FEM simulation study on the free drop of electronic modules based on calibrated and validated models

Modal, harmonic and transient simulations have been performed on typical electronic modules consisting of a printed circuit board to which ball grid array (BGA) components are mounted. The BGA solder joints are modeled as continuous layers applying effective values for stiffness and density. This way, the simulation run time was minimized without reducing the accuracy of the targeted global results: natural frequencies, spatial distribution and magnitudes of acceleration, deformation, and strain. These results allow the identification of the first failing component correctly as it was found in subsequent validation experiments of vibration and shock tests. Applying the validated models, a case study was conducted investigating the response of the electronic module to a typical free drop test scenario, in which one corner of the module´s printed circuit board hits the rigid ground after falling from a height of 1 meter. In particular, the effect of the boundary conditions was assessed, which determine the specifics of loading and response. As practical consequence, the use of a drop plate of polished steel with a hardened surface is recommended for achieving most reproducible drop test results. In general, the paper demonstrates an FEM simulation procedure that provides trustworthy and detailed results on the free drop test.