Editorial note: This article is going to be split up into more pages than usual. Don’t worry, this is no new policy.
The reason why we’re doing it for this article is that we have some blurry pictures, and we didn’t want to shrink them even more.)
Overclocking often means active cooling, and extreme overclocking often means employing Peltier-junction thermoelectric cooling (or TEC) modules to actively pump the heat off the processor die.
Of course, pumping heat off the processor often has the effect of lowering the temperature of the processor, the cold side of the TEC, and the coldplate if one is used, to well below ambient air temperature, and occasionally below the freezing point of water.
If this happens in a high-humidity environment, the moisture will condense out of the air on all such cold surfaces, in much the same way that a cold glass of soda starts growing a wet bottom over time.
Given that water is a decent conductor of electricity, one minute droplet of it in the wrong place is a Very Bad Thing ™.
Due to this, TEC cooling for computers is considered risky, even dangerous, unless extraordinary precautions are taken to prevent condensation from forming to begin with, or to route or contain it if it does form.
What I Did About It
What You Need
This article combines several techniques developed by other people into one technique for total or near-total condensation prevention.
This method not only greatly decreases condensation formation, but also adds a safety factor in waterproofing components to prevent water damage.
The method is suitable for socketed processors mounted on socket-to-slot adapters (often called “slotkets”) in turn mounted on slot-processor motherboards. It may be possible to adapt this for socket-processor motherboards.
However, for this article we will concentrate on socketed processors in slotkets. This also assumes that water cooling is in use, as this level of TEC action precludes air cooling in most cases.
The materials for this project:
Pocket the Socket
The first part of the process is prepping the slotket. I’m using an Asus S370-133 slotket on an Asus P3V4X motherboard, and this particular slotket has a plastic frame that helps latch the slotket into place.
I removed this plastic frame to expose the rest of the slotket’s PC board. I also removed all jumpers after noting their positions.
WARNING: The next step is VERY, VERY TOUCHY. You can EASILY damage the slotket doing this, and if you damage anything that’s your responsibility! Some folks may elect to skip this step.
My next act was to dismantle the processor socket, which involves removing the sliding portion and actuator arm. Most processor sockets are snap-together affairs; a little careful prying allowed me to pop that mobile part off safely. If you do this, though, BE CAREFUL as it’s very easy to break the plastic, sever a trace on the slotket’s PC board, pop a surface-mounted component right off the PC board, and any number of other unsavory, slotket-killing things.
If you’re wondering why I took the socket apart, patience until it’s time to fill it with dielectric grease.
Putting on a silicone overcoat
The second step is to coat the ENTIRE slotket, front and back, with the conformal silicone. All large parts are to be sealed at their bases, and you should coat the PC board all the way to its edges and as close to 1mm from the exposed portion of the contacts where the slotket plugs into the motherboard as you can get.
You should also aim to get the silicone about 0.5mm from the sides of the socket. All ICs (the black chips on the slotket’s PC board) should have their pins thoroughly coated and their undersides sealed as well. Since most slotkets have headers for setting voltage, etc., these should be also coated up to the base of the headers, but no silicone should coat the pins as the jumpers will need to be reinstalled later.
This silicone takes several hours to set, so this is best done one side at a time in the evening and let to set up overnight. When both sides are coated and the coating has set, check carefully for exposed connections aside from the required ones above.
Once the slotket’s silicone coating has set and a thorough check reveals that all is well sealed and none got under the socket, on the header pins, or on the motherboard connector, it’s time to backfill the socket with dielectric grease.
If you cannot obtain this substance, petroleum jelly may be used as a substitute, although you should use it only if you must. It breaks down some plastics and rubbers and may attack the coating on the slotket or the foam you’ll be using later to insulate it.
The best way to apply the grease is to press it into each and every hole with your finger. I found that applying a thick layer and pressing on a fingertip’s worth of holes with a rolling motion was very effective. Keep adding more and pressing it in until it begins to ooze out from under the socket to fill the gaps between socket and silicone.
This is MUCH easier to do if you have dismantled the socket first. If you did not, it’ll just take a bit longer.
If you did, once you’ve reached the point where the grease has filled the socket and the gap between socket and silicone coating at the base of the socket, reassemble the socket and actuating arm, make sure it works properly, and then fill it with the same technique.
At this point, you have a largely waterproof slotket. Reinstall all jumpers as you need to, and set the slotket aside for later.
(Be sure to set the jumpers as you will need them to be set later, as changing jumpers later on will require disassembling the whole thing you’re about to make.)
Now we move on to fabricating the brackets that will clamp the insulation around the slotket, as well as clamping the Peltier, coldplate (if you are using one), and waterblock against the processor.
This part requires basic fabricating skills. My waterblock uses straight fittings that come out one side. If your waterblock’s fittings come out the top (the “top” being the opposite side from the side that is pressed against the processor) you will need to perform an additional step – drilling the holes for your fittings to clear.
The best bet is to use 3” wide aluminum stock. If this is not available, 1 ½” stock may be used (which is what I had to do) but it will add to the complexity of the project. For 1 ½” stock, you’ll have to cut three pieces to form each side, using one piece to cover the seam between the other two.
First, cut two 6” long pieces of the bar stock. These two pieces will form the front and back clamp plates.
Be sure to do this somewhere totally different from where the computer and slotket you’ll be using are located, as you do NOT need aluminum chips getting into anything. Be sure to clean and deburr the cut edges as well.
Measure ¼” in from both shorter sides and scribe lines – this will be the centerline for the four bolts that will clamp everything together. Do this on both plates.
Place the slotket onto the plate, previously scribed lines up, and align the slotket so it is even and its connector extends past the edge of the plate 2mm past the connector’s gold contact areas.
This will allow the clearance necessary to plug the slotket into the motherboard.
Make reference marks on the center lines you made earlier that line with the top and bottom edges of the processor, but do not come any closer than ½” from the top and bottom edge.
Remove the plates to a safe work area and clamp both together, making sure to align all edges as precisely as possible. Drill four 3/’16” holes through both plates. Unclamp the plates and check the holes by slipping the four 8-32 bolts through them. Remove the bolts and deburr the holes, front and back.
If your waterblock’s fittings pass out the opposite side from the processor side of the waterblock, measure and drill holes to permit the fittings to pass through the front plate.
Important: Make sure the waterblock will line up with the processor once the package is buttoned down! If your waterblock’s fittings extend out one side, this step can be skipped.
Now we move to phase three – making the layers of insulation.
The mouse pads I used are cheapies made by Allsop. They only cost a buck and change each, which is good, as you’ll need three of them. They are coated on one side with cloth, which has to be removed, so peel off the cloth.
From this point on, you’ll need to use the back plate to mount everything as you go, and the front plate as the template to cut out the layers of foam from the mouse pads. I found that the 8-32 bolts could make decent punches.
I placed the plate onto the foam once it was trimmed to match, aligned the edges, and poked the bolt through each hole to press into the foam. Then I could punch the bolt through each mark to form the holes.
The first layer will be the backing layer between the back plate and the slotket. Once it’s cut and punched, pass the bolts through the holes in the back plate and the foam and press it down flat against the plate with the bolts all the way through.
Then position the slotket, again so its connector has 2mm of clearance from the edge of the gold contacts to the bottom of the plate.
The next two or three layers will need to be trimmed to clear the socket, jumpers, and any larger components (capacitors, for example) on the slotket’s PC board.
The best method is to trim the layer and punch the boltholes, and then slip it into place and press it against whatever is sticking up off the PC board. Then remove it and trim out the areas dimpled by obstructions.
Once you’ve cleared all PC board parts, make sure you leave a 2” x 2” opening over the processor on all subsequent layers.
Repeat the above for a total of six layers. Cut two additional layers if you have the material in case you need them.
If your waterblock’s fittings will pass out a narrow side of the waterblock, you’ll need to cut out the layers of foam to clear the fittings. After you install the assembled slotket/TEC/coldplate/waterblock unit, you can use scrap foam to fill in the gaps.
When all is cut and trimmed, assemble the unit with the coldplate, TEC, and waterblock in place as well as all layers of insulation.
Then place the top plate into position, check alignment, and bolt it all together to form a single unit.
Be careful not to get too carried away with tightening the bolts – they must be evenly torqued and fragile processors (AMD’s Durons and Thunderbirds, most notably) could be crushed and destroyed by too much pressure. The goal is firm, not crushing pressure. Save that for arm wrestling. 🙂
To further improve the seal, wrap the foam edges with a good insulating tape.
All that’s left to do is install the slotket unit onto the motherboard and fire up the computer. (You will probably have to remove the retention brackets.)
How well does all this work? Quite well. I am using an 80-watt TEC, which is powered by the 12-volt lines from a spare computer power supply (pulling about 60 watts).
It maintains the processor at 10 deg. C under full load. Ambient case temp is 30 deg. C.
Dismantling it revealed no condensation until I exposed the coldplate to air, when it frosted up almost immediately!
Thanks to this setup, my 700 MHz Pentium 3 is running nicely at 1035 MHz for burn-in testing. It’ll do 1050 MHz without any troubles until I fire up a 3D application.
OddOne is an almost-thirty-year-old professional webmaster and consultant in real life, and an overclocking psychopath in the off-season. His exploits include technical writing, and seriously crazed 3D gaming. He can be reached via E-mail at email@example.com.
NOTE: Please excuse the picture quality – I just got the digital camera and still don’t quite have the “hang” of not moving slightly as I press the shutter button.
The Allsop mouse pads I victimized for this project.
My P3-700 resting on the baseplate and backing foam layer. Note how the connector hangs off the edge of the plate.
My BIOS, after letting the TEC run for two minutes and then booting to 1050 MHz. Note the CPU temperature reading ONE degree C.
The computer, going nuts. This was a screen capture of my desktop at 1024×768 resolution, scaled down to fit this web page. Note Sandra 2000 reporting my RAM timings are CAS2 (6-1-1-1/4-1-1-1) at 148 MHz FSB. Also note that with SETI@Home 3.0 running, the processor temperature is 10 degrees C as reported by Motherboard Monitor 5.0 (send graph on the top row at bottom-right). Idle temp is 6-8 deg. C.