Drop impact life model development for FBGA assembly with lead-free solder joint

Drop performance for fine-pitch ball grid array (FBGA) assembly is one important issue because FBGA is widely used in handheld electronic products in which the solder joints are prone to failure when subjected to drop impact load during application. It is necessary to assess and improve the FBGA solder joint drop performance during design and engineering stage. The drop impact life model is needed for predicting solder joint drop life. In this paper, total 13 different FBGA assemblies with lead free solder joints were tested under drop impact load. Failure analysis for each FBGA assembly was conducted to investigate failure mode and mechanism. Bulk solder cracking is one dominant failure mode. Drop testing life was obtained from Weibull distribution model analysis of failure data. Drop impact life model was developed for FBGA assembly with lead free solder based on experiment data and finite element modeling and simulation result with considering strain rate dependant plastic behavior of solder. The good correlation between tested drop life and prediction using developed life model was achieved. The effect of package size and design on solder joint drop life was investigated through drop test and FE modeling.