Thermal Compound : wrong way to put it ?

Hi, everyone
I just changed the thermal compound of my CPU (gonna change it again anyway, it's cheap one) i would be happy if s.one tells me if i put it the right way.

 

First rule of thumb and it's important. More is NEVER good.

1) Place a bead of thermal paste in the center about the size of a grain of rice. You could go as much as the size of 1.5 grain of rice.

2) Place the cooler on top.

3) If you have screws to lock down. Tighten one screw (3-4 turns only) then go to the opposing side then move on to the next third screw and continue the process until all 4 screws are tight. The object here is to create even pressure downward.

Alternative method: ( I use this one a lot )

1) 1-1.5 bead of a grain of rice. Use the flat edge of a plastic card and work your way outward on all sides until the CPU is completely covered with thermal paste. The object here is to have a complete even thin layer of paste before you apply the cooler.

 

different ways of applying thermal paste https://www.youtube.com/watch?v=EyXLu1Ms-q4

 

IMO, I believe that on such a small area of die like on the mobile CPUs you can use spread method without any bubbles. Besides they were using glass which bents easier than metal on the heat pipes.

 

I used to do it like this (albeit, I used a new, flat razor blade to spread it). But I was told NEVER EVER spread it as you will create air pockets which defeat the purpose of using the heatsink's pressure to evenly spread it. (Will not reveal who told me never to spread it as they will ban me right quickly).

So confused...

 

I have tried it both ways and tbh there is no difference. The spread method looks nicer especially if one suffers from OCD. Also when you lock down the cooler the pressure alone removes any bubbles created with either method. And that's why it's important to work your way around the cooler mounting screws so as to create even pressure downward i.e. like putting lug nuts on a tire. You work your way around.

I also forgot to mention that I prep the CPU surface with a purifier before the application. If I am reapplying thermal paste, I use a cleaner first then a purifier and give it a couple of short burst of compressed air to remove any lint that may have fallen on top of the CPU.

 

That's what I've always though. Plus, most of the newer stock heatsinks will have a number next to each screw telling you which one to tighten first. Just like the lugs on a tire, you start on the first one, getting each screw half way on until they're all on, then go back and tighten them all the way down in order.

I have never used a purifier before (not even sure what that is). I always clean it with isopropyl first then hit it with the air can to get any lingering contaminants off before I apply the new paste.

 

I have blobbed since the beginning of time and it's the best and easiest way, especially for a mobile CPU die. There is no heat spreader on a mobile CPU so you *NEED* 100% coverage on the face of the die, unlike a desktop CPU where you have a heat spreader. I'd rather put a little too much to ensure better coverage, because the excess will just bleed over the edge, and the force of the heatsink being fastened down will leave only as much as is needed for the die. The only time this is not good is if the thermal paste is electrically conductive, like AS5. But I would never use that kind of paste on a laptop anyhow.

If the die is square then it's just a big blob in the middle. If it's rectangular then a short line along the length down the middle. I've added at least 10-12 different kinds of thermal pastes literally hundreds of times on dozens of laptop and desktop CPU's over the years and can say that there is very little difference between spread and blob, if anything I've had worse results with spread. Blob is just simple and effective. More than anything else, it is critical that you thoroughly clean the CPU and heatsink of previous thermal paste residue.

 

Put a small ball or line in the middle and press down. Friends don't let friends spread thermal paste the wrong way.

 

Artic Silver 5 is not electrically conductive, but it is slightly capacitive. " Not Electrically Conductive: Arctic Silver 5 was formulated to conduct heat, not electricity. (While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and couldpotentially cause problems if it bridges twoclose-proximity electrical paths.)"

And Artic Silver has recomendations for how to put the compound down. For AMD mobile processors they recommend a surface spread. For Intel, it looks like for previous mobile they recomended surface spread, but for Haswell they say use a vertical line.

Arctic Silver, Inc. - Intel® Application Methods

 

Ok, maybe not conductive but same end result is possible, a short between two leads. Direct from AS5 website:

"(While much safer than electrically conductive silver and copper greases, Arctic Silver 5 should be kept away from electrical traces, pins, and leads. While it is not electrically conductive, the compound is very slightly capacitive and could potentially cause problems if it bridges two close-proximity electrical paths.)"

 

I always use the spread method for laptop components, for several reasons.

1. As Wingnut mentioned, desktop CPUs have a heatspreader, which is much larger than the actual CPU die. If you only cover 2/3 of the IHS, you'll be covering the CPU underneath, and that's what counts. If you only cover 2/3 of the bare die, bad things happen. Spreading ensures you're covering the entire area, especially if you're not used to how much paste you need.

2. The pressure from the retention arms on a laptop heatsink don't have the brute strength of a desktop heatsink. I don't have numbers, but I can definitely say those arms don't feel as strong as jamming those locking arms (or whatever they're called) into your desktop motherboard. This can mean you don't generate enough downward pressure to make an optimally thin layer.

3. Speaking of downward pressure, on all the notebook CPUs that I've repasted I couldn't put the heatsink assembly straight down the same way you put down a heatsink on a desktop. You have to go in at an angle. This could mean that a blob of paste could get distributed unevenly, which is again suboptimal.

 

Mmm, that is what I posted...

 

I've been using the spread method as well without problems for a long while now.
The blob method produced a hit and miss results for me, but the spread method worked properly every time, and there have not been any air pockets.

 

yes bad things happen but if you spread you risk air pockets, and very unlikely to not get full coverage unless you use a very very small amount of paste.

I agree to a point. But it doesn't take much pressure to squish a near liquid material.

Never had that problem. Always been able to seat heatsink straight down.

My point is that blob is simple with little risk for error really. Spreading just opens up to risk of error. And you don't know if you have any air pockets unless you have a transparent heatsink.

 

What if that's why burning out is doing after repaste? Under high temperature paste becomes softer and under pressure bubbles go away...

 

You guys need to take a look at this: Application

 

I'm not here to tell anyone how to paste their machines. Do what you want, I don't care. I'm only sharing years, heck decades, of experience from the original 286 through CPU's today... yes I've been a geek that long. /shrug/

 

This isn't rocket science, and paste are cheap. (ok not dirt cheap, but a 99c tube of mx-2 can probably do 7-8 set of cpu+gpu)

If it is your first time or you have doubt, sit/screw the heatsink then lift it back up. Check the spread, wipe it, then do it again.

 

I was about to say that it's hard to screw it up. If temps are too high, try it again. That's why I blob. Quick and easy.

 

There's a chance you'll still get air pockets because of the third point I made, about the angle of placing the heatsink.

And, of course, if you're not used to applying TIM you don't have to play the guessing game with spread method like you would have to with blob-squish.

It's not necessarily pressure to spread it around. It's about pressure to spread it optimally, and I just can't see those little retention arms having the strength to do that.

Then the issue of user error involving the heatsink doesn't apply to you I suppose. I know in all the laptops I've owned, I had to go in at an angle to make sure the radiator grill lined up with the exhaust opening. It was never 90-degree vertical like it is with a desktop heatsink.

 

Here's an image of what we're used to seeing. Clevo

Also, once you get the feel for the blob technique, it's never a guessing game. You know exactly how much you need to put down for proper coverage. I have yet to experience air pockets in all the systems I've owned/built using this method.

 

If you're so nervous about under-coverage with the blob method, just apply a little more than you need. The worst that'll happen is when it spreads out it'll overflow the edges of the die a little bit. I use OCZ Freeze and it really doesn't care if I've applied a little too much, it performs just as well, and it won't damage anything if it gets on the PCB.