| 摘要 |
<p>An environmentally innocuous effective replacement for thiourea is disclosed for use as a complexing agent in displacement plating processes in which the plating solution is applied to the substrate surface to be plated by immersion or by spraying, cascading, pouring and the like. The replacement complexing agent is an unsymmetrical dialkylimidazole-2-thione compound having the formula: <CHEM> wherein A is methyl or ethyl, and when A is methyl, B is a C3 to C6 alkyl or cycloalkyl group, and when A is ethyl, B is a C4 to C6 alkyl or cycloalkyl group. Of this class of compounds, 1-methyl-3-propyl-2-thiocarbonyl-2,3-dihydroimidazole is preferred for immersion tin plating. This class of complexing agents is particularly useful in spray displacement tin plating for the manufacture of printed circuit boards wherein free tin metal is added to the plating solution.</p> |
