#46
Post
by ThinkPadophile » Tue Jan 19, 2010 11:20 am
I've considered making this mod to my T60p as well. I do agree that the GPU temperatures would come down significantly if the thermal conductive pad were replaced with a metal shim. However, I do not think it wise to eliminate the thermal conductive pad altogether. I doubt that the only reason that IBM chose to use it was to keep manufacturing costs down; there was probably a design reason as well. The problem is manufacturing tolerances. We all know that the Northbridge chip stands higher than the GPU chip. What we don't know is whether their top surfaces (the surfaces that must make contact with the heat pipe) are perfectly parallel to each other. The design engineer had to assume that they would not be parallel, but would be slightly misaligned. This causes a significant problem: to have good heat transfer, the heat pipe must lie perfectly flat on top of each chip. However, if the tops of the chips are slightly off-angle with each other, then the heat pipe would have to twist in order to maintain the desired contact with both chips. Because the distance between the chips is rather small and the heat pipe is rather rigid, a great deal of twisting force would be needed, and this twisting force must be supplied entirely by the chips. The most likely result would be that the heat pipe could not twist enough to make perfect contact with either chip, yet would place great stress on both.
In light of this, it seems to me that the better solution is this. Rather than trying to eliminate the thermal conducting pad altogether, minimize it. Use a metal shim to span the greater part of the gap between heat pipe and chip surface, but place a very thin section of thermal conducting pad between them. This would eliminate the need for the heat pipe to twist in order to conform to the chips and thus eliminate the stress problem. Thermal conductivity, on the other hand, would be better since the majority of the thermal conducting pad would have been replaced by metal.
Here's my proposed procedure:
1) Remove the thermal fan.
2) Calculate the gap between the heat pipe and each of the chips. Simply examine the way the thermal pad conformed to the chip. The amount of thermal pad between the heat pipe and chip surface tells you the depth of the gap.
3) Make a metal shim that is slightly undersized. If the gap is 1mm, for instance, make a metal shim that is slightly thinner, say .8mm. This eliminates most, although not all, of the gap, but allows enough of a gap so that the heat pipe doesn't have to twist.
4) Apply the metal shims to the heat pipe with thermal bonding paste.
5) Apply a thin section of the thermal conducting pad onto the bottom surface of the shim.
5) Reinstall the heat fan.
I must repeat that I haven't yet tried this myself due to time constraints, but intend to as soon as I have a chance.
T60p UXGA Flexview T7200 3 GB RAM 128GB Samsung SSD Windows 7 Ultimate 64-bit