Process development and reliability evaluation of Electrically conductive adhesives (ECA) for low temperature SMT assembly

Conductive adhesives have been widely used in die mounting and component terminal bonding in certain types of hybrid circuits for a number of years. ECA (Electrically conductive adhesive) is an alternative to lead-free solder for certain specific applications in electronic products. Low processing temperature, fine pitch, flexible process steps, and no flux residues are some of the major advantages when using ECA for electrical interconnection between SMDs (surface mount devices) and the printed circuit board (PCB) in SMT (surface mount technology). ECA use a polymer matrix (such as epoxy) filled with conducting fillers (such as copper or silver); silver is used commonly due to its high conductivity and wide availability. The particle size (typically less than 40 microns) is controlled by the screen mesh used to sort the fillers. The study results indicated that it is feasible to incorporate ICA into current SMT production lines and can provide an alternative for solder replacement for specific product applications.