Mission: To lap/resurface your heat sink
Purpose: To even out the irregular surface of the heat sink; to reduce thermal resistance; to increase thermal conductivity
Cost(s): $2.99 (plus tax) for Wet/Dry sandpaper (spring for this stuff, it makes all the difference), piece of glass (got one out of a small picture frame), water, 15 minutes to 1 hour of free time.
CAUTION: Before beginning this procedure, completely remove your fan assembly and retaining clip. Failure to do so may result in the assembly shorting out. Also, before reassembling the HSF, Make certain that the heat sink is completely dry. (I’d recommend overnight). If not, it could short out the CPU and/or the motherboard. Be prepared to be at this a while – your heat sink may seem flat, but I assure you, it’s probably not!
Introduction
Alright kiddies, it’s time for a quick demonstration on how to properly lap a heat sink. Most heat sinks come with either a convex or concave bottom, which means that the surface is not making full contact with the die. In ye olden days of Pentiums and K5’s this wasn’t much of a problem. The die was humongous (OLD=half dollar, NEW-dime), the heat sinks were smaller, and power dissipation wasn’t really an issue (most early Pentiums were cooled by heat sink only and threw out a whopping 11.9 watts and rated for a max ambient temp of 80’C).
In a November 1995 white paper, Intel stated: “Higher Temperatures result in earlier failure of the devices in the system. Every 10’C rise above the operating temperature means a halving of the mean time between failures”
Now you know why it’s important, so let’s get to it. Gather up your supplies, roll up your sleeves and let’s start lapping.
Start by tearing your sandpaper into ?’s. Begin with the roughest grit you have. In my case it was 220. Fold the paper over the glass like so:
Click On Image To Enlarge
Next, I dipped the paper in a bowl of water (the reason why I sprang for wet/dry), shook off most of the excess and began lapping. I prefer this method to taping an entire sheet to a larger pane of glass and sprinkling it with water, as I feel I have more control over the work piece.
Next, let’s examine the surface.
Click On Image To Enlarge
Look at this mess! Mine had some horrendous scratches on the base. This was partly my fault…I tried to scrape off some that god-awful thermal putty with a dull knife. I assure you though; this lapping would still be necessary even if I hadn’t gauged the heck out of the base -- as we’ll see after a few minutes of sanding.
