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The electronics industry relies on step-soldering during device attachment or subsequent reworking of heavily populated hybrid microcircuits and multilevel networks. Although there are many low to intermediate melting solder alloys that are commercially available, their wettability on typical base metals, such as Cu, Ni, Au, and Sn, are not well characterized. This investigation examines the wetting behavior of several In, Sn, Pb, Bi, and Ag containing solder alloys on Ni-Sn plated aluminum alloy substrates with soldering temperatures ranging from 145 to 200(degrees)C. Two rosin mildly activated (RMA) fluxes were included in the study. The wettability experiments were conducted with a Sandia designed wetting balance system. Wetting differences were observed between the two fluxes. The more active flux gave better wetting results and less variability in the meniscus terminations at the lower soldering temperatures. Wetting generally varied from adequate to very good. The Bi-bearing alloys generally gave the lowest wetting values. Work is in progress to determine the effects of aging on intermetallic growth and subsequent mechanical strength. 12 refs., 12 figs., 2 tabs.