Role of Bi, Sb and In in microstructure formation and properties of Sn-0.7Cu-0.05Ni-X BGA interconnections

The Sn-0.7Cu-0.05Ni solder composition was first introduced in 1999 as a Pb-free interconnection material for the electronics industry and quickly earned widespread popularity as a cost-effective alternative to the Ag-containing solders then being widely promoted as the best way of meeting the requirement of the impending EU RoHS regulations. Recently there has been ongoing industrial interest in the development of next-generation Pb-free and Ag-free electronic solder alloys with enhanced reliability in a wider range of applications. In the search for improved reliability, first generation Pb-free solders are being modified with alloying additions, such as Bi, Sb and In to improve their performance in harsh environments. The present investigation explores microstructures formed in Sn-0.7Cu-0.05Ni-X/Cu solder joints (where X = 0-5wt%Bi, Sb, In or combinations thereof) and explores the correlation between the resulting solder joint microstructures and their mechanical response during shear impact testing.