Development and application of innovational drop impact modeling techniques

Due to demand for short time-to-market, drop testing has become a bottleneck for semiconductor and telecommunication industry. Therefore, there is a need for a faster and cheaper solution, i.e. validated drop impact model, which is accurate, reliable, and enables understanding of physics-of-failure for design improvement. Currently, there has been increasing interest and effort by researchers on board level drop test studies by numerical modeling. Several different modeling methods have been developed to satisfy the requirements in package design analysis, product qualification, and impact life prediction. In this paper, for the first time, various advanced drop test modeling techniques developed are systematically introduced, integrated, compared, and recommended for various applications, consisting of analysis type (dynamic vs. static), loading method (free-fall vs. input-G), and solver algorithm (explicit vs. implicit). Each combination of modeling techniques has its unique advantages, depending on applications. All the models are validated to show excellent first level correlation on the dynamic responses of PCB, second level correlation on the solder joint stress and failure mode, and third level correlation on impact life prediction. Dynamic model is required for accurate drop impact simulation, whereas static model is useful for quick design analysis and optimization. The free-fall drop model can be applied to provide fundamental understanding of different drop test conditions, i.e. drop height, contact surface, drop block, felt layer on the impact pulse. Once the impact pulse has been established, the input-G method can be used as a standard "numerical drop test" to perform design analysis and optimization for product qualification. Implicit solver is an alternative to explicit solver, saving software cost by maintaining only one type of solver, but the technical challenge is greater.