Group routes by electrical need
Separate interfaces by destination, timing constraints, noise sensitivity, and reference requirements. Assign preferred routing regions before individual traces consume the available channels. A low-speed control group should not force a critical clock or memory group into a complicated layer transition simply because it was routed first.
For an illustrative processor board, reserve coherent paths for memory, external high-speed links, and power delivery. The exact assignments depend on placement and device guidance, so a generic signal/plane sequence is only a starting sketch.
Choose access depth after assigning roles
Compare a 1+8+1 concept with a 2+6+2 concept if both are candidates for the product. The first has more central copper layers; the second offers another build-up access level. Determine which arrangement lets the package reach the planned interface regions with sufficient routing and reference margin.
Keep the arithmetic separate from manufacturability. Neither notation specifies material thickness, intermediate drilling, fill requirements, or accepted via stacks. Obtain an actual construction proposal before freezing CAD rules.
Review power paths as physical routes
TI's PDN guidance treats power and ground plane placement as an electrical design input. On a ten-layer board, avoid relegating rail assignments to whichever planes remain after signal routing. Review how current reaches the package and how decoupling connects to the same reference structure.
- Map major rails from source to load and local capacitors.
- Identify plane splits beneath critical routes.
- Check reference changes at signal and power transitions.
- Coordinate dielectric choices with impedance and interconnect geometry.
Use the extra capacity to gain margin
If ten layers were selected to ease routing, preserve the resulting benefit. Widen unconstrained conductors, reduce unnecessary transitions, and retain room for test access. Filling every available channel with the tightest geometry recreates the original congestion and leaves little tolerance for manufacturing feedback or product revisions.
Adjacent-layer access, one connection at a time
Dielectric · geometry + material
Core or build-up dielectric
Illustrative only. Copper thickness, dielectric construction and via spans require a reviewed stackup.
Common questions
Should all interfaces use the same via structure?
No. Use approved structures suited to each route, while keeping the overall set understandable and covered by manufacturing review.
Can extra plane layers compensate for poor decoupling placement?
They may improve part of the path, but do not eliminate connection inductance or placement constraints. Evaluate the complete power network.
References & further reading
Method & assumptions · General design guidance. Validate the proposed construction and acceptance criteria for your project.