Effects of zinc on the reliability of conductive adhesives

This paper discusses on stabilizing contact resistance of conductive adhesives, referred to CA, with Sn plated components by using electrochemical methods. First, the reason for the instability was investigated. It was confirmed that Sn was corroded at the interface of Ag fillers according to the order of electrode potential. Secondly, we tried to protect Sn from corrosion by adding non-noble metal fillers into the CA. In this case, where the corrosion potential of the non-noble metal is lower than that of Sn, the non-noble metal tends to corrode while Sn is protected against corrosion. As a result, among the non-noble metal fillers evaluated, it was found that the addition of Zn fillers demonstrated significant improvement in stability of contact resistance. XMA analysis demonstrated that oxide was not detected on Sn electrode while Zn was fully corroded after exposure to humidity. From these results, it is cleared that Zn protects Sn electrode from corrosion. A developed new CA based on this method showed stable bonding resistance, less than 20% shift for 3000 h, during 85°C/85%RH exposure. However, the one without this method exhibited 75% increase in resistance after 100 h