Preparation of highly conductive adhesives by in situ generated and sintered silver nanoparticles during curing process

The lower resistivity (7.5 x 10(-5) Omega cm) of nano-electrically conductive adhesives (nano-ECAs) with silver flakes and in situ formed and sintered silver nanoparticles was developed. At room temperature,the silver nanoparticles (Ag NPs) could not be generated in ECAs due to no reaction between silver nitrate and N,N-dimethyl-4-aminobenzaldehyde (DABA). However, during curing process, Ag NPs were immediately generated through reducing silver nitrate by DABA in absence of stabilizing agents. At the same time, the increased viscosity of epoxy due to the curing could prevent the agglomerates of Ag NPs. Morphology studies showed that most Ag NPs have been attached onto the surfaces of silver flakes due to the good affinity between them, resulting in more effectively interconnecting with silver flakes by the sintered Ag NPs. Thus, the lower bulk resistivity was obtained. On the other hand, DABA, containing a tertiary amine, can stabilize contact resistance of nano-ECAs by effectively preventing galvanic corrosion at the interface between nano-ECAs and Sn surfaces due to the fact that amines can strongly bond to a Sn surface.