Environmental work goes on - Packaging

Electronic News, Jan 21, 2002 by Edwin Bradley

Though environmental concerns have abated somewhat during the current economic slump, the electronics industry's efforts to eliminate lead from solder are moving ahead on many fronts.

More than a dozen consortia and many leading manufacturers around the globe are studying alternatives to the tin-lead solder that's been used for decades. As more and more groups study the many implications of adopting lead-free solders, researchers are beginning to share data and work together to minimize duplication of effort to avoid a chaotic situation where different regions and industry segments use different solder alloys. The efforts are in response to increasing pressure from governments that want to stem the growing amount of consumer electronic wastes.

Even though estimates attribute only 0.5 percent to 2 percent of the world's lead usage to the electronics interconnection industry, the increasing production and disposal of consumer electronics is a growing concern. The European Commission (EC) plans to ban lead usage by 2007, with tightened controls for lead-bearing electronic waste beginning in 2006. The EC's proposed directive, Waste from Electrical and Electronic Equipment (WEEE), noted that electrical and electronic waste now represents 4 percent of total waste products, but that segment is growing at triple the rate of most other waste materials. Though Japanese legislators haven't yet set a date for removing lead, electronics manufacturers are pushing hard to eliminate it.

Asian manufacturers and research agencies are pushing forward. Japanese OEMs have led the way with investigations and have laid out very aggressive timetables to convert to lead-free production. The Japan Electronics and Information Technology Industries Association (JEITA) has done extensive studies on lead-free solder alloys and lead-free finishes, while in Singapore, the Gintic Consortium's lead-free effort is well underway.

In the United States, The National Center for Manufacturing Sciences (NCMS) undertook one of the earliest large-scale studies of lead-free solder alloy alternatives. The group's 1997 report evaluates approximately 80 lead-free alloys and identifies seven as the most promising for lead-free assemblies. This report, along with others analyzing lead-free solders, found no drop-in replacement for tin-lead solder. Based on the work of NCMS and others, the National Electronics Manufacturing Initiative's (NEMI) lead-free project recommended an industry standard alloy in early 2000.

The High Density Packaging User Group International Inc. (HDPUG) endorsed NEMI's recommended alloys for general-purpose applications. HDPUG is also working on a low-temperature SnBi solder for consumer products. In Europe, the European Co-operative in the fields of Science and Technical research (COST) is studying three primary solder alternatives, including the same two wave soldering alloys recommended by NEMI. These recommendations have served to focus efforts on a limited number of alloys in the United States and Europe. However, convergence on one or two alloys is far from certain.

JEITA is examining tin-silver-copper alloys with slightly different compositions than those recommended by NEMI and COST. The Japanese group is also studying solder alternatives that replace lead with bismuth. These solders are attractive because their melting points are lower than those for lead-based solders. There is also concern over the reliability of bismuth-bearing solders in commercial applications and the contamination of copper by bismuth in recycling operations. Several Japanese consumer products companies are studying zinc-based solders, but those have issues related to excessive oxidation and corrosion compared to tin-lead solder.

In addition to finding acceptable alloys to replace tin-lead in electronic assemblies, the industry must also agree on what constitutes "lead-free." NEMI, HDPUG and IPC proposed the first definition for lead-free products. They defined lead-free products as ones where no lead has been purposely introduced during manufacture and has solder joints with less than 0.2 percent lead (by weight). This definition is consistent with the IPCJ-STD-006A standard, which is published and awaiting ANSI approval.

In Europe, a collaborative effort between chipmakers Infineon Technologies, Philips Semiconductors and ST Micro-electronics has set a more stringent guideline, targeting less than 0.1 percent of the material weight as the maximum amount of lead for semiconductor packages. The three companies have also agreed to common approaches for solderability testing and assessment of moisture-sensitivity level of lead-free semiconductor devices. ( See www.onboard-technology.com/online/200109/index.html for additional information.)

Though all this research is both necessary and good, it highlights a critical issue. If different regions or industries move into production using different materials and techniques, it will create many inefficiencies. Continued research in reliability issues will be dissipated. Contract manufacturers will have to set up multiple production lines based on different recipes, removing the leverage of volume and driving up costs.