Polyimide Cure Determination

A technique was developed for monitoring the conversion of polyamic acid to polyimide. The technique was used to characterize the cure reaction and to assist in understanding the relationship between degree of cure and etchability of films by a wet alkaline method. Interpretation of infrared spectra using a band ratio method gave consistent degree of cure determinations. Dynamic monitoring of films undergoing cure demonstrated that the rate of reaction is dependent on temperature and film thickness. Thicker films or thicker regions of nonuniform films were found to cure to a greater extent than thinner films or regions with identical thermal processing. Etchability was shown to have a high linear correlation with degree of cure. The study indicated that for optimal etch results film thickness uniformity and thermal treatment must be closely controlled.