Effect of Thermo-Set Process on MP35N Cable

MP35 cables such as 1x7 and 1x19 were used in medical devices as leads conductor.  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 was set at temperature below the annealing temperature and higher than 500ºC 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 lost ductility significantly.   The experimental data demonstrated that 1x7 cable has a low damage tolerance which may causes the leads fail prematurely if not used properly.  To safely use the leads made with 1x7 or 1x19 cables, the bending radius of the lead has to be large enough to prevent the damage.