How do you clean and protect you PCB from dust and humidity?

 

Cleaning, remove rosin residue with alcohol, and brush down for dust. Extreme cases, cleaning in a dishwasher with Alconox. Protection from moisture, painting PCB with a conformal coating of which there are several options from shellac like coatings to silicone rubber. Dust protection, an enclosure with filter and fan if needed for cooling.

 

Cleaning, remove rosin residue with alcohol, and brush down for dust. Extreme cases, cleaning in a dishwasher with Alconox. Protection from moisture, painting PCB with a conformal coating of which there are several options from shellac like coatings to silicone rubber. Dust protection, an enclosure with filter and fan if needed for cooling.

Back in the day we used to clean with Tolulene and coat with clear varnish to fungus proof.

 

Toluene was/is good! There was another one also used before all the chlorinated hydrocarbon restrictions started which is playing hide and seek with my memory. Carbon Tetrachloride?

 

Toluene was/is good! There was another one also used before all the chlorinated hydrocarbon restrictions started which is playing hide and seek with my memory. Carbon Tetrachloride?

Yes!
The varnish caused alot of headaches for our Field return/repair team...but it sure provided the needed protection for the PCB assembly.

 

There was another one also used before all the chlorinated hydrocarbon restrictions started which is playing hide and seek with my memory. Carbon Tetrachloride?

I think you mean TCE (trichloroethylene). Carbon tetrachloride was used in dry cleaning; learned about it from the Lost In Space series.

 

Toluene was/is good! There was another one also used before all the chlorinated hydrocarbon restrictions started which is playing hide and seek with my memory. Carbon Tetrachloride?

Carbon tet was nasty stuff. During it's final phase out period we would still use it carefully and always dump the waste in proper containers for proper disposal.

But it seems someone was cleaning parts in a container next to a sink, and the very small drops that happened to go down the drain were actually detectable. Not sure if we got a fine or a warning, but everyone was strongly instructed not to use in the same room with any sink.

Now the funny story. A few years before I started someone from the government paid them a visit mid December. Seems a groundwater check turned up something nasty we were authorized to use. The place did wafer fab so the list of permissible substances was long. Despite out CEO stating we never used that particular chemical the gov't guy began a rant of the sanctions he would impose.

Our CEO is a tough guy. He stood up and said "listen, the company is just getting by. We don't have the money to hire attorneys to fight you on this. So you win, the company is yours" and tosses his keys on the desk. "Turn the lights out on your way out and tell everyone on the floor merry Christmas and that they don't have a job anymore."

He never made it to the door before the gov't guy reconsidered his position.

 

He never made it to the door before the gov't guy reconsidered his position.

Interesting story. I once made a similar ultimatum to a bunch of FDA attorneys at the Federal Courthouse in Philadelphia. The room was full: me, our CFO, and our counsel. On the other side was about 17 Federal attorneys. At issue: The same FDA inspectors are responsible for blood banks and packing houses. To me, there was a difference.

So as not to keep you in suspense, I learned the FDA inspector was upset she had to park in the visitor lot. I arranged a special parking space for her right next to the entrance. Our next inspection was flawless. Cynical? No way.

 

I think you mean TCE (trichloroethylene). Carbon tetrachloride was used in dry cleaning; learned about it from the Lost In Space series.

actually...I made a mistake.
It was Trichloroethylene, not Tolulene.

we used to blast the whole finished PCB assembly with the stuff. It dried very quickly and the board ended up clean and shiney.

 

Tric and Perc (perchlorethylene) are/were both very common. They have the advantage over carbon tetrachloride or chloroform of being higher boiling. You can still/were able get perc as brake cleaner. I have CRC brand. I like absolute ethanol plus a little acetone for now and have been experimenting with low boiling cellosolves, So far, those results are promising. I need to get some really old solder/board stuff that leaves the "white powder" with IPA or ethanol. Since cellosolves work with considerable water present, I think they may be a great alternative.

 

I have a friend who cleans his boards with (what else?) Eucalyptus oil.

Other than removing flux from parts of circuits with alcohol where leakage current might be an issue I don't bother. Some boards are placed in plastic or metal enclosures and that's enough protection.

I have a small project from 2006 open for repair on my desk and everything is as clean as it was when I put the top on the enclosure 14 years ago.