Research On Preparation And Properties Of Glass-Ceramic For LTCC

With the development of hybrid IC technique, further requests for materials have been put forward. Recently, low temperature co-fired ceramics (LTCC) technology is the most attractive multi-chip integrated method which has such advantages as low cost, space-saving and high density. CaO-B₂O₃-SiO₂ (CBS) system belongs to one wollastonite-type glass-ceramic and has achieved industrial application in electronic package fields because it has excellent electrical properties and low-temperature co-firable characteristics.A sol-gel soft chemical route was used to prepare CaO-B₂O₃-SiO₂ glass powder, not only avoid the B volatilizing under high melting temperature in conventional way to prepare CBS glass powder, but also obtain more pure and uniformity powders. This paper is focused on the mechanism of hydrolyze and polymerization and the structural evolution in xerogel at various heat-treat temperatures. The xerogel exhibits [SiO₄] or [BO₃] based three-dimensional network structure whose interstices Ca ions fill in, which becomes more orderly and stable after heat treatments, for the formation of Si-O-B bond made the adjustment between molecules smaller in devitrification.Six compositions of CaO-B₂O₃-SiO₂ system were designed in this research based on the phase diagram. The glass-ceramics are obtained with CaSiO₃ and CaB₂O₄ phases through the nucleation and crystallization processes which are predefined by experiments. After sintered at 800-900℃, their dielectric properties at 1MHz of as-sintered glass-ceramics areεr=5.15 and tanδ=0.00095, respectively. Ca is the bases of main phase, excess will lead to the increase of dielectric loss. Si and B is the network former, too much Si in existence will result in a higher sintering temperature and suitable B will promote sinter for forming more liquid phase. The results indicate that the densification and dielectric property are strongly dependent on the content of each component. So the most excellent dielectric constant of the six is 4.83, corresponding the dielectric loss is 0.00089.In order to relieve the influence of sintering on glass-ceramic, investigation on the densification properties, structure and dielectric properties of the CaO-B₂O₃-SiO₂ glasses + CaSiO₃ crystalline ceramic were performed in this study. The result shows that CaSiO₃ plays a role on inductive and improve crystallization when the content of CS is small, which promotes the densification of glass+ceramic. The glass phase and ceramic phase are homogeneous mixed to a certain extent for the sample's structure is more compact consequently. When a sintering temperature is 850℃with the CBS:CS=1:9, the optimum dielectric properties are obtained with the dielectric constantεr is 5.06 and the dielectric loss tanδis 0.00064 at 1MHz.