Simulation Of Thermal Conductivity Of Filled Epoxy Composites

With the rapid development of the electronics industry,the problem of short chip capacity cooling increasingly prominent.Underfill is the most attractive chip package,has very good connection reliability,but the low thermal conductivity of the epoxy resin limits its development,therefore,epoxy resin composites with high thermal conductivity have become the focus of the research.The thermal conductivity of the epoxy resin composites is related to the volume fraction of the filler,the physical shape,its own attributes,the particle size,and the distribution of the filler in the matrix.Due to the influence factors,the experimental study is time consuming and labor intensive.In this paper,models were established by Digimat,and the relationship between the effective thermal conductivity and the microstructure of the filled epoxy resin composites was studied by numerical simulation based on representative volume element.Taking the Al₂O₃/Epoxy composites as the research example,the reliability of the thermal conductivity simulation method based on the representative volume element is verified by comparing the simulated and experimental values of the thermal conductivity of the composite system.At low filling（mass fraction less than 30%）,the simulated value is consistent with the experimental value.Under high filling（mass fraction greater than 30%）,the simulated value has the same trend as the experimental value.First,the effects of thermal conductivity,shape,orientation and aspect ratio on the thermal conductivity of the composites were investigated.the results show that:Under the same volume fraction,the cylinder type filler has better effect on the thermal conductivity of the composite than the regular spherical particles.Rely on increasing filler thermal conductivity to obtain high thermal conductivity epoxy composites have some limitations.The cylinder type filler has the strongest thermal conductivity along the elongation direction.The longer the aspect ratio is far away from 1,cylinder or flake type filler packing has a better effect on the thermal conductivity of composite materials.Then mixing system with different sizes of fillers and with different shapes of fillers were studied,the simulation results show that:Filling with different sizes of fillers is better than filling a single particle size filler with epoxy.At the same volume fraction,cylinder type or flake type fillers with diffident aspect ratio filled epoxy have a better effect than those epoxy composites filled with different size of spherical fillers.Filling with different types of fillers is better than filling a single type filler with epoxy.At the same volume fraction,cylinder type and flake type fillers combine together has the best effect on the thermal conductivity of epoxy composites.