Effects of contact metallizations on electrical resistance reliability of ACF interconnection for chip on flex application

Although there have been many years of development, the reliability of the electrical performance of anisotropically conductive adhesives or films (ACAs or ACFs) interconnection for flip chip assembly is still a critical drawback despite wide application. In-depth study about the reliability and degradation mechanism of ACF interconnection is necessary. In this paper, effects of contact metallizations on electrical resistance reliability of ACF interconnection for flip chip on flex substrate was investigated using different bump/pad metallizations couple. Contact resistance changes were monitored during reliability tests such as high humidity and temperature, and thermal cycling. Both the higher initial contact resistance and rapid increment were investigated in ACF assemblies with Ni-Cu coupled metallization. The potential causes for the bigger degradation of Ni-Cu coupled ACF were analysed.