10 Common PCB Design Mistakes and How to Avoid Them

Practical DFM tips from the factory floor

Introduction

You‘ve spent weeks designing your PCB. The schematic is clean. The routing is complete. You’re ready to send it to production.

Then the boards arrive. Some work. Some don‘t.

What went wrong?

After reviewing thousands of designs on our production line, I’ve seen the same mistakes appear again and again. The good news is that most of them are easy to catch — if you know what to look for before you hit “send.”

This guide covers the 10 most common PCB design mistakes and how to avoid them.

Let‘s dive in.

1. Incorrect Trace Width

The mistake: Using traces that are too thin for the current they need to carry.

Why it’s a problem: Thin traces act like fuses. Too much current, and they burn open.

The fix: Use a trace width calculator. For 1oz copper, a 10 mil (0.25mm) trace handles about 1 amp. For higher currents, use wider traces or add multiple vias to distribute current.

Pro tip: Power traces should be 2–3x wider than signal traces. When in doubt, add 50% margin.

2. Missing or Wrong Annular Rings

The mistake: Annular rings (the copper pad around a drilled hole) that are too small.

Why it‘s a problem: If the annular ring is too small, the drill can “break out” of the pad, creating an open circuit.

The fix: Follow these minimums:

Pro tip: Add teardrops to your vias. They strengthen the connection between the trace and the pad.

3. No Fiducials for Assembly

The mistake: Forgetting to add fiducial marks when your boards will be assembled by machine.

Why it’s a problem: Pick-and-place machines need fiducials to align properly. Without them, components can be placed incorrectly or the machine may stop entirely.

The fix: Add at least 3 fiducials on your board — one in each corner and one near the center. Keep a clear area around each (no copper, no silkscreen within 2–3mm).

4. Over-specifying Surface Finish

The mistake: Choosing ENIG (gold finish) for every project out of habit.

Why it‘s a problem: ENIG costs 30–50% more than HASL or OSP. For many designs, you don’t actually need it.

The fix: Match the finish to your needs:

Pro tip: If your smallest component pitch is 0.5mm or above, HASL is probably fine.

5. Ignoring Thermal Relief

The mistake: Connecting large copper pours directly to component pads without thermal relief spokes.

Why it‘s a problem: Large copper areas sink heat away from the pad during soldering, making it hard to get a good joint. This can cause tombstoning for small components.

The fix: Use thermal relief pads for any pad connected to a large copper pour. Your EDA software has this feature — turn it on.

6. Incorrect Hole Sizes

The mistake: Specifying odd or non-standard hole sizes.

Why it’s a problem: Non-standard drill sizes require custom tooling, which adds cost and lead time.

The fix: Stick to standard drill sizes:

Standard sizes (mm)

0.3, 0.35, 0.4, 0.5, 0.6, 0.8, 1.0, 1.2, 1.6, 2.0, 2.4, 3.0, 3.2

Pro tip: For vias, use 0.3mm or 0.4mm. These are the most common and cheapest.

7. Copper Pours Too Close to Board Edge

The mistake: Running copper fills or traces right up to the board outline.

Why it‘s a problem: During routing (cutting boards apart), copper near the edge can short or peel back.

The fix: Keep copper at least 0.3mm from the board edge on inner layers, and 0.5mm on outer layers.

8. Missing Silkscreen Polarity Markers

The mistake: Not marking the polarity of diodes, capacitors, and IC pin 1.

Why it’s a problem: Assembly technicians have no way to know which way a component goes. This leads to incorrect placement, rework, and debugging headaches.

The fix: Always add:

• A “+” symbol for polarized capacitors
• A line or dot for diodes (cathode side)
• A dot or chamfer for IC pin 1

Pro tip: Don‘t put silkscreen over pads or vias — it will get scraped off or cause soldering issues.

9. No Testing Strategy

The mistake: Sending your design to production without any way to test it.

Why it’s a problem: When the boards come back, you won‘t know if they work until you fully assemble and power one up. If something is wrong, you waste components and time.

The fix: Add test points for critical nets (power, ground, clocks, data lines). Make them large enough for a probe — 1mm diameter minimum.

Test point checklist:

• Power input
• Main voltage rails
• Critical clocks
• Programming/debug interface

10. Sending Incomplete Files

The mistake: Sending only Gerber files with no documentation or missing layers.

Why it’s a problem: The manufacturer has to guess your requirements or email back and forth — both add time and increase the risk of errors.

The fix: Create a simple readme file that includes:

Pro tip: Zip everything into one clearly named file: ProjectName_Gerbers_v1.zip

Quick Summary

Here‘s a final checklist before you hit send on your next design:

• Trace widths — sized for current
• Annular rings — ≥0.25mm outer, ≥0.15mm inner
• Fiducials — 3+ for automated assembly
• Surface finish — don‘t over-spec
• Thermal relief — on large copper pours
• Hole sizes — use standard diameters
• Copper to edge — keep 0.3–0.5mm clearance
• Polarity markers — on all polarized components
• Test points — for critical nets
• Complete files — Gerbers + BOM + centroid + readme

Final Thoughts

Most PCB problems are avoidable. The mistakes listed above account for the majority of manufacturing issues we see daily.

Take an extra 30 minutes to review your design against this checklist before sending files. That small investment of time can save you weeks of debugging and hundreds (or thousands) of dollars in respins.

Good luck, and happy designing.

About the Author

This article is brought to you by **AnyPCBA**, a China-based PCB manufacturer specializing in small-to-medium volume production. We help hardware startups and engineering teams bring their designs to life with reliable PCB fabrication and assembly services.