Polyphenylene oxide/boron nitride–alumina hybrid composites with high thermal conductivity, low thermal expansion and ultralow dielectric loss

Abstract Traditional integrated circuit (IC) packaging materials and printed circuit board substrate materials suffer from several limitations including low thermal conductivity, high coefficient of thermal expansion (CTE), and poor dielectric properties. Although significant efforts have been made to enhance these properties, achieving a single composite system with simultaneous high thermal conductivity, extremely low CTE, and dielectric loss remains a formidable task. In this study, we propose a hybrid polymer composite system that addresses these challenges. Our approach involves utilizing a thermosetting polyphenylene oxide (PPO) as the resin matrix, while incorporating boron nitride (BN) sheets with high thermal conductivity and alumina (Al 2 O 3 ) spheres with favorable fluidity as fillers. To optimize the composite properties, the filler surfaces are modified using dopamine and silane coupling agents, ensuring proper interface control. The composites exhibit significant improvements in thermal conductivity, reduced dielectric loss and CTE, while maintaining excellent processibility. Specifically, with a composition of 25 vol% BN and 25 vol% Al 2 O 3 , the thermal conductivity of the composite reaches 2.18 W·m −1 K −1 , surpassing neat PPO resin by a factor of 10.9. Simultaneously, the CTE decreases from 2.27% to 1.18% between 50 and 260°C, and the dielectric loss reduces from 0.0024 to 0.0011 at 10 GHz, as compared to neat PPO resin. Highlights The reported novel hybrid composite offers a promising solution to the limitations of traditional IC packaging materials. The reported hybrid composite exhibits significantly improved thermal conductivity, ultralow dielectric loss, and reduced coefficient of thermal expansion, while maintaining excellent processibility. The thermal conductivity of the composites reaches 2.18 W·m −1 K −1 , surpassing that of the neat resin by a factor of 10.9, meanwhile the dielectric loss is as low as 0.0011 at 10 GHz, which is extremely difficult to achieve simultaneously for thermosetting polymer composites. Synergetic effects were realized with the hybridization of fillers with different dimensionality, and proper filler surface modification.