JPH0279482A - Electrostriction effect element and manufacture thereof - Google Patents

Abstract

PURPOSE:To relieve stress in a capacitor structure by making connections of every other electrode layers with the aid of through holes formed in a piezo film layer, accomplishing a material indicating electrostriction effect with through holes evenly distributed, and thereby dispersing uniformly the portions with no generation of electrostriction. CONSTITUTION:A ceramic crude sheet with uniform thickness is fabricated from slurry obtained by dispersing powder of electrostriction material, containing chiefly magnesium lead niobate, in a solvent together with an organic binder. After punching off this crude sheet into rectangular shape, boring for a through hole is made, whereon a Pt paste is printed. Such sheets are laminated, compressed, and cut into element articles. In this laminate structure, connections from takeout electrodes 13, 14 provided on the uppermost sheet 11 and undermost sheet 12 are made with every other layers with the aid of through holes 15 in each layer 15 and a through hole runoff 16. Therein the through hole connection with electrodes of the layers as next couple is formed dislocated, and laminating them and baking will accomplish a laminate type piezo element in which electrodes as mating electrode couple are connected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostrictive effect element and a method for manufacturing the same.

[Conventional technology]

An electrostrictive element is a transducer that converts electrical energy into mechanical energy by utilizing the electrostrictive effect of a solid state. Specifically, electrodes such as metal films are formed on opposing surfaces of a solid that has a large electrostrictive effect, and the strain in the solid that occurs when a potential difference is applied between the electrodes is utilized. The strain that occurs in the direction parallel to the electric field (longitudinal effect strain) is the strain that occurs in the perpendicular direction (
(lateral effect distortion), so using the former has higher energy conversion efficiency. Further, the magnitude of strain is related to the electric field strength, and the greater the electric field strength, the greater the generated strain.

In an electrostrictive element that utilizes transverse strain, it is possible to obtain a displacement proportional to the dimension in the direction perpendicular to the electric field even with a constant applied voltage. However, in an electrostrictive element that utilizes longitudinal effect strain with high energy conversion efficiency, when the externally applied voltage is kept constant and the dimension in the direction in which strain occurs is increased, the electric field strength decreases and the amount of displacement does not increase.

Therefore, in order to obtain a large amount of displacement in this case, it is necessary to increase the applied voltage so that the electric field strength does not decrease. However, increasing the voltage requires a large and expensive power supply, which also increases the risk of handling.

Furthermore, the control circuit for driving this electrostrictive element cannot use a very high voltage due to limitations from the withstand voltage of the IC used.

In order to improve the above drawbacks, a multilayer chip capacitor type structure has been proposed. This structure is shown in Figure 4(a),
Shown in (b).

In FIG. 4(a), internal electrodes 62 are formed at regular intervals inside an electrostrictive material 61, and every other electrode is connected to an external electrode 63. The spacing between the internal electrodes can be reduced to about several tens of microns using ordinary chip capacitor technology. If this structure is adopted, the distance between the electrodes becomes narrower, so an electrostrictive effect element using the longitudinal effect that can be driven at a low voltage can be realized.

By the way, as is clear from FIG. 4(b), which is a perspective view seen from the stacking direction, in this structure, the overlapping area of the internal electrodes 62 (the central rectangular portion) is smaller than the cross-sectional area of the element. Therefore, basically, the overlapping parts of the internal electrodes 62 deform according to the electric field, but the other parts do not deform. Therefore, when a high voltage is applied and a large strain is generated, some parts deform and are difficult to deform. A drawback is that a large concentration of stress occurs at the interface between the parts, resulting in mechanical destruction of the element.

For this reason, in order to improve reliability, it was necessary to use a structure in which the electrodes inside the element are formed on the entire surface of the element, and the pairs of these electrodes are connected externally after being laminated.

FIGS. 5(a) and 5(b) show one method used for this electrode connection.
2, and by applying an external electrode 73 thereon, a pair of opposing electrodes can be taken out to the outside. Insulation formation by electrophoresis has been put into practical use as a method for forming an insulator every other layer. Special request 1977
No. 7-225168 and Japanese Patent Application No. 57-225169 show this method of forming an insulating layer.

In this method, an insulator 72 is deposited on an electrode 71 by electrophoresis, and this is treated at high temperature to produce the element shown in FIG. 5(a).

[Problem to be solved by the invention]

However, in the electrophoresis method, insulating layers are formed alternately every other layer, so if the thickness of the material that exhibits the electrostrictive effect is thin, the insulating layer may adhere to electrode parts where no insulating layer should be formed. However, there is a drawback that electrical continuity between the electrode 71 and the external electrode 73 cannot be established. For this reason, there is a limit to how thin a material that exhibits an electrostrictive effect can be made to be, and it has therefore been impossible to obtain a large strain with a low applied voltage.

An object of the present invention is to provide an electrostrictive effect element and a method for manufacturing the same that solve the above problems.

[Means to solve the problem]

In order to achieve the above object, the electrostrictive element of the present invention is an electrostrictive element in which a material exhibiting an electrostrictive effect and an internal electrode are alternately laminated, and a through hole is formed in each of the materials exhibiting an electrostrictive effect. is distributed uniformly as a whole when viewed from the stacking direction, and each internal electrode is connected to every other layer via the through hole, and an external electrode for voltage application is formed at the top or bottom of the electrostrictive element. It is connected to.

Further, the electrostrictive effect element of the present invention is an electrostrictive effect element in which a material exhibiting an electrostrictive effect and an internal electrode are alternately laminated.
Through holes formed in each of the materials exhibiting the electrostrictive effect are uniformly distributed as a whole when viewed from the stacking direction, and each internal electrode is connected every other layer through the through holes, and the uppermost part of the electrostrictive element is connected to each other through the through holes. Alternatively, it is connected to an external electrode for voltage application provided on the side surface of the material exhibiting an electrostrictive effect formed at the bottom.

The electrostrictive effect element of the present invention includes a step of creating a green sheet containing a material exhibiting an electrostrictive effect, forming a through hole in the green sheet, and further printing a conductive paste and embedding the conductive paste in the through hole. and a step of forming an electrode pattern, a step of laminating a plurality of the green sheets and a green sheet on which an electrode pattern is formed and integrating them by thermocompression bonding, and a step of firing the integrated laminate. This is achieved by performing the process.

(Function) The present invention provides a laminated piezoelectric element having a structure in which piezoelectric thin film layers and electrode layers are alternately laminated and each electrode layer is connected to a common electrode every other layer. The alternate connections are made through through holes formed in the piezoelectric thin film layer, and the through holes are uniformly distributed as a whole when viewed from the stacking direction, and are formed in a material that exhibits an electrostrictive effect. The purpose is to uniformly distribute areas where electrostriction does not occur (ie, through-hole areas) to alleviate stress that is a problem in capacitor structures.

The electrostrictive effect element of the present invention is not a simple through-hole connection, but as a whole when viewed from the stacking direction.

Or, when the through-hole positions are projected in the stacking direction, the through-holes are uniformly distributed, and a counter electrode is formed, and there are parts where distortion occurs due to the electric field, and where the counter electrode cannot be formed in the through-hole part. The stress that occurs between the electric field and the portions where no strain occurs is also eliminated within a few layers at most.

Therefore, in the electrostrictive element of the present invention, stress between the electrostrictive part and the non-electrostrictive part does not accumulate even if the number of laminated layers is increased, and the element is not destroyed even when the element is driven.

In the electrostrictive effect element of the present invention, since each internal electrode is connected every other layer by the method described above, the insulating layer 72 shown in FIG. 5(b) is unnecessary, and the insulating layer 72 shown in FIG. Layers can be used. Therefore, it is possible to create an element that can obtain a large strain by applying a low voltage.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS The laminated piezoelectric element of the present invention will be described below with reference to illustrated embodiments.

First, as one of the embodiments of the present invention, an element formed by printing and laminating a piezoelectric material onto a green sheet will be described.

The green sheet is magnesium lead niobate pb (Mg
Powder of an electrostrictive material containing l/3Nb2/3)Oa as a main component is dispersed in a solvent together with an organic binder to form a slurry. This is made into a ceramic green sheet having a uniform thickness of 30 ρ to 200 ρ by a casting method using a doctor blade. This ceramic raw sheet is 6
Punch out a rectangle of 0ma+X40m. Next, holes for through holes are formed in the green sheet using a punch and a die. Furthermore, platinum paste is printed on this perforated green sheet using a screen printer.

At the same time, platinum paste is also embedded inside the through hole. A plurality of green sheets, including the green sheet printed with this platinum paste, are laminated and pressure-bonded to form an integrated laminate, which is cut into individual elements, and then subjected to a binder removal process at 900°C. ~1200
It is sintered at a temperature of °C to obtain a laminated piezoelectric element.

FIGS. 1(a) and 1(b) are diagrams showing a laminated structure of a laminated piezoelectric element according to an embodiment of the present invention. In the figure, connections from extraction electrodes 13 and 14 provided on the top layer sheet 11 and bottom layer sheet 12 of the stack are connected every other layer by through holes 15 and through hole ridges 16 provided in each layer. In addition, through-hole connections to the electrodes of the next pair of layers are formed at different positions, and by stacking and sintering these, the electrodes of the opposite electrode are connected, as shown in Figure 2. The laminated piezoelectric element shown is obtained.

FIG. 3 is a laminated cross section taken along the line x-y in FIG. 2. As is clear from this figure, in the structure of the present invention, the stress between the part where an electric field is applied between opposing electrodes and causes elongation, and the part where no elongation occurs because a through hole is formed, is completely reduced at the position where the same pattern is returned. It will be resolved in Therefore, even if the number of laminated layers is further increased, stress will not be accumulated.

Element breakdown, which is a problem in capacitor structures, does not occur.1゜An even greater effect is that in the manufacturing process of the multilayer piezoelectric element of the present invention, there is a hole-drilling process in the green sheet, a subsequent electrode printing process, a lamination process, a cutting process, Binder removal/
Since it can be obtained only through the firing process, the process can be significantly shortened and the cost can be sufficiently reduced when insulation is formed by electrophoresis, which is a method for producing piezoelectric elements that eliminates the generation of internal stress. Furthermore, if the number of through holes is increased to 2 to 3 per location, the reliability of the connection can be further improved, and the exterior finishing etc. will also give good results in improving reliability.

Although the external electrode is divided into the top layer and the bottom layer, it is also possible to take it out only to the top layer or the bottom layer.
This can be achieved by simply changing the pattern of this one layer, and it is clear that the above effect can be obtained in this case as well.

Furthermore, by laminating a green sheet that exhibits an electrostrictive effect on the top or bottom layer as a dummy layer and forming external electrodes in the lateral direction of the device, it is also possible to apply a voltage in the lateral direction from the side of the device. .

Even with this structure, there is no external electrode for voltage application in the driving direction of the element, that is, the direction in which the load is applied to the element, so even if the load is made of a conductor such as metal, there is no need to insulate between the element and the load. It has the advantage of being good.

〔Effect of the invention〕

As described above, according to the present invention, there is no need to provide an insulating layer between the internal electrode and the external electrode, and therefore it is possible to obtain an element that generates large distortion even when driven at a sufficiently lower voltage than conventional ones. have an effect.

[Brief explanation of the drawing]

Fig. 1 is an exploded perspective view showing the laminated structure of the multilayer piezoelectric element of the present invention, Fig. 2 is an external perspective view of the laminate, and Fig. 3 is a sectional view showing the connection state of electrodes inside the laminate. Figure 4(a)
5(a) is a side view showing a conventional capacitor-type multilayer piezoelectric element structure, (b) is a plan view seen from the stacking direction, and FIG.
(b) is an enlarged view of part A in (a).

Claims (3)

[Claims] (1) In an electrostrictive element in which materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated, through holes formed in each of the materials exhibiting an electrostrictive effect are uniformly distributed as a whole when viewed from the stacking direction. , an electrostrictive effect element characterized in that each internal electrode is connected every other layer through the through hole, and is also connected to an external electrode for voltage application formed at the top or bottom of the electrostrictive effect element. . (2) In an electrostrictive element in which materials exhibiting an electrostrictive effect and internal electrodes are alternately laminated, through holes formed in each of the materials exhibiting an electrostrictive effect are uniformly distributed as a whole when viewed from the stacking direction. , an external electrode for applying a voltage provided on the side surface of the material exhibiting an electrostrictive effect formed at the top or bottom of the electrostrictive effect element and connecting the internal electrodes every other layer through the through hole; An electrostrictive effect element characterized by being connected to. (3) The process of creating a green sheet containing a material that exhibits an electrostrictive effect, forming through holes in the green sheet, printing conductive paste, embedding the conductive paste in the through holes, and forming an electrode pattern. A step of stacking the green sheet and a plurality of green sheets on which electrode patterns are formed and bonding them together by thermocompression, and a step of firing the integrated laminate. A method of manufacturing a strain effect element.