Analytical and experimental studies to determine the effective thermal conductivity of particulate thermal interface materials

Thermal Interface Materials (TIMs) are widely used in the microelectronics industry to reduce the thermal resistance between two contacting surfaces. They are typically particulate composite materials consisting of a matrix and filler particles. Both experimental characterization and predictive modeling using fundamental physical principles are critical to the development of new TIMs. In this work, both the laser flash method and steady-state conduction apparatus are used to determine the effective thermal conductivity of a series of TIMs with different filler particle volume fractions. Computational modeling is used to quantify the effect of particle volume fraction and particle size distribution on the effective thermal conductivity. A Random Network Model (RNM) is used that captures the near-percolation transport in these particle-filled systems, that takes into account the inter-particle interactions and random particle size distributions (polydispersivity).;As part of the modeling effort, a novel semi-spherical approximation to the conductance of the fillers is presented which is more accurate for systems with larger polydispersivity, since it is better able to treat the conductive transport between two spherical particles with significantly different diameters. The effective thermal conductivity was also determined using three-dimensional finite element modeling. The different modeling approaches were utilized to study the impact of polydispersivity, thermal conductivity ratio of filler and matrix and particle volume fraction on the effective thermal conductivity of the particulate TIMs. Based on the comparisons of RNM results with the finite element model and experimental data, it was possible to determine relationships between the basic geometrical and material parameters and the particle volume fraction in order to provide a more accurate prediction of the effective thermal conductivity of the particulate TIMs.;As a final component of the dissertation research, the steady state heat conduction between eccentrically positioned thin disks was studied. This configuration is used to model flat filler particles. It could be used to develop a semi-analytical solution to approximate the effective thermal conductivity between disc shaped particles in the domain. In addition, the solutions can be applied to the thermal management of three-dimensional stacks of electronic devices and as a model of the interconnection layers in thermoelectric devices.