The indentation size effect in SnAgCu lead-free BGA solder joints at elevated temperatures

This paper investigated the influence of different temperatures on the indentation size effect by nanoindentation test. The Sn-Ag-Cu-Bi-Ni lead-free BGA solder joints with the diameter of 400µm were used. Nanoindentation tests were carried out at 293K, 323K, and 353K, and the homologous temperature of Sn-Ag-Cu-Bi-Ni lead-free BGA solder was 0.60, 0.66, 0.72, respectively. The results showed that as the temperature rose, the plastic material length scale (h*) declined accordingly. Especially when the temperature ranged from 323K to 353K, the h* dropped rapidly from 34.35nm to 18.64nm. Moreover, over this range of the test temperatures, the size effect was reduced considerably. The higher temperature resulted in a low h* of Sn-Ag-Cu-Bi-Ni lead-free micro solder joints, and h* has an obvious dependence relationship on the temperature.