Significantly Enhanced Thermal Conductivity and Dielectric Properties of Epoxy Composite Films Derived by Constructing Networks of Surface Coated Alumina Fillers

Electronic packaging technology is experiencing rapid evolution, marked by increased device integration and power density. The effective dissipation of accumulated internal heat during device operation lies as a pivotal factor in determining the long-term reliability of devices. Thermally conductive polymer composites, extensively employed in the realm of electronic packaging, exhibit relatively limited thermal conductivity. The strategy of integrating copious amounts of ceramic and conductive particles into the polymer matrix has been shown to significantly enhance the thermal attributes of the composites. However, this approach concurrently imposes detrimental effects on their mechanical and electrical characteristics, manifested by reduced fracture strength and a notable increase in dielectric loss. Herein, the thermal conductivity of the epoxy composite is enhanced upon the addition of alumina particles surface coated with polydopamine (Al2O3-PDA), which facilitates their uniform dispersion within the epoxy resin matrix and enables dense interfacial adhesion between the filler and the resin. This methodology circumvents the adverse impacts on mechanical and electrical properties that typically accompany increased filler content. According to the Dinger-Funk densest packing theory, a thermal conductive network is established by the orderly arrangement of multi-sized filler particles, which substantially elevates the thermal conductivity. Al2O3-PDA/Epoxy composite films display an exceptional thermal conductivity of 1.62 Wm(-1)K(-1), alongside low dielectric loss (Df similar to 0.006 at 1 kHz), a low coefficient of thermal expansion (CTE, alpha(1 similar to)54.5 ppm K-1 between 30-120 degrees C). The success in applying the polydopamine surface coating strategy and the multi-sized densest packing theory not only underscores a significant leap in the field but also paves the way for advancing the performance of thermally conductive composites.