METHOD TO FORM SOLDER ALLOY DEPOSITS ON SUBSTRATES

摘要

Described is a method of forming a solder alloy deposit on a substrate comprising the following steps i) provide a substrate including a surface bearing electrical circuitry that includes at least one inner layer contact pad, ii) form a solder mask layer that is placed on the substrate surface and patterned to expose the at least one contact area, iii) contact the entire substrate area including the solder mask layer and the at least one contact area with a solution suitable to provide a metal seed layer on the substrate surface, iv) form a structured resist layer on the metal seed layer, v) electroplate a first solder material layer containing tin onto the conductive layer, vi) electroplate a second solder material layer onto the first solder material layer, vii) remove the structured resist layer and etch away an amount of the metal seed layer sufficient to remove the metal seed layer from the solder mask layer area and reflow the substrate and in doing so form a solder alloy deposit from the metal seed layer, the first solder material layer and the second solder material layer.