Moderately waterproofing electronics (such as cellphones)

Nazo

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Apr 2, 2002
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So, I got a large tube of dielectric grease some time ago for various things in the car as it's pretty common to use it for things such as battery terminals, contacts on things such as lights, and etc to help protect the metal from corrosion while still allowing a physical connection (it has a high viscosity so physical contacts push the grease out of the way and aren't insulated from each other.) The grease is also used for things like waterproofing outdoor antenna connections and other such things.

So I'm having a bit of a thought. What would happen if I used it on something like a cellphone? I've heard of people using it to do things such as completely waterproofing an iPod Shuffle for instance, which is nice I suppose, but it's a very minimal system. A cellphone is much higher end and produces a lot more heat. A dielectric should also insulate thermally as well shouldn't it? For normal uses this doesn't matter, but a cellphone already can produce a lot of heat when playing games or that sort of thing...

Along these lines I've also kind of wondered about another, different direction: thermal paste. Some, such as Arctic Silver 5, can be really bad due to being capacitive or even slightly conductive, but many such as Arctic Cooling MX-4 and ceramic-based compounds are supposed to be completely non-capacitive and non-conductive. I have quite a bit of AC MX-4 on hand still, so this is a possibility. I don't have much I can really test this on though as I don't particularly want to destroy my electronics just to test -- I just know that they push this as one of the many selling points of the material.


Note that the idea I have is not complete waterproofing. I'm just thinking of brushing it onto contacts and SMD components with a q-tip. The goal is not to be able to dunk in water, but just to ensure that if rain or something gets in it won't short anything.

Any thoughts? Too crazy to work, or maybe it might just protect things against reasonable amounts of water?
 

stormy1

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a: holds in heat
b: can throw rf circuits out of spec by creating capacitance between the traces.

As far as thermal compound that sounds interesting but without the testing equipment to insure it is not capacitive at RF frequencies I would hate to recommend it.

To be legal from a business perspective the device would have to be fcc re-certified after it is applied.
 

Nazo

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That would probably be just as heat resistant as the dielectric I'd imagine.

Bear in mind though, I'm just talking about brushing a little bit on around traces mostly. As for the thermal compound, it very explicitly states that this kind does not have any capacitance and can't harm components that way, so if it does it is actually very false advertising since this is a key selling point. I don't really have the means to properly test it. There is a small question of whether water could penetrate, but thermal compounds are usually fairly thick and I think maybe this is not an issue. I just wish I had something I could test on, but I can't think of anything suitable.

This might not be necessary on my phone though. Looking at the insides a bit more carefully (I have an old broken one from eBay I switched the working components out with broken ones on mine to make a repair, so basically little is left that's salvageable and I can just pull it apart all I want) it seems it's sealed up better than I thought and it looks like they may have even put something or other on a lot of the components to help protect them. (Also of interest to me is the fact that the SoC doesn't even really have much by way of any sort of heatsink or anything. I realize you can't do much for a SoC due to their design, but it still generates heat when the CPU or GPU portions are being used heavily does it not? Ironically the SDRAM seems to have the most heat dissipation...)
 
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Nenu

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Apr 28, 2007
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The spray cant be as heat resistant, the layer is extremely thin.

Fair idea you have but bear in mind that grease shifts with temperature (reducing water resistance) and may pose a fire hazard or could pool/run out of the case.
The main worry I would have with grease is that it can cause overheating (aside from a greasy pocket :p).
The components that get hot will have a tolerance to heat that will be within a usable metric.
Grease is sure to affect this in a large way.
You can get away with it on many components, but probably not all.
 
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