The stack-up is the foundation
Every high-speed board starts as a stack-up decision. The number of layers, the spacing between them, and the dielectric material define your trace impedance before you route a single net.
Get the stack-up wrong and the rest of the design is an exercise in compensation. Fix the impedance, the return paths, and the layer discipline first, and routing becomes much more forgiving.
Routing high-speed signals
High-speed traces are transmission lines, not wires. Keep them short, keep them referenced to a solid plane, and control the geometry so the impedance stays consistent from driver to receiver.
Avoid right-angle bends and stubs, match lengths on differential pairs and buses, and give clocks the cleanest path on the board. The return current follows the path of least inductance — give it a continuous plane to follow.
Power and grounding
Clean power is part of the signal chain. Decouple every rail close to the load, use a mix of bulk and local capacitance, and keep switching noise out of sensitive analog sections.
One solid, continuous ground plane is almost always the right answer. Splits create return-path discontinuities that show up as emissions and crosstalk.
Design for manufacture
A board that cannot be built reliably is not finished. Respect clearances and minimum trace widths, keep components away from board edges, and add fiducials and test points for assembly and bring-up.
Review the design-rule check, not just the ERC. The best layout is the one that passes the fabricator's rules on the first submission.
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