Reduced cycle time epoxies for flip chip underfill

Abstract

The further development of the epoxy flip chip underfill encapsulant material has been demonstrated as necessary to enhance the temperature cycle performance of the solder ball connections. A reduction of the epoxy encapsulant under fill processing and cure time is needed in order to better fit into the production line environment. This paper reports and discusses the improvement of under fill flow speed and distance, the various material properties such as resin viscosity, filler effects and the overall rheology with respect to under fill flow. The reduction of oven cure time is a key requirement for faster "throughput" and reduction of "work in process". The minimum cure times needed in order to maintain the level of reliability required as a flip chip under fill material are discussed. Physical material properties of these flip chip materials such as; glass transition temperature, coefficient of thermal expansion, tensile modulus, and adhesion are discussed in relation to reliability performance.