Patent ID: 7352272

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 matrix at least comprising a first crystalline polymer and a second crystalline polymer, with the melting temperature of the second crystalline polymer being higher than that of the first crystalline polymer by at least 50° C.; and (2) a conductive filler distributed in the polymer matrix with the volumetric resistance thereof being less than 500 μΩ-cm; wherein the PTC material layer has a volumetric resistivity less than 0.1Ω-cm, and the trip temperature at which a resistance of the PTC material layer increases to 1000 times initial resistance thereof subtracting a melting temperature of the first crystalline polymer is less than 15° C.