| abstract |
A bridged polysilsesquioxane-based flame retardant filler imparts flame retardancy to printed circuit boards (PCBs). In an exemplary synthetic method, a bridged polysilsesquioxane-based flame retardant filler is prepared by sol-gel polymerization of a monomer having two or more trialkoxysilyl groups attached to an organic bridging group that contains a fire retardant group (e.g., a halogen atom, a phosphinate, a phosphonate, a phosphate ester, and combinations thereof). Bridged polysilsesquioxane particles formed by sol-gel polymerization of (((2,5-dibromo-1,4-phenylene)bis(oxy))bis(ethane-2,1-diyl))bis(trimethoxysilane), for example, and follow-on sol-gel processing may serve both as a filler for rheology control (viscosity, flow, etc.) and a flame retardant. In an embodiment of the present invention, a PCB laminate stack-up includes conductive planes separated from each other by a dielectric material that includes a bridged polysilsesquioxane-based flame retardant filler. |