Solder of the Ages


Salutations SparkFunions (are we going to get sued for that?)!

Before I get to the real meat of the post, I'd like to make an announcement. In case all of you aspiring techno-freaks haven't noticed, we've got a new position open in the engineering department. Two, in fact. So are you tired of working for "the Man"? Need more dogs in your workplace? Looking for a job where the words "that's not how you're supposed to use that" get uttered more than once a day? Well, this could be the chance of a lifetime! Check out our jobs section and drop us a resume.

Now on to other things. It's recently come to our attention that (dramatic pause) solder can possibly go bad with age. "What's that?," you say. How did we come to this realization? Before you freak out about all of your SpakFun toys being made with inferior materials, let me say that we have a continuously rotating stock of solder paste and everything's cool. Refrigerated, actually. You gotta do that. No, we came to this by way of an interesting email exchange with a gentleman named Jim Optimus Prime (names have been altered to protect the innocent). Anyway, Jim did a bunch of legwork on this and we want to share his efforts.


What Jim may look like

Does solder have a shelf life? Actually, we never really thought about it. We all use solder that is perhaps 5-10 years old, but does this cause some ill mannered demon to activate? We really aren't sure. Says Jim on the subject:

"Before I emailed SparkFun, I did some online searches on the topic. Summarized the answer is yes, no, and maybe. Solder manufacturers say yes solder has a shelf life (~ 6 months for leaded solder, ~1 year for non-leaded). They have to certify that their solder will have specific characteristics when used by a company to make, say, 10,000 radio units. Large companies buy solder in bulk. They get the solder manufactures to re-certify the solder as their solder stocks age.

"There are a number of hobby users online telling how they still use solder 10+ years old without problems. There are an equal number that talk about all the problems they have with old solder.

"The maybe is the overall conclusion I came to before contacting SparkFun to see if you had a similar take on the question of solder shelf-life. Solder shelf-life centers on oxidation and the deterioration of the rosin core. Tin/Lead solder can oxidize as it ages. Proper storage can slow the process (and no, sitting in a junk drawer isn't considered proper storage). The more oxidation on the solder, the less effective the rosin. The rosin has to overcome the oxidation from the solder as well as whatever oxidation on the parts being soldered. Sometimes with old solder you just can't get the solder to properly "wet" the parts. If solder oxidation is really bad, the way the solder melts and re-solidifies changes, creating a whole new series of problems."


I don't see a problem here.

Jim continues: "The rosin core discussion is a greater mystery. It composition has changed over the years. Some types continue to work. Some types deteriorate. The older versions of rosin were a harsher mix than today and can create corrosion problems.

"For now, I came to the conclusion you can use old solder, but you add another potential problem to your project. In my next SparkFun order I'm going to get a small quantity of fresh 63/37 solder from SparkFun and use it to compare the characteristics of the new solder to the older solder I have on hand. Until I know better I'll stick with buying limited quantities of fresh solder for any project. I'd only use old solder for the 'will this work, what do I need to change' projects. When I reach the stage for a working version I think its best to use 'fresh' solder."

Seems like sound advice, yes? Honestly, I've never bothered considering whether or not solder goes bad. To me, everything I build is a work-in-progress and I'll use anything and everything within eye-shot as raw materials. Heck, I once built a shortwave receiver using 40-year old plumbing solder and that still works. So while I definitely recognize the need to have good solder where large numbers of commercial-grade electronics are concerned (and medical-grade! Nobody wants the machine that goes "ping" to be built with 40-year old solder), I'll likely continue to use whatever is in reach for my own projects.

Thanks for the note, Jim, and thanks for schooling us.


Comments 26 comments

  • Definitely came across this problem last night. Solder that comes in those ‘Computer Repair Kit’ cases. Decent gun for rare soldering, but solder is done after 2-3 years. Not sure how long it was on the shelf before it shipped though :-(

  • That’s interesting. I never knew solder could expire.

  • Nice read, kind of interesting should i ever stumble upon some really old solder…
    Nice reference to Monthy Python by the way! Love that one… :-)
    Youtube:
    http://www.youtube.com/watch?v=NcHdF1eHhgc
    “Ping!” at 0:57
    Cheers

  • I have had a spool of Kester rosin solder for a least 15 years now and I not noticed any degradation. I use it to solder even the smallest SMD’s without any issues. I never even thought about it possibly going bad until reading this thread. You mileage may vary I guess.

  • I recall some discussion (maybe online, maybe at work), not necessarily about un-used raw materials, but solder already applied to circuits. Specifically toward the phenomena called “tin whiskers”; small bits of solder which break off already soldered connections.
    http://en.wikipedia.org/wiki/Whisker_(metallurgy)
    This also devolved into some arguments about not using lead free solder in critical application, since it just hasn’t has as many years in service and studied as thoroughly.
    Something to chew on. I’m not making satellites but I want my stuff to work for a few years and not burn down my house.

  • Well, from the Kester datasheet for my solder’s flux (Flux “88”), it has a shelf life of 3 years, which would make my spool expired since I got it about half a decade ago. It still works for me though, and I doubt I’ll get through that spool any time before a few decades has past, so I’ll stick with it. If I really need more flux I’ve got a bottle or two of Kester 1544 sitting here as well. You can get a GALLON of that stuff for about $50 shipped, though I bought a much smaller amount for my own needs.

    • You make a good point, the expiration date is not like the flip of a switch on the flux’s ability to perform, similar to an expiration date on a bag of chips doesn’t mean the chips go instantly stale on that date. The activity of the flux begins to diminish at some point in time from the date of manufacture and companies like Kester use expiration dates to ensure that users of their product are within that timeline. This ensures happy customers, but doesn’t mean that the flux isn’t still usable after that date.
      A few years ago, I was part of an analysis where we took an expired cartridge of solderpaste and ran print tests with it every month. We did not start seeing undesirable results until the past was 19 months past it’s expiration.

  • Proper shelf storage would only slow oxidization. but for ultimate solder storage you should keep your solder in a jar of mineral oil in your fridge. Your solder should keep forever because how could something oxidize in a area where there is no oxygen. but this is really just for people that buy large ammounts of solder but dont really use it much or need to store solder for a long time. a ziplock bag would be fine for everything else

  • I am using a spool of solder that’s at least thirty years old, I wasn’t even around when it was made and it still works fine, it says on the top of the red spool: “Fry’s metals”, my Dad has had one for 35 years, still works fine. There’s some of the 30 year old solder on every electronics project I’ve ever made, never had a problem with it. shelf life of six months? Ha!

  • It’s already been said, but solder does NOT have a shelf life, flux does. Any flux cored solder will have an “activation quality” shelf life. It will still be usable as long as you use a good flux with it. In other words, feel free to use expired flux cored solder as long as you use a non-expired flux with in. Flux plays a vital role in soldering. The metals are just there for the party……..

  • The flux is what has a shelf-life, the metal in the solder lasts nearly forever. For instance, the bars they use for wave solder won’t have an expiration date but the flux does and is often refrigerated to last longer.

  • I would like to bring up a great alternative that I have used for years. FLUX. I have used flux on EVERY soldering job I have done within the last 10 years and am always happy with the results. I have noticed that the rosin core does degrade over time, but if you use flux on every project it no longer becomes an issue. I get stronger connections with less solder and in much tighter places because of flux. I bought a large tub-o-flux that is kester brand a LONG time ago and it is still in great shape. heat it up slightly, and you can easily pack some in a clean hypodermic needle to get to small places. to use later with the tip covered of course, roll it between your hands slowly it will pick up the heat and come right out with no problems.

  • If only I was born a few years later I would no longer fall in the “seasoned” engineer category. Then I would apply for the job in a heartbeat!

  • So, if solder does go bad with age, why doesn’t used solder in assemblies go bad ?

    • The two things that would cause a problem with old solder would be the loss/degrade of flux and oxidization on the outside of the solder. Once you have the solder joint the flux has already been used and served it purpose of cleaning. Oxidization should only happen on the outside and not effect the connection of the joint already made. You may run into problems when working on older solder joints though, possibly contaminating the joint.

  • Regarding the job openings, do you take foreign people?
    I am from Panama, and currently pushing more paper than a man is ever supposed to. There are no places here that would offer anything similar to your job opening which would allow mi to do what I love most. I work on this stuff every day at home, if I could get paid for it…
    … by the way, if I got a faulty sensor(dont really want to mention the brand here), what should I do?

    • I’m not Pete-O but like Pete-O I do hire for SparkFun positions and have been approached before by international folks wanting to come join us.
      The major sticking point is the work visa. If you’re a US Citizen, great! Otherwise, you’ll have to demonstrate that you are a cut above all the US citizens who may apply and be so desirable that it’s worth all the extra time, money, and effort to bring you on board. This will not be easy. That said, I sincerely hope you can find something in Panama that stimulates your electronic creativity and allows you to tinker!
      As for your faulty sensor it’s best to contact techsupport@sparkfun.com.

    • How about hiring Canucks (AKA Canadians)? I could send in Sparky Jr. in my place. :)
      http://sparkyjr.ning.com/

      • Sparkfun could look a the bigger picture. Why settle for North America, Sparkfun should take over the continent! For that they would require a spanish/english speaking, PIC programming Agent: ME!!!
        Panama would offer the best geografic expansion hub…. Did i mention i live there? hehehehe
        … oh, I studied in the U.S. I dont know if that helps.

  • My 7+ year old Kester 60/40 Rosin core wasn’t as ‘flowey’ as the new Kester I ordered.
    I dunno if it’s going to help, but I keep my roll in a zip-lock baggie now.

  • If the problem is oxidisation one could always use a reducing agent. This is probably a little excessive especially considering the cheapness (the word doesn’t look right) of a new tube/roll of solder.

  • Some metals oxidize only on the surface (such as aluminum or copper), while others (such as iron) develop a cancerous form of oxidization. I suspect that lead/tin are in the first camp. In this case scraping off the top layer of oxide with a scotchbrit pad would probably remove the problem. If the end of the solder is sealed (as it would be if melted during the last use) the flux inside couldn’t be exposed to air and should not oxidize. If you add extra flux during soldering (which you should when soldering SMT parts) this would also reduce the issue. I should also point out that soldering old parts has it’s own problems with oxidization!

  • The picture, btw, is of acid core solder. I’d highly suggest not using that in any electronic device. :)


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