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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

  • No photos? Maybe best not for your first attempt! Of course you can now practice some rework until either the LEDs light up or you destroy it by lifting a track. It won't take long to get used to SMD. I must admit I was scared at first but soon found I prefer it to through hole - at least until I get to QFN packages!

     

    I can thoroughly recommend a microscope. I went with a non-branded eBay version of the usual Amscope one and I'm glad I did. Review here if you're interested.

     

    Solder paste and hot air is definitely your friend if you're planning on more SMD work. I've also found that the low end (Yihua 898D+ in my case) does a reasonable job for without spending loads on something you're not sure you'll need yet.

  • in reply to Fred27

    I can do you a photo, I'm not ashamed image.  Don't look too closely at the Capacitors though - those were (some of) the evil 0603s, one of which has gone on holiday.  This was all done by eyesight as well. 

     

    image

  • Hi Andrew,

     

    Well done for your exploits into the SMT field - I'm sure in time you'll get more confident and start to expand on your equipment required to make things a bit easier (like David suggests a microscope). To answer your questions:

     

         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.

         Not in my opinion, but it will cause the tip to deteriorate quicker....not that you'll probably notice much if you only solder occasionally.

     

         2.     Would I fair better with a thinner tip? 

         Always handy to make sure you only get the heat onto the required pad, in which case keeping the tip temperature up is probably a good thing.

     

         3.     I used flux but my experience was it burnt off immediately and seemed to do nothing - related to questions 1 and 2?

         A flux pen does definitely help the solder flow; it cleans off impurities and helps prevent solder bridging between tracks.

     

    I find the best way to solder the smallest resistors is to:

    • apply flux to the pads
    • heat and apply the slightest dab of solder (a thin solder wire helps here)
    • if too much solder is applied then use de-soldering braid to remove the excess
    • holding the components on the long sides with some fine tweezers, position with one hand and heat the pre-tinned pad to make the initial solder joint
    • I then use the tweezers to push lightly on the top of the component and reheat that first joint to get the component to sit down flush onto the pad
    • I then apply solder to the second end
    • Once that has solidified I often give the first side another quick touch of the soldering iron to ensure a better joint

     

    As you have found, it can still go wrong: the tweezers ping the component off to oblivion, the 0603 gets wicked into the solder on the end of your iron, solder bridges remain hidden....all part of the fun image

     

    Rod

  • in reply to 14rhb

    All those things happened Rod! 

     

    The approach you you laid out is, essentially, what I did except the 5th bullet (press on top), I shall remember that.  I did use a flux pen but it just seemed to burn off immediately.  I also think I could do with some thinner solder which is a shame as it isn’t cheap.

     

    if I give it another go (get another practice kit), I may try a smaller tip and experiment with the temperature.  If only it was as easy as they make it look on YouTube image

  • in reply to 14rhb

    Rod,

     

    I would second all of your suggestions (almost like you looked over my shoulder when I was soldering.

     

    Gene

  • in reply to Andrew J

    Andrew,

     

    If you did the above work with eyesight (no magnification) then your vision is not too bad (I don't think that I could that well without my microscope).  David is right, a microscope (even a relatively cheap one) is the way to go.  I bought mine, used, off of ebay and I have not looked back.  Also, with a microscope, good lighting is very important (I ended up building my own light ring, but before that I used a halogen desk lamp).

     

    Practice makes perfect, or at least better.  I find that 0603 is doable, but 0402 was absolutely crazy (I could do it, but it was not always pretty).

     

    Well done and good luck on your future attempts.

     

    Gene

  • in reply to Andrew J

    Wow, are you sure this is your first go at SMT? It is really good.

     

    Sometimes a dab of flux on the couple of ragged joints and a quick touch of the soldering iron and they pull back into a nice 'wetted' joint. Sometimes it is possible to burn the flux/rosin and with other board contamination you end up with a horrible joint that never seems to want to take solder properly. The small brass brush or fibreglass cleaning pens plus some Isopropyl Alcohol help clean the area up for a new attempt (some of the joints along the top edge may have gone down that route ? ).

     

    Rod

  • Hi Andrew,

     

    That's a good first attempt! I agree with the comments from everyone too. By the way it's almost inevitable that there will be a lot of solder on each component with 0.46mm solder, incidentally that's the thickest size I own too. It's pricey, but this 0.274mm really helps with 0603 and 0402: https://cpc.farnell.com/omega/62s-32swg-lr-250g/omega-62s-low-res-1-250g-32swg/dp/SD00160 otherwise 0.38mm solder is ok for 0603.

    350 degrees with your 1.2mm tip sounds reasonable but depends on the iron power. I use a similar ballpark with leaded solder, about 330 degrees C, with a 1mm tip (slice off conical tip) for nearly all SMD work.

  • in reply to 14rhb

    Thanks for the encouragement, appreciate it.

     

    I’ll remember you’re point about flux touch up.  I struggled with it to be honest as it didn’t seem to help - everything I saw on YouTube showed it ‘flowing into place’ but I just didn’t find that.  I expect I just need more practice and a better view of what I’m doing!

  • 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.