Indentation depth dependent micromechanical properties and rate dependent pop-in events of (Au,Cu)5Sn

The indentation depth dependent micromechanical properties of (Au,Cu)5Sn were investigated using nanoindentation. A correction model was proposed to eliminate the overestimation of the hardness for small indentation around the nano-characteristic depth (hnano) by the Nix-Gao model. The indentation hardness of (Au,Cu)5Sn around hnano is proved to be constant by nanoindentation experiment and our analytic model. Pop-in events of (Au,Cu)5Sn exhibit obvious rate dependent effects: pop-in becomes inconspicuous as the loading rate increases, while the first pop-in load and the maximum shear stress increase with the loading rate. Potential mechanism of the rate dependent pop-in events is analyzed based on our experimental results.