Creep properties of Sn-Ag solder joints containing intermetallic particles

The creep behavior of the eutectic tin-silver joints and tin-silver composite solder joints containing 20 vol.% of Cu₆Sn₅, Ni₃Sn₄, and FeSn₂ intermetallic reinforcements introduced by in-situ methods was investigated. These creep tests were carried out using single shear lap solder joints at room temperature, 85°C, and 125°C. The creep resistance was similar in magnitude for all alloys, and with increasing temperature, the stressexponents decreased in a manner consistent with power-law breakdown behavior. The FeSn₂ intermetallic reinforced composite solder was found to be the most creep-resistant alloy at room temperature. Creep failure was observed to occur within the solder matrix in all these solder joints. Although a detailed analysis of the processes involved was difficult because of smearing of the features in the fracture surface, there were indications of grain-boundary separation, ductile fracture, and interfacial separation. For more information, contact K.N. Subramanian, Michigan State University, Department of Materials Science and Mechanics, 3536 Engineering Building, East Lansing, Michigan 48824-1226; (517) 353-5397; fax (517) 353-9842; e-mail subraman@egr.msu.edu.