Modal analysis of board-level electronic package

The reliability of board-level electronic package subjected to drop impact is one of the most concerned issues. After drop impact, the Printed Circuit Board (PCB) experiences free vibration which leads to the deformation of PCB, hence the failure of solder joints. The free vibration is dependent on the inherent parameters of PCB. So it is necessary to study the inherent parameters of board-level package. Modal analysis is a common way to characterize the inherent dynamic parameters of a system. By modal analysis, we can understand the inherent vibration features of board-level package system. In this paper, the theoretical vibration model of the JEDEC standard PCB assembled with three Chip Size Packages (CSPs) is performed. Then the results of theoretical analysis are validated by that of finite element analysis (FEA) and modal test. A series of modal parameters are obtained during the modal analysis such as the mode shapes, the natural frequencies and the damping ratios. These parameters are useful for studying the dynamic response of PCB and the strain rate of solder joints during drop test. The Modal Assurance Criterion (MAC) value is used to validate the correlation between two modal shapes obtained from two different modal parameters estimation methods during modal analysis. The MAC value is computed for the first two order mode shapes, indicating the high correlation between the experimental and predicted (including theoretical and FE results) mode shapes.