Where to Put Panel Tabs

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Many small quantity PCBs are ordered individually cut. They come to us as a set of unconnected boards. For small quantities of reasonable size boards, it makes the most sense to order them this way. However, for really small boards, and larger quantities (50 or more), purchasing boards in a panel (also called an array) is more appropriate. It reduces errors and assembly time.

There are a few additional factors to consider with panelized boards.

  • First, don’t try to create a panel in your CAD software. Just lay it out as a single board and have the fabricator put it in a panel. You’ll get the most efficient use of PCB space that way, and the fabricator will create the files in the format that the assembly shop (Screaming Circuits) needs.
  • Avoid family panels. A family panel is when several different boards are put onto the same panel. The boards in family panels often repeat reference designators, which causes problems at assembly. See this blog article on how to properly assign reference designators on a family panel.
  • If you have overhanging parts, like the increasingly common micro USB connector, make sure that the panel tabs aren’t placed near the overhanging them.

This blog article gives some background on the connectors.

Some components, such as the connector in the link above, have protrusions that will keep them from laying flat on a panel tab. In all cases, even without the protrusions, the operation of separating the panels with a component on the tab can weaken the component solder joints, or even pop it off the board completely.

How not to do it:

Figure 1

Instead, make sure that the tabs don’t end up under your overhanging component. Have the tab moved like this:

Figure 2

You can put this instruction in the document layer of your CAD file, or in a separate document covering fab instructions. In the CAD image below, the overhanging component has a keepout area. The document layer has instructions to keep panel tabs out of the area.

Figure 3

If in doubt, don’t hesitate to contact us or Sunstone Circuits directly to ensure that your instructions are clearly communicated.

Duane Benson
Wood paneling as a wall covering is really out of style

http://blog.screamingcircuits.com/