Effects of Multi-modal Filler Size Distributions on Thermal Conductivity of Electrically Conductive Adhesives Containing Ag Micro and Nanoparticles

Abstract

Electrically conductive adhesives composed of a multi-functional epoxy-based matrix containing micro- and nano-fillers with bimodal and trimodal size distributions were prepared in order to investigate their electrical and thermal conductivities. When Ag flakes were used as the filler, anisotropy was clearly observed in the thermal conductivities due to the alignment of the flakes along the in-plane direction. A bimodal adhesive containing Ag flakes and spherical micro-particles exhibited a maximal value for thermal conductivity in the vertical direction when the content of the micro-particles was 50–60 wt% of the total filler loading, although its conductivity in the in-plane direction decreased monotonically with increasing content of micro-particles. With trimodal adhesives containing Ag flakes, micro- and nanoparticles, the Ag nanoparticles could be sintered during the curing process. Adequate dispersion and sufficient sintering of the nanoparticles were found to be essential in order to improve the electrical and thermal conductivities of these adhesives.