Lorenzo wrote: >> You can tell IPC standards was written by engineers that haven't done real >> life design work -- >> some of the text sounds like it was written by lawyers <yuck>. > > You actually have found the specs or have you paid for them? I'd love to see > the rationale for > some of their formulas (like SOIC pads that sometimes are round and sometimes > are squareds)
You can find the specs via google A key to seeing what they are up to is in the ipc software that I posted the link to yesterday.. > >> Anyway - the problem is there really isn't one pad size for an 0805 that >> works - there are >> variants for density vs reliability trade offs and to really optimize the >> pad you need to >> consider the thickness of the part. (should the 0805 (2012 Metric) be >> called a 201250 Metric?) >> > > Not only that, there are other technological constraint. Like when you work > on 70um copper or you > do a board to be conformal-coated, the pads' shapes change a little... > >> I found this: http://www.xs4all.nl/~ljh4timm/pcb-fpw/pcb-fpw.html >> >> It would be cool if someone tweaked pcb-fpw to to produce kicad footprint >> libraries.. > > I could give it a look. I've already done some library generation, kicad > format is actually > trivial... > pcb-fpw is sort of an opensource version of http://landpatterns.ipc.org/files/PCBM_LP_Calculator_V2009-0831.zip All of it is for supporting IPC-7351. pcb-fpw was written to support the competing opensource 'pcb' package - might work to have a script to translate the modules? pcb-fpw is open source, so it would be possible to modify add it to the kicad suite .. seems to be written in java-bloat.. The separate names for a cap and resistor 0805 package is silly - I could see building a library with 080505 to specify the thickness for out of the ordinary parts. I could also see having three libraries - as the SNM7351B SNL7351B SMN7351B. (I found a thermistor that is thin and matches the thickness of the SM MOSFETS so it it touches the heatsink).. The M,N,and L are for most, Nominal and least -- describes most compromises folks would run into.. I'm also making my modules with different silk screen and a part outline on the drawing level. There are also custom case numbers that should probably be organized via part vendor. One thing to point out is these case sizes originate in metric - the imperial notation is approximate. -------------------------------------------------------------------------------- Karl Schmidt EMail k...@xtronics.com Transtronics, Inc. WEB http://xtronics.com 3209 West 9th Street Ph (785) 841-3089 Lawrence, KS 66049 FAX (785) 841-0434 When angry count four; when very angry, swear. --Mark Twain --------------------------------------------------------------------------------
