Dynamic secondary ion mass spectroscopy (D-SIMS) was applied to analyze the copper (Cu) migration behavior at the interface between polyimide (PI) and Cu. The (PI/Cu) bilayer specimen was prepared by curing polyamic acid (PAA) coated on the Cu substrate. It was found that the Cu deeply migrates into the PI phase across its interface. On the contrary, the Cu migration was not detected at all when the (PI/Cu) bilayer was built up by the vapor deposition of Cu onto the PI film. These results clearly indicate that the Cu migration behavior is strongly dependent on how the bilayer is prepared.