Why PCB autorouters fall short and how one handles unfinished boards

An autorouter converts schematic connections into copper across chosen layers while respecting design rules, but many tools fall short in practice. The article argues that a useful router should work across many layers, rework routing around difficult nets, and handle impedance during routing rather than afterward. It also stresses reporting every unrouted net by name instead of a vague completion figure. Using a four-layer RP2040 board as an example, the author describes a run that left nine nets open and refused to export Gerbers, which they present as the proper way to fail. Finally, the piece notes that component placement and dense fine-pitch parts often cause routing failures more than the router itself.