JLM0204 :
As the title says, I am planning to build a rig with a i7 6700k CPU that has the Cooler master nepton 240 m to cool it, so do I still need some thermal paste on the CPU when it already has a water cooler?
And if so how do I apply it and what is the best one?
Multipack :
Yes you need it, but it will come pre-applied on the cooler's copper plate.
That unit comes with a tube of thermal compound(syringe style). That little syringe is enough for 20+ applications. DO NOT THINK YOU SHOULD USE IT ALL!!!! Watch a YouTube cideo or 3 on the correct way to apply thermal paste.
My CPU came in a clamshell like
I used the edge of it to spread a tiny(about the size of a normal grain of rice(not long) dab on the CPU lid. I then did the same to the heatsink and spread it over to and onto the heatsink pipes. Understand I am applying an ultrathin layer. Paint that is applied to walls is thicker than the amount of thermal paste one should use. You are looking to fill
microscopic valleys and level microscopic peaks. A sort of tape and float(drywall repair, sorry) without the tape.
In short, yes it comes with paste. Yes, all CPUs that use a heatsink need thermal compound. No it isn't pre-applied like Intel does with their non-K units. Be careful, watch some videos and make sure you notice the orientation point on the CPU that needs to line up to the orientation point on the motherboard(read socket). Take it slow. Avoid needless mistakes.