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CPU Lapping questions

464 Views 7 Replies 7 Participants Last post by  riddler2k6
-What does it mean for a CPU to be concave?
-What kind of sandpaper do I want to use?
-Also, I'd imagine if you sand one area down too much it will go in too deep compared to the surrounding and not have full contact with the heatsink. Is there something in particular you do to prevent this?

Thanks in advance.
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1. the IHS (Integrated Heat Spreader) on top of the CPU die can be concave or convex, both resulting in heat transfer not as good as it can be. you want a perfectly flat surface.

2. I think most people start around 400 grit or 800 and work up to 1500 or if possible, 2000 grit.

3. Use a piece of glass or some other extremely flat surface to have the sand paper on and make sure you hold the CPU or heatsink level.
Why do you want to go so fine grained? I mean, if you're going to use thermal compound, istn't it better to get as much surface area as possible (=coarse surface as opposed to smooth surface) ???
Nah a smooth surface means more of the IHS is in contact with the HSF, so heat is transferred quicker.
no, smoother surface allows for less distance between the hsf/cpu meeting point. I thought the same, like on a car setup, wrinkle finsh adds more surface area. This is different, as the amount of distance between the hsf and cpu is detrimental to where the heat is tranferred. Besides, you have all the surface area of the hsf to take care of dissipation.
AS5 isnt really that conductive

metal is like 10x better

as5 is used becasue of the microscopic gaps

the less gaps the better temps
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Ok, so the best results should be had with surfaces as smooth as possible, and with as thin a layer of compound as possible? I think I had a tad too much compound, one layer on the IHS, and one on the HSF...

Need to check for CPU smoothness :)
btw make sure you use wet and dry paper and wet it every now and again
and yes do you glass if you dont have glass look for the next best thing kitchen table or a work suface
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