Effect of Ni, Zn, Au, Sb and In on the Suppression of the Cu₃Sn Phase in Sn-10 wt.%Cu Alloys

Since manufacturing is transitioning into Pb-free solder development for electronic assembly and packaging, consumer demands for more compact electronics have increased the importance of reliability issues brought about by the increased density of circuitry. Therefore, the role of alloying elements that can be added to common Pb-free solders such as Sn-Cu or Sn-Ag-Cu alloys in enhancing the properties and performance of the solder becomes important. Microstructural analysis along with direct observation in situ synchrotron radiography were used to study the effect of Ni, Zn, Au, In and Sb on the development of phases in Sn-10 wt.%Cu (Sn-10Cu). It was found that adding Ni and Zn to a Sn-10Cu alloy had the greatest impact on the microstructure with the Cu₃Sn phase completely absent after these additions were made. Additions of Au and In also resulted in a reduction in the amount of Cu₃Sn; however, the effect was not as pronounced. Removing the Cu₃Sn phase from Sn-Cu Pb-free solder alloys is a possible approach for the design of more desirable microstructures that translate to better performance in modern electronic packaging.