Toxicity and worldwide environmental regulation of lead-free solders

Although the movement to regulate and eliminate lead bearing solders picks up speed worldwide, there has been little published research on the environmental effects of the available lead free formulations. Most detrimental environmental effects from soldered products occur in their final disposal. Soldered products are disposed in municipal landfills, not the highly regulated hazardous waste landfills. Waste products such as dross, scrap boards and assemblies, and raw metal are disposed of during various manufacturing processes. This article shows the results of the study of seven lead free solder alloys: Tin/Silver/Copper, Tin/Silver, Tin/Copper, Tin/Antimony, Tin/Indium, Tin/Silver/Bismuth, and Tin/Bismuth. These alloys were tested in the various physical forms most likely to occur from PCB fabrication, assembly, and finished product disposal to determine the environmental impact from each alloy. Management of waste in industrialized countries ranges from highly regulated, specific, government controlled operations to practical non-existence. Within this range fall most industrialized countries which significantly regulate industrial/commercial hazardous waste, with or without also regulating household hazardous waste disposal. Hazardous waste is defined as any waste that may `pose a substantial present or potential threat to human health and the environment when improperly treated, stored, or otherwise managed'. When waste is disposed it is weathered by rainfall and reactions with other wastes, which allows metal elements and their salts to be leached from the metal surfaces of the waste. If the metal bearing leachate is allowed to contact stormwater, groundwater, or to migrate into groundwater, local drinking water supplies are threatened with contamination. The research presented found that alloys containing antimony leached above regulatory limits in all cases. Alloys containing silver also showed potential for environmental impact.