Wetting and Bonding Behavior of SUS 304 Metal and Forsterite Ceramic with a PbO-Bi2O3-B2O3-ZnO Glass Frit

Abstract

The joining behavior of metal to ceramic was investigated using glass frit media. Glass frit with a composition of 71.5PbO-24Bi2O3-2.5B2O3-1.5ZnO-0.5SiO2 in mol. % was designed to bond forsterite ceramic and SUS 304 metal. The glass frit demonstrated a glass transition temperature of 250°C and a thermal expansion coefficient of 15.9 x 10-6/°C, which isbetween the values of SUS 304 (17.8×10-6/°C) and forsterite (9.9×10-6/°C). The contact angle was smaller than 90° at a temperature of 460°C. Redox reaction at the interface between forsterite and SUS304 was found to appear when the electrons in the metal part moved toward the glass part and the oxygen ions in glass moved to the metal side. The decrease of the surface tension due to the PbO solubility on the forsterite side contributed to the better wetting behavior at low temperature. Due to the ionic bonding nature, the glass was able to chemically react with forsterite ceramic and form a rough boundary. The Fe metal in the SUS 304 was oxidized to form FeO ceramic. A thin FeO layer on the SUS 304 surface helped the glass frit to wet the SUS 304, and clear tight bonding between the glass and SUS 304 was achieved.