The consequences of using lead-free solders for the repair of electronic hardware after initial assembly are addressed. As a method to understand the effects of Pb contamination in binary eutectic Sn-Ag solder, microstructural changes were studied as a function of both Pb concentration and cooling rate. Additions of 0.01, 0.10, 1.00 and 10.00 %, by weight, Pb were alloyed into 96.5Sn-3.5 Ag eutectic solder. Three different cooling rates were used to simulate equilibrium, moderate and rapid solidification. Microstructural characterization and phase identification were performed by optical microscopy, scanning electron microscopy (SEM), back scattered electron (BSE) imaging and x-ray mapping. Overall, melting temperatures and the microstructures were not significantly altered until the lead concentrations reached 1.00 wt. % or greater. At these concentrations, the formation of a distinct Pb-rich () phase occurred. This phase was evident at both the equilibrium and moderate cooling rates At all Pb concentrations, increasing the cooling rate resulted in refining the Ag3Sn intermetallic needles and the Sn-rich (-phase) regions. Pb concentrations of up to 0.10 wt. % refined the equilibrium structure, while coarsening was noted to occur at 1.00 wt. % Pb. At 10.00 wt. % Pb, the structure consisted of three predominant phases (Ag3Sn, -Sn, and -Pb) and did not resemble the structures exhibited at the lower Pb Concentrations. At this composition the eutectics containing the Ag3Sn phase were divorced at all solidification steps. .