Ion beam and RF-plasma modification of metal-polymer interfaces for improved adhesion

Abstract

Summary form only given, as follows. The surfaces of Lexan Polycarbonate (PC) and ABS polymers were treated initially with low energy (300 eV) ion bombardment prior to and during deposition of a thin (200 nm) Al film. The effects on the adhesion characteristics, the type of ions used (Ar, N), and the type of bombardment (sputtering or during deposition) were studied for eight different deposition conditions for each polymer. The adhesion characteristics were compared by the tape and stud-pull tests. The ion beam treatment causes substantial improvement in adhesion strength in all seven cases where sputtering was involved. Based on the ion beam studies, and using statistically designed experiments, a new RF-sputtering-plasma technique was developed and tested in both laboratory and manufacturing environments. Results from the N/sub 2/-plasma treatment show drastic improvement in film adhesion to molded and clean polymers. Adhesion was compared again using the tape and stud pull tests. In the case of the stud-pull test for the PC samples, the failure was along the interface for the non-sputtered case only. In all others, with sputtering, we observed cohesive failure within the polymer, as confirmed by SEM. This suggests that the actual interface strength in all the sputtered cases was higher than that of the polymer itself. SEM, RES, and profilometry were used to study the failure modes, Al film quality, and the effect of morphology on adhesion characteristics, respectively. Surface roughness did not seem to be an important factor for adhesion improvement. XPS studies suggest that the Al is bonded in identical ways at the bombarded and virgin interfaces. Improved adhesion is likely due to surface sputter cleaning.