Wetting and spreading behavior of borosilicate glass on Kovar

The wetting and spreading behavior of borosilicate glass on Kovar with oxides of FeO + Fe3O4 was investigated as a function of wetting time by the sessile drop method. The contact angle and drop base diameter were measured by the VHX-100K digital microscopy. The top view of spreading and cross-sectional microstructure of glass/Kovar was investigated by SEM, and elements distribution of Fe, Co, Ni and Si in interfacial regions was characterized by EDS line scanning. The results showed two halos were formed at the fringe of glass base in the wetting process. By analyzing the change of contact angle and drop base diameter, wetting process could be divided into three stages: incubation period, reaction period and equilibrium period. Chemical reaction is occurred between glass and oxides, and the reaction product is Fe2SiO4. Chemical and mechanical bonding effects are all present in the wetting of glass to Kovar.