Free Gerber Viewer Apps to Preview and Verify Your PCB Gerbers

How to Use a Gerber Viewer to Catch PCB Design ErrorsA Gerber viewer is an essential tool for anyone involved in printed circuit board (PCB) design and manufacturing. It allows you to inspect Gerber files—the standard file format PCB manufacturers use to fabricate boards—so you can catch errors before production. This article walks through the steps to effectively use a Gerber viewer to find common design mistakes, explains what to look for on each layer, and offers practical tips to streamline verification.

What is a Gerber Viewer and why it matters

A Gerber viewer reads and displays Gerber files (RS-274X and variants), letting you visualize copper layers, solder mask, silkscreen, drill data, and other manufacturing files. Because Gerber files are what manufacturers actually use to make your PCB, reviewing them is the last chance to spot issues that might not be obvious in your PCB CAD tool—such as layer misalignment, missing features, or incorrect drill sizes.

Key takeaway: Use a Gerber viewer as a mandatory pre-manufacture quality check.

Typical files to load into a Gerber viewer

When preparing to inspect a PCB with a Gerber viewer, gather:

Copper layers (Top/Bottom and internal plane layers)
Solder mask layers (Top/Bottom)
Silkscreen layers (Top/Bottom)
Board outline (mechanical layer)
Drill file (Excellon or embedded drill in Gerber)
Paste layers (for stencil generation), if applicable
Any keepout or assembly layers provided by your CAD tool

Load all relevant files simultaneously so the viewer can align layers correctly and present an accurate composite view.

Setup and initial checks

Open the viewer and import all Gerber and drill files.
Verify units (mm vs. inches) and resolution—wrong units are a common root cause of scaling errors.
Ensure layer stackup and ordering are correct; the viewer should let you toggle visibility or change layer opacity.
Turn on grid and rulers if available to measure distances quickly.

Quick checks: Confirm board outline matches intended size, and that layer alignment looks correct when all layers are visible.

Layer-by-layer inspection checklist

Copper layers

Look for broken traces, unintended gaps, or hairline traces that could open.
Check trace widths and clearances, especially around fine-pitch components and high-current nets. Use the viewer’s measurement tool to confirm widths.
Inspect thermal reliefs and via connections on pads to ensure manufacturability and soldering reliability.
Verify plane shapes and ensure no accidental islands of copper that should be connected.

Solder mask

Ensure mask openings align with pads; excessive mask between pads can cause solder bridging, while insufficient mask can expose copper.
Check for mask slivers—very thin mask areas that might peel or fail to register.
Confirm that solder mask expansion (clearance) matches your manufacturer’s capabilities.

Silkscreen

Make sure text and reference designators aren’t printed over pads, vias, or too close to edges.
Verify font sizes and orientation for assembly readability.
Remove any silkscreen overlapping plated through-holes or exposed copper.

Drill file / Vias

Cross-check drill coordinates against pad locations using the viewer. Misplaced drills can render the board unusable.
Confirm drill sizes, via annular rings, and that plated/non-plated through holes are properly specified.
For multi-layer boards, ensure microvias and blind/buried via designs are represented correctly (if supported by your foundry and export format).

Board outline and mechanicals

Verify cutouts, slots, and edge clearances.
Ensure board outline is a single continuous contour or uses the correct mechanical layer conventions for your manufacturer.
Check for conflicts between outline and components or silkscreen.

Paste layers (stencil)

Confirm paste openings match pad geometry; too large can cause solder balling, too small can starve joints.
Check for paste layers on vias that should be tented or plugged.

Common errors a Gerber viewer helps catch

Unit mismatches leading to incorrectly scaled boards.
Layer misalignment from wrong file origins or missing offsets.
Missing layers (e.g., no solder mask or drill file included).
Overlapping or mirrored silkscreen causing misplaced text.
Unintended copper features or isolated copper islands.
Incorrect drill sizes or missing plated/non-plated specifications.
Solder mask openings too small or too large for reliable assembly.

Using measurement and DRC features

Many Gerber viewers include measurement tools and basic design rule checks (DRC). Use them to:

Measure trace widths, spacing, and annular rings.
Verify minimum clearances meet your manufacturer’s spec.
Run automated checks for overlapping objects, shorted nets (viewer-level), or minimum feature sizes.

Automated DRCs are helpful but don’t skip manual visual inspection; some issues are contextual and require human judgment.

Tips for efficient review

Create a checklist tailored to your PCB type (high-speed, high-current, fine-pitch BGA, RF).
Use layer coloring and opacity to quickly spot anomalies.
Zoom to 400–1000% around BGAs and fine-pitch ICs to inspect pad shapes and solder mask.
Compare Gerbers to your original PCB design (some viewers overlay CAD exports or ODB++) to ensure nothing was lost during export.
For teams: export annotated screenshots from the viewer to communicate issues to designers or manufacturers.

When to involve your manufacturer

If you find ambiguous issues—such as unclear drill specifications, unusual plane constructions, or questions about mask expansion—ask your PCB manufacturer for clarification. They can confirm capabilities (minimum mask sliver, drill tolerances, minimum annular ring) and sometimes adjust CAM settings to correct minor issues.

Example workflow (quick practical sequence)

Export Gerbers + drill from your CAD tool using manufacturer’s recommended settings.
Load all files into the Gerber viewer.
Confirm units and layer alignment.
Do a coarse visual scan for obvious errors (scale, outline, missing layers).
Inspect critical areas (BGAs, connectors, high current traces) at high zoom.
Run measurement checks and viewer DRC.
Annotate and correct issues in the CAD tool, re-export, and re-check.
Send final verified Gerbers to manufacturer with a README specifying stackup, finish, and special notes.

Conclusion

A Gerber viewer is your last line of defense against costly PCB manufacturing mistakes. By systematically loading all files, checking units and alignment, inspecting each layer closely, and using measurement/DRC tools, you can catch most common errors before they become expensive problems. Make Gerber review a fixed step in your release workflow to save time and production cost.