why no heatpipes making direct cpu contact?

yeha · Post by **yeha** » Wed Feb 02, 2005 11:32 pm

of all the heatsinks i've seen using heatpipes, they always seem to be jammed into some holes that were drilled in a metal block, with a few mm between them and the die (including whatever bonding agent is between the heatpipe and its surrounding metal.

is there any reason we haven't seen heatpipes with a flattened section forming the base of the heatsink itself? picture this - two 6mm-thick heatpipes bent into a U, with the base of the U flattened out so it's about 10mm wide. stick those two flat bases together to form the bottom of the heatsink, and you have a flat base of about 20x30mm of pure heatpipe for the cpu to interface with. on top of those, you could blob some solder or attach a metal block with thermal adhesive, it'd only be there for structural reasons. then you could use the 4 heatpipe ends that are sticking up to attach fins to.

it just seems that having the heatpipes make a direct connection would do much better than going through a an interface material and then a section of copper/aluminum. so why does everyone jam them into a block? is there really that little difference, or are flattened heatpipe sections much worse at conducting heat?

meglamaniac · Post by **meglamaniac** » Thu Feb 03, 2005 1:29 am

I imagine it's because that would disrupt the operation of the heatpipes.
I don't know an awful lot about them, but from what i've read the tube shape seems to be integral to how they work...

Tibors · Post by **Tibors** » Thu Feb 03, 2005 2:24 am

Probably a manufacturing issue. The base of a heatsink has to be really flat. Usually this is done by milling and polishing. You can't do that with a heatpipe, since they are hollow.

Qwertyiopisme · Post by **Qwertyiopisme** » Sat Feb 05, 2005 5:24 am

You would probably also deform the base of the heatpipes when you attach them to the die, beacuse they are made of relativly thin material. The bending would give an awfull contact to the die.

silvervarg · Post by **silvervarg** » Mon Feb 07, 2005 5:17 am

The heatpipe coolers that use one fat heatpipe in the middle does basicly this. They may either let the headpipe go all the way down to the chip or they make have a thin part of the bas in between. I guess this depends on what works best in manufacturing.

I use the DP-102 cooler that works like this, and it cools my CPU perfectly fine without any help from fans even when room temperature is 30C.
It was a while since I did this build, but it is quite well documented at my site:
http://borg.silvervarg.net/henrik/dator ... build.html