Purafil Inc., Doraville, GA
The European Union RoHS directive took effect in 2006, and of the 6 restricted materials, the elimination of lead from electronic devices took the most development effort and had the worst degrading effect on hardware reliability. One negative impact was the brittleness of the lead-free solder alloys that replaced the industry favorite, ductile Sn-Pb eutectic alloy. Another was the unexpected occurrence of creep corrosion on printed circuit boards using alternative PCB surface finishes.
Along with the implementation of RoHS, the miniaturization of circuits, the expansion of IT markets in developing countries with high-levels of sulfur-bearing gaseous pollution, and the trend towards energy saving by resorting to free-air cooling, have all led to increased rates of corrosion-related hardware failures associated with particulate and gaseous contamination. The IT industry has taken a two-pronged approach to mitigating these failures: (1) by making the products more robust against contamination and high humidity levels; and (2) by gaining better understanding of the allowable levels of contamination, temperature and humidity under which IT equipment can operate reliably.
Additionally, many points along the supply chain have been identified where corrosion can form, and the additive effects may or may not be detected by testing or manifest themselves before delivery to the end-user. Failures at this point may be due to the cumulative effect of numerous "micro-failures" generated throughout the supply chain. However, what remains most frequent are product failures resulting from exposure to elevated pollutant levels and inadequate environmental controls at manufacturing locations. The result is an operating environment that does not meet current manufacturers' warranty requirements - requirements that have been put into place since the implementation of RoHS.
This paper will describe the common modes of corrosion-related hardware failures in the past 10 years, the actions taken to make the products more robust, the understanding of the role played by contamination, and the means of negating their detrimental effects. The case will also be presented for environmental monitoring at various points along the supply chain and the addition of enhanced air cleaning for those locations that do not meet the air quality requirements of the finished devices. Data will be presented that highlight the need for air quality assessments of manufacturing facilities, where enhanced air cleaning is indicated, and the benefit of establishing an ongoing real-time air monitoring program to assure compliance with air quality specifications and warranty requirements.
From 2006 to 2008, the number of corrosion-related failures of IT/datacom equipment directly attributable to lead-free manufacturing regulations - by conservative estimates - increased by upwards of 250%. This was primarily due to failures caused by silver sulfide creep corrosion on devices using an ImmAg surface finish, corrosion of silver metal on the legs of ICs, and corrosion of silver finish component leads.