The Variation of Microstructure and the Improvement of Shear Strength in SAC1205-xNi/OSP Cu Solder Joints Before and After Aging

The correlations between different Ni contents in Sn-1.2Ag-0.5Cu-xNi (wt.%; x = 0, 0.05, 0.1)/organic solderability preservative Cu solder joints and shear test performance before and after aging were probed. With the aid of electron back scattering diffraction analysis and a scanning electron microscope, complexity in microstructure of Ni-doped solder joints was investigated. The results of a slow speed shear test revealed that the peak force of solder joints was efficiently enhanced by the addition of Ni before and after aging. The improvement of mechanical strength was ascribed to the modification of microstructure by the introduction of minor Ni addition. Spread and tiny intermetallic compounds, and the oriented interlaced structure in Ni-doped solder joints acted as hindrances for propagation of cracks and dislocations. It is revealed that solder joints with minor Ni doping tend to exhibit better mechanical reliability in advanced electronic packaging no matter before or after aging.