Makeshift Potting Compound Alternative? - Page 1
Forum section: electronics / general

author: @rt
author_rank: Super Contributor
timestamp: January 10, 2019, 09:36:23 am
content: HiAnyone have any ideas?I have broken out the SPI interface between the microcontroller and RF transceiver chip in a Garmin chirp (geocaching beacon).This is to watch exchanges between the two chips, and perhaps playback with my own microcontroller program.https://imgur.com/a/KW9Bsvlhttps://imgur.com/a/jwwdZ3uhttps://imgur.com/a/Hq9yMiYI’m afraid to handle the board much now, and it still needs the mcu circuit.Normally, a blob of potting compound would be great, but it’s a lot to buy just for this. It also only has to last about a month or so.A blob of PVA glue would be good, but I fear that would contract too much as it cures.Does anyone have any other suggestions?Cheers.

author: helius
author_rank: Super Contributor
timestamp: January 10, 2019, 09:39:24 am
content: Neutral cure silicone (methoxy system) such as GE Silicone II (not Silicone I) can be used.

author: @rt
author_rank: Super Contributor
timestamp: January 10, 2019, 09:47:57 am
content: Ok. That’s not too much of an investment. Cheers

author: JackJones
author_rank: Regular Contributor
timestamp: January 10, 2019, 10:08:39 am
content: I too have used a general purpose silicone on occasion for potting. The keyword to avoid is acid cure silicone. Acid cure silicone apparently has a vinegary smell to it if you're unsure which type you have.Or if it's just a temporary thing maybe just a dab of hot glue would do the trick.

author: JVR
author_rank: Regular Contributor
timestamp: January 10, 2019, 01:30:41 pm
content: This is literally why hot glue was invented

author: tsman
author_rank: Frequent Contributor
timestamp: January 10, 2019, 02:12:32 pm
content: Yeah. Careful application of hot glue + some Kapton tape is probably your best option here.

author: rdl
author_rank: Super Contributor
timestamp: January 10, 2019, 02:22:22 pm
content: For just a month or two, even the so called "acid cure" silicone would work. It's not as corrosive as people think. I had part of a board coated with "Loctite Clear Silicone Waterproof Sealant" (strong vinegar smell) that didn't show any visible corrosion when I peeled the glue off after many years.These days though, I'd definitely just use hot glue.

author: coppercone2
author_rank: Super Contributor
timestamp: January 10, 2019, 02:29:54 pm
content: hot glue absorbs moisture!home depot sells "liquid nails" (I think) brand of glue that is silicone but uses some other chemicals then acid. I have looked at solder joints after 1 year with no problem. 24 hour cure time.https://www.homedepot.com/p/Liquid-Nails-2-5-oz-Clear-Small-Projects-Silicone-Adhesive-LN-207/2022039794in regards to GEII, I am pretty sure I threw a tube of this out because it did not seal right (but the liquid nails has been good for a long time).

author: rdl
author_rank: Super Contributor
timestamp: January 10, 2019, 03:01:07 pm
content: Quote from: coppercone2 on January 10, 2019, 02:29:54 pmReally? The cheaper stuff is made mostly from EVA copolymers and waxes, both are fairly moisture resistant. Of course, there's thousands of other things that can be added for various reasons, but I wouldn't think making the glue absorb moisture would be desirable, unless maybe it's a specialized application where there is some kind of moisture-cure component.

author: BravoV
author_rank: Super Contributor
timestamp: January 10, 2019, 05:12:57 pm
content: Quote from: coppercone2 on January 10, 2019, 02:29:54 pmRead this .. just read carefully ->THIS POSTand subsequently the ->Proofs.

author: coppercone2
author_rank: Super Contributor
timestamp: January 10, 2019, 05:23:15 pm
content: Quote from: BravoV on January 10, 2019, 05:12:57 pmmaybe if you get 3M it will be better but I read some where they pack whatever the hell they feel like as a hot glue filler. It's like mystery plastic. Even the silicone glue has 10% sand in it as a filler.Most people think its going to be used for holding together arts and crafts or making temporary wooden structures for carpentry, so there will be little qualms to cutting it with whatever can be acquired cheaply. Its not like it has a moisture spec it meets up to like glue meant to seal bath tubs (people will complain eventually because its a shitty job).I mean when they make even like elmers glue they think yea this might be used to put a chair together so we need to make it work and be safe. I don't think anyone takes hot glue seriously at all, unless its maybe the industrial 3M stuff for manufacturing, but that is very hot and expensive.

author: LaserSteve
author_rank: Super Contributor
timestamp: January 10, 2019, 06:09:22 pm
content: Probably not for use at 1.57 Ghz with GPS, However JB Weld Quick is useful if the iron nano-powder additive does not mess up your signal bandwidth. I've backfilled large numbers of DB9 shells on serial cables and 25 pin analog signal cables needing 150 KHz bandwidth with it for years. Have also used it when you need a magnet to hold the epoxy in place till hardened. I know it is unconventional but it is readily available in the US and in many cases offers less corrosion potential then RTV. AND NO, It does not conduct except very, very, slightly (10s of Meg Ohms on adjacent DB9 pins. ) when still wet Makes for a tough cable or a good way to protect low speed circuit boards from undergraduate students and musicians.... A few seconds with a heat gun will make it very fluidic.I've had VERY bad luck with store grade hot melt. Never again. Materials by companies like Nordsen are designed and adapted for circuit board work, Ordinary hot-melt is very bad long term.Hysol 1C White Epoxy with the ceramic loading is my favorite for tamper-proofing, high temperature work, and hiding the identity of chips, and when I need a very low outgassing material. Not what I'd use for filling large voids.Steve

author: tpowell1830
author_rank: Frequent Contributor
timestamp: January 10, 2019, 08:44:26 pm
content: Quote from: @rt on January 10, 2019, 09:36:23 amFor a month? Parafin or candle wax or silicone or any glue available in the shop, such as hot glue. Be creative...

author: rbm
author_rank: Regular Contributor
timestamp: January 11, 2019, 12:29:23 am
content: Hackaday article on potting alternative:https://hackaday.com/2012/06/04/potting-electronics-with-silicone/#more-76158

author: @rt
author_rank: Super Contributor
timestamp: January 11, 2019, 02:08:55 am
content: I have beeswax here for vintage radio! How did that not occur to me?I’m not touching the RF stuff. I can target the SPI interface where the wiring is quite specifically with that, and perhaps add some strain relief elsewhere with something else.Quote from: tpowell1830 on January 10, 2019, 08:44:26 pm