Influence of Material Combination on Package Stress and Verification of Numerical Model

This paper demonstrates the experimental approach of using various packaging material combination and their effect on package stress at 260degC IR reflow condition. The study is extended into validating the results with the use of simulation and modeling tool using finite element analysis (FEA). Large leadless package (7.0 times 7.0 mm) was selected for this study. Samples were built with different material combination of epoxy based die attach and mold compound materials and subjected to specially designed stress tests. Scanning Acoustic Tomography (SAT) was used to detect the presence of delamination after the stress cycle. Mechanical properties of these materials are fed into FEA tool and simulation was done to predict package stress under the designed special testing condition. A correlation between experimental and FEA simulation result was established. The numerical and experimental analyses of the specially designed test confirmed the accuracy of the FEA prediction, which could be convenient for future virtual prototyping analyses. This will help to reduce the experimental and test time for future package design and development.