[Amps] Anodizing aluminum, painting etc.

[Will Matney]

Gary,

Correct, I don't think anyone is saying this isn't so. I know the fins are what make up the large surface area and are what dissapate the heat to the atmosphere. The mass of the solid portion merely helps as far as heat up time and the spreading of the heat through the heatsink. Generally the ones used for RF power transistors are around 0.200 to 0.250 thick. One can use a copper spreader to make the heat spread more quickly to be dissapated. The problem arises with the color and the anodized coating which can act as an insulator, and also absorb heat from an IR radiating source. I'm going to try and investagate this later today, and see what I find about the use of black on heatsinks. I'll let everyone know what I dig up.

Best,

Will

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

On 8/17/06 at 12:42 PM Gary Schafer wrote:

>Some of the confusion about heat sinks I think comes from referring to
>"mass" of the sink. Mass is really the same thing as weight. Weight of a
>sink by itself has no real effect on its ability to dissipate heat. If it
>did then lead would probably be the desired material.
>Each type of material has its own thermal conducting characteristics.
>Aluminum happens to be quite good at it.
>
>A heat sink is really a heat exchanger just like an air conditioner. Making
>the heat sink heavier by making it a larger block doesn't necessarily make
>it a better heat sink. Larger will hold more heat but it is surface area
>that gets rid of the heat.
>
>Think of a heat sink as a surface transformer. It effectively enlarges the
>surface area of a device.
>
>73
>Gary  K4FMX
>
>
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