Thermal Interface Materials (TIM) used in high performance electronics must satisfy multiple contradictory characteristics including high filler loading, while maintaining low viscosity for liquid dispensing and low hardness after cross-linking. Recent improvements in synthesis have made long chain silicon hydride available with terminal SiH hydride groups. By combining an SiH polymer and a divinyl polymer of equivalent molecular weights (MW) an overall lowering of the viscosity of the binder formulation can be achieved. This allows the final formulation to retain low hardness and high flexibility even when highly filled with thermally conductive materials. To minimize the viscosity a low MW, low viscosity vinyl polymer is used. To create long polymer chain lengths necessary for low hardness, a dihydride chain extender is selected. Use of an SiH chain extender of equivalent MW to the vinyl polymer can minimize property variation due to weigh-up deviation.