Article not Q: How to clean off rosin flux

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
In performing these tests I'd like to point out that I didn't operate under laboratory conditions. I know none of you are likely to do so when cleaning flux off of your hands or a board, so there's no point in me putting in the extra effort to do so. I was careful to ensure that every precaution was taken to ensure that no reasonable variable was left unaccounted for.

If you'd like to see more tests with different things, you're welcome to conduct them yourselves and post a reply here. Alternatively, I might be willing and able to do so.

Test conditions:
Hot water: 90F - 98F (32.2C - 36.7C )(Just below a temperature that would be painful to work with.)
Cool water: 55F - 60F (12.8C - 15.6C)
Scrubbing force: 21.5oz (610g) - 24oz (680g) (You'd consider this as moderate pressure when scrubbing.)
Area of scrubbing head (toothbrush): 1.2in (30.5mm) x 0.4in (10.2mm)
Toothbrush type: Firm
House temperature: 74F - 78F (23.3C - 25.6C)

All cleaners selected are nonabrasive (for the easily confused, an abrasive cleaner could damaged the electronics and PCB).
All methods prescribed online were attempted, although of course, the "dish washer and dish detergent method" became "the toothbrush and dish detergent method" because using a dishwasher for some cleaners would leave the other cleaners at a disadvantage. Likewise, no ultrasonic cleaner was used either.
The method of cleaning was identical for all but the alcohol, acetone (aka. nail polish remover), and scrubbing bubbles which had to be reapplied between scrubbing methods due to evaporation or lack of product retention in the brush. Three scrubbing methods were used, each for 10s and then a rinse with the specified water under a normal tap was performed. Only circles should be necessary as it is the most effective and covers the other methods well. For completeness I also used vertical and horizontal scrubbing.
The PCB had no components on it when these tests were being conducted so that a lack of surface contact with the brush would not affect the results. It did have some left over solder on it.
The flux was applied and then I waited till it dried before doing any testing. This process had to be repeated several times each time the board became clean.
It's possible that whenever I write "A little" came off that the flux simply couldn't take the scrubbing anymore or that I scrubbed a little harder that time (about 31.7oz (900g)) is about the amount of force you need to remove it without any cleaner), not that the cleaner had any affect (which is what I'm testing for).
I did not let the cleaners soak for any great period of time, about 5 to 15s. I don't expect much change if I altered that (and only a few call for it), but you never know.
I chose not to use soaps like Dial because they're not recommended online, they are not detergents so they're unlikely to be effective, and I didn't have a good selection anyway.

I have close ups of all the cleaners used in case my description and general cleaner pictures are unclear.

Here are the results:
ProductCleaning effectCleaning effect
Hot waterCool water
Clorox dish detergentA littleA little
Palmolive Ultra OxyNo effectA little
Palmolive Ultra StrengthNo effectA little
Ajax Ultra Vinegar & LimeNo effectNo effect
Windex Original with ammonia-DNo effectNo effect
Clorox Foaming Glass CleanerNo effectNo effect
Kaboom OXI-CleanNo effectNo effect
Scrubbing BubblesWorksWorks
Lysol Power Bathroom CleanerNo effectNo effect
Topcare AcetoneWorksWorks
Alcohol 70%WorksWorks
Alcohol 91%WorksWorks
For those cleaners that worked, the temperature of the water didn't make much of an effect, so the following are done only at one temperature which I didn't record.



Next is the "bathe and rinse method" where I use those cleaners that seemed to dissolve the flux and apply and rinse them:
ProductCleaning effect
Alcohol 60%Needs addition soap of some kind for full effect.
Alcohol 91%Works
AcetonePCB is clean, component pads are still dirty.
Scrubbing BubblesNo effect
I used these cleaners on my hands to get the flux off of them:


ProductCleaning effect
Alcohol 60%No effect
Alcohol 91%*Works
Acetone*Works
Scrubbing BubblesWorks
* On a hot day (84F, 28.9C) this will not work (I have tried it), because the alcohol will evaporate too quickly. The same applies to the acetone.



As an aside, if you ever want to know where you missed when washing your hands you can use some flux and Scrubbing Bubbles to find out.

Finally, I took my container with flux inside of it and washed the outside to get the flux off (the pictures are of a different bottle of the same product). The Scrubbing Bubbles worked, but did not get it all off. I ended up using the 91% alcohol, but even that was hard because of the buildup in the crevasses in the bottles lid which none of the working cleaners could properly penetrate.


Conclusions:
People report multiple successful methods with glass cleaner, dish detergent, and alcohol. Only one of those methods worked for me. So, why do they work for them? The higher pressure of the water coming out of the dishwasher's jets when washing could easily clean the flux off. The same applies to an ultrasonic cleaner. The detergent just ensures that the flux goes down the drain as opposed to a different location in the dishwasher.^ In the case of the mirror cleaner I can only guess that the person was using a cleaner I don't have, or they are using more force then I am.

^ Please don't use a dishwasher for both dishes and PCBs that use lead in some capacity.


Mod: Removed Duplicated images.E
 

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jpanhalt

Joined Jan 18, 2008
8,459
1) You seem to have a lot of duplicate pictures. Why?
2) "Alcohol" describes a class of chemicals, not a specific one. Was it benzyl alcohol?
 

Janis59

Joined Aug 21, 2017
965
For my experience the most effective ever, just touch and all is shiny clean is amylalkohol, however it is enormously smelly (for pears). Next strong is toluene but carcinogenic, acetone but very harmful about liver, of course dichloretane tetrahydrofurane and dimetylether what all are poisons, but cheap and 3/4 effective is isopropylalkohol. At least it is some 10 fold cheaper as typical vine sprit. Ah ya, may try with buytylacetate ot better etylacetate - thus all the series of "solvent 647, 646" etc. Rather good result in low toxicity gives a pine resin terpentine.
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
Isopropyl alcohol is the type I used
When I posted I did not have any duplicate images. This maybe a fluke of the editor.
Now I'm missing 2 images. 1 of the side of my bottle of flux, the other was of 4 of the cleaners I used. I'll repost the latter.DSCF7424a.jpg

I don't have any of the chemicals you mention @Jasis59 , except the isopropyl alcohol I already tried. As it would be stupid for me to buy them just for this test I'll leave it to others to experiment with them.
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
Also, the flux I was using was a liquid. If you use a jelly flux, like I see a lot of people using today, you might get different results.
 

jpanhalt

Joined Jan 18, 2008
8,459
I may have misread the images. There are still 2 views of the flux.

You seem to have validated that 91% isopropyl alcohol and acetone work. 60% isopropyl alcohol sort of works , but not as good as 91% works.

Scrubbing bubbles "works." Scrubbing bubbles is the new addition to what is widely accepted. According to its MSDS, it contains 5 to 10% each of isobutane and diethylene glycol monobutyl ether. NVR's description says the flux can be removed with "petrol." I suspect that means a hydrocarbon solvent of which isobutane would be considered one. It is low boiling (-12°C), which probably causes the bubbles. The latter compound (monobutyl ether) is a pretty good solvent in its own right (https://en.wikipedia.org/wiki/DEG_monobutyl_ether ).

If you tested the products in sequence on the same board, there might be some additive properties that would not be observed with a single product.

If you are in a mood for editing, I would focus your article on Scrubbing Bubbles. You might mention for perspective that other household products were tried and were not effective. Then compare Scrubbing Bubbles to 91% isopropyl alcohol and include before and after pictures of pcb's cleaned with each after soldering. Do not use them sequentially on the same section of a pcb.
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
I posted 2 pictures of the flux bottle. They are from different angles. Likewise, in case there was some debate about the PCB used I posted pictures of both front and back.
In the case of the particular product having "A little" effect then you might be correct about the additive properties. But I was careful to retest, or I happened to use a fresh side, when a product was effective.
The focus of my article was not to promote the Scrubbing Bubbles product, but instead to try the methods others recommend. Only as an after thought did I try the Scrubbing Bubbles and other products.
 

Janis59

Joined Aug 21, 2017
965
RE:<<I don't have any of the chemicals you mention @Janis59 >>
May say the same about trade names You refer. Simply each continent have different trade names, that is reason why I used the chemical nomenclature names instead. Chemistry have identical names everywhere.
But generally, idea to substitute active solvents by different home-soap mixtures is very very kidish.
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
I had removed the components prior to testing. One or more parts were defective. I chose to do it this way because it allowed me to work without the chance that a component was in the way of the brush, the water, or the cleaner.
 

atferrari

Joined Jan 6, 2004
3,628
I had removed the components prior to testing. One or more parts were defective. I chose to do it this way because it allowed me to work without the chance that a component was in the way of the brush, the water, or the cleaner.
So, to clean a board that I just finished to assemble, to ensure a proper cleaning of the rosin flux, I should take all the components out and then the bottle of a bathroom cleaner of sorts... Not a realistic scenario from your part, methinks.

Two days ago, in the lack of IPA, I did quite well using "alcohol etílico" (whatever it translates to you). Had to use quite a lot, let us admit.
 

jpanhalt

Joined Jan 18, 2008
8,459
Two days ago, in the lack of IPA, I did quite well using "alcohol etílico" (whatever it translates to you). Had to use quite a lot, let us admit.
Google translates "alcohol etílico" to ethyl alcohol ("drinking alcohol"). I prefer that to IPA for flux removal as do others. Like IPA, ethanol is adversely affected by water. Thus, its usual concentrations of 70% (for antisepsis) or 95% may not be sufficient -- I haven't tried it. I use absolute (100%) ethanol with a little acetone. Denatured alcohol is probably a good substitute, depending in the denaturants added. Those can vary and are largely mandated by laws and purposes for which it is sold. Methanol (wood alcohol) used to be the most common denaturant and is still used, but products sold for consumers may contain bitterants and other additives to avoid the obvious problem of people drinking denatured alcohol instead of booze.
 

OBW0549

Joined Mar 2, 2015
3,139
I had removed the components prior to testing. One or more parts were defective. I chose to do it this way because it allowed me to work without the chance that a component was in the way of the brush, the water, or the cleaner.
Removing the components before de-fluxing a board is not a realistic scenario. In real life we not only have to deal with components "in the way" but a crucial part of evaluating a de-fluxing agent or technique is assessing what effect it has on the electronic components. Without that information, your "report" is of little or no value.
 

jpanhalt

Joined Jan 18, 2008
8,459
Now that we know the author is apparently a young student, this article appears to be a "science fair" project. With that in mind, I will reiterate the design flaw of doing sequential tests on the same area of flux. The fact that some of the cleaners didn't appear to have an effect doesn't mean they actually didn't have an effect and affect the action of the subsequent cleaner. That is a very serious flaw and cannot be ignored.

Flaws that should be addressed:
1) Sequential testing as already described
2) Why is it important to remove residual soldering flux? How does flux work? What does electronic soldering flux contain?
3) Was fresh flux tested or were the tests done on residues of flux had been used for soldering? Fresh flux may be far easier to remove than flux that has undergone partial pyrolysis during soldering and contains dissolved stuff.
4) If one reviews the "contents" of the cleaners, there will be a listing of surfactants, and in some cases, disinfectants included. Most of those will be ionic, such as quaternary ammonium salts, that may linger on the PCB even after washing in water. In fact, some may even advertise a "protective" residue. Will those residues undermine any of the reasons to remove flux residue? Remember, with components on the board, it may be very difficult to remove residual cleaner under them.
 

Thread Starter

ballsystemlord

Joined Nov 19, 2018
37
Answers off the top of my head.
1) I already answered this above by pointing out that I either:
A: Used a fresh side.
B: Reapplied the flux and retested.
2) There are 3 points here. I'll address them as A, B, and C.
A: There are several reasons. I can't pull a complete list off the top of my head, but these should do: It's sticky so the board can get pieces of stuff on it and this can cause a short. It's ugly.
B: I don't know the exact chemical actions involved. From a high level view, it cleans the parts, removes some corrosion, prevents new corrosion, and enables the solder to stick and flow correctly.
C: Rosin and an agent to keep it in a liquid state. I think it's a form of alcohol, but don't remember which. Rosin is a derivative of a particular tree sap (I don't recall which tree).
3) My original post contains the information. I applied the flux and allowed it to dry. I then cleaned the board. No soldering was done.
4) Considering that most, if not all, of the tested products don't contain a list of ingredients (and people discussing the removal of flux never even listed the product that they used, much less the chemical that did the actual cleaning), it was pointless to try to verify this one way or the other.

@OBW0549 @Everyone who keeps saying my tests were not real world enough. If I actually soldered, if I actually left components on the board, my tests could not be repeated!!! Watch this video:
Notice that he keeps warning that he had to "do this" or "not do that" even though you'd do it in the real world (Like leaving the cases side on!) so that he could get repeatable tests. He said he could only test with that one case because of air flow. He said there were a million other things he could mention, but chose not to and you shouldn't worry about it.

I did worry about it. I did type it all out above. I did mention it. I did make it reproducible. You can repeat these tests yourself and you should get the same results. I'll even tell you the ordering I did it in so you can do it differently.

As for cleaning off the fresh flux vs. flux and whatever it picked up from soldering, yes, there will be a difference. I don't know how much, but if the cleaner removes the rosin, and rosin is flux and flux has contaminants in it then the cleaner should remove the contaminants also.
There's always a chance that a chemical reaction took place which causes part of the rosin to change form, but not being a chemist, and wanting a reproducible testing method, makes me have to use the simple method I used.
 
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