Overcurrent protection device

Abstract

An overcurrent protection device and a method for the production thereof is provided wherein a fusible link is bonded across a pair of electrodes. A composite layer envelops the fusible link and is formed from a gelatinous composition. The composite layer and the fusible link are further encased within a molded housing. The gelatinous composition includes a nonconductive inorganic powder and a synthetic resin. The inorganic powder has a melting temperature below a fusion temperature of the fusible link. In an embodiment, the inorganic powder includes lead glass powder and alumina powder, and the synthetic resin is a low viscosity silicone resin. The inorganic powder is mixed with the silicone resin in a three to one ratio. Heat treatment dries the composite layer. The composite layer includes air pockets between particles of the inorganic powder elastically bound together by the synthetic resin. The air pockets support fusion combustion of the fusible link, contribute to the elasticity of the composite layer, and provide spaces for melted portions of said fusible link to flow into. The elasticity of the composite layer absorbs stresses thereby protecting the fusible link from damage. Melting of the fusible link concurrently melts the inorganic powder which flows into a gap created in the fusible link. The melted inorganic powder hardens forming an electrically insulating barrier between remaining portions of the fusible link. An alternate embodiment of the present invention interposes a flexible elastic film between the gelatinous composition and the housing which provides further stress absorption capacity.