Mail Archives: geda-user/2015/09/13/14:54:40
> > You don't support multiple silk layers on top/bottom (different
> > colors?)
>
> Is this really needed? It is so rare, one can define an addition layer, and
> tell the fab house "I want layer 1234 in color pink on top of the regular
> white top-silk".
>
> Is this doable?
The fab house only cares about gerbers. If you tell them "see this
copper layer? I want a silkscreened copy in bright pink on the top,
too" they'll do it.
The reason to care about it internally is that the layout person is
going to want to see and edit the board as close to "as it will be
built" as possible. *Seeing* the extra layer in the silk group, with
the right color, along with the other silkscreens, may be helpful to
that person.
So if the design has a layer that's specifically "silk, top, bright
pink" that embeds the intention and presentation into the design
itself.
> > Do you want to support flex cables, where the "top" layer changes
> > depending on where you are on the pcb?
>
> Yes, I want to support that. But I think the 'top' layer becomes the flex
> cable, and the prepreg below is milled from the board. So the conductive layer
> structure doesn't change. I've never seen SMDs on the milled part.
>
> However, SMDs can be placed on inner layers. This is called buried components.
> Although I've never seen such board, but I know they exist.
The case I'm thinking of is a cable with built-up "boards" on each
end. I.e. extra prepreg and copper might be bonded to the ends,
meaning the "top" and "bottom" layers change as you go:
--------- <- extra layers
----------------------------------------------- <- flex cable
---------- <- extra layers
See http://techdocs.altium.com/display/ADOH/PCB+Layer+Stack+Management
for some examples.
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