As the speed and degree of integration of semiconductor devices increases, more heat is generated, and the performance and lifetime of semiconductor devices depend on the dissipation of the generated heat. Tungsten-copper alloys have high electrical and thermal conductivities, low contact resistances, and low coefficients of thermal expansion, thus allowing them to be used as a shielding material for microwave packages, and heat sinks for high power integrated circuits ( ICs). In this study, the thermal conductivity and thermal expansion of several types of tungsten-copper (W-Cu) composites are investigated, using compositions of 5-30 wt.% copper balanced with tungsten. The tungsten-copper powders were produced using the spray conversion method, and the W-Cu alloys were fabricated via the metal injection molding. The tungsten-copper composite particles were nanosized, and the thermal conductivity of the W-Cu alloys gradually decreases with temperature increases. The thermal conductivity of the W-30 wt.% Cu composite was 238 W/(m K) at room temperature. (C) 2012 Elsevier B.V. All rights reserved.