Microstructure and Intermetallic Growth at the Sn-Ag-Cu/Ni Interface after Thermal-shearing Cycling

In this work, microstructure and intermetallic growth at the Sn-Ag-Cu/Ni interface were researched under the thermal-shearing cycling condition varying from 25 degC to 125 degC. The results show that two kinds of intermetallic compounds, identified as (Ni_xCu _1-x)Sn₃ and (Cu_xN_1-x)₆ Sn₅, were found at the interface between Sn-3.5Ag-0.5Cu and Ni after thermal-shearing cycling. The (Cu_xN_1-x)₆Sn₅ IMC grows up slowly as scallop-like grains into the solder under the initial reflow process and subsequent thermal-shearing cycling condition. Nevertheless, the (Ni_xCu_1-x)Sn₃ IMC grows extremely fast as platelets after thermal-shearing cycling . The Ag₃Sn IMC forms planar layer at the solder/Ni interface and grows up remarkably