Shear Stress Evaluation of Plastic Packages

A study has been performed to determine the impact of package assembly on shear stress phenomena in plastic encapsulated integrated circuits (IC's). Test structures were used which allowed quantitative measurements of compressive stresses along with qualitative observation of shear Stress effects. Results from experiments with various mold compounds, lead frame materials, and mount compounds Will be presented. The experiments led to the development of a simplified stress model which can be applied to evaluating package and chip designs of future products.