Highly flame retardant and thermal conductive epoxy composites using curing agent and boron nitride modified by phosphorus containing group

High flame retardancy and thermal conductivity are key performances for advanced electronic packaging materials. Herein, boron nitride (BN) and epoxy curing agent were chemically bonded with highly flame retardant DOPO moieties to obtain BN-DOPO thermal conductive filler and DOPO-PA curing agent with flame retardancy. The effect of BN-DOPO and DOPO-PA on the thermal stability, flame retardancy, combustion behavior and thermal conductive performance of EP composites were analyzed in detail. Compared with EP/Al(OH)₃, up to 32.5% in LOI, V0 rating in UL-94, prolonged 125 s of TTI, 22% reduction of PHRR and 29% reduction of THR in cone test were observed when both BN-DOPO and DOPO-PA were incorporated into EP cross-linking network. According to the residual char morphology, the excellent flame retardancy of EP/Al(OH)₃ composite containing BN-DOPO and DOPO-PA was attributed to the formation of compact front char covered by fluffy porous carbon and thick continuous back char with tiny aluminum oxide particles. Moreover, the introduction of a small amount of BN-DOPO and DOPO-PA could also greatly improve the thermal conductivity of EP/Al(OH)₃ by 107% due to the better compatibility resulting in lower interface thermal resistance and more effective thermal transfer caused by the participation of BN-DOPO and DOPO-PA into epoxy curing reactions.