Solid state intermetallic compound growth between copper and high temperature, tin-rich solders—part I: Experimental analysis

Abstract

An experimental study was performed which examined the solid state growth kinetics of the interfacial intermetallic compound layers formed between copper and the high temperature, tin-rich solders 96.5Sn-3.5Ag (wt.%) and 95Sn-5Sb. These results were compared with baseline data from the 100Sn/copper system. Both the 96.5Sn-3.5Ag and 95Sn-5Sb solders exhibited the individual Cu₃Sn and Cu₆Sn₅ layers at the interface; the thickness of the Cu₃Sn layer being a function of the aging time and temperature. The total thickness of the intermetallic compound layer formed in the 96.5Sn-3.5Ag solder/copper couple showed a mixture of linear and √t dependencies at the lower temperatures of 70,100, and 135°C, and a t^0.42 dependence at 170 and 205°C. The combined apparent activation energy was 59 kJ/mol, the Arrhenius plot showed a knee between the low and high temperature data. The total layer thickness of the 95Sn-5Sb/copper system exhibited √t dependence at the three lower temperatures and t^0.42 growth kinetics at 170 and 205°C. The combined apparent activation energy was 61 kJ/mol.