Steven Michalske wrote: > 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 > >
Yes, that's a better model. I can't say if that meets the needs of people going to high-volume assembly houses, but it certainly meets the needs of and goes beyond the kind of process controls I can get on my workbench with my squeegee and toaster oven. -dave _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
