Panelization is usually treated as the last step before fabrication: finish the design, send it out, and let the fabricator work out the panel. But how many boards fit on the production panel is what drives your cost per board at volume, and that number is mostly set by the board outline. The outline is settled early, while the enclosure, the circuit and the routing are still being worked out. By the time anyone lays out a panel, that number is already set. This page shows where the panel check belongs in the design flow, and why finishing it before the quote means your fabricator prices the layout you planned.
A fabricator produces your board on a production panel. An 18 x 24 inch panel is common, but panel sizes vary by fabricator, material and process. Borders reserved for tooling and other production requirements reduce the space available for boards.
Many fabrication costs are charged per panel or per production run rather than per board. A panel that carries more boards spreads those costs across more boards, so for a given construction and process, boards per panel is one of the strongest drivers of cost per board at volume. The savings repeat on every panel, in every run.
The catch is that the two decisions behind that number happen at opposite ends of the flow. The outline, which sets how many boards can fit, takes shape early in your design loop. The panel layout is done at the very end by the fabricator's CAM engineers, whose job is to prepare your data for their process, not to reshape your board. By then the outline is expensive to change. So the decision falls into a gap: the people who could still change the outline never see a panel, and the people who lay out the panel can't change the outline. The only way to close the gap is to run the panel math early, inside the same loop where the outline is decided.
A quick word on terms. The board is the individual PCB in your product. An array is a sub-panel of boards with its own borders that repeats across the production panel; your assembler may call it an assembly or customer array. The production panel is the larger panel the fabricator actually processes, and it can carry individual boards, one array, or several.
In many products the outline is constrained by something real: the enclosure it must fit, connector locations, the circuit it must carry, or a standard form factor. That's why the advice to design for panelization can feel out of touch. You're not going to resize a board that mechanical handed you as a fixed envelope, and a precise outline is often precise for good reasons.
But an outline that hasn't been frozen yet is a different story. Many designs hold a few tenths of an inch of slack while the enclosure and the board are being designed together, and those last tenths are rarely chosen with the production panel in mind. A slightly smaller outline can cross the threshold where more boards fit on every panel. In our panelization example, trimming a 1 x 2 inch board to .934 x 2 takes an 18 x 24 panel from 99 boards to 108, an 8.33% cost savings from a 66 mil trim. Whether a threshold like that is within reach depends on the design and on the fabricator's panel rules. Testing it while the outline can still move costs a conversation. Testing it after layout, mechanical drawings and tooling are done costs a redesign.
Every KwickFit calculation runs against a specific panel, so the first thing to collect isn't a layout. It's your fabricator's panel rules: the panel sizes they run, the spacing they require between boards, and the borders they reserve for tooling. If your boards will be delivered in an array, collect your assembler's requirements as well. Generic defaults aren't a substitute. The values differ between fabricators, and the best layout changes with them.
The loop is how a design converges. KwickFit checks how the outline panelizes and, where there is room, finds a smaller size that fits more boards per panel. Layout and routing follow, and a board that runs out of routing room can push the outline back open. The cycle repeats, in smaller and smaller adjustments, until the board fits its enclosure, meets its routing requirements, and panelizes well.
Inside the loop, KwickFit's Analyze Part Size to Increase Yield is how the size question gets answered with numbers instead of instinct. It takes your board and your fabricator's panel rules and finds the reduced size at which more boards fit per panel. If that size is a tenth of an inch away, you bring a concrete number to the conversation with mechanical while both sides still have room to move. If it's out of reach, you commit the outline you already had, knowing what it costs.
If the outline was never yours to choose, you enter the loop with the size already settled and skip the size question. The panel question is still open, and it doesn't need to wait for routing to finish, because the panel math only needs the board dimensions and the fabricator's rules.
Auto Matrix Array finds the best array for each panel size automatically, and you can compare the result across the panel sizes your fabricator runs, with no CAD or Gerber files. Two different array configurations of the same board can yield different board counts on the production panel, because their outer dimensions fill the available space differently, and the difference repeats on every panel in the run.
Many designers do. They submit the individual board, the fabricator's CAM team works out the production panel, and the fabricator keeps final control of the manufacturing data, as they should. But it means panel utilization is first considered after the design is finished, by a team optimizing for their process rather than your unit cost. If the board sits awkwardly on their panel, the only signal you may ever see is a higher quote. The waste is real either way. It's just baked into the board price instead of showing up as a line item.
Running the panel work yourself doesn't replace CAM review, and it shouldn't try to. It changes what that review starts from. A panel proposal built on the fabricator's own sizes, spacing and borders travels with your design package, so the fabricator prices the layout you planned and CAM is more likely to build the panel with little or no rearrangement. To compare fabricators, run the same board against each one's numbers, so every quote is priced on a layout built for that fabricator's panel.
Nothing here adds a stage to the design flow, and nothing takes final control away from the fabricator. The panel check closes the gap between the people who decide the outline and the people who lay out the panel. It rides inside a loop you already run and needs only your board dimensions and your fabricator's panel rules. It ends with one of two good outcomes: an adjustment that fits more boards on every panel for the life of the product, or evidence that the outline you were about to commit was already the right one.
No CAD or Gerber files. Enter your board size and your fabricator's panel dimensions and see boards per panel.
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Related: how to fit more boards per panel covers each lever in detail, and which PCB panel tool you actually need maps the tools to the jobs in this flow.