Over-current protection device

An over-current protection device, comprising:

• two metal foils;
• and
• a PTC material layer laminated between the two metal foils and having a volumetric resistivity ranging from 0.07 to 0.45 Ω-cm, the PTC material layer comprising:
• at least one crystalline polymer;
• a first conductive filler being a carbon black powder;
• a second conductive filler comprising at least one of metal powder, conductive ceramic powder or mixture thereof, the second conductive filler having a particle size ranging from 0.1 to 50 μm, and a volumetric resistivity less than 0.1 Ω-cm;
• wherein the first and second conductive fillers are dispersed in the crystalline polymer, and a weight ratio of the second conductive filler divided by the first conductive filler is less than 4;
• wherein resistance jump R300/Ri of the over-current protection device is in the range of 1.5 to 5;
• Ri is an initial resistance and R300 is a resistance of the over-current protection device after tripping 300 times.