The micro-wedge scratch technique was applied to characterize interfacial properties of copper fine lines on PMDA-ODA polyimide. A 20 pm wide, 0.1 μm radius wedge-shapeddiamond tip was used to mechanically debond Cu fine lines from polyimide substrate. Copper fine lines varies from 0.2 to 0.4 μm thick, and from 1.μm to 100 μm wide. Both cohesive and adhesive delaminations were obtained. Loaddisplacement curves were recorded and the scratch morphologies were observed by SEM. From a first order calculation, the fracture toughness of the polyimide and interfacial strength of Cu-PI were obtained.