Structural analysis of SAC solder with Bi addition

The microstructural characterization and properties of solder joints made from lead-free solder alloys SnAg3.0Cu0.5 and SnAg1.0Cu0.5Bi1.0 (composition given in weight %) with Cu plate were studied in this work. The influence of Bi addition to the SAC solder was studied. The melting temperatures, optical microscopy, EDX, and point chemical analyses were observed and evaluated. Thermo-Calc software was used for phase's composition prediction. Altogether, 1500cycles were carried out for the thermal cycling test in the range from +150 to -40 degrees C where the solder joints' reliability was assessed due to practice requirement. Optical microscopy and scanning electron microscopy (EDX microanalysis) tests were used for the evolution of microstructure and structural integrity of thermal cycled solder joints.