Using Thermal Grease on a Processor Heat Sink

As I described in an earlier article, cleaning the lint out of the processor cooling fins is the best way to stop your laptop from overheating. The cleaning process requires removing the heat sink. To ensure that your computer runs as cool as possible, one more step will optimize heat transfer.

When the heat sink is removed, a thermal bond between the processor and the heat sink is broken. While it is fine to just pop the heat sink back in after cleaning, the new thermal bond is not quite as good as the original. The solution, as mentioned by several readers of the cleaning article, is to apply a bit of thermal grease.

Thermal grease has two basic components. The grease part is often silicone oil, a thick, synthetic oil that dries very slowly, even when heated. Its ability to remain in place with high heat is what made it the material of choice for bonding two parts thermally. The second component is a heat conductor. This material is added to the oil to make it conduct heat. Together they form a grease or paste that is easy to apply to surfaces.

There are several different materials used for the heat conductor. The original is zinc oxide. If that sounds familiar, you probably know it as sun-block, that white goo life guards smear on their noses. In addition to being opaque, zinc oxide is also a very good heat conductor. White, thermal grease made with zinc oxide is by far the most common, and usually the least expensive. Some people refer to this type of thermal grease as ceramic grease because the zinc oxide particles are a kind of ceramic. The tiny tube (6.5 grams) of zinc oxide grease I purchased at my local, independent electronics store was $3.50.

That same store also carried a thermal grease containing what the tube called “branched carbon.” This is the newest type on the market, and it supposedly provides superior heat conduction. The patent applications for this grease claimed it would be far superior and less expensive. My local store only had a six-ounce tube of the stuff, far more than I could ever use, even if I operated a computer repair shop.

One brand of grease is Arctic Silver. This is in the class of greases called metal-filled. It contains very fine particles of silver, an excellent thermal conductor. However, silver and other metals are also excellent electrical conductors. Stray grease that gets between circuit board traces could cause shorts and malfunctions. If you are careful to keep Arctic Silver where it belongs, it will perform better than zinc oxide.

This procedure assumes you have already removed the heat sink and cleaned out the lint. If not, please visit the earlier article about fixing an overheating laptop. The link is below – “Fix Overheating Laptop.”

Cleaning the two contact surfaces is usually a good idea. You can use a cotton swab moistened with rubbing alcohol. Just rub the top of the processor until it looks clean. Do the same to the matching area in the center of the heat sink bottom. Don’t get overly aggressive. Just take off the obvious bits of debris.

To apply the thermal grease, I used a toothpick. Only a very tiny amount is needed. The photo shows my first attempt. It looked like a bit much, but I decided to just try it. I then inserted the heat sink and tightened the screws.

Next, I removed the heat sink again to see what happened. The photo above shows that my dab of grease was more than enough, but it spread out unevenly. There is a small area in the top left corner of the processor contact area that did not get good coverage.

To start over, I cleaned both contact surfaces. I used a cotton swab dipped in rubbing alcohol (70% isopropyl). I really scrubbed the top of the processor because that is a very hard and sturdy material with a mirror finish. I wanted to remove all traces of old thermal material.

On the heatsink I was much more gentle. Not knowing much about the dark pad, I wanted to leave as much of the original material in place as possible. However, you could also take the opposite view and really clean it down to the bare metal. I had previously determined that the pad is made of some sort of metal foil. This photo shows the results of my cleaning work.

For the second attempt, I applied a thin line of grease down the middle of the processor top along the long axis. Then I reinstalled the heat sink. This approach resulted in complete coverage of the contact area. Only time will tell if the fan runs any less as a result.