Effect of minor alloying additions on the BIT reliability of SnAgCu solder joints

In this work, the SAC solder joints with minor Mn or RE (rare earth) additions were bonded on the substrate of OSP Cu surface finishes for evaluating the influence of minor alloying on BIT (ball impact test) behavior. The Mn-doped samples had a better resistance to the degradation in BIT performance suffering long time aging at 150°C. The greater impact force and toughness compared to the other samples could be attributed to the hardened matrix and the difference in the thickness of Cu₃Sn at the interface. It was deduced that a higher thickness fraction of Cu₃Sn which has lower hardness but greater Young´s modulus than Cu₆Sn₅ may be beneficial for the solder joint reliability subjected to high strain rate impact deformation if there are no excessive Kirkendall voids formed.