Lapping
Your Heatsink
Warning: Lapping your heatsink is a delicate procedure.
Improper lapping can cause performance loss or damage to your heatsink. Do not attempt
to lap bare microprocessor chips.
Since very few heatsink manufacturers
provide a truly flat and even surface on a heatsink, lapping your heatsink can increase
performance dramatically by increasing the contact area between your heatsink and your
processor. Some people may even want to lap the surface of their processor to further
increase the contact area as the processor may also not be perfectly flat. (This
only applies to newer processors that are manufactured with a heatspreader. You
cannot lap bare microprocessor chips.) SVC.com has put together a extensive heatsink
lapping kit that will allow you to refine your heatsink to bring out its full potential.
The premium heatsink lapping kit
consists of sandpaper ranging from 400 grit to 2500 grit and a flat lapping surface.
The whole process will take approximately 1 hour depending on the condition of your heatsink. Extremely flawed or uneven surfaces will require more time to level out
the surface.
Have a flat, hard surface to work
on. For small heatsinks and water blocks, you will be able to hold the block on
top of the sandpaper. For larger heatsinks, it is best to have a vise or something
similar to hold it secure while sanding.
Always start with the lowest grit
sandpaper. The 220 grit sandpaper will help shape and remove uneven areas on the heatsink. Be extra careful to keep the sandpaper completely flat and level during
this process. If possible, keep the sandpaper on a flat surface and hold the heatsink
against the sandpaper. If the heatsink is too large or awkward to be held, use the
flat lapping block. Use slow, steady motions to ensure a flat and even finish. As
you begin sanding, you will notice that certain parts of the heatsink will make
contact with the sandpaper while other parts do not. This is due to the uneven finish
left from the manufacturing process. Just keep sanding with the lowest grit sandpaper
on a flat surface until all parts come in contact with the sandpaper. You should
sand in a back and forth motion and only go in one direction. Once the surface looks
even, sand the surface in a a directional perpendicular to your original direction.
This will allow you to verify that the surface is flat.
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This image illustrates the initial stages of lapping your heatsink. You
can clearly see that the nickel plating is being scrubbed off to reveal
the copper underneath, you will need to continue this process until you
can no longer see any raised nickel plating on your heatsink.
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Once the surface is completely
flat, move on to the next level of sandpaper and repeat the process. The finer sandpaper
should remove all the deeper scratches left over by the previous step. Again, sand
in a back and forth motion in one direction and change directions to verify there
no scratches left over by the previous sandpaper and that surface is still flat.
Use less pressure as you move onto finer grits. Your goal is to remove scratches
left by the previous grit.
Repeat the process all the way
up to 2500 grit. On the 2500 grit sandpaper, apply minimal pressure and continue to
sand until the paper gets "saturated" with dust. After a few minutes of sanding,
you should start noticing the material beginning to get shinier and most of the
scratches should start to disappear. It is not possible to achieve a true "mirror" shine on 2500
grit sandpaper. There will still be very fine scratches that will be
visible upon close inspection. You should be able to achieve the same results as
the first picture in this article.
After sanding, carefully wipe off the dust and
shavings left behind. If you wish, you may use a polishing compound to get a
finer finish. Clean the surface with water, alcohol, or
ArctiClean.
Congratulations, you have finished
lapping your heatsink. Again, you may choose to use the same process for your processor
it it comes with a heatspreader.
Lapping Your Heatsink 
