Tensile fracture behavior of Sn-3.0Ag-0.5Cu solder joints on copper

Microstructural features and tensile properties of Sn-3.0Ag-0.5Cu solder joints on copper with various aging time at 150 degrees C were examined. The solder inner and solder/Cu interface were analyzed by SEM to identify the fracture location, morphology and compositions. The study has showed, the tensile fracture strength of the solder joints decreases with the increased aging time, and the crack initiates mostly at the interfaces between the solder and IMC layer or/and IMC and IMC layer. The morphology of fracture surface changes from dimple-like to cleavage-like surfaces. The needle-like or block-like interfacial IMCs form at the interface of Cu/solder and grow into the solder matrix. Otherwise, the Kirkendall voids can be observed in the multilayer structure close to the copper substrate. These voids have probably a detrimental effect on the tensile fracture behavior.