Improvements in thermo-mechanical and rheological properties of SiO_2/epoxy composites using different types of SiO_2

摘要

Single-size 400 nm-SiO_2 and multi-size 1 and 5 μm-SiO_2 were used as fillers in epoxy matrix. The fillers with the larger particle size and multi-size SiO_2 particles mixing is beneficial to lower the viscosity and increase the filler loading. Among the composites, the 60 wt% 5 um-SiO_2 epoxy composite has the best properties with both low coefficients of thermal expansion (CTE) of 28.8 ppm/℃ and low viscosity of ～ 50 Pa s, which shows its capability to achieve the required low CTE and viscosity values in the electronic packaging. Different theoretical proposals were used to estimate the CTE. Maxwell-Garnett equation fits the experimental data well. In addition, the mixture law and Bruggeman effective medium theory offer the upper and lower limits to the CTE.