Every now and then I have to work with hardware, be it assembling a new box, or just cleaning it a little bit, and I always have this question: how should I apply the thermal compound to the CPU? When should I have to do it (should I clean it and apply it again for a CPU that already has it)?
When you have to replace compound on an existing cooler, a common problem is, that the compound ends up sticking the heatsink to the processor, making it difficult to remove the cooler. You could use a hairdryer to heat the heatsink a little, in order to melt the thermal compound and then remove the heatsink moving it slightly in a lateral way. But I wouldn't use the hairdryer too long.
To remove the rest of the old compond, use a cotton swab with isopropyl alcohol. It is alcohol that doesn't contain water. Use a utility knife to eliminate the last rests of the remaining substance, but be careful not to scratch the surface.
It is a common misconception that the more thermal compound is applied, the better. Too much grease can be insulating spoiling the correct heat dissipation, and worse: that grease could end up dropping on motherboard contacts. Normally they don't conduct electricity, but there are compounds with some metal, they will work as conductors, which could lead to a short circuit and destroy your motherboard.
To apply the new compound, again use a cotton swab. Don't put too much of the substance on the processor. You don't necessarily have to cover the whole area of the processor, because the pressure of the cooler will do that for you. How to apply the cooler will depend on the model of processor/cooler you will use. Do it carefully.
I recently needed to fix a problem with an over-heating machine. I found this video very helpful:
Basically, the steps are:
Remove heat sink
Use 100% Isopropal alcohol and lint free cleaning rag (microfiber works well) to clean both the CPU and the heat sink
Apply a small amount of compound
Spread compound evenly
Re-attach heat sink
I followed the "grain of rice" method, where you apply a small amount of compound and let the heat sink spread it out for you. So far, so good
You should always clean off all the old compound before applying new compound. Thinly and evenly would be best - you're smoothing out microscopic scratches in the metal - it's not tile adhesive :)
edit: If you meant "how" as in what with - a razor blade would be perfect.
Here's a great place to start: Arctic Silver Route to Product Instructions. In general, a little bit goes a long way.
Ideally you'll have 100% CPU-package-to-heatsink-metal contact to get the maximum possible heat transfer direct from CPU to heatsink. Alas, our world ain't ideal and there will be some possibly-microscopic surface irregularities in each. The job of thermal transfer compound is to fill up those irregularities and thus improve the heat transfer (it conducts heat better than air, but not as well as direct CPU-to-heatsink contact), and so it's best to apply as little as you possibly can but enough to ensure there are no gaps.
It depends. Reading the instructions for Arctic Silver, there's basically a separate sheet for each cpu family - mostly depending on the paste itself, the design, size and form of the heat spreader and the position of the chip beneath it.
For instance, on a Core 2 Duo, you should squeeze out a short, thin line along the middle in a specific direction and then just put on the heatsink - apply some pressure while twisting it ~45 degrees back and forth once to spread the paste out, then fasten it.
I always apply thermal compound to a CPU just before I install the heat sink. I apply a very small amount and then user a razor blade to spread it thinly across the surface of the CPU. You do NOT want a lot of compound. You want to apply just enough that you can get a very thin layer across the entire CPU surface.
When I remove and restore a heat sink, I always clean the CPU with a thin cloth and reapply thermal compound, but I don't know if this is strictly necessary. I would always, however, re-spread the compound to ensure that the whole surface of the CPU has a thin layer.
This isnt an answer, but...
I have 13 Gateways at one location, the majority experience sporadic shutdowns due to a 'thermal event.'
When I attempted to remove the heatsink from the processor ON ALL 13 of them, the thermal paste had hardened and was acting like a glue. The processor was ripped from its socket by the block on almost all of them. It was impossible to get under the block to release the bar that holds the processor in place.
I still havent found a good solution for removing the heatsink blocks.
Thanks for all the advice here.