Influence of Alumina Contents on the Properties of Alumina Substrates

We studied the effect of alumina content on the sinterability of alumina substrate in relation to the firing temperature. The surface roughness, sintered density, and bending strength of alumina substrate were improved as the alumina content increased. The optimum firing temperature for alumina substrate was defined as the minimum temperature at which the characteristics of alumina substrate were satisfied all the following conditions, 1) The ratio of water absorption is almost zero. 2) The ratio of the sintering shrinkage is 0 to -0.4% of the maximum sintering shrinkage. 3) The sintering density is above 97% of the maximum sintering density. 4) The average surface roughness is 1.3 times of the minimum surface roughness. 5) The bending strength is above 85% of the maximum bending strength. The optimum firing temperature shifted toward higher-temperature side when the content of alumina increased. Thus, the optimum firing temperature for 1.1μm alumina substrate was 1, 520°C for an alumina content of 91.5% 1, 560°C for 96.4%, and 1, 600°C for 98.8%.