JPH0832131A - Laminated piezolectric element and its manufacture - Google Patents

Abstract

PURPOSE:To surely connect and insulate external electrodes to and from internal electrodes in a laminated piezoelectric element used as an actuator. CONSTITUTION:Conductive projecting sections 16 are formed at every other layer on the side face of a laminated body constituted by alternately piling up piezoelectric material films 11 and internal electrodes 12 and an insulating film 13 containing glass beads 17 is formed in the laminating direction of the laminated body so that the film 13 can cover all piezoelectric material films 11. In addition, copper foil 15 carrying conductive particles 31 adhering to the surface of the foil 15 is formed on the film 13 as external electrodes and the external electrodes are electrically connected to the internal electrodes 12 through the projecting sections 16.

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 large number of thin films of piezoelectric material are laminated and a longitudinal displacement can be obtained by applying a voltage, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, when a laminated piezoelectric element is manufactured, it is necessary to connect internal electrodes every other layer. However, when the conventional laminated capacitor method is used, the internal electrode area is smaller than the cross-sectional area of the element, so that the electric field However, there is a fatal defect that not only does not occur on the entire surface but hinders the displacement, but also stress concentration occurs on a non-uniform part and eventually breaks. In addition, it is difficult to perform positioning during stacking, and the number of stacked sheets is limited to several tens at most, and the displacement amount of the element is proportional to the number of stacked layers at the same applied voltage. Therefore, an element that generates a large displacement amount is manufactured. It was difficult.

In order to solve this drawback, a method of printing and laminating electrodes on the entire surface of the piezoelectric sheet, that is, a structure in which the area of the internal electrode and the area of the element are equalized is common.

In this case, the internal electrodes are connected every other layer by the method shown in FIG. That is, in FIG. 8, the conductive protrusions 16 are formed every other layer on the side surface of the stacked body in which the piezoelectric material 11 and the internal electrode 12 are alternately overlapped, and all the piezoelectric materials 11 are arranged in the stacking direction of the element. The insulating layer 13b and the layer 13a containing the conductive particles 31 are formed on the surface of the insulating layer 13b to form the conductive film 13. A copper foil 15 is formed thereon as an external electrode, and is electrically connected to the conductive convex portion 16 and further to the internal electrode 12 via the conductive particles 31.

[0005]

However, in the piezoelectric element having the structure shown in FIG. 8, since conductive particles are used as a medium for breaking through the insulating film and connecting the external electrode and the internal electrode, the following problems occur. Was happening often. In other words, due to the variation in particle size and the dispersed state, a layer that is not electrically conductive and is supposed to be insulated becomes conductive, or a sufficient insulation resistance value cannot be obtained until it does not become conductive. That is, it causes trouble in driving.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to reliably connect and insulate an external electrode and an internal electrode.

[0007]

In order to achieve this object, a laminated piezoelectric element of the present invention comprises a laminated body composed of a plurality of piezoelectric materials and a plurality of internal electrodes alternately laminated, and a laminated body of the laminated body. Insulation forming a conductive convex portion integrally formed at the end of the internal electrode exposed on the side surface and continuously formed on the side surface of the laminated body so as to cover the conductive convex portion and forming at least one layer structure. A film, an external electrode that is formed continuously on the insulating film, is selectively compressed to break through the insulating film, and is electrically connected to the conductive protrusion, and an insulating film formed by the external electrode. In order to prevent the breakage of the non-conductive particles, the non-conductive particles densely interposed in the insulating film in the valley portion between the conductive convex portions are provided.

Further, it is desirable that the particle diameter of the non-conductive particles is approximately the same as the height of the conductive convex portions.

Further, it is desirable that the external electrode comprises a conductive film and conductive particles applied to the film.

[0010]

In the laminated piezoelectric element of the present invention having the above-mentioned structure, when the external electrode is compressed and formed on the insulating film, it selectively breaks through the insulating film and is electrically connected to the conductive convex portion, Further, in the valleys between the conductive protrusions, the non-conductive particles in the insulating film prevent the external electrodes from breaking through the insulating film.

[0011]

EXAMPLES An example of the present invention will be described below.

FIG. 1 is a sectional view of a laminated piezoelectric element according to the present invention. As the conductive convex portions 16 are formed every other layer on the side surface of the stacked body in which the piezoelectric material films 11 and the internal electrodes 12 are alternately overlapped with each other, the conductive convex portions 16 are formed as non-conductive particles so as to cover all piezoelectric material films in the stacking direction of the element. The insulating film 13 containing the glass beads 17 is formed. Furthermore, a copper foil 15 with conductive particles 31 is formed thereon as an external electrode, and is electrically connected to the internal electrode 12 via the conductive convex portion 16.

An embodiment of the present invention will be described below with reference to the drawings.

After mixing a piezoelectric material containing PZT as a main component to a desired composition, 5 parts by weight of a binder and a small amount of a plasticizer and an antifoaming agent were added to powder calcined at 850 ° C. and then added to an organic solvent. Disperse into a slurry. This slurry is formed into a green sheet by a doctor blade method to a predetermined thickness.

A Pd paste is screen-printed as the internal electrodes 12 on the green sheet, 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 temporary external electrodes 22 and 23 are applied and baked onto the sintered body 21 cut at positions where the internal electrodes 12 are exposed every other layer as shown in FIG. It cuts so that another pair of side surfaces 24 and 25 may be exposed.

The entire one side surface 25 and the other side surface 24
Mask the part other than the convex part of the tape with tape,
A temporary external electrode 22 is connected to the negative electrode of the DC power source and immersed in a nickel plating bath. In this state, the current of 50mA is about 5
After flowing for a minute, nickel plating grows on the internal electrodes connected to the temporary external electrodes 22, and when the masking tape is peeled off, convex portions are formed every other layer as shown in FIG.

Next, a convex portion is similarly formed on the side surface 25 on the opposite side. First, after masking and protecting the entire side surface 24 and a part of the side surface 25 on which the convex portion has already been formed, the negative electrode is connected to the temporary external electrode 23 and nickel plating is grown to shift the side surface 24 layer by layer. A convex portion is formed.

After washing, the negative electrode of the DC power supply is used as a temporary external electrode 2.
2 and 23, and submerged in an epoxy cation electrodeposition paint bath to which a predetermined amount of pigment and glass beads 17 having a particle size of about 30 μm were added, and a voltage of 100 V was applied for 2 minutes, as shown in FIG. Paint on the end of 12 is glass beads 17
It is electrodeposited with. After that, when heat-treated at 150 ° C. for 30 minutes in an oven, since the epoxy resin component has fluidity in the process of hardening, it is flattened as shown in FIG. Flows and becomes the insulating film 13.

Separately from the sintered body 21, as shown in FIG. 6, an adhesive agent containing, for example, a conductive particle 31 made of copper powder having an average particle size of 20 to 30 μm on the copper foil 15, such as a thermosetting adhesive. An epoxy adhesive is applied uniformly to a thickness of about 50 μm. As shown in FIG. 7, each of the conductive projections 16 is formed on the side surfaces 24 and 25 of the sintered body 21.
Cut it to the size that it will touch and temporarily fix it. When a pair of flat pressing jigs (only one side is shown in FIG. 7) 53 heated to approximately 180 ° C. are subjected to thermocompression bonding with a load of several kg of scissors, only the conductive convex portions 16 are formed. Will be partly pressurized at a higher pressure than the other parts.

As a result, as shown in FIG. 1, the conductive particles 31 of the copper foil 15 pierce the insulating film 13 only in the pressed portion and come into contact with the conductive protrusions 16 to connect the internal electrodes 12 every other layer. . At this time, the thickness of the insulating film 13 is ensured by the presence of the glass beads 17, and the internal electrode 12 having no conductive protrusion 16 is completely insulated.

In this way, the sintered bodies 21, which are connected to each other on opposite sides, are cut into one element, and then a lead wire for power supply is attached to a part of the copper foil 15, and a resin sheath is formed. And polarization treatment is applied to complete the product.

As described above, in this embodiment, since the non-conductive glass beads 17 are densely present in the valleys between the conductive convex portions 16, the size of the conductive particles 31 may vary. Even when the dispersed state is not good, the film thickness of the insulated portion is ensured, and the conductive particles 31 are completely insulated without reaching or approaching the internal electrode 12 without the conductive convex portion 16.

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, the same effect can be obtained by using particles of an insulator such as alumina or resin instead of glass beads.

[0024]

As is apparent from the above description, the multilayer piezoelectric element of the present invention can reliably connect and insulate the external electrodes and the internal electrodes for every other layer, thereby improving reliability and yield. Become.

[Brief description of drawings]

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

FIG. 2 is a perspective view of a cut laminated sintered body in a manufacturing process of the laminated piezoelectric element.

FIG. 3 is a perspective view of a sintered body in a state where conductive protrusions are formed in the above manufacturing process.

FIG. 4 is a partial cross-sectional view showing a state where the electrodeposition coating material containing glass beads is electrodeposited in the above manufacturing process.

FIG. 5 is a partial cross-sectional view showing a state in which the glass beads and the electrodeposition coating material are fluidized by heating in the above manufacturing process.

FIG. 6 is a partial cross-sectional view showing a state in which a layer containing conductive particles is formed on the copper foil in the above manufacturing process.

FIG. 7 is an explanatory diagram for explaining a state in which the electrodeposition layer and the copper foil are pressed in the above manufacturing process.

FIG. 8 is a partial cross-sectional view of a conventional laminated piezoelectric element.

[Explanation of symbols]

 11 Piezoelectric Material Film 12 Internal Electrodes 13 Insulating Film 15 Copper Thin 16 Conductive Convex Part 17 Glass Beads 31 Conductive Particles

Claims (4)

[Claims] 1. A laminated body composed of a plurality of piezoelectric materials and a plurality of internal electrodes that are alternately laminated, and a conductive protrusion integrally formed at an end of the internal electrode exposed on a side surface of the laminated body. An insulating film that is continuously formed on the side surface of the laminated body so as to cover the conductive convex portion and has at least a single layer structure, and that is continuously formed on the insulating film and is compressed. An external electrode selectively pierced through the insulating film and electrically connected to the conductive convex portion, and between the conductive convex portion in order to prevent the external electrode from piercing the insulating film. A multi-layer piezoelectric element, comprising: non-conductive particles densely interposed in an insulating film in a valley. 2. The multilayer piezoelectric element according to claim 1, wherein the particle diameter of the non-conductive particles is approximately the same as the height of the conductive protrusions. 3. The multilayer piezoelectric element according to claim 1, wherein the external electrode includes a conductive film and conductive particles applied to the film. 4. A step of forming a laminated body by alternately laminating a plurality of piezoelectric materials and a plurality of internal electrodes, and a conductive convex portion at an end of the internal electrode exposed on a side surface of the laminated body. A step of integrally forming, a step of forming an insulating film containing non-conductive particles on the side surface of the laminated body so as to cover the conductive convex portion, a conductive film and a conductive film applied to the film. And a step of compressing the external electrode into the insulating film so that the external electrode including the conductive particles selectively penetrates through the insulating film and is electrically connected to the conductive convex portion. Method of manufacturing a piezoelectric element.