Flame Retarding Cyanate Ester Resin with Low Curing Temperature, High Thermal Resistance, Outstanding Dielectric Property, and Low Water Absorption for High Frequency and High Speed Printed Circuit Broads

High-end electric products require high frequency and high speed printed circuit broads (HFS-PCBs), while high performance resin is the key for fabricating HFS-PCBs. A new resin system (DPDP/CE) was developed by copolymerizing 10-(2,5-dihydroxyphenyl)-9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DPDP) and 2,2′-bis(4-cyanatophenyl) propane (CE). Compared with CE resin postcured at 250 °C for 4 h, the DPDP/CE system that was only postcured at 220 °C for 2 h has outstanding flame retardancy, greatly reduced water absorption, low dielectric loss, and high thermal resistance. For DPDP1.4/CE resin with 1.4 wt % phosphorus content, its dielectric constant and loss at 1 GHz are 2.71 and 0.005, respectively, and hardly change after staying in boiling water for 100 h. Different from UL-94 V-2 rating of CE resin, the flame retardancy of DPDP1.4/CE resin is desirable UL-94 V-0 rating, resulting from both gas-phase and condensed-phase mechanisms. These attractive features suggest that the DPDP/CE system is suitable to fabricate HFS-PCBs for high-performance electric products.