Is tacky flux valid for more one year after the expiration date? - Page 1
Forum section: electronics / beginners

author: fabriciofx
author_rank: Newbie
timestamp: January 25, 2021, 08:01:01 pm
content: Hi guys!I bought from an official Amtech resealer 04 (four) syringes of tacky flux Amtech NC-559-ASM-TF with the expiration date at Dec. 20, 2020. The resealer said that the manufacturer (Amtech) ensures this tacky flux is valid for more ONE YEAR AFTER the expiration date. So, is it true? This tacky flux is valid for more ONE YEAR AFTER the expiration date?Best Regards.

author: james_s
author_rank: Super Contributor
timestamp: January 25, 2021, 08:03:58 pm
content: I have some that expired over a year ago that I'm still using. It's been working fine for me, but this hobby use, I'm not doing production work.

author: fabriciofx
author_rank: Newbie
timestamp: January 25, 2021, 08:13:04 pm
content: Hi James!I'll use for hobby too, but I tought it very strange: if is it valid for more one year after expiration date, why not the manufacturer already use it in the expiration date (so it should be Dec. 20, 2021)?Best Regards.

author: Kerlin
author_rank: Regular Contributor
timestamp: January 25, 2021, 09:32:57 pm
content: At home I have some that is kept in the freezer.It is 15 years old, it still works well.I only use it in difficult to solder situations.I only do prototypes that I use for advance testing of my professional embedded designs.I gave up on lead free even with the right tools it just don't as work well.

author: Doctorandus_P
author_rank: Super Contributor
timestamp: January 25, 2021, 10:00:37 pm
content: Expiration date is mostly a marketing ploy to sell more stuff.There were (are?) lots of medicines for example with an expiration date of a few years, and this was a big problem for people who maintain stocks for emergencies such as nuclear disasters and other big calamities, so they started doing some serious research. They found out that a lot of the medicines could be stored (and used after) 20 years or so safely, and some had an asterisk with "probably much longer, but we can't test it".Stuff like that also greatly depends on the quality of packaging. For example hygroscopic (water attracting) stuff goes bad quickly if packaging is not adequate. Just open a bag of chips and let it sit for a day or two before you eat it. And that is not due to the plastic (which lets through moisture) but to the aluminum foil barrier in the plastic (which is why the chips bags are shiny on the inside). The aluminum foil is so thin you can look though it with strong light, and still it stops (almost all) moisture. Foodstuffs sometimes have higher quality packaging to extend the expiration date.I have a 15+ year old syringe of flux that still works fine, and I just store it in a drawer. I put a needle though the "LUER" tip to prevent it from clogging up. It may be the plastic syringe that gives the ghost first."Expiration date" is often a note for "we guarantee it works up to that time" (and have not bothered to test more) and has nothing to do with when the stuff actually goes bad. And it's often overly cautios to prevent lawsuits. If it were up to the manufacturers, they will be happy to sell you a new tube of flux each month, but the problem there is the length of the supply chain. So stores would start complaining if it has "expired" before they can sell it to you. Therefore they suck a number out of their thumbs which gives stores enough time to sell the stuff, and it expires some short time later.In factories and "industrial applications" there is also a factor of tightly controlled manufacturing parameters. For example if the flux gets a bit tackier, it still works OK, but it may result in a higher fault rate during the production process, and that gets expensive quickly.Solder paste often has a quite short pot life. The solder gets out of suspension and sinks to the bottom and the flux floats on top. For industrial applications this is definately "end of life" but for hobby use you can probably just stir it a bit or add some extra (compatible!) flux to change it's consistency. AdaFruit has made some Youtube vid's about doing this.

author: thm_w
author_rank: Super Contributor
timestamp: January 25, 2021, 10:42:26 pm
content: Previous thread:https://www.eevblog.com/forum/reviews/would-you-complain-(flux)/No ones actually answered the question there or here. Without contacting Amtech I don't think you will get a firm response.Here is a quote from their solder paste though:"Use older batches of solder paste first. The batch age will be identified by the manufacturing date printed on the box or product label. If a container is opened, note the time and date on the label.Use prior to printed expiration date."So most likely reseller has no clue.

author: james_s
author_rank: Super Contributor
timestamp: January 26, 2021, 02:05:48 am
content: Expiration dates are a gray area in general, it's not like something just suddenly completely changes after a certain date. Many times it's just a somewhat arbitrary number which is used to guarantee freshness, after that date the stuff may be fine or it may loose efficacy or change in some way so it is not guaranteed. I once found a box of orange Jell-o mix in the back of the pantry that had expired almost a decade earlier and decided to make it in the name of science. The powder had caked into several solid clumps in the package but mixed with boiling water it looked and smelled fine, so I let it sit and it set up like Jell-o. Tasted it and it tasted fine so I ate more of it, didn't notice anything unusual about it. I wouldn't try that with similarly expired dairy or meat though.

author: wizard69
author_rank: Super Contributor
timestamp: January 26, 2021, 04:17:46 am
content: In some cases, the medical world for example, expiration dates are required by law. Often not a lot of test goes on beyond ensuring that something as packaged will last for the time stamped on the box.The thing that will get you is that some medical products do have very limited shelf life. So you might not know if a specific item has such a short shelf life.Now for other stuff that is much more complicated. Some things like glues do have limited shelf life, some materials really start ot degrade when the packaged is open. In the case of flux it should be rather simple to learn if an expired product is beyond us simply by trying it out.

author: Nusa
author_rank: Super Contributor
timestamp: January 26, 2021, 11:31:52 am
content: So far as the manufacturer is concerned, the product isvaliduntil the expiration date. They'd never say otherwise for legal reasons.In practice, of course, the product isusablefor some time after the expiration date. How much longer will likely depend on storage conditions more than anything else.The difference between usable and valid may be subtle when translated, so perhaps that's where this is coming from. When talking about expiration dates of products, the word "valid" is used to mean the warranty time until the expiration date.

author: BrokenYugo
author_rank: Super Contributor
timestamp: January 26, 2021, 11:32:25 pm
content: I'll hazard a guess the worst that can happen is something screwy in the chemistry that gives it a corrosive or conductive residue. Polish a piece of copper clad and give it a test if you're worried, but as everyone else said most expiration dates are more of a suggestion.

author: Jeff1946
author_rank: Regular Contributor
timestamp: January 27, 2021, 12:48:31 am
content: Also manufacturers assume worst case storage conditions, especially with meds. Might be left in a car in the summer in say, Arizona.

author: uli12us
author_rank: Contributor
timestamp: January 27, 2021, 09:13:39 am
content: I think, without proof, the expiration date is only valid for mixed solder paste. From amtech you can buy solderpaste with separate Flux and solderballs. In this case they write, that the shelflife begins with the day of mixing the parts together. The problem is that the plastic cases are not completely tight against gas so oxygen migrate inside and solvent outside. If you have a glass or tin container and a protecting gas instead the plastic cans or syringes, the shelf life should be 10s of years.

author: Ian.M
author_rank: Super Contributor
timestamp: January 27, 2021, 10:50:33 am
content: Flux in small syringes is going to loose solvents and gain moisture from ambient humidity, as it ages, as the seal at the cap and plunger will always be imperfect. As it ages past date expired, it may become harder to apply and increasingly tend to spit more when heated, but typically there's no drastic change in behavior or effectiveness.Solder paste is a different matter - the surface area of the fine solder balls is very large compared to their volume so there's a lot of exposed tin (or tin/lead) for the activators to attack. The rate of reaction is very small, but anything that can clear off oxides in a fraction of a second at soldering temperatures will tend to do the same over many months at room temperature. Atmospheric oxygen diffusing into the paste will keep on oxidizing the fresh solder surfaces until the activators are pretty much used up. Therefore expired paste will become increasingly full of dross and will have lost much of its flux activity, hence the typical poor results from long-expired paste.

author: uli12us
author_rank: Contributor
timestamp: January 28, 2021, 02:34:35 pm
content: Not only the seal, each plasticcase is permeable for oxygen, dissolved water and other gases. Not much, but its enough to degradethe content. If you buy a larger amount of the Flux and put it in a jam jar, add a heavy gas like argon up and close the cap, than the flux should last nearly forever. The seal on the cap is as well a sort of Plastic or rubber, but thats only few mm² in comparison to more than 10 cm² from a syringe. Or eventually more practicable, put 5 or so syringes in a big Jar from olives, cucumbers, pickles, sausages add protecting gas and close it. The only possibility to degrade is a reaction of the solo parts of the flux or solder paste together.

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2021, 06:24:41 am
content: Quote from: Ian.M on January 27, 2021, 10:50:33 amI used some expired paste for several years by mixing a little fresh liquid flux into it immediately prior to use. This was for personal hobby projects of course, I would never advocate doing this assembling products for sale.