Provided are a semiconductor lead frame, a semiconductor package having the semiconductor lead frame, and a method of plating the semiconductor lead frame. The method includes preparing a substrate formed of a Fe--Ni alloy (alloy 42), and a plating layer that contains grains less than 1 micrometer in size and is plated on the substrate. The growth of whiskers when a Sn plated layer is formed on a substrate formed of a Fe--Ni alloy (alloy 42) can be suppressed by minimizing the grain size of the Sn plated layer.