Microstructural characterization of electroplating Sn on lead-frame alloys

Electroplating Sn plays an important role in the lead-free age because of its excellent solderability and many other advantages. In this work, bright Sn was electroplated onto both C194 and FeNi42 alloys. The plating parameters, substrate effect, barrier layer effect and IMC formation were investigated through detailed microstructural characterization of the Sn films, barrier layers and cross-sections. It was found that the current density, plating time, substrate type and barrier layer play an important role in determining the fine structures of the Sn deposition. Interfacial reactions to form intermetallic compounds (IMC) was also observed. Replacing the traditional Ni barrier with Ni nanocone barrier was found to result in a quite different IMC formation/distribution.