Testing failure of solder-joints by ESPI on board-level surface mount devices

Fast and nondestructive welding quality inspection on board-level BGA and PLCC devices is relatively difficult due to small size and special location of solder joints. In this study, a novel testing method combing Electronic Speckle Pattern Interferometry (ESPI) and Finite Element Analysis (FEA) was proposed to detect joint failures in surface-mount devices. ESPI technology was utilized to compare the difference of assembly deformation between damage solder joints and the good counterparts under simple mechanical loadings. Using finite element analysis, the location and failure modes of damage joints were identified. The testing results from pseudo BGA sample and real PLCC device illustrated the validity of the method; especially for testing corner solder joints.