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Re: Liquid Immersion Cooling

Posted: Tue Dec 02, 2014 12:38 pm
by robespierre
Did you get anywhere with this?
I was thinking about some of the new manycore processors and how they really could use a denser cooling solution. for fpgas, too.
I stumbled on this presentation that gives a lot of useful details including a blueprint for a whole tank system (near the end):
http://youtu.be/ivVoANqFBuY
One detail I hadn't seen before is that they use a special heat transfer material on the outside of the metal chip case, made of sintered copper. since it's sintered, it has a much larger surface area and lower thermal resistance, similar to the reason ultracaps have high capacitance. what I don't know is if they apply it chemically, as a paste or what.

Re: Liquid Immersion Cooling

Posted: Tue Dec 02, 2014 2:04 pm
by hazelden
Hi. I've done a few small tests with fluorocarbons but haven't gotten to the point of doing open bath immersion due to the cost of the fluid.

The surface enhancement coating is called a BEC "boiling enhancement coating" that is applied using a spraying process. Phil Tuma from 3M has prepared a few youtube videos that show how it is applied to a CPU's heatsink.

After a heatsink has the BEC compound applied it is bonded to the CPU using a Multicore Solder Vaporette Heater. A Vaporette heater is an SMD soldering device that works by immersing CPUs and heatsinks in a hot vapour of Flourinert FC-40 which offers a precision temperature controlled CPU soldering environment.

Spray Coating of Pin Fin Boilers for Sandybridge CPUs
https://www.youtube.com/watch?v=fMl3cnbsbUg

CPU Soldering
https://www.youtube.com/watch?v=kUVtvfsaZbY

Re: Liquid Immersion Cooling

Posted: Fri Dec 05, 2014 5:45 pm
by robespierre
i watched more of his slide presentations...
it's hugely interesting, but there are a lot of problems with routing cables and plastic components leaching into the dielectric fluid. PVC insulation seems to be a particular problem, so you really want to custom engineer the entire device using materials that aren't attacked by the fluid. Teflon insulated wires instead of PVC, and so forth (you may have noticed that the cables in his test computer are not standard ethernet Cat5). At least the epoxy chip underfill is compatible.

Re: Liquid Immersion Cooling

Posted: Fri Dec 05, 2014 8:49 pm
by hamei
robespierre wrote:i watched more of his slide presentations....

Aren't the radar systems in military aircraft liquid-cooled ? Seems like there would be a lot of high-dollar experience there to be utilized.

Re: Liquid Immersion Cooling

Posted: Fri Dec 05, 2014 9:27 pm
by robespierre
Yes, many are. There are also a huge number of power converters for trains that use it, but they tend to be hermetically sealed.
That solves a lot of problems, but at a high cost, since multi-pin hermetic connectors can cost several hundred dollars... per connector.

Re: Liquid Immersion Cooling

Posted: Sun Dec 07, 2014 2:13 am
by hamei
robespierre wrote:That solves a lot of problems, but at a high cost, since multi-pin hermetic connectors can cost several hundred dollars... per connector.

Well, as John Arbuckle would say .... :P

Re: Liquid Immersion Cooling

Posted: Thu Sep 07, 2017 12:03 am
by robespierre


Looks like the fluid loss problem is pretty serious (there are also a lot of material compatibility problems).