It’s been a year since the Waste Electrical and Electronic Equipment Directive and the Restriction of Hazardous Substances Directive (RoHS) have mandated that lead be eliminated from electronic systems. Consequently, this has led engineers to a high interest in using lead-free soldering alloys. Some of the harmful alloys that are used in normal soldering are tin, copper, silver bismuth, indium, zinc, and antimony.
So why are these dangerous to humans everywhere? Prior to 1930, all homes used lead pipes to transport water to and from houses. Now, most homes use copper piping. However, this is still a problem because most of these copper pipes were assembled using solder, which is approximately 50% lead. This harmful lead, whether through piping or from the solder used to blend the pipes, is especially prominent in the water a few years after installation of the pipes.
In addition to lead solder being applied in piping, it is often used in some basic household staples like canned food. Canned fruit and vegetables, canned juices, and tomato sauce are extremely likely to contain high levels of lead from the solder used to solder the tops of the cans on. In spite of these dangers, the FDA still has not banned lead solder in food packaging, but many manufacturers are taking precautions against this.
Some of the alloys that could replace soldering products containing lead are Sn95.5Ag3.9Cu0.6 for surface mount reflow soldering and Sn99.3Cu0.7 for wave soldering. Sn96.5Ag3.0Cu0.5 is recommended for reflow soldering with SnAg and SnZnBi as alternative alloys. The SnAgCu alloy family is the most popular choice at present for lead-free alternatives.
There are many lead-free products for sale including lead-free solder paste, lead-free flux, lead-free solder wire, and other lead-free products that can be used as substitutes for lead products. If you haven’t been living under a rock lately, you have probably heard of the Mattel fiasco where over a million toys were recalled because of the lead paint that was used on them. People are so worried about children being exposed to lead that they are pushing Mattel to set up a fund to test children for lead poisoning. This recent disaster will hopefully bring much needed attention to the dangers of lead.
For more information on how you can safely solder using lead-free products click here or for some technical information on lead-free alloys visit the NIST website. For ways to guard yourself against lead in your environment check out the Environmental Health Threats website.