An oxidation study of Cu leadframes

The oxidation of Cu leadframes was studied at 175 and 200 degrees C, for bake times of 2, 5, 10, 20, 30, 50, 100 and 200 minutes, and 15 and 99 hours. Depending on the temperature and the bake time, the leadframe displayed the following range of colors: reddish, purplish, silvery, golden, greenish, brown, black or a blend of these colors. Associated changes in the thickness of the copper oxide was measured by sequential electrochemical reduction analysis (SERA) and secondary ion mass spectroscopy (SIMS), the composition of the oxide layer was evaluated by x-ray photoelectron spectroscopy (XPS) analysis, and the surface roughness was measured by a scanning probe microscope (SPM). The mechanical properties of the oxide layer were evaluated by the stud pull test and Vickers micro-indentation.