| 摘要 |
PURPOSE:To prevent the generation of defects, such as the stains, discoloration, etc. of a plating surface or the discoloration (unevenness of baking) of a lead frame blank due to heating by executing noble-metal plating and washing a lead frame by a washing by the aqueous solution of a weak acid. CONSTITUTION:Noble-metal plating is executed, and a lead frame is washed by a washing by the aqueous solution of a weak acid. That is, alkaline dust, mists, etc., causing the stains and discoloration of a plating surface and discoloration in case of the heating of a lead frame blank are neutralized by the action of the weak acid and removed, and the whole lead frame is etched extremely slightly, and impurities such as plating-liquid residue are removed. A substance containing one kind or two kinds or more of tartaric acid, citric acid, succinic acid, maleic acid, malic acid, oxalic acid, formic acid, acetic acid, propionic acid, lactic acid, boric acid and potassium hydrogen phthalate is preferable as the weak acid in the washing. It is desirable that the pH of the washing is kept within a range of 2-5. 40-50 deg.C are preferable as the temperature of the washing on washing. |
