On Jun 7, 2007, at 9:04 AM, Dave N6NZ wrote: > > 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.) > I agree that this would go in the foot print definitions.
This is something that needs a touch finer control. some of the larger devices require a grid of solder paste on a pad. This might be something to have a calculator on. define a volume of paste per pad, and weather it is a grid. this then gets scaled by paste mask thickness so that if i used a 1/16th paste mask i'd get small holes, and a 1mill would error out saying that the paste mask apertures were larger than the pad dimensions - x% Steve > 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 > > > _______________________________________________ > geda-user mailing list > [email protected] > http://www.seul.org/cgi-bin/mailman/listinfo/geda-user _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
