Abstract
Electronic ceramics with the refractory metallization are fired in a reducing atmosphere to prevent oxidation of the metals. Firing and binder burn-out phenomena of 92% alumina ceramics (Al2O3-MgO-SiO2) with polyvinyl butyral binder was discussed by the first to third reports. In this, the fourth report, a method to minimize the firing shrinkage dispersion was studied referring to moisture in the atmosphere, binder concentration, ambient gas pressure, gas charging rate and furnace structures. The increase in moisture in the reducing gas, and decrease in the binder concentration in the ceramic batch decreased the dispersion of the firing shrinkage (Figs. 6 and 9). When a sufficient amount of fresh gas was circulated on the sample surface in the furnace, the dispersion in the firing shrinkage decreased. The gas inlet structure, gas flow rate, and especially the stacked setter structure should be considerd for the gas circulation uniformity (Figs. 10 and 11). Increased ambient gas pressure in the furnace disturbed the gas-out from the ceramic body, greater dispersion of firing shrinkage (Fig. 12). Through the reports from the first to fourth, the interaction between the binder burn-out and firing shrinkage is indicated as the phenomena of Fig. 13 during heating up. Consequently, Fig. 14 was conducted as a method for the firing shinkage control.
