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Common SMD size

Discussion in 'Electronic Basics' started by Michael, Jan 31, 2006.

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  1. qrk

    qrk Guest

    I like MELFs for inboard components. Insert the component in a hole
    and solder to pads on the top and bottom of the board.

    Otherwise, stick with 0805 or 1206 as you can hand assemble quite
    easily - unless you have the coffee jitters. 0603 and 0402 can be hand
    assembled, but tends to be a very unpleasant task.
     
  2. Guest

    Spehro Pefhany skrev:
    absolutely, theres just too many variables; distance between eyes,
    strenght for
    each eye, etc...

    I wear glasses (-3.5 or theres about) and I've tried to buy a pair of
    ultra cheap one
    size fits all just to have and extra pair and they are just about
    useless

    -Lasse
     
  3. Joerg

    Joerg Guest

    Hello Lasse,
    They are ok if the eyes just age normally. I can work just fine with the
    cheap ones and so does my wife. And our neighbors. Of course, if one eye
    develops worse than the other that's a different story. Then I'd get
    prescription glasses as well.

    BTW a camera-TV setup is great for SMT but only for folks who can get
    used to looking into a different direction than where the work area is.

    Regards, Joerg
     
  4. Carl Smith

    Carl Smith Guest

    When I worked for a while at one of the major computer
    manufacturers in the desktop systems engineering department I
    learned to solder SMT stuff rather well when reworking prototype
    motherboards. I could hand solder 0402 caps and resistors
    without much trouble. We did have a binocular microscope and
    fiber optic light and a good soldering iron though.

    It looks really weird in the microscope when you bring the
    solder into view and it is a "giant" metal rod twice the
    diameter of the SMT part. Yup, I used plain old fine roll
    solder. Oh, and if something possesed me to put a drop of
    liquid flux on the part it looked like a big flood on the PCB.
    :)
     
  5. Rich Grise

    Rich Grise Guest

    I got a pair of drugstore bifocals once, and I think the bi-parts were
    misaligned with my lines of sight - I got terrible eyestrain headaches
    after about 15 minutes. Now I have a 1.75 or so for the computer and a
    2.0 for the crossword puzzle. I was kind of bothered when the other
    day I happened to look at my TV, which is at the foot of my bed, with
    my computer glasses, and it was crystal-clear. Damn! I don't want my
    eyes to get even lazier! )-;

    Cheers!
    Rich
     
  6. DJ Delorie

    DJ Delorie Guest

    You made me look. My solder is 0.020", so I'm all set unless I start
    using 0201's. Now I have a better idea of how SMALL those things are,
    too.

    Here's my setup: Optivisor with 3.5x lens[1], Metcal STTC-043 tip
    (0.020" conical), and a Panavise model 333 board holder. Oh, and
    pointy-sharp tweezers. I've only gone down to 0805 so far, but that
    didn't seem that small.

    [1] http://www.woodcraft.com/family.aspx?familyid=4227
    [2] http://www.panavise.com/f/vises/vises_cbholders.html
     
  7. He just said that he passed 40, but not how many miles back :)
     
  8. Phil Hobbs

    Phil Hobbs Guest

    (lol)

    It's more the repeated blows to the head...the Krazy Glue helps keep the
    loose bits from falling off and inconveniencing passers-by.

    I still want to see the pictures of that snap rectifier gizmo. Could
    make a very cute Pockels cell driver.

    Cheers,

    Phil Hobbs
     
  9. John  Larkin

    John Larkin Guest


    I posted some pics of the mechanical assembly to a.b.s.e. If you like,
    I can privately send you schematics and stuff, and maybe even reveal
    the secret semiconductor we discovered. My original application,
    ripping atoms off samples in a 3d atom probe, has been replaced by
    femtosecond lasers. Oh well, I did get some shares of stock, which I
    am confident will buy me a bicycle in my retirement.

    John
     
  10. Phil Hobbs

    Phil Hobbs Guest

    Being replaced by a fs laser isn't so bad...could have been a computer. ;)

    Since I work for the Sirius Cybernetics Corporation, getting stuff like
    that is a little dicey for me, much as I appreciate the offer. Maybe
    you and I and perhaps one or two other people should write a book on
    circuits specifically for instruments. There's a _lot_ of cool tricks
    that ought to be preserved and transmitted, and not a lot of appropriate
    recipients graduating at the moment, more's the pity.

    That way you'd at least get some useful advertising in exchange for all
    the trade secrets. Not that there are that many people who'd even be
    able to _build_ a circuit like that, even from a book, but we must live
    by hope.

    (Maybe we can needle Jim T enough to get him off his duff with his book,
    which would be another good deed.)

    Cheers,

    Phil Hobbs
     
  11. Guest

    Don't worry Rich, the lenses won't make your eyes lazy.

    General reading glasses' considerations:

    They may bug you if the lenses' centers aren't spaced the same as
    your eyes are when converged on your work. If the lens is off-center
    with your pupil, prismatic distortion results, which displaces objects
    laterally from the position expected/predicted by the focusing effort
    now needed to focus on them. (The apparent displacement is also likely
    different for each eye.) Vertical displacement is disorienting, even
    nauseating.

    The result is that your extra-ocular muscles clash from the
    conflicting cues--e.g. simultaneously trying to _converge_ to match the
    focusing effort, and _diverge_ to line up the images from the two eyes.
    Fighting each other is tiring, producing a headache ("eyestrain").

    These difficulties can be avoided or fixed by
    1) just practicing and getting used to the lenses, if the adjustment
    isn't too severe,
    2) using weaker lenses and longer working distances,
    3) getting lenses with the correct spacing (IP / "interpupillary
    distance"), or
    4) using an optical aid with built-in prismatic correction, like the
    OptiVisor-style head-mounted magnifier (very nice, and not expensive).
    The latter, ideally, allows *you* to look straight ahead and focus at
    'infinity' while the device focuses and redirects your line-of-sight to
    the workpiece, thus avoiding any strain at all.

    The distortions and problems increase rapidly with stronger lenses,
    but, being ideally myopic, t'ain't a problem for me--I can usually get
    by with no lenses at all :-\

    If you're pre-presbyopic, e.g. <40 years old, you can use reading
    glasses to train yourself to reduce myopia by a diopter or so.

    Cheers,
    James Arthur
     
  12. John Larkin

    John Larkin Guest

    Sounds like fun. I'm in.
    The advertising doesn't matter, but maybe we can peel off a few of
    Win's groupies.
    Nah, only liberal weenies do stuff that's good for humanity.

    John
     
  13. Phil Hobbs

    Phil Hobbs Guest

    Terrific. You write and I'll direct. ;) Let's think about some topics
    and exchange them.

    BTW, all, please chime in with suggestions for things to include. No
    more than 20% pet peeves, please. (Well, maybe 60%--this is s.e.d,
    after all.)
    Nonononono. Might catch the never-get-overs. Besides, they're mostly
    male and probably poorly groomed.
    An excellent start.

    Cheers,

    Phil Hobbs
     
  14. Keith

    Keith Guest

    Because, like pens and pencils, I don't buy good ones because I lose them.
    I don't use them often enough to keep track of 'em and learned long
    ago the only way I'd have such things when I needed them was to saturate
    the area, so I'd have one whenever I needed one. I can't affort do
    saturate the area with Franklins. I *know* where they are, and they don't
    break when I sit on them.

    I talked to an optometrist a while back. She even recommended the
    cheapies for occasional use, with weaker ones for slightly longer viewing.
     
  15. John  Larkin

    John Larkin Guest

    I like being myopic. One of these years soon I think I'll get some new
    lenses, and I'm going to make sure the doctor leaves me this way.
    Being fixed-focused at infinity sounds like a real nuisance in my
    business.

    John
     
  16. Ken Smith

    Ken Smith Guest

    On doing 0402s.

    You need non-magnetic tweezers and good eyes to do 0402s. The other thing
    to have is a bunch of extras of each part. If you drop one its gone even
    if you drop it onto the PCB.

    After you finish, turn the PCB upside down to let the lost parts fall off.
     
  17. Ken Smith

    Ken Smith Guest

     
  18. SioL

    SioL Guest

    And totally clean tweezers, too. A bit of flux or even moist will
    make the part stick to the tweezers after you've released them.

    Can be frustrating.
     
  19. Bob Monsen

    Bob Monsen Guest

    I've got one myopic eye and one presbyopic eye. Strange, but it lets
    me read (and see smd parts) and yet also read street signs at a distance,
    both without glasses. It was annoying earlier in life to be basically
    blind in one eye for distances greater than 1m, particularly for sports in
    which stereo vision comes in handy, but has turned out to be quite useful.

    --
    Regards,
    Bob Monsen

    "I have called this principle, by which each slight variation, if
    useful, is preserved, by the term Natural Selection"
    -- Charles Darwin
     
  20. Guest

    Right - I'm not especially near-sighted, but enough so I can
    *read* SMD markings that my barely-myopic s.o. can't even see!
    Not to worry...the doc can't change your eyes' optics, the source
    of your myopia, and can set your glasses to any working distance
    you specify.

    (Lawfully, (s)he must, however, insist that you have at least
    one set of specs yielding 20/40 acuity (~=resolution) for driving,
    or caution you not to.)

    Best,
    James
     
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