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Archive for December 1st, 2009

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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