Author Topic: Myth busting solder-flux cleaning with isopropanol alcohol  (Read 131955 times)

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Offline astroschmidt

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Myth busting solder-flux cleaning with isopropanol alcohol
« on: July 21, 2012, 03:12:15 pm »
Dave,

could You bust (or confirm) another myth about cleaning PCBs from the solder flux.

I see it often that it is adviced to clean your PCB after soldering with isopropanol alcohol because

a.) the solder flux could oxidize the copper in the long run

b.) the solder flux is not as high-ohm as a cleaned PCB and can create high-ohm connections on the PCB


I believe that it is much better to NOT clean the PCB from (pure rosin!) solder flux, because

a.) Isopropanol is aggressive to some plastics and can intrude into parts creating undesired effects.
It can e.g. dissolve polystyrene capacitors AFAIK

b.) By this dissolving of other materials a potential low-ohm film is spread over the PCB while the rosin itself is very high-ohmig when left untouched at the solder joints.

Please comment

Roger
 

Offline mikeselectricstuff

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #1 on: July 21, 2012, 04:10:51 pm »
It depends on the flux. Some fluxes are corrosive over time, although not generally the ones you's normally use. Even good flux, if contaminated can become corrosive - I had a bottle some a while ago that was OK for a while but then started corroding things a few days after application.
Some types will also absorb moisture, so if you have high impedance stuff it can cause long-term problems.
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Offline astroschmidt

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #2 on: July 21, 2012, 04:43:34 pm »
It depends on the flux. Some fluxes are corrosive over time, although not generally the ones you's normally use. Even good flux, if contaminated can become corrosive - I had a bottle some a while ago that was OK for a while but then started corroding things a few days after application.
Some types will also absorb moisture, so if you have high impedance stuff it can cause long-term problems.

Hi Mike,

in the days of youth I first used solder intended for plumbers because nothing else was available at the local warehouse and I didn't know about the deifference.
That one of course corroded everything through its halogenated solder.

But I never had any issue with electronic solder with a (non-halogenated) pure rosin flux-core solder.
Even when I sometimes open a case with a 2 decade-old PCB soldered by me I never saw any corrosion.
This is also what the german wikipedia-entry says about rosin ("Kolophonium" as it is called in German)
http://de.wikipedia.org/wiki/Kolophonium#Elektronik.2FL.C3.B6ten
There they even say it is better to leave a layer of rosin on the PCB because it is more protective against corrosion than a cleaned PCB.

Couldn't it be the same with moisture, that a thin layer of rosin protects high-impedance stuff more than it harms?

BTW I only speak of pure rosin flux.

Kind regards

Roger
 
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Online free_electron

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #3 on: July 21, 2012, 04:48:44 pm »
rosin based flux is generally not conductive unless you baked it at such high temperatures it turned caramel color or black ...

no-clean flux is just that. no-clean. you can leave it on. no problem

-low solids flux is a flux that under a correctly controlled process totally evaporates. if there is a lot of residue your process is wring and you need to remove it as it can be conductive

- water soluble flux needs to be removed simply because it is hygroscopic and leaves a soap-scum like residue on the board that is conductive.

isopropylalcohol does not attack plastics ( apart from one kind of transparent material that just falls apart like a smashed car window. very weird)  ipa is perfectly safe for electronics.

There are some very agressive fluxes like RA that must be removed as they contain acidic substances. RMA is the most prevalent rosin flux ( RMA ; Rosin Mildly activated. RA = rosin activated )
it is actually not the rosin that is the flux , but another substance in the compound. the rosin is just a carrying vessel for the real active ingredient.

flux works on two fronts :

When activated ( temperature controls this, most fluxes kick in around 100 degree C ) flux is a very reactive element that want to bind with oxygen molecules. It is so reactive it can strip oxygen molecules that have already bonded with copper. So it converts copper oxide back into copper.

The second thing it does is lower the surface tension of the solder. this lets the solder 'wlow' over the to be soldered surface.

under a correct process the flux is given some time to activate and do its work before soder is applied. wave solder machines apply  warm flux to the board first, let it soak for a few seconds as the conveyer moves over a warming plate and the flux is now activated.  then it goes through the solder wave where the flux totally evaporates leaving a clean board.

solder paste works in a similar way. when doing reflow you have a rampup to flux activation, a hold phase to ledt the flux do its work and evaporate for almost 75% and then you ramp up to liquid phase where the solder melts and flow on the remaining flux. if reflow is done correctly there is little or no flux residue and board wash is not required.

boards that have been reworked ( manually touching 1 component ) will have residue and those need washing with iehter solvent based flux removers or water.

the flux in solder wire is a different composition than the flux found in pens or liquid form ( for starters the flux in solder wire is dry powder .. ) it is also more agressive as it has a shorter time to do its work.

and then there are specially formulated fluxes like the gel fluxes or tacky fluxes. those are formulated for rework and the idea is to use a lot of it. so much that there is residue and you need to remove it.
The same goes for pen fluxes. Those are for rework. fluxes for wavesoldering come in 50 gallon drums ... not something to have on your workbench ...

in general :
when doing handwork you will need to clean the board unless no-clean is used
when doing reflow or wave correctly ( note the usage of the word correctly ) there will be no need to clean the board afterwards unless in special circumstances like medical or military stuff where they are extremely anal ( with perfectly fine reasons) .

if you care about the esthetical aspect : clean it up

every kind of flux has its own specific flux remover. some flux removers are broad spectrum. like chemtronics flux-off.
and flux remover need a LOT of remover to wash a board. simply squirting a tiny bit on does not work. it just leaves goopall over the board like a sticky film. you need ot squirt some on , let it soak for 10 seconds, scrub with brush then spray more on to wash the 'spent' stuff off. let the board drip out , spray once more.
apply warm air to dry. NEVER EVER blow air using your mouth . as the flux evaporates it cools down the board which pulls moisture out of the air. human breath contains saliva that is acidic .... you don't wan that on the board.
So : warm air is the way to go. use your reflow hot air gun.


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Offline astroschmidt

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #4 on: July 21, 2012, 08:03:17 pm »
Thanks free_electron for thorough explanation.

Roger
 

Offline ftransform

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #5 on: July 29, 2012, 05:03:47 am »
I use trichloroethylene break cleaner.
 

Offline dcel

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #6 on: July 29, 2012, 06:49:30 am »
For rosin cored wire solder, I always clean the flux off the board with lacquer thinner and a wooden stick Q-tip. The reason I said always is because when I started repairing amplifiers, I made the repairs and the damn thing oscillated crazily. Took some time to determine the flux at the repair sites were the problem. Also had the same problem in a large mixing console channel as well. Now, I make the repair, clean the board while the joints still warm ( flux removes easier when still soft ) and then proceed with power up and testing. I have used alcohol before (all that I had avail.) and it takes too freaking long to clean the flux off the board. I wouldn't 'wash' the board in lacquer thinner, it eats plastics, I'm just spot cleaning.

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Offline bradleytron

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #7 on: July 29, 2012, 02:50:00 pm »
I use trichloroethylene break cleaner.

Just a note to say that I think this stuff is CARCINOGENIC, please check the MSDS sheets for more detail.
 

Offline T4P

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #8 on: July 29, 2012, 03:31:56 pm »
I use trichloroethylene break cleaner.

da shit dangerous bro

For rosin cored wire solder, I always clean the flux off the board with lacquer thinner and a wooden stick Q-tip. The reason I said always is because when I started repairing amplifiers, I made the repairs and the damn thing oscillated crazily. Took some time to determine the flux at the repair sites were the problem. Also had the same problem in a large mixing console channel as well. Now, I make the repair, clean the board while the joints still warm ( flux removes easier when still soft ) and then proceed with power up and testing. I have used alcohol before (all that I had avail.) and it takes too freaking long to clean the flux off the board. I wouldn't 'wash' the board in lacquer thinner, it eats plastics, I'm just spot cleaning.

Chris

Eh ... really depends on what sort of alcohol you use. usually pure alcohol (IPA) is pretty smooth for my rosin fluxes
 

Offline ftransform

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #9 on: July 29, 2012, 05:08:58 pm »
Just don't get any on your hands (appropriately picked protective gloves) and do it down wind (fan). The stuff is not flammable, so do not worry about motor sparking. This stuff removes the flux like magic and evaporates very quickly. Unfortunately all the awesome solvents are bad for you. I bet liquid butane would work well but unfortunately the canned stuff has a slight odor and its rather flammable.

I would at least dry my IPA with some kind of dehydrator or use the anhydrous stuff (either methanol or ipa) sold as gasoline dehydrator... I remember I fried a video card once after giving it a wipe over with a high concentration of IPA because I did not dry it for long enough. You need to be careful with the dry times on that solvent. I'm pretty sure I used the 95% stuff too...
« Last Edit: July 29, 2012, 06:08:27 pm by ftransform »
 

Offline dcel

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #10 on: August 01, 2012, 10:29:24 am »
Quote

Eh ... really depends on what sort of alcohol you use. usually pure alcohol (IPA) is pretty smooth for my rosin fluxes

99% Isopropyl Alcohol. Is Isopropanol Alcohol better as a flux remover?
Its been a while since I have used it for flux cleaning because being spoiled by the speed at which lacquer thinner takes it off. I'll have to try it again just to make sure I wasn't brain damaged when I used it before. I have used brake clean as well, but NOT that chlorinated shit, yuk, makes me gag. I use the flamable stuff at work and its much easier on the lungs, esp. with the spray and run technique. I've cleaned boards with it also, I have a special can at work just for that, it stinks but does not eat plastics.

Chris
 

Offline ju1ce

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #11 on: August 02, 2012, 12:38:03 pm »
99% Isopropyl Alcohol. Is Isopropanol Alcohol better as a flux remover?
It's the same stuff.
http://en.wikipedia.org/wiki/Isopropyl_alcohol
 

Offline Short Circuit

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #12 on: August 02, 2012, 02:15:43 pm »
IPA does not work very well for flux removal.
Although (some) flux removers do contain a certain amount of IPA,
I use Electrolube Fluxclene (MSDS), which contains 10-30% IPA (Propan-2-ol).
So there can be similarities, but not the same.
 

Offline Dread

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #13 on: August 29, 2012, 10:02:08 pm »
So what is the best brand of Flux remover?
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Offline IanB

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #14 on: August 29, 2012, 10:06:36 pm »
So what is the best brand of Flux remover?

There is probably no simple answer to this.

It's worth bearing in mind that flux cleaner does not work just by rinsing. It requires mechanical action with a stiff bristle brush (or ultrasonic tank in production environments). The flux cleaning solvent is doing a balancing act between dissolving the flux and not dissolving the electronic components. Therefore the flux cleaner cannot be too aggressive and must be fairly gentle in its action.

If you use mechanical assistance then pure IPA or pure ethyl alcohol will work fine with most fluxes.
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Offline ablacon64

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #15 on: August 30, 2012, 03:54:18 am »
I use mostly IPA but I don't like the results of IPA to clean BGA flux paste, I use Methyl Acetate, very good.
 

Offline amyk

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #16 on: August 30, 2012, 10:40:10 am »
I use trichloroethylene break cleaner.

Just a note to say that I think this stuff is CARCINOGENIC, please check the MSDS sheets for more detail.
It's classified as a group 2A carcinogen, meaning "probably carcinogenic" and thus in the same group as emissions from deep frying. I'd worry about the other toxic effects of it more than its possibly carcinogenic properties...
 

Offline Fava

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #17 on: July 25, 2018, 09:16:46 pm »
I use the Ethyl Alcohol. It clean so good than Isopropyl Alcohol. :-+
 

Offline schmitt trigger

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #18 on: July 25, 2018, 10:35:28 pm »
Unfortunately all the awesome solvents are bad for you.

Very true
And few chemicals as potent and as nasty as CCl4.
 

Offline David Hess

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #19 on: July 26, 2018, 12:47:57 am »
a.) the solder flux could oxidize the copper in the long run

I have never actually seen this happen to a point where it mattered even after decades but it is possible.

Quote
b.) the solder flux is not as high-ohm as a cleaned PCB and can create high-ohm connections on the PCB

For most circuits this will not matter.  Where it does matter, extra cleaning steps should be used anyway.

Quote
a.) Isopropanol is aggressive to some plastics and can intrude into parts creating undesired effects.
It can e.g. dissolve polystyrene capacitors AFAIK

I have never had problems with IPA and board mounted parts but some plastics are susceptible although I do not think polystyrene capacitors would be affected.  Some parts like switches or trimmers which contain enclosed areas should be sealed before washing or soldered into place later no matter what solvent is used.

Quote
b.) By this dissolving of other materials a potential low-ohm film is spread over the PCB while the rosin itself is very high-ohmig when left untouched at the solder joints.

See above.  For most circuits this is irrelevant.

IPA does not work very well for flux removal.
Although (some) flux removers do contain a certain amount of IPA,

IPA is not my first choice either but it is inexpensive and less dangerous than most of the alternatives.

The common rosin flux thinner that I have is 50/50 IPA and toluene and it works great.  For better results and when cleaning rework, I use acetone or lacquer thinner.
 

Offline T3sl4co1l

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #20 on: July 26, 2018, 01:41:29 am »


;D

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Offline chris_leyson

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #21 on: July 26, 2018, 02:15:34 am »
Best stuff I've found is Electrolube "Fluxene", seems to be mainly cyclohexane and some IPA. https://docs-emea.rs-online.com/webdocs/001e/0900766b8001ed27.pdf
 

Online james_s

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #22 on: July 26, 2018, 04:39:52 am »
I use trichloroethylene break cleaner.

Just a note to say that I think this stuff is CARCINOGENIC, please check the MSDS sheets for more detail.
[/quote

Don't drink it, just use it to wash the board. I sometimes use a dish of solvent and scrub the board off with a toothbrush.
 

Offline CJay

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #23 on: July 26, 2018, 05:39:49 am »
I've a few tins of Electrolube LFFR, works fairly well.

 Isopropyl alcohol works well too, try not to get it on your skin, it's absorbed pretty quickly and it's *really* bad for your liver...

Rosin flux is pretty stable though, the kind of kit I restore for fun is usually liberally caked in the stuff and on the few I've cleaned off the ~40 year old boards are like new underneath it, no corrosion, they sparkle.
 

Offline mtdoc

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #24 on: July 26, 2018, 06:07:14 am »
Isopropyl alcohol works well too, try not to get it on your skin, it's absorbed pretty quickly and it's *really* bad for your liver...

No, not really. It is very safe and not very toxic. You would literally have to bathe in it or drink it to get any toxic range dosage.

It is less toxic than almost any other common solvent sans water. There should be zero concern for toxicity using it to clean flux from a pcb in the usual manner.
 

Offline CJay

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #25 on: July 26, 2018, 06:21:10 am »
Isopropyl alcohol works well too, try not to get it on your skin, it's absorbed pretty quickly and it's *really* bad for your liver...

No, not really. It is very safe and not very toxic. You would literally have to bathe in it or drink it to get any toxic range dosage.

It is less toxic than almost any other common solvent sans water. There should be zero concern for toxicity using it to clean flux from a pcb in the usual manner.

It is one of the safer solvents, yes, but it's still worth trying to avoid getting it into your body if possible as it's not good for your liver. Toxicity is low but there's also cumulative damage to consider.

(don't misunderstand me, I use the stuff almost daily and know it's pretty safe but I would feel negligent not to mention the skin absorption and potential damage it can cause)
« Last Edit: July 26, 2018, 06:25:21 am by CJay »
 

Offline schmitt trigger

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #26 on: July 26, 2018, 01:45:04 pm »
I feel embarrassed when i reply to a necro-thread  :palm:

But perhaps not. The subject matter is still quite relevant.  :D
 

Online james_s

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #27 on: July 26, 2018, 03:42:54 pm »
Isopropyl can't be very dangerous, it's the stuff doctors use to clean your skin prior to giving an injection.
 

Offline KaneTW

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #28 on: July 26, 2018, 03:46:25 pm »
Isopropyl is used extensively in healthcare and cosmetics for disinfection and cleaning. Don't bathe in it or drink it and the worst you'll get is dry skin.

I wear gloves when using it because my skin gets awfully dry afterwards, but it's really not necessary.
 

Offline IanB

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #29 on: July 26, 2018, 04:06:17 pm »
I would feel negligent not to mention the skin absorption and potential damage it can cause

Isopropyl alcohol is sold in pharmacies as "rubbing alcohol" with the specific intent that it shall be rubbed on the skin. It is quite safe, and it is also "safe" to drink, in as much as it won't kill you if you do.

Are you perhaps getting it mixed up with methanol, which is in fact a deadly poison that does get absorbed through the skin and does cause liver damage?
I'm not an EE--what am I doing here?
 
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Online james_s

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #30 on: July 26, 2018, 04:30:41 pm »
Something that has bothered me is that "denatured" ethanol has (or at least used to have) methanol mixed in to make it toxic so people won't bypass the liquor taxes and drink it. If I deliberately poisoned something in order to keep people from drinking it I'd go to prison.
 

Online free_electron

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #31 on: July 26, 2018, 04:42:31 pm »
a.) the solder flux could oxidize the copper in the long run

I have never actually seen this happen to a point where it mattered even after decades but it is possible.
i've seen plenty ...

Quote
b.) the solder flux is not as high-ohm as a cleaned PCB and can create high-ohm connections on the PCB
For most circuits this will not matter.  Where it does matter, extra cleaning steps should be used anyway.
[/quote]
i've seen microcontrollers refusing to boot due to flux residue. especially the water soluble flux. that stuff is in the tens of kiloohms ...


Chemtronix flux-off .  unbeatable !
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Offline CJay

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #32 on: July 26, 2018, 05:32:18 pm »
I would feel negligent not to mention the skin absorption and potential damage it can cause

Isopropyl alcohol is sold in pharmacies as "rubbing alcohol" with the specific intent that it shall be rubbed on the skin. It is quite safe, and it is also "safe" to drink, in as much as it won't kill you if you do.

Are you perhaps getting it mixed up with methanol, which is in fact a deadly poison that does get absorbed through the skin and does cause liver damage?
What can I say, the MSDS specifically mentions it can be absorbed via the skin and that it can cause liver damage, I don't write them, I jsut read them, maybe I've misinterpreted it?
« Last Edit: July 26, 2018, 05:41:32 pm by CJay »
 

Offline boffin

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #33 on: July 26, 2018, 05:48:03 pm »
Best solution: Flux cleaner (it's not expensive, widely available). Example MG Chemicals 4140
Cheap solution: 50/50 nail polish remover and isopropyl in a tiny spritz bottle

Look at what's in MG Chemicals 4140
  • Ethanol (pure alcohol)
  • 1,1,1,2 tetraflouroethane (propellant)
  • Propan-2-ol (aka Isopropyl Alcohol)
  • Ethyl Acetate (the primary ingredient in more nail polish removers)
 

Offline helius

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #34 on: July 26, 2018, 05:49:03 pm »
An anecdote from Nobel laureate Kary Mullis about how you should interpret those warnings:

Quote
The worst thing I remember about those days of swelling middle management was when the guy who used to empty the isotope disposal buckets became the "safety officer" and suddenly got a staff, an office, and power.
Safety officers have a vested interest in interpreting everything in terms of various degrees of danger. In order to live for another day and to develop respect for the safety officer, signs were posted everywhere reminding us that everything we did was dangerous. Enclosed with every chemical is a Materials Handling Data Safety Sheet that explains its potential hazards—it's the law. The person who wrote the instructions for sodium chloride must have thought it was a mixture of sodium metal and chlorine gas rather than a completely innocuous compound that people sprinkle on foods to enhance the taste, usually called salt. Sodium and chlorine are pretty serious separately but not when combined into sodium chloride. The safety sheet described in detail the method that should be used to clean up sodium chloride: "Wear rubber boots," it advised. "Wear a respirator. A small spill can be flooded with water. Cleaning up a larger spill may require more than one person." Since I did not want anyone in my lab to suffer serious salt injury, I posted this warning on the wall. This is what happens when government agencies, who have to answer to nobody in particular, run rampant. If you want to have sodium chloride in your lab, you must have safety equipment that would be appropriate for sodium metal and chlorine gas. If you want to have it in a restaurant, you just have to have a salt shaker.
 

Online rhb

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #35 on: July 26, 2018, 05:49:35 pm »
I have now "repaired" a number of pieces of electronics by the simple act of cleaning flux residue off the PCB.

The most recent was an eBay 34401A which arrived completely wonky.   At all settings it just produced a meaningless stream of numbers on the display.  Upon opening it up I observed a 1 cm diameter spot of what appeared to be solder flux in the vicinity of one of the LM358s that perform the integration for the ADC.  The device was slightly misaligned, suggesting a prior repair.

Upon cleaning  off the flux residue with a soft brush and isopropyl alcohol the DMM performs flawlessly and is in spec to the limits of calibration using a new DMMCheck Plus.

Rosin flux is hygroscopic.  It absorbs moisture from the air.  This leads to changes in resistance and capacitance between adjacent traces.  This has become particularly problematic with the switch to 3.3 and 1.8 V logic levels.  The noise margins get very small.  I have "rep[aired" my CD player, a TV remote and 3-4 other devices just by cleaning flux residue from the PCB.  The 34401A is simply the most dramatic example.
 

Offline mtdoc

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #36 on: July 26, 2018, 05:51:03 pm »
What can I say, the MSDS specifically mentions it can be absorbed via the skin and that it can cause liver damage, I don't write them, I jsut read them.

Toxicology is all about dosages. Vodka can be absorbed through the skin and cause liver damage too...

Bottom line for IPA is that no one will ever sustain liver damage from skin absorption of IPA using it to clean flux from PCBs.  Even if they were using it with an ultrasonic bath and briefly immersing their hands in it.
 

Offline David Hess

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #37 on: July 26, 2018, 06:22:04 pm »
a.) the solder flux could oxidize the copper in the long run

I have never actually seen this happen to a point where it mattered even after decades but it is possible.

i've seen plenty ...

Quote
Quote
b.) the solder flux is not as high-ohm as a cleaned PCB and can create high-ohm connections on the PCB

For most circuits this will not matter.  Where it does matter, extra cleaning steps should be used anyway.

i've seen microcontrollers refusing to boot due to flux residue. especially the water soluble flux. that stuff is in the tens of kiloohms ...

I should have been more clear; I was only referring to rosin based fluxes.  That water soluble stuff is trouble and should only be used in production.
 

Offline David Hess

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #38 on: July 26, 2018, 06:27:32 pm »
I use trichloroethylene break cleaner.

We used to use a lot of 1,1,1-Trichloroethane which is fabulous for removing rosin flux but no more.



As far as reviving an old subject, if the EEVBlog search facilities worked, maybe it would not happen as often.
 

Offline ogden

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #39 on: July 26, 2018, 06:51:48 pm »
a.) Isopropanol is aggressive to some plastics and can intrude into parts creating undesired effects.
It can e.g. dissolve polystyrene capacitors AFAIK

Ethanol is even more aggressive (than isopropanol) to some plastics. Thou, cleaning PCB solutions usually are mix of both and not only. Good idea to check safety data sheets of popular flux cleaner. You will not get exact recipe, but pretty good understanding of contents for sure. One example I know: KONTAKT PCC
 

Offline bsudbrink

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #40 on: July 26, 2018, 07:01:50 pm »
I have now "repaired" a number of pieces of electronics by the simple act of cleaning flux residue off the PCB.
I have as well.  Several hobbyist built S-100 bus boards.  Regardless of how well stored (and these boards were well stored) rosin eventually darkens and becomes conductive.  IPA and an old toothbrush was all that was required to bring them back to life.
 

Online rhb

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #41 on: July 26, 2018, 10:44:04 pm »
I tumbled to this living in Houston when a 2nd *very* lightly used VCR died after a year.  I took it apart to see if there were any usable parts and noticed that there was rosin flux everywhere.  There was nothing usable so it went in the trash, but I resolved to test the idea the next time something died.

I *did* have to clean my CD player a second time.   The only solder flux on it was a little bit around the MCU.  But apparently I didn't get all of it and after about a year and a half it died again ("no disc").  The 2nd cleaning did the trick and it's still working flawlessly 2-3 years after the 2nd cleaning.  I'm planning on building an alcohol pressure washer using a 100 psi fuel injection pump with a distillation system so I can reuse the alcohol.

A lot of consumer gear is to difficult to disassemble, so the idea is a flexible wand I can poke into the right places and a few gallons of clean alcohol in the tank.  I work in a thrift store and we throw away a lot of stuff I think this would fix.
 

Online james_s

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #42 on: July 27, 2018, 02:52:18 am »
I never understood why thrift stores throw away so much stuff. If there was an as-is section of broken stuff that's the first place I'd look when going into one of those places and I know lots of others who would as well.
 

Online rhb

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #43 on: July 27, 2018, 11:47:47 am »
I never understood why thrift stores throw away so much stuff. If there was an as-is section of broken stuff that's the first place I'd look when going into one of those places and I know lots of others who would as well.

Space.  The volume of stuff can be staggering and I'm in a town of 7500 where most people throw things in the trash.
 

Online james_s

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #44 on: July 27, 2018, 03:38:55 pm »
I guess I'm just a different sort of customer. I completely ignore the rows upon rows of clothing and knick-knacks and head straight for the electronics section, usually leaving empty handed. The best thrift stores are the ones that have a bunch of random junk in unknown condition, I've found all sorts of cool stuff. At one place I got a neat 1970s digital clock that was marked needs repair. Turned out it's electromechanical with a shutter mechanism for the 7-segment digits, only problem was the incandescent lamps that backlight the digits were burned out. It's the only one like it I've ever seen other than a picture I found online of the same mechanism in a clock radio. Most probably just got thrown away when the (easily replaceable) lamps burned out.
 

Offline linux-works

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #45 on: July 31, 2018, 01:45:14 pm »
my first job in high school (late 70's) was at a pcb assembly house.   a very small company that had a wave solder line and they made boards for gas station pumps (the digital displays).  I had been soldering a few years already, since I started as a very young kid, but I was surprised to see them use ACID flux (I remember it being pink or reddish and very low viscosity).

we would paint a lot of the flux on the board, the board would be sent thru the wave solder machine (it was all open back then, no cage around it like you'd see in today's big pcb lines) and once it cooled, we'd would work at little kitchen-sink areas, running the whole soldered board under hot running water, scrubbing with a brush and using some kind of cleaning fluid to remove as much of the remaining flux as we could.  we knew it was acid and could not stay on the board, but the boss was convinced that this was the best solution and all joints did come out very shiney, in the end.

it really surprised me to see these handled like dishes in a sink ;)  there was even a dish rack to hold the board vertically while they air dried.

all of us were teenagers (ie, low cost) ;)  I wonder how reliable those displays were.  but the memory of that first soldering job I had will never leave me.  scrubbing boards like dishes, under hot running water - that really surprised me.  it was all low density chips and TH parts and I suppose that once the boards were fully dry, all was well.

the lesson I learned was: acid flux can be used IF you don't let it sit very long and you take great pains to remove it after the process.  but again, this was the late 70's..
 

Offline T3sl4co1l

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #46 on: July 31, 2018, 01:59:52 pm »
They probably didn't fare too well -- the metal gets etched by the acidity, inevitably trapping some acid in the pores.  Once sealed over with solder, that still shouldn't do anything; but, if the solder corrodes through, or there's a sneak path through the porosity to an exposed surface, it will fail, some day.

The active ingredient is usually zinc chloride, a deliquescent salt and Lewis acid.  The former means it greedily absorbs moisture from the air, until hydrated to the point it forms a saturated solution.  The latter means it hydrolyzes (breaks down by water), giving HCl (a traditional [Bronsted-Lowry] acid) and a zinc hydroxide crust.  In both cases, the solution encourages electrolytic corrosion, and the acidity accelerates it further.

Tim
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Offline linux-works

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #47 on: July 31, 2018, 02:07:25 pm »
I don't know if the company did a 'sell and run', or if they knew the products would start to fail after X amount of time.  maybe the boards were only meant to last a certain amount of time.  back in the 70's, we didn't have quite the 'disposable' mentality of electronics that we have today; things that broke would be repaired, most likely.  the company didn't appear to be a 'sell and run' kind of thing; the owner seemed to be doing what he felt was the best thing for the process.

it would have been interesting to go back and find out how well the product did.  maybe our scrubbing and cleaning really was enough.  once the boards came off the line, it was less than an hour later that we were removing the acid residue.

I would not repeat this in today's world, of course.  just relating an old past experience.

fwiw, I've had tours of proper high-end pcb assembly houses and the size of the machines used just to clean the boards are larger than my whole living room space ;)  we could not see what was going on inside that machine, but the boards that came out were clean as could be.  modern tech can do a seriously good job at making pcb's, as long as the customer is ok paying for it!
 

Offline David Hess

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #48 on: July 31, 2018, 02:32:33 pm »
For precision analog boards, I remember where we had to install a reverse osmosis dishwasher to wash the board *before* assembly to reduce leakage but RMA flux and hand scrubbing in flux remover was completely sufficient.
 

Offline linux-works

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #49 on: July 31, 2018, 03:12:29 pm »
speaking of cleaning, when I get a batch of boards with HASL from pcbway (for example), I've found that there is some kind of coating on the solder that makes it really hard to work with.  scrubbing hard with IPA before I even start populating the board seems to work well.

first few boards I made, using pcbway board, were aweful until I realized this.
 
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Offline boffin

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #50 on: July 31, 2018, 03:40:53 pm »
I always give boards a quick wipe with flux cleaner before starting.  makes your life so much easier
 

Offline grantb5

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #51 on: September 06, 2018, 03:46:00 pm »
Anyone using a dehydrator?  I make small boards (HASL hot air surface leveling, not PB free) and solder using no-clean Kester 245 but for mainly cosmetic reasons I like to clean the boards. Mainly I use IPA but sometimes reach for MG 4140 or similar.  I've noticed with the high humidity we have lately that it's like there is water forming or at least that dried water look on the boards. Someone mentioned a no-heat dehydrator on Amazon but no details so I was wondering if some kind of dehydrator would help.  Or blowing/heaing maybe? My heat shrink gun is too hot I think to use and probably a hair dryer is static central.  Anyone use a food dehydrator or is a PCB one available for $100 kind of range?
 

Offline IanB

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #52 on: September 06, 2018, 04:19:18 pm »
Anyone using a dehydrator?  I make small boards (HASL hot air surface leveling, not PB free) and solder using no-clean Kester 245 but for mainly cosmetic reasons I like to clean the boards. Mainly I use IPA but sometimes reach for MG 4140 or similar.  I've noticed with the high humidity we have lately that it's like there is water forming or at least that dried water look on the boards. Someone mentioned a no-heat dehydrator on Amazon but no details so I was wondering if some kind of dehydrator would help.  Or blowing/heaing maybe? My heat shrink gun is too hot I think to use and probably a hair dryer is static central.  Anyone use a food dehydrator or is a PCB one available for $100 kind of range?

How might a dehydrator help here? As soon as you take a board out of the dry atmosphere it will get humidified again.

If you have some kind of filmy appearance on the boards after cleaning, I think that means there is residue left behind and the board is not properly clean. You should try extra rinsing with very clean solvent, maybe even de-ionized water. Remember that solvent after cleaning must not be left to dry in place as it will not physically remove dirt that way. Dirt must be washed off and carried away with copious rinsing.
I'm not an EE--what am I doing here?
 

Offline alsetalokin4017

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #53 on: September 06, 2018, 04:25:03 pm »
Desiccator?

Put sodium hydroxide pellets in the bottom to absorb moisture. Evacuate for even better performance. Reactivate the moist NaOH by baking in oven.

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Offline nanofrog

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #54 on: September 06, 2018, 04:27:44 pm »
Don't just use a solvent (IPA, acetone, ... or some sort of mixture as tends to be in aerosol flux cleaner cans), as all it will do is spread the flux around the board.

Instead, you need to mop it off using something like Kim Wipes or foam swabs (i.e. those sold for cleaning ink jet printers on eBay and the like) types of things to actually remove it from the PCB. Repeat until it's all gone, and voila, you're done.  :-+
 

Offline IanB

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #55 on: September 06, 2018, 04:44:50 pm »
Desiccator?

Put sodium hydroxide pellets in the bottom to absorb moisture. Evacuate for even better performance. Reactivate the moist NaOH by baking in oven.

Sodium hydroxide is not very safe. However, every supermarket and hardware store in the USA sells calcium chloride drying products for dehumidifying enclosed spaces. These would be a more practical solution for desiccators.

Even so, I think the problem is with cleaning, not with drying. If you just spray flux cleaner onto your board from a spray can, it will not clean the flux off. It needs to be scrubbed with a soft brush after application, and then the residue needs to be rinsed off using a separate application of solvent and/or de-ionized water.
I'm not an EE--what am I doing here?
 

Offline grantb5

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #56 on: September 06, 2018, 05:09:17 pm »
Thanks folks. Most of these are PTH (through hole) so swabs and wipes will probably get shredded. I do use a toothbrush with the IPA and/or MG. I will try harder. :)  It seems to me the moisture or film appears later but I will experiment with a few things.
 

Offline ogden

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #57 on: September 06, 2018, 05:52:40 pm »
Thanks folks. Most of these are PTH (through hole) so swabs and wipes will probably get shredded. I do use a toothbrush with the IPA and/or MG. I will try harder. :)

I do use Kontakt PCC aerosol bottle which is mostly Isopropanol, with built-in swab together with cheap "air duster" bottle. Duster shall be flammable type. You just blow all the remains of cleaning fluid away, evaporate it as well. It helps in tight places and under SOIC/LQFP IC's (!).
 

Offline grantb5

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #58 on: September 06, 2018, 06:02:21 pm »
I see Flux-Off has a product like that, maybe I'll give that a whirl.

https://www.chemtronics.com/flux-off-no-clean-plus
 

Offline nanofrog

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #59 on: September 07, 2018, 04:18:49 am »
I see Flux-Off has a product like that, maybe I'll give that a whirl.

https://www.chemtronics.com/flux-off-no-clean-plus
It's decent stuff, but it's a bit on the expensive side. Especially the 12oz. aerosol cans that are hobbyist friendly.
  • Amazon has it for $18.37 per can
  • Digikey for $20.58
  • Newark for $25.51
Then it gets really ugly when looking at CDN pricing (i.e. $44.16 CDN from Amazon.ca).  :palm:

FWIW, the Kim Wipes and foam swabs will work with PTH components quite well (they're older than SMD components). You mop/absorb the solved flux residue with them, not scrub at it. Use a brush first as you have been if you need to scrub a heavy deposit prior to mopping the mess off, repeating as necessary. You can even use Q-tips*; just clear off any cotton fuzz that might be left behind.

* Rotate in the same direction it was wound on the stick to help keep the cotton on it rather than your board.
 

Offline microMANIAC

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #60 on: October 21, 2018, 07:11:01 pm »
Back before I was a greybeard I used commercial flux cleaners, but since recently getting back into the field I have been using 91% isopropyl alcohol to clean flux from my personal project boards, although I have been frustrated by the gummy residue left over no matter how hard I scrub with an old toothbrush. One of the earlier posts in this thread mentioned brake cleaner, and since I recently bought about a dozen cans on sale for less than $3 each CDN I thought I would experiment with it on an inexpensive project. Brake cleaner is amazing stuff... extremely effective dissolving anything gummy or oily, dries quickly with no residue, safe on most plastics, comes in easy-to-use spray cans, and is relatively cheap (especially on sale like I got mine). It is, however, hard on rubber, but you don't find much of that on most circuit boards.

For a test I used it to clean off the flux after soldering the legs and ICSP pins onto an Arduino Nano clone. Initially I wasn't comfortable spraying it directly on the board, so instead I applied it to the old toothbrush bristles and then scrubbed the lines of header pins I had just soldered. The results were perfect... no damage to neighboring components or silkscreening, not a trace of flux or gumminess left on the board, and it air dried in about 60 seconds (blowing on it speeds up drying dramatically). I will definitely be turning to brake cleaner as my go-to flux remover.

I can't speak for all brands or formulations, but the product I used was "emzone Non-Chlorinated Brake & Parts Cleaner". The side label claims it leaves no residue, is fast drying, and has low odour, all of which I can confirm. It suggests pretesting on plastic components, and warns to avoid overspray on rubber parts, but I have used it on all kinds of plastic stuff, and almost all of it is impervious. Like I said, try it on a few lower-risk projects first, but I think you will find it fantastic for flux cleaning.
 
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Online thm_w

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #61 on: October 22, 2018, 07:16:10 pm »
Back before I was a greybeard I used commercial flux cleaners, but since recently getting back into the field I have been using 91% isopropyl alcohol to clean flux from my personal project boards, although I have been frustrated by the gummy residue left over no matter how hard I scrub with an old toothbrush. One of the earlier posts in this thread mentioned brake cleaner, and since I recently bought about a dozen cans on sale for less than $3 each CDN I thought I would experiment with it on an inexpensive project. Brake cleaner is amazing stuff... extremely effective dissolving anything gummy or oily, dries quickly with no residue, safe on most plastics, comes in easy-to-use spray cans, and is relatively cheap (especially on sale like I got mine). It is, however, hard on rubber, but you don't find much of that on most circuit boards.

For a test I used it to clean off the flux after soldering the legs and ICSP pins onto an Arduino Nano clone. Initially I wasn't comfortable spraying it directly on the board, so instead I applied it to the old toothbrush bristles and then scrubbed the lines of header pins I had just soldered. The results were perfect... no damage to neighboring components or silkscreening, not a trace of flux or gumminess left on the board, and it air dried in about 60 seconds (blowing on it speeds up drying dramatically). I will definitely be turning to brake cleaner as my go-to flux remover.

I can't speak for all brands or formulations, but the product I used was "emzone Non-Chlorinated Brake & Parts Cleaner". The side label claims it leaves no residue, is fast drying, and has low odour, all of which I can confirm. It suggests pretesting on plastic components, and warns to avoid overspray on rubber parts, but I have used it on all kinds of plastic stuff, and almost all of it is impervious. Like I said, try it on a few lower-risk projects first, but I think you will find it fantastic for flux cleaning.

I think this is the MSDS: http://emzone.ca/media/141950/p6-045046___________emzone_brake___parts_cleaner_-_the_big_can_-_482g_en_5.pdf

Heptane (including isomers) 64742-49-0 60-100%
Isopropyl Alcohol 67-63-0 5-10%
Carbon Dioxide 124-38-9 1-5%

Just make sure you have good ventilation, even if it doesn't have a strong odor.
 
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Offline microMANIAC

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #62 on: October 26, 2018, 11:04:34 pm »
Heptane (including isomers) 64742-49-0 60-100%
Isopropyl Alcohol 67-63-0 5-10%
Carbon Dioxide 124-38-9 1-5%

Somebody didn't check their math there... the Heptane can be up to 100%, but the other two can't be lower than 5% and 1% respectively. If the Heptane is at its maximum of 100% and the others are at their minimums... that adds up to 106%. Surely the maximum Heptane component should be 94%.

 :-DD

BTW, I used this cleaner on a couple more PCBs since my original post and the results were stellar.
« Last Edit: October 26, 2018, 11:06:56 pm by microMANIAC »
 

Offline helius

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #63 on: October 27, 2018, 07:51:41 am »
Somebody didn't check their math there...
You don't understand. They know exactly what their product contains, not a range of possibilities. Those aren't error bars.
What they aren't doing is telling you exactly what is in their product. They take the precise proportion of each hazardous ingredient (non-hazardous ingredients are not listed at all) and add sufficient "fuzz" on either side to obscure the content. Summing to 100% is nowhere in the procedure and would not improve anything from their perspective (the minimum possible information disclosure within the law).
 

Offline Fleetz

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #64 on: October 27, 2018, 03:21:25 pm »
Been looking into the best way for a hobbyist like myself to clean PCBs that I design. IPA was one method I explored however seems it can be somewhat problematic with residue unless follow up cleaning is implemented.

In the next day or so I will be trying out a water based flux cleaner in a ultrasonic bath cleaner I recent purchased on eBay for $100. The flux cleaner I am trying is https://www.shesto.co.uk/precision-engineering/ultrasonics-1/shesto-ultrasonic-cleaner-solution-for-flux-remover-pcb/

The flux cleaning solution needs to be elevated to around 50-60C which is no problem as the ultrasonic cleaner I purchased has an adjustable heater. Once it goes through the ultrasonic bath the PCB is rinsed in demineralised water then dried. Hopefully leaving a relatively clean streak free PCB.

I have seen a YouTube video of a user of using a flux cleaner solution similiar to what I am about to use where he uses a toothbrush once the board is in the ultrasonic bath to gently brush more heavily fluxed areas on the PCB to assist in the moving of the flux into solution so I will be using that technic to.

Then I intend using a IPA bath after the ultrasonic to displace the water based cleaner then dry the PCB. Hopefully finish with a very clean board.
 

Offline helius

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #65 on: October 27, 2018, 04:46:01 pm »
Many are leery of putting themselves in contact with ultrasonic cleaners, due to their known capability for tissue disruption.
 

Offline Fleetz

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #66 on: October 27, 2018, 04:51:52 pm »
Many are leery of putting themselves in contact with ultrasonic cleaners, due to their known capability for tissue disruption.

No intention of putting my fingers into an active ultrasonic bath, the ultrasonics will be switched off for any spot cleaning or any action that requires direct human intervention.
 

Offline floobydust

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #67 on: October 27, 2018, 04:57:14 pm »
Ultrasonic cleaning is very hard on electronics, IC bonding wires can fail and I've seen metals get etched as the solder fillets look roughed up. Keep the intensity and time as low as possible.
 

Offline microMANIAC

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #68 on: November 04, 2018, 02:34:11 am »
You don't understand.

Ummm... yes, I do. It's you that doesn't understand.

They clearly state that the IPA is at least 5%, and CO2 is at least 1%. They can't then claim that the Heptane can be up to 100%. The Heptane can't be more than 94%... it's simple math.
 

Offline helius

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #69 on: November 04, 2018, 05:15:18 am »
Looks like you still don't get it. It is not a "claim that heptane can be up to 100%". The only "claim" is that the exact, known, amount of heptane is somewhere between the figures given. "Simple math" is not involved at all, only legal requirements.
 

Offline Brumby

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #70 on: November 04, 2018, 07:42:34 am »
"Simple math" is not involved at all, only legal requirements.
.... and obfuscation of the real formula.
 

Offline boffin

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #71 on: November 05, 2018, 11:28:06 pm »
I did a little video on common alternatives

TLDR version:  Use real flux cleaner (or isopropyl if you don't have it)

 
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Offline microMANIAC

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #72 on: November 06, 2018, 12:27:45 am »
Ok, the last thing I want to do is get into a flame war with a longtime contributor, so this will be my last comment on this topic, but your argument is just semantics, and it's still wrong.

"the exact, known, amount of heptane is somewhere between the figures given"

Exactly!!! But that is ALSO true for the other listed components.

The amount of CO2 is somewhere between one and five percent (but not LESS than 1%). Isopropyl alcohol makes up five to ten percent of the product (but not LESS than 5%). That means that somewhere between six and fifteen percent of this brake cleaner is NOT heptane. There is absolutely no way the heptane can contribute more than 94% of the total. I'm not sure why this is so difficult to understand. Heptane is a distinct component in its own right, it is not itself made up of CO2 or IPA. If the product is indeed at least 1% CO2 and 5% IPA, it is IMPOSSIBLE for it to simultaneously be 100% heptane.

If your argument is that the numbers are correct because it is strictly true that a 94% heptane concentration is "between 60 and 100%", well that is just ludicrous. Nobody says a peanut butter cup is 20% chocolate and somewhere between 60% and 100% peanut butter. The most logical explanation is my original one, that the manufacturer made a simple mistake when listing the ingredients.
« Last Edit: November 06, 2018, 09:38:47 pm by microMANIAC »
 

Offline microMANIAC

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #73 on: November 06, 2018, 12:31:55 am »
I did a little video on common alternatives

TLDR version:  Use real flux cleaner (or isopropyl if you don't have it)


You really should have included brake cleaner in your test. Cleans at least as well as the MGC product with zero board or component damage, and MUCH cheaper. I swear by it now.
 

Offline boffin

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #74 on: November 06, 2018, 02:09:41 am »
I did a little video on common alternatives

TLDR version:  Use real flux cleaner (or isopropyl if you don't have it)


You really should have included brake cleaner in your test. Cleans at least as well as the MGC product with zero board or component damage, and MUCH cheaper. I swear by it now.

Not something I had at hand, but I'll give it a try sometime.
 
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Online rhb

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #75 on: December 18, 2018, 11:37:08 pm »
I had a Harbor Freight PIR sensor night light that had stopped working and been tossed in the junk bin.  I pulled it out yesterday to see if I could scavenge a AA batter holder and in the process took it apart.

It's a pretty simple device, so I thought I should be able to diagnose the fault.  In looking at it I noticed some flux residue.  So I cleaned it with a spray of isopropyl and an old toothbrush.

Now it works.  So I'll have to put it back together instead of removing the PIR to play with. :(

The surprising part was how little flux residue there was and that what I noticed was not close to the sensor or op amp, just the on-off-auto switch area.  I cleaned the whole board, so there may have been some I did not notice
 

Offline T3sl4co1l

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #76 on: December 19, 2018, 07:06:19 pm »
PIR detectors are pyroelectric, i.e., the electric field on a crystal changes with temperature.  Electric field means very high impedances, low leakage -- exceptionally so at the rates of change used here (low Hz).

If that's seen at board level or not, depends on if the sensor is internally buffered.  I think that's not uncommon, so you get a PIR module that looks very much like an electret mic: an internal JFET follower on the capacitive (charge based) element, giving reasonable circuit values (continuous current (fractional mA?) instead of charge).  Board contamination could still be a problem, but it would have to be much worse to kill operation.  Or the circuit is just that badly designed (you can always make a circuit worse; you can't always make a circuit better!).

Tim
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Offline SeanB

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #77 on: December 19, 2018, 07:46:39 pm »
No clean flux, or water soluble flux poorly cleaned, will leave a residue that affects high impedance circuits. as the detector typically use 100k or higher value resistors to get gain, any board leakage on either top or bottom will cause incorrect operation. Might work when new, but after a few months of absorbing ambient humidity and rain there will be conductive paths that are not intended. Clean board and give a coat of some conformal coating, or just mask off the pyro detector top with painters tape and spray board top and bottom, avoiding the variable resistors using more tape, and they will last for years.
 

Online rhb

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #78 on: December 19, 2018, 11:11:38 pm »
The circuit is very similar to the example in the datasheet for the PIR D203B sensor.  But it's driving an LED and timer circuit rather than a relay and uses an LP324 quad op amp.  It also has a sensor to keep it from turning on if the room lights are on

Putting it back together was a huge pain.  Every time I soldered a wire back on, another one broke off.  But I did eventually get it back together and it works just fine.  So I washed the "NG" written on the back off and put it to use.

I've not had trouble once the muck was cleaned off.  I did have to reclean a CD player after a few months, but that was several years ago.  It's never had a problem since.
 

Offline TheNewLab

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #79 on: January 07, 2019, 08:59:08 am »
I did a little video on common alternatives

TLDR version:  Use real flux cleaner (or isopropyl if you don't have it)


You really should have included brake cleaner in your test. Cleans at least as well as the MGC product with zero board or component damage, and MUCH cheaper. I swear by it now.
I am also about to buy an ultrasonic cleaner and wonder to bath solution to use.
1st, some auto parts, and Iknow what to use,
2nd electronic parts and boards, and that I do not know.
Does Brake cleanerreally  work that well and is safe on circuit boards?
IF so, that would be ideal. Do you dilute it?
 

Offline TheNewLab

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #80 on: January 07, 2019, 09:05:34 am »
Also, regarding ISO alcohol. I use 99% and I am not always happy. Some have mentioned how bought flux cleaner has additional chemicals
Can I make up a solution combining alcohol with other chemicals to make flux cleaning and PCB cleaning MORE effective?


or, some special blend that will not blow up or poison me?

I know acetone works on some stuff, I don't think PCBs though
ANd Naphtha (lighter fluid is great for plastics..but only for plastics as I understand.

So many questions?
one more:  any ultrasonic  homebrew solutions for electronics ?
 

Offline chickenHeadKnob

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #81 on: January 07, 2019, 11:03:58 am »
I did a little video on common alternatives

TLDR version:  Use real flux cleaner (or isopropyl if you don't have it)


You really should have included brake cleaner in your test. Cleans at least as well as the MGC product with zero board or component damage, and MUCH cheaper. I swear by it now.

Well I just gave this stuff: (Certified Brake Cleaner non-chlorinated) a try - https://www.canadiantire.ca/en/pdp/certified-non-chlorinated-brake-cleaner-390-g-0381430p.html
Certified appears to be a Canadian Tire house brand, it is just Heptane and Carbon Dioxide. First impression is that it works very well!, not egregiously smelly or toxic and cheap and locally abundant. Winner!

My test was not a full soldered board. Just recently I bought some Rose's metal from Russia. This is low temp. Bismuth/tin/lead that melts around 97 degrees Celsius, and it comes  from the seller in drops (small blobs). I wanted it in the form of wire so I can  hold it while using it to solder the lids on hermetic boxes I am making so I coated the drops with MG-835 liquid rosinRA flux and heated them on a hot plated griddle. I use a black and decker brand teflon surface 24 inch breakfast griddle as my hot plate. I got the drops warm enough to melt them and get them to coalesce into 10mm wide ribbons, which should be as good as wire. The flux never got to smoke temp. so this is not the same as hardened burned on flux typically seen on PCB's.

I let the hot plate cool down, peeled off the rose's metal and let the flux harden for a day. I scraped off as much as I could before hitting it with the brake cleaner. There was still a layer of hard powdery flux stuck on the teflon that came off like magic with the brake cleaner but admittedly this is not as a good test as a real PCB.
 

Online rhb

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #82 on: January 07, 2019, 03:19:38 pm »
One of these might help:

https://www.seattlefindings.com/Draw-Plate-Round-10-32-Gauge_p_4067.html

The normal routine is to make a narrow mold, cast an ingot and then successively draw until you get the desired diameter.  That's what jewelers have done for thousands of years and still do regularly all around the world.

A piece of 10 AWG copper wire pulled straight and pressed into plaster of paris that is almost set should work for the mold.  You can probably melt the drops in the mold with a hot air gun.
 
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Offline chickenHeadKnob

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #83 on: January 08, 2019, 03:51:08 am »
The normal routine is to make a narrow mold, cast an ingot and then successively draw until you get the desired diameter.  That's what jewelers have done for thousands of years and still do regularly all around the world.

A piece of 10 AWG copper wire pulled straight and pressed into plaster of paris that is almost set should work for the mold.  You can probably melt the drops in the mold with a hot air gun.

Thanks, a few similar approaches occurred to me. Rose's metal is new to me as it is the first time handling it. It is surprisingly hard and non-ductile, I don't think it will draw well. Plaster of paris is a good idea. As it turned out the teflon prevented the molten metal from alloying with the underlying aluminum and I could steer the liquid around with a popsicle stick to get ribbons so my hasty approach gave quick functional results.
 

Online rhb

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #84 on: January 08, 2019, 01:09:23 pm »
If it work hardens while drawing it will be really difficult to anneal without melting it.  It may be hard from being quenched in water to form the drops.

Jewelers commonly use solder in sheet form.  So another option is to cast a wire ingot and then either draw if out with a hammer and anvil or compressing it in a vise to make a thin ribbon that you can cut with nippers.

The plaster of paris mold should be baked in an oven at 250 F for several hours before use to make sure it is dry.
 

Offline T3sl4co1l

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #85 on: January 08, 2019, 01:40:21 pm »
A quick look at the literature suggests elongation (a measure of ductility) should be very good indeed.  You may have to go slowly, however (which implies the large elongation is due to creep).

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Offline chickenHeadKnob

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #86 on: January 08, 2019, 03:16:24 pm »
A quick look at the literature suggests elongation (a measure of ductility) should be very good indeed.  You may have to go slowly, however (which implies the large elongation is due to creep).

Tim
I have to play some more. i don't know the purity of the stuff I have, I always have some doubt when buying from ebay. One of my goals was to use the griddle and a thermocouple to ascertain the melting point to get a gauge on the quality. Well I screwed that up, somehow the thermocouple via my Brymen 869 was giving wild readings, plausible one moment implausible the next. I cranked up the heat after getting impatient and over shot 110+ degrees, then things started melting too quickly.
 
 I had a small container of water and a sponge and was using the sponge to drip water onto the griddle as a sanity temp test and the water drops were boiling off quickly when the metal started to melt. The water and sponge were also intended as a quench once I had the metal in the form I wanted. As the metal cooled a network of crystals could be seen forming, indicating to me that one component was coming out of alloying solution first and that the final result may not be all that homogenous. Once solid I tried bending it. It feels like something inbetween pot metal/white metal and standard 63/37 solder.

I feel embarrassed derailing this thread from the flux removal topic :-[
 

Offline grantb5

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #87 on: January 08, 2019, 03:47:57 pm »
I feel embarrassed derailing this thread from the flux removal topic :-[

Start a new one or bring it back on topic when you sort your current issues. :)
 

Offline T3sl4co1l

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #88 on: January 08, 2019, 06:30:25 pm »
Eutectic shouldn't be forming visible crystals.  Maybe you have rather more pure bismuth than you were expecting?  It should still be on the soft side if the melting point is obviously not that high, though, AFAIK...

If you leave a strip of the stuff cantilevered out, does it bend slowly over time?

Tim
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Online Ian.M

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Re: Myth busting solder-flux cleaning with isopropanol alcohol
« Reply #89 on: January 08, 2019, 09:36:26 pm »
The traditional Rose's alloy is non-eutectic.   See http://www.che.uc.edu/jensen/w.%20b.%20jensen/reprints/178.%20Fusible%20Alloys.pdf

You should be able to melt it under water in a glass beaker, with anti-bumping granules added so you cant superheat it by more than a few deg C.   If not, it not what its supposed to be.

I'm curious how effective the rosin RA flux was at such a low temerature.
 


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