Mail Archives: geda-user/2014/07/09/18:04:57
On 07/09/2014 10:50 AM, DJ Delorie wrote:
>> I think any layer objects embeded in footprints (might as well include silk and copper in the same way going forward), ought to reference predefined symbolic layer name or ID.
>>
>> "TOP-SILK" "TOP-MASK" "TOP-COPPER" "INNER-COPPER" "INNER-ANTI-COPPER"* "BOTTOM-COPPER" etc...
>>
>> *(inner anticopper might need some thought, possibly not one for today!).
> Yeah, IMHO symbolic layers is a must.
>
> I also think we need a way of "stacking" or "nesting" drawing layers
> within a physical layer to do fill/cut/draw operations. For example:
>
> * "Fill" - positive, first rendered, used for power plane polygons
> * "Cut" - used for keep-outs, and cutting planes into sub-planes with traces
> * "Trace" - used to draw traces over polygons (clear polygons but ignore cuts)
>
> Each layer needs a positive/negative flag, so you could (for example)
> draw negative text over a filled rectangle.
>
> But given that footprints might have their own fill/cut/trace layers,
> which may be drawn on top of the board-layer cuts, we need to be
> flexible in making these stacks...
>
> * board-level fill
> * board-level cut
> * footprint-level fill
> * footprint-level cut
> * traces
I agree with all that. The need for a footprint-level version of the
layers distinct from the lay-out level isn't extremely clear for me, but
I assume that makes internal operations easier to sort out.
>
> but if you want to support "sub-layouts" it gets even more complex.
>
> Perhaps a heirarchical design?
>
> * board-level fill
> * board-level cut
> * sub-layouts and footprints ->
> * . . .
> * . . .
> * . . .
> * board-level traces
>
> And all that is just *per layer*
And what are the chances of this happening in pcb? Is that a doable change?
So here is another one. I saw my KiCad-using friend (at the "Wednesday
Robot lunch" where we talk about robots and eat Thai food...) the topic
of buried parts in multi-layer boards came up. So that got me thinking
about how to represent voids. The void is a cut into the substrate of
the lamination(s) above the component. It seems to me this is another
footprint layer, with a Z-thickness, that causes voids in adjacent
layers depending on the particular stacking order and layer thickness.
I don't plan to build any of these any time soon... but it seems like
the concept should be considered along with all the rest.
>
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