Evaluation of cure conditions for polyimide thin films by pyrolysis–mass spectrometry

Films of a BTDA-mPDA-ODA polyimide copolymer (DuPont Pyralin PI-2555) were spin-coated onto silicon wafers and cured at either 300 or 350-degrees-C. Films cured at each temperature were then analyzed by various pyrolysis mass spectrometric methods. Low-temperature pyrolysis mass spectrometry showed that polyimide films cured at the lower temperature contained more residual water and N-methyl pyrrolidone solvent than did the films cured at the higher temperature. High-temperature pyrolysis mass spectrometry of the two samples showed subtle differences in the mass spectrum of the polyimide pyrolysate under electron impact (EI) ionization conditions. Principal components analysis was used to differentiate between the EI mass spectra of the high- and low-temperature cured films. Several pyrolysis products, primarily aromatic hydrocarbon and heterocyclic fragments, were separated and identified by gas chromatography/mass spectrometry.