Investigation on the mechanical and electrical properties of multiwall carbon nanotubes (MWNCTs) based isotropic conductive adhesives

Purpose The purpose of this paper is to characterise the electrical and mechanical properties of multiwall carbon nanotubes (MWCNTs)-based isotropic conductive adhesives (ICAs). The paper also compares the electrical and mechanical performance of MWCNTs-based ICAs with silver flakes and silver nanoparticles-based ICAs. Design/methodology/approach The ICAs were formulated with dyglycidyl ether bisphenol A epoxy resin and conductive fillers such as silver flakes, silver nanoparticles and MWCNTs. The four-point probe is used to measure the bulk resistivity of the ICAs. Findings The results from the study showed that the percolation threshold of the MWCNTs-based ICAs is 1.5 Wt.%. At 3 Wt.%, the drop in bulk resistivity is lower than the conventional ICAs. The addition of silver nanoparticles increased the overall bulk resistivity of the system. The mechanical properties improved with the introduction of carbon nanotubes into the silver flakes–epoxy system. Practical implications The results from bulk resistivity and mechanical properties of the MWCNTs could help to formulate MWCNTs-based ICAs with optimum weight fraction. Originality/value The paper demonstrates that the addition of MWCNTs to the silver-based ICAs will enhance their mechanical and electrical conductivity. In addition, the optimum weight percentage is also determined, which shows a bulk resistivity value lower along with improved mechanical property with the conventional ICA system.

Mechanical and Electrical Properties of Carbon Nanotubes Based Isotropic Conductive Adhesives

In the past few decades, the lead-tin soldering process had been widely used in electronics sector as an interconnection between the electronics components and printed circuit board. Due to the highly toxicity and environmental concerns, the lead-tin alloys were replaced by lead-free alloys and isotropic conductive adhesives (ICAs). The ICAs have a significant amount of conductive fillers and offers better electrical conduction seems to be more promising in the electronics sector. ICAs are usually filled with metal particles such as silver flakes with adhesive polymeric resin. For this research, the carbon nanotubes (CNTs) were used to replace silver flakes. The synthesis of CNTs was carried out by heating the mixture of ferrocene with ammonium chloride and went through purification process by hydrochloric acid. Meanwhile, the studies on CNTs were performed through several characterization methods such as scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. Then, the ICAs were produced by adding different weight percent of CNTs into DGEBA. Subsequently, the ICAs went through 4 points probe test and tensile test to examine their electrical and mechanical properties. The results show that the ICAs contain 1.5wt% and 2.5wt% of the CNTs exhibit the highest electrical conductivity and highest tensile strength respectively. Undoubtedly, there was a close relation between the electrical and mechanical properties, as both of the material of CNTs and DGEBA is necessary to achieve optimum and balance of weight percentage in order to sustain both novel properties. Meanwhile, the weight percentage of the curing agent greatly depends on the amount of DGEBA. An appropriate amount of curing agent may lead to a hard shape with all other properties are preserved. In this case, the ratio of curing agent to DGEBA is 0.088:1 which is considered as the optimum ratio.