The kinetics of formation of ternary intermetallic alloys in Pb-Snand Cu-Ag-Sn Pb-free electronic joints

摘要

A simple model of the formation ofAu_0.1Ni_0.1Sn_0.8 in Pb-Sn solder/Niinterconnects is examined by numerical simulation. Previous experimentalobservation has shown that after reflow the interface consists of the Ni₃Sn₄ alloy between Pb-Sn solder and Ni, with Audistributed through the PbSn solder ball. Au_0.1Ni_0.1Sn_0.8 was observed to form at the Pb-Sn solder/Ni₃Sn₄ interface during annealing at 150° C in a numberof studies. The numerical simulation was used to calculate the maximumflux of Au to the interface, and with the assumption that this Au wasimmediately incorporated in toAu_0.1Ni_0.1Sn_0.8 a maximum rate offormation of Au_0.1Ni_0.1Sn_0.8 wascalculated. This rate was found to be similar to measured rates offormation of Au_0.1Ni_0.1Sn_0.8 from twodifferent studies. The formation of(CuNi)6SnS in Sn-Ag-Cu/Ni solderinterconnects was discussed within the context of these observations