A Case Study for Transitioning Class a Server Motherboards to Lead-Free
The EU Restriction of Hazardous Substance (RoHS) legislation was formed in 2006. One, out of the many, exemptions that it had was developing of lead based solders in Class A servers, storage array products and network infrastructure equipment. This legislations current exemption is to allow the continued use of lead based solder in Class A servers until at least 2010. But there are some industries who are proposing to extend this exemption to 2012 or beyond; because of the added challenge of producing highly reliable lead-free server assemblies. Dell who began developing lead-free Class A servers in 2006, was soon able surpass the requirements of this legislation by transitioning its Class A server printed circuit board assemblies to lead-free. This case study outlines the process followed, the testing performed, the material changes made, and the challenges that were met and overcome in this dedicated year-long effort by a large team of people. A huge number of reliability testing was performed to ensure that no compromise was made on the expected life of the product. The most significant challenge was in selecting a PCB surface finish. After trying various products lead-free Hot Air Solder Level (HASL) finish was selected due to its superior solder ability and testability. The other products like laminate material, alloy type, and process conditions were selected according to the compatibility that they had with this surface finish.