Good Design – Bad Design
(Auto-Routers and Why We Don’t Use Them)

Poorly Designed Board

The top image is typical of auto-routing and cleanup.
The auto-router achieved 90 percent of the connections in 3 hours plus an hour of router setup.
( The designer had to clean up the mess and complete the remaining routes. That took 2 ½ days.)
Total routing time = 3 days.
You can see the results:
6 layers with 6 mil line and space.
Too many micro-vias (20/10).
No organized flow and signal integrity jeopardized.

Well Designed Board

The bottom image is the same board hand routed.
Every connection was routed by hand.
Total routing time = 5 days.
The results are impressive:
4 layers with 10 mil line and space.
Minimum number of standard vias (26/13).
Organized buss flow and intelligent signal routing.
Better signal integrity with less cross talk or coupling.
Bare board cost will be 15 to 25% less...forever.