Interconnection Design and Impact Life Prediction Subjected to Board Level Drop Test

In this study, the objective is to develop a proper impact life prediction model for stress-buffer-enhanced package which has a specific failure mode, the fatigued metal trace, during board level drop test. The so called stress-buffer-enhanced package applies a thick and soft buffer layer to protect solder joints; however, metal traces embedded inside the buffer layer are instead broken. The fatigued metal trace is not common for board level drop test, and there are few life prediction models to predict the performance of the package. Unlike thermal cycle test, the dynamic response of drop impact is irregular and not cyclic; therefore, the concept of cumulative damage is considered in the life prediction model. The results showed that the cumulative plastic strain of metal trace could accurately predict impact life. Besides, the interconnection designs are then proposed in this study. Results show that the curved trace layout and the sandwich structure can greatly enhance the drop performance of the stress-buffer-enhanced package.