The effects of temperature and humidity aging on the contact resistance of novel electrically conductive adhesives

Abstract

Conductive Surface Mount Adhesives (CSMAs) are an alternative to traditional solders used in the electronics industry. CSMAs provide an environmentally friendly alternative to conventional Sn/Pb metal solders offering additional attractive technical advantages including low temperature processing, fine pitch capability and better resistance to thermal cycling. The two major limitations of CSMAs have been their instability on common electronic metals such as copper and Sn/Pb solder and their performance under impact testing. Recent experimental work published by National Starch Corporate Research in collaboration with Georgia Institute of Technology has shown that the unstable contact resistance of CSMAs on copper and solder is due to electrochemical corrosion of these metals under adverse conditions. Based on the above fundamental understandings, Emerson & Cuming have been developing some new and unique formulas which exhibit exceptional contact resistance stability on previously unstable metal surfaces including OSP copper, Sn/Pb alloys and even 100 percent tin. Much progress has also been made in the area of mechanical performance. Recent advances in contact resistance stability have been incorporated along with the advances in impact performance to create novel materials. This paper examines the effects of thermoshock testing, high temperature aging and humidity aging on the contact resistance and the adhesion of these new formulas.