Wet etch recipe development for removing lead-free C4 bumps

To protect the environment, lead-free solder will be introduced in microelectronic products to replace lead solder. Proper lead-free bump removal is very important to the success of subsequent analysis steps. In this paper, a state-of-the-art wet etch recipe has been developed to remove Sn-Ag-Cu bumps. By optimizing the recipe, the resulting process has enabled the authors to identify defects within failing devices through front-side deprocessing.