Author(s)

Q Yu, H Kikuchi, S Ikeda, M Shiratori, M Kakino & N Fujiwara

Abstract

The purposes of this study are to clarify the dynamic behavior of BGA (Ball Grid Array) or CSP (Chip Scale Package) packaging subjected to an impact loading, and to establish a simple analytical method of impact reliability assessment for solder joints. A 3-D analytical model of PCB mounted with a BGA chip was used to simulate the impact behavior of BGA packaging, and explicit-based FEM code LS-DYNA was used to carry out the dynamic analysis. It was found that the impact reliability of solder joints is greatly affected by the falling posture. However, it was found that fine meshing of solder joints causes a rapid augmentation of calculation cost. In this study, the authors proposed a new method of transient response analysis by utilizing implicit-based FEM code NASTRAN to drop the calculation cost of impact study. It was shown that the present method can accurately simulate the dynamic behavior of BGA packaging including the time histories of the deformations and stresses, and it can drop the CPU time to about one tenth of that of LS-DYNA analysis. Furthermore, based upon the analytical and experimental results, it was found that the impact reliability of solder joints is dominantly affected by the first mode vibration of PCB, and the effect of the higher modes can be neglected. Finally, a basic concept for impact reliability assessment method was proposed for CSP solder joints based on the results of the present analytical method and set of free fall drop tests of PCB (Printed Circuit Board) mounted with a CSP chip.

Keywords