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We investigated the effect of reflow conditions (temperature and time above the liquidus temperature) on the growth, morphology and location of the ternary (Au,Ni)Sn4 phase in joints made with Ni or Au/Ni substrates. We considered joints created with Au0.1Sn99.9 or Au0.1Pb26Sn73.9 solders reflowed on Ni substrates, and Sn94.35Ag3.8Cu1.85 solder reflowed on Au/Ni metallization. The Au0.1Pb26Sn73.9 solder alloy reflowed on a Ni substrate at 185°C for 30 s above liquidus and subsequently annealed at 150°C gave rise to two layers of intermetallic compounds at the solder/substrate interface, Ni3Sn4 and (Au, Ni)Sn4. However, when this solder alloy was reflowed at 235°C for 30 s above liquidus, only one interface layer was observed, Ni3Sn4, while the (Au,Ni)Sn4 ternary phase was found to grow in the bulk of the solder. The SnAgCu/Au/Ni joints were reflowed for 74 s above liquidus and the peak temperature attained was 244°C. (Au,Ni)Sn4 phase was observed to form in the bulk of these joints upon reflow, with a Cu content less than 1 atomic percent. This intermetallic compound remained in the bulk of the joint as the samples were annealed at 150°C up to 261 hours. For the Au0.1Sn99.9/Ni system, only one layer, the Ni3Sn4 phase, was found to grow at the solder/substrate interface, both after reflow (at 260°C for 46 s above liquidus) and for an annealing schedule at 150°C of up to 49 hours.