Cleaning flux with Alcohol

[tooki]

Using isopropyl alcohol or acetone is the easiest way to perform this task.

No, it is not. As I’ve said repeatedly, many fluxes DO NOT fully dissolve in alcohol, resulting in white residue later on. Commercial flux removers not only clean more thoroughly, they also work faster (especially on burnt flux), and you also need less of it.

Commercial flux cleaners are often mostly IPA, e.g. Kontakt-LR from Kontakt Chemie that I have here - contains IPA + 15-30% of aliphatic hydrocarbons (possibly just the propane gas in the spray can). The white residue is the flux after the alcohol has evaporated because you didn't wash/wipe it off completely, not because the flux didn't dissolve.

Also even normal alcohol (ethanol) will work for flux cleaning, especially for rosin based fluxes.

The key is to use enough of it and make sure the dissolved flux is actually washed/wiped off and not left to dry on the board.

While I agree that proper wiping is essential, it’s not as simple as you say.

The white residues, which are most common with no-clean fluxes, are metal salts that are insoluble in alcohol. It’s not because of poor cleaning technique.

Yes, commercial flux removers contain IPA, but it’s the combination of solvents that makes them work so much better. On the one hand, they can dissolve the constituents that aren’t soluble in alcohol alone. Second, these combinations dissolve everything faster than IPA alone.

Kontakt LR is actually one cleaner I use. The hydrocarbons are not the propellant. (It uses carbon dioxide as the propellant.)

Yes, IPA and ethanol work fine for most old-school rosin fluxes, but they’re still not the best thing out there.

[janoc]

5. Tie a string to it (approx 80cm) and swing it around. Both the centrifugal force and the wind dry the PCB quickly.

 

I think I wouldn't want to be near during one of your flux cleaning sessions! Drying the board with a paper towel and a small fan will do the same service, without the risk of anything getting hit/destroyed.

[jpanhalt]

For those who are safety conscience or worried about breathing a little alcohol vapor, you could put the PCB in a dish towel and fling it around your head really fast.

My serious response is "it depends."  If there is a large amount of soldering or re-soldering, I use a water-based cleaner similar to the Kester ones (i.e., a cellosolve + ethanol amine + water) in an ultrasonic cleaner and rinse with DI water.  The resist is so hydrophobic, the boards come out almost dry.  A quick blast with compressed air finishes the job.

For just a few joints, I use ethanol (absolute) and a brush.  A quick flick of the wrist gets rid of most of the liquid.  A second or third wash removes everything, followed by compressed air for a final drying.  You want to blow residual off, not evaporate it in situ.

[tepalia02]

Thanks a lot to everyone who replied to my previous comment. This is what I appreciate about this forum. I was going through this blog earlier.

https://pcbtracks.com/how-to-manufacture-pcb-at-home/

It is regarding how to make a PCB at home. It has a few tips about cleaning. It does not mention alcohol. It only mentions water and using a hose to clear the PCB. Is it a good idea dear friend? Am I missing something?

[janoc]

Thanks a lot to everyone who replied to my previous comment. This is what I appreciate about this forum. I was going through this blog earlier.

https://pcbtracks.com/how-to-manufacture-pcb-at-home/

It is regarding how to make a PCB at home. It has a few tips about cleaning. It does not mention alcohol. It only mentions water and using a hose to clear the PCB. Is it a good idea dear friend? Am I missing something?

That website offers some pretty dubious advice, such as the etching with the hydrochloric ("muriatic") acid and peroxide combo. Which is about the worst etchant available. Along with this gobbledygook:

"Ferric chloride is normally used in the making of the acid. But, in our process, we shall be using another method because ferric acid is not easily found and if the ferric acid is available the purchase procedure is very tiring due to the documentation that is required."

 


The hose comment he has there is not about flux cleaning but about washing the etchant off after the etching. Terrible idea to do it like that because that guarantees splashing the acid around and the toxic waste getting in the soil and sewers.

As usual, that something is posted on the internet doesn't mean that it is correct, works or a good idea.



Flux cleaning discussed here is something different - that's what you need to do after soldering, to clean up the flux residue. Spraying a board with a hose with no cleaning agent (alcohol, flux cleaner, etc.) will only make the board wet but not really clean the flux residues properly.

[tepalia02]

Thanks a lot to everyone who replied to my previous comment. This is what I appreciate about this forum. I was going through this blog earlier.

https://pcbtracks.com/how-to-manufacture-pcb-at-home/

It is regarding how to make a PCB at home. It has a few tips about cleaning. It does not mention alcohol. It only mentions water and using a hose to clear the PCB. Is it a good idea dear friend? Am I missing something?

Thanks a lot for clarifying the issues. Much appreciated.
That website offers some pretty dubious advice, such as the etching with the hydrochloric ("muriatic") acid and peroxide combo. Which is about the worst etchant available. Along with this gobbledygook:

"Ferric chloride is normally used in the making of the acid. But, in our process, we shall be using another method because ferric acid is not easily found and if the ferric acid is available the purchase procedure is very tiring due to the documentation that is required."

 


The hose comment he has there is not about flux cleaning but about washing the etchant off after the etching. Terrible idea to do it like that because that guarantees splashing the acid around and the toxic waste getting in the soil and sewers.

As usual, that something is posted on the internet doesn't mean that it is correct, works or a good idea.



Flux cleaning discussed here is something different - that's what you need to do after soldering, to clean up the flux residue. Spraying a board with a hose with no cleaning agent (alcohol, flux cleaner, etc.) will only make the board wet but not really clean the flux residues properly.