Lead is one of the most developed elements on Earth, but in sufficient quantities, it can be a serious hazard to the environment. The lead in solder used in electrical and electronic equipment is dissolved by acid rain and leaches into the underground water supply, raising questions about polluted drinking water and food. Although component manufacturers are working toward removing lead from their products, it remains a challenge because of the diversity of manufacturers in the industry and the lack of lead-free solder alternatives. Still, the use of lead in solder has limited life expectancy and is likely be phased out in the next five to 10 years.
The push to eliminate lead comes from Europe and Japan. The European Commission directive on Restriction of Hazardous Substances requires certain substances (including various metals such as lead, mercury, cadmium and hexavalent chromium) to be phased out of new electrical and electronic equipment beginning in 2006. There are some exemptions to this ban on the use of lead, but not solder.
To meet Japanese consumer preferences for environmentally friendly products, Japanese component manufacturers and OEMs are already removing lead from their manufacturing processes. The Japan Electronics and Information Technology Industries Association Roadmap indicates that use of lead-free solder in all new products will be achieved in 2003. As a result, Japan is now well ahead of Europe and the United States in developing lead-free solder technologies.
In the United States, the debate still continues on the financial and environmental impact of moving to lead-free solder. In some areas, there is a reluctance to move away from traditional solders, especially when questions about the damage of leaching remain. Lead is one of the most inexpensive elements and replacing it with any other metal will increase costs. Also, lead-free solder alternatives are not thought to be as reliable as tin/lead solder. Although the United States has yet to move to lead-free, manufacturers selling products in Japan and Europe are going to have to comply with the new laws.
It is widely agreed that there is no drop-in replacement for tin/lead solder, but several lead-free solder alternatives have been identified. Tin/silver/copper is emerging as the main replacement for lead for solder paste and solder balls. The reliability of tin/silver/copper appears to equal that of tin/lead. Tin/silver/copper is capable of forming reliable solder joints and should be considered as a replacement for tin/lead.
However, there are still some problems with lead-free solder. Tin/silver/copper has a slightly higher melting point than tin/lead. Components have to be exposed to higher temperatures during the soldering process. The effects of higher processing temperatures and longer processing times raise concerns about the reliability of components from encapsulated devices to connectors.
Plastic molded parts must also be considered. Most plastic molded parts will need to be evaluated for thermal degradation ranging from simple discoloration to complete meltdown of the packaging. Thermoplastic materials will need to be monitored for heat stress. Plastic parts can also shrink, warp or have critical features move during exposure to these higher temperatures.
Manufacturers are already beginning the inevitable transition to lead-free on a global scale. It will accelerate over the next few years, as the perceived barriers to the implementation of the new technology are addressed and the industry reacts to the forces of legislation. Manufacturers need to be aware of the latest research and knowledge on lead-free. Only after companies have hands-on experience with lead-free products, will there be complete confidence in the lead-free process.
Please feel free to contact me if you have any questions or comments about this article or the magazine in general. Thanks for taking the time to read Connector Specifier.
Susan Woods, Editor-in-Chief
susanw@pennwell.com
