Patent ID: 7203049

Claim:
An over-current protection device, comprising: a current-sensing element exhibiting positive temperature coefficient behavior, the current-sensing element including an upper electrode foil, a bottom electrode foil and a conductive material; an upper metallic conductive sheet comprising: a first upper metallic conductive sheet; and a second upper metallic conductive sheet located between and attached physically to the first upper metallic conductive sheet and the upper electrode foil wherein the thermal expansion coefficient of the first upper metallic conductive sheet is smaller than that of the second upper metallic conductive sheet; and a bottom metallic conductive sheet, comprising: a first bottom metallic conductive sheet; and a second bottom metallic conductive sheet located between and attached to the first bottom metallic conductive sheet and the bottom electrode foil, wherein the thermal expansion coefficient of the first bottom metallic conductive sheet is smaller than that of the second bottom metallic conductive sheet; whereby unbalanced thermal expansion coefficients of the upper metallic conductive sheet and the bottom metallic conductive sheet generate a torque to deform outwardly during a burning of the over-current protection device, and at least one crack surface is generated in the current-sensing element.