Wetting Behavior and Interfacial Characteristic of the Sn-3.5Ag Alloy on Ni Substrates

Wetting behavior and interfacial characteristic of the Sn-3.5Ag/Ni system are investigated by sessile drop method at the temperature range of 523~773K. The reactive wetting processes demonstrate that: contact angles between the solder and Ni substrate decrease as exponential decay and the equilibrium contact angles decrease monotonously with the temperature increasing. Triple-line mobility is enhanced as the temperature increases. Compositions of the Sn-3.5Ag/Ni interface are identified by EPMA and EDS analysis as Ni3Sn4 adjacent to the solder and Ni3Sn adjacent to the Ni substrate, respectively. The formation of the interface IMC was known to greatly improve the reliability of the solder joints in integrated circuits.