Patent ID: 6965293

Claim:
An electrical device including a PTC (Positive Temperature Coefficient) conductive polymer sheet, and first and second electrodes physically contacted with opposite surfaces of the conductive polymer sheet, wherein the first and second electrodes have a plurality of protrusions protruded from surfaces thereof, respectively, wherein the protrusions have an surface roughness (Rz) of 1 to 20 μm and an average width ({overscore (Rw)}) which is 0.5 to 2 times of the surface roughness (Rz), and an average gap ({overscore (Rg)}) between adjacent protrusions is 0.5 to 2 times of the surface roughness (Rz), wherein the first and second electrodes respectively include a base layer made of a first metal having a microrough surface, and a surface layer made of a second metal and plated on the base layer with a uniform thickness, wherein the second metal has relatively more excellent chemical binding force to the conductive polymer than the first metal, and wherein the conductive polymer sheet has a thickness which is more than 5 times of the surface roughness (Rz).