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Redistribution Layers (RDLs)

Copper metal interconnects that electrically connect one part of a package to another.
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Description

Redistribution layers (RDLs) are the copper metal interconnects that electrically connect one part of the semiconductor package to another. RDLs are measured by line and space, which refer to the width and pitch of a metal trace. Higher-end RDLs may be at 2μm line/space and smaller.

The RDL is a layer of wiring metal interconnects that redistribute the I/O access to different parts of the chip and makes it easier to add microbumps to a die.

RDLs are used in fan-out and 2.5D/3D packages.


Fig 1. Interposer structure in 2.5D packaging. Source: Lam Research