means and the electrode plate, and each of the polarization change measuring devices is the piezoelectric ceramic. A polarization processing device that measures the polarization change of a substrate. 14. The polarization processing apparatus according to claim 12, wherein the heating unit and the voltage application unit are provided on a same work table.