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

ABSTRACT 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.