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First attempt at Surface mount soldering

Discussion in 'd.i.y.' started by glenn jarrett, Feb 4, 2019.

  1. glenn jarrett

    glenn jarrett pfm Member

  2. Barrymagrec

    Barrymagrec pfm Member

    I think you`ll find it easier if you got some thinner solder - I use 0.46mm or surface mount work.
  3. Vinny

    Vinny pfm Member

    Did you glue them in place first? It doesn't need to be weld-o-glue, just enough to keep the components in place - it's how it is done industrially. Without glue, you are fighting surface tension, unless you can very precisely solder both ends simultaneously.
    In many ways easier, but a faff at the same time - use solder paste rather than wire. Dispense the solder accurately from a syringe and then just touch with the iron.
    glenn jarrett likes this.
  4. misterdog

    misterdog Not the canine kind

    A large tip across both pads at once works also.
    glenn jarrett likes this.
  5. glenn jarrett

    glenn jarrett pfm Member

    No just tinned a pad placed the part over it with tweezers
    heat the pad up with part in place then solder the other side
  6. Barrymagrec

    Barrymagrec pfm Member

    Yes, that`s a good technique but you need less solder.

    I never use any glue, with practice you get the knack of positioning components neatly.

    Solder paste is a faff but sometimes, such as with large ICs and surface mount connectors it`s worth the trouble - it`s normally easier to apply if you warm the board slightly first.

    Solder braid is very useful for removing excess solder especially if you blob across IC pins.
  7. linnfomaniac83

    linnfomaniac83 I bet you can’t wheelie a unicycle!

    Not a bad first effort. Provided you have a steady hand and the right tools and materials, surface mount is super easy and I actually find it easier to rework than through hole. No need for glue, that’s just used on pick and place machines to hold the components in place before the PCBs go through the oven. When hand soldering SMT components, I find it’s best to tin one pad and solder one end (or leg if dealing with an IC, transistor etc) first and square the component up, once that’s done, solder the other pad/s, use solder sparingly and as suggested by others, try some 0.46mm solder. You’ll be soldering large, fine pitched quad flat packs in no time.
  8. Tony L

    Tony L Administrator

    Do you have a link to the kit? Worth a quid and a half to see if I can do it!
  9. sam_cat

    sam_cat ᶜ ᶦˢ ᶠᵒʳ ᶜᵒᵒᵏᶦᵉ

    Ha, Ditto!

    Share the link, we can have a 'how bad are we at SMT' competition.

    Done some SMT stuff in the past, always went with a touch of flux, tiny dot of solder on the pads with no components.
    Pin through the end of a lollystick to position things then got some good find tweezers which helped a lot.
    Touch the iron to the solder/component for a moment, up it wicks. Done.

    Good magnifying lens is a huge help.

    *edit - Found it, ordered it. I am in.

    @Tony L - See above
  10. Tony L

    Tony L Administrator


    PS My main concern is dropping and losing the parts on the carpet before I’ve soldered them down!
  11. davidsrsb

    davidsrsb pfm Member

    I use a stereo microscope, which helps a lot, but I hand solder 0.4mm pitch PQFP100, a lot trickier than SOIC
  12. a.palfreyman

    a.palfreyman pfm Member

    Feckin'eck, I struggle with through-hole due to fading eyesight! Would struggle without a binocular / magnifier.
    glenn jarrett likes this.
  13. bugbear

    bugbear pfm Member

    I think surface mount covers a multitude of sins; the regulator board that was recently discussed (re: rPi) appears to use a truly tiny format;

    Here's the board on eBay;


    But looks at the dimensions of the entire board - it's TO220... so pin spacing on the 3045 must be "quite fine"

    [​IMG]3045 by plybench, on Flickr

    EDIT; Pixel counting via the given dimension gives me a pitch of 0.46 mm

  14. Barrymagrec

    Barrymagrec pfm Member

    I don`t like to go any smaller than 0603 for resistors and caps - some of those parts look to be 0402. Some ICs have the pads under the chip, this makes it very difficult without hot air and very careful amounts of solder paste.
  15. Shadders

    Shadders pfm Member

    I also use surface mount and a stereo microscope to solder 0805 etc., components.

    I have implemented QFN packages with the thermal pad on the underside of the chip - which usually has the recommendation of implementing a thermal pad on the PCB with vias connecting the pad to all layers such as a ground plane.

    I have used the soldering iron to solder the paste through the via holes, but the ground plane usually causes problems and the connection is poor.

    i did not want to purchase a reflow oven (small desktop unit) as they are very expensive for good quality (circa £3k). So do the hot air guns work on the thermal pad on the PCB on the underside if you fill the via holes with solder paste ?

    Thanks and regards,
  16. davidsrsb

    davidsrsb pfm Member

    A frying pan works, but don't borrow the best one ;)
    Toaster ovens are another cheap option
    Shadders likes this.
  17. misterdog

    misterdog Not the canine kind

  18. misterdog

    misterdog Not the canine kind

    Don't sneeze either !
  19. Tony L

    Tony L Administrator


    PS There are some very good YouTube tutorials on soldering including surface-mount on the EEV Blog with the somewhat excitable Aussie bloke. I’ve watched them all, though will re-watch the surface mount episode before actually having a go. YouTube really is wonderful for this sort of thing; I watched hours of it before venturing onto the double-sided 1980s computer boards I’ve recently been restoring. So far it has ensured every job I’ve tried has gone smoothly and neatly with no issues. I’ve not dealt with anything I could so easily lose before sticking it to the board yet though!
  20. davidsrsb

    davidsrsb pfm Member

    Follow the advice and use 63/37 solder. The lower melting point and better wetting gives much better safety margins than lead free, which has to be "just right" or you wreck the parts.

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