JPS6317355B2 - - Google Patents

Description

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

When an element with a multilayer chip capacitor structure is constructed using a material with a large electrostrictive effect, an electrostrictive effect element (hereinafter abbreviated as an element) generates large distortion at low voltage.
is obtained. Figures 1a and 1b show the structure of this element.

Figure 1a is a sectional view when viewed from the front;
b is a plan view seen from above. 1 is an electrostrictive material, 2
and 2' are internal electrodes formed inside the electrostrictive material, one end of which is exposed to the surface of the electrostrictive material.
3 and 3' indicate external electrodes that electrically connect the exposed ends of the internal electrodes. The internal electrodes are electrically connected to every other layer by this external electrode. In FIG. 1b, 4 indicates a portion where the internal electrodes overlap in the stacking direction, 5 indicates a portion where they do not overlap, and 6 indicates a portion where no internal electrode exists. In an element having such a structure, as is clear from FIG. 1b, the overlapping portion of the internal electrodes exists only in the central part of the element.
When a voltage is applied between the external electrodes 3 and 3', the electric field strength basically increases only in the overlapped portion 4 of the positive and negative internal electrodes. Peripheral area near the end face, that is, a portion 5 where internal electrodes do not overlap and a portion 6 where internal electrodes do not exist
Since the electric field strength is weak, not only that part does not deform, but also moves that inhibits the deformation of the entire element. Therefore, in an element with such a structure, it is not possible to obtain the amount of strain inherent to the material, and stress concentration occurs at the boundary between the deformed part and the non-deformed part, and if a high voltage is applied or a voltage is applied for a long time, the element It has the disadvantage of being destroyed.

As an element that has improved the above-mentioned drawbacks, the present inventors have previously proposed an element having a structure in which all the ends of the internal electrodes are exposed to the surface of the electrostrictive material, as shown in FIGS. 2a and 2b. FIG. 2a is a front view of an element having this structure, and FIG. 2b is a cross-sectional view of a when cut at the electrode portion and viewed from above. 20 and 21 are electrostrictive materials, 22 and 22' are internal electrodes, 23 is a wire (positive side) connecting the internal electrodes every other layer,
Similarly, 24 is a wire (minus side). 2
5 and 26 are a positive electrode terminal and a negative electrode terminal, respectively.

As is clear from FIG. 2b, the internal electrodes occupy the entire cross-sectional area of the device, and as shown in FIG.
There is no peripheral area that is not sandwiched by the internal electrodes. In an element with this structure, the internal electrodes are electrically connected every other layer by wires to the electrode elements 25 and 2.
6 has been taken out. When a voltage is applied between both electrode terminals, an electric field is generated perpendicularly to the internal electrodes from the internal electrodes 22 to 22' as shown by arrows in the figure. Electrostrictive materials generally expand in the direction of the electric field in proportion to the absolute value of the electric field, and contract in the direction perpendicular to the electric field. In the element having this structure, the electric field intensity distribution between the internal electrodes is uniform except for the portion of the electrostrictive material 20 formed on the surface of the element and which moves as a protective film. Therefore, the element with this structure deforms much more uniformly than the element with the structure shown in FIG. 1, and stress concentration does not occur. Therefore, it exhibits a large strain inherent to the material and has the advantage of not breaking when deformed.

However, in order to apply a high electric field to the electrostrictive material, the interval between internal electrodes is about 250 μm, and it is extremely difficult to connect every other layer using wires from an industrial perspective.

Therefore, the present inventors first coated an insulating material on the element surface where the end of the internal electrode was exposed, baked it, covered the exposed end of the internal electrode every other layer, and then applied the external electrode over the entire side surface. We proposed a method to electrically connect internal electrodes by uniformly coating them.

However, when applying by printing, a fluid insulating material must be used, and it is difficult to stably form a fine insulating pattern. Furthermore, for the same reason, it is difficult to control the coating thickness. Unnecessarily thick insulating material inhibits device deformation. Moreover, if the thickness is insufficient, the dielectric strength voltage will be lowered.

The purpose of the present invention is to solve these two problems,
It is an object of the present invention to provide a method for manufacturing an electrostrictive effect element that can stably and efficiently electrically connect between internal electrodes of an electrostrictive effect element whose internal electrode end portions are exposed on the surface of the element.

That is, the present invention is a laminate having a multilayer capacitor type structure in which electrostrictive materials and internal electrodes are alternately laminated, and two external electrodes are connected to the internal electrodes at every other layer, and are parallel to the lamination direction. A process of producing a laminate having a structure in which internal electrode layers are exposed on two surfaces different from the external electrode forming surface, and between one external electrode of the laminate and an electrode plate installed outside the laminate. a step of forming an insulating material on and in the vicinity of every other internal electrode layer on one of the exposed surfaces of the internal electrodes by applying a DC voltage to the laminate; A direct current voltage is applied between the electrode plate and the external electrode different from the external electrode to the exposed surface of the internal electrode different from the formed surface and the internal electrode layer, the internal electrode layer, and the vicinity thereof, and the insulation is also insulated by the electrophoresis method. This is a method of manufacturing an electrostrictive effect element, which includes a step of forming a material, and a step of cutting a layered body formed with the insulating material in the vicinity of an external electrode forming portion.

When attempting to form an insulating material film only on the internal electrodes exposed on the element surface and their surroundings, the usual method is to prepare some kind of pattern in advance and align it with the exposed internal electrodes. However, if this method is applied to the electrostrictive element currently being considered, alignment accuracy of about 100 microns is required. At the same time, it is necessary to adjust the distance between the internal electrodes of the electrostrictive element to a predetermined value. These two problems make electrical connection of electrostrictive elements difficult.

If we change our way of thinking and use the exposed portions of internal electrodes to form insulation patterns, the problem of positional misalignment can be solved, and the method can be applied to devices with irregular distances between internal electrodes.

On the other hand, a technique is known in which glass powder charged in suspension is adhered to the surface of a conductive object by electrophoresis. For example, when glass powder particles become positively charged, a conductive object to which the glass powder is attached and a counter electrode are placed in a suspension, and an electric field is generated from the counter electrode in the direction of the conductive object to which the glass powder is attached. A DC voltage is applied between the two so that the The voltage applied is usually 10V to 200V DC.
That's about it. The charged glass particles move under the force of the electric field and adhere to the surface of a conductive object.
By firing and fixing this, a glass film with a thickness of several microns to several hundred microns is formed on the surface of the conductive object. It is said that according to this method, the glass powder adheres only to the surface of the target conductive object, and does not adhere to the surface of an insulating material or a conductive object that is not electrically connected to the target conductive object. ing. Due to the above characteristics, by applying this electrophoresis method to an electrostrictive material laminate including internal electrodes, it is possible to deposit an insulating material only on and around the internal electrodes exposed at the end faces. By firing and fixing, it is possible to form an insulating pattern with perfect precision.

It is easy to form a strip-shaped insulating pattern on all the exposed parts of the internal electrodes, but as mentioned above, in order to electrically connect the electrostrictive effect element, it is necessary to form a strip-shaped insulation pattern on all the exposed parts of the internal electrodes and the surrounding area. It is necessary to form the insulating material only on the surface of the electrostrictive material. The method of the present invention solves this problem and proposes a method for electrically connecting electrostrictive elements by forming an insulating pattern using electrophoresis.

First, an electrostrictive material laminate having a structure as shown in FIG. 3 having a large number of internal electrodes and external electrodes connecting them externally is produced. The internal electrodes are exposed on the end face, and are grouped into two sets with every other layer connected to two temporary external electrodes at both ends. To attach insulating material to the exposed part of the internal electrode and its surrounding area, which is indicated by number 32 in the figure, first protect the back side with adhesive tape or the like to prevent unnecessary adhesion, and then apply electrically charged glass powder to the laminate. Soak in a suspension containing Place the counter electrode plate in front of the front surface,
A DC voltage is applied between the counter electrode plate and the external electrode 33. The positively charged glass powder moves through the suspension under the force of the electric field generated from the counter electrode plate toward the internal electrode exposed area, and moves onto the internal electrode exposed area 32 connected to the external electrode 33. It adheres only to the periphery thereof, and does not adhere to the internal electrode exposed portion 34 connected to the external electrode 35. When this is pulled out of the suspension, dried, fired, and fixed, a band-shaped glass film is formed that covers every other exposed portion of the internal electrode. The situation is shown in Figure 4. A band-shaped glass coating 42 is formed every other layer, leaving the internal electrodes 42 exposed.

Next, an insulating pattern is similarly formed on the back side. First, the front side is covered with adhesive tape or the like to prevent excessive adhesion and immersed in the suspension. A counter electrode plate is placed in front of the back surface, and a voltage is applied between the counter electrode plate and the external electrode 45 to cause glass powder particles to adhere onto the internal electrode exposed portion 44 . After that, it is baked and fixed to form a band-shaped glass coating.

Next, the electrostrictive material laminate having band-shaped glass coatings formed on both sides is cut along the broken line shown in FIG. 5a to obtain the final dimensions of the electrostrictive effect element. Cut at least two places near the external electrode. The two small pieces 50 with temporary external electrodes at both ends cannot be used as electrostrictive elements. By cutting as shown in FIG. 5, a plurality of electrostrictive effect elements 51 can be obtained from one electrostrictive material laminate. FIG. 5b shows an electrostrictive element with a glass coating formed thereon. Next, as shown in FIG. 6, if external electrodes 66 are formed on the front and back sides of the band-shaped glass film and the exposed internal electrodes so as to cover the exposed internal electrodes, the electrostrictive element can be electrically connected. can.

The properties that the glass material used in the method of the present invention should have are, first of all, that it should not cause manufacturing problems even if it reaches the firing temperature multiple times, and once crystallized, it cannot be heated again beyond its softening point. It is also a crystallized glass that does not soften. Among these, it is necessary to have excellent mechanical strength, honey, and insulation properties, and a coefficient of thermal expansion comparable to that of the electrostrictive material.

By using the method of the present invention for electrically connecting electrostrictive elements, the following effects can be obtained. Since the glass powder adheres only to the exposed portions of the internal electrodes and their surroundings, the accuracy of the insulation pattern is almost ideal. Unlike printing methods, it is not necessary to match the distance between the insulating pattern to be formed and the internal electrodes of the laminate to which it is applied, and it is generally difficult to control the shrinkage rate and final shape as a manufacturing method for ceramic materials. Considered a good process. Because the deposition is an electrochemical reaction, uniformity in thickness and width is obtained. Because the adhesion tends to concentrate on the exposed parts of the internal electrodes, it is difficult to cause partial loss or defects, and even if an external electrode is formed on top of it after firing and fixing, and a voltage is applied, the withstand voltage is locally low. There are no parts, and a high dielectric strength voltage can be obtained as a whole.

The present invention will be described in detail below with reference to Examples.

First, an electrostrictive material laminate having a structure as shown in FIG. 3 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 further cut to obtain a laminate with exposed internal electrodes as shown in Figure 3. . Electrophoresis is applied to the electrostrictive material laminate thus obtained.
In FIG. 3, 30 is the electrostrictive material of the protective film portion, 3
1 indicates an electrostrictive material that causes strain. The inner electrodes 32, 34 are connected to temporary outer electrodes indicated at 33 and 35, respectively, and the other inner electrodes are connected to two temporary outer electrodes alternately on every other layer.

Next, a suspension containing glass powder as deposits is prepared by the following method. Mix 30 g of zinc borosilicate crystalline 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.

One side of the electrostrictive material laminate on which the internal electrodes are exposed is covered with adhesive tape to prevent it from getting wet with the suspension, and then submerged in a container filled with the suspension. A stainless steel counter electrode plate with a larger area than the surface to be attached is submerged at a distance of 1 cm in front of the surface to which it is to be attached. The counter electrode plate is connected to the positive terminal of a DC power supply, the temporary external electrode 33 is connected to the negative terminal, and a voltage of 20V is applied for 300 seconds. When the paper was dried, glass powder with a width of 200 microns was deposited on the surface of the electrostrictive material on and around the internal electrode exposed portion 32.

After removing the adhesive tape on the back, heat at 705℃ for 10
The glass film was baked by holding for a minute to fix the glass film to the electrostrictive material. The situation is shown in Figure 4. In FIG. 4, reference numeral 40 indicates an electrostrictive material of the protective film portion, and reference numeral 41 indicates an electrostrictive material that causes strain. The band-shaped glass coating 42 is formed on the exposed portion of the internal electrode connected to the temporary external electrode 43 and its periphery. 4 in Figure 4
Reference numeral 4 indicates an internal electrode left exposed, and reference numeral 45 indicates a temporary external electrode that brings them together.

Next, a glass coating is formed on the opposite side. First, protect the surface on which the glass coating has already been formed by covering it with adhesive tape, then connect the external electrode 45 to the negative terminal of the DC power supply and apply a voltage in the same manner as the first time to connect the exposed part of the internal electrode 44 and the Adhere glass powder around the area. This is fired in the same manner as the first time to form a band-shaped glass coating.

The electrostrictive material laminate having glass coatings formed on the front and back sides as described above is cut at the position shown by the broken line in FIG. 5a. 502 small pieces with temporary external electrodes indicated by number 50 in the figure cannot be used, and the small pieces 51 between them cannot be used.
becomes an electrostrictive element. The obtained electrostrictive element is shown in FIG. 5b. In the figure, numeral 52 indicates the electrostrictive material of the protective film portion, 53 indicates the electrostrictive material that causes strain, and 54 indicates the exposed internal electrode. Among the plurality of internal electrodes, for example, an odd-numbered internal electrode 55 counting from the top
is covered with a glass coating 56 on the front side, but is exposed on the back side. Conversely, even-numbered internal electrodes indicated by 54 are exposed on the front side, but are covered with a glass film indicated at 57 on the back side.

The obtained electrostrictive effect element has a shape of 2 as shown in FIG.
Electrical connection is easily achieved by forming two external electrodes on the front and back sides, and by applying a voltage between these external electrodes, a uniform electric field is generated throughout the electrostrictive material except for the protective film, causing large distortion. Occur.
In the figure, numeral 60 indicates the electrostrictive material of the protective film portion, and 61 indicates the electrostrictive material that causes strain. Number 62 in the diagram,
Reference numerals 63 indicate internal electrodes connected to the negative terminal and the positive terminal, respectively. Numbers 64 and 65 in the figure are glass coatings formed on internal electrodes indicated by 62 and 63, respectively. In the figure, numeral 66 is an external electrode formed on the front side, which is connected to a large number of internal electrodes 63 and brings them together. Further, on the back side, there is an external electrode indicated by 62 which brings together the internal electrodes.

The entire electrically connected electrostrictive effect element is coated with fluororesin to improve the moisture resistance of the element.

As is clear from the above examples, according to the method of the present invention, a stacked electrostrictive element in which all of the internal electrodes are exposed at the end face can be reliably electrically connected, and the yield is greatly improved. Furthermore, since this method is an electrochemical method, individual adjustment and setting of each sample is easy, large quantities can be processed simultaneously, and there are advantages in that the equipment is simple and costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a laminated chip capacitor type electrostrictive effect element, a is a sectional view seen from the horizontal direction, and b is a perspective view from the vertical direction. In the figure, number 1 is an electrostrictive material, 2 and 2' are internal electrodes, 3 and 3' are external electrodes, and 4
5 indicates an overlapping portion of internal electrodes, 5 indicates a non-overlapping portion of internal electrodes, and 6 indicates a portion without internal electrodes. FIG. 2 is a configuration diagram of a multilayer electrostrictive element in which internal electrodes are exposed at the end face of the element, where a is a side view and b is a vertical cross-sectional view. In the figure, numbers 21 and 21' are electrostrictive materials, 22 and 22' are internal electrodes, 23 and 24 are wires connecting the internal electrodes, and 25 and 26 are electrode terminals, respectively. FIG. 3 is an external view of an electrostrictive material laminate to which the method of the present invention is applied. In the figure, numbers 30 and 31 indicate a protective film portion and an electrostrictive material that generates strain, respectively. 32
and 33 are external electrodes. 34 and 35 are external electrodes. FIG. 4 is an external view of the electrostrictive material laminate shown in FIG. 3 in which a glass coating is formed on the electrostrictive material in the internal electrode exposed portion and its surrounding area. 42 is a glass coating. FIG. 5a is an external view of an electrostrictive material laminate with glass coatings formed on both sides. FIG. 5b is an external view of the electrostrictive effect element cut out from the broken line part in FIG. 5a. 54, 55, 56, and 57 indicate internal electrodes, respectively. FIG. 6 is an external view of the electrostrictive element shown in FIG. 5b on which external electrodes are formed. 60 and 61 are electrostrictive materials, 62 and 63 are internal electrodes, 64 and 65 are glass coatings, 66 is an external electrode, and 67 and 68 are external terminals.

Claims (1)

[Claims] 1 A laminate with a laminated capacitor type structure in which electrostrictive materials and internal electrodes are alternately laminated, and two external electrodes are formed that are connected to the internal electrodes at every other layer, parallel to the lamination direction, and in which the external electrodes are formed. A step of producing a laminate having a structure in which internal electrode layers are exposed on two different surfaces, and applying a DC voltage between one external electrode of the laminate and an electrode plate installed outside the laminate. and forming an insulating material on and in the vicinity of every other internal electrode layer on one of the exposed surfaces of the internal electrodes by electrophoresis, and the surface of the laminate on which the insulating material is formed. and applying a DC voltage between the electrode plate and the external electrode different from the external electrode to the exposed surface of the internal electrode different from the internal electrode layer, the internal electrode layer, and its vicinity, and forming an insulating material by electrophoresis. 1. A method of manufacturing an electrostrictive element, comprising: a step of cutting a layered body formed with the insulating material near an external electrode forming part.