The International Electronics Manufacturing Initiative (iNEMI), released a statement Monday indicating that the majority of its OEM and EMS members strongly support unique part numbers for BGA (ball grid array) components to differentiate any lead-free ball metallurgies other than SAC 305 or SAC 405, including low silver, added dopants such as nickel and other SAC (or non SAC) alloy compositions.
iNEMI members supporting the position include 3M, Agilent Technologies Inc., Alcatel-Lucent, Analogic, Celestica, Delphi Electronics and Safety, Huawei Technologies Intel, Jabil Circuit, Microsoft, Micro Systems Engineering, Plexus, Sanmina-SCI, Solectron and Tyco Electronics.
iNEMI notes that many suppliers are moving away from SAC 305 and 405 ball metallurgies in order to improve the ability to survive mechanical shock – drop tests of portable products. Changes include reductions in silver down to as low as 0.3 percent and the addition of other metals such as nickel. In response to these changes, iNEMI has asked that component manufacturers issue new part numbers when they vary the metallurgy. “A change in metallurgy without the ability to track the change through MPNs (manufacturing part numbers) will only make Pb-free conversion more difficult and could delay the process,” says Mike Davisson, RoHS technical program manager at Agilent Technologies.
iNEMI CEO, Jim McElroy notes that his members are concerned that changes in metallurgies that are not accompanied by unique part numbers can affect manufacturing processes. “It is inevitable that solder ball metallurgies will change as industry learns more about the performance of Pb-free technologies. However, use of these different compositions will most likely require changes in reflow profiles and corresponding adjustments to the assembly process.
As an example, he notes that lower-silver compositions directly affect manufacturing. “The lower-silver compositions have a higher melting point than SAC 305/405 alloys, which moves the melting range higher,” says McElroy. “Based on assembly process margins, especially for large complex boards, low-silver compositions could also impact the MSL rating. In order to maintain reliable assembly processes, manufacturers must know the metallurgical characteristics of the components they are using and be able to differentiate parts.”
Peter Tomaiuolo, corporate technology director for Celestica agrees. “Knowing what metallurgy is used by a particular manufacturer is not enough,” says Tomaiuolo. “It is equally or more important to be able to identify and track this difference on our manufacturing floors. We also would like component suppliers to proactively declare the timelines of proposed changes to device construction, including sphere metallurgy, ahead of the MPN and PCN (part change notice) release.”
For additional information and further discussion about transitioning to alternate metallurgies, see the EMS Forum’s article, “Guidelines for Suppliers Transitioning to RoHS Compliant Ball Grid Array (BGA) Packages with Low-Ag SAC Alloys.”