The adhesion strength of polyamideimide (PAI)/copper joints was investigated as a function of the curing temperature and time. The adhesion strength decreased as the thermal stress increased with the increase of both curing temperature and time. The effects of copper oxide formed by thermal treatment and alkaline treatment on the adhesion strength of PAI/copper joints were examined. The adhesion strength decreased with thermally oxidized copper and increased with alkali-oxidized copper. The locus of failure of PAI/copper joints was also studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The locus of failure appears to be partially cohesive in both PAI and copper oxide.