Environmental reliability and failure mechanism of ionic conductive adhesives

Environmental reliability is a quite important requirement for ionic conductive adhesives (ICAs) that determines the long-term durability of the bonding systems. However, little is known about the environmental reliability and failure mechanism of ICAs. In this study, four kinds of ICAs are prepared via physical blending of epoxy resin, polyethylene glycol diglycidyl ether (PEGDE) and ionic liquids (ILs). The environmental reliability of ICAs are presented through monitoring the bonding strength during aging treatment under 55 degrees C and 95% relative humidity. It is found that the introduction of ILs significantly deteriorates the environmental reliability and the size of the ILs shows remarkable influences on the environmental reliability. The investigation of the failure mechanism reveals the ILs migrate to the bonding substrates and enrich at the interfaces, which increases the free volume of the interfacial polymers and reduces the cohesive strength of ICAs, thus the interactions between ICAs and bonding substrates are destroyed. It is believed that this work provides a comprehensive understanding to long-term durability and the failure mechanism of the physical blended ionic conductive materials.