Topic: Oil Submerged Configurations Discussion Thread - page 3. (Read 13793 times)

http://www.ehow.com/how_7640669_circuit-board-fabrication-cleaning.html

Cleaning the Substrate

1 Put on a pair of latex or rubber gloves. One of the worst contaminants in the production of PCBs is oil, which comes from your hands and keeps the surface from accepting resist evenly.

2 Scrub each board with a plastic scrub pad to remove any oxide coating on the copper side of the board. You can acquire a plastic scrub pad at your local grocery store where dish washing products are sold. Do not use water when performing the scrubbing as this will promote a new oxide coating on the board during the process. Handle the board by the edges. The less contact with the copper cladding the less chance of fouling the surface. Many manufacturers use acid to remove the oxide coating, but physical scrubbing works just as well. When you have finished scrubbing it, the surface should appear shiny with no spots.

3 Mix a small amount of metal free soap in deionized water and place in a container large enough to hold the PCBs.

4 Rinse the board in the mild soap solution. This will remove most remaining oil and inorganic contaminants from the surface of the board.

5 Wash the board in an isopropyl alcohol bath to remove any other organic residues remaining.

6 Rinse the cleaned board with acetone. Isopropyl alcohol contains approximately 30% water and the acetone will remove any alcohol or water left adhering to the board. The acetone evaporates quickly and doesn't leave a residue.

Cleaning the Finished Board

7 Put on a pair of latex or rubber gloves to protect the board from the oil present on your skin.

8 Dip a cotton tipped swab into isopropyl alcohol and carefully scrub each solder connection on the PCB. Scrub both sides of the board where solder connections were made.

9 Dip a new cotton tipped swab in deionized water and repeat the process of cleaning each solder connection on both sides of the board. Depending on the type of flux used in the soldering of components on the boards, any residue will be soluble in either isopropyl alcohol or deionized water.

10 Rinse the cleaned board under cold deionized water. This will remove any remaining soap or isopropyl alcohol.

11 Place in an oven at 100 degrees C to dry for approximately five minutes. The heat will dry any remaining water and leave the finished product ready for testing.

Tips & Warnings
Keep your fingers off the surface of the board. Small traces of skin oil can short the board or components on the board.

As previously quoted in this thread, I'm using transformer oil on a quad E5-4650 xeon system and some other electronics.  Firstly, I've used various transformer oils, the easiest to acquire with best performance I've found is 76 transformer oil.  Also with regards to lexicon, I prefer this term because it refers to a quality and composition of mineral oil.  Using this term avoids confusion with the laxative grade (literally) mineral oil that some have tried.  These contain sulfides, PBAs, and other chemicals that you would not want to run electronics in.

As far as heat exchangers, there are two routes I've used with great success:
1) Liquid to air - Simple radiator style setup.  This however should _not_ be cheaped on.  Initially I tried a PC water cooling radiator (leftover from a friend's system).  PC radiators in general are crap.  They don't provide heat curves, operating tolerances, etc.  In the end I bought a radiator from Brazetek, http://www.brazetek.com/finned-coil-water-air-heat-exchangers.  This type of system is the best performance per price for < 35k BTU/hr (about 10kw).  Also, I would avoid using polymer tubing for any of the hoses.  I use silver solder welded copper pipe aka sweated copper.

2) Liquid to liquid - For this I milled a simple dual chamber, mutli-plate system from stainless steel.  You can buy them from brazetek, but I had a ton of 1/4" 316 stainless stock and a case of beer.  I sent the hot oil into one of the chambers, cool water into the other.   For cooling the water, you can use an evaporative system, and ideally one would.  You can get 5+ ton evaporative towers with pumps and controls locally for $3k+ pretty much anywhere in the US and probably the world. For my system, which was a prototype, I used a compressor to cool the water to various temperatures, some below the wet bulb temperature.  This system can basically scale infinitely and reaches a cost/performance advantage over the previous system at around 10-12kw.

I wouldn't cheap on the radiators, pipes, and especially pumps.  Avoid pond pumps and low duty cycle pumps.  Oh, and flush your system before use especially if chinese rads are used as they tend to have finishing bits inside.

If you'd like to experiment with this buy a gallon or two of transformer oil at a HAM shop for ridiculously high prices and construct a test load with some kanthal wire cast into a ceramic block.
I've got a bunch of data on this at home, but am on the road right now.

It isn't overkill when you have 10's or 100's of K16/K64/K256 units.

I put the caveats in the first post and my reply early on. You really do NOT need to do this in terms of a single K16 unless you are doing it to learn more about the process. My intention is to have as I said before a unit that can handle some thing like 5U to 10U as a prototype module that can then scale up by adding more modules. In terms of failures... with a larger array single chip failures are not going to matter much as at this scale you probably can easily remove a K16 board from the array and keep plugging along with no problem. Cleaning up a K16 is not going to be that hard given 100mm x 100mm size and placing a new Avalon chip on the board as will be reasonably simple to do. Infact given I have access to fabrication of boards I will probably have a few dry boards straight from the fabrication unopened. Replacement I don't think is a huge issue with the modular capabilities of the Klondike.

K256 X 10 = 2560 chips roughly 1,024,000 Mh/s if you can attain 400+ Mh/s per chip mineral oil cooled.
K256 X 10 = 2560 chips roughly 896,000 Mh/s if you can attain 350 per chip air cooled with a/c.

There is definitely potential in this.

So continuing on... anyone found problems with the silicone heat sink pads and mineral oil?

I think next I want to mock up is a 5U capacity tank, heat exchanger / cooling tower.

Assuming this is your plan for cooling overclocked (350-400M) Avalons

Oil cooling for stock 4.5-5Gh Klondikes is incredible overkill.
A decent heatsink and a fan is plenty

No one is going to overclock a server in a cooperate environment, with servers up time and longevity is key. When you have that much hardware in such a small space cooling becomes a huge issue thats where the oil cooling comes in. Also with that type of equipment once it breaks, its not repaired at the component level. There is not a specific issue with submerging QFN in oil or any other type of package for that matter. My point was this: Inevitably some chips with die from manufacture defects, power fluctuation, or hundreds of other unforeseen possibilities, cooling is just one of those. Having a 16 chip per board, if one chip dies then chances are you will lose that board because it will be too difficult to repair after being in oil. Ask any repair tech how easy it would be to repair an oil soaked board. I repair arcade equipment at work and can tell you it would not be easy with oil soaked boards.

Convection will draw the heat to the top of the tank pump that through a oil cooler to the bottom to aid in circulation. Straight mineral oil work good and can be purchased cheap by the gallon that's what we used. Transformer oil works well as it is designed to cool transformer windings.

I also had idea to submerge miner into oil, but in the end decided to avoid this. A/C will be enough for one device like in my case, and its not so safe to place tank full of hot oil in living room.

Anyway, you may find this advice useful:

But... 17.0 W/mK vs 3.2W/mK ...

If i had 400 chips to use up 1 expensive sheet (and all the time in the world), id put the expensive one just under the vias, use the cheap sheet (with holes) for rest of the board.

Sure there are cheaper alternatives directly from China.

http://www.aliexpress.com/item/5Pcs-lot-30CMx3CMx0-3MM-Thermal-Pad-CPU-GPU-DDR-RAM-CHIP-3320-01-05/632016505.html

US $3.22 / lot
5 pieces / lot , $0.64 / piece

http://www.frozencpu.com/products/17467/thr-178/Fujipoly_Ultra_Extreme_System_Builder_Thermal_Pad_-_Full_Sheet_-_200_x_150_x_05_-_Thermal_Conductivity_170_WmK.html

The best you can buy, and should do ~400 chips each sheet, if you cut them small enough. Don't need a whole 1/4 sheet to cover the whole board, esp since these are wicked expensive.

Ates  is right NEEEEEEED the sink.

There are other insoluble (non-grease) heat sink compounds but maybe the pads might be the best route.

I have had a mineral oil setup for my FPGAs for over a year. Total wattage  is ~65 and the temperature was OK @37-42c ish depending on ambient . Heat syncs are mandatory and so is forced convection (one fan to keep the oil moving) otherwise the hot oil seems to stay around the heat source and does not flow away like you would think because the oil is thick.  I planned on reusing the setup for a BFL single but that won't be happening since they came nowhere close to their power goals. I may try building a new one just because I enjoyed building it. For the much higher wattage it would need a complete redesign and much more oil and more metal/glass/acrylic to transfer heat from the oil to outside the case. Unless you are doing it for fun it is not really worth the expenditure.  Water blocks is probably the better route... but look nowhere as cool (or as silent).

Of course you still need a heatsink. You just won't need any fans on that heatsink, which helps you save power.

Mineral oil can absorb a lot more heat than air, but it can't absorb that much heat with that little surface area.

Wondering the same thing. Because the board is a fairly large surface area, if you keep the oil flowing using pumps, shouldnt it be sufficient? Need someone with knowledge of thermodynamics to pitch in...

Yeah, I saw that too, that's why I am wondering whether or not we need a heatsink.

Heat Exchanger / Cooling Tower

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GPC23  <10 GAL    105 LBS   50" X 28"   25 GPM



Evaporation Cooler (For Conception Purposes Only)

http://www.youtube.com/watch?v=EJKH1lqGvbQ

http://www.youtube.com/watch?v=TA847PhQaGE

Ya I was seriously looking into them a week or two ago. Lots of good stuff. I'd also be interested in this project, but a big question I had: How would you dissipate all that heat once you remove it from the electronics/oil?

Server Modification & Installation

While the CarnotJet system is being installed in your facility, we will also modify servers at the installation site. Having previously encapsulated server hard drives at GRC’s facility, our technicians now remove server fans (which are stored in case the server is ever reconverted to air use).  Conventional thermal grease will dissolve, and so we replace it with a non-soluble thermal interface material solution, a Heat-Spring® by Indium Corp of America (link), which helps enable this technology.  Solid State Drives do not require any modification.

- See more at: http://www.grcooling.com/product/installation/#sthash.yMkO2kNI.dpuf

Indium foil ... expensive... http://www.aliexpress.com/store/product/Indium-Foil-Size-0-15x100x100mm/334807_917979672.html


Thermal pads might be an option http://www.tglobalthermal.com/h48-2-thermal-conductive-pad.php

Any published data on this in terms of QFN chips having been submerged in oil and they have had failures or issues as you describe? Just want to see what has been written up about this. Considering that this sort of cooling in done in a fairly wide application commercially I have yet to see anything specifically about issues with QFN chips immersed in oil. Although the scenario you paint will possibly happen to someone I am sure what would be the likelihood of having to do that? It is a risk that is taking place daily but again I have not found anything yet on this being reported as widespread issue. They are dropping OEM 1U rack mount servers directly in this without any concerns about QFN or other types of chips. Seems strange can't find anything when I search about it.

Also what I am looking to do is scale this up for a data center applications for mining. So water blocks would at some point be more problematic however for a smaller number of boards I'd agree go with air or water blocks.

Another thing I have to decide on is whether or not to put a heatsink on the boards.
And if I do, which cooling paste.
Obviously I can't use the standard conducting cooling paste.

One of the challenges I got, is select a brand/type mineral oil here in Holland.
I found this one: http://www.sunoco.be/uk/whiteoils_med.html, the MSDS While Oil F.
This firm is located in Belgium, just 40 miles from me.
I have sent them an email with some questions.