Adhesion improvement of thermoplastic isotropically conductive adhesive

Abstract

Generally, isotropically conductive adhesive formulations include epoxy resin as the polymeric matrix. Although epoxy has superior adhesion capability, its drawbacks include the tendency to absorb moisture and lack of reworkability (thermosetting polymer). In this study, a thermoplastic polymer with low moisture absorption (0.279wt%), called polyarylene ether (PAE2), is used in isotropically conductive adhesive (ICA) formulation. Previous research work by Lu et. al. (1999) showed that the moisture absorbed into epoxy caused galvanic corrosion, which results in the formation of metal oxide. By using a polymer with low moisture absorption, the amount of water present in ICA will be small, and the corrosion rate and formation of metal oxide can be reduced. However, previous measurements of contact resistance stability of PAE2-based ICA showed that they are not stable on all surface finishes. It was determined that for thermoplastic-based ICA, poor adhesion was the main mechanism for unstable contact resistance. Two methods of adhesion improvement are evaluated in this work. The first is to use coupling agents and the second is to blend the thermoplastic with epoxy. Both methods showed promise in improving the contact resistance stability of polyarylene ether based ICA.