Post-Placement Congestion Types

• Congestion at macro corners from insufficient placement blockage.
• Standard cells squeezed into narrow channels.
• Macros of the same partition placed far apart, causing timing issues.
• Improper macro placement or macro channels.
• Missing placement blockages.
• No channel space left between macros.
• High cell density and high local utilization.
• Many high-pin-count complex cells (AOI/OAI) clustered together.
• Standard cells placed too close to macros.
• Poor logic optimization.
• High pin density at block edges.
• Too many buffers added during optimization.
• Criss-crossed IO ports that need proper alignment.

KEY Congestion comes from poor macro/blockage placement, high density and excessive buffering.

Fixing IR Drop and Congestion Together

• Spread the macros.
• Spread the standard cells.
• Increase strap width.
• Add more straps.
• Apply proper placement blockages.

KEY Spread macros and cells, strengthen the power straps, and use blockages.