Thermal Compounds

[Pat Pending]

The HP DV6 laptops are well known for loud fan noise, but lately my DV6 went into thermal shutdown.
Once the heat pipe was removed, it revealed grey heat sink compound caked solid around the processor.
I cleaned off the old solidified compound and applied some white no name Si grease - good enough for now.

So my questions are,

Will it (white Si) also dry out and how long till that happens.
And if the average metal loaded pastes perform say 5 times better (W/mK), well what does that mean, when the thickness of the layer is 3mil thick?
I tried reading the lit but some like imperial units and others metric while some quote the inverse ratio - marketing spin Tssh!

How would the temperature increase across the junction compare for a 40W processor.

I figured metal loaded pastes might show a 0.15 degrees junction increase whereas the white Si variety might be one whole degree. Yes/No?

[Rerouter]

1, it will though being a no name paste it is hard to say in how long, even the jaycar stuff i use is only now starting to degrade 8 years in,

2. 5 times better generally means nearly nothing in this application as its rarely the paste that is limiting the dissipation in a laptop

3. the layer should be as thin as possible! 0.3mm to a few microns, its purpose is only to fill in the irrgularities of the surfaces,

[M. András]

tighten the screw with feel, the excess will come out from the side if the stuffs is conductive large amount of excess can be a problem. this method works for me on computers for 10 years now

[ptricks]

It doesn't matter if the paste appears dried up as the liquid nature of the compound when it is fresh isn't what does the heat transfer. The liquid they put into paste is used to make the ingredients in the paste easier to apply. What matters most is an even thin coat. I have seen equipment 30+ years old working fine with plain silicon paste, the paste is so hard it seems like cement. 

You can use anything you like to replace the old compound. Some recommend the arctic silver stuff, but it isn't the easiest thing to apply.  I still use the old white heatsink compound, it works and it is cheap.

[SeanB]

I used to make my own, using Zinc oxide powder and Dow Silicone grease, blending them together with acetone to improve mixability then stirring for a half hour before leaving it in a warm spot outdoors to flash off the solvent. Worked well for all applications, most of the time was to fix heat spreaders onto the chassis to get the heat out and into the big casting. Did many a 2N3773 with this as well.