Liquid Metal Vertical Interconnects for Flip-Chip Assembly of GaAs C-Band Power Amplifiers onto Micro-Rectangular Coaxial Transmission Lines

Prior work has demonstrated a new process utilizing room temperature liquid metal, galinstan, as an interconnect material for flip chip bonding. This interconnect forms a flexible bond between chips and carriers and therefore a flip chip assembly using this technology is much less susceptible to thermomechanical stresses. This paper applies this concept to interconnect MMIC chips to 3D Polystrata transmission line structures. A prefabricated GaAs MMIC chip is post processed for liquid metal assembly. Measured results show, over the MMIC's 4.9 - 8.5 GHz frequency range, the system's overall reduction in gain of the MMIC is 1.4 dB or 0.7dB per RF transition as compared to direct probing of the MMIC chip.