PCB Design Tips

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LPKF Circuit Board Mill

If you want us to fabricate PCBs on the circuit board mill in Etcheverry, please consider the following advice from Christopher Sherman:

Down load the following ZIP file containing two design rule files: File:Lpkf-eagle-design-rules.zip

Put these into your dru folder in your eagle program directory. I would advise using them in the following order:

1) Prior to actually doing wire layout on the board (.brd), I recommend loading the standard_design.dru file into drc by the following:

  • type "drc" and hit Enter
  • Click "Load" and pick the standard_design.dru file
  • Click "Select" and then proceed with the wire layout

2) Lay out the components, traces, etc on the board as desired. Keep in mind the following limitation. This system does not plate through-holes, so if the students are using through-hole components (like, say, header connectors), they will want to avoid having traces routed to the pins on the component side in many cases. For example, if I were to use a header connector, in most cases I would not be able to access the joint between the header pin and the solder pad on the top side of the board. I would have to draw a box around the pin on the top of the board using the layer "tRestrict" so that the autorouter would not try and make a connect to this top pad. I've found for most many-pin through-hole components, this is often the case, and our design rule checker doesn't have a way of testing for this.

3) A note on vias: Part of what that "standard design" file does is specify a via size...0.9mm...for which we can use the a manual rivet system. The mill itself doesn't place the rivets, so it's up to the user to place these rivets to complete the contact on the via. They're relatively simple to use, though, and I can show any users who need to learn how to use this "Easycontac" kit.

4) After laying out the board, load the lpkf-strict.dru file via the same method as (1), only this time, perform a Check. This file is set to check against the absolute limits of the lpkf system, meaning if it gives an error for a part (with the exception of due to "restrict" errors, which are a result of (2) above), it will be problematic to try and produce on our machine.