PROBLEM TO BE SOLVED: To improve temporal stability of a mildly acidic or neutral electroless tin plating bath.;SOLUTION: The electroless tin plating bath has a pH of 2.5-7 and comprises (A) a soluble stannous salt, (B) at least one acid chosen from an inorganic salt and an organic salt, (C) thioureas, (D) a complexing agent comprising oxycarboxylic acid for stabilizing the bath and (E) a metal ion chosen from the group consisting of chromium, manganese, iron, aluminum, vanadium, zirconium and molybdenum, provided that the amount of the metal ion (E) is 0.01-6.0 mol/L. Due to the coexistence of a specific metal ion such as iron, manganese and chromium at a prescribed concentration with oxycarboxylic acid, the electroless tin plating bath becomes mildly acidic or neutral and shows an excellent temporal stability.;COPYRIGHT: (C)2009,JPO&INPIT
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