Improved Manufacturing Process of Cu/Mo70-Cu/Cu Composite Heat Sinks for Electronic Packaging Applications

This paper presents the results of an optimization study aimed at improving the thermal properties of Cu/Mo70-Cu/Cu (CPC) composites used for electronic packaging applications. The composites were manufactured by sandwiching a Mo70-Cu core with copper on either side using a hot-rolling process. The Mo70-Cu core was obtained by using a standard infiltration method used in powder metallurgy. Various process parameters and their influences on the mechanical properties of the composite have been studied. It has been observed that the cracking of the core material during hot-rolling can be improved by optimizing the infiltration time. Also, defects such as microvoids and microcracks could be reduced significantly by optimizing the intermediate anneal temperature of the core material. With an improved core, superior thermal properties could be achieved by joining the composite structures in an appropriate fashion. The optimized manufacturing method resulted in a CPC composite with a density of 9.52 g/cm³, thermal conductivity (TC) of 265 W/(m·K), coefficient of thermal expansion of 7.9-9.5 × 10^-6/K, and a hermeticity, or helium leak rate, of 8.85 × 10^-10 Pa. m³/s. The measured TC matches well with the calculated value.