Ultrasonic bonding of 2024 Al alloy using Ni-foam/Sn composite solder at ambient temperature

摘要

Ultrasonic bonding of 2024 Al alloy was successfully performed at ambient temperature by using Ni-foam reinforced Sn-based composite solder foils. Ni-foam sheets with porosities of 60% and 80% were used to strengthen pure Sn solder. The Ni skeletons in the solder seam changed from three-dimensional continuous network structure into strip type with increasing ultrasonic bonding time, accompanied with the formation of Ni3Sn4 phase on Ni skeleton surface and Al3Ni intermetallic compound (IMC) layer on Al substrate surface. While, further prolonging the ultrasonic bonding time could largely consume Sn solder and break the Ni skeletons. The Sn-based solder added with 80% porosity Ni-foam exhibited better soldering performance than that added with 60% porosity Ni-foam. The Al/Ni80-Sn/Al joint ultrasonically bonded for 4 s exhibited the highest shear strength of 52.34 MPa, the shearing failure mainly happened in the composite solder layers.