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#11
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CrackerJack wrote:
What exactly is the problem if too much cpu compound is put on the core and it gets squashed out onto the surrounding area? Apart from looking messy, is there any real problem with this? You'll always get a little but if you are squeezing a lot out it indicates you've applied far too much, meaning the layer of paste between the processor die/heatspreader and heatsink is too thick. Remember, the idea is NOT to form a layer between the two surfaces. The purpose of the paste is to fill the valleys in the contact surfaces with something which is more efficient at transferring heat away from the CPU core than the air which would otherwise fill the gaps. Even the best thermal material is less efficient than direct contact between the two metal surfaces. Also, some thermal materials can be slightly electrically conductive, so if leaks out and bridges gaps in electrical contacts it is possible that it will result in reliability problems or even permanent damage to components. -- iv Paul iv |
#13
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#14
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Rob Morley wrote:
In article , "Max" says... Rob Morley wrote: Yes as it acts as an insulator. The idea of thermal compound is to fill the very small scratches on the faces. Actually the thermal paste is non-conductive. Eh? You thought he meant thermally, we realised he meant electrically. I realised he could have meant either, so asked for elaboration. Actually some thermal compund is electrically conductive too, Which one? Any of the stuff that's filled with metallic particles is potentially electrically conductive. Please name one. |
#15
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Max wrote:
Which one? I do know that artic silver 1 is slightly conductive, but the more worrying thing is the capacitance if it gets too close to contacts. http://www.arcticsilver.com/arctic_s...structions.htm -- Mark Iligitimi Non Carborundum! Twixt hill and high water, N.Wales, UK |
#16
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CrackerJack wrote:
What exactly is the problem if too much cpu compound is put on the core and it gets squashed out onto the surrounding area? Apart from looking messy, is there any real problem with this? I propose this answer: 1) If the compound is not too viscous, and the heatsink is clamped on with some force, and you apply enough compound, the thickness of the layer of compound does not depend on the amount applied, which is to say that the excess gets squeezed out. 2) Thermal compounds are not electrically conductive. 3) Some thermal compounds (notably those containing silver compounds) have capacitative properties that can be problemmatic if compound gets between the chip's leads. 4) If you use a compound that doesn't have the problemmatic capacitative properties and is not too viscous, in general it won't hurt to use too much. |
#17
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Matt wrote:
I realised he could have meant either, so asked for elaboration. Actually some thermal compund is electrically conductive too, Any of the stuff that's filled with metallic particles is potentially electrically conductive. Please name one. Arctic Silver is capacitive, rather than conductive, but the same applies in terms of application. Their instructions state: "While much safer than electrically conductive silver and copper greases, Arctic Silver should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.)" I wouldn't doubt there are other compounds around which are electrically conductive. -- iv Paul iv |
#18
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On Sun, 11 Apr 2004 15:35:21 +0100, Piotr Makley wrote:
(John) wrote: What exactly is the problem if too much cpu compound is put on the core and it gets squashed out onto the surrounding area? Apart from looking messy, is there any real problem with this? Yes as it acts as an insulator. The idea of thermal compound is to fill the very small scratches on the faces. Actually the thermal paste is non-conductive. For maximum heat transfer from the core to the heatsink, the two metal pieces need to touch as much as possible. Hence, the addition on the paste fills in the imperfections. Other than being a mess, things should work just fine. So something like a pinhead or two should be enough? And a matchhead would be too much? I've heard a grain of rice size is good. A matchhead should work. I like to get single edged razor blades from the hardware to spread it thinly and evenly. Think of frosting a cakeG. I've even heard it said that you should even be able to almost read the CPU die thru a thin haze of compound but given the wide range of heatsink finishes, I would only go that thinly on a lapped HS. Take your time and run it out evenly to all corners of the die. Then at the last, try to run the razorblade all the way across from one side to the other making a single unbroken even surface. The Artic Silver people suggest rubbing compound into the base of the heatsink, and then wiping it all off (NOT with alcohol!) with a cloth before putting it straight down on top of the CPU (no twisting/slipping). Supposedly it will imbed some of the compound in the "pores" of the HS. Sounds like a good idea to me. ~~~~~~ Bait for spammers: root@localhost postmaster@localhost admin@localhost abuse@localhost ] ~~~~~~ Remove "spamless" to email me. |
#19
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#20
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Conor wrote:
Remember, the idea is NOT to form a layer between the two surfaces. The purpose of the paste is to fill the valleys in the contact surfaces with something which is more efficient at transferring heat away from the CPU core than the air which would otherwise fill the gaps How I apply mine.. Small pea sized lump on the heatsink. Spread thinly then scrape off with a razorblade. Very small dot on the CPU core. Spread extremely thinly so it is hardly visible. I use a similar technique but use a bit less. With the CPU fitted on the motherboard, I first apply a match head sized dot to the top of the core and smear it around so it covers the surface, then scrape most of it off with the edge of an old credit card to leave very thin translucent layer covering the core. I then clean the residue from the edge of the credit card with a ball of cotton wool and use that to wipe the bottom the heatsink, just sufficiently that it discolours the surface around where the core or heat spreader will make contact, before fitting the cooler to the board. That way I use less compound and have cleaned my "applicator" in the process; leaving just the cotton wool to discard. :-) -- iv Paul iv |
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