Re: gEDA-user: Has anyone used SSOP28.fp?

[Dave N6NZ <n6nz@xxxxxxxx>]

L.J.H. Timmerman wrote:
> Hi Dave and all,
> 
> On Wed, 2007-06-06 at 11:24 -0700, Dave N6NZ wrote:
> 
>> a) pcb paste layer gerber is directly from the pad layer, and I think in 
>> many cases that lays down too much solder.  I haven't experimented 
>> enough to be able to say for sure.  I'd like to see some paste layer 
>> control added to the footprint definition.
>>
> Since this is on a per thickness, per material basis for the stencil
> involved, I think this could be better handled in a specific "stencil"
> exporter with a configurable positive(=larger) or negative(=smaller)
> offset value for the pad-outline.

That would be cool.  But I also think you want to be able so specify 
different shrinks on a per-footprint/pad basis.  For example, for those 
packages with a big heat-sink pad, that pad may want a different shrink 
from the rest of the pins on the package, and different from the 
default.  So, I could see some kind of format like:

default -10% # any footprint, any pad
sot223.2 -30% # sot223 footprint, pin #2 gets special treatment

Maybe something like that should even go into the footprint definition? 
(I'm thinking newlib here, I never use the M4 stuff.)

But in the end, I think the pad size adjustment in pcb should apply to 
what is written to the paste layer gerber.  Converting to pad outline 
vectors is better done in the gerber previewer or some other gerber 
reader, since that yields a more general tool suite.  Of course, I won't 
complain if pcb directly puts out the file that I need :)

> 
>> b) My current method for prepping a file for the laser cutter is a bit 
>> of a kludge.  Ideally, I'd like to see the gerber previewer have the 
>> option of exporting .dxf of the pad outlines from the paste layer.
>>
> If the exporter can be made configurable for not doing fill operations
> on a pads in a pads-only-mode, then it's also possible to do this for a
> DXF exporter.

Yes, the fill just gets in the way as far as my laser cutting s/w is 
concerned.

-dave


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