Can Solder Go Bad?

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After finding some old solder lying around, you may be wondering if it is still good to use. Can solder go bad? Knowing the answer to this question can be the difference between a quality soldering joint and a faulty one. 

Solder can go bad, but a specific solder’s shelf life depends on several factors: 

  • Alloy type
  • Solder Type
  • Brand
  • Storage

Some solder types have a short shelf life, while others can be good for an indefinite amount of time.

If you want to know more about the shelf life of solder and how to maximize it, then keep on reading! 

Solder Does Go Bad

You may have been surprised to find out that solder can, and does, go bad. This is why solder manufacturers often include an expiration date on the packaging. To get the best soldering joint results, you should always make sure that your solder has not gone bad. 

There are several factors that determine how quickly your solder will go bad, and the following sections will explore each of them:

  • Shelf Life Based on Solder Formula 
  • Solder comes in several forms, and the shelf life of your solder will depend largely on this. 

The following list will explore different formulations of solder and how they affect shelf life: 

  • Solder Preforms: Solder preforms do not expire, even though they may begin to look a little dull after a while. The appearance of solder preforms is not indicative of its functionality. When they are stored properly, you can expect them to be usable for an indefinite amount of time.
  • Flux-Pens: Flux pens have a limited shelf life. According to the technical data sheet at Kester, they can last up to 2 years from the manufacturing date. However, if the solder is improperly stored, its shelf life may be shortened. It’s important to keep this solder in a room that is between 50 and 77 degrees Fahrenheit
  • Solder Paste: The shelf life of solder paste is also limited. It is known to last around six months, but only when it is refrigerated at the right temperature for the duration of use. If it is not refrigerated at all, this will drastically shorten its shelf life. 
  • Solder Powder: Solder powder has a similar shelf life as solder paste does. You can expect your solder powder to last around six months
  • Solder Wire: If you are using a solder wire that was made with an alloy that is higher than 70% lead, then you can expect the solder to last a couple of years from its manufacturing date. This solder has a relatively short shelf life compared to other types of solder. 

For solder made from non-lead alloys, the shelf life will be a bit longer, often lasting three or more years from the date it was manufactured. 

Note: The time frames mentioned above are general estimates. You may find that the specific solder product that you’re working with has a different expiration date. 

How the Brand Affects Solder Shelf Life

There may be slight variations in how to solder manufacturers make their solder. This is why some brands of solder seem to go bad quicker than others. 

Some people say that they are able to use their solder for decades without a noticeable decrease in quality, while others have problems with their solder after the first couple of years. 

When it comes to solder brands, Kester is the best. Their solder products last longer than competitors’, in addition to the fact that their solder is easy to work with and produces high-quality joints. 

Signs Solder is Bad

If the expiration date on your solder is not visible, there are some clear signs that you can look out for. The following signs indicate that solder is bad: 

  • The solder wire or preform is oxidizing. With exposure to oxygen and moisture over time, solder can show signs of oxidation and corrosion. Solder made of a combination of tin and lead has a higher tendency to oxidize as it gets older than some other solder types. 
  • The solder doesn’t wet the parts efficiently. Old solder does not work properly. If, after you have heated the solder, it is not spreading like you’d expect it to, this is a sign that the solder is past its prime. 
  • The solder doesn’t finish well. If, after you’ve melted and shaped the solder, the shape of the soldering joint changes into a random shape, you may need to go out and get more solder. 
  • The solder paste is separating. If your solder paste no longer has the consistency of a paste and looks nonuniform, there’s a good chance that it shouldn’t be used.

If you are still not sure whether you should toss your solder, give the manufacturer a call. They can ask you specific questions about how you stored the product, when you bought it, how you used it, and more. Then they will let you know if you should continue to use it. 

How to Store Solder to Maximize Shelf Life

Storage requirements for your solder will depend exclusively on the specific type of solder you are working with. The best advice to follow when storing solder is to read the packaging that your solder came in. If it came from a legitimate company, it would have storage instructions on the packaging. 

However, there will be situations where you can’t access the storage instructions. In which case, you should do a google search of the brand and type of solder you have. You should be able to locate instructions easily that way. 

In the event that you don’t know the brand of solder, you can follow these general guidelines for solder storage: 

  • Store solder paste in the refrigerator: Solder pastes generally need to be refrigerated, and you’d do well to do so immediately. The longer your solder paste sits out, the shorter its shelf life will be. If you need to thaw it, 
  • Store solder wire in a dry place: Solder wire has the tendency to corrode, so make sure you store it in a place that doesn’t get wet. You can place your solder wire in a plastic bag and seal it completely, so that moisture can’t possibly get in.
  • Store solder wire at the right temperature: It’s imperative to store solder wire at a moderate temperature, where it doesn’t get too hot or cold. A general guideline to use is above 50 degrees and below 80 degrees. 

Note: If you are serious about protecting your solder preforms, you can invest in a dry nitrogen box. This will help to get rid of any oxygen and reduce the chances of oxidation.

The Problem with Using Expired Solder

Some may read the above and wonder why they shouldn’t use expired solder. There are a couple of good reasons why bad solder should be avoided, and this section will examine those reasons. 

Expired solder is not fun to work with, as it may not perform correctly. You may have a hard time getting the solder to adhere to the connections or to wet the connections sufficiently. This results in frustration and wasted time. 

After struggling to get the solder to behave, you could end up with poorly soldered joints. In which case, you will have to determine whether to redo the connection. 

Final Thoughts

Not only do you know that solder could potentially go bad, but that it depends largely on the type of solder you have and how you’ve stored it. We hope that this article serves as a helpful guide to help you with your solder-related questions.  

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If you liked this article, have a look at my other articles I wrote about the topic!

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