Surface finishes of rolled copper foil for flexible printed circuit board

An oxidation treatment was conducted in a rolled copper foil of 9 μm in the thickness by a method of the electroless plating in the alkali liquid having sodium as the main element. The morphology of the oxidized surface was varied from patch type to grass type with increasing of oxidation time. According to the results of energy-dispersive X-ray spectrometry and X-ray photoemission spectroscopy analysis, its chemical composition was changed from Cu2O to CuO. The peel strength was steeply increased by the formation of oxides and was closely related to morphology and growing direction of oxide.