ABSTRACTRoom-temperature welding with gallium is regarded as a new strategy because of the low melting point of gallium and its affinity for forming intermetallic compounds with other metals. Benefitting from liquid gallium-based solder and an ultrasonic drive, the establishment of Cu/Cu diffusion-bond connections can be quickly completed. The underlying characteristics for the weld quality of room-temperature bonding were preliminarily clarified from the perspectives of welding process parameters and the solder composition. To further determine these characteristics, the research directions including features of welding product formed by ultrasonic-driven room-temperature bonding, the interface microstructure, the element distribution and the shear strength of the weld joint were then determined.