Low dielectric properties of alkali-free aluminoborosilicate fiber glasses for PCB applications at 10 GHz

Alkali-free aluminoborosilicate glasses without (GDMC-Si) and with La₂O₃ addition (GDMC-La) were fabricated with an aim to develop low dielectric glass fibers for use in printed circuit boards (PCBs) as a reinforcing material in high-speed 5G/6G telecommunications application. This study presents the structural, thermo-physical, and dielectric properties of the glasses. The decrease in glass transition temperature (T_g) and the increase in coefficient of thermal expansion (CTE) were found by the addition of SiO₂ and La₂O₃ in the present glass system, which are due to the depolymerization of the glass networks confirmed by the FTIR analysis. The dielectric constants (Dk) and the dissipation factors (Df) of the glasses were investigated at a high frequency of 10 GHz. The Dk values of the GDMC-Si and GDMC-La glass systems reached a minimum of 4.50 and 4.75, while their Df values reached a minimum of 2.86 × 10^-3 and 3.01 × 10^-3, respectively. Notably, the Dk and Df values of the present glasses were lower than the commercial E-glass (Dk: 6.9, Df: 7.0 × 10^-3 at 10 GHz) and L-glass (Dk: 4.8, Df: 3.0 × 10^-3 at 10 GHz). Glass fibers with a diameter of 10 μm were successfully drawn by the continuous melt-spinning process and their mechanical properties were investigated.