Printed circuit board assembly with lead free solder is now a reality for most global electronics manufacturers. Extensive research and development has been conducted to bring lead free assembly processes to a demonstrated proficiency. Failure analysis has been an integral part of this effort and will continue to be needed to solve problems in volume production. Many failure analysis techniques can be directly applied to study lead free solder interconnects, while others may require some modification in order to provide adequate analysis results. In this paper, several of the most commonly applied techniques for solder joint failure analysis will be reviewed, including visual inspection, x-ray radiography, mechanical strength testing, dye & pry, metallography, and microscopy/photomicrography, comparing their application to lead bearing and lead free solder interconnects. Common failure modes and mechanisms will be described with examples specific to lead free solders, following PCB assembly as well as after accelerated reliability tests.