HERNDON, VA — A set of recommendations issued today call for continued availability of tin-lead compatible components for products exempted from European restrictions. The International Electronics Manufacturing Initiative today said the measures are necessary in order to safeguard the dependability of high-reliability products as the supply chain converts to lead-free components and materials.
The consortium’s High-Reliability RoHS task force, made up of OEM and EMS companies, is also calling for a standardized strategy of mitigation practices and testing methods to minimize the risk of tin whiskers.
In a statement, iNEMI CEO Jim McElroy said, “Maintaining high product reliability is absolutely critical to these companies’ survival. They are very concerned about the transition to lead-free and have banded together to provide a unified voice and message to the supply chain. We are currently surveying the components supply base to see if it makes sense to organize an industry forum that will bring together high reliability users and suppliers to further discuss these needs.”
Products such as servers and telecom gears are exempt or out of scope under the European Union’s RoHS Directive and will be allowed continued use of lead in solder for reliability purposes. However, the supply chain, which is increasingly driven by high-volume, low-cost applications that do not have stringent reliability requirements, is converting (or has converted) to lead-free. Many suppliers plan to no longer offer SnPb products, iNEMI said.Several compatibility issues have been identified as high-reliability OEMs and EMS providers try to "mix and match" Pb-free components in exempted SnPb assembly processes.
Joe Smetana, principal engineer, advanced technology for Alcatel said, "RoHS Directive provides ‘lead in solder’ exemptions for important ‘mission-critical’ and high-reliability systems, ostensibly because the Commission recognized that industry does not yet have adequate field data or verified acceleration models to ensure the reliable functioning of these critical products if lead-free solders were used. Their intention was to guard against unnecessary risk in applications where failure could be anything from problematic to catastrophic. Companies that manufacture high-reliability, long-service-life systems must be assured of the availability of components that are compatible with tin-lead assembly, not only to provide continued quality and performance in new products but to maintain products already in use. Many telecom, server, monitoring and control instruments, or storage products, for example, often have a field life of 10 to 25 years and are high-end systems that customers will want to repair rather than replace.”
The other area of concern is tin whiskers. For more than 50 years, companies have added lead to tin plating to combat the problem. Many component suppliers are proposing the use of pure tin plating to meet RoHS requirements. This alternative poses reliability risks due to the whisker-forming tendencies of pure tin and tin alloy plating.
A host of companies are balking, saying they will require suppliers to combine mitigation practices with testing.
IBM senior technical staff member George Galyon said, “We are requiring that our suppliers employ a proven whisker mitigation strategy, such as nickel underlay or annealing. Since mitigation techniques can vary significantly in effectiveness, we are also asking for supporting measurements — meaning testing — to provide objective evidence of mitigation efficacy.”
The iNEMI Hi-Rel Task Force companies will require electronic component suppliers to implement the following recommendations for high-reliability applications:
1. Adopt one of the iNEMI-recognized whisker mitigation practices as an integral part of tin or high tin content (>95%) Pb-free plating processes, as outlined in the iNEMI Tin Whisker User Group’s Recommendations on Lead-Free Finishes for Components Used in High-Reliability Products, Version 3 (at
http://thor.inemi.org/webdownload/projects/ese/tin_whiskers/User_Group_mitigation_May05.pdf)
2. Perform testing and adhere to the qualification criteria of either the iNEMI Tin Whisker Acceptance Test Requirements (July 28, 2004) or the final agreement of the JEDEC JESD-201A qualification criteria (Environmental Acceptance Requirements for Tin Whisker Susceptibility of Tin and Tin Alloy Surface Finishes, currently in industry review), in conjunction with the JESD22-A-121 test method (Test Method for Measuring Whisker Growth on Tin and Tin Alloy Surface Finishes). The document can be downloaded at http://thor.inemi.org/webdownload/projects/ese/tin_whiskers/Tin_Whisker_Accept_paper.pdf.
3. Continue to provide an alternative non-whiskering finish, such as SnPb or nickel-palladium-gold (NiPdAu), until the requirements of the iNEMI/JEDEC acceptance tests have been met.
Besides IBM, participating OEMs include Cisco, Lucent, Sun, Agilent, HP and Delphi among others. EMS firms include Solectron, Celestica, Jabil, Plexus and Sanmina-SCI.
The group’s recommendations are available at www.inemi.org/cms/projects/ese/High_Rel_RoHS.html.