Devitrification kinetics of high lead glass for hybrid microelectronics

In order to elucidate crystallization phenomena in high lead glasses for hybrid microelectronics, we studied the devitrification in screen printed and annealed films made with borosilicate glass particles with the composition PbO-SiO2-B(2)iO(3) = 65:25:10 % wt. Formation of SiO2 polymorphs, beta -cristobalite and quartz, was observed in films printed on alumina (Al2O3) or beryllia (BeO) and fired in the temperature range from 700 to 1000 degreesC. X-ray diffraction of samples annealed in isothermal conditions enabled the collection of data for studying the kinetics of formation and dissolution of the crystalline phases. The crystallization of beta -cristobalite on both substrates is governed by an Avrami model. At lower temperatures, the reaction order coefficient indicates an interface controlled reaction with an instantaneous or deceleratory nucleation rate and 3D growth. The apparent activation energy of the crystallization process is independent of the substrate being 15(1) kcal/mol and 14.7(9) kcal/mol for samples on Al2O3 and BeO substrates, respectively, whereas the decomposition reaction is favored on alumina, with E-d = 30(2) kcal/mol in this case, but 55(3) kcal/mol for beryllia substrates. (C) 2001 Elsevier Science Ltd. All rights reserved.