The origins of nodule formation in electroless nickel-phosphorus deposition were investigated. It was found that the pretreatment and plating conditions influenced the formation of nodules.
Nodules were observed in the fractographs of the depositions depending on changes in the surface morphology of the copper substrate when the plating baths included mono- or di- carboxylic acids. On the other hand, nodules were not observed in the fractographs of the depositions with plating baths that contained hydroxycarboxylic acids.
Nodules tended to be less likely to form when the deposition rate was relatively low and the phosphorus content of the deposition was high.