AlN-Cu metal matrix composites containing AlN volume fractions between 0.1 and 0.5 were fabricated firstly by liquid phase sintering of AlN using Y2O3 as a sintering aid and then by hot pressing the powder mixtures of sintered AlN and Cu at 1050degreesC with a pressure of 40 MPa under flowing nitrogen. With Y2O3 additions of 1.5 to 10 wt%, the densification of AlN could be achieved by liquid phase sintering at 1900degreesC for 3 h and subsequently slow cooling. The sintered AlN showed a maximum thermal conductivity of 166 W/m/K at a Y2O3 level of 6 wt%. Dense AlN-Cu composites with AlN contents up to 40 vol% were achieved by hot pressing. The thermal conductivity and the coefficient of the thermal expansion (CTE) of the composites decreased with increasing AlN volume fractions, giving typical values of 235 W/m/K and 12.6 x 10(-6)/K at an AlN content of 40 vol%. (C) 2004 Kluwer Academic Publishers.