Electronic – How to indicate breakaway tabs in PCB design

pcb-design

I'm designing two boards that'll always be used together. I'd like to place them both on a panel and break them apart after manufacturing.

I found a document on PCB CAD Design Guidelines that explains breakaway tabs and lists guidelines for their design.

Board assemblies can be de-tabbed using perforated breakaway tabs, v-grooves breakaway tabs, or hand-cutting with a de-tabbing tool.

However, how would I indicate break away tabs in the CAD file? For the perforated tabs, I could add through-holes in a line (although I hope there's a more standardized method), but I'm not sure how to indicate v-grooves.

Also, what concerns should I be aware of with breakaway tabs?

Best Answer

I'm sure that processes vary from place to place, but it's been my experience so far that when a PCB needs to be panelized, two drawings are generated:

  • a standalone file, and
  • a panelization or array drawing.

The standalone file is the usual PCB drawing, showing the etching, vias, dimensions, etc. for the standalone PCB. There's no graphical indication on this drawing that the PCB is part of a panel.

The panelization drawing shows how many of the individual PCBs are to be included on a single panel by showing multiple standalone PCB outlines, along with the details of how they're joined (v-groove, breakaway tabs, etc.) - the specific PCB details other than the outlines (and any slots/holes therein) are omitted from this drawing.

For example:

panelization drawing excerpt

This excerpt uses breakaway tabs and v-grooves.

You generally need to keep components away from any depanelization areas, as the mechanical stress of depanelization can sometimes inflict some mechanical stress on nearby parts (ceramic capacitors can crack, for instance) - the tool that's used (v-groove cutting wheel) may need some clearance as well. You wouldn't want filet-o-capacitor on your finished goods.

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