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Finite element analysis (FEA) is widely used throughout the electronics industry to understand the thermal and thermo-mechanical behavior of electronic packages and interconnect during their manufacture and lifetime. After encapsulation, thermo-mechanical stress builds up within the package due to temperature coefficient of expansion mismatch between the respective materials within the package as it cools to room temperature. Due to the complexity and time consuming of the calculation, it is almost impossible for industry to carry out the numerical simulation using viscoelastic property which is the most close to the real material property of polymer material. However, FEA using temperature-dependent elastic property, temperature-dependent thermal expansion coefficient and accurate chemical cure shrinkage can help to improve the accuracy on the stress and warpage prediction. This study has developed an evaluation method for the chemical cure shrinkage based on the measurement of the warpage of bimaterial model. The results show that FEA simulations without chemical cure shrinkage fail to accurately predict the package warpage. On the other hand. FEA simulations with chemical cure shrinkage is outlined which show fair agreement with experimental measurements of package warpage over a range of temperatures.
Date of Conference: 14-17 Aug. 2007