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In this paper, the immersion method was used to study the dissolution behavior of Cu/Sn system with or without ultrasound at 523K, 553K and 573K.SIt is found that the dissolution rate of Cu wire in molten Sn under ultrasonic action is 6.79~24.106 times without ultrasonic effect.SCombined with the method of finite element simulation, this phenomenon is explained from the perspectives of ultrasonic cavitation effect, micro jet effect and acoustic streaming.SThe results show that the cavitation bubble collapse will produce a high temperature of about 1500K at the Cu/Sn interface, which not only increases the solid solubility limit of Cu in the Sn liquid, but also melts the Cu in the "micro-point" region; The micro jet effect can reduce the thickness of the intermetallic compound (IMC) layer and change its morphology, and increase the channel of atomic diffusion; the acoustic streaming will produce a stirring effect, and the solute Cu atom at the front of the Cu/Sn solid-liquid interface is continuously pushed to the Sn liquid.SInternally, the solute atom solubility is always lower than the saturated solubility.SCombining the above factors, the dissolved amount and dissolution rate of solid Cu in the Sn solution are significantly increased under the action of ultrasonic waves.