JPH077193A - Production of multilayer piezoelectric actuator - Google Patents

Abstract

PURPOSE:To provide a multilayer piezoelectric actuator uniformly coated with a glass insulating material which can be used even under a high humidity, environment. CONSTITUTION:The multilayer piezoelectric actuator having a titanic acid, zirconic acid, or lead based inner electrode layer 70 is produced by applying specified thickness of paste of glass insulating material on the four sides of the actuator by dry or wet transfer, firing the past for a specified time at a specified temperature, applying an exterior part 15 of glass insulating material, and then connecting a terminal 16 with the outer electrode 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention utilizes the piezoelectric longitudinal effect,
The present invention relates to a laminated piezoelectric actuator that converts electrical input energy into mechanical energy such as displacement or force, and more specifically to a structure of a laminated piezoelectric actuator having high moisture resistance.

[0002]

2. Description of the Related Art Generally, in a laminated piezoelectric actuator of this type, a plurality of internal electrode layers in a piezoelectrically active ceramics portion are formed into a pair of external electrodes so that adjacent internal electrodes form counter electrodes. It is connected. In this laminated piezoelectric actuator, a plurality of internal electrodes are glass-insulated so as to form opposed internal electrodes layer by layer at the ends of the ceramic portion. Such a laminated piezoelectric actuator has a large electric field-induced strain and a high-speed response. Therefore, this laminated piezoelectric actuator is being used as a drive source for printer heads, positioners, valves, relays and the like.

Conventionally, a laminated piezoelectric actuator of this type has a structure as shown in FIG. Reference numeral 21 is a ceramics, 22 is an internal electrode, 23 is an external electrode, 24 is an electrically insulating portion, 25 is a central exterior portion, 26 is a terminal, and 27 is a laminated piezoelectric actuator including a ridgeline exterior portion. As shown in FIG. 2, the side surface of the conventional laminated piezoelectric actuator has a structure in which the opposing internal electrodes 22 are exposed. Therefore, in order to ensure electrical insulation of the laminated piezoelectric actuator, the side surface is covered with resin. Is common.

[0004]

It is difficult for the organic resin-based outer package to prevent the infiltration and permeation of water, and when the laminated piezoelectric actuator is used for a long time in a high humidity environment, the insulation resistance decreases. However, there is a drawback that it may lead to a short circuit. This drawback is that it is possible to prevent the infiltration and permeation of water by coating the side surface of the laminated piezoelectric actuator with a glass insulating material to an appropriate thickness, that is, by covering the exterior. However, in order to coat the glass insulating material on the laminated piezoelectric actuator, generally, a method in which a liquefied glass insulating material paste is directly printed or an electrodeposition method such as electrophoresis is generally used. However, in these methods, as shown in FIG. 2, there is a difference in thickness between the central exterior portion 25 and the ridgeline exterior portion 27,
There is a problem in that the thickness of the ridge line portion b is about 1/2 of that of the central portion a, and a sufficient effect for preventing infiltration and permeation of water cannot be obtained. Further, the method using electrodeposition has a problem in that it is formed on the electrode exposed portion, and a thick and uniform exterior portion cannot be obtained.

Generally, the cause of the decrease in insulation resistance of the conventional laminated piezoelectric actuator during long-term use in an environment of high humidity is not clear, but migration of the silver component contained in the internal electrode is considered. It is well known that when a DC voltage is applied in an environment where water is present, the reaction of the following formula easily proceeds at the silver electrode. Positive pole: Ag → Ag ⁺ + e Negative pole: Ag ⁺ + e → Ag When the above reaction progresses, silver grows in a dendritic manner from the negative pole, and the distance between the plus and minus poles shortens, resulting in a decrease in insulation resistance. It is supposed to do.

Therefore, in order to solve the above-mentioned drawbacks, the technical problem of the present invention is to provide a laminated piezoelectric actuator having a sufficiently uniform outer thickness of the glass insulating material which can be used even in a high humidity environment. To do.

[0007]

According to the present invention, in a packaging process for manufacturing a laminated piezoelectric actuator having a plurality of internal electrodes, a glass insulating material paste patterned to a uniform thickness is transferred by a dry method or a wet method. A method for manufacturing a laminated piezoelectric actuator, characterized in that a glass insulating material is formed on the surface of the laminated piezoelectric actuator by transferring the glass insulating material onto the surface of the laminated piezoelectric actuator by a method and then firing.

[0008]

[Function] When the moisture resistance of the laminated piezoelectric actuator is improved by coating the glass insulating material having a low moisture permeability, the glass insulating material patterned to have a uniform thickness in order to form a thick and uniform glass insulating material. The paste is transferred to the laminated piezoelectric actuator by dry and wet transfer methods, and then baked to secure a uniform and thick film pressure.

[0009]

The present invention will be described in detail with reference to the drawings. FIG. 1 is an explanatory view showing an embodiment of the present invention. In FIG.
Using a titanic acid, zirconic acid, or lead-based piezoelectrically active ceramics 11 as a starting material, a cross-section 5
A prototype of a laminated piezoelectric actuator having dimensions of 5 mm and a length of 9 mm was manufactured. The material of the internal electrodes 12 is a silver-palladium alloy, the intervals between the internal electrodes 12 are 115 μm, and the number of internal electrode layers is 70. Next, a glass insulating paste having a thickness of 0.5 mm is formed on the four side surfaces of the laminated piezoelectric actuator by a dry or wet transfer method.
After forming the exterior part 15 coated with glass by baking at 0 ° C. for 2 hours, the terminal 16 was connected to the external electrode 13 of the laminated piezoelectric actuator.

FIG. 3 shows an example of a method of forming a glass insulating paste by a transfer method.

FIG. 3A shows a dry transfer paper, which is a mount 33.
A film 32 is formed on the glass film, and a glass insulating paste 31 is further formed on the film.

As shown in FIG. 3B, this is mounted on a pedestal 38.
Mount 3 on the laminated piezoelectric actuator 37 placed on top.
Set the glass insulation paste 36 peeled from 3,
Silicon rubber 34 is placed on it, and heated from the upper stage by an upper pedestal 35 with a heating function at 170 ° C. under a pressure of 5 kg / cm ² for 10 seconds to form a glass insulating paste 36 on the laminated actuator 37. To do. Hereafter 4
Apply to the side.

FIG. 3C shows a wet transfer paper, which is a mount 42.
A glass insulating material paste 41 is formed on top. This was peeled from the glass insulating paste 41 from the backing paper 42 in water, attached to the four side surfaces of the laminated piezoelectric actuator, dried at 100 ° C. for 30 minutes, and coated.

In order to investigate the reliability of the prototyped laminated piezoelectric actuator in a high humidity environment, aging was carried out by continuously applying a DC voltage of 100 V in an atmosphere of a temperature of 40 ° C. and a relative humidity of 95%. For comparison, four side surfaces were covered with an epoxy resin manufactured by a conventional method. Table 1 shows the results of simultaneous aging of the laminated piezoelectric actuators.
Shown in. The number of samples subjected to aging was 30, respectively, and a case where the insulation resistance was reduced by three digits or more from before the start of aging was regarded as a failure, and the failure occurrence rate was shown in Table 1 as a cumulative failure rate by aging time.

[0015]

[Table 1]

As is clear from Table 1, in the conventional laminated piezoelectric actuator, the insulation resistance is lowered due to the infiltration of water with the passage of time, and 80% becomes defective after 500 hours.

The laminated piezoelectric actuator according to the present invention has a defect of 3% in 500 hours, which shows that the moisture resistance performance is remarkably superior to the conventional manufacturing method.

[0018]

As described in detail above, the laminated piezoelectric actuator manufactured by the method of the present invention can be operated for a long time even in a high humidity environment, and a highly reliable laminated piezoelectric actuator can be provided. Therefore, the application field can be expanded.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a laminated piezoelectric actuator according to the present invention. FIG. 1A is a plan view of a laminated piezoelectric actuator according to the present invention. FIG. 1B is a front view of the laminated piezoelectric actuator according to the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a conventional laminated piezoelectric actuator. FIG. 2A is a plan view of a conventional laminated piezoelectric actuator. FIG. 2B is a front view of a conventional laminated piezoelectric actuator.

FIG. 3 is an explanatory diagram showing a structure of a glass insulating material paste by a dry or wet transfer method. FIG. 3A is an explanatory diagram of the dry transfer paper. FIG.3 (b) is explanatory drawing which shows the bonding method of a dry seal. FIG. 3C is an explanatory diagram of the wet transfer paper.

[Explanation of symbols]

11,21 Ceramics 12,22 Internal electrode 13,23 External electrode 14,24 Electrical insulating part 15 (Glass insulating material formed by transfer method) Exterior part 25 (by conventional technology) Central exterior part 16,26 Terminal 27 Ridge line Exterior part 31, 36, 41 Glass insulation paste 32 Film 33, 42 Mount 35, 38 Base 34 Silicon rubber 37 Laminated piezoelectric actuator a Central part b Ridge part

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[Procedure amendment]

[Submission date] February 18, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Added

[Correction content]

[Figure 3]

Claims (1)

[Claims] 1. In a packaging process for manufacturing a laminated piezoelectric actuator having a plurality of internal electrodes, a glass insulating paste patterned to have a uniform thickness is transferred onto the surface of the laminated piezoelectric actuator by a transfer method. A method of manufacturing a laminated piezoelectric actuator, characterized by forming a glass insulating material on the surface of the laminated piezoelectric actuator by firing later.