The Glazing of Vacuum‐Evaporated Gold‐Chromium Films with a Lead‐Containing Glass at 775°C

Abstract

The glazing of vacuum‐evaporated gold‐chromium duplex films on alumina substrates at 775°C using a lead‐containing glass has been investigated. This process forms a part in the construction of a multilayer hybrid circuit. A detailed examination of a unique glazing defect using electron beam analytical facilities has led to the identification of a fine needlelike deposit associated with the defect as single crystals of the compound .Examination of the other characteristic features of the defect, a central black spot and a porous gold film, has involved a study of the thermal stability of gold‐chromium duplex films under nonglazing and glazing conditions. From the nonglazing experiments it is concluded that the chromium content of the needlelike deposit results from grain boundary diffusion of chromium through the gold film to be followed by oxidation at the gold/air interface during the heating cycle of the glazing schedule. The resistivity changes observed to occur in films at 400°C appear qualitatively consistent with this view. The cohesion and adhesion of gold chromium films of various thickness ratios were found to be maintained or improved after heating at 775° C for 2 hr. Glazing the as‐deposited film gives rise to attack of the gold film by the lead constituent of the glass causing the black spot and a porous gold film.