High performance electrically conductive adhesives (ECAs) modified with novel aldehydes

Electrically conductive adhesives (ECAs) have been proposed as one of the major alternatives for tin/lead solders in electronic packaging. However, the conductivity of ECA is inferior to that of solders due to the physical contact between conductive fillers and insulative organic lubricants on Ag flakes. In this study, novel aldehydes were introduced into a typical ECA formulation. During the curing process, the aldehydes acted as a reducing agent and reduced metal oxide within ECAs. At the same time, aldehydes could consume ambient oxygen and prevent the oxidation of the metal fillers in the ECA. The oxidation product of aldehydes, carboxylic acids with shorter molecular chains, could partially replace or remove the long chain steric acid (C-18) surfactant on the Ag flakes and enhance the electrons tunneling between the Ag flakes in the ECAs. As such, the multiple effects of aldehydes in ECAs improved the conductivity significantly. Dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA) studies indicated the improved electrical performance was achieved without sacrificing the mechanical and physical properties of ECAs.