Nanoindentation for measuring mechanical properties of lanthanum-doped tin-silver-copper lead-free solders

摘要

The elimination of lead from electronics due to its toxic nature and hazardous environmental effects is pushing the manufacturers towards the lead free solders for which Sn-Ag-Cu (SAC) alloys are considered as the best substitute. These alloys still have coarse microstructure with soft tin matrix and hard Intermetallic Compounds (IMCs). Lanthanum is added for refining the microstructure and improving the mechanical properties of SAC solders. Nanoindentation is a useful technique to evaluate the mechanical properties at very small length scale. In this study, CSM nanoindentation setup is used to determine the Young's modulus and hardness of SAC and Lanthanum doped SAC alloys. Loadings from 100 μN to 1000 μN with 100 μN steps were applied and different dwell times from 10 seconds to 60 seconds were used to avoid the creep effects. The loading rates applied were twice that of loading. Average values for both Young's modulus and hardness were determined against indentation depth. Nanoindentation causes the pile-up effects in the soft β-tin phase and eutectic Sn phase which are determined and incorporated in the results. The new results are in a better agreement with the previous studies.