redistribution layer (chip) (RDL)
Redistribution means rewiring, redistribution or redistribution. Redistribution layers(RDL) are special layers in a package to redirect connections to desired locations.
Redistribution is performed on the wafer and can, for example, connect bumps located in the center of the chip to contacts near the chip edge. The redistribution technique can increase contact density, which can result in smaller packages. The redistribution layer is located above the wafer. After exposing the bond pads, metal leads are deposited with which the pads are routed to the desired positions. Metallization layers are also built up under the bumps to support the solder bumps.
Redistribution layers are used in the packages where the dice are internally bonded to the substrate and connect the input/output (I/O) systems of the dice to a bond pad( bump). This is the case in flip-chip technology, wafer level packaging(WLP) and chips with silicon through-silicon vias( TSV).