Microelectronic circuits require contact with a high thermal conductivity, and controlled low coefficients of thermal expansion packaging materials for the high performance and reliability of the semiconductor chips. The present study was carried out to investigate the microstructural and chemical properties of AIN-Cu nanocomposite powders created by planetary ball milling. X-ray diffraction and scanning electron microscopy analysis of the obtained powders were performed. The residual oxygen and carbon in ball milled AIN-Cu powders were analyzed. AIN-Cu composite powders of 15 mum size and copper crystallites of 25 nm were obtained after milling for 8 h. The amount of residual oxygen was considerably reduced after exposure to hydrogen reduction treatment at 600degreesC for 2 h. More significantly, 97% of the residual carbon was removed regardless of milling time and alloy composition. Furthermore, residual carbon was removed as a gaseous mixture of carbon monoxide and carbon dioxide. (C) 2004 Kluwer Academic Publishers.