Optimal design of thin-profile fine-pitch ball grid array package under drop impact test

摘要

This article describes the board-level drop reliability of thin-profile fine-pitch ball grid array (TFBGA) subjected to Joint Electron Device Engineering Council (JEDEC) drop test conditions featuring an impact pulse profile with a peak acceleration of 1500 G and a pulse duration of 0.5 ms. The solder ball is assumed to be an elastoplastic model and the other components linear elastic ones. Both the global/local finite element and the finite grid region methods are introduced to improve the accuracy and the convergence during the meshing process. Meanwhile, the contact impact process during the drop test is translated into the effective support excitation load on the printed circuit board (PCB) through the support excitation scheme to simplify the analysis. By means of optimal parameters of the Taguchi robust design, the average stress of the solder ball at the PCB side surface becomes 80.9 MPa, which shows a 57 per cent reduction compared to the original stress of 189.7 MPa. As a result, the impact reliability of the TFBGA package is significantly improved. Finally, the JEDEC drop test is conducted to verify the optimal results obtained by the Taguchi method.