Corrosion of In-Base Solders

Aqueous corrosion of In-base solders attached to Au conductors was studied by metallurgical analyses and galvanic cell tests. It was found that the solders, 90 In-10 Ag, 50 In-50 Pb, 70 In-30 Pb and 50 In-50 Sn, when coupled to Au, became susceptible to galvanic corrosion attack in solutions with pH < 4. The node of corrosion attack and corrosion products were investigated by SEM, microprobe, and x-ray diffraction analyses. Ways to avert the problem are also discussed.