A high performance, lead free, Ag paste thermal interface material (TIM) for die attachment and substrate bonding in electronic packaging includes: (i) multiscale silver particles, (ii) metal-coated carbon nanotubes (CNTs), (iii) a polymer, and (iv) a liquid carrier. The multiscale silver particles and metal-coated carbon nanotubes, which function as hybrid filler components, are uniformly dispersed within the TIM composition. The sintered TIM exhibits high density, high mechanical strength, and high thermal conductivity. The components of the liquid carrier including the solvent, binder, surfactants, and thinner are completely evaporated or burned off during sintering. Sintering of the TIM can be conducted at a relatively low temperature, without or with very low (