PCB panelisation calculator

What a panel is, and why it exists

A panel is a manufacturing sheet carrying several identical boards side by side, held by a frame and separated by scored lines or routed slots with mouse-bite tabs. They are broken out only after assembly.

What this tool does not say

• It calculates no cost. What a run costs depends on your machines, set-up times and hourly rates.
• It does not optimise the raw format at the PCB fabricator, it optimises the panel that runs through the assembly line.
• Separating the panel is not priced. Scoring and routing are done by the PCB fabricator, not by the assembler.
• The sag is computed freely supported. With support pins in the machine a panel carries more than shown here.
• The preset panel formats come from published figures of PCB fabricators, not from any particular supplier.

Frequently asked questions

What is PCB panelisation?

A panel is a manufacturing sheet carrying several identical boards side by side, held by a frame and separated by scored lines or routed slots with mouse-bite tabs. The whole panel is placed and soldered as one part; the boards are broken out afterwards. The panel is therefore the assembly the machine sees, while the single board is what the customer receives.

Why does a small board have to be panelised at all?

Because the conveyor of an assembly line accepts a board only from 50 mm edge length upwards. A board of 25 x 18 mm fits no placement machine. Without a panel the placement step drops out of the process chain, and the remaining chain looks cheaper in the costing because the most expensive step is missing from it. Panelisation is therefore not a packaging question but the condition for building the assembly by machine at all.

How large may a panel become?

As large as the sag allows. The panel rests on two conveyor rails and sags under its own weight; past a certain sag the placement nozzle misses the pad and the stencil no longer seals during solder paste printing. The limit here is 0.5 mm, computed freely supported. In practice this limit binds before the machine window almost every time: a 20 x 15 mm board on 1.55 mm reaches a panel of about 250 mm, while the conveyor would accept up to 460 mm.

V-scoring or routing with mouse-bite tabs: which carries more?

That follows from the grid, not from the method. A scored groove cuts through the copper and leaves about a third of the board thickness standing, which on 1.55 mm with two 35 µm layers amounts to 2.99 per cent of the flexural rigidity. A routed slot is bridged by mouse-bite tabs, which are perforated and carry only 37.5 per cent of their nominal width, plus the two frame rails. With many rows the scored line is the weaker section; with a single column the relation reverses.

How much money rides on the choice of panel?

On the reference board bsp4, calculated with a shipped machine park: 988 pieces need 247 runs on a four-up panel and cost 705.63 euros, against 13 runs and 558.30 euros on an 81-up panel. That is 26.4 per cent on the same order. The reason is not material but runs: printing, reflow, handling and inspection are billed per run, and only placement per board.

Does this tool calculate the same as PCBoffer?

The physics and the search are the same: sag, rigidity, machine window and the ranking of panels come from the same model PCBoffer uses. A check run recomputes 720 cases from the calculation core on every change, rows and columns with zero deviation, computed with the costing's frame model. On top come hand-calculated cases for rotation, a given panel size, a single board and a grid that fills the panel exactly. This calculator reads the frame rail as the frame left standing in production: with routing the slot is added on the outside between board and frame, with V-scoring the panel size stays the same. Because a larger panel sags more, the search then picks, with routing, the grid that can actually run on that panel. The second difference concerns the order size: a 1 means one board here, and the calculator looks for the smallest admissible panel. In PCBoffer the same 1 means "not stated", because an interface supplies it as a default value; there the answer would be the largest admissible panel. What PCBoffer adds beyond it is the costing: which panel needs the fewest runs, what a run costs in a specific plant, and which figure may go into a quote.

Does this apply to the fabrication panel at the PCB fabricator?

Only in part, and the distinction matters. An assembly panel runs through the line, where the machine window and the sag limit apply. A fabrication panel, 18 x 24 inches for instance, is the fabricator's raw format and is never assembled as a whole; it is cut into assembly panels at the fabricator. A 610 mm fabrication panel of 1.55 mm FR4 sags around 22 mm when freely supported. For a given panel the calculator states the number of boards and reports sag and window as findings instead of rejecting the sheet.

What does the calculator cost, and what happens to my inputs?

It costs nothing and asks for no sign-up. The arithmetic runs entirely in your browser, no input is sent to a server and nothing is stored. The reason is simple: this calculator causes no cost per use, while a bill-of-materials analysis costs real money in compute per run. The inputs live in the address bar so a particular result can be passed on.