JPH0256829B2 - - Google Patents

Abstract

PURPOSE:To improve the reliability of insulation and to obtain high field effect driving and generation of large strain simultaneously, by depositing an organic material on every second layer of internal electrodes on the side faces of a layered body, heating the material to secure it thereon and baking glass powder on the layered body. CONSTITUTION:A layered body of electrostrictive material is cut off along two lines such that every second layer of internal electrodes is exposed on the surface. Temporary external electrodes 25 and 26 are applied and baked on the surfaces of the body exposed by cutting. Two side faces different from the surfaces provided with the temporary external electrodes are further cut off so that whole layers of internal electrodes 23 and 24 are exposed. A beltlike film 27 of an organic material is formed by electrode position on the exposed portions of the internal electrodes on the layered body, and glass powders 28 and 29 are then deposited thereon. Only the glass powder 28 deposited on the organic material film 27 are scraped by a scraper or the like and baked to form glass coat films 31. Similar glass coat films are formed in a similar manner and procedures on the opposite end face at the positions each shifted by one internal electrode layer. External electrodes 32 are provided on the front and back end faces of the body, which is then cut off along the broken lines in the drawing to obtain the final electrostrictive effect elements.

Description

[Detailed Description of the Invention] (Industrial Application Field) The method of the present invention relates to a method for manufacturing electromechanical devices such as drive elements and minute displacement elements that utilize the electrical/mechanical energy conversion ability of piezoelectric or electrostrictive materials. It is.

(Prior Art and its Problems) In the structure of an electrostrictive element that utilizes the longitudinal effect, it is necessary to have internal electrodes with the same size as the cross-sectional area of the element. This is to generate a uniform electric field throughout the electrostrictive material or piezoelectric material when voltage is applied. If the area of the internal electrode is smaller than the cross section of the element, a non-uniform part of the electric field will always be created near the end of the internal electrode inside the electrostrictive or piezoelectric material, and strong stress concentration will occur accordingly.

Furthermore, in order to generate a large electric field at a low voltage and obtain a large strain, it is necessary to form a large number of internal electrodes inside the electrostrictive or piezoelectric material with a mutual spacing of about 100 microns.

For the above two reasons, it is extremely difficult to electrically connect electrostrictive elements that utilize longitudinal effects using conventional methods. In other words, due to the former restriction, it is not possible to use a connection method using external electrodes that covers the entire end face of the element, as is done with multilayer ceramic capacitors. Moreover, due to the latter limitation, it is difficult to apply the printing method of insulating films and conductors used in thick film processes etc. from the viewpoint of accuracy.

Therefore, the present inventors first developed an electrical insulator characterized by forming an inorganic insulator every other layer on the internal electrode layer exposed on the end face of the electrostrictive or piezoelectric material laminate and the ceramic in the vicinity by electrophoresis. A connection method was proposed. FIG. 1 is an external view of an electrostrictive effect element electrically connected by this method. An inorganic insulator 5 is formed every other layer on the internal electrode layer exposed at the end face of the element formed by laminating electrostrictive materials 1 and 2 and internal electrodes, and on the ceramic around the internal electrode layer. Similarly, an inorganic insulator 6 is formed on the internal electrodes which are further shifted from each other on the end face on the back side. A band-shaped external electrode 7 is formed across this insulator and the exposed internal electrode 4. A large number of internal electrodes indicated by numbers 3 and 4 in the figure are connected to the positive external connection terminal 10 and the negative external connection terminal 8 at every other layer, respectively.

A problem with the device having this structure is that the width of the formed insulator is narrow. FIG. 2 shows a structural diagram when a DC voltage is applied to an element having this structure. Arrows indicate lines of electric force. Looking at the vicinity of the surfaces where the external electrodes 7 and 9 are formed, it is found that because the widths of the insulators 5 and 6 are narrow, a stronger electric field is generated between the outer electrodes 7 and 9 and the inner electrodes 3 and 4 than in other parts. Recognize. Its direction is also different from most other locations, as it has a component parallel to the internal electrode plane. As a result, stress concentration occurs in this part due to uneven strain, and if a strong electric field of 1.5 kV/mm or more is applied to the element, the element will be destroyed. Further, when the internal electrode exposed layer and the surrounding ceramic are widely covered by the electrophoresis method, the thickness increases proportionally, and the volume of the formed insulator increases, suppressing the displacement of the element. Further, when insulation is performed by electrophoresis, if a defect occurs in the process, a short state will occur and the device will become completely unusable. It is preferable for the failure mode to be in the open state.

(Objective of the Invention) The present invention improves the reliability of insulation, and at the same time makes it possible to achieve high electric field drive and generation of large strain by uniformizing the electric field inside the electrostrictive material, thereby making it possible to improve the insulation voltage. It is an object of the present invention to provide a method for manufacturing a strain effect element.

(Structure of the Invention) The present invention is characterized in that electrostrictive materials and internal electrodes are alternately laminated, and an external layer is connected to the internal electrode end every other layer on two opposing sides of the laminate where the internal electrode end is exposed. A method of manufacturing an electrostrictive effect element forming an electrode, a step of precipitating an organic material by an electrodeposition method onto every other layer of internal electrodes on a side surface of a laminate in which an end portion of the internal electrodes is exposed, and heating and fixing the organic material; Depositing glass powder on other parts of the side surface, heat treating the laminate to decompose the organic material and baking the glass powder, and connecting the exposed internal electrode ends of every other layer to the laminate side surface. 1. A method of manufacturing an electrostrictive element, comprising the step of forming an electrode on the side surface.

(Detailed Description of Structure) The present invention solves the problems of the conventional method of manufacturing an electrostrictive effect element using electrophoresis by using the method described above.

First, since the insulator was formed by deposition, the reliability of the insulation was greatly improved. Furthermore, as a result of the failure mode being a connection failure and an open state, the occurrence of distortion in the defective element was reduced by several tenths, but the element could still be used satisfactorily. On the other hand, it has become possible to narrow the opening of an insulating film by forming an insulating pattern by forming an organic material by electrodeposition. Third
The figure is a schematic diagram of an electrostrictive effect element electrically connected by the method of the embodiment described below. Since the glass coatings 31 and 33 having a low dielectric constant widely cover the end faces of the element, a uniform electric field is generated inside the ceramic without being affected by the external electrodes on the sides of the element, and stress concentration is prevented. Here 21, 22
is an electrostrictive material, 23 and 24 are internal electrodes, 32 and 34
is an external electrode, and 35 and 36 are external connection terminals.

(Example) Examples of the present invention will be described in detail below with reference to the drawings. A slurry was prepared by adding a small amount of an organic binder to an electrostrictive material pre-fired powder containing magnesium lead niobate and lead titanate as main components, and dispersing this in an organic solvent. This slurry was coated onto a Mylar film to a thickness of about 100 microns using a casting film-forming device used in the production of conventional multilayer ceramic capacitors and dried.
This was peeled off from the film to obtain an electrostrictive material green sheet. Some of the green sheets were further screen-printed with platinum paste as internal electrodes.
Several hundred of these green sheets were stacked, pressed together using a hot press, and then fired at 1240°C to obtain an electrostrictive material laminate. This is cut at two locations where the internal electrodes are exposed on the surface every other layer, temporary external electrodes are applied and baked on the exposed surface, and two side surfaces different from the surface on which the temporary external electrodes are formed are cut. The entire electrode layer was exposed.

FIG. 4 is an external view showing the electrostrictive material laminate with temporary external electrodes produced as described above and the formation position of the organic material film 27 formed by the method described below. In the figure, numbers 21 and 22 are electrostrictive materials, 23 is an internal electrode, and temporary external electrodes 25 are placed every other layer.
and 26.

Next, an organic material is formed on such a laminate by electrodeposition. The suspension used in the electrodeposition method consists of a cationic electrodeposition coating emulsion, a resin curing agent, and water. Fill a container with this suspension, submerge the laminate and gold-metal-treated stainless steel counter electrode plate, and connect one of the temporary external electrodes to the negative terminal of a DC power source and the counter electrode plate to the positive terminal. When a DC voltage is applied for about 5 minutes, the emulsion particles adhere to the exposed portion of the internal electrode connected to the negative terminal. This at 200℃30
The film is heated for a minute to solidify and form a band-shaped film 27 of organic material. Next, this laminate is left standing for 15 minutes in a suspension consisting of zinc borosilicate-based crystallized glass powder and ethanol, with the surface on which the organic substance film is formed facing upward.

FIG. 5 shows an external view of an electrostrictive material laminate in which glass powder is deposited on the end face on which a band-shaped organic material film is formed. In the figure, numeral 28 indicates glass powder deposited on the end face of the laminate, and numeral 29 indicates a ridge-like bulge due to the glass powder deposited on the organic material film. FIG. 6 shows a cross section of this laminate. In the figure, numbers 21 and 22 indicate electrostrictive materials, 23 and 24 internal electrodes, 27 an organic material film, and 28 and 29 deposited glass powder, respectively.

Next, only the glass powder 28 deposited on the organic substance film is scraped off with a scraper or the like. then 500℃30
The organic substance film 27 is removed by gasification by thermal decomposition by heating for a minute. Next, the glass film 31 is formed by firing at 700° C. for 10 minutes.

FIG. 7 shows a cross section of the laminate from which glass powder on the organic material film has been removed. FIG. 8 is a cross-sectional view of a laminate from which an organic material film has been removed by thermal decomposition. In the figure, number 30 indicates a space where the organic material film has disappeared, and number 29 indicates the deposited glass powder. FIG. 9 and FIG. 10 are a sectional view and an external view of a laminate made of baked glass. During the melting process, the surface tension of the glass causes the glass to become rounded and slightly widened, and is fixed to the surface of the laminate. In the figure, numeral 31 indicates the formed glass coating, and 24 indicates the exposed end of the internal electrode. The opening of the glass coating is narrower than that in the case where the glass coating is formed by the electrophoresis method shown in FIG. According to the present invention, the width of the opening can be determined by controlling the flow of the glass by changing the holding time at the glass softening temperature.

Using the same method and procedure, a glass coating 33 is formed on the opposite end face at a position shifted by one layer of the internal electrode.

Next, external electrodes are formed on the front and back end surfaces by paste printing and baking. FIG. 11 is an external view of a laminate on which external electrodes 32 are formed. The final element shape is obtained by cutting at the position indicated by the broken line in the figure. FIG. 12 is an external view of the obtained electrostrictive effect element. FIG. 13 also shows a structural diagram. In the figure, numbers 21 and 22 are electrostrictive materials, 31 and 33 are glass coatings, 32 and 34 are external electrodes, and 35 and 36 are positive and negative external connection terminals, respectively. The element according to the present invention can be further coated with an organic insulating material or the like to improve its environmental resistance.

(Effects of the Invention) The method of the present invention deposits glass powder on the entire surface of the end face and then removes unnecessary parts, so the parts that should be insulated are reliably insulated, and the main cause is shortening due to poor insulation. The low yield that was supposed to be 50
% to 95%, the width of the insulator has expanded from ridge-like to film-like, and a solid glass film has been formed, increasing the dielectric strength from 500V to 900V.
has been greatly improved. Furthermore, as a result of the spread of the insulator, the component of the electric field generated inside the ceramic that is parallel to the internal electrodes is significantly reduced, and a uniform electric field is generated. As a result, it is possible to drive with a high electric field of 2 kV/mm or more and achieve a large displacement, and when driven with a normal electric field strength of about 1 kV/mm, the failure rate during long-term continuous driving of more than 100 million times is greatly reduced. An improvement in the characteristics was obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an electrostrictive effect element manufactured using electrophoresis. FIG. 2 is a diagram showing a cross section of the element shown in FIG. 1 and lines of electric force when a DC voltage is applied.
FIG. 3 is a diagram showing a cross section of an electrostrictive element manufactured by the method of the present invention and lines of electric force when a DC voltage is applied. FIG. 4 is an external view of an electrostrictive material laminate in which an organic material film is formed every other layer by electrodeposition on the internal electrodes exposed at the end faces and the ceramic around the internal electrodes. FIGS. 5 and 6 are a perspective view and a cross-sectional view, respectively, of an electrostrictive material laminate with glass powder deposited on its end faces. Figure 7 is a cross-sectional view of an electrostrictive material laminate in which only the glass powder deposited on the organic substance film has been scraped off, and Figure 8 is a sectional view of the electrostrictive material laminate obtained by heating the same laminate at 500°C to thermally decompose the organic substance film. A cross-sectional view of what was removed is shown. FIG. 9 is a cross-sectional view of this laminate which was fired at 700° C. to form a glass coating, and FIG. 10 is a perspective view showing the surface of the same laminate on which the glass coating was formed. FIG. 11 is a perspective view showing an electrostrictive material laminate in which a plurality of external electrodes are formed on the surface on which the glass coating is formed. FIG. 12 is an external view showing an electrostrictive effect element obtained by similarly forming a glass coating and an external electrode on the opposite end face and then cutting it into the final shape, and FIG. 13 is a sectional view thereof as well. Numbers 1, 2, 21, 22 in the figure are electrostrictive materials, 3,
4, 23, and 24 are internal electrodes, 5 and 6 are glass coatings, and 7, 8, 9, and 10 are external connection terminals, respectively. 25 and 26 indicate temporary external electrodes on the minus side and the plus side, respectively. 27 indicates an organic material film. 28 and 29 indicate glass powder deposited on the organic material film and the electrostrictive material, respectively. Reference numeral 30 indicates a gap created by the disappearance of the organic material film through thermal decomposition, and 31 and 33 indicate glass coatings. 32 and 34
indicate the positive and negative external electrodes, respectively. 35 and 36 are positive and negative external connection terminals, respectively, and 37 is a DC power supply.

Claims (1)

[Claims] 1 Electrostrictive effect in which electrostrictive materials and internal electrodes are alternately laminated, and external electrodes are formed every other layer on two opposing sides of the laminate where the internal electrode ends are exposed, and are connected to the internal electrode ends every other layer. In a method for manufacturing an element, an organic material is precipitated by electrodeposition on every other internal electrode layer on the side surface of the laminate where the end of the internal electrode is exposed, heated and fixed, and glass is applied to other parts of the side surface of the laminate. A step of depositing powder, a step of heat-treating the laminate to decompose the organic material and baking the glass powder, and forming an external electrode on the side surface of the laminate to connect the end of the internal electrode exposed every other layer. A method for manufacturing an electrostrictive element, comprising the steps of: