Suppression of the CPW leakage in common millimeter-wave flip-chip structures

Leakage phenomena in GaAs flip-chip structures, mounted on common GaAs and alumina main substrates, are studied using the spectral domain approach with the goal of reducing possible chip-to-chip crosstalk and transmission resonance. We have found that the TM/sub 0/ parallel-plate mode in the main substrate is dominant for the coplanar waveguide flip-chip leakage, and that the leakage can be suppressed by properly selecting the gap height and the main substrate thickness in addition to the dielectric constant.