Homebrew PCB (Eagle) tips & tricks

This is intended as a scratchpad with some tips I found handy. It is not big, but might be useful to somebody. The most useful part is probably the example eaglerc file here.

Cadsoft's Eagle

No doubt about it: This tool is female; highly impractical, but it grows on you and as it does, you learn lots of shortcuts and workarounds for recurring inconveniences.

  • Make consumate use of keyboard shortcuts. They make you work a lot faster. Here is a copy of my eaglerc.usr file. This file is still a work in progress, because I keep finding better ways of doing things with keyboard shortcuts.
  • Some particularly useful shortcuts I want to point out:
    • dis all;group all; cut (>0 0);dis last
      Use it to make a copy of a package or a symbol with a single keypress, which can then be pasted to a new package or symbol. This is useful because eagle still doesn't do decent library management.
    • dis none 116;group all;delete (>0 0);run drill-aid.ulp 0.3;grid inch;dis none 16 17 18 19 20 116;export image d:\bot.png monochrome 600;
      This (re)creates all drill-aid holes at 0.3mm , then save the top layer to a PNG file @ 600 dpi. The file can then, for example, be used for home-fabrication of a PCB.

PCB design

  • Always use run the drill-aid script with a hole size of 0.3mm before exporting your layers to an image. This script creates tiny centering holes on all through-hole components and vias, making drilling much easier. Also, don't forget to clear the drill-aid layer (#116) and rerun the script when you have modified the layout of your board. If you forget this, then you will end up with unexpected holes in your layout.
  • Always use the biggest useful trace and via size. Small traces and vias can be useful or necessary at times, but they have a bigger change to end up broken when the board has finally been etched. So use wide traces and big vias where possible to improve the yield of your etchings.

Drilling

  • Normally a new drill is metallic in colour and the really small drills are therefore pretty hard to see because the metallic colour does not contrast very well with the board which you are drilling. I have found that if you first drill a couple of random holes in a piece of scrap PCB, the white powder from the drilling process sticks slightly to the drill, making it much better visible when drilling. What also helps a lot is to not remove the toner from the board before you drill. The black toner creates a nice contrasting background for the whitish drill.
  • You can prevent the really small drills from breaking by drilling only as deep as necessary. So when you pull the lever of the drill press to puncture the board, try to feel the resistance. As the drill exists on the other side of the board, the resistance will suddenly drop. That is the exact time to stop pulling the lever and to retract the drill. If you drill too deep, the drills usually snap off in the blink off an eye.
  • Do not place anything under your PCB when drilling holes. When drilling double sided PCBs, I used to place a piece of wood under the PCB to prevent vias and pads from coming loose when the drill exits the underside. But stopped doing this very soon after I found out that it was costing me a lot of broken drills. The wood causes the drills to snap of in the blink of an eye if you accidentally move it more than tenths of a millimeter. So now I just make sure all my pads are big enough that they do not let go of the PCB when drilled.