Control PCB Fabrication Costs by Thinking About Panel Sizes
Getting the most for your money in custom printed circuit board manufacturing requires
a little upfront knowledge of how they are made. Unfortunately, your manufacturing
partner may not talk completely straight about their processes and pricing model
(kudos to those that have live pricing on the websites). If you're new to the
industry, or just looking for hints on how to lower your PCB costs, keep reading
and perhaps you'll learn something new. Nothing in this article is rocketscience,
it's really a matter of some commonsense math.
While designedin features are the predominant driver of PCB manufacturing costs,
the more subtle factor of panelization efficiency can also have a dramatic impact.
One of the key things to understand about your PCB order is that the manufacturer
(some would say "fabricator") probably doesn't build individual boards. For
the sake of automation and repeatability, their machinery and processes are setup
to handle uniformlysized "panels" of material. Unless your board is large, or requires
special processing, it's likely it will flow through the manufacturing process
on panels with other designs.
The second key thing to understand is that the cost of manufacturing panels is basically
fixed for a given set of technology. This obviously doesn't include nonreoccurring
charges (i.e. the "one time" setup required for a new design) but it is
the case for the actual fabrication processes. Other than the price of materials
and labor, not much varies from panel to panel.
Working from a fixed panel cost, you can quickly see that more boards packed into
a set of panels means more efficient (less costly) manufacturing. And, generally
speaking, the more boards that fit on a panel the lower the perboard price.
This works out well for both customers and fabricators. However, it's
one of those things that seems to be missed during PCB layout. Costs can skyrocket
when your design differs from "what everyone else is doing" because your
boards will need to be on panels all by themselves. Boards that are done using
"common" technology are easily aggregated; meaning the cost of manufacturing
the panel can be spread among multiple customers. This can be a huge cost
saver. But if you're boards are going to be on panels by themselves, you
have to take a close look at panelization efficiency.
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:


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 




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 perboard 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 


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 


What a difference! Getting 60% more boards per panel seems like a winwinwin
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 interboard 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 






This is obvious stuff, I know, but sometimes we miss the obvious. So here is a little
calculator to help you get the most boards for your buck. Just enter your
parameters in the fields below, and hit "Update" to get a visual of your
panel layout.
Panel Efficiency Calculator
This simple calculator estimates the efficiency of a matrix (grid) panel layout
given the characteristics of the boards and panel.


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



FINE PRINT: This utility is provided "asis" and is for advisory purposes
only. Please use it as you will, but be advised that the results are not verified
and may not be compatible with any given manufacturer's process.
