Full-Field Simulations of Particulate Thermal Interface Materials: Separating the Effects of Random Distribution from Interfacial Resistance

The effective behavior of particulate thermal interface materials depend, in addition to particle/matrix conductivities and volume loading of the particles, on the randomness of distribution, on the randomness of the size as well as on the interfacial thermal resistance between the particles and matrix. However, the relative contributions of these effects have not been identified in the literature with sufficient clarity owing to a lack of realistic simulations of these systems. In this paper we present a computationally efficient analysis procedure to simulate realistic three-dimensional microstructures of thermal interface materials. The computational procedure is based on constructing complex behavioral fields through Boolean operations (compositions) on primitive fields. It is demonstrated that the Boolean operations and an associated meshless implementation efficiently model topological changes caused by the modification/rearrangement of the second phases in the heterogeneous material microstructure. The developed method was applied to evaluate the effective thermal conductivity of the thermal interface material. Thirty three-dimensional simulations of random arrangements of the heterogeneous microstructure at a fixed 58% volume fraction were carried out. The microstructures were systematically characterized using void nearest surface exclusion probability functions. The results of the simulation range within 10% of the fifteen experimentally measured values of an identically constituted system. We demonstrate that in the absence of simulations of realistic microstructures, non-physical thermal interface resistance values may have to be assumed to describe the effect of random distributions of particles