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stereo microscope to do SMT?

Discussion in 'Electronic Repair' started by [email protected], May 16, 2007.

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  1. Guest

    Do I need a "stereo microscope" to do SMT? Or will a good lighted
    magnifing lens do it for an occasional MSOP-8 install? If a
    microscope will one of those "school lab" $75.00 ones work? Thanks All
    for your time. Wayne
  2. Smitty Two

    Smitty Two Guest

    This is a question for your optometrist and the answer is almost
    certainly age-dependent. What I could see clearly with naked eye twenty
    years ago, I now need a pair of strong reading glasses coupled with the
    good lighted magnifying lens to see. Nowadays, I use a high quality
    stereo zoom microscope to pull splinters out of my finger, let alone
    solder SMT.

    If you can't tell whether the solder has flowed to form a backside
    fillet (from inner edge of leg to pad) then you need to crank up the
    magnification. Because SMT is designed for automated soldering, the pads
    are often scarcely larger than the component leg, and it's easy to pile
    solder on top of the leg without making a good connection to the board.
  3. Arfa Daily

    Arfa Daily Guest

    There are stereo long-reach microscopes available for very reasonable prices
    nowadays, but perhaps not as cheap as $75. I paid about 5 times that for
    mine, but it has paid for itself many times over. I agree with everything
    that Smitty said on the subject. I suppose I would have to add that it
    depends on what your line of useage is going to be. If you are a hobbyist
    just doing the occasional bit of sm work on home projects, then a good light
    and a good quality headband magnifier ( I use one of those as well ) or a
    jewellers loupe might be all that you need. If you are going to be working
    with the stuff commercially, on a daily or even weekly basis, then I would
    recommend a decent self illuminating microscope, as a worth-every-penny
    addition to your workshop equipment.

  4. GregS

    GregS Guest

    I don't think you need a microscope, but i certainly use magnifiers,
    The scope is good for inspecting very closly.
    A cheap microscope is around $300

  5. Guest

  6. Guest

  7. GregS

    GregS Guest

  8. Arfa Daily

    Arfa Daily Guest

    I always tin the board first, then wick the excess back off until the pads
    are really smooth. I then 'tack' one end or one pin of the device to the
    board using just heat from the iron and the tinning on the component pin and
    pad. I then examine the positioning really closely with the magnification.
    If I am happy that the component is located exactly correctly, I will hold
    it in place with the tip of a scalpel, and tack solder another pin and then
    re-examine the positioning. If all is still well, then I go ahead and solder
    it in fully.

    A liquid flux is absolutely essential for the soldering process as it
    assists the solder to flow by capilliary action between the pins and pads
    much more readily, which helps really significantly with not getting
    inter-pin shorts with fine pin-pitch sm components. Very fine gauge 'angel
    hair' solder is also a must. The flux that I use comes in an aerosol can,
    and is made by Electrolube and is their product SMFL 200. It is very cheap,
    and very very effective.

    Of course, all this assumes that you are talking 'conventional' hand
    soldering. The best way is to use paste solder and hot air, but I don't
    think that you are talking that level of professional at this point ?? It is
    all down to practice and confidence to get good results, and is really not
    that difficult if you use a fine tipped iron with enough heat, and are
    reasonably skilled at normal size soldering. If you do get shorts between IC
    pins, don't worry about them at the time. Just note where they are, and
    carry on. Go back to them at the end with a good quality wick placed against
    the vertical face of the pin, and reheat. the excess solder will readily
    come out from between the pins, without compromising the joint. Before your
    final examination under magnification, clean up with a flux remover. For
    this I use a Servisol aerosol product. You will be amazed at how good a job
    you can do with a little practice.

  9. Guest

  10. Smitty Two

    Smitty Two Guest

    Keep us posted on how that works out. How will you be applying the
    solder paste?

    As far as electricity, it comes from the wall and also out of thin air.
    I guess most soldering irons have grounded tips, but of course for
    working on live circuits it's essential to break the damn ground plug
    off the power cord.

    As for the other stuff, I'm not too much of a believer in the ESD
    goblin, but it's rumored that some types of chips are sensitive, so you
    might want to take some small precaution there, too.
  11. Guest

    I have spray flux. I'll keep you'all posted as soom as the board gets
    finished and I get time to put it together. Might be a little time.
    Thanks much all!
  12. Guest

    I could not imagine doing the repair without a zoom stereo
    microscope. The problem with the lab type scopes is that you will not
    get the working distance needed to get tools under to manipulate nad
    solder the part. A maginifying glass setup may work or if you are
    really young and your eyes are really good you may can pull it off but
    it would be hit or miss at best.
  13. doug

    doug Guest

    I use an American Optical stereo zoom with a .5x accessory lens. This
    has two advantages. One, the working distance increases to about 7
    inches and two, the minimum magnification drops to 3.5x which is nice
    for viewing larger areas. By the way, do not try this with 5x eyepieces
    instead of the standard 10x as the tube size is such that you only get
    the central part of the image. The .5x AO575 lens shows up occasionally
    on ebay but they are not cheap.
  14. mc

    mc Guest

    Anyone want to recommend a specific stereo microscope for this kind of work?

    The eyepieces must work well for an eyeglass wearer.
  15. I have Madell on my bench at work and at home. Quite happy with them--didn't
    cost arm and leg and very nice to work with. I used to use various lenses
    before biting a bullet and buying a microscope. Now I can't even imagine how
    I could live without one...

    One suggestion--if buying Madell (they are selling them on eBay too,) go for
    dual-bar boom stand.
  16. mc

    mc Guest

    I have Madell on my bench at work and at home. Quite happy with
    Do you wear glasses? How is the eye relief -- do you have to put your eyes
    very close to the eyepieces?

  17. I always took my glasses off. It caused less eye strain, and the
    rubber eye cups could be cleaned with Isopropyl Alcohol to remove the
    body oil and bacteria.

    Service to my country? Been there, Done that, and I've got my DD214 to
    prove it.
    Member of DAV #85.

    Michael A. Terrell
    Central Florida
  18. I do wear glasses but I'm nearsighted so I always take them off when doing a
    delicate work. But yes, it works fine with glasses on.
  19. Dan

    Dan Guest

    A number of years ago I looked into cheap stereo microscopes for working on
    60's vintage Accutron wristwatches & other watch work & seriously consider
    these Russian ones Never got
    one so I don't know about the eyeglass aspect.

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