Cleaning a Board

Superman541

Well-Known Member
I've got a printed circuit board with some spots on it. Flux, probably. I have been told I can carefully clean those dark spots. Indeed, I have heard folks say that alcohol should be used after DeOxit on electronic circuits to remove residue. What kind of alcohol would I use? I am out of isopropyl. I do have ethanol that is denatured with methanol.
 
Alcohol AFTER DeOxit? The 'residue' is supposed to be left there - on contacts anyway - to slow down further corrosion. But it does have oil in it, so I suppose if you got it all over a board, yes.

Sorry for the tangent.

Not being a PCB expert I hesitate to say, but I would think ethanol/methanol should be fine.
 
Alcohol (isopropyl or ethanol) on a Q-Tip if the board is installed.
Tuner cleaner work better...but it's a spray.
 
I use Pure Acetone, then Windex, and Water to finish, with a toothbrush in a vented area, don't touch Acetone or inhale vapors.

After that treatment, your PCB cannot be cleaner.
 
Simple Green, a soft brush and rinse in warm water is my usual method. I've pulled boards out of old CNC mills that were so covered in dirt that the components were unidentifiable. I mean caked on, black dirt that was baked on from years of running hot. Wash the boards and all there weird problems went away. Go figure.
I've never seen any audio gear that was even 5% that dirty.
If they contain trimmer pots I just make sure they bake in the sun or near something hot for at least an hour before reinstalling. Fixed many a machine this way.

BillWojo
 
Interesting. I sounds like I have nothing to worry about. Simple Green first, then acetone, then windex, then put it in the dishwasher, then Isopropanol, then then alcohol, then DeOxit. I'm kidding. Thanks for the perspective, folks. I'll probably use a Q-tip to carefully clean it with acetone, then alcohol. That should work. Or just alcohol.
 
I purchased cans of different solvents from a local paint store years ago. Cheap to purchase and good to have around.
Try a few for yourself till you find a preference.
 
I would stay away from acetone, it's a universal solvent and attacks a lot of plastics.

BillWojo
 
Don't use deox-it to clean the boards...Its for electrical contacts. Not cleaning and defluxing circuit boards.
 
Acetone soluble in water and oils. It is a powerful solvent and is useful for cleaning areas where one would want absolutely clean surfaces. It will destroy finished plastic surfaces upon contact. Most PCB cleaning jobs don't need something like Acetone unless you encounter greasy or oily contamination. Test the surfaces it will come into contact first as it's reactions are instant and irreversible. Acetone is relatively safe to use and not particularly toxic but flammable. For cleaning PCB's 90% isopropyl alcohol is very good as it will remove shellac which is used on the foil side of the PCB [legacy Japanese boards]. This shellac was sprayed on the finished PCB for protection and it also is a non conductor. This shellac needs to come off if you are going to be soldering in new parts.

I use the dishwasher for most jobs but trimmer pots, oscillators, and tuning caps are a concern. The heat drying cycle of dishwasher's is a little to hot in my mind so I don't dry the components in the dishwasher. Hand washing with Simple Green is most likely the safest and best way followed with a tap water rinse, followed by a distilled water rinse [to remove hard water minerals of tap water] and finally a through rinse with isopropyl alcohol [also flammable] to remove traces of water. Dry in the sun or warm dry place.

I have a fellow audio fiend who swears that a water pic and 50% isopropyl alcohol works wonders but he has to do this outside because it makes a mess.

Conductive glue which has caused many problems in legacy boards does not come off easily and none of the above methods will get this stuff off. It must be scraped off with a blade like an Exacto knife to get it off most of the time.
 
I used denatured alcohol. Ethanol mixed with a little methanol. It worked well. Cleaned up the flux, residue. Did not attack the writing on the board. Proved to me that the dark spots were in fact flux residue and not carbon caused by too much heat. The board turned out purdy. 20170819_162906.jpg
 
I don't like water on any fiberglass-based PCBs. The cut or drilled edges are likely to absorb water and migrate inward.
 
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