JPS6356971A - Stacking type piezoelectric body - Google Patents

Abstract

PURPOSE:To improve the mechanical strength by baking the piezoelectric boards to be stacked with a conductive paste thereby to integrate them. CONSTITUTION:On piezoelectric boards 1 which are made by baking ceramic sheets and thereafter lapping the surfaces threof, an electrode paste is printed to form internal electrodes 2. The piezoelectric boards are dried and stacked so that patterns 11 appear in the same position on every other board. The stack is baked in an oxygen atmosphere while being applied with a load. Then, when an electroless nickel plating is applied to the integrated stack, metal projections 3(4) are formed in the edge of every other internal electrode on each of the opposing surfaces of the stack. Then, a board 13 is placed on the metal projections 3(4), and a resin is made to flow thereunder, dried and har dened to form an insulating coating layer 5. A conductive paste is printed over the insulating coating layer 5 thereby to form external electrodes 6(7). As to a terminal strip, a silver paste is baked to the piezoelectric board 14, the exter nal electrodes 6(7) are connected thereto, and an external lead wire 8 is soldered to the portion 15 to which the silver has been baked. With this, the mechanical strength can be enhanced and the cost can be reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a laminated piezoelectric material, and more specifically, it is formed by laminating a large number of plate-like members made of piezoelectric elements, and the piezoelectric material This invention relates to a laminated piezoelectric material that expands and contracts and acts as an actuator.

[Conventional technology]

Conventionally, as an actuator made of a laminated piezoelectric material, 3
4fi alternating metal electrode plates and piezoelectric plates with protrusions in the direction
An actuator formed by l'lJ is known. In this actuator, the metal electrode plates are electrically connected in parallel using side lead members, but piezoelectric The metal coating and metal electrode plate formed on the surface of the plate are kept inside the piezoelectric plate (Japanese Patent Laid-Open No. 6
(See Publication No. 0-4279).

(Problem to be solved by the invention) In recent years, the use of piezoelectric plates with high loads has increased, and in order to use the area of the actuator effectively, it is said that it is difficult to have areas on the piezoelectric plate that are loaded and areas that are not loaded. From this point of view, a full-surface electrode structure is becoming necessary.

In addition, in order to reduce the cost of the drive circuit, it is necessary to lower the voltage, but if the thickness of the piezoelectric element (piezoelectric plate) is reduced, the mechanical strength of the piezoelectric plate decreases, and the gold J1 electrode is If they are laminated in this way, there is a problem that the piezoelectric element will break.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention stacks a plurality of piezoelectric plates, fixes and integrates the piezoelectric plates with internal electrodes arranged between them, and forms an axis on the outer periphery of the laminate consisting of the piezoelectric plates and internal electrodes. a first row of metal protrusions is formed by electroless plating every other internal electrode in the direction, and the first row of metal protrusions is spaced apart from the first row in the outer circumferential direction of the laminate. A second row of metal protrusions is formed by electroless polishing on the internal electrodes on which no metal protrusions are formed, and an insulating coating layer is formed on the outer periphery of the laminate between the metal protrusions in each of the first and second rows. is formed to insulate the internal electrodes present between the metal protrusions in each row, the metal protrusions in the first row are electrically connected by a first external electrode to serve as the first electrode, and the metal protrusions in the first row are electrically connected by a first external electrode, 2nd row of metal protrusions
Provides a laminated piezoelectric material characterized in that the material is electrically connected to an external electrode of the material and serves as a second electrode.

In this laminated piezoelectric body, in order to prevent a short circuit between an external electrode and an internal electrode of the opposite potential even when the entire surface electrode structure is used, the outer peripheral portion of the laminated body where an internal electrode that may be short-circuited with the external electrode exists is Cover with an insulating layer. On the other hand, in order to enable electrical connection between the necessary internal electrodes and external electrodes even after this insulating coating layer is formed, metal protrusions are formed by plating the necessary internal electrodes on the outer periphery of the laminate. This metal protrusion is typically formed prior to the formation of the insulating coating layer, and a plate or the like is applied to the metal protrusion, and an insulating material such as resin is poured underneath to form the insulating coating layer. In this case, the method for selectively forming metal protrusions on necessary internal electrodes will be described in detail in the Examples, but is not limited thereto. When an insulating coating layer is formed by applying a plate or the like to the metal protrusion as described above, an external electrode can be formed by printing a conductive material thereon. Usually, all sides of the laminate including such external electrodes are further insulated by resin coating or the like.

〔Example〕

FIG. 1 shows a schematic cross-sectional view of a typical example of a laminated piezoelectric material according to the present invention. In the figure, ■ is a piezoelectric plate, 2 is an internal electrode that solidifies and integrates the piezoelectric plate 1, and 3 is a plated plate on every other internal electrode 2 on one side of the laminate consisting of the piezoelectric plate 1 and internal electrodes 2. Metal protrusions 4 are formed by plating the metal protrusions 3 and every other internal electrode 2 on the other side of the laminate (second column). , 5 is an insulating coating layer, 6
．． 7 is an external electrode. FIG. 2 is a front view of such a laminated piezoelectric material (a view of the laminated piezoelectric material in FIG. 1 viewed from the left or right), and as shown in the figure, the external electrode 6 (7) is a metal protrusion. The external electrodes 6 (7) are formed in a chisel shape on the rows 3 (4), and lead wires 8 connected to a power source are connected to the external electrodes 6 (7). As seen in these figures, each external electrode 6
．． 7 is a metal protrusion 3 extending from every other internal electrode 2;
4, the stacked piezoelectric elements are electrically connected in parallel, and the outer electrodes 6 and 7 are connected to the inner electrode 2 at the opposite potential.
An insulating coating layer 5 is formed between the two to prevent short circuits. In addition, in this example, the first and second rows 3,
Although one number 4 is formed on each opposing surface of the laminate, each may be formed in a plurality of rows.

Next, manufacturing of such a laminated piezoelectric body will be explained.

Referring to FIG. 3, after firing a molded ceramic sheet such as PZT, internal electrodes 2 are formed by screen printing an electrode paste on a piezoelectric plate 1 (for example, 0.3 mm thick) whose outer periphery is polished and the surface is lapped. At this time, as shown in the figure, the piezoelectric plate 1 is formed by cutting the opposing circumferential surfaces of a disc (diameter 151 m) parallel to each other to form side surfaces for drawing out external electrodes. In addition, the internal electrodes 2 are formed using two types of electrode pastes, and one pattern 11 is made of palladium (
or Fe, Co, Ni, Ru, Os
, Ir, PL, etc.) in 5 to 3
Another pattern 1 of the paste mixed with 0wt%
2 is one paste with lead (or Sb, Sn, Z
A paste containing 5 to 30 wt % of N, etc.) is used.

The pattern 11 contacts (extends) only the end surface for external electrode extraction (one of the side surfaces cut parallel to the circumferential surface of the disk) of the outer periphery of the piezoelectric plate 1, and the pattern 11 is formed on the remaining outer periphery. 1
2 are touching (extending).

This piezoelectric plate was dried at 100°C, and as shown in Figure 3,
A predetermined number of sheets are stacked so that the pattern 11 is placed at the same position on every other sheet. and l kg/c in the laminate
The paste is baked by increasing the temperature to 600° C. in an oxygen atmosphere while applying a load of about d. At this time, the piezoelectric plate 1 is fixed and integrated with the glass contained in the electrode paste.

The integrated stack is electrolessly plated as follows.

First, the first method is to perform alkaline degreasing with an alkaline degreasing solution (manufactured by Henkel Hakusuisha), rinse with water, soak in hydrochloric acid (1:1) for 1 to 2 minutes, rinse with water, and soak in hypochlorite at approximately 80°C. Soak in sodium phosphate for about 10 minutes. And metal protrusion 3
(4) Immerse in S-780 electroless coating solution (manufactured by Nippon Kanigen Co., Ltd.) at about 90°C until the height becomes 50 to 100 μm.

The second method is to first master the areas where you do not want electroless plating using Teflon tape or the like, and then expose only the areas you want to plate. Then, perform alkaline degreasing with alkaline degreasing liquid (manufactured by Henkel Hakusuisha) and wash with water. Then, it is immersed in hydrochloric acid (1:1) for 1 to 2 minutes, washed with water, and immersed in active liquid 3 (manufactured by Nippon Kanigen Co., Ltd.) at about 60° C. for 10 minutes, and washed with water.

Then, it was further immersed in hydrochloric acid (1:1) for 1 to 2 minutes, washed with water, and immersed in sodium hypophosphite at about 80°C for about 10 minutes.
5B-55 electroless plating solution (manufactured by Nippon Kanizen Co., Ltd.) at 5°C
Soak in water for about 10 minutes, wash with water, and heat the S-780 at about 90°C until the height of metal protrusion 3 (4) reaches 50 to 10 (lcjm).
Immerse in electroless mebuki solution. Once plating is complete, remove the mask.

When plating is performed, nickel plated portions (metal protrusions 3 (4)) are formed at the edges of every other internal electrode on each of the opposing surfaces of the stack, as shown in FIG. The height of this metal protrusion 3 (4) is approximately 50 to 100 μm. In this electroless plating, the part of pattern 11 is activated by palladium, so the plating adheres well, but the part of pattern 12 has lead that acts as a catalyst poison and has difficulty in adhering to the plating. A protrusion is formed.

Next, metal protrusions 3 (
4) and the internal electrodes on which no plating is formed have an opposite potential, so they must be insulated. Therefore, as shown in FIG. 5, a plate 13 is applied to the metal protrusion 3 (4), and resin is poured under the plate 13 and dried and hardened. In this way, the insulating coating layer 5 is formed, and the unplated internal electrodes are insulated. This resin is preferably one that has excellent heat resistance and flexibility that can easily follow expansion and contraction, such as epoxy resin, silicone resin, and fluorosilicone resin.

Then, referring to FIG. 2, when the plate 13 is removed, the metal protrusions 3 (4) are exposed, so conductive paste is applied across the resin (insulating coating layer) 5 so that these parts have the same potential. External electrodes 6 (7) are formed by printing. The terminal extraction part is made by baking silver paste on piezoelectric plates (dummy) 14 without electrodes at both ends of the stack, connecting external electrodes 6 (7) to it, and then applying the silver (external electrodes) to the baked parts 15. Attach the external lead wire 8 with solder.

Then, the entire side surface is coated with resin and the external electrode 6
(7) etc. to prevent short-circuiting with a metal storage case (not shown). Note that the external electrode 6 (7) may be a straight line, but in the case of a piezoelectric material that utilizes high displacement, a chiral shape as shown in FIG. 2 is preferable.

In the above embodiment, as a method for selectively attaching electroless plating, a material containing a component that activates plating and a component that poisons the catalyst of plating were used in the internal electrode material, but the present invention is not limited to this.

For example, as shown in FIG. 6, a silver paste or one palladium paste 16 is applied to the entire surface of the piezoelectric plate l, but a pattern of silver paste is slightly applied only to the end surface where no plating is to be applied (see FIG. 6). (Part 17) may be retracted inward and printed (typically screen printing). Since the retractable distance is sufficient to be less than 0.1 mm,
The advantages of full surface electrodes are not compromised.

Further, as a means for slightly retracting such an electrode pattern inward, silver paste or the like having a different baking temperature may be used. For example, as shown in Fig. 7, the baking temperature is 540°C.
℃ silver paste on pattern 18 and remaining area 19
Apply silver paste with a baking temperature of 800℃. This is 80
When baked at 0°C, the glass lift contained in the paste with a baking temperature of 540°C will shrink and be pulled into the interior.

Furthermore, a silver paste with a silver content of 80 to 90-1% is used for the areas where plating is to be attached, while a silver content of approximately 60w is used for areas where plating is not to be attached.
% silver paste may be used.

Various modifications may be made, such as using copper, zinc, or the like instead of nickel for plating, or making the pattern of the internal electrodes square or other rather than triangular as in the above embodiments.

〔Effect of the invention〕

In the laminated piezoelectric body of the present invention, the piezoelectric plates to be laminated are baked and integrated with a conductive paste that forms the internal electrodes, and the use of metal electrode plates is omitted. Therefore, mechanical strength can be maintained even if thinner piezoelectric plates are used than before. It is possible to lower the drive voltage (to improve the Young's modulus), simplify the drive circuit, and reduce costs.

Furthermore, according to the present invention, even if the internal electrodes baked onto the piezoelectric plate are formed on the entire surface of the piezoelectric plate, that is, even if the entire surface electrode structure is used, the insulation necessary for a laminated piezoelectric material is achieved. This has the effect that the area of the piezoelectric element (piezoelectric element) can be used as effectively as possible and that it can withstand large loads.

[Brief explanation of the drawing]

Figures 1 and 2 are schematic cross-sectional views and front views of the laminated piezoelectric body of the present invention, and Figures 3 to 5 illustrate important points in the process of manufacturing the laminated piezoelectric body of Figures 1 and 2. It is a diagram that
Figure 3 is a perspective view showing how internal electrode paste is applied to a piezoelectric plate, Figure 4 is a perspective view of a stack with metal protrusions formed, and Figure 5 is an insulating internal electrode that has a potential opposite to that of the external electrode. FIGS. 6 and 7 are perspective views illustrating another aspect of the application pattern of the internal electrode paste on the piezoelectric plate. 1... Piezoelectric plate, 2... Internal electrode, 3.4
... Metal protrusion (row), 5... Insulating coating (resin) layer, 6.7... External electrode, 8... External lead wire, 1
1.12... Internal 78 Polar paste pattern 13...
・Plate, 13...Piezoelectric plate for terminal extraction, 16・
...Silver paste, 17...Blank pattern, 18,
19... Internal electrode paste pattern.

Claims (1)

[Claims] 1. A plurality of piezoelectric plates are laminated, the piezoelectric plates are fixed and integrated with internal electrodes arranged between them, and one piezoelectric plate is formed in the axial direction of the outer periphery of the laminate consisting of the piezoelectric plates and internal electrodes. A first row of metal protrusions is formed by electroless plating on alternate internal electrodes, and the first row of metal protrusions is not formed apart from the first row in the outer circumferential direction of the laminate. A second row of metal protrusions is formed by electroless plating on the internal electrodes, and an insulating coating layer is formed on the outer periphery of the laminate between each of the first and second rows of metal protrusions. internal electrodes existing between the metal protrusions in the row are insulated, the metal protrusions in the first row are electrically connected to each other by a first external electrode to serve as a first electrode; A laminated piezoelectric body characterized in that a row of metal protrusions are electrically connected to each other by a second external electrode, which serves as the second electrode. 2. The laminated piezoelectric body according to claim 1, wherein the internal electrode is formed on the entire laminated surface of the piezoelectric plate. 3. Claim 1 or 2, wherein the laminate has opposing surfaces, and the first row of metal protrusions and the second row of metal protrusions are formed on each of the opposing surfaces. The described laminated piezoelectric material. 4. The first and second external electrodes are formed by printing conductor strips on each row of metal protrusions and on an insulating coating layer existing between them. The laminated piezoelectric material according to item 3. 5. The multilayer piezoelectric material according to claim 4, further comprising an insulating layer covering the entire outer periphery of the multilayer body including the first and second external electrodes. 6. The internal electrode is composed of a combination of a pattern made of a material active in electroless plating of the metal protrusion and a pattern made of a material that acts as a catalyst poison for the electroless plating, and the metal protrusion is present on the outer periphery of the laminate. Claims 1 to 5, wherein the pattern of the electroless plating active material extends in the portion, and the pattern of the electroless plating catalyst poison material extends in the portion where the metal protrusion is not present. The laminated piezoelectric material according to any one of the above. 7. In a band-shaped region formed by the first and second rows of the metal protrusions on the outer periphery of the laminate, the internal electrode extends to the outer periphery of the laminate in the portion where the metal protrusions are formed. Claims 1 to 6, wherein the internal electrode is formed by being slightly recessed into the laminate from the outer periphery of the laminate in a portion where the metal protrusion is not formed. The piezoelectric laminate according to item 1. 8. The internal electrode is composed of a combination of a plurality of patterns,
the first and second metal protrusions on the outer periphery of the laminate;
In the band-shaped region formed by the rows of , the pattern of internal electrodes extending in the portion where the metal protrusions are formed is made of a material whose internal electrode material has a substantially high baking temperature;
8. The piezoelectric laminate according to claim 7, wherein the internal electrode pattern corresponding to the portion where the metal protrusion is not formed is made of a material whose internal electrode material has a substantially low baking temperature.