Poly(biphenyl dianhydride-para-phenylene diamine) (BPDA-PDA, Upilex-S) polyimide (PI), was exposed to 185 and 254 nm UV radiation in the presence of oxygen at atmospheric pressure. SEM micrographs revealed only a small change in surface morphology following treatment. XPS showed an approximate doubling of the O/C ratio on the modified surfaces which appeared mostly as the carbonyl moiety. UV photo-oxidation degraded Upilex-S to produce a locus of failure below the interface (cohesive failure). XPS and TOF-SIMS results indicated that the Upilex-S thickness remaining on sputtered Cu after the tape test on the Cu-modified surface was <= 10 nm. Cohesive failure occurred at shorter treatment times when Cu was sputter coated on modified BPDA-PDA than on poly(pyromellitic dianhydide-oxydianiline) (PMDA-ODA) PI.