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Homemade SMD prototyping - with hot air

Discussion in 'Electronic Design' started by Robert Scott, Feb 26, 2005.

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  1. Robert Scott

    Robert Scott Guest

    I have seen various postings about doing SMD prototyping with very
    fine point irons and solder wick for cleanup, but I would like to try
    hot air. But I don’t want to invest in a several $k professional hot
    air SMD rework station. I just want to stick down a few SOIC-8
    packages. I occurred to me that something like a heat gun might work
    if the air flow rate were drastically reduced and the heating element
    power were controlled down to an level to produce 700 degree F air,
    and if a nozzle could be designed that squired out air in a little
    slit. In fact, forget about the heat gun. Just consider a length of
    nichrome wire, a controlled current, and a tiny fan. Has anyone tried
    to make their own SMD hot air tool for experimental use?


    -Robert Scott
    Ypsilanti, Michigan
     
  2. Si Ballenger

    Si Ballenger Guest

    I think most cheap DIY setups are based on the Radio Shack
    desoldering iron (part 64-2060). The general approach is to
    remove the rubber bulb, and replace it with a source of air, such
    as a piece of aquarium air line tubing you can gently blow into
    to force air out the tip. The tip is stuffed with some fine steel
    wool which absorbs heat from the tip and helps heat the air
    moving through and out the tip to the solder surface.
     
  3. mike

    mike Guest

    Cheap hot air guns designed for paint stripping can work well.
    Get the variable heat model if you can. The thermal part is open loop
    so dependent on air flow.
    The air flow is high, so there's risk of blowing the parts off the board.
    You can use a smaller tube do direct a portion of the air flow to the
    work and divert the rest. You can't just restrict the air because
    you'll blow the thermal fuse.

    For small chips, just waving the heat around works well. For bigger
    chips, it's helpful to form a rectangular opening and put in a baffle so
    the air goes around the leadframe area only.

    I just tripped over some Leister hot air wands. Having precise
    temperature control makes life much easier. Now I'm trying to cobble
    the thing onto a Dirt Devil Vacuum cleaner as an air source. 10 feet
    of hose with a wire down the middle results in a lot of back pressure.
    mike


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  4. Brian

    Brian Guest

    You must all be hobbiests, I assume? Heck, we end up with quite a bit of
    protowork here. I'll admit, while to our good customers we almost give it
    away, it can be expensive as a "one-off". But then again, if your time is
    worth something and you want it done well, perhaps it is cheap afterall.

    Brian - http://www.risingtechnologies.net
     
  5. Robert Scott

    Robert Scott Guest

    Actually I am a bit more than a hobbyist. I do embedded systems
    design, mostly software, and occasionally do some board design and
    prototype building. It would take me more time to explain to a
    contract assembly house such as yours what I want done than to do it
    myself. (Think of quantity 2 boards.) However if I ever wanted to
    make more than about 8 boards of the same type I would definitely
    consider a contract manufacturer.

    After having posted the original question, I now see that I was wrong
    in assuming that all hot air SMD prototyping stations were in the
    multi $k range. I found some systems for under $300 plus a little
    more for optional nozzles from Xeltek. Anyone have any experience
    with this company?


    -Robert Scott
    Ypsilanti, Michigan
     
  6. mike

    mike Guest

    This is the cheapest hot air gun I've found.
    http://www.mpja.com/directview.asp?product=15159+TL
    no experience with it tho.
    mike

    --
    Return address is VALID but some sites block emails
    with links. Delete this sig when replying.
    ..
    Wanted, PCMCIA SCSI Card for HP m820 CDRW.
    FS 500MHz Tek DSOscilloscope TDS540 Make Offer
    Wanted, 12.1" LCD for Gateway Solo 5300. Samsung LT121SU-121
    Bunch of stuff For Sale and Wanted at the link below.
    MAKE THE OBVIOUS CHANGES TO THE LINK
    ht<removethis>tp://www.geocities.com/SiliconValley/Monitor/4710/
     
  7. Rich Grise

    Rich Grise Guest

    Nah. I'm only hobby; John Larkin and John Fields are hobbier, but Watson
    A. Name is the hobbiest of us all!

    It's "hobbyist".

    Cheers!
    Rich
     
  8. Brian

    Brian Guest

    Unless you do something really ODDBALL, a BOM and silkcreen usually
    suffices. I have seen designers that have ZERO documentation, in those cases
    we really can't help much w/o the bill getting bigger quite rapidly.
     
  9. Brian

    Brian Guest

    I am always impressd with those that correct my typos. Wow.
     
  10. keith

    keith Guest

    Who is "we"? Yes, I've had stuff done by the biggies for what I
    considered cheap-money. Though I don't think they were doing me any major
    favors (contracted, perhaps). It was clear from the outset that they they
    were only going to build them in the single digets, with no repeat
    business.
     
  11. Rich Grise

    Rich Grise Guest

    It's a gift. Or a curse, depending on your POV.
    (in either case, please don't be too impressed -you'll find it quite
    annoying after a while. Ask anybody! ;-) )

    Thanks,
    Rich
     
  12. Richard H.

    Richard H. Guest

    Having bought one recently, I'm a big fan of the system at
    http://www.zeph.com. It looks like eBay has them occasionally for 10
    cents on the dollar, which puts it in the range of a one-man shop.

    The air pre-heater makes a big difference, especially with ground
    planes. Works like magic on 0402's and 0.5mm leadframes alike.
     
  13. Robert Scott

    Robert Scott Guest

    If it's that common to find them on eBay selling for such a loss, I
    have to wonder why the original owners were so anxious to get rid of
    them.


    -Robert Scott
    Ypsilanti, Michigan
     
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