Over the last few years, we have witnessed a major push around the globe to manufacture electronic assemblies using more expensive and problematic leadfree solders. The question is why. A number of different reasons have been given, although consumer demand and legislative requirements for more environmentally friendly products generally top the list. This effort is rooted in the sad effects of lead poisoning on children who have ingested paint chips with older lead-based pigments. But the link to electronics has been made without scientific proof.
Paradoxically, a careful look at the leadfree issue reveals that its supposed environmental benefits are very weak and faulty. In truth, leadfree solders appear to be a very serious misstep for the electronics industry. We are poised to take a nonproblem and create a truly serious situation in its place. This could be very costly for the industry in terms of the manufacture and reliability of our products. It now looks like we will do this as we actually degrade the environment with our good intentions. Because these are serious charges, let's examine a few points.
Is lead in electronic solders a demonstrable cause of environmental pollution? No. An EPA-funded study on landfills showed that only two of 146 sites were definitively problematic in terms of lead. That was because of large industrial lead waste deposits found at those sites. Interestingly, lead in human blood plasma has actually gone down dramatically over the last 20 years, mostly due to the elimination of leaded gasoline. Still, no direct link between lead in humans and electronic products has ever been demonstrated. Only the baseless claims of misguided marketing exist.
Is lead in solder a major use of lead and a reasonable target for reduction? No. According to lead- and tin-industry groups, lead use in all solders represents less than 0.5% of all the lead consumed annually, worldwide. Given that electronic solders represent about 50% of all solders, less than 0.25% of all lead comes from electronics.
Are the alternative solders really less toxic? Not necessarily, especially if you happen to be a fish larva or other freshwater microbe. Silver, which also leaches in water, is highly toxic to these creatures; it just isn't a problem for humans. Sweeping changes can only occur after doing a total risk analysis to see the effects at every level.
Are the major proposed lead-free solders more energy conservative? No. On average, these solders melt at temperatures of 40°C higher than traditional solders. A recent NEMI report states that moisture sensitivity ratings for IC packages typically degrade by one level for every 5°C to 10°C increase in peak reflow temperature. This requires a prebaking process that, in turn, consumes even more energy to meet JEDEC's moisture-sensitivity requirements. In light of California's current energy crisis, this seems to be going in precisely the wrong direction.
Moreover, Karl Tiefert of Agilent Technologies recently estimated that conversion to the most frequently proposed leadfree solders will introduce an additional, unneeded 1500 metric tons of carbon dioxide into the atmosphere. This is separate from the additional baking.
There's not enough space here to enumerate the many other undiscussed leadfree concerns. Ultimately, making products more attractive and amenable to recycling is the most environmentally friendly approach. Giving consumers a license to discard their leadfree electronics in a landfill is definitely not such an approach.