ISOLA PCB / DESIGN GUIDE
Six layers.
A complete design conversation.
Connect the signal paths, layer construction and fabrication drawing before committing to routing dimensions.
01 / START WITH CONNECTIVITY
Assign a purpose to every layer.
List critical interfaces, connector locations and plane transitions first. Then discuss a layer arrangement with the fabricator. The example below is a conversation starter; it is not a released stack-up or a universal recommendation.
| Layer | Example assignment | Review question |
|---|---|---|
| L1 | Signals and components | Which continuous plane will reference the critical surface routes? |
| L2 | Ground plane | Can the intended reference remain continuous under the signal path? |
| L3 | Signals | Which adjacent plane is the reference, and how will transitions be handled? |
| L4 | Power distribution | Where are the power domains, splits and decoupling connections? |
| L5 | Ground plane | How will ground connections support transitions to the bottom surface? |
| L6 | Signals and components | What constraints apply to routing and assembly on this side? |
Plane assignments and dielectric spacing must be reviewed together. This sketch does not validate return paths, power integrity or manufacturability.
02 / CONSTRUCTION REVIEW
Turn a layer diagram into a producible stack.
Material & construction
Record the requested grade, core thicknesses, prepreg constructions and substitution policy. Ask for current available constructions rather than specifying by family name alone.
Thickness & balance
Use finished copper and pressed dielectric values in the arithmetic. Review the arrangement across the board centre and copper distribution with the fabricator.
Manufacturing agreement
List finished thickness tolerance, hole requirements, surface finish and any required inspection records. Resolve drawing and fabrication-data differences before release.
03 / ELECTRICAL REQUIREMENTS
Specify the target and the verification.
| Include | What to record |
|---|---|
| Net class | Name the interfaces and distinguish single-ended from differential routing. |
| Target & tolerance | State the required impedance and acceptance tolerance. Do not rely on a calculator screenshot alone. |
| Geometry & reference | Identify signal layer, reference plane, trace width, pair spacing and finished copper assumptions. |
| Material data | Record the construction, design Dk source and modelling conditions used by the fabricator. |
| Acceptance | Agree coupon location, measurement method and required test documentation. |
04 / RELEASE GATE
A clear fabrication package.
- One revision: the drawing, layer files and drill files identify the same design release.
- One layer order: names in the drawing match the fabrication files.
- One specification: material, thickness, copper, finish and impedance requirements are unambiguous.
- Explicit exceptions: record approved substitutions and open questions.
- Review before production: obtain agreement on the final construction and acceptance criteria.
COMMON QUESTIONS
Before your next design review
Does a six-layer count guarantee signal integrity?
No. Layer count does not establish the quality of the routing, return paths or power distribution. Review the specific design and its operating conditions.
Can I use the example directly for production?
Treat it as an illustrative topology. Request a manufacturer-reviewed construction based on your routing and fabrication requirements.
What if the requested material is unavailable?
State whether substitutions are allowed and ask for a documented comparison. Approve the proposed material and construction before production.
CONTINUE YOUR DESIGN