| Abstract Scope |
Interfacial reactions during reflow between near eutectic SnAgCu solder and Au/Ni substrates profoundly affect final solder joint microstructure. Reaction products and morphologies are affected not only by time and temperature of anneals, but by small changes in the concentration of the noble metals in the solder. Such dependencies were examined for a range of conditions using differential scanning calorimetry to impose a precise thermal history upon the samples. Quantitative relationships between the growth kinetics of both (Cu,Ni,Au)6Sn5 and (Ni,Cu)3Sn4, and the initial Cu supply (Cu concentration and solder volume), and the thermal conditions were examined. As previously observed, for high Cu concentrations, (Cu,Ni,Au)6Sn5 initially formed at the SnAgCu/Ni interface. When the Cu concentration in the solder decreased to 0.32% wt., (Ni,Cu)3Sn4 was observed to form at the (Cu,Ni,Au)6Sn5 /Ni interface. Under certain conditions, the (Cu,Ni,Au)6Sn5 intermatellic layer or (Ni,Cu)3Sn4 was observed to spall at the interface. |