Microwave dielectric properties of SnO ‐ SnF 2 ‐ P 2 O 5 glass and its composite with alumina for ULTCC applications

Ultralow‐temperature sinterable alumina‐45 SnF 2 :25 SnO :30 P 2 O 5 glass ( Al 2 O 3 ‐ SSP glass) composite has been developed for microelectronic applications. The 45SnF 2 :25SnO:30P 2 O 5 glass prepared by melt quenching from 450°C has a low T g of about 93°C. The SSP glass has ε r and tanδ of 20 and 0.007, respectively, at 1 MHz. In the microwave frequency range, it has ε r =16 and Q u × f =990 GHz with τ f =−290 ppm/°C at 6.2 GHz with coefficient of thermal expansion ( CTE ) value of 17.8 ppm/°C. A 30 wt.% Al 2 O 3 ‐ 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 ε r =5.41 with a tanδ of 0.01 (1 MHz) and at microwave frequencies it has ε r =5.20 at 11 GHz with Q u × f =5500 GHz with temperature coefficient of resonant frequency (τ f )=−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.