| 摘要 |
A tin nickel surface, e.g. the protective plating on exposed metallic portions of electrical components such as printed circuit boards, is activated prior to immersion in an electroless gold solution to deposit thereon an even solderable layer of gold by degreasing the surface, e.g. first immersing in HCl solution then in hot alkaline cleaner, and rinsing, and then immersing it in an aqueous solution of O-phosphoric acid e.g. 30-60% by weight and at least one a -hydroxy polycarboxylic acid e.g. citric or tartaric acid, preferably at 100 DEG C. |
