Ecco Limited

Littlefuse, Inc.

Littelfuse, Inc.

Stephen P Cowman

Derek A Nicker

John M Shreeve

Anthony L Oliver

Alan J Ratcliffe

A process for forming a thixotropic ink for use in manufacturing the ceramic of a zinc oxide varistor where the ceramic includes zinc, oxygen and a plurality of additive elements. The process includes the steps of calcining a mixture of powders of zinc oxide and the additive elements to form a calcined product having a particle size larger than the particle size of the zinc ozide powders, mixing said calcined product with an organic liquid, mechanically working the mixture to produce a calcined particulate material in the organic liquid having a particle size less than the particle size of said calcined product, adding an organic binder to the mixture and mixing the composition to produce said ink.

Process for forming varistor ink composition

Varistor ink formulations

Apparatus for producing multilayer varistors using ceramic ink and electrode ink consists of a succession of stations, in which alternating layers of ceramic ink and electrode ink are laid down on a substrate. The stations may be printing stations in which either a ceramic ink screen or an electrode ink screen is used to apply the appropriate ink to the substrate. In a first printing step, a layer of ceramic ink is laid down, within a region determined by a mask area of a ceramic ink screen. In the following step, electrode ink is laid down in regions determined by mask areas of the electrode ink screen. The apparatus includes transfer mechanisms for advancing substrates from station to station for successive printing operations, and control mechanisms for regulating and coordinating the successive printing operations and substrate travel.

Varistor manufacturing method

A composition material for use in manufacturing a varistor consists of the following constituents:

Multilayer varistor with pin receiving apertures

A method for use in making multilayered varistors including the steps of forming a plurality of interleaved layers of ceramic material and conductive material, confining the conductive material to spaced areas arranged in rows and columns, displacing the spaced areas of adjacent layers of conductive material from each other, and cutting perpendicularly through the layers. The layers are formed by screen printing.

Method of manufacturing varistor precursors

In a varistor of generally cylindrical configuration, which may serve as a connector pin, layers of ceramic material are interleaved between layers of electrode material, each ceramic layer being sandwiched between two electrode material layers. Each layer of electrode material is generally planar and extends transversely to the axis of the cylindrical varistor, in the form of an annular ring. Each alternate annular ring is of different inner and outer diameter. The outer periphery of each larger diameter annular ring is in electrical contact with an outer terminal cap of the varistor, while the inner periphery of each smaller diameter annular electrode layer is in electrical contact with an inner terminal cap extending along a central bore passing axially through the varistor pin. Each ceramic layer may have a thickness dimension less than 30.0 microns, or may be formed by deposition of a powder suspension and subsequent heat treatment to provide a dense continuum of ceramic material of low porosity.

Varistor of generally cylindrical configuration

A multilayer varistor has alternating layers of ceramic material and electrode material. The layers are interleaved with each ceramic material layer sandwiched between two electrode material layers. One end portion of each electrode layer extends to an end face of the varistor where it is in electrical contact with an end terminal of the varistor. The other end of the layer is spaced by ceramic material from the opposite end terminal of the varistor. Thus alternate electrode material layers are in electrical communication with one and the other end terminal of the varistor unit. The ceramic material layer between each two electrode layers preferably has a thickness dimension less than 30.0 microns, or it may be formed by deposition of a powder suspension and subsequent heat treatment to provide a dense continuum of ceramic material of low porosity.

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Dundalk, Ireland

Stephen P Cowman