Ferro Corporation

Brian T Pointer

Vernon E Stygar

Jesus E Osuna

John J Ekis

The present invention relates to compositions for use in forming resettable electronic circuit protection devices or fuses, methods of forming resettable fuses using the compositions, and resettable fuses formed from the compositions. Resettable fuse compositions according to the present invention include a mixture of the reaction product of polyethylene glycol and a diepoxide having a molecular weight of at least 18,000, solvent, conductive particles, and optional solvent volatility adjusters. In a preferred embodiment, resettable fuses according to the present invention are formed by screen printing the compositions directly onto printed electric circuits to form fuses. During current overload conditions, the temperature of the resettable fuse material rapidly increases due to resistive heating generated by excessive current flow through the conductive particle chains or pathways. In such current overload conditions, resettable fuses according to the present invention rapidly convert from a low resistance solid state to a high resistance liquidus state wherein the chains of conductive particles become highly separated thus causing the flow of electric current through the fuse to become completely cut off. After the overload condition has been cleared, resettable fuses according to the present invention self cool, re-solidify, and return to their prior low resistance solid state without exhibiting any change in resistance or switching temperature due to changes in the degree of crystallinity of the heat cured reaction product.

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Brightlingsea, United Kingdom

Brian T Pointer