R: [kicad-users] Re: Module Library madness
--- In kicad-users@yahoogroups.com, Carlo Garberi res_elettron...@... wrote: For Cases, pads, etc., you can also refere to: New Surface Mount Design and Land Pattern Standard The official text for device farms. Which is *exactly* the ipc-7351a standard we're talking about:D:D And, my fault, I did remember wrong about resistor and capacitor pads... they're actually equal:P
[kicad-users] Re: Module Library madness
With the imperial / metric versions. the only thing I can think of is that it may be that because kicad (at least the 2009 versions) use imperial as it's base measurement system that someone created the imperial versions to avoid grid mismatches. That's not the reason, with its 1/10mil resolution pcbnew has no problem handling metric modules (well, maybe until you need chip bonding, at least :D) The metric/imperial usage with passives is mostly a cultural one in the industry and varies from country to country... For example, here in Italy when we talk about common capacitor/resistors we usually use the imperial units (0603 being the most common AMT). Tantalium are referred as metric (or with case letter coding) and for inductors... well, smaller one are imperial but bigger one are referred as metric... also electrolytic are referred using the panasonic case names and tank/choke inductors using the S/M/L/XL size from wurth! So, at the end, everyone make its own standard... The IPC standard naming is IMHO unwieldy, too complex to use in the usual cases! (and, anyway, remember that there are around a dozen or so of SOT-23 variants, too!)
Re: [kicad-users] Re: Module Library madness
Lorenzo wrote: The IPC standard naming is IMHO unwieldy, too complex to use in the usual cases! (and, anyway, remember that there are around a dozen or so of SOT-23 variants, too!) 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. 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?) 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.. 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 Gumption is 99% of success. kps
Re: [kicad-users] Re: Module Library madness
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
[kicad-users] Re: Module Library madness
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.. No, it's buggy plain C with GTK :P It actually contains a lot of hardwired size, too:P The separate names for a cap and resistor 0805 package is silly Actually it isn't... a ceramic cap has round plating, a chip resistor is an attached foil... I presume the mechanical properties are different (indeed the pads are different, too) The M,N,and L are for most, Nominal and least -- describes most compromises folks would run into.. You forgot Proportional for THT, too... and the Nominal one is good for 90% of the production projects, IMHO... One thing to point out is these case sizes originate in metric - the imperial notation is approximate. *Most* case size originate in metric:D
R: [kicad-users] Re: Module Library madness
For Cases, pads, etc., you can also refere to: New Surface Mount Design and Land Pattern Standard The official text for device farms. ciao Carlo, I2GOQ --- Mer 12/5/10, Lorenzo lomar...@tin.it ha scritto: Da: Lorenzo lomar...@tin.it Oggetto: [kicad-users] Re: Module Library madness A: kicad-users@yahoogroups.com Data: Mercoledì 12 maggio 2010, 18:19 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.. No, it's buggy plain C with GTK :P It actually contains a lot of hardwired size, too:P The separate names for a cap and resistor 0805 package is silly Actually it isn't... a ceramic cap has round plating, a chip resistor is an attached foil... I presume the mechanical properties are different (indeed the pads are different, too) The M,N,and L are for most, Nominal and least -- describes most compromises folks would run into.. You forgot Proportional for THT, too... and the Nominal one is good for 90% of the production projects, IMHO... One thing to point out is these case sizes originate in metric - the imperial notation is approximate. *Most* case size originate in metric:D
Re: [kicad-users] Re: Module Library madness
Lorenzo wrote: The separate names for a cap and resistor 0805 package is silly Actually it isn't... a ceramic cap has round plating, a chip resistor is an attached foil... I presume the mechanical properties are different (indeed the pads are different, too) ?? not the parts I looked at - they are different depending on thickness CAPC0603x33N and RESC0603x33N have the exact same land pattern.. 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 The government consists of a gang of men exactly like you and me. They have, taking one with another, no special talent for the business of government; they have only a talent for getting and holding office. Their principal device to that end is to search out groups who pant and pine for something they can't get and to promise to give it to them. Nine times out of ten that promise is worth nothing. The tenth time is made good by looting A to satisfy B. In other words, government is a broker in pillage, and every election is sort of an advance auction sale of stolen goods. -- H.L. Mencken
