Pretreatment of Copper and Copper Alloys Substrate for Electroplating of Thin Permalloy Film

Various pretreatments of copper and copper alloys (beryllium copper and phosphor bronze) were examined for electroplating of thin permalloy film. Attention was paid to internal stress relieving, surface leveling and adhesion of permalloy film. Heat treatment of the substrate was effective for homogenizing and adhesion of electrodeposited film. The higher temperature for treatment was required for the beryllium copper alloy than for copper or phosphor bronze. Electropolishing was the best method for surface leveling of the substrate. However, the surface of copper alloys was supposed to be covered with an oxide film after the electropolishing from the fact that it took a long time to reach a stable immersion potential. Therefore, the cyanide bath of high pH had to be used for the flush copper plating after the electropolishing. It was found that copper alloys can be used for the substrate of magnetic wires by the application of copper flush plating. The copper flush plating was also very effective for homogenizing of the permalloy film.