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Proper method of Lapping a CPU

Discussion in 'Hardware' started by Oxnard, 11 May 2006.

  1. Oxnard

    Oxnard What's a Dremel?

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    Ok I bought a cpu lapping kit from FrozenCPU.com and it includes a peice of plexiglass (to provide a flat surface) sand paper (400, 800, 1200, 2000 & 2500)

    It was all working fine until I got to the 1200 grit, and it seemed like it was dulling the finish?? I mean before i could see some reflection and now none?

    So for now I'm using the 800 grit and really sanding it down and its slowly becoming more reflective, but I fear that 1200 grit's going to ruin it again.

    Any ideas?
     
  2. Firehed

    Firehed Why not? I own a domain to match.

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    I do hope you're lapping the heatsink and not the chip itself...

    Anyways, put lowest grit on glass. Lap for a while, preferably in a random patter. Give it maybe ten minutes or so... though timing's not exact - you want the base to be as flat as possible for the grit. For the first couple levels, that could take quite a while - some heatsinks are pretty concave or convex and will need a lot of material taken off in order to become flat.

    From there, just progress up to finer (higher) grit papers. Keep using a random patter for most effectiveness. A lot of people swear by wet-lapping; personally, I just find it to make more of a mess and not a whole lot of benefit.

    The finish isn't what matters. You can have a vase that's really shiny, but it sure as heck isn't flat. The same applies for heatsinks. You want flat, not smooth. Smooth helps, but not if it isn't flat. Thermal paste fixes it not being smooth, it doesn't fix it not being flat.

    So don't worry about the finish. It'll become shinier as you increase the grit, but the flatness is most important. I once lapped the IHS on a P4 to 10 micron sandpaper (probably 5000grit or something), and while it was both flat and smooth, it really made squat-all difference in performace.

    Just don't go back down a level, or else you have to start that level all over again.
     
  3. Oxnard

    Oxnard What's a Dremel?

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    I was lapping a PolarFLO TT and a Swiftech Apogee, neither came out great, but good enough for my needs. The trick to the 1200+ grit was DRY, wet it would simply ruin the finish, it was driving me INSANE.

    Anyhow, they are done, thanks alot for the advice.
     
  4. Leeum

    Leeum What's a Dremel?

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    The finish of the waterblock isn't important, it's how flat the surface is :)
     
  5. Guest-18698

    Guest-18698 Guest

    hey dude, when lapping the block as said start with 800 work up to your highest grit 2500?

    move the block over the grit in a figure of 8, this way it covers the whole of the block and you will find that it wont stracth it.

    I know what you mean about it going dull, just keep going
     
  6. olv

    olv he's so bright

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    if you move in circles or a figure of eight then you are more likely to dome the surface you are trying to make flat which is not what you want.

    You need to apply an even pressure (hugely important) across the waterblock and start by moving the block back and forwards in a straight line. Make sure your wet and dry paper is thoroughly soaked (tape it to your surface to prevent it curling) and use a dot of washing up liquid at intervals to keep it lubricated.

    Start with your lowest grit paper and do 10-20 passes back and forwards. Lift the block and rotate 90 degrees and do the same number of passes back and forwards. Rotate 90 degrees and repeat. Rotate 90 degrees and repeat. Do severeal full cycles of this on each grade of paper working your way up. Remember to try and keep the pressure even.

    As has been said, the reflectiveness of the surface isn't important, it's how flat the surface is.
     
  7. felix the cat

    felix the cat Spaceman Spiff

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    now theres a blast from the past! still alive and kicking olv?
     
  8. Burnout21

    Burnout21 Mmmm biscuits

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    everyone has told you how to lap that block, best thing for you to do is work your way though the papers until it finished. trust me i was lapping back a while ago and when i used the 800 grit it gave me a factory finish, no reflection but nice and flat, when i moved up the grit scale after so moe work with a finer paper a mirror finish came back.
     
  9. olv

    olv he's so bright

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    oh yes ;)
     

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