ROLE OF IRON MONOXIDE ON THE KOVAR WETTAB ILITY BY GLASS

The processes of glass-kovar junctions, frequently used in industry, i nclude a pre-oxidation of the alloy, so covering the alloy of a thin l ayer mainly constitued of iron oxide. At the junction temperature (abo ut 900-degrees-C for borosilicate glasses) the superficial layer is co mposed of iron monoxide FeO which reacts with glass to make, first, a Fe2SiO4 type phase. Then this phase is dissolved by the glass whose co mposition is so modified, making it more fluid and more wetting. The f avourable effect of iron monoxide dissolution is maintained in a large range of FeO content, till 40 wt%, but even a low content is sufficie nt to strongly improve wetting. This is a good justification for the g reat attention paid to the pre-oxidation of kovar in the glass-making.