Why Blue and Green Color Anodization for Push Pin Heat Sinks?

ATS’s push pin heat sink line has a number of important characteristics but you’d think the least of them would be their color.   Why the colors and how do they help heat sinks be better heat spreaders – or do they?

First off, why the colors?   Are they there for marketing purposes or do they have a more engineering centric mission?  The colors are actually part of the anodization itself.    But first what is anodizing?   The Aluminum Anodizers Council has the key definition:

Anodizing is an electrochemical process that converts the metal surface into a decorative, durable, corrosion-resistant, anodic oxide finish. Aluminum is ideally suited to anodizing, although other nonferrous metals, such as magnesium and titanium, also can be anodized.

But most heat sinks are themselves inside electronic systems such as computers, telecommunications equipment.  Any electronic component that generates heat can benefit from a heat sink (also known as a heat spreader).   So, do heat sinks inside computers need to be protected by anodizing them?  The short answer is no.  There are use cases of course but in general, protection is not the reason heat sinks in general (and ATS’s Push Pin line of Heat Sinks) are anodized.  In many cases the anodization color makes it easier to brand the heat sink from a particular manufacture or to distinguish between different branches of a heat sink family.  In the case of ATS’s Push Pin Line, the green anodized heat sinks use ATS’s  ultra performance maxiFLOW™ fin geometries while the blue anodized heat sinks feature straight fin or cross-cut fin designs.

So anodization is just about marketecture?   Well, no.  While the colors are convenient and helpful the real answer is a technical reason.  As we’ve noted in our 2010 article series, “How Heat Sink Anodization Improves Thermal Performance (see them on qats.com at these links, part 1 and part 2)”  anodization is about treating the surface of the heat sink to improve the radiation heat transfer of the heat sink:

Radiation heat transfer can be as important as convection heat transfer in electronics cooling, especially in natural convection and low-airflow applications.  Depending on the type of surface treatment used, radiation heat transfer is enhanced in two distinct ways: by increasing the emissivity of the surface or by increasing the surface area.  Anodization is one such way to treat the surface area.

Various protective benefits and aesthetically pleasing colors have extended the use of anodization to many industrial and commercial applications. For electronics cooling, however, the advantages of surface anodizing are the dielectric isolation of the cooling components from their electronics environment, and the significant increase in their surface emissivity. The increase in the emissivity coefficient on the anodized surfaces of heat exchangers, electronics cabinets and enclosures, heat sinks, etc. is typically on the order of 0.83 to 0.86 [4]. When compared to the emissivity coefficient of bare aluminum, 0.04 to 0.06 [5], the importance and significance of enhancement of radiation heat transfer would become evident.

So for ATS’s push pin heat sinks and for other firms who anodize their heat sinks the reason is really for the purpose of improving the thermal performance of the heat sink.  Also available through Digi-Key!

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