US 6,183,685 B2Granted

Varistor manufacturing method

AssigneeLittlefuse, Inc.

InventorsStephen P. Cowman, Alan J. Ratcliffe, Derek A. Nicker, John M. Shreeve, Anthony L. Oliver

Life of this patent

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Abstract

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.

Claims33

Dependent claims

A process for forming a plurality of varistor precursors, said varistor precursors comprising alternating layers of a varistor ceramic precursor material and electrode precursor material, said varistor ceramic precursor material and said electrode precursor material being capable of forming ceramic layers and electrode layers, respectively, of a zinc oxide varistor when said varistor precursors are subjected to sintering conditions, said process comprising

(a) forming a first ceramic layer of said varistor ceramic precursor material,
(b) applying a first electrode layer on said first ceramic layer by coating said first ceramic layer with electrode precursor material, said first electrode layer comprising a plurality of discrete, spaced areas composed of said electrode precursor material, said plurality of spaced areas being arranged in a first pattern,
(c) forming a second ceramic layer by screen printing said first electrode layer with said varistor ceramic precursor material,
(d) applying a second electrode layer on said second ceramic layer by coating said second ceramic layer with electrode precursor material, said second electrode layer comprising a plurality of discrete spaced areas composed of said electrode precursor material, the plurality of spaced areas in said second electrode layer being arranged in a second pattern different from said first pattern,
(e) forming a third ceramic layer on said second electrode layer by screen printing to form a composite, and
(f) dividing the composite of step (e) into said plurality of varistor precursors.

3 more elements

Dependencies are inferred from the claim text.

Facts

Application: 08/468,247Filed 6 Jun 1995 · continuation
Priority: 26 Jun 1990
Granted: 6 Feb 2001
Term ends: Not estimatedThe source records don’t support an estimate.

Classification4 codes

H01C 7/1006
Voltage responsive, i.e. varistors: thick film varistors
H01C 7/18
Non-adjustable resistors formed as one or more layers or coatings; Non-adjustable resistors made from powdered conducting material or powdered…:…
H01C 17/065
Adapted for coating resistive material on a base: by thick film techniques, e.g. serigraphy
H01C
Resistors

Family

Application07/543,529Parent of this division · filed 26 Jun 1990
Application07/935,640Parent of this continuation · filed 25 Aug 1992
Application08/079,159Parent of this continuation · filed 18 Jun 1993
US 5,837,178 AParent of this continuation
Application07/935,640Parent of this division
US 6,183,685 B2This patent

From the US filing history. Foreign family members aren’t listed.