Enhancement of solder properties of Sn-9Zn lead-free solder alloy

The eutectic alloy Sn-9Zn was considered as a potential alternative to lead-tin solder alloys when compared with other solders. In this paper, ternary, quaternary and penternary additions of the elements Bi, Cu and In were added to the eutectic alloy as a trial to improve its properties. The results showed that, the penternary alloy has properties superior to those of the binary, ternary and quaternary alloys. The alloy of composition Sn-9Zn-1Bi-2Cu-2In has the most suitable properties as a candidate alloy for lead-free solder. It has a lower melting point, 186 degrees C, which is very close to that of Sn-37Pb solder, a lower value of electrical resistivity, 16.5 mu ohm.cm, compared with that of Sn-37Pb (17 mu ohm.cm), higher value of the Young's modulus, 47 GPa, compared with 45 GPa of Sn-37Pb and a higher value of the Vickers hardness, 191 MPa, compared with 129 MPa of Sn-37Pb eutectic alloy. (c) 2006 WILEY-VCH Verlag GmbH & Co. KGaA.