Warpage modeling for 3D packages

Package warpage is a primary concern in a package-on-package. To enhance the accuracy of modeling prediction, viscoelastic parameters, the change of material properties after injection mold cure (IMC) and post mold cure (PMC) temperature and it´s time, and cure shrinkage were studied with a dynamic modulus analysis (DMA) and a thermal mechanical analysis (TMA) for a mold compound. A nano-indentation tool was used to characterize a viscoelasticity of underfill material. Material properties obtained from the TMA, DMA and nano-indentation tools were introduced to finite-element-based models. The validation of models was verified with a shadow moiré for package warpage. As model simplification, inverse approach is described for an example of package warpage.