DIEs, prior to being processed to Flip Chips or wafer level packages, receive their electrical connections at the wafer level stage. During the wafer bumping process, solder paste deposits are applied to the wafer, soldered to result in wafer bumps.

Stainless steel stencils or screens are frequently used for the printing of the solder paste.

Furthermore the cleaning of soldered wafers is also necessary to avoid issues during the processing of the chips (i.e. during underfill and moulding). At the same time the used wafer passivation has to be fully compatible with the cleaning process.