Adhesion of flexible copper clad laminates (FCCL) on two different types of polyimide (PI), sputtering raw polyimide (SRPI) and casting raw polyimide (CRPI), were studied. Chromium (Cr), strongly reacts with dangling O bonds, was used as tie-coating layer in order to improve low adhesion between copper (Cu) and polyimide (PI). Polyimide surfaces were pretreated with gas plasma that was generated with a mixture of argon and oxygen before sputtering process. Adhesion measurement was performed on these samples according to IPC specification. The results show that the peel strength of the FCCL on SRPI was higher than on CRPI. This is considered to be due to the formation of Cu-Cr-O solid solution at the metal- PI interface.