Aligned Carbon Nanotubes to Reduce Contact Thermal Impedance

Introduction Heat dissipation is the most critical problem that limits the performance, power, reliability and further miniaturization of microelectronics. The thermal performance of these devices is greatly affected by the thermal resistance associated with interface between the heat sink and heat source. The improvement of a thermal contact is associated with a decrease of the thermal resistance imposed by this interface as the heat flows across it [1-5]. As surfaces are never perfectly flat, the interface comprises point contacts at asperities and air pockets. Some heat is conducted through the physical contact points, but much more is transmitted through the air gaps. Since air is a poor conductor of heat, it should be replaced by a more conductive material to increase the joint conductivity and thus improve heat flow across the thermal interface. Use of suitable interface materials can thus have a significant role in lowering thermal contact resistance. Carbon nanotubes (CNT) with their light weight and high thermal conductivity value have the potential to be used as thermal interface material. The high intrinsic thermal conductivity of CNT [5-6] suggests many heat transfer enhancement applications. They also have shown that CNT arrays with different properties produce measurable variations in thermal enhancement. Thus the CNT can play a significant role in reducing the thermal resistance by lowering or eliminating the micro-gaps at the same time providing a high thermal conductivity path through them. The focus of this study is first, to study the effect of thermal contact resistance on heat transfer capability of high thermal conductivity materials and second is to demonstrate the effectiveness of CNT as thermal interface materials.