GERBER FILES

 What Are Gerber Files?

Gerber files are the standard file format used to describe the physical layout of a PCB. They are essentially the blueprint that tells a PCB manufacturer exactly how to fabricate the board, layer by layer.

Each Gerber file corresponds to a specific layer or feature of the PCB, such as:

Copper traces
Solder mask
Silkscreen (component labels)
Drill holes
Board outline

These files are generated from PCB design software (like Altium Designer, KiCAD, Eagle, or OrCAD) and are used by fabrication and assembly houses to produce the physical board.

 How Gerber Files Are Used in PCB Manufacturing

Design Export: After designing the PCB layout, the designer exports the board layers into Gerber format.
Layer Separation: Each Gerber file represents one layer or process:

Top copper layer
Bottom copper layer
Solder mask (top/bottom)
Silkscreen (top/bottom)
Drill file (usually in Excellon format)
Board outline

Fabrication: The manufacturer uses these files to:

Etch copper traces
Apply solder mask
Print silkscreen
Drill holes
Cut the board to shape

Assembly: Assembly houses may also use Gerber files to align components and verify placement.

 Common Gerber File Types

Layer/Function Typical File Extension Description
Top Copper .gtl Gerber Top Layer
Bottom Copper .gbl Gerber Bottom Layer
Top Solder Mask .gts Gerber Top Solder
Bottom Solder Mask .gbs Gerber Bottom Solder
Top Silkscreen .gto Gerber Top Overlay
Bottom Silkscreen .gbo Gerber Bottom Overlay
Board Outline .gml or .gm1 Mechanical layer
Drill File .drl Excellon format for hole locations
Assembly Layer .gta, .gba Optional for pick-and-place machines

 Gerber File Formats

There are two main versions of Gerber files:

1. RS-274X (Extended Gerber)

Most widely used format today.
Supports embedded aperture definitions.
Includes layer polarity and other metadata.
Compatible with modern CAM tools.

2. RS-274D (Standard Gerber)

Older format, now largely obsolete.
Requires separate aperture list file.
Less reliable and harder to interpret.

 Supporting Files Often Included

Drill File (.drl): Specifies hole sizes and locations.
Readme or Fabrication Notes: Instructions for the manufacturer.
Pick and Place File: Used for automated component placement.
IPC-D-356 Netlist: Optional file for electrical testing.

 Best Practices When Submitting Gerber Files

Include all necessary layers: Copper, mask, silkscreen, outline, drill.
Use consistent naming conventions.
Verify with a Gerber viewer before sending to fabrication.
Include a README or fabrication drawing for clarity.
Compress into a ZIP folder for easy upload.