Microstructure and properties of SnAgCu-xPr solder

The effect of different Pr additions(0,0.05,0.5wt.%) on the solidification behavior,spreading property and microstructures of Sn-3.8Ag-0.7Cu(SAC) solder were investigated.The results showed that the undercooling of SAC,SAC-0.05Pr and SAC-0.5Pr solder in solidification were 23.2,7 and 8.6℃ respectively which indicated that the proper content of Pr addition could obviously decrease the undercooling of SAC solder.Meanwhile,with Pr addition,the microstructure of SAC solder was improved and the primary Ag₃Sn plate in SAC/Cu solder joint was restrained.Moreover,the SAC-0.05Pr solder has the best wetting property and microstructure;when the Pr addition was up to 0.5 wt%,PrSn₃ phase with large size formed in solder would deteriorate the property of SAC solder joint.