Influence of nanosilica on composite underfill properties in flip chip packaging

The nanosilica filled composite is a promising material as the no-flow underfill in flip-chip application. However, as the filler size decreases into the nano level, the rheological, mechanical, dielectric and thermal mechanical properties of the composite change significantly. The filler-filler and filler-polymer interactions have a profound impact on the material properties. The purpose of this paper is to achieve an in-depth understanding in the effect of the filler size and surface on material properties and therefore to provide guidance for the design of nanocomposite in no-flow underfill applications. Mono-dispersed nanosilica fillers of 100 nm in size were used in this study. An epoxy/anhydride mixture was used as the base resin formulation. Control samples with micron-size silica fillers were also formulated and characterized for comparison.