This invention relates to fluxing underfill compositions useful for fluxing metal surfaces in preparation for providing an electrical connection and sealing the space between semiconductor devices, such as chip size or chip scale packages (“CSPs”), ball grid arrays (“BGAs”), land grid arrays (“LGAs”), flip chip assemblies (“FCs”) and the like, each of which having a semiconductor chip, such as large scale integration (“LSI”), or semiconductor chips themselves and a circuit board to which the devices or chips, respectively, are electrically interconnected. The inventive fluxing underfill composition begins to cure at about the same temperature that solder used to establish the electrical interconnection melts.