JPH05259524A - Laminated layer type piezoelectric element - Google Patents

Abstract

PURPOSE:To manufacture the title laminated layer type piezoelectric element having excellent electromigration resistance characteristics by a method wherein insulator layers are notched so as to expose the ends of inner electrodes in every other layer. CONSTITUTION:The piezoelectric bodies 1a-1x with inner electrodes 2a-2x formed thereon are laminated and integrated to be sintered later for manufacturing a piezoelectric laminated body. Next, these piezoelectric bodies 1a-1x are cut off in specific size, the whole region in almost laminated layer direction on two sides is coated with glass so as to form insulator layers 3A, 3B and then a part of the insulator layer 3A on one side is notched away in every other layer to expose inner electrodes. Next, the parts of the insulator layer 3B in every other layer as well as the inner electrodes not yet exposed in the preceding notching step are likewise notched away. Next, both sides are coated with silver paste reaching the exposed inner electrode parts so as to form outer electrodes 4A, 4B. Through these procedures, the outer electrodes 4A, 4B can respectively be connected to the inner electrodes 2a-2x in every other layer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated piezoelectric element, and more particularly to a piezoelectric element having improved electrical insulation and improved reliability.

[0002]

2. Description of the Related Art A laminated body formed by laminating a thin plate-shaped or film-shaped piezoelectric material with an internal electrode having substantially the same area as that of the piezoelectric material interposed, and two side surface portions of the side surfaces of the laminated body. A laminated piezoelectric element having an insulating material layer and a conductive material layer (hereinafter referred to as a full-face electrode type piezoelectric element) formed on each side is known as a laminated piezoelectric element having large displacement and high reliability. Kaisho 58-19607
4). However, it is very difficult to electrically insulate the internal electrodes having different polarities from each other in the full-surface electrode type piezoelectric element. Therefore, an insulating material is formed on every other internal electrode layer by the electrophoresis method and in the vicinity thereof (Japanese Patent Laid-Open No. 59-59).
175176), or a laminate in which a photosensitive resin film is formed on the side end faces of the laminate and the layers are removed by etching (JP-A-58-196071).

[0003]

However, in the piezoelectric element by the electrophoretic method, the insulating material exemplified by 3a to 3x in FIG. 2 has a low density, and on the inner electrode layer exemplified by 2a to 2x and its vicinity. The insulating material adheres only to. Therefore, as shown in a partially enlarged view in FIG. 3, the insulation distance between the internal electrodes 2d and 2c which have different polarities is further shrunk during sintering.
YZ is smaller than about half of m), and there is a problem that the withstand voltage is lowered. In the laminated piezoelectric element, in order to increase the displacement amount, it is usually several 10 to 100.
This is because it is necessary to apply a high voltage of about 150 V between the internal electrodes connected in parallel at a narrow interval of μm. Further, there is a problem that electromigration is intensified due to the synergistic effect of moisture in the air and voltage application. On the other hand, the piezoelectric element by the etching method does not have the problem as in the case of the electrophoretic method, but the processing temperature cannot be raised because the photosensitive resin is used. For example, even in the case of a polyimide resin, which is said to have high heat resistance among photosensitive resins, it is as low as 350 ° C. or lower. For this reason, the external electrode layer applied by the paste must be baked at a low temperature, and the material and manufacturing method of the external electrode layer that can be used are limited.
There is a problem that materials such as t (baking temperature of about 800 ° C.) cannot be used. Further, since the selection of the resin is limited to the photosensitive one, there is a problem that a resin having water permeability and low moisture resistance must be used for the insulating layer, and electromigration is further intensified. Further, there is also a problem that the thickness of the resin layer cannot be made too thick because it is necessary to perform photoetching. This means that it is not possible to meet the demands of increasing the insulation distance and increasing the diffusion distance of water. Therefore, it is an object of the present invention to provide a laminated piezoelectric element having an insulating layer which can have a sufficient insulation distance and a large thickness, and which has excellent electromigration resistance.

[0004]

According to the present invention, as shown in FIG. 1, a plurality of thin plate-shaped or film-shaped piezoelectric materials are laminated with an internal electrode having substantially the same area as the piezoelectric material interposed therebetween. A laminated piezoelectric element having a body and an insulating material layer and a conductive material layer respectively formed on two side surface portions of the side surface of the laminated body, wherein the insulating material layer is formed on the side surface portion of the laminated body. In this structure, the end portions of the internal electrodes that are not exposed have cutting processing removal portions that are exposed every other layer, and the conductive material layer substantially fills the cutting processing removal portions of the insulating material layer and exposes the internal electrical charges. The laminated piezoelectric element is characterized in that it is formed on the insulating material layer so as to integrally have a connecting portion that is electrically connected to the extreme portion. In the present invention, the external electrodes having different polarities may be taken out from two different side surfaces or one side surface.

That is, the present invention solves the technical problem of the prior art by forming a groove by cutting. Here, the cutting process is a dicing saw,
Processing by automatic cutting machines, laser processing machines, water jets, etc. In the present invention, the width of the cut w
Since it can be made small, it is possible to obtain a small-sized and large-displacement laminated piezoelectric element without being restricted even when the piezoelectric material is thin. For example,
When using a dicing saw, the width of the cut groove is 2
It can be narrowed to about 0 μm, and the thickness t of the insulating layer is 100 μm
It can be formed to a certain degree thick. Needless to say, the piezoelectric material in the present invention also includes so-called electrostrictive material.

[0006]

EXAMPLES Examples of the present invention will be described in detail below. FIG. 1 is a sectional view showing an embodiment of the present invention. That is, a small amount of an organic binder is added to a pre-calcined powder of a piezoelectric material containing Pb (Zr, Ti) O ₃ as a main component, and a slurry is prepared by dispersing the organic binder in an organic solvent. To a predetermined thickness (for example, 10
0 μm) to form a piezoelectric body (1). The Pd paste is screen-printed on the entire surface of the piezoelectric body (1) to form the internal electrodes (2). A predetermined number (for example, 100) of piezoelectric bodies (1) having the internal electrodes (2) are formed.
Approximately 1250 after stacking and integrating by hot pressing
If sintered at 0 ° C., a piezoelectric laminate including the piezoelectric body 1 and the internal electrode 2 can be obtained. This piezoelectric body has the required size (for example, 10m
m × 10 mm), and glass is applied to the two side surfaces almost all over the stacking direction to form an insulating material layer (3A,
3B) and then one side of the insulating material layer (3A)
Every other layer is cut with a dicing saw to expose the internal electrodes. Next, a part of the insulating material layer (3B) on the other side surface is similarly exposed every other layer by cutting the internal electrodes that have not been exposed previously with a dicing saw. Next, a silver paste is applied so as to reach the end portions of the internal electrodes exposed on both sides and to be electrically connected to form a conductive material layer to form external electrodes (4A, 4B). As a result, the external electrodes (4A, 4B) are connected to the internal electrode (2) every other layer.

The laminated piezoelectric element thus obtained and the conventional structure (comparative example) were tested with a maximum voltage of 200 V,
A life test was performed by repeatedly and continuously applying a voltage pulse having a pulse width of 1 mS. The displacement of the laminated piezoelectric element of the present invention is 15
It was not destroyed even when a voltage pulse of 100 million times was repeatedly applied. On the other hand, the comparative example had a maximum displacement of 5 μm and was destroyed by repeated applied voltage pulses of about 25,000 times.

[0008]

As described above, according to the present invention, it is possible to obtain a laminated piezoelectric element having improved insulation characteristics and improved electromigration resistance.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a laminated piezoelectric element according to the present invention.

FIG. 2 is a diagram showing an example of a conventional laminated piezoelectric element.

FIG. 3 is a partially enlarged view of FIG.

[Explanation of symbols]

1a piezoelectric material, 1b piezoelectric material, 1c piezoelectric material,
1d piezoelectric material 1e piezoelectric material, 1f piezoelectric material, 1g piezoelectric material,
1x piezoelectric material 2a internal electrode, 2b internal electrode, 2c internal electrode,
2d internal electrode 2e internal electrode, 2f internal electrode, 2g internal electrode,
2x internal electrode 3A insulating material layer, 3B insulating material layer 4A external electrode, 4B external electrode w cut portion width, t insulating material layer thickness

Claims (2)

[Claims] 1. A laminated body formed by laminating a plurality of thin plate-shaped or film-shaped piezoelectric materials with an internal electrode having substantially the same area as the piezoelectric material interposed, and two side surface portions of the side surfaces of the laminated body. A laminated piezoelectric element having an insulating material layer and a conductive material layer respectively formed on the insulating material layer, wherein the insulating material layer has one end portion of the internal electrode not exposed at the other side surface portion of the laminate. The conductive material layer substantially fills the cut processing removed portion of the insulating material layer, and the connecting portion electrically connected to the exposed internal electrode end is integrally formed. 2. A laminated piezoelectric element, which is formed on the insulating material layer as described in 1. 2. A laminated body formed by laminating a plurality of thin plate-shaped or film-shaped piezoelectric materials with an internal electrode having substantially the same area as the piezoelectric material interposed, and an insulation formed on one side surface of each of the laminated bodies. A laminated piezoelectric element having a material layer and a conductive material layer, wherein the insulating material layer has a notch processing removal portion where the end portions of the internal electrodes of the laminated body which are not exposed are exposed alternately. The conductive material layer is formed on the insulating material layer so as to substantially fill the cut-and-removed portion of the insulating material layer and integrally have a connecting portion that is electrically connected to the exposed internal electrode end portion. A laminated piezoelectric element characterized in that