kicad-developers team mailing list archive

[Jeff Young <jeff@xxxxxxxxx>]

Yes, we’re talking about the same thing.  Net clearance only applies between items on the same layer: i.e. a track on F.Cu must not be within that distance of a pad on F.Cu.

But a track on B.Cu doesn’t have any clearance constraints against a pad on F.Cu.  It’s not that aperture pads have no clearance values, but rather that non-matching copper layers don’t have clearance values.  And that's the way it’s always been (unlike the behaviour of aperture pads which was just changed).

> On 6 May 2018, at 00:38, Eeli Kaikkonen <eeli.kaikkonen@xxxxxxxxx> wrote:
> 
> 
> Are we talking about the same thing, and have I completely understood what "net pad clearance" means? I don't quite get what you mean.
> 
> I'm talking about the pad-to-pad and pad-to-track clearances. Paste-only and mask-only pads don't seem to have that at all in practice and it's not applied to mask or paste layers even in pads which have copper layers.
> 
> For example I have experimental footprints with separate copper, paste and mask pads in separate locations. When they are put into a board the mask or paste pads of two different footprints can even overlap without DRC errors while copper pads can't be too close to each other. If in the Display Options I check Show pad clearance, the copper pads have clearance lines around them but paste and mask pads don't. So I think that "Net pad clearance" haven't had any effect for non-copper pads even before these recent changes. There's no clearance value left in these four fields which would be applied on non-copper pads (which Wayne called "aperture pads").
> 
> Based on that I think it would be correct to say "clearance values are used only for pads on copper layers". Unless "pads on copper layers" is too inaccurate. It looks like "pads which have at least one copper layer" would be more accurate because that seems to make the difference whether clearances are applied or not, and only the copper layers have "net pad clearance". Anyways, the current text leads one to think that "net pad clearance" would be used for non-copper pads.
> 
> 
> Eeli Kaikkonen
> 
> 
> 2018-05-06 1:38 GMT+03:00 Jeff Young <jeff@xxxxxxxxx <mailto:jeff@xxxxxxxxx>>:
> Hmmm… I actually changed that on purpose because I thought the other was misleading.
> 
> We build the masks for the mask layers differently depending on whether or not the pads have any copper layers.
> 
> We don’t treat the pad clearance differently based on that constraint.
> 
> Now it’s true that we only check clearance between two items on the same copper layer, but that’s subtly different than “not on any copper layer”.
> 
> Perhaps too subtle?
> 
> 
>> On 5 May 2018, at 20:19, Eeli Kaikkonen <eeli.kaikkonen@xxxxxxxxx <mailto:eeli.kaikkonen@xxxxxxxxx>> wrote:
>> 
>> 
>> 
>> 2018-05-03 23:39 GMT+03:00 Jeff Young <jeff@xxxxxxxxx <mailto:jeff@xxxxxxxxx>>:
>> I’m happy to clean up the dialog if JP wants to check in what he has.  Just let me know….
>> 
>> It looks cleaner now, but I noticed that the information is a bit misleading. It says "solder mask and paste values are used only for pads on copper layers" while actually it seems to be true for all the clearance values, also the net pad clearance. That would make the text simpler and shorter: "clearance values are used..."
>> 
>> I still don't know why the value fields should be editable for non-copper pads because they are not applied anyways. Well, this is nitpicking, so it can be ignored...
>> 
>> Eeli Kaikkonen
> 
>