Structure, crystallization, and dielectric properties of the Al2O3filled CaO–B2O3–SiO2–Al2O3glass composites for LTCC applications

The glass structures and crystallization behaviors of CaO–B2O3–SiO2 (C1) and CaO–B2O3–SiO2–Al2O3 (C1A03) glasses are investigated. The addition of Al3+ into CaO–B2O3–SiO2 glass acts as a glass former and bonds with the silicon tetrahedron with non-bridged oxygen to form Si–O–Al–O–Si, which increases the Q4 structural unit. The relative dielectric constants for C1 and C1A03 glass systems were all about 7.8–8.4. Compared to the C1 glass, the size and amount of pores decreased for the C1A03, leading to a higher dielectric constant. The C1A03 glass system exhibits better Qxf value than the C1 system due to the decrease in the size and amount of pores. The Qxf value roughly decreased with increasing glass addition for the densified samples. The C1A03 glasses with 50 wt% alumina exhibited the highest dielectric constant (8.4) and Qxf value (3150 GHz) due the maximum densification and highest amount of anorthite were obtained.