JPH07283452A - Multilayer piezoelectric element - Google Patents

Abstract

(57) [Abstract] [Purpose] A recess is formed at the end of each internal electrode.
By filling the concave portion with an insulating material, it is possible to reliably connect the other internal electrode and the external electrode, which are not formed with the concave portion, to each other, and prevent defective conduction and defective insulation. Providing an element. [Structure] The end portions of the internal electrodes 12 placed one layer apart are removed by electrolytic etching to form recesses 16. Then, the recess 16 is filled with an insulating material, the insulating layer 14 is formed so as to cover all the piezoelectric materials 11 in the stacking direction of the element, and the conductive film 13 including the conductive particles 17 is thermocompression bonded thereon. . Thereby, the conductive particles 17 in the conductive film 13
While being in contact with the copper foil 15 serving as an external electrode, the insulating layer 14 is pierced by the applied pressure and comes into contact with the internal electrode 12 in which the recess 16 is not formed.
The internal electrode 1 of one layer is placed through the conductive film 13 containing 7
2 electrically connected.

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 in which a plurality of thin films of piezoelectric material are laminated and a longitudinal displacement can be obtained by applying a voltage.

[0002]

2. Description of the Related Art Conventionally, when manufacturing a laminated piezoelectric element,
A general method is to print electrodes on the entire surface of the piezoelectric sheet and stack the electrodes. In the case of such a structure, it is necessary to electrically connect every other internal electrode. As an example thereof, the method shown in FIGS. 7 and 8 is considered.

First, as shown in FIG. 7 (a), film-shaped piezoelectric materials 71 on which the internal electrodes 72 are printed are laminated every other layer so that the ends of the internal electrodes 72 are exposed, and sintered. The sintered body 70 is formed. Then, temporary external electrodes 73 and 74 are applied to the side surfaces where the end portions of the internal electrodes 72 are exposed every other layer, and electroplating is performed using the temporary external electrodes 73 as a cathode. As shown, the conductive protrusions 75 formed by the electroplating method are formed in alternate layers.

The sintered body 70 will be described below with reference to a vertical sectional view.
As shown in FIG. 8C, the resin component 76 is electrodeposited on the end portions of the conductive convex portion 75 and the internal electrode 72 by an electrodeposition coating method or the like, and baked at around 150 ° C. As shown, the resin component is melted to form the insulating layer 77.

On the other hand, as shown in FIG. 8 (e), an anisotropic conductive film 78 capable of thermocompression bonding, having a unidirectional conductivity only in the pressed portion, and containing conductive particles 80, A copper foil 79 to be an external electrode is prepared and attached, and FIG.
As shown in (f), when thermocompression-bonded, the anisotropic conductive film 78 is formed.
Is only partially pressed with a higher pressure than the other parts, so that the conductive particles 80 in the part pressed with a high pressure are insulated from the insulating layer 77.
Through, and comes into contact with the conductive protrusions 75 and the copper foil 79, and the copper foil 79 serving as an external electrode, the conductive protrusions 75, and the internal electrodes 72 are electrically connected every other layer.

[0006] In the same manner, the sintered body 70 in which the internal electrodes and the copper foil, which are one layer apart, are connected by shifting the layers on the opposite side surface,
Is a finished product after undergoing steps such as lead wire attachment, resin coating, and polarization treatment.

[0007]

However, in the manufacturing process of the laminated piezoelectric element as described above, the conductive convex portion 75 is formed on the end portion of the internal electrode 72 having a width of 10 to 20 μm by the electroplating method. Therefore, due to the nature of the electroplating method, it is formed with a width much wider than the width of the internal electrodes.
As a result, depending on the degree of exposure of the end of the internal electrode 72 and the extent of expansion of the conductive convex portion 75, the conductive convex portion 75 may contact the internal electrodes 72 adjacent on both sides to electrically short-circuit, Alternatively, since the heights of the conductive protrusions 75 are likely to be uneven, there is a problem that electrical connection becomes incomplete during thermocompression bonding of the anisotropic conductive film 78 in a later step.

The present invention has been made to solve the above-mentioned problems, and a concave portion is formed by forming a concave portion at the end portion of an internal electrode having one layer and filling the concave portion with an insulating material. It is an object of the present invention to provide a highly reliable multilayer piezoelectric element capable of reliably connecting an internal electrode and an external electrode, which are placed in other layers, without fail to prevent conduction failure and insulation failure.

[0009]

In order to achieve this object, a laminated piezoelectric element of the present invention is provided with conductive particles on the side surface of a laminated piezoelectric element in which piezoelectric materials and internal electrodes are alternately laminated. A laminated layer including a conductive film to be contained and an external electrode which is continuously formed on the conductive film and is electrically connected to the internal electrode of one layer via the conductive particles by being compressed. In the piezoelectric device of the type, recesses from which the electrodes are removed are formed at the end portions of the internal electrodes that are not electrically connected and are placed in layers, and the recesses are filled with an insulating material.

Further, it is desirable that the recess be formed by electrolytic etching.

Further, it is desirable to use a thermosetting epoxy resin adhesive as the insulating material.

[0012]

In the laminated piezoelectric element of the present invention having the above-mentioned structure, the recesses are formed by removing the electrodes at the end portions of the internal electrodes which are not electrically connected and which are placed in a single layer, and the recesses are filled with the insulating material. By doing so, it is possible to reliably connect the other internal electrode and the external electrode that are not provided with the concave portion and are placed in a single layer.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the laminated piezoelectric element of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of the laminated piezoelectric element of the present invention. On the side surface of the laminate in which the film-shaped piezoelectric material 11 and the internal electrodes 12 are alternately stacked, the end portions of the internal electrodes 12 are selectively removed by electrolytic etching and the recesses 16 are formed. Then, an insulating layer 14 is formed so as to fill the concave portion 16 and to cover all the piezoelectric materials 11 in the stacking direction of the element, and the conductive film 13 containing the conductive particles 17 is thermocompression bonded thereon. . Therefore, the conductive particles 17 in the conductive film 13 come into contact with the copper foil 15 serving as an external electrode and pierce the insulating layer 14 by a pressing force, so that the concave portion 16 is not formed and is exposed on the side surface of the element. Contact the electrode 12. On the other hand, since the internal electrode 12 having the recess 16 formed therein is filled with an insulating material as the insulating layer 14, the conductive particles 17 do not come into contact with the internal electrode 12. As a result, the copper foil 15 serving as the external electrode is
Through the conductive film 13 containing the conductive particles 17, it is electrically connected to the internal electrodes 12 placed one layer at a time.

Next, a method of manufacturing the laminated piezoelectric element shown in FIG. 1 will be described with reference to FIGS.

First, after mixing a piezoelectric material containing PZT (lead zirconate titanate) as a main component to a desired composition, 85
An appropriate amount of binder, a small amount of a plasticizer and a defoaming agent are added to the powder calcined at 0 ° C., and the powder is dispersed in an organic solvent to form a slurry. This slurry is formed into a film-shaped piezoelectric material 11 by forming a predetermined thickness by the doctor blade method. On this piezoelectric material 11, an Ag-Pd (palladium) paste is screen-printed as an internal electrode 12, and a predetermined number of punched products having a predetermined size are stacked and integrated by hot pressing. After degreasing, sintering is performed at about 1200 ° C., and as shown in FIG. 2, a sintered body 21 cut at a position where the internal electrode 12 is exposed in every other layer is used as temporary external electrodes 22 and 23 by using Ag paste or the like. The conductive paste is applied and baked, and further cut so that another pair of side surfaces 24 and 25 is exposed.

Then, a masking tape is attached to the surface on which the temporary external electrodes 22 and 23 are applied, and a masking tape is also attached to the entire side surface 25 for electrolytic etching.

In electrolytic etching, a voltage of several volts is applied using the temporary external electrode 22 as an anode, and a copper plate or stainless plate as a cathode in an aqueous solution of dilute hydrochloric acid or dilute nitric acid, for example. As a result, of the internal electrodes 12 exposed on the side surface 24, the internal electrodes 12 connected to the temporary external electrode 22 are connected.
The surface layer of 1 is melted, and as shown in FIG. 3, the concave portion 16 is formed at the end portion of the internal electrode 12 having one layer.

Next, as shown in FIG. 4, an insulating material such as a resin is applied on the side surface 24 in which the recess 16 is formed to fill the recess 16 with the insulating material, and at the same time, in the stacking direction of the elements. The insulating layer 14 is formed so as to cover the piezoelectric material 11. The insulating material is, for example, a thermosetting epoxy resin adhesive, which is preferably applied and then heated to a semi-cured state at a temperature lower than the inherent curing temperature.

Further, in addition to the sintered body 21, as shown in FIG. 5, an epoxy resin adhesive containing conductive particles 17 such as copper powder having a particle diameter of about 20 to 50 μm is used as an external electrode for a copper foil. The conductive film 13 is uniformly applied to the film 15 in a thickness of about 50 μm and heated to a semi-cured state. This is cut into the same size as the side surface 24, and the side surface 24
Temporarily fix on top. Then, as shown in FIG.
Pressurize with a pair of flat pressing jigs 18 heated to 0 ° C.,
When a load of several kg is applied and thermocompression bonding is performed, the conductive particles 17 in the conductive film 13 come into contact with the copper foil 15 serving as an external electrode, and at the same time, pierce the insulating layer 14 by a pressing force to form the recess 16
The internal electrode 12 in a state where it is exposed on the side surface of the element without being formed
Contact with. On the other hand, the internal electrode 12 having the recess 16 formed therein
Since the insulating layer 14 is filled with an insulating material, the conductive particles 17 do not come into contact with the internal electrodes 12. As a result, the copper foil 15 that serves as an external electrode is electrically connected to the internal electrode 12 that is a single layer via the conductive film 13 that contains the conductive particles 17.

On the other hand, the side surface 25 on the side opposite to the side surface 24 where the recess 16 is formed is further shifted and the same treatment is performed.

In this way, the sintered body 21 in which the layers of the internal electrodes 12 and the copper foil 15 are electrically connected to each other by shifting the layers on the opposite side surfaces to each other, after being cut to a predetermined size, A lead wire for power supply is attached to a part of the copper foil 15 that is an external electrode, and a resin sheath and polarization treatment are performed to complete the product.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the invention. For example, platinum or palladium may be used as the electrode material of the internal electrodes, and various particles such as nickel, carbon, and silver can be used as the conductive particles. Further, if one of the copper foils used as the external electrodes is extended as it is, it will be used instead of the lead wire, and the lead wire attaching step can be omitted.

[0024]

As is apparent from the above description,
In the multi-layer piezoelectric element of the present invention, a recess is formed at the end of a single-layer internal electrode, and the recess is filled with an insulating material to form another single-layer internal electrode and external electrode in which no recess is formed. Can be reliably connected, and conduction failure and insulation failure can be prevented.

Further, since each recess is formed by electrolytic etching, the end of the internal electrode can be easily and surely removed.

Furthermore, since a thermosetting epoxy resin adhesive is used as the insulating material, it is easy to fill each recess with the insulating material and form an insulating layer having an adhesive force to the element surface. it can.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a laminated piezoelectric element of this example.

FIG. 2 is a perspective view showing a sintered body obtained by stacking and sintering piezoelectric material films.

FIG. 3 is a diagram showing a step of forming a recess on the side surface of a sintered body by electrolytic etching.

FIG. 4 is a diagram showing a step of forming an insulating layer on a side surface of a sintered body in which a recess is formed.

FIG. 5 is a diagram showing a step of forming a conductive film containing conductive particles on a copper foil.

FIG. 6 is a diagram showing a step of thermocompression-bonding a copper foil (external electrode) and a conductive film on a side surface of a sintered body on which an insulating layer is formed.

FIG. 7 is a diagram showing a method of manufacturing a conventional laminated piezoelectric element.

FIG. 8 is a diagram showing a method of manufacturing a conventional laminated piezoelectric element.

[Explanation of symbols]

 11 Piezoelectric Material 12 Internal Electrode 13 Conductive Film 14 Insulating Layer 15 Copper Foil (External Electrode) 16 Recess 17 Conductive Particle

Claims (3)

[Claims] 1. A conductive film containing conductive particles and a conductive film containing conductive particles are continuously formed on the side surface of a laminated piezoelectric element in which piezoelectric materials and internal electrodes are alternately stacked.
In a laminated piezoelectric element including an internal electrode that is placed one layer and an external electrode that is electrically connected via the conductive particles by compression, an end portion of each internal electrode that is not electrically connected To
A laminated piezoelectric element, characterized in that recesses are formed by removing electrodes, and each recess is filled with an insulating material. 2. The laminated piezoelectric element according to claim 1, wherein the recess is formed by electrolytic etching. 3. The laminated piezoelectric element according to claim 1, wherein a thermosetting epoxy resin adhesive is used as the insulating material.