Electrochemical migration of Ni and ENIG surface finish during Environmental test contaminated by NaCl

摘要

The electrochemical migration (ECM) mechanism occurs at the presence of moisture in the case of operating circuits and results in shorts (dendrites) between adjacent conductor lines/traces. Dendrite growth occurs as a result of metal ions being dissolved into a solution from the anode and deposited at the cathode, thereby growing in treelike formations. In this study the water condensation process and ECM behavior of Nickel (Ni), Electroless Nickel Immersion Gold (ENIG) and pure copper were investigated using Thermal Humidity and Bias (THB) test in NaCl environment. The THB results show that Cu has higher ECM resistance than Ni and ENIG surface finishes, which was an unexpected result. The main influencing factors of the water condensation (e.g.: surface roughness, thermal parameters) and the ECM processes (precipitates and dendrites) were investigated and discussed in details. Furthermore, a novel ECM model for Ni and NiAu surface finish was established using THB test in case NaCl contaminated samples.