BANNOCKBURN, IL — A new document from IPC's Pb-free Electronics Risk Management (PERM) Council assists design engineers in the development of electronics that are completely lead-free and meet the requirements of aerospace, defense and high performance (ADHP) products and systems.
IPC/PERM-2901, "Pb-free Design and Implementation Guide," provides an in-depth review of printed board defects, manufacturing and soldering processes, supply chain control, selection, use and assembly with commercial off-the-shelf (COTS) products and obsolescence management.
While the commercial electronics industry has almost eliminated the need for tin-lead (SnPb) based electronics systems and products, the ADHP industry, due to a lack of industry-accepted reliability models for Pb-free interconnections, has continued to rely on SnPb for their products. As it becomes more cost-prohibitive for the ADHP industry to continue to use SnPb products, and with failure mechanisms for Pb-free materials being significantly different than SnPb materials, gaining knowledge and understanding of how Pb-free materials affect the ADHP industry has become critical.
Although many technical papers and industry studies have been published addressing the Pb-free soldering process over the past 20 years, IPC says PERM-2901 is the first to assist design engineering, quality assurance and manufacturing engineering in understanding and appreciating the differences in mechanical and physical behaviors of Pb-free soldering and providing avenues for risk mitigation.
The guideline specifically addresses the “delta” differences between SnPb and Pb-free solder technologies relative to manufacturing the same products. The differences in these solder technologies are generally categorized (with respect to Pb-free solder alloys) as:
• Typically poorer wetting ability
• Differences in appearance and inspection criteria
• Typically higher melting temperature
• Potential tighter process window for repair/rework
• Increased potential of tin whiskers
The PERM Council, comprised of global participants from government, military, medical, academia and other not-for-profit organizations, along with private companies, was created to address the need for how Pb-free materials directly affect product performance, reliability and service life.
The European Union’s Restriction of Hazardous Substances (RoHS) profoundly affected the electronics industry when lead was listed as a restricted substance. According to Linda L. Woody, formerly of Lockheed Martin and former PERM Council Chair, “ADHP systems and products have a broad range of performance requirements, and have relied on SnPb products for decades. We created the guideline to ease the transition from SnPb to Pb-free, and to help the industry meet the demanding requirements of the ADHP systems and products.”