Phenolic and amine epoxy systems are widely used as hardeners in underfill materials for flip chip packaging. A comparison was made between these two systems in order to evaluate the reliability performance of a flip chip plastic ball grid array (FC-PBGA). The coefficient of thermal expansion, glass transition temperature (), Young’s modulus (E), and fracture toughness were revealed by using a thermal mechanical analyzer, a dynamic mechanical analyzer, and a single-edge notch three-point bending test, while moisture absorption study was performed using an /85% relative humidity chamber. The adhesion strength with different conditions of temperature and humidity was performed using a die shear test. The series of standard reliability tests such as accelerated temperature cycle test, pressure cooker test, thermal humidity storage test, and high temperature storage test were executed upon the FC-PBGA, which was filled by phenolic and amine epoxy systems of underfill materials. It was found that the adhesion strength of phenolic-based underfills is better than that of amine-based underfills in almost all test conditions. Phenolic-based underfills also demonstrated better reliability compared with amine-based underfills.