Low Cycle Fatigue Properties of Ni added Low Silver Content Sn-Ag-Cu Flip Chip Interconnects

Abstract

The straddle fatigue test has been performed to study the fatigue properties of Sn-1.2 mass%Ag-0.5 mass%Cu-0.05 mass%Ni for flip chip interconnections. The low cycle fatigue resistance of the alloy is equivalent to that of Sn-3 mass%Ag-0.5 mass%Cu alloy, even though the fatigue endurance of Sn-1 mass%Ag-0.5 mass%Cu alloy was poorer than that of the 3 mass%Ag alloy. The alloy has fine microstructure and Ag₃Sn intermetallic compound makes a network structure together with fine (Cu,Ni)₆Sn₅ compound. The microstructure resulted in high cyclic strain hardening exponents, which leaded to good low cycle fatigue endurance of the alloy.