Hydroxyl-Terminated Polyphenylene Oxide Improved Thermal and Dielectric Properties of Active Ester Cured SiO2/Epoxy Composites for Advanced Electronic Packaging

Low-dielectric epoxy-based composites are crucial for advanced electronic packaging in the high-speed digital communication field. An effective method to achieving low dielectric loss (D_f) is to construct active ester-curing system. However, the introduction of large ester groups negatively affects the thermal stability of cured epoxy composite. Herein, hydroxyl-terminated polyphenylene oxide (PPO) is incorporated into allyl bisphenol A-based active ester-cured SiO₂/epoxy composites, and their thermal and dielectric properties are evaluated. By incorporating 20 wt% of PPO, the SiO₂/epoxy composites achieve an ultralow D_f of 0.0022 at 1 kHz and a low coefficient of thermal expansion of 29.0 ppm °C⁻¹ below T_g, while the glass transition temperature (T_g) is increased from 97.7 to 117 °C and the value of Young's modulus is enhanced from 8610 to 10 331 MPa. Moreover, the introduction of PPO in the SiO₂/epoxy composites significantly enhances the thermal and humid stability of the dielectric constant (D_k) and D_f owing to the ultralow water absorption of 0.12%. These results demonstrate that the combination of PPO and active ester in SiO₂/epoxy composites should be a potential strategy for designing advanced electronic packaging materials.