PCB protective liquid


2019-06-11 1:12 am
Well, I think I have gotten enough information from the participants of this 3ad.
I plan to consult and look for the recommended products for the one that suits me best but if in the meantime there will be other future interventions in this 3ad, thank you in advance too.


Paid Member
2004-03-24 5:16 am
SF Bay Area
For sensitive circuits coatings may compromise the performance. On sensitive instruments like electrometers and 6 1/2 digit DVM they actually open the solder mask around the really sensitive areas because even that can degrade the insulation. On some instruments they use "air-wire" and Teflon inserts to isolate the sensitive nodes. Conformal coatings are usually reserved for instruments subjected to really challenging environments (shipboard, jungle etc.) and the circuits are all low impedance so they do not get compromised by the coatings. I have only seen coatings on a very few devices in the last 50 years, most of which were military.


2019-06-11 1:12 am
I read that several are going OT as if protecting pcb circuits was a rare procedure or coming from Mars; in the past, on the other hand, it was normal to coat the PCBs on the side of the welds with a coating which, in the event of replacement of faulty components, allowed the new components to be soldered onto the pads without removing the coating.

There are countless examples that I can show, in these photos you can see the semi-gloss coating applied by the manufacturer.
Photo 1 Technics
Photo 2 Victor Jvc
Photo 3 Denon



Last edited:

You are showing solder masking. This is done with a silkscreen that prints a solder mask to the circuit card. That way when wave soldering you do not get shorts. That is different than a conformal coating that is applied after soldering to protect the entire circuit card from corrosion.

I suspect just a language issue.
Here the Plastik spray smells like the bonding agent used for PVC pipes, which is acrylic or PVC in a solvent.

I mold plastics, so I can discern between most plastics just by the smell.
The commonly used material for solvent bonding acrylic is chloroform, again a familiar smell, which may also be mixed with aromatics like toluene.

Like mentioned above, this is not a regular factory process, but a special modification for harsh conditions like marine.

Come to think of it, not much seen in car audio either, which is a harsher environment than inside a home.


2019-06-11 1:12 am
After a closely studying your excellent pics, I'm not seeing much of what you described. Sorry

I am not referring and I not would not confuse minds with the copper coating which is the "solder resist" of which I hope we are all aware of how it is called in technical terms but I am referring to the further transparent varnish applied as a final protective transparent by the manufacturer

I hope that the photos are more explanatory than many words, more than this I don't know what to do.
See the photos

Clear coating from the manufacturer before cleaning


Transparent coating removed after cleaning with appropriate solvents


Clear coating from the manufacturer before cleaning


Transparent coating removed after cleaning pcb with appropriate solvents