Letter 18042

Best Heat Sink Surface Treatments  

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Hello,

I am trying to get more heat transfer out of a both a copper and an aluminium fin type heat sinks. I've heard anodising is good for the aluminium and enamel based paints are good for the copper. Can anyone suggest if there are any better ones?

Thanks in advance,

Ralph Coakley
Redfern Broadband Networks - Sydney, New South Wales, Australia

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Any coating that you put on a fin heat sink will act like an insulator. The thicker the coating, the less heat transfer.

James Watts
- FL

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Hey!,

Correct me if I'm wrong, but I understood that anodize dissipates heat better than uncoated aluminum.

Bill Grayson
- Santa Cruz, CA, USA

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What you need to look at is the thermal conductivity of the coatings. Both Al and Cu are excellent thermal conductors (copper is almost twice as good as aluminum). Aluminum is more popular due to cost, processability, and weight to name a few. In certain cases copper does have its place.

"A black object radiates the best - so all heatsinks should be black". Maybe. More importantly, are you using natural or forced convection? For forced, the color is irrelevant. Comparison testing of two otherwise identical heatsinks with different colors, the performance delta is usually negligible. Heatsink manufacturers anodize their heatsinks to make them look more attractive. I would focus more on surface finish/roughness of the area contacting the hot component.

Not all coatings degrade thermal conductivity i.e. copper over aluminum. I have never run across enamel over copper for heatsinks but enamel is a worse thermal conductor. Most copper heatsinks I've seen (CPU over-clocking heatsinks) are pure copper and, I believe, have no coating/plating. This is probably because of the rather benign operating environment.

Richard Huang
- San Jose, CA, USA

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