Microwave dielectric properties of SnO‐SnF2‐P2O5 glass and its composite with alumina for ULTCC applications

Ultralow-temperature sinterable alumina-45SnF2:25SnO:30P2O5 glass (Al2O3-SSP glass) composite has been developed for microelectronic applications. The 45SnF2:25SnO:30P2O5 glass prepared by melt quenching from 450°C has a low Tg of about 93°C. The SSP glass has er and tanδ of 20 and 0.007, respectively, at 1 MHz. In the microwave frequency range, it has er=16 and Qu × f=990 GHz with τf=−290 ppm/°C at 6.2 GHz with coefficient of thermal expansion (CTE) value of 17.8 ppm/°C. A 30 wt.% Al2O3-70 wt.% SSP composite was prepared by sintering at different temperatures from 150°C to 400°C. The crystalline phases and dielectric properties vary with sintering temperature. The alumina-SSP composite sintered at 200°C has er=5.41 with a tanδ of 0.01 (1 MHz) and at microwave frequencies it has er=5.20 at 11 GHz with Qu × f=5500 GHz with temperature coefficient of resonant frequency (τf)=−18 ppm/°C. The CTE and room-temperature thermal conductivity of the composite sintered at 200°C are 8.7 ppm/°C and 0.47 W/m/K, respectively. The new composite has a low sintering temperature and is a possible candidate for ultralow-temperature cofired ceramics applications.