Wettability, Interfacial Intermetallic Growth and Joint Shear Strength of Eutectic Sn�Cu Solder Reflowed on Bare and Nickel-Coated Copper Substrates

Abstract

In the present study, wettability, interfacial intermetallic growth and shear strength of Sn�Cu eutectic solder solidified on bare as well as nickel-coated copper substrates were examined. Sn�0.7Cu solder was reflowed over the substrate for reflow times ranging from 10 to 500�s at 270��C. Samples were cooled by quenching in water. The wetting behavior was similar on both the substrates. The corresponding time period to the end of gravity zone (Tgz) was measured from the relaxation curve obtained from wetting studies. Tgz was found to be 25�s for Sn�0.7Cu on bare and 50�s on Ni-coated copper substrates. The intermetallic compound layer thickness was fitted to a growth model to study the growth kinetics. The integrity of solder/substrate joint was assessed by performing ball as well as single-lap joint shear tests. The shear strength was found to be maximum at Tgz for all solder/substrate systems. � 2019, The Indian Institute of Metals - IIM.