Fabrication of low dielectric constant film based on CaO–B2O3–SiO2 glass/mullite composites for LTCC application

CaO–B 2 O 3 –SiO 2 (CBS) glass/mullite composite with low dielectric constant was fabricated by tape casting process. The effects of CBS glass content and particle size of mullite powders to the composites were investigated. Results showed that the optimum glass content and particle size of mullite powders ( D 50 ) were 40 wt% and 3.5 µm, respectively. From the analysis of the phase composition, we could know that CBS glass could react with mullite at high temperature to form a new phase of anorthite. Moreover, the sintering temperature, holding time and the increase of mullite content also could promote this reaction. Finally, we found that the best sintering process for this composite was sintered at 830 °C for 120 min and its composition was 40 wt% glass. The prepared CBS/mullite ( D 50 = 3.5 µm) composite with 40 wt% glass exhibited the best performance with the density of 2.93 g/cm 3 , ε r = 6.20 and tan δ = 11 × 10 −4 at 7 MHz.