| 摘要 |
PROBLEM TO BE SOLVED: To enhance adhesion between layers and to prevent a coating layer from being stripped off at the time of coating the copper alloy substrate of a lead frame with an Ni layer and a Pd layer to improve the corrosion resistance, solderability and bondability when wires are bonded by arranging an Au layer between both layers and forming a diffused layer contg. Ni and Pd. SOLUTION: An Ni plating is applied on the surface of the substrate 11 of a frame to improve the solder wettability, and then gold strike plating including diffusion treatment, Pd plating and further gold strike plating are successively conducted to form a laminated coating. Consequently, the upper face of an Ni layer 14 on the substrate 11 surface is bonded to the Au layer 16 through an Ni-Au diffused layer 15, and further a Pd layer 18 on the Au layer 15 is joined to the Au layer 16 through a Pd-Au diffused layer 17. Accordingly, a multilayer coating film consisting essentially of the Ni layer 14 and Pd layer 18 is firmly joined to the substrate 11, and the stripping and especially that of the Pd layer 18 are prevented when the frame is bent. |
