A circuit protection device includes a positive temperature coefficient (PTC) component, an insulating unit, and a device electrode unit. The PTC component includes a PTC layer, a first PTC electrode, and a second PTC electrode. The PTC layer has two side walls that are opposite to each other. The insulating unit is disposed on the PTC component. The device electrode unit is formed on the insulating unit and includes a first device electrode and a second device electrode. The first device electrode is electrically connected to the first PTC electrode and is spaced apart from one of the side walls of the PTC layer. The second device electrode is electrically connected to the second PTC electrode.

An over-current protection device includes a heat-sensitive layer and an electrode layer. The electrode layer includes a top metal layer and a bottom metal layer, and the heat-sensitive layer attached therebetween. The heat-sensitive layer exhibits a positive temperature coefficient (PTC) characteristic and includes a polymer matrix and a conductive filler. The polymer matrix includes a polyolefin-based homopolymer and a polyolefin-based copolymer. The polyolefin-based homopolymer has a first coefficient of thermal expansion (CTE), and the polyolefin-based copolymer has a second CTE lower than the first CTE. The polyolefin-based homopolymer and the polyolefin-based copolymer together form an interpenetrating polymer network (IPN).

A surface-mounted polymer PTC overcurrent protection element having a small package size, comprising a PTC chip, an insulating layer (30), end electrodes (41, 42), and at least one conductive member (60). A dividing gap is designed on a first conductive electrode (21) to form first and second conductive areas (211, 212); the conductive member (60) is arranged at the edge or at least a corner of the first conductive area (211) side of the PTC chip, is used for conducting the first conductive area (211) and a second conductive electrode (22) on the PTC chip, and is not in contact with the end electrodes (41, 42); the main portion comprised in the dividing gap (70) of the first conductive electrode (21) is parallel to the longitudinal direction of the first end electrode (41) and the second end electrode (42).