Re: gEDA-user: Finished drawing two sided board in PCB. Any comment?

[9000 VAX <vax9000@xxxxxxxxx>]

Stuart,
  Thank you very much for your suggestions. details follow...

On 4/30/05, Stuart Brorson <sdb@xxxxxxxxxx> wrote:
> Hi Vax 9000,
> 
> So I looked at your Gerbers again after you posted the whole set.
> Overall I am very impressed.  I suspect that this is not your first
> board!

I did two or three loose TTL boards ten years ago with Tango. I think
I am a newbie again after so many years! This time it is a very tight
board with high density chips and chips with fast edges that are
totally new to me.

> 
> Some comments:
> 
> *  As far as I could tell, you did a great job with all manufacturing
> tolerances.  I checked your design against the tolerances listed on
> the Advanced Circuits webpage:
> 
> http://www.4pcb.com/fast_design_quote_online_pcbs_tolerances.htm
> 
> Solder mask and solder paste look fine to me.   However, did you check
> the drill diameters against your PGA and DIP pin diameters?  I don't
> recall a typical pin diameter; your drill diameters are .029.  Is this
> enough?

Thank you for your suggestion. I will check the pins I have to make
sure that they fit.

> 
> *  Finally, your fab drawing shows the outline of the board extending
> waaaaay below the actual edge of the board.  You may want to examine
> this yourself.  PCB autogenerates the fab drawing based upon the
> active drawing area you used when laying out the board.  I suspect
> that you extended the drawing area down when you were working.

You are correct! I used the area to rotate parts, and to bring up
parts from foo.pcb.new. I forgot to resize the board though.

> 
> The problem is that your board is not a simple rectangle.  I suspect
> that you actually want to route out along the silkscreen outline of
> the board.  The problem is that PCB has autogenerated your board
> outline in the fab drawing assuming that it is the rectanglular
> drawing area.   PCB developers: this is a misfeature, IMHO.
 
I supposed that the silkerscreen out line is the board outline. I will
follow other's suggestion to use a outline layer.

vax, 9000

> 
> In commerical tools, you would have a separate layer calling out the
> board outline.  For PCB, you probably need to put a manual instruction
> somewhere for the fab house to route the boad along the silkscreen
> outline.  Maybe you can draw your desired outline on a new, separate
> Gerber layer?  Alternately, you can make a mechanical drawing of the
> desired board outline, and include it with your design materials.
> Don't forget to make it *totally* clear where the holes and outline of
> the board lie w.r.t. the positions of the features in teh Gerbers.  If
> you can speak to an engineer at the fab house in person, that would
> help you clarify exactly what board outline you want.  Otherwise, if
> the fab house operates "open loop" (like many of the el-cheapo places
> do) then you will get back a rectangular board which you will have to
> rework yourself.
> 
> Others, any opinions about how to create complex board outlines in
> PCB?
> 
> Stuart
>