Is Varathane for wood, and regular handyman silcone chalking ok for PCB's ?

[MathWizard]

I want to hold down and coat a few trace replacement wires, on a PCB. And looking up conformal coating, I see varathane/polyeurathane mentioned a few times. I have an old paint can of clear varathane. So is that ok on a PCB ?

I found it doesn't completely harden up, so it would make it easier to remove if I need to . I never tried super glue on a PCB, I see that's not recommended around the soldering iron. And I don't have nail polish or a GF with some.


Also for anti-vibration, is regular old indoor/outdoor white silicone chalking fine on PCBs ? Anything corrosive to pads or pins ?

[chickenHeadKnob]

There are two types of polyurethane; water based and oil based. The water based stuff is mostly poly-acrylic with just a hint of urethane. I wouldn't use it. The oil based stuff might be OK as a conformal coat.

Normal silicone caulking releases acetic acid on cure and will corrode your PCB, so a hard no. There are latex based, urethane based and acrylic based caulking formulations, tell us what it says on the tube.

You can use crazy glue (cyano-acrylic) to tack down bodge wires. Hot melt for anti-vibration.

[BurningTantalum]

If the caulking smells of vinegar - don't use it.
If it says on the tube - 'Neutral Cure' then it is probably safe to use.
Hot melt is much easier as it 'goes off' very quickly.
Other glues can have unexpected issues, sometimes years down the line viz. the brown glue of death used on so many PCBs even now. It turns conductive and can rot copper leads and traces.

[jeremy]

Be careful, a lot of silicone-based fillers/adhesives can negatively affect solderability: https://smtnet.com/library/files/upload/silicone-contamination.pdf

So I would try to avoid getting on anything conductive.

The mobile phone repair crowd use UV curable solder mask after repairing traces, often just the "mechanic" brand you can buy from aliexpress/amazon/ebay: https://www.amazon.com/MECHANIC-Prevent-Corrosive-Soldering-Welding/dp/B0747P2CWJ/

You just need to buy a 365nm torch or LED to cure it, but it cures very fast, is strong and has no outgassing or other contaminants to worry about.

[jpanhalt]

For bonding that needs great adhesion and a little flexibility, I use E6000 from Eclectic Chemical (https://eclecticproducts.com/product/e6000-craft/ ).  It may sell under different names but has a distinctive odor.  It applies as a goo like toothpaste, then cures into a much thinner clear adhesive.  Unlike silicones, it cannot be pulled off.

[david77]

I use clear nail varnish for that.

[MathWizard]

ok thanks guys, the varathane is water based, and the silicone has that vinegar smell.

I'll order some real stuff

Looking at the prices, maybe I will just get some nail varnish, I'll look up the brand/type other people use