Analytical equations for predicting the thermal properties of isotropic conductive adhesives

Abstract

This paper investigates a set of theoretical equations for analyzing the thermal properties of isotropic conductive adhesives (ICAs) containing several types of Cu filler particles. The thermal conductivity of ICAs containing randomly dispersed filler particles can be simulated well by Bruggeman’s equation for spherical particles and by Kanari’s equation for flake particles. The effect on the thermal conductivity of any residual voids can be taken into account in the analysis by the additional application of Bruggeman’s or Kanari’s equations with the appropriate shape factor. The linear thermal expansion coefficient of the ICAs was analyzed using Schapery’s scheme. The thermal expansion coefficients of ICAs with 40–50 vol.% of filler particles range between Schapery’s upper and lower limits. As the particle size of the filler decreases, the thermal expansion coefficient starts to approach the lower limit at a lowr volume fraction of the filler particles. The transition behavior of the thermal expansion coefficient is related to the characteristics of the network structure formed by percolating the filler particles.