Significantly Enhanced Conformal Contact by the Functional Layers on a Copper Film for Thermal Interface Materials

Low‐cost thermal interface materials with high thermal conductivity ( κ ) and low total thermal resistance ( R t ) receive considerable attention for thermal management. A copper film (CuFilm) is an excellent candidate due to the high κ (364 Wm −1 K −1 ) it possesses. However, the practical implementation is hindered by its high elastic modulus ( E s = 70.8 GPa), inducing a high contact thermal resistance ( R c = 91.6 mm 2 K W −1 ). Herein, the selective construction of electrically conducting or insulating layers on CuFilm to dramatically decrease E s , R c , and R t is reported. The highly electrically and thermally conducting layer is synthesized by incorporating in situ reduced copper nanoparticles (CuNPs, 35 vol%) and multiwalled carbon nanotubes embellished with CuNPs (1.5 vol%) in polyethylene glycol. The high effective κ (92.7 Wm −1 K −1 ) still maintains a low specimen thermal resistance ( R s = 4.9 mm 2 K W −1 ), while the dramatically softened surface ( E s = 5.7 GPa) decreases R c (8.3 mm 2 K W −1 ), resulting in a very small R t (13.2 mm 2 K W −1 ). Alternatively, the electrically insulating but thermally conducting layer is constructed using aluminum nitride particles. The κ is still high (72.1 Wm −1 K −1 ) with a small R t (47.5 mm 2 K W −1 ). The facile fabrication based on a CuFilm enables cost‐effective thermal interface materials with tunable electrical and thermal properties.