Thermomechanical and Electrical Material Characterization for a DLP Printing Process Simulation of Electrically Conductive Parts

Due to the steady development of conductive filled resins and multi-material techniques for the digital light processing (DLP) additive manufacturing technology, fabrication of complex conductive structures for microelectronic applications is becoming a potential use case for this technology. When processing electrically conductive systems, temperature effects are of special importance, as the highly filled systems often need elevated temperatures for an increase in reaction rate and to decrease viscosity to achieve printability. Thus, an accurate calculation of the temperature distribution during the process is needed for accurate process modeling. This study describes the thermomechanical material characterization and kinetic modelling including exothermic heat generation during curing for a thermal simulation as part of a DLP process simulation framework. The key properties for the simulation, such as specific heat capacity, thermal diffusivity and reaction enthalpy were characterized and compared between specifically developed conductive and non-conductive acrylic resins. In addition, the temperature dependent mechanical properties were studied and the electrical conductivity of the filled material was measured. A simulation was set up to calculate the heat generation due to the exothermic reaction during printing and the results were validated against measured data from printing trials with the nonconductive material. The results of this work show the temperature dependence of important properties of unfilled and electrically conductive materials for the thermal DLP process simulation and the capabilities of the proposed simulation strategy to calculate the temperature distribution during the process.