Black-oxide and/or brown-oxide layers were formed on the surface of copper-base leadframe sheets in hot alkaline solutions, and then the oxide-coated leadframe sheets were molded with epoxy molding compound (EMC). The molded bodies were machined to form sandwiched-double-cantilever-beam (SDCB) specimens, and the adhesion strength between oxide-coated leadframes to EMC was measured in terms of critical energy-release rate (G(IC)) using SDCB specimens. Results revealed that untreated leadframe and Cu2O-coated leadframe showed almost no adhesion to EMC, however once a continuous CuO layer formed on the leadframe surface (brown oxide) or on the Cu2O layer (black oxide), G(IC) increased to around 80 J/m(2). A study of failure surfaces base on the scanning electron microscopy (SEM), glancing-angle X-ray diffractometry (XRD), Auger electron microscopy (AES), electron dispersive spectroscopy (EDS), and atomic force microscopy (AFM) analyses indicated that the failure path was closely related to the surface condition of leadframe prior to molding with EMC.