[Amps] making aluminum heat sinks black

[Will Matney]

It could be that they think the same as I do. Any time you anodize aluminum, there is actually a coating formed 1-2 mils deep on the aluminum. This is similar to the way an electrolytic cap is formed. It could effect the thermal transfer between the transistor/device and the aluminum. I would think it would be ok for all the heatsink except for the mounting surface. The probelm is, all the commercial heatsinks are anodized all over. One uses silicon grease to maximum the heat transfer to the aluminum, but the coating could limit it.

Best,

Will

*********** REPLY SEPARATOR  ***********

On 7/22/06 at 11:58 AM pegasus at mho.net wrote:

>> In a former job, we built black body radiators used for calibration of
>> missile seekers.  We used Krylon ultra flat black paint.  It had very
>high
>> emissivity at long infrared wavelengths.  The aluminum was anodized first
>> so
>> that the paint would stick.
>
>   I'm still amazed why transmitter manufacturers continue to use bare
>aluminum material for heat sinks.  It is TERRIBLE at radiating heat. 
>Forced air is necessary for any degree of efficient cooling.  To
>illustrate this point try the following experiment...
>   Heat an empty teflon frypan on your stove... (use one that has an
>aluminum colored bottom) to something above boiling point, very hot to
>the touch but, of course, not hot enough to start burning the teflon. 
>Remove it from the fire.  Then raise the pan with one side facing your
>cheek... take note of the radiant heat you feel from the bottom side
>vs. the dark teflon side.  Dramatic to say the least.  Almost none is
>felt from the bottom, the dark side radiates a great deal of heat.
>   Yet, many radio heat sinks are bare aluminum.. go figure.
>
>Dennis
>NØSP
>
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