Effect of time, temperature and composition on the performance of conductive adhesives made of silver-coated copper powder

The effects of temperature and time (200, 250 and 300 °C for 15 h in total) on the electrical resistivity and phases of conductive adhesives were studied. Also, the effect of filler content (70 to 85 wt%) and graphite addition (2 to 15 wt%) on the performance of conductive adhesives in terms of electrical resistivity were investigated. These adhesives were prepared from [email protected] particles containing 20 and 50 wt% of silver. Two-point conductivity measurements, SEM, XRD, and TG/DSC analyses were used to evaluate the properties of the adhesives. The results showed that at a constant filler content, the electrical resistivity of adhesives prepared from powder containing 20 wt% silver increases with exposure time. However, the majority of the adhesives prepared from powder containing 50 wt% of silver under similar oxidation conditions had almost constant electrical resistivity. Moreover, the results of temperature change on the electrical resistivity showed that the electrical resistivity of adhesives prepared from powder containing 20 wt% of silver increases with temperature, although this increase was noticeable in some samples and negligible in the others. In contrast, an increase in temperature had very little effect on the electrical resistivity of most adhesives made from powders containing 50 wt% silver. The study of the effect of silver content in particles showed that adhesives prepared with filler containing 50 wt% of silver had significantly less electrical resistivity than adhesives prepared with filler containing 20 wt% of silver at all three temperatures. According to the XRD results, the formation of copper (II) oxide and its detrimental effect on electrical conductivity was the main reason of electrical conductivity reduction of adhesives. Graphite addition to an adhesive formula showed that the presence of graphite in appropriate amounts can prevent the oxidation of copper. Adhesives containing graphite after exposure at three temperatures in total for 15 h had electrical resistivities less than 0.028 Ω cm, while graphite-free adhesives under the same conditions had electrical resistivities of less than 0.072 Ω cm.