space between cpu and heat sink

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jlsw77

Commendable
May 21, 2016
4
0
1,510
Replacing TIM on Gateway sx2800. Heatsink has been replaced, but is not sitting snug on top of CPU. Checked spacing between cpu and heatsink and noticed a gap. Line of new AS5 that was applied to CPU has not spread as it does not touch heatsink. All stock components being used. I was not the one to remove old TIM so not sure what was there before. Anyone know if this one needs thermal pad or have idea for other solutions?
 
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J

jlsw77

Commendable
May 21, 2016
4
0
1,510
Already applied line of thermal paste (AS5). The line has not spread and does not touch bottom of heat sink. Gap is approx 3mm between bottom of heat sink and top of cpu.
 
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synphul

synphul

Champion
Mar 11, 2011
9,477
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54,965
+1 for what k1114 suggested. Cooler base to cpu ihs should be primarily metal to metal contact. The thermal paste is only for filling in microscopic nicks or voids where the machined surface may not be absolutely 100% perfect. Not a layer of cement like you're laying bricks. If the cooler and cpu are that far apart something isn't right and you'll be overheating all the time trying to use it like that.

Also wouldn't suggest using a weird shim or anything, a proper cooler properly mounted should fit. Newer pennies don't have much copper in them. Back in the 1830's they were pure copper. 1962-1982 they were 95% copper and 5% zinc. Since then they've changed them to 97.5% zinc and only 2.5% copper and zinc is a poor thermal conductor.

Copper conductivity is rated at 231 btu/hr-ft, silver is rated at 247, zinc is only rated at 67.
 
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J

jlsw77

Commendable
May 21, 2016
4
0
1,510
All parts are stock. Heat sink is like one found at http://m.ebay.com/itm/NEW-Gateway-SX2800-SX2801-SX2802-CPU-Heatsink-Cooling-Fan-18995-/231760028918. Are there any special steps for installing other than screwing into place, working diagonally?
 
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synphul

synphul

Champion
Mar 11, 2011
9,477
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54,965
Not that I am aware of, it seems pretty straight forward. Are you sure it's screwed down all the way? If it was working before and you removed the cooler, cleaned it, reapplied paste then reinstalled and now there's a gap then something isn't lining up right or it isn't screwed all the way down.
 
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J

jlsw77

Commendable
May 21, 2016
4
0
1,510
Heat sink attaches with captive spring screws. The clips on the screws seem to prevent the heat sink from going down far enough. Decided to remove the clips and now heat sink will touch top of cpu. Now to set back up and check temps.
 
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1

1davidmcallister

Jun 7, 2018
1
0
10
Now I don't want anyone to think I'm teaching them what they already know, I also work in the industry supplying heat solutions to aerospace and military customers. Putting a huge amount of deflection on the heat sink can do several things. If you are using a paste and over-deflect the paste will dry or cure quicker over time than usual and will require cleaning and reapplying more frequently. Over compressing does not give you a better connection between the heat sink and chip. The paste will wet both sides sufficiently just by using a small amount and applying the correct amount of deflection. Neither the heat sink base nor the chip have a smooth surface and when they meet there will be air trapped, they are made in their millions and it would not be cost effective to give the heat sink or the chip surface a truly smooth glass like surface. The components on a board are generally soldered but even done automatically by machine this does not make the solder precisely the same height under or around a chip. A small amount of paste, correctly deflected will fill most, but not all, of the gaps. By over deflection you are effectively squeezing out the paste and simply crushing the heat sink into the chip. The heat sink is generally a lot tougher than the chip and will damage the part over time, every time the chip heats up and cools down the static force on it changes slightly leading to a broken component. You are also putting more strain on the pcb than it should take. The points on the board at where the heat sink clips are situated will probably deform and this will easily break any solder connections or circuits around that immediate area. Last point - I promise. When you over deflect and you have to reapply the paste you will find in most cases that the heat sink will not sit exactly as it did when reapplied, and probably won't be level. Maybe look in to using a thermal pad or tape, there are plenty available.
 
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