RESIDUAL-STRESS AND THERMAL-EXPANSION OF SPUN-ON POLYIMIDE FILMS

The residual stress in spin coated films and the effect of heat treatments on this stress were determined by the Fizeau interference method. Three types of spin coated polyimide (PI) films have been studied. Two of them were prepared by thermal conversion of their poly(amic acid)s (PAAs) and the third one by solvent evaporation of the soluble preimidized PI. From the stress measurement, the thermal expansion coefficient and Young's moduli have also been obtained. The thermal expansion coefficient and the Young's modulus are in the order of 9. 0 multiplied by 10** minus **6 degree C** minus **1 and 10 GPa, respectively. These values deviate from those published for bulk material which is explained by the in-plane orientation of the molecular chains in spun-on PI films.