JPS6318352B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing an electrostrictive element using longitudinal effect.

In the structure of an electrostrictive element that utilizes the longitudinal effect, it is necessary to have internal electrodes that are the same size as the entire cross section of the element in order to prevent stress concentration when strain occurs by generating an electric field throughout the electrostrictive material. be. Furthermore, in order to generate a high electric field at a low voltage and obtain a large strain, it is necessary to set the distance between the internal electrodes to about 100 microns. For the above two reasons, it is very difficult to electrically connect an electrostrictive element having an internal electrode having the same area as the cross section of the element.

Therefore, the present inventors first developed an electrical connection method characterized by forming an insulator every other layer on the internal electrode layer exposed on the end face of the electrostrictive material laminate and the ceramic in the vicinity thereof by electrophoresis. proposed.
FIG. 1 is an external view of an electrostrictive effect element connected by this method. An insulator 7 is formed every other layer by electrophoresis on the internal electrode layer exposed on the end face and on the ceramic in the vicinity thereof. On the end face of the back side, an insulator 8 is also placed on the inner electrode which is shifted by one layer.
is formed. A band-shaped external electrode 11 is formed across this insulator and the exposed internal electrode 4. By similarly forming external electrodes for the internal electrodes 3 on the back side, a large number of internal electrodes are connected to the positive terminal 13 or the negative terminal 1 every other layer.
2, respectively. By applying a DC voltage between these external terminals, a uniform electric field is generated throughout the electrostrictive material 2 except for the protective film portion 1, and the element is expanded in parallel to the stacking direction. Since there is no stress concentration, the element will not be destroyed even if voltage is applied repeatedly, and the distance between internal electrodes is short, so it can be driven at a low voltage of 100V or less.

A method for manufacturing this element will be briefly explained.
First, a laminate in which internal electrodes 3, 4 and electrostrictive materials 1, 2 are alternately laminated as shown in FIG. 2 is fabricated by applying the manufacturing technology for laminated ceramic capacitors.
A large number of internal electrodes 3, 4 are exposed on the front and back end surfaces, and are alternately connected to two temporary external electrodes 5, 6 formed on the side surfaces at every other layer. When this laminate and a metal plate for a counter electrode are placed in a suspension and a DC voltage is applied from the counter electrode plate toward the temporary external electrode 5, the positively charged glass powder in the suspension is It is deposited on the internal electrode 3 and the electrostrictive material in its vicinity by electrophoresis. FIG. 3 is an external view of a laminate with glass powder adhered to the front end face. In the figure, numeral 1 indicates an electrostrictive material that functions as a protective film, and numeral 2 indicates an electrostrictive material in a portion where an electric field is generated to cause distortion. 4 indicates exposed internal electrodes, and the internal electrodes existing between them are covered with glass powder 7.

After the glass powder is baked and fixed, the glass powder is applied to the back end face in the same manner and fixed by baking. The laminated body formed with this insulator is cut at the positions shown by broken lines in FIG. 4, and external electrodes 11 are formed on several pieces 10 excluding the pieces 9 at both ends, resulting in the electrostrictive effect element shown in FIG. 1. is obtained.

The problem with this method is that the band-shaped insulator formed by the adhesion tends to be cut or constricted. The reason is thought to be that convection within the suspension generates locally weak electric field areas, and no adhesion occurs in those areas. If an external electrode is formed on top of it after firing and fixing, it will become short at the cut part and the withstand voltage will drop significantly at the constriction part, making it impractical.

The present invention aims to solve this problem. First, a laminate of an electrostrictive material and an internal electrode as shown in FIG. 2 is submerged in a suspension containing charged glass powder, and the internal electrode is exposed. Glass powder is deposited on the entire edge surface. Next, a counter electrode plate is placed in the same suspension, and a DC voltage is applied between the temporary external electrode 6 and this counter electrode plate. The internal electrode 4 connected to the temporary external electrode 6 and the glass powder deposited near it are positively charged even after deposition, so they are removed from the surface of the laminate by electrostatic force in the direction of the DC electric field. Ru. The pattern shape of the obtained insulator is exactly the same as that of the usual electrophoresis method, that is, when a DC voltage is applied from the counter electrode plate toward the temporary external electrode 5. However, the glass powder layer formed in advance by deposition is perfect with no defects, and the glass powder layer on the portion where the insulating film is to be formed, that is, the internal electrode 3 and the ceramic in the vicinity, is formed by applying a voltage after deposition. is never destroyed.

The feature of the present invention is that once the entire surface is deposited, only unnecessary portions are removed. According to this method, although some glass powder may remain in unnecessary areas, the adhesion of the glass powder to the areas that should be insulated is perfect, and the firing fixes the glass powder to a good condition with no cuts or constrictions. A band-shaped insulating coating is formed.

The present invention will be explained in detail below according to Examples.

First, an electrostrictive material laminate having a structure as shown in FIG. 2 and having a large number of internal electrodes and a set of temporary external electrodes is manufactured by the following method.

Magnesium lead niobate (Pb (Mg1/3Nb2/
₃ ) A slurry was prepared by adding a small amount of an organic binder to an electrostrictive material pre-fired powder containing lead titanate (PbTiO ₃ ) and lead titanate (PbTiO 3 ) as main components, and dispersing this in an organic solvent. This slurry was coated onto a Mylar film to a thickness of several hundred microns using a casting film forming apparatus used in the manufacture of ordinary 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 ten of these green sheets were stacked, pressed together by heat press, and then fired at 1250°C to obtain an electrostrictive material laminate. This was cut at a position where the internal electrodes were exposed on the surface every other layer, temporary external electrodes were applied and baked, and the sides were cut to obtain a laminate with exposed internal electrodes as shown in Figure 2. . Electrophoresis is applied to the electrostrictive material laminate thus obtained.
In FIG. 2, reference numeral 1 indicates the electrostrictive material of the protective film portion, and reference numeral 2 indicates the electrostrictive material that causes strain. The internal electrodes 3 and 4 are connected to temporary external electrodes indicated by 5 and 6, respectively, and the other internal electrodes are connected to the temporary external electrodes indicated by 2 alternately every other layer.
connected to two temporary external electrodes.

Next, a suspension containing glass powder as deposits is prepared by the following method. Mix 30 g of zinc borosilicate crystallized glass powder, 290 ml of ethanol, and 10 ml of 5% iodine ethanol solution using a high-speed homogenizer. Iodine acts as an electrolyte, and the glass powder is positively charged. After applying ultrasound for 30 minutes, let stand for 30 minutes to remove the precipitate, and use the remaining suspension.

After covering one end face of the electrostrictive material laminate with an exposed internal electrode with an adhesive tape to prevent it from getting wet with the suspension, submerge it in the suspension with the end face to be attached facing upward; Leave it for 15 minutes to deposit glass powder on the entire end surface. By increasing the standing time, the thickness of the deposited glass powder can be increased. Furthermore, it is also possible to forcibly accelerate the sedimentation rate and increase the density of the deposited layer by centrifugation.

Next, a counter electrode plate is submerged in the suspension and placed at a position 3 cm above the laminate. Connect the temporary external electrode 23 to the positive terminal of the DC power supply, connect the counter electrode plate to the negative terminal, and apply 20V for 200 seconds. In this case, ethyl alcohol may be used instead of the suspension. FIG. 5 is a conceptual diagram showing the installation method. In the figure, number 21 is an electrostrictive material laminate having internal electrodes, 2
Reference numeral 2 denotes a temporary external electrode that is a group of internal electrodes to be insulated, and 23 is a temporary external electrode that is a group of internal electrodes that should be exposed. 24 is glass powder deposited on the end face of the laminate. 25 is a counter electrode plate;
26 is the suspension or ethyl alcohol, 27 is a DC power supply, and 28 is a container.

After applying voltage, the laminate is pulled out of the suspension or ethanol, dried, and baked at 710° C. in an air atmosphere to fix it. After forming a pattern on the opposite end surface in the same manner, it is cut at the position of the broken line as shown in Fig. 4, and a band-shaped external electrode is formed on the two surfaces on which the insulator is formed. As shown in FIG. 1, electrostrictive elements whose internal electrodes are equal to the cross section of the element can be electrically connected.

According to the present invention, it is not only possible to form fine insulating patterns with high reliability, but also a simple method of controlling the layer thickness of the insulating material, which has been difficult to control in the past, by controlling the length of time the insulating material is left in the suspension. This manufacturing method is suitable for mass production.

[Brief explanation of the drawing]

FIG. 1 is an external view showing an electrostrictive effect element whose internal electrodes are equal in cross-sectional area to the element, which are electrically connected using electrophoresis. In the figure, number 1 is the electrostrictive material ceramic of the protective film part, 2 is the electrostrictive material ceramic of the part that causes strain, 3 and 4 are the internal electrodes, 7 and 8 are the insulating coatings that cover them, and 11 is the internal electrode layer External electrodes connected to each other are shown at intervals. 1
2 and 13 indicate negative and positive external terminals. FIG. 2 is an external view of an electrostrictive material laminate to which electrophoresis is applied. In the figure, number 1 is the electrostrictive material laminate of the protective film part, 2 is the electrostrictive material laminate of the part where strain is generated, 3 and 4 are internal electrodes exposed on the end surface,
Reference numerals 5 and 6 indicate temporary external electrodes interconnecting these. FIG. 3 is an external view of an electrostrictive material laminate in which glass powder is formed on the exposed portions of the internal electrodes on the end faces and the surrounding ceramics. In the figure, number 1 is the electrostrictive ceramic material of the protective film part, 2 is the electrostrictive material ceramic material of the part where strain is generated, 7 is the attached glass powder, and 5 and 6 are the temporary external parts that interconnect the internal electrodes every other layer. Electrodes 4 indicate exposed internal electrodes, respectively. FIG. 4 is an external view showing the cutting position (dotted line portion) of the electrostrictive material laminate on which the insulating coating is formed. In the figure, numeral 9 indicates an unusable portion at both ends, and numeral 10 indicates a portion that functions as an electrostrictive element by forming external electrodes. FIG. 5 is a schematic diagram showing a method of connecting an electrophoresis device according to the method of the present invention. In the figure, numeral 21 indicates an electrostrictive material laminate, 22 indicates a temporary external electrode that includes internal electrodes to which glass powder is to be attached, and 23 indicates a temporary external electrode that includes internal electrodes to which glass powder is not to be attached. 24 is a deposited glass powder, 25 is a counter electrode plate, 26 is a suspension containing charged glass powder or ethanol, 27 is a DC power source, and 28 is a container.

Claims (1)

[Claims] 1. Producing an electrostrictive material laminate in which electrostrictive materials and internal electrodes are alternately laminated, and attaching glass powder onto a portion of the internal electrodes exposed on the end face of the laminate and the electrostrictive material in the vicinity thereof. In a method for manufacturing an electrostrictive effect element having a step, the laminate is placed in a suspension containing charged glass powder, the glass powder is deposited on the entire surface of the end face by sedimentation in advance, and then the glass powder is attached. By applying an electric field between the internal electrode that does not allow the glass powder to adhere and a metal plate for a counter electrode placed in the suspension, only the glass powder deposited on the internal electrode that does not allow the glass powder to adhere is removed by electrostatic force. A method for manufacturing an electrostrictive element.