AbstractPolyimide-on-metal interfaces relevant to electronics packaging applications have been studied by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Two polyimides with different backbone structures were considered: (i) biphenyltetracarboxylic dianhydride (BPDA) - p-phenylene diamine (PDA) and (ii) 4,4′-(hexafluroisopropylidene)-bis(phthalic anhydride) (6FDA) - 4,4′-bis(4-aminophenoxy) biphenyl (APBP). Thin polymer films (10–100 nm) were cured on Al, Cr and Cu surfaces at different temperatures to allow probing of chemical interactions by surface spectroscopies. Anhydride intermediates were detected on all three substrates for both polyimides. Carboxylate intermediates were detected in BPDA-PDA films on Cr and Cu and resulted in increased adhesion at these interfaces. XPS data revealed a nitrogen deficiency at the BPDAPDA/Cr interface. A mechanism explaining the formation of this intermediate and the deficiency of nitrogen is proposed. Hydrolytic stability of the interface was investigated using ex situ total internal reflection FTIR spectroscopy and XPS. The results show that the fluorinated polyimide, 6FDA-APBP, is more stable than BPDA-PDA when treated at 85 °C and 85% relative humidity for 100 hours.