High-density blade servers (HDS) have been intensively demanded at IT markets in recent years since their outstanding performance, higher resource productivity and flexible manageability. Due to limited space arrangement in the chassis of the HDS, a high performance heat sink is necessary to be developed. Traditional heat sink with solid metallic base can not efficiently dissipate the heat generated by the high density chips, specially, when the area ratio which is the foot-print area of the heat sinks over the heat source area Aft/Ahs is relatively high. In the case of higher Aft/Ahs, the vapor chamber (VC) would be an idea thermal solution for the HDS applications. A VC is working based on the principle that a type of working fluid acting two-phase heat transfer within a vacuumed and sealed metallic container. The internal surface of the container is usually structured with a type of wick which can enhance evaporation and condensation heat transfer inside the device. On the other hand, the VC performance has much less effect by its total thickness comparing with solid base. Thus VC is a suitable solution when the total height of the heat sink is limited. In this paper, fundamental of thermal analysis, aspects of optimal designs as well as the factors that would impact the heat sink performance have been addressed. The performance comparisons with conventional heat sinks have also been revealed. The recommendation for implementing this kind of heat sinks to other high end applications has been also proposed.