Over-current protection device

An over-current protection device, comprising:

• a heat-sensitive layer having a top surface and a bottom surface;
• and
• an electrode layer comprising a top metal layer and a bottom metal layer, wherein the top metal layer and the bottom metal layer are attached to the top surface and the bottom surface of the heat-sensitive layer, respectively;
• wherein the heat-sensitive layer exhibits a positive temperature coefficient (PTC) characteristic and comprises:
• a polymer matrix comprising:
• a polyolefin-based homopolymer having a first coefficient of thermal expansion (CTE);
• and
• a polyolefin-based copolymer having a second CTE, wherein the second CTE is lower than the first CTE, and the polyolefin-based homopolymer and the polyolefin-based copolymer together form an interpenetrating polymer network (IPN), wherein the polyolefin-based copolymer is ethylene-butene copolymer, wherein the total volume of the heat-sensitive layer is calculated as 100%, and the polymer matrix accounts for 47% to 52%;
• and
• a conductive filler dispersed in the polymer matrix, thereby forming an electrically conductive path in the heat-sensitive layer.