Patent ID: 7286038

Claim:
An over-current protection device, comprising: two metal foils; and a positive temperature coefficient (PTC) material layer laminated between the two metal foils, comprising (1) a polymer substrate being 35-60% by volume of the PTC material layer and comprising a fluorine-containing crystalline polymer with a melting point higher than 150° C.; and (2) a conductive ceramic filler distributed in the polymer substrate and being 40-65% by volume of the PTC material layer and having a volume resistivity less than 500 μΩ-cm; wherein the PTC material layer has a volume resistivity less than 0.1 Ω-cm, and the ratio of a hold current of the PTC material layer at 25° C. to the area of the PTC material layer is between 0.05 and 0.2 A/mm 2 .