Sn-Co-(Cu) / Ni solid/solid interfacial reactions

Soldering is an important jointing technology in the electronic packaging industry. It has recently gained much more attention due to the Pb-free requirements and various emerging techniques, such as ball-grid array (BGA), flip-chip and through-silicon via (TSV). Although Sn-Ag-Cu solders are the most popular Pb-free solders, there are still various problems which need to be overcome. There are thus still a lot of continuing efforts to developing new solders and improving existing solders. Among the various Pb-free solders, Sn-based solders with added Co have been studied. It has been found Co additions are very effective in reducing the undercooling and refining the microstructures of solder joints.