Potting compound

enfield_freddy

a subject that many older viewers might remember from there old electronic kit building days


I have about 20 small boxes (abs/plastic) that have glue on covers (40 mm x 40 mm x 20mm) that are containing either relays (sealed) or a small printed circit board with a 8 pin ic and a few resistors , tight rubber grommets are use on the cable entry.


those are to be used in a car/motocycle environment.


potting compound is quite expensive now , and they are not being potted at the same time , so huge wastage.


I have been using a hot glue gun to glue the units to the base , then a covering of glue to seal/stop vibration , but have had several failures , ie: melted cases and possibly melted wires


potting compound is an old product , is there a modern (cheaper) product I could use ? first thoughts are bathroom silicone from the £1 shop?


any other suggestions


thanks


ab

forgotmyname

Modern, Epoxy works, But not cheap either.

Cheap silicone sealant or expanding foam?

enfield_freddy

yup modern epoxy , but expensive , I was thinking of clear silicone in a big tube from the £1 shop , but wondered if anyone had had any negatives about this (rotting components etc)


things must have moved on over 40 trs

epninety

Potting compound is still the stuff to use, but you can buy it in boxes of smallish sealed twin compartment bags. You can mix it up before opening the bags, reducing mess and waste. Try Rapid Electronics maybe?

Silicone sealant isn't ideal - the usual variety (with acetic acid in it) is corrosive to electronics in the long term. Also if you lay it on too thick it will never set in the middle. I've opened 10yo wiring and found the centre not yet solid.

Epoxy will work - especially the rapid setting variety, as tends not to set absolutely solid. Still not cheap though, and it can get very hot when curing in large quantities - can be a problem for some applications.

Clear casting compounds can be bought by the can - and mixed as required. I've used those occasionally.

If you just want to keep the moisture out, rather than prevent vibration damage, then either aerosol or brush on Conformal Coating is the way to go. Even the cheapo aerosol one Maplin sell is very effective, and spray cans are very good at getting effective coverage.

enfield_freddy

Silicone sealant isn't ideal - the usual variety (with acetic acid in it) is corrosive to electronics in the long term.


which sort are acetic? , which are not


Clear casting compounds can be bought by the can - and mixed as required. I've used those occasionally.

example product please


If you just want to keep the moisture out, rather than prevent vibration damage, then either aerosol or brush on Conformal Coating is the way to go. Even the cheapo aerosol one Maplin sell is very effective, and spray cans are very good at getting effective coverage.


maplins would be my last port of call , as I live within 5 miles of CPC, however , again product example please?

epninety

Are you blocked from access to Google and all the other search engines?

Silicone sealant isn't ideal - the usual variety (with acetic acid in it) is corrosive to electronics in the long term.
which sort are acetic? , which are not

All the cheap ones are, of course! Anything marked 'neutral cure' or similar should be ok, or buy 'proper' electronic RTV like Dow Corning 732

Clear casting compounds can be bought by the can - and mixed as required. I've used those occasionally.
example product please

Type 'water clear casting resin' into your favourite internet auction site. I've used 'polylite' to good effect.

Conformal Coating is the way to go. Even the cheapo aerosol one Maplin sell is very effective
maplins would be my last port of call , as I live within 5 miles of CPC, however , again product example please?

Well CPC have 11 products listed in the 'Conformal Coatings' section of their website. Take your pick, but I'd use the Ambersil one.

enfield_freddy

thank you , I have been to my local sealant specialist (sealants only) and had the acetic explained , its the bathroom type that are formulated like that , he has advised a LMN type sealant ,

this I have been advised does in fact go hard all the way thru , and for my useage is non rotting, in my case , any colour will do and Soudal Silirub LMN in brown is only a £1 each

I will try the Ambersil spray on the units first as a safety precaution

bluesnake

I would have tried cheap liquid body filler, but it can get hot when it sets. Hot enough to melt some plastics.

enfield_freddy

cheers , I tried filling some with the hot glue gun and it melted the wiring and plastic cases , I will try the silicone method tomorrow , I imagine that if I drill a small hole in the lid , fill to the brim , push lid on , in will push surplus thru hole (cut off when dry) therefore saving the lid gluing