Methodology development of warpage analysis of polymer based packaging substrate

Warpage of packaging substrate has been at issue due to thin and flexible substrate. It is occurred during manufacturing processes. Although warpage research based on thin metal film and silicon substrate was actively studied, it has difficulty about research of polymer based electronic due to its flexibility and low stiffness compared to metal and silicon substrate. We suggest a new methodology of warpage analysis to predict the warpage behavior of polymer composite substrate based bilayer specimen during temperature rising. The warpage analysis is performed in the sequence of scanning 3D surface, calculating curvature and built-in stress of film and verifying the result using FEM simulation. Two main factors of warpage behavior are built-in stress in film layer and stress induced by misfit of coefficient of thermal expansion between film and substrate. Built-in stress, arisen from built-in strain, is generated during film lay-up process such as electro-plating of copper, curing process of polymer. It is computed from the curvature at room temperature using the strain-curvature relation. Though this analysis method, the predicted curvature through temperature cycle showed good agreement with the experiment.