Conductivity improvement of thermoplastic isotropically conductive adhesive

Abstract

Electrically conductive adhesives (ECA) generally comprise of a thermosetting polymer and conductive filler. In this study, a thermoplastic polymer is used in isotropically conductive adhesive (ICA). The thermoplastic polymer is polyarylene ether (PAE-2), which has extremely low moisture absorption (0.279wt%). In thermoplastic ICA, drying (solvent evaporation) is the step when the conductive paths are established. In this study, it was shown that the drying process is critical for optimizing the properties of the ICA. To maximize the effectiveness of the drying process, the glass transition temperature (Tg) of the polymer was adjusted using a plasticizer. The bulk resistivity of ICA samples with plasticizer was three orders of magnitude lower than the sample without it. TGA data confirmed the improvement in drying efficiency of ICA with the use of plasticizer. An unexpected result is that the bulk resistivity and contact resistance showed an increasing trend with aging time. The polar nature of the plasticizer molecule increased the moisture uptake of the thermoplastic, but at the same time helped to improve the adhesion strength of the polymer. Plasticizer is a promising additive in thermoplastic ICA, but it must be compatible with the polymer, so that it does not negatively affect the overall properties of ICA.