Re: gEDA-user: Number of Layers

[Tony Radice <tradice1@xxxxxxxxxxx>]

Unfortunately that beast had:
1) Thru-board vias at the minimum diameter hole size the fab shop would
tolerate
2) Blinds, buried... lot's of 'em
3) Multiple independent power planes - boatloads of coupling and bypass
caps
4) matched length lines - most being differential pairs 
5) Controlled impedance lines
6) BMF Surface mount devices on both sides
7) AND the board was 24 inch by 18 inch 

a freaking beast - I was one of the Electrical Designers - I would not
even compare notes with the PWB designers - they were true masters of
their art. And the commercial package that was used, (Brand A) well - it
was pushed mighty hard. The board did, however, work - with a data
bandwidth of 144 GBits - no lie. 

I'm now a lowly laid-off electronics designer trying to peddle a buncha
services - and I gotta tell ya both schem and pwb are a major help!
(Now, if I can just get a paying customer...)

T.




On Fri, 2009-11-27 at 20:25 +0100, Gabriel Paubert wrote:
> On Fri, Nov 27, 2009 at 12:41:45PM -0500, Tony Radice wrote:
> > The idea of a 56 layer board makes my eyes water.
> > I Have worked on a 36, and that was (believe me) BAD ENOUGH!!
> 
> 
> I've never seen more than 24 myself, and designed with more than 6,
> but I suspect that your 36 layer PCB had blind and buried vias.
> 
> As long as you don't have blind and buried vias in PCB, I'm not
> sure that such a large number of layers is really useful in practice:
> vias that occupy all layers really complicate things like BGA
> exit patterns (on the inner rings).
> 
> 	Gabriel



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