The adhesion of sputtered Cu to fluoropolymer surfaces modified by vacuum UV photo-oxidation increased with treatment time for Teflon® PTFE while for Teflon® FEP and PFA there was cohesive failure within FEP and PFA and not at the Cu-fluoropolymer interface. Ar ion etching of the surfaces after cohesive failure showed that the depth of FEP and PFA left on the Cu was ca. 3-10 nm. The chemistry at the interface included the presence of copper fluorides. Control experiments involving Ar ion etching of untreated fluoropolymers showed no evidence for fluoride ions. Thin films of Cu were thermally evaporated and sputter deposited on untreated PTFE, FEP and PFA surfaces and analyzed by XPS. In contrast to thermal evaporation, the high energy Cu atoms from sputter deposition produced substantial yields of copper fluorides which were studied as a function of sputtering voltage, current and pressure. The formation of copper fluoride bonds correlated with good adhesion of sputtered Cu with untreated FEP and PFA compared to polycrystalline PTFE which was the most resistant to the production of fluoride ions. The formation of copper fluoride depends on the energy of the sputtered species and the stability of the bonds in the fluoropolymer. The maximum fluoride ion concentration is located at a depth of 5 ±1 nm.
After removing with sputter etching about 5 nm of surface material, CuF2 was exposed and there was an improvement of adhesion of evaporated copper to the modified PTFE, FEP and PFA. The largest concentrations of fluoride ion were found at the intermediate depth of analysis by XPS. Deeper into the surface there was more intact fluoropolymer. Energetic copper atoms appear to penetrate the surface, break fluoropolymer bonds and react to form copper fluoride. The results of the current study show that the presence of copper fluorides greatly improves the adhesion of evaporated Cu to PTFE, FEP and PFA.
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School of Chemistry and Materials Science (COS)
Abreu, Daliana Gava, "Chemistry at the Cu-fluoropolymer Interface: Relevance to Adhesion" (2006). Thesis. Rochester Institute of Technology. Accessed from
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