RF and mechanical characterization of flip-chip interconnects in CPW circuits with underfill

RF characterization of flip-chip interconnects in CPW circuits with underfill has been investigated by measuring the scattering-parameters up to 40 GHz for GaAs coplanar waveguide (CPW) through line chips flip-chip mounted on alumina substrate with and without underfill epoxy. Fatigue life of flip-chip assemblies has been computed for different chip sizes and substrates. The results show feasibility of using underfill encapsulant in microwave/mm-wave frequency range.