The lead frame includes outer leads plated with tin (Sn) alloy so as to withstand the high temperatures generated during a subsequent semiconductor packaging process. In addition to the outer leads, the lead frame includes a die pad and inner leads composed of a base metal, such as copper (Cu), a copper alloy, or a nickel alloy. The die pad and the inner leads are plated with silver for improved conductivity. In order to withstand relatively high temperatures as well as to resist corrosion and have good solder wettability, the outer leads are preferably plated with a tin antimony alloy, such as a tin-antimony alloy consisting of 90.+-.5 weight percent of tin and 10.+-.5 weight percent antimony. Alternatively, the outer leads can be plated with a tin-antimony-lead alloy, such as a tin-antimony-lead alloy consisting of 10.+-.5 weight percent of tin, 10.+-.5 weight percent of antimony and 80.+-.10 weight percent of lead. A method of plating a lead frame is also provided.