An interposer is an electrical interface routing between one socket and connection to another. The purpose of an interposer is to spread a connection to a wider pitch or to re-route a connection to a different connection, using RDL or Redistribution layers.
Today’s interposer serves as a bridge between the higher density of today’s die, and the IC package
Common interposer application comes in Silicon Package Designs as well as in ATE applications where an IC die is connected to BGA or Micro-BGA, using different interconnect techniques.
Interposers can be designed using either Organic Substrates such as FR4, Rogers, Polyimide or other relevant materials, or using In-Organic Substrates such as Gallium Arsenide (Ga As), Gallium Nitride (GaN), Silicon Carbide (SiC) or similar.
C2 and C4 are interposers that connect a small die in a FCBGA using Flip Chip on one side of the substrate BGA on the other side.
These interposer designs could use either C2 or C4 design techniques, which have different characteristics as well as Some of the considerations for Interposer design includes:
- Pad design and construction
- Bump pattern development
- System connection planning
- Net management
- Multi-Die support, if required