Insights into the role of interface in the rheological property of underfill composites

With the use of nano-sized silica particles as fillers, the rheological property of the underfill composites is greatly deteriorated, due to the excessive surface energy of the nano-sized fillers and their poor interfacial compatibility with the underfill matrix. Since interface property is one of the dominant factors for determining the properties of composites, in this study, four kinds of silica nanoparticles with different surface chemistry were used to comparatively study the role of interface in the rheological property of amine-cured epoxy underfill composites. And it is found that the fillers with surface functional groups, which have reactivity or good compatibility with the underfill base materials, could not only drastically decrease the viscosity, but also largely improve the viscosity stability of the underfill composites.