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layout question

Discussion in 'Electronic Design' started by Michael, Oct 30, 2006.

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  1. Michael

    Michael Guest

    Can anybody help me with this?
    I lay out my schematics by myself. It was done by outside contractror
    once - I had to redo it: few switchers on fairly densely populated
    board, one needs to look at the schematic (and understand it) while
    doing layout...
    Question 1.
    how do other EEs do it? Sensitive mix of analog and switching stuff...

    I need to lay out another PCB and first thing I have to do is to create
    footprints that are not in our library (some QFN packages, few
    connectors)...
    Question 2.
    Has anybody heard of the service/source where we can order the
    footprint from? Something that works like this: we send datasheets,
    and/or footprints names, give CC number and get either library of 1,
    2...10-20 parts..
    I do not want to buy library of 10,000 parts and spend hours trying to
    find my footprint there.
    And it would be nice if I could use the footprints WITHOUT having to
    check them (like Samtec QSH footprint I dealt with the other day)
    Am I daydreaming?
    Thank you for your help!
     
  2. I'm doing the required footprints myself. It just
    takes a couple of minutes. It is not that hard and
    you then know they are right.

    Rene
     
  3. deon

    deon Guest

    [Question1]
    difficult one, i've been the contractor as well as the in-house EE
    its possible to get good results from contractor if you specify completely,
    don't assume the oak is an expert in your domain.
    if there is any funnies spell them out ...
    [Question 2]
    i normally do it myself @ least i know what i'm getting
     
  4. What package are you using?

    But as Rene said, making a symbol should be pretty easy, if you can
    figure out the help file terminology


    martin
     
  5. One time I had to do a PCB layout in a hurry using software I was not
    very familiar with (and therefore had not created a library of my
    favorite oddball parts), so I paid a layout guy to come up with a
    couple of dozen footprints. It was sort-of worth it, and the job got
    finished on time.

    A lot of the work is just organizing all the information, actually
    creating the footprints should go pretty quickly if you're reasonably
    good at using the software. Every project typically involves creating
    some new footprints and some new schematic symbols. Unless they're
    multi-hundred pin chips, it shouldn't be such a big deal, particularly
    when you're laying out a lot of the board by hand. It also depends a
    bit on how fussy you are about creating schematic symbols- some people
    like to see the functionality represented inside, which might take a
    lot more time than just a rectangular block with properly labeled
    pins.

    Getting PCB layouts done by outside contractors can be tricky. Harry
    Delamano posted a checklist of how he does it a year or two back,
    Google groups should find it. I have also had the experience of having
    to redo a lot of the work. Aside from mixed low level and high level
    signals, also things like clearances for high voltages, isolation,
    minimum trace widths on certain traces and so on.. it's all doable
    with good people on both ends, but you do have to be careful.


    Best regards,
    Spehro Pefhany
     
  6. Some eval tools are availble for download here...
    http://www.pcblibraries.com/

    These are supposed to be IPC, good start tho.

    Cheers
     
  7. JeffM

    JeffM Guest

  8. Guest

    Being able to produce symbols and footprints is an abosolute basic
    skill you need to learn. libraries are often not laid out the way you
    want them so you have to modify them anyway.
     
  9. On 31 Oct 2006 08:20:35 -0800, in sci.electronics.design

    The biggest moan, on my antique Accel package is that all the TTL/CMOS
    components have the Ground and Vcc pin hidden in the schematic, which
    can be confusing when you use more than one 5V supply.So creating a
    modied part is essential. Apart from that it hasnt crashed in several
    years :)

    Making you own libs is essential, and part of the job, and can't be
    avoided


    martin
     
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