Heatsinks

The importance of a heatsink is given. How do you determine a good heatsink from a not-so-good one, though? There are a couple of different issues to consider when discussing heatsinks. Not only are there different sizes and different designs, but heatsinks can be made of different materials and have good circulation air of their own.

The bigger the better! Well, not necessarily.

The actual process by which heatsinks get rid of the heat that they absorb is a combination of radiation and convection. The heatsink's fins radiate heat, and convection occurs as the airflow created by the fans picks the heat up and takes it away. Thus, it is best to have a heatsink that has a greater exposure to air. In order to do this, the heatsink should have a large surface area. This can be done by either making the heatsink really large, which is not so smart, or by increasing the surface area of the heatsink fins. The latter is the choice that makes more sense, because we're not going to be able to fit a 1 foot x 1 foot heatsink on our CPUs given the cases that we use. So, heatsink fins are made thinner, longer, and more of them are crammed on the heatsink. In general, look for a heatsink that has a large base, but also has a lot of thin fins. This will insure the best exposure of the fins to the surrounding air. To insure a good contact with the CPU-side of the heatsink, the surface that touches the CPU should be very smooth. Thermally conducive paste or glue helps fill in the microscopic gaps that we can't see to have the best contact with the CPU's surface.

Extruded fins or folded sheets?

A vast majority of the heatsinks that you will deal with will be the kind with the fins that extrude, or stick out. However, there is another kind as well. This other design uses a thin sheet of metal that is folded back and forth many times. This folded design is good because it has a great surface area exposure to air, and also allows for good airflow. However, this is also expensive to produce,so there are not too many of these heatsinks around. As far as heat transfer, the extruded fin kind that we are used to performs closely enough that we are happy with them.