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Coating a Motherboard In Thermal Resin?
Bat Country writes "I've had an idea in the back of my head for some time (and I'm surely not the only one) that it would be a worthwhile project to coat a motherboard in thermally conductive electrically insulating resin — complete with all of its various components — for the purpose of immersion, shock resistance, whatever. I'm curious to find out if anyone's undertaken a similar project or if it's known to be a shockingly bad idea (due to shrinkage during the curing process) already. Thoughts?" If you've done anything similar (even an experiment that failed), how did you go about it?
Probably a lot easier to source yourself a few liters of Cray blood (or some similar non-conductive coolant) to submerge the board in instead.
Cheers,
The issue I see is with immersion. Sure you can coat the MB but what about the USB, VGA, etc connectors? Can you guarantee water will not leak in. Water has a way of getting inside any way it possibly can. Coating may be beneficial when you do not intend to put in case. Maybe to protect the MB as a bench system.
Wouldn't that conduct the heat from the CPU over to the other components?
If you use immersion, why do you need fans?
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Except that conformal coating would not be the greatest idea for use with immersion cooling. You would have to coat everything together, including memory modules, pci cards, power connectors, etc..., making them permanently attached and impossible to replace if/when necessary. Since it seems Bat Country's intention for this is so that a non-conductive coolant is not required for immersion, leading me to believe water or some other electrically conductive coolant is to be used, you add the risk that the coolant may enter through small holes and cracks that may develop at the places where the components are connected, immediately bringing everything to a halt.
For immersion, the only sensible means is to use a non-conductive coolant and not worry about having to protect your hardware from the coolant it will be immersed in. It might be more expensive than just cooling with water, but it will likely be cheaper than having to replace ALL of your hardware that you just fried.
...and it's a well known process - i've seen devices from the '80s with epoxy encased parts. Keep in mind though potting does practially nothing for heat dissipation. Even if you managed to get your hands on some thermally conductive resin, in PCs the principal way of heat dissipation is forced convection (coolers, that is), which allows to use very small dissipators for the given power. I don't think you could find a substance that allows good thermal transfer without a large surface area - meaning, a lot of resin.
If you're planning to pot and then submerge in Fluorinert or a similar compound, the resin coating, no matter how good transfering heat, will only raise the working temperature of the parts.
That's what he wants to do?
pfft. Waste of time and hardware. A leak will kill it.
Use something cool, maybe some old Cray coolant. It's out there.
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Insightful, not funny? I think this is slashdot (the community) indirectly declaring their political views.
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I see a lot of comments about the immersion side of things, for which I know it would probably be a lot cheaper to just pick up some nonconductive coolant.
How about other reasons for doing it - specifically shock resistance and hardening against slippage caused by vibration?
Additional value could be found in potting the board in marine/cave/jungle environments where the hardware might be exposed to caustic and humid air.
Also, presumably resin coating might get around problems with hungry insects. I'd imagine a really well designed medium-tight case suspending the components in a nonconductive coolant might work, but it seems like it would be a more bulky solution.
However, I'd be interested to hear of better solutions than coating the whole shebang in toxic goop.
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The contest was to build the most weight-efficient bridge, using only balsa wood sticks and wood glue. Efficiency was judged by (failure load)/(bridge mass). The highest load, by far, was born by a bridge that had been totally coated with wood glue. Unfortunately for them, this coating raised the bridge mass by nearly 50%, so their bridge was still less efficient than my team's, which used a more conventional truss design, with a coating of glue around the joints. Nearly every bridge in the class failed first at a joint, so reinforcing the beams themselves was a waste.
The point is that applying the same reinforcement everywhere tends to be a serious waste of resources that would be better applied to the most critical areas. This is why my shiny new motherboard has a few components embedded in epoxy, surrounded by metal heatsink-like rings. Unlike other motherboards I've used, this one has no large components sticking up from the PCB, so I'm guessing that they singled out those bulky components, shrunk them down, and then added the epoxy and rings to allow them to operate safely at a smaller size.
There's no failure quite as dissatisfying as a complete and total solution to the wrong problem.
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Some marijuana ought to cheer you right up!
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Most resins outgas really nasty fumes. Smell-wise, epoxy resin isn't nearly as bad as polyester (aka fiberglass) resin IMHO. Any major resin work should be done outside or in a professionally designed cross-ventilated room. A carbon respirator is also worth its weight in gold. Cancer and Nerological damage are pretty good things to avoid.
Molding & Casting (through replica propwork and creature prosthetic effecs) is a hobby of mine, so here's what I know about resins. Maybe it will help
Epoxy resin is good at holding up to high temperatures. It comes in a variety of cure times and is available in small quantities at hardware stores and large quantities at marine supply stores. The fumes are smelly and unsafe, but they at least dissapate soon after curing.
Polyester resin (aka fiberglass resin) is cheaper than epoxy. It is generally weaker. It's fumes are quite nasty and hang around for days, so it's really an outside thing. It's probably no good for this task as uncured resin ravenously dissolves polystyrene (I don't know if PCs ahve polystyrene, but I wouldn't risk it).
Polyurethane resins come in the widest variety of formulations. It varies from hard as rock to a very flexible rubber, and any mixture inbetween. It is very low odor, but the fumes are still nothing to mess around with. Some formulations use metal fillers like aluminum (reduces shrinkage/thermal warping), so look out for that. It will certainly shrink a bit, so thicker coatings should be done with more flexible varieties. Shrinkage can be reduced by adding loose chopped fiberglass, though this does raise thickness.
Silicone rubber, particularly Platinum cure silicone has low to zero shrinkage. It's also by far the least toxic. It's also the most expensive by volume. again wide range of cure times, thickness/thixotropy can be adjusted by adding fumed silica (just don't breath the stuff). It is thermally resistive, so you will want to keep coatings thin, and suppliment it with submersion. Still, if I was tinkering around with such hardhacks, I suspect I'd go this route. Silicone is a great electrical resistor and has fantastic waterproofing abilities
for thin coats of any of these materials, you'll want to brush or spray the liquid to minimize airbubbles. All types resins have sprayable formulations, either by using specialty spray devices sold by the resin manufacturer, or by thinning the resin with the appropriate solvent. The more solvent you add, the more shrinkage is an issue, which is supplanted by applying thin coats in good ventilation.
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Another option of course would be to just buy faster hardware in the first place (it sounds like this is for a single PC/mobo), which should be cheaper and easier than immersion. If you already have the fastest hardware available and have a lot of money to blow, then go for it. I'm just not sure it's worth the time/cost/effort to encode videos at 200FPS instead of 180FPS, or get a few more points in 3dmark. Don't get me wrong immersion is pretty cool, but it's just not that practical most of the time.
Its not clear what the poster is trying to do. Conformal coating or potting may not be a good option. Is he trying to protect the board from dust, an occasional spraydown, or condensing humidity? Maybe CC or potting would work. THough the heat issues would be pretty bad as mentioned 100 times above.
I would recommend a pressure housing with o-rings and proper feedthrus or liquid proof connectors. For high pressure and heat dissapation, filling the pressure housing with Flourinert would be a nice solution, just put a small pressure compensating bladder on the pressure housing so little air bubbles aren't a problem.
If one is pressed for time, a really good ziplock bag filled with Flourinert, and a potted feedthrough for the wires would also work in a pinch.
If you use the low power VIA chipsets like Eden you only have to dissipate under 10W of power, which these thermal goos could handle. But potting is very insulating compared to open air.
Don't forget the SSD. Standard hard drives won't handle any of this.
It might be useful to rethink the process and figure out what it is you are trying to address. Just moisture - conformal coating. Just vibration - make a better box? If you are strapping this to the outside of a Mercury outboard motor I would go with a better box.