kicad-developers team mailing list archive

["Brian F. G. Bidulock" <bidulock@xxxxxxxxxxx>]

Lorenzo,

You could take a look at the http://www.openss7.org/docs/NOTES.pdf
document for much more detail on layers.

The Eco, Comment and Drawing layers are simply as before.  Comment layer
is primarily for designer annotations.  There is some hope that the Eco
layer could be used for real Engineering change orders (trace breaking
and conductor overlay), but it is still useful for a designer to draw
anything that needs to be plotted that is not represented by any of the
other layers.

On Sat, 26 Nov 2011, Lorenzo Marcantonio wrote:
> 
> Are you sure you really *need* to hardcode the types? Why not use a generic
> approach like all the CAD/CAM out there?

258X expects the layer classes as laid out (except Eco and Comment).
I didn't invent them.

> For example Eco/Comment/Drawing are simply artworks layer, nothing would change
> that. And most of the others are simply artworks layer (maybe restricted to
> pads) (adhesive, probing, contacts and so on). 

No, each has special attributes and rules.  For example Dielectric layers is
for full stackup: core, prepreg, dielectic constant, thermal conductivity,
unfinished and finished thicknesses (with press factor calculations based on
copper mask, copper weight, etch factor, theiving, etc.).

Another example, SolderPaste is not just a "pad-master", it is the solder
paste stencil apertures, complete with stencil thickness considerations,
bow-ties, D-shapes or homeplates; consideration for TFN and CGBA; paste
in hole, etc.

Contacts is for edge fingers, carbon contacts, tie bars for plating lines,
etc.  These have additional rules so that they can be dipped or carbon
deposit masks generated.

> 
> I'd classify your choice as follow:
> 
>  	Copper - Copper, obviously
>  	Dielectric - Artwork (embedded capacitors, I suppose)
>  	Plating - Artwork (plating mask)
>  	HoleFile - Pad-only Artwork (hole plug dispenser)
>  	KeepOut - Special. I forgot it, it's useful to keep it aroud, top and bottom.
>  	ViaPlug - Pad-only  Artwork (hole plug dispenser)
>  	SolderMask - Special, solder mask, top and bottom
>  	Contacts - Pad-only Artwork. Depends on process (plating or foil application), 
> 	           but the fabricator just need the pad to be plated.
>  	PeelMask - Artwork
>  	Finish - Artwork. What's the difference with Plating?
>  	SilkScreen - Special, top and bottom.
>  	SolderPaste - Pad-only artwork, maybe special for DRC 
> 		    (there may be constraint on dispensing).
>  	Adhesive - Pad-only Artwork (glue dispenser)
>  	Courtyard - Special, useful for DRC, top and bottom. I call it playground :)
>  	Component - Artwork, top and bottom. 
> 	            Maybe special since refdes and value could go there.
>  	Coating - Artwork
>  	Edges - Special
>  	Eco - Artwork
>  	Probe - Pad-artwork (BTW I'm working on D-356)

I already did Lavenir Format 2 (IPC-D-356) Lavenir Format 4 (IPC-D-356
with NTD), IPC-D-356A and IPC-D-356B.  Also Barco DPF with netlist,
Gencad, Gencam (IPC-2511A), GenCAM-XML (IPC-2411B) and 258X (IPC-2851).

>  	Fixture - Artwork
>  	Comment - Artwork
>  	Drawing - Artwork
> 
> Less classes to handle are better IMHO. What do you gain, for example, in
> differentiating between Eco and Comment?
> 
> To fully exploit this you need to add masks to vias (to indicate if they need
> to be plugged, tented, probeable and so on).

I also provided several classes of layer-sets.  Layersets are groups
of substrate and copper in a buildup.  Layer set classes include:

  Laminate:- press cycle buildups.
  Pth:- plate through holes (not necessarily through entire board, but
	through sub-lamminate).
  Dcd:- Depth controlled drilling of outer layers of sublaminate.
  HoleFill:- Hole filling from outer layers of sublaminate.
  Laser:- Laser drilling from outer layers of sublaminate.
  Backdrill:- Backdrilling of Pth for sublaminate.
  Npth:- Non-plate-through holes in sublaminate.
  Route:- edges, slots, wells, cutouts in sublaminate.

The layer sets describe the entire board for sinlge press cycle
constructions.

--brian


-- 
Brian F. G. Bidulock    � The reasonable man adapts himself to the �
bidulock@xxxxxxxxxxx    � world; the unreasonable one persists in  �
http://www.openss7.org/ � trying  to adapt the  world  to himself. �
                        � Therefore  all  progress  depends on the �
                        � unreasonable man. -- George Bernard Shaw �