Tin Silver alloy (Lead-free) is currently the material of choice for bumping in WLP technology. The deposition of this material is accomplished with a selective electroplating method. The SnAg plating solution consists of several key components such as Ag, Sn, Acid and Organic additives. The concentrations of each of these components must be carefully controlled because an out of spec concentration will affect the plating deposition rate, uniformity, shape and/or void occurrence within the solder bumps. This paper describes the method of analyses for each of the plating components in the SnAg plating solution and their effects on the bumps when they are out of the specified control limits. The data obtained for actual electroplating process will be shown.

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