Interface failure in lead free solder joints

The phenomenon of interface failure in lead free solder joints was explored using solder joint array tensile testing. The effects of pad metallization, solder alloy, reflow conditions, and post reflow thermal aging were quantified. The joint strength ranged from 5 to 115MPa. The joint ductility dropped to zero in some cases. The interface microstructure and failure mode were characterized for each combination of factors. Most of the trends were linked to microstructural features of the interface. A ductile-to-brittle transition strain rate (DTBTSR) was defined as a metric to quantify the performance of a specific joint relative to interface failure. The DTBTSR ranged from 10
^-3
/sec to 10/sec for the conditions studied