JPS6262571A - Electrostrictive effect element - Google Patents

Abstract

PURPOSE:To prevent the end of a silver electrode conductor layer from migrating by coating the end of the layer exposed on the side of a sintered laminate with a thin film of metal which exhibits smaller migration characteristic than silver. CONSTITUTION:Powder of organic binder is mixed in powder of polycomponent solid solution ceramic having perovskite crystal structure to form a green sheet, silver paste is coated by printing thereon, 60-80 layers are laminated, sintered at high temperature to form a sintered laminate. Then, silver paste is coated by printing on the opposed sides of the block, baked to form a plurality pairs of external electrode conductor layers 1, 2, divided into small blocks including a pair, and coated with metal which exhibits smaller migration characteristic than silver on all the ends of the layer exposed on the side of the sintered laminate such as nickel metal film. Thus, since the ends of silver electrode conductor layers b1-bn are not contacted directly with the atmosphere, no migration with silver occurs even if the atmosphere contains moisture.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the structure of an electrostrictive element used in a piezoelectric actuator.

(Prior Art) Recently, the actuator for driving the print wire of an impact type dot printer head has begun to shift from the conventional actuator that uses electromagnetic force to one that uses piezoelectric effect. This piezoelectric actuator generates little heat, is compact and can be driven at high speed, so it
It is also very promising as a mechanical driving element for heads, various optical devices, precision positioning devices for precision machine tools, exposure devices for ULSI, and other devices.

However, since the mechanical displacement caused by the piezoelectric effect is essentially extremely small, the electrostrictive element that is to be the drive source of the actuator is , a structure in which piezoelectric ceramic members and internal electrode conductors are laminated in multiple layers to enhance the longitudinal effect of piezoelectricity is usually used. That is, this electrostrictive effect element is made by mixing an organic binder with a multi-component solid ceramic powder having a perovskite crystal structure to form a green sheet, and then coating the green sheet with a silver electrode conductor/IIfc paste, and then forming several tens of layers ( For example, 72 layers) are laminated and sintered. This sintered body has a static displacement of approximately 8 μm when the fired silver electrode conductor layers are connected alternately to form two comb-shaped internal electrodes and a DC voltage of approximately 90 layers is applied from the outside. Therefore, the problem of the mechanical displacement of the piezoelectric effect, which is essentially extremely small, has been solved to some extent by using it in conjunction with a "lever device."

(Problems to be Solved by the Invention) However, since the electrostrictive effect element made of this sintered body uses silver for the metal member forming the internal electrode, it is difficult to migrate in a humid atmosphere. 4E The side surfaces of the piezoelectric ceramic member are significantly contaminated.

That is, since the ends of the silver electrode conductor layer are all exposed on the side surfaces of the laminated sintered body, they are susceptible to migration, and the contaminated side surfaces of the piezoelectric ceramic member rapidly deteriorate its insulating properties. Therefore, when a moisture resistance test is performed, discharges occur frequently on the sides or corners, which greatly impedes yield and reliability.

(Object of the Invention) In view of the above circumstances, an object of the present invention is to provide an electrostrictive element made of a laminated sintered body that prevents migration of the ends of silver electrode conductor layers forming internal electrodes.

(Structure of the Invention) The electrostrictive effect element L of the present invention, a core J initial sintered body in which a pressure V ceramic member and a silver electrode conductor layer are alternately stacked, and the a.
A pair of external electrodes are provided on the opposing faces of the layered sintered body and are alternately connected to the gun electrode assembly dovetails every other layer through the blank layer to form two comb-shaped internal electrodes. The conductor layer includes a metal film with a small migration characteristic that covers the end of the silver electrode conductor layer that is transferred to the side surface of the sintered body.

(Means for Solving the Problems) That is, according to the present invention, the end portion of the silver electrode conductor layer exposed on the side surface of the laminated sintered body is made of a metal, such as copper, which exhibits a migration characteristic smaller than that of a metal.

Completely coated with a thin film of metal such as nickel or tin. These metal films can be easily formed using normal electroplating techniques. At this time, the metal film used may be formed of only one metal selected from copper, nickel, tin, etc., or may be a multilayer film containing one of these metals.5 (Function) This metal The membrane itself does not exhibit a small migration characteristic, and since it shields the ends of the conductor layer from the atmosphere, it can effectively prevent the occurrence of micromigration. The present invention will be described in detail below with reference to the drawings.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which the strain effect element 100 is composed of two thick piezoelectric ceramic members A,
and A2 between thin piezoelectric ceramic parts U'a+~a,
A laminated sintered body in which silver electrode conductor layers S and ~b0+1 are alternately stacked, and an insulating layer I and ~b0+1. Silver 1 based on +1
! The odd-numbered and even-numbered conductors of the other conductors rf'j b+ -b-+1 are connected in common on the side surface of the laminated sintered body, respectively, to form two comb-shaped interior 1) a pair of external electrode conductor layers with one pole at the bottom of the tank; ] and 2, and the silver electrode conductor FkE)+~b1 which is exposed on all sides of the aIW+ sintered body and the external part 1! The electrode conductor layer 1 and the nickel metal film 3 covering the entire exposed surface of the 2D are provided.

This nickel metal film 3 is formed by electroplating using the external electrode conductor layers 1 and 2 as a common negative electrode. Therefore, nickel gold f%@3 is fMt electrode layer ~bn
Naturally, the negative electrode is deposited not only on the +1 end but also on the seat surface of the negative electrode itself. The hatched portions in FIG. 1 represent the foil-covered surfaces of the nickel metal film 3, and although they are not cross sections, they are particularly hatched for the purpose of easy identification.

The electrostrictive effect element 100 of this embodiment has a perovskite crystal structure as a multicomponent solid solution ceramic powder (for example, Pb).
(ZrT+)Us) is mixed with powder of an organic binder (for example, polyvinyl butyseal resin) to make a green sheet, and after printing and applying silver paste on this sheet, 60~
An 8-layer sintered body is formed by laminating 80 layers and performing high-temperature sintering (for example, at LOOO° C. or higher). According to this laminated sintering technology, it is possible to easily produce a large block of laminated sintered bodies in which thin piezoelectric ceramic members with a thickness of approximately Q, l mm and silver electrode conductor layers with a film thickness of approximately 0.005 mm are alternately laminated. Obtainable. Then, a plurality of pairs of external electrode conductor layers are formed on opposing sides of this block by printing and baking a silver paste. Therefore, if a pair of external electrode conductor layers is divided into small blocks and nickel plated, a nickel metal film will be coated on all the bases of the silver electrode conductor 1- exposed on the side surface of the laminated sintered body. be done.

FIG. 2 is a partial cross-sectional view of FIG. 1 taken along the line xx' in the vertical axis direction, showing that the exposed ends of the silver electrode conductor layers S, ~bil+ are all covered with the nickel metal 3. It shows the situation in a way that is easier to understand. Since the ends of the silver electrode conductors Nb and -bn coated with the nickel metal film 3 do not come into direct contact with the atmosphere, even if the temporary atmosphere contains moisture, the migration due to the silver material can be prevented. It does not cause yo/.

The above describes the case where nickel metal is used as the deposited metal, but any metal that is less likely to cause migration than silver, such as copper, can achieve the same effect, and may be used alone or in combination as appropriate. . Furthermore, the deposition means may be other than plating, such as electrodeposition or other methods.

(Effects of the Invention) As described in detail above, according to the present invention, migration of the silver electrode conductor layer due to the silver material can be effectively and reliably prevented by extremely simple means, thereby significantly increasing the reliability of the piezoelectric element. This has a remarkable effect, for example, in making it possible to produce piezoelectric actuators that fully utilize the piezoelectric longitudinal effect in a timely manner.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing one embodiment of the present invention, and FIG. 2 is a perspective view showing one embodiment of the present invention.
It is a partial sectional view when the figure is cut along the line xx' in the longitudinal axis direction. 100... Electrostrictive piezoelectric element, L2... External electrode conductor layer, 3... Nickel metal film, A,
, A, , a, ~a,,... Piezoelectric ceramic member, b1-b, +1... Silver electrode conductor layer (internal electrode), ■1-In+ 1...・Glass insulation layer. XL, 〆ichi agent patent attorney Uchihara, 1 information f figure

Claims (2)

[Claims] (1) A laminated sintered body in which piezoelectric ceramic members and silver electrode conductor layers are alternately stacked, and the silver electrode conductor layers are placed every other layer through insulating layers provided on opposing sides of the laminated sintered body, respectively. A pair of external electrode conductor layers that are alternately connected to constitute two comb-shaped internal electrodes, and a silver electrode conductor layer that has a migration property smaller than that of silver and covers the ends of the silver electrode conductor layer exposed on the side surface of the laminated sintered body. An electrostrictive effect element comprising a metal film. (2) The electrostrictive effect element according to claim (1), wherein the metal film is formed containing one metal selected from copper, nickel, and tin.