SOLID-STATE INTERMETALLIC COMPOUND GROWTH BETWEEN COPPER AND HIGH-TEMPERATURE, TIN-RICH SOLDERS .1. EXPERIMENTAL-ANALYSIS

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 square-root t dependencies at the lower temperatures of 70, 100, and 135-degrees-C, and a t0.42 dependence at 170 and 205-degrees-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 square-root t dependence at the three lower temperatures and t0.42 growth kinetics at 170 and 205-degrees-C. The combined apparent activation energy was 61 kJ/mol.