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I am planning on use various PCB assembly houses to get my boards PCB assembled. To minimize process costs, I am told it is best to panelize/array the PCB such that there is multiple boards per array, so the pick and place machine can populate more efficiently.

I am planning on getting my boards manufactured from Company A, and getting them assembled from Companies B, C, and D. Companies B, C, and D can assemble on individually routed boards, but obviously the cost is higher.

When I get my board fabricated from Company A, is there a standard size for the PCB Array that would be most compatible with the PCBA companies?

I've watched various YouTube videos on PCBA pick and place and it seems the conveyor belt has a certain width. What is this width, and is there a standard? Most PCBA use the MYDATA pick and place machines.

Is there also a standard or most commonly used array template showing where the fudicials and tooling holes should be?

My PCB is rectangular, size 2.5" x 6.2". Trying to see how I should create the array when I order my PCB. I am planning on using v-scoring because I don't like the rough edges and I have no components near the edges.

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  • \$\begingroup\$ "A" can step up to any size so ask B,C,D to quote with optimal step up array size. \$\endgroup\$ – Sunnyskyguy EE75 Oct 22 '16 at 2:28
  • \$\begingroup\$ There is no 'standard', ask companies A, B, C and D what they do. The largest, up to the limit they can take, will usually give the lowest unit cost however reduces ordering flexibility. You may want to use boards smaller than get the build/assembly optimum price in order to gain the ability to have smaller runs, smaller stock supply batches etc. 2.5x6.2mm is tiny, and 2.5x6m is huge. What sort of board are you making that requires such extreme dimensions? \$\endgroup\$ – Neil_UK Oct 22 '16 at 6:23
  • \$\begingroup\$ @Neil_UK, the board is going inside of a remote control like device with a bunch of buttons. The remote has buttons all across it, so the PCB size isn't because of the amount of components, it's because of the amount and spacing of the push buttons that are mounted on the PCB. Think of it like a remote control for a TV. \$\endgroup\$ – Adam B Oct 22 '16 at 17:50
  • \$\begingroup\$ IME the "standard array size" is as many as you can fit on an 18"x24" panel (given design rules for route tool diameter, etc). \$\endgroup\$ – The Photon Oct 4 '17 at 5:01
  • \$\begingroup\$ @ThePhoton, wouldn't 18" x 24" be too big for many pick and pick and reflow machines? Most assemblers I've worked with indicate array sizes of up to 12 x 16. \$\endgroup\$ – Adam B Oct 4 '17 at 8:40
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Around an A4/letter size is usually fine for both PCBA and PCB maker. The conveyor fingers are adjustable over a certain range and are set up for each run. Of course you can customize/optimize it to certain assembly houses and the large panel size of a given PCB maker, but it's also useful to be able to switch to new suppliers when the price increases or when the supplier goes out of business. Typically the overall panel size used by the PCB maker is something like 18" x 24" so if your panel is too big you may end up wasting a lot of unseen material (at least you don't have to pay shipping for that wasted part).

There is no standard for the width of tooling strips, the size and position of tooling strips nor the design or placement of fiducials, just guidelines and some standard rules of thumb. Tooling holes should be unplated, and are typically some even size such as 2mm, 3mm or 1/8". Fiducials are typically a 1mm circle in the copper with solder mask pulled way back (say a 3mm circle) and are located near the tooling holes and at least 5mm from the panel edges so they are not obscured by the conveyor fingers. Tooling strips are typically around 10mm or 1/2". Here is a typical arrangement from this Mentor Graphics site showing the 'mouse bite' method.

enter image description here

There seems to be some confusion as to why one would want to add 'extra' PCB material to the outside of the board that has to be paid for, shipped, and so on, only to be discarded on the test/assembly production floor. The outer part provides a mechanical fixture that comes pre-assembled to the boards that will fit into the conveyor fingers used in the production line for solder paste printing, pick-and-place, soldering, testing and so on. The boards are held in an accurate alignment for all these steps so handling is reduced. Irregular or odd-shaped boards (such as round boards) have sacrificial material around them so they can be handled efficiently without requiring special fixtures to be manufactured and stored between production runs. If you search various PCB assembly and PCB shops you will find many rules, if you search PCB panel examples, you can find just about every rule being broken in one way or another. Keeping to a reasonable range of the rules means your boards can be made at a range of suppliers for a reasonable price. Using loose boards makes it hard on the assembly house (in most cases) and they will pass the costs along. For example, the fingers cannot typically be set closer than something like 50mm so a loose board that is smaller than that will require a CNC manufactured carrier to allow it to be machine handled.

Here, for example, is an odd-shaped board with routed outline + mouse bites, in a panel (source is this site. As you can see they've moved the fiducials away from the tooling holes, probably because the tooling strips are too narrow and the fiducials could be obscured by the conveyor fingers.

enter image description here

V-score still leaves rough-ish edges and lots of prickly fiberglass to irritate the skin. Consider combining V-groove and routing to get mostly smooth edges. Of course you may get fewer boards because you have to leave room for the router bit between the boards in your panelization.

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  • \$\begingroup\$ routed slots and 3 recessed holes per break leaves best clean edge. \$\endgroup\$ – Sunnyskyguy EE75 Oct 22 '16 at 3:11
  • \$\begingroup\$ What about using routed slots AND V-scoring? (i.e. no mouse bites) For instance, use V-scoring for the left over tabs that connect the boards together, such that the boards break off cleanly along a straight edge. \$\endgroup\$ – Adam B Oct 22 '16 at 6:28
  • \$\begingroup\$ @AdamB That is my preference, where possible. For example, you can have the routed outline curve inward to get a rounded corner on the PCB and the edge of the routed outline line up with a V-groove to give two perfectly smooth routed edges that will slide into slots and two that are at least partially V-groove. Where possible this is ideal (but V-grooves have to go right across the panel, and if you want proper depanelization with a machine you can't have parts too near so it's a bit constraining). \$\endgroup\$ – Spehro Pefhany Oct 22 '16 at 8:09
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There is no standard array size (like there are standard paper sizes). But each PCBA shop will have a comfortable max size. Above that size, it becomes more difficult1 to fit the panel into their assembly line. Another factor to consider is the stiffness of the array, which is influenced among other things by width2, PCB thickness. The PCBA shops want the array to be stiff.

Here's a useful and concise write up: The PCB array, and why we use it, (also this glossary).

If you have already identified the PCBA shops B, C, D, then the best thing is to ask them directly. You can then pick the smallest size that they mention.

1 But not necessarily impossible.
2 The dimension across the direction of travel through the assembly line.

An example

Three different PCB arrays.  PCBA pilot run.
(originally from here, also here)

These PCBs work together. A kit of PCBs for one device contains one PCB of each type. Each of the 3 arrays has got slightly different dimensions. The PCBs have been fabricated by 2 different companies. Boards have been populated by 2 different PCBA shops. Without design changes3.

3 Aside from a short-lived variant with V-score routing, which turned out to be somewhat more expensive.

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  • \$\begingroup\$ Thanks for the answer and example. In your example, it appears you've used routed slots between the boards, but did you also use V-scoring or mouse bites? \$\endgroup\$ – Adam B Oct 22 '16 at 6:35
  • \$\begingroup\$ Nice. Assuming it was you that added the copper thieving pattern to the tooling strips, what is your formula for getting that right? \$\endgroup\$ – Spehro Pefhany Oct 22 '16 at 11:44
  • \$\begingroup\$ @SpehroPefhany What is the purpose of copper thieving on the tooling strips? \$\endgroup\$ – Adam B Oct 22 '16 at 17:41
  • \$\begingroup\$ @Spehro, I didn't do the copper thieving pattern. The rails (fiducials, holes, thieving) were designed by the PCB fab house. \$\endgroup\$ – Nick Alexeev Oct 22 '16 at 18:30
  • \$\begingroup\$ @AdamB The variant in the answer has got tabs with mouse bites (if you zoom-in, you can see it). There was also a short lived variant with V-score. It worked just fine, but it was somewhat more expensive. The PCBs were fabbed in the US, if that matters. \$\endgroup\$ – Nick Alexeev Oct 22 '16 at 18:30
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In a lot of places, not panelizing is actually cheaper.

If you want 100 boards, they can panelize the order with a bunch of other orders for 100 or 200 boards and end up producing five different orders in one go. This allows to distribute the setup costs for your order across five orders, and leaves production running for 100 units without intervention.

If you panelize the boards yourself, you shorten the production run (so more idle time during retooling, which costs money), and you can no longer distribute the cost.

In addition, good board houses run their own DRC, and silently fix things that would become a problem in production. If you panelize your design, they have to repair the same thing multiple times.

Thus it is likely that the board house will charge you extra if you give them panelized boards.

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  • \$\begingroup\$ I see what you're saying. However, in my case I'm getting hundreds of boards manufactured and each board is 2.5 x 6.2, so my project will take up many PCB panels (standard panel size is 18 x 24 during PCB fabrication), so I don't think there will be other projects sharing the same PCB fabrication setup, tooling and panel. Good point about the silent changes they make -- I see them making silent changes all the time (mostly with silk screen stuff). The array at my board size might be 3 x 1 array, so perhaps it's not that bad for them. \$\endgroup\$ – Adam B Oct 22 '16 at 6:32
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    \$\begingroup\$ The point isn't to get the cheapest bare boards, the point is to design an array, complete with external tooling strips and fiducials, that the majority of different assembly houses can handle as a single unit. There is enough empty space left on the outside for fingers and conveyors so that the panel can move through pick and place and soldering processes and testing etc in an automated manner. Only at the end are the boards depanelized. Handling is greatly reduced. Components on individual boards can be crammed out to the edges provided the array has large enough tooling strips. Production! \$\endgroup\$ – Spehro Pefhany Oct 22 '16 at 6:50
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    \$\begingroup\$ P.S. A board house that silently 'fixes' things is one I would like to avoid. \$\endgroup\$ – Spehro Pefhany Oct 22 '16 at 8:17
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    \$\begingroup\$ Even if single boards are a bit cheaper, when you're going to you EMS for assembly, you'll pay an extra and it'll take a bit more time because you have a single board instead of a panel and that's more annoying for assembly by having only one board assembled at the time. So for the PCB fab it's cheaper but on the long run, with PCB assembly, you'll be even or pay extra. \$\endgroup\$ – zeqL Oct 22 '16 at 9:43

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