A highly reliable plated wire: Study on corrosion of magnetic films

Corrosion of magnetic films greatly affects the reliability of plated-wire memories. In plated films, additives in plating baths are codeposited onto films and affect the electrochemical state of the films. In this connection, a study was undertaken on the effects of thiourea and saccharin on corrosion. From current-potential curves and environmental tests it was found that the film deposited in a thiourea bath was easier to corrode than the film obtained from a saccharin bath. To protect the film from corrosion, a coating of Ni-P was made on it. This Ni-P coating was effective as an anticorrosive layer, but not to the required extent. Again when the wire was coated with a polyparaxylylen polymer on top of the Ni-P layer, no corrosion was found to occur. Moreover, no failure bit occurred from among the 6 × 10⁴bits during the test of 30 cycles of MIL-STD-202D-106C.