Effects of the matrix shrinkage and filler hardness on the thermal conductivity of TCA

Thermal conductive adhesives (TCA) have been widely used as the thermal interface material (TIM). The TCA are usually epoxy or silicone based mixtures containing fillers. The epoxy in TCA also applies a pressure on the filler particles as it shrinks during the curing process. This pressure leads to an increase in the contact area between the filler particles and thus improves the thermal conductivity. In our attempt to discover the effect of filler modulus on the contact areas between two particles we constructed a cell model assay. In order to study the different epoxy characteristics, 28 cases were simulated with different mixtures of epoxy and filler. The thermal conductivity of each case was calculated by FEM. When the shrinkage was higher than 1%, TCA with a filler modulus of 83 Gpa (silver) has the largest contact area, which suggests silver has the best TCA performance among the studied materials. Furthermore the viscoelasticity of the epoxy was simulated to evaluate the fully relax time of epoxy and the effect on the thermal conductivity of TCA.