THE IMPACT OF IMPROPER CONFORMAL COATING PROCESSES ON BGA SOLDER JOINT INTEGRITY

摘要

Avionics equipment manufacturers often use conformal coatings, such as acrylics or urethanes, on printed circuit board assemblies to improve product robustness or for tin whisker risk mitigation. Area array components, such as Ball Grid Arrays (BGAs), Chip Scale Packages (CSPs) and Flip Chips (FCs), tend to add complexity to conformal coating processes. Previous studies have shown that the presence of conformal coatings under an area array component can induce solder joint failure. Therefore, area array parts are often masked during the coating processes, which adds to the cost of the process as well as leaving the parts themselves uncoated. An investigation was conducted to better understand how conformal coatings impact the solder joint integrity of BGA components. Five different conformal coatings were applied to test boards with BGA components. The test boards were subjected to thermal cycling and the solder joint integrity of the parts was monitored. This showed that some of the coating configurations degraded component reliability while others actually improved it. The presence of coating, in at least some of the test configurations, appeared to introduce additional failure modes.