Thermal expansion and thermal conductivity characteristics of Cu–Al2O3 nanocomposites

Copper–alumina composites were prepared by powder metallurgy (P/M) technology. Nano-Cu/Al2O3 powders, was deoxidized from CuO/Al2O3 powders which synthesized by thermochemical technique by addition of Cu powder to an aqueous solution of aluminum nitrate. The Al2O3 content was added by 2.5, 7.5 and 12.5 wt.% to the Cu matrix to detect its effect on thermal conductivity and thermal expansion behavior of the resultant Cu/Al2O3 nanocomposites. The results showed that alumina nanoparticles (30 nm) were distributed in the copper matrix in a homogeneous manner. The measured thermal conductivity for the Cu–Al2O3 nanocomposites decreased from 384 to 78.1 W/m K with increasing Al2O3 content from 0 to 12.5 wt.%. The large variation in the thermal conductivities can be related to the microstructural characteristics of the interface between Al2O3 and the Cu-matrix. Accordingly, the coefficient of thermal expansion (CTE) was tailored from 33 × 10−6 to 17.74 × 10−6/K, which is compatible with the CTE of semiconductors in electronic packaging applications. The reduction of thermal conductivity and coefficient of thermal expansion were ascribed to the strong interface bonding in the Cu/Al2O3 nanocomposites.