The evaluation of mixed-mode interfacial fracture toughness is of great importance for the integrity of electronic devices because interfacial cracks are subjected to mixed-mode loading by vapor pressure, thermal stress and other factors. A lot of work has been done to clarify the unusual characteristics of the fracture of bimaterial interfaces. Since interfacial fracture toughness (G C ) greatly depends on phase angle (ψ), most work has focused on the determination of G C -ψ curves using various specimens. However, this requires a lot of time, expense and effort. In this work, the G C -ψ curves of oxidized Cu-based leadframe/EMC (epoxy molding compound) interfaces were determined by measuring interfacial fracture toughness under mode-I, mode-II and mixed-mode loading conditions using sandwiched-double-cantilever-beam (SDCB) specimens, Arcan specimens and sandwiched-Brazilian-nut (SBN) specimens, respectively. The experimental results showed that the measured G C -ψ curves obeyed the G C -ψ expression proposed by Ahmad first developed by Evans and Hutchinson based on the micromechanics modeling of mixed-mode fracture. Comparing data in the literature, the G C -ψ expression proposed by Ahmad was confirmed to be valid, and a method of predicting G C -ψ curves without much experiment was proposed.