Electroless Deposition of Highly Solderable Fe-Ni Films

The simultaneous electroless-deposition of Fe and Ni is challenging because Fe has a more negative standard reduction potential than Ni.In this study, FeNiP electroless deposits with Fe content up to 97 at.% were prepared by complexing with disodium ethylene diamine tetraacetate (EDTA-2Na).The addition of ETDA-2Na complexing agent effectively reduced the difference in the electrode potential between Ni and Fe from 0.21 V to 0.156 V, resulting in Fe-Ni depositions with very high Fe concentrations.The iron concentrations of deposited films were systematically investigated as functions of bath temperature, concentrations of EDTA-2Na and DTPA, mole ratio of Fe 2+ /Ni 2+ and contents of NH 3 •H 2 O in the plating bath.The solderability of electroless FeNiP deposits with Sn and SnAgCu solders was found to increase with the iron content in the deposits from 0 at.% to 85 at.%, and to be better than that of the electroless NiP.