Effect of lead-free BGA rework on joint microstructure and intermetallic compound formation

The last five years has seen a massive increase in area array type packages such as the ball grid array (BGA) and the chip scale package (CSP). Improvements in performance and yield, achieved by the greater interconnect density of this packaging format, have been responsible. However, one of the key challenges in using area array type packages such as the BGA, are the difficulties associated with inspecting and reworking the array type interconnects. In practice, a solder joint repair can only be affected by removal of the whole device and then replacement with a new device. Although there are numerous reports on lead-free soldering, investigating various alloy systems and other aspects of the soldering process reports on the effect of lead-free BGA rework are very scarce. In particular, there is very little documented regarding the combination of rework processes and the use of lead-free materials and their resultant effect on solder joint metallurgy and mechanical performance. We report on the investigation of a lead-free BGA rework technique. Two PCB pad-cleaning methods (solder wicking and hot air de-soldering) were investigated to assess their impact on the joint microstructure and the intermetallic compound formation.