Hybrid Electrically Conductive Adhesive (HECA) Properties as a Function of Hybrid Filler Ratio with Increasing Total Filler Loading

This paper presents a study on Hybrid Electrically Conductive Adhesive (HECA) properties as an in-depth analysis regarding hybrid filler ratio at low filler range. It is well established that the hybridization approach exhibits excellent functional properties of HECA. Still, the highest potential ability of the proposed HECA concerning relative amounts of involving fillers is the least being discovered. In this work, silver micro-flake (AgMF) and multiwalled carbon nanotube (MWCNT) conductive fillers were incorporated from 3 to 15 wt.%, while AgMF: MWCNT filler ratio is varied between 0.006 up to 0.2 to choose the best combination. Here, a planetary centrifugal mixer with different mixing time and sequence were considered to identify the most effective mixing method. The functional properties of HECA were characterized in terms of a four-point probe electrical test and a lap shear test via tensile mode. The morphological study suggests that a shorter centrifugal mixing period allows an adequate dispersion of the micro-nano fillers in the HECA system and revealed superior interfacial bonding between the fillers at the optimum ratio. Interestingly, electrical resistivity at critical concentration showed an optimum ratio by incorporating only 2.5% AgMF in the hybrid fillers to yield a 42.62% reduction. However, the significant effects of hybridization are observed until the percolation threshold of HECA at 9 wt% only, followed by a 38.5% reduction beyond this limit. Moreover, the lap shear strength is most reliable at a total filler of 6 wt%, an indication of an excellent filler-binder load distribution.