Getting the Lead Out Goes Slowly
Goaded by the European Commission and other governmental bodies, manufacturers look to cut lead from electronics products - but they have plenty of time to make their changes.
Rick Nelson, Senior Technical Editor -- Test & Measurement World, 10/1/2000
Environmental concerns are spurring a move toward lead-free solder—a move that could complicate the test of printed-circuit assemblies. Current indications, however, are that PCB manufacturers will have another seven years to comply with emerging regulations, which should give test-equipment makers plenty of time to adapt their fixtures and automated inspection systems to test lead-free products.
The major impetus toward adopting lead-free solders was the expectation that the European Commission (EC), as part of its Waste Electrical and Electronic Equipment (WEEE) initiative, would ban lead in most consumer products effective January 1, 2004, and that the Japanese government would promulgate a similar restriction as early as next year. In June, however, the EC delayed its ban until January 1, 2008.1 Indications from the Japan Electronic Industry Development Association (JEIDA) are that Japan will slow down to Europe’s pace in the move toward lead-free electronic products.
The JEIDA lead-free road map2 calls for the introduction of lead-free components and solders this year with full adoption taking place by the end of 2003. But that road map was prepared before the EC’s June extension, and JEIDA will likely modify its road map accordingly. Japanese manufacturers are unlikely to face imminent bans on lead from their own government. The Japanese Ministry of Trade and Industry (MITI) has drafted a recycling law that, beginning next year, would make electronics manufacturers responsible for disposing of obsolete products returned to them by consumers. Making those products lead-free to begin with might minimize companies’ disposal woes, but the MITI draft doesn’t specifically mention lead.
US companies making electronics products for sale in the US also appear to be safe from imminent government bans on lead, although they could face new reporting requirements detailing the lead compounds they use. Current regulations stipulate that companies that manufacture more than 25,000 lbs or use more than 10,000 lbs of lead annually must file reports with the Environmental Protection Agency; the EPA has proposed requiring reports from any facility that manufactures, processes, or uses more than 10 lbs annually.3
Test Issues
Test issues related to lead-free solders will likely be concentrated in the inspection area. A report prepared on behalf of the UK Department of Trade and Industry (DTI) states that “one of the perceived concerns in transferring to lead-free soldering technology is that the appearance and geometry of solder joints will be significantly different from those using conventional PbSn [lead-tin] solder.”4 The report concludes that lead coverage, fillet geometries, and wicking characteristics are different for lead-free alloys, and that copper halos surrounding solder fillets on PCB pads, a sign of poor solder coverage with lead-based alloys, may be acceptable with lead-free versions. Such changes will require retraining of manual inspectors and reprogramming of automated optical-inspection systems. The report also suggests automated x-ray systems might require higher voltage sources to compensate for the poorer image resolution afforded by lead-free solders.
One firm that’s done its own investigations, Agilent Technologies (Palo Alto, CA, www.agilent.com), hasn’t found this to be the case. The company announced in March the conclusion of an investigation showing its 5DX automated x-ray inspection system would require only a software tweak to handle lead-free solder alloys.
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| Figure 1. a) When joining a gull-wing package to a PCB, lead-free solders produce heel, toe, and side solder-fillet characteristics similar to those of leaded solders. b) BGA lead-free-solder x-ray images are also similar to images of leaded-solder versions. Lead-free solders do, however, absorb about 10% less x-ray energy than do their lead counterparts, requiring some software corrections to image profiles. (Courtesy of Agilent Technologies.) |
According to Agilent engineer Jeremy Jessen, “Joint profiles are relatively the same between lead-free alloys and eutectic tin/lead alloys. For example, the gull-wing joint still produces heel, toe, and side fillets” (Fig. 1). He says that with minor changes to the joint profiles, the current algorithms used to analyze the joints are still applicable. Agilent has found that lead-free solders absorb about 10% less x-ray energy than do leaded solders, resulting in a lighter image that can be compensated for by alterations in the solder thickness tables of inspection-system software.
Deft Rework Required
Rework is another area that a move to lead-free solder may affect, according to the DTI and the National Electronics Manufacturers Initiative (NEMI). The DTI report says lead-free solders will probably require soldering-iron tip temperatures beyond 300°C; rework-station operators will need retraining to develop sufficient dexterity to minimize the time sensitive components are exposed to such high temperatures. For its part, NEMI, according to a report issued May 9,5 is studying how to adapt rework processes for the removal and replacement of through-hole and surface-mount devices using lead-free solders, with an emphasis on how well PCBs will hold up under multiple repairs to a single board location.
The NEMI report says “tin-lead interconnect systems are the very heart of the high-reliability electronics industry,” and says moving to new interconnect systems entails risks. For the test industry, those risks might extend beyond inspection and rework. One executive at a firm that makes test fixtures and accessories says he’s keeping an eye on what the move to lead-free solder might mean with respect to test-probe spring forces and tip geometries, although he has seen no need for change, yet. The go-slow approach adopted by the EC should provide plenty of time for thorough investigations in all the areas relevant to test. T&MW
FOOTNOTES
1. “Proposal for a Directive of the European Parliament and of the Council on Waste Electrical and Electronic Equipment” and “Proposal for a Directive of the European Parliament and of the Council on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment,” Commission of the European Communities, Brussels, June 13, 2000. www.lead-free.org/download/files/pdf/Directive_Section_WEEE_Final_Proposal.pdf.
2. “Challenges and Efforts Toward Commercialization of Lead-free Solder—Road Map 2000 for Commercialization of Lead-free Solder—ver 1.2,” The Japan Electronic Industry Development Association, Lead-free Soldering R&D Project Committee, February 2000, www.jeida.or.jp/english/information/pbfree/roadmap.html.
3. “Lead and Lead Compounds; Lowering of Reporting Thresholds; Community Right-to-Know Toxic Chemical Release Reporting; Proposed Rule,” US Environmental Protection Agency, Federal Register, Vol. 64, No. 148, August 3, 1999. pp. 42222–42243. www.epa.gov/tri/pb_rule.htm#transcripts.
4. Richards, Brian, and Kay Nimmo, “Update 2000—An Analysis of the Current Status of Lead-free Soldering—One Year On,” UK Department of Trade and Industry, London.
www.lead-free.org/download/dti_form2000.html.
5. “NEMI Lead Free Interconnect Project: Statement of Work,” National Electronics Manufacturers Initiative, Herndon, VA, May 9, 2000. www.nemi.org/PbFreePUBLIC/index.html.
You can contact Rick Nelson at rnelson@tmworld.com.
