Figure 1. Human Toxicity Potential, Life-cycle Comparison
Tin/lead solder paste is the top formula. SAC is second from the bottom.3

RoHS Report Excludes Comparisons 
By George A. Riley, contributing editor
A European Union (EU) Commission for Environment report on scientific and technical progress in implementing RoHS declined to consider a U.S. Environmental Protection Agency (EPA) study showing that some lead-free solders may damage the environment more than the tin-lead solders they replace. The July 28, 2006 final report concluded that comparisons of no-lead solders to tin-lead were outside the scope of this scientific review.1           
The RoHS directive, issued in January 2003, bans lead from electronic equipment on the narrow grounds that leaching of lead from electronics equipment into ground water might be a significant health hazard. No comprehensive life-cycle environmental impact studies of lead or its substitutes were then available for consideration.

The directive triggered major worldwide technical efforts to identify and select lead solder replacements. As lead-free solders became known, independent groups initiated life-cycle studies of their environmental impact. A life-cycle study estimates the total environmental impact of a product system over its entire life, from the production of the raw materials to the end-of-life disposal of the product.
In August 2005 the EPA issued a comprehensive lifetime impact study of both leaded and lead-free solders. This 472-page study assesses the lifetime environmental impact of four leading candidate lead-free solders, compared to tin-lead solder.2
As shown in Table 1, in this study, the most popular lead-free solder, tin/silver/copper (SAC) has a higher environmental impact than tin/lead in 10 of the 16 categories, including energy use, global warming, ozone depletion, and public human health – cancer.
An earlier study, by the University of Stuttgart, Department of Life Cycle Engineering, performed life-cycle hazard testing covering fewer impact categories, but with a wider range of solders.3 The five potential impact categories were global warming, acidification, photochemical oxidants, ozone depletion, and human toxicity.
Nine possible lead-free solder replacements were compared with standard eutectic tin/lead solder. In this comparison, today's tin/lead solder shows the lowest or near-lowest adverse impact in every category. For example, Figure 1 shows the comparison for human toxicity potential of solder paste. Tin/lead is at the left; tin/silver/copper (SAC) is second from the right.
Excluding the results of the EPA study and similar comparative evaluations from the implementation report does not slam the door on assessing lead versus lead-free risks. The EU Commission for Environment is continuing to support a wide range of studies on both the RoHS and the related WEEE environmental directives. The impacts, efficacy, and efficiency of the directives will be evaluated from an environmental, economic, and social perspective. The stated objective is a future impact appraisal for review of the directive.4

REFERENCES
1. "Adaptation to scientific and technical progress under Directive 2002/95/EC," a report by Öko-Institut and Fraunhofer Institute for Reliability and Microintegration IZM, prepared for the European Commission, July 28, 2006.
2. "Solders in Electronics: A Life-Cycle Assessment Summary." United States Environmental Protection Agency Publication EPA-744-S-001, August 2005.
3. N. Warburg, IPC APEX 2003. Available at http:leadfree.ipc.org/files/RoHS_15.pdf.
4. EU Environmental Commission, //ec.europa.edu/environment/waste/weee_index.html.
 
Table 1. Environmental Impact: leaded vs. lead-free solder paste.2



         

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