Effect of surfactant on electrodeposited Ni–P layer as an under bump metallization

In the microelectronic industry, the nickel plating has been used as the under bump metallization (UBM). The electroplated process was demonstrated to be a favorable alternative approach to produce the Ni–P layer as UBM. In this study, the role of sodium dodecylsulfate (SDS) addition in electrodeposition was investigated. The variations on surface morphology and surface roughness in the SDS-added process of electroplated Ni–P were revealed with both field emission scanning electronic microscope and atomic force microscope. The influence of SDS addition process in wettability of several commercial solder pastes, including Sn–37Pb, Sn–3.5Ag, and Sn–3.0Ag–0.5Cu, on electroplated Ni–P with various phosphorous contents was evaluated. The surface morphology and the surface roughness of Ni–P layer were affected by SDS addition. It was demonstrated that modified surface morphology and surface roughness acted to enhance the wettability of electroplated Ni–P. In addition, the interfacial reactions between Sn–3.0Ag–0.5Cu and electroplated Ni–P UBM with SDS addition during deposition was also probed and discussed.