The effect of modulus on the performance of thermal conductive adhesives

By analyzing the effect of modulus of epoxy and modulus of filler particles on the thermal conductivity of thermal conductive adhesives (TCA), this paper concludes, in contrast to intuition, that the stiffer epoxy will generate a larger contact area, and the “soft” epoxy with modulus of 0.5GPa will create the largest contact area, hence the highest thermal conductivity. Therefore, it is advisable to adopt softer epoxy in TCA. On the other hand, this paper finds that if the shrinkage of epoxy is low, i.e. 1% linear shrinkage, fillers composed of a mixture of Ag flakes and certain high stiffness material will cause a higher thermal conductivity, i.e. 7% larger than that of pure Ag fillers. This suggests that with low shrinkage epoxy, it is advisable to mix Ag flakes with high stiffness particles, e.g. Diamond or SiC. However, when linear shrinkage of epoxy is high, i.e. 3%, the highest thermal conductivity is achieved by using pure Ag fillers. Therefore, in such cases it is not advisable to use Bi-model.