Simulation Model to Predict Failure Cycles in Board Level Drop Test

Abstract

Drop reliability of Ball Grid Array (BGA) packages has been a concern for electronic packages to meet drop performance requirement. Joint Electron Device Engineering Council (JEDEC) has provided a board-level drop standard to investigate the drop performance of electronic packages. Simulation models have been developed to simulate the drop dynamics in drop tests. However, thus far, there is no valid finite element model to predict the failure cycles for JEDEC drop tests. In this study, a finite element model is developed to simulate the drop response of package drop tests for JEDEC board level and further predict the failure cycles under a certain drop height. Solder joints are modeled as elastic-plastic materials that have been studied in drop tests. The simulation model is first correlated with the transient dynamic response of board in drop tests. Then a failure prediction model is determined by correlating the simulation results and test data. The averaged plastic energy density (SED) is used as a damage indicator to predict failure cycles and calculated using two different approaches. The first approach calculates the averaged SED for the critical volume at the solder-pad interface with a fixed thickness. The second approach calculates the averaged SED for a critical volume that is initiated from the element with the highest SED and then expands to the adjacent elements until a given percentage of volume is reached. The parameters in the drop cycle model were obtained by comparing with the test data. It would expect the developed model can well predict the failure cycles in board level drop tests. This study could serve as a foundation for modeling solder joint fatigue failure during drop tests and provide design guidance to improve BGA solder joint reliability in drop tests.