Electroplating on Connectors to Prevent Tin Reflow Discolouration

摘要

Now that lead-containing solders are prohibited in electrical and electronic assemblies, tin solders are a widely used replacement. During reflow, a colouring effect is observed which, though it has no adverse technical effects, is deemed unacceptable by most customers. A solution to this problem is to use a satin-finished tin coating with larger than usual grain size, or else an undercoating of nickel-phosphorus. An acidic post-treatment which selectively removes surface defects and oxidation products also ameliorates the problem. The optimum approach is to use all three methods, that is a nickel-phosphorus undercoat with satin-finish tin and a subsequent acid immersion.