Effect of Hybridization on the Functional Properties of AgMF–MWCNT-Filled Electrically Conductive Adhesive

Abstract

A combination of metal and non-metal filler in an epoxy resin, called a hybrid electrically conductive adhesive (ECA), is an important development in the field of highly conductive electronic interconnect materials. Carbon nanotubes (CNTs) are well known for contributing strength and stiffness to ECA and silver (Ag) has been widely used as a conductive metal. This study presents the characterization of a hybrid silver micro-flake (AgMF) with multiwalled carbon nanotubes (MWCNT) in an epoxy matrix ECA, in terms of electrical and mechanical properties. The weight percentage of AgMF used was varied, from 1 wt.% to 10 wt.%, whereas the weight percentage of MWCNT filler loading was maintained at 5 wt.%. The properties of the hybrid ECA were characterized using a four-point probe and a universal testing machine for lap shear tests. It was found that the filler hybridization lowered the performance of the ECA in terms of both electrical and mechanical properties, as compared with non-hybrid MWCNT-filled ECA. This may be attributed to the weak interaction between micro- and nano-filler particle sizes and agglomeration of the MWCNT in the epoxy matrix in the hybrid ECA system. The hybrid ECA electrical conductivity was successfully enhanced when a low ratio of AgMF and MWCNT was considered. In addition, failure analysis confirmed that the hybrid ECA with less AgMF filler loading exhibits improved adhesion strength, suggesting a superior epoxy-to-substrate bonding interface.