Influences of filler geometry and content on effective thermal conductivity of thermal conductive adhesive

Thermal interface materials (TIMs), including thermal conductive adhesives (TCAs), grease, phase change materials (PCMs) and thermal pads, are widely used in thermal management for electronics system. In this work, a bimodal thermal conductive adhesive (b-TCA) composed of epoxy matrix and silver fillers were developed. The silver fillers consist of silver flakes and silver particles. The specimens have been made with the same filler loading fraction, possessing different ratios of silver flake portion to silver particle one to study the filler geometry effects. The thermal conductivity in vertical and in-plane direction were tested, also the electrical resistance in in-plane direction has been measured. Meanwhile, the numerical simulation was carried out in addition to the experiment. An improved cubic cell model (CCM) was developed to calculate the effective thermal conductivity of the considered b-TCA. Both the experiment and the simulation show the anisotropic thermal conductive property in the b-TCA, but this anisotropy decreased with the increase of silver particle portion in the total filler. And the electrical conductivity also decreased with the increase of silver particles.