Development and characterization of imidazole derivative cured bisphenol A epoxy materials for flip-chip underfill applications

This paper aims to provide underfill manufacturers and electronic packaging companies with general information about imidazole derivative cured bisphenol A epoxy materials. Four selected imidazole derivatives and one bisphenol A epoxy resin were investigated in this paper. Differential scanning calorimetry (DSC) was used to study the curing kinetics of the prepared formulations and glass transition temperature (T_g) of the cured formulation. A thermo-mechanical analyzer (TMA) was used to investigate the heat flex temperature and coefficient of thermal expansion (CTE). A dynamic-mechanical analyzer (DMA) was used to measure the storage modulus (E´) and cross-linking density (ρ) over a temperature range from 25°C to 250°C of the cured materials. A rheometer was used to investigate the viscosity (η) of these formulations. The effects of the curing agent type and concentration on the curing kinetics, T_g, CTE, E´, ρ, and η were then investigated. The correlation between CTE (above T_g ) and cross-linking density was examined and discussed