Preparation of a CaO–Al2O3–B2O3–SiO2 glass/Al2O3 LTCC substrate material with high flexural strength for microwave application

A CaO-Al₂O₃-B₂O₃-SiO₂ (CABS) glass/Al₂O₃ LTCC substrate material with high flexural strength for microwave application has been successfully prepared through the avenue of investigating the effects of B₂O₃ in CABS glass and different glass/ceramic mass ratios on sintering shrinkage behavior, phase composition, microstructure, mechanical properties, and microwave dielectric properties of CABS glass/Al₂O₃ composites. The results show that adding an appropriate amount of B₂O₃ can lower the softening temperature of CABS glass and control the interfacial reaction between CABS glass and Al₂O₃, which is beneficial to the densification of CABS glass/Al₂O₃ and improves the microwave dielectric and mechanical properties. When the content of B₂O₃ is 22 wt% (in the CABS glass), the CABS glass/50 wt% Al₂O₃ sample sintered at 875 °C for 2 h exhibits the best comprehensive properties with the dielectric constant (ε_r) of 6.95, dielectric loss (tanδ) of 4.56 × 10^–3 (~ 10 GHz) and flexural strength of 223 MPa.