Electronic devices operate at higher power densities and higher temperatures than ever before. These heat flux levels lead to a reduced efficiency and reliability of power electronic systems if classical Cu heat sinks are used. The aim of the work is to develop materials having a low Coefficient of Thermal Expansion (CTE≈8.10-6 K-1) with reduced thermomechanical stresses and a high thermal conductivity to dissipate the heat produced by the components. The solutions are based on new composite materials processed by powder metallurgy (PM). The interesting thermal and thermomechanical properties of Carbon fibres (CF), Carbon NanoFibres (CNF), Carbon NanoTubes (CNT), can be associated to a metallic matrix like, Cu, Cu-alloy to reach the desired thermo-mechanical properties. Innovative composite materials processed by powder metallurgy (PM) and coating method for CNF using copper salt and their properties for thermal management of power electronic systems are presented. Properties and volume fraction of carbon reinforcement can be adjusted in order to process C/Cu composite materials with adaptive thermal properties. Endeed,CTE and thermal conductivity can be adjusted with the carbon content and carbon fibre thermal properties.