JPH10321411A - Laminated voltage nonlinear resistor and manufacture the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laminated voltage nonlinear resistor superior to junction and reliability of a junction section between varistor composite material and insulation composite material. SOLUTION: In the varistor ceramic 1, a plurality of inside electrodes 2 are laminated with their end alternately exposed from the varistor ceramic 1 and insulation ceramic 4, and an external electrode 3 is provided at the exposed end of the inside electrode 2. The top and bottom covers 5 and 6, and the side and end margin sections 9 and 10 of the varistor ceramic 1 are formed by the insulation ceramic 4. The shape of a junction face 11 in the direction of thickness of the two adjacent inside electrodes 2 is conbavo-convex simply interlaced by a concaveness and a convexity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated voltage non-linear resistor, and more particularly to a technique for improving the reliability of a material joining portion.

[0002]

2. Description of the Related Art In a conventional ZnO-based varistor, there is a problem in reliability under severe use conditions because the surface of the varistor where the sintered body is exposed is conductive. As a technique for solving such a problem, as shown in FIGS. 8A and 8B and FIG. 9, a cover portion, a side margin portion, and an end margin portion of a varistor composition material are made of an insulating composition material. There has been proposed one having improved reliability by being formed. Here, FIG.
Is a cross-sectional view schematically showing an example of a laminated varistor, (B)
9 is an enlarged cross-sectional view showing the X part of FIG. 8A, and FIG. 9 is a sectional view of FIG.
3 is a sectional view taken along the arrow Y in FIG.

First, in FIG. 8A, a plurality of internal electrodes 2 are alternately exposed from the varistor ceramic 1 inside a varistor ceramic 1 formed by sintering a varistor composition material. Staggered so that
An external electrode 3 is provided at an exposed end of the internal electrode 2. The surface of the varistor ceramic 1 is covered with an insulating ceramic 4 formed by sintering an insulating composition material. That is, as shown in FIGS. 8A and 9, the top cover 5 and the bottom cover 6 on both sides in the stacking direction of the varistor ceramic 1, the side margin portions 7 and 8 on both sides of the varistor ceramic 1, and the varistor End margin portions 9 and 10 between portions of both ends of ceramic 1 where internal electrode 2 is not exposed and external electrode 3
Are formed of the insulating ceramic 4.

[0004]

By the way, in the conventional laminated varistor described above, as shown in FIG. 8B, the insulating ceramic 4 forming the end margin portions 9 and 10 is made of a varistor ceramic. The varistor ceramic 1 is joined at a portion where the internal electrode 2 is not exposed at one end. In this joint portion, it is difficult to secure the joint accuracy due to the specialty of the end surface of the varistor ceramic 1 accompanying the arrangement of the internal electrodes 2, and thus a slight gap may be generated. If a gap is generated at the joint between the varistor ceramic 1 and the insulating ceramic 4 as described above, the varistor may be deteriorated due to voltage application or the like, and the reliability of the varistor is reduced.

SUMMARY OF THE INVENTION The present invention has been proposed to solve the above-mentioned problems of the prior art. The first object of the present invention is to provide bonding and reliability at the joint between a varistor composition material and an insulating composition material. An object of the present invention is to provide a laminated voltage non-linear resistor having excellent characteristics. A second object of the present invention is to provide an excellent manufacturing method capable of efficiently manufacturing such an excellent laminated voltage non-linear resistor.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an invention according to claim 1 is characterized in that a varistor composition material portion formed by sintering a varistor composition material and a varistor composition material portion are formed. An insulating composition material portion covering the surface of the varistor composition material portion, and a plurality of the varistor composition material portions are stacked such that their ends are alternately exposed from the ends of the varistor composition material portion and the insulating composition material portion. In the laminated voltage non-linear resistor composed of the internal electrodes, the joining surfaces of the two types of material are configured as follows.

That is, according to the first aspect of the present invention, the shape of the joining surface between the end portion of the varistor composition material portion and the insulating composition material portion in the thickness direction between two adjacent internal electrodes is a concave portion. And at least one element selected from the projections.

[0008] With the above-described structure, at the joint between the varistor composition material portion and the insulating composition material portion, a mechanical engagement force can be obtained by the uneven shape, and in addition, the thickness direction between the internal electrodes can be increased. In this case, since the creeping path between the varistor composition material portion and the insulating composition material portion becomes longer, the joining property and reliability of this joining portion can be improved.

According to a second aspect of the present invention, a varistor composition material portion made of a varistor composition material and an insulating composition material portion made of an insulation composition material coated on the surface of the varistor composition material portion are formed. At the same time, after forming a plurality of internal electrodes stacked so that their ends are alternately exposed from the ends of the varistor composition material portion and the insulating composition material portion to form a device, the device is sintered. In a method of manufacturing a laminated voltage non-linear resistor by providing external electrodes, two kinds of material parts are formed as follows.

In other words, the invention according to claim 2 provides, during the fabrication of a device, two or more varistor composition material layers having different dimensions between two adjacent internal electrodes and two or more layers joined to each of them. By forming the insulating composition material layer, the shape in the thickness direction of the joining surface between the end portion of the varistor composition material portion and the insulating composition material portion between two adjacent internal electrodes is changed to a concave portion and a convex portion. The varistor composition material portion and the insulating composition material portion are formed so as to have an uneven shape including at least one element selected from the following.

[0011] With the above-described structure, the relatively uneven process of forming the composition material layer is repeated without any complicated process, and the uneven shape as described in claim 1 can be obtained. It is possible to efficiently form the bonding surface having. Therefore, for the reason already described in the first aspect of the present invention, it is possible to obtain an excellent laminated voltage non-linear resistor having high joining performance and high reliability at the joining portion.

Further, the invention according to claim 3 is the same as the invention according to claim 2.
The varistor composition material layer and the insulating composition material layer are formed by a method selected from a sheet pressing method and a printing method. That is,
In the second aspect of the invention, the method of forming the material layer can be appropriately selected. However, by using any one of the sheet pressing method and the printing method according to the third aspect, the material layer can be efficiently and accurately formed. Can be formed.

[0013]

FIG. 1A is a cross-sectional view schematically showing one embodiment of a laminated varistor to which the present invention as described above is applied, and FIG. 1B is a sectional view of FIG. 2 is an enlarged cross-sectional view showing a portion X of FIG. 1, and FIG. 2 is a cross-sectional view of FIG. As shown in FIGS. 1A and 2, the basic configuration of the present invention is the same as that of the conventional laminated varistor shown in FIGS.

First, as shown in FIG. 1A and FIG.
In a varistor ceramic 1 formed by sintering a varistor composition material, a plurality of internal electrodes 2 are stacked while being shifted so that their ends are alternately exposed from the varistor ceramic 1. External electrode 3 on exposed end
Is provided. Then, the top cover 5 and the bottom cover 6 of the varistor ceramic 1, the side margin portion 7,
8 and the end margin portions 9 and 10 are formed of an insulating ceramic 4 formed by sintering an insulating composition material.

In addition to the above configuration, in the present embodiment, as shown in FIG. 1B, the joining between the insulating ceramic 4 forming the end margins 9 and 10 and the end of the varistor ceramic 1 is performed. The surface 11 has irregularities.
That is, the shape in the thickness direction of the joining surface 11 between the end portion of the varistor ceramic 1 and the insulating ceramic 4 between two adjacent internal electrodes 2 is an uneven shape obtained by simply combining one concave portion and one convex portion. It has been. In this case, each concavo-convex shape between each two internal electrodes 2 is uniformly and regularly formed.

According to the present embodiment having the above-described configuration, at the joint between the varistor ceramic 1 and the insulating ceramic 4, a mechanical engaging force is obtained by the uneven shape of the joint surface 11. That is, as compared with the case where the flat surfaces are simply brought into contact with each other as in the related art shown in FIG. 8B, the engagement force in the thickness direction can be ensured, so that the mechanical joining strength can be improved. In addition, by making the shape of the joint surface 11 uneven as described above, the creeping path between the varistor ceramic 1 and the insulating ceramic 4 in the thickness direction between the internal electrodes 2 can be lengthened, so that the electrical insulation strength can be improved. . Therefore, the jointability and reliability of the varistor ceramic 1, the insulating ceramic 4, and this joint can be improved.

[0017]

FIG. 3 is a flow chart showing an example of the manufacturing process of the laminated varistor according to the present invention, and FIG. 4 is a flow chart showing an example of the manufacturing process of the laminated body in FIG. FIG. 5 is a side view schematically showing a plurality of states in the laminated body manufacturing step of FIG. 4, and FIG. 6 is a plan view schematically showing a part of FIG. Hereinafter, this manufacturing process will be described.

First, an insulating composition green sheet and a varistor composition green sheet were prepared (step 10). That is, first, as an insulating composition material exhibiting insulating properties after firing, for example, a slurry is prepared by dispersing lead and niobium-based heroovskite powder in an organic binder, and the slurry is cast onto a base film to form a 1.
A 5 μm-thick insulating composition green sheet was prepared. Also,
Using a powder mainly composed of zinc oxide exhibiting varistor characteristics after firing, a varistor composition green sheet having a thickness of 15 μm was formed on the base film in the same manner as the insulating composition green sheet.

Then, using the insulating composition green sheet and the varistor composition green sheet prepared in Step 10, a laminate was prepared as follows (Step 2).
0). That is, first, an insulating composition green sheet was thermocompression-bonded on a 100 mm square pallet to form a bottom cover 6 as shown in FIG. 5A and FIG. 6A (step 21).

Next, as shown in FIGS. 5B to 5E, two varistor composition layers 1a and 1b and two insulating composition layers 4a and 4b joined to each of them are formed (step). 22). That is, first, (B) of FIG. 5 and (B,
As shown in D), the varistor composition green sheet is
₍₂₎ Cut to a size of 6.0 × 5.0 mm with a laser, and thermocompression-bonded to the center of the bottom cover 6 to obtain a varistor composition layer 1.
a was formed. Then, (C) of FIG. 5 and (C,
As shown in E), the insulating composition green sheet is cut with a CO ₂ laser so as to have an opening size of 6.0 × 5.0 mm, and is thermocompression-bonded on the exposed portion of the bottom cover 6 around the varistor composition layer 1a. Thus, an insulating composition layer 4a was formed. Further, as shown in (D) of FIG. 5 and (B, D) of FIG. 6,
On these varistor composition layer 1a and insulating composition layer 4a,
A varistor composition green sheet cut to a size of 5.7 × 5.0 mm with a CO ₂ laser was thermocompression bonded to form a varistor composition layer 1b. Then, it is shown in FIG. 5 (E) and in FIG. 6 (C, E) as shown in, 5.7 × 5 in CO ₂ laser.
The insulating composition green sheet cut so as to have an opening dimension of 0 mm was thermally pressed to form an insulating composition layer 4b.

Subsequently, as shown in FIG. 5F and FIG. 6F, an Ag / Pd internal electrode paste is applied to the varistor composition layer 1b.
And printing on a part of the insulating composition layer 4b.
Then, the internal electrode 2 overlapping the one end margin portion 10 was formed (Step 23).

Further, on the internal electrode 2, two varistor composition layers 1a and 1b and two insulating composition layers 4a and 4b joined to each of them are formed (step 24). (G), the internal electrode 2 was formed on the varistor composition layer 1b and the insulation composition layer 4b so as to overlap the end margin 9 on the opposite side of the insulation composition layer 15 (step 25).

By repeating the above steps 22 to 25 to form 20 internal electrodes 2 (step 26), the two varistor composition layers 1a and 1b and the two insulating compositions joined to each of them are formed. After forming the layers 4a and 4b (step 27), as shown in FIG. 6H, an insulating composition green sheet is thermocompression-bonded thereon to form the top cover 5, and a laminate is produced ( Step 28).

The laminate thus manufactured is heated and heated.
After pressurizing and crimping (step 30), 7.1 × 6.3
It was cut into mm dimensions (step 40). Then, 300
After degreased at ℃ (Step 50), sintering was performed at 1100 ° C to produce a varistor element (Step 60). further,
Dip externally applied paste on both ends of this varistor element,
An external electrode was formed by heat treatment at 850 ° C. (Step 7)
0). As a result, 18 having a size of 5.7 × 5.0 mm 18
A V-rated laminated varistor was obtained.

Among the above manufacturing steps, the step of manufacturing the laminate is a relatively simple step of repeating the thermocompression bonding of the varistor composition layer and the insulating composition layer and the printing of the internal electrodes 2. It is possible to efficiently and accurately form a bonding surface having an uneven shape.

Further, 50 laminated varistors according to the present invention were produced by the above-described series of steps, and 50 laminated varistors having no unevenness on the bonding surface 11 were produced as a conventional example. In this case, the laminated varistor of the conventional example was manufactured under exactly the same conditions as those of the process according to the present invention described above except for the shape of the bonding surface 11.

The following Table 1 shows that, for each of the 50 stacked varistors according to the present invention and the conventional stacked varistor, 50 were obtained at 121 ° C., 100% RH and 14 VDC.
It shows the defect occurrence rate when a voltage characteristic test is performed for 0 hours. In this case, the one in which the varistor voltage changed by -10% or more was regarded as defective.

[0028]

[Table 1]

As is apparent from Table 1, in the conventional laminated varistor, 4% of defects occur after 200 hours, and 6% of defects occur after 300 hours. . On the other hand, in the multilayer varistor according to the present invention, no failure occurred even after 500 hours, and excellent voltage stability was exhibited. This is due to the uneven shape of the joint between the varistor composition layers 1a and 1b and the insulating composition layers 4a and 4b according to the present invention.
This shows that the jointability and reliability of this joint can be improved.

It should be noted that the present invention is not limited to the above-described embodiments and examples, and specific irregularities in the joint surface between the end of the varistor composition material portion and the insulating composition material portion between the internal electrodes. Can be appropriately selected. For example, uneven shapes as shown in FIGS. 7A to 7C can be considered. Here, when considering from the varistor ceramic 1 side, FIG.
(A) is a concavo-convex shape in which one concave portion is combined between two convex portions, and the shape of FIG. 7B is a concavo-convex shape in which one convex portion is combined between two concave portions. Shape. Further, the shape of FIG. 7C is a concavo-convex shape combining two convex portions and two concave portions. In any case, excellent functions and effects can be obtained in the same manner as in the above embodiments and examples.

In the above embodiment, the bonding surface 11
Although each of the concave portions or convex portions is formed by one material layer, it is also possible to form one concave portion or convex portion by a plurality of material layers. Further, in the above-described embodiment, the varistor composition layer and the insulating composition layer were formed by the sheet pressing method in order to form the uneven shape of the bonding surface 11, but they can be formed by the printing method. Also in this case, it is possible to efficiently and accurately form the bonding surface having the uneven shape. Further, each material layer can be formed by a method other than the sheet pressing method and the printing method.

On the other hand, in the present invention, the dimensions of each part such as the unevenness of the uneven shape and the thickness of each material layer, the number of laminated internal electrodes, and the like can be freely selected. Alternatively, the type and composition of specific materials constituting the internal electrode and the external electrode can be freely selected.
Further, the present invention is applicable to a laminated varistor of various ratings.

[0033]

As described above, according to the present invention, the material in the thickness direction of the joining surface between the end portion of the varistor composition material portion and the insulating composition material portion is made uneven. In addition to providing a mechanical engagement force due to the uneven shape of the joining portion, the surface path between the varistor composition material portion and the insulating composition material portion in the thickness direction between the internal electrodes becomes longer, so that the varistor composition material and the insulation composition It is possible to provide a laminated voltage non-linear resistor excellent in joining property and reliability in a joining portion of materials.

Further, a relatively simple process of forming a composition material layer by forming two or more varistor composition material layers having different dimensions and two or more insulating composition material layers joined to each of them is also provided. By simply repeating, it is possible to provide an excellent manufacturing method capable of efficiently manufacturing a laminated voltage nonlinear resistor having a concave-convex bonding surface without requiring a complicated process.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view schematically showing one embodiment of a laminated varistor according to the present invention, and FIG. 1B is an enlarged cross-sectional view showing a portion X in FIG.

FIG. 2 is a sectional view taken along the arrow Y of FIG.

FIG. 3 is a flowchart showing an example of a manufacturing process of the multilayer varistor according to the present invention.

FIG. 4 is a flowchart showing an example of a laminate manufacturing step in FIG. 3;

FIG. 5 is a side view schematically showing a plurality of states of the laminated body manufacturing process of FIG.

FIG. 6 is a plan view schematically showing a part of FIG. 5;

FIG. 7 is a cross-sectional view schematically showing three different embodiments of a laminated varistor according to the present invention.

FIG. 8A is a cross-sectional view schematically showing an example of a conventional laminated varistor, and FIG. 8B is an enlarged cross-sectional view showing a portion X in FIG.

FIG. 9 is a sectional view taken along the arrow Y in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Varistor ceramic 1a, 1b ... Varistor composition layer 2 ... Internal electrode 3 ... External electrode 4 ... Insulating ceramic 4a, 4b ... Insulation composition layer 5 ... Top cover 6 ... Bottom cover 7, 8 ... Side margin part 9, 10 ... End Margin part 11: Joint surface

Claims (3)

[Claims] A varistor composition material portion formed by sintering a varistor composition material, an insulating composition material portion covering the surface of the varistor composition material portion, and an end portion inside the varistor composition material portion. In a laminated voltage non-linear resistor composed of a plurality of internal electrodes stacked so as to be staggered so as to be alternately exposed from the ends of the varistor composition material portion and the insulating composition material portion, between two adjacent internal electrodes, The shape in the thickness direction of the joining surface between the end portion of the varistor composition material portion and the insulating composition material portion is an uneven shape including at least one element selected from a concave portion and a convex portion. Stacked voltage non-linear resistor. 2. A varistor composition material portion made of a varistor composition material and an insulation composition material portion made of an insulation composition material coated on the surface of the varistor composition material portion, and the ends of the varistor composition material portion are formed. After forming an element by forming a plurality of internal electrodes stacked staggered so as to be alternately exposed from the end of the portion and the insulating composition material portion,
In a method of manufacturing a laminated voltage nonlinear resistor by sintering the element and providing an external electrode, at the time of manufacturing the element, two or more varistors having different dimensions are provided between two adjacent internal electrodes. Composition material layers and bonding to each of them 2
By forming at least two insulating composition material layers, the shape in the thickness direction of the joining surface between the end of the varistor composition material portion and the insulating composition material portion between two adjacent internal electrodes,
Manufacturing a varistor composition material portion and an insulation composition material portion in a concavo-convex shape including at least one element selected from a concave portion and a convex portion. Method. 3. The laminated voltage nonlinear resistor according to claim 2, wherein the varistor composition material layer and the insulating composition material layer are formed by a method selected from a sheet pressing method and a printing method. Production method.