2.6. PCB fabrication222
2.6.1. definition of PCB fabrication
PCB fabrication is the process of manufacturing a Printed Circuit Board (PCB) from a circuit design. The process transfers the electrical connections designed in software such as KiCad, EasyEDA, or Proteus into a physical board.
The process starts with creating the circuit schematic and PCB layout using PCB design software.
1. PCB Design
The designer determines:
- Component positions
- Copper tracks
- Vias
- Board dimensions
- Power and ground connections
- Mounting holes
2. Gerber File Generation
After completing the PCB layout, manufacturing files are generated. The most important are Gerber files, which contain information about different PCB layers.
Typical files include:
- Copper layers
- Solder mask
- Silkscreen
- Board outline
- Drill files
3. Preparing the PCB Material
A common PCB material is FR-4, which consists of fiberglass reinforced with epoxy resin and covered with copper.
The copper layer provides the electrical paths for the circuit.
4. Image Transfer
The desired circuit pattern is transferred onto the copper surface using a photographic or similar imaging process
The areas that should remain as copper are protected, while unwanted copper will later be removed.
5. Etching
The board is placed in an etching solution that removes the exposed copper
After etching, only the copper tracks required by the circuit remain.
6. Drilling
Holes are drilled for:
- Through-hole components
- Vias
- Connectors
- Mounting screws
Modern PCB manufacturers commonly use CNC or automated drilling machines.
7. Plating
For multilayer and professional PCBs, copper plating is used to create electrical connections between layers and inside plated through-holes.
8. Solder Mask Application
A solder mask is applied over the PCB. It protects copper tracks from oxidation and helps prevent accidental solder bridges.
The familiar green PCB color is often produced by the solder mask, although other colors are possible.
9. Silkscreen Printing
Text and symbols are printed onto the PCB, such as:
- Component reference numbers
- Pin labels
- Polarity indicators
- Company logos
- Warning symbols
10. Surface Finishing
The exposed copper pads receive a surface finish to protect them and improve solderability.
Common finishes include:
- HASL
- Lead-free HASL
- ENIG
- OSP
11. PCB Inspection and Testing
The manufactured PCB is inspected for defects such as:
- Broken tracks
- Short circuits
- Incorrect holes
- Missing copper
- Incorrect dimensions
- Manufacturing contamination
Electrical testing may also be performed to verify that the required connections are correct.
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