Effect of flux on the wetting characteristics of SnAg, SnCu, SnAgBi, and SnAgCu lead-free solders on copper substrates

• Published in: Journal of electronic materials 2006-07, Vol.35 (7), p.1530-1536
• Main Authors: ARENAS, Mario F, MIN HE, ACOFF, Viola L
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Contact angle; Copper; Exact sciences and technology; Intermetallic compounds; Lead free solders; Materials science; Physics; Solid-fluid interfaces; Substrates; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Wetting
• ISSN: 0361-5235; 1543-186X
• DOI: 10.1007/s11664-006-0144-7

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. [PUBLICATION ABSTRACT]