Study on the board-level drop test of WLCSP with RDL by finite element analysis

The dropping test of WLCSP with RDL on board-level was investigated by numerical method in this study. The asymmetric pattern of WLCSP devices mounted on the PCB board was considered. Using the finite element analysis, the stress and energy in the WLCSP with RDL was predicted under the dropping test conditions. The critical locations of WLCSP device on the PCB in the dropping test were identified by effective models, which simplified the detail structures, e.g. thin layers. Thereby, the fine models with RDL etc. in the critical locations were built in ANSYS and analyzed under mechanical shock loading of 2000G in 0.5ms. The stress in the RDL under the critical solder joints were compared when the device was in different locations and the effect of RDL was illustrated. On the basis of the above analysis, the suggestions for improving the reliability of WLCSP with RDL were proposed.