| Abstract: | Environmental issues have an ever-increasing influence on the selection of material and processes in electronic manufacturing. This paper discusses the use of conductive adhesives as a replacement for solder on SMT printed circuit boards. As a result of a world-wide market survey, a number of conductive adhesives has been selected. One of the two key issues of this paper has been to uncover the market for adhesive types and their composition. The other key issue has been the technical investigation of the influence of component termination and printed circuit surface types on adhesive bonding stability. Four different types of adhesives on two different metal surfaces are compared with conventional solder technology. Each adhesive has been applied to the PCBs by either screen printing or dispensing according to the manufacturer's recommendation, followed by curing. All PCBs went through thermal and humidity cycling followed by electrical measurements of resistance. Finally all variants have been adhesion tested. All adhesive variants have been microsectioned for metallurgical and microstructure examination. Energy dispersive analysis of X-ray (EDAX) of the metal particles in the adhesive has been carried out and documented. Rework of conductive joints is briefly commented on. Finally, aspects of occupational health are discussed concerning work with adhesive types. Work with epoxy based adhesives has been brought into special focus. |
