3 ms·

Any thermal impact after the coating?!

by tamimio 3y ago

9991 3y ago
Being submerged in water will substantially help thermals.
- alchemist1e9 3y ago
  Is it possible one could coat electronics like this, then submerge them in (distilled maybe) water within an ice pack, freeze them, then use them and the heat melts the ice?
  - kadoban 3y ago
    Yes. Freeze/thaw cycles are _remarkably_ destructive though. Water expands with insane pressure if it gets caught in any little cavities or grooves. You're very likely to destroy it over time, if not immediately.
    - alchemist1e9 3y ago
      Maybe it could instead be within some type of very thin pouch/layer of dielectric liquid, like in immersion cooling, and then water/ice outside of that so the force of expansion from freezing could be distributed?
      - tonyarkles 3y ago
        I’m not sure I’m following the end game here with freezing it. From what I recall ice is actually a pretty decent thermal insulator and since a given mass of ice is larger in volume than the same mass of water, you’d end up with a hole melting inside with… weird things happening as far as pressures go. If the goal is to keep the processor nicely chilled, you’d probably be better off running liquid water over/through the block of ice and then keeping the coated board chilled in the ice water bath. If you’re trying to get below 0C, you should probably keep using a liquid with a lower freezing point instead of having the board frozen in a block.
        alchemist1e9 3y ago
        > I’m not sure I’m following the end game here with freezing it. My kids playing on the Mega VR headset and complaining about it getting hot is one example of my line of thought. Let’s say you have to absorb the heat generated by a given amount of electricity but want to do it in the most weight efficient way possible. It turns out that regular old water has basically the highest latent heat of fusion at room temperature and pressure, which means a block of ice can absorb more heat by melting than pretty much anything else gram for gram. What if the VR headset could just freeze itself overnight and then no fans or reliance on dissipating heat into the external environment but instead into the ice. It’s probably stupid but I do know water is the best know molecule in terms of latent heat of fusion per gram at room temperature and pressure.
bruce511 3y ago
In air, I don't know. In water, thr cooling factor goes way up. Liquids are much better at absorbing heat than gasses are. Allowing for the fact that you can cool down the water, and circulate it, means you can overclock the device a lot, without heat becoming a factor. I don't know thd specifics of the coating, but its -unlikely- that it would change the thermal properties to any degree, and any difference would be dwarfed by the benefit of immersing in a liquid.
- tamimio 3y ago
  I meant in air. I made a while ago an Unmanned underwater vehicles (UUV), the on-board SBC (nvidia jetson), despite having a waterproof case I still did have heat shrink tube on it and the connectors as an extra measure, obviously it’s not as sophisticated as the OP coating tech, but the there were an around 45% thermal increase, would be interesting to see some benchmarks numbers on that!
  - bruce511 3y ago
    I agree, numbers would be interesting. My guess is that the effect in air is minimal, because the coating is so thin. If the coating had impressive thermal properties (such a steep thermal gradient) , even at such tiny thickness, it would have other applications (where thermal insulation is desired.)
  - tonyarkles 3y ago
    I’m curious about multiple things! - what kind of heat shrink was it? There’s the usual thin plastic type and the gooey double-layer type. I’m actually not sure which one would be worse for heat… the gooey type seems like it’d be a thermal insulator but maybe with that much close contact it might be a decent thermal conductor. The regular thin plastic type would probably have been trapping a bunch of air around the heatsink (dramatically reducing the surface area for convection) - how big was the waterproof enclosure? The stagnant air inside there seems like it would probably heat up pretty well. If the enclosure was plastic it would probably conduct that heat into the water quite poorly. If you end up in a similar situation down the road, you’re probably way better off making an aluminum plate with a raised pad that you can mount the CPU to directly and use a gasket to allow the outside of the aluminum to conduct the heat directly into the water. Assuming you’re not going to crazy depths I’d expect that to be viable and you’ll probably get “better than forced air” performance out of it
not_the_fda 3y ago
Yes, most conformal coatings are thermal insulators.

Any thermal impact after the coating?!

9991 3y ago

Being submerged in water will substantially help thermals.

alchemist1e9 3y ago
Is it possible one could coat electronics like this, then submerge them in (distilled maybe) water within an ice pack, freeze them, then use them and the heat melts the ice?
- kadoban 3y ago
  Yes. Freeze/thaw cycles are _remarkably_ destructive though. Water expands with insane pressure if it gets caught in any little cavities or grooves. You're very likely to destroy it over time, if not immediately.
  - alchemist1e9 3y ago
    Maybe it could instead be within some type of very thin pouch/layer of dielectric liquid, like in immersion cooling, and then water/ice outside of that so the force of expansion from freezing could be distributed?
    - tonyarkles 3y ago
      I’m not sure I’m following the end game here with freezing it. From what I recall ice is actually a pretty decent thermal insulator and since a given mass of ice is larger in volume than the same mass of water, you’d end up with a hole melting inside with… weird things happening as far as pressures go. If the goal is to keep the processor nicely chilled, you’d probably be better off running liquid water over/through the block of ice and then keeping the coated board chilled in the ice water bath. If you’re trying to get below 0C, you should probably keep using a liquid with a lower freezing point instead of having the board frozen in a block.
      - alchemist1e9 3y ago
        > I’m not sure I’m following the end game here with freezing it. My kids playing on the Mega VR headset and complaining about it getting hot is one example of my line of thought. Let’s say you have to absorb the heat generated by a given amount of electricity but want to do it in the most weight efficient way possible. It turns out that regular old water has basically the highest latent heat of fusion at room temperature and pressure, which means a block of ice can absorb more heat by melting than pretty much anything else gram for gram. What if the VR headset could just freeze itself overnight and then no fans or reliance on dissipating heat into the external environment but instead into the ice. It’s probably stupid but I do know water is the best know molecule in terms of latent heat of fusion per gram at room temperature and pressure.

bruce511 3y ago

In air, I don't know. In water, thr cooling factor goes way up. Liquids are much better at absorbing heat than gasses are. Allowing for the fact that you can cool down the water, and circulate it, means you can overclock the device a lot, without heat becoming a factor. I don't know thd specifics of the coating, but its -unlikely- that it would change the thermal properties to any degree, and any difference would be dwarfed by the benefit of immersing in a liquid.

tamimio 3y ago
I meant in air. I made a while ago an Unmanned underwater vehicles (UUV), the on-board SBC (nvidia jetson), despite having a waterproof case I still did have heat shrink tube on it and the connectors as an extra measure, obviously it’s not as sophisticated as the OP coating tech, but the there were an around 45% thermal increase, would be interesting to see some benchmarks numbers on that!
- bruce511 3y ago
  I agree, numbers would be interesting. My guess is that the effect in air is minimal, because the coating is so thin. If the coating had impressive thermal properties (such a steep thermal gradient) , even at such tiny thickness, it would have other applications (where thermal insulation is desired.)
- tonyarkles 3y ago
  I’m curious about multiple things! - what kind of heat shrink was it? There’s the usual thin plastic type and the gooey double-layer type. I’m actually not sure which one would be worse for heat… the gooey type seems like it’d be a thermal insulator but maybe with that much close contact it might be a decent thermal conductor. The regular thin plastic type would probably have been trapping a bunch of air around the heatsink (dramatically reducing the surface area for convection) - how big was the waterproof enclosure? The stagnant air inside there seems like it would probably heat up pretty well. If the enclosure was plastic it would probably conduct that heat into the water quite poorly. If you end up in a similar situation down the road, you’re probably way better off making an aluminum plate with a raised pad that you can mount the CPU to directly and use a gasket to allow the outside of the aluminum to conduct the heat directly into the water. Assuming you’re not going to crazy depths I’d expect that to be viable and you’ll probably get “better than forced air” performance out of it

not_the_fda 3y ago

Yes, most conformal coatings are thermal insulators.