Effect of coupling agents on underfill material in flip chip packaging

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