With the microelectronics technology going toward its physical limits and the emergence of three-dimensional chip stack architectures, now more than ever there are both needs and opportunities for novel materials to help address some of these pressing thermal management challenges. In this paper, a high-thermal-conductivity insulative SiO2-coated nano-Cu particle is prepared for new-type underfill materials of high-performance microelectronics packaging. It was found that nano-Cu can be successfully coated with SiO2 by using the surface modification between cetyltrimethyl ammonium bromide and silane coupling agent although nano-Cu particles have silicon-disordered property during the coating process of tetraethyl orthosilicate hydrolysis. Moreover, the thermal conductivity of epoxy mixed with nano-Cu@SiO2 as the packaging underfill is dramatically increased from 0.15W/mK of the pure-EP and 0.60W/mK of the EP/SiO2 to 2.9W/mK due to electronic heat transfer, heat network and fast heat transfer center. It effectively releases the heat generated by the IC device, and the service life of the device is significantly improved from 63min of pure-EP and 350min of the EP/nano-SiO2 to 1039min. The new material creates a challenging environment for keeping modern electronic devices cool, a critical factor in determining their speed, efficiency and reliability.