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Re: gEDA-user: pcb: Track routing strategies and tips

Colin D Bennett wrote:
As a rather inexperienced PCB designer, I find that I have to throw
away two or three layouts until I get one that is usable--and still
not entirely satisfactory.  I always end up with such a mess of traces
that I know I need better organization and a method to the madness.
But I am a newb with little knowledge so I fall back on trial-and-error.

I am also new to routing my own stuff but have a bunch of experience telling others how to do it for me (day job ;) On a prior job, the layout house did all auto-routes. They'd start several jobs with different router restrictions, allow them to route for a while, then pick one, and optimize it - probably by hand. Yes, starting over is common.

Kai-Martin posted that placement is more important than routing. I'd say they are equally important. The best layout guy in the world can't fix a lousy placement. Bogus layout guys throw more layers at the problem. So yeah, take the time to plan it out before routing.

Does anyone have any tips on how to plan a layout for easy and clean
track routing?  In particular for 2-layer boards.

No substitute for experience here. But, partitioning the design by type may help : analog, digital, low-speed, high-speed. Try to think beyond blindly connecting the parts. Sometimes swapping gates, adding parts or other strategies become clear as you route. This is a huge benefit when you route your own board. Layout guys just connect the pieces together.

One strategy that I have seen and recently tried is to use the top
layer for all horizontal trace runs and the bottom layer for all
vertical trace runs, or vice-versa.

2-layer is tough. You also have to account for power and ground. The parts themselves also crowd routing area. 2-layer is not particularly suitable for high-speed anything. Seems good for power supply design, and some audio work (I've seen a lot of audio ref boards on 2 layer). You can make good designs with 2-layer, just is more work. Cost difference to 4-layer is not bad.

Yes X-Y routing is the way to go to avoid blocking. Works great for digital stuff.

Do you ever use the pcb autorouter or do you always route by hand?

I have yet to make the auto router work - but haven't really tried very hard. Hand routing is my preference but it takes longer.

Do you ever study other people's PCB designs to learn from them?
Yeah, a lot. You will find good and bad. There's a whole world of opinion out there - and you know what they say about opinions :) SI-LIST is a great place to exchange ideas on layout. Several industry experts frequently post.


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