So alot of debate and whatnot (apparently, since geeks have no other way of showing off their e-boners) on what type and how to apply thermal paste to a CPU!
Well, since the cpu usually is one of the most expensive parts in your pc (usually the second most expensive, followed by a graphics card), I suppose it is a little troubling when you dont knwo how to "correctly" spread thermal paste. or use the el-cheapo stuff.
So heres some debunks on all these issues. I spent the money and time redoing thermal pastes and trying various types. Obviously, some brands are better than others, so I wont go into exact details, but I can comfortably say that my statements will be correct.
Firstly, application method.
There are 3 major types of application methods I've seen put to good use when it comes to thermal paste. The Middle Dot (or Pea Drop), The line, and Spreading.
Middle Dot is, as the name suggests, a dot about the size of a average Pea (hence pea drop) put right in the middle of the processor. As you apply the heatsink, it spreads the Thermal compound uniformly in a round shape. This will be the quickest and easiest method to apply thermal paste, but will have a few problems. Although you wont get many if any air bubbles in the compound, the force it takes to evenly spread the compound is a bit high. Although, if you are applying the heatsink via screws, I dont see this as a issue. Coverage isnt as good as I'd prefer, but others may be happy with it. Also, the layer of paste usually will be a bit thicker, which in turn means less efficient heat transfer.
The Line is the next method and usually seen on Ivy bridge intel processors (due to the shape of their Die). It pretty much is the same as the Middle dot, except you put a vertical line on the middle of the processor instead of a dot.
The third method (and the one in which I prefer) is the Spread method. Now the spread method involves putting a drop of paste in the middle of the cpu and then using a card (not a active credit card, please...) to evenly spread the compound out. Now I tend to do a very thin layer on the cpu and a very thin layer on the heatsink, but this can result in some serious air bubbles, so just on the cpu is a good idea. using less pressure on the heatsink will evenly spread out the compound to make a uniform connection. I prefer the spread method as it lets me control how much paste is on my cpu, unlike the middle dot method which its easier to over apply.
Now that being said, as the average user and builder, a middle dot on a AMD and a line on intels will apply more than enough compound and cool your processor more than adequately. It takes ALOT less time, cleanup is easier, and is less messier. But, on a Prime95 test with my FX 8320, the middle dot method proved to run 1-2*C higher under load than the spread. Consequently, the spread method initially idled 1-2*c higher than the middle dot method (and panned out to about 0.5*C after setting in overnight), so I'll let you be the judge. I'd say as long as you did one of the 3 above methods, you wont have to worry about your paste application.
As far as types of paste go, you pretty much have several types out there, but they all revolve around the same principles. They transfer heat uniformly from the CPU to the Heatsink.
Silicone greases are usually the cheapest and work exceptionally well. I have a tube of Delux Infinity Nitro A1 I've used for 2 years, and it transfers jsut as good as Antec Formula 6 Nano Diamond. Though, Greases tend to be harder to clean up (not always but usually) and the cheap stuff can dry out and crack, leading to poor performance.
Ceramics are the preferred budget paste. Ceramics dont conduct electricity, and they transfer heat very well. A 20G syringe around here costs around 8$, which is more than enough for 20+ applications. 40 if you do it thin enough. Personally, I haven't had a chance to try ceramics, but they tend to be the average performance.
Metal/Silver based greases are very popular, particularly AS5 or Arctic Silver 5. Usually, these pastes have a set in time, so they will get better as you use them, and contain metal particles (usually silver). Although these work great, keep in mind that they are indeed conductive, so use caution around system components.
Diamond pastes are somewhat new to the market. They contain nano-diamonds, which suppsoedly transfer heat better. Now some people will say "diamonds are insulators" but thats like saying "Aluminum Foil is an insulator because it helps to prevent the wings on your turkey from burning". Stones transfer and hold heat well, So people tend to have mixed feelings on diamond pastes. IC7 Diamond tends to run 1-2*C cooler under load than fully cured AS5.
Finally, we got those wonky ones, like Liquid Metal and Indigo Xtreme. Liquid metal is as the name says. Its a low melting point metal you put between the cpu and heatsink to transfer heat. Unfortunately, there isnt anyone around here who sells it, so I havent had a chance to try it.
Indigo Xtreme takes thermal pastes to a whole new level because it really isnt a paste, or even a liquid. Its a solid piece of metal you sandwich between the processor. As it heats up, it melts the metal to create a uniform flat layer of metal that joins the heatsink and processor (thankfully not permanently.). some people swear by this, others hate it. Personally, before dunking 20$ into it, I'd do all my homework and make sure not only is your CPU and Heatsink compatible, but if it is even practical to apply.
With all the choices and all the debates, what should you get and do at the end of the day? Application method is dependent on your processor, but the middle dot method is tried and true and will get the job done. If done RIGHT, the spread method is, in my opinion, optimal. As far as paste? You'll never go wrong with AS5, IC 7 has great reviews, and Thermaltake's TG-1 (NOT TG-2!) has the best results thus far.
I hope this helped, and please, constructive criticism is always welcome but flame wars are not.