Properties of borosilicate glass/Al2O3 composites with different Al2O3 concentrations for LTCC applications

This article aims to investigate the effect of Al₂O₃ in borosilicate glass on the sintering densification and properties of the borosilicate glass/Al₂O₃ LTCC composites. A series of CaO–Al₂O₃–B₂O₃–SiO₂ (CABS) glass with different concentrations of Al₂O₃ was synthesized, as well as the CABS glass/Al₂O₃ LTCC composites. The influence of Al₂O₃ on the sintering densification, phase composition, microstructures and properties of the CABS glass/Al₂O₃ LTCC composites was then systematically investigated. Result indicates that a proper amount of Al₂O₃ in CABS glass not only can strengthen the structural stability of the borosilicate glass, but also can promote the sintering densification and improve the properties of the glass/ceramic composites. CABS glass/Al₂O₃ composites prepared with CABS glass of 4 wt.% Al₂O₃ sintered at 875 °C exhibits excellent properties of a sintering density of 3.13 g/cm³, a Z axial shrinkage of 15.5%, a dielectric constant (ε_r) of 8.08, a dielectric loss (tanδ) of 0.9 × 10^–3 (at 7 GHz), a coefficient of thermal expansion (CTE) of 5.35 ppm/°C, a flexural strength of 206 MPa, demonstrating its great potential for LTCC applications.