Continue: Thinking About Panel Sizes for contral PCB Fabrication Costs

To make the best use of the available space on a panel (and thus lower your cost), carefully choose the size of your board. Ask you manufacturer for the details of the panel sizes they prefer, and if possible pick board dimensions that are an integer divisors of the length and/or width of the panel size. Don't forget to account for the margin around the edge of the panel and spacing between the boards.  Your manufacturer should be able to provide specific instructions for sizing your board for maximal efficiency -- if they can't (or won't), you may want to consider a more cooperative manufacturer.

The math behind finding the best board size isn't complex, but it's tedious.  So to save you a little time in a spreadsheet, we've added a little calculator at the bottom of this page. Before we get to that, however, I want to volunteer a couple examples of PCB panelization scenarios:

16 x 22

Layout of a 18x24 PCB fabrication panel containing 1 16x22 boards. The efficiency of this panel is roughly 81.5%.

5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1 5 x 3.1

Layout of a 18x24 PCB fabrication panel containing 18 5x3.1 boards. The efficiency of this panel is roughly 64.6%.

7.9 x 8.01 7.9 x 8.01

Layout of a 18x24 PCB fabrication panel containing 2 7.9x8.01 boards. The efficiency of this panel is roughly 29.3%.

The point of the above examples is that size really does matter when it comes to effectively using the space on panels. Assuming panels have fixed cost (and they should, when they are identically built), then size choices can also impact your price. The difference between getting 2 boards per panel and 4 boards per panel may be a tiny fraction of an inch. The designer of the board in the third example above could cut their per-board price by as much as 50% by shaving a tiny bit off each dimension. Here are another couple examples, this time with the exact same size board and panel, but with the board rotated 90 degrees:

5.25 x 3.45 5.25 x 3.45 5.25 x 3.45 5.25 x 3.45 5.25 x 3.45 5.25 x 3.45 5.25 x 3.45 5.25 x 3.45 5.25 x 3.45 5.25 x 3.45

Layout of a 18x24 PCB fabrication panel containing 10 5.25x3.45 boards. The efficiency of this panel is roughly 41.9%.

3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25 3.45 x 5.25

Layout of a 18x24 PCB fabrication panel containing 16 3.45x5.25 boards. The efficiency of this panel is roughly 67.1%.

What a difference!  Getting 60% more boards per panel seems like a win-win-win situation to me.  Is your fabricator quoting your order based on only one rotation?  You'll never know if you don't ask.

And, finally, keep the spacing between boards in mind.  You might be temped to think that smaller boards would always lead to better panelization, but that isn't the case.  As the board size gets closer to the inter-board spacing, efficiency drops like a rock.  Consider these three cases:

2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2 2 x 2

Layout of a 18x24 PCB fabrication panel containing 63 2x2 boards. The efficiency of this panel is roughly 58.3%. Alice's PCB wonderland  alicebrain1992@gmail.com