Low temperature pressureless sintering of silicon nitride ceramics for circuit substrates in powder electronic devices

TiO2-MgO is proposed as new sintering additive for low temperature pressureless sintering of Si3N4 ceramics to be circuit substrate in power electronic devices. The effects of additive content on densification, mechanical and thermal properties of Si3N4 substrate were investigated systemically. Si3N4 ceramics with density of 3.20 g cm(-3) could be obtained with the addition of 10 wt% TiO2-MgO and sintered at 1780 degrees C. The flexural strength, fracture toughness and thermal conductivity were 668 MPa, 5.13 MPa m(1/2) and 55.3 W/(m K), respectively, and the highest thermal conductivity was 60 W/(m K) could be obtained after annealing. Phase compositions at different temperature were characterized by high temperature in-situ XRD. TiC0.3N0.7 s phase was observed and its formation mechanism was investigated. Results showed TiO2-MgO to be effective sintering additive for developing Si3N4 ceramics at low cost and with acceptable mechanical and thermal properties.