WHY PCBA DESIGNS REQUIRE PROCESS EDGES: BENEFITS, PURPOSE, AND SMT MANUFACTURING GUIDE

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When designing a PCB, engineers often add process edges (also called working edges) around the board. But why is this necessary? What benefits do process edges provide during manufacturing?
Today, we'll explain why PCBA requires process edges and how they impact the SMT assembly process.

What Is a PCBA Process Edge?

A PCBA process edge is a strip of unused board area added to one or more sides of the PCB.

Its main purpose is to:
- Provide space for the SMT conveyor rail
- Create room for panel fiducials (Mark points)
- Prevent components from being placed too close to the board edges

Because PCBAs are transported through SMT lines by rails, every board must include edges where no components can be placed. Typically, the two longer sides of the PCB or panel are used as the conveyor edges.



Why Process Edges Are Essential in SMT Assembly

During SMT production, the pick-and-place machine clamps the PCB and moves it through the assembly line.

If components are placed too close to the rail edge:
- The SMT nozzle may hit components
- Components may shift, tilt, or fail during placement
- The machine may be unable to run the board at all

By reserving process edges, these risks are avoided. The same applies to through-hole components during wave soldering—without sufficient edge spacing, components can be damaged or misaligned.
Therefore, process edges are a critical design consideration for stable SMT and DIP assembly.

Are Process Edges Part of the Final PCBA?

No.

Process edges are not part of the final functional PCB.

They are only added to assist with:
SMT placement
DIP insertion
Wave soldering
Conveyor travel

After assembly is complete, the process edges are removed.

How Are PCBA Process Edges Removed?

After SMT assembly, the process edges must be removed cleanly and without causing stress to the components.
There are three common methods:

1. V-Cut Depaneling Machine
Uses a blade to cut along V-grooves
Low cost and fast
Only suitable for straight cuts

2. Routing (Milling) Machine
Uses a router bit to mill along the board outline
Best quality, low stress, protects components
Higher cost and slower speed

3. Manual Removal
Breaking by hand or using pliers
Low cost and convenient
Higher risk of mechanical stress damaging components
From a quality perspective, routing provides the best results and minimizes stress on the PCB and components.

Conclusion

Adding process edges is a small design step that brings major benefits during PCBA manufacturing. It ensures:

- Smooth SMT conveyor transport
- Safe and accurate component placement
- Stable wave soldering
- Reduced risk of damage or misalignment

Although process edges are removed before the final product is delivered, they play an essential role in ensuring high-quality PCBA production.

Thank you for reading. We hope this article provided valuable insights for you.

With 16 years of expertise in PCBA design, manufacturing, and service, KingshengPCBA is ready to help turn your ideas into reality. Feel free to contact us anytime to discuss your requirements and get a professional quotation.