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Layout Footprint sot23

Discussion in 'CAD' started by visand, Jan 3, 2006.

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  1. visand

    visand Guest

    Hi to everybody! I'm new to this list
    I'm trying to learn to use Layout from Cadence and I've to place
    component in a SOT23 package. I've searched it in the standar
    libraries but I was not able to find it. Does anybody know where
    can find this footprint or how I can draw it by myself (an
    tutorial...?)
    Thanks a lot
    Andre
     
  2. Blastoff

    Blastoff Guest

    Andrea, the library would be the SM.LLB Library, atleast
    for v9.1 it was so it might be the same.

    A word of caution though ! Make sure the pin numbering
    scheme for the schematic symbol matches the correct pad
    placement numbering for the footprint in layout. Also alot
    of the sm parts in layout were not very well made i.e pad
    size were incorrect for manufacture of a real pcb. Soldermask
    on most of them was not oversized enough for the pad land.

    At one time Orcad created a ipc standard library of SM footprints for
    layout so the SOT23 part might be in such a library also. You can
    check the download section of the Orcad/Cadence website.

    Your safest bet on the footprint if in doubt is to look at the part
    manufacturers data sheet for a land pattern and create one or modify
    the existing one.

    Good Luck...

    Paul H









    On Mon, 02 Jan 2006 18:05:17 -0600,
     
  3. qrk

    qrk Guest

    It still can be found in the SM.LLB library in 20 flavors. Another way
    of finding parts is use GREP (or you can use M$ file search utility)
    to search for text strings in the library files. In your case,
    grep -i sot23 *.llb
    The reason I use GREP is I can use a batch file to find all the
    footprints for a project.

    As Paul states, don't trust Orcad's footprints. You should check them
    against trusted footprints and then store them in your own library.
    About 100% of Orcad's footprints are unusable out of the box. Better
    yet, learn to make this from scratch. Making your own footprints is a
    necessary skill to learn for any PCB program.
     
  4. Joerg

    Joerg Guest

    Hello Paul,

    Oh yeah! There really is no standard and even within the same
    manufacturer I have seen two different numbering schemes. And I have
    seen lots of people getting a black eye because of it. One of them is
    yours truly :-(

    Regards, Joerg
     
  5. Boris Mohar

    Boris Mohar Guest


    Count me in. Lately I made it a rule to always double check all three pin
    devices especially when it comes to function vs pin number and the
    corresponding footprint match. Been there and burned.
    Here is what prompted me.

    SOT-223 package 5 volt regulator

    http://www.zetex.com/3.0/pdf/zr78l.pdf

    We later decided that a LDO from National would be a better choice.
    Of course the board was already built.

    http://www.national.com/ds/LM/LM2937.pdf

    Like two gloves



    Regards,

    Boris Mohar

    Got Knock? - see:
    Viatrack Printed Circuit Designs (among other things) http://www.viatrack.ca

    void _-void-_ in the obvious place
     

  6. I have multiple copies of the same 3-pin footprint under different
    names. The footprint name I use is the same as the device name.
    This way, if I have not used the device before, the footprint is not
    found, and I can then make sure the schematic and footprint pins
    are matched when I make yet another copy of the specific footprint.
    So far I have not been bitten a second time by this particular
    problem.

    Regards
    Anton Erasmus
     
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