Over-current protection device

An over-current protection device, comprising:

• an electrode layer having a top metal layer and a bottom metal layer;
• and
• in a heat-sensitive layer contacting the top metal layer and the bottom metal layer, and being laminated therebetween, wherein the heat-sensitive layer exhibits a positive temperature coefficient (PTC) characteristic and comprises:
• a polymer matrix comprising a fluoropolymer, wherein the fluoropolymer has a plurality of spherulites, and a fractal dimension of each spherulite is equal to or less than 12;
• and
• a conductive filler dispersed in the polymer matrix, thereby forming an electrically conductive path in the heat-sensitive layer.