JPS6038245Y2 - ceramic barista - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ceramic varistor with an improved electrode configuration.

In general, ceramic varistors are made by molding and sintering ceramic powder as shown in Fig. 1.A varistor element body 1 is coated with a silver paste containing 50 to 8% silver powder, leaving the outer periphery on both sides of the varistor body 1, and then baking the electrodes. 2 and connect the terminals 3a, 3 to the electrode 2.
It is constructed by applying the exterior 4 after attaching b.

However, the silver constituting the electrode 2 is very expensive, resulting in an expensive ceramic varistor.

Therefore, it is conceivable to use a relatively inexpensive and non-solderable conductive material, such as a carbon-based material, on which silver paste is coated and baked to reduce the amount of expensive silver used, but the composition of each of the carbon and silver paste is Since the baking conditions are different, the adhesion between the two is very weak.
Furthermore, when the terminal is immersed in solder to attach the terminal to the electrode, the low temperature baked carbon part peels off, resulting in a loss of function as an electrode.

The present invention was developed in view of the above points, and the object is to provide an inexpensive varistor with features in the electrode structure that makes it possible to reduce the amount of silver used without deteriorating the varistor characteristics. It is.

An embodiment of the present invention will be described below with reference to the drawings.

That is, as shown in FIG. 2, a varistor element body 11 is made by molding a ceramic powder containing zinc oxide as a main component and mixing small amounts of several kinds of metal oxides into, for example, a disk shape and sintering it at a high temperature of 800 to 1500°C. ZnO on carbon leaving outer periphery on both front and back sides.

B2O3, V2O5, GeO3, SiO2, BaO9M
g09A1203. PbO, Li2O, NaF,
TiO2, Na2O.

K2O, P2O5, CaO9SiO2, As2O3,5
b203°SnO2, ZnO2, Na5NF6. AlF
3. CaF2. Cr2O3゜Cub, Fe2O3,N
A first electrode paste containing a mixture of several types of glass frits such as ip, MnO3, etc. is applied, and a glass frit having the same composition as the glass frit constituting the first electrode paste is coated on the first electrode paste with a silver powder content of 10 to 4%. The second mixture of
300-70 in a normal pressure oxidizing atmosphere after applying the electrode paste.
Baking is performed at 0°C to form a two-layer electrode structure of the carbon electrode layer 12 and the silver electrode layer 13, and then the terminal 1 is attached to the silver electrode layer 13.
4a and 14b are attached and covered with a synthetic resin or housed, and an outer device 5 is applied thereto.

According to the varistor constructed as described above, the first electrode paste and the second electrode paste constituting the carbon electrode layer 12 and the silver electrode layer 13 contain glass frit of the same composition, so that they are baked under the same conditions. Even so, the adhesion between the varistor element 11 and the first electrode paste and the second electrode paste is good, making it possible to completely integrate the carbon electrode layer 12 and the silver electrode layer 13. This has the advantage that the layer 12 does not peel off and the varistor characteristics do not deteriorate, making it possible to significantly reduce the amount of silver used.

In the above embodiments, the shape of the varistor element was explained as being plate-shaped, but it goes without saying that the present invention can be applied to column-shaped elements other than plate-shaped.

As described above, according to the present invention, ceramic powder containing zinc oxide as the main component and mixed with several kinds of metal oxides is molded into a plate or column shape and sintered, leaving outer peripheral edges on both the front and back sides of the varistor element. The electrode structure is a two-layer electrode structure consisting of a carbon electrode layer and a silver electrode layer, and a terminal is attached to the silver electrode layer constituting the two-layer electrode, which improves solderability and prevents electrode breakage. By significantly reducing the amount of unused material, it is possible to obtain a ceramic varistor that greatly contributes to cost reduction.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a conventional ceramic varistor, and FIG. 2 is a sectional view showing a ceramic varistor according to an embodiment of the present invention. 11... Varistor element, 12... Carbon electrode layer, 13... Silver electrode layer, 14a, 14
b...Terminal, 15...Exterior.

Claims (1)

[Scope of utility model registration request] A varistor element formed by molding and sintering ceramic powder containing zinc oxide as a main component and mixed with small amounts of several types of metal oxides, a carbon electrode layer with an outer periphery left on both sides of the element, and the carbon electrode. A silver electrode layer formed on the layer,
A ceramic varistor comprising a terminal attached to the silver electrode layer, wherein the carbon electrode and the silver electrode are made of a paste mixed with glass frit having the same composition.