Oxidation of Lead Frame Copper Alloys with Different Compositions and Its Effect on Oxide Film Adhesion

Oxidation of four typical lead frame copper alloys was investigated. The oxidation rate and adhesion strength of oxide films to copper alloy substrates were studied by measuring the thickness and carrying out peel tests. The results show that, although copper alloys C5191 and C7025 have thinner oxide films, a lower adhesion strength and a higher proportion of CuO were obtained than in the other copper alloys EFTEC64T and C194. The adhesion strength is mainly influenced by the structure of the oxide film of the copper alloys, especially the CuO/Cu₂O ratio in the film. The highest adhesion strength is obtained for the copper oxide film with a basic structure of CuO/Cu₂O/Cu and a CuO/Cu₂O ratio of about 0.1. The segregation of additional elements in the copper alloy plays an important role in the oxide film structure.