Effect of Pr on microstructure and properties of Sn58Bi solder

A novel type of lead-free solder was prepared by adding Pr to Sn58Bi alloy solder.The influence of Pr dosage on the lattice change,tensile strength and wettability of the solder were studied after the solder was welded.XRD results indicated that the addition of Pr could cause lattice distortion of the solder.SEM analysis showed that a micro amount addition of Pr could inhibit the growth and coarsening of Bi phase and refine the grain size of the solder.The wettability test results showed that the wettability of Sn58Bi solder could be improved with the increase of Pr addition.When the mass fraction of Pr was 1.5%,the spreading rate of solder increased from 81.97% to 88.41%,being improved by 7.86%.The solder mechanical properties results showed that the tensile strength of the soldered joint was 7.631 8 MPa without Pr addition,while the tensile strength increased with the addition of Pr.When the mass fraction of Pr was 1.5%,the maximum the tensile strength of the soldered joint of 11.126 3 MPa could be obtained,which increased by 45.79%.To sum up,it could be concluded that proper Pr addition could improve the microstructure,tensile strength and wettability of Sn58Bi solder effectively.Highlights:(1)Sn58BiPr lead-free solder was prepared by adding trace rare earth elements.(2)The mixed Pr could make the solder lattice distortion to refine solder’s grains.(3)Wettability and tensile strength of the solder could be effectively improved by adding Pr.