Light-weight Compressible and Highly Thermal Conductive Graphene-based Thermal Interface Material

Abstract

High density packaging in combination with increased transistor integration inevitably leads to challenging power densities in terms of thermal management. Thermal interface materials (TIMs) play a key role in thermal management by transferring heat from the surface of power devices. The conventional TIMs used in the microelectronics industry today basically are particle laden polymer matrix composites, which have the advantages of good reliability and ease of use. However, the thermal conductivity (K) of these composites is generally limited to 10 W/mK, which is hard to meet the goal for efficient thermal management in power devices. Here, we solve the problem by applying a novel highly thermal conductive and compressible graphene based TIMs (GTs). Composed by vertical graphene structures, GTs provide a continuous high thermal conductivity phase along the path of thermal transport, which lead to outstanding thermal properties. By tailoring ratios of graphene in the polymer binder, bulk thermal conductivity of GTs can be varied from 50 to 1000 W/mK. This result isorders of magnitude higher than conventional TIMs, and even outperforms the pure indium TIMs by over ten times. Meanwhile, the highly flexible and foldable nature of vertical graphene enables at least 20% compressibility of the GTs upon small applied pressures ($\le$ 400 KPa). As excellent gap fillers, GT can provide complete physical contact between two surfaces and thereby minimize the contact resistance to heat flow. The measured minimum thermal resistance and maximum effective thermal conductivity for GTs reaches to $\sim $ Kmm$^{2}$/W and $\sim \mathrm{W} /$mK, respectively. Such values are significantly higher than the randomly dispersed composites presented above, and show almost comparable thermal performance as pure indium bonding. In addition, the GTs has more advantages than indium/solder bonding, including low weight (density $\lt2\mathrm{g} /$cm}$^{3}$), low complexity during assembly and maintainability. The resulting GTs thus opens new opportunities for addressing large heat dissipation issues both in through-plane and in-plane directions for form-factor driven electronics and other high power driven systems.