INFLUENCE OF MULTI-WALLED CARBON NANOTUBE ASPECT RATIO ON THE ELECTRICAL AND MECHANICAL RELIABILITY OF EPOXY-BASED ELECTRICALLY CONDUCTIVE ADHESIVES UNDER HYGROTHERMAL AGING

Abstract

Electrically conductive adhesives (ECAs) are gaining attention as promising alternatives to traditional solder in electronic packaging, particularly for applications requiring low processing temperatures and compatibility with heat-sensitive components. This study investigates the effect of multi-walled carbon nanotube (MWCNT) aspect ratio on the electrical and mechanical performance of epoxy-based ECAs under hygrothermal ageing (85 °C/85 % RH). Low-aspect ratio (L-MWCNT) and high-aspect ratio (H-MWCNT) fillers were incorporated at different loadings, and the resulting adhesives were characterised in terms of volume resistivity and lap shear strength (LSS) before and after up to three weeks of hygrothermal ageing. The results show that H-MWCNT adhesives exhibited markedly lower initial resistivity and higher LSS compared to L-MWCNT adhesives. Under hygrothermal ageing, the H-MWCNT ECAs retained up to 87 % of their initial LSS and showed only a marginal increase in resistivity, while L-MWCNT ECAs degraded more significantly. Optimising filler aspect ratio is thus essential for enhancing the performance and long-term reliability of ECAs in harsh service environments.