Cleaning the PCB's after solder

Hi, after soldering the main PCB, there is a lot of dirt and flux and finger tips on the PCB. After a few tests how to clean the PCB i found the following.
Attention. Don’t clean with active elementes like IC’s and potis and switches or with the output connectors.
Step 1:) use Spiritus, Spüli and a toothbrush.
Step 2:) clean first the complete PCB with Spiritus and a toothbrush
Step 3:) make an emulsion with Spüli, aqua and Spiritus and clean it again, and again and again.
Step 4:) if there is a dirt film on some places, use Spiritus again, and than Step 3:)
Step 5:) this takes 20 min… and you had to repeat it some times until the PCB is clean.
Step 6:) dry it with a Fön, or dry it on a heater for 30 min. and not too hot.
In the end , the PCB looks brand new. And you better see some mistakes on soldering.



what are Spiritius, what are Spueli?

Spiritus = burning alcohol (alcohol + some junk to keep you from drinking it, usually methanol, which you can still drink if you don’t mind going blind)
Spüli = dishwasher product

99% IPA works great. Takes me 4 passes with a toothbrush to get the board squeeky clean. I’ve since bought a can of flux remover and a hog hair brush though. Works only marginally better than isypropyl alcohol.

I think Spiritus is ethyl alcohol, there is no methanol in it. The extra stuff only makes it so bitter you won’t drink it (mainly for tax reasons).


85% ethanol, 10% water, 3% methanol, 1% aceton , 1% pyridine (some smelly stuff) and blue colorant is the usual composition. The other additives are intended to make it very distasteful in case you don’t mind going blind, and to induce vomiting if you’re past caring about distasteful.

In the US, I think this stuff is called ‘denatured’ (i.e. poisoned) alcohol. I use Kester natural core leaded solder, cleans up with water (water soluble flux).

Yes, it’s also sometimes called Methylated Spirit(s).
‘He’s a terrible person. He denaturated his wife.’

prost, salute… don’t drink it, use it for PCB cleaning.

And don’t use what you drink for PCB cleaning.

I am not able to understand the term you use like what is Aqua? The other terms I understood and can you please tell me why this method is not suitable with the active components and what would happen if I will clean my active element with this solution?

Hello André, this is very nice from you to highlight into detail on how to clean the PCB´s!

But from my understanding and experiences I highly do not recommend to use any ethyl alcohol based cleaning! (I have done so before and regret it)
It contains a high amount of water, water contains and/or attracts contaminants to the solder surface and pin / leads surfaces. These contaminants will attract humidity (water) over time and corrosion will occur. It only will not corrode if you maintain the pcb/solder-work/synth/whatever in a 24h/365days acclimatized ambient with humidity under 20-30%.

All electronic components and related hardware are 100% IPA proof, but not all are waterproof.
Do not “wash” the shaft area of pots or faders with IPA, this will take away their lubricants, not good!
Also don´t splash lots of IPA directly on a LCD screen, you can wipe it with a little amount on a microfiber towel though

The best way to clean PCB´s is still {Please be sure to watch the video I have linked below}:

  1. 99,8% IsoPropylAlcohol ---- Note: 99% IPA is not equal to 99,8% - get lab-grade 99,8%
  2. hog hair brush (different dimensions, shorter=harder, look at aquarelle/oil painting supplies)
  3. double sheet quality (with cotton) toilette paper (or dry Kleenex, Kim-Wipes, etc.).

The paper is to absorb the flux diluted in IPA.

Have a little recipient with IPA, 10 - 20 ml, pick up some IPA with your hog hair brush, brush over the to be cleaned area until all flux is diluted (area need to be no bigger than the sheets of paper you´ve got), drop a sheet of paper FLAT on it, pass over it with the brush, let the flush cut pins / solder points peak through the paper, pull the paper off before the IPA has dried.

Repeat this procedure with new sheets of “paper” until all cloudy / haze is gone. Rosin flux will take a bit more cleaning than a tacky Kester no-clean flux.

Your PCB will look like a new graphics card or a new motherboard out of its ESD bag.

The best video I have seen on how to clean properly your solder work (also hand-solder smd/smt) is here

Good cleaning!

Personally, I use this, with a hoghair brush:

I also have a bottle of 99.9% IPA. I’ve gone back and forth between the two and I find the Flux Remover does a better job. It still does take several passes. I pretty much use the same method as MusicCircus. As long as you keep a can of air at hand to blow out any residual liquid, you should be good.

I just leave it dirty. I already have too many things to clean.

@qp which one is cheaper for you per liter / quart?

@piscione: same here. why bother.

@MusicCircus, didn’t really pay attention. I believe the Flux Remover was more expensive, but I like the results better so I’ll pay whatever the cost. But, I use it all of the time and haven’t had to replace it yet. Next trip to Fry’s and I’ll probably pick up another bottle though.

@piscione & mic.w, only reason why I go through all of the trouble is primarily for boards that I build for other people. I don’t like selling dirty boards :). Most of my own stuff is covered with flux, for the most part. :slight_smile:

I suppose I’m always worried that the stuff used to clean the flux is worse for me, the environment and the PCB than the flux is.

I’d imagine there are more toxins in the flux fumes than in the flux remover. The main ingredients are Ethanol, Isopropyl & Ethyl acetate. The only somewhat harmful one is tetrafluotoethane, but it’s such a minuscule amount that it’s nothing to be worried about. Flux, on the other hand can corrode the PCB over time.

Good that I only use the purest isopropyl alcohol that I can get, even though I have a full ventilated “workplace”, complete exchange of air in the room happens every minute :slight_smile:
Also how would this affect any environment (evaporated IPA)?
Ok I leave some sheets of paper extra in the trash for cleaning a PCB…