PCB Design Guidelines
Build a PCB design around clear electrical requirements, realistic fabrication rules and a complete release package. Use this guide to connect the schematic, layout and manufacturing review.
A good layout starts before the first trace.
Treat PCB design as a set of documented decisions—not a collection of default CAD settings.
Write down what the board must do, how it fits the enclosure and how it will be assembled and tested. Then translate those requirements into net classes, geometry constraints and drawing notes.
Minimum trace width and spacing are tied to the fabrication process, including copper thickness. Select the intended construction before adopting a supplier’s rule set.
Define rules that describe the finished board.
Swipe horizontally to read the full table.
| Design item | What to define | What to review |
|---|---|---|
| Copper width & spacing | Separate routing rules for power, signals, fine-pitch escapes and special net classes. | Match the rule set to the intended copper construction; do not use the process minimum everywhere. |
| Holes & annular rings | Finished hole size, tolerance, plating status and pad geometry. | Distinguish plated component holes, vias and non-plated holes. Do not confuse finished diameter with the drill tool. |
| Board edges & cutouts | Copper-to-profile rules, slot shape, plating and any intentional edge copper. | Review routed edges and scored edges separately. Call out exceptions rather than letting CAM infer intent. |
| Solder mask | Pad openings, intended covered vias and narrow mask webs. | Inspect the generated mask layers. Mask expansion is not the same as electrical clearance. |
| Component footprints | Exact package variant, pad numbering, exposed pads and land pattern. | Compare the footprint with the component manufacturer’s drawing, not just a matching package name. |
| Controlled nets | Signal layer, reference planes, width/gap constraints and target impedance. | Agree the stackup before locking geometry; check the return path at layer transitions. |
| Mechanical features | A closed outline, dimensioned critical features and assembly keepouts. | Supply unambiguous routing and slot information on the mechanical drawing. |
Review the board in functional groups.
Freeze mechanical anchors first
Start your placement review with the board boundary, connectors, mounting hardware and restricted volumes. Record which dimensions are fixed and which may change before optimizing component density.
Use device-specific placement guidance
Check the selected device’s reference layout and application notes for critical support components. Keep a record of deliberate departures so the reviewer knows which areas need closer attention.
Trace the complete current loop
For fast signals, keep the reference structure continuous. A short signal route that crosses a plane gap still needs attention; review the return connection when the signal changes layers.
Keep high-current decisions separate
Document load current, duty cycle, copper construction and the allowed temperature rise. Mark bottlenecks such as connector pins, neck-downs and vias for project-specific electrical and thermal analysis.
Reserve test and assembly access
Add test points, programming access and assembly clearances to the placement review. Ask the assembler which edges, surfaces and locations must remain accessible for the selected process.
Inspect generated output, not only CAD
Use a separate fabrication-data viewer to check layer assignment, outline, holes, mask and markings. A saved layout file and the exported production package should describe the same revision.
Use four review gates, not one final inspection.
- 01
Requirements review
Approve the electrical brief, mechanical interfaces and a list of unresolved requirements. Assign an owner to each open question.
- 02
Construction review
Request a stackup and agreed fabrication rules. Flag fine-pitch areas or fixed geometry before completing the full route.
- 03
Layout review
Check connectivity, mechanical fit and design-rule results. Review documented exceptions rather than suppressing warnings without explanation.
- 04
Release review
Compare the final exports, drawing, BOM and assembly outputs. Record the exact revision approved for fabrication and assembly.
Before you send the design for review.
Use this as a personal release check. A checkmark records your review, not manufacturer approval.
0 / 10 items checkedWorks only in this browser tab. Refreshing clears the checkmarks. No design files or form data are uploaded.
Frequently asked questions
Check the design, files and manufacturing requirements before sending your next board for production.
What trace width and spacing should I use?
Use a construction-specific fabrication rule set and your electrical requirements. Thicker copper and other process choices can change the available geometry. Ask for review rather than assuming a number from another PCB is suitable.
Does passing DRC mean the PCB is ready to manufacture?
No. DRC checks the rules and connectivity conditions configured in the CAD project. A separate release review should address fabrication interpretation, assembly details and unresolved requirements.
Should I remove every warning?
Investigate every relevant warning. Correct genuine problems and document deliberate exceptions with a reason and an owner. A suppressed message is not evidence that the underlying design intent is correct.
When should I request a stackup?
Request it before fixing controlled-impedance widths and gaps. Model the transmission line using the intended dielectric, reference structure and finished copper geometry.
What should be included in the first review request?
Send the board revision, proposed construction, fabrication data and drawing, quantity, and the questions you need answered. Include assembly files when the review also covers placement, parts or testing.
Related engineering resources
Use this guide to define your design constraints. For project delivery and engineering scope, see PCB design services; for placement and routing work, see PCB layout services.
Technical references & scope notes
- Würth Elektronik — BASIC Design Rules (PDF)
- Würth Elektronik WEdirekt — Design Guide for PCBs from the online shop (PDF)
- Würth Elektronik — Technical Delivery Specification for PCBs (PDF)
- KiCad — PCB Editor: Manufacturing Outputs and Design Rules
- Texas Instruments — High-Speed Layout Guidelines, SLLA414A
- KiCad 10 — PCB Editor manual
- Polar Instruments — Microstrip structures, AP122
- Polar Instruments — Modeling precision and fabrication geometry, AP170
References support general engineering guidance. Supplier-specific limits, example constructions and qualification results are not GlobalWellPCB capabilities. Use the approved project specification and confirmed manufacturing rules for each order. Content reviewed: September 2026.
GlobalWellPCB · Engineering resources
Back to top