Preventing aging of electrically conductive adhesives on metal substrate using graphene based barrier

The Electronic Conductive Adhesive (ECA) is a promising material as a substitute of traditional tin-lead solder, with many advantages outperforming tin-lead containing solder such as environmentally friendly, requiring much lower processing temperature and a much finer pitch. However, one critical problem related to ECA application is that the contact resistance increases significantly during an aging test, particularly at 85°C/85% relative humidity (RH) when ECA is bonded onto non-noble metal surfaces due to galvanic corrosion. Recently, it has been reported that graphene has an interesting and wonderful property, impermeability; it can prohibit most molecules from going through due to the fact that graphene is one of the most impermeable barrier materials, and it has become a potential candidate for anti-corrosion applications. Some papers studying the application of graphene for anti-corrosion of steel and other metals have already been published. In this paper, graphene film [12] barriers were introduced between the ECA and metal pad to alleviate the galvanic corrosion problem, which can lead to the deterioration of contact resistance, then the aging test @85°C/85% was performed for 500 hours. It was found that the contact resistance increased quickly during the first 200 hours of aging test for samples without graphene film barriers, while the contact resistance for samples with graphene barrier remained stable. Samples with graphene film barriers showed a smaller shift of the contact resistance than those without graphene barrier. The results indicated that the graphene film barrier can be used to improve ECA's reliability, especially @85°C/85% conditions.