The development of a natural graphite heat-spreader

The ongoing need for miniaturization and speed in the electronics industry has brought about a requirement for better performing thermal management sy stems. Thermal management technology remains a vital part of electronics in novations for notebook computers, high-performing CPU chipsets, mobile elec tronic appliances and power conversion [1]. Typical thermal management syst ems consist of external cooling mechanisms, heat dissipaters, and thermal i nterfaces. The primary function of the heat dissipaters, e.g. heat sinks, i s to create the maximum effective surface area where heat is transferred in to and carried away by the external cooling medium. Performance of a heat d issipater is conventionally characterized by its intrinsic thermal conducti vity, physical surface area, and pressure drop (or drag) coefficient [2]. A n additional variable, namely heat spreading coefficient (a), has been intr oduced by Tzeng [3]. The heat spreading coefficient has to be considered wh en the heat dissipater is a thermally anisotropic material. A high degree o f thermal anisotropy reduces the temperature gradient in the plane of the p art and increases the effective heat transfer area, characteristics that ar e most desirable for electronics with high heat-intensity components. The a bility to direct heat in a preferred direction is an additional advantage o f an anisotropic heat-spreader material. Carbon and graphite-based material s are attracting interest as anisotropic heat-spreaders, with an additional advantage being their low density. Most carbon and graphite-based material s used to date are based around carbon fibers. These are high cost by virtu e of the need to conduct high temperature graphitization processes to devel op the required thermal properties in the fiber. A new form of graphite hea t-spreader material is described in this paper, based around naturally occu rring graphite. Because this material has been graphitized "by nature", ani sotropic heat-spreaders with high thermal conductivity can be manufactured without using traditional carbon fiber-based additives.