Properties of (Fe-B)-doped Sn-1.0Ag-0.5Cu solders prepared by mechanical alloying

To introduce boron (B) into the Sn-1.0Ag-0.5Cu (SAC 105) solder, based on the thermodynamic calculations, iron (Fe) is a competent carrier component for bonding B and Sn. The Sn-Fe-B master alloys were prepared by mechanical alloying initially;then, the SAC 105- 0.05(Fe-B) and SAC 105-0.1 (Fe-B) solder alloys were prepared using 72-h-milling Sn-Fe-B master alloys. The preparation process and the properties of solders were studied in this work. For the Sn-Fe-B master alloys, the results show that with the increase in the ball-milling time, the powder changes illustrate a cold welding-crushingcold welding cyclic process. Moreover, the supersaturated solid solubility of (Fe-B) increases gradually in the alloys, matrix and the lattice distortion increases to 0.167% after 72-h milling. Meanwhile, the alloying degree is increasingly apparent, and after 72-h milling, the content of B in the Sn matrix reaches 2.38 wt%. For the solder alloys, with the (Fe-B) content in creasing, the melting point decreases and a significant grain refinement occurs in the matrix. Compared to the benchmark SAC105, the hardness of SAC105-0.05(Fe-B) and SAC 105-0.1 (Fe-B) solder alloys prepared by this method is improved by 20.65% and 34.79%, respectively. The present research provides a novel approach for introducing the immiscible component into the lead-free solder alloys.