The influence of chromium addition on the metallurgical, mechanical and fracture aspects of Sn–Cu–Bi/Cu solder joint

One of the candidate alloying elements is Cr which is used to make solder suitable for severe conditions. The current study has been conducted to investigate the addition of Cr along with Bi to Sn–Cu base solder. Accordingly, the effect of adding Cr on the joint properties of the new Sn-0.8Cu-1.8Bi-xCr (x = 0, 0.01, and 0.1 wt%) solders is compared to Sn-0.8Cu and Sn-0.8Cu-1.8Bi base solders. For investigating the joint interfacial microstructure and phase transformation, the synthesized solders were bonded to the Cu-substrate. Also, to evaluate the joint properties, the shear test, fractography, and microhardness were carried out. The characterizations are carried out using SEM-EDS to predict the mechanism governing the grain refinement and decrease of intermetallic compounds (IMCs) thickness. The presence of Cr and Bi improved the IMC layer microstructure and changed the joint properties of Sn–Cu. The thickness of the IMCs at the solder/substrate interface decreased by the addition of selected alloying elements because of the Sn and Cu diffusion power changing. Also, the Sn–Cu–Bi-0.01Cr/Cu joint showed the best shear properties and elongation among the others. The best metallurgical, mechanical and fracture behavior results were obtained from the Sn–Cu–Bi-0.01Cr/Cu joint.