I*really* want to remove Kester 44 flux - what do I need to buy?

[cvanc]

I know you don't have to remove it but I just hate looking at it if nothing else. Plus it gets in the way of rework.

What will get this off nice and clean? I'm constrained for the need for 'hobbyist quantity' and don't want a gallon can of anything. Thanks...

[Kim Christensen]

I use a sharpened chop-stick to scrape/pick the bigger chunks off. Then I use 99% isopropyl alcohol with a brush and scrub/wash/flush the rest away. I'll also use a paper towel to soak up any now dirty alcohol while tilting the PCB so it runs toward the towel pressed against the PCB. This minimizes the cleaning area if the PCB already has large clean areas.

[GLouie]

I think I've found pure ethanol ("Everclear" sold at USA liquor stores) a bit better than the 91% isopropyl I can get from the drugstore at removing Kester 44. I'll hold the board vertically over a little tray of alcohol and dip a toothbrush in it and scrub the board a bit. However, I think the alcohol gets contaminated immediately, so when it dries it leaves still some flux residue. Then I'll dribble some fresh alcohol over the board with a fresh toothbrush a couple of times. Then some spot cleaning with an alcohol soaked rag and cotton buds. It's still never perfect, but it's cheap.

[jpanhalt]

Use ZEP Heavy Duty Acrylic Floor Sflripper diluted one part to 3 parts total with water and an ultrasonic for about 1 minute.

[nctnico]

I've found ethanol works better as flux remover compared to alcohol for cleaning up small bits of rework. But using real flux remover works even better but that stuff is in my shed for cleaning entire boards.

[johansen]

I've found ethanol works better as flux remover compared to alcohol for cleaning up small bits of rework. But using real flux remover works even better but that stuff is in my shed for cleaning entire boards.

without knowing what "real flux remover" you are talking about,

your post is a waste of space.

[jpanhalt]

I agree with the comments about ethanol; however, there seems to be some ambiguity.  Without a modifier, "alcohol" in casual conversations usually refers to ethanol.  Of course, an alcohol is simply a class of organic chemical.  I don't believe methanol works very well for flux.  E85 fuel may work.  I tried it once, but I haven't pursued that path.

Like others, I use ethanol for spot cleaning.  I sometimes mix it with about 25% acetone.  I prefer absolute ethanol versus 95% (Everclear), but absolute is harder to find.  At retail, I would not consider either inexpensive. 

ZEP floor stripper costs $10 to $14 per gallon at American box stores.  Considering the dilution, it is hard to beat for price in gallon quantities.  It can be saved between sessions if you use it frequently.  I don't, so I usually just discard after use.

[johansen]

acetone is a gamble, it can dissolve stuff you don't expect.

methanol has an undesirable smell, ethanol of course its denatured with stuff you shouldn't drink (but i have found out by experience that eucalyptus oil does not give me a hangover)

dishwasher detergent is very cheap, i have heard from many across 4 decades of folks that you can just toss your boards in the dishwasher.

alconox is also reasonably cheap and will probably work to remove flux very well in an ultrasonic cleaner. if the only thing you need to remove is the flux than 60$ of alconox should last you 100 pounds of solder.

[tooki]

I know you don't have to remove it but I just hate looking at it if nothing else. Plus it gets in the way of rework.

What will get this off nice and clean? I'm constrained for the need for 'hobbyist quantity' and don't want a gallon can of anything. Thanks...

A spray can of flux remover? Techspray, Electrolube, Microcare, and many others sell them. Look at the SDS and you should find a blend of one or more alcohols and some other solvent (often a very light petroleum like hexane). Some are heavy-duty versions containing acetone, but Kester 44 is fairly easy to remove, so I would avoid acetone since it can be aggressive to plastics.

There are also more expensive ones that use nonflammable solvents instead. IIRC 3M makes this.

My favorites so far are from Electrolube, thanks to the orange terpenes they contain, which give them a pleasant odor.

[GLouie]

acetone is a gamble, it can dissolve stuff you don't expect.

methanol has an undesirable smell, ethanol of course its denatured with stuff you shouldn't drink (but i have found out by experience that eucalyptus oil does not give me a hangover)

dishwasher detergent is very cheap, i have heard from many across 4 decades of folks that you can just toss your boards in the dishwasher.

alconox is also reasonably cheap and will probably work to remove flux very well in an ultrasonic cleaner. if the only thing you need to remove is the flux than 60$ of alconox should last you 100 pounds of solder.

At least in the USA, you can get ethanol meant for human consumption, which I assume is not denatured. I see Everclear is available in 151 and 190 proof (95%) at a liquor store. At work, we were able to order gallons of what was labelled as 200 proof ethyl alcohol USP, no mention of adulterants. I believe one use would be for food grade potions such as vanilla flavoring.

[Grandchuck]

Just curious ... will turpentine work?

[macboy]

For Kester 44 i have always just used 99% IPA. I place paper towel (kitchen roll across the pond) over to the area to be cleaned, saturate with IPA, scrub with a brush (toothbrush works) through the paper towel. Don't rub the paper towel around, literally scrub through it so it barely moves. The flux residue will be almost entirely trapped in the paper. Lift it off and discard then repeat once more and the board will be quite clean.  This works much better than just pouring IPA onto the board and scrubbing... That loosens and dissolves the flux, but then where does it go? The paper towel traps it.

[tooki]

For what it’s worth, despite the fact that tons of people do so, Kester itself says that “IPA will not clean the residues off the surface of the circuit board after the soldering process.”

This suggests that invisible ionic contaminants or activators remain (which otherwise would have remained entombed in rosin). Probably no big deal for most circuits, but still, I think it’s wiser to use flux remover.

[macboy]

For what it’s worth, despite the fact that tons of people do so, Kester itself says that “IPA will not clean the residues off the surface of the circuit board after the soldering process.”

This suggests that invisible ionic contaminants or activators remain (which otherwise would have remained entombed in rosin). Probably no big deal for most circuits, but still, I think it’s wiser to use flux remover.

Most or all solvent based flux removers will do no better. Salts don't dissolve into alcohols or petrochemical solvents. Kester specifically recommends a saponifier, a water based cleaner that will literally convert the organic rosin into soap, and will wash away the halide salts. The ZEP floor finish stripper recommended above is supposedly such a product and is available to consumers.
When using the paper towel method I described above, I don't get any visible residue left behind (especially not that white gunk commonly encountered) and for most purposes of mine, that's good enough. I absolutely agree that for sensitive precision circuits, a better cleaning is needed.

[eetechTom]

I've never used the ZEP floor stripper, might have to give it a try. Listed "Hazardous components" on the SDS for the ZEP stripper are: 2-butoxyethanol 111-76-2 >= 10% - < 30% and 2-aminoethanol 141-43-5 >= 5% - < 10%. I have typically used a flux remover such as MG "Flux remover for PC boards", followed by a IPA rinse. I see the MG product contains Ethanol, isopropanol, and ethyl acetate.

[jpanhalt]

I have typically used a flux remover such as MG "Flux remover for PC boards", followed by a IPA rinse. I see the MG product contains Ethanol, isopropanol, and ethyl acetate.

That's the difference between water-based removers and nonaqueous removers.  When you get a white residue, like between the pins of a fine-pitch IC, you will appreciate what Kester has said about needing a saponifier.  The chemical compositions of both versions of flux remover are quite similar across the spectrum of manufacturers.  There are subtle differences in formulations and differences in naming the very same thing.

[joeqsmith]

I use ProClean.

https://www.microcare.com/en-US/Products/Alcohol-Enhanced-Flux-Remover-ProClean

[Calambres]

Mr. Carlson swears by "Lacquer Thinner" for flux removal. The problem I find is that what it is known for that in North America is apparently not the same here in Europe, that is, I do not know *exactly*what that "lacquer thinner" is: turpentine?, white spirit? anything else?

[tooki]

For what it’s worth, despite the fact that tons of people do so, Kester itself says that “IPA will not clean the residues off the surface of the circuit board after the soldering process.”

This suggests that invisible ionic contaminants or activators remain (which otherwise would have remained entombed in rosin). Probably no big deal for most circuits, but still, I think it’s wiser to use flux remover.

Most or all solvent based flux removers will do no better. Salts don't dissolve into alcohols or petrochemical solvents. Kester specifically recommends a saponifier, a water based cleaner that will literally convert the organic rosin into soap, and will wash away the halide salts. The ZEP floor finish stripper recommended above is supposedly such a product and is available to consumers.
When using the paper towel method I described above, I don't get any visible residue left behind (especially not that white gunk commonly encountered) and for most purposes of mine, that's good enough. I absolutely agree that for sensitive precision circuits, a better cleaning is needed.

In my experience, mixed-solvent based flux cleaners do a far better job than straight IPA or ethanol.

The fact that straight IPA in an ultrasonic bath produces far better results than when hand cleaning suggests that the salts are somewhat soluble in IPA, and that redeposition (or just adhesion) are the real issue.

[johansen]

For what it’s worth, despite the fact that tons of people do so, Kester itself says that “IPA will not clean the residues off the surface of the circuit board after the soldering process.”

This suggests that invisible ionic contaminants or activators remain (which otherwise would have remained entombed in rosin). Probably no big deal for most circuits, but still, I think it’s wiser to use flux remover.

Most or all solvent based flux removers will do no better. Salts don't dissolve into alcohols or petrochemical solvents. Kester specifically recommends a saponifier, a water based cleaner that will literally convert the organic rosin into soap, and will wash away the halide salts. The ZEP floor finish stripper recommended above is supposedly such a product and is available to consumers.
When using the paper towel method I described above, I don't get any visible residue left behind (especially not that white gunk commonly encountered) and for most purposes of mine, that's good enough. I absolutely agree that for sensitive precision circuits, a better cleaning is needed.

In my experience, mixed-solvent based flux cleaners do a far better job than straight IPA or ethanol.

The fact that straight IPA in an ultrasonic bath produces far better results than when hand cleaning suggests that the salts are somewhat soluble in IPA, and that redeposition (or just adhesion) are the real issue.

Its just dilution, the ultrasonic works because you have to fill it with a liter or 3 of liquid.

Company i work for has two ultrasonic cleaners, one for prewash and you change the ipa when it turns pink from loctite, and the final wash which gets dumped into the pre wash on a regular basis. Evaporation makes most of thr ipa disappear. Final wash gets changed when you start to notice a sheen on the boards.

[BrokenYugo]

Mr. Carlson swears by "Lacquer Thinner" for flux removal. The problem I find is that what it is known for that in North America is apparently not the same here in Europe, that is, I do not know *exactly*what that "lacquer thinner" is: turpentine?, white spirit? anything else?

Impossible to say beyond "solvent or blend thereof you can still sell suitable for thinning lacquer" without seeing the can and looking up the SDS. Same problem with people who say "brake cleaner" works well, which one? I've seen more or less straight acetone, hydrocarbon blends, acetone-hydrocarbon blends, and that's just the non chlorinated options in broad strokes. You have to be very picky using solvent products off label like this.

[tooki]

For what it’s worth, despite the fact that tons of people do so, Kester itself says that “IPA will not clean the residues off the surface of the circuit board after the soldering process.”

This suggests that invisible ionic contaminants or activators remain (which otherwise would have remained entombed in rosin). Probably no big deal for most circuits, but still, I think it’s wiser to use flux remover.

Most or all solvent based flux removers will do no better. Salts don't dissolve into alcohols or petrochemical solvents. Kester specifically recommends a saponifier, a water based cleaner that will literally convert the organic rosin into soap, and will wash away the halide salts. The ZEP floor finish stripper recommended above is supposedly such a product and is available to consumers.
When using the paper towel method I described above, I don't get any visible residue left behind (especially not that white gunk commonly encountered) and for most purposes of mine, that's good enough. I absolutely agree that for sensitive precision circuits, a better cleaning is needed.

In my experience, mixed-solvent based flux cleaners do a far better job than straight IPA or ethanol.

The fact that straight IPA in an ultrasonic bath produces far better results than when hand cleaning suggests that the salts are somewhat soluble in IPA, and that redeposition (or just adhesion) are the real issue.

Its just dilution, the ultrasonic works because you have to fill it with a liter or 3 of liquid.

Company i work for has two ultrasonic cleaners, one for prewash and you change the ipa when it turns pink from loctite, and the final wash which gets dumped into the pre wash on a regular basis. Evaporation makes most of thr ipa disappear. Final wash gets changed when you start to notice a sheen on the boards.

Nope, it’s not just dilution. Aside from the fact that filling a normal ultrasonic cleaner with flammable solvent is a bad idea for multiple reasons, including the hazard and the amount of solvent needed (not a problem if used constantly.) Which is why I don’t do that. I fill the bath with DI water, then put the board in a small container or baggie containing a minimum of IPA.

I’ve actually used the baggie-with-a-small-amount-of-IPA to remove white residue that earlier hand cleaning failed to remove.

Also, the white residue issue is well documented, and it is known to NOT be an issue of dilution, or use of too little solvent.

[nctnico]

I've found ethanol works better as flux remover compared to alcohol for cleaning up small bits of rework. But using real flux remover works even better but that stuff is in my shed for cleaning entire boards.

without knowing what "real flux remover" you are talking about,

  Geez, some people really need their hands to be held all the time.  It is simple: you go online to your favorite electronics dealer and order a bottle / can which says 'flux remover' after reading what kind of flux types the flux remover can remove.

[johansen]

I've found ethanol works better as flux remover compared to alcohol for cleaning up small bits of rework. But using real flux remover works even better but that stuff is in my shed for cleaning entire boards.

without knowing what "real flux remover" you are talking about,

  Geez, some people really need their hands to be held all the time.  It is simple: you go online to your favorite electronics dealer and order a bottle / can which says 'flux remover' after reading what kind of flux types the flux remover can remove.

I prefer trichloroethylene.

[helius]

MG Chemicals Safety Wash II:
https://www.digikey.com/en/products/detail/mg-chemicals/4050A-450G/14563348
The SDS lists isohexanes, ethyl alcohol, isopropyl alcohol, and ethyl acetate. It is "effective at cleaning ionic flux residues".
There are other comparable products from Microcare, Chemtronics, Techspray, etc. The "safety" aspect is that none of the ingredients are harmful, unlike those containing chlorinated solvents. The odor is mild, slightly fruit-like due to the ethyl acetate. This is probably all you need unless your flux is baked on with hot air, in which case a stronger acetone mixture might be required:
Heavy Duty Flux Remover:
https://www.digikey.com/en/products/detail/mg-chemicals/413B-425G/9657986
You need to be careful when using acetone as it can melt many plastics. But it is superior at removing black crusty flux residues, cigarette smoke, and soot from burned components. The smell of this product is much stronger, not nasty necessarily, but somewhat unpleasant. It is still very safe toxologically.