Fatigue and failure behavior of silver-filled electronically-conductive adhesive joints subjected to elevated temperatures

Abstract

The use of adhesives to replace mechanical connectors and other joining methods has enjoyed rapid growth in recent years. There are a number of issues of concern in the design of joints bonded using electronically-conductive adhesives (ECAs). One of these is the cyclic fatigue behavior of conductive adhesive interconnects under different environmental conditions, in which fatigue failure might occur due either to mechanical or thermal stresses varying in a cyclic manner. This paper addresses the effect of elevated temperatures on the fatigue and failure behavior of ECAs. For this purpose, joints were prepared using stainless steel adherend specimens bonded with a commercial ECA, and tested using monotonic and cyclic loadings, at two elevated temperatures, namely 50°C and 90°C. When the temperature was increased to 90°C, close to the glass transition temperature of the adhesive, we observed consistently parallel fatigue curves at different load ratios (R = P min /P max) for joints, as in the case of 50°C test condition, along with significant reduction in fatigue lives. Joint failure mechanisms were also analyzed using optical techniques, and joint conductivity measurements.