Best Practices for PCB Panel Design in Manufacturing and Assembly
1. The Importance of a Well-Designed Panel Structure
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If a PCB is not panelised for a pick-and-place machine, assembly becomes inefficient and error-prone because the machine relies on standardized panel dimensions and fiducials for accurate positioning. Irregular-shaped boards, very small PCBs, components appearing in the edges of the PCB are especially problematic, as they cannot be properly clamped or conveyed, leading to misalignment, poor placement accuracy, and increased risk of component loss or damage. This often results in slower throughput, more manual handling, higher defect rates, and increased manufacturing cost.



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Machine Compatibility: The panel must fit within the minimum and maximum dimension constraints of the assembly line equipment (e.g., solder paste printers, pick-and-place machines, reflow ovens). A typical minimum size is around 50mm x 50mm, while maximums can reach 330mm x 530mm or more.
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Panel Borders (Edge Rails): A crucial element of any panel is the handling edge or border. This is a component-free zone around the perimeter of the panel that allows automated machines to transport and clamp the board during processing.
The image below illustrates a typical PCB panel layout with a 2×3 array of boards, clearly showing the surrounding handling edge.


2. Common types of PCB panelization include:
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Tab Routing (Tab + Mouse Bites)  – Individual boards are held together by small tabs with perforated holes; boards are snapped apart after assembly. Consider tab routing when your design has an irregular shape or if you need space between your boards to allow for overhanging components. Default is to add a 0.1″ (2.0mm) gap between the boards to allow the router bit to pass between them. Small tabs of material will remain to hold the boards in place. To make separation easier, add small non-plated holes to the tabs called ‘mouse bites’ to perforate the tab. The breakaway tab closest to the PCB corner should be located between 10 mm and 12 mm from the edge to reduce sagging during reflow or wave soldering. It is also preferred to have at least one tab per side. If the PCB placement is too dense for a Tooling Hole, then it should be placed on the breakaway tab. See Figure 3 for the optimized breakaway tab solution.

One important aspect is to have a clean edge after the breakaway tab is removed. Slight inset of perforation is preferred because it provides an edge which requires little to no additional labor to clean up. Figure 2 illustrates the perforation location preferences.

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V-Groove (V-Scoring) – This method involves cutting a V-shaped groove into both the top and bottom surfaces of the panel, leaving a thin web of material connecting the boards, allowing clean separation by snapping; best for straight-edge designs.


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Solid Routing – Boards are fully routed with no breakaway until final depaneling using a router; used for complex or sensitive boards.
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Frame Panelization – Multiple boards are placed inside a rigid outer frame, improving handling for small or irregular-shaped PCBs.
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Mixed Panelization – Combination of V-groove and tab routing in a single panel, depending on board geometry.
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Array Panelization – Identical PCBs arranged in rows and columns to maximize panel utilization and assembly efficiency.
2. Critical Handling Area and Essential Features
The panel’s edge rails are not just empty space; they are critical for the successful operation of pick-and-place and screen printing machines.
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Conveyor Transport: Most SMT (Surface Mount Technology) machines use edge conveyors to transport panels down the line. The conveyor belts or clamps grip the panel by its edges. A clear, flat area is essential to ensure a secure grip and prevent damage to components.
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Recommended Dimensions: A minimum border width of 3mm to 5mm is typically required on at least two parallel sides for conveyor transport.
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Component Keep-Out Zone: No components should be placed within this handling area. A general rule is to keep components at least 3mm to 5mm away from the panel edge to avoid interference with conveyor clamps and to prevent damage during depaneling.
The handling edge is also the designated location for essential manufacturing features:
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Fiducial Markers: These are precise copper circles that act as reference points for the machine vision systems of pick-and-place machines. They ensure accurate alignment of the panel and individual boards.
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Size & Placement: Typically 1.0mm to 3.0mm in diameter. A minimum of three global fiducials should be placed in the corners of the panel border for overall alignment.
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Clearance: A clear, solder-mask-free area with a radius of at least twice the fiducial’s diameter must surround each marker.
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Tooling Holes: These unplated holes, usually located in the corners of the panel border, are used to physically secure and align the panel during processes like stencil printing and drilling.

Conclusion
Adhering to these PCB panel design best practices is a critical step in ensuring a smooth and cost-effective manufacturing process. By correctly dimensioning the panel, providing a dedicated handling edge for automated equipment, and incorporating essential features like fiducials and tooling holes, designers can significantly reduce the risk of assembly errors and product defects.