There is growing evidence that the RoHS directive banning lead solders in electronic equipment has fallen victim of the Law of Unintended Consequences. The ban led to a massive technical effort to bring a variety of lead-free solder substitutes into production. But comprehensive studies now show that some of the lead-free solders may cause more environmental damage than the leaded solder they replace.
How could this happen? The decision to ban lead solders was based upon the hypothesis that the leaching of lead solder from discarded electronic equipment in landfills is a significant health hazard. No studies before or since the directive was issued have proven this hypothesis. Without comprehensive or comparative hazard studies for guidance, the EU Council chose in good faith to err on the side of caution - and err they apparently did.
The RoHS directive triggered major world-wide efforts to find lead solder replacements. Thousands of technical people spent tens of millions of dollars to identify and develop possible candidates for lead-free solders; independent research groups initiated life-cycle studies of anticipated environmental life-cycle impacts.
A life-cycle study estimates the total environmental impact of a product system over its entire life: from obtaining and processing the raw materials through to disposal of the discarded final product. Impacts may include air and water pollution, use of scarce resources, contribution to global warming, and human health hazards.
A 2003 study by the University of Stuttgart estimated the hazards of eleven solders in five potential impact categories: 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, eutectic tin/lead solder ranked in the lowest group in every category. Today’s most popular lead-free solder, tin/silver/copper (SAC), showed more than ten times the human toxicity potential of eutectic tin/lead solder.
In August 2005 the U.S. Environmental Protection Agency (EPA) issued a comprehensive, 472-page lifetime impact study of both leaded and lead-free solders that assesses the lifetime environmental impact of four leading candidate lead-free solders compared to tin/lead solder, in 16 categories.
The EPA study found that SAC has a higher environmental impact than tin/lead in 10 of the 16 environmental impact categories, including energy use, global warming, ozone depletion, photochemical smog, water quality, and public health /cancer. This study does not compare or assign weights between categories, because those are social and political decisions. But the results show that SAC comes with enough environmental baggage to be a dubious environmental improvement over tin/lead.
If SAC is indeed an environmental step backward, can anything be done to reverse the RoHS error? In theory, the EU could remove lead solder from the list of banned materials under RoHS. The EU Commission for Environment is supporting several studies to evaluate both the RoHS and the related WEEE environmental directives from environmental, economic, and social perspectives. The results will support a 2008 proposal by the Commission to the European Parliament for legislative action on any recommended amendments.
But history shows that many non-technical considerations may influence a decision by the political representatives from 25 countries. Companies benefiting from RoHS can be expected to support it strongly, and to resist changes vigorously. Solder manufacturers, equipment suppliers, training organizations, and related businesses have profited from the switchover. They will not stand idly by while this new market is threatened.
For example, a recent pro-RoHS article by a senior technologist at a lead-free solder supplier (Ronald Lasky, SMT Magazine, 8/2006, pg. 8) conceded that lead in electronics is likely not a significant contributor to environmental pollution, nor is it a likely human health hazard. Instead, his justification for the RoHS ban on lead in electronics is to make recycling easier. This will be news to some recyclers, who already recycle 97% of lead that goes into U.S. lead-acid storage batteries.
Regardless of any studies of the effects of RoHS implementation, the political and economic hurdles may already be too high for a significant change. The lead-free solder genie is out of the bottle, and the stopper is hard to replace. Enacted in good faith, tripped up by unintended consequences, the new perils posed by RoHS lead-free solders may exemplify the cynical maxim: “No good deed shall go unpunished.”
GEORGE A. RILEY, contributing editor, may be contacted at Flip Chips Dot Com, 210 Park Ave. #300, Worcester, MA 01609; 508/753-3572; E-mail: firstname.lastname@example.org.