Surface Mounted Devices (SMDs) are widely used throughout microelectronics and power electronics. They mostly employ epoxy molding compound (EMC) based encapsulations. Thus, enhanced lifetime assessment methods are necessary. To understand the stress situation in SMDs at the end of the production cycle, an improved model approach for the curing of EMC is implemented within Finite Element Analysis (FEA) simulations. During production, e.g., in a Resin Transfer Molding (RTM) process, material properties are spatially varying due to different curing degrees. Hence, a mismatch of mechanical properties is present, which in return leads to internal stresses. The introduced model approach is an extension of the work of Gschwandl et al. (2017) and includes a stress-free deformation before vitrification, changing material properties during curing, as well as plastic deformations and visco-elastic effects. The implementation in numerical FEA simulations allows for a better understanding of arising residual stresses and helps optimize the production cycle of SMDs.