Abstract
The effect of flux on the wetting characteristics of four lead-free solders, Sn-3.5Ag, Sn-0.7Cu, Sn-3.5Ag-4.8Bi, and Sn-3.8Ag-0.7Cu (wt.%), on copper substrates have been studied at 240, 260, and 280°C. The fluxes investigated were rosin (R), mildly activated rosin (RMA), and activated rosin (RA). The wetting tests were conducted using the sessile-drop method. Results showed that fluxes significantly affect the wetting properties of the solders. Contact angles ranging from 10° to 30° for RMA, 20° to 30° for RA, and 35° to 60° for R were obtained. The effect of temperature on contact angle depended on the type of flux used. The contact angle decreased with increasing temperature; however, in some cases the contact angle was independent of temperature. The Sn-3.5Ag-4.8Bi exhibited the lowest contact angles indicating improved wettability with addition of bismuth. The microstructure of the solder/copper interface was analyzed by scanning electron microscopy.
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Arenas, M.F., He, M. & Acoff, V.L. Effect of flux on the wetting characteristics of SnAg, SnCu, SnAgBi, and SnAgCu lead-free solders on copper substrates. J. Electron. Mater. 35, 1530–1536 (2006). https://doi.org/10.1007/s11664-006-0144-7
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DOI: https://doi.org/10.1007/s11664-006-0144-7