Emerald Group Publishing Limited
Copyright © 2000, MCB UP Limited
Lead free - will it help our environment?
Keywords Lead-free soldering
It is now two years since I took over the editorship of SSMT and I have found it a very rewarding experience. During that time the journal has reported on the rapid growth in the use of advanced SMT technologies, such as µBGA and flip chip, and other continuing advances in soldering science and technology. However, I believe one of the most significant recent developments in our industry is the now widespread awareness of its environmental responsibilities and many engineers I have talked with have a genuine personal concern for minimising the environmental impact of their products and processes. This growing awareness has been promoted to a large extent by the proposed WEEE directive and, in particular, the looming prospect of a move to lead-free soldering processes. However, while many see the core WEEE proposals for encouraging the recycling of electronic products as an important step in achieving a sustainable industry, I have not found one person who will unequivocally say that they believe that a move to lead free is the right thing to do. So, will a move to lead free really benefit the environment or will it just give the public and politicians the cosy feeling that we are all working together for a better world?
There is no doubt that lead is a particularly nasty poison (and hopefully none of us would force our children to eat their games consoles to try to prove otherwise!) so we should strive to reduce the possibility of its entering the food chain, but is its use in soldering really a significant risk? It is well established that only a tiny proportion of lead production is for electronic solders, so their elimination will make little difference to the emissions from the mining and refining industry. There is also no reason why the assembly industry has to produce significant emissions or why any product containing lead based solder should release it during its normal life. The major concern must therefore be at the end of life, but there are existing technologies for the recovery and re-use of lead from electronic products, which, within Europe at least, the WEEE recycling proposals should ensure occurs. So where will the benefit be from a lead ban? One argument is that not all electronic products will end up being recycled, but one of the major uses of lead is in vehicle batteries and the fact that the majority are recycled is used as an argument that they are not the most serious lead related problem. Yet if only one of these batteries ends up in a landfill or a road side ditch then how many thousands of video recorders or computers would have to be dumped to release the same quantity of lead?
So going lead-free may have minimal benefits for the environment, but what of the potential disbenefits? Higher reflow temperatures inevitably mean higher energy costs and even if superheats are reduced significantly this is likely to result in at least a 10 per cent rise in energy consumption. These higher temperatures may have further knock on effects - perhaps a need for the energy hungry use of inert atmospheres or more aggressive cleaning processes to remove baked on flux residues. PCB laminate and component packaging materials may also have to change. Will the manufacture of these materials be more or less damaging to the environment? And does anyone yet know how to recycle products containing lead free solders, particularly if there is to be a mix of solder alloys used, perhaps containing a mix of tin, zinc, copper, silver, antimony, bismuth, indium, plus numerous other minor constituents?
Early in the history of the environmental movement simplistic and emotional arguments were often used, such as that using glass containers only once was wrong because a lot of energy goes into their manufacture and they are usually capable of being used several times. Subsequent detailed life cycle analysis, however, showed that the (environmental) costs of collection, return and cleaning in the majority of cases outweighed the benefits and in many countries glass recycling, rather than re-use is now the norm. It is depressing, though not surprising, that now legislators are taking the environment seriously they should be making proposals based on the simplistic argument that lead is bad so it must go, without commissioning studies comparing the overall life cycle costs of the alternatives. Someone needs to take a long hard look at the real costs and benefits of going lead free to make sure that it is really the right thing to do. For if a ban happens and we subsequently find out it was the wrong decision, in actual fact harming the environment, what chance will there be for a return to using tin-lead? Probably none.