Lead-free borosilicate glass/fused quartz composites for LTCC applications

In this work, novel lead-free composites based on AlF3-B2O3-SiO2 (ABS)/fused quartz (FQ) were synthesized for the low temperature-co-fired ceramic (LTCC) applications. The phase structure, sintering behavior, dielectric properties, and thermal expansion coefficient (TEC) of ABS/FQ composites have been investigated in detail. The crystallization of cristobalite phase was not observed within the whole range of compositions, leading to low TEC values. However, with the increase in FQ content, the densification was found to degrade. The optimized properties were observed for the composite with 65 wt% ABS glass and 35 wt% FQ (65ABS/FQ), sintered at 850 degrees C, which exhibited excellent relative density of 98.5%, dielectric constant of 4.61 (10 MHz), dielectric loss of 1.5 x 10(-3) (10 MHz), TEC value of 3.75 ppm/degrees C, and cofiring compatibility with Ag electrode, making 65ABS/FQ composites an interesting potential candidate for LTCC substrate material.