Re: gEDA-user: Handling odd solder paste shapes

[Steven Michalske <smichalske@xxxxxxxxx>]

On Jun 25, 2009, at 4:36 PM, Dave N6NZ wrote:

> John Luciani wrote:
>> On Thu, Jun 25, 2009 at 12:24 PM, DJ Delorie<dj@xxxxxxxxxxx> wrote:
>>
>>> Me, I have a perl script that post-processes that layer to adjust  
>>> the
>>> sizes for the paste I want.
>>
>> I was thinking of doing a Perl script that would substitute stencil
>> footprints (.sfp) if they were found. Otherwise a generic adjustment
>> would be made.
>>
>> (* jcl *)
>>
> I've thought about this problem off-and-on but never sat down to  
> code up
> a patch.  My latest thinking is to extend the footprint definition  
> with
> an optional "paste" command along the lines of:
>
> paste("material", x1, y1, x2, y2, picoliters);

I can see an issue here where the required volume cannot be placed  
without spreading over adjacent pins/pads

paste("material", x1, y1, x2, y2, picoliters, constraining pad);
paste("material", x1, y1, x2, y2, picoliters, x3, y3, x4, y4 );

Where constraining pad is the pad that this should be constrained to.
xy3 and xy4 for a bounding box.....

paste("material", x1, y1, x2, y2, picoliters, x3, y3, x4, y4, x5, y5,  
x6, y6 );
Using a bounding polygon.

If the process is a stencil then the aspect ration for the mask can be  
modeled after the pad.
The computer then can be smart about low volumes on large pads, such  
as an automatic matrix of minimum volumes.
DRC errors when the stencil can't place that volume in that area.


>
> Which says: Apply a stripe of <material> from x1, y1 to x2, y2, with
> total volume of <picoliters>.  This handles solder paste, mounting
> adhesive, potting epoxy, etc -- my assumption that each material would
> be exported in its own layer since it is applied at a different
> processing step.  If you need a blob instead of a strip, simply set
> x1==x2, y1==y2.  It is specified in terms of volume instead of a pad
> shape since for a stencil, the size of the aperture would depend on
> stencil thickness and stencil fabrication process.  So you would  
> convert
> volumetric output to gerber via some magic script tuned to your  
> process,
> presumably.  Or you might use volume/x/y data directly to feed one of
> the smaller systems designed for prototyping that deposits solder  
> using
> a syringe on an X/Y mechanism.
>
> -dave
>
>
>
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