kicad-developers team mailing list archive

[Wayne Stambaugh <stambaughw@xxxxxxxxx>]

On 9/18/2018 7:20 AM, Jeff Young wrote:
> When calculating obstacles we currently use the diff-pair gap as a
> clearance between a diff-pair trace and a diff-pair pad.
> 
> I’m pretty sure that’s wrong.  I’m just not sure how wrong.
> 
> I suspect the diff-pair gap shouldn’t be used as a clearance /at all/.
>  It’s the gap between the traces, not a clearance.

Why wouldn't you use the netclass clearance or the default netclass
clearance if a netclass is not defined?  It seems to me that the gap has
nothing to do with the clearances other than the gap between the diff
pair traces.

> 
> But maybe we should consider it a clearance between two /tracks/ of a
> diff-pair.  This would allow you to manually route each wire.  But if
> you do that, should we consider it a diff-pair or not?  (Even if we use
> the gap as a clearance, it’s only going to enforce minimum distance; it
> won’t keep the tracks gap-width apart.  And I imagine you won’t be able
> to tune it.  So I’m not sure it’s really a diff-pair.)
> 
> Thoughts?
> 
> Cheers,
> Jeff.
> 
> https://bugs.launchpad.net/kicad/+bug/1789690
> 
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