what a pile of drivel
replacing thermal pads because they 'age' ... total and utter nonsense !
Do they leak an oily substance ? yes, some do.
Does it matter ? no, not a bit.
Thermal pads or thermal grease is an emulsion made from alumina (aluminum oxide) suspended in a carrier material.
The thermal properties are determined by the alumina. The rest is just a carrier to be able to manipulate it.
You only need very little paste. Heaping it on works aversely. It is not a refrigerant. It's a transfer material. One that has worse properties than then materials it is trying to transfer between. Yes, you read that right. The heatsink and the copper slug on the device have much better thermal properties than the alumina.
Why do you need it then ? because, at microscopic level, neither the heatsink nor the heatslug on the device (processor,gpu) are 'flat'. They contain pits. The thermal compound fills these potholes and lowers the thermal resistance. When the device goes hot for the first time the "oil" goes fluid , the alumina particles settle under pressure and that's it. Components mounted on a heatsink where paste is used will always be mounted "spring loaded", either by special retaining clips made from spring steel, or using split-washers under the screw, or the heatsink itself spring loaded. the reason is what i came to mention before : at first operation of the assembly, the first time this stuff gets hot, the oily carrier goes liquid , squeezes out, while the alumina particles remain trapped. the carrier material is a very bad thermal conductor, you want it out of there.
The same nonsense goes for statements like "this paste is totally dried out , let me replace it".
It MUST be dried out ! That's when it is most effective.
Aluminum has a thermal conductivity of 230-ish watts per metre-kelvin
Alumina is 30 ...
Copper is 401
Oil is 0.1
Now you get it why you want that oil out of there ?
As for the thermal pads : they need to be compressed for the same reason : get the carrier out of there and compress the TIM ( thermal interface material )
There is a tendency to go away from alumina based materials and go to carbon based material ( a material called Vertical Carbon ) or graphite.
Carbon, under certain circumstances, is a much better thermal conductor than most other materials out there. Diamond, which is the crystalline form of carbon, can handle 2000 watts per metre-kelvin. Nothing else comes close to that apart from graphite. There are some exotic materials such as magnesium oxide, boron nitride and aluminum nitride that perform very good. Some of these are actually used inside the semiconductor package.
And yes, you can actually buy thermal paste that uses , industrial, diamond . It is used in cooling applications for high performance lasers and processor modules like for IBM Z-series mainframes.