How does too much thermal paste give you higher temps?

[tigersty1e]

I've seen a post or 2 from people that say too much thermal paste will cause temps to be higher than normal.

If I put too much, won't the heatsink just spread the gunk out to the sides?

Explain how too much goo hurts?



I'm not talking about a huge drop. Maybe the size of a dime. Just enough to have the paste slightly ooze out the sides.

 

[krotchy]

Thermal paste usually accounts for 1-3 degrees celsius when applied improperly.

However none at all can account for 50 degrees C

Overall a grain of rice should do and having the heat sink press it down to spread it should be fine. More elaborate methods of getting a smooth layer might give you another degree or two. Depends on your anal-retentiveness or how much you care I suppose. I personally take a little extra effort, but nothing too elaborate.

 

[Zepper]

The current theory is that heat is transfered thru radiation only. Perhaps there is some distance(s) where reflection of the infrared waves becomes a problem.

.bh.

 

[par0dox99]

I believe the fundamental issue is that the thermal paste is a poor thermal conductor compared to the thermal conductors that it couples. It serves as a method to fill the grooves and imperfections of the surfaces of both interfaces. The paste improves the over all surface contact area. To much would increase the thermal resistance compared to using the correct amount.

Now you would think that with the amount of pressure that heat sinks are applied to chips these days that it would squeeze the excess out, but you have to think about this on the micrometer scale of surface imperfections. The two metal interfaces will make contact at their respective highest points leaving reservoirs for paste to build up and the more paste the more thermal resistance.

So you just want enough to make the lowest resistance thermal path as possible but maximize the contact surface area.

 

[tigersty1e]

The aftermarket hsf I'm using has a wide contact area that covers the whole chip. It's a Zalman CNPS 9500 AT covering an e6300.


The directions say to just put a 1 line strip straight down the chip because that's the way the C2D chip is oriented inside. I just decided to cover the whole chip because it seemed like a good idea.

Best case scenario: How much lower can I get temps on a perfect application?

 

[aznxk3vi17]

You show those manufacturers who test and test their products and figure the optimal procedures for application. Show them you won't be bossed around!

 

[tigersty1e]

Originally posted by: aznxk3vi17
You show those manufacturers who test and test their products and figure the optimal procedures for application. Show them you won't be bossed around!

It helps to read the whole thread.

 

[mercanucaribe]

I think they tell you to put a drop or a line because they figure it's foolproof. The best way IMO is to spread a very thin layer on the HS and the CPU using a Zip Loc bag (because it should be very clean).

 

[Howard]

The purpose of thermal compound is to displace the air between the mating surfaces so as to reduce the contact [thermal] resistance. Too much, however, and the thickness of the layer increases, and with it the thermal resistance.

 

[MotF Bane]

Paradox99 got it perfectly correct.

As for how heat transfers... it has to be some sort of radiation, the only two methods to transfer energy would be an exchange of substance or a variant on radiation. Obviously, the IHS metal and the HSF metal are not melting and switching positions (if they are, you have issues).

 

[Howard]

I'm not used to this new science. Is conduction a form of radiation, then?

 

[lenjack]

If all the excess could be sqeezed out, it wouldn't matter if you used too much, but you simply can't get all the excess to squeeze out.

 

[soydios]

The point of thermal grease is to fill in any microscopic valleys on the CPU's heat spreader and the heatsink's base, and to correct for any misaligned or concave heatspreaders or heatsinks. The reason for this is that thermal grease is a far better conductor than the insulating air that it replaces (why do think insulation is fluffy? answer: more air). Too much thermal grease, and you start insulating the CPU, though a tightly mounted heatsink should squeeze it all out over time.

 

[Puffnstuff]

Well the rice size bead that as instructs you to use has worked pretty well for me keeping temps lower than the spread method that I used to use. Now I see that as wants you to place a line across the cpu heat spreader oriented with the core underneath, aka the line running from side to side just above the orientation slots. I'm about to replace the stock intel hsf so I'll probably follow those instructions. Pressure and heat will spread the as5 around on the spreader for me so I'm not particularly worried.