Wetting in an Electronic Packaging Ceramic System: 1, Wetting of Tungsten by Glass in Controlled Oxygen Partial Pressure Atmospheres

The wetting of tungsten by a Cr2O3-colored, CaO-MgO-Al2O3-SiO2 glass was found to be independent of temperature between 1300° and 1500°C, but strongly dependent on furnace atmosphere. Similar results using two gas buffer systems (CO/CO2 and H2/H2O) established oxygen partial pressure, p02 as the critical parameter. the contact angle decreased over a narrow p02 range as the p02 increased, with a stable contact angle existing in both lower and higher p02 ranges. the solid-liquid interfacial energy, γSL, controlled the wetting behavior. an increase in the adsorbed oxygen layer at the solid-liquid interface resulted in a lower γSL and a lower contact angle. the equilibrium contact angles, established after 8-h isothermal holds, ranged from 50-55° at a p02= 10−15.5 atm to 30° at a p02= 10−10.9 atm. Two different drop formation techniques were used to show that the temperature and atmospheric conditions at the time of solid-liquid interface formation affect the stable contact angles. the contact angle was higher when the solid-liquid interface was established at the test temperature (doser tube technique) than when the drop was formed in situ from a piece of glass placed on the substrate at room temperature (nondoser method). This contact angle difference was again attributed to a higher γSL from the doser method due to the presence of less adsorbed oxygen at the time of the creation of the solid-liquid interface