| The objective of this paper was to model the vibration and shock response of computer motherboards using explicit dynamic analysis software, ANSYS LS-DYNA. The motherboard was built using simple block finite element model. The acceleration due to gravity from a free fall was calculated for a calibration aluminum plate, a plain FR4 board and an Intel ATX motherboard at six critical points. Good correlation was observed between predicted and the measured (g's). In particular, the shapes of the acceleration response curves were quite accurate to the measured curves. The accuracy of the results did not vary with the drop height and hence a constant drop height of 12 inches was employed for all three cases. The material properties for the components of the motherboard were previously calculated using 3 point bend test and FEA simulation. The mesh of the aluminum plate model and ATX motherboard was refined and the results were shown to be independent of mesh density. The results obtained from this analysis were equivalent in accuracy to the results obtained from other methods such as Mode Superposition and Time Marching, which were used in previous studies. Another aspect of this study was to calculate the plastic strain developed in the solder balls of a standard BGA package due to drop testing. A simple 2-D model of the BGA package was built and the plastic strains on the solder balls was calculated and plotted for different drop heights. |
