“…Wetting is realized by removing the oxide layer on the surface of the substrate [5] . Since its first development, ultrasonic-assisted soldering has been successfully used to join various types of materials, such as Al alloys [6] , [7] , Mg alloys [8] , Ti alloys [9] , ceramics [10] , [11] , and sapphire. However, the mechanism of oxide layer removal via ultrasonication remains unclear.…”