The use of silane coupling agents in the design of electrically stable interfaces of 6061 T6 aluminum alloy surfaces and epoxy-based electrically conductive adhesives

Abstract

Electrically conductive interfaces between metal surfaces, including aluminum, are commonly formed by means of bonding with an electrically conductive adhesive. Humid environments induce an increase in electrical resistance between aluminum objects bonded in this manner. However, joints that are electrically stable through stress testing in environments of elevated temperature and humidity (85°C and 80% RH for up to 137.5 h) have been obtained by treating the aluminum surface with a thin layer (less than 50 A) of an organo-silane coupling agent, that is, a material capable of bonding chemically with the aluminum oxide surface layer and potentially bonding with the polymer binder in the adhesive. The present study shows that besides their traditional use as surface modifiers for adhesion improvement, organo-silanes can act as corrosion inhibitors of aluminum surfaces to stabilize electrical performance. Whereas other treatments used for preparation of metal surfaces for bonding, using electrically-insulating structural adhesives, typically do not ensure reliable electrical performance, minimal and reproducible increase in resistance has been observed for joints prepared using the procedure described here. Application of this method does not require any significant investment in equipment and the surface pretreatment of the metal surface is quite simple.