INTERFACIAL REACTIONS BETWEEN ALUMINUM AND BPDA-PDA

Interaction of evaporated aluminum with BPDA-PDA polyimide surfaces have been studied using x-ray photoelectron spectroscopy. At low coverage, aluminum reacts primarily with carbonyl groups as in the PMDA-ODA and also diffuses into the polyimide substrate to react with inner carbonyls. No trace of metal clusters are detected in the initial metallization. When the covering rate becomes somewhat higher, additional interfacial reactions occur, involving the formation of N-Al and C-Al bonds. In general, the chemical interactions of Al at BPDA-PDA and PMDA-ODA are similar. It is suggested that the observed difference in adhesion strength between the two polyimides comes from the diamine moiety (PDA and ODA). In the PMDA-ODA the macromolecules can rotate around the ether function which is not the case in the BPDA-PDA where the conjugation makes the macromolecule more rigid. Thus the difference in adhesion may be attributed to the chain conformation of polyimide.