Low profile heat pipe heat sink and green performance characterization for next generation CPU module thermal designs

Increasing thermal demands of high-end server CPUs require increased performance of air-cooling systems to meet industry needs. Improving the air-cooled heat sink thermal performance is one of the critical areas for increasing the overall air-cooling limit. One of the challenging aspects for improving the heat sink performance is the effective utilization of relatively large air-cooled fin surface areas when heat is being transferred from a relatively small heat source (CPU) with high heat flux. Increased electrical performance for the computer industry has created thermal design challenges due to increased power dissipation from the CPU and due to spatial envelope limitations. Local hot spot heat fluxes within the CPU are exceeding 100 W/cm², while the maximum junction temperature requirement is 105 C, or less. The CPU power dissipation continues to increase and the number of CPUs per server continues to increase for next generation servers. This has resulted in increased data room energy costs associated with supplying additional power to the server, and also cooling the server. Typically in the past, if two heat sink technologies met the thermal performance requirements along with meeting the reliability performance requirements, the least expensive technology would be utilized. In the future, heat sink thermal performance specifications will consider including the impact of energy cost savings attained through reduced server air flow rate requirements if utilizing a superior heat sink technology warrants a potential increase in heat sink cost.