INFLUENCE OF OXIDATION OF A MULTILAYER METALLIZATION ON THE ADHESION OF AN SN-SB SOLDER

The influence of oxidation of an Al-Cr-Ni-Ag multilayer metallization on the adhesion of Sn-5wt%Sb solder was investigated. Oxidation of the multilayer metallization prevents the solder from wetting the multila yer metallization uniformly. The nonuniform wetting of the solder caus ed localization of thermal stress on the wetted regions and promoted d ifferential degradation of the regions. The interface between Ni and A g was oxidized when exposed to air without cooling to a low temperatur e. The nickel oxide at the interface prevented the formation of metall urgical bonds between the multilayer metallization and the molten sold er. In some interface regions where the molten solder eliminated the n ickel oxide either chemically or physically, the solder wetted the mul tilayer metallization but did not wet in the regions where the nickel oxide was not eliminated.