Metal-graphite Composite Heat Spreaders having High Thermal Conductivity and Low Thermal Expansion Coefficient

摘要

A new type of metal-graphite composite heat spreaders having high thermal conductivity and low thermal expansion coefficient were fabricated by the powder metallurgy, and their thermal and mechanical properties were evaluated. A copper alloy and graphite were used as the starting powders. Their powder mixtures with graphite content of 50 to 75vol% were prepared then pressed to the dimensions of 35mm diameter and 12mm thick. Subsequently, the powder compacts were sintered using a modified hot-pressing. The resulting metal-graphite composites had anisotropic thermal properties; the in-plane thermal conductivity and through-plane thermal expansion coefficient increased with the increase in graphite content and the through-plane thermal conductivity and in-plane thermal expansion coefficient decreased with the graphite content. The in-plane thermal conductivity and thermal expansion coefficient of a composite having a graphite content of 75vol% were 450W/mK and 6.3ppm/K, respectively. Thermal analysis of a package assembled with the Cu alloy-75vol% graphite composite heat spreader indicated that the cooling performance of the composite neared that of copper with decreasing thickness of the composite.