JPH09260736A - Laminated ceramic element and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the migration and insulation breakdown of an element and to improve the reliability by purifying the surface of the element by plasma, and to form a resin film on the surface of the element by plasma polymerization. SOLUTION: The fat, oil and other fine contaminant substances on the surface of a laminated ceramic element 6, which cannot be completely removed merely by cleaning it with organic solvent, are decomposed and removed by the operations of radical, electron and ion in plasma 3 such as tetrafluoromethane or oxygen. After the cleaning of the surface of the element 6 is finished by the plasma 3, a monomer gas for forming tetrafluoroethylene or polymerized film is introduced into an apparatus, and again plasma 3 is generated. Then, the surface of the element 6 can be formed with the polymerized film of fluororesin without recontaminating it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated type ceramic element such as a piezoelectric actuator or a piezoelectric transformer that generates a high electric field and a method for manufacturing the same, and its internal electrodes are resin-sealed in a cleaner state than before. However, the reliability of the device can be significantly improved.

[0002]

2. Description of the Related Art Some laminated ceramic elements have a structure in which internal electrodes are exposed on the element surface like a piezoelectric actuator. In such an element, in order to prevent dielectric breakdown or the like on the element surface, the element surface is cleaned and then sealed with epoxy resin, silicone resin, or the like. Since manufacturing of the laminated ceramics element requires operations such as cutting, polishing, and soldering of lead wires, the element surface is contaminated with oil and fat containing various contaminants.

Conventionally, the dirt on the surface of the element has been simply ultrasonically cleaned using a nonionic aqueous detergent, an organic solvent such as methylene chloride or propanol. However, such cleaning alone may not be sufficiently cleaned, or even if it is sufficiently cleaned, the element surface may be re-contaminated during subsequent drying and sealing operations. In a multilayer ceramic element, a high electric field of up to 1 kv / mm is often generated between the internal electrodes. In the element with the internal electrodes exposed, if the element surface is slightly contaminated, the internal electrodes with different potentials may be present. In some cases, defects such as dielectric breakdown may occur within a relatively short period of time due to the reason that migration easily occurs during the period.

[0004]

According to the present invention, the surface of a laminated ceramics element having a structure in which internal electrodes are exposed is completely cleaned so that no dirt remains, and resin-sealed without recontamination. It is an object of the present invention to provide a method for producing a monolithic ceramic element in which migration does not occur, that is, dielectric breakdown of the element is prevented and reliability is greatly improved, and a monolithic ceramic element produced by the present production method.

[0005]

According to the present invention, in resin sealing of a laminated ceramics element having a structure in which internal electrodes are exposed on the element surface, a step of cleaning the element surface with plasma, and an element surface by plasma polymerization And a step of forming a resin coating on the surface of the laminated ceramic element.

Further, according to the present invention, there is provided a monolithic ceramic element having a structure in which internal electrodes are exposed on the element surface, wherein the element surface is resin-sealed by plasma polymerization.

[0007]

[Function] Even if oil and other minute contaminants on the surface of the laminated ceramics element, which cannot be completely removed only by washing with an organic solvent, radicals, electrons and ions in plasma such as tetrafluoromethane (CF ₄ ) and oxygen Can be decomposed and removed by the action of. After cleaning the surface of the laminated ceramics element with plasma, introducing a monomer gas for forming a polymerized film such as tetrafluoroethylene into the device and generating plasma again will recontaminate the element surface. Instead, a polymerized film such as a fluororesin can be formed.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described as an embodiment of the present invention by the following method for manufacturing a piezoelectric actuator. However, the present invention is not limited to a piezoelectric actuator and can be applied to a laminated ceramic element such as a piezoelectric transformer.

A fine powder of lead zirconate titanate (PZT), a binder, a solvent, a dispersant, and a defoaming agent are added, and the mixture is dispersed in a medium stirring mill. After degassing in a vacuum, a doctor blade is formed into a green sheet having a thickness of 100 μm. Got the sheet. Ag / Pd paste is printed on this as an internal electrode.
~ 130 sheets were laminated and pressure-bonded. After firing these laminates,
The laminate was cut and silver was baked as an external electrode, and a lead wire was soldered to this to produce a laminated piezoelectric actuator element.

In order to remove dirt from the surface of the device, ultrasonic cleaning was performed with methylene chloride and nonionic detergent, and then rinsed with pure water. In order to prevent the external electrodes from being plasma-etched, a silicone resin was baked only on the external electrode portions. The laminated piezoelectric actuator element subjected to such pretreatment was loaded in the vacuum apparatus shown in FIG. 1 having parallel plate electrodes.

In FIG. 1, the laminated piezoelectric actuator element 6 which has been subjected to the above-mentioned pretreatment is arranged between the parallel plate electrodes 2 arranged above and below in the apparatus as shown in the drawing. While exhausting the gas in the device from the exhaust port 4 with a rotary pump (not shown), tetrafluoromethane mixed with 5% of oxygen gas is supplied from the gas supply port 5 so that the pressure inside the device becomes 0.1 Torr. Introduced. In this state, 13.5 is applied to the parallel plate electrode 2.
A high frequency power of 6 MHz and 100 W was applied by the high frequency power source 1 to generate plasma 3. The method of generating the plasma 3 may be any of the RF method, the direct current method, and the microwave method. By standing in the plasma 3 for 10 minutes, the contaminants on the surface of the laminated piezoelectric actuator element 6 were decomposed and removed.

After the surface of the laminated piezoelectric actuator element 6 is cleaned, the supply of tetrafluoromethane is stopped,
After the gas in the apparatus was once exhausted from the exhaust port 4, a gas in which tetrafluoroethylene and argon were mixed in the same amount was introduced from the gas supply port 5 so that the pressure inside the apparatus became 0.5 Torr. In this state, 13.56 MH is applied to the parallel plate electrode 2.
A high frequency power of z and 20 W was applied from the high frequency power source 1 to generate plasma 3, which was left for 3 hours to form a polymer film of tetrafluoroethylene on the surface of the laminated piezoelectric actuator element 6. The coating thickness was about 3 μm. After exhausting the mixed gas of tetrafluoroethylene and argon from the exhaust port 4, helium was introduced from the gas supply port 5 in order to further open the unsaturated bond in the coating resin and accelerate the crosslinking of the resin, and in the same manner as above. Plasma 3 was generated and left in this for 3 minutes to form a fluororesin coating. To further protect the coating, add 50% epoxy resin.
It was overcoated to a thickness of 0 μm. As the overcoat material, the same epoxy resin, silicone resin, or the like as the conventional one can be used.

As described above, according to the manufacturing method of the present invention, it is possible to form a stable fluororesin film while maintaining a highly clean state. Although the fluororesin coating film is formed on the surface of the laminated piezoelectric actuator element 6 in the above-mentioned embodiment, it is possible to change the kind of the monomer gas introduced into the apparatus to the silicone resin, the styrene resin, the ethylene resin, or other purposes for sealing. It is possible to form various resins in combination.

For comparison, an element coated with epoxy resin without ultrasonic treatment was also prepared, which was a conventional method of ultrasonic cleaning with methylene chloride and nonionic detergent, followed by rinsing with pure water. The laminated piezoelectric actuator element according to the present invention and the laminated piezoelectric actuator element manufactured by the conventional manufacturing method were prepared for each 500 pieces. These are 0-150v (3 ℃ in a constant temperature and humidity tank of 85 ℃, 60% RH.
(kv / mm), it was driven 100 million times at 100 Hz.

Eight (1.6) elements were manufactured by the conventional manufacturing method.
%) Caused dielectric breakdown by the time it reached 100 million times. On the other hand, in the device according to the present invention, there was no device that caused dielectric breakdown during 100 million driving.

[0016]

According to the present invention, the surface of the element is not recontaminated by simply cleaning the laminated ceramic element with plasma and changing the gas introduced into the apparatus to generate plasma. Since it is possible to perform resin encapsulation in a clean state, migration is suppressed between internal electrodes connected to different external electrodes on the element surface even when a high electric field is applied, and the element is insulated in a short time. It will not be destroyed and the reliability of the device will be greatly improved. In addition, the resin polymerized by plasma has a higher cross-linked structure than the resin produced by the usual synthetic method, and thus has high heat resistance and improved withstand voltage at high temperatures. Therefore, even if the element is used in a high temperature environment, dielectric breakdown is less likely to occur, and the operating temperature range of the element can be expanded to the high temperature side.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for plasma-processing a laminated ceramics element.

[Explanation of symbols]

 1 high frequency power supply 2 parallel plate electrode 3 plasma 4 exhaust port 5 gas supply port 6 multilayer ceramic element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 41/22 H01L 41/22 Z

Claims (3)

[Claims] 1. A resin sealing of a laminated ceramic element having a structure in which internal electrodes are exposed on the element surface, including a step of cleaning the element surface with plasma, and a step of forming a resin film on the element surface by plasma polymerization. A method for manufacturing a laminated ceramic element, comprising: 2. The laminated ceramics element according to claim 1, wherein the resin forming the coating film on the surface of the element by plasma polymerization is at least one selected from a fluororesin, a silicone resin, a styrene resin, and an ethylene resin. Manufacturing method. 3. A monolithic ceramic element having a structure in which internal electrodes are exposed on the element surface, wherein the element surface is resin-sealed by plasma polymerization.