BAE Systems, Endicott, N.Y.
Polina Snugovsky, Jeff Kennedy, Zohreh Bagheri, and Eva Kosiba
Celestica Inc., Toronto, ON, Canada
Driven by European Union directives, most commercial electronics manufacturers began delivering lead-free electronic components, assemblies, and equipment in 2006. As a result of a global movement away from using lead (Pb), component manufacturers are increasingly applying tin-rich finishes to the leads of their devices and soldering with lead(Pb)-free solders.
Unfortunately, this can create a risk of tin whisker formation that can result in electrical failures. Motivated by its unique requirements such as long service lifetimes, rugged operating environments, and high consequences of failure, the aerospace and defense industries must mitigate the detrimental effects of tin whisker formation when lead-free materials are used.
The present paper provides a status on the effort associated with a multi-year testing and modeling program that aims to assess and quantify tin whisker growth on lead-free manufactured assemblies. The tin whisker growth of tin finished parts soldered with SAC305 (Sn-3.0Ag-0.5Cu) solder alloy under high temperature/high humidity (85 degrees C/ 85 percent relative humidity) conditions were evaluated.
Significant whisker growth was observed from the SAC305 solder alloy, particularly in the fillet regions where it was less than 25 microns thick. Details of the sample inspection and whisker growth results are provided.
Initially Published in the SMTA Proceedings