JP3057967B2 - 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 multi-layer piezoelectric element, and more particularly, to a multi-layer piezoelectric element in which an external electrode which is electrically connected to an internal electrode is disposed outside a laminated body of a piezoelectric layer and an internal electrode. The present invention relates to a piezoelectric element.

[0002]

2. Description of the Related Art As a laminated piezoelectric actuator using a piezoelectric material, for example, as shown in FIG. 5, an internal electrode 52 having a partial electrode structure is provided between a plurality of piezoelectric layers 51, and a piezoelectric device is provided. A laminate formed by arranging an external electrode 54 made of a thick-film electrode so that a laminate 53 composed of a body layer 51 and an internal electrode 52 extends from the side from which the internal electrode 52 is drawn to the upper and lower surfaces thereof. A multilayer piezoelectric actuator has been proposed in which a plurality of piezoelectric elements 55 are stacked via a metal plate 56, a predetermined metal plate 56 is connected by a lead wire 57, and is fixed by a spring pressure or the like.

[0003] In the multilayer piezoelectric element 55 constituting the above-described multilayer piezoelectric actuator, the internal electrodes 5 are provided.
As shown in FIG. 6, 2 is alternately drawn to the opposite end so as to be electrically connected to the external electrode 54 (FIG. 5) on the opposite side.

In this laminated piezoelectric actuator, a metal plate 56 inserted between each laminated piezoelectric element 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.

[0005]

However, in the above-described multilayer piezoelectric actuator, the multilayer piezoelectric element 55
Are formed so as to extend from the side surfaces of the stacked body 53 to the upper and lower surfaces (for example, thick film electrodes are printed on the upper and lower surfaces and directly connected to the thick film electrodes formed on the side surfaces). The external electrode 54 is formed by such a method as to make the external electrode 54 formed of a thick-film electrode at the corner of the laminated body 53 as shown in FIG.
8 are generated, and 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 problems, and has excellent flatness of upper and lower surfaces on which electrodes are formed.
When a multi-layer piezoelectric actuator is configured by stacking and joining a plurality of layers, it is possible to obtain a highly reliable multi-layer piezoelectric actuator that has excellent joining stability and does not break down due to external force. An object of the present invention is to provide a laminated piezoelectric element.

[0007]

In order to achieve the above object, a laminated piezoelectric element of the present invention comprises a plurality of piezoelectric layers, an internal electrode disposed between the piezoelectric layers, and an internal electrode extending from the piezoelectric layer. and external electrodes formed on the side surface which, in the laminated piezoelectric device comprising an external electrode formed on the upper and lower surfaces, the upper and lower surface of the external electrode of the laminated body of the piezoelectric layers and the internal electrode At least one of which is a thin-film electrode, and at least one of the external electrodes formed on the side surface of the laminate
Is formed so as to cover a part thereof , thereby directly conducting to external electrodes formed on the side surfaces of the laminate.

The present invention is not limited to the case where both the upper and lower external electrodes are thin film electrodes, but also includes the case where only one of the upper and lower external electrodes is thin film electrodes.

In the multilayer piezoelectric element of the present invention, as a method of forming thin film electrodes on the upper and lower surfaces, various thin film forming methods such as a sputtering method and a vapor deposition method can be applied.

Further , the laminated piezoelectric element according to the second aspect is characterized in that
The external electrode formed on the side surface is a thick film electrode.
Sign.

[0011]

According to the multilayer piezoelectric element of the present invention,
Since thin-film electrodes with small thickness and excellent flatness are used as external electrodes on the lower surface, the rise at the corners between the upper and lower surfaces and the side surfaces of the laminate has been increased, and the conventional thick-film electrodes The outer electrodes are much smaller than the external electrodes, and the flatness of the upper and lower surfaces after forming the external electrodes can be improved. Wrap around and form on the side of the laminate
Formed so as to cover at least a part of the formed external electrode.
Thus, even when the external electrodes on the upper and lower surfaces are directly connected to the external electrodes formed on the side surfaces of the laminate, the flatness of the upper and lower surfaces can be ensured.

Further, according to the laminated piezoelectric element of the second aspect ,
When the external electrode formed on the side surface is a thick film electrode,
By keeping the conduction resistance low,
To prevent disconnection due to heating
And increase the mechanical strength
(Especially to prevent scratching), reliability
Can be improved.

[0013]

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 according to one embodiment of the present invention. In the laminated piezoelectric element 5 of this embodiment, a plurality of piezoelectric layers (for example, a piezoelectric layer made of a lead zirconate titanate-based material) 1 and a plurality of piezoelectric layers 1 are disposed between the piezoelectric layers. The laminated body 3 is formed from the internal electrodes 2a and 2b extended to two side surfaces facing each other.

The two opposing side surfaces 3c and 3d of the laminated body 3 have external electrodes formed of thick film electrodes that are electrically connected to the internal electrodes 2a and 2b of the same polarity drawn to the side surfaces 3c and 3d. Electrodes 4c and 4d are formed. further,
External electrodes 4a and 4b formed of thin film electrodes are formed on the upper and lower surfaces 3a and 3b of the laminate 3. In addition,
The lower surface side external electrodes (thin film electrodes) 4a and 4b
Side 3c through the corners, Nde around write up to 3d, the laminate
Of external electrodes 4c and 4d formed on side surfaces 3c and 3d of
The side surface 3 of the laminate 3 is formed so as to cover a part thereof.
It is directly electrically connected to the external electrodes 4c and 4d formed on c and 3d.

Next, a method of manufacturing the multilayer piezoelectric element 5 of the above embodiment will be described. In manufacturing the laminated piezoelectric element 5, first, in order to manufacture a piezoelectric layer (green sheet), the raw materials are weighed, pulverized, mixed with a binder, defoamed, and formed into a sheet. Then, punch into a predetermined shape. Then the internal electrodes are printed on this.

Next, each piezoelectric layer (green sheet) is laminated and pressed, cut into a predetermined shape, and fired to obtain a laminated body. Then, after forming an external electrode (thick film electrode) on the side surface from which the internal electrode is drawn out of the obtained laminate, the upper and lower surfaces of the laminate are wrapped and flattened.

Then, as shown in FIG. 2A, after a metal mask 6 having a predetermined shape is applied to two corners at diagonal positions of the laminate 3, for example, a vapor deposition method, a sputtering method, or the like is performed. 2 (b), the upper and lower surfaces 3a, 3b of the laminated body 3 pass through the corners to the side surfaces 3c, 3c, as shown in FIG.
Look around write to the 3d, formed on the side surfaces 3c, 3d of the stack 3
External electrodes 4a and 4b formed of thin film electrodes are formed so as to cover a part of the external electrodes 4c and 4d . At this time, since the metal mask 6 is provided, it is possible to prevent the thin film electrode from adhering to unnecessary portions during vapor deposition or sputtering. In this manner, the outer electrodes 4a and 4b on the upper and lower surfaces are wrapped around the side surfaces 3c and 3d of the multilayer body 3, and the outer electrodes formed on the side surfaces 3c and 3d of the multilayer body 3 are formed.
The external electrodes 4a and 4b on the upper and lower surfaces are directly connected to the external electrodes 4c and 4d formed on the side surfaces of the multilayer body 3 by forming the partial electrodes 4c and 4d so as to cover a part of them. Then, by removing the metal mask 6, the laminated piezoelectric element 5 as shown in FIG. 1 can be obtained.

In the laminated piezoelectric element 5 thus formed, the external electrodes 4a and 4b on the upper and lower surfaces are formed of thin-film electrodes, and almost no swelling occurs at the corners of the laminated body 3. No (for example, when a conventional thick film electrode is used, the height of the protrusion reaches about 100 μm, whereas when a thin film electrode is used, the height of the protrusion is suppressed to about several μm. Therefore, the flatness of the upper and lower surfaces after the external electrodes 4a and 4b are formed can be remarkably improved as compared with the case of the conventional laminated piezoelectric element using a thick film electrode. Further, the upper and lower surface of the external electrodes 4a, 4b are side 3c through the corners of the laminated body 3, viewed around write up to 3d, the side surface 3c of the laminate 3, formed in 3d
Since the outer electrodes 4c and 4d are formed so as to partially cover the outer electrodes 4c and 4d , the upper and lower outer electrodes 4a and 4b are directly conducted to the outer electrodes 4c and 4d formed on the side surfaces 3c and 3d of the multilayer body 3. In this case, the flatness of the upper and lower surfaces is not impaired. In the multilayer piezoelectric element 5 of the above embodiment, the external electrodes 4a and 4b on the upper and lower surfaces and the external electrodes on the side surfaces can be conducted with a resistance of 10Ω or less.

Since the laminated piezoelectric element 5 has flat upper and lower surfaces, a plurality of laminated piezoelectric elements 5 are stacked via a metal plate 7 as shown in FIG. When a multilayer piezoelectric actuator is formed by fixing with a mechanical force, the multilayer piezoelectric element 5 can be stably stacked, so that the bonding stability is excellent and the multilayer piezoelectric actuator has high reliability. Can be obtained.

As shown in FIG. 4, the internal electrodes 2a, 2b and the external electrodes 4c, 4 extending from the upper and lower surfaces to the side surfaces of the laminated piezoelectric element 5 are different from each other.
d, two external electrodes 14a, 15a and 1
4b and 15b are formed, and the external electrodes 14a and 14b and 15a and 15b facing each other on the joint surface are directly connected to each other, and the multilayer piezoelectric elements 5 are bonded with an adhesive 8 to form a multilayer piezoelectric actuator. By eliminating the need for disposing a metal plate or connecting external electrodes formed on the side surfaces by soldering lead wires, the structure and manufacturing method of the multilayer piezoelectric actuator Can be simplified.

The present invention is not limited to the above embodiment, but includes the type and composition of the material constituting the piezoelectric layer, the specific shape and the number of layers of the piezoelectric layer, the internal electrode and the external electrode. It is possible to make various applications and modifications within the scope of the invention with respect to the constituent material of the above, the method of forming the external electrode (thin film electrode), and the like.

[0022]

As described above, in the laminated piezoelectric element of the present invention, at least one of the external electrodes on the upper and lower surfaces of the laminate of the piezoelectric layer and the internal electrode is a thin-film electrode, To the side of the laminate,
To cover at least a part of the external electrode formed on the side
By forming the conductive layer directly on the external electrodes formed on the side surfaces of the laminated body, the occurrence of swelling on the external electrodes on the upper and lower surfaces is suppressed, and the flatness of the upper and lower surfaces is reduced. This makes it possible to obtain a laminated piezoelectric element having excellent characteristics.

Further, according to the laminated piezoelectric element of the second aspect,
When the external electrode formed on the side surface is a thick film electrode,
By keeping the conduction resistance low,
To prevent disconnection due to heating
And increase the mechanical strength
(Especially to prevent scratching), reliability
Can be improved.

Further, when a multilayer piezoelectric actuator is constructed by stacking a plurality of multilayer piezoelectric elements of the present invention, the stability of the stack (connection and fixing) is excellent, and no breakage occurs due to external force. Thus, a highly reliable laminated piezoelectric actuator can be obtained.

[Brief description of the drawings]

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

FIGS. 2A and 2B are views showing a method for manufacturing a laminated piezoelectric element according to one embodiment of the present invention, wherein FIG. 2A is a cross-sectional view showing a state before upper and lower external electrodes are formed, and FIG. FIG. 3 is a cross-sectional view showing a state after the upper and lower external electrodes are formed.

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

FIG. 4 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. 5 is a cross-sectional view showing a conventional laminated piezoelectric actuator.

FIG. 6 is an exploded perspective view showing a pattern of an internal electrode of a multilayer piezoelectric element constituting a conventional multilayer piezoelectric actuator.

FIG. 7 is a cross-sectional view showing a main part of a multilayer piezoelectric element constituting a conventional multilayer piezoelectric actuator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric layer 2a, 2b Internal electrode 3 Laminated body 3a, 3b Upper / lower surface of laminated body 3c, 3d Side surface of laminated body 4a, 4b External electrode of upper / lower surface 4c, 4d External electrode of side surface 5 Laminated piezoelectric element 6 Metal mask 7 Metal plate 8 Adhesive

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-84907 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 41/083

Claims (2)

(57) [Claims] A plurality of piezoelectric layers, an internal electrode disposed between the piezoelectric layers, and a side surface from which the internal electrodes are drawn out.
And an external electrode, the external electrode and the stacked piezoelectric device comprising comprising a formed in the upper and lower surfaces, at least one of the thin-film electrode of the piezoelectric layers and the internal electrode and the upper and lower surface of the external electrode of the stack of And at least a part of the external electrode formed on the side surface of the laminate with the thin film electrode
A multilayer piezoelectric element, which is formed so as to cover the first electrode and directly conducts to an external electrode formed on a side surface of the multilayer body. 2. An external electrode formed on said side surface is a thick film electrode.
2. The multilayer piezoelectric element according to claim 1, wherein
Child.