the present description describes back - end processes , the use of which may help overcome these problems and limitations of the prior art . in one optional embodiment , the back - end process includes depositing a layer over a wafer . the wafer contains a plurality of circuit die for respective rfid tags . the wafer also has exposed metallic regions . the exposed metallic regions include first regions having electrical contacts to the plurality of circuit die and second regions having electrical contacts to the wafer &# 39 ; s electrical test sites . the method includes forming exposed first regions and unexposed second regions by etching the layer over the first regions but not over the second regions . the method also includes plating metallic bumps on the exposed first regions .