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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

Parents

  • Hi Andrew,

     

    I will chime in with everyone else.  It looks quite good.  I am pretty new to SMD soldering myself but I can promise you will get better, it just takes practice.  Like you, 0805 is what I feel comfortable with manually soldering although I can go 0603 in a pinch.  Kind of repeating what others have said but try some flux on the pads especially with cheap PCBs.   I use 0.3 mm rosin core solder.  My technique is very similar to 14rhb.  Sometimes I use solder paste instead of solder with an iron and that works too.  Great start!  I actually prefer SMD to through hole now if the parts are 0805 or larger.

  • in reply to fmilburn

    Thanks Frank. 

     

    Actually, I might try solder paste - that seems like it might be a good start with tinning the first pad.  I did that with the solder but it wasn't easy - I could actually use my magnifying glass with paste.  Clearly I need to work with the flux more because that just didn't seem to help.  It is MG Chemicals as well, so not a bad brand.

  • in reply to Andrew J

    If you tin all pads first, they become wobbly. It is then hard to keep your component in place.

    Tinning one pad of each component, and use that pad as the first one to solder, is an option.

    Push the component down with something (I use a pincet), then heat that single pre-tinned path.

    Your component can now no longer run away and you can solder the remaining pads.

     

    Don’t go easy on the flux. I use a lot.

  • in reply to Jan Cumps

    I only tinned one pad at a time to secure the component and that worked for me.  I’m going to try a flux paste next time as well.

  • in reply to Andrew J

    I've never used solder paste either (perhaps I should give it a go?) but I am aware it has a shelf life of typically 3-6 months at room temperatures. I'm not sure what happens to it after that and whether you can still use it. Maybe it dries into a solid block in time so you cannot get it out of the syringe.

     

    Rod

  • in reply to 14rhb

    As I understand it, it does have a shelf life - people seem to keep it in the fridge.  I read somewhere it goes off because of the IPA in it but I haven't really looked into it; I've also read that people have re-activated it by mixing IPA back into it but who knows. 

     

    You can buy it in tins as well as syringes - I guess it would depend on the amount you used as to what you got.  Anecdotally, I've read that syringes can be awkward as it tends to drag it around, but again I have no experience - I expect it's like all the other YouTube videos where people make it look dead easy!  With a tin, you could use a cocktail stick or craft knife.  I suppose you could syringe a blob out and then apply it the same way.

     

    Anyway, I guess if you never try it, you'll never know; it's always a learning experience image

  • in reply to Andrew J

    Good points, the cocktail stick is always a nice cheap solution to so many engineering problems. If you try out the solder paste in some shape or form I'd be interested to hear how you get on.

     

    Rod

  • in reply to 14rhb

    I am no expert but have kept it in use for up to about a year at room temperature.  The problem is that it dries out and becomes hard to apply with time even though the joints look OK.  I had one syringe where I noticed separation after a year or so.  Note that this is my hobby, not for commercial use. I have always bought it in a syringe.  I usually squirt some out until it looks fresh and then apply it with a plastic toothpick if not using a stencil. I have a friend who always uses stencils and buys it in small tins. He has also kept it in use up for a year or so.  I keep it sealed up tight by capping the syringe and then putting it in a sealed plastic bag with air expelled.

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  • in reply to 14rhb

    I am no expert but have kept it in use for up to about a year at room temperature.  The problem is that it dries out and becomes hard to apply with time even though the joints look OK.  I had one syringe where I noticed separation after a year or so.  Note that this is my hobby, not for commercial use. I have always bought it in a syringe.  I usually squirt some out until it looks fresh and then apply it with a plastic toothpick if not using a stencil. I have a friend who always uses stencils and buys it in small tins. He has also kept it in use up for a year or so.  I keep it sealed up tight by capping the syringe and then putting it in a sealed plastic bag with air expelled.

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