Thread: Lapping FTW
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Old 03-17-09, 01:43 PM   #38
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Join Date: Jan 2006
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Default Re: Lapping FTW

Originally Posted by Zapablast05 View Post
Is that what's recommended? I'm really thinking about lapping my CPU and HS when I get home now that I found a guide on lapping my Xigmatek HDT-S1283. I found a grit guide and is it better to start rough with a low grit sheet then move up to smooth grit sand paper to give it a final polish?
Well there are a lot of different guides but they generally follow the same rule. Yes, you would start with a lower grit sandpaper to work out the bigger gaps and move to a higher grit to finish the polish. A visual image is think of your HSF like a mountain range. When you first start to sand it you need to do a lot of work to make the highest points even with the lowest points. So starting with a 150 or 200 will require a lot less strokes than say a piece of 400 grit to get the surface smooth. The reason for going up gradually is that you will reach a point where 150 grit will make more gouges into the surface than fix them. If you just jumped up to a 1500 grit sandpaper then you would sand the tops of your peaks but wouldn't really get the surface smooth. Using a few steps in between will bring the overall surface closer to smoothness before you make the jump to the final polish.

Originally Posted by mailman2 View Post
I used to start with 400. Now I start with 180 and get it to copper in minutes. Then I jump to 400 and finish with 600. The mirror finish makes it hard for the TIM to actually work. It has been recomended among veterns of OC and lapping that 600 or 800 is better cause there are actually slight imperfections for the TIM to settle in.

Its not how mirror smooth the finish is, its the fact that you are levelling the surface making it true so that you get better contact across the IHS.
Actually, the smoother the better. The only reason for needed TIM at all is because there are holes to fill so there isn't just air. (TIM conducts heat better than air) The ideal situation would be having both surfaces so flat that when you combine them together it makes both pieces of copper bond to each other making one solid piece of copper. Now I don't have physical data to back up that claim so maybe they know some special case where that may help, but from a science standpoint it makes a lot more sense to have one solid piece of copper for the best possible heat exchange. The only thing I could see changing that is if TIM conducts heat better than copper. Given that too much TIM makes it act like an insulator would make me think otherwise.
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