ProcirelGerber Files: What Each Layer File Means
Gerbers are the vector plot files describing every layer of your board. Understanding the standard set and previewing the composite is the last line of defence between a design mistake and a two-week, paid-for error.
> At a glance: 6 minute guide · part 8 of 10 in the PCB design complete guide track · includes a worked example and a quick-reference table.
## The standard file set
Copper layers (top, bottom, inners), solder mask top/bottom, silkscreen top/bottom, edge cuts, and a separate drill file. Naming varies by tool (KiCad, Altium exports). The fab’s viewer does not care as long as the set is complete and mapped.
| File | Layer role | Check in preview |
| — | — | — |
| Copper top/bottom | Conductive art | Clearances, text mirroring |
| Solder mask | Openings over pads | Pads fully exposed |
| Silk | Legends | Not overlapping pads |
| Edge cuts | Board outline | Closed, no stray lines |
| Drill | Hole positions | Centred in pads |
## Preview like the fab will
What this means at the bench. Load the Gerbers in a viewer (or the fab’s own online preview) and inspect. Copper against mask openings, silk not on pads, board outline closed, drills aligned to pads. The composite view exposes mapping mistakes that the layout editor never shows.
## What fabs add
Fabs panelise your board, add tooling borders and their own plated drill processes. Your job ends at a clean, verified single-board file set including a fab drawing for anything non-standard (controlled impedance, stack-up, finish).
## How to apply this in your build
Work through the sequence below each step assumes the previous one passed. For numbers that need calculating, the linked tools at the end of this guide do the arithmetic instantly.
1. Export the complete Gerber set plus drill
2. Open the composite in a Gerber viewer
3. Walk every layer against the checklist
4. Upload to the fab preview and inspect once more before ordering
### Worked example
A designer’s mirrored bottom silkscreen printed gibberish on delivered boards a five-second viewer check would have caught the mirror flag left at default. Run the numbers yourself with the related calculator and the result should agree to within rounding.
> Practical note from the bench. Order ritual on our bench: Gerber preview screenshot saved into the project log every fab order leaves a visual audit trail.
## Field mistakes we see again and again
– Uploading project source files instead of Gerbers
– Missing drill file the classic incomplete order
– Outline drawn with multiple overlapping segments confusing fab tooling
## Key takeaways
– The standard file set the foundation of this guide; revisit it if any measurement here surprises you.
– Preview like the fab will the foundation of this guide; revisit it if any measurement here surprises you.
– What fabs add the foundation of this guide; revisit it if any measurement here surprises you.
## Prerequisites and preparation
Before starting: export the complete gerber set plus drill and open the composite in a gerber viewer. Keep a calculator to hand every number in the worked example is reproducible. Total time including the bench steps: about 6–6 minutes.
## Who benefits most
Hobbyists meeting this topic for the first time, students who want the version with real numbers instead of abstract symbols. Returning engineers refreshing a corner of the craft. The mistake list alone justifies the visit every entry in it was learned the expensive way.
### Quick reference card
| Aspect | Where to find it in this guide |
| — | — |
| Core theory | The standard file set |
| Application steps | How to apply this in your build |
| Worked numbers | Worked example |
| Failure modes | Field mistakes we see again and again |
## How this fits the PCB design complete guide track
This guide is one stop in the structured learning path. Start from the [PCB design complete guide](/tutorial/pcb-design-complete-guide) pillar page for the full map, or continue with [how boards are made](/tutorial/pcb-manufacturing-process) and [KiCad workflow](/tutorial/kicad-schematic-tutorial).
## Frequently asked questions
Should I send the netlist/IPC-2581 too?
Many fabs accept it for automated electrical verification if offered, include it.
Zip structure: flat or folders?
Follow your fab’s uploader; most want one zip of all layers.
Where do I go next?
Back to the [PCB design complete guide](/tutorial/pcb-design-complete-guide) pillar page it indexes every guide in this track and updates as new ones are published.
## Continue this track
– Building a foundation? The [pcb design complete guide](/tutorial/pcb-design-complete-guide) maps every step in order.
– Next: [PCB Vias: Through, Blind and Buried Types and Trade-offs](/tutorial/pcb-via-types-guide)
– Next: [What Is VLSI Design? Building Chips With Billions of Transistors](/tutorial/what-is-vlsi-design)
– Next: [Common PCB Assembly Defects and How to Prevent Them](/tutorial/pcb-assembly-defects)
– Work the numbers: [trace width calculator](/tools/pcb-trace-width) · [resistor decoder](/tools/resistor-color-code) · [SMD code decoder](/tools/smd-resistor-code)
## Measurement discipline
When a result here disagrees with your expectation, write down both numbers before changing anything. The gap between predicted and measured is where the real engineering lives. It is usually a tolerance, a parasitic or an assumption that was never checked.
Keep a lab notebook entry for every build in this track. The measured values, the deviations from the guide and the reason for each. Six months from now, those notes are worth more than any tutorial. They describe your bench and your components rather than a general case.
## Formulas and checks from this guide
Verification checklist for this track: run DRC early and often, verify footprints against the datasheet drawing. Walk the return path of every fast signal before ordering. A five-minute Gerber preview has saved more fab cycles than any other habit.
Bookmark this page against your next build in the track. The checklist above is the same one used across 15 guides in this series.
## Hard-won notes
Run DRC continuously, then once more after every final edit. The last small change breaks the most boards.
Two for hobby density, four the moment ground integrity or impedance matters. The cost gap has collapsed.
## How to revisit this guide
Second readings work best with a purpose. Pick one section from The standard file set,Preview like the fab will,What fabs add and rebuild only that part at the bench, predicting each value before measuring. Prediction errors mark exactly which concept needs the next pass, and the linked pcb design calculators resolve any arithmetic doubt in seconds. Keep the marked sections in your notebook: after a month of builds, that list becomes your personal PCB Design syllabus.