Finite element analysis of lead-free drop test boards

Lead-free CSP assemblies were drop tested according to the JEDEC standard (JESD-B111) and the finite element analysis of the test assembly was carried out to simulate the strain and stress distributions generated in the assemblies. The vibration of the board during the test was measured with strain gauges and the results were compared to the FE model predictions. The eigenfrequency analysis was executed to determine the mechanical properties of the assemblies under very fast deformations and the results were used to improve the FE model. The calculated strains correspond well with the measured ones and there was good correlation between the calculated stresses and the observed failure modes.