Microwave dielectric characterization and densification mechanism analysis of CaO‐B 2 O 3 ‐SiO 2 glass–ceramic/Al 2 O 3 composites for LTCC applications

Abstract In this study, nine component points were designed based on a CaO‐B 2 O 3 ‐SiO 2 (CBS) glass system with a high boron content, and CBS glass/Al 2 O 3 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 Al 2 O 3 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 with DTA and X‐ray diffraction. It was proven that the formation of the CaAl 2 (BO 3 )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°C exhibited a coefficient of thermal expansion of 4.55–6.35 ppm/◦C, ε r of 3.5–5.0, and a minimum tan δ of 0.0018 at 15 GHz. Therefore, these properties make the CBS–LTCC more suitable for high‐frequency applications.