Re: gEDA-user: [pcb] Using psbloat - I've been hosed

[Dave N6NZ <n6nz@xxxxxxxx>]

Dan McMahill wrote:
> Dave N6NZ wrote:
> 
> 
>> So.... is there any way I can quickly get back to a filled rectangle 
>> for every pad?  Otherwise I'm going to abandon doing this out of PCB 
>> and do it the "right" way, which is to figure out a way to read the 
>> gerber.
> 
> Is that the right way or is a direct dxf export the right way?

There are two parts to that question.

Part A: What's the logical place in the tool flow?

For a long time, I've felt that the right place was to read a gerber 
file for a paste layer, and convert that into whatever the process 
needed.  Sometimes that is laser cut 3-5 stainless steel. Sometimes that 
  is X/Y/volume to drive a robotic syringe type system for low quantity 
runs.

However, I'm now thinking that it might also make sense to have pcb be 
able to directly export paste information in a more abstract format than 
a gerber file.

My need for a .dxf file has more to do with the specifics of my back-end 
process than anything generic.  Going down the dxf path I think would 
make pcb less general.

Part B: How should pcb handle paste?

PCB needs to be more intelligent about paste.  My current thinking is:
Footprints need a "Paste" keyword:

Paste(x1,y1,x2,y2,volume,material)

Volume is in the neighborhood of picoLiters. The above says:
deposit <volume> of <material> along a stripe from X1,Y1, to X2,Y2.
(x1,y1) may equal (x2,y2) in which case you get a dot or puddle. In many 
cases, there is not a 1:1 correspondence btw pads and paste dots.

This could be exported as a gerber similar to the current paste layer by 
having reasonable defaults in pcb.  Someone with a well-characterized 
stencil process may want to generate vector cutting instructions that 
make sense for whatever the stencil is... 003 stainless, 005 stainless, 
005 plastic, my cheezy 005 drafting mylar.  Someone with a robot syringe 
would turn the above pretty much directly into G-codes.  So the question 
of how to export the information to facilitate post-processing scripts 
comes up -- I haven't thought at all about that.

BTW -- <material> would probably be one of "solder paste" or "adhesive". 
  But the syntax allows you to specify both (or other arbitrary goops) 
in the footprint.  Although it is a bit of a conceptual kink, because 
each material is essentially a layer.  In practice it probably only 
comes down to two materials anyway, adhesive for the big TQFP and such 
in addition to solder paste, and everything else just has solder paste.

> 
> -Dan
> 

-dave

> 


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