A composite server heat sink with a metal base having a thermal conductivity of at least 200W/mK. Plural fins extend from the metal base, each fin having an anisotropic thermal conductivity in a range of approximately 300 to 650 W/mK in a longitudinal direction of the fin and less than approximately 30 W/mK in a widthwise direction of the fin. Each fin includes graphite in an amount of approximately 45-70 wt. %, diamond in an amount of approximately 2.5 to 10 wt. % with the balance comprising a metal selected from one or more of copper and aluminum. To create the anisotropic thermal properties, the graphite is aligned along the longitudinal direction of the fin.