Potting Compound

[tigoe]

So I'm working on a telemetry project where the parts need to be REALLY waterproofed. Manufacturers of boards like I'm doing tend to just use potting compound, and discard the telemetry unit when it dies. This bothers me. I'd like to make a unit that's re-usable, but cheap. I could make an openable housing, but before going down that road, I'm curious: does anyone know a good safe way to dissolve potting compound without damaging the components?

[westfw]

does anyone know a good safe way to dissolve potting compound without damaging the components?

It depends on the potting compound. For instance you could probably use any number of common waxes and just melt them off... Other common potting compounds are really inert, and or get very similar to the materials chips are packaged in (silicone, epoxy.)

I've been wanting to build electronics into PET pre-forms.

Tough as nails, cheap, designed to be gas and water-tight, and neat-looking. Unfortunately, I haven't found a good source of low to moderate quantities in the desirable range of sizes...

[tigoe]

Waxes wouldn't work in this case. Whatever we use has to withstand a year and a half in a rainforest, and probably multiple dunkings in the river. And the whole package has to be less than 30g, and attach nicely to a small animal collar.

There's plenty on the market already, and we've looked into lots of options, but the subject of potting compound came up the other day, and no one had an answer on how to dissolve the epoxy types in a way that you could re-use the components inside.

[pstemari]

Epoxy polymerizes when it sets up, there's not any solvent in it. Once that happens, the only way to remove it is to break it down chemically. Anything that can do that won't stop at the epoxy, I'm afraid.

[charliex]

I remove epoxy from devices that are completely encapsulated with MEK and a lot of time with dental picks etc. So far i have not damaged a PCB or components. I've dunked stuff for as much as six hours.

Look at the silicon based ones, a lot of cars, motorbikes and boats use it to protect electronics as hard setting epoxy can shrink and damage components, they're probably not great in direct sunlight though.

[ALLENCOSTA]

Hi Tigoe,

Did you end up using a silicone potting or something else? How did that work for you?

Allen

[IHeartEngineering]

One option is to use a conformal coating spray.

https://webvia.techni-tool.com/VIA/viaI ... ewWindow=Y
754CH012 Tech Spray Conformal Coating, Fine-L-Kote, Acrylic, 12 oz.

[mikeselectricstuff]

There are soft potting compounds designed to be cut away easily - sometimes called 're-enterable'.
e.g. http://www.raytech.it/inglese/home-magic-gel.php

[benha]

I'm late to the table on this one, but if you're still mulling this:

What about encasing it in wax and then coating the wax with a layer of epoxy. The wax would keep the epoxy from bonding to the electronics, and the epoxy would form a shield that could be cracked off like a nutshell. Once you've removed it you could just melt the wax off.