THE HEATSINK GUIDE: Information about heatsinks - part 1
General heatsink information

Heatsink Design

What characteristics make a heatsink a good one? There's a number of factors to consider:

Measuring heatsink performance; thermal resistance θ

Heatsink performance is measured in °C/W (or K/W - since we're dealing with temperature differences, there is no difference between Celsius and Kelvin scale here). We refer to this as thermal resistance (θ).

An example for what these values mean: if a thermal load of 20W is applied to a heatsink, and this causes the temperature of the heat source to raise by 10°C, the heatsink has a rating of of 10°C/20W = 0.5°C/W.

A θ value is valid only for a certain power load and a certain temperature range.

The thermal resistance of standard coolers for PC CPUs is usually not specified by the heatsink manufacturers, and if it is, it's often inaccurate or intentionally skewed for marketing purposes. You cannot judge heatsink performance by comparing θ specifications from different manufacturers.

The θ values specified by manufacturers specialized in heatsinks for industrial applications (especially large passive heatsinks) are usually more accurate, though.

Heatsink testing is not an easy task; many of the heatsink reviews found on the countless cooling-related sites on the net are not done properly. Check out my article about common mistakes in heatsink reviews to help you read reviews critically and decide which review to trust.

Heatsink materials

The thermal conductivity of the heatsink's material has a major impact on cooling performance. Thermal conductivity is measured in W/mK; higher values mean better conductivity.

As a rule of thumb, materials with a high electrical conductivity also have a high thermal conductivity. See this Wikipedia article for more information on thermal conductivity.

Alloys have lower thermal conductivity than pure metals, but may have better mechanical or chemical (corrosion) properties.

The following materials are commonly used for heatsinks:

Go to part 2 of this article for info about heatsink production methods.

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