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 Post subject: Trace widths
PostPosted: Mon Jan 15, 2018 7:13 pm 
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I was wondering what widths people use for their traces in their 65C02 projects?

I'm currently using 0.01 inches (0.254mm), but think I can probably get away with thinner traces.
Power wise, I either use entire layers or 0.016 inches (0.4064mm) or greater.


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 Post subject: Re: Trace widths
PostPosted: Mon Jan 15, 2018 8:13 pm 
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usually .006/.006. Below that, many board manufacturers start charging more. But for more of the reasons and possibly unexpected considerations, see this post:
viewtopic.php?f=4&t=3519&p=41840#p41840
If you want to pay, some board houses can make the trace as narrow as its thickness, so it has a square cross section. How they can do that is beyond me, but I've seen photomicrographs of it. Narrow traces are not any more delicate than wide ones.

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 Post subject: Re: Trace widths
PostPosted: Tue Jan 16, 2018 7:28 am 
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banedon wrote:
I was wondering what widths people use for their traces in their 65C02 projects?

I'm currently using 0.01 inches (0.254mm), but think I can probably get away with thinner traces.
Power wise, I either use entire layers or 0.016 inches (0.4064mm) or greater.

All of the signal traces in my POC units are 6 mils width. Also, I used 26 mil diameter via drilled to 8 mils. Generally speaking, I use the narrowest traces I can consistent with the expected current flow. That makes it easier to get a dense layout.

As for power distribution, all my POC designs are four-layer boards, with one internal ground layer and one internal power layer. Non-computer projects are mostly built on two-layer boards, in some cases, using filled planes (aka "pours") for ground.

For the purpose of sizing power-handling traces I use the following:

    0.010" — 0.3 amps
    0.015" — 0.4 amps
    0.020" — 0.7 amps
    0.025" — 1.0 amps
    0.050" — 2.0 amps
    0.100" — 4.0 amps
    0.150" — 6.0 amps
    0.200" — 8.0 amps
    0.250" — 10.0 amps

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 Post subject: Re: Trace widths
PostPosted: Tue Jan 16, 2018 4:49 pm 
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PCBtrain (who I'm currently getting PCBs made with) have advised that they can go down to 0.125mm (0.0049 inches / 4.92thou) trace/gap width without charging extra.
Looks like some rerouting is in order. I've been struggling with my 65C02GPDv2 design as it uses PLCC44 sockets which isn't as handy routing wise as DIPs.

Thanks for the info on trace widths vs power - very useful :).


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 Post subject: Re: Trace widths
PostPosted: Tue Jan 16, 2018 8:31 pm 
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banedon wrote:
Looks like some rerouting is in order. I've been struggling with my 65C02GPDv2 design as it uses PLCC44 sockets which isn't as handy routing wise as DIPs.

Fortunately the PLCC thru-hole sockets have their pins on .100" centers, so you can still run 3 traces between pads if necessary. :) With .005" trace/space, you could even get four traces between pads. I don't think I'll be doing that anytime soon myself though.

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 Post subject: Re: Trace widths
PostPosted: Tue Jan 16, 2018 10:10 pm 
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GARTHWILSON wrote:
banedon wrote:
so you can still run 3 traces between pads if necessary.

Yep I already discovered that this evening :). I'm a bit concerned about running traces around VCC pins. Do you normally give them a wide berth or is it ok to run them straight past?


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 Post subject: Re: Trace widths
PostPosted: Tue Jan 16, 2018 10:20 pm 
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Why would there be any problem? A .007" gap would take over five hundred volts to arc in dry air, if I did my calculation correctly. It should be a lot more more with soldermask over the trace.

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 Post subject: Re: Trace widths
PostPosted: Tue Jan 16, 2018 10:32 pm 
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Not worried about arcing (should have been clearer), but about signal being affected. I did seem to get a bit of this on one of my bus monitor projects when I ran a trace passed the VCC connection to a backlit 44780 LCD module.


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 Post subject: Re: Trace widths
PostPosted: Tue Jan 16, 2018 10:42 pm 
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The capacitive coupling between a trace and a Vcc pin it runs past is a fraction of a pF, totally inconsequential. OTOH, the inductive coupling between two traces that run parallel to each other for a significant length, and with the two much closer to each other than they are to the ground plane, can be another matter. However, if the Vcc trace is bypassed to the ground plane at every Vcc pin, there should be very little AC signal on it to get into other things. If you have a Vcc plane as well, there's nothing to worry about.

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 Post subject: Re: Trace widths
PostPosted: Tue Jan 16, 2018 10:57 pm 
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In that case I'll not worry about the VCC pins - thanks for advising :). I'm off now to do some routing.


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