Densification and properties of calcium borosilicate low temprature co-fired ceramics

The CaO-B₂O₃-SiO₂ (CBS) green tape was prepared by tape-casting crystallizable CBS glass powders. After the binder burn-out process, the low temperature co-fired ceramics (LTCC) could be successfully sintered in the temperature range of 775-950°C. The densification and crystallization behaviors of the CBS green tape were investigated. The effects of sintering temperature on sintering and dielectric properties were studied. The results show that the major crystalline phase is always β-CaSiO₃ and a little CaB₂O₄ existed in the temperature range of 850-900°C. The densification process occurred prior to the crystallization process, which is favorable for densification. This may be due to the bulk crystallization of the CBS glass. The bulk densities decrease with the increase of firing temperature. This can be interpreted by considering the difference in bulk density between the crystalline phases and residual glass. Increasing the sintering temperature can promote crystallization. The dielectric constant decreases with the increase of the sintering temperature because the crystals have a lower dielectric constant than CBS glass.