PCB cleaning

myleftear

Member
Paid Member
2017-09-10 6:33 pm
Luzern
Hello :)

I have a ses/no question:

Can I clean a board that has relays on it?
I use alcohol/demineralized water and a toothbrush.

(Long story: It's a B1 mesmerize, I'm using Cardas Audio Quad Eutectic with Cardas Rosin Flux Solder Paste. The molten solder-paste make the board look very stainy, I _have_ to clean it with alcohol/water/toothbrush. Somewhere I read that mechanical parts—pots etc.—shouldn't get this treatment...)

Thank you!
david
 

Mark Johnson

Member
Paid Member
2011-05-27 3:27 pm
Silicon Valley
The "two solvent" method is my favorite. One of the solvents is 99% isopropyl alcohol, the other is soapy water. IPA dissolves and carries away flux, soapy water dissolves and carries away IPA. Then rinse with clear water, flood with IPA. Then high speed air carries away the final solvent.

I find that a four step process works beautifully. Protip: have the hairdryer plugged in and ready to go before you begin.

1. Flood the board with 99% isopropyl alcohol ("IPA") and scrub with a toothbrush. Do this top and bottom. Repeat twice more, for a total of 3 floodings and brushings on each side.

2. (sounds crazy but it works) Flood the board with tap water, pour on 15 milliliters (1 tablespoon) of liquid dish soap, and scrub with a different toothbrush. Do this top and bottom. The soap gets rid of the hazy flux residue on the board. Rinse the board thoroughly, top and bottom. Rinse with water at least three times per side to get rid of every molecule of soap

3. Flood the board again with 99% IPA and scrub with original toothbrush. Do this top and bottom. Rinse with IPA, top and bottom. Rinse again with IPA. This gets rid of all the water and any minerals that may have been in the water.

4. Immediately after the final IPA rinse, use a high speed pistol style hair dryer to blow all liquid off the board, top and bottom. Do this at the highest airspeed but medium or low temperature.

I buy 99% IPA from Amazon (link) but you might also find it at your pharmacy or grocery store or paint store or big box home improvement store.
 
I clean the solder/track side of PCBoards after reworking them with Flux Cleaner or if really stubborn, Amberklene in an aerosol, fitted with a cleaning brush. It contains Trichloroethylene, which is an excellent cleaning solvent. A quick coat of Conformal Coating, (PCBoard varnish) finishes them of with a protective gloss.

Cleaning components can only lead to problems.
 

myleftear

Member
Paid Member
2017-09-10 6:33 pm
Luzern
So many replies!



Well, if you "_have_" to do it, then it´s already decided , isn´t it?

On the practical side: I guess you want to clean the solder side, not the component side, so no harm done.

Why would you soak relays and pots in cleaning fluid is beyond me.

Sort of, the board really doesn't look nice. Both sides, but the solder side is obviously worse.

I'd rather not soak relays/pots. I asked before I soldered them onto the board, so that I could do the heavy cleaning before those parts were at risk. :cool:


The "two solvent" method is my favorite. One of the solvents is 99% isopropyl alcohol, the other is soapy water. IPA dissolves and carries away flux, soapy water dissolves and carries away IPA. Then rinse with clear water, flood with IPA. Then high speed air carries away the final solvent.

Thanks mark. I saw the thread you quoted from ;-) and remember it well. It was just that I wasn't sure about the relays...

I clean the solder/track side of PCBoards after reworking them with Flux Cleaner or if really stubborn, Amberklene in an aerosol, fitted with a cleaning brush. It contains Trichloroethylene, which is an excellent cleaning solvent. A quick coat of Conformal Coating, (PCBoard varnish) finishes them of with a protective gloss.

Cleaning components can only lead to problems.

And thanks JonSnell too! This seems quite a professional solution. Haven't those chemicals at hand. (Only paint-solvents, IPA, or kirsch ;-)

again, thank you very much! I appreciate!

david
 
The "two solvent" method is my favorite. One of the solvents is 99% isopropyl alcohol, the other is soapy water. IPA dissolves and carries away flux, soapy water dissolves and carries away IPA. Then rinse with clear water, flood with IPA. Then high speed air carries away the final solvent.

+1 to this method - I have used it for years but use distilled water instead of tap water with a couple of drops of washing up liquid and plenty of rinsing afterwards. You can get large quanties of distilled water from a local motor shop. IIRC it used to be used for topping up car batteries.

I use a garage vacuum cleaner set to 'blow' to clean off.

Cheers

Mike
 
I wouldn't use washing up liquid, its crammed full of salt(*), likely to stimulate corrosion of the copper over the years as the chloride ions leach back out of the FR4.


To clean flux off PCBs why not use a PCB flux cleaning solvent? Its specifically designed to be safe on circuit boards and dries quickly.


Also there is such a thing as no-clean solder paste, wonderful stuff.



(*) to make it viscous.
 

amplidude

Member
2016-02-04 3:20 pm
+1 to this method - I have used it for years but use distilled water instead of tap water with a couple of drops of washing up liquid and plenty of rinsing afterwards. You can get large quanties of distilled water from a local motor shop. IIRC it used to be used for topping up car batteries.

I use a garage vacuum cleaner set to 'blow' to clean off.

Cheers

Mike
Just burned a iraud9 amp board after cleaning this way, guess it wasn't totally dry,, :mad:
 

Mark Johnson

Member
Paid Member
2011-05-27 3:27 pm
Silicon Valley
If your final three or four rinses / "floods" before blow-drying use 99% isopropyl, you're well on your way to completely dry. IPA evaporates much faster than water and actively blowing it off the board, accelerates drying even more. You can fiddle with the hot/cold settings of the hair dryer so the PCB surface becomes very-warm-but-not-painfully-hot at the end of your blow off procedure.
 
I avoid "improved" flux like the plague, not knowing what additives they used.
Remember ultra poisonous Mercuric Bichloryde used to be one of them.
I only use plain (Pine?) Rosin dissolved in Ethylic alcohol.
Works good enough, and if not, that means metal surface needs some extra mechanical cleaning.
Do not rely on ultra aggressive add-ons.

Same reason I make 99% of industrial processes in-shop EXCEPT Galvanizing.

Actually set up a rotary (small parts) and a static bath (chassis and speaker frames) and after a week got rid of it.

*Every* d*mn solution had some Cyanide into it!!!!

One of the few Processes I gladly outsource.
 
I wouldn't use washing up liquid, its crammed full of salt(*), likely to stimulate corrosion of the copper over the years as the chloride ions leach back out of the FR4.


To clean flux off PCBs why not use a PCB flux cleaning solvent? Its specifically designed to be safe on circuit boards and dries quickly.

Also there is such a thing as no-clean solder paste, wonderful stuff.

(*) to make it viscous.

I also use a water-based flux solder but it never really gets clean.

The very small amount of washing up liquid does get it off, (I am talking about a couple of drops to a half a lire of distilled water) but as I said, a thorough cleaning with clean distilled water is necessary along with a very thorough drying off. My boards are tinned over the copper and never had any problem with leeching. Don't forget that flux is fundamentally 'acid action' to clean the surfaces and allow the solder to adhere to them both.

Sorry to hear that myleftear had a problem - yes thorough drying is neccessary with a high pressure blower like a VAX wet/dry vacuum cleaner.

Mike
 

Vovk Z

Member
2011-10-30 10:32 pm
Kyiv
Isopropil alcohol plus clean gasoline ("Galosha" ukr/rus, not that which is for cars) I think is the best. I don't know ratio, I buy ready-made compound (it's name is "Compound for PCB cleaning").

Pure isopropil alcohol without anything works bad and needs too much work and liquid.
 
Last edited:
Hi JMFahey

Pine-Rosin... this sounds very nice. You brew it yourself, don't you?
([url]http://dangerousprototypes.com/docs/Flux,_flux,_flux)[/URL]

gottatry :cool:
david
Yes, that one.

I use 94% Ethyl Alcohol , also called Anhydrous Alcohol, simply because you can buy it anywhbere here in Argentina and is Medical Grade (=pure).
In some Countries it´s controlled or harder to use so theIPA may be a better option.

Paint Thinner/Acetone works fine but evaporates too fast and attacks plastic, so .....

Unless in a hurry I don´t even care about grinding it, just smash the big chunks into thumb sized pieces, drop them in an old jam bottle, fill it with alcohol and let it sit on a bench corner.

It WILL dissolve in a few days.

The beauty is since it has no mystery chemicals I feel safe and having been dissolved in alcohol once, it means boards are easily cleaned with a toothbrush and more alcohol, same type.

Which I repeat, is cheap and freely available here.
 

PRR

Member
Paid Member
2003-06-12 7:04 pm
Maine USA
> 94% Ethyl Alcohol.... In some Countries it´s controlled

Ethyl is drinking alcohol. In the USA it is heavily taxed(*). The most likely source is EverClear. Not available in all states, and many states don't allow the 95% product. (Like they don't know a whole shot of the 60% has the same effect as a 2/3rd shot of the 95%...) I have bought EverClear for cleaning, paying about $7 in sin-tax.

US "American Vodka" is 40%-50% Ethyl with water. (Real vodka has potato in it, but that's not allowed in US AV.)

Yes, for many purposes classic Lacquer Thinner is good or better; but the LT market is loaded with "Green" and "low VOC" products and you don't know what is really in it now.

(*)Actually the Federal Tax apparently applies only when the alcohol crosses state lines. (I still don't understand it.) There is a company in Maine who will sell me 90% Ethyl in large containers. For cleaning kitchens?? (I suspect marijuana and other extracts.)
 
Just steer clear of any ethanol more than 96%, since that is made by distillation with benzene and is carcinogenic (more so than the ethanol alone, that is!).


Usually high alcohol/methanol products for cleaning etc are loaded with bitrex or similar foul-tasting chemicals to discourage drinking.


And all solvent based cleaning products are fire and explosion hazards, and in particular outdoors in sunlight alcohol flames are often invisible, compounding the hazard. And never store flamable solvents in a fridge.