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Using Eagle for mac, I am trying to autoroute the board. I have set the trace width to 8. He start the process and it takes him about 2 minutes, than he stops at some point and show the next percentage (see the image ).

  1. Why it stops on 84%? I could see other people on 97% , but why is that?
  2. How can I fix that in the most fastest and simplest way?

enter image description here

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    \$\begingroup\$ Autorouting is a really hard problem to solve, it probably is making glacial progress. Autorouting also does very often not lead to really good results, so this might be a good opportunity to learn routing yourself. \$\endgroup\$
    – PlasmaHH
    Commented Jun 18, 2015 at 9:11
  • \$\begingroup\$ it sounds strange, some pcb are so big , it would take years to solve their puzzle . how can you route so much lines by yourself? and how would you DO let it finish it automatically? \$\endgroup\$
    – Curnelious
    Commented Jun 18, 2015 at 9:14
  • \$\begingroup\$ It has been very long since I last used eagle and I never used autorouting other than for maybe a halfway start point. On better packages (I heard altium circuit maker will be useful) you have semi-automatic routing options that make work on big designs easier. Like routing a whole bus in parallels at once etc. When you go for e.g. a 12 layer motherboard like pcb, you already have enough experience and big tools that help you there, but for the critical stuff you spend lots of hours. With experience this gets so much faster with time, and no one starts with huge boards. \$\endgroup\$
    – PlasmaHH
    Commented Jun 18, 2015 at 9:19
  • \$\begingroup\$ Eagle's autorouter is appallingly bad, and you should avoid using it. Just because it can't find a solution doesn't mean there isn't one, either - although your board is certainly densely populated! \$\endgroup\$ Commented Jun 18, 2015 at 9:32
  • \$\begingroup\$ @Curnelious it takes good planning of your nets, and component placement. For a good layout, there are things that a good designer will know that good software simply cannot. It takes time of course. A good layout is not just about connecting from point A to point B, there is alot of thought that should go into a layout. \$\endgroup\$
    – efox29
    Commented Jun 18, 2015 at 9:51

1 Answer 1

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Something that is inherently difficult can't be made easy.

A few tips to get better results, most are in the comments too:

  • place the components carefully. look at what the autorouter has produced, especially at the places where he had to take weird roues, or could not route at all, and think of a better way to arrange your components. Another way to approach this is to vieuw the ratsnet lines, imagine they are all elastic wires pulling at the components, and imagine where that would draw each component. BTW placing includes rotating and mirroring to the other side (if you want to allow that).

  • route the 'obvious' traces by hand, save your PCB, and then start the autorouter. you can route a trace whith the rest of the traces in mind, an autorouter is stupid and looks at one trace at a time. Even when I use the autorouter, I often first route the power and ground traces (and other high-current or noise-sensitive traces, if any) myself. That is a good moment to check the placement of your decoupling capacitors!

  • use a finer routing grid (as always, this is a trade-off: a finer grid has more routing opportunities, but also takes more time to autoroute)

  • use smaller via's, finer traces, smaller distances, more layers. but check with your PCB manufacturer!

  • use a bigger PCB so there is more room between the components for traces.

  • play with the autorouters settings, especially the cost of via's and the preferred direction on each layer. My experience (in hand routing) is that strictly keeping to (for instance) horizontal on the top and vertical on the bottom often gives better results in the end than making that shortcut to a nearby pad in the 'other' direction. (You can make such shortcuts after full routing to clean up the design.)

  • route yourself. even if you don't use the result, it will give you a better feeling for what the issues of routing are. (One of my sons (then 12y old) played routing with the concenration that he otherwise reserved for video games.)

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  • \$\begingroup\$ @Curnelious thanks for accepting, but for a next question consider waiting at least 24 hours before accpeting, to give people all over the world a chance to answer. \$\endgroup\$ Commented Jun 18, 2015 at 11:05

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