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Thread: Heatsink Lapping Advice

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    Heatsink Lapping Advice

    I had a go at lapping yesterday this is my first attempt.
    I used an old AMD heatsink as a trial run before I try it on a good one.
    I used 800,1000 and 1200 grit wet & dry
    is this good enough or do I still need to do some work on it?


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    Looks okay to me! In my opinion, lapping is somewhat overrated. Using a decent thermal compound and applying it correctly will get you far better improvements in contact and thermal conductivity then slaving away for hours to make your heatsink that little bit more shiny. Again, my opinion, please feel free to correct me if you don't think I'm right!

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    Shine isn't half as important as the heatsink being flat. If the heatsink is already flat but a bit dull you can reduce performance by hand-lapping it shiny as it's very hard to keep them flat when lapping by hand.

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    I agree with Decemoto, I've spent hours lapping in valves, resurfacing cly heads, but never thought it necessary to lap a heatsink, it's got to be a bad heatsink not to fit flat, just use thermal compound and that's it.

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    Think i agree with you guys too, the point in the thermal past is to provide the best possible surface for heat transfer by filling all those microscopic bumps and rough on the surface of the sink and the chip to give as good a possible contact as possible. I personally dont bother wet and drying mine and have decent temperatures. If both surfaces were 100% flat and smooth you wouldnt actually need a layer of thermal paste and this would be the ideal situation as your eliminating the use of an "extra" material in which heat transfer has to take place. However, due to it being far to expensive to get a perfectly smooth and flat surface we use the paste to "fill" those rough bumps and gaps in..

    Hope this helps

    Chris

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    Homestarr Mod
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    i always lap my heatsinks on my own pc's just for that warm perfection feeling and then finish it off with a small rub and rinse of Brasso

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    I'd go for a wipe down with isopropanol or similar after the brasso myself.

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    Prize winning member. rajagra's Avatar
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    There's an interesting argument against lapping here:
    Why Heatsink Polishing Might Be A Bad Idea
    Could be complete BS - but it does sound plausible.
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    Sounds pretty plausible to me - and if the claims are true, it looks as if he has the experience to back them up... Certainly flatness is critical to ensure the gretest contact area, and any thermal compound applied should be the minimum amount possible so that it just fills the microscopic gaps, and not splodged on like buttering toast!

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    Lapping is a very good idea, for many heatsinks, but having a mirror finish won't help in the slightest.

    I only lap to 600 or 800 grit, sometimes its rougher than the original finish, but every time I get noticeably better temps. Why? Because the heatsinks are now flat.

    As others have said, a little roughtness won't hurt anything, with a good thermal compound. However, if the heatsink is not level (concave, convex, ridges, ect), no thermal material will make up for it.

    Flat trumps smooth.
    Last edited by oralpain; 21-09-2005 at 06:22 PM.

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    Quote Originally Posted by oralpain
    Lapping is a very good idea, for many heatsinks, but having a mirror finish won't help in the slightest.

    I only lap to 600 or 800 grit, sometimes its rougher than the original finish, but every time I get noticeably better temps. Why? Because the heatsinks are now flat.

    As others have said, a little roughtness won't hurt anything, with a good thermal compound. However, if the heatsink is not level (concave, convex, ridges, ect), no thermal material will make up for it.

    Flat trumps smooth.

    Thanks for the input in future I will concentrate on flatness and not keep going to get the shine.

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