US Patent 10229871 Lead frame

A lead frame includes a metal plate, having a surface partitioned, by a concavity, into columnar areas, and a plating layer including stacked Ni, Pd and Au layers on the surface at top faces of the columnar areas, to form columnar pieces, which serve as internal connecting terminals, respectively, or as internal connecting terminals and pads, respectively. Each of the columnar pieces has, around a circumference of an upper portion thereof, curved regions intervening between straight regions. In each curved region, a side face of the plating layer protrudes outwardly in a horizontal direction from an uppermost portion of a side face of the metal plate in each of the columnar pieces. At a center of each straight region, the side face of the plating layer has substantially a same horizontal position as the uppermost portion of the side face of the metal plate in each of the columnar pieces.