An object of the present invention, prevention and good solderability of the whisker with juggle (low melting point), the Sn alloy thin film having a thin and uniform thickness without the inconvenience of fine sliding abrasion, etc. and to provide a method of forming.
The invention relates to a method of forming an Sn-Ag-Cu ternary alloy thin film on a substrate, the method and the substrate was immersed in the plating bath, Sn-Ag-Cu ternary are those formed by electroplating an alloy thin film on the entire surface or part of the base material, the plating bath includes at least Sn compound, and Ag compound, a Cu compound, an inorganic chelating agent, and an organic chelating agent wherein the inorganic chelating agent is compounded in the Ag compound 1 by weight 300 parts by mass or less of ratio of more than 1 parts by mass per unit, the organic chelating agent is 1 with respect to the Cu compound 1 part by weight it is characterized in being formulated in parts by mass or more 200 parts by mass ratio.
.BACKGROUND