Flip-chip packaging configuration with coplanar strip lines for millimeter electromagnetic waves

Flip-chip configuration based on coplanar strip (CPS) lines is reported for millimeter-wave device applications. We designed and implemented the flip-chip configuration using a test chip directly on dielectric boards with CPS lines for wideband interconnections. The chip is connected to the board using solder balls. The flip-chip assembles are evaluated up to 40GHz by S-parameters. Insertion loss, 10LOG|1/S₂₁|², as low as 3dB is achieved at 30GHz. The corresponding return loss, 10LOG|1/S₁₁|², is 15dB. We also analyzed the attenuation coefficient of CPS based on geometrical configuration to achieve optimum design on PCBs. For CPS lines built on RT/Duroid, the measured attenuation coefficient is as low as 1.1dB/cm at 40GHz. Attenuation analysis was performed by employing numerical full wave calculation with HFSS tool