Electrically conductive adhesives: a prospective alternative for SMD soldering?

Conductive adhesives offer a new prospective way for electrical connection of SMD components to printed circuit boards, because of their lower possible curing temperature, fine pitch capability, higher flexibility than solder, and process simplicity. However, the long-term behavior of conductive adhesive joints under various climatic conditions shows large variations with the type of adhesive and metallization used and needs further clarification. In this paper electrical and mechanical behavior of conductive adhesives are discussed for bonding R 1206 jumpers with SnPb or AgPd terminations on bare copper, SnPb or Au plated boards, both directly after bonding and after climate testing (damp heat, hot storage, and rapid change of temperature). The influence of the component terminations is found to be dominant. AgPd terminations show only small increase in contact resistance. Processing characteristics, shrinkage and moisture uptake for some of the adhesives also were determined