Cleaning flux residue

[MudAndSnow]

Isoprop alch will loosen the flux but that doesn't remove it from the board.

I do this:
1 - scrub with brush and isoprop
2 - wipe off brush and pcb with kimwipe
3 - lay new kimwipe on pcb and then use brush to push kimwipe into tight spots

Kimtech wipes:
https://www.digikey.com/product-detail/en/mg-chemicals/830-34155/473-1118-ND/1278230

Brushes (I cut the bristles to make it stiffer):
https://www.digikey.com/product-detail/en/mg-chemicals/855-5/473-1048-ND/949490

[nanofrog]

The last Kester i bought from CML Supplies came unusable, too thick and dry. Do not know if they perform any quality inspection when repackaging. Will not buy from them anymore.

I've never run into this from them thus far, so good to know (have made my few orders during the winter).

FWIW I buy Kester's RF741 flux from typical distributors, but it's not been repackaged. There are even sellers on eBay that repackage some of Kester's liquid flux products (I bought some 186 to see if it was genuine before knowing anything about CML Supply; turns out it was).

[aandrew]

I typically use isoprop alone to clean boards, but have noticed that it doesn't actually *remove* flux, just dissolve it and spread it around everywhere. I'm going to give that 1:1 acetone:isoprop a try, although I can't seem to find reasonable quantities of not-super-smelly nail polish remover. I can buy pure acetone by the gallon but that's far far far too much for what I use.

[nanofrog]

I typically use isoprop alone to clean boards, but have noticed that it doesn't actually *remove* flux, just dissolve it and spread it around everywhere. I'm going to give that 1:1 acetone:isoprop a try, although I can't seem to find reasonable quantities of not-super-smelly nail polish remover. I can buy pure acetone by the gallon but that's far far far too much for what I use.

Check the paint department of Home Depot or similar. I get it in quart sizes, but they offer it in a pint sized can too (Klean Strip brand).

[KL27x]

The last Kester i bought from CML Supplies came unusable, too thick and dry. Do not know if they perform any quality inspection when repackaging. Will not buy from them anymore.

I haven't used Kester, but the solvent used in MG 835 RA is very difficult to contain. Even in the original bottle, the solvent slowly escapes through the plastic. In smaller quantities the packaging would be even more important.

I store my main supply in a glass bottle with a thick O-ringed HDPE stopper I fabbed up after the original plastic cap to the bottle started to crack and break into pieces. That works fine, as long as you don't let the O-ring get direct contact with the flux.

[nanofrog]

I haven't used Kester, but the solvent used in MG 835 RA is very difficult to contain. Even in the original bottle, the solvent slowly escapes through the plastic. In smaller quantities the packaging would be even more important.

I store my main supply in a glass bottle with a thick O-ringed HDPE stopper I fabbed up after the original plastic cap to the bottle started to crack and break into pieces. That works fine, as long as you don't let the O-ring get direct contact with the flux.

FWIW, I store mine in amber round glass Boston bottles for that reason.

[aandrew]

Check the paint department of Home Depot or similar. I get it in quart sizes, but they offer it in a pint sized can too

I don't know why I didn't think of paint stores. I can get 1L of acetone for $10 there. Thank you!

[mmagin]

I really like using a water soluble flux to assemble everything that is washable.  I don't use an ultrasonic cleaner yet, but a good soak in 60C water with detergent, followed by a lot of hot water rinsing, final rinse in distilled/di water with a some isopropanol as a wetting agent, then forced air drying.

I'll go back and solder the non-washable parts with a no-clean or conventional rosin flux.

I don't especially like the idea of using a non-water-soluble flux and then just solvent cleaning by hand, I think it just smears it all over, probably negating the value of that step.  (Sure, a whole tank of solvent or better yet, vapor phase cleaning would be good.)  Some day I should make a test board and do some electrometer measurements to put some science to my opinions.

[ANTALIFE]

Why not just get a more liquidy flux like this:
https://au.element14.com/multicore-loctite/mfr-301/flux-mfr-301-5l/dp/1115469

and then dilute it with a thinner like IPA?

[usagi]

i use whatever flux i like without limitation or worry.

i'm lazy, harbor freight ultrasonic cleaner with branson EC gets them spotless. and takes zero effort. doesn't matter what flux it is.

[nanofrog]

i use whatever flux i like without limitation or worry.

i'm lazy, harbor freight ultrasonic cleaner with branson EC gets them spotless. and takes zero effort. doesn't matter what flux it is.

Branson EC is definitely good stuff. And if you clean a lot of boards, that's definitely the way to go.

But I don't think most of us are cleaning boards all that often; maybe 1 or 2 per week max in my case, so harder to justify (and make room for).

[usagi]

i don't clean a lot of boards. i'm just lazy so the ultrasonic does all the work for me and i don't have to lift a finger. gets the boards spotless with zero effort.

if you have the room for a loaf of bread you have the room for the ultrasonic.

[nanofrog]

i don't clean a lot of boards. i'm just lazy so the ultrasonic does all the work for me and i don't have to lift a finger. gets the boards spotless with zero effort.

if you have the room for a loaf of bread you have the room for the ultrasonic.

True, I wouldn't need a big one (think a 2.5L would be plenty). I'd love to have an Elma, but that's well out of my budget (S30H).

I'd want one with degas and sweep functions as well as heated, and the X-Tronic 3L Platinum Edition ticks the boxes for $230. Tempting, so I'll have to mull this one over as I'm on the lazy side myself.  Toss in a gallon of Branson EC, and it's still under $300. 

[usagi]

for cleaning PCBs, just heated with branson EC is all that is needed. you can manually degas.

sweep is only needed for large items in large cleaners which require heavy duty cleaning. not something needed for your average hobbyist PCBs.

HF Ultrasonic Cleaner + 20% coupon + basket
branson EC

and there you go.

[mrpackethead]

I use Henkel GC10 paste and do most of my reflow using Vapour Phase. The really nice thing about that is that the flux ends up in the bottom of the tank and not on the board.    The nasty thing about that is the periodic job of cleaning the tank, which beomces very brown and sticky after several hundred cycles.  However the result is amazingly clean boards.

[nanofrog]

branson EC

Forget Amazon. All-Spec sells the 1 gallon size of Branson EC for $33.97 (here).   

[electronics man]

I typically use isoprop alone to clean boards, but have noticed that it doesn't actually *remove* flux, just dissolve it and spread it around everywhere. I'm going to give that 1:1 acetone:isoprop a try, although I can't seem to find reasonable quantities of not-super-smelly nail polish remover. I can buy pure acetone by the gallon but that's far far far too much for what I use.

I wouldn't use acetone as it very harsh to plastics and could damage components

[electronics man]

i have found that soaking a lint free cloth in IPA and wiping the board does a good job of cleaning, also i have started using less flux in the first place.

[usagi]

I'm going to give that 1:1 acetone:isoprop a try

not a good idea. acetone destroys many plastics. ABS, polyethylene, acrylic, polycarbonate, pvc, etc.

[nanofrog]

I'm going to give that 1:1 acetone:isoprop a try

not a good idea. acetone destroys many plastics. ABS, polyethylene, acrylic, polycarbonate, pvc, etc.

Agreed.

I'd actually recommend giving an 80/20 mix of IPA or (50/50*) Denatured Alcohol with Xylene a try for more stubborn deposits. Past that, would be MEK if you can get it (MEK = Methyl Ethyl Ketone), and finally, acetone on stuff you know it's not going to solve (i.e. you'll need to test it first, but generally speaking, connectors don't tolerate it well at all).

* Klean Strip brand (not the green crap) that's a ~50/50 mix of ethanol & methanol. Regardless of the mix or brand, it needs to leave zero residue on the surface of the glass it evaporates from in order to be usable.

[eb4fbz]

If you want to clean your boards to have them free of flux residue, dont use no-clean flux solder paste, that thing is a PITA to remove. Use a water based flux instead.

[nanofrog]

If you want to clean your boards to have them free of flux residue, dont use no-clean flux solder paste, that thing is a PITA to remove. Use a water based flux instead.

Depends on what it uses for resin. Some are based on modified rosin, which can be cleaned without Herculean effort (not much different than typical rosin based fluxes, with low solids versions being the easiest to clean, even for rosin based fluxes).

It's the synthetic resin based versions of no-clean that are a serious PITA to get off your PCB's with typical hand cleaning techniques. So check the datasheets to see which type it uses, and choose accordingly. 

That said, there are standard rosin based fluxes available, and it seems TME carries such products from well known manufacturers at reasonable prices in syringes, jars, and metal tins (here). 

[chickenHeadKnob]

MG Chemicals Heavy duty Flux remover contains Ethyl Acetate, Acetone, 1,1-Difluoroethane and isopropyl. It works with reasonable aggression on rosin flux and hasn't damaged any of my boards (yet) but I am just a hobby low-time user. I don't let it soak in too long, maybe a minute, scrub with brush  and then follow up with a isopropanol rinse.

 I have heard of 20/80 % ratio of Ethyl Acetate/isopropanol as a home mix substitute.  I am not an economic nationalist however because MG Chem is Canadian my local electronics shop 60Km away has it in stock and I like to patronize them so they stay in business. Enlightened self interest you could say.

[SeanB]

I have a potted module that has been soaking in MEK for a month now, trying to soften the potting compound so I can see what this electrometer amplifier looks like ( my bets are a JFET and some resistors), and still no joy. Might have to get a little more aggressive on the solvent, but still want to have the plastic survive.

Flux residue start first with a new toothbrush, some alcohol and scrub it, then only if that fails move up to spot cleaning with more aggressive solvents in the spots only.  Generally IPA is fine for 99% of the cleaning, as you cannot get Freons any more, which were a superior cleaner.

[nanofrog]

Flux residue start first with a new toothbrush, some alcohol and scrub it, then only if that fails move up to spot cleaning with more aggressive solvents in the spots only.  Generally IPA is fine for 99% of the cleaning, as you cannot get Freons any more, which were a superior cleaner.

Indeed.  Saw that stuff in action decades ago at Martin Marietta, later becoming Lockheed Martin whilst I was there, and it was amazing. Former boss of mine told me about using at Fluke back in the early '80's as well.

Benzine is highly restricted these days IME, but getting your hands on some Toluene may actually be feasible (local paint store might have it). FWIW, it's available to me and I keep a quart on-hand. Rarely used, but still nice to have if needed.

As per removing the potting compound you mentioned, you may want to start with mechanical removal using a rotary tool of some sort (Proxxon, Dremel, air powered die grinder, ...).  Should speed up the process greatly once you find the right solvent.