docs/wiki/geda-add_a_ground_plane_to_your_layout.html

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  13 <p>
  14 How to do no-fuss auto-routing with ground planes that works well:
  15 </p>
  16 <ul>
  17 <li class="level1"><div class="li"> Group bottom, ground, and bottom layer together.</div>
  18 </li>
  19 <li class="level1"><div class="li"> Group top, power, and power layer together.</div>
  20 </li>
  21 <li class="level1"><div class="li"> Lay out your circuit, yadda yadda.</div>
  22 </li>
  23 <li class="level1 node"><div class="li"> Run ground traces on the ground layer and power traces on the power layer:</div>
  24 <ul>
  25 <li class="level2"><div class="li"> Turn off all layers but the ground (or power) layer.</div>
  26 </li>
  27 <li class="level2"><div class="li"> Use Ctrl-F on any ground (or power) connection.</div>
  28 </li>
  29 <li class="level2"><div class="li"> Use Select/Select all found.</div>
  30 </li>
  31 <li class="level2"><div class="li"> Use Connects/Auto-route selected rats.</div>
  32 </li>
  33 <li class="level2"><div class="li"> Auto-optimize and miter.</div>
  34 </li>
  35 </ul>
  36 </li>
  37 <li class="level1"><div class="li"> Turn on the top and bottom layers.</div>
  38 </li>
  39 <li class="level1"><div class="li"> Route everything else using Connects/Auto-route all rats.</div>
  40 </li>
  41 <li class="level1"><div class="li"> The Message Log will report that your layout is complete.</div>
  42 </li>
  43 <li class="level1"><div class="li"> Auto-optimize and miter.</div>
  44 </li>
  45 <li class="level1"><div class="li"> Select the power and draw a rectangle.</div>
  46 </li>
  47 <li class="level1"><div class="li"> Select the ground and draw a rectangle.</div>
  48 </li>
  49 <li class="level1"><div class="li"> This fills-in the ground plane, but you&#039;re not done, because you still have the traces.</div>
  50 </li>
  51 <li class="level1 node"><div class="li"> Do these steps for both ground and power:</div>
  52 <ul>
  53 <li class="level2"><div class="li"> Use Ctrl-F on any ground connection (best where the power comes in).</div>
  54 </li>
  55 <li class="level2"><div class="li"> While you&#039;re there, select the Thermal (THRM) tool and drop a thermal on that connection.</div>
  56 </li>
  57 <li class="level2"><div class="li"> Use Select/Select all found</div>
  58 </li>
  59 <li class="level2"><div class="li"> Use Select/Rip up selected auto-routed tracks.</div>
  60 </li>
  61 <li class="level2"><div class="li"> Use Connects/Optimize rats nest again.</div>
  62 </li>
  63 </ul>
  64 </li>
  65 <li class="level1"><div class="li"> Use Connects/Auto-route all rats.</div>
  66 </li>
  67 <li class="level1"><div class="li"> The Message Log will report that your layout is complete.</div>
  68 </li>
  69 </ul>
  70
  71 <p>
  72 There&#039;s a bunch of steps, but it will work a champ every time, because first routing power and ground ensures that when you flood it with power and ground planes, you&#039;ll have full connectivity. The only drawback is that you can get unnecessarily long traces and jumps to the other plane involving extra vias. On a 27 part board, I only spotted two jumps and one derp trace.
  73 </p>
  74
  75 <p>
  76 All of this is necessary because the auto-router doesn&#039;t know that the ground plane will magically disappear when you lay a trace across it.
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