Microwave dielectric characterization and densification mechanism analysis of CaO-B₂O₃-SiO₂ glass-ceramic/Al₂O₃ composites for LTCC applications

In this study, nine component points were designed based on a CaO-B2O3-SiO2 (CBS) glass system with a high boron content, and CBS glass/Al2O3 composites were developed for low-temperature co-fired ceramic (LTCC) applications. Furthermore, the densification process, phase compositions, microstructures, and properties were investigated. The results indicated that the softening of glass and interfacial reaction between the glass and Al2O3 were the two most important factors affecting LTCC's densification process. The real-time shrinkage rate of LTCC during sintering was simulated using the thermal shrinkage curve and combined withDTAand X-ray diffraction. Itwas proven that the formation of the CaAl2(BO3)O phase contributed to the reduction in glass viscosity and promoted the formation of a dense structure. The LTCC composite with 30 vol% glass sintered at 850 degrees C exhibited a coefficient of thermal expansion of 4.55-6.35 ppm/oC, epsilon(r) of 3.5-5.0, and a minimum tan delta of 0.0018 at 15GHz. Therefore, these properties make the CBS-LTCC more suitable for high-frequency applications.