Patent ID: 8446245

Claim:
An over-current protection device, comprising: two metal foils; and a PTC material layer laminated between the two metal foils and having a volume resistivity between 0.07 Ω-cm and 0.32 Ω-cm, the PTC material layer comprising: at least one crystalline polymer; a conductive ceramic carbide filler dispersed in the crystalline polymer, wherein the conductive ceramic carbide filler has a particle size between 0.1 μm and 50 μm and a volume resistivity less than 0.1 Ω-cm; and a conductive carbon black filler dispersed in the crystalline polymer, wherein a weight ratio of the conductive carbon black filler to the conductive ceramic carbide filler is between 1:90 and 1:4; wherein a resistance ratio R 100 /Ri is between 3 and 20, where Ri is an initial resistance of the PTC material layer, and R 100 is the resistance of the PTC material layer after the PTC material layer is tripped 100 times.