Conductivity of carbon black (CB) and graphite (G) addition in silicone-based electrically conductive adhesives (ECAs) / Nur Elissa Ahmad Izuddin

Electrically conductive adhesives (ECAs) have raised a massive interest among researchers to replace traditional Tin-Lead (Sn-Pb) solders especially in electronic manufacturing devices due to its greater attributes than utilizing lead (Pb) which is harmful to human health. In this study, silicone-based ECAs was proposed with the addition of hybrid fillers namely, carbon black (CB) and graphite (G) in which CB and G are both conductive fillers while silicone, specifically polydimethylsiloxane (PDMS) is used as the polymer matrix. By incorporating wet-ball milling method to achieve optimum dispersion of the fillers in the matrix and adopting film casting technique to form thin films beforehand, then the optimum ratio of CB and G (1:2, 2:1, 2:2, 1:3 and 3:1 ratio) on its conductivity properties of CB/G/PDMS composite via multimeter and 4-point probe was identified and the CB/G/PDMS films were characterized via ATR-FTIR and UV-Visible spectroscopy. It was found out that 1:3 ratio had the lowest resistivity of 1.615 × 103 with the optimum conductivity value 6.19 × 10-4 Ω⋅cm-1 while 3:1 ratio had the second lowest conductivity at 5.49 × 10-4 Ω⋅cm-1 with a resistivity of 1.82 × 103 Ω⋅cm via multimeter testing. From four-point probe analysis, 1:3 ratio had the optimum conductivity value of 4.35 × 10-6 S/m while the lowest conductivity value belongs to 2:1 at 3.69 × 10-6 S/m. ATR-FTIR was also used to determine the functional groups contained within CB, G and PDMS. CB can be seen having peaks around 2700 – 3000 cm-1, denoting the C-H stretching, PDMS at peaks of 1000 – 1100 cm-1 which corresponds to Si-O-Si stretching, 1250 – 1260 cm-1 of Si-CH3 stretching and 800 – 850 cm-1 for Si-C stretching. As for graphite, the G band of graphitic carbon could be spotted at around 1580 – 1600 cm-1. UV-Visible spectroscopy spectra depicted the maximum wavelength values for samples ranging from 293 to 302 nm, showing π - π* transition. This study is significant to observe the effects of ball milling process and the influences of incorporation of CB and G in improving the electrical conductivity of a silicone-based ECAs.