|lapping a heatsink|
I am sure that many of you have heard of lapping a heatsink on DH in the forums, as well as other places. This is probably one of the most common of all modifications done to a computer. That is basically because it is also one of the easiest modifications that there is to do. Lapping of the heatsink, is smoothing out, as well as making sure that it is a perfectly flat surface that makes contact with the CPU. This, along with replacing the stock thermal pad, will lower your CPU temperatures.
Every serious computer enthusiast will lap a heatsink as soon as they get it. For some of you that haven’t taken the step of building your own system yet, or may be getting ready to take a shot at it following Wildchild’s guide, this would be a very worthwhile modification for you, as well as for those of you that would just like to make your existing heatsink perform better.
• Wet/Dry grade sand paper: 320,
600, 1000 (finer grit is optional)
This is the heatsink that I will be lapping for this guide. It is an older unit that came bundled with an Athlon XP 1600+ barebones kit. This unit is made by Speeze and is all aluminum. It really doesn’t make any difference what material the heatsink is made from, as this guide pertains to all heatsink’s on the market today, new and old.
First thing that you want to do is prepare your heatsink for lapping by removing the fan and also the thermal pad that makes contact with your CPU. Removing the thermal pad, in some cases can be pretty tedious work. I normally use a razor blade to remove the bulk of the pad, and then clean off the rest using an acetone based cleaner. Most finger nail polish removers are acetone based and will work very well. Lay the razor blade almost flat and try to be as careful as possible, so you don’t gouge the heatsink material. A piece of plastic, like a credit card, can also be used.
Once prepared, find the flattest surface that you can. This can either be a laminate kitchen counter top, marble surface, a pane of glass, or the equivalent. Once you have decided on a surface, tape your 320 grit paper on the surface, apply a few small drops of dish soap, for lubrication, in the center of the sand paper and then apply a small amount of water.
When looking at the bottom of the heatsink you will see the machining scratches on the surface. These scratches should pretty much all be going in the same direction. You will want to do what is known as “cross hatching” when sanding. To do this you will always move the heatsink in the opposite direction of the existing scratches. You need to lightly move the heatsink in a straight, back and forth motion, rotating ¼ turn every so often, until the beginning scratches have pretty much disappeared. Make sure to clean the surface of your heatsink occasionally and rinse off your sand paper if needed. Always clean your heatsink thoroughly before using a finer grit sand paper. Then change to a finer, higher numbered, sand paper, and repeat the process, making sure that you move the heatsink, crossing, the previous marks.
Once you have sanded using all of the grades of sand paper, wash off the heatsink with warm water and then dry completely. Once dried you want to then clean the surface with rubbing alcohol, to make sure that all deposits are removed. The above picture shows the sanded and cleaned surface.
Polishing the surface is not required if you have used a fine enough grade of sand paper, but really makes your work look good. And also the more mirrored your surface is, the more surface area will make contact and dissipate heat from the CPU. Always polish by hand, using a lent free cloth and move in a small circular motion.
Here is a picture of the finished heatsink. All that is needed now is to reassemble your heatsink and apply your favorite thermal compound properly and install it. The finished heatsink should lower your CPU temperatures about 2-5 degree’s or more depending on how rough the surface was at the start, the material of the heatsink, and the thermal compound that you use.