Cleaning PCB after soldering

[sairfan1]

In videos, I saw cleaning PCB with some liquid after soldering, I wanted to know what commonly available liquid can we use to clean PCBs

[planet12]

Probably the easiest to get and most commonly used is isopropyl alcohol aka isopropanol. It's pretty cheap, dries very quickly and doesn't leave a residue.

I've used methylated spirits before, but it's not the best, as it has dye and bitterants in it that will get left behind - so I wouldn't use it on a high voltage or very sensitive board where the residues might cause problems.

[Benta]

Isopropyl alcohol (IPA, 99%)  and a small paint brush is the thing. All components I've encountered have no issue with it. Used it for years myself.

[jmelson]

If you really want to clean your boards, use water soluble flux.  But, then you MUST wash the boards.  But you will be amazed how quickly they clean up!  But, for general-purpose electronics, you can use no-clean flux and just not bother with cleaning.
Jon

[tooki]

As always, I suggest using commercially available flux cleaner instead of isopropyl (IPA). Many fluxes are not 100% soluble in IPA, leaving white residue behind. And even with fluxes that are fully soluble, the solvent blends of flux removers dissolve the flux noticeably faster, saving time.

[jpanhalt]

For whole boards, I use ZEP heavy duty floor stripper diluted 1:3 with DI or distilled water and an ultrasonic cleaner ( 2 minutes) + rinse.  For spot cleaning, I use absolute ethanol plus a little acetone if there are no susceptible plastic components on the board.  If there are, then just ethanol.

[BlackICE]

By volume, 90% solution of 99% IPA with 10% heptane.

[EPAIII]

Yes, any electronics store or supply or E-bay or Amazon will have flux cleaner. Don't confuse it with contact cleaner. The flux removers are better than IPA, even the 99% IPA. You will use a lot less of them.

A good brand:
https://www.amazon.com/Chemtronics-ES1696-FLUX-REMOVER-CLEAN/dp/B000E9TMC4/ref=sr_1_26?crid=OF2EKV8KP990&keywords=flux+remover+for+electronics&qid=1665292346&qu=eyJxc2MiOiIwLjAwIiwicXNhIjoiMC4wMCIsInFzcCI6IjAuMDAifQ%3D%3D&sprefix=flux+remover+for+electronics%2Caps%2C388&sr=8-26

Another that I have used:
https://www.ebay.com/itm/401848286028?hash=item5d90063b4c:g:9PYAAOSwRuFjH6EA&amdata=enc%3AAQAHAAAA4FWQqGtyTV9aIfbfXO6E%2BTmi%2FnrP17fIPvSYkKpbT3IiHo%2BfcOOFn98HSyShNPMcXUrI1uuugUkssEBXNzi5Qh2E%2FGvM1OLeBck1iAWcfYbAWv0uYk%2BgoJRfv18c0tk9b9Z%2FSHSClxWO1J2mpXVs%2BMMCbMI7GzSlpXHLfR9C4sqNac%2BBApUs7O1A3soF5GnHStQknkI1IEDETuV833AXQfcrFNTI4IwumZGkn0GA6sImHj2viRgneNL0C%2FqX5FR%2FXLXLe1SCagIejrpWa%2BxmRHXcw3OxTDfJ97aiHEXSIi5K%7Ctkp%3ABk9SR86F8bL3YA

As always, I suggest using commercially available flux cleaner instead of isopropyl (IPA). Many fluxes are not 100% soluble in IPA, leaving white residue behind. And even with fluxes that are fully soluble, the solvent blends of flux removers dissolve the flux noticeably faster, saving time.

[TC]

As others have said... the quick/easy way is to use isopropyl alcohol, a brush, and lint free cloth to clean off excess. But this will leave some residue.

If you want to get it cleaner then flux remover is the way to go. I don't use spray. I use a flux remover concentrate mixed with distilled water. I keep a small pre-mixed amount in a dispenser. My quick method is to use a brush and flux cleaner and then follow it with isopropyl and a lint free cloth. That works much better.

But when I really want it clean I use a cheap jewelry ultrasonic cleaner, flux remover mixed in warm distilled water (degassed), and follow that with a water bath, then a isopropyl bath. That yields excellent results.

Nothing new in any of these suggestions. These are commonly used methods.

[jpanhalt]

If you want to get it cleaner then flux remover is the way to go. I don't use spray. I use a flux remover concentrate mixed with distilled water. I keep a small pre-mixed amount in a dispenser.

You don't name the flux cleaner you use.  If it is one of Kester's water-based cleaners, then the MSDS/SDS will show it is essentially the same as ZEP floor stripper, which is much cheaper and more readily available at home improvement stores.  That's why I switched to ZEP.  Actually, there is nothing special about the brand.  Any product for stripping acrylic floor wax is probably very similar. 

Frankly, I was amazed at how clean an Oshpark reflowed board with TGFP parts came out.  It was Kester's solder paste with rosin-based flux.

[Benta]

Looking through the safety sheets of the "flux cleaners" available in the EU. Main ingredient:

Propan-2ol

Which is (TaaDaaaah!):

Isopropyl alcohol.

Go buy your over-priced snake oil where ever you want. It's your money. I'll save mine and use what always worked: pure IPA.

[KaneTW]

[DI] Water with suitable ultrasonic detergent in an ultrasonic cleaner. Rinse with DI water, then IPA to displace the water and dry the board.

Careful with ultrasonic cleaning if you have a low frequency crystal[1].

[1]https://www.iqdfrequencyproducts.com/media/pg/1589/1524142577/ultrasonic-cleaning-of-pcb-s-with-quartz-based-products.pdf

[jpanhalt]

Looking through the safety sheets of the "flux cleaners" available in the EU. Main ingredient:

Propan-2ol

Which is (TaaDaaaah!):

Isopropyl alcohol.

True for the non-aqueous cleaners, but not for any cleaner that is water based.  Kester has made a point that many fluxes require a "saponifier" to get rid of the bothersome "white precipitate" that one sees.  Saponification does not happen pure IPA.  (Methanolysis might be considered a type of saponification, but that reaction, as I remember, is pretty specific to methanol.)  The neat thing I saw and should have realized beforehand is that solder resist is quite hydrophobic.  So, when using a water-based remover, the boards come out virtually dry.  As I said earlier, for spot cleaning, I still use an anhydrous alcohol, typically ethanol.

[tooki]

Looking through the safety sheets of the "flux cleaners" available in the EU. Main ingredient:

Propan-2ol

Which is (TaaDaaaah!):

Isopropyl alcohol.

Go buy your over-priced snake oil where ever you want. It's your money. I'll save mine and use what always worked: pure IPA.

It’s not snake oil. The other ingredients make a difference. Most have a hydrocarbon, and some heavy-duty ones also acetone. Some use citrus terpenes, too.

IPA alone does NOT clean all fluxes well. It’s fine for some, but it leaves white residue with many fluxes.

Additionally, even for fluxes that are fully soluble in IPA, they dissolve faster in flux cleaner, and need less of it.

[tooki]

Circuit boards can be contaminated by common grease and dirt, oxidation of exposed metal surfaces, and the effects of PCB manufacturing.

So it is very important that we need to choose the cleaning agent of the circuit board according to the type of flux, if using a no-clean flux in all cases it is not necessary to clean after soldering.
Three types of flux:
No-Clean Flux: Many PCBs used for non-critical applications can be safely manufactured with no-clean flux. As long as the flux is fully activated by reaching full soldering temperature, it does not require any special cleaning to achieve regular performance.

Water Soluble: While these fluxes should be removed after soldering, cleaners such as deionized water and cleaners will do the job.

Rosin-based: These fluxes require cleaning with specific chemical solvents that typically contain fluorocarbons.
If you don't know anything about soldering, you can click aixun soldering tips https://www.aixuntech.com/news/ to learn more.

Assuming this isn’t just spam: Most rosin fluxes do NOT need to be removed in most applications. They can be removed with solvent cleaners (doesn’t need to be fluorocarbon, and usually isn’t!) or with water and saponifying agent.

[Benta]

It’s not snake oil. The other ingredients make a difference. Most have a hydrocarbon, and some heavy-duty ones also acetone. Some use citrus terpenes, too.

Sure, sure. Like I said, it's your money, spend it as you like. Citrus terpenes is a great argument, and if you throw in folic acid it'll be a killer flux remover.

[tooki]

It’s not snake oil. The other ingredients make a difference. Most have a hydrocarbon, and some heavy-duty ones also acetone. Some use citrus terpenes, too.

Sure, sure. Like I said, it's your money, spend it as you like. Citrus terpenes is a great argument, and if you throw in folic acid it'll be a killer flux remover.

Stop being a smartass. Citrus terpenes aren’t there as fragrance, they’re there because they’re an effective solvent.

[coppice]

Looking through the safety sheets of the "flux cleaners" available in the EU. Main ingredient:

Propan-2ol

Which is (TaaDaaaah!):

Isopropyl alcohol.

Go buy your over-priced snake oil where ever you want. It's your money. I'll save mine and use what always worked: pure IPA.

The main ingredient in humans is water. Are you the same as a puddle?

[rdl]

Years ago I tried to find information on the solubility of "rosin". Never did find much. I still wonder what it is actually soluble in and what gives the lowest viscosity.

[Psi]

isopropyl alcohol is fine but you have to brush it in and all around the pcb, then rinse with fresh clean isopropyl alcohol.

The rinse is important otherwise the flux dissolved in the IPA will leave streaks on the PCB as it evaporates.

If you have two containers, a scrub and a rinse tub, then it works pretty well.
When the rinse bath starts leaving streaks you swap that for the scrub bath and get new IPA for rinse.

But you still go through lots of IPA and you shouldn't pour used IPA down the drain.

Compressed air is nice to dry off the PCB instantly, but you are aerosolizing flammable liquid, so you do need to be careful.

[jpanhalt]

Years ago I tried to find information on the solubility of "rosin". Never did find much. I still wonder what it is actually soluble in and what gives the lowest viscosity.

Knowing the solubility of rosin won't help much.  It's the pyrolytic products from rosin and anything else in the flux that you need to know how to dissolve.  From Wikipedia:  "It is soluble in alcohol, ether, benzene and chloroform."  To which you can add a long list of other organic solvents.

[rdl]

That's a good point, but I'd be willing to bet all that gunk is held together mostly by rosin. A just because a given organic solvent will dissolve something doesn't mean it's the best solvent for that purpose. For medium to high molecular weight polymers in general, the best solvents usually result in the lowest viscosity solutions. I don't know how well that applies to "rosin" though.

[tooki]

The white residue in question is not from insufficient rinsing. (I.E. it’s not just flux being redeposited.) It’s compounds that won’t dissolve. From a Kester article on the subject (attached):
“Chlorinated or fluorinated solvent, alcohols and saponifier/water cleaning seem to have little effect for removing this residue.” And that’s just for one of the several types of residues created.

[jpanhalt]

Reading just a little further in the report,

Some alkaline saponifier added to the water will help remove this residue.

Note additional cautions about using alkaline anything.  I wish Kester defined what it meant by a "saponifier" in water that was not alkaline.

My guess is that technical personnel wrote what was actually used (e.g., ethanolamine and related).  Legal got involved and warned they couldn't be that specific, so marketing came up with "saponifier."  (tongue in cheek)

[KaneTW]

As long as you don't add hydroxide to the cleaning bath, you'll be fine.

[Vovk_Z]

many fluxes require a "saponifier" to get rid of the bothersome "white precipitate" that one sees. 

That's why good cleaning liquid ('a flux cleaner') contains not only pure IPA, but some (10-35 %) amount of some benzine/gas, e.g. nefras (pure gasoline) etc (don't know the right English/Americal equivalent).
Yes, it stinks much (better for me   ), but it does its job without 'a white residual'.

[tooki]

many fluxes require a "saponifier" to get rid of the bothersome "white precipitate" that one sees. 

That's why good cleaning liquid ('a flux cleaner') contains not only pure IPA, but some (10-35 %) amount of some benzine/gas, e.g. nefras (pure gasoline) etc (don't know the right English/Americal equivalent).
Yes, it stinks much (better for me   ), but it does its job without 'a white residual'.

That’s what I’ve been saying all along. But some people insist that it’s “snake oil”…