Effect of plasma treatment on adhesion of low thermal expansion polyimide films

To fabricate a multilayer wiring using a low thermal expansion polyimide film, the adhesion of polyimide film on a thermally cured polyimide film must be secured. When the surface was plasma-treated by O2-CF4 = 1:1 gas, the adhesion was 30 times stronger (peel strength: at least 500 g/cm) than in the untreated case (peel strength: 15 g/cm). The film on the plasma-treated surface maintained strong adhesion for long periods of time in a high-temperature and high-humidity environment. The cause of improved adhesion was investigated by evaluating the plasma-treated polyimide surface by XPS and it was found that functional group, which seems to be COF, was formed.