What is the best choice for a thermal interface material for the best heat transfer?

Question

My senior design group has the task of creating a micro-cooling of electronics system. our biggest problem is the interface between the chip and the heat sink. right now we are using a few types of greases, is there anything better available. it needs to be removeable from the chip after use

Answer 1

Generally speaking you want your interface to have as much surface contact area as possible, and as high a thermal conductivity as possible. Consequently liquids are a better medium than solids. Greases are a good solution, but if it needs to be removable I'd suggest going with a heat transfer gel. They can mold to irregular surfaces and their semi-liquid properties maximize surface area for transport. Take a look at the website I'm referencing for more information.

Answer 2

The simplest is probably to just pick up thermal pastes from a local computer parts store like Fry's Electronics. Put some on the chip and put your sink on top. If you can, put pressure on the sink to squeze out the paste. The thermal resistance of the interface is going to be directly related to the thickness of the film. You want to displace all the air, but keep the thickness of the film down. There's nice goop that you can get that computer overclocking people use, but they are still pastes. Beyond this, you might want to try films that aren't based on ceramic oxides. You might want to try or silver based thermal interface material with higher thermal conductivity. The really exotic ones aren't pastes at all but actually metal alloys based on indium or gallium. These aren't really commercial items. You will probably need to make your own and experiment with them. The long term stability of these things aren't known either.

Look around the web at computer enthusiast websites, and you can get ideas on where to pick up high performance, commercially available thermal goops. I'll start you off at www.arcticsilver.com.

Not that I doubt your problem, but I have a hard time imagining that you have a component generating more heat than those 100W computer CPU's. They manage to transfer heat fine with thermal pastes. How many watts do you need to remove? Is the heatsink size or airflow sufficient?

Answer 3

Use a metal or something else that will help transfer the heat easily. A copper plate might work nicely, and a film of high heat oil might help with it being removed instead of grease.