Lead frame having outer leads coated with a four layer plating

A lead frame comprising a die pad for mounting a semiconductor element thereon, inner leads electrically connected to electrode pads of the semiconductor element and outer leads connected to the inner leads to function as external terminals, wherein

• at least both the ends of the respective inner leads and the ends of the respective outer leads opposite to the inner leads are coated with a four-layer plating,
• first three layers in the four-layer plating from the topmost surface thereof are made of Au, Ag and Pd, respectively,
• a Au layer made of Au is the topmost layer, and a Ag layer made of Ag is formed between the layer made of Au and a Pd layer made of Pd, and
• the Ag layer is not less than 0.05 μm and not more than 0.5 μm in thickness.