3
\$\begingroup\$

I've been soldering on and off for quite some time, and I've always used whatever Radio Shack had available. Now, I'm about to attempt a bit of SMT soldering (by hand), and I'm having some difficulty sourcing appropriate combinations of diameter and composition.

The general consensus seems to be that Sn63/Pb37 solder is easier to work with than 60/40 solder, and it seems to be widely available. One wonders, in fact, why 60/40 solder continues to be as common as it is today.

When it comes to SMT, the general consensus seems to be "smaller is better", and I'm probably looking for 0.015" diameter solder, if I can get it.

If I wanted to buy in quantities of one pound, I could locate appropriate solder, but it is quite expensive in quantities that high, and I am fairly unlikely to use that much solder in less than a decade or two. I tried Allied, Grainger, Mouser, and even Amazon.com without success.

The closest thing I could find, in fact, ends up being available from Radio Shack: 0.015" diameter 62/36/2 silver-bearing solder.

What I don't know, however, is how this compares to "normal" 63/37 solder. Is this just as good, almost as good, or better? Is it the "right stuff" to use for everyday PTH and SMT soldering (other than it being too small for PTH)?

\$\endgroup\$
5
  • \$\begingroup\$ FWIW, I use that same 0.015" RS silver-bearing solder for SMD and through-hole work along with a 'no clean' flux pen and have had good results. \$\endgroup\$ – Craig Oct 5 '11 at 17:52
  • 1
    \$\begingroup\$ I prefer 0.031" solder for SMT. There is no reason you must use the skinny stuff... Once melted, the solder forgets size of the wire it came from. Flux is more important. \$\endgroup\$ – markrages Oct 5 '11 at 22:28
  • \$\begingroup\$ Solder size does not matter if you are applying it to the iron and wiping it onto the pins, a technique that often does work with SMT. On the other hand, if you use traditional soldering technique - heat the pin and pad and apply solder to those RATHER than the iron, then you need solder that's smaller than the pin pitch. \$\endgroup\$ – Chris Stratton Oct 6 '11 at 15:40
  • \$\begingroup\$ Affordable 63/37 solder: sparkfun.com/products/9161 \$\endgroup\$ – Eric Falsken Dec 5 '12 at 18:05
  • 1
    \$\begingroup\$ Just a bit of detail: 63/37 solder is called "eutectic" solder. The reason it's easier to work with is that it does not go through a plastic state when it cools, but goes directly from liquid to solid. It's that plastic state that kills you: if the joint moves while the solder is plastic you get a cold-solder joint that is brittle and doesn't conduct electricity well. \$\endgroup\$ – Pete Becker Apr 25 '15 at 11:47
3
\$\begingroup\$

I prefer the solder with 2% silver - melting point is lower and joints are shinier. Agree re.flux - you can never have too much flux.

\$\endgroup\$
10
\$\begingroup\$

Personally I use Sn/Ag/Cu solder in a 95.5/4.0/0.5 ratio. I use it for both through-hole and SMD work, and find it perfectly usable for either.

My main reason for using it is it's cheap at about £18 for 100g.

http://www.rapidonline.com/Tools-Equipment/Rapid-Premium-Lead-Free-Solder-22SWG-100G-Reel-85-6612/?sid=45a99737-fdcf-4278-82ef-0af239d9deae

With SMD it's not really the size that matters but what you do with it.

More important than the solder is:

Flux!

Get a decent flux pen and don't worry too much about the solder.

I usually prime the pads with flux, then put solder on the soldering iron's tip, and wipe it across the pads, thus depositing a nice little pillow of solder on each pad. I then add more flux, and place the component in position. Applying the right heat with a hot-air rework station then melts that solder and the component gets sucked into place with the surface tension of the molten solder.

Oh, and if it's a home-made board, invest in some Spot-On solder resist (effectively liquid latex) and some fine paint brushes.

\$\endgroup\$
12
  • \$\begingroup\$ Why, oh why, doesn't RS carry flux pens? They only have paste... \$\endgroup\$ – Mark Oct 5 '11 at 18:17
  • 1
    \$\begingroup\$ It does, but the search is terrible. RS code 425-9379 \$\endgroup\$ – Majenko Oct 5 '11 at 18:24
  • 3
    \$\begingroup\$ The point I am making though is that I am using lead free with no issues whatsoever. Yes, the melting profile is slightly different, but that is irrelevant as it's more about the flux when working with SMD as you use such a tiny amount of solder anyway. \$\endgroup\$ – Majenko Oct 5 '11 at 18:55
  • 1
    \$\begingroup\$ I agree, it's all about the FLUX. Lead vs RoHS, thick vs thin. None of that matters as much as getting a good flux, and lots of it! I also agree that water soluble is the best-- just keep in mind that most fluxes are CONDUCTIVE and must be cleaned off. This is especially true of the water soluble kind. \$\endgroup\$ – user3624 Oct 5 '11 at 20:19
  • 2
    \$\begingroup\$ @Mark - Not a bit. Neither does the lead in the 37/63 leaded solder I use for larger connections to wires: I don't eat it, heat it to its vapor point, or powderize and breathe it. The amount of metal in solder which gets metabolized by the assembler is tiny. RoHS is for reducing the prevalence of heavy metals at landfills, not for protecting engineers and users. \$\endgroup\$ – Kevin Vermeer Oct 6 '11 at 14:31
0
\$\begingroup\$

Silver solder, from what i currently think, is great for audio electronic pcb soldering (resistors, capacitors, ic's, ect...) yet takes extra patience and skill.

In the last seven years that i have been soldering, not much has even possibly compared to the "PC Work" or standard solder from Radio Shack.

Out of at least seven kinds (from companies other than r-sh.), the pc-work solder (from r-sh.) has worked the best.

That being said, i must also mention that it's not only 'shiny,' it takes less patience (fusion point about 275 deg C) than most other kinds, even when their labels say 60/40. Other kinds often take more time and either come out dull and 'pasty' and often do not have the 'fluidity behavior' of the pc-work alloy combination. This can lead to frustration, unwanted fumes, broken circuit connections, (over-heated pcbs/components), and unwanted misery.

One thing i can say, though, is that with patience, i may have a 'jem' for you.

    Sparkfun dot com.

The above website was found by me off amazon by electronics123 dot com when i was looking for a bass synth. I wanted to solder together a circuit, found one, and did it (the sound generator). I was low on solder; they have incredible instructional articles that better explain many things for us beginners/enthusiasts who find some notions challenging; they recommend a solder for their circuits (which they carry, and they have info on it); i think it contains mostly silver with a pinch of copper. It has a higher melting point and takes longer and is of better quality for audio. The time it takes is its obvious drawback, yet another important thing to know is the extra heat. If a connection requires 340 deg C, as opposed to 275 deg C, (which is an honest guess), there is risk of the extra heat damaging the circuit board or component. Some components/connections are of no worry, such as a beneficial socket-spacer for an ic (who even knew those existed?), yet some components, (in my opinion), risk damage from excess heat. Extra skill may be required to avoid over-heating components like 'glass' diodes, electrolytic capacitors, transistors (voltage regulators), or otherwise heat-sensitive components like mosfet chips [the ones in my pyle pda7bu receiver are embedded in an amazing heat sync, looks nearly 'alien'].

So, my advice is to get some solder from sparkfun dot com and use it with a soldering station. My soldering station has worked for over a year and can be changed to a specific temperature (Sunfire) - got it off amazon, it was the least expensive one and is not digital yet takes under 25 seconds to heat to its 'blinking light stage.' Get the '.99 silver' solder and try it out on a simple circuit (like: 9v+led+470ohm resistor+switch on a pcb (<- manual on/off light)). Notice the heat and the time, as well as the fluidity. If it works for you, then using solder high in silver may be best for you. From what i understand, it makes a higher quality connection for projects like audio circuits. If you want to know more, contact the knowledgeable and creative genius' at sparkfun dot com, or read some of the info on their website. I recommend their sound generator over anything else they sell, for now; the sequencer goes with it fine yet was not as important for the effort as the generator - many varieties of options can be used as a sequencer for the sound generator's single trigger button; it can hit a preferably low bass note (shook a wall). I installed a photo-resistor to the trigger and used a strobe to make a song with a consistent, tempo-changing beat; hope this helps you along your way. :)

\$\endgroup\$
3
  • 1
    \$\begingroup\$ Welcome to EESE. Thanks for helping out by answering a question and sharing your experience. I just want to point out in case you didn't notice that this question is 9 years old and already has an accepted answer. I recommend you look for newer questions that don't already have accepted answers to build up your reputation. \$\endgroup\$ – mkeith Nov 27 '20 at 6:09
  • \$\begingroup\$ I will try to always check when a question on a product or idea was posted; thank you for noticing and your prompt reply. If a question already has an "accepted answer," I imagine we can still re-answer it so long as we are not redundant or our answer, in our opinion, adds to or corrects the answered question; thank you again for the advice. I will try to pay better attention. I plan to answer a few questions, as time permits, especially since I am sure my own questions will arise as I further pursue circuit development. [I try not to forget to check the date of product questions.] \$\endgroup\$ – jcm3rockstar Nov 27 '20 at 6:39
  • 1
    \$\begingroup\$ It is OK to answer questions that already have an answer. But you will probably get more upvotes if you answer newer questions that don't yet have an answer. Anyway welcome. Hope you enjoy the site. \$\endgroup\$ – mkeith Nov 27 '20 at 6:41

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.