Application on HDT Coolers

Heat-pipe Direct Touch coolers have taken the market by storm. In our recent Best CPU Cooler Performance - Q1 2008 article, all of the top-placed products were built from HDT technology. The excellent concept performs very well in practice - but it's far from perfect.

There are two flaws in the HDT design currently used in CPU cooler products:

1. The surface is rough and occasionally uneven.
2. There are channels created between the mounting base and heat-pipe.

Fixing the first problem required some wet-sand paper and elbow grease (that's a metaphor for hard work, so don't go searching the web for another product). By lapping down the surface to a flat even base, you can then polish it down to minimize the grain-like finish inherent of HDT products.

Solving the second problem can be done with potentially less time. Assuming you're not so hard-core that brazing the heat-pipe and mounting base surface gaps together with tin solder is an option, then I would recommend filling the inner channels with thermal paste as pictured above. I have used a black permanent marker to show where the corners of the CPU contact the coolers surface, so use this as a guide for your own application.

As previously mentioned, it's best to avoid oxidizing "white-grease" type TIM's, since they can tarnish the copper surface and bleed out. So with a more solid compound, pack the channels level so that your thermal paste doesn't fill them when the unit is compressed. I didn't bother to fill the outside channels, because the CPU doesn't come in contact with them.

Using a single drop of material resulted in a spread pattern remarkably similar to that of the single line method for square mounting bases in the previous section. The alloy mounting base creates channels which dramatically limits the depth of material spread over the surface. For this reason alone, HDT coolers must not be treated the same way as other traditional cooler surfaces.

Since the single drop pattern pushed most of the material over to the two forward sides, perhaps two drops spaced out roughly 1/3 the width of the processor would prove more successful.

Once the HDT cooler was lifted from the processor, I was humored by what looked like a pair of "kissing lips". Needless to say, the two drops of material did a much better job of covering the surface, it didn't reach the to the corners very well.

Thus far, I have learned that channels created by the heat-pipe rods being pressed into the mounting base pose a serious problem for thermal paste spread. To compensate, the two drop method proved that separating the material will offer good coverage over the directional surface.

For my final application method, two short lines measuring half the total length of the processor were placed on the two center mounting base partitions. Keep in mind that for this method, as well as the others, it is important to fill the channels level with thermal compound so that the the additional material may spread somewhat unrestricted to the edges.

It looks to me like HDT coolers have the uncanny ability to perform well using an unorthodox design, but they also require an equally unique method for properly applying thermal paste to the surface.

This guide wasn't created to become a set of rules to be cast in stone, but rather a collection of methods which I personally tested to help assist you with your own project. As with anything, the results are relevant to the product and methods used. Use these methods as a starting point, and make your own refinements from there to achieve the best performance possible.

Once you've mastered the art of thermal paste application, it's time to search out the best cooler for your project. Benchmark Reviews constantly tests the Best CPU Cooler Performance and offers perspective on the products worth your time and money.

Benchmark Reviews invites you to share your comments and suggestions for this topic in our Discussion Forum.

Related Items:

• 80-way Thermal Interface Material Performance Test
• 33-Way Thermal Interface Material Comparison