DENSIFICATION KINETICS OF GLASS-FILMS CONSTRAINED ON RIGID SUBSTRATES

The kinetics of constrained-film sintering were studied in a borosilic ate glass (BSG) + silica system because of their applications in micro electronic packaging technologies. Samples with a silica content by 20 % by volume were prepared from slurries of powder mixtures in a commer cial polyvinyl butyral (PVB) binder solution. Constrained films about 0.2 mm thick were formed by doctor-blade casting the slurries on silic on wafers. Free-standing films about 0.6 mm thick were also produced b y casting the slurries on a treated mylar sheet for easy lift-off. Sin tering,o experiments were carried out in a hot stage at temperatures b etween 715 degrees C and 775 degrees C. Shrinkage profiles of the free and constrained (shrinkage in thickness only) films were determined i a situ using a custom-designed optical system, The densification rates measured in the constrained films were slower than those in the free films, However, the substrate constraint had no effect on the activati on energy of densification which was found equal to 385 +/- 10 kJ/mol, the same for both free and constrained films. A relation between the constrained-film and free-film densification profiles was derived usin g the viscous analogy for the constitutive equations of a porous sinte ring body.