Effect of Particle Arrangement on the Effective Thermal Conductivity of Polymer Composites

Alternative thermal management solutions for electronic devices are being widely explored due to the increasing power density that results from shrinking sizes and increasing power of modern electronics. Clearly, there is a need to spread the heat effectively in these systems, and polymer composites can potentially provide high thermal conductivity at low filler fraction while maintaining desirable mechanical properties for electronic packaging. The present study aims to investigate the effect of filler particle arrangements on the thermal conductivity of a polymer matrix. Although typical composites consist of particles randomly distributed in a polymer matrix, this work focuses on a 2D analog of these composites with well controlled filler configurations to directly observe the impact of filler arrangement and validate models for thermal conductivity. With these methods, we aim to improve the physical understanding of thermal transport in composite TIMs. Here, the composites are fabricated using laser cut acrylic templates to embed vertically aligned copper rods in a polymer and create different configurations, while maintaining a constant volume fraction. The arrangements of interest are a cubic grid, a hexagonal grid, and random placement. Heat conduction through the cross-section of the composites is directly observed with an infrared (IR) camera that enables 2D mapping of temperatures. The effective thermal conductivity of the composites is obtained using a simplified 1D reference-bar type technique. The experimentally obtained effective thermal conductivity is compared to COMSOL numerical simulations and effective medium models. Furthermore, the experimental and simulation results help provide an understanding of the thermal behavior of composite materials. Such polymer composites, with enhanced conductive properties, can be implemented in electronic packaging as an alternative to conventional heat dissipation methods (i.e. mechanical fans, heat sinks, fins).