Device for mounting semiconductor element, lead frame, and substrate for mounting semiconductor element

Abstract

A device for mounting a semiconductor element includes a metal plate serving as a base, a roughened silver plating layer with acicular projections, formed on at least either of: (a) top faces; and (b) faces that form concavities or through holes between the top faces and bottom faces; of the metal plate, and a reinforcing plating layer covering, as an outermost plating layer, an outer surface of the acicular projections in the roughened silver plating layer. The roughened silver plating layer has a crystal structure in which the crystal direction <101> occupies a largest proportion among the crystal directions <001>, <111>, and <101>. An outer surface of the reinforcing plating layer is shaped to have acicular projections with a surface area ratio of 1.30 or more and 6.00 or less to the corresponding smooth surface, as inheriting the shape of the acicular projections in the roughened silver plating layer.