JP2000262075A - Multilayer piezoelectric actuator - Google Patents

Abstract

(57) [Problem] To provide a laminated piezoelectric actuator that solves a short circuit or a reduction in insulation resistance between an outer internal electrode layer and an external electrode due to migration of an external electrode. SOLUTION: When manufacturing a multilayer piezoelectric actuator, an electrode stack is formed and an insulator layer 4 is formed so that upper and lower outer internal electrodes 2 have the same polarity, and then an external electrode 5 is formed. . Further, the polarization process is performed so that the polarity of the outer internal electrode layer 2 becomes the anode from which the material of the external electrode 5 is dissolved and moved by migration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a laminated piezoelectric actuator.

[0002]

2. Description of the Related Art Conventionally, in this field, as shown in FIG. 2, piezoelectric ceramic layers 103 and internal electrodes 101 are alternately stacked, and external electrodes 105 are formed such that every other layer forms an opposing electrode. It is connected to the. Internal electrode group (internal electrode layer) formed by laminating a plurality of internal electrodes 101
The polarities of the outer internal electrodes 102 and the other internal electrodes 101 at the outermost (uppermost and lowermost, that is, both ends) are the outer electrodes 1
The migration and the layered structure of the material No. 05 were not taken into consideration, and were determined by performing a polarization process. Hereinafter, the two outer internal electrodes at both ends are collectively referred to as an outer internal electrode layer.

[0003]

In the above-mentioned prior art, the polarity of the material of the external electrode 105 with respect to the migration was not taken into consideration for the polarity of the laminated piezoelectric actuator. Therefore, when the polarity of the anode serving as a dissolution source due to the migration of the external electrode 105 and that of the outer internal electrode layer 102 are different, the amount of the external electrode closer to one inner electrode layer is smaller than that of the other internal electrode layers. Much migration occurs between the electrode 102 and the external electrode 105, and this migration causes a short circuit or a decrease in insulation resistance.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a laminated piezoelectric actuator which can solve the problem of short-circuit between the outer internal electrode layer and the external electrode due to migration of the external electrode or decrease in insulation resistance.

[0005]

When manufacturing a laminated piezoelectric actuator, an electrode stack is formed and an insulator layer 4 is formed so that upper and lower outer electrodes 2 have the same polarity, and then external electrodes are formed. 5 is formed. Further, the polarization process is performed so that the polarity of the outer internal electrode layer 2 becomes the anode from which the material of the external electrode 5 is dissolved and moved by migration.

[0006]

According to the present invention, the material ratio of the adjacent external electrodes 5 can be reduced by making the polarity of the source from which the external electrodes 5 are dissolved and moved by migration and the polarity of the outer internal electrodes 2 the same. Since the migration of the external electrode 5 with respect to the outer internal electrode 2 is often eliminated, a short circuit between the outer internal electrode 2 and the external electrode 5 or a decrease in insulation resistance can be solved.

[0007]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a laminated piezoelectric actuator according to an embodiment of the present invention. FIG. 1 is a view showing the structure of a laminated piezoelectric actuator according to the present invention. In the present embodiment, silver is used. In the multilayer piezoelectric actuator, the total number of layers of the internal electrode 1 is l
01, and an insulating layer 4 is formed so that the internal electrode 1 becomes a counter electrode every other layer.
Is formed of silver. Thereafter, a polarization treatment was performed so that the upper and lower outer internal electrodes 2 became anodes.

[0008] The laminated piezoelectric actuator manufactured by the above method is subjected to DCl 50 at 40 ° C and 90% environment.
V voltage is applied to each of the upper and lower inner electrodes 1 (total of 4 layers).
An investigation was made on the occurrence of a short circuit or deterioration of insulation resistance between the semiconductor device and the external electrode 5.

For comparison, the total number of layers of the internal electrode 1 is set to 1
A similar investigation was also conducted on a laminated piezoelectric actuator manufactured with 00 layers and upper and lower internal electrode layers having different polarities. Up to 500 hours, internal electrode 1 in each of upper and lower two layers
Table 1 below shows the number of occurrences of short-circuit or insulation resistance reduction between the external electrode 2 and the external electrode 2.

[0010]

[Table 1]

From the results shown in Table 1, in the multilayer piezoelectric actuator of the present invention, no short-circuit or reduction in insulation resistance between the upper and lower outer electrode two layers and the adjacent inner and outer electrodes 1 and 5 was observed. The difference from the conventional method was confirmed.

[0012] The above effect is not limited to silver as an external electrode material, and any electrode material can be produced by migration.
When the material of the external electrode 5 melts and moves at the anode, the same effect as described above can be obtained by manufacturing the outer internal electrode 2 to be the anode.

As shown in FIG. 2, the uppermost outer internal electrode and the lower inner electrode are continuously made to have the same polarity,
On the other hand, the same effect as described above can be obtained even when the lowermost outer internal electrode and the upper inner electrode are continuously made to have the same polarity.

Also, as shown in FIG. 3, even if a part of the piezoelectric ceramic is used as an insulating layer without forming a part of the internal electrode so that the internal electrode becomes a counter electrode every other layer, the same as above. The effect of is obtained.

[0015]

According to the present invention, there is an advantage that occurrence of a short circuit or a decrease in insulation resistance between the outer inner electrode due to migration of the outer electrode and the inner electrode and the outer electrode having a different polarity adjacent thereto can be reduced. It has become possible to provide a laminated piezoelectric actuator.

[Brief description of the drawings]

FIG. 1 is a diagram showing a sectional structure of a multilayer piezoelectric actuator of the present invention.

FIG. 2 is a diagram showing a cross-sectional structure of a laminated piezoelectric actuator in which upper and lower outer electrodes and adjacent inner electrodes have the same polarity.

FIG. 3 is a diagram showing a cross-sectional structure of a laminated piezoelectric actuator having a structure in which an internal electrode is not formed in a portion connected to an external electrode.

FIG. 4 is a diagram showing a cross-sectional structure of a conventional laminated piezoelectric actuator.

[Explanation of symbols]

 Reference Signs List 1 internal electrode (including external internal electrode) 2 external internal electrode 3 piezoelectric ceramic layer 4 insulator layer 5 external electrode

Claims (3)

[Claims] 1. A laminate in which two or more piezoelectric ceramic layers and three or more internal electrodes are laminated, an insulator layer on the side surface of the laminate such that every other internal electrode becomes a counter electrode, In the laminated piezoelectric actuator having an external electrode formed thereon, each of the uppermost and lowermost outer internal electrodes of the internal electrode layers is moved when the external electrode dissolves and moves by migration. A multilayer piezoelectric actuator characterized by using an anode as a moving source. 2. The multilayer piezoelectric actuator according to claim 1, wherein the upper and lower outer internal electrodes and each of the internal electrodes adjacent to the upper and lower outer internal electrodes are continuously used as anodes. Actuator. 3. The multilayer piezoelectric actuator according to claim 1, wherein a part of the internal electrode is not formed so that the internal electrode becomes a counter electrode every other layer.
A laminated piezoelectric actuator, wherein a part of the piezoelectric ceramic layer is an insulator layer.