Properties of spin coated epoxy/silica thin film composites: Effect of nano- and micron-size fillers

With the increasing interest in high density electronics packaging, dimensional scaling becomes the key to evolution. Low coefficient of thermal expansion (CTE) thin film composites with silica fillers were fabricated using spin coating. In comparison with the conventional thin film fabrication, spin coating has the ability to control film thickness and uniformity. In this paper, the mechanical and thermal properties of the thin film composites using micron-silica and nano-silica were compared. The 2 wt% nano-silica thin film composite was found to have the lowest CTE and is able to achieve an equivalent tensile strength compared with the 15 wt% micron-silica thin film composite. The 2 wt% nano-silica samples also gave an equivalent thermal stability as compared with that of the 30 wt% micron-silica. Hence, with the higher surface area to volume ratio, nano-silica shows its capability to achieve a substantial performance with a lower weight fraction compared with μ-Si.