Mail Archives: geda-user/2012/07/10/12:22:10
On Tue, 10 Jul 2012 11:12:34 -0400
Nathan Stewart <therealnathanstewart AT gmail DOT com> wrote:
> > Again we see that the pcb terminology of "layer groups"
> > containing one or more "layers" is biting someone.
>...
>
> I interpreted it as follows: 'Layer' is a conceptual layer
> 'Group' is a physical layer
>
> Thus my two layer board had two 'groups', but 6 or 8 layers. I see
> that 'silk', 'solder mask', and 'rat lines' are global conceptual
> layers which do not belong to any group, as they don't show up in
> the group dialog.
Right, there are different kinds of layers, some of which are
"electrical" meaning in general that they are physical copper
patterns. The "silk" layer is another positive drawing layer, and
"solder mask" is a negative drawing layer. The "rat lines" layer
is a dynamic virtual overlay layer that has no physical
representation. How to generalize and unify treatment of layers
has been discussed in recent times, and if done right, if will make
lots of new things possible and will make many other things much
cleaner and easier. The ability to draw both positive and negative
things on the solder mask, for instance.
> When I export, I do get a correct by default bottom solder mask,
> but there doesn't appear to be any way for me to actually make
> changes on the bottom solder mask layer due to the current
> arrangement.
I'm not sure what you mean. Any pins or pads on the bottom side of
the board ("solder side" group) will create openings in the bottom
solder mask.
> Likewise
> - I haven't figured out how to do bottom silk.
If you have any silk on the "solder side", it will be exported as a
"bottom silk" gerber file. It's pretty confusing, however, since
"silk" is sort of two layers in one. If you just want component
outlines and reference designators, all you have to do is move the
element to the "solder side" by putting the mouse over it and
hitting 'b'. Its associated silk outline/refdes will then be
exported to the "bottom silk" gerber.
To draw on the "bottom silk", you need to switch to the "solder
side view" by hitting the Tab key. You'll notice that all silk on
the top side then is drawn in a different color (the "far side"
color; click "far side" layer to disable this completely, really
useful for complex boards).
> Rat lines probably should be global.
Yes, rat lines can connect nodes on different layers and have no
physical meaning. They are a drawing aid only.
> I think defaults for N
> layer boards should be outline, layer N, top silk, top mask,
> bottom silk, bottom mask.
I have no need for the silk and mask to be mixed in with electrical
layers. That just makes it harder. When laying out a board, I
spend 99% of my time working only on the copper layers. So I want
to hit '1', '2', '3', '4' keys are pop back and forth between the
appropriate copper layers. So I certainly want all electrical
layers together at the top of the layer list.
> I think a 2 layer board startup default
> should probably be the default - since that 1) probably fits 80%
> of the boards done with PCB, and 2) is going to be less confusing
> to new users.
Agreed. A simple and clean default 2-layer board is the way to go.
Ideally we'd have the "new layout from template" feature that has
been discussed, but this is easy enough to do already (just not
integrated nicely into the GUI) by saving your template .pcb files
and loading them manually to start a new layout.
Regards,
Colin
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