Warpage Investigation of PCB Embedding Technology – Determination of Relevant Modelling Parameters by Means of FEM and Experiments

The focus of this study concerns the thermo-mechanical understanding of prepreg materials during the lamination process in order to predict the correct warpage behavior of a multi-layer stack-up, and with that, the corresponding mechanical stress state. During the lamination process, under temperature and pressure, the polymeric resin reacts and forms a three-dimensional structure. This process causes the material to reduce its volume and initiates stress. The part of the volume shrinkage, which causes these stresses, are in this work referred to the process induced shrinkage of the prepreg, and is determined by combining thermo-mechanical Finite Element (FE) simulations and warpage measurements of a two-layer stack-up. This stack-up consists of a core (fully cured) with a second, pre-cured prepreg layer identical to the core material. After characterization of the temperature and time dependent mechanical properties, the warpage is characterized by topographic measurements based on phase shifting line patterns. A parameter identification approach will be introduced to determine the unknown process induced shrinkage of the pre-cured prepreg.