Increased Surface Contact to Carbon Nanotube Arrays From Solvent Evaporation

It is necessary to dissipate heat generated by certain computer products using microelectronics via thermal conduction. Carbon nanotube (CNT) thermal interface materials (TIMs) could facilitate that heat conduction more effectively than typical metal solders since CNTs are more mechanically pliable than most metal solders. The difficulty with using CNTs within an interface lies in producing sufficient thermal contact because variability in CNT heights inhibits many CNTs from bridging the interface. The objective of this study is to determine the effects on CNT interfacial contact area and thermal resistance when a CNT array is pressurized in the presence of a solvent that is evaporated from the interface under pressure. A photoacoustic (PA) technique was used to measure thermal contact resistance and distinguish the effects of changing interfacial contact area on thermal resistance. Three different PA measurements were performed: 1. Dry contact measurements where Ag foil is placed atop CNT arrays grown on silicon. 2. Dry contact measurements taken after compressing CNTs at 20 psi and 100 psi. 3. Dry contact tests conducted on CNTs that were compressed at 20 psi and 100 psi with toluene wetted to and evaporated from the CNTs under pressure. All samples were tested in the PA cell at 1 psi and 20 psi of contact pressure. Results show that solvent evaporation from CNT arrays under pressure increases the length of CNT contacts to the interface surface, producing an increase in contact area and a reduction in thermal resistance compared to CNT arrays not exposed to solvent.