Fd. Egitto et al., OXYGEN PLASMA MODIFICATION OF POLYIMIDE WEBS - EFFECT OF ION-BOMBARDMENT ON METAL ADHESION, Journal of adhesion science and technology, 8(4), 1994, pp. 411-433
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+.