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PSPICE LAYOUT PROBLEMS

Discussion in 'Electronic Design' started by Lost'n Found, Jul 22, 2007.

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  1. Lost'n Found

    Lost'n Found Guest

    Hello,

    I am trying to implement a small design on a PCB for the first time. I am
    using Orcad Pspice Family 9.2 Layout Plus

    I drew the design in Capture, created Netlists. However, I realized that all
    components I use don't have footprints, and I have to manually specify them.

    For example, say I have 5 resistors. When I go the properties of any of
    those resistors (or other components), the Footprint cell will be empty.

    I tried to go to Layout Plus and search through the Library manager, but
    there didn't seem to be a trivial library which contains resistors and other
    basic components.

    My questions are:
    Am I asking in the right Newsgroup?

    If No, where whould I ask?

    If yes:

    Is Capture supposed to automatically figure out which footprints to use for
    basic components?

    How can I figure out which library to use for these components? Lets say I
    wanted to use a transistor now, 2n222


    Are the footprints supposed to be built in? (At least these basic ones!)

    Thank you very much in advance.
     
  2. linnix

    linnix Guest

    They are so simple. Why do you need the library? Just two or three
    pads or holes.
    Yes, but people do things differently. I generate them in a C
    program.
    How can it tell whether you use SMT or not?
    Don't know any 2n222. You can use SOT-23 (SMT) or TO-92 (TH) for
    2N2222.
    They should be somewhere, but not tieing to the components.
     
  3. qrk

    qrk Guest

    Although, I'm not real familiar with Capture, I enter the footprints
    in manually when stuck having to use Capture. You can also use a stuff
    file if you want to save some time. Perhaps CIS is helpful.

    What do you consider a basic part. For me, my standard resistor is a
    0402 conforming to a reflow soldering process. One of my customer's
    standard resistor is 0805 with a standard board thickness of 0.093".

    What kind of resistors are you using? Thru-hole or surface mount? What
    wattage? What PCB specification do you need to adhere to (MIL spec,
    commercial, high vibration, ...)? If surface mount, what sort of
    assembly process (wave solder or reflow)? These all make a difference
    on what sort of footprint you will choose.

    2N2222 comes in a few package styles. A real 2N2222 is a TO18 package.
    However, you can get them in TO92 or SOT23 with a different prefix.
    BTW, the TO18 and TO92 packages are in the to.llb library.

    You can find common surface mount resistor and capacitor footprints in
    sm.llb. Through hole in tm_*.llb.

    You will find that the Orcad supplied footprints need lots of help.
    For a production board or a complex board, I wouldn't use the Orcad
    footprints directly. Generally, one will either create their own
    footprint or modify an Orcad supplied footprint and store it in their
    own library. If you plan on using Layout, learn to make your own
    footprints as there are many parts not covered in the Orcad libraries.
    Every time I do a new PCB project, I always end up making a new parts.
     
  4. Hammy

    Hammy Guest

    This group may have been a better choice for CAD related ?
    sci.electronics.cad
    No layout package I know of can do this.Some may have a default
    footprint in the parts properties but dont assume its correct.
    For a thru hole 2n2222a for example I would use a TO/92/100 footprint,
    this gives you more room to resize the pads (easier if your fabbing
    your PCB yourself). Just be sure the pins are properly matched to the
    footprint. Thru- hole resistor footprints are located in TM axial
    library. Most of the components you listed if not all will be in one
    of the TM libraries you just have to select the proper size. If you
    don't have a footprint just browse through similar packages and resize
    one.
    Just so you know OrCAD layout is being discontinued, so if you are
    just starting out you may want to try and learn an alternative layout
    package.
     
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