Effect of Stress Relief Process on Mechanical Performance of MP35N Cable as Lead Conductor in Medical Device

Abstract

MP35N cables such as 1×7 and 1×19 are widely used in medical devices as leads conductors. The difference between the MP35N cable and MP35N wire is that a thermo-set process is applied to stress relive MP35N cable at high temperature to prevent the unwinding of the cable structure. The process of thermo-set is set at a temperature below the annealing temperature and higher than 500°C to have an effective stress relief to set the cable structure. However, there is a precipitation transformation occurred at stress relief temperature which has a strong effect on the wire properties. In this work, it was observed that the high temperature stress relief process makes the cable to lose ductility significantly. To safely use the leads made with 1×7 or 1×19 cables, the bending radius of the lead has to be large enough to prevent the damage.