West Lafayette (IN) - Researchers at Purdue University have discovered that carbon nanotubes can move the heat generated by silicon chips more efficiently and less costly than other methods.  By taking the heat from a chip and moving it to the metal casing more efficiently, our silicon based products (CPUs) can be pushed further.


CPUs generate heat from electrons in motion and the resistance they encounter within the semiconductors.  This generated heat is one of the biggest stumbling blocks toward achieving better performance through higher clock speeds.  Transistors, the base components operating at the very heart of a CPU, can only switch on and off so fast within a given thermal envelope.  Beyond that the generated heat begins to grow quickly and, without sufficient mechanisms to remove that heat, the hotter CPUs will just eventually stop working.

Scientists at Purude have discovered a way to grow carbon nanotubes which affix themselves directly to a processor die, allowing for very efficient heat removal.  According to the research, the carbon nanotubes are grown vertically on the silicon die between the die and metal casing.  The surface is so full of nanotubes that under a microscope it looks like a thick, dense carpet.  When the metal casing is mounted, the tubes bend slightly as they come in contact with the metal.  This would be like placing a thick sheet of plexiglass on carpet where you could see the fibers bending under the weight.  This has the effect of creating a great deal of contact surface area with the metal.  And, since the carbon nanotubes are physically affixed to the silicon substrate material, the heat flow becomes significant toward the cooler metal.

Scientists physically create the nanotubes using a process called "microwave plasma chemical vapor deposition."  It involves taking a silicon substrate (like the back side of a CPU die), and introducing branching molecules called dendrimers which anchor to the silicon.  Metal catalyst particles are then applied in a solution.  The solution is removed by adding heat, leaving only the particles behind.  From there the surface is exposed to methane gas in a microwave field.  The microwave signal breaks down the methane gas and deposits the carbon onto the dendrimer/catalyst combos in the form of self-growing nanotubes.

While somewhat technical, the process being used by the researchers is not expensive or difficult to employ.  This is especially true when compared with some of the processes involved in manufacturing semiconductors today.  In addition it has been shown that existing alternative solutions, such as indium foil, grease and waxes, are all less efficient than the carbon nanotube solution.

Researchers believe this process could be introduced to large scale semiconductor manufacturing.  This would allow consumers to buy products which require smaller heatsinks while making our processors run faster.  The smaller heatsinks would be required because with a more efficient transfer rate of heat away from the silicon die, the temperature delta between the heatsink and CPU could be less while still achieving the same effective transfer rate.

Research for this project was funded by NASA, through the Institute for Nanoelectronics and Computing in Purdue's Discovery Park.  One of the researchers also received undisclosed forms of support from Intel and Purdue.

carbon

Oct 02, 2007 12:11     

Excellent, we need more uses for carbon. :P
Rob report abuse vote down vote up Votes: +0

Advancements to an ever changing field

Oct 02, 2007 12:23     

This will defantly bring a great benifit to those who overclock and use high effectivness heat sinks. But the main question is when this will be used, and how much will it effect the price given a standard economic curve. If this rases the price per waffer of CPUs, it wont cetch on quick enough before they can get data to improve upon it. They need testers so that the tecnology can get a base of data so that maybe they can get better thermal transfer even yet than just the nano tubes.

Jiggz88 report abuse vote down vote up Votes: +0

Listen Up AMD/Intel!!!

Oct 02, 2007 13:32     

This is what Intel/AMD should use to secure the heatspreaders on their chips to the CPU die. Lapping a nickel-plated C2D to get a better heat transfer helps, but using copper to fix the heat spreader to the die as opposed to just merely soldering it on, as Intel does now, would help lower temperatures AND boost CPU performance dramatically. Since this only at a development stage right now, and Intel is already ramping 45nm production, we will probably only see this being used when they have hit the wall beyond 32nm. It is, still, a great development - something that I hope will be used in the near future.

Luscious report abuse vote down vote up Votes: +0

Carbon Nano Tubes are Expensive

Oct 02, 2007 18:01     

Just to let you know a gram of carbon nanotubes is $100-$1000 depending on purity. They are cool and have neat properties but until they can mass produce them cheap or use very small amounts of them it's just not happening.
Ben report abuse vote down vote up Votes: +0

Expense

Oct 03, 2007 08:59     

So, if you use .001 grams of nanotubes (you need to connect the die to the heat spreader, think PIII flip chip size area), and assume the least pure nanotubes, which are probably more than adequate for heat transfer, and you have 1$ per chip.
BOM report abuse vote down vote up Votes: +0

Expensive? Read the article

Nov 01, 2007 05:09     

"While somewhat technical, the process being used by the researchers is not expensive or difficult to employ." And they are produced in place, so nobody has to go to the nanotube store.
Matt report abuse vote down vote up Votes: +0