While Colorado PCB Assembly is always happy to have your boards fabricated as part of our turnkey service, supplying bare boards for assembly is quite common. It seems all assembly houses have different rules for how boards should be supplied. Below, we’ll go through the optimal ways to have your boards printed for assembly along with ways other assembly houses prefer to have boards supplied to them.

The TLDR version of everything below that you can copy and paste to send to your board house: “Please panelize boards for assembly and add .4″ rails on the two long edges” but we’ll get more descriptive of what this means below.

Panelization – Almost all assembly houses prefer to have boards supplied in a panel. Also known as an array, these boards are supplied in a matrix, having not been broken apart during fabrication. For very small boards, especially if a high number need to be assembled, having them in a panel is very helpful.

If 50 boards that are an inch by an inch need assembly, and they are supplied single up, each board needs to be individually loaded into the paste or stencil printer, aligned, printed, then individually loaded into the machine, one by one. If, however, these same 50 boards are in an array (or panel) that is two by five (2×5 boards, a total of 10 per array), then the print load, align, print, machine load process only has to be done 5 times, rather than 50.

What if I already ordered boards and they’re not panelized? It’s okay. We’ll assemble them single-up. We might need to build a small fixture or mount them on a flat substrate for assembly, but either way, we’ll find a way to make it work.

How many boards should I put in each array? Size is what matters here. Handling a panel that’s somewhere between 3″x3″ to 7″x7″ is optimal.

Do I use my CAD software to put these in a panel/array? No, actually, it’s so much easier than that! You can just ask your fab house to “put these in an array” or “please panelize these boards” and they’ll take care of figuring out which way the boards fit together best. When boards are complete, your board house will send you the “panelized gerbers” or “working data” so we have the panelized files to order your stencil and load boards on our machines.

The board house wants to know if we need fiducials on the panel. Do we? Nope. We don’t need fiducials on the PCBs or the rails.

Do you depanelize the boards or is that something I have to do when I receive them? We depanelize them prior to shipping unless you ask us not to (for testing or handling purposes).

Rails – Rails are pieces of PCB substrate on the edge of the boards that are intended to be broken off when assembly is complete. Rails allow us two long edges along the PCB to easily load boards into our machines.

What if I already ordered boards and they don’t have rails? It’s no problem; we have fixtures and custom mounts. We’ll find a way to make it work with or without rails.

My PCB vendor is asking if I want mouse bites or v-score – which is correct? Either one works for us. V-Score tends to be sturdier in the process so it’s a little better, but mouse bites allow for odd-shaped boards and are sometimes required.

My boards are large and don’t have any SMT parts near the edges – do you still need rails? No, actually, we don’t. If there are no parts on the edges and we have half an inch on the two long sides for our machines to grab onto, we don’t need rails at all.

Fiducials – We don’t need fiducials, but we’re including them on the list just to let you know they’re not required – our machines set their own.

In general, we ask for panelized boards with rails whenever possible. Benefits include:

• Ease of Handling: Panelized PCBs are easier to handle during the assembly process. The rails provide a sturdy and consistent frame that allows easy machine loading. 
• Faster Assembly: Our machine operators can load your boards more quickly so we can ship boards back to you even faster.
• Improved Assembly Efficiency: When PCBs are in a panel, the assembler can process multiple boards simultaneously, which increases efficiency and reduces assembly time. This is especially beneficial for high-volume production runs, but helps in proto runs, too.
• Enhanced PCB Support: The rails on the sides of the panel provide additional support to the PCBs, preventing flexing or bending that might occur during handling and assembly. This ensures that the boards remain flat and stable during soldering and other manufacturing processes.
• Easier Testing and Inspection: Panelized PCBs can be more easily tested and inspected, as they remain secured within the panel. This simplifies quality control and ensures that all PCBs on the panel are checked before they are separated and packaged.