Arc spraying Ag-based coating on aluminum alloy surface and its low-temperature soldering behavior

In waveguide devices, large-area and reliable low-temperature soldering bonding between the aluminum alloy shell and the microstrip circuit board were difficult because of the poor wettability of the Al alloy. In this study, Ag-15%Ni coating layer and Ni-5%Al/Ag-15%Ni composite coating layers with a thickness approximately of 80 μm were prepared on the surface of 5A06 Al alloy by arc spraying technology to improve the wettability of Sn-Pb alloy solder on the Al alloy surface. Comparable studies were performed on the microstructure, interfacial bonding behavior, low-temperature soldering behavior of the two kinds of coating layers, and the shearing failure mechanism of joints were investigated. Results showed that sound interfacial bonding was realized between the coating layer and the Al alloy substrate. Moreover, the two kinds of coating layers both exhibited good solderability at low-temperature. The bonding strength between the Ag-15%Ni coating layer and the Al alloy substrate was 40 MPa, and the shear strength of the soldering joint formed by the sprayed aluminum alloy substrate and T2 copper was 26 MPa. While, the Ni-5%Al/Ag-15%Ni composite coatings exhibited better bonding strength with the Al alloy substrate (42 MPa) and higher shear strength of the soldering joint (31 MPa) than the Ag-15%Ni single coating layer.