To make oxidation difficult to occur in the surface of metal by preventing the formation of pinholes in the surface of the metal as much as possible and to suppress the occurrence of solder transcription by reducing a contact resistance value.
By performing electroless plating on a substrate 10 made of a rod-shaped copper alloy with nickel as backing metal 11, nickel of a thickness between 1 μm and 3 μm is formed on the surface of the substrate 10. By performing electrolytic plating on the backing substrate 11 with gold as surface metal 12, gold of a thickness between 1 μm and 3 μm is formed on the surface of the backing metal 11. In the surface metal plating processes, titanium oxide particles of a few volume percents of having an average particle diameter D between 0.1 μm and 0.3 μm are suspended in a gold plating solution for the electrolytic plating. The titanium oxides are dispersed in the gold after the electrolytic plating and subjected to heat treatment at temperatures between 300°C and 350°C for a predetermined time after the surface metal plating processes.
ONODA MASAHIRO
UNO YUJI
SANYUU KK
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