OXYGEN PLASMA MODIFICATION OF POLYIMIDE WEBS - EFFECT OF ION-BOMBARDMENT ON METAL ADHESION

Webs of Kapton 200-H and Upilex-S polyimide films were treated using o xygen plasma prior to sequential sputter deposition of chromium and co pper in a roll metallization system. Two plasma system configurations were employed for treatment. In one configuration, the sample traveled downstream from a microwave plasma; in the other, the web moved throu gh a DC-generated glow discharge. For the DC-glow treatment, the poten tial difference between the plasma and the web, phi(f), and relative i on densities, n+, were measured at various values of chamber pressure and DC power using a Langmuir probe. Although samples treated downstre am from the microwave plasma were not subjected to bombardment by ener getic ions, psi(f) for the DC-glow operating conditions was between 5 and 13 eV. For both films, advancing DI water contact angles of less t han 20-degrees were achieved using both modes of treatment. Contact an gles for untreated films were greater than 60-degrees. However, 90-deg rees peel tests yielded values of 15 to 20 g/mm for microwave plasma t reatments and 40 to 60 g/mm for DC-glow treatment. Peel values for unt reated Kapton and Upilex films were about 25 g/mm. High-resolution X-r ay photoelectron spectroscopy in the C1s region for Kapton film surfac es treated downstream from the microwave plasma showed increases in ca rbonyl groups, with concentrations inversely proportional to web speed . In contrast, DC-glow modification was due mainly to formation of car boxylates with a small increase in carbonyl component. It is proposed that treatment downstream from the microwave plasma results in formati on of a weak boundary layer at the polyimide surface. Ion bombardment occurring in the DC-plasma configuration results in relatively more cr osslinking at the polymer surface. Furthermore, adhesion between the s putter-deposited chromium and the DC-glow modified polyimide improved with increasing values of psi(f)n+.