Using Uncertainty Analysis to Validate Reliability Prediction in WLP with Idealized Solder Joint Modeling

The reliability of solder joints in semiconductor packaging is crucial as it significantly impacts the performance and reliability of electronic devices. The industry typically uses Accelerated Thermal Cycling Test (ATCT) tests to predict the lifetime of solder joints in packages. However, due to the high costs and lengthy time requirements of ATC tests, replacing traditional ATCT tests with finite element simulation is crucial. Simulation can improve design efficiency and further reduce time costs. Idealized solder joints are often used for modeling in simulation. However, real-world manufacturing processes introduce dimensional uncertainties, commonly referred to as tolerances, which affect the lifetime of solder joints. Therefore, uncertainty analysis is needed to validate the reliability analysis of using idealized solder joints for modeling. This research conducted an uncertainty analysis of solder joint dimensions to verify the effectiveness of using idealized solder joints for modeling and predicting the lifetime of solder joints under inherent manufacturing uncertainties. Specifically, for the wafer-level packaging (WLP) simulations, idealized solder joints were initially used for modeling, and the lifetime was predicted using the Coffin-Manson model. Uncertainty analysis was then performed with simulation, introducing variations in the upper pad diameter, lower pad diameter, and solder ball volume, resulting in 5 × 5 × 5, or 125 different geometric combinations of solder joints with manufacturing errors. The Coffin-Manson model was used again to predict the lifetimes of these solder joint combinations. A Weibull distribution analysis was conducted to determine the 63.2 percentile of the lifetime distribution under simulated manufacturing errors, also known as the characteristic life, which served as our standard metric for reliability evaluation. This characteristic life was then compared with the predicted lifetime from the idealized solder joint modeling to assess the reliability of the idealized modeling. The uncertainty analysis conducted in this research demonstrates that although manufacturing uncertainties lead to variations in the reliability of individual WLP reliability, the results from idealized solder joint modeling are very close to the overall characteristic life This result validates the robustness of using idealized solder joint modeling to simulate and predict WLP reliability, even in the presence of manufacturing uncertainties.