JPH0316245Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Technical Field of the Invention] The present invention relates to a laminated ceramic varistor with an improved electrode structure. [Technical background of the invention and its problems] Multilayer ceramic varistors are generally small and have excellent surge resistance, and demand for them is likely to increase in the future. Conventionally, a commonly used multilayer ceramic varistor has a large number of internal electrodes 22 formed in layers between ceramic semiconductors 21, as shown in FIG. External electrode 2
3 and 24 are electrically connected in parallel. As a means for forming the laminated ceramic varistor constructed in this manner, as shown in FIG. Using a plurality of ceramic semiconductors 21, the internal electrodes 22 are formed by printing and coating an electrode paste containing an electrode material such as Au, Pt, Ag, or Pd, leaving a margin part 26 on one side of the ceramic semiconductor 25,
A plurality of layers of the ceramic semiconductor 21 are stacked and pressure bonded so that the positions of the margin parts 26 are alternately on opposite sides, and then sintered and integrated. Then, for example, Ag or Ag-Pd paste is applied to both end faces and baked to form an external structure. It is formed by forming electrodes 23 and 24. However, in the laminated ceramic varistor configured as described above, alignment of the internal electrodes 22 is an important point, but misalignment of the tips of the internal electrodes 22 between layers may occur, for example, due to misalignment of the printing of the internal electrodes 22. In this case, the effective inter-electrode area becomes smaller and the desired surge resistance or energy resistance cannot be obtained, and the internal electrodes 22 that should be exposed on both end faces forming the external electrodes 23 and 24 during the sintering process are If the internal electrodes 22 and external electrodes 23 and 24 are not exposed sufficiently, the internal electrodes 22 and external electrodes 23 and 24 will be in a non-contact state, so the internal electrodes 22 must be exposed by sand blasting or grinding after sintering, which requires a lot of man-hours. After forming ceramic green sheets for varistors, batch processing is required, resulting in poor workability.Furthermore, a sufficient margin 26 must be ensured to prevent shortening between the electrodes due to the external electrodes 23 and 24. This has become an impediment to downsizing. [Purpose of the invention] The present invention has been made in view of the above points, and aims to provide a highly reliable multilayer ceramic varistor with a novel structure that is easy to work with and can contribute to miniaturization or thinning. This is the purpose. [Summary of the invention] The laminated ceramic varistor of the invention uses a ceramic varistor sheet body in which electrode parts are formed on both sides, leaving arbitrary parts of both ends of the longitudinal direction as green sheet parts, and a plurality of electrode parts are formed in the electrode parts. The ceramic varistor sheet body is provided with a bent portion, and the ceramic varistor sheet body is folded into a zigzag so that the raw sheet surface becomes the outer surface, and the ceramic varistor sheet body is stacked and integrated, and the outer surface of the bent portion is used as an external electrode. [Embodiment of the invention] An embodiment of the invention will be described below with reference to the drawings. That is, as shown in Fig. 2, a ceramic material containing zinc oxide, barium titanate, strontium titanate, silicon carbide, iron oxide, etc. as its main components, with several other metal oxides added and mixed, is used by extrusion method or Ceramic green sheet for baristas formed by doctor blade method etc. 1
Both ends of both sides are left as green sheet parts 2 and 3, and an electrode paste made of Au, Pt, Cu, Ag, Pd, Ni, etc. is printed on both sides, or the electrode material is vapor-deposited to form an electrode part 4. Then, a ceramic varistor sheet body 5 is obtained. Therefore, as shown in FIG. 3, using the ceramic varistor sheet body 5,
The electrode portion 4 is provided with a plurality of bends 6 and folded in a spiral manner so that the green sheet portions 2 and 3 are the outer surfaces, and then sintered to integrate the folded sheets as shown in FIG. The electrode portion 4 located on the outer surface of the curved portion 6 is used as an external electrode 7, and an external terminal (not shown) is attached to the external electrode 7 as necessary, and an exterior (not shown) is provided as necessary. It is what it is. The laminated ceramic varistor constructed as described above has a structure in which the electrode part 4 located inside by the zigzag fold serves as the internal electrode as it is, so there is no need for alignment of the internal electrode, which is an important point, and it is different from the conventional method. The cause of characteristic deterioration due to the positional deviation of the internal electrodes that has occurred is completely eliminated, and the conventionally required margin section 26 shown in FIG. 8 is no longer necessary, which contributes to miniaturization and thinning. In addition, since the structure is such that the electrode part 4 located on the outer surface of the bent part 6 provided by zigzag folding becomes the external electrode 7 as it is, there is no need to form a special external electrode, which not only simplifies the process but also reduces the risk of the conventional method. It is possible to completely ignore the problem of characteristic deterioration due to the non-contact state between the internal electrode and the external electrode, which had the same characteristics. Furthermore, since the ceramic varistor sheet body 5 obtained by continuously forming the electrode portions 4 on both sides of the ceramic green sheet 1 for varistor is simply folded in the required size and number of times,
Compared to conventional batch processing, this method has the advantage of better workability, easier automation, and greatly contributing to cost reduction. Next, the actual state of miniaturization or thinning according to the present invention will be described based on specific examples shown below. In other words, the main ingredient is zinc oxide, and the thickness of the molded product using the doctor blade method is 50 μm after baking.
Pt is used as the electrode material using a ceramic green sheet for varistors with a voltage of 10V and surge resistance of 50A to 100A.
The present invention (A) set at 200A and 400A, respectively,
As a result of examining the volumes of each of the conventional reference examples (B) shown in FIG. 7, the results are as shown in the table.

[Table] As is clear from the table above, there are differences depending on the surge withstand capacity, but the same surge withstand capacity of this invention
(A) can be made approximately 15 to 20% smaller in volume than the conventional reference example (B), demonstrating an effect that can greatly meet the market demand for smaller and thinner products. In the above embodiment, the case where the unit element is made singly was explained as an example, but as shown in FIG.
Using a large ceramic varistor sheet body 11 with electrode parts 10 formed on both sides of the ceramic varistor sheet body 11, the raw sheet parts 8 and 9 are folded in a zigzag manner, and then crimped and sintered. By cutting the material in a straight line, a large amount of elements can be obtained at one time, which greatly contributes to work efficiency. Further, in the above embodiment, the structure in which the electrode portions are provided up to the full extent of both side surfaces has been exemplified and explained, but if necessary, as shown in FIG. , 13, and a large ceramic varistor sheet body 16 in which a plurality of electrode portions 14 of the width necessary for forming the element are formed with margin portions 15 at arbitrary intervals, and is folded and crimped using a large ceramic varistor sheet body 16.
By sintering and cutting in the direction of the arrow at the center of the margin 15, a structure with a certain margin at both ends can be obtained. Furthermore, in the above embodiment, the thickness of the electrode part on the outer surface of the bent part which becomes the external electrode is the same as the thickness of the electrode part which becomes the internal electrode. In this case, the thickness of the electrode part on the outer surface of the bent part 18 of the electrode part 17 can be reduced by making the mesh rougher in that part, or by printing twice in that part, or in the case of vapor deposition, by depositing a little more on that part. Using a thick ceramic varistor sheet 19 is effective in increasing the strength of the external electrode. [Effects of the Invention] According to the present invention, it is possible to obtain a laminated ceramic varistor that is highly reliable, inexpensive, and has high industrial value, as well as contributing to miniaturization or thinning with good workability.

[Brief explanation of the drawing]

1 to 3 relate to one embodiment of the present invention, FIG. 1 is a perspective view showing a completed laminated ceramic varistor, and FIG. 2 is a partially broken ceramic varistor as shown in FIG. 1. A perspective view showing a sheet body, FIG. 3 is an explanatory diagram of a sheet body in the middle of manufacturing, FIGS. 4 and 5 are explanatory diagrams of other embodiments of the present invention in the middle of manufacturing, and FIG. 6 is an explanatory diagram of another embodiment of the present invention. FIG. 7 and FIG. 8 are explanatory diagrams showing the process of manufacturing using a ceramic varistor sheet body according to the embodiment, and FIG. 7 is a perspective view showing a completed laminated ceramic varistor, and FIG. 8 is a conventional reference example. 7 is an explanatory diagram showing the state in the middle of manufacturing. 1... Ceramic green sheet for barista,
2, 3, 8, 9, 12, 13...raw sheet part,
4, 10, 14, 17... Electrode, 5, 11, 1
6,19...ceramic varistor sheet body, 6,
18...Bending part, 7...External electrode, 15...Margin part.

Claims (1)

[Claims for Utility Model Registration] (1) Using a ceramic varistor sheet body in which electrode parts are formed on both sides while leaving arbitrary parts on both ends of the longitudinal direction as green sheet parts, the electrode parts have a plurality of folds. A laminated ceramic varistor characterized in that the ceramic varistor sheet body is folded in a zigzag manner and stacked and integrated so that the raw sheet portion becomes the outer surface. (2) The laminated ceramic varistor according to claim 1, which is characterized in that a blank space is provided at both ends in the width direction of the ceramic varistor sheet body. (3) The laminated ceramic varistor according to claim 1 or 2, characterized in that the outer surface of the bent portion of the electrode portion serves as an external electrode. (4) The laminated ceramic varistor according to any one of claims 1 to 3, which is characterized in that only the portion of the electrode portion located on the outer surface of the bent portion is thickened.