4200 on a circuit board?

[Peregrine1983]

Hi all,

Is it dangerous for any reason to secure the back of a circuit board (SCAD Holding tank monitor control surface) to a bulkhead directly with 4200 or glue? It will not be energized u til the 4200 is cured, but will dry 4200 cause it to short or create a fire risk?

Thanks for any help.

[Cheechako]

I dont know, I doubt it, but silicone is commonly used on circuit boards.

[tkeithlu]

Do you mean 3M 5200? Well, it's not conductive. It is rather permanent, such that you might damage your item when you try to take it off. Plenty of glues are flammable, and the solvents in them are very flammable until the evaporate, but I can't think of one that is conductive. But then, assuming that you are talking about a fiberglass boat, the bulkhead itself is flammable.

[Peregrine1983]

Thanks all. I am asking about 3m 4200 - the softer drying version of 5200. Haven’t decided if I’m going to do it or not.

[s/v Jedi]

Originally Posted by Peregrine1983

Thanks all. I am asking about 3m 4200 - the softer drying version of 5200. Haven’t decided if I’m going to do it or not.

Use a good double sided tape. Real strong: 3M VHB tape.

[Lake-Effect]

Originally Posted by s/v Jedi

Use a good double sided tape. Real strong: 3M VHB tape.

Double-sided foam tape is especially tenacious.

But for the OP, I would not choose to just mount a printed-circuit board somewhere without an enclosure. Servicing would be much harder, and after a few years, who knows what corrosion and dirt could be accumulating on the board itself, or happening behind the sealant or tape.

[RaymondR]

And you need spacers to keep it away from the surface, if water from leaks or condensation runs down without it being spaced it will most certainly get into the electronics.

[bradfordharley]

4200 is fine. If you gave a thick enough glob you can cut it off later. Just don’t glue any chips that expect ambient air cooling as 4200 will be a thermal insulator.
On another note, If you are worried about moisture, T-9 boeshield is a surprisingly good moisture barrier. I’ve coated things like raspberry pi’s successfully. Obviously if you want both, adhere with 4200 before you coat with T-9. .

[Richv]

Originally Posted by Peregrine1983

Hi all,

Is it dangerous for any reason to secure the back of a circuit board (SCAD Holding tank monitor control surface) to a bulkhead directly with 4200 or glue? It will not be energized u til the 4200 is cured, but will dry 4200 cause it to short or create a fire risk?

Thanks for any help.

I've been working with electronics for about 1/2 a century. I've seen many circuit boards which had the back side coated with a thin (1/16-1/8") layer of epoxy. You can also use "circuit board potting compound." As long as the mounting force does not twist or stress the board or crack the potting compound, it works just fine.

[jamhass]

Make sure you don't adversely affect any cooling the board's components might need.

[a64pilot]

The SCAD tank monitor board is already conformal coated, look at it, you can see the shiny coating, so you don’t need to do anything to it coating wise for corrosion, and some things may attack the conformal coating.
If you want to glue it 4200 will work, but is slow cure. I usually use double sided Velcro for things like this.
Foam tape is next strength wise.

The 3M VHB Jedi speaks of is incredibly strong, it’s what holds body molding onto cars etc.
Use Very High Bond tape if you really, really want a strong bond.

The tapes and Velcro etc don’t need to set, things like 4200 can run, drip and make a mess if put on a vertical surface.

[a64pilot]

Originally Posted by Cheechako

I dont know, I doubt it, but silicone is commonly used on circuit boards.

A lot of conformal coating is silicone based, but most window types of silicone etc sweats acetic acid when it cures, that’s why it smells like vinegar, and acetic acid is corrosive, so I wouldn’t use that on a circuit board myself.
Many types of silicone don’t sweat acetic acid and would I assume be OK?

[wingless]

When I use silicone on a circuit board, I select a product specified for that usage, such as this Loctite SI 5145 silicone, that specifically lists non-corrosive attribute.

The 3M Fast Cure 4200 adhesive by contrast lists that metal primer may be required. For those reasons it doesn't appear appropriate for electronics.