How to build a T43 southbridge cooler

The T43 and T43p have a serious thermal design problem, where the area under the touchpad gets very hot. This causes a problem with fan noise and a problem with hot surfaces.

The culprits are the Intel 82801FBM southbridge and the mini-PCI WiFi card, which generate significant heat and don't get adequate cooling. Moreover, these components are adjacent to the GPU, whose potentially high temperature affects the whole region of the planar board.

This page documents a successful hardware mod for thermally attaching the southbridge (and to a lesser extent the mini-PCI card) to the PCMCIA card cage. Since the PCMCIA cage is a major air intake and gets significant air flow when the fan is running, this effectively cools the southbridge to a comfortable temperature even under full system load. Here is what it looks like:

ATTENTION!

This hack may damage your ThinkPad or you, and will surely void your warranty.

What you'll need

• Phillips #1 screwdriver
• Sharp knife
• Thermal epoxy (e.g., Arctic Silver Thermal Adhesive)
• A 4"x2" sheet of 0.0135"-thick copper plate (e.g., from OnlineMetals.com). You can probably get away with slightly a thicker plate, but much thicker will make the palm rest bulge against the LCD.
• Heat-resistant electrical tape, or a thin sheet of some heat-resistant electrically-isolating material
• Ruler
• Heavy-duty scissors
• Patience

Opening up

• Disconnect power and batteries
• Remove hard disks
• Remove the keyboard
• Remove the palm rest. Use the knife to carefully peel the screw covers; you'll need them back later.
• Remove the mini-PCI card

You can now see the southbridge, which is the big black chip under the mini-PCI slot.

Making the copper heatpipe

Cut and bend the copper sheet as follows, using the scissors and ruler. Make the flat areas as straight as possible.

Cover all areas that may touch exposed electronics (see below) with heat-resistant electrical tape.

Fit the copper heatpipe in place under the mini-PCI slot and bend it so it sits snugly, as in the photos below. Push it all the way to the left against the mini-PCI slot (I have a small gap between the two, which was a mistake).

Try putting the palmrest back in place and make sure the heat pipe doesn't get in the way.

Gluing the heat pipe

Cover the southbridge with thermal epoxy. Be generous, since it needs to fill the gaps under the copper plate (which is not that flat by now). Do the same with the relevant area of the mini-PCI cage, being careful not to smear glue on or near the moving parts.

Put the heatpipe in place:

Hold it firmly in place until the epoxy settles (10-15 minutes). While doing so, you can amuse yourself by inspecting the alleged "stereo speakers" at the front of the unit (ever wondered why ThinkPads sound so bad?).

The result

Potential improvements

• Do a neater job with the epoxy. Ugh.
• Extend the copper heatpipe further to the left, to improve heat dissipation. The thin stainless-steel PCMCIA cage seems to be a very poor heat conductor.
• Find the maximum copper thickness that won't interfere with the palmrest.
• Get better a thermal connection to the mini-PCI WiFi card. This is tricky because the underside of the Intel card has an uneven surface with many components sticking out.