Abstract: The development of flexible substrate resin materials featuring low dielectric constant, low dielectric loss, excellent thermal stability, and moisture resistance is essential for meeting the escalating demands of high-frequency and high-speed signal transmission in modern electronic devices. Herein, we report a facile and controllable strategy for synthesizing core-shell structured KH570-ZIF-8@SiO₂ (KZ@S) nanofillers in a non-methanol solvent system. These KZ@S nanofillers were incorporated into bismaleimide-triazine (BT) resin to fabricate a series of nanocomposites. By precisely tailoring the pore structure of the silica shell, the release of catalytic Zn²⁺ species and active hydrogen from 2-methylimidazole was effectively restricted. This regulation mechanism enhances the interfacial compatibility between the two constituent phases of the BT resin, thereby optimizing the curing behavior and significantly improving the flowability and processability of the BT prepolymer. The resultant BT nanocomposites exhibit superior thermal stability and excellent dielectric performance, achieving a low dielectric constant of 2.82 and an ultralow dielectric loss of 0.0086 at 10 GHz with a glass transition temperature exceeding 280 °C. Furthermore, the composite demonstrates strong moisture resistance with a water contact angle of 105.8°. This work successfully demonstrates the feasibility of impregnation processing for BT resin prepolymers at lower temperatures, enabling their further processing into flexible resin-coated copper foil and offering a promising pathway for next-generation flexible electronic packaging.

Key words: Core-shell nanofillers, Dielectric properties, Processability, Flexible electronics, Substrate material