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November 2014 • SMT Magazine 67 superior—to the older generation of halogen- containing solder materials. In addition, the reflow performance of the halogen-free materi- als with the high-reliability alloy is also particu- larly good. It should be noted, however, that the high-reliability alloy solder joints look less shiny than standard SAC joints because of the slightly non-eutectic nature of the alloy. This is a factor of the alloy and not the fluxing system. conclusions Increasing utilisation of electronics in high- reliability applications—especially within the automotive sector—has driven the develop- ment of higher-reliability solder products. The combination of the novel (90iSC) al- loy pushes the boundary of thermal cycle and thermal shock resistance. The utilisation of the new halogen-free flux platforms offer reduced risk of electro- chemical failures associated with trace levels of halide species present in the post-reflow flux residues. The combina- tion of the new 90iSC high-reliability alloy in combination with cutting edge halogen-free flux platforms signify the future trends for harsh environment/ safety-critical electronics. smt references 1. Seelig K., et al. "Round Robin Test- ing and Analysis of Lead-Free Solder Pastes with Alloys of Tin, Silver and Cop- per," Solder Products Valuation Council, May 2005. 2. Siewart T., et al. "Database for Solder Properties with Emphasis on New Lead- Free Solders," National Institutes for Stan- dards and Technology, February 2002. 3. Engelmeier, W. "Reliability of Lead Free (LF) Solder Joints Revisitied," Global SMT & Packaging. November 2003 [pp. 34–35]. 4. BMW Group Standard GS95011-5. 5. Sornette D., et al. "The Physical Origins of the Coffin-Manson Law in Low Cycle Fatigue," Europhysics Letters, 1992, Vol 20, Number 5 [pp 433–438]. 6. Albrecht H. J., et al. "Pb-Free Alloy Alternatives: Reliability Investigation," SMTA Proceedings, 2009. Figure 10: Comparative reflow of halogen-free solder pastes utilising standard SaC (top) and high-reliability 90iSC (bottom) alloys. HigH-reLiabiLity, Pb-Free, HaLogen-Free soLDer continues arTiCle ian J. Wilding is director of product development, solder materials at henkel ltd. gavin J. Jackson is technical manager, adhesives general industry at henkel ltd.