Having trouble applying TIM (Artic MX-2 and MX-4) to mobile cpu

[carbide]

Hi guys,

I'm a bit of a TIM application newbie. At the weekend I repasted my laptop cpu (4700MQ). Used Vodka to clean it up as I couldn't find anything else, and some artic MX-2 I found at PC world.
Great spread, good coverage 15c lower temps at idle and about the same at load.
Was given some MX-4 and me being me, couldn't leave things alone. I've got some Isopropyl alcohol to clean things up now, and did to clean/re applications last night. Both times I was getting idle temps about 20c higher and under load, the cpu hit TDP before getting any higher than 80c and pushing the multiplier down to base frequency.
Bit of a disaster. Starting to wonder if the MX-2 just spreads better but it shouldn't do. Have been using the line down the middle method. Wonder if a bit of overconfidence has got me to put too much on (mx-2 application could see the chip under the TIM, other times with MX-4 couldn't) or whether the heatsink screws just can't spread the MX-4 as well?
Going to try one last time with the MX-4 tonight with absolute minimal application, otherwise I'm going back to the MX-2...

 

[alyoshka]

Use Vodka again.... maybe the CPU prefers that to foul tasting Isoprop.
Anyway... give us a read out once you've done it again....

 

[carbide]

I am tempted to just clean up and repeat exactly what I did the first time around.

looking at
http://www.engineeringtoolbox.com/thermal-conductivity-d_429.html

copper is 400, aluminium is 200, thermal paste is between 5-8

I'm actually thinking of just grouting the two surfaces with an extremely thin surface, almost a polish, and seeing if that gets better.

better go get some more smirinoff

 

[alyoshka]

That grouting is called Lapping.... and I would advise against it..... since the surfaces worked perfectly well with the older TIM ....

 

[carbide]

I thought lapping was sanding/polishing the faces smoother with a fine abrasive prior to TIM application?

I'm just thinking along the lines that my heatsink assembly is incapable of applying any real pressure so, the less the better, though I appreciate maybe a hairline line might be worth it.

Ever have those moments when you just wish you left things alone?!

 

[alyoshka]

yup.... That's what I thought you were going to do.... my bad... missed grouting in the sentence.....
But I'd really avoid that in anycase.....
And yeah...... those moments...... damn keep happening even though we've had eons of experience.....

 

[carbide]

sorry i'm being simple; you'd avoid lapping or avoid wiping a thin film of TIM across the surface?!

 

[alyoshka]

Avoid lapping.....

 

[carbide]

so, temps are back where they were, woo hoo! the MX-4 is just too thick for my puny laptop heatsink to spread. 35-40c across cores at idle, max temp of 75c with small ffts on the CPU.

Adding a GPU torture test still trips the throttle down to 8x though, starting to wonder if it's the voltage regulation MOSFETs overheating?

surely not though, seeing as the multiplier is already down from a max possible 30x to 25x I just don't understand why it doesn't keep dropping the multiplier in increments to remain in equilibrium, it's like a circuit breaker just tripping :-/