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Put Hand Wiring on EAGLE Layer 15

Hand wiring on Layer 15

Hand wiring on Layer 15

Because nearly all of my printed circuit boards are for one-off homebrew projects, I tend to not obsess over getting the last air wire down on the copper. Instead, I route those pesky all-the-way-across-the-board stragglers on Layer 15 with big fat vias on each end, then solder a jumper wire across the board.

In effect, my Layer 15 is outside the board.

The screen shot shows a chunk of a board with some Layer 15 wires. I make ’em fat and use swooping semicircular arcs on the ends: they’re easily visible.

I don’t worry about actually routing the traces; they’re just straight lines and arcs. This generates all manner of overlaps with the rest of the components & wiring, but after I go down through the DRC list and approve ’em all one time, that’s the end of that hassle.

Two key advantages:

  • All the remaining air wires are genuine unrouted connections
  • I can print out Layer 15 separately to get a hand wiring map

I make the vias fairly large (here, 100 mils) and a unique shape (octagonal) so that I know each one should get a wire.

I usually wind up doing the power connections the same way; those vias are square. Conversely, ground vias stitching the top & bottom planes together are round; they get a short Z-wire through the board.

This probably won’t work if you’re having the boards built by an actual PCB vendor, as they’ll try to make a three-layer board or kick the board out on layout rule violations… but, on the other hand, if you can afford a four-layer board, then most likely you won’t have any trouble routing the wires.

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  1. #1 by randomdreams on 2009-12-01 - 23:22

    If you’re on the fence about a four layer board, sparkfun’s associated batchpcb.com does four layer boards for $8/square inch. Not cheap, still, but it can be awfully nice to run a ground plane.
    I like it that Eagle can represent jumpers that way.

    • #2 by Ed on 2009-12-02 - 06:29

      That’s a great service, but I generally don’t have that much leadtime: many of the boards are for projects I write up in Circuit Cellar, so there’s a hard deadline at the end!

      Besides, then I’d have to figure out how to route those last few wires…