A study of contact resistance of conductive adhesives based on anhydride-cured epoxy systems

Electrically conductive adhesives (ECAs) are an environmentally friendly al ternative to tin/lead (Sn/Pb) solders in electronics packaging applications . However, current conductive technology is still in its infancy and limita tions do exist. One of the critical reliability issues is that contact resi stance of silver flake-filled ECAs on nonnoble metals increases in elevated temperature and humidity environments. The main objective of this study is to investigate the contact resistance behaviors of a class of conductive a dhesives, which are based on anhydride-cured epoxy systems, Curing profiles , moisture pickup, and shifts of contact resistance of the ECAs on a nonnob le metal, tin/lead (Sn/Pb), during aging are investigated. Also, two corros ion inhibitors are employed to stabilize: the contact resistance. The effec ts of these corrosion inhibitors on contact resistance are compared. It is found that: 1) this class of ECAs shows low moisture absorption, 2) the con tact resistance of the ECAs on Sn/Pb decreases first and then increases slo wly during 85 degrees C/85% relative humidity (RH) aging, 3) one of corrosi on inhibitors is very effective to stabilize contact resistance of these EC As on Sn/Pb, and 4) the corrosion inhibitor stabilizes contact resistance t hrough adsorption on Sn/Pb surfaces. From this study it can be concluded th at ECAs based on anhydride cured epoxy systems are promising formulations f or electronics packaging applications.