Preparation and thermal expansion behavior of glass coatings for electronic applications

PbO–B2O3–SiO2 based alkali-free glass coatings were prepared and deposited on alumina ceramics, in order to: (1) decrease the sintering temperature of the coatings, and (2) keep a close match of thermal expansion between the coatings and the ceramics. Influence of different dopants on sintering temperature and thermal expansion behavior was studied, and an optimized composition was obtained. The effects of annealing processing on the coefficient of thermal expansion (CTE) and softening temperature (Ts) of the glass were investigated by using X-ray diffraction (XRD) spectra and thermal–mechanical analysis (TMA). The results showed that high annealing temperature would be helpful to obtain the closely packed structural with lower CTE, but long annealing time would lead to increasing of CTE. This could be due to the structural rearrangement of glass during the thermal treatment. Furthermore, the variation in coordination of the glass network would also be responsible for the change of CTE. The results showed that an optimized annealing scheme must be determined for producing glass coatings that can match to the ceramic.