The Impact of Varying Feature Dimensions on Substrate Reliability Risks

A sensitivity study is undertaken to characterize the impact of varying feature dimensions in emerging electronic packaging technologies. Specifically, the overall structural performance of the substrate under use conditions (thermal and combined thermomechanical loading) is investigated. The study consists of both modeling and experimental efforts. Modeling approaches are employed within the framework of a finite element code to simulate performance of different design geometry combinations in the known failure mode of solder resist layer cracking. In the models, two levels of complexity are used to better identify the impact of the individual features on the overall substrate reliability. First, local geometry is captured by including each substrate layer. Individual component geometries like microvias and PTHS are also explicitly modeled to capture synergistic failures modes. Second, more realistic non-linear material properties are used to characterize time, temperature, and rate-dependant constitutive behavior of individual substrate materials such as buildup, core, metal, etc. In the experiments, substrate warpage and reliability data is collected for validating the predictive modeling capability. From this study, directions for future design guidelines varying feature dimensions while maintaining substrate reliability are proposed.