PCB stackup: align electrical and lamination structures
Stackup tables support layout, impedance solving, and production. Each layer needs its function, finished copper weight, and adjacent dielectrics; dielectric layers need core/PP models and dielectric thicknesses after lamination, rather than only total board thickness. Submit preliminary drafts for factory review before routing.
| Structural Item | Content to Fill | Inspection Purpose |
|---|---|---|
| Signal/reference layer | Layer-by-layer functions, critical nets, and continuous reference planes | Maintain return-path continuity and identify layer transitions |
| Copper layer | Base copper and target finished copper thickness, copper distribution | Distinguish outer plating and check copper balance |
| Dielectric Layer | Model, glass style/resin, and target finished thickness | Constrain lamination and the impedance model |
| Via Layer Pair | Through holes, blind vias, buried vias, and backdrill stop layers | Map lamination/drilling operations |
| Impedance Group | Trace geometry, W/S, reference layers, targets, and tolerances | Corresponding test coupons and TDR acceptance |
How to compare two candidate stackups
Compare reference-plane continuity and interlayer connections first, then calculate routing margin, total thickness, and hole aspect ratios. Compare costs using the material specifications, lamination count, and testing requirements. Reducing layer count while adding HDI build-up cycles does not necessarily reduce total cost. Symmetry checks must consider dielectric thickness, copper weight, and actual copper distribution together.
Changes after version confirmation
Material substitutions, dielectric-thickness adjustments, copper-weight changes, and via layer-pair changes can affect impedance and fabrication. Re-solve affected nets for each new stackup; after compensation approval, update Gerber/impedance tables so production files and design models use the same revision.
Inputs and outputs
Inputs include layer functions, board thickness, material candidates, copper weight, hole tables, and electrical constraints. Outputs are the approved stackup, via layer-pair diagram, impedance groups, permitted compensation range, and first-article verification requirements.
Multi-Layer Routing, HDI build-up structures, Impedance Acceptance, Material Review, Submit stack-up draft
Engineering reference | Digital PCB stackups: material databases and controlled manufacturing structures: methodological reference; third-party design methods or material documentation do not represent KFPCBA manufacturing capabilities.
Six-layer stack-up example: determine layer function first
| layers | Example Function | Manufacturing and electrical notes |
|---|---|---|
| L1 | Signal | Critical traces reference the adjacent L2 ground plane |
| L2 | Ground Plane | Maintain continuous return paths and check splits and vias |
| L3 | Signal | Correspond to approved reference plane and adjacent dielectric thickness |
| L4 | Power Plane | Allocate core copper thickness by load and plane distribution |
| L5 | Ground Plane | Provide a continuous reference plane for adjacent signal layers |
| L6 | Signal | Reference the L5 ground plane and account for port transitions |
The diagram is not to scale and specifies no layer copper weights or dielectric thicknesses. Add core/PP models, dielectric thicknesses after lamination, and base/finished copper to the formal stackup; determine layer functions for four-, eight-, twelve-, and sixteen-layer boards according to nets, routing, and hole structures.
What else should the stackup table sent to the factory include
| Documentation | Required Content |
|---|---|
| Materials and copper layers | Complete grades, core/PP, and base/finished copper for every layer |
| Via Layer Pair | Through holes/blind vias/buried vias, start/end layers, and fabrication sequence |
| Impedance Group | Nets/trace geometry, targets, tolerances, and corresponding reference planes |
| Approval Boundary | Compensation permissions, substitution rules, revisions, and first-article inspections |
Compare multi-layer board types → Compare HDI build-up structures →
