β-Si₃N₄ Whisker-Reinforced CaO-B₂O₃-SiO₂ Glass-Ceramic with High Flexural Strength and Low Dielectric Loss for LTCC Applications

CaO-B₂O₃-SiO₂ (CBS) glass-ceramics with different β-Si₃N₄ whisker composites were prepared by tape-casting and sintering methods. The dielectric properties, flexural strength, and strengthening mechanism were systematically investigated. The dielectric constants of the prepared composites ranged from 4.8 to 5.0, and the dielectric loss of the samples ranged from 0.78 × 10^–3 to 1.66 × 10^–3 (14.5–15.5 GHz). The CBS-SN16 composite exhibited flexural strength of 229.02 MPa and elastic modulus of 52.25 GPa, which are 18.85% and 36.22% higher than the 192.69 MPa and 38.35 GPa of the CBS matrix, respectively. Crack deflection, crack branching, and whisker pull-out were found to be the dominant mechanisms for improving the mechanical properties of the composites. In this study, the CBS-SN16 composite sintered at 810°C for 30 min demonstrated the optimal properties: dielectric constant of 4.80, low dielectric loss of 1.66 × 10^–3, and high flexural strength of 229.02 MPa. Such a low-temperature co-fired ceramic with high flexural strength and low dielectric loss is a promising candidate for electronic packaging applications.