Sintering behavior of mullite with addition of SiO2-MgO-Y2O3-SrCO3

As the size of semiconducting silicon (Si) wafers increases, that of the ceramic substrate, which is main part of a semiconductor probing system, has also increased. The increased number of layers due to high integrity of Si wafers and the narrow pattern linewidths for impedance matching require the use of Cu-Mo conducting paste, rather than conventional Mo paste, for low electrical resistivity. For co-firing of a Cu-Mo electrode with a ceramic substrate, a green ceramic substrate with a printed pattern must be sintered at a temperature below 1400 °C. To obtain a mullite composition that can be co-fired with a Cu-Mo electrode at a temperature below 1400 °C, we added 1.0 wt% of SiO 2 , 1.0 wt% of MgO, 1.5 wt% of Y 2 O 3 , and 7.0 wt% of SrCO 3 to a commercial mullite composition, and we sintered the specimen with that composition at 1350 °C in a reducing atmosphere to obtain a density of 3.20 g/cm 3 . The sintered specimen’s coefficient of thermal expansion at temperatures from room temperature to 200 °C was 4.53 ppm/°C, which is acceptable for a semiconductor probing system.