JP2958505B2 - Connection structure between internal electrode and external electrode of multilayer piezoelectric element - Google Patents

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 method for electrically connecting external electrodes formed on upper and lower surfaces to internal electrodes disposed between piezoelectric layers. Regarding the connection structure.

[0002]

2. Description of the Related Art As a laminated piezoelectric actuator using a piezoelectric material, for example, as shown in FIG. 4, an internal electrode 52 having a partial electrode structure is disposed between a plurality of piezoelectric A laminated piezoelectric element 55 in which an external electrode 54 is provided so that a laminated body 53 composed of a body layer 51 and an internal electrode 52 extends from the side surface from which the internal electrode 52 is drawn to the upper and lower surfaces thereof, A plurality of stacked piezoelectric actuators have been proposed in which a plurality of stacked piezoelectric actuators are connected via a lead 56, and a predetermined metal plate 56 is connected by a lead wire 57 and fixed by spring pressure.

[0003] In the multilayer piezoelectric element 55 constituting the above-described multilayer piezoelectric actuator, the internal electrodes 5 are provided.
As shown in FIG. 5, 2 is alternately drawn to the opposite end so as to be electrically connected to the external electrode 54 (FIG. 4) on the opposite side every other layer.

The external electrodes 54 include the internal electrodes 5.
A thick-film electrode is used in consideration of the reliability of conduction with the second electrode.

[0005] In this laminated piezoelectric actuator, a metal plate 56 inserted between the laminated piezoelectric elements 55 and an external formed so as to extend to the upper and lower surfaces of each laminated piezoelectric element 55. There is an advantage that continuity between the internal electrode 52 and the metal plate 56 can be obtained only by contacting the electrode 54.

[0006]

However, in the above-described multilayer piezoelectric actuator, the multilayer piezoelectric element 55
The external electrodes 54 are formed so as to extend from the side surfaces of the stacked body 53 to the upper and lower surfaces, and therefore, as shown in FIG. As a result, the flatness of the upper and lower surfaces of the multilayer piezoelectric element 55 is impaired. Therefore, when a plurality of stacked piezoelectric elements 55 are stacked via the metal plate 56, the stacked state (connected and fixed state) becomes unstable, and the stacked state cannot be reliably fixed. When used, there is a problem that destruction is caused by an external force.

The present invention has been made to solve the above-mentioned problem, and it is possible to arrange an external electrode formed on the upper and lower surfaces and a piezoelectric layer without impairing the flatness of the upper and lower surfaces of the laminated piezoelectric element. It is an object of the present invention to provide a connection structure between an internal electrode and an external electrode of a laminated piezoelectric element which can surely connect a provided internal electrode.

[0008]

In order to achieve the above object, a connection structure between an internal electrode and an external electrode of a multilayer piezoelectric element according to the present invention is provided between a plurality of piezoelectric layers and between the piezoelectric layers. Internal electrode, a side surface from which the internal electrode is drawn out, and a laminated piezoelectric element comprising external electrodes formed on the upper and lower surfaces, wherein the internal electrode is provided on at least one of the upper and lower external electrodes. A connection structure for connecting
A pore is formed in the piezoelectric layer near the external electrode on the lower surface, and a conductive material is penetrated therein, and the internal electrodes and the external electrodes on the upper and lower surfaces are passed through the conductive material and the external electrodes formed on the side surfaces. Is made conductive.

The present invention is not limited to the case where the internal electrode is connected to both the upper and lower external electrodes, but the connection structure when the internal electrode is connected to only one of the upper and lower external electrodes. Is also included.

In the connection structure between the internal electrode and the external electrode of the multilayer piezoelectric element according to the present invention, as a method for selectively forming pores in a predetermined piezoelectric layer, for example, it is intended to form pores. The defoaming process is performed on the green sheet of the piezoelectric layer not to be performed, while the defoaming process is not performed on the green sheet of the piezoelectric layer on which the pores are to be formed, or a process of actively mixing bubbles is performed. It is possible to use a method of forming pores by applying the method.

As a method of infiltrating the conductive material into the pores, a conductive paste is applied to the green sheet of the piezoelectric layer in which the pores are formed as described above, and the paste is baked, so that the inside of the pores of the piezoelectric layer is formed. A method of infiltrating a conductive material or the like can be used.

The method for selectively forming pores in a predetermined piezoelectric layer and allowing a conductive material to penetrate into the pores is not limited to the above method, and other methods can be used. It is.

[0013]

In the structure for connecting an internal electrode and an external electrode of a laminated piezoelectric element according to the present invention, pores are selectively formed in a piezoelectric layer located close to the external electrode, and a conductive material is formed therein. The penetration allows the piezoelectric layer to have conductivity. Therefore, unlike the conventional laminated piezoelectric element, the external electrodes formed on the side surfaces (which are electrically connected to the internal electrodes) do not extend to the upper and lower surfaces thereof, and are formed on the side surfaces. Thus, each internal electrode can be electrically connected to the upper and lower external electrodes via the piezoelectric layer provided with conductivity.

Therefore, as in the case of the conventional multilayer piezoelectric element, the external electrodes formed on the corners of the multilayer body are seen when the external electrodes formed on the side surfaces of the multilayer body are wrapped around the upper and lower surfaces. Prevents the formation of bumps on the electrodes (thick film electrodes) and ensures the flatness of the upper and lower surfaces of the laminated piezoelectric element, while ensuring that each internal electrode and the upper and lower external electrodes are connected. It becomes possible to conduct.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The features of the present invention will be described in more detail with reference to the embodiments of the present invention. FIG. 1 is a sectional view showing a laminated piezoelectric element in which an internal electrode and an external electrode are connected by a connection structure according to one embodiment of the present invention.

The laminated piezoelectric element 5 includes a plurality of laminated piezoelectric layers (piezoelectric layers made of a lead zirconate titanate-based material) 1 and an inner portion disposed between the plurality of piezoelectric layers 1. Electrodes 2, external electrodes 4 a and 4 b formed on the side from which the internal electrodes 2 of the multilayer body 3 including the plurality of piezoelectric layers 1 and the internal electrodes 2 are drawn out, and upper and lower surfaces of the multilayer body 3 It is configured to include the formed external electrodes 14a and 14b.

The upper and lower external electrodes 14a, 14
b (ie, the uppermost layer 1 (1
a), the next piezoelectric layer 1 (1b), the lowermost piezoelectric layer 1 (1c), and the next piezoelectric layer 1 (1d)) have pores 10a, 10b formed in the center thereof. At the same time, a conductive material (electrode for conduction) 11 (11
a, 11b). In the multilayer piezoelectric element 5 of this embodiment, the upper and lower external electrodes 14
internal electrodes 2 (2a), 2 (2c) closest to a, 14b
Are arranged in a floating state without conducting with the external electrodes 4a and 4b on the side surfaces, and are configured to function as relay electrodes.

The conductive material 11 (1) in the pore 10a
1a) and the second inner electrode 2b from the uppermost layer is electrically connected to the upper outer electrode 14a via the inner electrode 2a functioning as a relay electrode, and one side surface (left side surface).
Each internal electrode 2 drawn out and connected to the external electrode 4a
Are connected to the external electrode 14a on the upper surface via a path of the external electrode 4a → the internal electrode 2b → the conductive material 11a → the internal electrode 2a → the conductive material 11a.

The conductive material 11 (11
b) and the second inner electrode 2d from the lowermost layer conducts to the lower outer electrode 14b via the inner electrode 2c functioning as a relay electrode, and the other side surface (right side surface).
Each internal electrode 2 drawn out and connected to the external electrode 4b
Is connected to the lower external electrode 14b via a path of the external electrode 4b → the internal electrode 2d → the conductive material 11b → the internal electrode 2c → the conductive material 11b.

Therefore, in the multilayer piezoelectric element 5 of this embodiment, the external electrodes 4a and 4b formed on the side surfaces of the multilayer body 3 do not extend to the upper and lower surfaces,
External electrodes 4a, 4b and internal electrodes 2a, 2b, 2c, 2d and conductive materials 11a, 1 formed on the side surfaces of the laminate 3
1b, each internal electrode 2 and upper and lower external electrodes 14
a and 14b can be conducted.

Therefore, as in the case of the conventional laminated piezoelectric element, the external electrodes formed on the side surfaces of the laminated body are turned around the upper and lower surfaces to reach the external electrodes (thicknesses) at the corners as seen when the external electrodes are extended to the upper and lower surfaces. The internal electrodes 2 and the external electrodes 14a and 14b on the upper and lower surfaces are reliably secured while preventing the occurrence of protrusions (bulges) of the film electrodes) and securing the flatness of the upper and lower surfaces of the multilayer piezoelectric element 5. Can be conducted. In the multilayer piezoelectric element 5 of the above embodiment, the internal electrode 2 and the upper electrode
The external electrodes 14a and 14b on the lower surface can be made conductive with a resistance of 10Ω or less.

Next, a method of manufacturing the laminated piezoelectric element of the above embodiment will be described. In manufacturing the multilayer piezoelectric element, the raw materials are first weighed, pulverized, and crushed to produce a piezoelectric layer (green sheet) in the same manner as in a normal manufacturing method of a multilayer piezoelectric element. After defoaming, the mixture is formed into a sheet and punched into a predetermined shape. Then the internal electrodes are printed on this.

The green sheet of the piezoelectric layer, which is not intended to form pores, is subjected to a defoaming treatment. (If a pore is formed in the green sheet, a short circuit occurs between adjacent green sheets. On the other hand, the pores are formed by not performing the defoaming process on the green sheet of the piezoelectric layer on which the pores are to be formed. It should be noted that not only the defoaming process is not performed, but also the process of actively mixing bubbles (such as stirring).
, A pore may be formed in a green sheet of a predetermined piezoelectric layer.

Then, an electrode material (for example, conductive paste) is printed on the green sheet in a predetermined pattern, and each piezoelectric layer (green sheet) is laminated and pressed, and then fired at a predetermined firing temperature to obtain a laminate. . In this laminate, a predetermined pattern of internal electrodes is disposed between the piezoelectric layers, and in a predetermined piezoelectric layer having pores formed therein, a conductive material penetrates into the pores to increase conductivity. I have.

Next, the upper and lower surfaces of the obtained laminate are wrapped, and external electrodes are formed on the side surfaces from which the internal electrodes are drawn and the upper and lower surfaces (at this time, the external electrodes on the upper and lower surfaces of the laminate are Thus, the laminated piezoelectric element 5 as shown in FIG. 1 is obtained.

Since the upper and lower surfaces of the laminated piezoelectric element 5 are flat, a plurality of laminated piezoelectric elements 5 are stacked via a metal plate 6 as shown in FIG. When the multilayer piezoelectric actuator is formed by fixing with a mechanical force, the multilayer piezoelectric elements 5 can be stably stacked, so that the plurality of multilayer piezoelectric elements 5 can be reliably connected and fixed to ensure reliability. It is possible to obtain a laminated piezoelectric actuator having high performance.

As shown in FIG. 3, two external electrodes 14a, 15a and 1 are connected to the upper and lower surfaces of the laminated piezoelectric element 5 so that the internal electrodes 2 drawn to different sides are electrically connected to each other.
4b and 15b (provided that the external electrodes 14a and 1b of the uppermost and lowermost piezoelectric layers 1 (1a) and 1 (1c) are formed).
4b, 15a, and 15b are formed in the pore 12
a, and 12b are formed, and the conductive material 13a is formed therein.
a, 13b are infiltrated), and the external electrodes 14a and 14b and 15a and 15
b is connected directly to each of the laminated piezoelectric elements 5
Is bonded with an adhesive 9, thereby eliminating the need for disposing a metal plate or connecting external electrodes formed on the side surfaces by soldering lead wires. In addition, the manufacturing method can be simplified.

In the above-described embodiment, pores are formed in the uppermost layer and the next piezoelectric layer on which the upper and lower external electrodes are formed, and in the lowermost layer and the next piezoelectric layer, and conductive layers are formed therein. The case where the conductivity is imparted by penetrating the material (FIG. 1), and the case where the pores are formed only in the uppermost and lowermost piezoelectric layers and the conductive material is penetrated therein to impart the conductivity (FIG. 1) Although 3) has been described, in the present invention, the piezoelectric layer to be provided with conductivity by selectively forming pores and penetrating a conductive material into the pores is not limited to these, and may be used as needed. It is also possible to provide a structure in which a conductive material is penetrated into a plurality of piezoelectric layers close to the external electrodes on the upper and lower surfaces to impart conductivity. In this case, it is preferable to print an electrode material on each of the green sheets on which the pores are formed, in order to easily obtain conductivity.

The present invention is not limited to the above-described embodiment in other respects. The type and composition of the material constituting the piezoelectric layer, the specific shape and the number of laminated layers of the piezoelectric layer, Various applications and modifications can be made within the scope of the invention with respect to the type of conductive material to be penetrated into the pores, the constituent materials of the internal electrode and the external electrode, their patterns, and the like.

[0030]

As described above, the connection structure between the internal electrode and the external electrode of the multilayer piezoelectric element according to the present invention forms pores in the piezoelectric layers near the external electrodes on the upper and lower surfaces and forms the pores therein. Since the conductive material is infiltrated and the internal electrodes and the external electrodes on the upper and lower surfaces are made conductive through the conductive material and the external electrodes formed on the side surfaces, as in a conventional laminated piezoelectric element, In addition, there is no need to form external electrodes by wrapping around from the side surfaces to the upper and lower surfaces, and the outer electrodes are disposed between the external electrodes formed on the upper and lower surfaces and the piezoelectric layer while ensuring the flatness of the upper and lower surfaces. It is possible to reliably connect the internal electrodes.

Therefore, when a multilayer piezoelectric actuator is formed by stacking a plurality of multilayer piezoelectric elements,
It is possible to obtain a highly reliable laminated piezoelectric actuator that is excellent in the stability of stacking (connecting and fixing) of the laminated piezoelectric elements and is not broken by an external force.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view showing a main part of a laminated piezoelectric actuator constituted by laminating laminated piezoelectric elements according to one embodiment of the present invention.

FIG. 3 is a sectional view showing a main part of another multilayer piezoelectric actuator formed by stacking multilayer piezoelectric elements according to one embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a conventional laminated piezoelectric actuator.

FIG. 5 is an exploded perspective view showing a pattern of an internal electrode of a multilayer piezoelectric element constituting a conventional multilayer piezoelectric actuator.

FIG. 6 is a cross-sectional view showing a main part of a conventional laminated piezoelectric actuator.

[Explanation of symbols]

Reference Signs List 1 piezoelectric layer 2 internal electrode 3 laminated body 4a, 4b external electrode formed on side surface 5 laminated piezoelectric element 6 metal plate 9 adhesive 10a, 10b, 12a, 12b pore 11a, 11b, 13a, 13b conductive material 14a , 14b, 15a, 15b External electrodes formed on upper and lower surfaces

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01L 41/083

Claims (1)

(57) [Claims] 1. A laminated piezoelectric device comprising a plurality of piezoelectric layers, internal electrodes disposed between the piezoelectric layers, side surfaces from which the internal electrodes are drawn, and external electrodes formed on upper and lower surfaces. A connection structure for connecting the internal electrode of the body element to at least one of the external electrodes on the upper and lower surfaces, wherein pores are formed in a piezoelectric layer close to the external electrodes on the upper and lower surfaces; The interior of the laminated piezoelectric element, wherein each internal electrode is electrically connected to the upper and lower external electrodes via the conductive material and the external electrodes formed on the side surfaces by penetrating the conductive material. Connection structure between electrodes and external electrodes.