Creep mechanism fractography analysis on SnPb eutectic solder joint failure

Microstructural fracture mode observed in creep can be divided into intergranular and transgranular fracture. Depending on temperature and stress condition, creep fracture mode is decided. To design an accelerated life test, it should be confirmed that the failure mode in the accelerated test is identical to the mode in real field condition. Selecting optimal conditions of temperature and stress in accelerated creep rupture test requires extensive fractography analysis. In this study, SnPb eutectic solder joints for holding an anchor from heat sink system are subjected to creep rupture tests. After the test, failed solder joints are investigated and analyzed to identify creep fracture mode. Fracture microstructures of solder joints are analyzed using SEM and FIB. It is observed that transgranular fractures are predominant in the condition of low temperature and high stress and intergranular fractures are predominant in the condition of high temperature and low stress. Analysis results confirmed creep deformation mechanism map made by X.Q.Shi et al. and suggested optimal conditions of temperature and stress for accelerated creep rupture test with SnPb eutectic solder joints.