Impact of wall region particle volume fraction distribution on thermal resistance of particle filled thermal interface materials

Increasing chip power densities require thermal interface materials (TIMs) with lower thermal resistance. The thermal resistance of particle-filled polymer-based TIMs is measured using a high-resolution cross-sectional IR imaging technique, and simulated using a finite volume technique and a closed-form model. It is found that the TIM thermal resistance is strongly influenced by the change in particle volume fraction near the TIM-chip and TIM-spreader boundaries, which yields an effective thermal boundary resistance near the TIM-wall boundaries. This effective boundary resistance increases with increasing filled panicle size, increasing ratio of particle to matrix thermal conductivity and decreasing TIM thickness. These findings are valuable to achieve better TIM thermal performance.