Studies of dielectric characteristics and surface energies of spin-coated polyimide films

A two-step method, that is, polyamic acid formation with subsequent curing, was used to synthesize six kinds of polyimides. Dielectric constants and s urface energies were investigated to determine the nature of the fluorinate d and nonfluorinated polyimides. The dielectric constant decreased from 3.3 (at 100 kHz) for PMDA/ODA to 2.6 (at 100 kHz) for 6FDA/4,4 ' -6F when the fluorine content increased from 0 to 30.7 wt %. Simultaneously, the water c ontact angle increased from 65 degrees for PMDA/ODA to 78 degrees for 6FDA/ 4,4 ' -6F. Experimental results indicated that fluorinated polyimides conta ined a lower dielectric constant with improved water resistance. The surfac e energy values obtained from experiments agreed well with Holmes' correlat ion between surface energy and dielectric constant. The surface energies an d dielectric constants were significantly affected by the polymer backbone structures, especially by the fluorination effect. Therefore, by choosing t he appropriate monomers, polyimides of low dielectric constants with hydrop hobic surfaces could be obtained. (C) 2001 John Wiley & Sons, Inc.