| 摘要 |
PURPOSE:To enable to reduce an Ag-plating layer in a leadframe in which Ag- plating is performed on the surface to improve soldering by sequentially laminating an Ni-primary plating layer, an Sn-Ni-Co alloy plating layer and a plating layer of metal including Ag. CONSTITUTION:After a substrate 1 made of phosphorus bronze is punched, pretreated such as degreased, pickled, an Ni-primary plating layer 2, an Sn- Ni-Co alloy plating layer 3 and an Ag-plating layer 4 are sequentially laminated on a semiconductor element stationary portion 5 and an internal lead terminal 6 by an electrolytic plating method. The Sn-Ni-Co alloy is required that the total of the content rates of Sn and Co is 20-90% and the content rate of the Co is 0.5-15% as well as the residue is Ni. Thus, the bondability of the Ag-plating layer is not decreased even by the high temperature heating in the packaging step such as plastic, and the decrease in the characteristics such as the discolor to the Ag-plating layer can be suppressed, and the reduction in the thickness of the Ag-plating layer can be accordingly performed. |
