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 (kappa) and low total thermal resistance (Rt) receive considerable attention for thermal management. A copper film (CuFilm) is an excellent candidate due to the high kappa (364 Wm-1 K-1) it possesses. However, the practical implementation is hindered by its high elastic modulus (Es = 70.8 GPa), inducing a high contact thermal resistance (Rc = 91.6 mm2 K W-1). Herein, the selective construction of electrically conducting or insulating layers on CuFilm to dramatically decrease Es, Rc, and Rt 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 kappa (92.7 Wm-1 K-1) still maintains a low specimen thermal resistance (Rs = 4.9 mm2 K W-1), while the dramatically softened surface (Es = 5.7 GPa) decreases Rc (8.3 mm2 K W-1), resulting in a very small Rt (13.2 mm2 K W-1). Alternatively, the electrically insulating but thermally conducting layer is constructed using aluminum nitride particles. The kappa is still high (72.1 Wm-1 K-1) with a small Rt (47.5 mm2 K W-1). The facile fabrication based on a CuFilm enables cost-effective thermal interface materials with tunable electrical and thermal properties. A copper film is an excellent candidate for low-cost thermal interface materials due to the high thermal conductivity. However, its high elastic modulus results in a high contact thermal resistance. The selective construction of electrically conducting or insulating soft functional layers on a copper film dramatically decreases elastic modulus and contact thermal resistance, while maintaining the high thermal conductivity.image (c) 2023 WILEY-VCH GmbH