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Re: Padstacks, layernames, process files


On 11/14/2012 03:19 AM, Rick Walker wrote:
> Hi Dick,
>> In this thread, mostly we are trimming pad descriptions down with
>> this, since we do not have padstack support.  
> For what it's worth, I just fabbed a kicad board that uses the bitfield
> mask to control the inner annular rings for a BGA footprint.  I had to
> write a custom script to build my BGA footprints from a textual
> description file.  By leaving the annular rings off of selected layers
> of the outer pads it made it possible to route out all the traces from
> the inner pads. 
> I'd hate to see kicad lose it's current ability to fully control all the
> annular rings in a padstack independently through the textual
> description file. 

I will attempt to answer your concern by assuming you were using a mixture of through hole
pads interspersed in an among the the BGA SMD pads.

The strategy should still be possible with changes I committed last night.

  (pad 2 thru_hole circle (at 1.27 0) (size 1.651 1.651) (drill 0.8128)
    (layers *.Cu *.Mask F.SilkS)

becomes something like:

  (pad 2 thru_hole circle (at 1.27 0) (size 1.651 1.651) (drill 0.8128)
    (layers F.Cu Inner3.Cu *.Mask F.SilkS)

So it should work if you were to do it again today with a modified script, except now you
can read the result.

> I don't mind if all the layers have english names, but it is nice to
> succinctly say: "put rings on layers 1,3 4 and 5 only" only", by using a
> hex number: 0x0000001D.  Will the proposed changes still have some way
> to control all the annular ring layers independently in the
> textual description file? 

See above.

> Some IC layout programs handle the layer names by internally referring
> to all layers by integers and having a process text file that gives the
> binding between user names and the integers.  The process file also
> allows assigning things like layer colors, classes and characteristics. 
> The user can either use the integer directly (or a bitmask), or can use
> the layer name defined in the process file as a synonym. 

We talked about that, did not go that way after considering it.  Footprint files would be
burdened with layer maps in that approach.  We have no such burden.

> One nice thing that could be put in such a file would be the gerber
> extensions for each layer.  My current PCB fab house (4pcb.com) numbers
> the layers in opposite order to kicad, 

I've expressed concerns about our sequence also, but at least now it will not show up in
the data files in a hard coded way.  So we could change sequence without impacting the new
data files.

> and also prefers a different set
> of gerber extensions than kicad's default.  I currently run a custom
> "tapeout" script on every design to rename all the layers to 4pcb.com's
> conventions. 

Enjoy it.

> I really appreciate all the great work that has gone into kicad.  It is
> one of the shining stars in the open source world. 
> kind regards,
> --
> Rick Walker
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