Mk. Shi et al., FLUOROPOLYMER SURFACE MODIFICATION FOR ENHANCED EVAPORATED METAL ADHESION, Journal of adhesion science and technology, 8(10), 1994, pp. 1129-1141
Adhesion of evaporated Cu to Teflon PFA (polytetrafluoroethylene-co-pe
rfluoroalkoxy vinyl ether) was greatly enhanced by plasma pretreatment
. The efficiency of the treatment decreased in the following order: N-
2 > O-2 > (N-2 + H-2) > (O-2 + H-2) > H-2. X-ray photoelectron spectro
scopy (XPS) showed the loss of fluorine and the incorporation of oxyge
n and nitrogen at the polymer surface. Among the gases, H-2 was found
to be the most efficient for fluorine elimination, and (N-2 + H-2) for
surface functionalization. Based on this investigation, it is propose
d that Cu reacts with both oxygen and nitrogen to form, respectively,
Cu-O and Cu-N bonds at the interface but no reaction occurs with carbo
n and fluorine. While greater enhancement in polymer surface wettabili
ty and stronger interfacial reactions can account for the higher perfo
rmance of N-2 over O-2 in improving adhesion, these effects cannot exp
lain the lower efficiency of H-2. Several possibilities are discussed,
including surface cleaning, oxygen incorporation and the formation of
weak boundary layers.