8
\$\begingroup\$

I've looked online at PCB fabrication companies, and they invariably price their boards according to the size of the board as the primary factor.

Why is this? The physical board itself isn't that expensive, is it? I'm guessing it's because the size of the boards dictates how many they can produce simultaneously, and that's the primary limiting factor in their profitability - Is that right?

Anyway, is there a way to keep the costs down when fabricating large (~8x10 in.) but sparsely populated (~50 components) boards (other than just ordering from the cheapest Chinese factory I can find)?

It seems silly to pay $50 for a board that's only gonna have $10 in parts on it.

\$\endgroup\$
  • 4
    \$\begingroup\$ Maybe there's some other way of achieving your end goal without a giant PCB? \$\endgroup\$ – brhans Jun 15 '15 at 19:15
  • 1
    \$\begingroup\$ @LeonHeller, sorry if this question is inappropriate here. Do you feel there is some other more appropriate stack exchange? I looked around this site first and found lots of similar questions about PCB fabrication options, techniques, and such, and mine seemed to fit right in. Compare, for example, to other not-strictly-electrical questions like this: electronics.stackexchange.com/questions/50160 \$\endgroup\$ – Josh Jun 15 '15 at 20:07
  • 26
    \$\begingroup\$ @LeonHeller since when PCB fabrication economics is not related to electronic design? \$\endgroup\$ – Lorenzo Donati supports Monica Jun 15 '15 at 20:14
  • 1
    \$\begingroup\$ Is it possible that making 50 small mounts for the LEDs could have a cost savings for you? They could be mounted on extruded plastic or milled (whatever). \$\endgroup\$ – Sean Boddy Jun 15 '15 at 22:03
  • 1
    \$\begingroup\$ Not sure why its costing you $50, unless your qty is low. I get a 9.5x11.4 done for right at $17 overseas. \$\endgroup\$ – Erik Friesen Jun 15 '15 at 22:25
9
\$\begingroup\$

10*8 isn't really large, but you may get only 2 per panel which will impact the cost. Panel sizes will vary from fab to fab so it is worth talking to a few - and negotiating the details - as The Photon says, you may get 4 per panel and half your price that way. And the economics of setting up a fab for small jobs dictate that buying 50 boards instead of 10 can half the price again, 100 or more even lower.

In addition to The Photon's good suggestions, use the simplest process possible for the large board. Single-sided PCB may be MUCH cheaper than 2-layer, especially since there's no through-hole plating stage, omitting silk screen and solder mask may save a little more money. Some fabs may still offer phenolic material - much cheaper than FR4 fibreglass.

You might be able to use an Arduino-sized full spec PCB to hold the complicated stuff or customization, which you then plug into a much larger single-sided board which - because it omits the personalization for a specific project - you can buy in larger quantities and re-use for multiple projects.

\$\endgroup\$
  • \$\begingroup\$ +1 Paper-base phenolic can be much cheaper especially punched- it's priced by the square meter not square inch or cm. Of course if you're only buying a few square meters that won't help, but it's not necessarily stupid high quantities- definitely worth looking at changing the specs if phenolic is good enough and if you're looking for 10K pieces or so (per shipment). Solder mask and silk screen won't add much cost. Shipping by air will be more costly for big boards because the mass is larger. Paper phenolic is lower density, but usually it gets shipped by surface (eg. ocean freight). \$\endgroup\$ – Spehro Pefhany Jun 15 '15 at 19:43
  • \$\begingroup\$ The components that have to be laid out sparsely over a large area can definitely be single-sided, and the rest can be on a small, more complex board. I'll definitely have to look into single-sided and phenolic, thanks! \$\endgroup\$ – Josh Jun 15 '15 at 19:59
6
\$\begingroup\$

@Josh: You might be able to reduce board fab costs if you could work out a way to use a number of smaller boards to achieve your goal. For example, if you have either one long series string of LEDs, or, say, ten strings of five, and could use ten long, skinny boards (say, 8 inches x 0.25 inch). That'd reduce the material cost, and allow for a variety of panelization alternatives, but with substantial impact on total assembly cost (as you'd have to connect the small boards together electrically and mechanically).

Perhaps this illustrates a more general rule: If something seems unexpectedly expensive or difficult, see if you can look at your problem differently to see if you can find an easier or cheaper approach.

\$\endgroup\$
5
\$\begingroup\$
  1. Be sure to know what size panel you are building, and design your board to fit well on that panel. For example, if you use an 18x24" panel (very common), and your vendors want 1" spacing around the edges, and 1/2" spacing between boards, a 7 x 10 board will be priced substantially lower tha 8 x 10 board because you'll fit 4 per panel rather than 2. Note the board spacing might be driven by your assembly vendor rather than your fabrication vendor.

  2. Buy larger quantities. If you are buying less than maybe 10 boards at a time, you are paying a relatively large amount per board for per-lot processes (programming machines, ordering materials, ...). Your price per board will go down quickly as your lot size increases.

\$\endgroup\$
  • \$\begingroup\$ I'm certainly aware that larger quantities are much cheaper. And it makes sense to me that for large orders, board area is a main factor. But I'm confused as to why, for example, ordering 5 8x10 boards costs 4 times more than ordering 5 4x5 boards. The real cost is the setup, not the boards themselves, so why does price scale with board area? (I'm still in the prototype stage, though I'm planning a much larger order later, and thinking about ways to minimize costs for both/either.) \$\endgroup\$ – Josh Jun 15 '15 at 20:17
  • 1
    \$\begingroup\$ @Josh, I wouldn't expect 5 8x10 boards to cost 4 times more than 5 4x5 boards. Maybe some web-only services use pure square-inch pricing, but most full-service shops wouldn't price that way. \$\endgroup\$ – The Photon Jun 15 '15 at 20:32
  • \$\begingroup\$ Once they have a software for combining boards from different customers to fill the available space optimally, actually the cost is the material and process. I am not surprised that the price scales with the surface if the process is automated and the cost for human labour is low. \$\endgroup\$ – FarO Jun 16 '15 at 11:49

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.