We give you the low-down on how to get your CPU and heatsink flatter - and running cooler - by lapping it to within an inch of its silicon life!

In the mad enthusiast rush to squeeze more clocks and speed out of our gear, there are a few hurdles along the way that hold us back, one of the largest being heat. Heatsinks draw it away from the CPU, and radiate it, but it is in this step that they sometimes fall down.

Assuming ours is a perfect world, every heatsink would have a perfectly flat base, and every Integrated Heat Spreader (IHS) on a CPU would also be flat, needing only a smidgeon of thermal goop to provide the material needed for the very small gaps between them. Sadly, our assumption was a little misguided, and neither of those things exist.

The IHS on a CPU is nearly always extremely convex (raised in the middle, and falling off towards the outer edges), and is made of copper coated with nickel. We’ve chosen the Core i7 920 chip (mostly because we’re crazy, and have no respect for misbehaving tech) and a
Thermalright Ultra 120 Extreme 1366 cooler for this experiment, and we’ll show you not only how to get great results for little money, but what we managed to achieve.


What you’ll need
Naturally, you can’t just jump into something like this without preparation, but being the helpful lads we are, we’ve done some of the work for you.
• Wet/Dry sandpaper in 400, 800, 1200 grit (you can get up to 2000, but this gives diminishing returns for the effort used)
• Flat piece of glass or mirror – has to be a very flat surface, and clean
• Willing subject, aka a CPU or heatsink
• Small glass or bottle of water
• Strong duct tape, and some scissors



After you’ve assembled your array of tools to get the job done, the first step is to clear the CPU of all thermal goop. Once you’re finished, cut some duct tape and completely cover the underside of the CPU, leaving only the IHS bare.



Next Page

This post has been edited by -YellowSn0w-: Feb 15 2009, 02:54 PM

i7 CPU Lapping

Once we were finished with the 400 grit, the next step up is the 800. Follow exactly the same steps with this as before, taping down and using only a small amount of water. You’ll know you’re finished with this grit once the deeper scratches left by the previous grit have mostly been rubbed away.



Moving from the 800, you can move up in steps of four hundred all the way to 2000, though we stopped at 1200 simply due to the fact that going that far isn’t worth the time spent. This will take you a while, so make sure you have the TV on, or some beer to drink (just not too much, it makes it…tricky). Once you’re finished with the 1200 grit, you should have something very flat, with only a few incredibly fine scratches.



To give an idea of just how flat this has made the CPU, here’s a side-on shot:



Not content with just the CPU, we did the same to the base of our Thermalright Ultra 120 Extreme, removing the nickel base and exposing the copper, making it as flat as needed to mate with the CPU. You can even see our chosen location (piece of glass on a kitchen bench), and this can really be done anywhere comfortable.



All the lapping completed for both the CPU and heatsink, the tape was removed from the CPU and it was cleaned with a slightly damp piece of paper towel. The heatsink can simply be run underneath the tap, and left to dry (though not getting water in the fins is recommended, because it takes ages!). Don’t run the CPU underneath the tap, it might be water but that doesn’t make it water cooling! For proof of just how flat these two have been made, here’s a shot without any pressure or thermal paste, just gravity:



Lapping is an exercise not only in willingness to move a piece of metal or silicon back and forth for a drop in temps, but in patience for the thing to be over. Our best advice is to take your time with it, and expect to spend at least two hours per piece, rushing this means potentially making the bases worse in the long run. So long as you keep turning the same ninety degrees, keep up the same pressure and ‘laps’ of the sandpaper, you’ll get a very good result.

Final Results

We recorded an average temperature drop at idle of 2.25 degrees celcius, and an average drop at load of 2.5 degrees. While this might not sound like too much, it can be the difference between stability and crashing, and is a great way to increase the cooling potential of any heatsink, or even a waterblock. So long as you’re careful, lapping is a great way to play with your tech, and will grant you some extra overclockability to boot – just forget about your warranty!

Good Luck and happy Moddling.

Sources :I7 CPU lapping sources

This post has been edited by -YellowSn0w-: Feb 15 2009, 03:14 PM

is there any difference between lapping this proc and any other proc?

slowpoke.................I already post the link to the guide over on the Cooling And Hard Modding section.


http://forum.lowyat.net/index.php?showtopi...post&p=23321430


there.

Haha john, all "ur" effort gonna be closed by bryan.

How many mm are we suppose to lap the IHS

Thanks john

till its flat


for me, i just use grit 120 and grind it down about 1 or 2 mm, then i use 800, 1200 and 2000 in sequence to polish it off., its flat as heck, this is the lazy way to do it

I try to made it super flat but still can see a little bit of light when lay flat on the heatsink, last time when i lapped my Q6600 i manage to made it super flat but not this time , any ideal?

anyone know how to oc with laptop?

Hello there guys, i've got this question regarding lapping. When we lap till we get a mirror shine, there have been reports that because of the increase in the amount of contact between the HS and the proc, too much thermal paste will cause the heat transfer to become weaker. So i would like to ask all of you who have lapped till you have achieved a mirror shine on your proc's if this is true and how much thermal paste do you guys apply onto your proc's after lapping it?

from what i know, thermal paste function is to cover gap between your heatsink base and IHS. no matter how flat you lap, it doesnt mean there wont be gap. there will always be some small tiny micro gap that you could not see with naked eye. hence, thermal paste is always needed.

for applying thermal paste, it always not good to apply too much. apply it moderately. everything you do, if u do it too much the result wont be good too. anyway, there are many ways to apply thermal paste. you can look at some guides at Air Cooling Discussion under "Thermal Paste"

very nice job lapping

i jus lapped my processor only yesterday
12 degreee dropped lol

you guys influence me alot to lapping the proc.. hish..

could it be risky? (sorry for noob question)

take a look at my lapped Hyper 212 and Titan Fenrir over at Air Cooling Discussion thread.

here's my 1st lapped job on HSF - Cooler Master Hyper TX2 and its sold

upload all the pic first, will put in description later on. thanks.























after left it expore to the air for a few days and i got my autosol, managed to polish off the oxided and make it shine shine




This post has been edited by tryifelsecatch: Apr 29 2009, 12:13 AM

just in case I need extra post, the previous one is full

First of all , u cant do sales here.

2ndly, u just lapped your heatsink, either you do some before and after temp result. Else others will hesitate what has happened.