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Liquid–Metal V ertical Interconnects for Flip Chip Assembly of GaAs C-Band Power Ampli fiers Onto Micro-Rectangular Coaxial Transmission Lines Parrish Ralston, Student Member , IEEE
利用液态金属Galinstan实现GaAs MMIC芯片与3D传输线结构的低损耗互连
0.11 dB损耗（至26.5 GHz），4.9–8.5 GHz频段增益降低1.4 dB
液态金属GalinstanGaAs MMICFlip-Chip高频互连
▸创新点1：室温液态金属互连技术（方法创新）。该论文首次将室温液态金属Galinstan应用于GaAs MMIC芯片与3-D Polystrata传输线结构的互连，解决了传统互连材料在高温下易失效的问题，显著提高了互连的可靠性和稳定性。
▸创新点2：抗热机械应力设计（系统创新）。通过液态金属的柔性特性，实现了芯片与载体之间的柔性连接，有效降低了热机械应力对系统的影响，提升了系统的长期可靠性。
▸创新点3：高频低损耗性能（电路创新）。实验结果表明，液态金属互连在26.5 GHz频率下每过渡的平均损耗仅为0.11 dB，显著低于传统互连材料，适用于高频应用场景。
▸创新点4：GaAs MMIC芯片的后处理优化（方法创新）。通过对预制GaAs MMIC芯片进行后处理，优化了液态金属互连的组装工艺，确保了系统在4.9-8.5 GHz频率范围内的性能稳定性，增益损失仅为1.4 dB。
Abstract
Prior work has demonstrated a new process utilizing room-temperature liquid metal, Galinstan, as a n interconnect ma- terial 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 susceptibl e to thermomechan- ical stresses. This paper applies t his concept to interconnect GaAs MMIC chips to 3-D Polystrata tran smission-line structures. Pas- sive assemblies are utilized to model, tes t, and verify liquid–metal interconnections, giving average lo sses per liquid–metal transition of about 0.11 dB out to 26.5 GHz, low parasitics per transition, and demonstrated reliability after temperature cycling. A prefab- ricated GaAs MMIC chip is postprocessed for liquid–metal as- sembly. Measured results show, over the MMIC’s 4.9–8.5-GHz fre- quency range, the system’s overal l reduction in gain of the MMIC is 1.4 dB or 0.7 dB per RF transition as compared with direct probing of the MMIC chip.