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SMD components for a hobbyist

Discussion in 'Electronic Basics' started by Dmitri, Nov 9, 2004.

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  1. Dmitri

    Dmitri Guest

    Hello everybody!

    I feel that I have to tell you: this is a great group, and I have real
    pleasure reading posts here. This community seems very supportive and
    extremely knowledgeable. Keep up good work!

    Here is a question I wanted to bring respectfully to the group's attention:

    Long story short: 15+ years ago I worked in electronics industry, being
    involved into anything from PCB assembly to business ownership and
    anything in between. 15 years and couple careers later I look back at the
    electronics as a great hobby I would like to get back into.

    Anyways, it seems that SMD components have grown to dominate the market
    and suppliers' parts lists, and in majority of cases are mighty cheaper
    that their through-hole counterparts. Besides, having no drilling in PCBs
    somehow makes me feel that it would be easier to master homebrewed PCBs
    (for parts with reasonable spaces between the leads, nothing
    nano-tech-ish). With that said, I have realized that I would need to
    completely re-tool in order to be able to do any SMD handling. My old
    soldering iron seems too big, even multimeter probes don't seem to cut it
    anymore for SMD.

    What would you suggest as a reasonable set of brick-and-mortar SMD tools?
    Something I would use for 90% of SMD work, something like my trusty iron,
    tweezers and snips would do for through-hole? I see ads for hot air rework
    stations, never used one of them, are they any good/relatively easy to
    master? Are they of any use if I initially populate a PCB instead of
    actually re-working it? BTW, I already got that vacuum pickup tool, I
    would guess it will have to replace my tweezers. Still, how do you
    (conveniently?) pickup or hold something like 1206-type SMD resistor or
    SOT-23 part?

    And, I think the biggest question is: should I even bother messing around
    with SMD components on a hobbyist level?

    Thank you all responded!

    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
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  2. Steve Evans

    Steve Evans Guest

    You don't have much choice but to get sutck into them if you are to
    have any future in electronics, even as a hobbyinst. :(
     
  3. John Larkin

    John Larkin Guest

    Small-tip iron, skinny solder, solder wick, tweezers, and good light
    and optics! Liquid rosin flux is sometimes handy, too.
    Overkill, quirky, not really needed. Mostly just blows the parts away.
    Small, sharp-point tweezers are fine for big parts like this. I like
    the stainless ones with the curvy ends. I was just replacing an 0805
    and remember thinking what a big part it seemed; 1206's are getting
    rare these days, so skip them unless you really need the power
    dissipation.
    Sure, just do it. It's not actually hard... just takes a little
    practice.


    John
     
  4. (Dmitri(Cabling-Design.com))
    wrote:

    Yes, they are actually more convenient in many ways. No need for
    drilling, for example.

    I do protype boards and simple projects by taking a piece of pcb board,
    use a sharp file or similar tool to make grooves in it, dividing the
    copper layer into different parts, nodes, rubbing it with scotch-brite
    kitchen pad to clean off the oxide, and then solder smd components
    between these islands of copper.

    I use a simple soldering iron with a very fine tip. I hold down the
    component in the right position while soldering one connection, then
    solder the other connection(s).

    I often mix older types of components with smd components.
    The older components can be mounted without holes too, with some
    mechanical bending of its wires. Older chips can be laid on its back,
    with the legs up in the air, looking like a dead bug.

    For some inspiration on pcb techniques look up
    "dead bug" "manhattan style"
    on google.

    Add smd components to such innovative styles of building circuit boards
    and you have a lot of variations to combine in any way you like.

    You can create smaller and neater bords by photographic methods and
    etching, but they are more difficult to change and need a lot more effort.
    The size and look are usually not important because the board will be
    hidden inside a box.
     
  5. Dmitri

    Dmitri Guest

    Hi John,

    Thank you for the insight! Do you think it may be practical to mount a
    small SMD part with some sort or semi-permanent clay-like glue (I forgot
    how they call it in the craft store) BEFORE actually soldering? I have a
    great interest in LEDs and all sorts of display technologies. So, the SMD
    LEDs are basically a piece or epoxy resin with metal contacts on the
    sides. How do they hold the heat while soldering? I guess, what I'm trying
    to say is: when you solder, the epoxy becomes softer, but this is the only
    place you can hold with the tweezers. So, chances are you can squeeze too
    hard and damage every other LED. Any tips you can give on soldering an SMD
    LEDs?


    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------




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  6. Dmitri

    Dmitri Guest

    Thanks, Roger, I appreciate your suggestions!

    I totally agree with you on the drilling, having no holes is a great plus.
    There is only one problem, however: the holes are also a great way to
    neatly align the components. Having no holes means you no longer have any
    point of reference on the PCB. As you correctly pointed out, most of the
    time the PCB is just going to sit inside the box, so that would not
    matter. However, I'm going to try to attempt to solder SMD LEDs in a
    rather orderly fashion, a pattern rather, and I'm going to need alignment
    big times. Is it a no-no in a manual SMD PCB soldering to make it look
    neat or there is some technique I'm not aware of that can help?


    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------



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  7. John Larkin

    John Larkin Guest


    I did use some tiny edge-emitting surfmount LEDs a while back. They
    were OK for solder paste/reflow oven production, but if you tried to
    mount one with tweezers and an iron, it would melt in the tweezers
    like a tiny marshmallow. 0805-type (ceramic substrate) LEDs seem OK,
    but I think the clear epoxy they use on the SOT-23 and similar types
    melts easier than the black epoxy used on regular ICs. SOT-23 LEDs
    fail a lot if soldered by hand.

    If you're doing quantities, solder paste the pads (syringe or better
    yet stencil), goosh down the parts, and reflow in an oven. Or buy a
    ceramic-base part.

    John
     
  8. Dmitri

    Dmitri Guest

    Hi John,

    Don't mean to be a pain in the neck, but can you elaborate on "reflow in
    an oven"? Would this be something I can attempt in a residential setup?

    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------


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  9. (Dmitri(Cabling-Design.com))
    wrote:
    If you create a straight pattern to solder them to, like a straight
    groove and solder them bridging that groove they will be neatly lined up.

    For even more precision clamp a straight object to the pcb and push the
    leds against it while soldering one side. That will ensure that they are
    accurately lined up in a straight line. Another object, very small,
    between two leds while positioning will help keep the same distance
    between them.

    These are common tricks in woodworking, only applied at a miniature
    scale.

    All smd component can stand the heat from a small soldering iron for a
    few seconds. If that time is not enough let it cool down completely
    before making a new try.

    With some training you can solder small joints fast and with precision.

    The real challenge are smd chips with lots of pins very close to each
    other. For that you need to design and etch a pattern, and solder it by
    dragging a drop of solder along the row of pins. If the temperature and
    the size of the drop is good enough it will leave exactly the amount of
    solder needed at each pin.
    The surface tension of molten solder makes this method work.

    The temperature at the tip of the soldering iron is important to get
    right in all soldering, but even more important when working with smd
    components.
    It has to be hot enough to make the solder quickly flow like mercury, yet
    not too hot so the components are damaged.
    Keep the copper islands or tracks small/thin so they do not need too much
    heat and time to solder.
    Big copper areas cool down the solder and make it much more difficult.
     
  10. For leds, make sure you heat the solder and the copper surface first,
    making them flow together. Then move the little drop of solder to the
    contact of the led and remove the soldering iron quickly.

    Use as little solder as possible.
     
  11. John Larkin

    John Larkin Guest

    I think people use toaster ovens. Try googling "toaster oven surface
    mount" or something. Heat is heat, although the time-temperature
    profile should be controlled pretty well to properly reflow solder
    paste. I've heard of people doing BGAs at home in a toaster oven, but
    that scares even me.

    An array of surfmount led's, solder pasted, placed, reflowed in an
    oven shouldn't be too nasty. Hey, try it!

    John
     
  12. Dmitri

    Dmitri Guest

    Thanks again, Roger.

    I'm getting some SMD LEDs on eBay right now, will hopefully try to solder
    them pretty soon.

    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------




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  13. Dmitri

    Dmitri Guest


    Thanks, John!

    I'm going to try your technique in a few days as soon as my parts arrive.
    I have to admit, it does look scary to me to put in an oven, but, hey, if
    it gets me results I want - I'm all for it.

    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------


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  14. Neil Preston

    Neil Preston Guest

    In doing mostly repair of SMD boards, I have found a few tools useful:

    Fine-tip variable heat solder iron: Xytronic 258 (about $25 from MCM or
    Electronix Express) Get the finest point tips.

    Tweezer iron with tips of several widths: Xytronic 236 (about $60 from
    Electronix Express) I use this with a variable autotransformer or a light
    dimmer.

    Pinpoint heat gun HeJet HJ500S (about $150 from MCM) This one is also very
    useful for through-hole. Just be carefull not to blow off parts you don't
    want to remove!

    I have also found it very helpful to have liquid rosin flux in a needlepoint
    dispenser bottle for use while soldering. Then clean it off with acetone or
    alcohol.

    Neil
     
  15. Steve Evans

    Steve Evans Guest

    Do yourself a favor and buy a few dozen SMD capacitors or resistors at
    the same time. They're great to practice the technique with and it
    doesn't matter if you damage them since they're *so* cheap. When your
    confidence is gained, go on to the LEDs.
     
  16. Dmitri

    Dmitri Guest

    Steve Evans wrote:

    Good point!

    I knew quick soldering will be a problem at first, so I got myself ceramic
    body 1206-type LEDs for starters.

    Where do you stock up on discrete SMD components, anyways? They are rather
    chap on eBay but the problem is variety: I don't really need 10,000 of the
    same type on a tape, I may hardly use 100 in a year or so. What's the best
    strategy to procure the small amounts?

    --
    Dmitri Abaimov, RCDD
    http://www.cabling-design.com
    Cabling Forum, color codes, pinouts and other useful resources for
    premises cabling users and pros
    http://www.cabling-design.com/homecabling
    Residential Cabling Guide
    -------------------------------------



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  17. John Larkin

    John Larkin Guest


    Sometimes I put parts on both sides of a board. My production people
    paste/place/reflow the botttom, cool, then repeat for the top. Second
    pass through the oven, all the bottomside parts are hanging down, held
    on by the surface tension of their re-melted solder. Works!

    John
     
  18. John Larkin

    John Larkin Guest

    Sample kits. Mouser, Digikey, Garrett.

    John
     
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