Design of ultra-microporous COF for effectively enhancing the dielectric and fire resistance of bismaleimide based electronic packaging material

Abstract

Most common flame retardants have high polarizability, so introducing flame retardants with simple structures to simultaneously improve the flame retardancy and dielectric properties of bismaleimide resin is a technical challenge. This work utilized the unique microporous structure of covalent organic framework (COF) as a low dielectric factor combined with molecular design to synthesize phosphonitrile based COF-N with a pore size of approximately 1.8 nm. The dielectric constant (Dk) of BMI composite containing 1 wt% COF-N (BMI/COF-N 1.0) is as low as 2.76, far exceeding the requirement of less than 3. Moreover, BMI/COF-N 1.0 achieved UL94 at V0 rating, with a 37.9 % reduction in total heat release (THR) and a 55.6 % reduction in total smoke production (TSP), demonstrating excellent fire safety. In addition, the glass transition temperature (Tg) exceeds 290 ℃, which is greater than the heat resistance required for lead-free reflow soldering at 260 ℃. Therefore, a simple method is provided to prepare high-performance BMI based electronic packaging substrates.