Natural graphite sheet heat sinks: A review of the material properties, benefits, and challenges

Abstract

A multidisciplinary feasibility study of natural graphite sheet (NGS) heat sinks, addressing the thermal, EMI/EMC, reliability, cost and manufacturing perspectives, is presented together with a brief overview of the relevant graphitic materials and a summary of the NGS properties (thermal conductivity, heat capacity, weight, electrical conductivity, emissivity, coefficient of thermal expansion). The high in-plane thermal conductivity (up to 600 W-m−1·K−1) of NGS and low interface resistance of NGS heat sinks can lead to good thermal performance despite the low through-plane thermal conductivity of NGS, but new designs are required. Low electrical conductivity offers a potential to decrease conducted and radiated electromagnetic emissions and significant weight reduction can be achieved due to the low density of NGS. The raw material cost of natural graphite is shown to be lower than aluminum and a high-volume manufacturing method is discussed. Low mechanical strength of NGS does not allow mounting using threaded holes in the heat sink, limits applications where a chance collision with other objects exists, and might have an impact on reliability of large power modules.