An Image-Based Effective Property Method for Strip Warpage Modeling

QFN (Quad Flat No Lead) package strip warpage simulation is challenging due to the size of the model and intricate features of the lead frame. A simple and efficient image-based approach is applied for a QFN lead frame strip, treating it as two half-etch layers. The approach is found to be accurate and efficient for simulating strip warpage as a function temperature, as demonstrated through validation with detailed 3D model and empirical measurements. For large strips over wide temperature range, Reuss method of averaging Young's modulus shows good correlation with empirical data on mold block.