# Cleaning PCB



## IPv6Freely (Jul 16, 2021)

I finally bought some 99% IPA and used a (new) toothbrush to clean a PCB. Now it's sticky for some reason and the solder joints are dull, like they've been oxidized (I assume that's just the sticky residue, whatever it is).

What have I done wrong, here?


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## Coda (Jul 16, 2021)

Clean it some more.


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## IPv6Freely (Jul 16, 2021)

Coda said:


> Clean it some more.


That simple, huh? Okay...


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## peccary (Jul 16, 2021)

IPv6Freely said:


> That simple, huh? Okay...



The sticky stuff is the rosin from the flux, and it's pretty gnarly stuff. But yeah, submerge it in alcohol, agitate it, scrub it, repeat till it's clean. I like using compressed air to dry.


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## Stickman393 (Jul 16, 2021)

You're basically pushing the flux around unless you either let the alcohol run off the board, or if you use something to absorb the alcohol before it dries.

Kimwipes make for a suitable solution...or paper towels.  Just make sure you get the lint off afterwords.  

Happy scrubbing!


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## peccary (Jul 16, 2021)

Stickman393 said:


> You're basically pushing the flux around unless you either let the alcohol run off the board, or if you use something to absorb the alcohol before it dries.
> 
> Kimwipes make for a suitable solution...or paper towels.  Just make sure you get the lint off afterwords.
> 
> Happy scrubbing!



@Stickman393 is right. I should have mentioned: when I scrub with a toothbrush I am actually scrubbing a Kimwipe that is covering the board.


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## jubal81 (Jul 16, 2021)

I've dumped the alcohol into a Tupperware container and brushed the PCB while it's submerged. I've got a friend who even uses and ultrasonic cleaner, like what they advertise for cleaning jewelry.


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## IPv6Freely (Jul 16, 2021)

jubal81 said:


> I've dumped the alcohol into a Tupperware container and brushed the PCB while it's submerged. I've got a friend who even uses and ultrasonic cleaner, like what they advertise for cleaning jewelry.


Can you really just dunk an assembled PCB into a tub of alcohol like that?


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## Coda (Jul 16, 2021)

IPv6Freely said:


> Can you really just dunk an assembled PCB into a tub of alcohol like that?


As long as there are no pots/switches attached.


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## IPv6Freely (Jul 16, 2021)

Coda said:


> As long as there are no pots/switches attached.


Hmm, okay. Good to know!


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## bowanderror (Jul 16, 2021)

With 99% IPA, I usually have to douse the board (or apply with toothbrush) & let it sit for a minute before I start scrubbing with a toothbrush. Then dry it off and FULLY clean the toothbrush with IPA. Now you should have the easy stuff off, so you can re-soak the toothbrush and go at it again, focussing on the built-up areas of flux. Repeat until clean and place in front of a fan to dry. The surface of your joints may look dull, but it won't affect the connectivity. Note that if you need to resolder something after cleaning, you may have to add extra flux to do it.

Some fluxes don't come off easily, even with 99% IPA, so I have moved mostly over to a dedicated spray flux cleaner. I've had good results with MG Chemical 4140 Flux Remover, but other dedicated sprays should work. It only takes me 2-3 passes with minimal scrubbing to remove even the toughest fluxes.


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## IPv6Freely (Jul 16, 2021)

bowanderror said:


> With 99% IPA, I usually have to douse the board (or apply with toothbrush) & let it sit for a minute before I start scrubbing with a toothbrush. Then dry it off and FULLY clean the toothbrush with IPA. Now you should have the easy stuff off, so you can re-soak the toothbrush and go at it again, focussing on the built-up areas of flux. Repeat until clean and place in front of a fan to dry. The surface of your joints may look dull, but it won't affect the connectivity. Note that if you need to resolder something after cleaning, you may have to add extra flux to do it.
> 
> Some fluxes don't come off easily, even with 99% IPA, so I have moved mostly over to a dedicated spray flux cleaner. I've had good results with MG Chemical 4140 Flux Remover, but other dedicated sprays should work. It only takes me 2-3 passes with minimal scrubbing to remove even the toughest fluxes.


Thank you! I had wondered if there was something better out there. I'll check it out!


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## mistersparkle (Jul 16, 2021)

I may get flamed for this, but I use spray brake cleaner to de-flux my PCBs. And even though the stuff I use is advertised as containing <10% VOCs, I realize it's still horribly wrong environmentally. But, I guarantee I clean waaay fewer PCBs in a year than my local auto mechanic cleans brake parts, not to mention that Isopropyl Alcohol isn't an entirely innocent solvent either. So, like everything else, use these chemicals responsibly and in moderation. And I *will* check out that MG 4140 when my brake cleaner runs out.....promise!


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## bowanderror (Jul 16, 2021)

I've heard of people using brake cleaner, with mixed results. They are usually acetone and/or methanol, with a bit of toluene in there. Acetone will melt some plastics, so it may not be the best option, but methanol should work fine (although it's toxic, so keep it off your skin & work in a ventilated area).

I have seen a few brake cleaners that use tetrachloroethylene, which is HELLA toxic, so I would steer clear of those.

Brake cleaners that use naptha or petroleum distillates should be ok, but you might want to test it on plastics first.


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## IPv6Freely (Jul 17, 2021)

Is the 4140A the same stuff, for the most part? It's readily available on Amazon, whereas the 4140 doesn't seem to be. I'm sure for my needs it's plenty either way. I guess I don't really NEED to clean any of it, but damn it looks so good when you do!


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## Feral Feline (Jul 17, 2021)

What about good ol' contact cleaner?
No, not the stuff for your corrective-vision lenses, but spray-can contact cleaner for electronics (I just picked up a can).

I've been using alcohol and a toothbrush, but not pleased with the results.


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## danfrank (Jul 17, 2021)

bowanderror said:


> I have seen a few brake cleaners that use tetrachloroethylene, which is HELLA toxic, so I would steer clear of those.


Yeah, the "brake cleaners I've seen use chlorinated solvents which will eat through a lot of things used in electronics. A big No No...

Go to the hardware store and buy a can of acetone. Mix it 50/50 with your 99% isopropyl alcohol, the mixture will work much better than your 99 iso only. In fact, many flux cleaners are exactly that... Iso + acetone. Most plastics used in electronic components (polyethylene and polypropylene) aren't affected by acetone. Acrylics are affected though, so watch out with other plastics. Mixing it up yourself will save you money!!! Lol.
I wouldn't dunk the assembled board in a Tupperware of solvent either. Just use a polyethylene squirt bottle to squeeze the solution out plus a toothbrush ti "brush" the solvent and flux off.


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## uranium_jones (Jul 20, 2021)

Feral Feline said:


> What about good ol' contact cleaner?
> No, not the stuff for your corrective-vision lenses, but spray-can contact cleaner for electronics (I just picked up a can).
> 
> I've been using alcohol and a toothbrush, but not pleased with the results.


Yeah, once someone buys another pedal from me, a can of the WD-40 contact cleaner is at the top of my list. Well, that and it's time to re-do my potentiometer inventory.


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## james5 (Mar 2, 2022)

Most grime can be removed with a cleaning agent, such as isopropyl alcohol (IPA) and a Q-tip, small brush or clean cotton cloth. Cleaning a PCB (custom pcb printing) with a solvent like IPA should only be done in a well vented environment, ideally under a fume hood. Demineralized water can be used as an alternative.


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## Gordo (Mar 2, 2022)

Bio77 turned me on to this trick.  Use a piece of cotton (old t-shirt) or paper towel on the board and scrub that with the soaked toothbrush.  The flux tends to stick to the cotton and makes it much easier.


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## IPv6Freely (Jul 16, 2021)

I finally bought some 99% IPA and used a (new) toothbrush to clean a PCB. Now it's sticky for some reason and the solder joints are dull, like they've been oxidized (I assume that's just the sticky residue, whatever it is).

What have I done wrong, here?


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## pcb rookie (Mar 5, 2022)

One of my best compagnon to clean my boards: https://www.mgchemicals.com/products/soldering-supplies/flux-removers/flux-remover-for-pc-boards/


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## Grubb (Apr 25, 2022)

Any tips for cleaning the component side of boards? I can scrub the back clean no trouble but getting in and around the stuff that runs through from the back is not so easy. And then there's always some left after soldering in pots and switches, which I have no clue how to tackle, seeing as IPA can damage them. I read a post on here from a guy who scrapes it off when it's dry but my flux didn't come off well doing that and left a powdery mess.


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## Coda (Apr 25, 2022)

Feral Feline said:


> What about good ol' contact cleaner?
> No, not the stuff for your corrective-vision lenses, but spray-can contact cleaner for electronics (I just picked up a can).
> 
> I've been using alcohol and a toothbrush, but not pleased with the results.



I start with a few healthy sprays of CRC. Then I go at it with IPA and a toothbrush, and wick it all up with a paper towel…


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## SYLV9ST9R (Apr 25, 2022)

Grubb said:


> Any tips for cleaning the component side of boards? I can scrub the back clean no trouble but getting in and around the stuff that runs through from the back is not so easy. And then there's always some left after soldering in pots and switches, which I have no clue how to tackle, seeing as IPA can damage them. I read a post on here from a guy who scrapes it off when it's dry but my flux didn't come off well doing that and left a powdery mess.


I use Q-tips to clean the pot/switches legs, works great.


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## Feral Feline (Apr 26, 2022)

I've switched to the MG stuff (IPA/Ethanol blend), cleaned my first time with it on a board the other night. Scrubbed with a toothbrush then wiped with a cloth. No sticky residue, but it did dull the board itself along with the solder joints (I inspected them prior to cleaning, all nice and shiny cones before the chemical clean dulled them).

Q-tips for the component side.

Straight IPA was just a gummy mess, the MG 4140 has the afore mentioned ethanol with the IPA, but I think the Ethyl Acetate is the magic ingredient (but I'm no chemist). Overall, happy with the results.

PS: I've got a 1L bottle of the 4140, but it also comes in a pen-like dealio, which I imagine would be great for the component side of our little noise-maker PCBs.


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## Bricksnbeatles (Jun 10, 2022)

Anyone have tips on getting the PCB nice looking after all the flux is gone? I’ve noticed with the black PCBs that no matter how much I clean them, there’s always a haze left on the solder mask that takes a long time to buff away with a dry q tip. Just gotta put the time in I guess?
Edit: a dry soft bristle toothbrush does the job in 30 seconds flat; much better than the 30 minutes with a q tip I used to spend


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## Betty Wont (Jun 10, 2022)

Bricksnbeatles said:


> Anyone have tips on getting the PCB nice looking after all the flux is gone? I’ve noticed with the black PCBs that no matter how much I clean them, there’s always a haze left on the solder mask that takes a long time to buff away with a dry q tip. Just gotta put the time in I guess?
> Edit: a dry soft bristle toothbrush does the job in 30 seconds flat; much better than the 30 minutes with a q tip I used to spend


I clean mine with a dry method that doesn't leave the film behind. I use a tiny awl and poke at the flux and it comes off completely in flakes.


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