A Novel Phosphorus Containing Flame-Retardant Benzocyclobutene Composite Materials With Low Dielectric Constant

In the era of high-frequency 5G technology, the exigency for copper clad laminate (CCL) substrate materials of unparalleled performance has grown exponentially. These materials necessitate possessing not only a diminutive dielectric constant, elevated thermal stability, and robust mechanical properties but also an inherent flame-retardant nature to ensure utmost safety and unwavering stability. However, conventional phosphorus-based epoxy systems, erstwhile employed as CCL substrate materials, have proven inadequate in meeting the demands of high-performance applications. Consequently, the development of novel phosphorus-based flame-retardant systems has become an imperative pursuit. In this study, we synthesized a series of flame-retardant cured resins by incorporating octavinyloctasilasesquioxane ((vinyl) 8 -POSS) and DVSBCB prepolymers (pDVSBCB) into three different BCB functionalized phosphorus-containing monomers (Ph 2 POB, PhPOB 2 , and POB 3 ), followed by thermal curing. Among these cured resins, POB 3 /BCBNPs/(vinyl) 8 -POSS/pDVSBCB (M4) exhibits remarkable properties, including an extremely low dielectric constant ( D k : 2.53) and dielectric loss ( D f : 2.09 × 10 −3 ), excellent thermal stability with a T 5% value of 451°C, a coefficient of thermal expansion (CTE) of 19.94 ppm/°C over the temperature range of 30°C–300°C, a high thermal release (THR) value of 31.6 kJ/g, and superior mechanical characteristics, such as an elastic modulus of 22.96 GPa and a remarkable hardness of 1.46 GPa. These exceptional properties position M4 as a promising candidate for the development of advanced CCL substrate materials.