Liquid flux storage - Page 1
Forum section: electronics / beginners

author: ckambiselis
author_rank: Regular Contributor
timestamp: September 05, 2014, 02:38:02 pm
content: Hello everyone,While watching one of Daves old videos I found out that you have to store solder paste in the fridge, something as an SMD noob didn't really come to mind.So now that put me in question, since I ordered two 100ml bottles of Rosin Based, No Clean, Liquid Flux, is liquid flux stored in a specific environment (tightly closed bottles of course)?ThanksOscar

author: Simon
author_rank: Unknown
timestamp: September 05, 2014, 02:46:07 pm
content: I'm no expert but the flux is the reason solder paste is stored in the fridge.........

author: nanofrog
author_rank: Super Contributor
timestamp: September 05, 2014, 03:59:39 pm
content: Just store liquid flux in a cool dry place.

author: DanielS
author_rank: Frequent Contributor
timestamp: September 05, 2014, 04:10:02 pm
content: You "need" to store solder paste in a fridge because the solder paste is just a colloidal suspension of micron-scale solder beads with flux and possibly other substances to help with delivery/application. The low temperature increases the liquid components' viscosity so the paste does not separate as quickly.If you leave solder paste at room temperature for a few days, the flux and solder will separate, the solder will clump together and render the paste unusable unless you have some method of re-mixing it without crushing the solder powder into a solid.

author: Simon
author_rank: Unknown
timestamp: September 05, 2014, 04:12:01 pm
content: So are you saying that it needs to be kept cold to stop it separating and not to "keep" the flux ?I think I'm going solder paste and stencils as soon as I can

author: DanielS
author_rank: Frequent Contributor
timestamp: September 05, 2014, 11:57:30 pm
content: Quote from: Simon on September 05, 2014, 04:12:01 pmMost plain fluxes do not have specific storage requirements.With flux pens, cool/cold storage may help with preventing their tips from drying if you do not use them regularly.

author: ovnr
author_rank: Frequent Contributor
timestamp: September 06, 2014, 12:03:07 am
content: Quote from: DanielS on September 05, 2014, 04:10:02 pmNo. Just no. I've had both cheap eBay solder paste and more expensive stuff (which issomuch nicer) sitting on my bench for months. Some solder pastes are spec'd to >6 months at room temperature; if in doubt, just stir it up before using it.

author: mazurov
author_rank: Frequent Contributor
timestamp: September 06, 2014, 01:55:16 am
content: Quote from: DanielS on September 05, 2014, 04:10:02 pmYou need to stop buying this crap. Normal paste won't separate - ever, even when hot and liquid, right to to the point when metal component starts melting and clumping together. It is also thixotropic, which means it will become more viscous with time even when stored in the fridge. "Some method of remixing" is called large flat screwdriver and works very well for this purpose.I store production paste in the fridge. The paste dries out more slowly (much slower than 6 months though, I have a jar of SnBi with 2008 date code which is still top notch), but you need to bring it to room temperature before using, 6-8 hours in still air or couple of hours in my pants pocket.Out of the fridge the paste tends to dry out quicker; it can be thinned with 99% IPA but it will dry out again very quickly after application. Still works OK for prototypes which are stuffed manually; you just keep a IPA-loaded Q-tip handy and touch the lands just before placing a part. I keep a jar of old paste at room temperature at all times for cases I can't wait for the good paste to warm up.I also have a half kilo of Amtech NC-560-LF (ENIG-specific formula, good for nothing; was very cheap, likely for this very reason) which I'm using as thinning agent for production Amtech LF-4300.

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 06, 2014, 05:09:59 am
content: Quote from: ovnr on September 06, 2014, 12:03:07 ambut his reasoning is a total valid. but you also right some paste speced to >6 months at room temp, but it'll probably be >6years (longer lifetime) in the fridge. i have flux laying around for years in room temp. the only diffrence i see is it become darker and darker from time to time. i guess due to the liquid part evaporating, i sometime liquify it with my "helping chemical" aka thinner, when i want to use it. conclusion is... you should store it in a very tight container in room temp. storing it in fridge, you'll need time to liquify it to room temp before comfortable use, ymmv.

author: DanielS
author_rank: Frequent Contributor
timestamp: September 06, 2014, 10:23:46 am
content: Quote from: ovnr on September 06, 2014, 12:03:07 amAnd some pastes, even those with claims of 6+ months shelf life, still ship frozen or "on ice" with express-only shipping.

author: Falcon69
author_rank: Super Contributor
timestamp: September 06, 2014, 06:14:45 pm
content: He's right,When I purchased my paste from Manncorp, they sent it packed in a sealed enveloped with a cold pack and next day air.But, the OP was talking about flux, just plain flux, no solder involved.I've had my flux pen sitting on my desk for over a year now, and it still works fine.

author: timb
author_rank: Super Contributor
timestamp: September 06, 2014, 07:53:48 pm
content: Liquid flux is fine at room temperature 99% of the time. There are a number of various formulations however, so check the label on the bottle or pen if you're unsure.Sent from my Smartphone

author: DanielS
author_rank: Frequent Contributor
timestamp: September 06, 2014, 08:09:53 pm
content: Quote from: Falcon69 on September 06, 2014, 06:14:45 pmAnd as I said in my second post in this thread (fourth from the top): most fluxes have no special storage requirementsAs far as flux pens go, I have one that started caking up only a few weeks after its first use. Either the cap was not on tight enough or since it was new, the core of its tip might not have soaked all the way through and that may have let the surface dry up enough to make it difficult to use until the whole tip got wet again. Hot weather and sun exposure probably did not help it either

author: Falcon69
author_rank: Super Contributor
timestamp: September 06, 2014, 08:51:55 pm
content: yea, i'm sure hot weather and dry temperature have a lot to do with it.I wander though if storing the flux pen like you would wine bottles would prolong it's life, like the fluid would keep the tip moist (like wine keeping the cork moist).Did you have your pen sitting up right (tip facing up, so all the fluid floats to bottom.)

author: Galaxyrise
author_rank: Frequent Contributor
timestamp: September 06, 2014, 09:39:13 pm
content: In addition to temp, there is the question of storage vessel. I highly recommend storing the flux in a bottle with a needle. I went for years using the original bottle and brushing it on, but I switched after I finally messed up and tipped the bottle over with the cap off. And now I feel the fool for not having switched earlier, the needle is so nice to apply the flux with! My needle occasionally clogs, but it opens right up if I heat the tip with my iron.Just store it sealed and I suspect any room temperature will do. As others have mentioned, storage temps should be on the bottle. (Or datasheet)

author: DanielS
author_rank: Frequent Contributor
timestamp: September 07, 2014, 03:02:47 am
content: Quote from: Falcon69 on September 06, 2014, 08:51:55 pmIt was lying flat on my workbench.I hadn't used it in a while since last time and there has been quite a few warm days since as well but when I checked it earlier today, the tip was still wet. I would edge my bet on the felt tip not getting a thorough soak the first time I used it - I only had the problem with the tip getting stuck and crusty/dry when I opened it for use the second time after getting it.

author: nanofrog
author_rank: Super Contributor
timestamp: September 07, 2014, 04:32:49 am
content: Quote from: Galaxyrise on September 06, 2014, 09:39:13 pmFWIW,BonKotemakes some pen type applicators that might be of interest (different tips that screw onto the same pen body).BON-102 for example.

author: pcm81
author_rank: Regular Contributor
timestamp: September 05, 2025, 03:09:10 pm
content: Just to add a data point to this thread: I have a 15 year old gallon of Kester 2331-ZX flux that i store in a sealed jar (the 1 gal jar it came in) in my garage in Florida. Liquid fluxes tend to evaporate over time, higher temperature accelerates this process, but having it in a sealed container prevents evaporation. Pastes are usually recommended to store n a fridge or freezer to prevent evaporation of solvents used in them. Pastes and gels have allot less of solvent to spare than in liquid flux, so are more sensitive to drying out. Having said that, i have a jar of acid flux paste (plumbers type) and after 10 years of sitting not in the fridge, it still looks good.