Modelling of Effective Thermal Conductance of Metal Foam Contact Thermal Interfaces Available to Purchase

We present a modeling study of the effective thermal conductance of metal foams as a thermal interface focusing on the electronics cooling applications. Metal foam material as a porous media has been considered for several applications because of its significantly large surface area for a given volume. In the electronics cooling, aluminum porous heat sinks have been well studied. It is not only cost effective due to the unique production process, but also attractive for the theoretical modeling study to determine the performance. In the past studies, effective thermal conductivity for heat transfer through solid with the tetrahedral geometry, while the pores, assumed to have vacant volumes, has been modeled. Instead of allowing the refrigerant flow through the connected pores in the porous medium, we considered the vacant space filled with stationary air. The major transport of the heat is considered to flow through the solid bridges, which connect the onside to the other side directly. Thus, the porous density for our application shall be relatively lower than the best value for heat sink applications. It must, however, be in a specific range such that it is mechanically compliant to make proper contact to both, the cooling target surface and the heat sink surface. It is obvious that the smaller pore ratio makes the metal foam stiffer. We model the contact thermal performance with considering the mechanical stiffness as a function of pore ratio as well as an intrinsic thermal conductance across the metal foam. Due to the limited literature of the variation of the pore size, we present the first order analysis assuming a fixed and uniform pore size.