kicad-developers team mailing list archive
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where footprints come from (was Re: Re: Internal PCB Units?)
Thu, 17 Dec 2009 11:01:16 -0000
--- In kicad-devel@xxxxxxxxxxxxxxx, Werner Almesberger <werner@...> wrote:
> The scenario I was thinking of was that you're given a data sheet with
> a footprint drawing and then you recreate that footprint in your EDA
The combicon were done this way, using pad sizes according to the IPC calculator... the sheet only states the drill hole, pad size is a consequence: the rule of thumb is to make the pad 1,5-2.0 the size of the drill, taking care of annulus requirement and other process constraint: for example our 'standard' process has a drill position tolerance of 0,2mm, you can have 0,1mm but you have to pay... also you pay a lot more if you need holes less than 0,4mm but it all depends on you fab facility...
> > Shell scripts :D I've done the whole Phoenix Combicon series with these.
> Whee ! Shell math is for the very brave :) Bourne Shell or bash ?
Actually zsh because I was lazy and zsh has floating point (maybe recent bashes have, too). It could be done in a fully posix compliant manner with expr(1) and fixed point... (guess that? the usual quantum thing :D)
Anyway it's done like this (snippet):
for PIN in $(seq 2 $PINS); do
Sh "$PIN" C $PADSIZE $PADSIZE 0 0 1800
Dr $DRILL 0 0
At STD N 00E0FFFF
Ne 0 ""
Po $PINPOS 0
> > Not sure about this but have you looked into gencam?
> No, but what I found looks interesting. Would you happen to have the
> URL of the specification ?
http://webstds.ipc.org/ then follow the menu...
> Yup, excellent point. A parametric design helps a lot with such cases.
Too bad you have to pay to have the design rules for IPC patterns :(