ABSTRACT
Electrically conductive adhesives have attracted significant attention during the last decades due to their increased usage in electronics industry to replace lead soldering [1-18]. The major applications are die attachment, liquid crystal display and surface-mounted assembly of packaged components on printed wiring boards. In general, conductive adhesive pastes are formulated by mixing polymeric resins (such as epoxies, silicones and polyimides) and highly conductive metallic fillers. Theoretical and experimental studies have been performed on basic conduction mechanisms [2-9]; the effects of particle size, shape and type [4-9]; behavior in the bonded form [6, 8-16]; processing effects, such as pressure [2, 4, 9], adhesive film thickness [3, 5, 8], silver coating [4, 5, 7], anisotropic alignment of nickel particles in magnetic field [17]; as well as the possibility of using polymeric emeraldine salt particles as conductive fillers [18]. So far, the most popular conductive adhesive formulation has been silver (Ag) particles in epoxy resin [19-22]. Nickel fillers with lower cost than silver and comparatively less oxidation, and better thermal stabil-
ity than copper, offer an alternative to silver fillers, while the copper-filled systems may be unstable after exposure to elevated temperatures due to oxide growth on the particle surfaces [23]. Furthermore, silver-filled conductive adhesives suffer from the problem of silver migration, which may lead to failure in electrical conduction [24].
