SWELLING STRESSES AND STRAINS ASSOCIATED WITH MASS-TRANSPORT IN POLYMERIC FILMS

An experimental technique using a force-strain setup has been develope d to measure the swelling stresses and strains of polymeric films. The idea of the force-strain setup is similar in concept to the thermomec hanical analyzer (TMA) except that the driving force is the moisture d istribution, not the temperature distribution. This technique has been used to characterize the swelling behavior of polyimide film that has been used as passivation coatings in integrated circuit fabrication. Coatings are often used to protect moisture attack; an understanding o f the swelling stress and strain will allow better choice of the mater ial and processed condition. One objective of this investigation is to use the swelling information to determine diffusion coefficients. Gra vimetric measurements are also performed to verify the results calcula ted from the swelling experiment. With the information of mass uptake and swelling strain, the swelling coefficient can also be determined.