PCB Array Design and Depanelling for Efficient SMT Assembly

A PCB array is a group of identical boards laid out on a single panel so that the assembly line can handle them as one unit, and the depanelling step is what separates them again afterwards. The array is a design decision, not a manufacturing convenience, because the way the boards are joined determines how they break, how much material is wasted and how much handling damage reaches the finished product.

What an Array Is and Why It Exists

Automated assembly equipment is built around standard panel sizes, so a small board that is only thirty millimetres square cannot be fed reliably on its own. Grouping several of them into an array gives the machine a stable, standard sized carrier and lets one program place the same part many times across the panel.

The array also improves throughput, because the placement head spends less time travelling between small boards and more of its motion produces useful work. The cost is the material used for the rails and the spaces between the boards, and that cost is what makes panel utilisation the second half of the design problem.

Depanelling Methods Compared

Depanelling is done by hand, by a router, by a laser or by a punch, and the choice follows the edge quality the product requires and the volume being built. Hand snapping is the cheapest method and the least controlled, because it relies on the operator to apply the force in the right place.

Routing gives a clean edge and works on almost any outline, but it is slow per board and it generates dust that has to be removed. Laser depanelling avoids mechanical stress entirely and is used where the board carries brittle components near the edge, at the cost of a heat affected zone that must be considered.

Breakaway Tab Design

A tab is the small bridge of material that holds the board in the array, and its width and position decide where the board breaks and how much stress the break puts into the laminate. Tabs are usually placed near the corners and along the long edges, spaced closely enough that the board cannot flex during handling.

The number of tabs matters more than their width. A few wide tabs concentrate the breaking force and can tear the laminate, while several narrow tabs distribute it and leave a cleaner edge. The rules for sizing them are set out in the guide to breakaway tab design.

<img src="https://www.gopcba.com/wp-content/uploads/2026/08/high-speed-pcb-manufacturing-high-speed-circuit-board-signal-intergrity-high-speed-pcb-fabricator-high-speed-pcb-design-guidlines.webp" alt="V-score grooves cut along a PCB panel ready for depanelling” />

V-Score Design and Limits

A v-score is a pair of shallow grooves cut into both faces of the panel along a straight line, leaving a thin web of material that snaps when the board is bent. It is fast, it needs no tabs and it gives a straight edge, which is why it is common on rectangular boards with a modest thickness.

The method has limits. It only works on straight lines, it cannot be used with thick copper or with a board that is very thin, and the groove consumes material along the edge. A v-score also fixes the edge of the board, so it cannot be used where a component or a connector sits close to the outline.

Panel Utilisation and Material Cost

Panel utilisation is the area of useful board divided by the area of the panel, and it is the number that drives the material cost of the whole order. Rails, tabs, tooling strips and the gaps between boards all consume area, so an array that is easy to handle is usually less efficient than one that is tight.

The compromise is found by testing the array in the line rather than on paper. An array that saves material but flexes during printing will produce defects that cost more than the laminate it saved.

Component and Keep-Out Clearance

Components must stay clear of the edges that will be broken or routed, because a part placed near a tab is loaded when the array is separated. The usual keep out is a band around the board outline that carries no tall parts, and the width of the band grows with the stiffness of the components involved.

Edge plating, castellated holes and press fit connectors need their own clearance, since they require a clean edge and cannot tolerate the burr left by snapping. The tolerances that apply to the finished outline are described in the guide to board outline tolerance.

Array Design for Assembly Equipment

The array has to fit the machine. The panel size is set by the conveyor width, the fiducials must be placed where the vision system expects them and the tooling holes must match the pins on the printer table. A board that is correct on its own can be unusable once it is placed in an array.

Tooling holes are the reference for the whole panel, so they should be drilled in the rail rather than in the product, where they would be lost when the board is separated. Their position and tolerance are covered in the guide to tooling hole registration.

Array Qualification and Test

An array is qualified by building a full panel and breaking it, then inspecting the edges and the joints that sit near them. The check looks for laminate damage, for cracks at the tab and for solder joints that were disturbed by the separation rather than by the reflow.

The equipment used to separate the boards is part of the qualification. A router bit that is worn or a punch that is misaligned will pass a first article and then produce edge damage on every panel that follows, so the tool is checked on a schedule.

Faults Caused by Poor Array Design

The characteristic faults are all mechanical. A board that flexes in the printer shows uneven paste volume, a tab that is too narrow tears and leaves a rough edge, and a component placed too close to a v-score cracks when the panel is snapped.

Most of these faults appear at the edge of the board, which makes them easy to dismiss as handling damage. The array drawing, the tab positions and the depanelling tool together decide whether that damage is possible in the first place.

FAQ

Is a v-score or a tab better for a small board? A tab is more flexible and allows a shaped outline, while a v-score is faster and cheaper but needs a straight edge and a suitable thickness. The outline decides the answer.

How much clearance should be left at the board edge? Enough that the break or the cut does not reach a component or a plated feature, with the exact figure set by the depanelling method and by the tolerance of the outline.

Can an array be used for boards that will be tested on a fixture? Yes, and it is often the preferred approach, because the panel is easier to handle and the fixture can be built for the array rather than for each small board.