Applying heatsink grease is a common question on many computer related forums. I recall it on overclockers.com as well as on my current favorite forum, Ars Technica. It's really a simple thing. I'll post a few pictures of a Chemtronics Silver Thermal Grease being applied to an FC-PGA chip here and will plan to update this later with PPGA and t-bird applications.

27 January 2001: Chemtronics silver on Intel FC-PGA and standard silicone thermal grease on i815E (BGA?).

You want a thin layer of grease on anything that you apply. It has to be thin enough that it doesn't inhibit thermal contact between the heatsink and CPU, yet it has to be thick enough to ensure that the heatsink and CPU are in good, even contact. Too thin and you don't get enough contact between the heatsink and CPU, and your chip cooks. Too much, and the heat transfer between the heatsink and CPU is inhibited.

Chemtronics Silver Grease application

1. Clean both surfaces-- the bottom of the heatsink and the raised die of the CPU. I use rubbing alcohol, but acetone can also be used. Make sure both surfaces are dust-free after you wipe them down with a damp (w/alcohol) tissue, I use a can of compressed air. Let both surfaces dry.
   
2. Squeeze a tiny drop of grease from the syringe. 1~2mm in size should do it, 2mm may be much too big. On FC-PGA (Socket 370) and Socket A chips, the clamping pressure is very high-- squeeze the heatsink on to the chip and most of the excess grease should be forced out.
   
3. Pull the heatsink vertically (with a slight twist or angle if needed) off of the chip. Examine the pattern and thickness of the grease left on both the heatsink and CPU. You should see little raised peaks or ridges evenly spread all over the chip and heatsink where there is good contact between the two.
   
4. Reinstall the heatsink and remove it again to check. If both CPU die and heatsink are reasonably flat, you should be able to see through the thermal grease and see the color below the little peaks of grease. Note the ridges of grease on the CPU die in some of these pictures-- those are areas of excess grease. Any areas of poor contact should be filled in with a tiny dab of grease.
   
5. Examine the heatsink. You doubtless see areas of excess grease around the edges of the area w/grease. That is NORMAL. You can try to wipe some of it off, but do NOT touch the center area with grease. You want signs of even, continuous contact on both the CPU die and heatsink.
   
6. If everything is satisfactory, install the heatsink!
   
7. Plug in the CPU fan and see how things go!
   

The keys are being able to see the color of the surface through the thermal grease and an even distribution of the tiny peaks all over the CPU and heatsink contact areas. These are pictures from what is only my second FC-PGA chip install and my technique is not yet very good. The small surface area does make things difficult compared to PPGA chips. Note the ridge of thermal grease off to one side of the center... that is not a good thing. I'll be switching from an Alpha PAL6035 w/Sunon 60mm fan to an Alpha PEP66 w/Delta thin 60mm fan soon and will try to post pictures of that install if I remember to do so.

Installing thermal grease on the i815E chip of my Asus CUSL2-C was much easier. It was regular silicone thermal grease as you can see from the pictures, and getting a thin layer was not as critical because the i815E produces much less heat. Still, note the even contact all over the surface and the tiny peaks I keep talking about. Intel chips seem to be more concave than they should be, so a little more thermal grease is needed for this application.