DIFFUSION AND SELF-ADHESION OF THE POLYIMIDE PMDA-ODA

The relationship between the interdiffusion of two layers of the polyimide PMDA-ODA and the adhesion between the two layers has been examined. The polyimide layers were made by successively depositing a polyamic acid layer from solution and then curing the layers at elevated temperature to the polyimide. Diffusion occurred during the curing process of the second layer and was controlled by the cure schedule. The interdiffusion was measured using forward recoil spectrometry (FRES) and the adhesion measured by peel tests. Good correlation was found between the interdiffusion distance and the adhesion. It was found that a large diffusion distance, at least 200 nm, was required to obtain a bond whose strength was equal to that of bulk material.