Study on effect of coupling agents on underfill material in flip chip packaging

Coupling agents are widely used in order to improve the adhesion property of underfill. In this study, three different silane coupling agents, two titanate coupling agents, and one zirconate coupling agent were added into an epoxy underfill material. Their effects on the flow behavior and curing profile of the epoxy underfill were studied with a rheometer and a differential scanning calorimeter, respectively. The thermal stability of the cured underfill material was studied with a thermogravimetric analyzer. A thermal mechanical analyzer and a dynamic mechanical analyzer were used to measure the coefficient of thermal expansion, the glass transition temperature (T_g), and the storage modulus (E´). In addition, the adhesion of the underfill on benzocyclobutene passivated silicon die and polyimide passivated silicon die was measured through die shear test. The effects of aging in an 85°C/85% relative humidity chamber were also studied through moisture absorption test and die shear test