GoPro cameras are not waterproof, but they do come with a separate waterproof enclosure.
The waterproof versions are thick and heavy. Basically the waterproof version has the additional waterproof shell around the thin version.
The circuits are vulnerable because they have connections formed just by touching part A to part B… The connection then has for example, 100 leads (like wires but on the surface of the circuit board…) to send through… Water gets into that and contaminates the connector…
I was in the market for a new watch, and I went to several well known watch dealers. The explanation i got was that “water proof” is no longer used, only “water resistant.” The reason is that pressure plays a role in the seams on any device that keeps water out.
On the other hand, modern electronics can be very liquid resistant (not water) as long as the liquid is not conducive.
many diy sites.
Soap is one thing. Soapy water gets into all kind of places ordinary water won’t. Salt is another thing: once you get salt on it, it corrodes, and it’s dead.
Distilled water is better for cleaning things out, but not very good. Distilled water tends to become Ionized water when mixed with metalic copper, and those are copper ions that have been stripped off the board. Worse, it’s very hard to get dry – that’s one of the reasons you use alcohol instead of plain water.
And yes, we coat our boards, and you can drop them into water and they will still work. You can drop them into salty water, and if you take them out fairly quickly, and clean them afterwards, they will still work – at least for a couple of years. You can drop them into soapy water and they will still work for a couple of years, expecially if you try to clean them properly.
We can’t ship the coating fluid, it has to be local at the manufacturing plant, and it has to have safety approval at the manufacturing plant, and it hides faults, and it makes testing more difficult, and so on – it’s not something you would do unless you had too.
Wow this is possibly the worst advice I ever heard here. You don’t even mention depth or pressure. I could kiss a mermaid, lick my finger, touch a CPU with the same advice you are giving.
I work on equipment that is used outdoors all the time.
If the equipment was not powered up when it got wet. Was not left too long for corrosion to happen. It often is fine after cleaning and drying.
We see equipment partially functioning with quite a bit of water inside. But current is high. Many things are not working right. Often the power supplies are stressed and need replacement. Some other parts as well. Sometimes nonvolatile memory is erased or degraded. Probably due to bad signals initiating unwanted erase cycles.
Just a small amount of moisture can cause the voltage difference between ground and positive to narrow. Logic levels cannot latch properly.
Surface mount components can hold liquids underneath for quite a log time. Even electronics cleaning compounds can cause problems in that case. I dry thoroughly with heat gun. Then leave it out in the open air for a long time after. An oven cycle too if you have one.
Some of these have already been mentioned:
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Water will become an electrical conductor when it gets “dirty.” (Ions in the water due to contamination will become mobile charges.)
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Water has a very high dielectric constant. So even if the water was very pure, moisture between two solder joints or two traces is equivalent to inserting a capacitor in the circuit.
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Dendritic growth. Conductive dendrites can grow (via electrochemical migration) between two solder joints when moisture is present, causing shorts.
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Galvanic corrosion (moisture + dissimilar metals).
The #1 (and most spectacular) reason it might not work is the water creating a path from “high” (3.3V say) to ground. Best case, the chip won’t work because there is no voltage difference between power and ground. Somewhat worse case, you have a substantial current, so the power supply is pushing as hard as it can to keep the voltage up, so there is overheating, voltage spikes, etc. Worst case, say it’s something you plug into the wall - 120 volts going to ground through a short makes parts blow up.
Specific to chips, some digital types draw more current if they are between high and low. Heating, failure, etc. For analog chips, some have inputs that are much less than the battery voltage. Hit one of those with 3.3V, and that part of the chip goes away.
The term I’ve always heard is potting compound. Primary uses are to make sure heavy parts don’t fall of the board, and to hide trade secret stuff. Some of the mags will take an iphone or whatever apart and do some reverse engineering by identifying the chips used. Hard to see through black plastic. 
Reasons you don’t? Almost always cheaper and easier in the long run to put the board in a box, then use gaskets and such to make the box watertight. Fewer points to seal, easier to check the board, more controlled heat, etc.
And of course, you don’t slap a “waterproof” label on unless you like getting sued. More like “leave it in water at this depth for 60 minutes, and it will still work.” What’s the depth equivalent for a waterjet cutter? :eek:
That’s odd, I didn’t see a single word of advice in that post. Just a description of how they manufacture things.
I went through a “High Reliability Soldering and Electronic Repair” course. We were trained with PACE kits that were pretty versatile . We were told they were called conformal coatings. They could be light epoxy like coverings of circuit boards and their components or heavy coverings. You could scrape them off with a knife like tip in the soldering iron or with a brush type wheel in the drill thing. Either way, there was no fast way to do it and the heat way really smelled badly.
Anyway, sure, you can water resist a circuit board. I’m not at all optimistic about water resisting any connections to the circuit board, though. And it’ll add bulk, weight, and cost to the consumer. And retain heat if that’s an issue. It’s easier to just get a water resistant case.
For our cubesat, we used a silicone-based conformal coat. It stayed reasonably soft and could be scraped away, though not without damaging things. We had UV-resistant stuff that we applied to our solar panels. It seemed pretty heat resistant.