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First attempt at SMD soldering

Andrew J

I bought a practice kit that, in theory at least, lights up LEDs in some sequence.  I say in theory, but as all the instructions (presumably) are in Chinese, who knows??  Anyway, it has components in a number of sizes: 1206, 0805, 0603, 3528, not sure for the ICs.

 

I've spent the afternoon soldering away - 76 components - and what can I take away from the experience?  Well:

  1. forget 0603, I'm not going there again.  Just too small for hand soldering.  I did of course lose a 0603 capacitor to the God of Misery and the kit had no spares.  One day, I expect to find it. Or not.
  2. forget resistor arrays as well (I think that's what they are), especially in 0603.  Seriously, what sadist invents such a thing??
  3. 0805 is likely to be the minimum I go with.
  4. I need a microscope to do this stuff.  At my age, my eyes aren't good enough and I have a bit of handshake too.  See also (1)!
  5. I need more practice at (a) soldering; and (b) keeping care of my tip.
  6. 0.46mm solder is still a bit thick, but just about do-able.  I dare say if I was better at 5a then it would be ok
  7. Still unsure of the best tip to use.  I had a 1.2mm chisel tip which is the smallest that I have, bar a pointy one
  8. Solder wick (decent stuff) is very useful
  9. It's not clear what the markings on a LED are - there were two variants (green marks on one lot, cut corner on the other lot.)  I did search but found the information results confusing: I assumed the marks referred to the Cathode.
  10. The ICs weren't too bad: I can't detect bridging, solder wick helped
  11. I don't think I'd be too worried about it in the future, at least I've taken the plunge right!  I'm not convinced I'd do better with paste and a hot-air gun either.

 

Questions I have:

  1. Is 350c too hot?  I used leaded solder: Sn 62, Pb 36, 2Ag with 505 rosin cores from Multicore.  It has a melting temperature of 179C.
  2. Would I fair better with a thinner tip?
  3. I used flux but my experience was it burnt off immediately and seemed to do nothing - related to questions 1 and 2?

 

I suppose the question on everyone's lips is "did it do anything?"  Well, in short, no.  I tested the resistors and they seemed ok, the ICs were getting voltage to the correct pins so I know they are the right way around.  Perhaps the LEDs are on the wrong way, perhaps the soldering isn't right, perhaps components are not in the right place (no markings on the tapes so I may have deduced incorrectly), perhaps it doesn't do anything anyway, perhaps, perhaps.  I'm not too bothered: it was a test/practice of soldering SMDs which it achieved.

 

I could definitely do with more practice but I expect I'll get better over time.  I also think that these practice kits are a good idea and I would recommend one to someone whose not done this before.

 

Thanks for listening image

 

EDIT: I have a follow up thread as well - https://www.element14.com/community/message/275494/l/second-attempt-at-smd-soldering#275494

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  • in reply to shabaz

    I think I will have to invest in some of that as well.  I have a Hakko Fx-888D with official tips, but the smallest chisel tip is 1.2mm.  I’ll look for someone a smidgen smaller.

     

    I’m sort of geared up for another try now after all these comments.  This is a great site.

  • in reply to Andrew J

    The IMHO, smaller tips are rarely helpful for improving SMD. Instead, invest in:

    • Thinner solder (0.02”ish happens to be the sweet spot for me) of high quality, like Multicore/Loctite/Stannol or Kester, so that you can feed solder in a more controlled fashion.
    • Good paste flux (I use the no-clean paste flux from MG Chemicals)
    • A drag soldering tip

     

    What’s the latter, you ask? It’s a bevel tip with a hollowed out, concave face that holds onto solder. So it actually drags away excess solder from the joint. If you were going to spend money on a tip, I’d get one of these instead. I use one and it’s great for this kind of thing. (Also, I’ve found it handy for other non-SMD uses, like tinning thin wire, or cleaning up some through-hole stuff.)

     

    Now, Hakko doesn’t officially make one in the T18 series your FX888 uses. But on this discussion, people say that the ones in the 900M series fit anyway (in which case I’d get the 3mm one, the 900M-T-3CM900M-T-3CM Shape-3C), and there’s a reputable third party that makes compatible tips (the “SMD flow” tips).

     

    I also highly recommend watching some videos on how to solder SMD, namely those from EEVblog (episodes 186, 434, and 997) and John Gammell. (Don’t bother looking at any other YouTube videos on SMD soldering; none come even close to these, regardless of video production quality. Too many show awful technique.)

     

     

    As for your questions, I’d go down with the tip temperature a bit. This will slow oxidation and give you more time to work before the flux burns off. Once you’re more experienced with SMD, you won’t need as long and this won’t matter as much.

     

    Use good tweezers and keep them clean. SMD components weigh so little that just a bit of sticky flux can grab your component away.

     

    Use good light and magnification. You will be shocked at how much less your hands shake when using magnification.

     

    Go lighter on the solder. As others have said, your first attempt wasn’t actually too bad. The positioning is ok for a first try. The biggest thing I observe is just way too much solder on the joints. The videos I linked to show what good joints should look like. (The Gammell ones are gold standard.)

     

    I’d suggest getting some SMD LED clock kits on eBay/Banggood/AliExpress for practice. Look for “DIY LED clock  kit DS3231” (that’s the model number of an accurate clock chip used in the good kits) and choose ones that use a bunch of SMD LEDs. At $7-20 a pop, depending on how fancy a model, they’re cheap practice, fun to build, and produce something you might actually use in the end! I have a few around the house now. image

     

    Good luck! You’ll get comfortable with SMD in no time!

  • in reply to tooki

    Thanks Antonio.

     

    I’ve got the thinner solder on order and will pick up a tip as you suggest.  I was also, this month, going to acquire a microscope and another kit to give it a go, specifically with solder paste (also on order) and a lower temperature: my latest project I’ve designed with mostly SMD components so want to get more practice in.

     

    Thanks

     

    Andrew

  • in reply to Andrew J

      wrote:

     

    Thanks Antonio.

     

    ....  I was also, this month, going to acquire a microscope ...

    One could also keep on practicing with the bigger SMD parts (e.g.: 1206), where you don't need a microscope. It will help you to fully get the hang of it without frustration.

    And then invest in a microscope ... ?

     

    I learned more from doing SMD soldering often (very often) than from using smaller parts.