Strain rate sensitivity of Sn-3.0Ag-0.5Cu solder investigated by nanoindentation

In this paper, nanoindentation tests with CSM technique were conducted on Sn-3.0Ag-0.5Cu(SAC) lead-free solder under different strain rates at room temperature. Results show that the nanomechanical properties of SAC solder depend on the strain rate remarkably. The contact stiffness increases almost linearly with indentation depth. Under different strain rates, contact stiffness and elastic modulus basically remain unchanged, but the hardness increases with increasing strain rate. For the same holding time, creep deformation is more evident under high strain rate. The “bulge” phenomenon for SAC solder weakens as unloading rate increases, residual indentation depth after unloading is larger under high strain rate.