Why Do PCBs Require Process Edges?

July 20, 2026

When designing circuit boards, PCB designers often reserve process edges. Do you know the reasons behind this practice? What are the benefits of designing process edges?

PCB process edges, also known as working edges, are long, narrow blank board margins set aside for SMT assembly—specifically to provide space for rail transport and placement of panel fiducial marks. PCBs are ultimately destined for pick-and-place processing; on the production line, they are conveyed via guide rails. Therefore, one pair of opposite edges must be kept clear of components to serve as the transport edges. Typically, the two long edges of the PCB or the larger panel after depaneling are used as the transport edges.

In the PCB manufacturing workflow, reserving process edges is of great significance for subsequent pick-and-place assembly. Process edges are additional margin areas added along two or four sides of the PCB to facilitate SMT placement, DIP insertion, and wave soldering board transport. Since the SMT machine rails clamp and move the PCB through the machine, electronic components placed too close to the rail edge are prone to collision with the machine's suction nozzles during placement, making production impossible. Thus, reserving a certain process edge effectively resolves these issues encountered during SMT assembly. Similarly, process edges are also applicable to through-hole components, preventing similar problems during wave soldering. Process edges are not part of the PCB itself and can be removed after PCBA processing is completed.

In addition, removing the process edges after SMT assembly is also very important, and the edges must be kept flat. The methods for removing PCBA process edges can be broadly divided into three categories: V-cut routing machines, milling/routing separators, and manual removal. Purely from a quality perspective, milling/routing separators yield the best results; V-cut machines are much cheaper, cutting along PCBA V-grooves with blades, but can only perform straight-line cuts. Manual removal involves breaking off the edges by hand or using tools like pliers; it offers low cost and convenience, but it tends to generate stress that can damage components.