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Linkages: Manufacturing Trends in Electronic Interconnection Technology Appendix E Lead-Free Electronics Lead is a common component in electronics manufacturing, adding functionality to a variety of solders, capacitors, glasses, and paints. For as long as lead has been used, however, the hazards of lead mining, smelting, industrial use, and recycling have also been known. The Department of Defense (DoD) has put forth a number of technical reasons why defense acquisition need not fully comply with European Union (EU) regulations on the use of lead in electronics products.1 While many manufacturers in the printed circuit board (PrCB) industry are expected to be able to meet the standards set in the European Union, and in California, some board manufacturers are seeking exemptions from the European Union so that compliance can be delayed.2 HEALTH EFFECTS OF LEAD Toxic lead exposure is the most significant and prevalent disease of environmental origin in the world today. Despite all that is known regarding the hazards of lead exposure for children, it has taken over a century for primary prevention to be adopted in the most highly developed countries. The developing world is woefully behind in the development of programs to protect children from lead poisoning. The demonstrable success and societal benefits of preventing lead exposure are unarguable. Irrefutable evidence associates lead at different exposure levels with a wide spectrum of health and social effects, including mild intellectual impairment, hyperactivity, shortened concentration span, poor school performance, violent or aggressive behavior, and hearing loss. Lead has an impact on virtually all organ systems, including the heart, brain, liver, kidneys, and circulatory system, resulting in coma and death in severe cases. 1 Restriction of hazardous substances (RoHS), lead-free legislation, or, more accurately, “Directive 2002/95/EC on the restriction of the use of certain hazardous substances in electrical and electronic equipment,” will be enforced throughout the European Community beginning July 1, 2006. 2 Fern Abrams. 2005. Lead free electronics: Should the military be concerned? Presentation at the Diminishing Manufacturing Sources and Materials Shortages (DMSMS) Conference, Nashville, Tenn., April 14.
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Linkages: Manufacturing Trends in Electronic Interconnection Technology Lead’s neurotoxicity has long been recognized in industrial workers in lead processing and production and in the health care community.3-11 Many studies relate increased blood pressure and hypertension in adults to elevated blood lead levels.12-20 These conditions, in turn, increase the risk of cardiovascular disease. The effect of lead on blood pressure, a major risk factor for coronary artery disease and stroke, is seen at levels quite prevalent in the general population. Lead also 3 M. Payton, K.M. Riggs, A. Spiro, S.T. Weiss, and H. Hu. 1998. Relations of bone and blood lead to cognitive function: The VA normative aging study. Neurotox Teratol. 20:19-27. 4 D. Rhodes, A. Spiro, A. Aro, and H. Hu. 2003. Relationship of bone and BLLs to psychiatric symptoms: The VA normative aging study. J. Occup. Environ. Med. 45:1144-1451. 5 B.S. Schwartz, B.-K. Lee, G.S. Lee, W.F. Stewart, S.S. Lee, K.Y. Hwang, K.D. Ahn, Y.B. Kim, K.I. Bolla, D. Simon, P.J. Parsons, and A.C. Todd. 2001. Association of blood lead, dimercaptosuccinic acid-chelatable lead, and tibia lead with neurobehavioral test scores in South Korean lead workers. American Journal of Epidemiology 53:453-464. 6 B.S. Schwartz, W.F. Stewart, K.I. Bolla, M.S. Simon, K. Bandeen-Roche, B. Gordon, J.M. Links, and A.C. Todd. 2000. Past adult lead exposure is associated with longitudinal decline in cognitive function. Neurology 55:1144-1150. 7 B.S. Schwartz, B.-K. Lee, K. Bandeen-Roche, W.F. Stewart, K.I. Bolla, J. Links, V. Weaver, and A. Todd. 2005. Occupational lead exposure and longitudinal decline in neurobehavioral test scores. Epidemiology 16:106-113. 8 W.F. Stewart, B.S. Schwartz, D. Simon, K.I. Bolla, A.C. Todd, and J. Links. 1999. Neurobehavioral function and tibial and chelatable lead levels in 543 former organolead workers. Neurology 52:1610-1617. 9 R.O. Wright, S.W. Tsaih, J. Schwartz, A. Spiro, K. MacDonald, S.T. Weiss, and H. Hu. 2003. Independent and modifying effects of lead biomarkers on minimental status exam scores in elderly men: The normative aging study. Epidemiology 14:713-718. 10 N. Fiedler, C. Weisel, R. Lynch, K. Kelly-McNeil, R. Wedeen, K. Jones, I. Udasin, P. Ohman-Strickland, and M. Gochfeld. 2003. Cognitive effects of chronic exposure to lead and solvents. American Journal of Industrial Medicine 44:413-423. 11 M.G. Weisskopf, R.O. Wright, J. Schwartz, A. Spiro, D. Sparrow, A. Aro, and H. Hu. 2004. Cumulative lead exposure and prospective change in cognition among elderly men: The normative aging study. American Journal of Epidemiology 160:1184-1193. 12 Y. Cheng, J. Schwartz, D. Sparrow, A. Aro, S.T. Weiss, and H. Hu. 2001. Bone lead and BLLs in relation to baseline blood pressure and the prospective development of hypertension: The normative aging study. American Journal of Epidemiology 153:164-171. 13 B.S. Glenn, W.F. Stewart, J.M Links, A.C. Todd, and B.S. Schwartz. 2003. The longitudinal association of lead with blood pressure. Epidemiology 14:30-36. 14 B.S. Glenn, W.F. Stewart, B.S. Schwartz, and J. Bressler. 2001. Relation of alleles of the sodium-potassium adenosine triphosphatase alpha 2 gene with blood pressure and lead exposure. American Journal of Epidemiology 153:537-545. 15 H. Hu, A. Aro, M. Payton, S. Korrick, D. Sparrow, S.T. Weiss, and A. Rotnitzky. 1996. The relationship of bone and blood lead to hypertension. JAMA 275:1171-1176. 16 S.A. Korrick, D.J. Hunter, A. Rotnitzky, H. Hu, and F.E. Speizer. 1999. Lead and hypertension in a sample of middle-aged women. American Journal of Public Health 89:330-335. 17 B.K. Lee, G.S. Lee, W.F. Stewart, K.D. Ahn, D. Simon, K.T. Kelsey, A.C. Todd, and B.S. Schwartz. 2001. Associations of blood pressure and hypertension with lead dose measures and polymorphisms in the vitamin D receptor and d-aminolevulinic acid dehydratase genes. Environmental Health Perspectives 109:383-389. 18 D. Nash, L. Magder, M. Lustberg, R. Sherwin, R. Rubin, R. Kaufmann, and E. Silbergeld. 2003. Blood lead, blood pressure, and hypertension in perimenopausal and postmenopausal women. JAMA 289:1523-1531. 19 S.J. Rothenberg, V. Kondrashov, M. Manalo, J. Jiang, R. Cuellar, M. Garcia, B. Reynoso, S. Reyes, M. Diaz, and A.C. Todd. 2002. Increases of hypertension and blood pressure during pregnancy with increased bone lead. American Journal of Epidemiology 156:1079-1087. 20 J. Schwartz. 1988. The relationship between blood lead and blood pressure in NHANES II survey. Environmental Health Perspectives 78:15-22.
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Linkages: Manufacturing Trends in Electronic Interconnection Technology damages the kidneys and causes anemia.21-25 Lead has a number of untoward effects on reproductive health26-31 and may be a cause of cataracts.32 Recent epidemiological and experimental work confirms that inorganic lead compounds are associated with increased risks of cancer.33 Various chelating agents have been used to treat lead poisoning. Unfortunately, because many people think that a treatment for lead poisoning exists, they see no further reason to limit lead exposure. There is no conclusive evidence that chelation improves therapeutic outcome in patients with lead poisoning.34 Although chelation reduces blood lead levels and increases excretion of lead in the urine, there is very little evidence that it prevents or reverses the damage resulting from lead exposure.35 Moreover, chelation does not have a beneficial effect on growth and may even have an adverse effect.36 Global Lead Exposure The public health problem of environmental lead exposure has been widely investigated in developed countries such as the United States, where actions taken have led to significant reductions in blood lead concentrations in children. In contrast, little has been done regarding lead poisoning in developing countries, particularly in African countries, despite evidence of widespread and excessive lead 21 R. Kim, A. Rotnitzky, D. Sparrow, S.T. Weiss, C. Wager, and H. Hu. 1996. A longitudinal study of low-level lead exposure and impairment of renal function: The normative aging study. JAMA 275:1177-1181. 22 J.L. Lin, D.T. Lin-Tan, K.H. Hsu, and C.C. Yu. 2003. Environmental lead exposure and progression of chronic renal diseases in patients without diabetes. New England Journal of Medicine 348:277-286. 23 M. Payton, H. Hu, D. Sparrow, and S.T. Weiss. 1994. Low-level lead exposure and renal function in the normative aging study. American Journal of Epidemiology 140:821-829. 24 J.A. Staessen, R.R. Lauwerys, J.P. Buchet, C.J. Bulpitt, D. Rondia, Y. Vanrenterghem, and A. Amery. 1992. Impairment of renal function with increasing blood lead concentrations in the general population: The Cadmibel study group. New England Journal of Medicine 16:151-156. 25 S.-W. Tsaih, S. Korrick, J. Schwartz, C. Amarasiriwardena, A. Aro, D. Sparrow, H. Hu. 2004. Lead, diabetes, hypertension, and renal function: The normative aging study. Environmental Health Perspectives 112:1178-1182. 26 A. Gomaa, H. Hu, D. Bellinger, J. Schwartz, S. Tsaih, T. Gonzalez-Cossio, L. Schnaas, K. Peterson, A. Aro, and M. Hernandez-Avila. 2002. Maternal bone lead as an independent risk factor for fetal neurotoxicity: A prospective study. Pediatrics 110:110-118. 27 T. Gonzalez-Cossio, K.E. Peterson, L. Sanin, S.E. Fishbein, E. Palazuelos, A. Aro, M. Hernandez-Avila, and H. Hu. 1997. Decrease in birth weight in relation to maternal bone lead burden. Pediatrics 100:856-862. 28 B.L. Gulson, C.W. Jameson, K.R. Mahaffey, K.J. Mizon, N. Patison, A. Law, M.J. Korsch, and M.A. Salter. 1998. New findings on sources and biokinetics of lead in human breast milk: Bone lead can target both nursing infant and fetus. Environmental Health Perspectives 106:667-674. 29 B.L. Gulson, K.J. Mizon, M.J. Korsch, J.M. Palmer, and J.B. Donnelly. 2003. Mobilization of lead from human bone tissue during pregnancy and lactation: A summary of long-term research. Sci. Total Environ. 303:79-104. 30 M. Hernandez-Avila, K.E. Peterson, T. Gonzalez-Cossio, L.H. Sanin, A. Aro, L. Schnaas, and H. Hu. 2002. Effect of maternal bone lead on length and head circumference at birth. Archives of Environmental Health 57:482-488. 31 L.H. Sanin, T. Gonzalez-Cossio, I. Romieu, K.E. Peterson, S. Ruz, E. Palazuelos, M. Hernandez-Avila, and H. Hu. 2001. Effect of maternal lead burden on infant weight and weight gain at one month of age among breastfed infants. Pediatrics 107:1016-1023. 32 D.A. Schaumberg, F. Mendes, M. Balaram, M.R. Dana, D. Sparrow, and H. Hu. 2004. Accumulated lead exposure and risk of age-related cataract extraction in men: The normative aging study. JAMA 292:2750-2754. 33 E.K. Silbergeld, M. Waalkes, and J.M. Rice. 2000. Lead as a carcinogen: Experimental evidence and mechanisms of action. Am. J. Ind. Med. 38:316-323. Review. 34 K.N. Dietrich, J.H. Ware, M. Salganik, J. Radcliffe, W.J. Rogan, G.G. Rhoads, M.E. Fay, C.T Davoli, M.B. Denckla, R.L. Bornschein, D. Schwarz, D.W. Dockery, S. Adubato, and R.L. Jones. 2004. Treatment of lead-exposed children clinical trial group: Effect of chelation therapy on the neuropsychological and behavioral development of lead-exposed children after school entry. Pediatrics 114:19-26. 35 W.J. Rogan, K.N. Dietrich, J.H. Ware, D.W. Dockery, M. Salganik, J. Radcliffe, R.L. Jones, N.B. Ragan, J.J. Chisolm, Jr., and G.G. Rhoads. 2000. Treatment of lead-exposed children trial group: The effect of chelation therapy with succimer on neuropsychological development in children exposed to lead. New England Journal of Medicine 344:1421-1426. 36 K.E. Peterson, M. Salganik, C. Campbell, G.G. Rhoads, J. Rubin, O. Berger, J.H. Ware, and W. Rogan. 2004. Effect of succimer on growth of preschool children with moderate blood lead levels. Environmental Health Perspectives 112:233-237.
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Linkages: Manufacturing Trends in Electronic Interconnection Technology exposure during childhood.37,38 Estimates of lead exposure and surveys of blood lead in the most populous developing countries, India, Indonesia, and China, indicate that most of the world’s children are already at risk from the effects of environmental lead exposure.39,40 The same can be said of the risk to children in Latin America and Central Europe.41-44 There has been a laudable effort in many developed countries to protect the public from lead exposure. Government regulation followed public health recommendations to remove or severely limit the amount of lead in gasoline, paint, and food containers.45 Litigation and environmental education programs have driven most lead smelting and refining out of populous areas. Vigorous enforcement of environmental standards in one country, however, has resulted all too often in a transfer of its industrial hazards to other, poorer countries.46 The record of decreasing lead exposure in developed countries masks a shameful record of the export of lead to developing countries, most of which are unaware of the extent of lead’s toxicity and equally unaware of the long-term costs associated with environmental degradation and damage to the health of workers and community residents. Public health agencies in many countries have responded to growing awareness of the severity and prevalence of lead poisoning by promulgating regulations to reduce exposure to lead.47 These regulations apply to lead in products, environmental media, or the workplace and define restrictions on specific uses of lead. Public health policies have not adequately prevented lead exposure or lead poisoning. This is related in part to the complexity of limiting exposures and also to an unresolved debate over the value of screening. Despite considerable regulatory attention and voluntary changes that have occurred in reducing lead use, lead poisoning continues in developed as well as developing countries.48 The Electronics Industry The electronics industry was not regulated for its impact on the environment for many decades and has never been held accountable for the actual cost of the environmental damage that it has caused. Billions of electronics products have been discarded in every region of the world. Not until 1997 did the U.S. Environmental Protection Agency (EPA) begin to address the relationship between product and process design and environmental impact. By that time, the international pollution of the world with what has come to be known as e-waste was readily apparent. Lead use is ubiquitous in electronics manufacturing. It is present in solder and interconnects, finishes, batteries, paints, piezoelectric ceramic devices, discrete components, sealing glasses, and 37 L.J. Fewtrell, A. Pruss-Ustun, P. Landrigan, and J.L. Ayuso-Mateos. 2004. Estimating the global burden of disease of mild mental retardation and cardiovascular diseases from environmental lead exposure. Environ. Res. 94:120-133. 38 D. Bellinger, H. Hu, V. Kartigeyan, T. Naveen, R. Pradeep, S. Sankar, R. Padmavathi, and B. Kalpana. 2005. A pilot study of blood lead levels and neurobehavioral function in children living in Chennai, India. Int. J. Occup. Environ. Health 11:138-143. 39 I. Heinze, R. Gross, P. Stehle, and D. Dillon. 1998. Assessment of lead exposure in school children from Jakarta. Environmental Health Perspectives 106:499-501. 40 M. Lacasana, I. Romieu, L.H. Sanin, E. Palazuelos, and M. Hernandez-Avila. 2000. Blood lead levels and calcium intake in Mexico City children under five years of age. Int. J. Environ. Health Res. 10:331-340. 41 P. Factor-Litvak, G. Wasserman, J.K. Kline, and J. Graziano. 1999. The Yugoslavia prospective study of environmental lead exposure. Environmental Health Perspectives 107:9-15. 42 L. Schnaas, S.J. Rothenberg, M.F. Flores, S. Martinez, C. Hernandez, E. Osorio, and E. Perroni. 2004. Blood lead secular trend in a cohort of children in Mexico City (1987-2002). Environmental Health Perspectives 112:1110-1115. 43 A. Mathee, Y. von Schirnding, M. Montgomery, and H. Rollin. 2004. Lead poisoning in South African children: The hazard is at home. Rev. Environ. Health 19:347-361. 44 I. Romieu, M. Lacasana, and R. McConnell. 1997. Lead exposure in Latin America and the Caribbean. Lead research group of the Pan-American Health Organization. Environmental Health Perspectives 105:398-405. 45 L.R. Goldman. 1998. Linking research and policy to ensure children’s environmental health. Environmental Health Perspectives 106 (Suppl 3):857-862. 46 J. LaDou. 2003. International occupational health. Int. J. Hygiene Environ. Health 206:303-313. 47 Organization for Economic Cooperation and Development. 1999. Review of Implementation of OECD Environment Ministerial Declaration on Risk Reduction for Lead. Paris: OECD Environmental Directorate. 48 E.K. Silbergeld. 1995. The international dimensions of lead exposure. Int. J. Occup. Environ. Health 1:336-348.
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Linkages: Manufacturing Trends in Electronic Interconnection Technology cathode-ray-tube glass. Lead is also used as a stabilizer for plastics such as PVC (polyvinyl chloride), commonly used in cable assemblies. The early PrCB industry produced electronics products using prodigious quantities of lead and other toxic materials, systematically shipping them to every corner of the world, where, to this day, they are improperly disposed of in landfills, waterways, and incinerators. The elimination of lead plating has been a goal of many PrCB manufacturers, in part because of strict local discharge limitations. Tin-lead is plated as an etch resist; then, on panels subsequently processed with solder-mask-over-bare-copper (SMOBC), the tin-lead coat is promptly stripped. Therefore, when the predominant SMOBC process is specified, tin-lead is easily replaced by tin as the etch resist of choice. Unfortunately, a minority of PrCBs still require tin-lead reflow, and these panels must be processed with a tin-lead etch resist, which is subsequently fused into solder. Many shops do not, for economic or other reasons, maintain both tin and tin-lead plating lines and are thus unable to employ tin-only plating on that portion of their product which is SMOBC. In short, the transition from tin-lead plating to tin-only has been slow. As part of the EPA’s Design for the Environment project, the U.S. government found that the range of water use among participants was very large, and there was evidence of wide variation in the water practices among facilities. The survey data show that the majority of the respondents are indirect dischargers (i.e., facilities that discharge process wastewaters to publicly owned treatment works). This was especially true for the small to midsize PrCB-manufacturing facilities. The regulated pollutants most often found in PrCB wastewater are copper, lead, nickel, silver, and total toxic organics. Accidental or unauthorized release of these pollutants into surface waters can harm aquatic life.49 The next most commonly shipped waste product is tin or tin-lead stripping solutions. Moreover, current PrCB manufacturing processes generate a variety of scrap materials containing lead, copper, tin, nickel, gold, and other metals. Most manufacturers collect these materials for recycling, disposing of them through brokers. Flux, solder dross from the hot-air-solder-level process, and other lead-bearing solutions are shipped off-site for recycling by 20 percent of the EPA survey respondents. The United States exports 50 to 80 percent of its e-waste for recycling. In many cases, manufacturers are not aware of where their brokers ship these materials.50 GLOBAL ENVIRONMENTAL REGULATION Regulatory initiatives are emerging that require the electronics industry to incorporate environmental, health, and safety considerations into design and manufacturing decisions. The electronics industry is preparing to comply with a number of restricted materials laws. In 2003, the European Union (EU) enacted the restriction of hazardous substances (RoHS) directive that bans the use of lead, mercury, cadmium, hexavalent chromium, and certain brominated flame retardants (BFRs) in most electronics products sold in the EU market beginning July 1, 2006.51 Both business-to-business and consumer products are covered. Although there are some exemptions to the directive’s chemical restrictions, this directive, by banning the use of critical materials in electronics products sold in key world markets, may result in a significant change in the way products are designed for global sale. The European Parliament and the European Council are considering legislation—Regulation, Evaluation, and Authorization of Chemicals (REACH)—that will require industry to prove that chemicals being sold and produced in the European Union are safe to use or handle. REACH policy will require the registration of all substances that are produced or imported into the European Union. The amount of information required for registration will be proportional to the health risks related to the chemical and its production volumes. Companies will also need to seek authorization to sell and produce problematic chemicals, such as carcinogens, mutagens, and teratogens. Toxic chemicals that persist in the 49 Environmental Protection Agency. Design for the Environment. Available at http://www.epa.gov/dfe/projects/pwb/index.htm. Accessed October 2005. 50 Environmental Protection Agency. Design for the Environment. Available at http://www.epa.gov/dfe/projects/pwb/index.htm. Accessed October 2005. 51 European Union. Directive 2002/95/EC of the European Parliament and of the Council of 27 January 2003 on the Restriction of the Use of Certain Hazardous Substances in Electrical and Electronic Equipment (RoHS). Available at http://europa.eu.int/eur-lex/pri/en/oj/dat/2003/l_037/l_03720030213en00190023.pdf. Accessed October 2005.
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Linkages: Manufacturing Trends in Electronic Interconnection Technology environment or that bioaccumulate will also need authorization. The policy is slated for enactment in 2006.52 California recently enacted the first law in this country to establish a funding mechanism for the collection and recycling of computer monitors, laptop computers, and most television sets sold in the state. That law, the Electronic Waste Recycling Act of 2003, also contains a provision that prohibits a covered electronics device from being sold or offered for sale in California if the device is prohibited from being sold in the European Union by the RoHS directive.53 The electronics industry is likewise beginning to take responsibility for its products at the end of their useful life. This responsibility also forms the basis for the “take-back” legislation that is being implemented in the European Union under the Waste Electrical and Electronic Equipment (WEEE) directive, beginning in August 2005.54 The directive encourages the design and production of electronics equipment to take into account and facilitate dismantling and recovery, in particular the reuse and recycling of electronics equipment, components, and materials necessary to protect human health and the environment. In the European Union, since July 1, 2003, materials and components have not been allowed deliberately to contain lead, mercury, cadmium, or hexavalent chromium.55 Lead was classified as category 1, toxic to reproduction (embryotoxic), and as a precaution, the EU classified lead chromate pigments as category 3 carcinogens. In the United States, environmental regulation is not moving in the same direction as in Europe. In 2003, the EPA proposed revisions to the definition of solid waste that would exclude certain hazardous waste from the Resource Conservation and Recovery Act (RCRA) of 1976 if the waste is reused in a “continuous industrial process within the same generating industry.” The proposal may eventually exempt all appropriately recycled materials from RCRA hazardous-waste regulations. Final action on the proposal is expected in 2006. The EPA is also considering a rule that would exempt electroplating sludge from RCRA hazardous-waste regulations if the sludge is recycled. Workplace exposures to airborne chemicals are regulated in the United States by the Occupational Safety and Health Administration (OSHA) via the promulgation of Permissible Exposure Limits (PELs). These limits, usually defined as 8-hour time-weighted average values, are enforced as concentrations never to be exceeded. In the case of toxicants with chronic or delayed effects, the PEL is determined from toxicological or epidemiological evidence and assessment of risk of disease or material impairment of heath resulting from exposure to the PEL over an occupational lifetime of 45 years. Industry guidelines and federal standards have failed to fully protect workers from chemical toxicity: no such guidelines or standards exist for most chemicals, many are biased toward what can easily be achieved, and many were developed long after health consequences became evident. Although exposure limits or guidelines for many large-volume chemicals have been established, federal OSHA has PELs for fewer than 500 toxic substances out of the more than 10,000 chemicals that are routinely used in industrial facilities. Additionally, more than 90 percent of the substances with established PELs have standards based on toxicological study results and case reports from 35 to 50 or more years ago: lead is among them.56 TECHNICAL CHALLENGES A number of technical challenges face the PrCB industry in this transition period. Foremost is the integration of new materials and processes coupled with the need to maintain product quality. Process 52 P.D. Thacker. 2005. U.S. Companies Get Nervous about EU’s REACH. Environmental Science and Technology Online, January 5. Available at http://pubs.acs.org/subscribe/journals/esthag-w/2005/jan/policy/pt_nervous.html. Accessed October 2005. 53 California Department of Toxic Substances Control. Electronic Waste Recycling Act of 2003 (SB20). Available at http://www.dtsc.ca.gov/HazardousWaste/CRTs/SB20.html. Accessed September 2005. 54 European Union. Directive 2002/96/EC of the European Parliament and of the Council of 27 January 2003 on Waste Electrical and Electronic Equipment (WEEE). 55 European Union. Directive 67/548/EEC on the Classification, Packaging and Labelling of Dangerous Substances, Annex 1, as last amended by Directive 2003/32/EC (28th ATP). 56 Historical information on permissible exposure levels is available from the Occupational Safety and Health Administration, at http://www.osha.gov. Accessed October 2005.
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Linkages: Manufacturing Trends in Electronic Interconnection Technology challenges include the higher reflow temperatures (+20°C to 40°C) for lead-free solders, which will affect soldering processes for the entire system. This change is expected to require the requalification of military suppliers and (if widely implemented) will involve potential incompatibilities with legacy systems. Current testing indicates that most products that are manufactured to be lead-free could be used with a leaded connection, but this is a difficult paradigm for military systems owners to trust. One inherent difficulty stems from the reason that lead was introduced into coatings and solders a century ago. Pure tin metal is susceptible to spontaneous growth of filament-like structures commonly referred to as tin whiskers. The problem of tin “whiskers, needles or filaments” was first reported just after World War II. It was discovered that these whiskers could cause problems in electronic devices by breaking off and causing shorts between exposed leads. Whisker growth rates and final sizes are unpredictable, and growth can begin soon after manufacturing or may take years to initiate. Whiskers have been observed to grow with a wide range of morphologies and a wide range of diameters and lengths. Currently, a thorough understanding of the problem is lacking, and many approaches are being tested. The cross-contamination of leaded components and no-lead components is an additional worry. Many small and some large manufacturers will not be able to maintain dual production for military and nonmilitary uses. This problem is expected to result in fewer suppliers for both systems, because some will have to choose whether or not to transition. The industry already manufactures PrCBs that can be used in leaded and no-lead systems, but this will further serve to limit qualified suppliers and will narrow supply-chain options. Current exemptions from the restriction include high-lead solders (over 85 percent lead) because there is no viable materials substitute for these solders. Other exemptions include lead in the glass of cathode ray tubes, electronic components, and fluorescent tubes; lead in solders for servers, storage and storage array systems; lead in solders for network infrastructure equipment for switching, signaling, transmission as well as network management for telecommunication; and lead in electronic ceramic parts (e.g., piezoelectronic devices). The legislation also does not cover medical electronics and monitoring and control instrumentation. It is important to note that all of these exemptions are subject to future legislative action and that the committee believes that the transition to no-lead systems will continue. While these exemptions may ease the design challenges inherent in any transition to a new technology, the net effect is an extension of the problem faced by designers and users. Such extensions may contribute to further cross-contamination of systems and will delay the underlying intent of the restriction, which is to eliminate hazardous waste from electronics at the beginning and end of life. CONCLUSIONS The public health effects associated with lead are well established. An appropriate governmental function may be, for example, that of pressing the PrCB industry to make every effort to solve the technical problems resulting from the substitution of lead in its products. During routine maintenance, printed circuit boards are replaced periodically because they collect moisture over time. This offers the Department of Defense an opportunity to put policy into practice in a timely manner. In doing so, DoD will need to consider the impacts of environmentally unsafe practices occurring in PrCB fabrication as well as the technical challenges associated with the substitution of lead in PrCBs.
Representative terms from entire chapter: